Pulse radiolysis studies on reaction of .OH radical with N-acetyl methionine in aqueous solution

In neutral aqueous solutions, hydroxyl radicals were observed to react with N-acetyl methionine (N-AM) to form transient absorption bands at 290, 360 and 490 nm. The absorbance at 290 and 360 nm bands decreased, whereas the absorbance at 490 nm band increased with solute concentration. The bands at 290 and 360 nm were observed to be quenched by oxygen, whereas the band at 490 nm was not affected. These bands were assigned to alpha-thio radical, OH-adduct and dimer radical cation, respectively. In acidic solutions, dimer radical cation was the only transient species formed on hydroxyl radical reaction. Cl-2(center dot-) was able to react with N-AM and formed a dimer radical cation absorbing at 490 nm. Redox studies revealed that the one-electron oxidation potential of N-AM is between 1.3 and 2.1 V vs. NHE.