Theoretical study on primary reaction of photosynthetic bacteria

Theoretical calculation was carried out on the primary electron donor P-870 Of photosynthetic bacteria. The results show that: (i) the bimolecular str ucture of the primary electron donor is more advantageous in energy than 'm onomolecular structure; (ii) the initial configuration of primary electron donor is no longer stable and changes to the configuration with lower energ y and chemical reactivity after the charge separation. In the P870, such st ructural change is completed through the rotation of C-3 acetyl, so the oxy gen atom of acetyl interacts with the magnesium atom of another bacterio-ch lorophyll molecule, and the total energy and chemical reactivity are reduce d evidently. It is suggested that the structural change of the primary elec tron donor is important in preventing the occurrence of charge recombinatio n during the primary reaction and maintaining the high efficiency of the co nversion of sun-light to chemical energy. A new mechanism of primary reacti on has been proposed, which can give reasonable explanations to the results of kinetic and site mutation studies.