Thiyl and Thiyl-peroxyl Radicals produced from the irradiation of Antioxidant Thiol Compounds

The transients involved in the mechanism of protection by thiol compounds against oxidative damage have been characterized by pulse radiolysis technique. The oxidizing properties of both thiyl (RS) and thiyl-peroxyl radical (RSOO), with E lying in the range +0.9 to +1.0 V, are well emphasized from the rates for their interactions with nucleophilic agents, including naturally occurring antioxidants. By applying a plausible kinetic treatment to the decay pattern of RSOO, the rates for both the interaction of the radical with the parent thiol and the structural rearrangement to sulphonyl radical (RSO2) were measured to bbe 1.4 × 106 mol-1dm3s-1 and 1.4 × 103s-1, respectively. The roles of thiol-derived radicals in oxidative damage in biological systems are discussed.