Oxidation of methionine-containing peptides by OH radicals: Is sulfoxide the only product? Study by mass spectrometry and IRMPD spectroscopy

Although the first steps of the oxidation of methionine containing peptides by OH radicals have been very well documented, not much is known about the final products. They have been characterized and unraveled by mass spectrometry and IR Multiple Photon Dissociation (IRMPD) spectroscopy carried out with model dipeptides and methionine enkephalin, often involving the transformation of residues other than methionine. Several products were found, in addition to methionine sulfoxide, which is omnipresent. Thus IRMPD proved to be very useful in oxidative proteomics.