Characterization of liposome membrane containing chlorophyll a molecules and its photosensitized functions

Liposomes (phospholipid vesicles) including Chlorophyll a (Chla) have practically been utilized as a simplified photochemical energy conversion system. However, poor knowledge about the detailed liposomal membrane properties has hampered the progress in this field. In this paper, we therefore clarified the liposomal membrane properties based on the analyses of the membrane fluidity, the Chla absorption bands, and the Chla polarization. Moreover, we examined the influence of the membrane properties on the photoreduction with methylviologen. Consequently, it was revealed that the kinetic constant value of the reduced species formation decreased with the increase in temperature over the phase transition temperature of the membrane, which means that the membrane properties largely influence the photochemical reaction. Based on our results, we conclude that the behaviors and the orientations of Chla molecules on the liposomal membrane are significantly important in the photochemical energy conversion system.