Purine or pyrimidine bases attached to a ribose or deoxyribose. (From King & Stansfield, A Dictionary of Genetics, 4th ed)
Purines with a RIBOSE attached that can be phosphorylated to PURINE NUCLEOTIDES.
Pyrimidines with a RIBOSE attached that can be phosphorylated to PYRIMIDINE NUCLEOTIDES.
Proteins involved in the transport of NUCLEOSIDES across cellular membranes.
A subtype of equilibrative nucleoside transporter proteins that is sensitive to inhibition by 4-nitrobenzylthioinosine.
Sulfhydryl analog of INOSINE that inhibits nucleoside transport across erythrocyte plasma membranes, and has immunosuppressive properties. It has been used similarly to MERCAPTOPURINE in the treatment of leukemia. (From Martindale, The Extra Pharmacopoeia, 30th ed, p503)
An enzyme that catalyzes the reaction between a purine nucleoside and orthophosphate to form a free purine plus ribose-5-phosphate. EC 2.4.2.1.
A purine nucleoside that has guanine linked by its N9 nitrogen to the C1 carbon of ribose. It is a component of ribonucleic acid and its nucleotides play important roles in metabolism. (From Dorland, 28th ed)
An enzyme that is found in mitochondria and in the soluble cytoplasm of cells. It catalyzes reversible reactions of a nucleoside triphosphate, e.g., ATP, with a nucleoside diphosphate, e.g., UDP, to form ADP and UTP. Many nucleoside diphosphates can act as acceptor, while many ribo- and deoxyribonucleoside triphosphates can act as donor. EC 2.7.4.6.
A purine nucleoside that has hypoxanthine linked by the N9 nitrogen to the C1 carbon of ribose. It is an intermediate in the degradation of purines and purine nucleosides to uric acid and in pathways of purine salvage. It also occurs in the anticodon of certain transfer RNA molecules. (Dorland, 28th ed)
Uridine is a nucleoside, specifically a derivative of pyrimidine, that is composed of a uracil molecule joined to a ribose sugar molecule through a β-N1 glycosidic bond, and has significant roles in RNA synthesis, energy transfer, and cell signaling.
A modified nucleoside which is present in the first position of the anticodon of tRNA-tyrosine, tRNA-histidine, tRNA-asparagine and tRNA-aspartic acid of many organisms. It is believed to play a role in the regulatory function of tRNA. Nucleoside Q can be further modified to nucleoside Q*, which has a mannose or galactose moiety linked to position 4 of its cyclopentenediol moiety.
A subtype of equilibrative nucleoside transporter proteins that is insensitive to inhibition by 4-nitrobenzylthioinosine.
An enzyme which catalyzes the hydrolysis of nucleoside triphosphates to nucleoside diphosphates. It may also catalyze the hydrolysis of nucleotide triphosphates, diphosphates, thiamine diphosphates and FAD. The nucleoside triphosphate phosphohydrolases I and II are subtypes of the enzyme which are found mostly in viruses.
A pyrimidine nucleoside that is composed of the base CYTOSINE linked to the five-carbon sugar D-RIBOSE.
Nucleosides in which the purine or pyrimidine base is combined with ribose. (Dorland, 28th ed)
The monomeric units from which DNA or RNA polymers are constructed. They consist of a purine or pyrimidine base, a pentose sugar, and a phosphate group. (From King & Stansfield, A Dictionary of Genetics, 4th ed)
A nucleoside that is composed of ADENINE and D-RIBOSE. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter.
Pyrazolopyrimidine ribonucleosides isolated from Nocardia interforma. They are antineoplastic antibiotics with cytostatic properties.
Enzymes of the transferase class that catalyze the transfer of a pentose group from one compound to another.
A family of nucleotide diphosphate kinases that play a role in a variety of cellular signaling pathways that effect CELL DIFFERENTIATION; CELL PROLIFERATION; and APOPTOSIS. They are considered multifunctional proteins that interact with a variety of cellular proteins and have functions that are unrelated to their enzyme activity.
Inhibitors of reverse transcriptase (RNA-DIRECTED DNA POLYMERASE), an enzyme that synthesizes DNA on an RNA template.
A class of sodium-independent nucleoside transporters that mediate the facilitative transport of NUCLEOSIDES.
A purine or pyrimidine base bonded to DEOXYRIBOSE.
Adenosine molecules which can be substituted in any position, but are lacking one hydroxyl group in the ribose part of the molecule.
A purine base and a fundamental unit of ADENINE NUCLEOTIDES.
Coronary vasodilator with some antiarrhythmic activity.
The rate dynamics in chemical or physical systems.
Nucleosides that have two hydroxy groups removed from the sugar moiety. The majority of these compounds have broad-spectrum antiretroviral activity due to their action as antimetabolites. The nucleosides are phosphorylated intracellularly to their 5'-triphosphates and act as chain-terminating inhibitors of viral reverse transcription.
An antibiotic purine ribonucleoside that readily substitutes for adenosine in the biological system, but its incorporation into DNA and RNA has an inhibitory effect on the metabolism of these nucleic acids.
A dideoxynucleoside compound in which the 3'-hydroxy group on the sugar moiety has been replaced by an azido group. This modification prevents the formation of phosphodiester linkages which are needed for the completion of nucleic acid chains. The compound is a potent inhibitor of HIV replication, acting as a chain-terminator of viral DNA during reverse transcription. It improves immunologic function, partially reverses the HIV-induced neurological dysfunction, and improves certain other clinical abnormalities associated with AIDS. Its principal toxic effect is dose-dependent suppression of bone marrow, resulting in anemia and leukopenia.
Nucleosides containing arabinose as their sugar moiety.
Agents used in the prophylaxis or therapy of VIRUS DISEASES. Some of the ways they may act include preventing viral replication by inhibiting viral DNA polymerase; binding to specific cell-surface receptors and inhibiting viral penetration or uncoating; inhibiting viral protein synthesis; or blocking late stages of virus assembly.
A series of heterocyclic compounds that are variously substituted in nature and are known also as purine bases. They include ADENINE and GUANINE, constituents of nucleic acids, as well as many alkaloids such as CAFFEINE and THEOPHYLLINE. Uric acid is the metabolic end product of purine metabolism.
An enzyme that catalyzes reversibly the phosphorylation of deoxycytidine with the formation of a nucleoside diphosphate and deoxycytidine monophosphate. Cytosine arabinoside can also act as an acceptor. All natural nucleoside triphosphates, except deoxycytidine triphosphate, can act as donors. The enzyme is induced by some viruses, particularly the herpes simplex virus (HERPESVIRUS HOMINIS). EC 2.7.1.74.
Carbon-containing phosphonic acid compounds. Included under this heading are compounds that have carbon bound to either OXYGEN atom or the PHOSPHOROUS atom of the (P=O)O2 structure.
Pentosyltransferases that catalyze the reaction between a pyrimidine nucleoside and orthophosphate to form a free pyrimidine and ribose-5-phosphate.
Thymidine is a pyrimidine nucleoside, consisting of a thymine base linked to a deoxyribose sugar by a β-N1-glycosidic bond, which plays a crucial role in DNA replication and repair processes as one of the four nucleosides in DNA.
Nucleosides in which the base moiety is substituted with one or more sulfur atoms.
Nucleotides in which the purine or pyrimidine base is combined with ribose. (Dorland, 28th ed)
2'-Deoxyuridine. An antimetabolite that is converted to deoxyuridine triphosphate during DNA synthesis. Laboratory suppression of deoxyuridine is used to diagnose megaloblastic anemias due to vitamin B12 and folate deficiencies.
A dideoxynucleoside compound in which the 3'-hydroxy group on the sugar moiety has been replaced by a hydrogen. This modification prevents the formation of phosphodiester linkages which are needed for the completion of nucleic acid chains. The compound is a potent inhibitor of HIV replication at low concentrations, acting as a chain-terminator of viral DNA by binding to reverse transcriptase. Its principal toxic side effect is axonal degeneration resulting in peripheral neuropathy.
An enzyme that catalyzes the transfer of ribose from uridine to orthophosphate, forming uracil and ribose 1-phosphate.
Agents used to treat AIDS and/or stop the spread of the HIV infection. These do not include drugs used to treat symptoms or opportunistic infections associated with AIDS.
A phosphodiesterase inhibitor that blocks uptake and metabolism of adenosine by erythrocytes and vascular endothelial cells. Dipyridamole also potentiates the antiaggregating action of prostacyclin. (From AMA Drug Evaluations Annual, 1994, p752)
A reverse transcriptase encoded by the POL GENE of HIV. It is a heterodimer of 66 kDa and 51 kDa subunits that are derived from a common precursor protein. The heterodimer also includes an RNAse H activity (RIBONUCLEASE H, HUMAN IMMUNODEFICIENCY VIRUS) that plays an essential role the viral replication process.
Phosphate esters of THYMIDINE in N-glycosidic linkage with ribose or deoxyribose, as occurs in nucleic acids. (From Dorland, 28th ed, p1154)
A group of enzymes that catalyze the hydrolysis of diphosphate bonds in compounds such as nucleoside di- and tri-phosphates, and sulfonyl-containing anhydrides such as adenylylsulfate. (Enzyme Nomenclature, 1992) EC 3.6.
A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.
An adenine nucleotide containing three phosphate groups esterified to the sugar moiety. In addition to its crucial roles in metabolism adenosine triphosphate is a neurotransmitter.
The phosphate esters of DIDEOXYNUCLEOSIDES.
Catalyze the hydrolysis of nucleosides with the elimination of ammonia.
A purine and a reaction intermediate in the metabolism of adenosine and in the formation of nucleic acids by the salvage pathway.
A dideoxynucleoside analog that inhibits reverse transcriptase and has in vitro activity against HIV.
Guanine is a purine nucleobase, one of the four nucleobases in the nucleic acid of DNA and RNA, involved in forming hydrogen bonds between complementary base pairs in double-stranded DNA molecules.
The movement of materials (including biochemical substances and drugs) through a biological system at the cellular level. The transport can be across cell membranes and epithelial layers. It also can occur within intracellular compartments and extracellular compartments.
A nucleoside consisting of the base guanine and the sugar deoxyribose.
Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.
A photoactivable URIDINE analog that is used as an affinity label.
Purines attached to a RIBOSE and a phosphate that can polymerize to form DNA and RNA.
Membrane proteins whose primary function is to facilitate the transport of molecules across a biological membrane. Included in this broad category are proteins involved in active transport (BIOLOGICAL TRANSPORT, ACTIVE), facilitated transport and ION CHANNELS.
The location of the atoms, groups or ions relative to one another in a molecule, as well as the number, type and location of covalent bonds.
Cytidine 5'-(tetrahydrogen triphosphate). A cytosine nucleotide containing three phosphate groups esterified to the sugar moiety.
The ability of viruses to resist or to become tolerant to chemotherapeutic agents or antiviral agents. This resistance is acquired through gene mutation.
A rather large group of enzymes comprising not only those transferring phosphate but also diphosphate, nucleotidyl residues, and others. These have also been subdivided according to the acceptor group. (From Enzyme Nomenclature, 1992) EC 2.7.
A dideoxynucleoside compound in which the 3'-hydroxy group on the sugar moiety has been replaced by a hydrogen. This modification prevents the formation of phosphodiester linkages which are needed for the completion of nucleic acid chains. Didanosine is a potent inhibitor of HIV replication, acting as a chain-terminator of viral DNA by binding to reverse transcriptase; ddI is then metabolized to dideoxyadenosine triphosphate, its putative active metabolite.
A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.
Purine bases related to hypoxanthine, an intermediate product of uric acid synthesis and a breakdown product of adenine catabolism.
Adenine nucleotides are molecules that consist of an adenine base attached to a ribose sugar and one, two, or three phosphate groups, including adenosine monophosphate (AMP), adenosine diphosphate (ADP), and adenosine triphosphate (ATP), which play crucial roles in energy transfer and signaling processes within cells.
A purine or pyrimidine base bonded to a DEOXYRIBOSE containing a bond to a phosphate group.
A group of enzymes within the class EC 3.6.1.- that catalyze the hydrolysis of diphosphate bonds, chiefly in nucleoside di- and triphosphates. They may liberate either a mono- or diphosphate. EC 3.6.1.-.
A pyrimidine nucleoside formed in the body by the deamination of CYTARABINE.
Drugs that inhibit ADENOSINE DEAMINASE activity.
Guanine nucleotides which contain deoxyribose as the sugar moiety.
The small RNA molecules, 73-80 nucleotides long, that function during translation (TRANSLATION, GENETIC) to align AMINO ACIDS at the RIBOSOMES in a sequence determined by the mRNA (RNA, MESSENGER). There are about 30 different transfer RNAs. Each recognizes a specific CODON set on the mRNA through its own ANTICODON and as aminoacyl tRNAs (RNA, TRANSFER, AMINO ACYL), each carries a specific amino acid to the ribosome to add to the elongating peptide chains.
A compound that, on administration, must undergo chemical conversion by metabolic processes before becoming the pharmacologically active drug for which it is a prodrug.
An enzyme that catalyzes the formation of ADP plus AMP from adenosine plus ATP. It can serve as a salvage mechanism for returning adenosine to nucleic acids. EC 2.7.1.20.
A class of enzymes that catalyze the conversion of a nucleotide and water to a nucleoside and orthophosphate. EC 3.1.3.-.
Uracil nucleotides are chemical compounds that consist of a uracil base, a sugar molecule called ribose, and one or more phosphate groups, which play crucial roles in DNA replication, repair, and gene expression as well as in RNA synthesis.
The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.
An antineoplastic agent used in the treatment of lymphoproliferative diseases including hairy-cell leukemia.
An enzyme that catalyzes the conversion of ATP and thymidine to ADP and thymidine 5'-phosphate. Deoxyuridine can also act as an acceptor and dGTP as a donor. (From Enzyme Nomenclature, 1992) EC 2.7.1.21.
A calcium-activated enzyme that catalyzes the hydrolysis of ATP to yield AMP and orthophosphate. It can also act on ADP and other nucleoside triphosphates and diphosphates. EC 3.6.1.5.
The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups.
Pyrimidinones are heterocyclic organic compounds that consist of a pyrimidine ring fused with a ketone group, which have significant applications in medicinal chemistry due to their wide range of biological activities, including antibacterial, antiviral, and anticancer properties.
Deoxycytidine is a nucleoside consisting of the pentose sugar deoxyribose linked to the nitrogenous base cytosine, which plays a crucial role in DNA replication and repair processes within cells.
A reverse transcriptase inhibitor and ZALCITABINE analog in which a sulfur atom replaces the 3' carbon of the pentose ring. It is used to treat HIV disease.
A pentose active in biological systems usually in its D-form.
Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.
A pyrimidine base that is a fundamental unit of nucleic acids.
An enzyme that catalyzes the phosphorylation of uridine and cytidine to uridine 5'-phosphate and cytidine 5'-phosphate, respectively. ATP, dUTP, dGTP, and dATP are effective phosphate donors. EC 2.7.1.48.
The type species of LENTIVIRUS and the etiologic agent of AIDS. It is characterized by its cytopathic effect and affinity for the T4-lymphocyte.
Adenine nucleotide containing one phosphate group esterified to the sugar moiety in the 2'-, 3'-, or 5'-position.
An antineoplastic antimetabolite that is metabolized to fluorouracil when administered by rapid injection; when administered by slow, continuous, intra-arterial infusion, it is converted to floxuridine monophosphate. It has been used to treat hepatic metastases of gastrointestinal adenocarcinomas and for palliation in malignant neoplasms of the liver and gastrointestinal tract.
A glycoprotein enzyme present in various organs and in many cells. The enzyme catalyzes the hydrolysis of a 5'-ribonucleotide to a ribonucleoside and orthophosphate in the presence of water. It is cation-dependent and exists in a membrane-bound and soluble form. EC 3.1.3.5.
The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.
Organic compounds that contain phosphorus as an integral part of the molecule. Included under this heading is broad array of synthetic compounds that are used as PESTICIDES and DRUGS.
Guanosine 5'-(tetrahydrogen triphosphate). A guanine nucleotide containing three phosphate groups esterified to the sugar moiety.
Polymers made up of a few (2-20) nucleotides. In molecular genetics, they refer to a short sequence synthesized to match a region where a mutation is known to occur, and then used as a probe (OLIGONUCLEOTIDE PROBES). (Dorland, 28th ed)
A GUANOSINE analog that acts as an antimetabolite. Viruses are especially susceptible. Used especially against herpes.
Ribose substituted in the 1-, 3-, or 5-position by a phosphoric acid moiety.
Liquid chromatographic techniques which feature high inlet pressures, high sensitivity, and high speed.
6-(Methylthio)-9-beta-D-ribofuranosylpurine. An analog of inosine with a methylthio group replacing the hydroxyl group in the 6-position.
A guanine nucleotide containing one phosphate group esterified to the sugar moiety and found widely in nature.
A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. (Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)
Uracil is a nitrogenous base, specifically a pyrimidine derivative, which constitutes one of the four nucleobases in the nucleic acid of RNA (ribonucleic acid), pairing with adenine via hydrogen bonds during base-pairing. (25 words)
Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING).
A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).
A group of hydrolases which catalyze the hydrolysis of monophosphoric esters with the production of one mole of orthophosphate. EC 3.1.3.
Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.
An enzyme that catalyzes the hydrolysis of ADENOSINE to INOSINE with the elimination of AMMONIA.
Cytosine nucleotides are organic compounds that consist of a nitrogenous base (cytosine), a pentose sugar (ribose in RNA or deoxyribose in DNA), and at least one phosphate group, playing crucial roles in genetic information storage, transmission, and expression within nucleic acids.
A nucleoside antibiotic isolated from Streptomyces antibioticus. It has some antineoplastic properties and has broad spectrum activity against DNA viruses in cell cultures and significant antiviral activity against infections caused by a variety of viruses such as the herpes viruses, the VACCINIA VIRUS and varicella zoster virus.
An adenosine monophosphate analog in which ribose is replaced by an arabinose moiety. It is the monophosphate ester of VIDARABINE with antiviral and possibly antineoplastic properties.
Pyrimidines with a RIBOSE and phosphate attached that can polymerize to form DNA and RNA.
Inorganic salts of phosphoric acid.
N(6)-[delta(3)-isopentenyl]adenosine. Isopentenyl derivative of adenosine which is a member of the cytokinin family of plant growth regulators.
A dideoxynucleoside compound in which the 3'-hydroxy group on the sugar moiety has been replaced by a hydrogen. This modification prevents the formation of phosphodiester linkages which are needed for the completion of nucleic acid chains. The compound is an inhibitor of HIV replication, acting as a chain-terminator of viral DNA by binding to reverse transcriptase. Its principal side effect is nephrotoxicity. In vivo, dideoxyadenosine is rapidly metabolized to DIDANOSINE (ddI) by enzymatic deamination; ddI is then converted to dideoxyinosine monophosphate and ultimately to dideoxyadenosine triphosphate, the putative active metabolite.
Includes the spectrum of human immunodeficiency virus infections that range from asymptomatic seropositivity, thru AIDS-related complex (ARC), to acquired immunodeficiency syndrome (AIDS).
The process of cleaving a chemical compound by the addition of a molecule of water.
The parts of a macromolecule that directly participate in its specific combination with another molecule.
Pseudouridine is a modified nucleoside, where the uracil component of a uridine residue in RNA molecules is linked to ribose through a carbon-carbon bond rather than the usual nitrogen-glycosidic bond, which can contribute to structural stability and functional diversity in RNA.
Established cell cultures that have the potential to propagate indefinitely.
An enzyme that catalyzes reversible reactions of a nucleoside triphosphate, e.g., ATP, with a nucleoside monophosphate, e.g., UMP, to form ADP and UDP. Many nucleoside monophosphates can act as acceptor while many ribo- and deoxyribonucleoside triphosphates can act as donor. EC 2.7.4.4.
Antimetabolites that are useful in cancer chemotherapy.
The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)
An active blood parasite that is present in practically all domestic animals in Africa, the West Indies, and parts of Central and South America. In Africa, the insect vector is the tsetse fly. In other countries, infection is by mechanical means indicating that the parasites have been introduced to these countries and have been able to maintain themselves in spite of the lack of a suitable intermediate host. It is a cause of nagana, the severity of which depends on the species affected.
A pyrimidine nucleoside analog that is used mainly in the treatment of leukemia, especially acute non-lymphoblastic leukemia. Cytarabine is an antimetabolite antineoplastic agent that inhibits the synthesis of DNA. Its actions are specific for the S phase of the cell cycle. It also has antiviral and immunosuppressant properties. (From Martindale, The Extra Pharmacopoeia, 30th ed, p472)
5'-Uridylic acid. A uracil nucleotide containing one phosphate group esterified to the sugar moiety in the 2', 3' or 5' position.
Transport proteins that carry specific substances in the blood or across cell membranes.
The sequential set of three nucleotides in TRANSFER RNA that interacts with its complement in MESSENGER RNA, the CODON, during translation in the ribosome.
2-Chloroadenosine. A metabolically stable analog of adenosine which acts as an adenosine receptor agonist. The compound has a potent effect on the peripheral and central nervous system.
A class of enzymes involved in the hydrolysis of the N-glycosidic bond of nitrogen-linked sugars.
An enzyme which catalyzes the catabolism of S-ADENOSYLHOMOCYSTEINE to ADENOSINE and HOMOCYSTEINE. It may play a role in regulating the concentration of intracellular adenosylhomocysteine.
A group of compounds which consist of a nucleotide molecule to which an additional nucleoside is attached through the phosphate molecule(s). The nucleotide can contain any number of phosphates.
4-Amino-5-cyano-7-(D-ribofuranosyl)-7H- pyrrolo(2,3-d)pyrimidine. Antibiotic antimetabolite isolated from Streptomyces toyocaensis cultures. It is an analog of adenosine, blocks RNA synthesis and ribosome function, and is used mainly as a tool in biochemistry.
Nucleoside Diphosphate Sugars (NDPs) are biomolecules consisting of a nucleoside monophosphate sugar molecule, which is formed from the condensation of a nucleotide and a sugar molecule through a pyrophosphate bond.
Analogs of those substrates or compounds which bind naturally at the active sites of proteins, enzymes, antibodies, steroids, or physiological receptors. These analogs form a stable covalent bond at the binding site, thereby acting as inhibitors of the proteins or steroids.
The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction.
A nucleoside diphosphate kinase subtype that is localized to the intermembrane space of MITOCHONDRIA. It is believed to play a role in the synthesis of triphosphonucleotides using ATP formed through OXIDATIVE PHOSPHORYLATION.
Nucleotides containing arabinose as their sugar moiety.
Proteins involved in the transport of nucleobases such as PYRIMIDINES and PURINES across membranes.
A potent inhibitor of ADENOSINE DEAMINASE. The drug induces APOPTOSIS of LYMPHOCYTES, and is used in the treatment of many lymphoproliferative malignancies, particularly HAIRY CELL LEUKEMIA. It is also synergistic with some other antineoplastic agents and has immunosuppressive activity.
High molecular weight polymers containing a mixture of purine and pyrimidine nucleotides chained together by ribose or deoxyribose linkages.
Leukemia L1210 is a designation for a specific murine (mouse) leukemia cell line that was originally isolated from a female mouse with an induced acute myeloid leukemia, which is widely used as a model in cancer research, particularly for in vivo studies of drug efficacy and resistance.
Adenosine 5'-(trihydrogen diphosphate). An adenine nucleotide containing two phosphate groups esterified to the sugar moiety at the 5'-position.
The characteristic three-dimensional shape of a molecule.
Linear polymers in which orthophosphate residues are linked with energy-rich phosphoanhydride bonds. They are found in plants, animals, and microorganisms.
Proteins prepared by recombinant DNA technology.
Adenine nucleotides which contain deoxyribose as the sugar moiety.
The spatial arrangement of the atoms of a nucleic acid or polynucleotide that results in its characteristic 3-dimensional shape.
Cytidine (dihydrogen phosphate). A cytosine nucleotide containing one phosphate group esterified to the sugar moiety in the 2', 3' or 5' position.
The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH = log 1/2[1/(H+)], where (H+) is the hydrogen ion concentration in gram equivalents per liter of solution. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)
Uridine 5'-(tetrahydrogen triphosphate). A uracil nucleotide containing three phosphate groups esterified to the sugar moiety.
A cytotoxic sulfhydryl reagent that inhibits several subcellular metabolic systems and is used as a tool in cellular physiology.
Substances used for the detection, identification, analysis, etc. of chemical, biological, or pathologic processes or conditions. Indicators are substances that change in physical appearance, e.g., color, at or approaching the endpoint of a chemical titration, e.g., on the passage between acidity and alkalinity. Reagents are substances used for the detection or determination of another substance by chemical or microscopical means, especially analysis. Types of reagents are precipitants, solvents, oxidizers, reducers, fluxes, and colorimetric reagents. (From Grant & Hackh's Chemical Dictionary, 5th ed, p301, p499)
The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.
A group of enzymes which catalyze the hydrolysis of ATP. The hydrolysis reaction is usually coupled with another function such as transporting Ca(2+) across a membrane. These enzymes may be dependent on Ca(2+), Mg(2+), anions, H+, or DNA.
Inosine 5'-Monophosphate. A purine nucleotide which has hypoxanthine as the base and one phosphate group esterified to the sugar moiety.
Six-membered heterocycles containing an oxygen and a nitrogen.
A group of deoxyribonucleotides (up to 12) in which the phosphate residues of each deoxyribonucleotide act as bridges in forming diester linkages between the deoxyribose moieties.
OXAZINES with a fused BENZENE ring.
Cytidine 5'-(trihydrogen diphosphate). A cytosine nucleotide containing two phosphate groups esterified to the sugar moiety. Synonyms: CRPP; cytidine pyrophosphate.
An ACYCLOVIR analog that is a potent inhibitor of the Herpesvirus family including cytomegalovirus. Ganciclovir is used to treat complications from AIDS-associated cytomegalovirus infections.
Deoxyribose is a 5-carbon sugar (monosaccharide) that lacks one hydroxyl group at the 2' carbon position, compared to ribose, and is a key component of DNA molecules, forming part of the nucleotides along with phosphate and nitrogenous bases.
The process of intracellular viral multiplication, consisting of the synthesis of PROTEINS; NUCLEIC ACIDS; and sometimes LIPIDS, and their assembly into a new infectious particle.
Ribonucleic acid that makes up the genetic material of viruses.
Tritium is an isotope of hydrogen (specifically, hydrogen-3) that contains one proton and two neutrons in its nucleus, making it radioactive with a half-life of about 12.3 years, and is used in various applications including nuclear research, illumination, and dating techniques due to its low energy beta decay.
The ability of viruses to resist or to become tolerant to several structurally and functionally distinct drugs simultaneously. This resistance phenotype may be attributed to multiple gene mutation.
Guanine nucleotides are cyclic or linear molecules that consist of a guanine base, a pentose sugar (ribose in the cyclic form, deoxyribose in the linear form), and one or more phosphate groups, playing crucial roles in signal transduction, protein synthesis, and regulation of enzymatic activities.
A ribonucleoside antibiotic synergist and adenosine deaminase inhibitor isolated from Nocardia interforma and Streptomyces kaniharaensis. It is proposed as an antineoplastic synergist and immunosuppressant.
Inhibitors of HIV PROTEASE, an enzyme required for production of proteins needed for viral assembly.
5-Thymidylic acid. A thymine nucleotide containing one phosphate group esterified to the deoxyribose moiety.
A basic science concerned with the composition, structure, and properties of matter; and the reactions that occur between substances and the associated energy exchange.
DNA-dependent DNA polymerases found in bacteria, animal and plant cells. During the replication process, these enzymes catalyze the addition of deoxyribonucleotide residues to the end of a DNA strand in the presence of DNA as template-primer. They also possess exonuclease activity and therefore function in DNA repair.
Drugs that selectively bind to and activate ADENOSINE A3 RECEPTORS.
A group of ribonucleotides (up to 12) in which the phosphate residues of each ribonucleotide act as bridges in forming diester linkages between the ribose moieties.
A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
A broad class of proteins involved in the transport of nucleobases, NUCLEOSIDES; NUCLEOTIDES; and NUCLEIC ACIDS; across membranes.
Determination of the spectra of ultraviolet absorption by specific molecules in gases or liquids, for example Cl2, SO2, NO2, CS2, ozone, mercury vapor, and various unsaturated compounds. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
The composition, conformation, and properties of atoms and molecules, and their reaction and interaction processes.
Inorganic salts of phosphoric acid that contain two phosphate groups.
The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.
Inborn errors of purine-pyrimidine metabolism refer to genetic disorders resulting from defects in the enzymes responsible for the metabolic breakdown and synthesis of purines and pyrimidines, leading to the accumulation of toxic metabolites or deficiency of necessary nucleotides, causing various clinical manifestations such as neurological impairment, kidney problems, and developmental delays.
Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing HEMOGLOBIN whose function is to transport OXYGEN.
A family of 6-membered heterocyclic compounds occurring in nature in a wide variety of forms. They include several nucleic acid constituents (CYTOSINE; THYMINE; and URACIL) and form the basic structure of the barbiturates.
A uracil nucleotide containing a pyrophosphate group esterified to C5 of the sugar moiety.
The study of crystal structure using X-RAY DIFFRACTION techniques. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
Inosine nucleotides are purine nucleotides that contain inosine, a nucleoside with a hypoxanthine base, which can function as a weak agonist at adenosine receptors and play a role in the salvage pathways of nucleic acid metabolism.
Inosine 5'-(tetrahydrogen triphosphate). An inosine nucleotide containing three phosphate groups esterified to the sugar moiety. Synonym: IRPPP.
A subtype of ADENOSINE RECEPTOR that is found expressed in a variety of locations including the BRAIN and endocrine tissues. The receptor is generally considered to be coupled to the GI, INHIBITORY G-PROTEIN which causes down regulation of CYCLIC AMP.
Ribonucleic acid in bacteria having regulatory and catalytic roles as well as involvement in protein synthesis.
Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.
Chromatography on thin layers of adsorbents rather than in columns. The adsorbent can be alumina, silica gel, silicates, charcoals, or cellulose. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
The relationship between the dose of an administered drug and the response of the organism to the drug.
An enzyme that catalyzes the transfer of 2-deoxy-D-ribose from THYMIDINE to orthophosphate, thereby liberating thymidine.
An enzyme that catalyzes the deamination of guanine to form xanthine. EC 3.5.4.3.
A purine that is an isomer of ADENINE (6-aminopurine).
Acidosis caused by accumulation of lactic acid more rapidly than it can be metabolized. It may occur spontaneously or in association with diseases such as DIABETES MELLITUS; LEUKEMIA; or LIVER FAILURE.
Organic compounds composed exclusively of carbon and hydrogen where no carbon atoms join to form a ring structure.
A species of gram-negative bacteria isolated from MILK, cheese, and compressed yeast.
An antiviral derivative of THYMIDINE used mainly in the treatment of primary keratoconjunctivitis and recurrent epithelial keratitis due to HERPES SIMPLEX virus. (From Martindale, The Extra Pharmacopoeia, 30th ed, p557)

Effects of nucleoside analog incorporation on DNA binding to the DNA binding domain of the GATA-1 erythroid transcription factor. (1/1525)

We investigate here the effects of the incorporation of the nucleoside analogs araC (1-beta-D-arabinofuranosylcytosine) and ganciclovir (9-[(1,3-dihydroxy-2-propoxy)methyl] guanine) into the DNA binding recognition sequence for the GATA-1 erythroid transcription factor. A 10-fold decrease in binding affinity was observed for the ganciclovir-substituted DNA complex in comparison to an unmodified DNA of the same sequence composition. AraC substitution did not result in any changes in binding affinity. 1H-15N HSQC and NOESY NMR experiments revealed a number of chemical shift changes in both DNA and protein in the ganciclovir-modified DNA-protein complex when compared to the unmodified DNA-protein complex. These changes in chemical shift and binding affinity suggest a change in the binding mode of the complex when ganciclovir is incorporated into the GATA DNA binding site.  (+info)

Base pairing of anhydrohexitol nucleosides with 2,6-diaminopurine, 5-methylcytosine and uracil asbase moiety. (2/1525)

Hexitol nucleic acids (HNAs) with modified bases (5-methylcytosine, 2,6-diaminopurine or uracil) were synthesized. The introduction of the 5-methylcytosine base demonstrates that N -benzoylated 5-methylcytosyl-hexitol occurs as the imino tautomer. The base pairing systems (G:CMe, U:D, T:D and U:A) obey Watson-Crick rules. Substituting hT for hU, hCMefor hC and hD for hA generally leads to increased duplex stability. In a single case, replacement of hC by hCMedid not result in duplex stabilization. This sequence-specific effect could be explained by the geometry of the model duplex used for carrying out the thermal stability study. Generally, polypurine HNA sequences give more stable duplexes with their RNA complement than polypyrimidine HNA sequences. This observation supports the hypothesis that, besides changes in stacking pattern, the difference in conformational stress between purine and pyrimidine nucleosides may contribute to duplex stability. Introduction of hCMeand hD in HNA sequences further increases the potential of HNA to function as a steric blocking agent.  (+info)

Smoothing of the thermal stability of DNA duplexes by using modified nucleosides and chaotropic agents. (3/1525)

The effect of alkyltrimethylammonium ions on the thermostability of natural and modified DNA duplexes has been investigated. We have shown that the use of tetramethylammonium ions TMA+along with the chemical modification of duplexes allow the fine adjustment of T m and the possibility of obtaining several duplex systems with varied isostabilizedtemperatures, some of which show greater stability than those of natural DNA. This approach could be very useful for DNA sequencing by hybridization.  (+info)

A new synthesis of 5'-deoxy-8,5'-cyclo-adenosine and -inosine: conformationally-fixed purine nucleosides (nucleosides and nucleotides. XVI). (4/1525)

A versatile method for the synthesis of 5'-deoxy-8,5'-cycloadenosine, a conformationally-fixed "anti" type of adenosine, was presented. Irradiation of 2', 3'-O-isopropylidene-5'-deoxy-5'-phenylthioadenosine with 60W Hg vapor lamp afforded 2',3'-O-isopropylidene-5'-deoxy-8,5'-cycloadenosine in high yield. The use of other 5'-alkylthio derivatives also gave the cycloadenosine, though the yields were rather poor. Deacetonation of the cyclocompound with 0.1N HCl gave 5'-deoxy-8,5'-cycloadenosine. The cycloinosine derivative was similarly prepared. The nmr, mass and CD spectra of 5'-deoxy-8,5'-cycloadenosine were given and discussed with the previously reported results.  (+info)

Hypotension induced by exercise is associated with enhanced release of adenyl purines from aged rat artery. (5/1525)

To determine whether the antihypertensive effects of exercise are associated with release of ATP and its metabolites from arteries, we assayed blood pressure and the release of adenine nucleotides and nucleosides from the caudal arteries of exercised and sedentary aged hypercholesterolemic rats. Exercise on a treadmill for 12 wk significantly decreased the rise in systolic and diastolic blood pressure by 7.5 and 15.9%, respectively, with advanced age. The concentrations of oleic, linoleic, and linolenic acids in the caudal artery decreased significantly with exercise, demonstrating an association between exercise and the unsaturation index of caudal arterial fatty acids. The amounts of total adenyl purines released by the arterial segments from exercised rats, both spontaneously and in response to norepinephrine, were significantly greater by 80.0 and 60.7%, respectively, than those released by tissues from sedentary rats. These results suggest that exercise alters the membrane fatty acid composition in aged rats as well as the release of ATP from vascular endothelial cells and that these factors are associated with the regression of the rise in blood pressure normally observed with advanced age.  (+info)

Human immunodeficiency virus type 1 genetic evolution in patients with prolonged suppression of plasma viremia. (6/1525)

Treatment of human immunodeficiency virus type 1 (HIV-1)-infected patients with combination drug regimens results in a reduction of plasma viral load to levels below the limit of detection. To investigate the genomic fluctuations in HIV-1 populations from long-term responders to antiviral therapies we analyzed the viral sequence evolution of env and pol genes from sequential peripheral blood mononuclear cell (PBMC) DNA samples of three infected patients. Analyses of sequences covering the V3 and flanking env regions obtained from blood samples at the beginning of the therapy and at 14 or 24 months from baseline revealed that HIV-1 quasispecies continue to evolve in the three patients following combination antiretroviral therapy. Minor drug-resistant mutant subpopulations were also searched for and found in one patient. Interestingly, no minor resistant subpopulations were found in the other two patients despite the fact that they showed evidence of ongoing viral replication. Finally, the genetic analysis of the env gene shows a reduction in PBMC env viral population diversity after long-term response to the therapy in all the patients analyzed.  (+info)

In vitro anti-human immunodeficiency virus activities of Z- and E-methylenecyclopropane nucleoside analogues and their phosphoro-L-alaninate diesters. (7/1525)

Nucleoside analogues with a Z- or an E-methylenecyclopropane moiety were synthesized and examined for activity against human immunodeficiency virus type 1 (HIV-1) in vitro. The addition of a methyl phenyl phosphoro-L-alaninate moiety to modestly active analogues resulted in potentiation of their anti-HIV-1 activity. Two such compounds, designated QYL-685 (with 2,6-diaminopurine) and QYL-609 (with adenine), were most potent against HIV-1 in vitro, with 50% inhibitory concentrations of 0.034 and 0.0026 microM, respectively, in MT-2 cell-based assays. Both compounds were active against zidovudine-resistant, didanosine-resistant, and multi-dideoxynucleoside-resistant infectious clones in vitro. Further development of these analogues as potential therapies for HIV-1 infection is warranted.  (+info)

Dynamic correlation of apoptosis and immune activation during treatment of HIV infection. (8/1525)

T cells from HIV infected patients undergo spontaneous apoptosis at a faster rate than those from uninfected patients, are abnormally susceptible to activation induced cell death (AICD), and undergo increased apoptosis in response to Fas receptor ligation. These observations have led to the hypothesis CD4 T cell apoptosis may be a mechanism of CD4 T cell depletion and the pathogenesis of AIDS. Successful treatment of HIV infected patients is accompanied by quantitative and qualitative improvements in immune function reflecting at least partial reversibility of the underlying pathogenesis of HIV. In this report we correlate improvements in markers of immune function with a decrease in apoptosis, and changes in its regulation. Therapy with nelfinavir plus saquinavir in combination with two nucleoside analogue inhibitors of reverse transcriptase dramatically reduces plasma viremia and increases CD4 T cell counts. Coincident with these improvements, CD38 and HLA-DR coexpression on both CD4 and CD8 T cells decrease, and CD45RA and CD62L coexpression increase. Furthermore, spontaneous apoptosis decreases in both CD4 and CD8 T cells (CD4 apoptosis 17.4 vs 2.6%, P=0.005; CD8 apoptosis 15.0 vs 1.0%, P<0.001), as does both Fas mediated apoptosis (CD4 apoptosis 19.0 vs 3.5%, P=0.03; CD8 apoptosis 13.7 vs 1.5%, P=0.002) and CD3 induced AICD (CD4 apoptosis 13.7 vs 3.2%, P=0.001; CD8 apoptosis 29 vs 2.2%, P=0.08). Changes in apoptosis are not associated with changes in Fas receptor expression, but are significantly correlated with changes in activation marker profiles. Although this suggests a possible regulatory role for the apoptosis inhibitory protein FLIP, direct assessment did not reveal quantitative differences in FLIP expression between apoptosis resistant PBL's from HIV negative patients, and apoptosis sensitive PBL's from HIV positive patients. These findings support the hypothesis that apoptosis mediates HIV induced CD4 T cell depletion, but indicate the need for further studies into the molecular regulation of HIV induced apoptosis.  (+info)

A nucleoside is a biochemical molecule that consists of a pentose sugar (a type of simple sugar with five carbon atoms) covalently linked to a nitrogenous base. The nitrogenous base can be one of several types, including adenine, guanine, cytosine, thymine, or uracil. Nucleosides are important components of nucleic acids, such as DNA and RNA, which are the genetic materials found in cells. They play a crucial role in various biological processes, including cell division, protein synthesis, and gene expression.

Purine nucleosides are fundamental components of nucleic acids, which are the genetic materials found in all living organisms. A purine nucleoside is composed of a purine base (either adenine or guanine) linked to a sugar molecule, specifically ribose in the case of purine nucleosides.

The purine base and sugar moiety are joined together through a glycosidic bond at the 1' position of the sugar. These nucleosides play crucial roles in various biological processes, including energy transfer, signal transduction, and as precursors for the biosynthesis of DNA and RNA.

In the human body, purine nucleosides can be derived from the breakdown of endogenous nucleic acids or through the dietary intake of nucleoproteins. They are further metabolized to form uric acid, which is eventually excreted in the urine. Elevated levels of uric acid in the body can lead to the formation of uric acid crystals and contribute to the development of gout or kidney stones.

Pyrimidine nucleosides are organic compounds that consist of a pyrimidine base (a heterocyclic aromatic ring containing two nitrogen atoms and four carbon atoms) linked to a sugar molecule, specifically ribose or deoxyribose, via a β-glycosidic bond. The pyrimidine bases found in nucleosides can be cytosine (C), thymine (T), or uracil (U). When the sugar component is ribose, it is called a pyrimidine nucleoside, and when it is linked to deoxyribose, it is referred to as a deoxy-pyrimidine nucleoside. These molecules play crucial roles in various biological processes, particularly in the structure and function of nucleic acids such as DNA and RNA.

Nucleoside transport proteins (NTTs) are membrane-bound proteins responsible for the facilitated diffusion of nucleosides and related deoxynucleosides across the cell membrane. These proteins play a crucial role in the uptake of nucleosides, which serve as precursors for DNA and RNA synthesis, as well as for the salvage of nucleotides in the cell.

There are two main types of NTTs: concentrative (or sodium-dependent) nucleoside transporters (CNTs) and equilibrative (or sodium-independent) nucleoside transporters (ENTs). CNTs mainly facilitate the uptake of nucleosides against a concentration gradient, using the energy derived from the sodium ion gradient. In contrast, ENTs mediate bidirectional transport, allowing for the equalization of intracellular and extracellular nucleoside concentrations.

Nucleoside transport proteins have been identified in various organisms, including humans, and are involved in numerous physiological processes, such as cell proliferation, differentiation, and survival. Dysregulation of NTTs has been implicated in several pathological conditions, including cancer and viral infections, making them potential targets for therapeutic intervention.

Equilibrative Nucleoside Transporter 1 (ENT1), also known as SLC29A1, is a protein that functions as a membrane transport protein. It is responsible for the facilitated diffusion of nucleosides and some related drugs across the cell membrane. The term "equilibrative" refers to the fact that this transporter moves substrates down their concentration gradient, meaning it facilitates the movement of molecules from an area of high concentration to an area of low concentration. ENT1 is widely expressed in various tissues, including the liver, kidney, intestine, and brain, playing a crucial role in nucleoside homeostasis and the cellular uptake of nucleoside-analog drugs used in cancer chemotherapy.

Thioinosine is not a medical term itself, but it is a chemical compound that has been studied in the field of medical research. Thioinosine is an analogue of the nucleoside inosine, where the oxygen atom in the heterocyclic ring is replaced by a sulfur atom.

In the context of medical research, thioinosine has been investigated for its potential immunomodulatory and antiviral properties. It has been studied as an inhibitor of certain enzymes involved in the replication of viruses, such as HIV and hepatitis C virus. However, it is not currently approved for use as a medication in clinical practice.

Purine-nucleoside phosphorylase (PNP) is an enzyme that plays a crucial role in the metabolism of purines, which are essential components of nucleic acids (DNA and RNA). The medical definition of 'Purine-Nucleoside Phosphorylase' refers to the physiological function of this enzyme in the human body.

PNP is responsible for catalyzing the phosphorolytic cleavage of purine nucleosides, such as inosine and guanosine, into their respective purine bases (hypoxanthine and guanine) and ribose-1-phosphate. This reaction is essential for the recycling and salvage of purine bases, allowing the body to conserve energy and resources needed for de novo purine biosynthesis.

In a clinical or medical context, deficiencies in PNP activity can lead to serious consequences, particularly affecting the immune system and the nervous system. A genetic disorder called Purine-Nucleoside Phosphorylase Deficiency (PNP Deficiency) is characterized by significantly reduced or absent PNP enzyme activity, leading to an accumulation of toxic purine nucleosides and deoxypurine nucleosides. This accumulation can cause severe combined immunodeficiency (SCID), neurological impairments, and other complications, making it a critical area of study in medical research.

Guanosine is a nucleoside that consists of a guanine base linked to a ribose sugar molecule through a beta-N9-glycosidic bond. It plays a crucial role in various biological processes, such as serving as a building block for DNA and RNA during replication and transcription. Guanosine triphosphate (GTP) and guanosine diphosphate (GDP) are important energy carriers and signaling molecules involved in intracellular regulation. Additionally, guanosine has been studied for its potential role as a neuroprotective agent and possible contribution to cell-to-cell communication.

Nucleoside-diphosphate kinase (NDK) is an enzyme that plays a crucial role in the regulation of intracellular levels of nucleoside triphosphates and diphosphates. These nucleotides are essential for various cellular processes, including DNA replication, transcription, translation, and energy metabolism.

NDK catalyzes the transfer of a phosphate group from a nucleoside triphosphate (most commonly ATP or GTP) to a nucleoside diphosphate (NDP), converting it into a nucleoside triphosphate (NTP). The reaction can be summarized as follows:

NTP + NDP ↔ NDP + NTP

The enzyme has several isoforms, which are differentially expressed in various tissues and cellular compartments. In humans, there are nine known isoforms of NDK, classified into three subfamilies: NM23-H (NME1), NM23-H2 (NME2), and NME4-8. These isoforms share a conserved catalytic core but differ in their regulatory domains and cellular localization.

NDK has been implicated in several physiological processes, such as cell proliferation, differentiation, and survival. Dysregulation of NDK activity has been associated with various pathological conditions, including cancer, neurodegenerative diseases, and viral infections.

Inosine is not a medical condition but a naturally occurring compound called a nucleoside, which is formed from the combination of hypoxanthine and ribose. It is an intermediate in the metabolic pathways of purine nucleotides, which are essential components of DNA and RNA. Inosine has been studied for its potential therapeutic benefits in various medical conditions, including neurodegenerative disorders, cardiovascular diseases, and cancer. However, more research is needed to fully understand its mechanisms and clinical applications.

Uridine is a nucleoside that consists of a pyrimidine base (uracil) linked to a pentose sugar (ribose). It is a component of RNA, where it pairs with adenine. Uridine can also be found in various foods such as beer, broccoli, yeast, and meat. In the body, uridine can be synthesized from orotate or from the breakdown of RNA. It has several functions, including acting as a building block for RNA, contributing to energy metabolism, and regulating cell growth and differentiation. Uridine is also available as a dietary supplement and has been studied for its potential benefits in various health conditions.

I'm sorry for any confusion, but "Nucleoside Q" is not a recognized or established term in medical or biological nomenclature. Nucleosides are organic molecules consisting of a pentose sugar (ribose or deoxyribose) linked to a nitrogenous base (adenine, guanine, cytosine, thymine, or uracil). There is no "Q" nucleoside in the standard nomenclature.

If you have any questions about specific nucleosides or related compounds, I'd be happy to try and help clarify those for you!

Equilibrative Nucleoside Transporter 2 (ENT2) is a type of protein found in the cell membrane that facilitates the bidirectional transport of nucleosides, which are the building blocks of DNA and RNA, between the intracellular and extracellular spaces. ENT2 is a member of the solute carrier 29 (SLC29) family of transporters and is widely expressed in various tissues, including the brain, liver, kidney, and intestine.

ENT2 plays an essential role in maintaining nucleoside homeostasis by regulating their uptake and efflux across the cell membrane. It has a high affinity for purine nucleosides such as adenosine and guanosine, and to a lesser extent, pyrimidine nucleosides such as uridine and thymidine. The activity of ENT2 is critical in regulating extracellular adenosine levels, which have important implications for various physiological processes, including neurotransmission, inflammation, and cancer.

In addition to its role in nucleoside transport, ENT2 has been implicated in the development of drug resistance in cancer cells. Certain chemotherapeutic agents, such as nucleoside analogs, utilize ENT2 for their uptake into cells. However, overexpression of ENT2 in cancer cells can lead to increased efflux of these drugs, resulting in reduced intracellular concentrations and decreased therapeutic effectiveness. Therefore, ENT2 is an attractive target for the development of novel strategies to overcome drug resistance in cancer therapy.

Nucleoside-triphosphatase (NTPase) is not a medical term per se, but rather a biochemical term. However, it is often used in the context of molecular biology and genetics, which are essential components of medical research and practice. Therefore, I will provide a definition related to these fields.

Nucleoside-triphosphatase (NTPase) refers to an enzyme that catalyzes the hydrolysis of nucleoside triphosphates (NTPs) into nucleoside diphosphates (NDPs) and inorganic phosphate (Pi). NTPs, such as adenosine triphosphate (ATP), guanosine triphosphate (GTP), cytidine triphosphate (CTP), and uridine triphosphate (UTP), are crucial for energy transfer in cells.

In the context of molecular biology, NTPases play essential roles in various cellular processes, including DNA replication, transcription, translation, and degradation. For example, DNA polymerase, an enzyme involved in DNA replication, is a type of NTPase that utilizes dNTPs (deoxynucleoside triphosphates) to synthesize new DNA strands. Similarly, RNA polymerase, which catalyzes the transcription of DNA into RNA, uses NTPs as substrates and has NTPase activity.

In summary, Nucleoside-triphosphatase (NTPase) is an enzyme that hydrolyzes nucleoside triphosphates (NTPs), releasing energy and playing a critical role in various cellular processes, including DNA replication, transcription, translation, and degradation.

Cytidine is a nucleoside, which consists of the sugar ribose and the nitrogenous base cytosine. It is an important component of RNA (ribonucleic acid), where it pairs with guanosine via hydrogen bonding to form a base pair. Cytidine can also be found in some DNA (deoxyribonucleic acid) sequences, particularly in viral DNA and in mitochondrial DNA.

Cytidine can be phosphorylated to form cytidine monophosphate (CMP), which is a nucleotide that plays a role in various biochemical reactions in the body. CMP can be further phosphorylated to form cytidine diphosphate (CDP) and cytidine triphosphate (CTP), which are involved in the synthesis of lipids, glycogen, and other molecules.

Cytidine is also available as a dietary supplement and has been studied for its potential benefits in treating various health conditions, such as liver disease and cancer. However, more research is needed to confirm these potential benefits and establish safe and effective dosages.

Ribonucleosides are organic compounds that consist of a nucleoside bound to a ribose sugar. Nucleosides are formed when a nitrogenous base (such as adenine, guanine, uracil, cytosine, or thymine) is attached to a sugar molecule (either ribose or deoxyribose) via a beta-glycosidic bond. In the case of ribonucleosides, the sugar component is D-ribose. Ribonucleosides play important roles in various biological processes, particularly in the storage, transfer, and expression of genetic information within cells. When ribonucleosides are phosphorylated, they become the building blocks of RNA (ribonucleic acid), a crucial biomolecule involved in protein synthesis and other cellular functions. Examples of ribonucleosides include adenosine, guanosine, uridine, cytidine, and inosine.

Nucleotides are the basic structural units of nucleic acids, such as DNA and RNA. They consist of a nitrogenous base (adenine, guanine, cytosine, thymine or uracil), a pentose sugar (ribose in RNA and deoxyribose in DNA) and one to three phosphate groups. Nucleotides are linked together by phosphodiester bonds between the sugar of one nucleotide and the phosphate group of another, forming long chains known as polynucleotides. The sequence of these nucleotides determines the genetic information carried in DNA and RNA, which is essential for the functioning, reproduction and survival of all living organisms.

Adenosine is a purine nucleoside that is composed of a sugar (ribose) and the base adenine. It plays several important roles in the body, including serving as a precursor for the synthesis of other molecules such as ATP, NAD+, and RNA.

In the medical context, adenosine is perhaps best known for its use as a pharmaceutical agent to treat certain cardiac arrhythmias. When administered intravenously, it can help restore normal sinus rhythm in patients with paroxysmal supraventricular tachycardia (PSVT) by slowing conduction through the atrioventricular node and interrupting the reentry circuit responsible for the arrhythmia.

Adenosine can also be used as a diagnostic tool to help differentiate between narrow-complex tachycardias of supraventricular origin and those that originate from below the ventricles (such as ventricular tachycardia). This is because adenosine will typically terminate PSVT but not affect the rhythm of VT.

It's worth noting that adenosine has a very short half-life, lasting only a few seconds in the bloodstream. This means that its effects are rapidly reversible and generally well-tolerated, although some patients may experience transient symptoms such as flushing, chest pain, or shortness of breath.

Formycins are a group of antibiotics that are derived from certain strains of Streptomyces bacteria. They include formycin B (also known as pyrazofurin), which is an antiviral and antimetabolite drug that works by interfering with the production of genetic material in cells. Formycins are not widely used in clinical medicine due to their potential toxicity and the availability of other effective antibiotics and antiviral drugs.

Pentosyltransferases are a group of enzymes that catalyze the transfer of a pentose (a sugar containing five carbon atoms) molecule from one compound to another. These enzymes play important roles in various biochemical pathways, including the biosynthesis of nucleotides, glycoproteins, and other complex carbohydrates.

One example of a pentosyltransferase is the enzyme that catalyzes the addition of a ribose sugar to form a glycosidic bond with a purine or pyrimidine base during the biosynthesis of nucleotides, which are the building blocks of DNA and RNA.

Another example is the enzyme that adds xylose residues to proteins during the formation of glycoproteins, which are proteins that contain covalently attached carbohydrate chains. These enzymes are essential for many biological processes and have been implicated in various diseases, including cancer and neurodegenerative disorders.

NM23 nucleoside diphosphate kinases are a group of proteins that play a role in regulating cellular functions, including signal transduction, cell proliferation, and differentiation. They are named after the NM23 gene that encodes them, which was initially identified as a potential metastasis suppressor.

NM23 nucleoside diphosphate kinases have the ability to transfer phosphate groups between nucleoside diphosphates (NDPs) and nucleoside triphosphates (NTPs), thereby maintaining the balance of these molecules in cells. This enzymatic activity is important for various cellular processes, such as DNA replication, repair, and transcription.

There are several isoforms of NM23 nucleoside diphosphate kinases, including NM23-H1, NM23-H2, and NM23-H4, which differ in their tissue distribution and functions. While the role of NM23 as a metastasis suppressor has been debated, recent studies suggest that it may be involved in regulating cell motility and invasion through its effects on actin dynamics and microtubule organization.

Overall, NM23 nucleoside diphosphate kinases are important regulators of cellular homeostasis and have been implicated in various physiological and pathological processes, including cancer metastasis, inflammation, and neurodegenerative diseases.

Reverse Transcriptase Inhibitors (RTIs) are a class of antiretroviral drugs that are primarily used in the treatment and management of HIV (Human Immunodeficiency Virus) infection. They work by inhibiting the reverse transcriptase enzyme, which is essential for the replication of HIV.

HIV is a retrovirus, meaning it has an RNA genome and uses a unique enzyme called reverse transcriptase to convert its RNA into DNA. This process is necessary for the virus to integrate into the host cell's genome and replicate. Reverse Transcriptase Inhibitors interfere with this process by binding to the reverse transcriptase enzyme, preventing it from converting the viral RNA into DNA.

RTIs can be further divided into two categories: nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs). NRTIs are analogs of the building blocks of DNA, which get incorporated into the growing DNA chain during replication, causing termination of the chain. NNRTIs bind directly to the reverse transcriptase enzyme, causing a conformational change that prevents it from functioning.

By inhibiting the reverse transcriptase enzyme, RTIs can prevent the virus from replicating and reduce the viral load in an infected individual, thereby slowing down the progression of HIV infection and AIDS (Acquired Immunodeficiency Syndrome).

Equilibrative nucleoside transport proteins (ENTs) are a type of membrane transporter that regulate the bidirectional movement of nucleosides across the cell membrane. They facilitate the diffusion of nucleosides down their concentration gradient, hence the term "equilibrative." These transport proteins play a crucial role in maintaining intracellular nucleoside concentrations and ensuring proper nucleotide synthesis for various cellular processes, including DNA replication, repair, and gene expression. There are two major families of ENTs: the human equilibrative nucleoside transporters (hENTs) and the concentrative nucleoside transporters (CNTs). The hENT family includes four members (hENT1-4), while the CNT family consists of three members (CNT1-3). These transport proteins have been identified as potential targets for cancer therapy, as inhibiting their function can selectively sensitize tumor cells to nucleoside analog-based chemotherapies.

Deoxyribonucleosides are chemical compounds that constitute the basic building blocks of DNA, one of the two nucleic acids found in cells. They consist of a sugar molecule called deoxyribose, a nitrogenous base (either adenine, guanine, cytosine, or thymine), and a phosphate group.

The nitrogenous base is attached to the 1' carbon atom of the deoxyribose sugar, forming a glycosidic bond. The phosphate group is linked to the 5' carbon atom of the deoxyribose sugar through an ester linkage, creating a phosphodiester bond with another deoxyribonucleoside.

When multiple deoxyribonucleosides are joined together through their phosphate groups, they form a polynucleotide chain, which is the backbone of DNA. The sequence of nitrogenous bases along this chain encodes genetic information that determines the characteristics and functions of living organisms.

Deoxyribonucleosides play a crucial role in various biological processes, including DNA replication, repair, and transcription. They are also used as therapeutic agents for the treatment of certain genetic disorders and cancer.

Deoxyadenosine is a chemical compound that is a component of DNA, one of the nucleic acids that make up the genetic material of living organisms. Specifically, deoxyadenosine is a nucleoside, which is a molecule consisting of a sugar (in this case, deoxyribose) bonded to a nitrogenous base (in this case, adenine).

Deoxyribonucleosides like deoxyadenosine are the building blocks of DNA, along with phosphate groups. In DNA, deoxyadenosine pairs with thymidine via hydrogen bonds to form one of the four rungs in the twisted ladder structure of the double helix.

It is important to note that there is a similar compound called adenosine, which contains an extra oxygen atom on the sugar molecule (making it a ribonucleoside) and is a component of RNA, another nucleic acid involved in protein synthesis and other cellular processes.

Adenine is a purine nucleotide base that is a fundamental component of DNA and RNA, the genetic material of living organisms. In DNA, adenine pairs with thymine via double hydrogen bonds, while in RNA, it pairs with uracil. Adenine is essential for the structure and function of nucleic acids, as well as for energy transfer reactions in cells through its role in the formation of adenosine triphosphate (ATP), the primary energy currency of the cell.

Dilazep is a medication that belongs to a class of drugs called calcium channel blockers. It is primarily used in the management of angina pectoris, which is chest pain caused by reduced blood flow to the heart muscle. Dilazep works by relaxing and widening the blood vessels that supply the heart, thereby improving blood flow and reducing the workload on the heart.

The chemical name for Dilazep is (E)-1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic acid diamide. It is not commonly used in many countries, and other calcium channel blockers such as verapamil, nifedipine, and amlodipine are more frequently prescribed for the treatment of angina pectoris.

It's important to note that like all medications, Dilazep can have side effects, including headache, dizziness, and swelling in the extremities. It should be used under the close supervision of a healthcare provider, who can monitor its effectiveness and potential side effects.

In the context of medicine and pharmacology, "kinetics" refers to the study of how a drug moves throughout the body, including its absorption, distribution, metabolism, and excretion (often abbreviated as ADME). This field is called "pharmacokinetics."

1. Absorption: This is the process of a drug moving from its site of administration into the bloodstream. Factors such as the route of administration (e.g., oral, intravenous, etc.), formulation, and individual physiological differences can affect absorption.

2. Distribution: Once a drug is in the bloodstream, it gets distributed throughout the body to various tissues and organs. This process is influenced by factors like blood flow, protein binding, and lipid solubility of the drug.

3. Metabolism: Drugs are often chemically modified in the body, typically in the liver, through processes known as metabolism. These changes can lead to the formation of active or inactive metabolites, which may then be further distributed, excreted, or undergo additional metabolic transformations.

4. Excretion: This is the process by which drugs and their metabolites are eliminated from the body, primarily through the kidneys (urine) and the liver (bile).

Understanding the kinetics of a drug is crucial for determining its optimal dosing regimen, potential interactions with other medications or foods, and any necessary adjustments for special populations like pediatric or geriatric patients, or those with impaired renal or hepatic function.

Dideoxynucleosides are a type of modified nucleoside used in the treatment of certain viral infections, such as HIV and HBV. These compounds lack a hydroxyl group (-OH) at the 3'-carbon position of the sugar moiety, which prevents them from being further metabolized into DNA.

When incorporated into a growing DNA chain during reverse transcription, dideoxynucleosides act as chain terminators, inhibiting viral replication. Common examples of dideoxynucleosides include zidovudine (AZT), didanosine (ddI), stavudine (d4T), and lamivudine (3TC). These drugs are often used in combination with other antiretroviral agents to form highly active antiretroviral therapy (HAART) regimens for the treatment of HIV infection.

Tubercidin is not a medical term itself, but it is a type of antibiotic that belongs to the class of compounds known as nucleoside antibiotics. Specifically, tubercidin is a naturally occurring adenine analogue that is produced by several species of Streptomyces bacteria.

Tubercidin has been found to have antimicrobial and antitumor activities. It works by inhibiting the enzyme adenosine deaminase, which plays a crucial role in the metabolism of nucleotides in cells. By inhibiting this enzyme, tubercidin can interfere with DNA and RNA synthesis, leading to cell death.

While tubercidin has shown promise as an anticancer agent in preclinical studies, its clinical use is limited due to its toxicity and potential for causing mutations in normal cells. Therefore, it is primarily used for research purposes to study the mechanisms of nucleotide metabolism and the effects of nucleoside analogues on cell growth and differentiation.

Zidovudine is defined as an antiretroviral medication used to prevent and treat HIV/AIDS. It is a reverse transcriptase inhibitor (NRTI) that works by blocking the action of the reverse transcriptase enzyme, thereby preventing the virus from replicating in human cells.

Zidovudine is often used in combination with other antiretroviral drugs as part of highly active antiretroviral therapy (HAART) to manage HIV infection and reduce the risk of transmission. It is also used to prevent mother-to-child transmission of HIV during pregnancy, labor, delivery, and breastfeeding.

The most common side effects of zidovudine include headache, nausea, vomiting, and muscle pain. Prolonged use of zidovudine can lead to serious side effects such as anemia, neutropenia, and lactic acidosis. Therefore, regular monitoring of blood counts and liver function tests is necessary during treatment with this medication.

Arabinonucleosides are glycosylamines derived from arabinose, a monosaccharide (simple sugar) that is a component of certain complex carbohydrates. In an arabinonucleoside, the arabinose molecule is linked to a nitrogenous base, such as adenine, guanine, cytosine, uracil, or thymine, through a glycosidic bond. These types of compounds are not typically found in nature but can be synthesized in the laboratory for research purposes. They may have potential applications in the development of new drugs, particularly in the area of antiviral and anticancer therapy.

Antiviral agents are a class of medications that are designed to treat infections caused by viruses. Unlike antibiotics, which target bacteria, antiviral agents interfere with the replication and infection mechanisms of viruses, either by inhibiting their ability to replicate or by modulating the host's immune response to the virus.

Antiviral agents are used to treat a variety of viral infections, including influenza, herpes simplex virus (HSV) infections, human immunodeficiency virus (HIV) infection, hepatitis B and C, and respiratory syncytial virus (RSV) infections.

These medications can be administered orally, intravenously, or topically, depending on the type of viral infection being treated. Some antiviral agents are also used for prophylaxis, or prevention, of certain viral infections.

It is important to note that antiviral agents are not effective against all types of viruses and may have significant side effects. Therefore, it is essential to consult with a healthcare professional before starting any antiviral therapy.

Purines are heterocyclic aromatic organic compounds that consist of a pyrimidine ring fused to an imidazole ring. They are fundamental components of nucleotides, which are the building blocks of DNA and RNA. In the body, purines can be synthesized endogenously or obtained through dietary sources such as meat, seafood, and certain vegetables.

Once purines are metabolized, they are broken down into uric acid, which is excreted by the kidneys. Elevated levels of uric acid in the body can lead to the formation of uric acid crystals, resulting in conditions such as gout or kidney stones. Therefore, maintaining a balanced intake of purine-rich foods and ensuring proper kidney function are essential for overall health.

Deoxycytidine kinase (dCK) is an enzyme that plays a crucial role in the phosphorylation of deoxycytidine and its analogs, which are important components in the intracellular metabolism of DNA precursors. The enzyme catalyzes the transfer of a phosphate group from adenosine triphosphate (ATP) to the hydroxyl group at the 5' carbon atom of deoxycytidine, forming deoxycytidine monophosphate (dCMP).

Deoxycytidine kinase is a key enzyme in the salvage pathway of pyrimidine nucleotide synthesis and is also involved in the activation of many antiviral and anticancer drugs that are analogs of deoxycytidine. The activity of dCK is tightly regulated, and its expression levels can vary depending on the cell type and physiological conditions.

In addition to its role in nucleotide metabolism, dCK has been implicated in various biological processes, including DNA damage response, cell cycle regulation, and apoptosis. Abnormalities in dCK activity or expression have been associated with several human diseases, including cancer and viral infections. Therefore, modulation of dCK activity has emerged as a potential therapeutic strategy for the treatment of these conditions.

Organophosphonates are a class of organic compounds characterized by the presence of a carbon-phosphorus bond. They contain a phosphonic acid group, which consists of a phosphorus atom bonded to four oxygen or nitrogen atoms, with one of those bonds being replaced by a carbon atom.

In a medical context, organophosphonates are commonly used as radiopharmaceuticals in diagnostic nuclear medicine procedures, such as bone scans. These compounds have the ability to bind to hydroxyapatite, the mineral component of bones, and can be labeled with radioactive isotopes for imaging purposes. They may also be used in therapeutic settings, including as treatments for conditions such as tumor-induced hypercalcemia and Paget's disease of bone.

It is important to note that organophosphonates are distinct from organophosphates, another class of compounds that contain a phosphorus atom bonded to three oxygen or sulfur atoms and one carbon atom. Organophosphates have been widely used as pesticides and chemical warfare agents, and can pose significant health risks due to their toxicity.

Pyrimidine phosphorylases are a group of enzymes that play a crucial role in the metabolism of pyrimidines, which are nitrogenous bases found in nucleic acids such as DNA and RNA. These enzymes catalyze the reversible phosphorolytic cleavage of pyrimidine nucleosides into ribose-1-phosphate and a free base.

There are two main types of pyrimidine phosphorylases: cytosine phosphorylase (CP) and thymidine phosphorylase (TP). CP catalyzes the conversion of cytosine to uracil, while TP converts thymidine to thymine. These enzymes are important in maintaining the balance of pyrimidines in cells and are also involved in the salvage pathway for nucleotide synthesis.

Deficiencies or mutations in these enzymes can lead to various genetic disorders, including neurological and developmental abnormalities. Additionally, TP has been studied as a potential target for cancer therapy due to its role in angiogenesis and tumor growth.

Thymidine is a pyrimidine nucleoside that consists of a thymine base linked to a deoxyribose sugar by a β-N1-glycosidic bond. It plays a crucial role in DNA replication and repair processes as one of the four nucleosides in DNA, along with adenosine, guanosine, and cytidine. Thymidine is also used in research and clinical settings for various purposes, such as studying DNA synthesis or as a component of antiviral and anticancer therapies.

Thionucleosides are a type of modified nucleoside where the oxygen atom in the sugar component (ribose or deoxyribose) is replaced by a sulfur atom. This modification can occur naturally or be introduced synthetically. The resulting compounds have been studied for their potential biological activity, including antiviral and anticancer properties. However, they are not typically used as a standard medical treatment at this time.

Ribonucleotides are organic compounds that consist of a ribose sugar, a phosphate group, and a nitrogenous base. They are the building blocks of RNA (ribonucleic acid), one of the essential molecules in all living organisms. The nitrogenous bases found in ribonucleotides include adenine, uracil, guanine, and cytosine. These molecules play crucial roles in various biological processes, such as protein synthesis, gene expression, and cellular energy production. Ribonucleotides can also be involved in cell signaling pathways and serve as important cofactors for enzymatic reactions.

Deoxyuridine is a chemical compound that is a component of DNA. It is a nucleoside, which means it consists of a sugar (deoxyribose) linked to a nitrogenous base (uracil). In the case of deoxyuridine, the uracil is not methylated, which differentiates it from thymidine.

Deoxyuridine can be converted into deoxyuridine monophosphate (dUMP) by the enzyme thymidine kinase. The dUMP can then be converted into deoxythymidine triphosphate (dTTP), which is a building block of DNA, through a series of reactions involving other enzymes.

Deoxyuridine has been used in research and medicine as a marker for DNA synthesis and repair. It can also be used to inhibit the growth of certain types of cells, such as cancer cells, by disrupting their DNA synthesis.

Zalcitabine (also known as ddC) is an antiretroviral medication used in the treatment of HIV infection. It belongs to a class of drugs called nucleoside reverse transcriptase inhibitors (NRTIs). Zalcitabine works by interfering with the replication of the virus, thus slowing down the progression of the disease.

The medical definition of Zalcitabine is: "A synthetic pyrimidine nucleoside analogue used as an antiretroviral agent in the treatment of HIV infection. It is converted to its active 5'-triphosphate form, which inhibits the activity of reverse transcriptase and results in chain termination."

It is important to note that Zalcitabine has been largely replaced by other antiretroviral drugs due to its significant side effects and the development of better treatment options.

Uridine phosphorylase is an enzyme that plays a role in the metabolism of nucleosides, specifically uridine. The medical definition of 'uridine phosphorylase' is:

An enzyme (EC 2.4.2.3) involved in the reversible phosphorolysis of uridine to uracil and ribose-1-phosphate. This enzyme also catalyzes the phosphorolytic cleavage of other pyrimidine nucleosides, such as cytidine and thymidine, into their respective bases and ribose-1-phosphate. Uridine phosphorylase has a role in the salvage pathway of pyrimidine nucleotide biosynthesis and is found in various tissues, including the liver, intestines, and blood cells. Deficiency or dysfunction of uridine phosphorylase can lead to impaired nucleotide metabolism and may be associated with certain medical conditions, such as hereditary orotic aciduria.

Anti-HIV agents are a class of medications specifically designed to treat HIV (Human Immunodeficiency Virus) infection. These drugs work by interfering with various stages of the HIV replication cycle, preventing the virus from infecting and killing CD4+ T cells, which are crucial for maintaining a healthy immune system.

There are several classes of anti-HIV agents, including:

1. Nucleoside/Nucleotide Reverse Transcriptase Inhibitors (NRTIs): These drugs act as faulty building blocks that the virus incorporates into its genetic material, causing the replication process to halt. Examples include zidovudine (AZT), lamivudine (3TC), and tenofovir.
2. Non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs): These medications bind directly to the reverse transcriptase enzyme, altering its shape and preventing it from functioning properly. Examples include efavirenz, nevirapine, and rilpivirine.
3. Protease Inhibitors (PIs): These drugs target the protease enzyme, which is responsible for cleaving viral polyproteins into functional components. By inhibiting this enzyme, PIs prevent the formation of mature, infectious virus particles. Examples include atazanavir, darunavir, and lopinavir.
4. Integrase Strand Transfer Inhibitors (INSTIs): These medications block the integrase enzyme, which is responsible for inserting the viral genetic material into the host cell's DNA. By inhibiting this step, INSTIs prevent the virus from establishing a permanent infection within the host cell. Examples include raltegravir, dolutegravir, and bictegravir.
5. Fusion/Entry Inhibitors: These drugs target different steps of the viral entry process, preventing HIV from infecting CD4+ T cells. Examples include enfuvirtide (T-20), maraviroc, and ibalizumab.
6. Post-Attachment Inhibitors: This class of medications prevents the virus from attaching to the host cell's receptors, thereby inhibiting infection. Currently, there is only one approved post-attachment inhibitor, fostemsavir.

Combination therapy using multiple classes of antiretroviral drugs has been shown to effectively suppress viral replication and improve clinical outcomes in people living with HIV. Regular adherence to the prescribed treatment regimen is crucial for maintaining an undetectable viral load and reducing the risk of transmission.

Dipyridamole is a medication that belongs to a class of drugs called antiplatelet agents. It works by preventing platelets in your blood from sticking together to form clots. Dipyridamole is often used in combination with aspirin to prevent stroke and other complications in people who have had a heart valve replacement or a type of irregular heartbeat called atrial fibrillation.

Dipyridamole can also be used as a stress agent in myocardial perfusion imaging studies, which are tests used to evaluate blood flow to the heart. When used for this purpose, dipyridamole is given intravenously and works by dilating the blood vessels in the heart, allowing more blood to flow through them and making it easier to detect areas of reduced blood flow.

The most common side effects of dipyridamole include headache, dizziness, and gastrointestinal symptoms such as diarrhea, nausea, and vomiting. In rare cases, dipyridamole can cause more serious side effects, such as allergic reactions, abnormal heart rhythms, or low blood pressure. It is important to take dipyridamole exactly as directed by your healthcare provider and to report any unusual symptoms or side effects promptly.

HIV Reverse Transcriptase is an enzyme that is encoded by the HIV-1 and HIV-2 viruses. It plays a crucial role in the replication cycle of the human immunodeficiency virus (HIV), which causes AIDS.

Reverse transcriptase is responsible for transcribing the viral RNA genome into DNA, a process known as reverse transcription. This allows the viral genetic material to integrate into the host cell's DNA and replicate along with it, leading to the production of new virus particles.

The enzyme has three distinct activities: a polymerase activity that synthesizes DNA using RNA as a template, an RNase H activity that degrades the RNA template during reverse transcription, and a DNA-dependent DNA polymerase activity that synthesizes DNA using a DNA template.

Reverse transcriptase inhibitors are a class of antiretroviral drugs used to treat HIV infection. They work by binding to and inhibiting the activity of the reverse transcriptase enzyme, thereby preventing the virus from replicating.

Thymine nucleotides are biochemical components that play a crucial role in the structure and function of DNA (deoxyribonucleic acid), which is the genetic material present in living organisms. A thymine nucleotide consists of three parts: a sugar molecule called deoxyribose, a phosphate group, and a nitrogenous base called thymine.

Thymine is one of the four nucleobases in DNA, along with adenine, guanine, and cytosine. It specifically pairs with adenine through hydrogen bonding, forming a base pair that is essential for maintaining the structure and stability of the double helix. Thymine nucleotides are linked together by phosphodiester bonds between the sugar molecules of adjacent nucleotides, creating a long, linear polymer known as a DNA strand.

In summary, thymine nucleotides are building blocks of DNA that consist of deoxyribose, a phosphate group, and the nitrogenous base thymine, which pairs with adenine in the double helix structure.

Acid anhydride hydrolases are a class of enzymes that catalyze the hydrolysis (breakdown) of acid anhydrides, which are chemical compounds formed by the reaction between two carboxylic acids. This reaction results in the formation of a molecule of water and the release of a new carboxylic acid.

Acid anhydride hydrolases play important roles in various biological processes, including the metabolism of lipids, carbohydrates, and amino acids. They are also involved in the regulation of intracellular pH and the detoxification of xenobiotics (foreign substances).

Examples of acid anhydride hydrolases include esterases, lipases, and phosphatases. These enzymes have different substrate specificities and catalytic mechanisms, but they all share the ability to hydrolyze acid anhydrides.

The term "acid anhydride hydrolase" is often used interchangeably with "esterase," although not all esterases are capable of hydrolyzing acid anhydrides.

Substrate specificity in the context of medical biochemistry and enzymology refers to the ability of an enzyme to selectively bind and catalyze a chemical reaction with a particular substrate (or a group of similar substrates) while discriminating against other molecules that are not substrates. This specificity arises from the three-dimensional structure of the enzyme, which has evolved to match the shape, charge distribution, and functional groups of its physiological substrate(s).

Substrate specificity is a fundamental property of enzymes that enables them to carry out highly selective chemical transformations in the complex cellular environment. The active site of an enzyme, where the catalysis takes place, has a unique conformation that complements the shape and charge distribution of its substrate(s). This ensures efficient recognition, binding, and conversion of the substrate into the desired product while minimizing unwanted side reactions with other molecules.

Substrate specificity can be categorized as:

1. Absolute specificity: An enzyme that can only act on a single substrate or a very narrow group of structurally related substrates, showing no activity towards any other molecule.
2. Group specificity: An enzyme that prefers to act on a particular functional group or class of compounds but can still accommodate minor structural variations within the substrate.
3. Broad or promiscuous specificity: An enzyme that can act on a wide range of structurally diverse substrates, albeit with varying catalytic efficiencies.

Understanding substrate specificity is crucial for elucidating enzymatic mechanisms, designing drugs that target specific enzymes or pathways, and developing biotechnological applications that rely on the controlled manipulation of enzyme activities.

Adenosine Triphosphate (ATP) is a high-energy molecule that stores and transports energy within cells. It is the main source of energy for most cellular processes, including muscle contraction, nerve impulse transmission, and protein synthesis. ATP is composed of a base (adenine), a sugar (ribose), and three phosphate groups. The bonds between these phosphate groups contain a significant amount of energy, which can be released when the bond between the second and third phosphate group is broken, resulting in the formation of adenosine diphosphate (ADP) and inorganic phosphate. This process is known as hydrolysis and can be catalyzed by various enzymes to drive a wide range of cellular functions. ATP can also be regenerated from ADP through various metabolic pathways, such as oxidative phosphorylation or substrate-level phosphorylation, allowing for the continuous supply of energy to cells.

Dideoxynucleotides are analogs of nucleotides, which are the building blocks of DNA and RNA. In a nucleotide, there is a sugar molecule (deoxyribose in DNA and ribose in RNA) attached to a phosphate group and one of four nitrogenous bases (adenine, guanine, cytosine, or thymine in DNA; adenine, guanine, cytosine, or uracil in RNA).

In a dideoxynucleotide, there are two fewer oxygen molecules on the sugar component. Specifically, instead of having a hydroxyl group (-OH) at both the 2' and 3' carbons of the sugar, a dideoxynucleotide has a hydrogen atom (-H) at the 3' carbon and a hydroxyl or another group at the 2' carbon.

Dideoxynucleotides are used in scientific research and medical diagnostics, most notably in the Sanger method of DNA sequencing. In this process, DNA polymerase adds nucleotides to a single-stranded DNA template during replication. When a dideoxynucleotide is incorporated into the growing DNA chain, it acts as a terminator because there is no 3' hydroxyl group for the next nucleotide to be added. By running multiple reactions with different dideoxynucleotides and comparing the lengths of the resulting DNA fragments, researchers can determine the sequence of the template DNA.

Dideoxynucleotides are also used as antiretroviral drugs in the treatment of HIV infection. They inhibit the reverse transcriptase enzyme that HIV uses to convert its RNA genome into DNA, thus preventing the virus from replicating. Examples of dideoxynucleoside analog reverse transcriptase inhibitors (ddNRTIs) include zidovudine (AZT), didanosine (ddI), stavudine (d4T), and lamivudine (3TC).

Nucleoside deaminases are a group of enzymes that catalyze the removal of an amino group (-NH2) from nucleosides, converting them to nucleosides with a modified base. This modification process is called deamination. Specifically, these enzymes convert cytidine and adenosine to uridine and inosine, respectively. Nucleoside deaminases play crucial roles in various biological processes, including the regulation of gene expression, immune response, and nucleic acid metabolism. Some nucleoside deaminases are also involved in the development of certain diseases and are considered as targets for drug design and discovery.

Hypoxanthine is a purine derivative and an intermediate in the metabolic pathways of nucleotide degradation, specifically adenosine to uric acid in humans. It is formed from the oxidation of xanthine by the enzyme xanthine oxidase. In the body, hypoxanthine is converted to xanthine and then to uric acid, which is excreted in the urine. Increased levels of hypoxanthine in the body can be indicative of various pathological conditions, including tissue hypoxia, ischemia, and necrosis.

Stavudine is an antiviral medication used to treat HIV (human immunodeficiency virus) infections. It works by blocking the action of reverse transcriptase, an enzyme that the virus needs to multiply. By preventing the multiplication of the virus, Stavudine helps reduce the amount of HIV in the body and slows down the progression of the disease.

Stavudine is often prescribed in combination with other antiretroviral drugs as part of a highly active antiretroviral therapy (HAART) regimen. It is available in oral form, typically taken twice daily, and is usually prescribed at a dose of 40 milligrams per dose for adults.

It's important to note that Stavudine can cause serious side effects, including peripheral neuropathy (nerve damage that causes pain, numbness, or tingling in the hands and feet), pancreatitis (inflammation of the pancreas), and lipoatrophy (loss of fat tissue under the skin). As a result, it is generally only prescribed when other antiretroviral drugs are not effective or tolerated.

If you have any questions about Stavudine or your HIV treatment regimen, be sure to talk with your healthcare provider.

Guanine is not a medical term per se, but it is a biological molecule that plays a crucial role in the body. Guanine is one of the four nucleobases found in the nucleic acids DNA and RNA, along with adenine, cytosine, and thymine (in DNA) or uracil (in RNA). Specifically, guanine pairs with cytosine via hydrogen bonds to form a base pair.

Guanine is a purine derivative, which means it has a double-ring structure. It is formed through the synthesis of simpler molecules in the body and is an essential component of genetic material. Guanine's chemical formula is C5H5N5O.

While guanine itself is not a medical term, abnormalities or mutations in genes that contain guanine nucleotides can lead to various medical conditions, including genetic disorders and cancer.

Biological transport refers to the movement of molecules, ions, or solutes across biological membranes or through cells in living organisms. This process is essential for maintaining homeostasis, regulating cellular functions, and enabling communication between cells. There are two main types of biological transport: passive transport and active transport.

Passive transport does not require the input of energy and includes:

1. Diffusion: The random movement of molecules from an area of high concentration to an area of low concentration until equilibrium is reached.
2. Osmosis: The diffusion of solvent molecules (usually water) across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration.
3. Facilitated diffusion: The assisted passage of polar or charged substances through protein channels or carriers in the cell membrane, which increases the rate of diffusion without consuming energy.

Active transport requires the input of energy (in the form of ATP) and includes:

1. Primary active transport: The direct use of ATP to move molecules against their concentration gradient, often driven by specific transport proteins called pumps.
2. Secondary active transport: The coupling of the movement of one substance down its electrochemical gradient with the uphill transport of another substance, mediated by a shared transport protein. This process is also known as co-transport or counter-transport.

Deoxyguanosine is a chemical compound that is a component of DNA (deoxyribonucleic acid), one of the nucleic acids. It is a nucleoside, which is a molecule consisting of a sugar (in this case, deoxyribose) and a nitrogenous base (in this case, guanine). Deoxyguanosine plays a crucial role in the structure and function of DNA, as it pairs with deoxycytidine through hydrogen bonding to form a rung in the DNA double helix. It is involved in the storage and transmission of genetic information.

Molecular sequence data refers to the specific arrangement of molecules, most commonly nucleotides in DNA or RNA, or amino acids in proteins, that make up a biological macromolecule. This data is generated through laboratory techniques such as sequencing, and provides information about the exact order of the constituent molecules. This data is crucial in various fields of biology, including genetics, evolution, and molecular biology, allowing for comparisons between different organisms, identification of genetic variations, and studies of gene function and regulation.

Thiouridine is not a medical term per se, but it is a term used in biochemistry and genetics. Thiouridine is a modified nucleoside that contains a sulfur atom, and it is found in the RNA (ribonucleic acid) of certain organisms, including yeast and mammals.

Thiouridine can be formed through the modification of uridine, one of the four basic building blocks of RNA, by the addition of a sulfur atom from a donor molecule such as cysteine or a derivative thereof. This modification can affect the stability, structure, and function of RNA molecules, including transfer RNAs (tRNAs) and ribosomal RNAs (rRNAs).

In medicine, thiouridine is not used as a therapeutic agent or diagnostic tool, but it may be studied in the context of genetic research or molecular biology.

Purine nucleotides are fundamental units of life that play crucial roles in various biological processes. A purine nucleotide is a type of nucleotide, which is the basic building block of nucleic acids such as DNA and RNA. Nucleotides consist of a nitrogenous base, a pentose sugar, and at least one phosphate group.

In purine nucleotides, the nitrogenous bases are either adenine (A) or guanine (G). These bases are attached to a five-carbon sugar called ribose in the case of RNA or deoxyribose for DNA. The sugar and base together form the nucleoside, while the addition of one or more phosphate groups creates the nucleotide.

Purine nucleotides have several vital functions within cells:

1. Energy currency: Adenosine triphosphate (ATP) is a purine nucleotide that serves as the primary energy currency in cells, storing and transferring chemical energy for various cellular processes.
2. Genetic material: Both DNA and RNA contain purine nucleotides as essential components of their structures. Adenine pairs with thymine (in DNA) or uracil (in RNA), while guanine pairs with cytosine.
3. Signaling molecules: Purine nucleotides, such as adenosine monophosphate (AMP) and cyclic adenosine monophosphate (cAMP), act as intracellular signaling molecules that regulate various cellular functions, including metabolism, gene expression, and cell growth.
4. Coenzymes: Purine nucleotides can also function as coenzymes, assisting enzymes in catalyzing biochemical reactions. For example, nicotinamide adenine dinucleotide (NAD+) is a purine nucleotide that plays a critical role in redox reactions and energy metabolism.

In summary, purine nucleotides are essential biological molecules involved in various cellular functions, including energy transfer, genetic material formation, intracellular signaling, and enzyme cofactor activity.

Membrane transport proteins are specialized biological molecules, specifically integral membrane proteins, that facilitate the movement of various substances across the lipid bilayer of cell membranes. They are responsible for the selective and regulated transport of ions, sugars, amino acids, nucleotides, and other molecules into and out of cells, as well as within different cellular compartments. These proteins can be categorized into two main types: channels and carriers (or pumps). Channels provide a passive transport mechanism, allowing ions or small molecules to move down their electrochemical gradient, while carriers actively transport substances against their concentration gradient, requiring energy usually in the form of ATP. Membrane transport proteins play a crucial role in maintaining cell homeostasis, signaling processes, and many other physiological functions.

Molecular structure, in the context of biochemistry and molecular biology, refers to the arrangement and organization of atoms and chemical bonds within a molecule. It describes the three-dimensional layout of the constituent elements, including their spatial relationships, bond lengths, and angles. Understanding molecular structure is crucial for elucidating the functions and reactivities of biological macromolecules such as proteins, nucleic acids, lipids, and carbohydrates. Various experimental techniques, like X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy, and cryo-electron microscopy (cryo-EM), are employed to determine molecular structures at atomic resolution, providing valuable insights into their biological roles and potential therapeutic targets.

Cytidine triphosphate (CTP) is a nucleotide that plays a crucial role in the synthesis of RNA. It consists of a cytosine base, a ribose sugar, and three phosphate groups. Cytidine triphosphate is one of the four main building blocks of RNA, along with adenosine triphosphate (ATP), guanosine triphosphate (GTP), and uridine triphosphate (UTP). These nucleotides are essential for various cellular processes, including energy transfer, signal transduction, and biosynthesis. CTP is also involved in the regulation of several metabolic pathways and serves as a cofactor for enzymes that catalyze biochemical reactions. Like other triphosphate nucleotides, CTP provides energy for cellular functions by donating its phosphate groups in energy-consuming processes.

Drug resistance, viral, refers to the ability of a virus to continue replicating in the presence of antiviral drugs that are designed to inhibit or stop its growth. This occurs when the virus mutates and changes its genetic makeup in such a way that the drug can no longer effectively bind to and inhibit the function of its target protein, allowing the virus to continue infecting host cells and causing disease.

