The facilitation of a chemical reaction by material (catalyst) that is not consumed by the reaction.
The facilitation of biochemical reactions with the aid of naturally occurring catalysts such as ENZYMES.
The rate dynamics in chemical or physical systems.
The region of an enzyme that interacts with its substrate to cause the enzymatic reaction.
Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.
A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.
The parts of a macromolecule that directly participate in its specific combination with another molecule.
The study of crystal structure using X-RAY DIFFRACTION techniques. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
Genetically engineered MUTAGENESIS at a specific site in the DNA molecule that introduces a base substitution, or an insertion or deletion.
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.
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 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).
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.
Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.
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)
RNA that has catalytic activity. The catalytic RNA sequence folds to form a complex surface that can function as an enzyme in reactions with itself and other molecules. It may function even in the absence of protein. There are numerous examples of RNA species that are acted upon by catalytic RNA, however the scope of this enzyme class is not limited to a particular type of substrate.
The process of cleaving a chemical compound by the addition of a molecule of water.
An essential amino acid that is required for the production of HISTAMINE.
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.
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.
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 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.
Proteins prepared by recombinant DNA technology.
Antibodies that can catalyze a wide variety of chemical reactions. They are characterized by high substrate specificity and share many mechanistic features with enzymes.
A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).
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)
The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.
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 sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.
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.
The naturally occurring or experimentally induced replacement of one or more AMINO ACIDS in a protein with another. If a functionally equivalent amino acid is substituted, the protein may retain wild-type activity. Substitution may also diminish, enhance, or eliminate protein function. Experimentally induced substitution is often used to study enzyme activities and binding site properties.
The extent to which an enzyme retains its structural conformation or its activity when subjected to storage, isolation, and purification or various other physical or chemical manipulations, including proteolytic enzymes and heat.
Biological molecules that possess catalytic activity. They may occur naturally or be synthetically created. Enzymes are usually proteins, however CATALYTIC RNA and CATALYTIC DNA molecules have also been identified.
One of the non-essential amino acids commonly occurring in the L-form. It is found in animals and plants, especially in sugar cane and sugar beets. It may be a neurotransmitter.
Electropositive chemical elements characterized by ductility, malleability, luster, and conductance of heat and electricity. They can replace the hydrogen of an acid and form bases with hydroxyl radicals. (Grant & Hackh's Chemical Dictionary, 5th 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.
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)
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.
The arrangement of two or more amino acid or base sequences from an organism or organisms in such a way as to align areas of the sequences sharing common properties. The degree of relatedness or homology between the sequences is predicted computationally or statistically based on weights assigned to the elements aligned between the sequences. This in turn can serve as a potential indicator of the genetic relatedness between the organisms.
A thiol-containing non-essential amino acid that is oxidized to form CYSTINE.
Stable elementary particles having the smallest known positive charge, found in the nuclei of all elements. The proton mass is less than that of a neutron. A proton is the nucleus of the light hydrogen atom, i.e., the hydrogen ion.
The characteristic three-dimensional shape of a molecule.
Proteins found in any species of bacterium.
A sequence of amino acids in a polypeptide or of nucleotides in DNA or RNA that is similar across multiple species. A known set of conserved sequences is represented by a CONSENSUS SEQUENCE. AMINO ACID MOTIFS are often composed of conserved sequences.
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.
The class of all enzymes catalyzing oxidoreduction reactions. The substrate that is oxidized is regarded as a hydrogen donor. The systematic name is based on donor:acceptor oxidoreductase. The recommended name will be dehydrogenase, wherever this is possible; as an alternative, reductase can be used. Oxidase is only used in cases where O2 is the acceptor. (Enzyme Nomenclature, 1992, p9)
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 art or process of comparing photometrically the relative intensities of the light in different parts of the spectrum.
An essential amino acid. It is often added to animal feed.
Multisubunit enzymes that reversibly synthesize ADENOSINE TRIPHOSPHATE. They are coupled to the transport of protons across a membrane.
The spatial arrangement of the atoms of a nucleic acid or polynucleotide that results in its characteristic 3-dimensional shape.
A trace element with atomic symbol Mn, atomic number 25, and atomic weight 54.94. It is concentrated in cell mitochondria, mostly in the pituitary gland, liver, pancreas, kidney, and bone, influences the synthesis of mucopolysaccharides, stimulates hepatic synthesis of cholesterol and fatty acids, and is a cofactor in many enzymes, including arginase and alkaline phosphatase in the liver. (From AMA Drug Evaluations Annual 1992, p2035)
Nicotinamide adenine dinucleotide phosphate. A coenzyme composed of ribosylnicotinamide 5'-phosphate (NMN) coupled by pyrophosphate linkage to the 5'-phosphate adenosine 2',5'-bisphosphate. It serves as an electron carrier in a number of reactions, being alternately oxidized (NADP+) and reduced (NADPH). (Dorland, 27th ed)
Derivatives of the dimethylisoalloxazine (7,8-dimethylbenzo[g]pteridine-2,4(3H,10H)-dione) skeleton. Flavin derivatives serve an electron transfer function as ENZYME COFACTORS in FLAVOPROTEINS.
The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.
An essential amino acid that is physiologically active in the L-form.
Unsaturated hydrocarbons of the type Cn-H2n, indicated by the suffix -ene. (Grant & Hackh's Chemical Dictionary, 5th ed, p408)
The characteristic 3-dimensional shape and arrangement of multimeric proteins (aggregates of more than one polypeptide chain).
Changing an open-chain hydrocarbon to a closed ring. (McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)
The process by which two molecules of the same chemical composition form a condensation product or polymer.
A condensation product of riboflavin and adenosine diphosphate. The coenzyme of various aerobic dehydrogenases, e.g., D-amino acid oxidase and L-amino acid oxidase. (Lehninger, Principles of Biochemistry, 1982, p972)
Preservative for wines, soft drinks, and fruit juices and a gentle esterifying agent.
The formation of crystalline substances from solutions or melts. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
A coenzyme composed of ribosylnicotinamide 5'-diphosphate coupled to adenosine 5'-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). (Dorland, 27th ed)
A non-essential amino acid that is involved in the metabolic control of cell functions in nerve and brain tissue. It is biosynthesized from ASPARTIC ACID and AMMONIA by asparagine synthetase. (From Concise Encyclopedia Biochemistry and Molecular Biology, 3rd ed)
Inorganic salts of phosphoric acid.
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 study of the structure, preparation, properties, and reactions of carbon compounds. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)
Any chemical species which accepts an electron-pair from a LEWIS BASE in a chemical bonding reaction.
A technique applicable to the wide variety of substances which exhibit paramagnetism because of the magnetic moments of unpaired electrons. The spectra are useful for detection and identification, for determination of electron structure, for study of interactions between molecules, and for measurement of nuclear spins and moments. (From McGraw-Hill Encyclopedia of Science and Technology, 7th edition) Electron nuclear double resonance (ENDOR) spectroscopy is a variant of the technique which can give enhanced resolution. Electron spin resonance analysis can now be used in vivo, including imaging applications such as MAGNETIC RESONANCE IMAGING.
The color-furnishing portion of hemoglobin. It is found free in tissues and as the prosthetic group in many hemeproteins.
A chemical element having an atomic weight of 106.4, atomic number of 46, and the symbol Pd. It is a white, ductile metal resembling platinum, and following it in abundance and importance of applications. It is used in dentistry in the form of gold, silver, and copper alloys.
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 metallic element of atomic number 30 and atomic weight 65.38. It is a necessary trace element in the diet, forming an essential part of many enzymes, and playing an important role in protein synthesis and in cell division. Zinc deficiency is associated with ANEMIA, short stature, HYPOGONADISM, impaired WOUND HEALING, and geophagia. It is known by the symbol Zn.
Proteins obtained from ESCHERICHIA COLI.
An element with atomic symbol O, atomic number 8, and atomic weight [15.99903; 15.99977]. It is the most abundant element on earth and essential for respiration.
The theory that the radiation and absorption of energy take place in definite quantities called quanta (E) which vary in size and are defined by the equation E=hv in which h is Planck's constant and v is the frequency of the radiation.
Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme.
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)
Processes involved in the formation of TERTIARY PROTEIN STRUCTURE.
A non-essential amino acid that occurs in high levels in its free state in plasma. It is produced from pyruvate by transamination. It is involved in sugar and acid metabolism, increases IMMUNITY, and provides energy for muscle tissue, BRAIN, and the CENTRAL NERVOUS SYSTEM.
The first chemical element in the periodic table. It has the atomic symbol H, atomic number 1, and atomic weight [1.00784; 1.00811]. It exists, under normal conditions, as a colorless, odorless, tasteless, diatomic gas. Hydrogen ions are PROTONS. Besides the common H1 isotope, hydrogen exists as the stable isotope DEUTERIUM and the unstable, radioactive isotope TRITIUM.
A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
The phenomenon whereby certain chemical compounds have structures that are different although the compounds possess the same elemental composition. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)
Stable elementary particles having the smallest known negative charge, present in all elements; also called negatrons. Positively charged electrons are called positrons. The numbers, energies and arrangement of electrons around atomic nuclei determine the chemical identities of elements. Beams of electrons are called CATHODE RAYS.
Positively charged atoms, radicals or groups of atoms with a valence of plus 2, which travel to the cathode or negative pole during electrolysis.
Compounds containing the -SH radical.
An isomerase that catalyzes the conversion of chorismic acid to prephenic acid. EC
The accumulation of an electric charge on a object
Short sequences (generally about 10 base pairs) of DNA that are complementary to sequences of messenger RNA and allow reverse transcriptases to start copying the adjacent sequences of mRNA. Primers are used extensively in genetic and molecular biology techniques.
Organic compounds containing a carbonyl group in the form -CHO.
Oxidases that specifically introduce DIOXYGEN-derived oxygen atoms into a variety of organic molecules.
Acyclic branched or unbranched hydrocarbons having two carbon-carbon double bonds.
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)
Small molecules that are required for the catalytic function of ENZYMES. Many VITAMINS are coenzymes.
Inorganic or organic compounds derived from phosphine (PH3) by the replacement of H atoms. (From Grant & Hackh's Chemical Dictionary, 5th ed)
Any member of the class of enzymes that catalyze the cleavage of the substrate and the addition of water to the resulting molecules, e.g., ESTERASES, glycosidases (GLYCOSIDE HYDROLASES), lipases, NUCLEOTIDASES, peptidases (PEPTIDE HYDROLASES), and phosphatases (PHOSPHORIC MONOESTER HYDROLASES). EC 3.
An essential amino acid that is necessary for normal growth in infants and for NITROGEN balance in adults. It is a precursor of INDOLE ALKALOIDS in plants. It is a precursor of SEROTONIN (hence its use as an antidepressant and sleep aid). It can be a precursor to NIACIN, albeit inefficiently, in mammals.
Enzymes that catalyze a reverse aldol condensation. A molecule containing a hydroxyl group and a carbonyl group is cleaved at a C-C bond to produce two smaller molecules (ALDEHYDES or KETONES). EC 4.1.2.
Commonly observed structural components of proteins formed by simple combinations of adjacent secondary structures. A commonly observed structure may be composed of a CONSERVED SEQUENCE which can be represented by a CONSENSUS SEQUENCE.
A species of GRAM-POSITIVE ENDOSPORE-FORMING BACTERIA in the family BACILLACEAE, found in soil, hot springs, Arctic waters, ocean sediments, and spoiled food products.
A non-essential amino acid naturally occurring in the L-form. Glutamic acid is the most common excitatory neurotransmitter in the CENTRAL NERVOUS SYSTEM.
The coenzyme form of Vitamin B1 present in many animal tissues. It is a required intermediate in the PYRUVATE DEHYDROGENASE COMPLEX and the KETOGLUTARATE DEHYDROGENASE COMPLEX.
Liquids that dissolve other substances (solutes), generally solids, without any change in chemical composition, as, water containing sugar. (Grant & Hackh's Chemical Dictionary, 5th ed)
Widely distributed enzymes that carry out oxidation-reduction reactions in which one atom of the oxygen molecule is incorporated into the organic substrate; the other oxygen atom is reduced and combined with hydrogen ions to form water. They are also known as monooxygenases or hydroxylases. These reactions require two substrates as reductants for each of the two oxygen atoms. There are different classes of monooxygenases depending on the type of hydrogen-providing cosubstrate (COENZYMES) required in the mixed-function oxidation.
Process of generating a genetic MUTATION. It may occur spontaneously or be induced by MUTAGENS.
Systems of enzymes which function sequentially by catalyzing consecutive reactions linked by common metabolic intermediates. They may involve simply a transfer of water molecules or hydrogen atoms and may be associated with large supramolecular structures such as MITOCHONDRIA or RIBOSOMES.
This is the active form of VITAMIN B 6 serving as a coenzyme for synthesis of amino acids, neurotransmitters (serotonin, norepinephrine), sphingolipids, aminolevulinic acid. During transamination of amino acids, pyridoxal phosphate is transiently converted into pyridoxamine phosphate (PYRIDOXAMINE).
Measurement of the intensity and quality of fluorescence.
The conformation, properties, reaction processes, and the properties of the reactions of carbon compounds.
A species of the genus SACCHAROMYCES, family Saccharomycetaceae, order Saccharomycetales, known as "baker's" or "brewer's" yeast. The dried form is used as a dietary supplement.
A coenzyme for a number of oxidative enzymes including NADH DEHYDROGENASE. It is the principal form in which RIBOFLAVIN is found in cells and tissues.
Liquid chromatographic techniques which feature high inlet pressures, high sensitivity, and high speed.
A non-essential amino acid. In animals it is synthesized from PHENYLALANINE. It is also the precursor of EPINEPHRINE; THYROID HORMONES; and melanin.
The protein components of enzyme complexes (HOLOENZYMES). An apoenzyme is the holoenzyme minus any cofactors (ENZYME COFACTORS) or prosthetic groups required for the enzymatic function.
The addition of an organic acid radical into a molecule.
Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.
Single chains of amino acids that are the units of multimeric PROTEINS. Multimeric proteins can be composed of identical or non-identical subunits. One or more monomeric subunits may compose a protomer which itself is a subunit structure of a larger assembly.
A non-essential amino acid present abundantly throughout the body and is involved in many metabolic processes. It is synthesized from GLUTAMIC ACID and AMMONIA. It is the principal carrier of NITROGEN in the body and is an important energy source for many cells.
A metallic element with atomic symbol Fe, atomic number 26, and atomic weight 55.85. It is an essential constituent of HEMOGLOBINS; CYTOCHROMES; and IRON-BINDING PROTEINS. It plays a role in cellular redox reactions and in the transport of OXYGEN.
The modification of the reactivity of ENZYMES by the binding of effectors to sites (ALLOSTERIC SITES) on the enzymes other than the substrate BINDING SITES.
A mutation caused by the substitution of one nucleotide for another. This results in the DNA molecule having a change in a single base pair.
A non-essential amino acid occurring in natural form as the L-isomer. It is synthesized from GLYCINE or THREONINE. It is involved in the biosynthesis of PURINES; PYRIMIDINES; and other amino acids.
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).
Enzymes that catalyze the transposition of double bond(s) in a steroid molecule. EC 5.3.3.
The branch of science that deals with the geometric description of crystals and their internal arrangement. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)
Chemical groups containing the covalent disulfide bonds -S-S-. The sulfur atoms can be bound to inorganic or organic moieties.
A class of enzymes that catalyze the cleavage of C-C, C-O, and C-N, and other bonds by other means than by hydrolysis or oxidation. (Enzyme Nomenclature, 1992) EC 4.
A subclass of enzymes which includes all dehydrogenases acting on primary and secondary alcohols as well as hemiacetals. They are further classified according to the acceptor which can be NAD+ or NADP+ (subclass 1.1.1), cytochrome (1.1.2), oxygen (1.1.3), quinone (1.1.5), or another acceptor (1.1.99).
Enzymes that catalyze the breakage of a carbon-oxygen bond leading to unsaturated products via the removal of water. EC 4.2.1.
Proteins produced from GENES that have acquired MUTATIONS.
Deuterium. The stable isotope of hydrogen. It has one neutron and one proton in the nucleus.
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)
Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction.
Adenine nucleotide containing one phosphate group esterified to the sugar moiety in the 2'-, 3'-, or 5'-position.
A computer simulation developed to study the motion of molecules over a period of time.
Placing of a hydroxyl group on a compound in a position where one did not exist before. (Stedman, 26th ed)
Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.
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.
A class of enzymes that catalyze geometric or structural changes within a molecule to form a single product. The reactions do not involve a net change in the concentrations of compounds other than the substrate and the product.(from Dorland, 28th ed) EC 5.
Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.
Covalent attachment of HALOGENS to other compounds.
A rod-shaped bacterium surrounded by a sheath-like structure which protrudes balloon-like beyond the ends of the cell. It is thermophilic, with growth occurring at temperatures as high as 90 degrees C. It is isolated from geothermally heated marine sediments or hot springs. (From Bergey's Manual of Determinative Bacteriology, 9th ed)
The creation of an amine. It can be produced by the addition of an amino group to an organic compound or reduction of a nitro group.
An atom or group of atoms that have a positive or negative electric charge due to a gain (negative charge) or loss (positive charge) of one or more electrons. Atoms with a positive charge are known as CATIONS; those with a negative charge are ANIONS.
Adenosine 5'-(trihydrogen diphosphate). An adenine nucleotide containing two phosphate groups esterified to the sugar moiety at the 5'-position.
Structurally related forms of an enzyme. Each isoenzyme has the same mechanism and classification, but differs in its chemical, physical, or immunological characteristics.
Compounds and molecular complexes that consist of very large numbers of atoms and are generally over 500 kDa in size. In biological systems macromolecular substances usually can be visualized using ELECTRON MICROSCOPY and are distinguished from ORGANELLES by the lack of a membrane structure.
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.
A trace element that is a component of vitamin B12. It has the atomic symbol Co, atomic number 27, and atomic weight 58.93. It is used in nuclear weapons, alloys, and pigments. Deficiency in animals leads to anemia; its excess in humans can lead to erythrocytosis.
The process by which ELECTRONS are transported from a reduced substrate to molecular OXYGEN. (From Bennington, Saunders Dictionary and Encyclopedia of Laboratory Medicine and Technology, 1984, p270)
A class of enzymes that catalyze the hydrolysis of one of the three ester bonds in a phosphotriester-containing compound.
A class of enzymes that transfers nucleotidyl residues. EC 2.7.7.
A cyclohexadiene carboxylic acid derived from SHIKIMIC ACID and a precursor for the biosynthesis of UBIQUINONE and the AROMATIC AMINO ACIDS.
Highly reactive molecules with an unsatisfied electron valence pair. Free radicals are produced in both normal and pathological processes. They are proven or suspected agents of tissue damage in a wide variety of circumstances including radiation, damage from environment chemicals, and aging. Natural and pharmacological prevention of free radical damage is being actively investigated.
Enzymes that catalyze either the racemization or epimerization of chiral centers within amino acids or derivatives. EC 5.1.1.
Procedures by which protein structure and function are changed or created in vitro by altering existing or synthesizing new structural genes that direct the synthesis of proteins with sought-after properties. Such procedures may include the design of MOLECULAR MODELS of proteins using COMPUTER GRAPHICS or other molecular modeling techniques; site-specific mutagenesis (MUTAGENESIS, SITE-SPECIFIC) of existing genes; and DIRECTED MOLECULAR EVOLUTION techniques to create new genes.
A non-essential amino acid. It is found primarily in gelatin and silk fibroin and used therapeutically as a nutrient. It is also a fast inhibitory neurotransmitter.
A colorless inorganic compound (HONH2) used in organic synthesis and as a reducing agent, due to its ability to donate nitric oxide.
Extrachromosomal, usually CIRCULAR DNA molecules that are self-replicating and transferable from one organism to another. They are found in a variety of bacterial, archaeal, fungal, algal, and plant species. They are used in GENETIC ENGINEERING as CLONING VECTORS.
A family of enzymes that catalyze the endonucleolytic cleavage of RNA. It includes EC 3.1.26.-, EC 3.1.27.-, EC 3.1.30.-, and EC 3.1.31.-.
An RNA-containing enzyme that plays an essential role in tRNA processing by catalyzing the endonucleolytic cleavage of TRANSFER RNA precursors. It removes the extra 5'-nucleotides from tRNA precursors to generate mature tRNA molecules.
Proteins that have one or more tightly bound metal ions forming part of their structure. (Dorland, 28th ed)
A subclass of enzymes of the transferase class that catalyze the transfer of a methyl group from one compound to another. (Dorland, 28th ed) EC 2.1.1.
A cytosolic carbonic anhydrase isoenzyme found widely distributed in cells of almost all tissues. Deficiencies of carbonic anhydrase II produce a syndrome characterized by OSTEOPETROSIS, renal tubular acidosis (ACIDOSIS, RENAL TUBULAR) and cerebral calcification. EC 4.2.1.-
Enzymes which transfer sulfur atoms to various acceptor molecules. EC 2.8.1.
The determination of the concentration of a given component in solution (the analyte) by addition of a liquid reagent of known strength (the titrant) until an equivalence point is reached (when the reactants are present in stoichiometric proportions). Often an indicator is added to make the equivalence point visible (e.g., a change in color).
Physiologic methyl radical donor involved in enzymatic transmethylation reactions and present in all living organisms. It possesses anti-inflammatory activity and has been used in treatment of chronic liver disease. (From Merck, 11th ed)
Dithionite. The dithionous acid ion and its salts.
Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.
The degree of 3-dimensional shape similarity between proteins. It can be an indication of distant AMINO ACID SEQUENCE HOMOLOGY and used for rational DRUG DESIGN.
Proteins, usually acting in oxidation-reduction reactions, containing iron but no porphyrin groups. (Lehninger, Principles of Biochemistry, 1993, pG-10)
Molecules of DNA that possess enzymatic activity.
Compounds which restore enzymatic activity by removing an inhibitory group bound to the reactive site of the enzyme.
Elements with partially filled d orbitals. They constitute groups 3-12 of the periodic table of elements.
A carboxy-lyase that plays a key role in photosynthetic carbon assimilation in the CALVIN-BENSON CYCLE by catalyzing the formation of 3-phosphoglycerate from ribulose 1,5-biphosphate and CARBON DIOXIDE. It can also utilize OXYGEN as a substrate to catalyze the synthesis of 2-phosphoglycolate and 3-phosphoglycerate in a process referred to as photorespiration.
The key substance in the biosynthesis of histidine, tryptophan, and purine and pyrimidine nucleotides.
A species of gram-positive, anaerobic bacteria in the family Clostridiaceae frequently used for the study of ENZYMES.
An enzyme of the transferase class that catalyzes the conversion of sedoheptulose 7-phosphate and D-glyceraldehyde 3-phosphate to D-ribose 5-phosphate and D-xylulose 5-phosphate in the PENTOSE PHOSPHATE PATHWAY. (Dorland, 27th ed) EC
The measurement of the amplitude of the components of a complex waveform throughout the frequency range of the waveform. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)
Hydrocarbons with at least one triple bond in the linear portion, of the general formula Cn-H2n-2.
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.-.
Stable oxygen atoms that have the same atomic number as the element oxygen, but differ in atomic weight. O-17 and 18 are stable oxygen isotopes.
Organic compounds that include a cyclic ether with three ring atoms in their structure. They are commonly used as precursors for POLYMERS such as EPOXY RESINS.
Enzymes that catalyze the joining of two molecules by the formation of a carbon-nitrogen bond. EC 6.3.
Addition of hydrogen to a compound, especially to an unsaturated fat or fatty acid. (From Stedman, 26th ed)
Enzymes that catalyze the cleavage of a carbon-carbon bond by means other than hydrolysis or oxidation. This subclass contains the DECARBOXYLASES, the ALDEHYDE-LYASES, and the OXO-ACID-LYASES. EC 4.1.
Inorganic or organic compounds that contain divalent iron.
Chromatography on non-ionic gels without regard to the mechanism of solute discrimination.
A somewhat heterogeneous class of enzymes that catalyze the transfer of alkyl or related groups (excluding methyl groups). EC 2.5.
A flavoprotein that catalyzes the synthesis of protocatechuic acid from 4-hydroxybenzoate in the presence of molecular oxygen. EC
A heavy metal trace element with the atomic symbol Cu, atomic number 29, and atomic weight 63.55.
The removal of a carboxyl group, usually in the form of carbon dioxide, from a chemical compound.
The measurement of the quantity of heat involved in various processes, such as chemical reactions, changes of state, and formations of solutions, or in the determination of the heat capacities of substances. The fundamental unit of measurement is the joule or the calorie (4.184 joules). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)

