The characteristic three-dimensional shape of a molecule.
The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).
Toxins isolated from the venom of Laticauda semifasciata, a sea snake (Hydrophid); immunogenic, basic polypeptides of 62 amino acids, folded by four disulfide bonds, block neuromuscular end-plates irreversibly, thus causing paralysis and severe muscle damage; they are similar to Elapid neurotoxins.
The scattering of x-rays by matter, especially crystals, with accompanying variation in intensity due to interference effects. Analysis of the crystal structure of materials is performed by passing x-rays through them and registering the diffraction image of the rays (CRYSTALLOGRAPHY, X-RAY). (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.
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).
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.
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.
The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.
The study of crystal structure using X-RAY DIFFRACTION techniques. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
The level of protein structure in which regular hydrogen-bond interactions within contiguous stretches of polypeptide chain give rise to alpha helices, beta strands (which align to form beta sheets) or other types of coils. This is the first folding level of protein conformation.
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 change from planar to elliptic polarization when an initially plane-polarized light wave traverses an optically active medium. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
The parts of a macromolecule that directly participate in its specific combination with another molecule.
The level of protein structure in which combinations of secondary protein structures (alpha helices, beta sheets, loop regions, and motifs) pack together to form folded shapes called domains. Disulfide bridges between cysteines in two different parts of the polypeptide chain along with other interactions between the chains play a role in the formation and stabilization of tertiary structure. Small proteins usually consist of only one domain but larger proteins may contain a number of domains connected by segments of polypeptide chain which lack regular secondary structure.
A rigorously mathematical analysis of energy relationships (heat, work, temperature, and equilibrium). It describes systems whose states are determined by thermal parameters, such as temperature, in addition to mechanical and electromagnetic parameters. (From Hawley's Condensed Chemical Dictionary, 12th ed)
Processes involved in the formation of TERTIARY PROTEIN STRUCTURE.
A low-energy attractive force between hydrogen and another element. It plays a major role in determining the properties of water, proteins, and other compounds.
The homogeneous mixtures formed by the mixing of a solid, liquid, or gaseous substance (solute) with a liquid (the solvent), from which the dissolved substances can be recovered by physical processes. (From Grant & Hackh's Chemical Dictionary, 5th ed)
The rate dynamics in chemical or physical systems.
NMR spectroscopy on small- to medium-size biological macromolecules. This is often used for structural investigation of proteins and nucleic acids, and often involves more than one isotope.
Variation in a population's DNA sequence that is detected by determining alterations in the conformation of denatured DNA fragments. Denatured DNA fragments are allowed to renature under conditions that prevent the formation of double-stranded DNA and allow secondary structure to form in single stranded fragments. These fragments are then run through polyacrylamide gels to detect variations in the secondary structure that is manifested as an alteration in migration through the gels.
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.
Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.
A computer simulation developed to study the motion of molecules over a period of time.
A molecule that binds to another molecule, used especially to refer to a small molecule that binds specifically to a larger molecule, e.g., an antigen binding to an antibody, a hormone or neurotransmitter binding to a receptor, or a substrate or allosteric effector binding to an enzyme. Ligands are also molecules that donate or accept a pair of electrons to form a coordinate covalent bond with the central metal atom of a coordination complex. (From Dorland, 27th ed)
Measurement of the intensity and quality of fluorescence.

Molecular dynamics studies of U1A-RNA complexes. (1/8682)

The U1A protein binds to a hairpin RNA and an internal-loop RNA with picomolar affinities. To probe the molecular basis of U1A binding, we performed state-of-the-art nanosecond molecular dynamics simulations on both complexes. The good agreement with experimental structures supports the protocols used in the simulations. We compare the dynamics, hydrogen-bonding occupancies, and interfacial flexibility of both complexes and also describe a rigid-body motion in the U1A-internal loop complex that is not observed in the U1A-hairpin simulation. We relate these observations to experimental mutational studies and highlight their significance in U1A binding affinity and specificity.  (+info)

Gangliosides of human kidney. (2/8682)

Five gangliosides isolated from human kidney have been characterized. The two main fractions were shown to be typical extraneural gangliosides in having lactose as their neutral carbohydrate moiety. Their structures were identified as: AcNeu(alpha2-3)Gal(beta1-4)Glc(beta1-1)Cer and AcNeu(alpha2-8)AcNeu(alpha2-3)Gal(beta1-4)Glc(beta1-1)Cer. The two main hexosamine-containing gangliosides are structurally related to human blood group substances of glycosphingolipid nature. The following structures are postulated: AcNeu(alpha2-3)Gal(beta1-4)GlcNAc(beta1-3)Gal(beta1-4)Glc(beta1-1)Cer and AcNeu(alpha2-3)Gal(beta1-4)[Fuc(alpha1-3)]GlcNAc(beta1-3)Gal(beta1-4)Glc(beta1-1) Cer. The third hexosamine-containing ganglioside belongs to a different series of glycolipids and was shown to have the structure of a major ganglioside of human brain: AcNeu(alpha2-3)Gal(beta1-3)GalNAc(beta1-4)[AcNeu(alpha2-3)]Gal(beta1-4)Glc(beta1- 1)Cer. The fatty acid structure of different gangliosides was shown to resemble that of neutral glycolipids of human kidney with the nonhydroxy acids C16:0, C22:0, and C24:0 as major components.  (+info)