Viral drug resistance can develop due to several factors, including:

1. Mutations in the viral genome that alter the structure or function of the drug's target protein.
2. Changes in the expression levels or location of the drug's target protein within the virus-infected cell.
3. Activation of alternative pathways that allow the virus to replicate despite the presence of the drug.
4. Increased efflux of the drug from the virus-infected cell, reducing its intracellular concentration and effectiveness.

Viral drug resistance is a significant concern in the treatment of viral infections such as HIV, hepatitis B and C, herpes simplex virus, and influenza. It can lead to reduced treatment efficacy, increased risk of treatment failure, and the need for more toxic or expensive drugs. Therefore, it is essential to monitor viral drug resistance during treatment and adjust therapy accordingly to ensure optimal outcomes.

Phosphotransferases are a group of enzymes that catalyze the transfer of a phosphate group from a donor molecule to an acceptor molecule. This reaction is essential for various cellular processes, including energy metabolism, signal transduction, and biosynthesis.

The systematic name for this group of enzymes is phosphotransferase, which is derived from the general reaction they catalyze: D-donor + A-acceptor = D-donor minus phosphate + A-phosphate. The donor molecule can be a variety of compounds, such as ATP or a phosphorylated protein, while the acceptor molecule is typically a compound that becomes phosphorylated during the reaction.

Phosphotransferases are classified into several subgroups based on the type of donor and acceptor molecules they act upon. For example, kinases are a subgroup of phosphotransferases that transfer a phosphate group from ATP to a protein or other organic compound. Phosphatases, another subgroup, remove phosphate groups from molecules by transferring them to water.

Overall, phosphotransferases play a critical role in regulating many cellular functions and are important targets for drug development in various diseases, including cancer and neurological disorders.

Didanosine is a medication used to treat HIV (human immunodeficiency virus) infection. It is an antiretroviral drug, specifically a nucleoside reverse transcriptase inhibitor (NRTI), that works by interfering with the replication of the virus in the body. Didanosine is often used in combination with other antiretroviral drugs as part of highly active antiretroviral therapy (HAART) to help control HIV infection and reduce the risk of HIV-related illnesses.

The medical definition of 'Didanosine' is:

A synthetic nucleoside analogue that inhibits the reverse transcriptase activity of the human immunodeficiency virus (HIV). It is converted in vivo to the active metabolite dideoxyadenosine triphosphate, which competitively inhibits HIV DNA polymerase and has antiviral properties. The drug is used in the treatment of HIV infection and AIDS.

'Escherichia coli' (E. coli) is a type of gram-negative, facultatively anaerobic, rod-shaped bacterium that commonly inhabits the intestinal tract of humans and warm-blooded animals. It is a member of the family Enterobacteriaceae and one of the most well-studied prokaryotic model organisms in molecular biology.

While most E. coli strains are harmless and even beneficial to their hosts, some serotypes can cause various forms of gastrointestinal and extraintestinal illnesses in humans and animals. These pathogenic strains possess virulence factors that enable them to colonize and damage host tissues, leading to diseases such as diarrhea, urinary tract infections, pneumonia, and sepsis.

E. coli is a versatile organism with remarkable genetic diversity, which allows it to adapt to various environmental niches. It can be found in water, soil, food, and various man-made environments, making it an essential indicator of fecal contamination and a common cause of foodborne illnesses. The study of E. coli has contributed significantly to our understanding of fundamental biological processes, including DNA replication, gene regulation, and protein synthesis.

Hypoxanthine is not a medical condition but a purine base that is a component of many organic compounds, including nucleotides and nucleic acids, which are the building blocks of DNA and RNA. In the body, hypoxanthine is produced as a byproduct of normal cellular metabolism and is converted to xanthine and then uric acid, which is excreted in the urine.

However, abnormally high levels of hypoxanthine in the body can indicate tissue damage or disease. For example, during intense exercise or hypoxia (low oxygen levels), cells may break down ATP (adenosine triphosphate) rapidly, releasing large amounts of hypoxanthine. Similarly, in some genetic disorders such as Lesch-Nyhan syndrome, there is an accumulation of hypoxanthine due to a deficiency of the enzyme that converts it to xanthine. High levels of hypoxanthine can lead to the formation of kidney stones and other complications.

Adenine nucleotides are molecules that consist of a nitrogenous base called adenine, which is linked to a sugar molecule (ribose in the case of adenosine monophosphate or AMP, and deoxyribose in the case of adenosine diphosphate or ADP and adenosine triphosphate or ATP) and one, two, or three phosphate groups. These molecules play a crucial role in energy transfer and metabolism within cells.

AMP contains one phosphate group, while ADP contains two phosphate groups, and ATP contains three phosphate groups. When a phosphate group is removed from ATP, energy is released, which can be used to power various cellular processes such as muscle contraction, nerve impulse transmission, and protein synthesis. The reverse reaction, in which a phosphate group is added back to ADP or AMP to form ATP, requires energy input and often involves the breakdown of nutrients such as glucose or fatty acids.

In addition to their role in energy metabolism, adenine nucleotides also serve as precursors for other important molecules, including DNA and RNA, coenzymes, and signaling molecules.

Deoxyribonucleotides are the building blocks of DNA (deoxyribonucleic acid). They consist of a deoxyribose sugar, a phosphate group, and one of four nitrogenous bases: adenine (A), guanine (G), cytosine (C), or thymine (T). A deoxyribonucleotide is formed when a nucleotide loses a hydroxyl group from its sugar molecule. In DNA, deoxyribonucleotides link together to form a long, double-helix structure through phosphodiester bonds between the sugar of one deoxyribonucleotide and the phosphate group of another. The sequence of these nucleotides carries genetic information that is essential for the development and function of all known living organisms and many viruses.

Pyrophosphatases are enzymes that catalyze the hydrolysis or cleavage of pyrophosphate (PPi) into two inorganic phosphate (Pi) molecules. This reaction is essential for many biochemical processes, such as energy metabolism and biosynthesis pathways, where pyrophosphate is generated as a byproduct. By removing the pyrophosphate, pyrophosphatases help drive these reactions forward and maintain the thermodynamic equilibrium.

There are several types of pyrophosphatases found in various organisms and cellular compartments, including:

1. Inorganic Pyrophosphatase (PPiase): This enzyme is widely distributed across all kingdoms of life and is responsible for hydrolyzing inorganic pyrophosphate into two phosphates. It plays a crucial role in maintaining the cellular energy balance by ensuring that the reverse reaction, the formation of pyrophosphate from two phosphates, does not occur spontaneously.
2. Nucleotide Pyrophosphatases: These enzymes hydrolyze the pyrophosphate bond in nucleoside triphosphates (NTPs) and deoxynucleoside triphosphates (dNTPs), converting them into nucleoside monophosphates (NMPs) or deoxynucleoside monophosphates (dNMPs). This reaction is important for regulating the levels of NTPs and dNTPs in cells, which are necessary for DNA and RNA synthesis.
3. ATPases and GTPases: These enzymes belong to a larger family of P-loop NTPases that use the energy released from pyrophosphate bond hydrolysis to perform mechanical work or transport ions across membranes. Examples include the F1F0-ATP synthase, which synthesizes ATP using a proton gradient, and various molecular motors like myosin, kinesin, and dynein, which move along cytoskeletal filaments.

Overall, pyrophosphatases are essential for maintaining cellular homeostasis by regulating the levels of nucleotides and providing energy for various cellular processes.

Arabinofuranosyluracil (AraU) is a nucleoside analogue, which means it is a synthetic compound similar to the building blocks of DNA and RNA. AraU is formed by combining the sugar arabinose with the nucleobase uracil. Nucleoside analogues like AraU are often used in cancer chemotherapy and antiviral therapy because they can interfere with the replication of DNA and RNA, disrupting the growth or replication of cancer cells or viruses.

In the context of medical research and treatment, AraU has been studied for its potential use as an anticancer and antiviral agent. However, it is not currently approved for use as a medication in humans. Like many nucleoside analogues, AraU can have toxic effects on normal cells as well as cancerous or virus-infected cells, which limits its usefulness as a therapeutic agent.

Adenosine deaminase inhibitors are a class of medications that work by blocking the action of the enzyme adenosine deaminase. This enzyme is responsible for breaking down adenosine, a chemical in the body that helps regulate the immune system and is involved in the inflammatory response.

By inhibiting the activity of adenosine deaminase, these medications can increase the levels of adenosine in the body. This can be useful in certain medical conditions where reducing inflammation is important. For example, adenosine deaminase inhibitors are sometimes used to treat rheumatoid arthritis, a chronic autoimmune disease characterized by inflammation and damage to the joints.

One common adenosine deaminase inhibitor is called deoxycoformycin (also known as pentostatin). This medication is typically given intravenously and is used to treat hairy cell leukemia, a rare type of cancer that affects white blood cells.

It's important to note that adenosine deaminase inhibitors can have serious side effects, including suppression of the immune system, which can make people more susceptible to infections. They should only be used under the close supervision of a healthcare provider.

Deoxyguanine nucleotides are chemical compounds that are the building blocks of DNA, one of the fundamental molecules of life. Specifically, deoxyguanine nucleotides contain a sugar molecule called deoxyribose, a phosphate group, and the nitrogenous base guanine.

Guanine is one of the four nitrogenous bases found in DNA, along with adenine, thymine, and cytosine. In DNA, guanine always pairs with cytosine through hydrogen bonding, forming a stable base pair that is crucial for maintaining the structure and integrity of the genetic code.

Deoxyguanine nucleotides are synthesized in cells during the process of DNA replication, which occurs prior to cell division. During replication, the double helix structure of DNA is unwound, and each strand serves as a template for the synthesis of a new complementary strand. Deoxyguanine nucleotides are added to the growing chain of nucleotides by an enzyme called DNA polymerase, which catalyzes the formation of a phosphodiester bond between the deoxyribose sugar of one nucleotide and the phosphate group of the next.

Abnormalities in the synthesis or metabolism of deoxyguanine nucleotides can lead to genetic disorders and cancer. For example, mutations in genes that encode enzymes involved in the synthesis of deoxyguanine nucleotides have been linked to inherited diseases such as xeroderma pigmentosum and Bloom syndrome, which are characterized by increased sensitivity to sunlight and a predisposition to cancer. Additionally, defects in the repair of damaged deoxyguanine nucleotides can lead to the accumulation of mutations and contribute to the development of cancer.

Transfer RNA (tRNA) is a type of RNA molecule that plays a crucial role in protein synthesis, the process by which cells create proteins. In protein synthesis, tRNAs serve as adaptors, translating the genetic code present in messenger RNA (mRNA) into the corresponding amino acids required to build a protein.

Each tRNA molecule has a distinct structure, consisting of approximately 70-90 nucleotides arranged in a cloverleaf shape with several loops and stems. The most important feature of a tRNA is its anticodon, a sequence of three nucleotides located in one of the loops. This anticodon base-pairs with a complementary codon on the mRNA during translation, ensuring that the correct amino acid is added to the growing polypeptide chain.

Before tRNAs can participate in protein synthesis, they must be charged with their specific amino acids through an enzymatic process involving aminoacyl-tRNA synthetases. These enzymes recognize and bind to both the tRNA and its corresponding amino acid, forming a covalent bond between them. Once charged, the aminoacyl-tRNA complex is ready to engage in translation and contribute to protein formation.

In summary, transfer RNA (tRNA) is a small RNA molecule that facilitates protein synthesis by translating genetic information from messenger RNA into specific amino acids, ultimately leading to the creation of functional proteins within cells.

A prodrug is a pharmacologically inactive substance that, once administered, is metabolized into a drug that is active. Prodrugs are designed to improve the bioavailability or delivery of a drug, to minimize adverse effects, or to target the drug to specific sites in the body. The conversion of a prodrug to its active form typically occurs through enzymatic reactions in the liver or other tissues.

Prodrugs can offer several advantages over traditional drugs, including:

* Improved absorption: Some drugs have poor bioavailability due to their chemical properties, which make them difficult to absorb from the gastrointestinal tract. Prodrugs can be designed with improved absorption characteristics, allowing for more efficient delivery of the active drug to the body.
* Reduced toxicity: By masking the active drug's chemical structure, prodrugs can reduce its interactions with sensitive tissues and organs, thereby minimizing adverse effects.
* Targeted delivery: Prodrugs can be designed to selectively release the active drug in specific areas of the body, such as tumors or sites of infection, allowing for more precise and effective therapy.

Examples of prodrugs include:

* Aspirin (acetylsalicylic acid), which is metabolized to salicylic acid in the liver.
* Enalapril, an angiotensin-converting enzyme (ACE) inhibitor used to treat hypertension and heart failure, which is metabolized to enalaprilat in the liver.
* Codeine, an opioid analgesic, which is metabolized to morphine in the liver by the enzyme CYP2D6.

It's important to note that not all prodrugs are successful, and some may even have unintended consequences. For example, if a patient has a genetic variation that affects the activity of the enzyme responsible for converting the prodrug to its active form, the drug may not be effective or may produce adverse effects. Therefore, it's essential to consider individual genetic factors when prescribing prodrugs.

Adenosine kinase (ADK) is an enzyme that plays a crucial role in the regulation of adenosine levels in cells. The medical definition of adenosine kinase is:

"An enzyme (EC 2.7.1.20) that catalyzes the phosphorylation of adenosine to form adenosine monophosphate (AMP) using ATP as the phosphate donor. This reaction helps maintain the balance between adenosine and its corresponding nucleotides in cells, and it plays a significant role in purine metabolism, cell signaling, and energy homeostasis."

Adenosine kinase is widely distributed in various tissues, including the brain, heart, liver, and muscles. Dysregulation of adenosine kinase activity has been implicated in several pathological conditions, such as ischemia-reperfusion injury, neurodegenerative disorders, and cancer. Therefore, modulating adenosine kinase activity has emerged as a potential therapeutic strategy for treating these diseases.

Nucleotidases are a class of enzymes that catalyze the hydrolysis of nucleotides into nucleosides and phosphate groups. Nucleotidases play important roles in various biological processes, including the regulation of nucleotide concentrations within cells, the salvage pathways for nucleotide synthesis, and the breakdown of nucleic acids during programmed cell death (apoptosis).

There are several types of nucleotidases that differ in their substrate specificity and subcellular localization. These include:

1. Nucleoside monophosphatases (NMPs): These enzymes hydrolyze nucleoside monophosphates (NMPs) into nucleosides and inorganic phosphate.
2. Nucleoside diphosphatases (NDPs): These enzymes hydrolyze nucleoside diphosphates (NDPs) into nucleoside monophosphates (NMPs) and inorganic phosphate.
3. Nucleoside triphosphatases (NTPs): These enzymes hydrolyze nucleoside triphosphates (NTPs) into nucleoside diphosphates (NDPs) and inorganic phosphate.
4. 5'-Nucleotidase: This enzyme specifically hydrolyzes the phosphate group from the 5' position of nucleoside monophosphates, producing nucleosides.
5. Pyrophosphatases: These enzymes hydrolyze pyrophosphates into two phosphate groups and play a role in regulating nucleotide metabolism.

Nucleotidases are widely distributed in nature and can be found in various tissues, organs, and biological fluids, including blood, urine, and cerebrospinal fluid. Dysregulation of nucleotidase activity has been implicated in several diseases, such as cancer, neurodegenerative disorders, and infectious diseases.

Uracil nucleotides are chemical compounds that play a crucial role in the synthesis, repair, and replication of DNA and RNA. Specifically, uracil nucleotides refer to the group of molecules that contain the nitrogenous base uracil, which is linked to a ribose sugar through a beta-glycosidic bond. This forms the nucleoside uridine, which can then be phosphorylated to create the uracil nucleotide.

Uracil nucleotides are important in the formation of RNA, where uracil base pairs with adenine through two hydrogen bonds during transcription. However, uracil is not typically found in DNA, and its presence in DNA can indicate damage or mutation. When uracil is found in DNA, it is usually the result of a process called deamination, where the nitrogenous base cytosine is spontaneously converted to uracil. This can lead to errors during replication, as uracil will pair with adenine instead of guanine, leading to a C-to-T or G-to-A mutation.

To prevent this type of mutation, cells have enzymes called uracil DNA glycosylases that recognize and remove uracil from DNA. This initiates the base excision repair pathway, which removes the damaged nucleotide and replaces it with a correct one. Overall, uracil nucleotides are essential for proper cellular function, but their misincorporation into DNA can have serious consequences for genome stability.

A base sequence in the context of molecular biology refers to the specific order of nucleotides in a DNA or RNA molecule. In DNA, these nucleotides are adenine (A), guanine (G), cytosine (C), and thymine (T). In RNA, uracil (U) takes the place of thymine. The base sequence contains genetic information that is transcribed into RNA and ultimately translated into proteins. It is the exact order of these bases that determines the genetic code and thus the function of the DNA or RNA molecule.

Cladribine is a medication used in the treatment of certain types of cancer and multiple sclerosis. It is a type of drug called a purine nucleoside analog, which means it interferes with the production of DNA and RNA, the genetic material of cells. This can help to stop the growth and multiplication of abnormal cells in the body.

In cancer treatment, cladribine is used to treat hairy cell leukemia and certain types of lymphoma. In multiple sclerosis, it is used to reduce the frequency of relapses and slow down the progression of disability. Cladribine works by selectively targeting and depleting certain white blood cells called lymphocytes, which are thought to play a role in the immune response that damages the nervous system in multiple sclerosis.

Cladribine is usually given as an injection into a vein or under the skin, and it may be given on its own or in combination with other medications. Common side effects of cladribine include nausea, vomiting, diarrhea, and weakness. It can also lower the body's ability to fight infections, so patients may need to take precautions to avoid infection while receiving treatment. Cladribine should be used with caution in people with a history of certain medical conditions, such as liver or kidney disease, and it should not be used during pregnancy or breastfeeding.

Thymidine kinase (TK) is an enzyme that plays a crucial role in the synthesis of thymidine triphosphate (dTMP), a nucleotide required for DNA replication and repair. It catalyzes the phosphorylation of thymidine to thymidine monophosphate (dTMP) by transferring a phosphate group from adenosine triphosphate (ATP).

There are two major isoforms of thymidine kinase in humans: TK1 and TK2. TK1 is primarily found in the cytoplasm of proliferating cells, such as those involved in the cell cycle, while TK2 is located mainly in the mitochondria and is responsible for maintaining the dNTP pool required for mtDNA replication and repair.

Thymidine kinase activity has been used as a marker for cell proliferation, particularly in cancer cells, which often exhibit elevated levels of TK1 due to their high turnover rates. Additionally, measuring TK1 levels can help monitor the effectiveness of certain anticancer therapies that target DNA replication.

Apyrase is an enzyme that catalyzes the hydrolysis of nucleoside triphosphates (like ATP or GTP) to nucleoside diphosphates (like ADP or GDP), releasing inorganic phosphate in the process. It can also hydrolyze nucleoside diphosphates to nucleoside monophosphates, releasing inorganic pyrophosphate.

This enzyme is widely distributed in nature and has been found in various organisms, including bacteria, plants, and animals. In humans, apyrases are present in different tissues, such as the brain, platelets, and red blood cells. They play essential roles in several biological processes, including signal transduction, metabolism regulation, and inflammatory response modulation.

There are two major classes of apyrases: type I (also known as nucleoside diphosphate kinase) and type II (also known as NTPDase). Type II apyrases have higher substrate specificity for nucleoside triphosphates, while type I apyrases can hydrolyze both nucleoside tri- and diphosphates.

In the medical field, apyrases are sometimes used in research to study platelet function or neurotransmission, as they can help regulate purinergic signaling by controlling extracellular levels of ATP and ADP. Additionally, some studies suggest that apyrase activity might be involved in certain pathological conditions, such as atherosclerosis, thrombosis, and neurological disorders.

A Structure-Activity Relationship (SAR) in the context of medicinal chemistry and pharmacology refers to the relationship between the chemical structure of a drug or molecule and its biological activity or effect on a target protein, cell, or organism. SAR studies aim to identify patterns and correlations between structural features of a compound and its ability to interact with a specific biological target, leading to a desired therapeutic response or undesired side effects.

By analyzing the SAR, researchers can optimize the chemical structure of lead compounds to enhance their potency, selectivity, safety, and pharmacokinetic properties, ultimately guiding the design and development of novel drugs with improved efficacy and reduced toxicity.

Pyrimidinones are a class of heterocyclic organic compounds that contain a pyrimidine ring fused with a ketone group. The basic structure of a pyrimidinone consists of two nitrogen atoms and four carbon atoms in a six-membered ring, with a carbonyl (C=O) group attached to one of the carbon atoms.

In a medical context, pyrimidinones are important because many naturally occurring and synthetic compounds that contain this structure have been found to have biological activity. For example, some pyrimidinones have antiviral, antibacterial, or anticancer properties, making them useful in the development of new drugs for various medical conditions.

One well-known drug that contains a pyrimidinone ring is the antiviral medication Ribavirin, which is used to treat hepatitis C and certain viral hemorrhagic fevers. Other pyrimidinones are being studied for their potential therapeutic benefits in areas such as cancer therapy, neuroprotection, and inflammation.

Deoxycytidine is a chemical compound that is a component of DNA, one of the nucleic acids in living organisms. It is a nucleoside, consisting of the sugar deoxyribose and the base cytosine. Deoxycytidine pairs with guanine via hydrogen bonds to form base pairs in the double helix structure of DNA.

In biochemistry, deoxycytidine can also exist as a free nucleoside, not bound to other molecules. It is involved in various cellular processes related to DNA metabolism and replication. Deoxycytidine can be phosphorylated to form deoxycytidine monophosphate (dCMP), which is an important intermediate in the synthesis of DNA.

It's worth noting that while deoxycytidine is a component of DNA, its counterpart in RNA is cytidine, which contains ribose instead of deoxyribose as the sugar component.

Lamivudine is an antiretroviral medication used in the treatment and management of HIV (Human Immunodeficiency Virus) infection and HBV (Hepatitis B Virus) infection. It is a nucleoside reverse transcriptase inhibitor (NRTI), which means it works by blocking the action of the reverse transcriptase enzyme that the viruses need to multiply. By doing this, Lamivudine helps to reduce the amount of the virus in the body, which in turn helps to slow down or prevent the damage that the virus can cause to the immune system and improve the patient's quality of life.

The medical definition of Lamivudine is: "A synthetic nucleoside analogue with activity against both HIV-1 and HBV. It is used in the treatment of HIV infection and AIDS, as well as chronic hepatitis B."

Ribose is a simple carbohydrate, specifically a monosaccharide, which means it is a single sugar unit. It is a type of sugar known as a pentose, containing five carbon atoms. Ribose is a vital component of ribonucleic acid (RNA), one of the essential molecules in all living cells, involved in the process of transcribing and translating genetic information from DNA to proteins. The term "ribose" can also refer to any sugar alcohol derived from it, such as D-ribose or Ribitol.

A mutation is a permanent change in the DNA sequence of an organism's genome. Mutations can occur spontaneously or be caused by environmental factors such as exposure to radiation, chemicals, or viruses. They may have various effects on the organism, ranging from benign to harmful, depending on where they occur and whether they alter the function of essential proteins. In some cases, mutations can increase an individual's susceptibility to certain diseases or disorders, while in others, they may confer a survival advantage. Mutations are the driving force behind evolution, as they introduce new genetic variability into populations, which can then be acted upon by natural selection.

Cytosine is one of the four nucleobases in the nucleic acid molecules DNA and RNA, along with adenine, guanine, and thymine (in DNA) or uracil (in RNA). The single-letter abbreviation for cytosine is "C."

Cytosine base pairs specifically with guanine through hydrogen bonding, forming a base pair. In DNA, the double helix consists of two complementary strands of nucleotides held together by these base pairs, such that the sequence of one strand determines the sequence of the other. This property is critical for DNA replication and transcription, processes that are essential for life.

Cytosine residues in DNA can undergo spontaneous deamination to form uracil, which can lead to mutations if not corrected by repair mechanisms. In RNA, cytosine can be methylated at the 5-carbon position to form 5-methylcytosine, a modification that plays a role in regulating gene expression and other cellular processes.

Uridine kinase is an enzyme that phosphorylates the pyrimidine nucleoside uridine to produce uridine monophosphate (UMP). This reaction plays a crucial role in the salvage pathway of pyrimidine nucleotide synthesis, which recycles nucleosides generated from the degradation of RNA.

The human genome encodes two isoforms of uridine kinase, UCK1 and UCK2, which share a high degree of sequence similarity but have distinct tissue expression patterns and subcellular localization. UCK1 is primarily expressed in the liver and kidney, while UCK2 is more widely expressed in various tissues.

Uridine kinase activity has been implicated in several physiological processes, including the regulation of intracellular nucleotide pools, the biosynthesis of glycosaminoglycans and proteoglycans, and the modulation of antiviral responses. Dysregulation of uridine kinase activity has been associated with various pathological conditions, such as cancer, viral infections, and neurological disorders.

HIV-1 (Human Immunodeficiency Virus type 1) is a species of the retrovirus genus that causes acquired immunodeficiency syndrome (AIDS). It is primarily transmitted through sexual contact, exposure to infected blood or blood products, and from mother to child during pregnancy, childbirth, or breastfeeding. HIV-1 infects vital cells in the human immune system, such as CD4+ T cells, macrophages, and dendritic cells, leading to a decline in their numbers and weakening of the immune response over time. This results in the individual becoming susceptible to various opportunistic infections and cancers that ultimately cause death if left untreated. HIV-1 is the most prevalent form of HIV worldwide and has been identified as the causative agent of the global AIDS pandemic.

Adenosine monophosphate (AMP) is a nucleotide that is the monophosphate ester of adenosine, consisting of the nitrogenous base adenine attached to the 1' carbon atom of ribose via a β-N9-glycosidic bond, which in turn is esterified to a phosphate group. It is an important molecule in biological systems as it plays a key role in cellular energy transfer and storage, serving as a precursor to other nucleotides such as ADP and ATP. AMP is also involved in various signaling pathways and can act as a neurotransmitter in the central nervous system.

Floxuridine is a chemotherapeutic antimetabolite medication that is primarily used in the treatment of colon cancer. It is a fluorinated pyrimidine nucleoside analogue, which means it is similar in structure to the building blocks of DNA and RNA, and can be incorporated into these molecules during cell division, disrupting their normal function and preventing cell replication.

Floxuridine works by inhibiting the enzyme thymidylate synthase, which is necessary for the synthesis of thymidine, a nucleoside that is essential for DNA replication. By blocking this enzyme, floxuridine can prevent the growth and proliferation of cancer cells.

Floxuridine is often used in combination with other chemotherapy drugs as part of a treatment regimen for colon cancer. It may be administered intravenously or via continuous infusion, depending on the specific treatment plan. As with all chemotherapy drugs, floxuridine can have significant side effects, including nausea, vomiting, diarrhea, and myelosuppression (suppression of bone marrow function), which can lead to anemia, neutropenia, and thrombocytopenia.

5'-Nucleotidase is an enzyme that is found on the outer surface of cell membranes, including those of liver cells and red blood cells. Its primary function is to catalyze the hydrolysis of nucleoside monophosphates, such as adenosine monophosphate (AMP) and guanosine monophosphate (GMP), to their corresponding nucleosides, such as adenosine and guanosine, by removing a phosphate group from the 5' position of the nucleotide.

Abnormal levels of 5'-Nucleotidase in the blood can be indicative of liver or bone disease. For example, elevated levels of this enzyme in the blood may suggest liver damage or injury, such as that caused by hepatitis, cirrhosis, or alcohol abuse. Conversely, low levels of 5'-Nucleotidase may be associated with certain types of anemia, including aplastic anemia and paroxysmal nocturnal hemoglobinuria.

Medical professionals may order a 5'-Nucleotidase test to help diagnose or monitor the progression of these conditions. It is important to note that other factors, such as medication use or muscle damage, can also affect 5'-Nucleotidase levels, so results must be interpreted in conjunction with other clinical findings and diagnostic tests.

An amino acid sequence is the specific order of amino acids in a protein or peptide molecule, formed by the linking of the amino group (-NH2) of one amino acid to the carboxyl group (-COOH) of another amino acid through a peptide bond. The sequence is determined by the genetic code and is unique to each type of protein or peptide. It plays a crucial role in determining the three-dimensional structure and function of proteins.

Organophosphorus compounds are a class of chemical substances that contain phosphorus bonded to organic compounds. They are used in various applications, including as plasticizers, flame retardants, pesticides (insecticides, herbicides, and nerve gases), and solvents. In medicine, they are also used in the treatment of certain conditions such as glaucoma. However, organophosphorus compounds can be toxic to humans and animals, particularly those that affect the nervous system by inhibiting acetylcholinesterase, an enzyme that breaks down the neurotransmitter acetylcholine. Exposure to these compounds can cause symptoms such as nausea, vomiting, muscle weakness, and in severe cases, respiratory failure and death.

Guanosine triphosphate (GTP) is a nucleotide that plays a crucial role in various cellular processes, such as protein synthesis, signal transduction, and regulation of enzymatic activities. It serves as an energy currency, similar to adenosine triphosphate (ATP), and undergoes hydrolysis to guanosine diphosphate (GDP) or guanosine monophosphate (GMP) to release energy required for these processes. GTP is also a precursor for the synthesis of other essential molecules, including RNA and certain signaling proteins. Additionally, it acts as a molecular switch in many intracellular signaling pathways by binding and activating specific GTPase proteins.

