Bimolecular proton-coupled electron transfer from tryptophan with water as the proton acceptor
2012 (English)In: Energy & Environmental Science, ISSN 1754-5692, Vol. 5, no 7, 7732-7736 p.Article in journal (Refereed) Published
Proton-coupled electron transfer (PCET) from amino acids with water as the primary proton acceptor is a fundamental model reaction of wide relevance. We have investigated the kinetics and mechanism of PCET from tryptophan derivatives to laser flashgenerated [Ru(bpy)(3)](3+) oxidants in aqueous solutions. The PCET reaction followed either a concerted electron-proton transfer (CEP) mechanism or a step-wise electron transfer-proton transfer (ETPT) mechanism, depending on pH and the identity of the Ru-III oxidant. The CEP reaction showed a pH-dependent rate constant, with an increase in log k(CEP\) of 0.3-0.5 per pH unit, and a significant kinetic isotope effect (KIE = 2-4), both in intramolecular and bimolecular model systems. Our results suggest that CEP with water as the proton acceptor is a general feature of amino acid oxidation, and provide further experimental observations towards a detailed understanding of the PCET process in water.
Place, publisher, year, edition, pages
2012. Vol. 5, no 7, 7732-7736 p.
IdentifiersURN: urn:nbn:se:uu:diva-177565DOI: 10.1039/c2ee03137jISI: 000305530900005OAI: oai:DiVA.org:uu-177565DiVA: diva2:541275