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  • 1
    Electronic Resource
    Electronic Resource
    Protein structure, electron transfer and evolution of prokaryotic photosynthetic reaction centers (1994)
    Springer
    Antonie van Leeuwenhoek 65 (1994), S. 311-329 
    Details
    ISSN: 1572-9699
    Keywords: photosynthesis ; chlorophyll ; bacteriochlorophyll ; reaction center ; electron transfer ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthetic reaction centers from a variety of organisms have been isolated and characterized. The groups of prokaryotic photosynthetic organisms include the purple bacteria, the filamentous green bacteria, the green sulfur bacteria and the heliobacteria as anoxygenic representatives as well as the cyanobacteria and prochlorophytes as oxygenic representatives. This review focuses on structural and functional comparisons of the various groups of photosynthetic reaction centers and considers possible evolutionary scenarios to explain the diversity of existing photosynthetic organisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00872216
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Redox effects on the bacteriochlorophyll α-containing Fenna-Matthews-Olson protein fromChlorobium tepidum (1994)
    Springer
    Photosynthesis research 41 (1994), S. 89-96 
    Details
    ISSN: 1573-5079
    Keywords: photosynthesis ; Chlorobium tepidum ; antenna ; bacteriochlorophylla protein ; energy transfer ; chlorosome ; green bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The BChla-containing Fenna-Matthews-Olson (FMO) protein from the green sulfur bacteriumChlorobium tepidum was purified and characterized. Fluorescence spectra indicate that efficient excited state quenching occurs at neutral or oxidizing redox potentials. The major fluorescence lifetime at room temperature is approximately 60 ps in samples that are in neutral or oxidizing conditions, and approximately 2 ns in samples where the strong reductant sodium dithionite has been added. A similar change is observed in pump-probe picosecond absorbance difference experiments, where the long life time component increases after dithionite addition. A 16 Gauss wide EPR signal with g factor =2.005 is observed in samples without dithionite. This signal largely disappears upon addition of dithionite. Dithionite induces large reversibile changes in the 77 K absorbance spectra of the purified FMO protein and in whole cells. These results indicate that the FMO protein contains redox active groups, which may be involved in the regulation of energy transfer. Room temperature circular dichroism and low temperature absorption spectra show that dithionite also induces conformational or structural changes of the FMO protein complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02184148
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Isolation and characterization of the membrane-bound cytochrome c-554 from the thermophilic green photosynthetic bacterium Chloroflexus aurantiacus (1990)
    Springer
    Photosynthesis research 23 (1990), S. 29-38 
    Details
    ISSN: 1573-5079
    Keywords: cytochrome c ; photosynthesis ; photosynthetic bacteria ; electron transport ; Chloroflexus aurantiacus ; green bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The membrane-bound photooxidizable cytochrome c-554 from Chloroflexus aurantiacus has been purified. The purified protein runs as a single heme staining band on SDS-PAGE with an apparent molecular mass of 43 000 daltons. An extinction coefficient of 28 ± 1 mM−1 cm−1 per heme at 554 nm was found for the dithionite-reduced protein. The potentiometric titration of the hemes takes place over an extended range, showing clearly that the protein does not contain a single heme in a well-defined site. The titration can be fit to a Nernst curve with midpoint potentials at 0, +120, +220 and +300 mV vs the standard hydrogen electrode. Pyridine hemochrome analysis combined with a Lowry protein assay and the SDS-PAGE molecular weight indicates that there are a minimum of three, and probably four hemes per peptide. Amino acid analysis shows 5 histidine residues and 29% hydrophobic residues in the protein. This cytochrome appears to be functionally similar to the bound cytochrome from Rhodopseudomonas viridis. Both cytochrome c-554 from C. aurantiacus and the four-heme cytochrome c-558-553 from R. viridis appear to act as direct electron donors to the special bacteriochlorophyll pair of the photosynthetic reaction center. They have a similar content of hydrophobic amino acids, but differ in isoelectric point, thermodynamic characteristics, spectral properties, and in their ability to be photooxidized at low temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00030060
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Spectroscopic evidence for the presence of an iron-sulfur center similar to Fx of Photosystem I inHeliobacillus mobilis (1994)
    Springer
    Photosynthesis research 41 (1994), S. 115-123 
    Details
    ISSN: 1573-5079
    Keywords: photosynthesis ; bacteriochlorophyll ; electron acceptor ; iron-sulfur center ; Photosystem I ; heliobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Treatment of membranes ofHeliobacillus mobilis with high concentrations of the chaotropic agent urea resulted in the removal of the iron-sulfur centers FA and FB from the reaction center, as indicated by EPR spectra under strongly reducing conditions. In urea-treated membranes, transient absorption measurements upon a laser flash indicated a recombination between the photo-oxidized primary donor P798+ and a reduced acceptor with a time constant of 20 ms at room temperature. Benzylviologen, vitamin K-3 and methylene blue were found to accept electrons from the reduced acceptor efficiently. A differential extinction coefficient of 225–240 mM−1 cm−1 at 798 nm was determined from experiments in the presence of methylene blue. Transient absorption difference spectra between 400 and 500 nm in the presence and absence of artificial acceptors indicated that the electron acceptor involved in the 20 ms recombination has an absorption spectrum similar to that of an iron-sulfur center. This iron-sulfur center was assigned to be analogous to FX of Photosystem I. Our results provide evidence in support of the presence of FX in heliobacteria, which was proposed on the basis of the reaction center polypeptide sequence (Liebl et al. (1993) Proc. Natl. Acad. Sci. USA 90: 7124–7128). Implications for the electron transfer pathway in the reaction center of heliobacteria are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02184151
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    Paper (German National Licenses)
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