The chemical biology of hydropersulfides (RSSH): Chemical stability, reactivity and redox roles

• Hydropersulfides are superior nucleophiles compared to thiols.
• As electrophiles, hydropersulfides react quickly with “soft” nucleophiles.
• As electrophiles, hydropersulfides react poorly with “hard” nucleophiles.
• Hydropersulfides are electrophilic and prefer reaction on the terminal sulfur atom.
• Hydropersulfides are good one-electron reductants.

Recent reports indicate the ubiquitous prevalence of hydropersulfides (RSSH) in mammalian systems. The biological utility of these and related species is currently a matter of significant speculation. The function, lifetime and fate of hydropersulfides will be assuredly based on their chemical properties and reactivity. Thus, to serve as the basis for further mechanistic studies regarding hydropersulfide biology, some of the basic chemical properties/reactivity of hydropersulfides was studied. The nucleophilicity, electrophilicity and redox properties of hydropersulfides were examined under biological conditions. These studies indicate that hydropersulfides can be nucleophilic or electrophilic, depending on the pH (i.e. the protonation state) and can act as good one- and two-electron reductants. These diverse chemical properties in a single species make hydropersulfides chemically distinct from other, well-known sulfur containing biological species, giving them unique and potentially important biological function.

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