A study of the use of NH4I for the reduction of methionine sulfoxide in peptides containing cysteine and cystine

Article abstract of DOI:10.1016/0040-4020(95)00234-Y

Methionine sulfoxide reduction by NH₄I has been studied in some disulfide containing peptides. In general, this reagent has proved to be effective in neat TFA at 0°C, with the obtention of the unprotected peptides in more than 99% yields and without reduction of the disulfide bridge bond. The use of Me₂S as an additive resulted in faster reactions and disulfide scrambling was not observed. Whereas the Acm group proved to be stable to the reaction conditions, unprotected cysteine containing peptides afforded the corresponding parallel dimers.