Oxidation of methionine methyl ester in aqueous solution: A combined pulse radiolysis and quantum chemical study

A combined experimental and theoretical study is employed to elucidate one- electron oxidation mechanism of methionine methyl ester (MME) in aqueous solution. In neutral solution, (center dot)OH radical reaction leads to the formation of a monomer transient species absorbing at 380 nm and a dimer transient species absorbing at 480 nm is formed in acidic solution. Quantum chemical calculations suggest that the transient species formed on reaction of (center dot)OH radicals in neutral solution has 5-member ring structure. The transient absorption band formed on reaction of Cl(2)(center dot-) or Br(2)(center dot)- with MME is shown to be due to hemi bonded adduct between Cl or Br atoms and S in MME. (c) 2005 Elsevier B.V. All rights reserved.