Speaker
Description
Light-Harvesting Complex II (LHCII) is the most abundant photosynthetic membrane pigment-protein complex in higher plants, enabling extremely efficient solar energy harvesting. Their light-harvesting function is finely controlled by processes that switch the complexes into a photoprotective state. LHCII aggregates, that feature strong quenching of excitation light, are often believed to be enhance a plant’s photoprotective capability. Finding new ways to study these aggregates can lead to important insights into the fundamental mechanisms by which plants protect themselves against high sunlight intensities, which could, for example, inform efforts to improve crop yields in a changing climate. In our project, we have developed techniques that combine fluorescence correlation spectroscopy (FCS) and time-correlated single-photon counting (TCSPC). The aggregation of LHCII was investigated at increasing levels by step-wise removal of detergent from low-concentration purified samples. Applying pulse-interleaved excitation (PIE) enabled advanced FCS to accurately measure translational and estimated rotational diffusion coefficients, yielding the hydrodynamic radii of LHCII during aggregation. Furthermore, extending measurement times and using both pulsed and continuous excitation unveiled photophysics from microseconds down to picosecond timescales. The results show a rich combination of dimensional information and excitation dynamics in these photosynthetic aggregates, highlighting the importance of singlet-triplet annihilation when studying quenching in LHCII.
