title: Ultrafast carotenoid band shifts probe structure and dynamics in photosynthetic antenna complexes.
abstract: We report observations of ultrafast carotenoid band shifts correlated with energy transfer dynamics between bacteriochlorophyll (BChl) molecules within the peripheral light-harvesting complex (LH2) from the photosynthetic bacterium Rhodobacter sphaeroides. Direct excitation of the bacteriochlorophyll Qy bands yielded distinct changes in the carotenoid S2 absorption from 430 to 530 nm. Transient absorption spectra and kinetics were measured in a femtosecond pump-probe experiment, revealing the ultrafast carotenoid response to excited BChl pigments. These data are an indication of a new property of carotenoids that is manifested as a unique ability to detect and report changes in their immediate environment, thereby serving as sensitive probes of local structure and dynamics.
authors.affiliation: Department of Chemical Physics, Lund University, Sweden.
authors.forename: J L
authors.initials: JL
authors.lastname: Herek
authors.forename: T
authors.initials: T
authors.lastname: Polívka
authors.forename: T
authors.initials: T
authors.lastname: Pullerits
authors.forename: G J
authors.initials: GJ
authors.lastname: Fowler
authors.forename: C N
authors.initials: CN
authors.lastname: Hunter
authors.forename: V
authors.initials: V
authors.lastname: Sundström
mesh_terms: D001429:Bacteriochlorophylls / Q000737:chemistry; D002338:Carotenoids / Q000737:chemistry*; D004735:Energy Transfer; D007700:Kinetics; D045342:Light-Harvesting Protein Complexes; D008958:Models, Molecular; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D012242:Rhodobacter sphaeroides / Q000737:chemistry*; D013053:Spectrophotometry
chemical_list: D001429:Bacteriochlorophylls; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D002338:Carotenoids