The theoretical studies on the mechanism of the primary electron transfer in the mutant photosynthetic reaction center

The electronic structure of the primary electron donor D - 2A and other pig ments in photosynthetic reaction center (RC) of the mutant HM202L of Rhodob acter sphaeroides has been studied with the ab initio DFT method. The mecha nism of primary electron transfer in this mutant was studied. The results i ndicated 1) HOMO of super- molecule D - 2A mainly consists of the atomic or bitals of atoms located at the composition unit BChl(L), and its LUMO mainl y consists of atomic orbitals of atoms located at the composition unit MBPh eo(M). These rsults indicate that there exist internal charge separated sta tes [BChl(L)(-) - MBPheo(M)(+)] and [BChl(L)(+) - MBPheo(M)(-)] in the grou nd state and excited state of super- molecule D - 2A, respectively. The pos itive charge of the D - 2A cation completely localizes on the composition u nit BChl(L), which is in agreement with the experimental fact. 2) There mig ht be a reaction channel, in which the primary electron transfer reaction m ay be driven by ABChla(L)(h)* in the HM202L photosynthetic reaction center.