- Kinetics and mechanism of the peptide synthesis in solution
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The kinetics of the reaction of Boc-Xaa fluorophenyl esters (where Xaa = Ala, Val, Phe, Ser, Leu, Gly, Met, Pro, or Ile) with leucinamide was studied in order to measure changes in fluorescence emission at 375 nm of the fluorophenyl chromophore accompanying the reaction. It was found that the experimental kinetic data could not be described by a simple scheme of the second order reaction. Measurements of the kinetic parameters of the reaction at various initial concentrations of reagents indicated that the reaction rate can be expressed as: v = kCNaCAEb, where k is the reaction rate constant, CN is the concentration of leucinamide, and CAE is the concentration of fluorophenyl ester. The a and b reaction orders were close to 1/2 and 3/2 for Xaa = Ala, Val, Phe, Ser, or Leu, 1/2 and 1 for Gly, Met, or Pro, and 1 and 2 for Ile. The experimental equations for the reaction rate can theoretically be derived from a single scheme of chain reactions with various deactivation ways for active intermediates.
- Permyakov,Permyakov,Medvedkin
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- Oxidative Damage in Aliphatic Amino Acids and Di- and Tripeptides by the Environmental Free Radical Oxidant NO3?: the Role of the Amide Bond Revealed by Kinetic and Computational Studies
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Kinetic and computational data reveal a complex behavior of the important environmental free radical oxidant NO3? in its reactions with aliphatic amino acids and di- and tripeptides, suggesting that attack at the amide N-H bond in the peptide backbone is a highly viable pathway, which proceeds through a proton-coupled electron transfer (PCET) mechanism with a rate coefficient of about 1 × 106 M-1 s-1 in acetonitrile. Similar rate coefficients were determined for hydrogen abstraction from the α-carbon and from tertiary C-H bonds in the side chain. The obtained rate coefficients for the reaction of NO3? with aliphatic di- and tripeptides suggest that attack occurs at all of these sites in each individual amino acid residue, which makes aliphatic peptide sequences highly vulnerable to NO3?-induced oxidative damage. No evidence for amide neighboring group effects, which have previously been found to facilitate radical-induced side-chain damage in phenylalanine, was found for the reaction of NO3? with side chains in aliphatic peptides.
- Nathanael, Joses G.,Wille, Uta
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p. 3405 - 3418
(2019/03/11)
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- Interactions between Terminally Substituted Amino Acids in an Aqueous and a Non-Aqueous Environment. Enthalpic Interaction Coefficients in Water and in N,N-Dimethylformamide at 25 deg C
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Enthalpies of dilution of the N-acetyl amides of glycine, L-alanine, L-valine, L-leucine, and L-phenylalanine, dissolved in N,N-dimethylformamide (DMF) as a solvent have been measured at 25 deg C.The results obtained have been analyzed to give the enthalpic interaction (or virial) coefficients of the solutes and these are compared with information previously obtained in aqueous systems.There are marked differences in the interaction properties in the two solvents and, while the additivity approache of Savage and Wood is applicable to the solutes in water it is suitable for representing the interactions in DMF.A correlation is presented between the enthalpic second virial coefficients in DMF and the propensity of side-chains to be in proximity in globular proteins.
- Kent, Hilary E.,Lilley, Terence H.,Milburn, Peter J.,Bloemendal, Michael,Somsen, Gus
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p. 101 - 116
(2007/10/02)
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- Heterocycles as Masked Diamide/Dipeptide Equivalents. Formation and Reactions of Substituted 5-(Acylamino)oxazoles as Intermediates en route to the Cyclopeptide Alkaloids
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A variety of novel 2,4-dialkyl-5-(acylamino)oxazoles have been prepared by using either amide nitriles or diamides/dipeptides as starting materials.Ring closure calls for the use of trifluoroacetic acid/trifluoroacetic acid anhydride or an acid halide in
- Lipshutz, Bruce H.,Hungate, Randall W.,NcCarthy, Keith E.
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p. 7703 - 7713
(2007/10/02)
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- Aqueous Solutions Containing Amino Acids and Peptides. Part 11.-Enthalpy of Dilution of Single and Binary Solute Solutions of N-Acetylglycine Amide, N-Acetyl-L-alanine Amide, N-Acetyl-L-valine Amide and N-Acetyl-L-leucine Amide at 298.15 K
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The enthalpies of dilution of aqueous solutions containing N-acetylglycine amide (G), N-acetyl-L-alanine amide (A), N-acetyl-L-valine amide (V) and N-acetyl-L-leucine amide (L) and equimolal solutions of G+A, G+V, G+L, A+V, A+L and V+L have been measured at 298.15 K.The results obtained have been used to calculate the pairwise enthalpy coefficients for like-like and like-unlike solute interactions.These coefficients have been compared with the predictions of the group additivity approach proposed earlier by Savage and Wood.The group additivity approach works well considering the experimental error and the standard deviation of the original correlations although it seems likely that some refinement of the group interaction parameters is required.
- Blackburn, G. Michael,Lilley, Terence H.,Walmsley, Elizabeth
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p. 915 - 922
(2007/10/02)
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