PHOTOINDUCED CHARGE SEPARATION IN LIPOSOMES CONTAINING CHLOROPHYLL-A .1. PHOTO-REDUCTION OF COPPER(II) BY POTASSIUM ASCORBATE THROUGH LIPOSOME BILAYER CONTAINING PURIFIED CHLOROPHYLL-A

Photosensitivity of a dispersion of phosphatidylcholine bilayer liposomes containing purified chlorophyll a was examined. The reduction of Cu(II) in the solution outside liposomes was observed upon illumination with visible light under anaerobic condition by means of ESR. The rate of photoreduction was significantly increased by a reductant, potassium ascorbate, localized in the solution of the opposite side of the membrane. The action spectrum of the reduction agreed with the absorption spectrum of chlorophyll a in the dispersion. The amount of bleached chlorophyll a was negligible compared with that of reduced Cu(II). These facts lead to the conclusion that the photoinduced redox reactions at both the membrane-solution interfaces are coupled with each other through the bilayer of each liposome. Kinetic analysis of the reactions based on a possible reaction scheme was carried out and some of the kinetic parameters were determined. © 1979.