Quantum chemistry study of proteins in bacterial photosynthetic reaction center

AbstractQuantum chemistry study on proteins L and M in the Rhodopseudomonas viridis (Rh. viridis) photosynthetic reaction center (PRC) are presented. The calculations were performed at ab initio level with Clementi minimal basis set by means of the overlapping‐dimer approximation (ODA)–extended negative factor counting (ENFC) method. Additional point charges were added to individual residues to simulated ionized aqueous environment of the proteins in the calculations. Meanwhile, the electronic structure of protein complex MH (protein M plus the α‐helix segment of protein H) was studied as well to examine the weak interaction between proteins M and H. As the first case of global quantum chemistry calculation for proteins in PRC, details of the electronic structure and the influence of proteins on the electron transfer process (ET) were studied. Moreover, new three‐dimensional structure plots of subunit L and M were given based on the distribution of the components of frontier orbitals in order to more clearly understand the structure–function relationship of the proteins in electron transfer reactions. Calculation results indicated that the components of frontier orbitals are extrem