The electron structure of teh primary electron donor P960 in Rhodopseuodomonas (Rps.) uiridis photosynthetic reaction center (RC) and P680 in photosystem Ⅱ (PSⅡ) RC have been studied with B3LYP DFT quantum chemical ab initio method at 3-21G level. The influence of the surrounding proterins and the axial coordination of histindine residues on the electronic structure of the primary electron donor has also been studied. Finally, the mechanism of the primary electron transfer (ET) is discussed. The results indicate: (1) the HOMO of super-molecule P960 - h in bacerial RC mainly consists of atomic orbitalsof atoms lacated at the composition unit M. The corresponding LUMO mainly consists of atomic orbitals of atoms located at both L and M composition units. Both HOMO and LUMO of super-molecule P680-h in PSⅡ RC mainly consist of atomic orbitals of atoms located at composition unit Dl. These calculated results are helpful for understanding the experimental fact that the primary ET in RC of bacterial and PSⅡ mainly perform along L branch and D1 branch, respectively. (2) Although the His residues, which are axially coordinated to teh primary electron donor P960 in the bacterial RC, do not contribute to the compositions of HOMO and LUMO of super-molecule P960-h, they make the ELUMO of P960-h much greater than that of P960 and greater than those of ABChl and BPheo. This cause the primary ET in bacterial RC to proceed easily. Otherwise, it will be very difficult for the primary ET to perform. For PSⅡ RC, the case is similar. (3) The distance between the Mg ion in ABChl and the N in the His residues is similar to that between the Mg ion in P960 and the N atom in the corresponding His, so that the His residues coordinating to ABChl must be taken into consideration. At this condition, the primary ET in bacterial RC should be a two-step ET process form P960-h to BPheo bL via ABChl bL^h along the L branch. For PSⅡ RC, there does not exist the axial coordination of His to accessory 光合反应中心原初电子转移机理的理论研究

Key words: ELECTRONIC STRUCTURE