Dutton's Lab
Photosynthetic Reaction Center
This is a scheme of the electron transfer steps that occur in the
reaction centers of Rp. viridis. Excitation with light or resonance
energy transfer from an antenna complex first promotes the special pair of
bacteriochlorophyll (BChl2) to an excited singlet state. The excited BChl2
transfers an electron
to one of the two bacteriophaeophytins (BPhl) in 3ps. The electron probably
passes through the accessory bacteriochlorophyll (BChll) located between the
Bchl2 and Bphl. Then the electron moves from BPhl
to one of the quinones (QA) in about 200ps, and proceeds from QA to the
other quinone (QB) in about 100 microsecond. Meanwhile, BChl2 extracts an
electron from the nearest heme (Heme1) of the four-heme cytochrome that is bound
tightly to the reaction center. An electron is probably transferred from
an electron donor to Heme1 through the other hemes (Heme4, Heme3, Heme2)
in the four-heme cytochrome.
