Role of 2-oxo and 2-thioxo modifications on the fragmentation reactions of the histidine radical cation

Abstract

The fragmentation reactions of the radical cations, M.+, of histidine, 2-oxo-histidine and 2-thioxo-histidine were examined using a combination of experiments performed on a linear ion trap and density functional theory (DFT) calculations at the UB3-LYP/6-311++G(d,p) level of theory. Low-energy collision-induced dissociation (CID) on [CuII(terpy)(M)] 2+ complexes, formed via electrospray ionisation, produced the radical cations in sufficient yield to examine their unimolecular chemistry via an additional stage of CID. The CID spectrum of the radical cation of histidine is dominated by loss of water with the next most abundant ion arising from the combined loss of H2O and CO. In contrast, the..