- Degradation of pyrimidines in Saccharomyces kluyveri: Transamination of β-alanine
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Beta-alanine is an intermediate in the reductive degradation of uracil. Recently we have identified and characterized the Saccharomyces kluyveri PYD4 gene and the corresponding enzyme β-alanine aminotransferase (SkPyd4p), highly homologous to eukaryotic γ-aminobutyrate aminotransferase (GABA-AT). S. kluyveri has two aminotransferases, GABA aminotransferase (SkUga1p) with 80% and SkPyd4p with 55% identity to S. cerevisiae GABA-AT. SkPyd4p is a typical pyridoxal phosphate-dependent aminotransferase, specific for α-ketoglutarate (αKG), β-alanine (BAL) and γ-aminobutyrate (GABA), showing a ping-pong kinetic mechanism involving two half-reactions and substrate inhibition. SkUga1p accepts only αKG and GABA but not BAL, thus only SkPydy4p belongs to the uracil degradative pathway. Copyright Taylor & Francis Group, LLC.
- Schnackerz,Andersen,Dobritzsch,Piskur
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- Kinetics and Mechanism of Electron Transfer Reactions in Aqueous Solutions: Silver(I) Catalyzed Oxidation of Aspartic Acid by Cerium(IV) in Acid Perchlorate Medium
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Silver(I) catalyzed oxidation of aspartic acid by cerium(IV) was studied in acid perchlorate medium.The stoichiometry of the reaction is represented by the eq. (i), (i) R-CHNH3+COOH + 2 Ce(IV) -H2O-> R-CHO + NH4+ + CO2 + 2 Ce(III) + 2 H+.Dimeric cerium(IV) species has been indicated and employed in calculations of monomeric cerium(IV) species concentrations.The reaction is second-order and uncatalyzed reaction also simultaneously occurs along with silver(I) catalyzed reaction conforming to the rate law (ii), (ii) , where k is an observed second-order rate constant.A probable reaction mechanism is suggested.
- Sharma, Indu,Devra, Vijai,Gupta, Divya,Gangwal, C. M.,Sharma, P. D.
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- Autocatalytic oxidation of β-alanine by peroxomonosulfate in the presence of copper(II) ion
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Kinetics and mechanism of oxidation of β-alanine by peroxomonosulfate (PMS) in the presence of Cu(II) ion at pH 4.2 (acetic acid/sodium acetate) has been studied. Autocatalysis was observed only in the presence of copper(II) ion, and this was explained due to the formation of hydroperoxide intermediate. The rate constant for the catalyzed (k2obs) and uncatalyzed (K1obs) reaction has been calculated. The kinetic data obtained reveal that both the reactions are first order with respect to IPMS]. K1obs values initially increase with the increase in [β-alanine] and reach a limiting value, but k2obs values decrease with the increase in [β-alanine]. k1 obs values increase linearly with the increase in [Cu(II)], whereas k2obs values increase with [Cu(II)]2. Furthermore, k1obsvalues are independent of [acetate], but K2obs values decrease with the increase in acetate. A suitable mechanism has been proposed to explain the experimental observation. The reaction has been studied at different temperatures, and the activation parameters are calculated.
- Sayee Kannan,Easwaramoorthy,Vijaya,Ramachandran
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- Oxidation of L-Aspartic Acid and L-Glutamic Acid by Manganese(III) Ions in Aqueous Sulphuric Acid, Acetic Acid, and Pyrophosphate Media: A Kinetic Study
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Kinetics of oxidation of L-aspartic acid and L-glutamic acid by manganese(III) ions have been studied in aqueous sulphuric acid, acetic acid, and pyrophosphate media.Manganese(III) solutions were prepared by known electrolytic/chemical methods in the three media.The nature of the oxidizing species present in manganese(III) solutions was determined by spectrophotometric and redox potential measurements.The raction shows a variable order in 0: the order changes from two to one as the reactive oxidizing species changes from an aquo ionic form to a complex form.There is a first-order dependence of the rate on 0 in all the three media while the other common features include an inverse dependence each on and on .Effects of varying ionic strength and solvent composition were studied.Added anions such as pyrophosphate, fluoride, or chloride alter the reaction rate and mechanism by changing the formal redox potential of Mn(III)-Mn(II) couple.Activation parameters have been evaluated using the Arrhenius and Eyring plots.Mechanisms consistent with the kinetic data have been proposed and discussed.
