CHARGE DISPLACEMENTS IN INTERFACIAL LAYERS CONTAINING REACTION CENTERS

Reaction centers from the photosynthetic bacterium Rhodobacter sphaero ides were oriented in phospholipid interfacial layers adsorbed to a Te flon film separating two electrolyte-filled compartments of a Teflon c ell. Light-induced voltage changes were measured as a function of time across electrodes immersed in the cell compartments. The experimental system is characterized both experimentally and theoretically to rela te the measured signals to the light-induced displacement currents in the reaction centers. Mathematical relations between the measured sign als and the distances and geometries of the charge-transfer reactions are derived. At pH 8.0 the reaction centers were found to be oriented with similar to 60% of the population oriented with the donor facing t he aqueous phase. The density of the reaction centers in the layer was similar to 10(11) cm(-2), which is close to that found in the native system. Reconstitution of the secondary quinone, Q(B), in 90% of the R Cs was achieved with an similar to 100-fold excess of ubiquinone in th e vesicle preparation.