title: Lifetime of fluorescence from light-harvesting chlorophyll a/b proteins. Excitation intensity dependence.
abstract: The fluorescence from a purified, aggregate form of the light-harvesting chlorophyll a/b protein has a lifetime of 1.2 +/- 0.5 ns at low excitation intensity, but the lifetime decreases significantly when the intensity of the 20-ps, 530-nm excitation pulse is increased above about 10(16) photons/cm2. A solubilized, monomeric form of the protein, on the other hand, has a fluorescence lifetime of 3.1 +/- 0.3 ns independent of excitation intensity from 10(14)-10(18) photons/cm2/pulse. We interpret the lifetime shortening in the aggregates and the lack of shortening in monomers in terms of exciton annihilation, facilitated in the aggregate by the larger population of interacting chlorophylls.
mesh_terms: D002734:Chlorophyll / Q000378:metabolism*; D003580:Cytochromes / Q000378:metabolism*; D007700:Kinetics; D007834:Lasers; D008027:Light; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins / Q000378:metabolism*; D010944:Plants / Q000378:metabolism; D013050:Spectrometry, Fluorescence
chemical_list: D003580:Cytochromes; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D010940:Plant Proteins; D002734:Chlorophyll