- Sherigara, B. S.,Bhat, K. Ishwar,Pinto, Ivan,Gowda, N. M. Made
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- Interaction between Pyridoxal Hydrochloride and L-α-Asparagine in Comparison to L-α- and D-α-Aspartic Acids
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Abstract: The kinetics and mechanism of condensation of pyridoxal hydrochloride with L-α-asparagine, L?α- and D-α-aspartic acids are analyzed via UV spectroscopy and polarimetry. It is found that L?α?asparagine containing α-NH2 and γ-NH2/
- Pishchugin,Tuleberdiev
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- Kinetic and mechanistic studies on the oxidation of DL-aspartic acid with manganese(III) in sulphuric acid medium
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The kinetics of oxidation of DL-aspartic acid by manganese(III) was studied spectrophotometrically at 500 nm in sulphuric acid medium at 40oC. The reaction was observed to be fractional order with respect to substrate and first order with respect to oxidant. Further the rate of reaction found to decrease with increase in ionic strength and [H+], while [HSO4-] and [MnII] were found to have negligible effect. The energy of activation, Ea and the entropy of activation, ΔS# computed from thermal studies were found to be 102.23±11.1 KJ mol-1 and 18.45±35.40 JK-1 mol-1 respectively.
- Makena, Rama Rajeswari,Rambabu, Rallabandi,Vani, Parvataneni
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p. 1073 - 1078
(2020/06/26)
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- MICROORGANISMS AND METHODS FOR PRODUCTION OF 4-HYDROXYBUTYRATE, 1,4-BUTANEDIOL AND RELATED COMPOUNDS
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The invention provides non-naturally occurring microbial organisms having a 4-hydroxybutyrate, 1,4-butanediol, or other product pathway and being capable of producing 4-hydroxybutyrate, 1,4-butanediol, or other product, wherein the microbial organism comprises one or more genetic modifications. The invention additionally provides methods of producing 4-hydroxybutyrate, 1,4-butanediol, or other product or related products using the microbial organisms.
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Page/Page column
(2015/06/03)
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- Substrate profile of an ω-transaminase from Burkholderia vietnamiensis and its potential for the production of optically pure amines and unnatural amino acids
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A new (S)-enantioselective ω-transaminase (ω-TA) gene from Burkholderia vietnamiensis G4 was functionally expressed in Escherichia coli BL21 (DE3), and the purified recombinant N-terminal His-tagged ω-TA (HBV-ω-TA) had a dimeric structure with optimum pH and temperature of 8.4 and 40 C, respectively. The enzyme showed higher activities toward aromatic amines than aliphatic amines and (S)-1-methylbenzylamine ((S)-α-MBA) was the most active amino donor. For amino acceptor, keto acids, keto esters and aldehydes were more reactive than ketones with pyruvate ethyl ester being most active. Several chiral amines and unnatural amino acids or esters were synthesized using HBV-ω-TA as the catalyst and isopropylamine or (S)-α-MBA as amino donor. Notably, HBV-ω-TA catalyzed the amino transfer to β-keto esters to give optically pure β-amino acid esters. In addition, glyoxylate was used as amino acceptor for the first time in the kinetic resolution of racemic amines and optically pure amines, such as (R)-1-methylbenzylamine, (R)-1-phenylpropylamine, (R)-2-amino-4-phenylbutane and (R)-1-aminotetraline, were obtained.
- Jiang, Jinju,Chen, Xi,Feng, Jinhui,Wu, Qiaqing,Zhu, Dunming
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- Kinetics and mechanism of oxidation of malic acid by N-bromoanisamide
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The kinetics of the oxidation of the malic and by N-bromoanisamide in HC1O4 and in the presence of Hg(OAc)2 have been studied. The reactions exhibit a first order rate dependence with respect to the oxidant and substrate. The reactions are acid catalyzed and retarded by the addition of anisamide, a byproduct of reaction. The rate of oxidation decreases with decrease in dielectric constant of the medium. The effect of temperature on the reaction has been investigated in the temperature range 313-328 K. The stoichiometric studies revealed 1:1 mole ratio. Various thermodynamic parameters have been computed and a possible operative mechanism is proposed.
- Malviya,Siriah,Badole
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p. 767 - 770
(2013/11/06)
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- Aggregation in oxidation of aspartic and glutamic acids by chloramine-T in presence of surfactants: A kinetic study
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The kinetics of oxidation of aspartic and glutamic acids by chloramine-T in HClO4 medium have been investigated in the absence and presence of anionic (sodium lauryl sulphate), cationic (cetyltrimethylammonium bromide) and non-ionic (Brij 35) surfactants. In the absence of surfactant the rate of oxidation may be represented as, d[Chloramine-T]/dt=k[Chloramine-T] 2[Amino acid]/(1+K[H+]) where k and K are constants. The presence of a small amount of surfactant (below its critical micelle concentration) strongly enhances the rate of oxidation and the observed rate constant attains constancy at higher surfactant concentration. Using Piszkiewicz's cooperativity model, the cooperative index n has been calculated for these reactions to be between 1-3, indicating the existence of catalytically productive submicellar aggregates. The values of n have been used to calculate the binding constants of reactants with the surfactant using Raghvan and Srinivasan's model proposed for biomolecular micellar catalysed reactions. The evaluated binding constants are in good agreement from those obtained by Piszkiewicz's model. The formation of aggregate is further supported by the enhancement of rate in presence of a common hydrotrope, namely, sodium benzoate.
