title: Fluorescence of the various red antenna states in photosystem I complexes from cyanobacteria is affected differently by the redox state of P700.
abstract: Photosystem I of cyanobacteria contains different spectral pools of chlorophylls called red or long-wavelength chlorophylls that absorb at longer wavelengths than the primary electron donor P700. We measured the fluorescence spectra at the ensemble and the single-molecule level at low temperatures in the presence of oxidized and reduced P700. In accordance with the literature, it was observed that the fluorescence is quenched by P700(+). However, the efficiency of the fluorescence quenching by oxidized P700(+) was found to be extremely different for the various red states in PS I from different cyanobacteria. The emission of the longest-wavelength absorbing antenna state in PS I trimers from Thermosynechococcus elongatus (absorption maximum at 5K: ≈ 719nm; emission maximum at 5K: ≈ 740nm) was found to be strongly quenched by P700(+) similar to the reddest state in PS I trimers from Arthrospira platensis emitting at 760nm at 5K. The fluorescence of these red states is diminished by more than a factor of 10 in the presence of oxidized P700. For the first time, the emission of the reddest states in A. platensis and T. elongatus has been monitored using single-molecule fluorescence techniques.
authors.affiliation: Max-Volmer-Laboratorium für Biophysikalische Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany.
authors.forename: Eberhard
authors.initials: E
authors.lastname: Schlodder
authors.forename: Martin
authors.initials: M
authors.lastname: Hussels
authors.forename: Marianne
authors.initials: M
authors.lastname: Cetin
authors.forename: Navassard V
authors.initials: NV
authors.lastname: Karapetyan
authors.forename: Marc
authors.initials: M
authors.lastname: Brecht
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D002734:Chlorophyll / Q000737:chemistry*; D003116:Color; D000458:Cyanobacteria / Q000737:chemistry* / Q000378:metabolism*; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D045331:Photosystem I Protein Complex / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D002734:Chlorophyll; C001785:chlorophyll P 700