Mechanism of the reaction of hydrated electrons with ferrocytochrome c.

1. The hydrated electron reacts with ferrocytochrome c to form an unstable intermediate. This intermediate decays in a first-order manner to give, in the first instance, a product which has a similar absorption spectrum in the range 400-610 nm as normal ferricytochrome c. 2. At 21 degrees C the rate constant for the reaction of hydrated electrons with ferrocytochrome c at pH 7.4 (2 mM phosphate buffer) is (3.0 +/- 0.3) = 10(10) M-1 - S-1. As the pH is increased above pH 8.0 the rate constant steadily decreases. The dependence of the rate constant on pH can be explained if ferrocytochrome c has a pK of around 9.2. 3. At 21 degrees C and pH 7.4, the rate constant for the decay of the intermediate is (1.40 +/- 0.15) - 10(5) S-1. This reaction shows no pH dependence in the range 6-2-11.0. 4. A mechanism is proposed whereby the central metal atom of the ferrocytochrome c is oxidased and a thioether bond is reduced. The resulting ferricytochrome c species then slowly develops an absorbance at 606 nm due to the attack of the sulfhydryl group on the haem.