RuIII(EDTA) mediated S-nitrosylation of cysteine by nitrite

Abstract

Reported here is the first example of a ruthenium(III) complex [Ru^III(EDTA)(H₂O)]⁻ (EDTA⁴⁻ = ethylenediaminetetraacetate) that mediates S-nitrosylation of cysteine in the presence of nitrite at pH 4.5 (acetate buffer) and results in the formation of [Ru^III(EDTA)(SNOCy)]⁻. The kinetics of the reaction was studied by stopped-flow and rapid-scan spectrophotometry as a function of [Cysteine], [NO₂⁻] and pH (3.5–8.5). Formation of [Ru^III(EDTA)(SNOCy)]⁻, the product of the S-nitrosylation reaction, was identified by ESI-MS experiments. A working mechanism in agreement with the spectroscopic and kinetic data is presented.