title: Photoprotection Mechanism of Light-Harvesting Antenna Complex from Purple Bacteria.
abstract: Photosynthetic light-harvesting apparatus efficiently capture sunlight and transfer the energy to reaction centers, while they safely dissipate excess energy to surrounding environments for a protection of their organisms. In this study, we performed pump-probe spectroscopic measurements with a temporal window ranging from femtosecond to submillisecond on the purple bacterial antenna complex LH2 from Rhodobacter sphaeroides 2.4.1 to clarify its photoprotection functions. The observed excited state dynamics in the time range from subnanosecond to microsecond exhibits that the triplet-triplet excitation energy transfer from bacteriochlorophyll a to carotenoid takes place with a time constant of 16.7 ns. Furthermore, ultrafast spectroscopic data suggests that a molecular assembly of bacteriochlorophyll a in LH2 efficiently suppresses a generation of triple bacteriochlorophyll a.
authors.affiliation: Institute of Pulsed Power Science, Kumamoto University , 2-39-1 Kurokami, Chuo-ku Kumamoto, 860-8555 Japan.|Department of Physics, Graduate School of Science and Technology, Kumamoto University , Chuo-ku Kumamoto, 860-8555 Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kosumi
authors.affiliation: Department of Applied Chemistry for Environment, Faculty of Science and Technology, Kwansei Gakuin University , 2-1, Gakuen, Sanda, Hyogo 669-1337 Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Horibe
authors.affiliation: Department of Physics, Graduate School of Science, Osaka City University , 3-3-138 Sugimoto, Sumiyoshi-ku Osaka 558-8585, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Sugisaki
authors.affiliation: Glasgow Biomedical Research Centre, University of Glasgow, 126 University Place , Glasgow, G12 8QQ, Scotland, U.K.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Cogdell
authors.affiliation: Department of Applied Chemistry for Environment, Faculty of Science and Technology, Kwansei Gakuin University , 2-1, Gakuen, Sanda, Hyogo 669-1337 Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Hashimoto
mesh_terms: D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*; D010788:Photosynthesis; D020560:Proteobacteria / Q000378:metabolism*; D012242:Rhodobacter sphaeroides / Q000378:metabolism
chemical_list: D045342:Light-Harvesting Protein Complexes