Abstract
Picosecond time-resolved fluorescence emission spectroscopy at 80 K was used to investigate excitation-energy migration in LHC II isolated from spinach chloroplasts. Time-resolved spectra were obtained for solubilised LHC II trimers and for LHC II in a semi-crystalline aggregated state. In solubilised LHC II, the main decay lifetime is about 4.3 ns. Upon aggregation, the main decay lifetime becomes about 110 ps, indicating the presence of a highly-efficient energy-quenching process. Several red-shifted chlorophyll species can be resolved in aggregated LHC II, but none of these appears to be directly involved in energy quenching. The zeaxanthin / violaxanthin ratio has no influence on the time-resolved fluorescence emission spectrum for LHC II in these states. We suggest that a quenching process similar to that observed in aggregates of isolated LHC II is the basis of the ΔpH-dependent quenching ( q E) observed in intact thylakoid membranes.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA) - Bioenergetics
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