Induction of Efficient Energy Dissipation in the Isolated Light-harvesting Complex of Photosystem II in the

ing antenna of higher plants has the ability to switch into an efficient photoprotective mode, allowing safe dissipation of excitation energy into heat. In this study, we show induction of the energy dissipation state, monitored by chlorophyll fluores-cence quenching, in the isolatedmajor light-harvesting complex (LHCII) incorporated into a solid gel system. Removal of deter-gent caused strong fluorescence quenching, which was totally reversible. Singlet-singlet annihilation and gel electrophoresis experiments suggested that the quenched complexeswere in the trimeric not aggregated state. Both the formation and recovery of this quenching state were inhibited by a cross-linker, imply-ing involvement of conformational changes.Absorption andCD measurements performed on the samples in the quenched state revealed specific alterations in the spectral bands assigned to the red forms of chlorophyll a, neoxanthin, and lutein 1 molecules