Detection of Oxidation of L-Cysteine by Dimethyl Sulfoxide in Aqueous Solutions by IR Spectroscopy

We have used IR spectroscopy to study the reaction between L-cysteine and dimethyl sulfoxide in aqueous medium. We have found that reaction occurs with formation of an insoluble product, which we have identified. We show that oxidation of L-cysteine by dimethyl sulfoxide can occur at an appreciable rate under mild conditions, with formation of L-cystine, dimethyl sulfide, and water.