Radical species generated from the reactions of a basic amino acid, L-lysine ( Lys), with hydroxyl radicals ((OH)-O-center dot) and sulfate radical anion (SO4-center dot 4) have been detected by the method of pulse radiolysis. On the basis of electron transfer reactivities toward tetranitromethane (TNM), it was demonstrated that reducing carbon-centered radicals are generated as a result of hydrogen abstraction from CH2 of Lys with a G-value of 1.9 x 10 x 7 mol J (1). On the other hand, direct oxidation of L-Lys by SO4-center dot 4 formed a transient species with different spectroscopic properties, most likely, the epsilon-N-centered Lys radical. (c) 2008 Elsevier B. V. All rights reserved.