Interactions of thiyl free radicals with oxygen: a pulse radiolysis study

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 (Formula: see text) appears to be an equilibrium whose kinetic constants have been estimated (kf = 2.0 X 10(9) dm3 mol-1, kb = 6.2 X 10(5) 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 X 10(8) dm3 mol-1 s-1.