Flash Photolysis of Liposomes Containing Chlorophyll and Zeaxanthin, as a Function of Temperature (2°—34 °C)

The transfer of triplet excitation from chlorophyll to zeaxanthin in liposom es is a function o f temperature and pigment concentration. At 525 nm both chlorophyll and zeaxanthin triplet states are observed. The result is a biphasic increase in absorption. The rise time o f absorption by the chlorophyll triplet is much faster, than by the zeaxanthin triplet. With increasing temperature the contribution o f absorption by zea­ xanthin (relative to that o f chlorophyll) at 525 nm increases, and its rise tim e gets faster. At high ratios o f zeaxanthin to chlorophyll, temperature has less effect on both the rise tim e and absorption by the zeaxanthin triplet state. The chlorophyll triplet is measured at 780 nm. It decays faster with increasing temperature and or increasing ratio o f zeaxanthin to chlorophyll. The results are interpreted in terms of: increasing fluidity o f the lipid liposom e with temper­ ature, formation of zeaxanthin-chlorophyll com plexes at high ratios o f zeaxanthin and chloro­ phyll, presence of different lipid phases in the liposom e bilayer.