Effect of xanthophyll pigments on fluorescence of chlorophyll a in LHC II embedded to liposomes

A major light-harvesting pigment-protein complex of Photosystem II (LHC II) isolated from rye leaves was incorporated to egg yolk lecithin Liposomes containing various amounts (0-0.6 mol% with respect to lipid) of xanthophyll pigments: violaxanthin, lutein or zeaxanthin. It appeared that the addition of xanthophylls increased the level of the chlorophyll a fluorescence emission despite the screening effect of additional pigments in the system. Another phenomenon documented by the 77 K fluorescence emission spectra was the xanthophyll-related desaggregation of LHC II within the lipid phase of liposomes. The analysis of the parameters of chlorophyll a fluorescence decay in comparison to steady state fluorescence emission let us conclude that the fluorescence reabsorption in aggregated LHC II was a major cause of the lower level of fluorescence emission in that state of antenna proteins. Chlorophyll singlet excitations quenching brought about by violaxanthin, lutein and zeaxanthin is also documented in liposomes containing incorporated LHC II and exogenous xanthophyll pigments, and in liposomes containing xanthophyll pigments and chlorophyll b.