Changes in conformation of reduced cytochrome c in neutral aqueous solution

Abstract

In neutral aqueous solution, high concentrations of alcohols perturb cytochrome c in such a way that reduction by means of ionizing radiation results in the formation of abnormal conformers of ferrocytochrome c resembling those previously seen on reduction in alkaline solution. These relax to normal ferrocytochrome c in about 0.1 s.

The reaction of ferric cytochrome c with dithionite at very low ionic strength

“…The data for the reduction of ferricytochrome c by dithionite is in partial agreement with the results of pulse radiolysis [5,6] where ferricytochrome c is reduced by hydrated electrons. The major difference concerns observations near neutrality where Pecht and Faraggi [S] reported slow secondary spectral changes while Land and Swallow [6] saw none.…”

“…The major difference concerns observations near neutrality where Pecht and Faraggi [S] reported slow secondary spectral changes while Land and Swallow [6] saw none. Lambeth et al [3], in agreement with Land and Swallow [6], found the reduction of cytochrome c by dithionite to be biphasic only in the alkaline region, and tried to explain Pecht's data by poor control of pH in unbuffered solutions [3].…”

“…The major difference concerns observations near neutrality where Pecht and Faraggi [S] reported slow secondary spectral changes while Land and Swallow [6] saw none. Lambeth et al [3], in agreement with Land and Swallow [6], found the reduction of cytochrome c by dithionite to be biphasic only in the alkaline region, and tried to explain Pecht's data by poor control of pH in unbuffered solutions [3]. Pecht and Faraggi [5] found the specific rate for the slow transition to be 8.5 s-l, very similar to the specific rate (k,, 10 s-') for the slow interconversion of the unstable [B'*] conformer found by us in neutral, very low ionic strength buffered solution (Tris-cacodylate 0.002 M); so that we attribute Pecht's findings to the low ionic strength of the medium rather than to improper pH caused by unbuffered solutions.…”

Reduction of ferricytochrome c, methemoglobin and metmyoglobin by hydroxyl and alcohol radicals

“…In agreement with several authors [5,20] we have found that the ethylene glycol and glycerol radicals do not reduce ferricytochrome c. These radicals also do not reduce metmyoglobin. After ~'-irradiation of metmyoglobin there is however a build up of a characteristic low spin spectrum.…”