My research revolves around mechanistic studies of proton coupled electron transfer (PCET), which are complex redox reactions that transfer electrons and protons sequentially or in concert. These reactions are ubiquitous in natural or artificial processes that produce electrochemical energy, extractable as electricity or as chemical fuels of high energy content. My project was to study the oxidation of the natural thiol glutathione (GSH) by the metal complexes K4Mo(CN)8, and Fe(phen)3SO4, in aqueous solution and using glassy carbon electrodes. This PCET reaction involves the transfer of 1 electron and 1 proton to produce the thiyl radical GS● that further dimerizes to GSSG. The GSH oxidation does not occur directly at the electrode but through reaction with the electrogenerated oxidant from the metal complex. Previous published work in our lab, had revealed that at pH &lt; 7.0, GSH is protonated and its oxidation is dominated by a concerted mechanism involving the oxidant and the base from the buffer system. My goal in continuing this project was to ascertain the oxidation mechanism when GSH is deprotonated (pH &gt; 10) and contrast it with our previous findings. My results, show that at pH 10, the preferential pathway for GSH oxidation is the step-wise sequence PT-ET while the concerted mechanism appears to be marginal. Digital simulation was used to determine thermodynamic and kinetic parameters of respective steps by quantitative fitting experimental cyclic voltammograms. In some cases, other analytical techniques are used to aid in the system characterization.

Stepwise proton-coupled electron transfer oxidation of glutathione in phosphate buffer

254th National Meeting (2017)

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