Oligonucleotides are short sequences of nucleotides, the building blocks of DNA and RNA. They typically contain fewer than 100 nucleotides, and can be synthesized chemically to have specific sequences. Oligonucleotides are used in a variety of applications in molecular biology, including as probes for detecting specific DNA or RNA sequences, as inhibitors of gene expression, and as components of diagnostic tests and therapies. They can also be used in the study of protein-nucleic acid interactions and in the development of new drugs.

Acyclovir is an antiviral medication used for the treatment of infections caused by herpes simplex viruses (HSV) including genital herpes, cold sores, and shingles (varicella-zoster virus). It works by interfering with the replication of the virus's DNA, thereby preventing the virus from multiplying further. Acyclovir is available in various forms such as oral tablets, capsules, creams, and intravenous solutions.

The medical definition of 'Acyclovir' is:

Acyclovir (brand name Zovirax) is a synthetic nucleoside analogue that functions as an antiviral agent, specifically against herpes simplex viruses (HSV) types 1 and 2, varicella-zoster virus (VZV), and Epstein-Barr virus (EBV). Acyclovir is converted to its active form, acyclovir triphosphate, by viral thymidine kinase. This activated form then inhibits viral DNA polymerase, preventing further replication of the virus's DNA.

Acyclovir has a relatively low toxicity profile and is generally well-tolerated, although side effects such as nausea, vomiting, diarrhea, and headache can occur. In rare cases, more serious side effects such as kidney damage, seizures, or neurological problems may occur. It is important to take acyclovir exactly as directed by a healthcare provider and to report any unusual symptoms promptly.

Ribose monophosphates are organic compounds that play a crucial role in the metabolism of cells, particularly in energy transfer and nucleic acid synthesis. A ribose monophosphate is formed by the attachment of a phosphate group to a ribose molecule, which is a type of sugar known as a pentose.

In biochemistry, there are two important ribose monophosphates:

1. Alpha-D-Ribose 5-Phosphate (ADP-Ribose): This compound serves as an essential substrate in various cellular processes, including DNA repair, chromatin remodeling, and protein modification. The enzyme that catalyzes the formation of ADP-ribose is known as poly(ADP-ribose) polymerase (PARP).
2. Ribulose 5-Phosphate: This compound is a key intermediate in the Calvin cycle, which is the process by which plants and some bacteria convert carbon dioxide into glucose during photosynthesis. Ribulose 5-phosphate is formed from ribose 5-phosphate through a series of enzymatic reactions.

Ribose monophosphates are essential for the proper functioning of cells and have implications in various physiological processes, as well as in certain disease states.

High-performance liquid chromatography (HPLC) is a type of chromatography that separates and analyzes compounds based on their interactions with a stationary phase and a mobile phase under high pressure. The mobile phase, which can be a gas or liquid, carries the sample mixture through a column containing the stationary phase.

In HPLC, the mobile phase is a liquid, and it is pumped through the column at high pressures (up to several hundred atmospheres) to achieve faster separation times and better resolution than other types of liquid chromatography. The stationary phase can be a solid or a liquid supported on a solid, and it interacts differently with each component in the sample mixture, causing them to separate as they travel through the column.

HPLC is widely used in analytical chemistry, pharmaceuticals, biotechnology, and other fields to separate, identify, and quantify compounds present in complex mixtures. It can be used to analyze a wide range of substances, including drugs, hormones, vitamins, pigments, flavors, and pollutants. HPLC is also used in the preparation of pure samples for further study or use.

Methylthioinosine is not a widely recognized or used term in medicine, and it does not have a specific medical definition. It is a chemical compound that is formed by the addition of a methylthio group (-CH3S-) to the nucleoside inosine. Inosine is a purine nucleoside that is formed from the deamination of adenosine.

Methylthioinosine has been studied in some laboratory experiments, but it is not commonly used in clinical medicine or treatment. Therefore, it is not a term that most medical professionals would be familiar with.

Guanosine monophosphate (GMP) is a nucleotide that is a fundamental unit of genetic material in DNA and RNA. It consists of a guanine base, a pentose sugar (ribose in the case of RNA, deoxyribose in DNA), and one phosphate group. GMP plays crucial roles in various biochemical reactions within cells, including energy transfer and signal transduction pathways. Additionally, it is involved in the synthesis of important molecules like nucleic acids, neurotransmitters, and hormones.

RNA (Ribonucleic Acid) is a single-stranded, linear polymer of ribonucleotides. It is a nucleic acid present in the cells of all living organisms and some viruses. RNAs play crucial roles in various biological processes such as protein synthesis, gene regulation, and cellular signaling. There are several types of RNA including messenger RNA (mRNA), ribosomal RNA (rRNA), transfer RNA (tRNA), small nuclear RNA (snRNA), microRNA (miRNA), and long non-coding RNA (lncRNA). These RNAs differ in their structure, function, and location within the cell.

Uracil is not a medical term, but it is a biological molecule. Medically or biologically, uracil can be defined as one of the four nucleobases in the nucleic acid of RNA (ribonucleic acid) that is linked to a ribose sugar by an N-glycosidic bond. It forms base pairs with adenine in double-stranded RNA and DNA. Uracil is a pyrimidine derivative, similar to thymine found in DNA, but it lacks the methyl group (-CH3) that thymine has at the 5 position of its ring.

Magnetic Resonance Spectroscopy (MRS) is a non-invasive diagnostic technique that provides information about the biochemical composition of tissues, including their metabolic state. It is often used in conjunction with Magnetic Resonance Imaging (MRI) to analyze various metabolites within body tissues, such as the brain, heart, liver, and muscles.

During MRS, a strong magnetic field, radio waves, and a computer are used to produce detailed images and data about the concentration of specific metabolites in the targeted tissue or organ. This technique can help detect abnormalities related to energy metabolism, neurotransmitter levels, pH balance, and other biochemical processes, which can be useful for diagnosing and monitoring various medical conditions, including cancer, neurological disorders, and metabolic diseases.

There are different types of MRS, such as Proton (^1^H) MRS, Phosphorus-31 (^31^P) MRS, and Carbon-13 (^13^C) MRS, each focusing on specific elements or metabolites within the body. The choice of MRS technique depends on the clinical question being addressed and the type of information needed for diagnosis or monitoring purposes.

Deoxyribonucleic acid (DNA) is the genetic material present in the cells of organisms where it is responsible for the storage and transmission of hereditary information. DNA is a long molecule that consists of two strands coiled together to form a double helix. Each strand is made up of a series of four nucleotide bases - adenine (A), guanine (G), cytosine (C), and thymine (T) - that are linked together by phosphate and sugar groups. The sequence of these bases along the length of the molecule encodes genetic information, with A always pairing with T and C always pairing with G. This base-pairing allows for the replication and transcription of DNA, which are essential processes in the functioning and reproduction of all living organisms.

Phosphoric monoester hydrolases are a class of enzymes that catalyze the hydrolysis of phosphoric monoesters into alcohol and phosphate. This class of enzymes includes several specific enzymes, such as phosphatases and nucleotidases, which play important roles in various biological processes, including metabolism, signal transduction, and regulation of cellular processes.

Phosphoric monoester hydrolases are classified under the EC number 3.1.3 by the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (IUBMB). The enzymes in this class share a common mechanism of action, which involves the nucleophilic attack on the phosphorus atom of the substrate by a serine or cysteine residue in the active site of the enzyme. This results in the formation of a covalent intermediate, which is then hydrolyzed to release the products.

Phosphoric monoester hydrolases are important therapeutic targets for the development of drugs that can modulate their activity. For example, inhibitors of phosphoric monoester hydrolases have been developed as potential treatments for various diseases, including cancer, neurodegenerative disorders, and infectious diseases.

Molecular models are three-dimensional representations of molecular structures that are used in the field of molecular biology and chemistry to visualize and understand the spatial arrangement of atoms and bonds within a molecule. These models can be physical or computer-generated and allow researchers to study the shape, size, and behavior of molecules, which is crucial for understanding their function and interactions with other molecules.

Physical molecular models are often made up of balls (representing atoms) connected by rods or sticks (representing bonds). These models can be constructed manually using materials such as plastic or wooden balls and rods, or they can be created using 3D printing technology.

Computer-generated molecular models, on the other hand, are created using specialized software that allows researchers to visualize and manipulate molecular structures in three dimensions. These models can be used to simulate molecular interactions, predict molecular behavior, and design new drugs or chemicals with specific properties. Overall, molecular models play a critical role in advancing our understanding of molecular structures and their functions.

Adenosine Deaminase (ADA) is an enzyme that plays a crucial role in the immune system by helping to regulate the levels of certain chemicals called purines within cells. Specifically, ADA helps to break down adenosine, a type of purine, into another compound called inosine. This enzyme is found in all tissues of the body, but it is especially active in the immune system's white blood cells, where it helps to support their growth, development, and function.

ADA deficiency is a rare genetic disorder that can lead to severe combined immunodeficiency (SCID), a condition in which babies are born with little or no functional immune system. This makes them extremely vulnerable to infections, which can be life-threatening. ADA deficiency can be treated with enzyme replacement therapy, bone marrow transplantation, or gene therapy.

Cytosine nucleotides are the chemical units or building blocks that make up DNA and RNA, one of the four nitrogenous bases that form the rung of the DNA ladder. A cytosine nucleotide is composed of a cytosine base attached to a sugar molecule (deoxyribose in DNA and ribose in RNA) and at least one phosphate group. The sequence of these nucleotides determines the genetic information stored in an organism's genome. In particular, cytosine nucleotides pair with guanine nucleotides through hydrogen bonding to form base pairs that are held together by weak interactions. This pairing is specific and maintains the structure and integrity of the DNA molecule during replication and transcription.

Vidarabine is an antiviral medication used to treat herpes simplex infections, particularly severe cases such as herpes encephalitis (inflammation of the brain caused by the herpes simplex virus). It works by interfering with the DNA replication of the virus.

In medical terms, vidarabine is a nucleoside analogue that is phosphorylated intracellularly to the active form, vidarabine triphosphate. This compound inhibits viral DNA polymerase and incorporates into viral DNA, causing termination of viral DNA synthesis.

Vidarabine was previously used as an injectable medication but has largely been replaced by more modern antiviral drugs such as acyclovir due to its greater efficacy and lower toxicity.

Vidarabine phosphate is a antiviral medication used to treat herpes simplex encephalitis, a severe form of brain infection caused by the herpes simplex virus. It works by inhibiting the replication of the virus in human cells. Vidarabine phosphate is the salt of vidarabine, which is a nucleoside analogue that gets incorporated into viral DNA during replication, leading to termination of the DNA chain and preventing further viral reproduction. It is administered through intravenous (IV) infusion in a hospital setting.

Pyrimidine nucleotides are organic compounds that play crucial roles in various biological processes, particularly in the field of genetics and molecular biology. They are the building blocks of nucleic acids, which include DNA and RNA, and are essential for the storage, transmission, and expression of genetic information within cells.

Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring. Pyrimidine nucleotides are derivatives of pyrimidine, which contain a phosphate group, a pentose sugar (ribose or deoxyribose), and one of three pyrimidine bases: cytosine (C), thymine (T), or uracil (U).

* Cytosine is present in both DNA and RNA. It pairs with guanine via hydrogen bonding during DNA replication and transcription.
* Thymine is exclusively found in DNA, where it pairs with adenine through two hydrogen bonds.
* Uracil is a pyrimidine base that replaces thymine in RNA molecules and pairs with adenine via two hydrogen bonds during RNA transcription.

Pyrimidine nucleotides, along with purine nucleotides (adenine, guanine, and their derivatives), form the fundamental units of nucleic acids, contributing to the structure, function, and regulation of genetic material in living organisms.

Phosphates, in a medical context, refer to the salts or esters of phosphoric acid. Phosphates play crucial roles in various biological processes within the human body. They are essential components of bones and teeth, where they combine with calcium to form hydroxyapatite crystals. Phosphates also participate in energy transfer reactions as phosphate groups attached to adenosine diphosphate (ADP) and adenosine triphosphate (ATP). Additionally, they contribute to buffer systems that help maintain normal pH levels in the body.

Abnormal levels of phosphates in the blood can indicate certain medical conditions. High phosphate levels (hyperphosphatemia) may be associated with kidney dysfunction, hyperparathyroidism, or excessive intake of phosphate-containing products. Low phosphate levels (hypophosphatemia) might result from malnutrition, vitamin D deficiency, or certain diseases affecting the small intestine or kidneys. Both hypophosphatemia and hyperphosphatemia can have significant impacts on various organ systems and may require medical intervention.

Isopentenyladenosine (IPA) is a derivative of adenosine, which is a nucleoside consisting of adenine attached to ribose sugar via a β-N9-glycosidic bond. In Isopentenyladenosine, an isopentenyl group (a hydrocarbon chain with five carbon atoms) is added to the N6 position of the adenine base.

Isopentenyladenosine is a key intermediate in the biosynthesis of cytokinins, a class of plant hormones that play crucial roles in cell division and differentiation, shoot initiation, leaf expansion, apical dominance, root growth, and other developmental processes.

It's worth noting that Isopentenyladenosine is not typically used as a medical term or definition but rather in the context of biochemistry and plant physiology.

Dideoxyadenosine (ddA) is a type of synthetic nucleoside analogue, which is a synthetic compound that resembles one of the building blocks of DNA or RNA. More specifically, ddA resembles adenosine, one of the four nucleosides that make up DNA.

Dideoxyadenosine is used in research and medicine as an inhibitor of reverse transcriptase, an enzyme that is produced by retroviruses such as HIV. By blocking the action of this enzyme, ddA can prevent the virus from replicating and infecting new cells.

Dideoxyadenosine is often used in combination with other antiretroviral drugs as part of highly active antiretroviral therapy (HAART) to treat HIV infection and AIDS. It is usually administered as a prodrug, such as didanosine or ddI, which is converted to the active form of the drug in the body.

It's important to note that Dideoxyadenosine itself is not used directly as a medication but its derivatives like Didanosine are used in treatment.

HIV (Human Immunodeficiency Virus) infection is a viral illness that progressively attacks and weakens the immune system, making individuals more susceptible to other infections and diseases. The virus primarily infects CD4+ T cells, a type of white blood cell essential for fighting off infections. Over time, as the number of these immune cells declines, the body becomes increasingly vulnerable to opportunistic infections and cancers.

HIV infection has three stages:

1. Acute HIV infection: This is the initial stage that occurs within 2-4 weeks after exposure to the virus. During this period, individuals may experience flu-like symptoms such as fever, fatigue, rash, swollen glands, and muscle aches. The virus replicates rapidly, and the viral load in the body is very high.
2. Chronic HIV infection (Clinical latency): This stage follows the acute infection and can last several years if left untreated. Although individuals may not show any symptoms during this phase, the virus continues to replicate at low levels, and the immune system gradually weakens. The viral load remains relatively stable, but the number of CD4+ T cells declines over time.
3. AIDS (Acquired Immunodeficiency Syndrome): This is the most advanced stage of HIV infection, characterized by a severely damaged immune system and numerous opportunistic infections or cancers. At this stage, the CD4+ T cell count drops below 200 cells/mm3 of blood.

It's important to note that with proper antiretroviral therapy (ART), individuals with HIV infection can effectively manage the virus, maintain a healthy immune system, and significantly reduce the risk of transmission to others. Early diagnosis and treatment are crucial for improving long-term health outcomes and reducing the spread of HIV.

Hydrolysis is a chemical process, not a medical one. However, it is relevant to medicine and biology.

Hydrolysis is the breakdown of a chemical compound due to its reaction with water, often resulting in the formation of two or more simpler compounds. In the context of physiology and medicine, hydrolysis is a crucial process in various biological reactions, such as the digestion of food molecules like proteins, carbohydrates, and fats. Enzymes called hydrolases catalyze these hydrolysis reactions to speed up the breakdown process in the body.

In the context of medical and biological sciences, a "binding site" refers to a specific location on a protein, molecule, or cell where another molecule can attach or bind. This binding interaction can lead to various functional changes in the original protein or molecule. The other molecule that binds to the binding site is often referred to as a ligand, which can be a small molecule, ion, or even another protein.

The binding between a ligand and its target binding site can be specific and selective, meaning that only certain ligands can bind to particular binding sites with high affinity. This specificity plays a crucial role in various biological processes, such as signal transduction, enzyme catalysis, or drug action.

In the case of drug development, understanding the location and properties of binding sites on target proteins is essential for designing drugs that can selectively bind to these sites and modulate protein function. This knowledge can help create more effective and safer therapeutic options for various diseases.

Pseudouridine is a modified nucleoside that is formed through the enzymatic process of pseudouridylation, where a uracil base in RNA is replaced by a pseudouracil base. Pseudouridine is structurally similar to uridine, but the uracil base is linked to the ribose sugar at carbon-5 rather than carbon-1, which leads to altered chemical and physical properties. This modification can affect RNA structure, stability, and function, and has been implicated in various cellular processes such as translation, splicing, and gene regulation.

A cell line is a culture of cells that are grown in a laboratory for use in research. These cells are usually taken from a single cell or group of cells, and they are able to divide and grow continuously in the lab. Cell lines can come from many different sources, including animals, plants, and humans. They are often used in scientific research to study cellular processes, disease mechanisms, and to test new drugs or treatments. Some common types of human cell lines include HeLa cells (which come from a cancer patient named Henrietta Lacks), HEK293 cells (which come from embryonic kidney cells), and HUVEC cells (which come from umbilical vein endothelial cells). It is important to note that cell lines are not the same as primary cells, which are cells that are taken directly from a living organism and have not been grown in the lab.

Nucleoside-phosphate kinase (NPK) is an enzyme that plays a crucial role in the synthesis and metabolism of nucleotides, which are the building blocks of DNA and RNA. NPK catalyzes the transfer of a phosphate group from a donor molecule, typically ATP, to a nucleoside or deoxynucleoside, forming a nucleoside monophosphate (NMP) or deoxynucleoside monophosphate (dNMP).

There are several isoforms of NPK found in different cellular compartments and tissues, each with distinct substrate specificities. These enzymes play essential roles in maintaining the balance of nucleotides required for various cellular processes, including DNA replication, repair, and transcription, as well as RNA synthesis and metabolism.

Abnormalities in NPK activity or expression have been implicated in several human diseases, such as cancer, viral infections, and neurological disorders. Therefore, understanding the function and regulation of NPK is crucial for developing novel therapeutic strategies to target these conditions.

Antimetabolites are a class of antineoplastic (chemotherapy) drugs that interfere with the metabolism of cancer cells and inhibit their growth and proliferation. These agents are structurally similar to naturally occurring metabolites, such as amino acids, nucleotides, and folic acid, which are essential for cellular replication and growth. Antimetabolites act as false analogs and get incorporated into the growing cells' DNA or RNA, causing disruption of the normal synthesis process, leading to cell cycle arrest and apoptosis (programmed cell death).

Examples of antimetabolite drugs include:

1. Folate antagonists: Methotrexate, Pemetrexed
2. Purine analogs: Mercaptopurine, Thioguanine, Fludarabine, Cladribine
3. Pyrimidine analogs: 5-Fluorouracil (5-FU), Capecitabine, Cytarabine, Gemcitabine

These drugs are used to treat various types of cancers, such as leukemias, lymphomas, breast, ovarian, and gastrointestinal cancers. Due to their mechanism of action, antimetabolites can also affect normal, rapidly dividing cells in the body, leading to side effects like myelosuppression (decreased production of blood cells), mucositis (inflammation and ulceration of the gastrointestinal tract), and alopecia (hair loss).

Stereoisomerism is a type of isomerism (structural arrangement of atoms) in which molecules have the same molecular formula and sequence of bonded atoms, but differ in the three-dimensional orientation of their atoms in space. This occurs when the molecule contains asymmetric carbon atoms or other rigid structures that prevent free rotation, leading to distinct spatial arrangements of groups of atoms around a central point. Stereoisomers can have different chemical and physical properties, such as optical activity, boiling points, and reactivities, due to differences in their shape and the way they interact with other molecules.

There are two main types of stereoisomerism: enantiomers (mirror-image isomers) and diastereomers (non-mirror-image isomers). Enantiomers are pairs of stereoisomers that are mirror images of each other, but cannot be superimposed on one another. Diastereomers, on the other hand, are non-mirror-image stereoisomers that have different physical and chemical properties.

Stereoisomerism is an important concept in chemistry and biology, as it can affect the biological activity of molecules, such as drugs and natural products. For example, some enantiomers of a drug may be active, while others are inactive or even toxic. Therefore, understanding stereoisomerism is crucial for designing and synthesizing effective and safe drugs.

Trypanosoma vivax is a species of protozoan parasite that causes the disease surra in horses, mules, and donkeys, as well as other animals such as camels, dogs, and cats. It belongs to the family Trypanosomatidae and the order Kinetoplastida.

The parasite is transmitted through the bite of infected tsetse flies (Glossina spp.) and occurs in parts of Africa and Asia. The parasites multiply in the bloodstream and lymphatic system of the host, causing symptoms such as fever, anemia, weakness, and edema.

In advanced stages, surra can lead to severe neurological signs, coma, and death if left untreated. Diagnosis is typically made through microscopic examination of blood or tissue samples, and treatment involves the use of drugs such as diminazene accurate or suramin. Prevention measures include avoiding exposure to tsetse flies and using insect repellents or protective clothing.

Cytarabine is a chemotherapeutic agent used in the treatment of various types of cancer, including leukemias and lymphomas. Its chemical name is cytosine arabinoside, and it works by interfering with the DNA synthesis of cancer cells, which ultimately leads to their death.

Cytarabine is often used in combination with other chemotherapy drugs and may be administered through various routes, such as intravenous (IV) or subcutaneous injection, or orally. The specific dosage and duration of treatment will depend on the type and stage of cancer being treated, as well as the patient's overall health status.

Like all chemotherapy drugs, cytarabine can cause a range of side effects, including nausea, vomiting, diarrhea, hair loss, and an increased risk of infection. It may also cause more serious side effects, such as damage to the liver, kidneys, or nervous system, and it is important for patients to be closely monitored during treatment to minimize these risks.

It's important to note that medical treatments should only be administered under the supervision of a qualified healthcare professional, and this information should not be used as a substitute for medical advice.

Uridine Monophosphate (UMP) is a nucleotide that is a constituent of RNA (Ribonucleic Acid). It consists of a nitrogenous base called Uridine, linked to a sugar molecule (ribose) and a phosphate group. UMP plays a crucial role in various biochemical reactions within the body, including energy transfer and cellular metabolism. It is also involved in the synthesis of other nucleotides and serves as an important precursor in the production of genetic material during cell division.

Carrier proteins, also known as transport proteins, are a type of protein that facilitates the movement of molecules across cell membranes. They are responsible for the selective and active transport of ions, sugars, amino acids, and other molecules from one side of the membrane to the other, against their concentration gradient. This process requires energy, usually in the form of ATP (adenosine triphosphate).

Carrier proteins have a specific binding site for the molecule they transport, and undergo conformational changes upon binding, which allows them to move the molecule across the membrane. Once the molecule has been transported, the carrier protein returns to its original conformation, ready to bind and transport another molecule.

Carrier proteins play a crucial role in maintaining the balance of ions and other molecules inside and outside of cells, and are essential for many physiological processes, including nerve impulse transmission, muscle contraction, and nutrient uptake.

An anticodon is a sequence of three ribonucleotides (RNA bases) in a transfer RNA (tRNA) molecule that pair with a complementary codon in a messenger RNA (mRNA) molecule during protein synthesis. This interaction occurs within the ribosome during translation, where the genetic code in the mRNA is translated into an amino acid sequence in a polypeptide. Specifically, each tRNA carries a specific amino acid that corresponds to its anticodon sequence, allowing for the accurate and systematic addition of amino acids to the growing polypeptide chain.

In summary, an anticodon is a crucial component of the translation machinery, facilitating the precise decoding of genetic information and enabling the synthesis of proteins according to the instructions encoded in mRNA molecules.

2-Chloroadenosine is a synthetic, chlorinated analog of adenosine, which is a naturally occurring purine nucleoside. It acts as an antagonist at adenosine receptors and has been studied for its potential effects on the cardiovascular system, including its ability to reduce heart rate and blood pressure. It may also have anti-cancer properties and has been investigated as a potential therapeutic agent in cancer treatment. However, further research is needed to establish its safety and efficacy in clinical settings.

N-Glycosyl hydrolases (or N-glycanases) are a class of enzymes that catalyze the hydrolysis of the glycosidic bond between an N-glycosyl group and an aglycon, which is typically another part of a larger molecule such as a protein or lipid. N-Glycosyl groups refer to carbohydrate moieties attached to an nitrogen atom, usually in the side chain of an amino acid such as asparagine (Asn) in proteins.

N-Glycosyl hydrolases play important roles in various biological processes, including the degradation and processing of glycoproteins, the modification of glycolipids, and the breakdown of complex carbohydrates. These enzymes are widely distributed in nature and have been found in many organisms, from bacteria to humans.

The classification and nomenclature of N-Glycosyl hydrolases are based on the type of glycosidic bond they cleave and the stereochemistry of the reaction they catalyze. They are grouped into different families in the Carbohydrate-Active enZymes (CAZy) database, which provides a comprehensive resource for the study of carbohydrate-active enzymes.

It is worth noting that N-Glycosyl hydrolases can have both beneficial and detrimental effects on human health. For example, they are involved in the normal turnover and degradation of glycoproteins in the body, but they can also contribute to the pathogenesis of certain diseases, such as lysosomal storage disorders, where mutations in N-Glycosyl hydrolases lead to the accumulation of undigested glycoconjugates and cellular damage.

Adenosylhomocysteinase is an enzyme that plays a crucial role in the methionine cycle, which is a biochemical pathway involved in the synthesis and metabolism of various essential molecules in the body. The formal medical definition of adenosylhomocysteinase is:

"An enzyme that catalyzes the reversible conversion of S-adenosylhomocysteine to homocysteine and adenosine. This reaction is the first step in the recycling of methionine, a sulfur-containing amino acid that is essential for various metabolic processes, including the synthesis of proteins, neurotransmitters, and phospholipids."

In simpler terms, adenosylhomocysteinase helps break down S-adenosylhomocysteine, a byproduct of methylation reactions in the body, into its component parts: homocysteine and adenosine. This breakdown is essential for the proper functioning of the methionine cycle and the maintenance of normal levels of homocysteine, which can be toxic at high concentrations.

Deficiencies or mutations in the adenosylhomocysteinase gene can lead to an accumulation of S-adenosylhomocysteine and homocysteine, which can contribute to various health issues, including neurological disorders, cardiovascular disease, and developmental abnormalities.

Dinucleoside phosphates are the chemical compounds that result from the linkage of two nucleosides through a phosphate group. Nucleosides themselves consist of a sugar molecule (ribose or deoxyribose) and a nitrogenous base (adenine, guanine, cytosine, thymine, or uracil). When two nucleosides are joined together by an ester bond between the phosphate group and the 5'-hydroxyl group of the sugar moiety, they form a dinucleoside phosphate.

These compounds play crucial roles in various biological processes, particularly in the context of DNA and RNA synthesis and repair. For instance, dinucleoside phosphates serve as building blocks for the formation of longer nucleic acid chains during replication and transcription. They are also involved in signaling pathways and energy transfer within cells.

It is worth noting that the term "dinucleotides" is sometimes used interchangeably with dinucleoside phosphates, although technically, dinucleotides refer to compounds formed by joining two nucleotides (nucleosides plus one or more phosphate groups) rather than just two nucleosides.

I'm sorry for any confusion, but "Toyocamycin" does not appear to be a recognized term in medical literature or pharmacology. It's possible that there may be a spelling error or it could be a very specialized or obscure term that is not widely known. I would recommend checking the spelling and, if necessary, consulting a specific scientific or medical text or expert for further clarification.

Nucleoside diphosphate sugars (NDP-sugars) are essential activated sugars that play a crucial role in the biosynthesis of complex carbohydrates, such as glycoproteins and glycolipids. They consist of a sugar molecule linked to a nucleoside diphosphate, which is formed from a nucleotide by removal of one phosphate group.

NDP-sugars are created through the action of enzymes called nucleoside diphosphate sugars synthases or transferases, which transfer a sugar molecule from a donor to a nucleoside diphosphate, forming an NDP-sugar. The resulting NDP-sugar can then be used as a substrate for various glycosyltransferases that catalyze the addition of sugars to other molecules, such as proteins or lipids.

NDP-sugars are involved in many important biological processes, including cell signaling, protein targeting, and immune response. They also play a critical role in maintaining the structural integrity of cells and tissues.

Affinity labels are chemical probes or reagents that can selectively and covalently bind to a specific protein or biomolecule based on its biological function or activity. These labels contain a functional group that interacts with the target molecule, often through non-covalent interactions such as hydrogen bonding, van der Waals forces, or ionic bonds. Once bound, the label then forms a covalent bond with the target molecule, allowing for its isolation and further study.

Affinity labels are commonly used in biochemistry and molecular biology research to identify and characterize specific proteins, enzymes, or receptors. They can be designed to bind to specific active sites, binding pockets, or other functional regions of a protein, allowing researchers to study the structure-function relationships of these molecules.

