Don DeVault

Abstract

The geometry of the R. viridis reaction center as revealed by the x-ray studies of Deisenhofer et al (1) may be adapted to enhancing the coupling of specific porphyrin vibrations to electron transfer. The orientations of the two BChl (acceptors from BChl₂) and the two BPhe (acceptors from BHcl) are edge-on toward their donors while the donors, incn]YZk ‘whe two BPhe as donors to Q (quinone) are broadside toward their acceptors. This should enhance coupling of the out-of-plane flat-plate type of vibrations of the donor porphyrin to the electron transfer. The equilibrium position of this vibration is a function of the charge on the donor in an electric field perpendicular to the donor plane. This electric field can be that of the transferring electron if the donor is left in a charged state and in this case the electron is directed broadside from the donor. Otherwise the field can come from fixed electric charges in the environment.