Stabilization and reactions of sulfur radical cations:: Relevance to one-electron oxidation of methionine in peptides and proteins

Methionine is a key amino acid that has numerous roles in essential vital processes. Moreover, methionine oxidation is biologically important during conditions of oxidative stress and represents an important step in the development of some severe pathologies. Considerable work has been performed to understand the mechanisms of one-electron oxidation of the Met-residue as a function of its proteic environment. The most important recent results obtained by means of time-resolved techniques (laser flash photolysis and pulse radiolysis) on model peptides containing single or multiple Met-residues and in selected naturally occurring peptides (Met-enkephalin and P-amyloid peptide) and proteins (thioredoxin and calmodulin) have been reviewed.