Sequence dependence of oxidation of some repeating pentapeptide sequences of elastin with electrolytically generated Mn(III): synthesis, kinetics and mechanistic study

Abstract

The repeating sequence of elastin, valylprolylglycylvalylglycine (VPGVG), its permutation pentamer glycylvalylglycylvalylproline (GVGVP), and its more hydrophobic pentamer glycylphenylalanylglycylvalylproline (GFGVP) were synthesized by classical solution-phase methods and characterized. The kinetics of the oxidation of these pentapeptides (PP) by Mn(III) was studied in the presence of sulphate ions in acidic medium at 25°C. The reaction was followed spectrophotometrically at l max = 500 nm. A first-order dependence of rate on both [Mn(III)] and [PP] was observed. The rate is independent of concentration of the reduction product, Mn(II) and hydrogen ions. Effects of varying dielectric constant of the medium and addition of anions such as sulphate, chloride and perchlorate were studied. Activation parameters were evaluated using Arrhenius and Eyring plots. The oxidation products were isolated and characterized. A mechanism involving the reaction of PP with Mn(III) in the rate-limiting step is suggested. An apparent correlation was noted between the rate of oxidation and the hydrophobicity of these sequences where increased hydrophobicity results in an increased rate of oxidation. Further, it was observed that the pentamers with Pro as C-terminus are more susceptible to oxidation than the pentamer with Gly as C-terminus.

Mn(III) oxidation of peptides: A mechanistic investigation of kinetic variations in hydrophobic‐induced oxidation of tetrapeptides of elastin sequences

“…Gly-Ala-Pro, Gly-Val-Pro, Gly-Ile-Pro and Gly-PhePro, dipeptides, Ala-Pro, Val-Pro, Ile-Pro and Phe-Pro and free amino acid in the presence of different aqueous acid mediums [8][9][10][11]. The change in each case is due to the increased distance between the functional groups and consequently weaker electrostatic effects.…”

“…The peptide Boc-Gly-Val-Pro-OBzl and the TETPs GGAP, GGIP, and GGFP were synthesized as previously described [9,11]. The synthesis and characterization of GGVP are described here.…”

“…Mn(III) porphyrins have been studied as possible models for closely related biologically significant systems [7]. In recent years, kinetics of oxidation of amino acids, its derivatives, peptides, and proteins have been studied using Mn(III) in different mediums [8][9][10][11][12].…”

A comparative study of quinolinium dichromate oxidation with hydrophobic dependence amino acids. A kinetic and mechanistic approach

“…In any case, QDC, the reagent employed is a very useful and versatile oxidant and has a maximum usage in organic synthesis [8][9][10][11]. Therefore, in continuation of our investigations to exploit the sensitivity of amino acids (AA) to various metal-catalyzed oxidation systems [12][13][14], we herein report the oxidation of amino acids using QDC as an oxidant.…”

The kinetic and mechanistic study of levetiracetam oxidation with chloramine-B in acid medium

“…Sulfonamides and NaCl or HCl are reduction products when monohaloamines suffer two electron changes and dihaloamines undergoes four electron variations. The most well-known member of this family of compounds is chloramine-T (p-CH3C6H4SO2NClNa.3H2O (CAT), whereas chloramine-B (sodium N-chlorobenzene sulfonamide) has been used to oxidise a range of organic and inorganic molecules, and the kinetics of their oxidation have been carefully characterised 4,5,6,7,8 .…”