Carbon 13 NMR study of nonenzymatic reactions of pyridoxal 5'-phosphate with selected amino acids and of related reactions. (3/8682)

Carbon 13 nuclear magnetic resonance spectroscopy has been used to monitor the nonenzymatic reactions of pyridoxal 5'-phosphate with glycine, alanine, valine, serine, and with several other model compounds. Isotopically enriched amino acids were employed so that low concentrations could be utilized while still allowing relatively rapid acquisition of spectral data. The results for alanine and serine are particularly noteworthy in that alanine is deaminated to pyruvate and pyruvate is aminated to alanine, but contrary to the enzymatic reactions of various serine dehydratases wherein serine is converted to pyruvate, the nonenzymatic reaction utilizing serine results in hydroxypruvate rather than pyruvate formation. In the reverse reaction, hydroxypyruvate is aminated to serine but very inefficiently relative to the amination of pyruvate to alanine. The experimental results have been formulated into a proposed reaction mechanism for deamination of amino acids by pyridoxal-P.  (+info)

Voltage sensors in domains III and IV, but not I and II, are immobilized by Na+ channel fast inactivation. (4/8682)

Using site-directed fluorescent labeling, we examined conformational changes in the S4 segment of each domain of the human skeletal muscle sodium channel (hSkM1). The fluorescence signals from S4 segments in domains I and II follow activation and are unaffected as fast inactivation settles. In contrast, the fluorescence signals from S4 segments in domains III and IV show kinetic components during activation and deactivation that correlate with fast inactivation and charge immobilization. These results indicate that in hSkM1, the S4 segments in domains III and IV are responsible for voltage-sensitive conformational changes linked to fast inactivation and are immobilized by fast inactivation, while the S4 segments in domains I and II are unaffected by fast inactivation.  (+info)

Quantitative study of polymer conformation and dynamics by single-particle tracking. (5/8682)

We present a new method for analyzing the dynamics of conformational fluctuations of individual flexible polymer molecules. In single-particle tracking (SPT), one end of the polymer molecule is tethered to an immobile substratum. A microsphere attached to the other end serves as an optical marker. The conformational fluctuations of the polymer molecule can be measured by optical microscopy via the motion of the microsphere. The bead-and-spring theory for polymer dynamics is further developed to account for the microsphere, and together the measurement and the theory yield quantitative information about molecular conformations and dynamics under nonperturbing conditions. Applying the method to measurements carried out on DNA molecules provides information complementary to recent studies of single DNA molecules under extensional force. Combining high precision measurements with the theoretical analysis presented here creates a powerful tool for studying conformational dynamics of biological and synthetic macromolecules at the single-molecule level.  (+info)

The structure of human parathyroid hormone-related protein(1-34) in near-physiological solution. (6/8682)

Parathyroid hormone-related protein plays a major role in the pathogenesis of humoral hypercalcemia of malignancy. Under normal physiological conditions, parathyroid hormone-related protein is produced in a wide variety of tissues and acts in an autocrine or paracrine fashion. Parathyroid hormone-related protein and parathyroid hormone bind to and activate the same G-protein-coupled receptor. Here we present the structure of the biologically active NH2-terminal domain of human parathyroid hormone-related protein(1-34) in near-physiological solution in the absence of crowding reagents as determined by two-dimensional proton magnetic resonance spectroscopy. An improved strategy for structure calculation revealed the presence of two helices, His-5-Leu-8 and Gln-16-Leu-27, connected by a flexible linker. The parathyroid hormone-related protein(1-34) structure and the structure of human parathyroid hormone(1-37) as well as human parathyroid hormone(1-34) are highly similar, except for the well defined turn, His-14-Ser-17, present in parathyroid hormone. Thus, the similarity of the binding affinities of parathyroid hormone and parathyroid hormone-related protein to their common receptor may be based on their structural similarity.  (+info)

Apolipoprotein A-I charge and conformation regulate the clearance of reconstituted high density lipoprotein in vivo. (7/8682)

