Asymmetric electron transfer in reaction centers of purple bacteria strongly depends on different electron matrix elements in the active-and inactivebranches
D. Kolbasov et A. Scherz, Asymmetric electron transfer in reaction centers of purple bacteria strongly depends on different electron matrix elements in the active-and inactivebranches, J PHYS CH B, 104(8), 2000, pp. 1802-1809
We have re-examined the contribution of electronic matrix elements (V-1) be
tween the primary electron donor and the accessory bacteriochlorophylls in
the active (A) and inactive (B) branches of bacterial reaction centers (RC)
to the unidirectional light-induced electron transfer (ET) (a preliminary
report was recently given by Kolbasov and Scherz in Photosynthesis: Mechani
sms and Effects; Garab, G., Ed.; Kluwer Academic Publishers: Dordrecht, 199
8; Vol. II; pp 719-722). Our calculations showed that V-1B(2) is probably s
maller by 3 orders of magnitude than V-1A(2) in Rb. sphaeroides and by at l
east 1 order of magnitude in Rps. viridis. These phenomena reflect the quan
tum interference and mutual cancellation of the resonance integrals corresp
onding to different ET pathways between atoms of P and the accessory bacter
iochlorophyll in the inactive branch. The calculated values of V and the co
rresponding ET rate constants for mutated Rd further support this conclusio
n Zhang and Friesner (Proc. Natl. Acad. Sci. U.S.A. 1998, 95, L3603-13605),
using more elaborate calculations, showed that V-1A/V-1B, for Rps. viridis
can reach a value of 14 for same reason, indicating that differences in th
e overlap matrix elements are key factors in the unidirectional electron fl
ow in both organisms.