Interactions of Thiyl Free Radicals with Oxygen: A Pulse Radiolysis Study

Abstract
A pulse radiolysis study of glutathione in aqueous solution at pH 5·5 containing N2O/O2 mixtures at various ratios indicates that oxygen rapidly adds to the thiyl glutathione radical yielding a transient absorption, with a maximum at 540 nm, whose characteristics appear to be compatible with assignment to the GSOO· radical. The reaction appears to be an equilibrium whose kinetic constants have been estimated (kf = 2·0 × 109 dm3 mol−1 s−1, kb = 6·2 × 105 s−1). Evidence for electron transfer from ascorbate to the GSOO· radical has been obtained and the respective rate constant has been determined to be 1·75 ± 0·15 × 108 dm3 mol−1 s−1.