title: Ultrafast time-resolved spectroscopy of the light-harvesting complex 2 (LH2) from the photosynthetic bacterium Thermochromatium tepidum.
abstract: The light-harvesting complex 2 from the thermophilic purple bacterium Thermochromatium tepidum was purified and studied by steady-state absorption and fluorescence, sub-nanosecond-time-resolved fluorescence and femtosecond time-resolved transient absorption spectroscopy. The measurements were performed at room temperature and at 10 K. The combination of both ultrafast and steady-state optical spectroscopy methods at ambient and cryogenic temperatures allowed the detailed study of carotenoid (Car)-to-bacteriochlorophyll (BChl) as well BChl-to-BChl excitation energy transfer in the complex. The studies show that the dominant Cars rhodopin (N=11) and spirilloxanthin (N=13) do not play a significant role as supportive energy donors for BChl a. This is related with their photophysical properties regulated by long π-electron conjugation. On the other hand, such properties favor some of the Cars, particularly spirilloxanthin (N=13) to play the role of the direct quencher of the excited singlet state of BChl.
authors: Photosynthetic Antenna Research Center, Washington University in St. Louis, Campus Box 1138, St. Louis, MO 63130, USA. niedzwiedzki@wustl.edu
authors: Dariusz M
authors: DM
authors: Niedzwiedzki
authors: Marcel
authors: M
authors: Fuciman
authors: Masayuki
authors: M
authors: Kobayashi
authors: Harry A
authors: HA
authors: Frank
authors: Robert E
authors: RE
authors: Blankenship
mesh_terms: D001429:Bacteriochlorophylls / Q000737:chemistry / Q000502:physiology*; D002338:Carotenoids / Q000737:chemistry* / Q000502:physiology; D002841:Chromatiaceae / Q000737:chemistry* / Q000502:physiology; D003080:Cold Temperature; D004735:Energy Transfer; D007700:Kinetics; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000302:isolation & purification; D010788:Photosynthesis / Q000502:physiology; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013696:Temperature; D013997:Time Factors; D024341:Xanthophylls / Q000737:chemistry / Q000502:physiology
chemical_list: D001429:Bacteriochlorophylls; D045342:Light-Harvesting Protein Complexes; D024341:Xanthophylls; C522079:rhodovibrin; D002338:Carotenoids; C113102:rhodopin; C055255:spirilloxanthin