Ao. Goushcha et al., NONLINEAR DYNAMIC PROCESSES IN AN ENSEMBLE OF PHOTOSYNTHETIC REACTIONCENTERS - THEORY AND EXPERIMENT, JOURNAL OF PHYSICAL CHEMISTRY B, 101(38), 1997, pp. 7612-7619
The results of a theoretical study of the dynamic self-organization ph
enomenon in the photosynthetic reaction center (RC) from purple bacter
ia are presented accounting for the stochastic effects an RC ensembles
. The adiabatic approximation is applied to determine the specific rol
e of slow structural (protein/cofactors) modes in the correlated behav
ior of the electronic and structural variables, it is shown that, at c
ertain values of light intensity, the system undergoes bifurcation. Th
e bistability region for the generalized structural variable occurs wh
ere the system has two stable stales, one characteristic for the dark-
adapted sample (i.e., the sample under very low illumination intensity
) and the other for the light-adapted sample. The description is based
on the solution of the ''forward'' Kolmogorov equations using the Mar
kov approach, A distribution function describing the probability of fi
nding the electron localized on a particular cofactor with a certain v
alue of the generalized structural variable is used. Modeling shows a
good agreement with the results of experimental investigations of tran
sient optical absorbance changes of the isolated RCs from the purple b
acterium Rhodobacter sphaeroides. The results indicate that the free e
nergy difference between Q(A)(-) and Q(B)(-) changes substantially in
different conformational states of the protein/cofactors induced by li
ght over a wide range of the illuminating light intensity.