Human topoisomerase I promotes initiation of simian virus 40 DNA replication in vitro. (1/16180)

Addition of purified human topoisomerase I (topo I) to simian virus 40 T antigen-driven in vitro DNA replication reactions performed with topo I-deficient extracts results in a greater than 10-fold stimulation of completed molecules as well as a more than 3-fold enhancement of overall DNA replication. To further characterize this stimulation, we first demonstrate that bovine topo I but not Escherichia coli topo I can also enhance DNA replication. By using several human topo I mutants, we show that a catalytically active form of topo I is required. To delineate whether topo I influences the initiation or the elongation step of replication, we performed delayed pulse, pulse-chase, and delayed pulse-chase experiments. The results illustrate that topo I cannot promote the completion of partially replicated molecules but is needed from the beginning of the reaction to initiate replication. Competitive inhibition experiments with the topo I binding T antigen fragment 1-246T and a catalytically inactive topo I mutant suggest that part of topo I's stimulation of replication is mediated through a direct interaction with T antigen. Collectively, our data indicate that topo I enhances the synthesis of fully replicated DNA molecules by forming essential interactions with T antigen and stimulating initiation.  (+info)

A novel H2A/H4 nucleosomal histone acetyltransferase in Tetrahymena thermophila. (2/16180)

Recently, we reported the identification of a 55-kDa polypeptide (p55) from Tetrahymena macronuclei as a catalytic subunit of a transcription-associated histone acetyltransferase (HAT A). Extensive homology between p55 and Gcn5p, a component of the SAGA and ADA transcriptional coactivator complexes in budding yeast, suggests an immediate link between the regulation of chromatin structure and transcriptional output. Here we report the characterization of a second transcription-associated HAT activity from Tetrahymena macronuclei. This novel activity is distinct from complexes containing p55 and putative ciliate SAGA and ADA components and shares several characteristics with NuA4 (for nucleosomal H2A/H4), a 1.8-MDa, Gcn5p-independent HAT complex recently described in yeast. A key feature of both the NuA4 and Tetrahymena activities is their acetylation site specificity for lysines 5, 8, 12, and 16 of H4 and lysines 5 and 9 of H2A in nucleosomal substrates, patterns that are distinct from those of known Gcn5p family members. Moreover, like NuA4, the Tetrahymena activity is capable of activating transcription from nucleosomal templates in vitro in an acetyl coenzyme A-dependent fashion. Unlike NuA4, however, sucrose gradient analyses of the ciliate enzyme, following sequential denaturation and renaturation, estimate the molecular size of the catalytically active subunit to be approximately 80 kDa, consistent with the notion that a single polypeptide or a stable subcomplex is sufficient for this H2A/H4 nucleosomal HAT activity. Together, these data document the importance of this novel HAT activity for transcriptional activation from chromatin templates and suggest that a second catalytic HAT subunit, in addition to p55/Gcn5p, is conserved between yeast and Tetrahymena.  (+info)

Pseudouridine mapping in the Saccharomyces cerevisiae spliceosomal U small nuclear RNAs (snRNAs) reveals that pseudouridine synthase pus1p exhibits a dual substrate specificity for U2 snRNA and tRNA. (3/16180)

Pseudouridine (Psi) residues were localized in the Saccharomyces cerevisiae spliceosomal U small nuclear RNAs (UsnRNAs) by using the chemical mapping method. In contrast to vertebrate UsnRNAs, S. cerevisiae UsnRNAs contain only a few Psi residues, which are located in segments involved in intermolecular RNA-RNA or RNA-protein interactions. At these positions, UsnRNAs are universally modified. When yeast mutants disrupted for one of the several pseudouridine synthase genes (PUS1, PUS2, PUS3, and PUS4) or depleted in rRNA-pseudouridine synthase Cbf5p were tested for UsnRNA Psi content, only the loss of the Pus1p activity was found to affect Psi formation in spliceosomal UsnRNAs. Indeed, Psi44 formation in U2 snRNA was abolished. By using purified Pus1p enzyme and in vitro-produced U2 snRNA, Pus1p is shown here to catalyze Psi44 formation in the S. cerevisiae U2 snRNA. Thus, Pus1p is the first UsnRNA pseudouridine synthase characterized so far which exhibits a dual substrate specificity, acting on both tRNAs and U2 snRNA. As depletion of rRNA-pseudouridine synthase Cbf5p had no effect on UsnRNA Psi content, formation of Psi residues in S. cerevisiae UsnRNAs is not dependent on the Cbf5p-snoRNA guided mechanism.  (+info)

Molecular dynamics of the sodium channel pore vary with gating: interactions between P-segment motions and inactivation. (4/16180)

Disulfide trapping studies have revealed that the pore-lining (P) segments of voltage-dependent sodium channels undergo sizable motions on a subsecond time scale. Such motions of the pore may be necessary for selective ion translocation. Although traditionally viewed as separable properties, gating and permeation are now known to interact extensively in various classes of channels. We have investigated the interaction of pore motions and voltage-dependent gating in micro1 sodium channels engineered to contain two cysteines within the P segments. Rates of catalyzed internal disulfide formation (kSS) were measured in K1237C+W1531C mutant channels expressed in oocytes. During repetitive voltage-clamp depolarizations, increasing the pulse duration had biphasic effects on the kSS, which first increased to a maximum at 200 msec and then decreased with longer depolarizations. This result suggested that occupancy of an intermediate inactivation state (IM) facilitates pore motions. Consistent with the known antagonism between alkali metals and a component of slow inactivation, kSS varied inversely with external [Na+]o. We examined the converse relationship, namely the effect of pore flexibility on gating, by measuring recovery from inactivation in Y401C+E758C (YC/EC) channels. Under oxidative conditions, recovery from inactivation was slower than in a reduced environment in which the spontaneous YC/EC cross-link is disrupted. The most prominent effects were slowing of a component with intermediate recovery kinetics, with diminution of its relative amplitude. We conclude that occupancy of an intermediate inactivation state facilitates motions of the P segments; conversely, flexibility of the P segments alters an intermediate component of inactivation.  (+info)

Phosphorylation by protein kinase C decreases catalytic activity of avian phospholipase C-beta. (5/16180)

The potential role of protein kinase C (PKC)-promoted phosphorylation has been examined in the G-protein-regulated inositol lipid signalling pathway. Incubation of [32P]Pi-labelled turkey erythrocytes with either the P2Y1 receptor agonist 2-methylthioadenosine triphosphate (2MeSATP) or with PMA resulted in a marked increase in incorporation of 32P into the G-protein-activated phospholipase C PLC-betaT. Purified PLC-betaT also was phosphorylated by PKC in vitro to a stoichiometry (mean+/-S. E.M.) of 1.06+/-0.2 mol of phosphate/mol of PLC-betaT. Phosphorylation by PKC was isoenzyme-specific because, under identical conditions, mammalian PLC-beta2 also was phosphorylated to a stoichiometry near unity, whereas mammalian PLC-beta1 was not phosphorylated by PKC. The effects of PKC-promoted phosphorylation on enzyme activity were assessed by reconstituting purified PLC-betaT with turkey erythrocyte membranes devoid of endogenous PLC activity. Phosphorylation resulted in a decrease in basal activity, AlF4(-)-stimulated activity, and activity stimulated by 2MeSATP plus guanosine 5'-[gamma-thio]triphosphate in the reconstituted membranes. The decreases in enzyme activities were proportional to the extent of PKC-promoted phosphorylation. Catalytic activity assessed by using mixed detergent/phospholipid micelles also was decreased by up to 60% by phosphorylation. The effect of phosphorylation on Gqalpha-stimulated PLC-betaT in reconstitution experiments with purified proteins was not greater than that observed on basal activity alone. Taken together, these results illustrate that PKC phosphorylates PLC-betaT in vivo and to a physiologically relevant stoichiometry in vitro. Phosphorylation is accompanied by a concomitant loss of enzyme activity, reflected as a decrease in overall catalytic activity rather than as a specific modification of G-protein-regulated activity.  (+info)

Regulation and function of family 1 and family 2 UDP-glucuronosyltransferase genes (UGT1A, UGT2B) in human oesophagus. (6/16180)

Human UDP-glucuronosyltransferases (UGTs) are expressed in a tissue-specific fashion in hepatic and extrahepatic tissues [Strassburg, Manns and Tukey (1998) J. Biol. Chem. 273, 8719-8726]. Previous work suggests that these enzymes play a protective role in chemical carcinogenesis [Strassburg, Manns and Tukey (1997) Cancer Res. 57, 2979-2985]. In this study, UGT1 and UGT2 gene expression was investigated in human oesophageal epithelium and squamous-cell carcinoma in addition to the characterization of individual UGT isoforms using recombinant protein. UGT mRNA expression was characterized by duplex reverse transcriptase-PCR analysis and revealed the expression of UGT1A7, UGT1A8, UGT1A9 and UGT1A10 mRNAs. UGT1A1, UGT1A3, UGT1A4, UGT1A5 and UGT1A6 transcripts were not detected. UGT2 expression included UGT2B7, UGT2B10 and UGT2B15, but UGT2B4 mRNA was absent. UGT2 mRNA was present at significantly lower levels than UGT1 transcripts. This observation was in agreement with the analysis of catalytic activities in oesophageal microsomal protein, which was characterized by high glucuronidation rates for phenolic xenobiotics, all of which are classical UGT1 substrates. Whereas UGT1A9 was not regulated, differential regulation of UGT1A7 and UGT1A10 mRNA was observed between normal oesophageal epithelium and squamous-cell carcinoma. Expression and analysis in vitro of recombinant UGT1A7, UGT1A9, UGT1A10, UGT2B7 and UGT2B15 demonstrated that UGT1A7, UGT1A9 and UGT1A10 catalysed the glucuronidation of 7-hydroxybenzo(alpha)pyrene, as well as other environmental carcinogens, such as 2-hydroxyamino-1-methyl-6-phenylimidazo-(4, 5-beta)-pyridine. Although UGT1A9 was not regulated in the carcinoma tissue, the five-fold reduction in 7-hydroxybenzo(alpha)pyrene glucuronidation could be attributed to regulation of UGT1A7 and UGT1A10. These data elucidate an individual regulation of human UGT1A and UGT2B genes in human oesophagus and provide evidence for specific catalytic activities of individual human UGT isoforms towards environmental carcinogens that have been implicated in cellular carcinogenesis.  (+info)

