[Absorption spectra and magnetic circular dichroism of ferrocytochrome b5 formed during low temperature reduction in a nonequilibrium state].

Under gamma-irradiation of frozen water--glycerol solutions of ferrocytochrome b5 at 77 degrees K ferrocytochrome b5 in a non-equilibrium state is formed. Its absorption and MCD spectra are displaced by 1,5 nm to the long wave region. When the temperature is increased to 140 degrees K the non-equilibrium form of reduced protein is relaxes. A comparison of optical characteristics of ferrocytochrome b5 in equilibrium and non-equilibrium states shows that the structure of the protein active centre slightly depends on the state of metal oxidation. It is concluded on the basis of earlier published data on low temperature reduction of different electron transport proteins that a small effect of the oxidation state of a metal ion on the active centre structure is a common property of all the electron transport proteins. This phenomenon makes these systems an effective carrier of electrons.