title: Energy transfer processes in chlorophyll f-containing cyanobacteria using time-resolved fluorescence spectroscopy on intact cells.
abstract: We examined energy transfer dynamics in the unique chlorophyll (Chl) f-containing cyanobacterium Halomicronema hongdechloris. The absorption band of Chl f appeared during cultivation of this organism under far-red light. The absorption maximum of Chl f in organic solvents occurs at a wavelength of approximately 40 nm longer than that of Chl a. In vivo, the cells display a new absorption band at approximately 730 nm at 298 K, which is at a significantly longer wavelength than that of Chl a. We primarily assigned this band to a long wavelength form of Chl a. The function of Chl f is currently unknown. We measured the fluorescence of cells using time-resolved fluorescence spectroscopy in the picosecond-to-nanosecond time range and found clear differences in fluorescence properties between the cells that contained Chl f and the cells that did not. After excitation, the fluorescence peaks of photosystem I and photosystem II appeared quickly but diminished immediately. A unique fluorescence peak located at 748 nm subsequently appeared in cells containing Chl f. This finding strongly suggests that the Chl f in this alga exists in photosystem I and II complexes and is located close to each molecule of Chl a. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy.
authors.affiliation: Faculty of Science, Tokyo University of Science, Tokyo 162-8601, Japan; PRESTO, Japan Science and Technology Agency (JST) , Saitama 332-0012, Japan. Electronic address: tomo@rs.tus.ac.jp.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Tomo
authors.affiliation: Faculty of Science, Tokyo University of Science, Tokyo 162-8601, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Shinoda
authors.affiliation: School of Biological Sciences, University of Sydney, Sydney, New South Wales 2006, Australia.
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.affiliation: Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya Street 35, Moscow 127276, Russia; Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia.
authors.forename: Suleyman I
authors.initials: SI
authors.lastname: Allakhverdiev
authors.affiliation: Molecular Photoscience Research Center, Kobe University, Kobe 657-8501, Japan; CREST, Japan Science and Technology Agency (JST) , Kobe 657-8501, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Akimoto
mesh_terms: D002734:Chlorophyll / Q000031:analogs & derivatives* / Q000737:chemistry; D000458:Cyanobacteria / Q000378:metabolism*; D004735:Energy Transfer; D013050:Spectrometry, Fluorescence / Q000379:methods*
chemical_list: C583352:chlorophyll f; D002734:Chlorophyll
keywords: Chlorophyll f; Energy transfer; Fluorescence; Photosynthesis