Melatonin biosynthesis: the structure of serotonin N-acetyltransferase at 2.5 A resolution suggests a catalytic mechanism. (7/16180)

Conversion of serotonin to N-acetylserotonin, the precursor of the circadian neurohormone melatonin, is catalyzed by serotonin N-acetyltransferase (AANAT) in a reaction requiring acetyl coenzyme A (AcCoA). AANAT is a globular protein consisting of an eight-stranded beta sheet flanked by five alpha helices; a conserved motif in the center of the beta sheet forms the cofactor binding site. Three polypeptide loops converge above the AcCoA binding site, creating a hydrophobic funnel leading toward the cofactor and serotonin binding sites in the protein interior. Two conserved histidines not found in other NATs are located at the bottom of the funnel in the active site, suggesting a catalytic mechanism for acetylation involving imidazole groups acting as general acid/base catalysts.  (+info)

Histone octamer transfer by a chromatin-remodeling complex. (8/16180)

RSC, an abundant, essential chromatin-remodeling complex related to SWI/SNF complex, catalyzes the transfer of a histone octamer from a nucleosome core particle to naked DNA. The newly formed octamer-DNA complex is identical with a nucleosome in all respects. The reaction requires ATP and involves an activated RSC-nucleosome intermediate. The mechanism may entail formation of a duplex displacement loop on the nucleosome, facilitating the entry of exogeneous DNA and the release of the endogenous molecule.  (+info)

