The peculiarities of the electron transfer from cytochrome to the cation-radical of bacteriochlorophyll dimer in reaction centers from Rps. viridis

Abstract

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 BC1 + 2 from the neighbour heme C 380 is almost twice as long as that from the almost twice as distant heme C 20. (2) At low temperature (77 K) the majority (≈ 80%) of nearby hemes C 380 is unable to reduce BCl 2 + while all remote hemes C 20 participate effectively in such reductions as though they disconnect C 380 hemes. Both these peculiarities find their explanation on the basis of the mechanism of two-electron relay tunneling: C 380→ e−BCl 2 +, C 20→ e−C 380 +.