Role of Thiols in Radioprotection: Radiation Chemical Aspects

Abstract

Using the technique of pulse radiolysis, it has been demonstrated that thiyl radicals (RS˙) derived from glutathione (GSH), cysteine (CYSH), penicillamine (PnSH) and 2-m ercaptoethanol (M E) 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.