TY - JOUR. T1 - Effects on general acid catalysis from mutations of the invariant tryptophan and arginine residues in the protein tyrosine phosphatase from Yersinia. AU - Hoff, Richard H.. AU - Hengge, Alvan C.. AU - Wu, Li. AU - Keng, Yen Fang. AU - Zhang, Zhong Yin. PY - 2000/1/11. Y1 - 2000/1/11. N2 - General acid catalysis in protein tyrosine phosphatases (PTPases) is accomplished by a conserved Asp residue, which is brought into position for catalysis by movement of a flexible loop that occurs upon binding of substrate. With the PTPase from Yersinia, we have examined the effect on general acid catalysis caused by mutations to two conserved residues that are integral to this conformation change. Residue Trp354 is at a hinge of the loop, and Arg409 forms hydrogen bonding and ionic interactions with the phosphoryl group of substrates. Trp354 was mutated to Phe and to Ala, and residue Arg409 was mutated to Lys and to Ala. The four mutant enzymes were studied using steady state kinetics and ...
TY - JOUR. T1 - Implication of substrate-assisted catalysis on improving lipase activity or enantioselectivity in organic solvents. AU - Tsai, Shau Wei. AU - Chen, Chun Chi. AU - Yang, Hung Shien. AU - Ng, I. Son. AU - Chen, Teh Liang. PY - 2006/8/1. Y1 - 2006/8/1. N2 - In comparison with the biocatalyst engineering and medium engineering approaches, very few examples have been reported on using the substrate engineering approach such as substrate-assisted catalysis (SAC) for naturally occurring or engineered lipases and serine proteases to improve the enzyme activity and enantioselectivity. By employing lipase-catalyzed hydrolysis of (R,S)-naproxen esters in water-saturated isooctane as the model system, we demonstrate the proton shuttle device to the leaving alcohol of the substrate as a new means of SAC to effectively improve the lipase activity or enantioselectivity. The result cannot only provide a strong evidence for the rate-limiting proton transfer for the bond-breaking of tetrahedron ...
A highly efficient and stable [email protected] catalyst was successfully prepared by immobilizing Pd onto diimine-functionalized mesoporous silica SBA-15. With the help of diimine functional groups grafted onto the SBA-15, Pd could be anchored on a support with high dispersion. [email protected] catalyst exhibited excellent catalytic performance for the Suzuki coupling reaction of electronically diverse aryl halides and phenylboronic acid under mild conditions with an ultralow amount of Pd (0.05 mol % Pd). When the catalyst amount was increased, it could catalyze the coupling reaction of chlorinated aromatics with phenylboronic acid. Compared with the catalytic performances of Pd/SBA-15 and [email protected] catalysts, the [email protected] catalyst exhibited higher hydrothermal stability and could be repeatedly used four times without a significant decrease of its catalytic activity.
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The full potential in catalyst development will only be realized if characterization techniques are available that can probe materials with subnanometer resolution. One of the most employed techniques to image heterogeneous catalysts at the nanometer and subnanometer scale is transmission electron microscopy (TEM). As suggested by the name, TEM uses ... read more electrons transmitted through the object for imaging. Since the interaction between electrons and matter is very strong, only thin parts, commonly much less than a micron in thickness, are imaged. Since heterogeneous catalysts are, in most cases, structured on a much smaller length scale, the sample thickness can be reduced to TEM requirements by appropriate preparation techniques and is, therefore, no limitation. show less ...
Deoxygenation of sulfoxides to their corresponding sulfides is an important reaction, and the development of efficient heterogeneous catalysts that can utilize molecular hydrogen (H2) as a reducing agent is highly desired. In this study, we successfully developed a new concept in heterogeneous catalysts, pla
Nanostructured single-site heterogeneous catalysts possess the advantages of classical solid catalysts, in terms of easy recovery and recycling, together with a defined tailored chemical and steric environment around the catalytically active metal site. The use of inorganic oxide supports with selected shape and porosity at a nanometric level may have a relevant impact on the regio- and stereochemistry of the catalytic reaction. Analogously, by choosing the optimal preparation techniques to obtain spatially isolated and well-characterised active sites, it is possible to achieve performances that are comparable to (or, in the most favourable cases, better than) those obtained with homogeneous systems. Such catalysts are therefore particularly suitable for the transformation of highly-functionalised fine chemicals and some relevant examples where high chemo-, regio- and stereoselectivity are crucial will be described.
A carbon-based solid acid catalyst was prepared by incomplete carbonization of H3PO4-impregnated pulp fibers followed by sulfonation. XRD, FT-IR, BET, TGA, and acid density test were employed to characterize the structure and performance of the catalyst. Results showed that the catalyst was amorphous carbon composed of aromatic carbon sheets with -COOH, -OH and -SO3H groups. Previous impregnation with H3PO4 could promote porosity formation of the catalyst. The optimized carbonization temperature and time for the catalyst were 250 °C and 1.5 h. The -SO3H density and specific surface area for the catalyst prepared under the optimized conditions were 1.1 mmol g−1 and 118 m2 g−1, respectively. Compared to HZSM-5, Amberlyst-15 and previous reported carbon catalysts, the catalyst showed higher catalytic activity for transesterification of methyl acetate with n-butanol as hydrophobic reaction. The catalyst had good thermal stability, which could bear 200 °C without decomposition. The catalyst ...
TY - JOUR. T1 - Optically active β-ketoiminato manganese(III) complexes as efficient catalysts in enantioselective aerobic epoxidation of unfunctionalized olefins. AU - Nagata, Takushi. AU - Imagawa, Kiyomi. AU - Yamada, Tohru. AU - Mukaiyama, Teruaki. PY - 1994/6/1. Y1 - 1994/6/1. N2 - A novel manganese(III) complex having an optically active N, N′-ethylenebis-β-ketoimine ligand was prepared and characterized crystallographically. The manganese(III) complexes behave as effective catalysts in enantioselective epoxidation of unfunctionalized olefins by combined use of molecular oxygen, an oxidant, and pivalaldehyde, a reductant. Dihydronaphthalene derivatives were converted into the corresponding optically active epoxides with good to high enantioselectivities.. AB - A novel manganese(III) complex having an optically active N, N′-ethylenebis-β-ketoimine ligand was prepared and characterized crystallographically. The manganese(III) complexes behave as effective catalysts in enantioselective ...
Novel Bi2S3/TiO2 Heterogeneous Catalyst: Photocatalytic Mechanism for Decolorization of Texbrite Dye and Evaluation of Oxygen Species - Heterogeneous;Sonochemical;Visible light;$Bi_2S_3$;DPCO;
Sie sind hier: Enhanced catalytic performance of immobilized Parvibaculum lavamentivorans alcohol dehydrogenase in a gas phase bioreactor using glycerol as an additive. ...
TY - JOUR. T1 - Synthesis and characterization of novel chiral sulfonato-salen-manganese(III) complex in a zinc-aluminium LDH host. AU - Bhattacharjee, Samiran. AU - Anderson, Jim. PY - 2004/3/7. Y1 - 2004/3/7. N2 - A novel heterogeneous catalyst, [Zn2.15Al0.86(OH)6.02] [Mn]0.19[C6H5COO]0.48·2H2O, where {[Mn] = chiral sulfonato-salen-manganese(III) complex, Na2MnC20H22N2S2O12Cl, intercalated into ZnII-AlIII layered double hydroxide host}, has been synthesized and found to be an effective heterogeneous catalyst for the stereoselective epoxidation of R-(+)-limonene using molecular oxygen. The catalyst could be recycled without loss of performance.. AB - A novel heterogeneous catalyst, [Zn2.15Al0.86(OH)6.02] [Mn]0.19[C6H5COO]0.48·2H2O, where {[Mn] = chiral sulfonato-salen-manganese(III) complex, Na2MnC20H22N2S2O12Cl, intercalated into ZnII-AlIII layered double hydroxide host}, has been synthesized and found to be an effective heterogeneous catalyst for the stereoselective epoxidation of ...
Catalysis is at the heart of chemical transformations; therefore, there are continuous efforts to develop new catalysts and increase catalytic performance for various applications. Metallic nanoparticles (NPs) have become essential tools for many chemical processes employed in industry and academia during recent decades.1-5 NPs possess high specific surface area, various shapes and sizes, and high reactivity, and they often exhibit activity different from that of the corresponding bulk materials, due to their distinctive quantum properties. Handling of NPs, however, is not easy, because NPs are often prone to self-aggregation, and it is difficult to separate them from reaction media because the classical, convenient filtration methods are not applicable. One economical way to overcome or minimise these limitations is to anchor NPs on supports, with the latter also serving as modifiers of catalytic properties. Nowadays, economic considerations and health issues are gaining more and more ...
We describe a new class of heterogeneous catalysts called supported molten metal catalysis (SMMC), in which molten metal catalysts are dispersed as nanodroplets on the surface of porous supports, allowing much larger active surface area than is possible in conventional contacting techniques for catalytic metals that are molten under reaction conditions, thus greatly enhancing their activity and potential utility. Specific examples of different types of reactions are provided to demonstrate the broad applicability of the technique in designing active, selective, and stable new catalysts. It is shown that dispersing the molten metal on a support in the suggested manner can enhance the rate of a reaction by three to four orders of magnitude as a result of the concomitant increase in the active surface area. New reaction examples include {gamma}-Al{sub 2}O{sub 3} supported molten Te (melting point 450 C) and Ga (MP 30 C) catalysts for bifunctional methylcyclohexane dehydrogenation. These catalysts provide
Introduction. Catalysis-catalysing for success Catalysing for success This presentation will discuss what catalysts are, their mechanisms of action and their significance to the chemical industry. Introduction Catalysis is a remarkable phenomenon. Quite apart from the scientific reality, the financial and environmental benefits of harnessing its power are very impressive. Catalysts in definition developed by scientists in the last century, are materials that change the rate of attainment of equilibrium without themselves being changed or consumed in the process. To illustrate the importance of catalysis, here are some of the many applications of it: Chemical and materials manufacturing, Fuel cells, Combustion devices, Pollution control systems, Laundry detergents. The mechanisms of catalytic action in some of the above applications will be discussed later. Types of Catalyst There are two types of catalyst: Industrial catalysts - These are non-biological catalysts, which include solid state, ...
2 Sheets-Sheet 1 w. L. HENDERSON I CATALYTIC OXIDATION UNIT FOR DOMESTIC OVEN EXHAUST Oct. 27,1970 Filed Feb WAYNE L. HENDERSON ms ATTORNEY Oct. 27 41970 w, HENDERSON 3,536,?!- CATALYTIC OXIDATION UNIT FOR DOMESTIC-OVENBXIIAUST Filed Feb. 21, 1968 2 shms snm a was I FIG.4 . l I I l I I I I I I I I I o 5 l 3o 4o so 6o INVENTOIL WAYNE L. neuoaasou HIS ATTORNEY United States Patent US. Cl. 23-288 2 Claims ABSTRACT OF THE DISCLOSURE A catalytic oxidation unit useful in eliminating smoke and odors issuing from the exhaust vent of a domestic cooking oven, particularly a high temperature, selfcleaning oven using a pyrolytic process for degrading food soils. The oxidation unit comprises a hollow housing supporting a plurality of catalyst coated gas burners of cellular ceramic construction and having a high surface-tovolume ratio. The housing has an intake port and an exhaust port and includes a partition which separates the housing into intake and afterburner compartments; with the gas flow being ...
кислотный катализ microheterogeneous catalysis микрогетерогенный катализ polyfunctional catalysis полифункциональный катализ photochemical catalysis фотохимический катализ fermentation catalysis ферментативный катализ acid base catalysis кислотно
The selective catalytic oxidation (SCO) of ammonia to N2 was studied by using a series of noble metal-V2O5-WO3 catalysts supported on titania-silica (TS) prepared by coprecipitation method. In the V2O5- WO3 catalyst system, the use of TS as a support was very effective to enhance catalytic activity compared with TiO2 or SiO2 alone. The addition of a slight amount of Pd and Ir to V2O5-WO3/TS catalyst caused also remarkable enhancement of the catalytic activity without decreasing the selectivity to N2. The present catalysts provide remarkably high catalytic performance for SCO of ammonia to N2 under the practical reaction conditions for an industrial application.
Enzyme catalysis can be regarded as a catalytic reaction between homogeneous and heterogeneous reactions. It can be seen as the reaction between the enzyme and the reaction for formation of intermediate compounds, and it can also be seen as the reaction after the surface of the enzyme adsorbs the reactant.. What are enzymes?. It is an organic colloidal substance composed of protein. It plays a catalytic role for biochemical reactions.. Fermentation also is finished by its role of protease enzyme.. Enzyme catalysis. Accelerating or slowing down a chemical reaction by enzymes is called enzyme catalysis. Hundreds of different reactions performing simultaneously in a living cell are accomplished by a considerable number of enzymes. In many cases, small structural changes in the substrate molecule will make the compound loss the ability to act as a substrate.. Features. Enzyme catalysis shows a characteristic which is not seen in non-enzymatic reaction. It can be saturated with substrate. When the ...
For a seminal work in HOMO activation via enamineintermediates, see: a) List B., Lerner R. A., Barbas III C. F. J.,Proline-Catalyzed Direct Asymmetric Aldol Reactions, J. Am.Chem. Soc., 2000, 122, 2395-2396. For a review in enamineactivation, see: b) Mukherjee S., Yang J. W., Hoffmann S.,List B., Asymmetric Enamine Catalysis, Chem. Rev. 2007,107, 5471-5569. For a seminal work in HOMO-activation viadienamine intermediates, see: c) Bertelsen S., Marigo M.,Brandes S., Dinér P., Jørgensen K. A., Dienamine Catalysis:Organocatalytic Asymmetric γ-Amination of α,β-UnsaturatedAldehydes, J. Am. Chem. Soc. 2006, 128, 12973-12980.For reviews in dienamine activation, see: d) Ramachary D. B.,Reddy Y. V., Dienamine Catalysis: An Emerging Technologyin Organic Synthesis, Eur. J. Org. Chem., 2012, 865-887. e)Parra A., Reboredo S., Alemán J., Asymmetric Synthesis ofCyclobutanes by a Formal [2+2] Cycloaddition Controlled byDienamine Catalysis, Angew. Chem. Int. Ed. 2012, 51, 9734-9735 ...
Winning commercial heterogeneous catalysts satisfy numerous key require- ments: as well as excessive catalytic task for the specified response, with excessive selectivity the place applicable, in addition they have a suitable advertisement existence and are rugged sufficient for transportation and charging into plant reactors. extra requisites contain the necessity to come on-line easily very quickly and reproducible production approaches that contain handy methods at appropriate expense. the advance of heterogeneous catalysts that meet those (often at the same time unique) calls for is much from basic, and likewise a lot of the particular production tech- nology is stored mystery for advertisement reasons-thus theres no smooth textual content that offers with the full of this significant topic. rules of Catalyst improvement, which offers comprehensively with the layout, improvement, and manufacture of functional heterogeneous catalysts, is for this reason specially helpful in assembly the ...
Research presented in this work describes investigations into the synthesis, structure, and reactivity of cooperative catalysts. Cooperative catalysis, the concept of actively involving ligands in catalytic transformations, is used extensively in enzymatic systems and has been shown to enable organometallic catalysts to realize improved enantioselectivity, chemoselectivity, or activation of otherwise unreactive bonds. Two types of cooperative catalysts are investigated in this work: non-innocent ligands and ligand-based directing groups. Initial investigations detailed in this work revolve around a catalyst of the first type: Shvos catalyst ({[Ph₄(η⁵-C₄CO)]₂H]}Ru₂(CO)₄(μ-H)) which is known for containing a non-innocent cyclopentadienone ligand. Shvos catalyst is shown to be a competent catalyst for alkylation of amines with alcohols and amines and is superior to other reported catalysts in some cases. Subsequent studies investigated the potential of Shvos catalyst to mediate ...
Fingerprint Dive into the research topics of Mechanism investigation on the formation of olefins and paraffin from the thermochemical catalytic conversion of triglycerides catalyzed by alkali metal catalysts. Together they form a unique fingerprint. ...
Development of oxygen evolution reaction (OER) catalysts with reduced precious metal content while enhancing catalytic performance has been of pivotal importance in cost-effective design of acid polymer electrolyte membrane water electrolyzers. Hollow multimetallic nanostructures with well-defined facets are ideally suited for saving the usage of expensive precious metals as well as boosting catalytic performances; however, Ir-based hollow nanocatalysts have rarely been reported. Here, a very simple synthetic scheme is reported for the preparation of hollow octahedral nanocages of Co-doped IrCu alloy with readily tunable morphology and size. The Co-doped IrCu octahedral nanocages show excellent electrocatalytic activity and long-term durability for OER in acidic media. Notably, their OER activity represents one of the best performances among Ir-based acidic OER catalysts.. ...
Homogeneous catalysts are in the same phase as the reactants while heterogeneous catalysts are not. As far as I understand, the phase matters in terms of effectivity depending on the phase that the reactants are in. For example, a solid catalyst in an aqueous solution or a liquid catalyst in an aqueous solution, versus a case where the reactants sit on the surface of the catalyst, which would be called adsorption ...
The role of carbonaceous deposits (coke) formed in dehydrogenation catalysis has been extensively investigated over the last few decades mainly with respect to the deactivation of metal-based and metal-free heterogeneous catalysts. Although much less emphasized, coke deposits grown on selected metal oxides have also been described as active and selective phases for alkene dehydrogenation under an oxidative or non-oxidative atmosphere. This work describes the straightforward preparation of coked γ-Al2O3 composites and their catalytic performance in the ethylbenzene (EB) direct dehydrogenation (DDH) to styrene (ST) under steam- and oxygen-free conditions. The study unveils the effective potentiality of a catalytic system already known to the scientific community but never employed for EB DDH under severe conditions, close to those commonly used in industrial plants (600 °C, 10 vol % EB/He, GHSV = 3000 h-1). Such a simple catalytic system has revealed a significant stability on long-term trials ...
Acid catalysis plays an important role in biomass conversion processes for producing chemicals and fuels. We report a relatively simple procedure for synthesizing versatile, strong acid catalysts based on carbon and carbon-silica composites with sulfonic acid groups. The process involves chemical activation of a sulfonic acid organic precursor at low temperature. The synthesis conditions can be modified to tune the surface composition, texture, and the acid properties of the materials towards superior catalytic performances. Molecular level insights into the nature and strength of the acid sites were gained by combining high resolution XPS and 1H-decoupled 31P MAS NMR spectroscopy of adsorbed triethylphosphine oxide. These materials are effective acid catalysts for the conversion of different biomass-derived chemicals to useful bio products such as furanic ethers and levulinate esters ...
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Single-site catalysts can demonstrate high activity and selectivity in many catalytic reactions. The synthesis of these materials by impregnation from strongly oxidizing aqueous solutions or pH-controlled deposition often leads to low metal loadings or a range of metal species. Here, we demonstrate that simple impregnation of the metal precursors onto activated carbon from a low-boiling-point, low-polarity solvent, such as acetone, results in catalysts with an atomic dispersion of cationic metal species. We show the generality of this method by producing single-site Au, Pd, Ru and Pt catalysts supported on carbon in a facile manner. Single-site Au/C catalysts have previously been validated commercially to produce vinyl chloride, and here we show that this facile synthesis method can produce effective catalysts for acetylene hydrochlorination in the absence of the highly oxidizing acidic solvents previously used.
SLAC and Stanford researchers have shown for the first time that a cheap catalyst can split water and generate hydrogen gas for hours on end in the harsh environment of a commercial electrolyzer -- a step toward clean, large-scale hydrogen production for fuel, fertilizer and industry.
The reduction of automotive exhaust emissions has been one of the hottest topics in catalysis community since 1970s. Thanks to the development of three-way catalysts, main auto-exhaust pollutants, such as carbon monoxide, nitrogen oxides and unburned hydrocarbons, can be removed simultaneously. Nowadays, diesel engines and lean-engines become more and more popular due to their high fuel-efficiency and low CO2 emissions. Unfortunately, conventional three-way catalysts are not effective at reducing the NOx emissions from these engines due to the excess oxygen in the exhaust stream. Platinum catalysts were found to be highly active for selective NO reduction with hydrocarbons in excess oxygen and has good thermal stability and sulfur resistance. However, discrepancies still exist in the reaction mechanism of NO reduction with hydrocarbons on platinum catalysts. In this thesis, fundamental surface science studies were performed with in situ IR spectroscopic techniques combined with mass spectrometry, aiming