While low apolipoprotein A-I (apoA-I) levels are primarily associated with increased high density lipoprotein (HDL) fractional catabolic rate (FCR), the factors that regulate the clearance of HDL from the plasma are unclear. In this study, the effect of lipid composition of reconstituted HDL particles (LpA-I) on their rate of clearance from rabbit plasma has been investigated. Sonicated LpA-I containing 1 to 2 molecules of purified human apoA-I and 5 to 120 molecules of palmitoyl-oleoyl phosphatidylcholine (POPC) exhibit similar charge and plasma FCR to that for lipid free apoA-I, 2.8 pools/day. Inclusion of 1 molecule of apoA-II to an LpA-I complex increases the FCR to 3.5 pools/day, a value similar to that observed for exchanged-labeled HDL3. In contrast, addition of 40 molecules of triglyceride, diglyceride, or cholesteryl ester to a sonicated LpA-I containing 120 moles of POPC and 2 molecules of apoA-I increases the negative charge of the particle and reduces the FCR to 1.8 pools/day. Discoidal LpA-I are the most positively charged lipoprotein particles and also have the fastest clearance rates, 4.5 pools/day. Immunochemical characterization of the different LpA-I particles shows that the exposure of an epitope at residues 98 to 121 of the apoA-I molecule is associated with an increased negative particle charge and a slower clearance from the plasma. We conclude that the charge and conformation of apoA-I are sensitive to the lipid composition of LpA-I and play a central role in regulating the clearance of these lipoproteins from plasma. conformation regulate the clearance of reconstituted high density lipoprotein in vivo.  (+info)

Application of distance geometry to 3D visualization of sequence relationships. (8/8682)

SUMMARY: We describe the application of distance geometry methods to the three-dimensional visualization of sequence relationships, with examples for mumps virus SH gene cDNA and prion protein sequences. Sequence-sequence distance measures may be obtained from either a multiple sequence alignment or from sets of pairwise alignments. AVAILABILITY: C/Perl code and HTML/VRML files from http://www.nibsc.ac.uk/dg3dseq/  (+info)

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.

Protein conformation refers to the specific three-dimensional shape that a protein molecule assumes due to the spatial arrangement of its constituent amino acid residues and their associated chemical groups. This complex structure is determined by several factors, including covalent bonds (disulfide bridges), hydrogen bonds, van der Waals forces, and ionic bonds, which help stabilize the protein's unique conformation.

Protein conformations can be broadly classified into two categories: primary, secondary, tertiary, and quaternary structures. The primary structure represents the linear sequence of amino acids in a polypeptide chain. The secondary structure arises from local interactions between adjacent amino acid residues, leading to the formation of recurring motifs such as α-helices and β-sheets. Tertiary structure refers to the overall three-dimensional folding pattern of a single polypeptide chain, while quaternary structure describes the spatial arrangement of multiple folded polypeptide chains (subunits) that interact to form a functional protein complex.

Understanding protein conformation is crucial for elucidating protein function, as the specific three-dimensional shape of a protein directly influences its ability to interact with other molecules, such as ligands, nucleic acids, or other proteins. Any alterations in protein conformation due to genetic mutations, environmental factors, or chemical modifications can lead to loss of function, misfolding, aggregation, and disease states like neurodegenerative disorders and cancer.

Erabutoxins are a group of toxic proteins found in the venom of some species of sea snakes. They belong to the family of three-finger toxins, which also includes alpha-neurotoxins from elapid snakes. Erabutoxins can be divided into several subtypes (A-E), based on their biological properties and amino acid sequences.

Erabutoxins primarily target the nervous system, affecting the neuromuscular junction and causing muscle weakness, paralysis, and respiratory failure in severe cases. Erabutoxin a, for example, is a potent postsynaptic neurotoxin that binds to nicotinic acetylcholine receptors at the motor endplate, preventing the binding of acetylcholine and inhibiting neuromuscular transmission.

Erabutoxins have been studied for their potential therapeutic applications, such as in pain management and neurodegenerative disorders, but further research is needed to fully understand their mechanisms of action and potential side effects.

X-ray diffraction (XRD) is not strictly a medical definition, but it is a technique commonly used in the field of medical research and diagnostics. XRD is a form of analytical spectroscopy that uses the phenomenon of X-ray diffraction to investigate the crystallographic structure of materials. When a beam of X-rays strikes a crystal, it is scattered in specific directions and with specific intensities that are determined by the arrangement of atoms within the crystal. By measuring these diffraction patterns, researchers can determine the crystal structures of various materials, including biological macromolecules such as proteins and viruses.

In the medical field, XRD is often used to study the structure of drugs and drug candidates, as well as to analyze the composition and structure of tissues and other biological samples. For example, XRD can be used to investigate the crystal structures of calcium phosphate minerals in bone tissue, which can provide insights into the mechanisms of bone formation and disease. Additionally, XRD is sometimes used in the development of new medical imaging techniques, such as phase-contrast X-ray imaging, which has the potential to improve the resolution and contrast of traditional X-ray images.

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.

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.

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.

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.

Protein binding, in the context of medical and biological sciences, refers to the interaction between a protein and another molecule (known as the ligand) that results in a stable complex. This process is often reversible and can be influenced by various factors such as pH, temperature, and concentration of the involved molecules.

In clinical chemistry, protein binding is particularly important when it comes to drugs, as many of them bind to proteins (especially albumin) in the bloodstream. The degree of protein binding can affect a drug's distribution, metabolism, and excretion, which in turn influence its therapeutic effectiveness and potential side effects.