One example of an affinity label is a substrate analogue that contains a chemically reactive group. This type of affinity label can be used to identify and characterize enzymes by binding to their active sites and forming a covalent bond with the enzyme. The labeled enzyme can then be purified and analyzed to determine its structure, function, and mechanism of action.

Overall, affinity labels are valuable tools for studying the properties and functions of biological molecules in vitro and in vivo.

Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst, which remains unchanged at the end of the reaction. A catalyst lowers the activation energy required for the reaction to occur, thereby allowing the reaction to proceed more quickly and efficiently. This can be particularly important in biological systems, where enzymes act as catalysts to speed up metabolic reactions that are essential for life.

Nucleoside diphosphate kinase D (NDKD), also known as NM23-H4, is an enzyme that belongs to the nucleoside diphosphate kinase family. This family of enzymes plays a crucial role in cellular energy metabolism by catalyzing the transfer of phosphate groups between different nucleotides. Specifically, NDKD catalyzes the conversion of nucleoside diphosphates (NDPs) to nucleoside triphosphates (NTPs) and vice versa, using another NTP as a phosphate donor.

NDKD is primarily located in the mitochondria and has been found to be involved in various cellular processes, including DNA replication, repair, and transcription, as well as cell signaling and differentiation. Mutations in the gene encoding NDKD have been associated with certain types of cancer, such as neuroblastoma and hepatocellular carcinoma, suggesting that this enzyme may play a role in tumor suppression or progression. However, further research is needed to fully understand the functional significance of NDKD in these contexts.

Arabinonucleotides are nucleotides that contain arabinose sugar instead of the more common ribose or deoxyribose. Nucleotides are organic molecules consisting of a nitrogenous base, a pentose sugar, and at least one phosphate group. They serve as the monomeric units of nucleic acids, which are essential biopolymers involved in genetic storage, transmission, and expression.

Arabinonucleotides have arabinose, a five-carbon sugar with a slightly different structure than ribose or deoxyribose, as their pentose component. Arabinose is a monosaccharide that can be found in various plants and microorganisms but is not typically a part of nucleic acids in higher organisms.

Arabinonucleotides may have potential applications in biochemistry, molecular biology, and medicine; however, their use and significance are not as widespread or well-studied as those of the more common ribonucleotides and deoxyribonucleotides.

Nucleobase transport proteins are a type of membrane transport protein that facilitate the passive or active transport of nucleobases across biological membranes. Nucleobases, which include adenine, guanine, cytosine, thymine, and uracil, are fundamental components of nucleic acids (DNA and RNA) and are essential for genetic information storage, replication, and expression.

These transport proteins play a crucial role in maintaining the intracellular concentration of nucleobases by enabling their movement between intracellular and extracellular compartments or between cellular organelles. They can be specific to certain nucleobases or operate as broad-specificity transporters, depending on the protein's structure and function.

The transport process may involve uniport (transport of a single type of molecule), symport (coupled transport of multiple types of molecules in the same direction), or antiport (coupled transport of multiple types of molecules in opposite directions). The precise mechanisms governing nucleobase transport protein function are still under investigation, and further research is required to fully understand their regulation and significance in various physiological and pathophysiological contexts.

Pentostatin is a medication used in the treatment of certain types of cancer, including hairy cell leukemia and certain T-cell lymphomas. It is a type of drug called a purine nucleoside analog, which works by interfering with the production of DNA and RNA, the genetic material found in cells. This can help to stop the growth and multiplication of cancer cells.

Pentostatin is given intravenously (through an IV) in a healthcare setting, such as a hospital or clinic. It is usually administered on a schedule of every other week. Common side effects of pentostatin include nausea, vomiting, diarrhea, and loss of appetite. It can also cause more serious side effects, such as low blood cell counts, infections, and liver problems.

It's important to note that this is a medical definition of the drug and its use, and it should not be used as a substitute for professional medical advice. If you have any questions about pentostatin or your treatment, it is best to speak with your healthcare provider.

Nucleic acids are biological macromolecules composed of linear chains of nucleotides. They play crucial roles in the structure and function of cells, serving as the primary information-carrying molecules in all known forms of life. The two main types of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA is responsible for storing genetic information in a stable form that can be passed down from generation to generation, while RNA plays a key role in translating the genetic code stored in DNA into functional proteins.

Each nucleotide consists of a sugar molecule, a phosphate group, and a nitrogenous base. The sugar in DNA is deoxyribose, while in RNA it is ribose. The nitrogenous bases found in both DNA and RNA include adenine (A), guanine (G), and cytosine (C). Thymine (T) is found in DNA, but uracil (U) takes its place in RNA. These nucleotides are linked together by phosphodiester bonds between the sugar of one nucleotide and the phosphate group of another, forming a long, helical structure with backbones made up of alternating sugar and phosphate groups.

The sequence of these nitrogenous bases along the nucleic acid chain encodes genetic information in the form of codons, which are sets of three consecutive bases that specify particular amino acids or signals for protein synthesis. This information is used to direct the synthesis of proteins through a process called transcription (converting DNA to RNA) and translation (converting RNA to protein).

In summary, nucleic acids are essential biomolecules composed of chains of nucleotides that store, transmit, and express genetic information in cells. They consist of two main types: DNA and RNA, which differ in their sugar type, nitrogenous bases, and functions.

Leukemia L1210 is not a medical definition itself, but it refers to a specific mouse leukemia cell line that was established in 1948. These cells are a type of acute myeloid leukemia (AML) and have been widely used in cancer research as a model for studying the disease, testing new therapies, and understanding the biology of leukemia. The L1210 cell line has contributed significantly to the development of various chemotherapeutic agents and treatment strategies for leukemia and other cancers.

Adenosine diphosphate (ADP) is a chemical compound that plays a crucial role in energy transfer within cells. It is a nucleotide, which consists of a adenosine molecule (a sugar molecule called ribose attached to a nitrogenous base called adenine) and two phosphate groups.

In the cell, ADP functions as an intermediate in the conversion of energy from one form to another. When a high-energy phosphate bond in ADP is broken, energy is released and ADP is converted to adenosine triphosphate (ATP), which serves as the main energy currency of the cell. Conversely, when ATP donates a phosphate group to another molecule, it is converted back to ADP, releasing energy for the cell to use.

ADP also plays a role in blood clotting and other physiological processes. In the coagulation cascade, ADP released from damaged red blood cells can help activate platelets and initiate the formation of a blood clot.

Molecular conformation, also known as spatial arrangement or configuration, refers to the specific three-dimensional shape and orientation of atoms that make up a molecule. It describes the precise manner in which bonds between atoms are arranged around a molecular framework, taking into account factors such as bond lengths, bond angles, and torsional angles.

Conformational isomers, or conformers, are different spatial arrangements of the same molecule that can interconvert without breaking chemical bonds. These isomers may have varying energies, stability, and reactivity, which can significantly impact a molecule's biological activity and function. Understanding molecular conformation is crucial in fields such as drug design, where small changes in conformation can lead to substantial differences in how a drug interacts with its target.

Polyphosphates are compounds consisting of many phosphate groups linked together in the form of chains or rings. They are often used in various medical and healthcare applications, such as:

* Dental care products: Polyphosphates can help prevent the formation of dental plaque and calculus by binding to calcium ions in saliva and inhibiting the growth of bacteria that cause tooth decay.
* Nutritional supplements: Polyphosphates are sometimes used as a source of phosphorus in nutritional supplements, particularly for people who have kidney disease or other medical conditions that require them to limit their intake of phosphorus from food sources.
* Medical devices: Polyphosphates may be used in the manufacture of medical devices, such as contact lenses and catheters, to improve their biocompatibility and resistance to bacterial growth.

It's worth noting that while polyphosphates have various medical uses, they can also be found in many non-medical products, such as food additives, water treatment chemicals, and cleaning agents.

Recombinant proteins are artificially created proteins produced through the use of recombinant DNA technology. This process involves combining DNA molecules from different sources to create a new set of genes that encode for a specific protein. The resulting recombinant protein can then be expressed, purified, and used for various applications in research, medicine, and industry.

Recombinant proteins are widely used in biomedical research to study protein function, structure, and interactions. They are also used in the development of diagnostic tests, vaccines, and therapeutic drugs. For example, recombinant insulin is a common treatment for diabetes, while recombinant human growth hormone is used to treat growth disorders.

The production of recombinant proteins typically involves the use of host cells, such as bacteria, yeast, or mammalian cells, which are engineered to express the desired protein. The host cells are transformed with a plasmid vector containing the gene of interest, along with regulatory elements that control its expression. Once the host cells are cultured and the protein is expressed, it can be purified using various chromatography techniques.

Overall, recombinant proteins have revolutionized many areas of biology and medicine, enabling researchers to study and manipulate proteins in ways that were previously impossible.

Deoxyadenine nucleotides are the chemical components that make up DNA, one of the building blocks of life. Specifically, deoxyadenine nucleotides contain a sugar molecule called deoxyribose, a phosphate group, and the nitrogenous base adenine. Adenine always pairs with thymine in DNA through hydrogen bonding. Together, these components form the building blocks of the genetic code that determines many of an organism's traits and characteristics.

Nucleic acid conformation refers to the three-dimensional structure that nucleic acids (DNA and RNA) adopt as a result of the bonding patterns between the atoms within the molecule. The primary structure of nucleic acids is determined by the sequence of nucleotides, while the conformation is influenced by factors such as the sugar-phosphate backbone, base stacking, and hydrogen bonding.

Two common conformations of DNA are the B-form and the A-form. The B-form is a right-handed helix with a diameter of about 20 Å and a pitch of 34 Å, while the A-form has a smaller diameter (about 18 Å) and a shorter pitch (about 25 Å). RNA typically adopts an A-form conformation.

The conformation of nucleic acids can have significant implications for their function, as it can affect their ability to interact with other molecules such as proteins or drugs. Understanding the conformational properties of nucleic acids is therefore an important area of research in molecular biology and medicine.

Cytidine monophosphate (CMP) is a nucleotide that consists of a cytosine molecule attached to a ribose sugar molecule, which in turn is linked to a phosphate group. It is one of the four basic building blocks of RNA (ribonucleic acid) along with adenosine monophosphate (AMP), guanosine monophosphate (GMP), and uridine monophosphate (UMP). CMP plays a critical role in various biochemical reactions within the body, including protein synthesis and energy metabolism.

Hydrogen-ion concentration, also known as pH, is a measure of the acidity or basicity of a solution. It is defined as the negative logarithm (to the base 10) of the hydrogen ion activity in a solution. The standard unit of measurement is the pH unit. A pH of 7 is neutral, less than 7 is acidic, and greater than 7 is basic.

In medical terms, hydrogen-ion concentration is important for maintaining homeostasis within the body. For example, in the stomach, a high hydrogen-ion concentration (low pH) is necessary for the digestion of food. However, in other parts of the body such as blood, a high hydrogen-ion concentration can be harmful and lead to acidosis. Conversely, a low hydrogen-ion concentration (high pH) in the blood can lead to alkalosis. Both acidosis and alkalosis can have serious consequences on various organ systems if not corrected.

Uridine Triphosphate (UTP) is a nucleotide that plays a crucial role in the synthesis and repair of DNA and RNA. It consists of a nitrogenous base called uracil, a pentose sugar (ribose), and three phosphate groups. UTP is one of the four triphosphates used in the biosynthesis of RNA during transcription, where it donates its uracil base to the growing RNA chain. Additionally, UTP serves as an energy source and a substrate in various biochemical reactions within the cell, including phosphorylation processes and the synthesis of glycogen and other molecules.

4-Chloromercuribenzenesulfonate is a chemical compound with the formula C6H5ClHgSO3. It is an organomercury compound, where mercury is bonded to a phenyl ring and a sulfonate group. This compound is an white crystalline powder that is soluble in water and denser than water.

It has been used historically as a diuretic and antiseptic, but its use in medicine has been discontinued due to the toxicity of mercury. Exposure to mercury can have serious health consequences, including damage to the nervous system, kidneys, and digestive system. Therefore, handling and disposal of 4-chloromercuribenzenesulfonate should be done with caution and in accordance with local regulations for hazardous materials.

Indicators and reagents are terms commonly used in the field of clinical chemistry and laboratory medicine. Here are their definitions:

1. Indicator: An indicator is a substance that changes its color or other physical properties in response to a chemical change, such as a change in pH, oxidation-reduction potential, or the presence of a particular ion or molecule. Indicators are often used in laboratory tests to monitor or signal the progress of a reaction or to indicate the end point of a titration. A familiar example is the use of phenolphthalein as a pH indicator in acid-base titrations, which turns pink in basic solutions and colorless in acidic solutions.

2. Reagent: A reagent is a substance that is added to a system (such as a sample or a reaction mixture) to bring about a chemical reaction, test for the presence or absence of a particular component, or measure the concentration of a specific analyte. Reagents are typically chemicals with well-defined and consistent properties, allowing them to be used reliably in analytical procedures. Examples of reagents include enzymes, antibodies, dyes, metal ions, and organic compounds. In laboratory settings, reagents are often prepared and standardized according to strict protocols to ensure their quality and performance in diagnostic tests and research applications.

Molecular cloning is a laboratory technique used to create multiple copies of a specific DNA sequence. This process involves several steps:

1. Isolation: The first step in molecular cloning is to isolate the DNA sequence of interest from the rest of the genomic DNA. This can be done using various methods such as PCR (polymerase chain reaction), restriction enzymes, or hybridization.
2. Vector construction: Once the DNA sequence of interest has been isolated, it must be inserted into a vector, which is a small circular DNA molecule that can replicate independently in a host cell. Common vectors used in molecular cloning include plasmids and phages.
3. Transformation: The constructed vector is then introduced into a host cell, usually a bacterial or yeast cell, through a process called transformation. This can be done using various methods such as electroporation or chemical transformation.
4. Selection: After transformation, the host cells are grown in selective media that allow only those cells containing the vector to grow. This ensures that the DNA sequence of interest has been successfully cloned into the vector.
5. Amplification: Once the host cells have been selected, they can be grown in large quantities to amplify the number of copies of the cloned DNA sequence.

Molecular cloning is a powerful tool in molecular biology and has numerous applications, including the production of recombinant proteins, gene therapy, functional analysis of genes, and genetic engineering.

Adenosine triphosphatases (ATPases) are a group of enzymes that catalyze the conversion of adenosine triphosphate (ATP) into adenosine diphosphate (ADP) and inorganic phosphate. This reaction releases energy, which is used to drive various cellular processes such as muscle contraction, transport of ions across membranes, and synthesis of proteins and nucleic acids.

ATPases are classified into several types based on their structure, function, and mechanism of action. Some examples include:

1. P-type ATPases: These ATPases form a phosphorylated intermediate during the reaction cycle and are involved in the transport of ions across membranes, such as the sodium-potassium pump and calcium pumps.
2. F-type ATPases: These ATPases are found in mitochondria, chloroplasts, and bacteria, and are responsible for generating a proton gradient across the membrane, which is used to synthesize ATP.
3. V-type ATPases: These ATPases are found in vacuolar membranes and endomembranes, and are involved in acidification of intracellular compartments.
4. A-type ATPases: These ATPases are found in the plasma membrane and are involved in various functions such as cell signaling and ion transport.

Overall, ATPases play a crucial role in maintaining the energy balance of cells and regulating various physiological processes.

Inosine monophosphate (IMP) is a nucleotide that plays a crucial role in the metabolic pathways of energy production and purine synthesis in cells. It is an ester of the nucleoside inosine and phosphoric acid. IMP is an important intermediate in the conversion of adenosine monophosphate (AMP) to guanosine monophosphate (GMP) in the purine nucleotide cycle, which is critical for maintaining the balance of purine nucleotides in the body. Additionally, IMP can be converted back to AMP through the action of the enzyme adenylosuccinate lyase. IMP has been studied for its potential therapeutic benefits in various medical conditions, including neurodegenerative disorders and ischemia-reperfusion injury.

Oxazines are heterocyclic organic compounds that contain a six-membered ring with one nitrogen atom, one oxygen atom, and four carbon atoms. The structure of oxazine is similar to benzene, but with one methine group (=CH−) replaced by a nitrogen atom and another methine group replaced by an oxygen atom.

Oxazines have important applications in the pharmaceutical industry as they are used in the synthesis of various drugs, including anti-inflammatory, antiviral, and anticancer agents. However, oxazines themselves do not have a specific medical definition, as they refer to a class of chemical compounds rather than a medical condition or treatment.

Oligodeoxyribonucleotides (ODNs) are relatively short, synthetic single-stranded DNA molecules. They typically contain 15 to 30 nucleotides, but can range from 2 to several hundred nucleotides in length. ODNs are often used as tools in molecular biology research for various applications such as:

1. Nucleic acid detection and quantification (e.g., real-time PCR)
2. Gene regulation (antisense, RNA interference)
3. Gene editing (CRISPR-Cas systems)
4. Vaccine development
5. Diagnostic purposes

Due to their specificity and affinity towards complementary DNA or RNA sequences, ODNs can be designed to target a particular gene or sequence of interest. This makes them valuable tools in understanding gene function, regulation, and interaction with other molecules within the cell.

Benzoxazines are a class of heterocyclic organic compounds that contain a benzene fused to an oxazine ring. They are known for their diverse chemical and pharmacological properties, including anti-inflammatory, antimicrobial, and antitumor activities. Some benzoxazines also exhibit potential as building blocks in the synthesis of pharmaceuticals and materials. However, it is important to note that specific medical definitions for individual compounds within this class may vary depending on their unique structures and properties.

Cytidine diphosphate (CDP) is a nucleotide that is a constituent of coenzymes and plays a role in the synthesis of lipids, such as phosphatidylcholine and sphingomyelin, which are important components of cell membranes. It is formed from cytidine monophosphate (CMP) through the addition of a second phosphate group by the enzyme CTP synthase. CDP can also be converted to other nucleotides, such as uridine diphosphate (UDP) and deoxythymidine diphosphate (dTDP), through the action of various enzymes. These nucleotides play important roles in the biosynthesis of carbohydrates, lipids, and other molecules in the cell.

Ganciclovir is an antiviral medication used to prevent and treat cytomegalovirus (CMV) infections, particularly in individuals who have undergone organ transplants or have weakened immune systems due to conditions like HIV/AIDS. It works by inhibiting the replication of the virus, thereby reducing its ability to cause damage to the body's cells and tissues.

The medical definition of Ganciclovir is:

A synthetic nucleoside analogue with antiviral activity against herpesviruses, including cytomegalovirus (CMV). Ganciclovir is converted intracellularly to its active form, ganciclovir triphosphate, which inhibits viral DNA polymerase and subsequently prevents viral replication. It is primarily used for the prevention and treatment of CMV infections in immunocompromised patients, such as those who have undergone organ transplants or have HIV/AIDS. Ganciclovir is available in various formulations, including oral capsules, intravenous solution, and ocular implants.

Deoxyribose is a type of sugar that makes up the structural backbone of DNA (deoxyribonucleic acid), one of the two main types of nucleic acids in cells. The chemical formula for deoxyribose is C5H10O4, and it has a five-carbon ring structure with four hydroxyl (-OH) groups and one hydrogen atom attached to the carbons.

The key difference between deoxyribose and ribose, which makes up the structural backbone of RNA (ribonucleic acid), is that deoxyribose lacks a hydroxyl group on the second carbon atom in its ring structure. This small difference has significant implications for the structure and function of DNA compared to RNA.

Deoxyribose plays an essential role in the replication, transcription, and repair of genetic material in cells. It forms the sugar-phosphate backbone of DNA by linking with phosphate groups through ester bonds between the 3' carbon atom of one deoxyribose molecule and the 5' carbon atom of another, creating a long, twisted ladder-like structure known as a double helix. The nitrogenous bases adenine, thymine, guanine, and cytosine attach to the 1' carbon atom of each deoxyribose molecule in the DNA strand, forming pairs that are complementary to each other (adenine with thymine and guanine with cytosine).

Overall, deoxyribose is a crucial component of DNA, enabling the storage and transmission of genetic information from one generation to the next.

Virus replication is the process by which a virus produces copies or reproduces itself inside a host cell. This involves several steps:

1. Attachment: The virus attaches to a specific receptor on the surface of the host cell.
2. Penetration: The viral genetic material enters the host cell, either by invagination of the cell membrane or endocytosis.
3. Uncoating: The viral genetic material is released from its protective coat (capsid) inside the host cell.
4. Replication: The viral genetic material uses the host cell's machinery to produce new viral components, such as proteins and nucleic acids.
5. Assembly: The newly synthesized viral components are assembled into new virus particles.
6. Release: The newly formed viruses are released from the host cell, often through lysis (breaking) of the cell membrane or by budding off the cell membrane.

The specific mechanisms and details of virus replication can vary depending on the type of virus. Some viruses, such as DNA viruses, use the host cell's DNA polymerase to replicate their genetic material, while others, such as RNA viruses, use their own RNA-dependent RNA polymerase or reverse transcriptase enzymes. Understanding the process of virus replication is important for developing antiviral therapies and vaccines.

A viral RNA (ribonucleic acid) is the genetic material found in certain types of viruses, as opposed to viruses that contain DNA (deoxyribonucleic acid). These viruses are known as RNA viruses. The RNA can be single-stranded or double-stranded and can exist as several different forms, such as positive-sense, negative-sense, or ambisense RNA. Upon infecting a host cell, the viral RNA uses the host's cellular machinery to translate the genetic information into proteins, leading to the production of new virus particles and the continuation of the viral life cycle. Examples of human diseases caused by RNA viruses include influenza, COVID-19 (SARS-CoV-2), hepatitis C, and polio.

Tritium is not a medical term, but it is a term used in the field of nuclear physics and chemistry. Tritium (symbol: T or 3H) is a radioactive isotope of hydrogen with two neutrons and one proton in its nucleus. It is also known as heavy hydrogen or superheavy hydrogen.

Tritium has a half-life of about 12.3 years, which means that it decays by emitting a low-energy beta particle (an electron) to become helium-3. Due to its radioactive nature and relatively short half-life, tritium is used in various applications, including nuclear weapons, fusion reactors, luminous paints, and medical research.

In the context of medicine, tritium may be used as a radioactive tracer in some scientific studies or medical research, but it is not a term commonly used to describe a medical condition or treatment.

Multiple drug resistance (MDR) in viruses refers to the ability of a virus to resist or inhibit the effects of multiple antiviral agents. This occurs when a virus mutates and develops mechanisms that prevent antiviral drugs from effectively binding to their target sites, rendering the drugs unable to suppress viral replication.

In the context of virology, "multiple" typically means resistance to at least three or more classes of antiviral drugs. This is a significant concern in the management of viral infections such as HIV, HCV, and influenza, where MDR can lead to reduced treatment options, increased risk of disease progression, and potential transmission of resistant strains. Regular monitoring and appropriate use of antiviral agents are crucial for preventing and managing multiple drug resistance in viruses.

Guanine nucleotides are molecules that play a crucial role in intracellular signaling, cellular regulation, and various biological processes within cells. They consist of a guanine base, a sugar (ribose or deoxyribose), and one or more phosphate groups. The most common guanine nucleotides are GDP (guanosine diphosphate) and GTP (guanosine triphosphate).

GTP is hydrolyzed to GDP and inorganic phosphate by certain enzymes called GTPases, releasing energy that drives various cellular functions such as protein synthesis, signal transduction, vesicle transport, and cell division. On the other hand, GDP can be rephosphorylated back to GTP by nucleotide diphosphate kinases, allowing for the recycling of these molecules within the cell.

In addition to their role in signaling and regulation, guanine nucleotides also serve as building blocks for RNA (ribonucleic acid) synthesis during transcription, where they pair with cytosine nucleotides via hydrogen bonds to form base pairs in the resulting RNA molecule.

Coformycin is an antimetabolite antibiotic, which means it interferes with the growth of bacteria by inhibiting the synthesis of nucleic acids, the genetic material of bacteria. It is derived from Streptomyces coelicolor and is used primarily in research to study bacterial metabolism.

Coformycin is a potent inhibitor of bacterial enzyme adenosine deaminase, which is involved in purine biosynthesis. By inhibiting this enzyme, Coformycin prevents the bacteria from synthesizing the building blocks needed to make DNA and RNA, thereby inhibiting their growth.

Coformycin has not been approved for use as a therapeutic drug in humans or animals due to its narrow spectrum of activity and potential toxicity. However, it is still used in research settings to study bacterial metabolism and the mechanisms of antibiotic resistance.

HIV Protease Inhibitors are a class of antiretroviral medications used in the treatment of HIV infection. They work by blocking the activity of the HIV protease enzyme, which is necessary for the virus to replicate and infect new cells. By inhibiting this enzyme, the medication prevents the virus from maturing and assembling into new infectious particles.

HIV protease inhibitors are often used in combination with other antiretroviral drugs as part of a highly active antiretroviral therapy (HAART) regimen. This approach has been shown to effectively suppress viral replication, reduce the amount of virus in the bloodstream (viral load), and improve the health and longevity of people living with HIV.

Examples of HIV protease inhibitors include saquinavir, ritonavir, indinavir, nelfinavir, amprenavir, fosamprenavir, atazanavir, darunavir, and tipranavir. These medications are usually taken orally in the form of tablets or capsules, and may be prescribed alone or in combination with other antiretroviral drugs.

It is important to note that HIV protease inhibitors can have significant side effects, including gastrointestinal symptoms such as nausea, diarrhea, and abdominal pain, as well as metabolic changes such as increased cholesterol and triglyceride levels. Therefore, regular monitoring of liver function, lipid levels, and other health parameters is necessary to ensure safe and effective use of these medications.

Thymidine Monophosphate (TMP or dTMP) is a nucleotide that is a ester of phosphoric acid with thymidine, a nucleoside consisting of deoxyribose sugar linked to the nitrogenous base thymine. It is one of the four monophosphate nucleotides that are the building blocks of DNA, along with adenosine monophosphate (AMP), guanosine monophosphate (GMP), and cytidine monophosphate (CMP). TMP plays a crucial role in DNA replication and repair processes. It is also used as a marker in biochemical research and medical diagnostics.

In the context of medicine, "chemistry" often refers to the field of study concerned with the properties, composition, and structure of elements and compounds, as well as their reactions with one another. It is a fundamental science that underlies much of modern medicine, including pharmacology (the study of drugs), toxicology (the study of poisons), and biochemistry (the study of the chemical processes that occur within living organisms).

In addition to its role as a basic science, chemistry is also used in medical testing and diagnosis. For example, clinical chemistry involves the analysis of bodily fluids such as blood and urine to detect and measure various substances, such as glucose, cholesterol, and electrolytes, that can provide important information about a person's health status.

Overall, chemistry plays a critical role in understanding the mechanisms of diseases, developing new treatments, and improving diagnostic tests and techniques.

DNA-directed DNA polymerase is a type of enzyme that synthesizes new strands of DNA by adding nucleotides to an existing DNA template in a 5' to 3' direction. These enzymes are essential for DNA replication, repair, and recombination. They require a single-stranded DNA template, a primer with a free 3' hydroxyl group, and the four deoxyribonucleoside triphosphates (dNTPs) as substrates to carry out the polymerization reaction.

DNA polymerases also have proofreading activity, which allows them to correct errors that occur during DNA replication by removing mismatched nucleotides and replacing them with the correct ones. This helps ensure the fidelity of the genetic information passed from one generation to the next.

There are several different types of DNA polymerases, each with specific functions and characteristics. For example, DNA polymerase I is involved in both DNA replication and repair, while DNA polymerase III is the primary enzyme responsible for DNA replication in bacteria. In eukaryotic cells, DNA polymerase alpha, beta, gamma, delta, and epsilon have distinct roles in DNA replication, repair, and maintenance.

Adenosine A3 receptor agonists are a type of pharmaceutical compound that bind to and activate the adenosine A3 receptor, which is a type of G-protein coupled receptor found in various tissues throughout the body. Activation of the A3 receptor has been shown to have anti-inflammatory and analgesic effects, making it a target for the development of drugs to treat conditions such as rheumatoid arthritis, inflammatory bowel disease, and chronic pain. Examples of adenosine A3 receptor agonists include IB-MECA, Cl-IB-MECA, and MRS1523.

Oligoribonucleotides are short, synthetic chains of ribonucleotides, which are the building blocks of RNA (ribonucleic acid). These chains typically contain fewer than 20 ribonucleotide units, and can be composed of all four types of nucleotides found in RNA: adenine (A), uracil (U), guanine (G), and cytosine (C). They are often used in research for various purposes, such as studying RNA function, regulating gene expression, or serving as potential therapeutic agents.

Magnesium is an essential mineral that plays a crucial role in various biological processes in the human body. It is the fourth most abundant cation in the body and is involved in over 300 enzymatic reactions, including protein synthesis, muscle and nerve function, blood glucose control, and blood pressure regulation. Magnesium also contributes to the structural development of bones and teeth.

In medical terms, magnesium deficiency can lead to several health issues, such as muscle cramps, weakness, heart arrhythmias, and seizures. On the other hand, excessive magnesium levels can cause symptoms like diarrhea, nausea, and muscle weakness. Magnesium supplements or magnesium-rich foods are often recommended to maintain optimal magnesium levels in the body.

Some common dietary sources of magnesium include leafy green vegetables, nuts, seeds, legumes, whole grains, and dairy products. Magnesium is also available in various forms as a dietary supplement, including magnesium oxide, magnesium citrate, magnesium chloride, and magnesium glycinate.