Researchers at the Department of Energys SLAC National Accelerator Laboratory and Stanford University have shown for the first time that a cheap catalyst can split water and generate hydrogen gas for hours on end in the ...
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This work was supported by the Spanish Government (contract MICINN-12-CTQ2011-29272-C04-02). M. León and L. Faba thank the Government of the Principality of Asturias for the Ph.D. fellow-ships (Severo Ochoa Program). ...
Dr. Sievers research interests are in heterogeneous catalysis, reactor design, applied spectroscopy, and characterization and synthesis of solid materials. Combining these interests he seeks to develop processes for the production of fuels and chemicals. His research program combines fundamental and applied research.. In fundamental studies, a suite of analytical and spectroscopic techniques (e.g. IR, NMR, XAS, Raman) is used to gain knowledge on structure-reactivity relationships of heterogeneous catalysts. Moreover, surface reactions are studied on a molecular level so that mechanisms and reaction pathways can be derived. Information obtained from these studies provides the foundation for intelligent catalyst design.. Applied studies focus specific catalytic processes. For these projects, continuously operated flow reactor systems are designed. Different catalysts are tested for reactivity, selectivity and stability and the influence of the operating conditions is investigated. Catalyst ...
A catalyst has been imaged with lattice resolution whilst surrounded by flowing gas, using a specially constructed in-situ cell for an electron microscope. This advancement demonstrates the...
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The measurement of reaction rate as a function of pH provides essential information about mechanism. and hydrolysis actions. Stronger coupling however is predicted for the Lys41 and His119 protonation says in apo RNase A leading to the requirement for a microscopic kinetic model. This type of analysis may be important for other catalytic systems where the active forms of implicated general acid and base are oppositely charged and more highly correlated. These results suggest a new way for CpHMD/pH-REMD simulations to bridge the gap with experiments to provide a molecular-level interpretation of pH-activity data in studies of enzyme mechanisms. Acid-base catalysis is usually a common catalytic strategy in protein and RNA enzymes 1 and is employed in the cleavage of the RNA phosphodiester backbone by RNase A2 3 as well as small nucleolytic RNA enzymes.4 General base and acid catalysts facilitate nucleophile activation through proton abstraction and promote leaving group departure through proton ...
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Traditionally, both processes have worked with vegetable refined. With a RBD refined is enough to obtain a quality product preserving installations and heterogeneous catalysts.. Biofuels based on vegetable oils are in extinction, with the incorporation of advanced raw materials being the reality and the growing trend today.. Advanced raw materials are generally waste materials. The residual materials have much higher refining needs than a first-use vegetable oil. The most abundant materials of this type today are recovered frying oils (UCO), cat1 & cat2 animal fats, tall oil, high acidity products, etc.. These raw materials cannot in any way be used directly in the manufacture of HVO. Since they would be a serious risk to the installation, in addition to poisoning the heterogeneous catalyst used, shortening the life of this expensive supply.. The elements and their repercussions are detailed below:. ...
Stringent new emission regulations pose challenges for the development of diesel catalyst technology. Future 4-way catalyst technology must provide for the simultaneous control of CO, HC, NOx and particulate matter (PM). Since NOx abatement is a reduction process while control of CO, HC and PM emissions requires catalytic oxidation, it is difficult to simultaneously control all four regulated pollutants under the oxidizing conditions found in diesel exhaust. New catalysts for lean NOx control have been developed for systems that operate with injection of reductant (active systems) and without injection of reductant (passive systems).In this study, two experimental catalysts which have potential as lean NOx catalysts, Pt/ZSM-5 and an Ir catalyst, were evaluated under both passive and active conditions. Conditions required for simultaneous PM and NOx abatement are discussed for a lean NOx + a conventional diesel oxidation catalyst (DOC) system. It was found that a Pt/ZSM-5 catalyst with mild HC ...
Oxidation of NO to NO₂ over a Diesel Oxidation Catalyst (DOC) plays an important role in different types of aftertreatment systems, by enhancing NOx storage on adsorber catalysts, improving the NOx reduction efficiency of SCR catalysts, and enabling the passive regeneration of Diesel Particulate Fil
TY - JOUR. T1 - Recent developments in olefin polymerizations with transition metal catalysts. AU - Imanishi, Yukio. AU - Naga, Naofumi. PY - 2001/10. Y1 - 2001/10. N2 - Discovery of effective homogeneous transition metal catalysts for olefin polymerization must be one of the most dramatic technologies for polymer synthesis in the 1980s. Especially, development of group 4-metallocene catalysts not only improved the property of manufactured polyolefins but also made us possible to synthesize new type polyolefins. A large number of studies have also been made on structure and property of the resultant polyolefins with the advance of catalyst technology. Over the past few years, trend in catalyst development has moved from modification of group 4-metallocene catalysts to search for new generation catalysts, such as non-metallocene catalysts and late transition-metal catalysts. Some of the new catalysts can proceed specific polymerizations, which are not achieved with existent olefin polymerization ...
In a transition metal catalyst system, the improvement comprising including in the catalyst system an autoacceleration inhibitor, which (i) at about the temperature at which the catalyst system autoaccelerates, decomposes into a poison for the catalyst system; (ii) is present in the catalyst system in an amount sufficient to provide the quantity of poison required to inhibit the autoacceleration of the catalyst system at the autoacceleration temperature; and (iii) is either essentially inert at the normal operating temperature of the catalyst system or will cause substantially less inhibition of the catalyst system at the normal operating temperature than at the autoacceleration temperature.
TY - CONF. T1 - Conversion of methanol to olefins over zeolites with DDR topology: the role of template on catalytic performance. AU - Prokopyeva, I. AU - Gucuyener, C. AU - Gascon, J. AU - Kapteijn, F. PY - 2014. Y1 - 2014. M3 - Abstract. SP - 66. EP - 66. T2 - DPTI Annual Event 2014. Y2 - 6 November 2014 through 7 November 2014. ER - ...
A composite with well-dispersed metal nanoparticles at a ceramic surface was produced by partial reduction of solid solution. It was found that a small amount of dopant, such as Al2O3, Cr2O3, or Sc2O3, accelerated the precipitation of the metal nanoparticles during the reduction. Catalytic performance of the composite for methanol reforming was evaluated. In the Ni-based catalysts, the dopant decreased the CO production by promoting a methanation reaction, while in the Co-based catalysts, the dopant did it by inducing a water-gas shift reaction. Co/MgO with Sc2O3 doping showed the most preferable reforming performance, high H2 production, and CO2 selectivity. ...
Disclosed is a method for producing a biofuel. It comprises hydrolyzing an extract from a seaweed selected from a group consisting of red algae, brown algae, green algae or a combination therof in a presence of a heterogeneous catalyst; and converting the hydrolysate through enzymatic fermentation or chemical reaction into the biofuel. The heterogeneous catalyst can be recycled without a load of wastewater treatment and make the process simpler, thus enjoying a comparative advantage in terms of production cost and by-product treatment expense. In addition, the heterogeneous catalyst can be applied to a fixed bed reactor, allowing the process to be performed in a continuous manner. As a result, a smaller reactor can be employed at higher efficiency and productivity ...
A series of bifunctional organic catalysts containing acid and basic sites with ionic liquid characteristics have been prepared and their catalytic activity and reaction coordinate for aldol and Knoevenagel condensations have been compared. While the only factor controlling catalyst activity for the Knoevenagel condensation was the distance between the acid and base sites, the spatial orientation of the organocatalyst is also key to achieve high activity and selectivity in the Claisen-Schmidt condensation. Mechanistic studies based on theoretical DFT calculations show that the acid-base bifunctional organocatalyst follows a mechanism inspired in natural aldolases for the synthesis of trans-chalcones, being able to produce a large variety of these compounds of industrial interest. The combination of the acid-base pairs within the proper geometry and the ionic liquid nature makes this catalyst active, selective and recyclable.
TY - JOUR. T1 - Cooperative catalysis. T2 - A new development in heterogeneous catalysis. AU - Lee, Jeong Kyu. AU - Kung, Mayfair C.. AU - Kung, Harold H.. PY - 2008/8/1. Y1 - 2008/8/1. N2 - Whereas cooperative effect in catalysis, in which multiple chemical interactions participate cooperatively to achieve significant enhancement in catalytic activity and/or selectivity, is common in enzymatic reactions, it has been sparingly employed in heterogeneous catalytic systems. Here, some recent literature examples of abiotic catalysis, with emphasis on heterogeneous systems, that employ cooperation between acid and base and two metal centers are briefly described to demonstrate the principles involved. Since effective cooperation places strict demand on the positions of the different functional groups, new synthetic methods and strategies are needed to design and construct structures useful for cooperative catalysis. Recent progress in our laboratory in synthesizing new nanocage structures that ...
This thesis describes the use of rational redesign to modify the properties of the enzyme Candida antarctica lipase B. Through carefully selected single-point mutations, we were able to introduce substrate-assisted catalysis and to alter the reaction specificity. Other single-point mutations afforded variants with greatly changed substrate selectivity and enantioselectivity.. Mutation of the catalytic serine changed the hydrolase activity into an aldolase activity. The mutation decreased the activation energy for aldol addition by 4 kJ×mol-1, while the activation energy increased so much for hydrolysis that no hydrolysis activity could be detected. This mutant can catalyze aldol additions that no natural aldolases can catalyze.. Mutation of the threonine in the oxyanion hole proved the great importance of its hydroxyl group in the transition-state stabilization. The lost transition-state stabilization was partly replaced through substrate-assisted catalysis with substrates carrying a hydroxyl ...
A facile strategy for the synthesis of acidic ionic liquid based UiO-67 type MOFs was developed in this study. Bronsted acids (H2SO4, CF3SO3H and hifpOSO(3)H (hexafluoroisopropyl sulfuric acid)) were introduced into UiO-67-bpy (bpy = 2,2-bipyridine-5,5-dicarboxylic acid) frameworks by reacting with bipyridyl nitrogen to introduce the properties of an acidic ionic liquid into the frameworks. The prepared catalysts, denoted as UiO-67-HSO4, UiO-67-CF3SO3 and UiO-67-hifpOSO(3), were characterized by XRD, SEM, FT-IR, EA, TGA and N-2 adsorption-desorption studies. The relatively high surface area was still maintained and acidic active groups were uniformly dispersed in the frameworks. The catalytic performance of UiO-67-HSO4, UiO-67-CF3SO3 and UiO-67-hifpOSO(3) was evaluated by the esterification of acetic acid with isooctyl alcohol. The prepared catalysts showed good catalytic activities in the esterification, of which UiO-67-CF3SO3 gave the maximum isooctyl alcohol conversion of 98.6% under ...
According to Prof Song Jin, who led the research team, the new catalyst is almost as efficient as platinum and appears to show the highest catalytic performance among the non-noble metal catalysts reported so far.. The advance emerges from a long line of research in Jins lab that has focused on the use of iron pyrite and other inexpensive, abundant materials for energy transformation. Jin and his students discovered the new catalyst by replacing iron to make cobalt pyrite, and then added phosphorus.. Whats more, although electricity is the usual energy source for splitting water into hydrogen and oxygen, Jin said that the new catalyst can also work with energy from sunlight. We have demonstrated a proof-of-concept device for using this cobalt catalyst and solar energy to drive hydrogen generation, he claimed. ...
TY - JOUR. T1 - Catalytic conversion of pure glycerol over an un-modified H-ZSM-5 zeolite to bio-based aromatics. AU - He, Songbo. AU - Zuur, Kenny. AU - Santosa, Dian Sukmayanda. AU - Heeres, Andre. AU - Liu, Chuncheng. AU - Pidko, Evgeny. AU - Heeres, Hero Jan. PY - 2021/2. Y1 - 2021/2. N2 - The catalytic conversion of pure glycerol to bio-aromatics (bio-BTX) over an un-modified H-ZSM-5 (SiO2/Al2O3 molar ratio of 23) via an ex-situ catalytic pyrolysis approach in a continuous tandem-micro reactor at a scale of 1 g glycerol h−1 was investigated. A BTX peak carbon yield of 28.1 ± 0.2 % was obtained at a pyrolysis temperature of 400 °C, catalytic upgrading temperature of 500 °C, atmospheric pressure and a WHSV of 1 h−1. About 70 % of the bound oxygen in glycerol was converted to water. The latter was mainly formed in the catalytic upgrading unit (70 %), though conversion of glycerol to other oxygenates with water formation was also observed in the pyrolysis unit. Catalyst deactivation ...
The results of the studies on the influence of the phase transfer catalyst on the epoxidation of (Z,E,E)-1,5,9-cyclododecatriene (CDT) to 1,2-epoxy-5,9-cyclododecadiene (ECDD) in the H2O2/H3PW12O40 system by a method of phase transfer catalysis (PTC) were presented. The following quaternary ammonium salts were used as phase transfer catalysts: methyltributylammonium chloride, (cetyl)pyridinium bromide, methyltrioctylammonium chloride, (cetyl)pyridinium chloride, dimethyl[dioctadecyl(76%)+dihexadecyl(24%)] ammonium chloride, tetrabutylammonium hydrogensulfate, didodecyldimethylammonium bromide and methyltrioctylammonium bromide. Their catalytic activity was evaluated on the basis of the degree of CDT and hydrogen peroxide conversion and the selectivities of transformation to ECDD in relation to consumed CDT and hydrogen peroxide. The most effective PT catalysts were selected based on the obtained results. Among the onium salts under study, the epoxidation of CDT with hydrogen peroxide proceeds ...
A series of C2 symmetrical 1:2 Ni:L complexes derived from α-amino amides were studied for the enantioselective addition of dialkylzinc reagents to aldehydes. Different structural elements on the ligands seem to play an important role in determining the observed enantioselectivity. Through optimization of structure and reaction conditions, the best ligand provided secondary alcohols in excellent yields (up to 98%) and enantioselectivity of up to 99% ee for (R)-enantiomer. A transition state model has been proposed to explain the observed enantioselectivities based on computational calculations at the DFT level. Very interestingly, calculations suggest a coordination model of the aldehyde to the metal complex through association of a lone pair of the carbonyl oxygen to the hydrogen atom of an amino group ...
ABSTRACT. Electrophilic substitution reaction of indole with various aldehydes and cyclohexanone were carried out in the presence of electron-transfer (K5CoW12O40.3H2O) and green Lewis acid ([(n-C4H9)4N]3PMo2W9(Sn4+.H2O)O39) catalysts. These catalysts were characterized by N2-adsorption measurements, FT-IR, UV-Vis, 31P NMR, TGA, cyclic voltammetry and elemental analysis. Mechanisms for their catalytic activity are proposed. Both of these catalysts can be recovered and reused.. Keywords: Dodecatungstocobaltate, Sn (IV)-substituted polyoxometalate, bis(indolyl)methanes, electrophilic substitution, solvent-free conditions. ...
TY - JOUR. T1 - Chiral Co(II) metal-organic framework in the heterogeneous catalytic oxidation of alkenes under aerobic and anaerobic conditions. AU - Tuci, Giulia. AU - Giambastiani, Giuliano. AU - Kwon, Stephanie. AU - Stair, Peter C.. AU - Snurr, Randall Q.. AU - Rossin, Andrea. PY - 2014/3/7. Y1 - 2014/3/7. N2 - The chiral Co(II) MOF [Co(l-RR)(H2O)·H2O] ∞ [1; l-RR = (R,R)-thiazolidine-2,4-dicarboxylate] has been exploited in the catalytic oxidation of different alkenes (cyclohexene, (Z)-cyclooctene, 1-octene) using either tert-butyl hydroperoxide ( tBuOOH) or molecular oxygen (O2) as oxidants. Different chemoselectivities are observed, both substrate- and oxidant-dependent. A moderate enantioselectivity is also obtained in the case of prochiral precursors, revealing the chiral induction ability of the optically pure metal environment. The interaction of O2 with the exposed metal sites in 1 (after material preactivation and consequent removal of the coordinated aquo ligand) has been ...
The pH-responsive core-shell microspheres of poly(styrene-co-methylacrylic acid) (PS-co-PMAA) containing a polystyrene (PS) core and a poly(methylacrylic acid) (PMAA) shell are synthesized by one-stage soap-free copolymerization and the catalyst system palladium-iminodiacetic acid (IDA-Pd) is immobilized on the outer shell-layer of the core-shell microspheres to form the quasi-homogeneous and easily accessible catalyst PS-co-PMAA-IDA-Pd. This quasi-homogeneous PS-co-PMAA-IDA-Pd catalyst is highly dispersed in the reaction medium just like a homogeneous one and can be separated like a heterogeneous catalyst by adjusting the pH of the reaction medium. Suzuki reactions employing the quasi-homogeneous PS-co-PMAA-IDA-Pd catalyst are efficiently performed in water as the sole solvent under mild conditions such as room temperature. The PS-co-PMAA-IDA-Pd catalyst is also used in Heck reactions of a wide range of aryl halides with styrene and proves to be efficient in aqueous solution. The ...
Angewandte Chemie Kinetic Resolution DOI: 10.1002/anie.200503291 Self-Assembled Nanoreactors as Highly Active Catalysts in the Hydrolytic Kinetic Resolution (HKR) of Epoxides in Water Benjamin M. Rossbach, Kerstin Leopold, and Ralf Weberskirch* The synthesis of optically active organic compounds is a central research topic in chemistry because of their widespread use in the pharmaceutical industry as well as in the production of fine chemicals.[1] Catalytic enantioselective organic reactions can be achieved by metal catalysis,[2] by biocatalysis,[3] and more recently also by organocatalysis.[4] Despite the increased industrial demand for enantiomerically pure compounds, to date only a few catalytic asymmetric processes have found commercial application.[5] One rare exception is the hydrolytic kinetic resolution (HKR) of terminal epoxides, which allows the production of enantiopure epoxides and diols from the racemic stating materials.[6] These chiral compounds play a key role as intermediates in ...
Abstract: With the development of synthetic chemistry, more and more efficient catalysts are exploited to activate inert chemical bonds and organic molecules. In the synthetic chemistry, catalysts play an important role, scientists are paying more and more attention to the design and synthesis of catalysts. The majority of catalysts in homogeneous catalytic systems belong to mononuclear active species. In addition to the development of catalysis science, major research is also being conducted on the development of the coordination environment for metal centers to increase their catalytic ability and thereby create enhanced catalytic processes. The catalytic activity of dinuclear catalysts varies from those of mononuclear catalysts. Due to the synergistic effect between the two metal centers, the catalytic activity of dinuclear catalytic systems exhibits particular performance characteristics. The first row of elements in group Ⅷ of the periodic table, Fe, Co, and Ni, are also known as the ...
TY - JOUR. T1 - The comparative effect of particle size and support acidity on hydrogenation of aromatic ketones. AU - Kim, Kyung Duk. AU - Wang, Zichun. AU - Tao, Yongwen. AU - Ling, Huajuan. AU - Yuan, Yuan. AU - Zhou, Cuifeng. AU - Liu, Zongwen. AU - Gaborieau, Marianne. AU - Huang, Jun. AU - Yu, Aibing. PY - 2019/10/7. Y1 - 2019/10/7. N2 - A comparative study was reported for both the effects of shape-confined cubic Pd particle size (8, 13, and 21 nm) and surface property of most commonly used supports (SiO2, Al2O3, and silica-alumina) on catalytic performance in the chemoselective hydrogenation of three model bio-oil chemicals (benzaldehyde, acetophenone, and butyrophenone). The results showed that the size of Pd particles could be more associated with the hydrogenation reaction than acidities of the supports. Smaller size of Pd particles, regardless of the type of the support, provided the higher catalytic performance. XPS data showed that the electronic properties of Pd particles were ...
EDX analysis showed that the residual Mn composition of the 0 °C dealloyed sample (cat-4) is &4 at. 2 Results and Discussion 21 Fig. 7 (cat-10) Fig. 01 M MnSO4; B: HCl solution b 1 H NMR yield determined using CH2Br2 as an internal standard c Isolated yield remains approximately constant at &2 at. % for cat-5 to cat-7 (Fig. 4). Dealloying of the 200 lm thickness Cu30Mn70 alloy in HCl solution resulted in large ligaments with an average diameter of 60-70 nm (Fig. 3a, b, cat-8 and cat-9); in the reduced concentration, a non-nanopore structure was observed (Fig. 1314. 0793. 0845. 1158. 0900. 1266. 0885. 1764. 2233. 1451. 4 Experimental Section 49 50 2 Nanoporous Copper Metal Catalyst in Click Chemistry References 51 References 1. Zielasek V, Jürgens B, Schulz C et al (2006) Gold catalysts: nanoporous gold foams. Angew Chem Int Ed 45:8241-8244 2. Xu C, Su J, Xu X et al (2007) Low temperature CO oxidation over unsupported nanoporous gold. J Am Chem Soc 129:42-43 3. Xu C, Xu X, Su J et al (2007) ...