Protein-bound drugs may be less available for interaction with their target tissues, as only the unbound or "free" fraction of the drug is active. Therefore, understanding protein binding can help optimize dosing regimens and minimize adverse reactions.

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.

Secondary protein structure refers to the local spatial arrangement of amino acid chains in a protein, typically described as regular repeating patterns held together by hydrogen bonds. The two most common types of secondary structures are the alpha-helix (α-helix) and the beta-pleated sheet (β-sheet). In an α-helix, the polypeptide chain twists around itself in a helical shape, with each backbone atom forming a hydrogen bond with the fourth amino acid residue along the chain. This forms a rigid rod-like structure that is resistant to bending or twisting forces. In β-sheets, adjacent segments of the polypeptide chain run parallel or antiparallel to each other and are connected by hydrogen bonds, forming a pleated sheet-like arrangement. These secondary structures provide the foundation for the formation of tertiary and quaternary protein structures, which determine the overall three-dimensional shape and function of the protein.

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.

Circular dichroism (CD) is a technique used in physics and chemistry to study the structure of molecules, particularly large biological molecules such as proteins and nucleic acids. It measures the difference in absorption of left-handed and right-handed circularly polarized light by a sample. This difference in absorption can provide information about the three-dimensional structure of the molecule, including its chirality or "handedness."

In more technical terms, CD is a form of spectroscopy that measures the differential absorption of left and right circularly polarized light as a function of wavelength. The CD signal is measured in units of millidegrees (mdeg) and can be positive or negative, depending on the type of chromophore and its orientation within the molecule.

CD spectra can provide valuable information about the secondary and tertiary structure of proteins, as well as the conformation of nucleic acids. For example, alpha-helical proteins typically exhibit a strong positive band near 190 nm and two negative bands at around 208 nm and 222 nm, while beta-sheet proteins show a strong positive band near 195 nm and two negative bands at around 217 nm and 175 nm.

CD spectroscopy is a powerful tool for studying the structural changes that occur in biological molecules under different conditions, such as temperature, pH, or the presence of ligands or other molecules. It can also be used to monitor the folding and unfolding of proteins, as well as the binding of drugs or other small molecules to their targets.

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.

Tertiary protein structure refers to the three-dimensional arrangement of all the elements (polypeptide chains) of a single protein molecule. It is the highest level of structural organization and results from interactions between various side chains (R groups) of the amino acids that make up the protein. These interactions, which include hydrogen bonds, ionic bonds, van der Waals forces, and disulfide bridges, give the protein its unique shape and stability, which in turn determines its function. The tertiary structure of a protein can be stabilized by various factors such as temperature, pH, and the presence of certain ions. Any changes in these factors can lead to denaturation, where the protein loses its tertiary structure and thus its function.

I'm sorry for any confusion, but "thermodynamics" is not a term that has a specific medical definition. It is a branch of physics that deals with the relationships between heat and other forms of energy. However, the principles of thermodynamics can be applied to biological systems, including those in the human body, such as in the study of metabolism or muscle function. But in a medical context, "thermodynamics" would not be a term used independently as a diagnosis, treatment, or any medical condition.

Protein folding is the process by which a protein molecule naturally folds into its three-dimensional structure, following the synthesis of its amino acid chain. This complex process is determined by the sequence and properties of the amino acids, as well as various environmental factors such as temperature, pH, and the presence of molecular chaperones. The final folded conformation of a protein is crucial for its proper function, as it enables the formation of specific interactions between different parts of the molecule, which in turn define its biological activity. Protein misfolding can lead to various diseases, including neurodegenerative disorders such as Alzheimer's and Parkinson's disease.

Hydrogen bonding is not a medical term per se, but it is a fundamental concept in chemistry and biology that is relevant to the field of medicine. Here's a general definition:

Hydrogen bonding is a type of attractive force between molecules or within a molecule, which occurs when a hydrogen atom is bonded to a highly electronegative atom (like nitrogen, oxygen, or fluorine) and is then attracted to another electronegative atom. This attraction results in the formation of a partially covalent bond known as a "hydrogen bond."

In biological systems, hydrogen bonding plays a crucial role in the structure and function of many biomolecules, such as DNA, proteins, and carbohydrates. For example, the double helix structure of DNA is stabilized by hydrogen bonds between complementary base pairs (adenine-thymine and guanine-cytosine). Similarly, the three-dimensional structure of proteins is maintained by a network of hydrogen bonds that help to determine their function.

In medical contexts, hydrogen bonding can be relevant in understanding drug-receptor interactions, where hydrogen bonds between a drug molecule and its target protein can enhance the binding affinity and specificity of the interaction, leading to more effective therapeutic outcomes.

In the context of medical terminology, "solutions" refers to a homogeneous mixture of two or more substances, in which one substance (the solute) is uniformly distributed within another substance (the solvent). The solvent is typically the greater component of the solution and is capable of dissolving the solute.

Solutions can be classified based on the physical state of the solvent and solute. For instance, a solution in which both the solvent and solute are liquids is called a liquid solution or simply a solution. A solid solution is one where the solvent is a solid and the solute is either a gas, liquid, or solid. Similarly, a gas solution refers to a mixture where the solvent is a gas and the solute can be a gas, liquid, or solid.

In medical applications, solutions are often used as vehicles for administering medications, such as intravenous (IV) fluids, oral rehydration solutions, eye drops, and topical creams or ointments. The composition of these solutions is carefully controlled to ensure the appropriate concentration and delivery of the active ingredients.

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.

Nuclear Magnetic Resonance (NMR) Biomolecular is a research technique that uses magnetic fields and radio waves to study the structure and dynamics of biological molecules, such as proteins and nucleic acids. This technique measures the magnetic properties of atomic nuclei within these molecules, specifically their spin, which can be influenced by the application of an external magnetic field.

When a sample is placed in a strong magnetic field, the nuclei absorb and emit electromagnetic radiation at specific frequencies, known as resonance frequencies, which are determined by the molecular structure and environment of the nuclei. By analyzing these resonance frequencies and their interactions, researchers can obtain detailed information about the three-dimensional structure, dynamics, and interactions of biomolecules.

NMR spectroscopy is a non-destructive technique that allows for the study of biological molecules in solution, which makes it an important tool for understanding the function and behavior of these molecules in their natural environment. Additionally, NMR can be used to study the effects of drugs, ligands, and other small molecules on biomolecular structure and dynamics, making it a valuable tool in drug discovery and development.

Single-Stranded Conformational Polymorphism (SSCP) is not a medical condition but rather a laboratory technique used in molecular biology and genetics. It refers to the phenomenon where a single-stranded DNA or RNA molecule can adopt different conformations or shapes based on its nucleotide sequence, even if the difference in the sequence is as small as a single base pair change. This property is used in SSCP analysis to detect mutations or variations in DNA or RNA sequences.

In SSCP analysis, the denatured single-stranded DNA or RNA sample is subjected to electrophoresis on a non-denaturing polyacrylamide gel. The different conformations of the single-stranded molecules migrate at different rates in the gel, creating multiple bands that can be visualized by staining or other detection methods. The presence of additional bands or shifts in band patterns can indicate the presence of a sequence variant or mutation.

SSCP analysis is often used as a screening tool for genetic diseases, cancer, and infectious diseases to identify genetic variations associated with these conditions. However, it has largely been replaced by more sensitive and accurate methods such as next-generation sequencing.

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.

A chemical model is a simplified representation or description of a chemical system, based on the laws of chemistry and physics. It is used to explain and predict the behavior of chemicals and chemical reactions. Chemical models can take many forms, including mathematical equations, diagrams, and computer simulations. They are often used in research, education, and industry to understand complex chemical processes and develop new products and technologies.

For example, a chemical model might be used to describe the way that atoms and molecules interact in a particular reaction, or to predict the properties of a new material. Chemical models can also be used to study the behavior of chemicals at the molecular level, such as how they bind to each other or how they are affected by changes in temperature or pressure.

It is important to note that chemical models are simplifications of reality and may not always accurately represent every aspect of a chemical system. They should be used with caution and validated against experimental data whenever possible.

Molecular Dynamics (MD) simulation is a computational method used in the field of molecular modeling and molecular physics. It involves simulating the motions and interactions of atoms and molecules over time, based on classical mechanics or quantum mechanics. In MD simulations, the equations of motion for each atom are repeatedly solved, allowing researchers to study the dynamic behavior of molecular systems, such as protein folding, ligand-protein binding, and chemical reactions. These simulations provide valuable insights into the structural and functional properties of biological macromolecules at the atomic level, and have become an essential tool in modern drug discovery and development.

A ligand, in the context of biochemistry and medicine, is a molecule that binds to a specific site on a protein or a larger biomolecule, such as an enzyme or a receptor. This binding interaction can modify the function or activity of the target protein, either activating it or inhibiting it. Ligands can be small molecules, like hormones or neurotransmitters, or larger structures, like antibodies. The study of ligand-protein interactions is crucial for understanding cellular processes and developing drugs, as many therapeutic compounds function by binding to specific targets within the body.

Fluorescence spectrometry is a type of analytical technique used to investigate the fluorescent properties of a sample. It involves the measurement of the intensity of light emitted by a substance when it absorbs light at a specific wavelength and then re-emits it at a longer wavelength. This process, known as fluorescence, occurs because the absorbed energy excites electrons in the molecules of the substance to higher energy states, and when these electrons return to their ground state, they release the excess energy as light.

Fluorescence spectrometry typically measures the emission spectrum of a sample, which is a plot of the intensity of emitted light versus the wavelength of emission. This technique can be used to identify and quantify the presence of specific fluorescent molecules in a sample, as well as to study their photophysical properties.

Fluorescence spectrometry has many applications in fields such as biochemistry, environmental science, and materials science. For example, it can be used to detect and measure the concentration of pollutants in water samples, to analyze the composition of complex biological mixtures, or to study the properties of fluorescent nanomaterials.