- Pandey, Ekta,Grover, Neeti,Kambo, Neelu,Upadhyay, Santosh K.
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p. 1186 - 1192
(2007/10/03)
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- Oxidative deamination and decarboxylation of L-isomers of amino acids by potassium permanganate in moderately concentrated sulphuric acid medium
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The oxidation reactions of L-isomers of amino acids, viz. asparatic acid, glutamic acid, asparagine and glutamine have been carried out in moderately concentrated sulphuric acid medium. The reactions are found to be two-stage processess. In both the stages the reactions follow first order behaviour with respect to each of substrate and permanganate. The reactions are acid-catalysed and the rate is related to the activity of water and also to the acidity function. Primary salt-effect is nil, but at higher concentration of neutral salts the logarithm of the rate constant is linearly related to ionic strength. Specific ionic effects have also been investigated. Activation parameters have been reported. Mechanism pertinent with the observation has been suggested.
- Sahu,Chourey, Vijay R.,Pandey, Shakuntala,Shastry,Shastry
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p. 131 - 134
(2007/10/03)
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- Kinetics and mechanism of oxidation of amino acids by N-chloronicotinamide in aqueous acetic acid medium
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Kinetics of oxidation of ten α-amino acids by N-chloronicotinamide (NCN) in aqueous acetic acid medium in presence of hydrochloric acid have been investigated. The observed rate of oxidation is first order in both [oxidant] and [HCl]. A small increase in rate is observed with increase in [amino acid]. A decrease in the dielectric constant of the medium increases the rate. Addition of nicotinamide (NA), the reduction product of NCN, has a retarding effect on the rate of oxidation. The corresponding aldehydes, ammonia and carbon dioxide have been identified as the oxidation products. Molecular chlorine has been postulated as the reactive oxidising species in the reaction.
- Vivekanandan,Nambi
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p. 198 - 201
(2007/10/03)
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- Kinetics and mechanism of the oxidation of some amino acids with cerium(IV)
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Kinetics of oxidation of some amino acids (L-aspartic acid, L-phenyl alanine, L-serine and L-methionine) with cerium(IV) have been studied in HNO3-HClO4 medium. Oxidation of L-aspartic acid, L-phenyl alanine and L-serine by cerium(IV) has been found to follow pseudo-first order kinetics and the oxidation of L-methionine has been found to follow second order kinetics. The kinetic experiments have been used for the suggestion of a probable mechanism. The oxidation products were identified as corresponding aldehydes, ammonia and carbon dioxide. by R. Oldenbourg Verlag, Muenchen 1998.
- Bayuelken,Sarac
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p. 181 - 192
(2007/10/03)
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- Evaluation of individual rate constants and activation parameters of acid bromate oxidation of hydroxy acids catalysed by aquachlororuthenium complex
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The oxidation of citric and malic acids by bromate in acidic aqueous solutions is catalysed by aquachlororuthenium complex and the kinetics of the reaction is investigated.The rate law is interpreted by a mechanism involving the oxidation of Ru(III) to Ru(V) by oxidant (Kf), followed by a complex formation (Kc) between Ru(V) and substrate, which decomposes (kd) to products in a slow rate determining step with regeneration of Ru(III).All individual rate constants are determined at different temperatures and their activation parameters are also evaluated and discussed.
- Reddy, Ch. Sanjeeva,Kumar, T. Vijaya
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p. 871 - 877
(2007/10/03)
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- Kinetics and mechanism of palladium(II) catalysed oxidation of some hydroxyacids by N-bromosuccinimide in perchloric acid medium
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The kinetics of oxidation of palladium(II) catalysed oxidation of some hydroxyacids, viz., malic, citric and tartaric acids by N-bromosuccinimide have been studied in perchloric acid medium in the presence of mercuric acetate.A first order dependence of rate each in and has been observed.The order of reaction in substrate decreases at higher .A retarding effect of +> on the rate has also been observed.A suitable mechanism consistent with observed kinetic data is proposed and discussed.
