Role of thiols in radioprotection: radiation chemical aspects.

Using the technique of pulse radiolysis, it has been demonstrated that thiyl radicals (RS.) derived from glutathione (GSH), cysteine (CYSH), penicillamine (PnSH) and 2-mercaptoethanol (ME) interact with oxygen at a high rate. The resulting transient absorption, with a maximum around 540-560 nm, is characteristic of the sulphur peroxyl radical (RSOO.). The yield and the kinetic of formation of RSOO. further support our previous suggestion that thiyl/O2 reaction is an equilibrium. The redox properties of RSOO. are discussed on the basis of the interaction with reductants. Studies on the radio-induced enzyme inactivation in the presence of thiols seem to suggest a damaging role for RSOO. radicals.