title: Modulation of fluorescence in Heliobacterium modesticaldum cells.
abstract: In what appears to be a common theme for all phototrophs, heliobacteria exhibit complex modulations of fluorescence yield when illuminated with actinic light and probed on a time scale of micros to minutes. The fluorescence yield from cells of Heliobacterium modesticaldum remained nearly constant for the first 10-100 ms of illumination and then rose to a maximum level with one or two inflections over the course of many seconds. Fluorescence then declined to a steady-state value within about one minute. In this analysis, the origins of the fluorescence induction in whole cells of heliobacteria are investigated by treating cells with a combination of electron accepters, donors, and inhibitors of the photosynthetic electron transport, as well as varying the temperature. We conclude that fluorescence modulation in H. modesticaldum results from acceptor-side limitation in the reaction center (RC), possibly due to charge recombination between P(800) (+) and A(0) (-).
authors.affiliation: Departments of Biology and Chemistry, Washington University in St. Louis, MO 63130, USA.
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Collins
authors.forename: Kevin E
authors.initials: KE
authors.lastname: Redding
authors.forename: Robert E
authors.initials: RE
authors.lastname: Blankenship
mesh_terms: D004583:Electrons; D005453:Fluorescence; D006094:Gram-Positive Bacteria / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008954:Models, Biological; D009586:Nitrogen Fixation / Q000187:drug effects; D016877:Oxidants / Q000494:pharmacology; D011090:Polyenes / Q000494:pharmacology; D019163:Reducing Agents / Q000494:pharmacology; D013696:Temperature
chemical_list: D016877:Oxidants; D011090:Polyenes; D019163:Reducing Agents; C041573:stigmatellin
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