1. Nucleobase: A nucleobase is one of the basic units that make up the structural components of nucleic acids, such as DNA and RNA. The four nucleobases in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T). In RNA, uracil (U) takes the place of thymine.

2. Nucleoside: A nucleoside is a organic compound that consists of a nucleobase attached to a sugar molecule, either ribose or deoxyribose. The formation of a nucleoside occurs when a nucleobase links to a sugar through a beta-N-glycosidic bond. Nucleosides can be further modified by the addition of phosphate groups to form nucleotides.

3. Nucleotide: A nucleotide is a molecule composed of a nucleobase, a sugar (ribose or deoxyribose), and one or more phosphate groups. Nucleotides are the monomeric units of nucleic acids, with DNA consisting of deoxyribonucleotides and RNA consisting of ribonucleotides. The phosphate group connects to the sugar molecule through an ester bond, creating a phosphodiester linkage between nucleotides that forms the backbone of a nucleic acid polymer.

4. Nucleobase, Nucleoside, Nucleotide, and Nucleic Acid Transport Proteins: These proteins are responsible for the translocation of nucleobases, nucleosides, nucleotides, and/or nucleic acids across biological membranes. They facilitate the movement of these molecules between intracellular and extracellular spaces or within different cellular compartments. These transport proteins can be classified into various categories based on their structure, mechanism, and energy requirements. Examples include equilibrative nucleoside transporters (ENTs), concentrative nucleoside transporters (CNTs), nucleobase transporters, and nucleic acid transporters. Dysfunction of these transport proteins can lead to various diseases, including neurological disorders, cancer, and viral infections.

Spectrophotometry, Ultraviolet (UV-Vis) is a type of spectrophotometry that measures how much ultraviolet (UV) and visible light is absorbed or transmitted by a sample. It uses a device called a spectrophotometer to measure the intensity of light at different wavelengths as it passes through a sample. The resulting data can be used to determine the concentration of specific components within the sample, identify unknown substances, or evaluate the physical and chemical properties of materials.

UV-Vis spectroscopy is widely used in various fields such as chemistry, biology, pharmaceuticals, and environmental science. It can detect a wide range of substances including organic compounds, metal ions, proteins, nucleic acids, and dyes. The technique is non-destructive, meaning that the sample remains unchanged after the measurement.

In UV-Vis spectroscopy, the sample is placed in a cuvette or other container, and light from a source is directed through it. The light then passes through a monochromator, which separates it into its component wavelengths. The monochromatic light is then directed through the sample, and the intensity of the transmitted or absorbed light is measured by a detector.

The resulting absorption spectrum can provide information about the concentration and identity of the components in the sample. For example, if a compound has a known absorption maximum at a specific wavelength, its concentration can be determined by measuring the absorbance at that wavelength and comparing it to a standard curve.

Overall, UV-Vis spectrophotometry is a versatile and powerful analytical technique for quantitative and qualitative analysis of various samples in different fields.

Chemical phenomena refer to the changes and interactions that occur at the molecular or atomic level when chemicals are involved. These phenomena can include chemical reactions, in which one or more substances (reactants) are converted into different substances (products), as well as physical properties that change as a result of chemical interactions, such as color, state of matter, and solubility. Chemical phenomena can be studied through various scientific disciplines, including chemistry, biochemistry, and physics.

Diphosphates, also known as pyrophosphates, are chemical compounds that contain two phosphate groups joined together by an oxygen atom. The general formula for a diphosphate is P~PO3~2-, where ~ represents a bond. Diphosphates play important roles in various biological processes, such as energy metabolism and cell signaling. In the context of nutrition, diphosphates can be found in some foods, including milk and certain vegetables.

Sequence homology, amino acid, refers to the similarity in the order of amino acids in a protein or a portion of a protein between two or more species. This similarity can be used to infer evolutionary relationships and functional similarities between proteins. The higher the degree of sequence homology, the more likely it is that the proteins are related and have similar functions. Sequence homology can be determined through various methods such as pairwise alignment or multiple sequence alignment, which compare the sequences and calculate a score based on the number and type of matching amino acids.

Inborn errors of purine-pyrimidine metabolism refer to genetic disorders that result in dysfunctional enzymes involved in the metabolic pathways of purines and pyrimidines. These are essential components of nucleotides, which in turn are building blocks of DNA and RNA.

Inherited as autosomal recessive or X-linked recessive traits, these disorders can lead to an accumulation of toxic metabolites, a deficiency of necessary compounds, or both. Clinical features vary widely depending on the specific enzyme defect but may include neurologic symptoms, kidney problems, gout, and/or immunodeficiency.

Examples of such disorders include Lesch-Nyhan syndrome (deficiency of hypoxanthine-guanine phosphoribosyltransferase), adenosine deaminase deficiency (leading to severe combined immunodeficiency), and orotic aciduria (due to defects in pyrimidine metabolism). Early diagnosis and management are crucial to improve outcomes.

Erythrocytes, also known as red blood cells (RBCs), are the most common type of blood cell in circulating blood in mammals. They are responsible for transporting oxygen from the lungs to the body's tissues and carbon dioxide from the tissues to the lungs.

Erythrocytes are formed in the bone marrow and have a biconcave shape, which allows them to fold and bend easily as they pass through narrow blood vessels. They do not have a nucleus or mitochondria, which makes them more flexible but also limits their ability to reproduce or repair themselves.

In humans, erythrocytes are typically disc-shaped and measure about 7 micrometers in diameter. They contain the protein hemoglobin, which binds to oxygen and gives blood its red color. The lifespan of an erythrocyte is approximately 120 days, after which it is broken down in the liver and spleen.

Abnormalities in erythrocyte count or function can lead to various medical conditions, such as anemia, polycythemia, and sickle cell disease.

Pyrimidines are heterocyclic aromatic organic compounds similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring. They are one of the two types of nucleobases found in nucleic acids, the other being purines. The pyrimidine bases include cytosine (C) and thymine (T) in DNA, and uracil (U) in RNA, which pair with guanine (G) and adenine (A), respectively, through hydrogen bonding to form the double helix structure of nucleic acids. Pyrimidines are also found in many other biomolecules and have various roles in cellular metabolism and genetic regulation.

Uridine diphosphate (UDP) is a nucleotide diphosphate that consists of a pyrophosphate group, a ribose sugar, and the nucleobase uracil. It plays a crucial role as a coenzyme in various biosynthetic reactions, including the synthesis of glycogen, proteoglycans, and other polysaccharides. UDP is also involved in the detoxification of bilirubin, an end product of hemoglobin breakdown, by converting it to a water-soluble form that can be excreted through the bile. Additionally, UDP serves as a precursor for the synthesis of other nucleotides and their derivatives.

X-ray crystallography is a technique used in structural biology to determine the three-dimensional arrangement of atoms in a crystal lattice. In this method, a beam of X-rays is directed at a crystal and diffracts, or spreads out, into a pattern of spots called reflections. The intensity and angle of each reflection are measured and used to create an electron density map, which reveals the position and type of atoms in the crystal. This information can be used to determine the molecular structure of a compound, including its shape, size, and chemical bonds. X-ray crystallography is a powerful tool for understanding the structure and function of biological macromolecules such as proteins and nucleic acids.

Inosine nucleotides are chemical compounds that play a role in the metabolism of nucleic acids, which are the building blocks of DNA and RNA. Inosine is a purine nucleoside that is formed when adenosine (a normal component of DNA and RNA) is deaminated, or has an amino group (-NH2) removed from its structure.

Inosine nucleotides are important in the salvage pathway of nucleotide synthesis, which allows cells to recycle existing nucleotides rather than synthesizing them entirely from scratch. Inosine nucleotides can be converted back into adenosine nucleotides through a process called reversal of deamination.

Inosine nucleotides also have important functions in the regulation of gene expression and in the response to cellular stress. For example, they can act as signaling molecules that activate various enzymes and pathways involved in DNA repair, apoptosis (programmed cell death), and other cellular processes.

Inosine nucleotides have been studied for their potential therapeutic uses in a variety of conditions, including neurological disorders, cancer, and viral infections. However, more research is needed to fully understand their mechanisms of action and potential benefits.

Inosine triphosphate (ITP) is not a medical condition, but rather a biochemical compound that plays a role in the body's energy metabolism and nucleic acid synthesis. It is an ester of inosine and triphosphoric acid. ITP can be produced from adenosine triphosphate (ATP) by the action of enzymes such as adenylate kinase or nucleoside diphosphate kinase, and it can also be degraded back to inosine monophosphate (IMP) by the enzyme ITP pyrophosphatase.

In certain disease states, such as some types of anemia, there may be an accumulation of ITP due to impaired breakdown. However, ITP is not typically used as a diagnostic or clinical marker in these conditions.

Adenosine A3 receptor (A3R) is a type of G-protein coupled receptor that binds to adenosine, a purine nucleoside, and plays a role in various physiological processes. The activation of A3R leads to the inhibition of adenylate cyclase activity, which results in decreased levels of intracellular cAMP. This, in turn, modulates several downstream signaling pathways that are involved in anti-inflammatory and neuroprotective effects.

A3R is widely expressed in various tissues, including the brain, heart, lungs, liver, kidneys, and immune cells. In the central nervous system, A3R activation has been shown to have neuroprotective effects, such as reducing glutamate release, protecting against excitotoxicity, and modulating neuroinflammation. Additionally, A3R agonists have been investigated for their potential therapeutic benefits in various pathological conditions, including pain management, ischemia-reperfusion injury, and neurodegenerative diseases.

Overall, the Adenosine A3 receptor is an important target for drug development due to its role in modulating inflammation and cellular responses in various tissues and diseases.

Bacterial RNA refers to the genetic material present in bacteria that is composed of ribonucleic acid (RNA). Unlike higher organisms, bacteria contain a single circular chromosome made up of DNA, along with smaller circular pieces of DNA called plasmids. These bacterial genetic materials contain the information necessary for the growth and reproduction of the organism.

Bacterial RNA can be divided into three main categories: messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA). mRNA carries genetic information copied from DNA, which is then translated into proteins by the rRNA and tRNA molecules. rRNA is a structural component of the ribosome, where protein synthesis occurs, while tRNA acts as an adapter that brings amino acids to the ribosome during protein synthesis.

Bacterial RNA plays a crucial role in various cellular processes, including gene expression, protein synthesis, and regulation of metabolic pathways. Understanding the structure and function of bacterial RNA is essential for developing new antibiotics and other therapeutic strategies to combat bacterial infections.

"Cells, cultured" is a medical term that refers to cells that have been removed from an organism and grown in controlled laboratory conditions outside of the body. This process is called cell culture and it allows scientists to study cells in a more controlled and accessible environment than they would have inside the body. Cultured cells can be derived from a variety of sources, including tissues, organs, or fluids from humans, animals, or cell lines that have been previously established in the laboratory.

Cell culture involves several steps, including isolation of the cells from the tissue, purification and characterization of the cells, and maintenance of the cells in appropriate growth conditions. The cells are typically grown in specialized media that contain nutrients, growth factors, and other components necessary for their survival and proliferation. Cultured cells can be used for a variety of purposes, including basic research, drug development and testing, and production of biological products such as vaccines and gene therapies.

It is important to note that cultured cells may behave differently than they do in the body, and results obtained from cell culture studies may not always translate directly to human physiology or disease. Therefore, it is essential to validate findings from cell culture experiments using additional models and ultimately in clinical trials involving human subjects.

Thin-layer chromatography (TLC) is a type of chromatography used to separate, identify, and quantify the components of a mixture. In TLC, the sample is applied as a small spot onto a thin layer of adsorbent material, such as silica gel or alumina, which is coated on a flat, rigid support like a glass plate. The plate is then placed in a developing chamber containing a mobile phase, typically a mixture of solvents.

As the mobile phase moves up the plate by capillary action, it interacts with the stationary phase and the components of the sample. Different components of the mixture travel at different rates due to their varying interactions with the stationary and mobile phases, resulting in distinct spots on the plate. The distance each component travels can be measured and compared to known standards to identify and quantify the components of the mixture.

TLC is a simple, rapid, and cost-effective technique that is widely used in various fields, including forensics, pharmaceuticals, and research laboratories. It allows for the separation and analysis of complex mixtures with high resolution and sensitivity, making it an essential tool in many analytical applications.

A dose-response relationship in the context of drugs refers to the changes in the effects or symptoms that occur as the dose of a drug is increased or decreased. Generally, as the dose of a drug is increased, the severity or intensity of its effects also increases. Conversely, as the dose is decreased, the effects of the drug become less severe or may disappear altogether.

The dose-response relationship is an important concept in pharmacology and toxicology because it helps to establish the safe and effective dosage range for a drug. By understanding how changes in the dose of a drug affect its therapeutic and adverse effects, healthcare providers can optimize treatment plans for their patients while minimizing the risk of harm.

The dose-response relationship is typically depicted as a curve that shows the relationship between the dose of a drug and its effect. The shape of the curve may vary depending on the drug and the specific effect being measured. Some drugs may have a steep dose-response curve, meaning that small changes in the dose can result in large differences in the effect. Other drugs may have a more gradual dose-response curve, where larger changes in the dose are needed to produce significant effects.

In addition to helping establish safe and effective dosages, the dose-response relationship is also used to evaluate the potential therapeutic benefits and risks of new drugs during clinical trials. By systematically testing different doses of a drug in controlled studies, researchers can identify the optimal dosage range for the drug and assess its safety and efficacy.

Thymidine phosphorylase (TP) is an enzyme that plays a role in the metabolism of nucleosides, specifically thymidine. The medical definition of thymidine phosphorylase is:

An enzyme that catalyzes the conversion of thymidine to thymine and deoxyribose-1-phosphate. Thymidine phosphorylase has been identified as a key enzyme in the angiogenic (formation of new blood vessels) pathway, where it facilitates the release of pro-angiogenic factors such as vascular endothelial growth factor (VEGF).

In addition to its role in nucleoside metabolism and angiogenesis, thymidine phosphorylase has been implicated in cancer biology. Increased levels of thymidine phosphorylase have been found in various human cancers, including colorectal, breast, lung, and pancreatic cancers. These high levels of thymidine phosphorylase are associated with poor prognosis and increased angiogenesis, contributing to tumor growth and metastasis.

Thus, thymidine phosphorylase is a crucial enzyme in nucleoside metabolism, angiogenesis, and cancer biology, making it an important target for the development of novel anti-cancer therapies.

Guanine Deaminase is an enzyme that catalyzes the chemical reaction in which guanine, one of the four nucleotides that make up DNA and RNA, is deaminated to form xanthine. This reaction is part of the purine catabolism pathway, which is the breakdown of purines to produce energy and eliminate nitrogenous waste. The gene that encodes this enzyme in humans is located on chromosome 2 and is called GDA. Deficiency in guanine deaminase has been associated with Lesch-Nyhan syndrome, a rare genetic disorder characterized by mental retardation, self-mutilation, spasticity, and uric acid overproduction.

2-Aminopurine is a fluorescent purine analog, which means it is a compound that is similar in structure to the naturally occurring molecule called purines, which are building blocks of DNA and RNA. 2-Aminopurine is used in research to study the structure and function of nucleic acids (DNA and RNA) due to its fluorescent properties. It can be incorporated into oligonucleotides (short stretches of nucleic acids) to allow for the monitoring of interactions between nucleic acids, such as during DNA replication or transcription. The fluorescence of 2-Aminopurine changes upon excitation with light and can be used to detect structural changes in nucleic acids or to measure the distance between two fluorophores.

Lactic acidosis is a medical condition characterized by an excess accumulation of lactic acid in the body. Lactic acid is a byproduct produced in the muscles and other tissues during periods of low oxygen supply or increased energy demand. Under normal circumstances, lactic acid is quickly metabolized and cleared from the body. However, when the production of lactic acid exceeds its clearance, it can lead to a state of acidosis, where the pH of the blood becomes too acidic.

Lactic acidosis can be caused by several factors, including:

* Prolonged exercise or strenuous physical activity
* Severe illness or infection
* Certain medications, such as metformin and isoniazid
* Alcoholism
* Hypoxia (low oxygen levels) due to lung disease, heart failure, or anemia
* Inherited metabolic disorders that affect the body's ability to metabolize lactic acid

Symptoms of lactic acidosis may include rapid breathing, fatigue, muscle weakness, nausea, vomiting, and abdominal pain. Severe cases can lead to coma, organ failure, and even death. Treatment typically involves addressing the underlying cause of the condition and providing supportive care, such as administering intravenous fluids and bicarbonate to help restore normal pH levels.

Acyclic hydrocarbons, also known as aliphatic hydrocarbons, are organic compounds consisting entirely of hydrogen and carbon atoms. They are characterized by the absence of aromatic rings or cyclic structures in their molecular structure. Instead, they contain open chains of carbon atoms that are saturated (containing only single bonds) or unsaturated (containing double or triple bonds).

Acyclic hydrocarbons can be further classified into several subcategories based on the nature and arrangement of their carbon-carbon bonds. These include:

* Alkanes: saturated acyclic hydrocarbons with only single bonds between carbon atoms (e.g., methane, ethane, propane, butane)
* Alkenes: unsaturated acyclic hydrocarbons containing at least one carbon-carbon double bond (e.g., ethene, propene, butene)
* Alkynes: unsaturated acyclic hydrocarbons containing at least one carbon-carbon triple bond (e.g., ethyne, propyne, butyne)

Acyclic hydrocarbons are important components of fossil fuels such as natural gas, crude oil, and coal. They are also used in the production of a wide range of chemicals, materials, and consumer products, including plastics, synthetic fibers, solvents, and fuels.

I'm sorry for any confusion, but 'Lactobacillus leichmannii' is not a currently valid species name in the genus Lactobacillus. It was previously used to refer to a particular species of lactic acid bacteria, but recent taxonomic revisions have led to its renaming. The organism that was once known as 'Lactobacillus leichmannii' is now classified as Lacticaseibacillus rhamnosus.

Lacticaseibacillus rhamnosus is a gram-positive, facultatively anaerobic, non-spore forming rod that produces lactic acid as one of its major end products. It's commonly found in the human gastrointestinal tract and is often used in various industrial applications, including food production and probiotics.

Trifluridine is an antiviral medication that is primarily used to treat herpetic keratitis, which is a viral infection of the eye caused by the herpes simplex virus. It works by interfering with the replication of the virus's DNA, thereby preventing it from multiplying and causing further damage to the eye.

Trifluridine is available as an ophthalmic solution (eye drops) and is typically applied directly to the affected eye every 2 hours while awake, for a total of 9 doses per day. The treatment period usually lasts for up to 14 days or until the symptoms have resolved.

It's important to note that trifluridine is not used to treat other forms of herpes simplex infections, such as cold sores or genital herpes, and should only be used under the supervision of a healthcare professional.