TY - JOUR. T1 - Hydrogenation of Lactic Acid to 1,2-Propanediol over Ru-Based Catalysts. AU - Liu, Kaituo. AU - Huang, Xiaoming. AU - Pidko, Evgeny A.. AU - Hensen, Emiel J.M.. PY - 2018. Y1 - 2018. N2 - The catalytic hydrogenation of lactic acid to 1,2-propanediol with supported Ru catalysts in water was investigated. The influence of catalyst support (activated carbon, γ-Al2O3, SiO2, TiO2, and CeO2) and promoters (Pd, Au, Mo, Re, Sn) on the catalytic performance was evaluated. Catalytic tests revealed that TiO2 yields the best Ru catalysts. With a monometallic Ru/TiO2 catalyst, a 1,2-propanediol yield of 70 % at 79 % lactic acid conversion was achieved at 130 °C after 20 h reaction. Minor byproducts of the hydrogenation reaction were propionic acid, ethanol, 1-propanol, and 2-propanol. For the bimetallic catalysts, the addition of Pd and Au slightly enhanced the performance of Ru/TiO2, whereas the addition of common hydrogenation promoters such as Re, Mo, and Sn impaired the activity.. AB - ...
Read Palladium-catalyzed synthesis of diarylbenzenes from coupling reactions between equal amount of diiodoarenes and arylboronic acids, Russian Journal of Applied Chemistry on DeepDyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips.
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The catalytic performances of different commercial cobalt oxides(CoxOy, i.e., Co2O3, Co3O4, and CoO) for peroxymonosulfate(PMS) activation in dye degradation were compared in this study. The CoO/PMS system exhibited the highest catalytic oxidation performances with more than 96% methylene blue(MB) removal at 90 min. The concentration of dissolved cobalt ions from CoO was 1.474 mg/L at neutral pH and 5.231 mg/L at acidic pH at 90 min which accounted for the high MB removal and CoO activated PMS homogeneously compared to the associated CoSO4/PMS. Co3O4 and Co2O3 exhibited similar catalytic performances and characteristics. The MB removal in Co3O4/PMS and Co2O3/PMS system were more than 88% at neutral pH and over 64% at acidic pH, respectively, in 90 min. The concentration of dissolved cobalt ions from Co3O4 and Co2O3 was less than 0.018 mg/L at neutral pH and 0.036 mg/L at acidic pH at 90 min. The MB removal achieved by Co3O4/PMS and Co2O3/PMS were approximately three times higher than that ...
We explore RNA catalysis to learn about the catalytic potential of RNA and to decipher what is fundamental to all biological catalysts through comparison with protein enzyme catalysis. These studies also define the unique properties of RNA and proteins lead to catalytic and behavioral distinctions. The fundamental properties and behaviors of RNA molecules that we uncover teach us about how the potential function of RNA early in evolution and about the function of RNA molecules in modern-day biology. This knowledge may also be applied as RNA is co-opted for medical, technological and industrial applications.. Energy from binding interactions can be used to facilitate reactions of bond substrates, a fundamental precept of enzymology posited by Jencks for protein enzymes and demonstrated in our studies of RNA enzymes.. We currently focus on the group I ribozyme, the most well-studied catalytic RNA in both structure and function. We harness previous studies, including multiple crystal structures, a ...
We explore RNA catalysis to learn about the catalytic potential of RNA and to decipher what is fundamental to all biological catalysts through comparison with protein enzyme catalysis. These studies also define the unique properties of RNA and proteins lead to catalytic and behavioral distinctions. The fundamental properties and behaviors of RNA molecules that we uncover teach us about how the potential function of RNA early in evolution and about the function of RNA molecules in modern-day biology. This knowledge may also be applied as RNA is co-opted for medical, technological and industrial applications.. Energy from binding interactions can be used to facilitate reactions of bond substrates, a fundamental precept of enzymology posited by Jencks for protein enzymes and demonstrated in our studies of RNA enzymes.. We currently focus on the group I ribozyme, the most well-studied catalytic RNA in both structure and function. We harness previous studies, including multiple crystal structures, a ...
Ju, Y.-D., Xu, L.-W., Li, L., Lai, G.-Q., Qiu, H.-Y., Jiang, J.-X., Lu, Y. (2009-01-07). Erratum to Noyoris Ts-DPEN ligand: an efficient bifunctional primary amine-based organocatalyst in enantio- and diastereoselective Michael addition of 1,3-dicarbonyl indane compounds to nitroolefins [Tetrahedron Lett. 49 (2008) 6773] (DOI:10.1016/j.tetlet.2008.09.025). Tetrahedron Letters 50 (1) : 135-. [email protected] Repository. ...
View Cell Theory from BIOLOGY MCB2010 at Broward College. • Genetic material -> catalyst (RNA catalyst not regulated. Protein catalyst can be regulated.) • Metabolism (get energy -> grow
Again, if a pathway, even a prebiotic one, is making nonracemic chiral amino acids, it is catalyzed by a nonracemic chiral catalyst.* Setting aside the issue of how active and selective such prebiotic catalysts could be, a nonracemic chiral catalyst can arise either by chance due to low total number (if you only have 1 molecule, it can either be L- or D-, not racemic) or by specific synthesis by some other pathway. In the former case, that randomly synthesized catalyst will be destroyed or diluted away rather quickly - it must be amplified to remain effective, which means that its activity must feed back into its production, or in this case, amino acid synthesis must increase specific production of the catalyst, which is not all that plausible for reasons Ive discussed above. In the latter case, the specific synthesis of a chiral catalyst must again use another chiral catalyst - the origin of homochirality has just been displaced to an earlier event ...
Hydrogen could be an important source of clean energy, and the cleanest way to produce hydrogen gas is to split water into hydrogen and oxygen. But the catalyst currently used to facilitate this water-splitting reaction is platinum. And thats a problem.. When an electric current is run through water, it can split some of the water molecules. A catalyst lowers the amount of energy needed to split those molecules, and platinum is really, really good at this.. But platinum is also really, really expensive - much too expensive for widespread use in hydrogen production.. So, researchers have long viewed molybdenum sulfide (MoS2) as a promising, much cheaper alternative to platinum. The drawback is that MoS2s catalytic performance is far worse than platinums. To get around that problem, researchers have been trying to find ways to improve MoS2s catalytic performance. And now they may be on to something.. The biggest stumbling block to improving MoS2s performance has been a lack of understanding ...
A series of Ni/SBA-16 and NiMo/S16 catalysts were prepared by the impregnation methods and their performance on synthetic natural gas (SNG) production were systematically investigated in a continuous flow fixed-bed reactor. Coexistence of MoO3 in Ni-catalysts resulted in forming uniformly sized Ni particles and better heat-resistant performance because of the large surface area of SBA-16 supports and the strong interaction between Ni and SBA-16, while high MoO3(,3%) content will reduce the activity because of the partial coverage of nickel. Adopting the Mo-Ni impregnation sequence can significantly improve the activity of catalyst due to the moderate interaction between nickel and support and the electron transfer from MoO3 to Ni species. Ni-Mo/S16(1%) achieves the best activity with 100% CO conversion and 97% CH4 selectivity and yield at 350°C, 0.1MPa, and15000mL/g/h. The activity of Ni-Mo/S16(1%) remain stable after calcination in reactant gases at 700°C and during a 100 h reaction period. ...
Jointly promoting catalysis research. Researchers from Germany and Austria met for the first interdisciplinary conference of the CataLysis CRC-network Catalysis initiates central processes of our entire life on earth - from enzyme catalysis in metabolic processes in all organisms to natural photosynthesis and the production of synthetics and environmentally friendly energy sources. Scientists in four Collaborative Research Centres (CRCs) of the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) are currently investigating how these fundamental and at the same time diverse processes of chemical catalysis work exactly and how their principles can be used for sustainable value creation.. In order to set new research impulses and create synergies in the field, the four DFG-funded Collaborative Research Centres have now organised the first joint CataLysis conference. Around 170 researchers from Germany and Austria presented their latest research findings in a joint online conference ...
Y2Ce2O7 nano powders were synthesized via sol-gel reactions at 900 (S1), 1000 (S2) and 1100 (S3) ˚C for 4 h using yttrium acetate (C6H9O6Y.xH2O), ammonium cerium nitrate ((NH4)2Ce(NO3)6) and stearic acid (C18H36O2) as raw materials at stoichiometric 1:1 Y:Ce molar ratio. The synthesized materials were characterized by powder X-ray diffraction (PXRD) technique and Fourier transforms infrared (FTIR) spectroscopy. Structural analysis was performed by the FullProf program employing profile matching with constant scale factors. The results showed that the patterns had a main cubic Y2Ce2O7 structure with space group of Fm3m. The data showed that the lattice parameters were increased with increasing the reaction temperature. FESEM images showed that the synthesized Y2Ce2O7 particles had mono-shaped sphere morphologies. However, with increasing the reaction temperature to 1100 ˚C, the particle size scale was in micrometre range. Ultraviolet-visible spectra analysis showed that the nanostructured Y2Ce2O7
June 19, 1945- s. B. BECKER CATALYTIC CONVERSION OF RESIDUAL HYDROCARBON OILS Filed Sept. 30, 1941 Pstented June 19, 194s cArALYrIo CONVERSION oF RESIDUALv mnocARoN oms Sam B. Becker, Chicago, Ill., assignor to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application September30, 1941, Serial No. 412,942 7 Claims. v (Cl. 196-52) Ihis invention relates to the conversion oi hydrocarbon oils and particularly heavy oils, such as petroleum residuums and heavy gas oils, into gasoline. The invention also relates to an ap- .paratus for carrying out the desired conversion. More specifically the invention relates to improvements in the process of converting unvaporizable residual oils by the action of subdivided, solid catalysts at high temperature. - One object of the invention is to increase the life of the catalyst in such a conversion process. Another object of the invention is to treat the heavy oil preliminarily immediately before contacting with the catalyst, thereby removing ...
Using cyclopropanation reactions catalyzed by dendrimer-encapsulated gold and other metal nanoclusters, including platinum, palladium and rhodium, we have demonstrated that changing the dendrimer properties allows catalytic reactivity in a heterogeneous catalyst to be tuned in a similar fashion to ligand modification in a homogeneous catalyst, says world renowned catalysis chemist Gabor Somorjai, one of the leaders of this research. Furthermore, we have shown that these heterogeneous catalysts employed in a fixed-bed flow reactor allow fine control over the residence time of the reactants and thus enable control over product distribution in a way that is not easily available for homogeneous catalysts ...
Active and stable metal-free heterogeneous catalysts for CO2 fixation are required to reduce the current high level of carbon dioxide in the atmosphere, which is driving climate change. In this work, we show that defects in nanosilica (E′ centers, oxygen vacancies, and nonbridging oxygen hole centers) convert CO2 to methane with excellent productivity and selectivity. Neither metal nor complex organic ligands were required, and the defect alone acted as catalytic sites for carbon dioxide activation and hydrogen dissociation and their cooperative action converted CO2 to methane. Unlike metal catalysts, which become deactivated with time, the defect-containing nanosilica showed significantly better stability. Notably, the catalyst can be regenerated by simple heating in the air without the need for hydrogen gas. Surprisingly, the catalytic activity for methane production increased significantly after every regeneration cycle, reaching more than double the methane production rate after eight ...
A system for controlled heat generation in exhaust pipeline is studied, consisting of fuel injector and oxidation catalyst (plus connecting pipes). A 3D-CFD software (StarCD) coupled with a tailored 1D model of catalytic monolith channel (XMR) are employed for simulations of realistic, fully 3D system geometry. Exhaust gas flow, fuel injection, and distribution at the catalyst inlet is solved by 3D-CFD, while the processes inside individual representative channels are simulated by the effective 1D model. The 3D-CFD software calls iteratively the 1D channel model with proper boundary conditions and solves 3D temperature profile over the monolith, utilizing local enthalpy fluxes (including gas-solid heat transfer and reaction enthalpy) calculated by the 1D channel model.Seven representative hydrocarbons are used for characterisation of Diesel fuel composition with respect to catalytic oxidation kinetics. Each representative component possesses its own light-off behaviour (described by a global ...
The objective of this project is to develop novel non-precious metal electrocatalysts for oxygen reduction reaction (ORR), and demonstrate the potential of the catalysts to perform at least as good as conventional Pt catalysts currently in use in polymer electrolyte membrane fuel cell (PEMFC) with a cost at least 50 % less than a target of 0.2 g (Pt loading)/peak kW and with durability | 2,000 h operation with less than 10 % power degradation. A novel nitrogen-modified carbon-based catalyst was obtained by modifying carbon black with nitrogen-containing organic precursor in the absence of transition metal precursor. The catalyst shows the onset potential of approximately 0.76 V (NHE) for ORR and the amount of H2O2 of approximately 3% at 0.5 V (NHE). Furthermore, a carbon composite catalyst was achieved through the high-temperature pyrolysis of the precursors of transition metal (Co and Fe) and nitrogen supported on the nitrogen-modified carbon-based catalyst, followed by chemical post-treatment. This
In the last decade, chemists have increasingly focused on the development of new and more efficient methods for the catalytic conversion of carbon dioxide into value-added organic molecules. Homogeneous catalysis has proved to be a key technology for the conversion of carbon dioxide under particularly mild reaction conditions that meet the increasing societal demands for sustainable chemical processing. In this account article, we focus on the most effective routes developed for ring expansion-addition reaction of carbon dioxide to epoxides mediated by either metal catalysts or organocatalyst systems to give cyclic organic carbonates.. ...
Hydr-) oxidic PdOxHy colloids were prepared by H2PdCl4 hydrolysis in presence of poly(vinylpyrrolidone) under pH control. After immobilization, the resulting catalysts show a high chemo- and stereo selectivity in the hydrogenation of C-C triple bonds. Systematic investigations of the preparation parameters indicate that the hydrolysis pH, the PVP amount and chainlength as well as the colloid aging time are of major importance for catalytic performance.. ...
Abstract (EN): A large number of studies can be found in the literature regarding the production of new catalysts for methanol steam reforming. This work summarizes the latest developments on catalysts for this application and is divided in two main groups: copper-based and group 8-10 metal-based catalysts. In each section, the strategies proposed by several authors to enhance the performance of the catalysts are described. An overall comparison between the two groups shows that copper-based catalysts are the most active ones, while the 8-10 group catalysts present better results in terms of thermal stability and long-term stability. Very promising results were reported for both groups, enhancing the value of methanol as a hydrogen carrier for fuel cell applications ...
TY - JOUR. T1 - Review of Enantioselective Homogeneous Supported Catalysis edited by Radovan Šebesta.. AU - Notestein, Justin M.. PY - 2012. Y1 - 2012. N2 - Enantioselective Homogeneous Supported Catalysis: RSC (Green Chemistry Series) edited by Radovan Sebesta, UK: Royal Society of Chemistry, 2011, 300pp. ISBN: 9781849731768.. AB - Enantioselective Homogeneous Supported Catalysis: RSC (Green Chemistry Series) edited by Radovan Sebesta, UK: Royal Society of Chemistry, 2011, 300pp. ISBN: 9781849731768.. U2 - 10.1007/s10562-012-0851-z. DO - 10.1007/s10562-012-0851-z. M3 - Book/Film/Article review. VL - 142. SP - 1150. EP - 1151. JO - Catalysis Letters. JF - Catalysis Letters. SN - 1011-372X. ER - ...
The side-chain of the nucleophilic residue performs covalent catalysis on the substrate. The lone pair of electrons present on the oxygen or sulfur attacks the electropositive carbonyl carbon.[3] The 20 naturally occurring biological amino acids do not contain any sufficiently nucleophilic functional groups for many difficult catalytic reactions. Embedding the nucleophile in a triad increases its reactivity for efficient catalysis. The most commonly used nucleophiles are the hydroxyl (OH) of serine and the thiol/thiolate ion (SH/S−) of cysteine.[2] Alternatively, threonine proteases use the secondary hydroxyl of threonine, however due to steric hindrance of the side chains extra methyl group such proteases use their N-terminal amide as the base, rather than a separate amino acid.[1][24]. Use of oxygen or sulfur as the nucleophilic atom causes minor differences in catalysis. Compared to oxygen, sulfurs extra d orbital makes it larger (by 0.4 Å)[25] and softer, allows it to form longer bonds ...
Development of sustainable catalytic systems for fundamentally important synthetic transformations and energy storage applications is an intellectually stimulating challenge. Catalytic dehydrogenation of feedstock chemicals, such as alcohols and amines to value-added products with the concomitant generation of dihydrogen is of much interest in the context of hydrogen economy and is an effective alternative to the classical oxidation reactions. Despite a number of homogeneous catalysts being identified for the acceptorless dehydrogenation, the use of high price and limited availability of precious metals and poor recovery of the catalyst have spurred interest in catalysis with more earth-abundant alternatives, especially iron. However, no report has described a reusable iron-based heterogeneous catalyst for oxidant-free and acceptorless dehydrogenation reactions. Here we replace expensive noble metal catalysts with an inexpensive, benign, and sustainable nanoscale iron catalyst for the efficient
Heterogeneous catalysis[edit]. The most commonly encountered form of chemisorption in industry, occurs when a solid catalyst ... a b Philippe Serp, José Luis Figueiredo, Carbon Materials for Catalysis, Wiley, - 2009, - 550 p. ... Applied Catalysis A: General. 335 (2): 241-251. doi:10.1016/j.apcata.2007.11.029.. ... Catalysis Communications. 27: 33-37. doi:10.1016/j.catcom.2012.06.018.. ...
Journal of Molecular Catalysis B: Enzymatic. 28 (4-6): 155-166. doi:10.1016/j.molcatb.2004.01.016. Archived from the original ( ... "True" catalysis?[edit]. Because most deoxyribozymes suffer from product inhibition and thus exhibit single-turnover behavior, ... Other uses of DNA in chemistry are in DNA-templated synthesis, Enantioselective catalysis,[43] DNA nanowires and DNA computing. ... García-Fernández A, Roelfez G (2012). "Chapter 9. Enantioselective catalysis at the DNA Scaffold". In Sigel A, Sigel H, Sigel ...
Catalysis. Silver metal is a good catalyst for oxidation reactions; in fact it is somewhat too good for most purposes, as ... in catalysis of chemical reactions, as a colorant in stained glass and in specialised confectionery. Its compounds are used in ...
... catalysis. Main article: Acid catalysis. Acids are used as catalysts in industrial and organic chemistry; for example, ...
Catalysis[edit]. Organometallic complexes are commonly used in catalysis. Major industrial processes include hydrogenation, ... Leeuwen, Piet W.N.M. van (2004). Homogeneous catalysis : understanding the art. Dordrecht: Springer. ISBN 978-1-4020-3176-2.. ... P. W.N.M. van Leeuwen "Homogeneous Catalysis: Understanding the Art, 2004 Kluwer, Dordrecht. ISBN 1-4020-2000-7 ... The world's polyethylene and polypropylene are produced via both heterogeneously via Ziegler-Natta catalysis and homogeneously ...
Catalysis[edit]. Magnetite is the catalyst for the industrial synthesis of ammonia.[45] It is also used to catalyze the ...
Catalysis[edit]. Catalysis is achieved by one of two mechanisms: *Aspartic, glutamic and metallo- proteases activate a water ... In a second step, water is activated to hydrolyse this intermediate and complete catalysis. Other enzyme residues (not shown) ... This covalent acyl-enzyme intermediate is then hydrolysed by activated water to complete catalysis by releasing the second half ...
Tandem catalysis[edit]. In tandem catalysis two or more different catalysts are coupled in a one-pot reaction. ... Catalysis impacts the environment by increasing the efficiency of industrial processes, but catalysis also plays a direct role ... Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst[1] (/ˈkætəlɪst ... a Father of Catalysis". ACS Catalysis: 8531-8539. doi:10.1021/acscatal.8b02310.. ...
Catalysis[edit]. Application of MW heating to heterogeneous catalysis reactions has not been explored intensively due to ... Applied Catalysis B: Environmental, 33, (2), 137-148 *^[permanent dead link ... "Heterogeneous catalysis under microwave heating" (PDF). La Chimica & L'Industria. Società Chimica Italiana (4): 78-80. ...
Catalysis[edit]. In catalysis silver is active as silver oxide in the Wolff rearrangement. Silver nitrate is used to separate ... The chemistries have much in common but organosilver catalysis is much less common (mostly academic study) than organocopper ...
Mechanism of catalysis[edit]. The conversion of chorismate to prephenate is the first committed step in the pathway to the ... The presence of chorismate mutase increases the rate of the reaction a million fold.[6] In the absence of enzyme catalysis this ... The data obtained suggests that effective catalysis is derived from stabilization of both the NAC and transition state.[10] ... and thereby promotes catalysis. As a result, there is no formal intermediate, but rather a pseudo-diaxial chair-like transition ...
