Hydroxy sulfuranyl radical

Pogocki D., Ghezzo- Schbneich E., Schbneich C., Conformational flexibility controls proton transfer between methionine hydroxy sulfuranyl radical and the N-terminal amino group in Thr-(X) -Met peptides, J. Phys. Chem. B, 2001,105,1250-1259. 

Oxidation of methionine residues has been widely studied. Reaction of OH is fast (k= 10 mol I s l) and proceed via formation of an OH-adduct > S-OH, the hydroxy sulfuranyl radical (42). This radical eliminates water, yielding the monomeric radical cation >S + which then stabilizes through formation of >S-X radical species, X= N, O or S (56). In methionine amino-acid, the free radical undergoes ring closure with the amine function to give cyclic >SN radical (57) which then gets decarboxylated. Final compound seems to be methionine sulfoxide. When methionine is in a peptide, the fate of the hydroxy sulfuranyl radical is strongly dependent on the position of methionine in the peptide. 

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