... are derivatives of the nucleosides. They contain - in contrast to most nucleosides - instead of the β-D- ... v t e (Nucleosides, Arabinosides, All stub articles, Organic chemistry stubs). ... "Rational design of arabinosyl nucleosides as antitumor and antiviral agents", Jpn J Antibiot. 1977 Dec;30 Suppl:104-120; PMID ...
Heating the blocked nucleoside in Eq. (6) in the presence of a protected sugar chloride provides the nucleoside in 59% yield. ... 4)). Glycosylation of thymine with protected 1-acetoxy ribose produced 60% of the N1 nucleoside and 23% of the N3 nucleoside. ... yielding the desired β-nucleoside 2. A second reaction of this nucleoside with 1 generates bis(riboside) 3. Depending on the ... is the most common method for forming nucleosides in this manner. Nucleosides are typically synthesized through the coupling of ...
... is a monthly academic journal published by Taylor & Francis since 2000, continuing the ... earlier Nucleosides and Nucleotides in series. It discusses topics relating to the biochemistry of molecules in these classes. ...
Nucleosides are glycosylamines that can be thought of as nucleotides without a phosphate group. A nucleoside consists simply of ... Arabinosyl nucleosides Nucleobase Salvage enzyme Synthesis of nucleosides Ramesh, Deepthi; Vijayakumar, Balaji Gowrivel; Kannan ... into nucleosides (such as thymidine) and phosphate. The nucleosides, in turn, are subsequently broken down in the lumen of the ... In a nucleoside, the anomeric carbon is linked through a glycosidic bond to the N9 of a purine or the N1 of a pyrimidine. ...
Nucleoside analogues are nucleosides that are structurally similar (analogous) to the nucleosides used in DNA and RNA synthesis ... A nucleoside triphosphate is a nucleoside containing a nitrogenous base bound to a 5-carbon sugar (either ribose or deoxyribose ... Nucleoside analogues may also be used to treat viral infections. For example, azidothymidine (AZT) is a nucleoside analogue ... Nucleoside triphosphates cannot be absorbed well, so all nucleoside triphosphates are typically made de novo. The synthesis of ...
... s (NTs) are a group of membrane transport proteins which transport nucleoside substrates like adenosine ... There are two known types of nucleoside transporters, concentrative nucleoside transporters (CNTs; SLC28) and equilibrative ... "Physiological and pharmacological roles of nucleoside transporter proteins". Nucleosides, Nucleotides & Nucleic Acids. 27 (6): ... Baldwin SA, Beal PR, Yao SY, King AE, Cass CE, Young JD (February 2004). "The equilibrative nucleoside transporter family, ...
Carbocyclic nucleosides were originally limited to a five-membered ring system, matching the ring-size of the nucleosides; ... Carbocyclic nucleosides (also referred to as carbanucleosides) are nucleoside analogues in which a methylene group has replaced ... There are two approaches used in the synthesis of carbocyclic nucleosides. Linear approaches to chiral carbocyclic nucleosides ... Zhu XF (March 2000). "The latest progress in the synthesis of carbocyclic nucleosides". Nucleosides, Nucleotides & Nucleic ...
This enzyme is also called nucleoside N-ribosyltransferase. Koch AL (November 1956). "Some enzymes of nucleoside metabolism of ... In enzymology, a nucleoside ribosyltransferase (EC 2.4.2.5) is an enzyme that catalyzes the chemical reaction D-ribosyl-base1 ... The systematic name of this enzyme class is nucleoside:purine(pyrimidine) D-ribosyltransferase. ...
Lysidine is an uncommon nucleoside, rarely seen outside of tRNA. It is a derivative of cytidine in which the carbonyl is ... Sonawane, Kailas D.; Tewari, Ravindra (19 September 2008). "Conformational Preferences of Hypermodified Nucleoside Lysidine ( ... k2C) Occurring at 'Wobble' Position in Anticodon Loop of tRNAIle". Nucleosides, Nucleotides & Nucleic Acids. 27 (10-11): 1158- ...
... (EC 1.1.3.28) is an enzyme with systematic name nucleoside:oxygen 5'-oxidoreductase. This enzyme catalyses ... Nucleoside+oxidase at the U.S. National Library of Medicine Medical Subject Headings (MeSH) Portal: Biology (EC 1.1.3). ... Isono Y, Sudo T, Hoshino M (1989). "Purification and reaction of a new enzyme, nucleoside oxidase". Agric. Biol. Chem. 53: 1663 ... Isono Y, Sudo T, Hoshino M (1989). "Properties of a new enzyme, nucleoside oxidase, from Pseudomonas maltophilia LB-86". Agric ...
Other names in common use include nucleoside triphosphate phosphohydrolase, nucleoside-5-triphosphate phosphohydrolase, and ... In enzymology, a nucleoside-triphosphatase (NTPase) (EC 3.6.1.15) is an enzyme that catalyzes the chemical reaction NTP + H2O ... LEWIS M, WEISSMAN S (1965). "Properties of a soluble nucleoside triphosphatase activity in mammalian liver". Arch. Biochem. ... Matsushita S, Raacke ID (1968). "Purification of nucleoside triphosphatases from pea seedling ribosomes". Biochim. Biophys. ...
In enzymology, a nucleoside phosphotransferase (EC 2.7.1.77) is an enzyme that catalyzes the chemical reaction a nucleotide + a ... The systematic name of this enzyme class is nucleotide:nucleoside 5'-phosphotransferase. Other names in common use include ... Prasher DC, Carr MC, Ives DH, Tsai TC, Frey PA (1982). "Nucleoside phosphotransferase from barley. Characterization and ... Brunngraber EF, Chargaff E (1967). "Purification and properties of a nucleoside phosphotransferase from carrot". J. Biol. Chem ...
... s are structural analogues of a nucleoside, which normally contain a nucleobase and a sugar. Nucleotide ... so it is possible to design nucleoside analogues that are preferentially incorporated by the former. Some nucleoside analogues ... Since nucleoside analogues require two phosphorylations to be activated, one carried out by a viral enzyme and the other by ... Nucleoside and nucleotide analogues can be used in therapeutic drugs, including a range of antiviral products used to prevent ...
... type B nucleoside diphosphatase, GDPase, CDPase, nucleoside 5'-diphosphatase, type L nucleoside diphosphatase, NDPase, and ... In enzymology, a nucleoside-diphosphatase (EC 3.6.1.6) is an enzyme that catalyzes the chemical reaction a nucleoside ... The systematic name of this enzyme class is nucleoside-diphosphate phosphohydrolase. Other names in common use include thiamine ... GIBSON DM, AYENGAR P, SANADI DR (1955). "A phosphatase specific for nucleoside diphosphates". Biochim. Biophys. Acta. 16 (4): ...
In enzymology, a nucleoside phosphoacylhydrolase (EC 3.6.1.24) is an enzyme that catalyzes the chemical reaction Hydrolyses ... Spahr PF, Gesteland RF (1970). "Purification and properties of a new enzyme from Escherichia coli: nucleoside phosphocyl ... The systematic name of this enzyme class is nucleoside-5'-phosphoacylate acylhydrolase. ...
... s are derivatives of natural or synthetic nucleosides. They are used to synthesize oligonucleotides, ... nucleosides modified at the 2'-position (OMe, protected NH2, F), nucleosides containing non-canonical bases (hypoxanthine and ... derivatives of nucleosides (nucleoside phosphoramidites) that serve as building blocks in phosphite triester methodology. To ... RO)2P-N(R1)2 + R2-N3 + H2O ---- (RO)2P(=O)-N(R1)2 + R2-NH2 + N2; The naturally occurring nucleotides (nucleoside-3'- or 5'- ...
... nucleoside trans-N-deoxyribosylase, trans-deoxyribosylase, trans-N-deoxyribosylase, trans-N-glycosidase, nucleoside ... nucleoside deoxyribosyltransferase II [purine(pyrimidine), and nucleoside:purine(pyrimidine) deoxyribosyltransferase]. This ... In enzymology, a nucleoside deoxyribosyltransferase (EC 2.4.2.6) is an enzyme that catalyzes the chemical reaction 2-deoxy-D- ... The systematic name of this enzyme class is nucleoside:purine(pyrimidine) deoxy-D-ribosyltransferase. Other names in common use ...
"Purification and characterization of purine nucleoside phosphorylase and pyrimidine nucleoside phosphorylase from Bacillus ... In enzymology, a pyrimidine-nucleoside phosphorylase (EC 2.4.2.2) is an enzyme that catalyzes the chemical reaction a ... The systematic name of this enzyme class is pyrimidine-nucleoside:phosphate alpha-D-ribosyltransferase. This enzyme is also ... Saunders PP, Wilson BA, Saunders GF (1969). "Purification and comparative properties of a pyrimidine nucleoside phosphorylase ...
The systematic name of this enzyme class is nucleoside-triphosphate diphosphohydrolase. This enzyme is also called nucleoside- ... In enzymology, a nucleoside-triphosphate diphosphatase (EC 3.6.1.19) is an enzyme that catalyzes the chemical reaction a ... Chern CJ, MacDonald AB, Morris AJ (1969). "Purification and properties of a nucleoside triphosphate pyrophosphohydrolase from ... the two substrates of this enzyme are nucleoside triphosphate and H2O, whereas its two products are nucleotide and diphosphate ...
... and functions as a substrate-specific channel for nucleosides and deoxy-nucleosides. The protein contains 294 amino acids, the ... Nucleoside-specific porin (the tsx gene of Escherichia coli) is an outer membrane protein, Tsx, which constitutes the receptor ... Bremer E, Martinussen J, Middendorf A, Valentin-Hansen P (1990). "Analysis of the tsx gene, which encodes a nucleoside-specific ...
In enzymology, a nucleoside-phosphate kinase (EC 2.7.4.4) is an enzyme that catalyzes the chemical reaction ATP + nucleoside ... the two substrates of this enzyme are ATP and nucleoside monophosphate, whereas its two products are ADP and nucleoside ... This enzyme is also called NMP-kinase, or nucleoside-monophosphate kinase. A number of crystal structures have been solved for ... Nucleoside monophosphate binding induces further changes that render the enzyme catalytically capable of facilitating a ...
SLC28A1 is a Na+-dependent nucleoside transporter selective for pyrimidine nucleosides and adenosine. It also transports the ... Human concentrative nucleoside transporters include SLC28A1, SLC28A2 and SLC28A3 proteins. SLC28A2 is a purine-specific Na+- ... nucleoside cotransporter". The Journal of Biological Chemistry. 270 (23): 13596-9. doi:10.1074/jbc.270.23.13596. PMID 7775409. ... "Cloning and functional expression of a complementary DNA encoding a mammalian nucleoside transport protein". The Journal of ...
Nucleoside phosphorylase is an enzyme which cleaves a nucleoside by phosphorylating the ribose to produce a nucleobase and ... Purine nucleoside phosphorylase, PNP, PNPase or inosine phosphorylase (EC 2.4.2.1) is an enzyme that in humans is encoded by ... Purine nucleoside phosphorylase deficiency Canduri F, dos Santos DM, Silva RG, Mendes MA, Basso LA, Palma MS, de Azevedo WF, ... Borgers M, Verhaegen H, De Brabander M, De Cree J, De Cock W, Thoné F, Geuens G (Nov 1978). "Purine nucleoside phosphorylase in ...
Nucleoside diphosphate kinase activity involves the transfer of the γ-phosphate of nucleoside triphosphate (NTP) to nucleoside ... Nucleoside Nucleotide Nucleoside monophosphate Nucleoside triphosphate Thymidine kinase Thymidylate kinase Thymidine kinase in ... Nucleoside-diphosphate kinases (NDPKs, also NDP kinase, (poly)nucleotide kinases and nucleoside diphosphokinases) are enzymes ... Nucleoside-Diphosphate+Kinase at the U.S. National Library of Medicine Medical Subject Headings (MeSH) EC 2.7.4.6 Portal: ...
Solute carrier family Equilibrative nucleoside transporters Nucleoside transporters Augustine blood group system GRCh38: ... Nucleoside transporters are required for nucleotide synthesis in cells that lack de novo nucleoside synthesis pathways, and are ... "A single glycine mutation in the equilibrative nucleoside transporter gene, hENT1, alters nucleoside transport activity and ... Equilibrative nucleoside transporter 1 (ENT1) is a protein that in humans is encoded by the SLC29A1 gene. Multiple ...
Mangravite LM, Badagnani I, Giacomini KM (2004). "Nucleoside transporters in the disposition and targeting of nucleoside ... Solute carrier family Equilibrative nucleoside transporters Nucleoside transporters GRCh38: Ensembl release 89: ENSG00000174669 ... Equilibrative nucleoside transporter 2 (ENT2) is a protein that in humans is encoded by the SLC29A2 gene. ... 2004). "The equilibrative nucleoside transporter family, SLC29". Pflügers Arch. 447 (5): 735-43. doi:10.1007/s00424-003-1103-2 ...
In enzymology, a diphosphate-purine nucleoside kinase (EC 2.7.1.143) is an enzyme that catalyzes the chemical reaction ... The systematic name of this enzyme class is diphosphate:purine nucleoside phosphotransferase. This enzyme is also called ... Tryon VV, Pollack D (1984). "Purine metabolism in Acholeplasma laidlawii B: novel PPi-dependent nucleoside kinase activity". J ... Tryon VV, Pollack JD (1985). "Distinctions in Mollicutes purine metabolism: pyrophosphate-dependent nucleoside kinase and ...
Concentrative nucleoside transporters Nucleoside transporters Solute carrier family GRCh38: Ensembl release 89: ENSG00000156222 ... 2004). "Transport of physiological nucleosides and anti-viral and anti-neoplastic nucleoside drugs by recombinant Escherichia ... Concentrative nucleoside transporter 1 (CNT1) is a protein that in humans is encoded by the SLC28A1 gene. ... 2004). "Nucleoside transporter profiles in human pancreatic cancer cells: role of hCNT1 in 2',2'-difluorodeoxycytidine- induced ...
Concentrative nucleoside transporters Nucleoside transporters Solute carrier family GRCh38: Ensembl release 89: ENSG00000137860 ... "Molecular determinants of specificity for synthetic nucleoside analogs in the concentrative nucleoside transporter, CNT2". J. ... Concentrative nucleoside transporter 2 (CNT2) is a protein that in humans is encoded by the SLC28A2 gene. ... Wang J, Su SF, Dresser MJ, Schaner ME, Washington CB, Giacomini KM (Feb 1998). "Na(+)-dependent purine nucleoside transporter ...
... (EC 1.1.3.39) is an enzyme with systematic name nucleoside:oxygen 5'-oxidoreductase (H2O2- ... Nucleoside+oxidase+(H2O2-forming) at the U.S. National Library of Medicine Medical Subject Headings (MeSH) Portal: Biology (EC ... Koga S, Ogawa J, Cheng L, Choi Y, Yamada H, Shimizu S (November 1997). "Nucleoside Oxidase, a Hydrogen Peroxide-Forming Oxidase ...
Arabinosyl nucleosides are derivatives of the nucleosides. They contain - in contrast to most nucleosides - instead of the β-D- ... v t e (Nucleosides, Arabinosides, All stub articles, Organic chemistry stubs). ... "Rational design of arabinosyl nucleosides as antitumor and antiviral agents", Jpn J Antibiot. 1977 Dec;30 Suppl:104-120; PMID ...
Nucleosides, Nucleotides and Nucleic Acids Publication Information. Title. Nucleosides, Nucleotides and Nucleic Acids [English] ...
PURINE NUCLEOSIDE PHOSPHORYLASE1,4-DIDEOXY-4-AZA-1-(S)-(9-DEAZAHYPOXANTHIN-9-YL)-D-RIBITOLMAGNESIUM IONPHOSPHATE ION ...
... and the other is purine nucleoside phosphorylase (PNP) deficiency, which i... ... encoded search term (Purine Nucleoside Phosphorylase Deficiency) and Purine Nucleoside Phosphorylase Deficiency What to Read ... Novel mutations and hot-spots in patients with purine nucleoside phosphorylase deficiency. Nucleosides Nucleotides Nucleic ... Purine Nucleoside Phosphorylase Deficiency. Updated: Aug 07, 2019 * Author: Alan P Knutsen, MD; Chief Editor: Harumi Jyonouchi ...
... J Antimicrob ... Results: The prodrugs showed decreased antibacterial activity compared with the parent nucleosides. cycloSal-GEM-monophosphate ... of antiviral and anticancer FDA-approved nucleoside drugs [zidovudine (AZT), floxouridine (FUDR) and gemcitabine (GEM)] against ...
Novel Point-of-Care Diagnostic Method for Neonatal Encephalopathy Using Purine Nucleosides. Edward Beamer1,2† Mary Isabel ODea ... Purinergic signaling, characterized as a complex regulatory system governed by purine nucleotides such as ATP and nucleosides, ... In summary, this study demonstrates that blood purine nucleoside concentrations are increased following NE and have potential ... Thauerer, B., Zur Nedden, S., and Baier-Bitterlich, G. (2012). Purine nucleosides: endogenous neuroprotectants in hypoxic brain ...
... called Protein Nucleoside 2-deoxyribosyltransferase from c.23.14.1: Nucleoside 2-deoxyribosyltransferase. *Protein Nucleoside 2 ... Timeline for Protein Nucleoside 2-deoxyribosyltransferase from c.23.14.1: N-deoxyribosyltransferase: *Protein Nucleoside 2- ... Nucleoside 2-deoxyribosyltransferase in SCOP 1.65. *Protein Nucleoside 2-deoxyribosyltransferase from c.23.14.1: N- ... Lineage for Protein: Nucleoside 2-deoxyribosyltransferase. *Root: SCOP 1.67 *. Class c: Alpha and beta proteins (a/b) [51349] ( ...
Crystal structure of Staphylococcus aureus nucleoside diphosphate kinase complexed with UDP ... Nucleoside diphosphate kinases (NDK) are characterized by high catalytic turnover rates and diverse substrate specificity. ... Conformational basis for substrate recognition and regulation of catalytic activity in Staphylococcus aureus nucleoside di- ... Crystal structure of Staphylococcus aureus nucleoside diphosphate kinase complexed with UDP. *PDB DOI: https://doi.org/10.2210/ ...
Nucleoside antagonist. Inhibits NF-κB signaling. Achieve your results faster with highly validated, pure and trusted compounds. ...
Fluorescent Nucleosides (2 suppliers). Fluorescent Particles (2 suppliers). Fluorescent Peptidase Substrates (4 suppliers). ...
Nucleobases, nucleosides, and nucleotides,state=autocollapse}}. *. {{navbar}}. , {{sidebar}}. , അഥവാ ഉള്ളടക്കം മറയ്ക്കാൻ നിർ ... Nucleobases, nucleosides, and nucleotides,state=expanded}}. ഈ ഫലകത്തിന്റെ ഉള്ളടക്കത്തെ എപ്പോഴും മുഴുവനായി കാണിക്കാൻ ഇങ്ങനെ ... Nucleobases, nucleosides, and nucleotides,state=collapsed}}. ഈ ഫലകത്തിന്റെ ഉള്ളടക്കത്തെ മറച്ചുവെച്ച് പ്രധാന തലക്കെട്ട് ... "https://ml.wikipedia.org/w/index.php?title=ഫലകം:Nucleobases,_nucleosides,_and_nucleotides&oldid=2111113" എന്ന താളിൽനിന്ന് ...
Deoxyuridine nucleosides embodied into diarylethenes form an especial class of photoswitchable compounds that are designed to ... Ultrafast Ring Closing of a Diarylethene-Based Photoswitchable Nucleoside. By Yang Li, Jose Luis Perez Lustres, Hans Robert ... Home / KnowledgeBase Articles / Ultrafast Ring Closing of a Diarylethene-Based Photoswitchable Nucleoside ...
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Nucleoside polyphosphates and their conjugates, such as nucleoside triphosphates, nucleoside tetraphosphates, sugar nucleotides ... Instead nucleoside 2,3-cyclic phosphates were obtained in good yield with the ribonucleoside substrates. This represents a ... The procedure is rapid, produces a wide variety of nucleoside polyphosphates and their conjugates in high yield, does not ... Attempts to prepare nucleoside triphosphates by subjecting unprotected ribonucleosides and 2-deoxyribonucleosides to activated ...
Nucleosides and Ribonucleosides for MEM-alpha (500X) complete media formulation available at Biological Industries ...
Non-nucleoside Reverse Transcriptase Inhibitors. The definition of "adolescent" may differ depending on the regimen; for ... Nucleoside/Nucleotide Reverse Transcriptase Inhibitors. The definition of "adolescent" may differ depending on the regimen; for ... When given with nucleoside reverse transcriptase inhibitors, ENF, TPV/RTV, NVP, raltegravir (RAL), and drugs that are not ...
Synthesis of N,O-nucleosides via an Ene Reaction. Paolo Quadrelli presents the synthesis of N,O-nucleosides from ( ... The importance of nucleoside analogues. in a number of areas of drug discovery and chemical biology continues to act as a spur ... N,O-Nucleosides. from Ene Reaction of (Nitrosocarbonyl)mesitylene with Crotyl Alcohol: Selectivity, Scope, and Limitations: S. ...
... ... The mechanism of HBV resistance to nucleoside analogs are described as well as the concept for multiple drug therapy and ...
Recent advances in synthetic approaches for medicinal chemistry of C-nucleosides ... Pfeiffer, M.; Nidetzky, B. Biocatalytic cascade transformations for the synthesis of C-nucleosides and N-nucleoside analogs. ... Roy, V.; Agrofoglio, L. A. Nucleosides and emerging viruses: A new story. Drug discovery today 2022, 27, 1945-1953. doi:10.1016 ... Mukhin, E. M.; Savateev, K. V.; Rusinov, V. L. Approaches to the synthesis of heterocyclic C-nucleosides. Russian chemical ...
Methylthioadenosine Nucleoside Transition State Analogs Show Potent In vitro and In vivo Activity Against Giardia intensinalis ... "Methylthioadenosine Nucleoside Transition State Analogs Show Potent In vitro and In vivo Activity Against Giardia intensinalis ...
Fluorescently labeled dideoxy-Nucleoside triphosphates (ddNTPs). Single nucleotide polymorphisms (SNPs) are single base pair ... You are here: Nucleotides & Nucleosides , Nucleotides by Application , ... on DNA , Sequencing & SNP Genotyping , Fluorescently ...
You are here: Probes & Epigenetics , Epigenetics , RNA (De)Methylation , Nucleotides & Nucleosides , 5-Methyl-CTP ...
Trichomonas vaginalis purine nucleoside phosphorylase (Trichomonas vaginalis). Find diseases associated with this biological ...
Author Summary The histiocytoses are a group of systemic disorders usually confined to childhood and are caused by an excessive number of histiocytes which phagocytose other cells and process antigens. Although nearly a century has passed since histiocytic disorders were recognised, their pathophysiology remains largely unclear, and treatment is nonspecific. The identification of SLC29A3 mutations as the molecular basis for a familial form of syndromic histiocytosis (FHC/RDD) confirms a direct link between Faisalabad histiocytosis and Rosai-Dorfman disease and links these disorders to other SLC29A3-associated phenotypes.
Nucleoside-modified messenger RNA (modRNA) is a modified form of mRNA that encodes the spike (S) glycoprotein of the SARS-CoV-2 ... How is RNA modified? Simply put, one of the four compounds in RNA is modified (e.g., the natural nucleoside uridine is modified ... modRNA (modified mRNA): modRNA is a man-made short-lived heterologous 5′-capped messenger RNA (mRNA), in which some nucleosides ... In the clinical trial for participants aged 12 through 15 who received the vaccine, which contains 30 mcg of nucleoside- ...
News stories and articles referencing nucleoside/nucleotide analogue therapy on European Pharmaceutical Review ... an antisense oligonucleotide therapy aided in long-term prevention of chronic hepatitis B in patients on and not on nucleoside/ ...
Nucleoside Phosphonate Interactions with Multiple Organic Anion Transporters in Renal Proximal Tubule. David S. Miller ... Nucleoside Phosphonate Interactions with Multiple Organic Anion Transporters in Renal Proximal Tubule. David S. Miller ... Nucleoside Phosphonate Interactions with Multiple Organic Anion Transporters in Renal Proximal Tubule. David S. Miller ... Nucleoside Phosphonate Interactions with Multiple Organic Anion Transporters in Renal Proximal Tubule ...
Protection against filovirus diseases by a novel broad-spectrum nucleoside analogue BCX4430. Travis K. Warren,,SUP,1,/SUP,,SUP ... Protection against filovirus diseases by a novel broad-spectrum nucleoside analogue BCX4430 April 16, 2014, 02:38 PM. ... Protection against filovirus diseases by a novel broad-spectrum nucleoside analogue BCX4430. ...
... a nucleoside reverse transcriptase (RT) inhibitor, is an antiretroviral agent which is potent against drug-resistant HIV ... 4-Ethynyl-2-deoxyadenosine (4-E-dA), a nucleoside reverse transcriptase (RT) inhibitor, is an antiretroviral agent which is ... 4-Ethynyl-2-deoxyadenosine (4-E-dA), a nucleoside reverse transcriptase (RT) inhibitor, is an antiretroviral agent which is ...
Through mathematical modeling, we assess the mechanisms by which HIV-1 can develop resistance against nucleoside analog reverse ... Author Summary Nucleoside analogs (NAs) represent an important drug class for the treatment of viral infections and cancer. ... natural nucleosides has been produced, but where the last nucleoside in the chain is a chain-terminating . At each state , the ... prolonged with a nucleoside (polymerase reaction ) or -terminated by a nucleoside analog (reaction ). If the chain has been ...
  • Nucleoside polyphosphates and their conjugates, such as nucleoside triphosphates, nucleoside tetraphosphates, sugar nucleotides, dinucleoside pyro- and higher order polyphosphates, 2',3'-cyclic nucleoside monophosphates, and 2´-deoxynucleoside-5´-tetraphosphates in which a fluorescent label is attached to the terminal phosphate have many biological roles and have been developed into drugs. (uwaterloo.ca)
  • Poster session presented at RSC Symposium on Nucleosides and Nucleotides: synthetic and biological chemistry, London, United Kingdom. (qub.ac.uk)
  • Nidetzky, B. Biocatalytic cascade transformations for the synthesis of C-nucleosides and N-nucleoside analogs. (beilstein-journals.org)
  • The mechanism of HBV resistance to nucleoside analogs are described as well as the concept for multiple drug therapy and combination with immunostimulatory approaches. (nih.gov)
  • Nucleoside analogs ( NA s) are used to treat numerous viral infections and cancer. (plos.org)
  • Nucleoside analogs ( NA s) represent an important drug class for the treatment of viral infections and cancer. (plos.org)
  • von Kleist M, Metzner P, Marquet R, Schütte C (2012) HIV-1 Polymerase Inhibition by Nucleoside Analogs: Cellular- and Kinetic Parameters of Efficacy, Susceptibility and Resistance Selection. (plos.org)
  • CONCLUSION: Combination antiretroviral therapy during pregnancy with two nucleoside analogs was well-tolerated by mothers and newborns, with no significant short-term toxicities or side effects noted. (jefferson.edu)
  • macologic classes: nucleoside analogs, interferons, The aim of this study was to investigate whether a panel protease inhibitors, reverse transcriptase inhibitors, and of currently available antiviral agents exhibit in vitro neuraminidase inhibitors. (cdc.gov)
  • The importance of nucleoside analogues in a number of areas of drug discovery and chemical biology continues to act as a spur to develop practical and efficient synthetic methods for accessing these compounds. (thieme.de)
  • Rauter, A. P. Nucleoside analogues: N-glycosylation methodologies, synthesis of antiviral and antitumor drugs and potential against drug-resistant bacteria and Alzheimer's disease. (beilstein-journals.org)
  • Bepirovirsen, an antisense oligonucleotide therapy aided in long-term prevention of chronic hepatitis B in patients on and not on nucleoside/nucleotide analogues in a Phase II trial. (europeanpharmaceuticalreview.com)
  • Continued interest in imino-sugar nucleosides derives from the observations that N-ribosyltransferases are powerfully inhibited by imino-C-nucleoside analogues that mimic the ribooxacarbenium ion nature of their transition states. (elsevierpure.com)
  • The synthesis of such compounds is challenging, and synthetic routes to imino- and imino-C-nucleosides are reviewed, together with the nature of the N-ribosyltransferases that are targets for these analogues. (elsevierpure.com)
  • Explore our uniquely large collection of reagents that contains popular nucleoside building blocks, nucleosides that facilitate epigenetics research and a family of pseudouridine analogues. (biosearchtech.com)
  • In purine nucleoside phosphorylase deficiency, similar changes occur, resulting in elevated deoxy-GTP (dGTP) levels. (medscape.com)
  • In a further description of the mechanism of T-cell depletion in purine nucleoside phosphorylase deficiency, Arpaia et al reported increased in vivo apoptosis of T cells and increased in vitro sensitivity to gamma irradiation in a murine model. (medscape.com)
  • [ 4 ] The immune deficiency in purine nucleoside phosphorylase deficiency may be the result of inhibited mitochondrial DNA repair due to the accumulation of dGTP in the mitochondria. (medscape.com)
  • Diagnosis of purine nucleoside phosphorylase deficiency is by DNA analysis. (msdmanuals.com)
  • Treatment of purine nucleoside phosphorylase deficiency is with bone marrow or stem cell transplantation. (msdmanuals.com)
  • Several novel and efficient approaches to the synthesis of nucleoside polyphosphates and their conjugates were developed. (uwaterloo.ca)
  • Finally an entirely new approach to the synthesis of nucleoside tetraphosphates (Np4's), dinucleoside pentaphosphates (Np5N's) and nucleoside tetraphosphates in which a fluorescent dye is attached to the terminal phosphate is described employing an activated form of cyclic trimetaphosphate as a novel phosphorylating agent. (uwaterloo.ca)
  • Paolo Quadrelli presents the synthesis of N,O-nucleosides from (nitrosocarbonyl)mesitylene. (thieme.de)
  • Rusinov, V. L. Approaches to the synthesis of heterocyclic C-nucleosides. (beilstein-journals.org)
  • Banerjee, S. Efficient synthesis of novel 2-deoxy-C-nucleosides containing oxa and thiadiazole derivatives and their biological activity. (beilstein-journals.org)
  • A convenient selective synthesis of 2′,3′-di-O-acetyl-nucleo- tide-5′-phosphates, 2′,3′-di-O-acetyl-nucleotide-5′-triphosphates and 2′,3′,5′-tri-O-acetyl-nucleosides in water has been developed. (ucl.ac.uk)
  • Nucleosides are precursors for nucleic acid synthesis and are essential for metabolism and cell growth. (biosearchtech.com)
  • We offer over 300 nucleosides, precursors, and reagents to synthesise nucleosides and make them incorporation-ready for oligo synthesis. (biosearchtech.com)
  • Use our reagents to generate reactive nucleosides for oligo synthesis. (biosearchtech.com)
  • Synthesis, Base Pairing Properties, and Biological Activity Studies of Platinum(II) Complexes Based on Uracil Nucleosides. (bvsalud.org)
  • The synthesis and base pairing properties of platinum complexes based on uridine and deoxyuridine nucleosides and preliminary studies of their antiproliferative activity are described. (bvsalud.org)
  • First, the synthesis was performed with protected nucleosides to generate complexes 1 and 2, which were deprotected under basic conditions, affording complexes 3 and 4 in good yields. (bvsalud.org)
  • The synthesis with the unprotected nucleosides was also performed and provided complexes 3 and 4 effectively. (bvsalud.org)
  • Qualitative and quantitative analyses of nucleosides and nucleobases in Ganoderma spp. (ganoherb.com)
  • Following a drug repurposing approach, we aimed to investigate and compare the antibacterial and antibiofilm activities of different classes of phosphate prodrugs (HepDirect, cycloSal, SATE and mix SATE) of antiviral and anticancer FDA-approved nucleoside drugs [zidovudine (AZT), floxouridine (FUDR) and gemcitabine (GEM)] against a variety of pathogenic Gram-positive and -negative bacteria. (nih.gov)
  • Nucleotide is a compound consisting of a nucleoside linked to a phosphate group. (broadpharm.com)
  • Cytarabine Vidarabine Nelarabine Fludarabine Clofarabine Sorivudine Clevudine W. E. Müller: "Rational design of arabinosyl nucleosides as antitumor and antiviral agents", Jpn J Antibiot. (wikipedia.org)
  • The interactions of two antiviral, acyclic nucleoside phosphonates, adefovir and cidofovir, with xenobiotic transporters was studied in intact killifish ( Fundulus heteroclitus ) renal proximal tubules by using fluorescent substrates, confocal microscopy, and quantitative image analysis. (aspetjournals.org)
  • Nucleosides: Having the highest uridine content. (ganoherb.com)
  • Introduction: Institute of Chinese Medical Sciences, University of Macau and Hong Kong Baptist University jointly proved in Journal of Pharmaceutical and Biomedical Analysis that uridine is a nucleoside whose content is highest in Ganoderma samples. (ganoherb.com)
  • Attempts to prepare nucleoside triphosphates by subjecting unprotected ribonucleosides and 2'-deoxyribonucleosides to activated cyclic trimetaphosphate failed. (uwaterloo.ca)
  • Nucleobase, Nucleoside, Nucleotide, and Nucleic Acid Transport Proteins" is a descriptor in the National Library of Medicine's controlled vocabulary thesaurus, MeSH (Medical Subject Headings) . (umassmed.edu)
  • This graph shows the total number of publications written about "Nucleobase, Nucleoside, Nucleotide, and Nucleic Acid Transport Proteins" by people in this website by year, and whether "Nucleobase, Nucleoside, Nucleotide, and Nucleic Acid Transport Proteins" was a major or minor topic of these publications. (umassmed.edu)
  • Below are the most recent publications written about "Nucleobase, Nucleoside, Nucleotide, and Nucleic Acid Transport Proteins" by people in Profiles. (umassmed.edu)
  • Deoxyuridine nucleosides embodied into diarylethenes form an especial class of photoswitchable compounds that are designed to stack and pair with DNA bases. (jascoinc.com)
  • The procedure is rapid, produces a wide variety of nucleoside polyphosphates and their conjugates in high yield, does not require protection and subsequent deprotection of the nucleotide donors or acceptors and can be used to activate nucleoside mono-, di-, and triphosphates and a wide variety of acceptors. (uwaterloo.ca)
  • In the first approach dinucleoside polyphosphates (NpnN's where n = 2-4) are prepared via in situ trifluoroacetate protection and imidazolium activation of nucleoside 5'-monophosphates. (uwaterloo.ca)
  • In the presence of Ca2+, NTPDase4 hydrolyzes nucleoside diphosphates UDP, GDP, CDP and dTDP to nucleoside monophosphates UMP, GMP, CMP and dTMP, respectively (Wang and Guidotti 1998). (reactome.org)
  • [ 2 , 3 ] One disorder is adenosine deaminase (ADA) deficiency, which is Online Mendelian Inheritance in Man (OMIM) subject number 102700, and the other is purine nucleoside phosphorylase (PNP) deficiency, which is OMIM subject number 164050. (medscape.com)
  • In both adenosine deaminase and purine nucleoside phosphorylase deficiencies, thymocytes are thought to be selectively destroyed because of elevated levels of dATP and dGTP. (medscape.com)
  • Application of crystallographic and modeling methods in the design of purine nucleoside phosphorylase inhibitors. (lu.se)
  • Thymidine phosphorylase breaks down thymidine into smaller molecules, which helps regulate the level of nucleosides in cells. (medlineplus.gov)
  • Phosphoramidite is a synthetic nucleoside derivative containing a phosphite ester group. (broadpharm.com)
  • Through mathematical modeling, we assess the mechanisms by which HIV-1 can develop resistance against nucleoside analog reverse transcriptase inhibitors (NRTI). (plos.org)
  • Nucleoside is comprised of a nucleobase and a five-carbon sugar (ribose or 2'-deoxyribose). (broadpharm.com)
  • Comparison of the inhibitory potencies of the nucleoside phosphonates with other substrates and inhibitors showed them to be moderate inhibitors of OAT1- and Mrp2-mediated transport. (aspetjournals.org)
  • Our model correctly predicts for HIV-1 that resistance against nucleoside analog reverse transcriptase inhibitors (NRTIs) can be conferred by decreasing their incorporation rate, increasing their excision rate, or decreasing their affinity for the polymerase enzyme. (plos.org)
  • Inhibitors of IMP dehydrogenase stimulate the phosphorylation of the anti-human immunodeficiency virus nucleosides 2',3'-dideoxyadenosine and 2',3'-dideoxyinosine. (aspetjournals.org)
  • Nucleoside reverse transcriptase inhibitors (NRTIs) block reverse transcriptase (an HIV enzyme). (hiv.gov)
  • 4'-Ethynyl-2'-deoxyadenosine (4'-E-dA), a nucleoside reverse transcriptase (RT) inhibitor, is an antiretroviral agent which is potent against drug-resistant HIV variants, with an EC50 of 98 nM in MT-4 cells for anti-HIV-1 activity. (adooq.com)
  • Demographic, laboratory, and pregnancy outcome data were collected for 39 women whose antiretroviral treatment regimens were expanded to include more than one nucleoside analog for maternal indications. (jefferson.edu)
  • In a nucleoside, the anomeric carbon is linked through a glycosidic bond to the N9 of a purine or the N1 of a pyrimidine. (broadpharm.com)
  • Get high-quality unmodified nucleosides to synthesize reliable oligonucleotides for PCR and other downstream applications. (biosearchtech.com)
  • These molecules permit the sequential addition of new bases to the chain in a highly efficient reaction, to avoid undesired side reactions, reactive hydroxy and exocyclic amino groups present in nucleosides are appropriately protected. (broadpharm.com)
  • Nucleoside diphosphate kinases (NDK) are characterized by high catalytic turnover rates and diverse substrate specificity. (rcsb.org)
  • Incorporate fluorescent nucleosides into your oligo to observe the transition between DNA structural types. (biosearchtech.com)
  • Adenosine signaling is terminated by its uptake through equilibrative nucleoside transporters (ENTs). (ozgene.com)
  • Arabinosyl nucleosides are derivatives of the nucleosides. (wikipedia.org)
  • Poor reduction of HIV-1 RNA titres in nucleoside reverse transcriptase inhibitor experienced patients treated with indinavir combination therapy. (bmj.com)
  • METHODS: Samples of semen and blood were obtained from a cohort of 12 nucleoside reverse transcriptase inhibitor experienced men before and during 25-68 weeks of combination therapy, which included the protease inhibitor indinavir. (bmj.com)
  • CONCLUSIONS: These data show that stable reduction of blood and seminal fluid viral titres is not achievable in a significant proportion of nucleoside reverse transcriptase inhibitor experienced men. (bmj.com)
  • Initial multicenter experience with double nucleoside therapy for human immunodeficiency virus infection during pregnancy. (jefferson.edu)
  • LGC, Biosearch Technologies offers the largest range of specialised products for nucleosides on the market. (biosearchtech.com)
  • The chemical reactions and pathways involving any phosphorylated nucleoside. (yeastrc.org)
  • Nucleoside-modified messenger RNA (modRNA) is a modified form of mRNA that encodes the spike (S) glycoprotein of the SARS-CoV-2 virus, the virus that causes COVID-19. (republicbroadcasting.org)
  • The prodrugs showed decreased antibacterial activity compared with the parent nucleosides. (nih.gov)
  • Dive into the research topics of 'Imino-sugar-based nucleosides. (elsevierpure.com)
  • Aldrich, C. C. 1'-Cyano Intermediate Enables Rapid and Stereoretentive Access to 1'-Modified Remdesivir Nucleosides. (beilstein-journals.org)
  • OBJECTIVE: To study maternal and neonatal effects of combination nucleoside analog therapy administered to human immunodeficiency virus (HIV)-infected pregnant women for maternal indications. (jefferson.edu)