- Saxena, Rashmi,Upadhyay, S. K.
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p. 1060 - 1063
(2007/10/02)
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- Kinetics and Mechanism of Chloride Ion Catalysed Oxidation of Malonic Acid by Chloramine T in Aqueous Acid Medium - A Kinetic Distinction betwen Oxidation and Chlorination
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The kinetics of malonic acid (H2ma) oxidation by chloramine T has been studied in perchloric acid and chloride media.The stoichiometric results correspond to the oxidation of malonic acid to glyoxylic acid.The kinetics rate law is where k' and k'un are first order rate constants for Cl- catalyzed and uncatalyzed reactions respectively.
- Rao, Indu,Mishra, Som K.,Sharma, Prem D.
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p. 1573 - 1594
(2007/10/02)
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- Oxidative behaviours and relative reactivities of some α-hydroxy acids towards bromate ion in hydrochloric acid medium
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The oxidation kinetics of some α-hydroxy acids by potassium bromate in dilute hydrochloric acid medium have been studied. The reactions are first order with respect to bromate ion. α-hydroxy acid and hydrogen ion concentrations. The reaction rate is governed by two factors : (i) the ease with which the protonated hydroxy acid is produced and (ii) the stability of the intermediate (1:1) bromate ester. The activation parameters of the reactions have been compared. The plausible mechanism of the oxidation process has been suggested. The reactivity of the α-hydroxy acids towards bromate ion are as follows: 9-hydroxy-9-carboxy fluorene> atrolactic acid> mandelic acid> benzilic acid> α-hydroxyisobutyric acid> lactic acid> glycolic acid.
- Gupta, Kalyan Kali Sen,Banerjee, Amalendu,Chatterjee, Hrishikesh
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p. 5323 - 5330
(2007/10/02)
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- Kinetics and mechanism of oxidation of serine, threonine, arginine, aspartic acid and glutamic acid by N-bromoacetamide in alkaline medium
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The title amino acids are oxidised to the corresponding aldehydes, ammonia and carbon dioxide.The effect of varying , , -> and ionic strength have been studied.The data reveal that the reaction is first order in and fractional order each in and ->.Addition of acetamide does not affect the rate of oxidation.Thermodynamic parameters have been calculated and a suitable mechanism consistent with the experimental results is proposed.
- Reddy, M. Komal,Sribabu, Ch.,Sundaram, E. V.
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- Oxidative Kinetics of Unsaturated Carboxylic Acids by Bromate in the Presence of Bromo-Complex Forming Metal Ions
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The kinetics and mechanism of oxidation of unsaturated carboxylic acids viz., acrylic, crotonic (trans), cinnamic, α-methyl and α-phenylcinnamic (trans), angelic, tiglic, vinylacetic and itaconic acids by acid bromate (unmixed by any competing or faster oxidation/addition by generated molecular bromine) in the presence of Tl(III)/Hg(II) are dealt.The reaction exhibits a first-order in , an order and accelerates with acidity of the medium.The reaction rate increases when deuterium replaces either α- or β-proton of substrate (kD/kH = 1.27).The factors governing the oxidative reaction rates are multifarious (electrostatic, electronic and steric effects), none alone can play a predominant role over a wide range of substrates.An attempt is made to propose a suitable mechanism which is consistent with the data concerning the reaction and also accounts satisfactorily the array of products that are obtained under various conditions.Tl(III) and Hg(II) behave only as bromo-complex forming metal ions and their effect on the bromate oxidation is displayed by their complex forming ability.
- Sanjeeva Reddy, Ch.
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p. 1009 - 1019
(2007/10/02)
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- Mechanism of Bromamine-T Oxidation of Glutamic and Aspartic Acid
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Kinetics of oxidation of glutamic and aspartic acids by bromamine-T (BAT) has been carried out in HClO4 (30 deg) and NaOH (20 deg).In acid medium the rate shows first order dependence on and and an inverse first order in the measured .Succinic and malonic acids have been identified as the products.At higher , the rate of reaction is independent of and the rate law changes to, rate = kx, where x is a fraction.In alkaline medium, the rate is first order in , fractional each in and and is retarded by the added p-toluenesulphonamide, one of the products of oxidation.Aldehydes are found to be the other products under these conditions.Solvent isotope studies have been made in D2O medium.The rate laws derived are in agreement with experimental results.
- Mahadevappa, D. S.,Puttaswamy,Ananda, S.
