The reduction mechanism of ferricytochrome c

The second-order rate constant of the reaction between the hydrated electron and ferrinitrocytochrome c exhibits a marked pH dependence that could not be fully ascribed to changes in geometrical parameters and in net charge of the protein molecule.

The correlation between the pH dependence of the rate constant, the 695-nm absorbance and the ionization state of the nitrated tyrosyl-67 residue indicates that tyrosine-67 is of importance in maintaining the specific structure for the electron transfer mechanism in ferricytochrome c upon reduction.