  • Here, we used Aβ42 oligomer structures previously determined in a membrane-mimicking environment as putative model systems to study the pore formation process in phospholipid bilayers with all-atom molecular dynamics simulations. (nih.gov)
  • The experimental findings are compared with GROMOS molecular dynamics simulations of antamanide with up to eight bound water molecules. (umassmed.edu)
  • Molecular dynamics simulations served to visualize induced fit procedures. (nih.gov)
  • Ligand docked GC conformations after dynamics simulations were used for generation of a 3D quantitative structure-activity relationship model. (nih.gov)
  • Molecular dynamics (MD) simulations are a popular method of studying protein structure and function, but are unable to reliably sample all relevant conformational space in reasonable computational timescales. (bvsalud.org)
  • An autoencoder is used to map snapshots from MD simulations onto a user-defined conformational landscape defined by principal components analysis or specific structural features, and we show that we can predict, with useful accuracy, conformations that are not present in the training data. (bvsalud.org)
  • Using amide I vibrational spectroscopy, isotope labeling strategies, and computational modeling based on molecular dynamics simulations and Markov state models allows us to characterize distinct peptide conformers and conformational variation. (aps.org)
  • We support our results with molecular dynamic simulations that provide insight into the mechanisms of film formation that occur at interfaces between orientationally distinct layers. (aps.org)
  • Using Molecular Dynamics simulations, we evidence these multiple coupling modes and the operation of their associate disconnections. (cemes.fr)
  • abstract = "Molecular dynamics simulation is used to model the adsorption of the barley lipid transfer protein (LTP) at the decane-water and vacuum-water interfaces. (hw.ac.uk)
  • Despite these differences, Aβ42 molecules adopt a common S-shaped conformation in all previously described high-resolution Aβ42 fibril structures. (nih.gov)
  • Conformation of macrocyclic molecules, while presenting specific challenges, is of a particular interest due to a resurgence in the exploration of macrocyclic compounds as potential therapeutics. (ivanmr.com)
  • We will provide several examples of modern methods that combine NMR data and computation to determine conformation of small molecules as well as peptidic and non-peptidic macrocycles. (ivanmr.com)
  • Protein x-ray and NMR structures often lead to impressions of rigid or well-defined conformations, even though these are dynamic molecules. (aps.org)
  • Our approach characterizes the molecular orientation throughout the film and reveals how molecules near the substrate and free surface have a nearly isotropic orientation compared to an anisotropic bulk. (aps.org)
  • Conformation zoning of large molecules using the analytical ultracentrifuge. (hud.ac.uk)
  • fougera sotalol StereoisomersCompounds, the molecules of molecular conformation, mutual interaction, dynamics and form. (etest.lt)
  • Predicting new protein conformations from molecular dynamics simulation conformational landscapes and machine learning. (bvsalud.org)
  • Fibrils formed by the 42-residue amyloid-β peptide (Aβ42), a main component of amyloid deposits in Alzheimer's disease (AD), are known to be polymorphic, i.e., to contain multiple possible molecular structures. (nih.gov)
  • Descriptions of protein and peptide conformation are colored by the methods we use to study them. (aps.org)
  • Millisecond Time-Resolved Solid-State NMR Reveals a Two-Stage Molecular Mechanism for Formation of Complexes between Calmodulin and a Target Peptide from Myosin Light Chain Kinase. (nih.gov)
  • Understanding molecular conformation of ligands is critical for the discovery and development of new therapeutic compounds. (ivanmr.com)
  • Crystal structures of the isolated GluN2D LBD in complex with various ligands reveal that the binding of L-glutamate induces a unique conformation at the backside of the ligand-binding site in proximity to the region at which the transmembrane domain would be located in the intact receptors. (nih.gov)
  • October 1972 - Dr. Christian B. Anfinsen, chief of the Institute's Laboratory of Chemical Biology, shared the Nobel Prize in Chemistry with two other American scientists for demonstrating one of the most important simplifying concepts of molecular biology: that the three-dimensional conformation of a native protein is determined by the chemistry of its amino acid sequence. (nih.gov)
  • Both these classes of membrane proteins are extremely important for our health," observes Nieng Yan, the Shirley M. Tilghman Professor at Princeton's Department of Molecular Biology. (phys.org)
  • Extensive characterization of film properties has identified bulk molecular orientation as a key structural motif that determines optoelectronic performance. (aps.org)
  • Despite its importance, few if any systematic studies have been performed to identify, as it has been the case for kappa and heavy chains, a set of structural conformations adopted by the loops forming its Antigen Binding Site (ABSs). (dtu.dk)
  • In this paper, thermal and structural properties, as well as molecular dynamics of co-amorphous binary mixtures composed of itraconazole (ITZ) and four other active pharmaceutical ingredients (APIs) with antifungal activity (posaconazole (POS), ketoconazole (KET), fluconazole (FLU), and voriconazole (VOR)), have been investigated. (researchgate.net)