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- Kinetics and Mechanism of Ruthenium(III)-Catalysed Oxidation of Amino Acids by Peroxodiphosphate in Acid Medium
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The kinetics of oxidation of amino acids (AA) such as glycine, alanine, phenylalanine, serine, threonine, aspartic acid and glutamic acid by peroxodiphosphate (PP) in presence of Ru(III) have been studied.The reactions are found to be acid-catalysed and an analysis of rate dependence on reveals that the active oxidizing species is H3P2O8(-).The Ru(III)-catalysis of PP-AA reaction is explained in terms of formation of a 1:1 complex between Ru(III) and AA, which later reacts with PP to give the products.The products obtained are ammonia, carbon dioxide and the corresponding aldehyde.
- Rao, M. Anand
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p. 417 - 419
(2007/10/02)
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- A Comparative Kinetic and Mechanistic Study of Oxidation of Structurally related Organic Substrates viz. Glycolic, Thioglycolic, DL-Lactic, DL-Malic and DL-Mandelic acids with manganic Pyrophosphate in Sulphuric acid Medium
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The kinetics of oxidation of structurally related hydroxy acids viz.Glycolic, DL-Lactic, DL-Malic and DL-Mandelic acids and also α-mercapto carboxylic acid viz.Thioglycolic acid were extensively studied.Second order rate constants obtained in these investigations are utilized to correlate the effects of variation of , , dissociated +>, total 2->, total 4-> and added .The mechanism of the reaction involved the formation of a transitory intermediate 1:1 cyclic complex and the disproportionation of the complex through a C-C bond cleavage in case of hydroxy-acids and a S-H bond cleavage in thioglycolic acid, which is a rate determining step.Thermodynamic parameters also substantiate the proposed mechanisms.
- Gandhi, P.K.,Rao, B.M.
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p. 513 - 521
(2007/10/02)
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- Kinetics and mechanism of uncatalysed and Chloride-catalysed Oxidative Decarboxylation of Glycine and Aspartic Acid by Chloramine-T in Perchloric Acid medium
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The kinetics of oxidative decarboxylation of glycine and L-aspartic acid by chloramine-T has been investigated both in the absence and presence of chloride ion in perchloric acid medium.In the absence of chloride ion, the rate followed second order kinetics in (CAT)0, first order in (substrate), inverse first order in (H+) with both the amino acids.Chloride was found to enhance the rate of oxidation and affect the kinetics.In the presence of chloride, the rate followed first order kinetics in (CAT)0 in both cases.But the rate was fractional and zero order in (substrate) with glycine and aspartic acid, respectively.The kinetic order in (H+) was also different, i.e. inverse fractional order and fractional order respectively with glycine and aspartic acid.The effect of chloride was more pronounced with aspartic acid.Effects of added reaction product and the variation of ionic strength and dielectric constant of the reaction medium have also been investigated.Reaction schemes in conformity with the observed kinetics have been proposed and the related rate laws derived.The constants of the rate limiting and other steps have been calculated in some cases.
- Gowda, B. Thimme,Rao, R. Vijayalakshmi
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p. 467 - 473
(2007/10/02)
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- Kinetics and Mechanism of Oxidation of Some Amino Acids by N-Bromoacetamide in Acid Medium
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Aspartic acid, glutamic acid, arginine and histidine are oxidised to corresponding aldehydes, ammonia and carbon dioxide by N-bromoacetamide in acid medium.The reaction is first order each in and and inverse first order each in and .The effect of changing the dielectric constant of the medium on the rate indicates the reaction to be of dipole-dipole type.Hypobromous acid has been postulated as the reactive oxidising species.A plausible mechanism consistent with the experimental results has been proposed.
- Komal Reddy, M.,Sundaram, E. V.
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p. 471 - 473
(2007/10/02)
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- KINETICS AND MECHANISM OF THE OXIDATION OF α-AMINO ACIDS BY N-BROMOACETAMIDE
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The kinetics of the oxidation of eight α-amino acids by N-bromoacetamide have been studied in aqueous perchloric acid solution.The main products of the oxidation are the corresponding carbonyl compounds.The reaction is of first order with respect to the oxidant and the amino acid.The rate of oxidation decreases linearly with an increase in hydrogen ion concentration.The rate is decreased by the addition of acetamide.The oxidation of deuteriated glycine indicated the absence of a primary kinetic isotope effect.The reaction rate has been determined at different temperatures and activation parameters have been caculated.Hypobromous acid has been postulated as the reactive oxidizing species.A rate-determining reaction of the neutral amino acid and hypobromous acid to give an N-bromo derivative has been proposed.The slow step is followed by a fast decomposition of the N-bromo derivative to yield the ultimate product.
- Bishnoi, Mangi Lal,Banerji, Kalyan K.
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p. 6047 - 6050
(2007/10/02)
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