Evaluation of the “radical sink” hypothesis from a chemical-kinetic viewpoint

Radicals produced in cellular systems are frequently “repaired” by thiols, but the sulphur-centred (thiyl) radical resulting has to “sink” its unpaired electron in other reactions. It has been suggested that superoxide is the major radical sink, via thiyl conjugation with thiolate and electron transfer to oxygen. It is argued here, from chemical kinetic data largely obtained by pulse radiolysis methods, that ascorbate probably provides the major radical sink when radicals are produced in most mammalian tissues at typical physiological pH.