  • Molecular simulation tools for investigating structure and dynamics of intrinsically disordered proteins / Robert Best. (nih.gov)
  • Ihle and colleagues from The University of Texas MD Anderson Cancer Center in Houston recently assessed associations between specific mutant K-Ras proteins and progression-free survival and tumor gene expression in NSCLC tissue from 215 patients involved in a clinical trial of molecular targeted therapy. (ascopost.com)
  • Heat shock proteins (HSPs) are molecular chaperones that stabilize folding and conformation of normal as well as oncogenic proteins. (eurekaselect.com)
  • Polymorphs, crystals with different structure and properties but the same molecular composition, arise from the subtle interplay between thermodynamics and kinetics during crystallisation. (nature.com)
  • To identify the molecular mechanisms governing specific voltage sensing properties, we combined structure modeling, mutagenesis, and electrophysiology to analyze the structures, free energy, and transition kinetics of the activated and resting states of two functionally distinct voltage sensing domains (VSDs) of the eukaryotic calcium channel Ca V 1.1. (elifesciences.org)
  • Molecular conformation generation, a critical aspect of computational chemistry, involves producing the three-dimensional conformer geometry for a given molecule. (arxiv.org)
  • In response to this, we propose a novel molecular conformation generation approach driven by the observation that the disintegration of a molecule can be viewed as casting increasing force fields to its composing atoms, such that the distribution of the change of inter-atomic distance shifts from Gaussian to Maxwell-Boltzmann distribution. (arxiv.org)
  • Molecular conformation generation aims to generate three-dimensional coordinates of all the atoms in a molecule and is an important task in bioinformatics and pharmacology. (openreview.net)
  • Previous methods usually first predict the interatomic distances, the gradients of interatomic distances or the local structures (e.g., torsion angles) of a molecule, and then reconstruct its 3D conformation. (openreview.net)
  • In type A fibrils, residues 12 to 42 adopt a ν-shaped conformation, with both intra-subunit and intersubunit hydrophobic contacts to form a compact core. (nih.gov)
  • Nanoscale Heterogeneity of the Molecular Structure of Individual hIAPP Amyloid Fibrils Revealed with Tip-Enhanced Raman Spectroscopy. (mpg.de)
  • Unraveling the Link between Molecular Conformation and Morphology and Mechanics of Amyloid Fibrils. (mpg.de)
  • Molecular structure and interactions within amyloid-like fibrils formed by a low-complexity protein sequence from FUS. (nih.gov)
  • NMR is an information-rich technique that provides information about molecular structure, configuration, and conformation. (ivanmr.com)
  • The backbone conformation of the 27-residue polypeptide hormone secretin has been investigated using nuclear magnetic resonance spectroscopy and restrained molecular dynamics calculations under conditions where it adopts a fully ordered structure (40% v/v trifluoroethanol). (nih.gov)
  • To investigate interactions of GCs with the ligand-binding domain of the glucocorticoid receptor (GR), we measured receptor-binding potency of a series of GC esters including their metabolites and performed a molecular modeling study using progesterone receptor crystal structure data. (nih.gov)
  • The following examples show how to set up alternate conformations for structure factor calculations as well as for empirical energy calculations. (nih.gov)
  • The first step is to append the alternate conformations to the current molecular structure file. (nih.gov)
  • The constraints interaction statements make sure that the alternate conformations do not interact with each other but rather interact only with the remaining molecular structure. (nih.gov)
  • Amyloids: From molecular structure to mechanical properties. (mpg.de)
  • Molecular structure of a prevalent amyloid-β fibril polymorph from Alzheimer's disease brain tissue. (nih.gov)
  • The understanding of the organisation, structure and function of SAC components is essential for the molecular understanding of the process and to identify and evaluate new targets for cancer drug therapy. (eurekaselect.com)
  • Here the adsorption behavior of high molecular weight, non-ionic, polyethylene oxide (PEO) and anionic partially hydrolyzed polyacrylamide (HPAM) polymers to a model clay, LAPONITE® (a trademark of BYK Additives, Inc.), was studied by small angle neutron scattering over a range of polymer concentrations. (rsc.org)
  • The adsorption of PEO was dependent on polymer concentration at all molecular weights, first adsorbing onto the radial edge of the clay particles and then to the clay faces as polymer concentration increased. (rsc.org)
  • This behavior arises from formation of inter- and intrachain dipole-dipole crosslinks which causes more dense molecular packing and cohesion. (aps.org)
  • The conformation and optoelectronic behavior were further assessed utilizing temperature dependent DFT simulation, GIWAXS, solid-state NMR, and OFET charge mobility, thus providing the 1st holistic picture of the influence of RAF on the performance of semiconducting polymers. (aps.org)
