Jump to main content
Jump to site search


Interplay of Proton and Electron Transfer to Determine Concerted Behavior in the Proton-Coupled Electron Transfer of Glutathione Oxidation

Abstract

Glutathione (GSH), whose thiol group dictates its redox chemistry, oxidizes to the thiyl radical (GS•) that rapidly dimerizes to GSSG. Previously, we found that the oxidation rate of GSH by IrCl62- depends on the base (B) concentration and the pKa of its conjugate acid BH+, so that collateral to a stepwise mechanism, the concerted pathway GSH + IrCl62- + B = GS• + IrCl63- + BH+, was proposed as rate determining step. Herein, this investigation is extended to include oxidant-base pairs that render exothermic and endothermic conditions of G˚′ for electron transfer (ET) and proton transfer (PT). Experiments were conducted by reaction of GSH with an electrogenerated oxidant M+ and using digital simulations to infer the mechanism Data analysis shows that despite parallel mechanisms, the concerted one seems to predominate for the oxidant-base pair that renders the most isoenergetic coupled state, whereby a PT with G˚′PT  0 is capable of producing an ET with appG˚′ET  0, as a result of the Nernstian shift of E˚’GSH with pKa. In contrast, the stepwise PT-ET appears to dominate when GS- grows in stability as G˚′PT becomes more negative. Understanding the interplay between ET and PT will help the design of catalysts for energy harvesting processes that rely on proton-coupled electron transfer.

Back to tab navigation

Supplementary files

Publication details

The article was received on 03 Mar 2018, accepted on 13 Jun 2018 and first published on 13 Jun 2018


Article type: Paper
DOI: 10.1039/C8CP01415A
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
  •   Request permissions

    Interplay of Proton and Electron Transfer to Determine Concerted Behavior in the Proton-Coupled Electron Transfer of Glutathione Oxidation

    K. Meng, J. Medina-Ramos, E. Yibeltal-Ashenafi and J. C. Alvarez, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C8CP01415A

Search articles by author

Spotlight

Advertisements