A computational study on the possible role of oxygen in the oxidation of methionine and dimethylsulfide initiated by OH radicals

The oxidation of methionine residues (Met) is related with the pathogenesis of diseases like Alzheimer’s. Density functional theory (B3LYP) calculations are used to investigate the thermochemistry of several possible reactive intermediates that may be involved in the oxidation of Met and its radical cation. The computational results are calibrated using dimethyl sulfide (DMS) as a model system which has been studied at the DFT, CCSD(T) and G3(MP2)//B3LYP levels of theory. The results suggest that molecular oxygen may be an important participant in the OH-radical initiated oxidation of Met.