  • Finally, it is worth mentioning about the studies on binary systems composed of this API and high as well as low molecular weight compounds (polymers: hypromellose acetate succinate, poly(acrylic acid), methacrylic acid−ethyl acrylate copolymer and acetylated saccharides, respectively) [40,41], which revealed that the addition of both types of excipients results in suppressing the LC order in ITZ. (researchgate.net)
  • High molecular weight polymers are used in industrially important applications where the polymers adsorb onto surfaces of inorganic particles and facilitate dispersion, stabilization or flocculation of formulations. (rsc.org)
  • The surface conformation of these adsorbed polymers is key to their performance, yet an understanding of the effects of polymer charge, concentration and molecular weight on polymer conformation is incomplete. (rsc.org)
  • Cryo-EM reveals the molecular basis oflaminin polymerization and LN-lamininopathies. (nih.gov)
  • The Frydman Lab uses a multidisciplinary approach to address fundamental questions about molecular chaperones, protein folding and degradation. (nih.gov)
  • The basis for the restrained molecular dynamics calculations consists of 52 nuclear-Overhauser-enhancement-derived interproton distance restraints involving the NH, C alpha H and C beta H protons. (nih.gov)
  • Pairing our results with NEXAFS enables a determination of the molecular conformation. (aps.org)
  • Here, using HDX-MS,we identified changes in spike dynamics that we associate with the transition fromclosed to open conformations, to ACE2 binding, and to specific mutations in VOCs.We show that the RBD-associated subdomain plays a role in spike opening, whereasthe NTD acts as a hotspot of conformational divergence of VOC spikes drivingimmune evasion. (kcl.ac.uk)
  • We propose an approach for transforming the sampling of a molecular conformation distribution into an analytical model based on Hidden Markov Models. (kobv.de)
  • Experimental results on molecular datasets demonstrate the advantages of the proposed shifting distribution compared to the state-of-the-art. (arxiv.org)
  • Molecular modeling studies indicated that different conformations resulting from different K-Ras mutants may result in different associations with downstream signaling transducers. (ascopost.com)
  • Now our goal is to produce 3-D movies," says Yan, "to capture different conformations of the same molecular machinery to reveal their working cycle. (phys.org)
  • This is probably because of its molecular flexibility, allowing multiple binding conformations in reverse transcriptase. (medscape.com)
  • Biophysical characterization capabilities include measurement of molecular weight, shape, and conformation of biological macromolecules. (nih.gov)
  • SEDPHAT--a platform for global ITC analysis and global multi-method analysis of molecular interactions. (nih.gov)
  • This was first achieved through temperature dependent in-situ ellipsometry, whereby, the thermal expansion, optical profile, and conformation were all assessed. (aps.org)
  • Our work focuses on the molecular mechanisms underlying chromatin topology, transcription, and alternative splicing during inflammatory and oncogenic processes . (ens-lyon.fr)
  • Controlling molecular conformation through macroscopic mechanical stimulus may have applications in chiroptical devices, but achieving this in a 3D material is challenging. (nature.com)
  • Furthermore, it enables us to visualize typical conformations. (kobv.de)
  • The topic of our June round-table workshop (Thursday June 23, 2022, 1:00 PM EDT) will be a discussion of Molecular Conformation via NMR. (ivanmr.com)
  • Experiments show the strength of our networks for processing geometric data, in tasks including: molecular graph regression, learning expressive graph representations, and learning neural fields on triangle meshes. (icml.cc)
  • In this particular case, one wants to generate alternate conformations for the side chains of residues 1 and 7. (nih.gov)
  • How to directly generate the conformation without the above intermediate values is not fully explored. (openreview.net)
  • Molecular conformation, receptor binding, and hormone action of natural and synthetic estrogens and antiestrogens. (nih.gov)
  • 29. Correlation between antitumor activity, molecular weight, and conformation of lentinan. (nih.gov)
  • The molecular weight distribution and conformation of citrus pectins in solution studied by hydrodynamics. (hud.ac.uk)
  • Vapor-deposition enables precise control over the nanostructure in molecular glasses which are an important class of materials used in organic electronics. (aps.org)
  • Further analysis shows that our generated conformations have closer properties (e.g. (openreview.net)
  • Molecular analysis of prion strain variation and the aetiology of `new vari- ant' CJD. (cdc.gov)
  • A 1H-NMR study of the solution conformation of secretin. (nih.gov)
  • In particular, we use RNA-seq, qChiP, ChiP-seq, Cut&Run, 3C (Chromosome Conformation Capture), 4C and Hi-C methods for assessing transcriptomic and chromatin changes. (ens-lyon.fr)
  • NMR studies and restrained molecular dynamics. (nih.gov)
  • Molecular conductors κ-type (BEDT-TTF) 2 X [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene ( Figure 1 a), X = anion] are interesting materials in terms of unconventional superconductivity neighboring Mott insulating state, which is similar to high critical temperature ( T C ) cuprate superconductors [ 1 , 2 ]. (mdpi.com)
  • The method is closely related to the QMOD approach, substituting a learned scoring field for a pocket constructed of molecular fragments. (springer.com)