Fe(III) - Sulfide interaction in globins: Characterization and quest for a putative Fe(IV)-sulfide species

Oxidation of sulphide-methemogobin by hexachloroiridate leads to a sulfoferryl species which, unlike the classical ferryl (Compound II, obtained by oxidation of hydroxo-methemoglobin), is very unstable and decomposes to a ferric form with distinct EPR features. The affinity of hemoglobin for sulphide is an order of magnitude than that of myoglobin.196