Reduction of the ferrous alpha-verdoheme-cytochrome b5 complex |
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Authors: | Damaso Christopher O Rubie Nick D Moënne-Loccoz Pierre Rivera Mario |
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Institution: | Department of Chemistry, University of Kansas, Lawrence, Kansas 66045-7582, USA. |
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Abstract: | The ferrous alpha-verdoheme-cytochrome b(5) 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 pineutral radical best formulated as a Fe(II)(verdoheme*)] --> Fe(I)(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 Fe(II)(verdoheme)](+) complex and the two-electron-reduced Fe(II)(verdoheme:)](-) anion. The latter might also be formulated as a resonance hybrid Fe(I)(verdoheme*)](-) --> Fe(II)(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 O(2) results in rapid and quantitative reoxidation to the resting state Fe(II)(verdoheme)](+) complex. |
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