Catalysis[edit]. Using silver nanoparticles for catalysis has been gaining attention in recent years. Although the most common ... 3.1 Catalysis *3.1.1 Supported on silica spheres - reduction of dyes. *3.1.2 Mesoporous aerogel - selective oxidation of ... With this in mind, it is important to note that heterogeneous catalysis takes place by adsorption of the reactant species to ... NOTE: This paragraph is a general description of nanoparticle properties for catalysis; it is not exclusive to silver ...
Catalysis[edit]. Thorium dioxide has almost no value as a commercial catalyst, but such applications have been well ...
In catalysis, the reaction does not proceed directly, but through reaction with a third substance known as catalyst. Although ... In heterogeneous catalysis, typical secondary processes include coking where the catalyst becomes covered by polymeric side ... Of particular importance in heterogeneous catalysis are the platinum group metals and other transition metals, which are used ... acid/base catalysis), electrostatic interactions and many others.[57] ...
Oxidation catalysis[edit]. Many useful compounds are produced by the reactions of hydrocarbons with oxygen, a conversion that ...
Applications to homogeneous catalysis[edit]. One of the first applications of phosphine ligands in catalysis was the use of ... 4 Applications to homogeneous catalysis. *5 Complexes of other organophosphorus ligands *5.1 Complexes of primary and secondary ... Tolman, C. A. (1977). "Steric Effects of Phosphorus Ligands in Organometallic Chemistry and Homogeneous Catalysis". Chem. Rev. ... Because of these two features, metal phosphine complexes are useful in homogeneous catalysis.[1] Prominent examples of metal ...
Proteins are optimised for catalysis[edit]. Proteins are functional macromolecules responsible for catalysing the biochemical ...
Fluorocarbon anions in Ziegler-Natta catalysis[edit]. Fluorine-containing compounds are often featured in noncoordinating or ... and reagents in catalysis. In addition to these applications, some organofluorine compounds are pollutants because of their ... are useful in Ziegler-Natta catalysis and related alkene polymerization methodologies. The fluorinated substituents render the ...
Catalysis of ASR by NaOH or KOH[edit]. However, the ASR reaction significantly differs from the pozzolanic reaction by the fact ... and this greatly facilitates the catalysis process because the reaction in aqueous solution occurs much faster than in the dry ... so that the catalysis mechanism becomes negligible. ... 1.1 Catalysis of ASR by NaOH or KOH. *1.2 Analogy with the soda ...
Ru(bpy)3]2+ and photoredox catalysis[edit]. Photoredox catalysis using combination of [Ru(bpy)3]2+ catalyst and visible light ... J. M. R. Narayanam; C. R. J. Stephenson (2011). "Visible light photoredox catalysis: applications in organic synthesis". Chem. ... Romero, Nathan A.; Nicewicz, David A. (10 June 2016). "Organic Photoredox Catalysis". Chemical Reviews. 116 (17): 10075-10166. ... F. Teply (2011). "Photoredox catalysis by [Ru(bpy)3]2+ to trigger transformations of organic molecules. Organic synthesis using ...
This literally opened up a new branch of chemistry research...Catalysis... and had enormous import at the time in the ...
The company is focused on four business areas: care chemicals (consumer and industrial); catalysis; natural resources (oil & ...
Kemball, Charles; Dowden, D. A. (1978-01-01). Catalysis. Royal Society of Chemistry. p. 53. ISBN 978-0-85186-544-7. Retrieved ...
He was also awarded the Queen Elizabeth II Diamond Jubilee Medal (in 2013), Catalysis Medal from the Chemical Institute of ... Rempel's main research interests in the field of chemical engineering were applied catalysis and polymer science. He was known ... CS1 maint: discouraged parameter (link) Monnier, Jacques; Sanger, Alan R. (2006). "Garry L. Rempel". Catalysis in Canada (PDF ... CS1 maint: discouraged parameter (link) "Author biographies". Catalysis. Royal Society of Chemistry. 30: xiv. 2018. doi:10.1039 ...
"Catalysis". Design Tasmania. January 2019. Retrieved 27 August 2019. Catchpole, Paula. "Pete Mattila". Tasmanian Life. ... Vinall, Frances (11 January 2019). "Mona Foma: Pete Mattila's Catalysis exhibition uses Tasmanian steel". The Examiner. ...
James J. Spivey; K. M. Dooley (August 2007). Catalysis. Royal Society of Chemistry. pp. 33-. ISBN 978-0-85404-244-9. "All ...
Catalysis. Catalytic reagents that can be used in small quantities to repeat a reaction are superior to stoichiometric reagents ... Green chemistry emerged from a variety of existing ideas and research efforts (such as atom economy and catalysis) in the ... Sheldon, R. A.; Arends, I. W. C. E.; Hanefeld, U. (2007). Green Chemistry and Catalysis. doi:10.1002/9783527611003. ISBN ...
695-. ISBN 978-3-527-61033-4. Spivey, James J. (2002). Catalysis. Royal Society of Chemistry. pp. 239-. ISBN 978-0-85404-224-1 ...
Catalysis[change , change source]. When using a catalyst the activation energy is made smaller. This means that the reaction ...
Catalysis[change , change source]. Catalysis is using a catalyst to change the rate of a chemical reaction. For the reactants ...
... covers all areas of catalysis, incorporating the work of scientists, engineers and industry. November issue ... Nature Catalysis provides coverage of the science and business of catalysis research, creating a unique journal for scientists ... It publishes work on homogeneous catalysis, heterogeneous catalysis and biocatalysts, incorporating both fundamental and ... Stay up to date with the latest in catalysis news and research. Register for the e-alert to get content delivered directly to ...
Tandem catalysis[edit]. In tandem catalysis two or more different catalysts are coupled in a one-pot reaction. ... Catalysis impacts the environment by increasing the efficiency of industrial processes, but catalysis also plays a direct role ... Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst[1] (/ˈkætəlɪst ... a Father of Catalysis". ACS Catalysis: 8531-8539. doi:10.1021/acscatal.8b02310.. ...
... Group. The Applied Catalysis Group is one of the many RSC Interest Groups and exists to bring together and ... The Applied Catalysis Group also has bursaries available specifically for members attending the European Congress on Catalysis ... MyRSC Applied Catalysis Group You will be required to register for MyRSC, then you can sign up to become a member of this group ... We also have an online community for anyone interested in catalysis based on MyRSC. Get Involved. We are always looking for new ...
... Featured events. Carbon Dioxide Utilisation: Faraday Discussion. 7 - 9 April 2021, Sheffield, United Kingdom ... Sep 06 2020 XXII International Symposium on Homogeneous Catalysis (XXII ISHC) to be held on 6-11 September 2020 in Lisbon ... Lisbon, Portugal XXII International Symposium on Homogeneous Catalysis (XXII ISHC) to be held on ... Lisbon, Portugal ... Reaction mechanisms in catalysis: Faraday Discussion. 17 - 19 February 2021, London, United Kingdom ...
This phenomenon, properly termed inhibition or retardation, is sometimes called negative catalysis. Concentrations of the ... catalysis: …a foreign substance, called an inhibitor, decreases the rate of a chemical reaction. ... catalysis. *. In catalysis. …a foreign substance, called an inhibitor, decreases the rate of a chemical reaction. This ... phenomenon, properly termed inhibition or retardation, is sometimes called negative catalysis. Concentrations of the inhibitor ...
This book series publishes monographs and edited books on all areas of molecular catalysis, including heterogeneous catalysis, ... Molecular Catalysis van Leeuwen, P. W. (Ed), Claver, C. (Ed) ... Catalysis , Series. This selection contains titles in Catalysis ... Catalysis by Metal Complexes Claver, C. (Ed), van Leeuwen, P. W. (Ed) ...
The catalytic system is prepared by impregnation of activated charcoal with a heterobimetallic Schiff base complex of cobalt and cerium (pictured), followed by pyrolysis. The resulting Co-Ce/C composite features small Co nanoparticles with a mean size of 6.8 nm surrounded by small Ce clusters (around 1 nm) highly dispersed in the carbon matrix. The authors benchmarked the activity of the system using the hydrodeoxygenation of acetophenone in the presence of hydrogen as a test reaction. Based on control experiments with monometallic Co or Ce catalysts, the simultaneous presence of both metals is crucial to achieve the selective formation of ethylbenzene over 1-phenylethanol. Similarly, employing supports other than charcoal for the preparation of the bimetallic system - that is, TiO2, CeO2, or γ-Al2O3 - has negative effects on both yield and selectivity. The mechanistic investigation also revealed that the synergy between metallic Co and mixed Ce3+/Ce4+ species at the surface of the catalyst is ...
Catalysis aimed at closing the carbon cycle (especially conversion of CO2, methane, and natural gas to fuels and chemical ... The Catalysis program is part of the Chemical Process Systems cluster, which also includes 1) Electrochemical Systems; 2) ... Heterogeneous catalysis represents the main thrust of the program. Proposals related to both gas-solid and liquid-solid ... Renewable energy-related catalysis with applications in electrocatalysis, photocatalysis, and catalytic conversion of biomass- ...
Catalysis aimed at closing the carbon cycle (especially conversion of CO2, methane, and natural gas to fuels and chemical ... Heterogeneous catalysis and biocatalysis represent the main thrusts of the program. Proposals related to both gas-solid and ... NOTE: For catalysis proposals involving aspects of sustainable chemistry, consider making proposal submissions to this program ... The goal of the Catalysis and Biocatalysis program is to advance research in catalytic engineering science and promote the ...
Catalysis (Nothing Left, Cleansed and more). 5 tracks (20:33). Discover more music, concerts, videos, and pictures with the ...
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This book provides detailed information on the base catalysis of group 5 (Nb, Ta) metal oxide clusters by elucidating how the ... This book provides an overview of the latest developments in the field of nanoparticle catalysis. It not only discusses ... Recent Advances in Nanoparticle Catalysis van Leeuwen, P. W. (Ed), Claver, C. (Ed) (2020) ... Transition metal catalysis is at the forefront of synthetic organic chemistry since … ...
You are invited to a series of catalysis webinars hosted by DuPont Water Solutions experts and their guests from the industry. ...
Energy & Environmental Catalysis Lab Our research group has focused on the "energy" and "environmental" related catalysis ...
The CAT Program does not support applied catalysis research focusing on engineering aspects of catalysis such as scale-up, ... The CAT Program also considers (but is not limited to) the following: polymerization catalysis, single site catalysis, ... Researchers focused on enzymatic or cellular catalysis should consult the Chemistry of Life Processes (CLP) Program. Catalysis ... organocatalysis, inorganic, organometallic, and photoredox catalysis, electrocatalysis, and biologically-inspired catalysis. ...
Advancing carbon dioxide catalysis. University of Delaware. Funder. Department of Energy Office of Energy Efficiency and ... Advancing carbon dioxide catalysis Engineering professor receives major Department of Energy grants ... to advance technologies for carbon capture and utilization through catalysis, the use of substances to speed the rate of ... a research center that has pioneered multidisciplinary research in the scientific and engineering principles of catalysis. ...
Catalysis by dihydrofolate reductase and other enzymes arises from electrostatic preorganization, not conformational motions ... Structure and Catalysis of Acylaminoacyl Peptidase: CLOSED AND OPEN SUBUNITS OF A DIMER OLIGOPEPTIDASE ... Transition state theory can be used in studies of enzyme catalysis: lessons from simulations of tunnelling and dynamical ... Computer simulations of enzyme catalysis: Finding out what has been optimized by evolution ...
Careers in Catalysis Research. 10/17/18. FRNY 1043 4:30 to 6:00 PM. Guest Seminar: Dr. Mark Kaminsky from Aramco Research ... Michigan Catalysis Society Symposium. 5/9/2018. G140 4:00 PM. Guest Seminar: Dr. Kristen Kulinowski from the Chemical Safety ... Group meetings for the Purdue Catalysis Center are held every Wednesday from 4:30pm to 6:00pm. table.tableizer-table { font- ...
Catalysis for Renewable Energy Storage and (iii) Catalysis for Bio-Renewables. ... Heterogeneous catalysis significantly shapes society, as it plays a crucial role in the production of base chemicals, fuels for ... The Inorganic Materials & Catalysis (IMC) group investigates heterogeneous catalysts that are pivotal to clean and sustainable ... Inorganic Materials & Catalysis Establishing fundamental insight into structure-performance relations for heterogeneous ...
Computation has continued to grow in significance in the field of catalysis. One routinely sees a wide range of relevant ... In this special issue, we present several current trends in computational catalysis, broadly organized in the areas of (1) ...
Surface Chemistry and Catalysis Group. The Surface Chemistry and Heterogeneous Catalysis Group at Oak Ridge National Laboratory ... A major portion of the groups basic research is aimed at research into the Fundamentals of Catalysis and Chemical ... Although perovskites have been widely used in catalysis, tuning of their surface termination to control reaction selectivity ... cooperative catalysis of hierarchically structured metal clusters and nanoparticles supported on oxides; electrocatalytic ...
Oxalate Catalysis. Without an appropriate catalyst some chemical reactions would be so slow as to appear not to occur at all on ... Catalysis: Chemical and Biochemical. This is a part of The Double Life of RNA ...
... molecular dynamics and microkinetic modeling in catalysis applications for the production of energy, including the chemical, ... electrochemical, and photochemical conversion of different feedstocks into fuels, and fuel cell catalysis. ...
From the themed collection: Single atom catalysis The article was first published on 25 Sep 2017. Catal. Sci. Technol., 2017,7 ... From the themed collection: Single atom catalysis The article was first published on 21 Aug 2017. Catal. Sci. Technol., 2017,7 ... From the themed collection: Single atom catalysis The article was first published on 07 Jul 2017. Catal. Sci. Technol., 2017,7 ... From the themed collection: Single atom catalysis The article was first published on 02 Jun 2017. Catal. Sci. Technol., 2017,7 ...
FUTURE DEVELOPMENT OF CATALYSIS. Homogeneous Catalysis. Heterogeneous Catalysis. SOLUTIONS TO THE EXERCISES. Index ... Green Chemistry and Catalysis. PHASE-TRANSFER CATALYSIS. Definition. Catalysts for PTC. Mechanism and Benefits of PTC. PTC ... HOMOGENEOUS CATALYSIS WITH TRANSITION METAL CATALYSTS. Key Reactions in Homogeneous Catalysis. Catalyst Concepts in Homogeneous ... ENVIRONMENTAL CATALYSIS AND GREEN CHEMISTRY. Automotive Exhaust Catalysis. NOx Removal Systems. Catalytic Afterburning. ...
Below is a list of all articles, highlights, profiles, projects, and organizations related specifically to catalysis. ... Below is a list of all articles, highlights, profiles, projects, and organizations related specifically to catalysis. ...
Applied catalysis has resolved many of the challenges faced in environmental protection. This session seeks contributions in ... the area of applied environmental catalysis including but not limited to photocatalytic and catalytic pollution control, ... and applications of catalysis in green chemistry. ... Anthraquinone Process Enabled By Phase Transfer Catalysis. * ...
Topics in Catalysis. ISSN: 1022-5528 (Print) 1572-9028 (Online) Description. Topics in Catalysis publishes topical collections ... Topics in Catalysis. Coverage. Volume 1 / 1994 - Volume 60 / 2017. Print ISSN. 1022-5528. Online ISSN. 1572-9028. Publisher. ... The publication of individual uninvited original research articles can be sent to our sister journal Catalysis Letters. This ... The journal documents todays emerging and critical trends in all branches of catalysis. Each themed issue is organized by ...
Catalysis may be classified as either homogeneous or heterogeneous. A homogeneous catalysis is one whose components are ... a Father of Catalysis". ACS Catalysis. 8 (9): 8531-39. doi:10.1021/acscatal.8b02310. Dhara SS; Umare SS (2018). A Textbook of ... includes Base catalysis) Autocatalysis BIG-NSE (Berlin Graduate School of Natural Sciences and Engineering) Catalysis Science ... Japan Inorganic Chemistry and Catalysis Group, Utrecht University, The Netherlands Centre for Surface Chemistry and Catalysis ...
Metal oxide catalysis. [S David Jackson; Justin S J Hargreaves;] -- With its two-volume structure, this handbook and ready ... The result is an up-to-date review of metal oxides in catalysis. The first volume covers a range of techniques that are used to ... The result is an up-to-date review of metal oxides in catalysis. The first volume covers a range of techniques that are used to ... Metal Oxide Catalysis; Contents to Volume 1; Contents to Volume 2; Preface; List of Contributors; 1: EPR (Electron Paramagnetic ...
  • Our research group has focused on the "energy" and "environmental" related catalysis researches with the series of bulk and supported metal oxide catalysts (MO x and MO x /support. (
  • Examples of sustainable chemistry appropriate for the Chemical Catalysis (CAT) Program include, but are not limited to: the design, preparation and reactivity studies associated with new catalysts and catalytic processes to replace rare, and/or toxic compounds with earth-abundant and benign alternatives and advanced catalytic methods for the reduction of dinitrogen to ammonia that will permit reductions in the energy requirements and greenhouse gas emissions. (
  • Catalysis research with immediate objectives in the synthesis of complex natural products using established catalysts should be submitted to the Chemical Synthesis (SYN) Program. (
  • The Inorganic Materials & Catalysis (IMC) group investigates heterogeneous catalysts that are pivotal to clean and sustainable chemical conversion processes for the production of fuels and chemicals. (
  • The Surface Chemistry and Heterogeneous Catalysis Group at Oak Ridge National Laboratory conducts research into surface chemistry and fundamentals of catalytic reactions at metal surfaces, metal oxide surfaces and supported metal catalysts. (
  • The development of single atom catalysts lies at the frontier of catalysis and nanoscience and is rapidly gaining prominence in the drive towards atom-efficient chemical transformations. (
  • Interface science and catalysis already play an important role in all of these areas, but new catalysts providing improved reactivity and selectivity at dramatically reduced cost need to be developed to enable the required transformations of processes and economies on a global scale. (
  • Our research program on Interface Science and Catalysis aims to discover and quantify nanoscale phenomena that can be exploited to boost the reactivity of future generations of energy-relevant catalysts, to enhance the efficiency of greenhouse gas capture and reforming processes, and for the controlled synthesis of novel high-performance materials. (
  • Oxides of nitrogen serve as catalysts for the oxidation of sulfur dioxide in the lead chamber process for producing sulfuric acid , an instance of homogeneous catalysis in which the catalyst and reactants are gases. (
  • Synergistic catalysis is a specialized approach to catalysis whereby at least two different catalysts act on two different substrates simultaneously to allow reaction between the two activated materials. (
  • Through the combination of two transition metal catalysts, synergistic catalysis has been reported to accelerate many chemical transformations, and even to induce high enantioselectivity, which could not be realized by the use individual catalysts. (
  • Besides using two transition metal catalysts, synergistic catalysis can also be carried out by utilizing one transition metal catalyst in combination with an organocatalyst. (
  • The contribution of catalysis to manufacturing adds up to almost 40% of global GDP--and the demand for such catalysts will only increase. (
  • A s this month's Industry Insider feature shows, catalysis, and the development of better and better catalysts, are extremely important to science-based industry. (
  • Kits contain sets of related catalysts, ligands, and scavengers with varying steric and electronic properties useful for rapid screening of catalysis conditions. (
  • The Catalysis group, lead by Prof. Puurunen, develops new types of solid heterogeneous catalysts and evaluates their performance, aiming for fundamental understanding and structure-activity relationships. (
  • Photoredox catalysis: A variety of organic transformations mediated by visible-light-active photoredox catalysts have been conducted in a photochemical flow reactor. (
  • This review article contains a reminder of the fundamentals of heterogeneous catalysis and a description of the main domains of heterogeneous catalysis and main families of metal oxide catalysts, which cover acid-base reactions, selective partial oxidation reactions, total oxidation reactions, depollution, biomass conversion, green chemistry and photocatalysis. (
  • The field of catalysis in chemistry was historically dominated by the use of transition metal catalysts. (
  • Simone Hauser, Mirza Cokoja and Fritz Kühn explore recent developments in homogeneous epoxidation catalysts in this hot Catalysis Science & Technology Perspective. (
  • To explore the potential of perovskites in acid-base catalysis, we. (
  • Brønsted studied a number of acid- and base-catalyzed reactions, including (1) the acid-catalyzed hydrolysis of an ester , ethyl orthoacetate, (2) the basic catalysis of nitramide decomposition (H 2 N-NO 2 → H 2 O + N 2 O), and (3) the acid-base catalysis of the conversion (mutarotation) of glucose to a closely related form. (
  • Heterogeneous catalysis significantly shapes society, as it plays a crucial role in the production of base chemicals, fuels for mobility and the synthesis of fine chemicals and pharmaceuticals. (
  • He gained his doctorate in 1975 in the field of catalysis and high-pressure synthesis. (
  • Advanced Synthesis & Catalysis (ASC) is the leading primary journal in organic, organometallic, and applied chemistry. (
  • The implementation of chiral iodine catalysis has tremendously been developed in the field of asymmetric synthesis over the past decade. (
  • Research in the catalysis and synthesis section encompasses a broad spectrum of interests from fundamental concepts in mechanistic chemistry to the application of new technology in projects of commercial and technological relevance. (
  • It treats historical background, concepts (including structures of mono- and polymetallic complexes), molecular orbitals, reactivity, implications in biology and applications to organic synthesis and catalysis. (
  • Subjects related to catalysis such as experimental techniques, adsorption , process technology , synthesis , in situ characterization, computational, theoretical modeling, imaging and others are included if there is a clear relationship to catalysis. (
  • Work involves synthesis, testing and characterization of novel organometallic compounds for a wide range of applications particularly in the areas of both green homogeneous and heterogeneous catalysis. (
  • This autumn SCI will bring together researchers from academia and industry to learn more about these emerging synthetic methods and how they have been used in fine chemical synthesis in a one-day meeting, Catalysis without Precious Metals . (
  • This program pursues an improved understanding of chemical catalysis for advanced fuel synthesis and energy conversion processes by elucidating catalytically important properties over well-defined surfaces, powders and nanostructures. (
  • Documents up-to-date developments in the study of catalysis and its applications to organic synthesis and industrial processes. (
  • The main goal of the project aims the synthesis of di- and trinuclear transition metal complexes and their application in homogeneous catalysis. (
  • The goal of the Asymmetric Catalysis and Photochemistry Research Line is to develop new general catalysis concepts and applying them to the synthesis of complex molecules and pharmaceuticals. (
  • Heidelberg University's organic chemistry Professor A. Stephen K. Hashmi , gave a fascinating lecture on new aspects of gold catalysis applied to the synthesis of a variety of functional products. (
  • The programme includes synthesis of carbon nanofibres and nanotubes of different morphology and the use of CNF/CNT in applications such as heterogeneous catalysis, fuel cells and conversion and storage of energy. (
  • Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst [1] ( / ˈ k æ t əl ɪ s t / ), which is not consumed in the catalyzed reaction and can continue to act repeatedly. (
  • In heterogeneous catalysis, typical secondary processes include coking where the catalyst becomes covered by polymeric side products. (
  • Advances in tools for catalyst characterization and theoretical/computational catalysis. (
  • Catalysis researchers determined that the cobalt-based catalyst (center) takes a different path to adding hydrogen (H) to carbon dioxide (CO 2 ) depending on whether it is in a traditional solvent or water. (
  • Getting more catalysis from potentially rare catalyst elements. (
  • In homogeneous catalysis, the catalyst is molecularly dispersed in the same phase (usually gaseous or liquid) as the reactants. (
  • In heterogeneous catalysis the reactants and the catalyst are in different phases, separated by a phase boundary. (
  • When the catalyst and the reacting substances are present together in a single state of matter, usually as a gas or a liquid, it is customary to classify the reactions as cases of homogeneous catalysis. (
  • Catalysis is a type of chemical reaction which is facilitated by a certain agent (a catalyst), which is, however, not consumed in the reaction. (
  • Catalytic microreactors, he explained, have a potential to bridge between homogeneous and heterogeneous catalysis by the microencapsulation of catalyst dissolved or dispersed in non-volatile phase such as a ionic liquid. (
  • Computation has continued to grow in significance in the field of catalysis. (
  • Journal of Catalysis is the premier scholarly publication in the field of catalysis and an indispensable source of information for chemists and chemical engineers in both industrial and academic fields. (
  • Catalysis Today offers researchers in the field of catalysis in-depth overviews of topical issues. (
  • Are you new to the field of catalysis and searching for a good starting point in the literature? (
  • Nature Catalysis covers all areas of catalysis, incorporating the work of scientists, engineers and industry. (
  • The PIs and co-PIs have extensive experience in the areas of catalysis, electrocatalysis, advanced materials, and synchrotron spectroscopies. (
  • Over the past year we have published a number of Perspectives and Mini Reviews authored by world-leading scientists and covering all areas of catalysis. (
  • Heterogeneous catalysis and biocatalysis represent the main thrusts of the program. (
  • Biocatalysis proposals should focus on enzymatic catalysis involving engineering of the active site involved in substrate conversion. (
  • Renewable energy-related catalysis (including applications related to biocatalysis, biomass refining, electrocatalysis, and photocatalysis). (
  • Throughout, the latest research from various disciplines is combined, such as homogeneous and heterogeneous catalysis, biocatalysis, and photocatalysis. (
  • The Chemical Catalysis (CAT) Program supports experimental and computational research directed towards the fundamental understanding of the chemistry of catalytic processes. (
  • We are improving the understanding of catalysis, developing new catalytic processes with industry and promoting the use of catalysis as a sustainable 21st century technology. (
  • This book highlights many powerful examples of how catalysis can impact society and also how catalysis science is making use of the most advanced capabilities and techniques to shed light on how catalytic processes work. (
  • Research into catalysis is a major field in applied science and involves many areas of chemistry, notably organometallic chemistry and materials science . (
  • This tutorial volume covers the basic and advanced aspects of organometallic chemistry of all metals and related catalysis topics. (
  • Organometallic Chemistry and Catalysis can profitably be read by beginners such as undergraduate and graduate students, as well as engineers, researchers and molecular scientists from academy and industry. (
  • Subjects such as catalysis of immobilized organometallic and biocatalytic systems are welcome. (
  • Our researches focuses on both fundamental and applied aspects in tailor-made organometallic compounds, nanostructured hybrid materials and catalysis. (
  • Researchers focused on enzymatic or cellular catalysis should consult the Chemistry of Life Processes (CLP) Program. (
  • With its multidisciplinary approach this is an essential reference for academic and industrial researchers in catalysis science aiming to design more sustainable and energy-efficient processes. (
  • The development of a fundamental understanding of the theory of heterogeneous catalysis and electro-catalysis chemical processes at the gas-solid and liquid-solid interface. (
  • We aim to develop fundamentally new and ground-breaking strategies to asymmetric catalysis via the intermediacy of light-mediated redox processes and excited-state reactivity patterns. (
  • In order to create greater efficiencies in the physical and chemical processes during upgrading, it is very important to study and understand the chemical transformation of hydrocarbon molecules involved in catalysis. (
  • This Research Topic aims to showcase cutting-edge research in the field of molecular recognition for catalytic purposes, spanning from phase transfer catalysis reactions to functional nanometric devices for supramolecular catalysis, although it is open to any example of catalysis in which supramolecular interactions play a role--for instance in product or substrate selectivity. (
  • Asymmetric Catalysis : Ligand Design and Conformational Studies. (
  • Over the last decade, Journal of Catalysis has been ranked among the top five chemical engineering . (
  • Journal of Catalysis publishes original, rigorous, and scholarly contributions in the fields of heterogeneous catalysis and homogeneous catalysis . (
  • Journal of Catalysis publishes manuscripts of archival value because of their significant fundamental and conceptual contributions to our understanding and practice of catalytic chemistries. (
  • Journal of Catalysis also publishes Priority Communications and Research Notes. (
  • Replacing noble metals using doped carbon nanomaterials in fuel cells, dehydrogenation reactions and in water treatment have been explored in a European project coordinated by the Catalysis group at NTNU. (
  • Quantitative studies of the energetics of enzymatic reactions and the corresponding reactions in aqueous solutions indicate that charge stabilization is the most important energy contribution in enzyme catalysis. (
  • However, despite substantial efforts from both the experimental and theoretical side, no real consensus has been reached regarding the origin of such large entropic contributions to enzyme catalysis. (
  • What better place to start than with NICE , a Network for Industrial Catalysis in Europe? (
  • If the emphasis is on renewable or sustainable energy systems as a whole, with catalysis as a sub-component, submit to Energy for Sustainability (CBET 7644). (
  • The successful candidate must have a PhD in physics, chemistry, chemical engineering, materials science or related areas and to have experience in the general area of catalysis for sustainable energy solutions. (
  • Sustainable Catalysis in Ionic Liquids provides an up-to-date overview of the relatively underexplored area of the use of room temperature ionic liquids as organocatalysts for a range of organic reactions, including polymerizations. (
  • in order to transition chemistry to a more sustainable use of the world's limited resources, finding alternative strategies for catalysis is a major driving force in contemporary research. (
  • In this spirit, this webinar will feature talks about four areas of sustainable catalysis from leaders in their respective fields, highlighting state-of-the-art approaches and providing guidance for future developments in these areas of research. (
  • The development and application of novel concepts for sustainable catalysis constitutes his major current research interest, and he has a topical focus on C-H activation. (
  • The goal of the Catalysis program is to advance research in catalytic engineering science and promote fundamental understanding and the development of catalytic materials and reactions that are of benefit to society. (
  • Jiao recently received two grants from the Department of Energy (DOE) to advance technologies for carbon capture and utilization through catalysis, the use of substances to speed the rate of chemical reactions. (
  • The goal of "Interfaces and Catalysis" is to gain insight and understanding in the fundamental aspects of interfaces, colloidal systems and catalytic reactions and the use this knowledge in practice. (
  • Modern Developments in Catalysis provides a unique learning opportunity for students and professionals studying and working towards speeding-up, improving and increasing the rate of catalytic reactions in science and industry. (
  • Stay up to date with the latest in catalysis news and research. (
  • Nature Catalysis provides coverage of the science and business of catalysis research, creating a unique journal for scientists, engineers and researchers in academia and industry. (
  • The CAT Program does not support applied catalysis research focusing on engineering aspects of catalysis such as scale-up, processing, transport dynamics, and long-term stability. (
  • We are working on turning carbon dioxide, which is considered a bad gas, and using it as a carbon source to produce the chemicals we use for every day," said Jiao, who is also the director of UD's Center for Catalytic Science and Technology, a research center that has pioneered multidisciplinary research in the scientific and engineering principles of catalysis. (
  • The main research directions within the IMC group are captured in the subprogrammes: (i) Catalysis for C1 Chemistry, (ii) Catalysis for Renewable Energy Storage and (iii) Catalysis for Bio-Renewables. (
  • A major portion of the group's basic research is aimed at research into the Fundamentals of Catalysis and Chemical Transformations sponsored by the DOE's Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. (
  • Professor Hagen's teaching and research at the faculty of Chemical and Process Engineering focused on chemical reaction engineering and technical catalysis. (
  • See the state-of-the-art equipment that enables our students and staff to drive catalysis research forward. (
  • Special focus will be given the research lines of the Competence Centre for Catalysis. (
  • The Catalysis Theory center is established with the ambition to become one of the leading research centers developing the theory of heterogeneous catalysis and electro-catalysis. (
  • Successful candidates must be able to develop an independent, vibrant research portfolio in the general area of the Catalysis Theory Center. (
  • The UK Catalysis Hub will coordinate and strengthen research efforts in catalytic science, allowing the UK to remain a world-leader in the field and tackle major global challenges. (
  • This month's Industry Insider resources page focuses on some of the European and national initiatives that aim to both promote catalysis research and get industry and academic scientists working together. (
  • The site also provides links to catalysis courses , academic groups carrying out catalysis research, and national catalysis societies . (
  • Read a lot more about catalysis research in the Netherlands in a special feature published in June 2002 by the American Chemical Society's magazine, Chemical and Engineering News . (
  • Our research interests center on the preparation and characterization of new coordination polymers/metal-organic framework with industrially relevant properties in catalysis, adsorption and separation, sensing properties and energy related applications. (
  • The Dutch National Research School Combination Catalysis Controlled by Chemical Design (NRSC-Catalysis) brings together scientists from various key disciplines at nine Dutch universities in a long-term effort to extend the boundaries of our knowledge. (
  • The purpose of the Synchrotron Catalysis Consortium (SCC) is to promote the utilization of synchrotron techniques to perform cutting-edge catalysis nano-science research under in-situ conditions. (
  • Theme: Accelerating New Research & Innovations in chemistry and Catalysis. (
  • The combination of the research expertise, the cutting-edge facilities and the complementary skills present in the consortium holds a great promise for the advancement of their careers, as well as of the knowledge of catalysis-based anticancer therapies and the development of marketable technologies and products. (
  • Jointly organized by Italy's Research Council and Palermo's University, the 6th edition of the " FineCat - Symposium on heterogeneous catalysis for fine chemicals " was held in Sicily's Royal Palace in Palermo on April 5th . (
  • In this special issue, we present several current trends in computational catalysis, broadly organized in the areas of (1) adsorption and molecular interactions, (2) kinetics and mechanistic studies, and (3) new methodologies. (
  • Interfaces and Catalysis starts with an empirical description of chemical kinetics and the relation with possible reaction mechanisms. (
  • Already used for the production of bulk chemicals, gold catalysis is poised to be introduced in the production of the basic ingredients of a wide variety of valued added products ranging from pharmaceuticals through liquid crystals and organic light emitting diodes (OLED) for computer, TV and mobile phone screens. (
  • This session focuses on the use of computational methods such as quantum chemistry, Monte Carlo methods, molecular dynamics and microkinetic modeling in catalysis applications for the production of energy, including the chemical, electrochemical, and photochemical conversion of different feedstocks into fuels, and fuel cell catalysis. (
  • Group meetings for the Purdue Catalysis Center are held every Wednesday from 4:30pm to 6:00pm. (
  • Graham J. Hutchings is the Director of the Cardiff Catalysis Institute and is the inaugural Director of the UK Catalysis Hub. (
  • The co-product inorganic pyrophosphate (PPO − , i.e., the PP i anion) is proposed to be the general base-general acid that mediates stereospecific proton transfers in catalysis. (
  • Douglas W. Stephan is a Professor at the University of Toronto and a world-leading researcher in inorganic chemistry/catalysis and the founder of the field of "frustrated Lewis pair" (FLP) chemistry. (
  • Nature Catalysis brings together researchers from across all chemistry and related fields, publishing work on homogeneous catalysis, heterogeneous catalysis, and biocatalysts, incorporating both fundamental and applied studies. (
  • This meeting is ideal for researchers working in any area of synthetic chemistry who want to find out more about the capabilities and applications of non-precious metals in catalysis. (
  • Prof. Riikka Puurunen is frequently getting inquiries from outside Aalto University for whether there are master's thesis students available with knowledge on the area of catalysis. (
  • The course covers the importance of catalysis in industry and society and basic principles. (
  • The fact that 85-90% of all chemical production is catalysis based, illustrates the importance of catalysis to the economic growth and the life-standard developed over the previous century. (
  • Target applications include fuels, specialty and bulk chemicals, environmental catalysis, biomass conversion to fuels and chemicals, conversion of greenhouse gases, and generation of solar hydrogen, as well as efficient routes to energy utilization. (
  • This session seeks contributions in the area of applied environmental catalysis including but not limited to photocatalytic and catalytic pollution control, stationary source and vehicle emission control, CO2 science and management (catalytic utilization and sequestration) and applications of catalysis in green chemistry. (
  • Although perovskites have been widely used in catalysis, tuning of their surface termination to control reaction selectivity has not been well established. (
  • Base catalysis is used in methanol carbonylation, in the aldol condensation to manufacture solvents, and in Knoevenagel Reaction used to make perfumes, pharmaceuticals and polymers. (
  • Accordingly, manganese dioxide catalyses this reaction. (
  • QED induced catalysis by nanoparticles [2] is not new. (
  • Deligon International welcomes you to attend the International Conference on Chemistry & Catalysis during August 10 - 12, 2020, Prague, Czech Republic. (
  • Some principles of biological catalysis are demonstrated. (
  • Links to and inspiration from related areas in homogeneous and biological catalysis are encouraged. (
  • DTU is seeking an outstanding professor in the field of theoretical catalysis. (
  • C. Richard A. Catlow has long standing experience in the development and application of both experimental and computer modelling techniques in catalysis and molecular sciences. (
  • We are relating supramolecular and molecular recognition chemistry to homogeneous catalysis. (
  • The result is an up-to-date review of metal oxides in catalysis. (
  • Catalysis is relevant to many aspects of environmental science , e.g. the catalytic converter in automobiles and the dynamics of the ozone hole . (
  • To promote heterogeneous, homogeneous & enzymatic catalysis in a wide range of applications which benefit society: energy, petrochemicals, industrial intermediates, pharmaceuticals, fine chemicals, consumer products & environmental protection. (
  • Environmental catalysis (including energy-efficient and green routes to fuels and chemicals). (
  • Applied catalysis has resolved many of the challenges faced in environmental protection. (
  • We are pleased to invite you to a full-day symposium on Environmental Catalysis. (
  • The symposium will include oral as well as poster presentations on progress within Environmental Catalysis. (
  • Catalysis will play a major role in tackling the grand challenges of the 21st Century, such as climate change, growing demands and subsequent environmental issues stemming from the predicted rise in global population. (
  • Catalysis for environmental protection and energy production. (
  • Natural gas is an abundant hydrocarbon fuel and chemical feedstock, and utilizing this resource with minimum environmental impact is a major challenge to catalysis. (
  • Both fundamental and applied aspects of catalysis are covered. (
  • Renewable energy-related catalysis with applications in electrocatalysis, photocatalysis, and catalytic conversion of biomass-derived chemicals. (
  • The production of most industrially important chemicals involves catalysis. (
  • Genuine, single-atom catalysis can be realized in the gas phase and probed by mass spectrometry combined with computational chemistry. (
  • The Catalysis Theory Center has a strong infrastructure and computational facility, as well as initial funding for students and postdocs. (
  • It turns out that the large entropy contributions to catalysis in these cases can now be rationalized by our computational approach. (
  • Complexities stemming from the inherent multi-component aspects of heterogeneous catalysis are explored using both ultra-high-vacuum surface science investigations of well-defined model systems, and powder diffraction and x-ray absorption studies of "real-world" systems. (
  • For more information on the efficiency of enzymatic catalysis, see the article on enzymes. (
  • These advances begin to allow for a more direct comparison of heterogeneous catalysis and electrocatalysis. (
  • Are you an experienced researcher on the hunt for a comprehensive overview on recent advances in catalysis? (
  • Acid catalysis and zeolites. (
  • The catalysis section includes the challenging activation and functionalization of the main classes of hydrocarbons and the industrially crucial heterogeneous catalysis. (