193 - Investigating the Redox Chemistry of Perthiyl Radicals: An Implication of Their Biological Functions

Abstract

Hydrogen sulfide (H2S) is reported to be an important endogenously generated signaling molecule with a number of beneficial biological effects. Though H2S is proposed to have numerous physiological functions, the specific roles, mechanisms and biological targets of H2S are not well defined. More recently, it has been considered that much of the proposed functions attributed to H2S are in fact largely due to its oxidized congeners, hydropolysulfides (RSnR) and hydropersulfides (RSSH/RSS–), making H2S merely a marker for their reactivity. To relieve this controversy, it seems reasonable to study the chemistry of hydropersulfides independent from that of H2S. Until now, such a task has been difficult. To address this issue, others and we have explored the use of hydropersulfide donors, which undergo spontaneous rearrangement for in situ generation of hydropersulfides. This has allowed for a more direct examination of the chemistry associated with hydropersulfides and their related redox species in the absence of other potentially interfering sulfur adducts. Of specific interest is the ability of hydropersulfides, in comparison to thiols, to act as potent one-electron reductants. Single electron oxidation of a hydropersulfide generates a perthiyl radical (RSS●), which in comparison to thiyl radicals (RS●), are considered to be relatively unreactive due to their enhanced stability through resonance. For these reasons, we have examined the redox chemistry of hydropersulfides and perthiyl radicals with biological molecules (i.e. O2 and nitric oxide) and we report the potential role of the RSSH/RSS● redox system as it pertains to biological processes.