THE PECULIARITIES OF THE ELECTRON-TRANSFER FROM CYTOCHROME TO THE CATION-RADICAL OF BACTERIOCHLOROPHYLL DIMER IN REACTION CENTERS FROM RHODOPSEUDOMONAS-VIRIDIS

The kinetics of tunnel electron transitions in reaction centers of photosynthetic bacteria Rhodopseudomonas viridis are characterized by paradoxical peculiarities. (1) The time of the high-temperature (300 K) transfer of an electron to the cation-radical of bacteriochlorophyll BCl2+ from the neighbour heme C380 is almost twice as long as that from the almost twice as distant heme C20. (2) At low temperature (77 K) the majority (almost-equal-to 80%) of nearby hemes C380 is unable to reduce BCl2+ while all remote hemes C20 participate effectively in such reductions as though they disconnect C380 hemes. Both these peculiarities find their explanation on the basis of the mechanism of two-electron relay tunneling: C380-->(e-)BCl2+, C20-->(e-)C380+.