The ferrous α-verdoheme-cytochrome b5 complex, [Fe II(verdoheme)]+, has been prepared and characterized spectroscopically. Anaerobic addition of excess sodium dithionite to [Fe II(verdoheme)]+ at pH 10 produces a one-electron-reduced species with spectroscopic characteristics that suggest a ferrous hexacoordinated verdoheme π neutral radical best formulated as a [Fe II(verdoheme•)] → [FeI(verdoheme)] resonance hybrid. At lower pH values (7.0 and 8.0) the one-electron-reduced species is shown to disproportionate to produce the resting state [FeII- (verdoheme)]+ complex and the two-electron-reduced [Fe II(verdoheme:)]- anion. The latter might also be formulated as a resonance hybrid [FeI(verdoheme•)]- → [FeII(verdoheme:)]-. The disproportionation reaction becomes very slow as the pH is raised above 9.0. Exposure of the one-electron- or two-electron-reduced verdoheme complexes of cytochrome b 5 to O2 results in rapid and quantitative reoxidation to the resting state [FeII(verdoheme)]+ complex.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry