The role of Ni(II) in the oxidation of glycylglycine dipeptide by peroxomonosulfatex

Abstract

The kinetics of oxidation of the dipeptide glycylglycine by peroxomonosulfate (PMS) was studied in the pH range of 3.42-5.89. The rate is first order in [PMS], glycylglycine concentration, and inverse first order in [H + ]. The kinetic data suggest that SO 2− 5 reacts, with glycylglycine, faster than H SO − 5 by five orders of magnitude. The observed kinetics can be explained as due to the formation of an intermediate by the nucleophilic interaction of peroxide with the terminal protonated amine of glycylglycine, which then decomposes in the rate-limiting step to the product aldehyde. The thermodynamic parameters are evaluated. The reaction is catalyzed by Ni(II) ions only when pH ≤ 4.63, and above this pH the rate is zero order with respect to [Ni(II)]. Perusal of the enhanced rate constant values suggests that the Ni-peroxide intermediate also reacts with glycylglycine. The Ni-dipeptide complex is not oxidized by PMS, and this complex in fact inhibits the formation of Ni-peroxide intermediate.

Studies on the oxygen atom transfer reactions of peroxomonosulfate: Oxidation of glycolic acid

“…Similar results were observed in the decomposition of PMS in the presence of Ni(II) at acidic pH [15] as well as in the oxidation of Ni-glycylglycine [16]. By analogy with the earlier studies we can assume the oxidation of glycolates proceeds through a molecular mechanism.…”

“…However, results from this laboratory show that Ni(II) ion catalyzed decomposition of PMS in acidic pH [15] proceeds through the oxygen atom transfer mechanism with nickel peroxide intermediate instead of redox mechanism. The oxidation of Ni-glycylglycine by PMS also involves an oxygen atom transfer mechanism [16]. Therefore, in continuation of exploring the possibility of Ni(II)-PMS system without redox process, we have studied the reaction of GLYCA with PMS in the presence of Ni(II) and Cu(II) and the results are reported.…”

Assembly, Disassembly and Reassembly of Complex Coacervate Core Micelles with Redox‐Responsive Supramolecular Cross‐Linkers

“…MR was used as a drug-model, based on its medium-strong association constant with βCD (k a around 5 • 10 3 M À 1 ) and the direct visual information. [54][55][56] Biphasic systems have proven to be very illustrative to study supramolecular interactions involving hydrophobic/hydrophilic building blocks via phase transfer. [57] In a biphasic system based on water and dichloromethane (DCM), MR resides mainly in the DCM layer, due to its hydrophobicity.…”

“…The peak shift from 420 nm to 520 nm is related to the pH and the MR protonation. [54,56] Figure S27 shows an increase in the absorbance of the dye when it is encapsulated inside the cyclodextrin. This effect is related to the transfer of the guest from a more protic Figure 4.…”

Kinetics of Ag(I) catalyzed oxidation of amino acids by peroxomonosulphate

“…The kinetic results revealed that silver catalyzed reaction occurred approximately 10 4 times faster than the uncatalyzed reaction and this is attributed to the formation of (adduct) 2+ . The bimolecular rate constant (k) for the slow step and the activation parameters were calculated and the results are discussed.Ó 2009 Elsevier B.V. All rights reserved.Oxidation of amino acids (AA) by peroxomonosulphate in acidic, basic and neutral media in the absence and in the presence of transition metal ions has been extensively studied by many researchers [1][2][3][4][5][6][7][8][9][10]. This apparently mimics the mechanism of biological oxidation of amino acids proceeding through formation of Schiff base intermediate with pyridoxal phosphate in living systems.…”