[RuIII(EDTA)(H2O)]− mediated oxidation of cellular thiols by HSO5−
The [RuIII(EDTA)(H2O)]− (EDTA4− = ethylenediaminetetraacetate) complex is shown to mediate the oxidation of thiols, RSH (RSH = cysteine, glutathione, N-acetylcysteine, and penicillamine), with peroxomonosulfate ion (HSO5−). The kinetics of the catalytic oxidation process were studied using stopped-flow and rapid scan spectrophotometry as a function of [RuIII(EDTA)(H2O)−], [HSO5−], and [RSH] at a constant pH (6.2). Spectral analyses and kinetic data are suggestive of a catalytic pathway in which the RSH reacts with the [RuIII(EDTA)] catalyst complex to form [RuIII(EDTA)(SR)]2− intermediate species. In a subsequent step the HSO5− ion reacts directly with the coordinated S-atom of [RuIII(EDTA)(SR)]2− yielding the disulfido species, RSSR, as a major oxidation product (as identified using HPLC and ESI-MS analyses) under the employed conditions. Based on the experimental data, a working mechanism is proposed for the [RuIII(EDTA)] catalyzed oxidation of thiols.