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  • Chloroflexus aurantiacus  (1)
  • circular dichroism  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Circularly polarized chlorophyll luminescence reflects the macro-organization of grana in pea chloroplasts (2000)
    Springer
    Photosynthesis research 65 (2000), S. 83-92 
    Details
    ISSN: 1573-5079
    Keywords: circular dichroism ; emission anisotropy factor ; ionic strength ; osmotic pressure ; photoinhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Circular polarization of luminescence (CPL; Steinberg IZ (1978) Annu Rev Biophys Bioeng 7: 113–137) was applied to study pea chloroplasts in different structural states. The structural changes of chloroplasts were induced by variation of osmotic pressure, concentration of magnesium-ions or photoinhibition. Both large CPL and psi-type circular dichroism (psi, polymerization and salt induced) signals appeared in the presence of granal macrostructure and were sensitive to structural changes of the grana. The relation was studied between the amount of CPL expressed as an emission anisotropy factor g em and amplitudes of the red psi-type CD bands. The positive psi-type CD band was not directly correlated with g em possibly due to a large contribution of circular intensity differential scattering to the measured CD spectra. However, a linear correlation between the amplitude of the negative psi-type CD band and g em was found. The CPL signal of pea chloroplasts was attributed to a psi-type origin, which is observed in macroaggregates with densely packed chromophores with a long-range chiral order, and directly depends on the level of macroorganization. With the use of CPL-based microscopy, the long-range packing of LHC II particles can be studied in individual chloroplasts in future. In addition, the CPL method in general allows the study of the macro-organization of grana in green leaves, where conventional light-transmission methods fail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006441719869
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  • 2
    Electronic Resource
    Electronic Resource
    The organization of bacteriochlorophyll c in chlorosomes from Chloroflexus aurantiacus and the structural role of carotenoids and protein (1997)
    Springer
    Photosynthesis research 54 (1997), S. 115-126 
    Details
    ISSN: 1573-5079
    Keywords: carotenoids ; Chloroflexus aurantiacus ; chlorosomes ; light harvesting ; polarized spectroscopy ; Stark spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The organization of bacteriochlorophyll c (BChl c) molecules was studied in normal and carotenoid-deficient chlorosomes isolated from the green phototrophic bacterium Chloroflexus aurantiacus. Carotenoid-deficient chlorosomes were obtained from cells grown in the presence of 60 µg of 2-hydroxybiphenyl per ml. At this concentration, BChl c synthesis was not affected while the formation of the 5.7 kDa chlorosome polypeptide was inhibited by about 50% (M. Foidl et al., submitted). Absorption, linear dichroism and circular dichroism spectroscopy showed that the organization of BChl c molecules with respect to each other as well as to the long axis of the chlorosomes was similar for both types of chlorosomes. Therefore, it is concluded that the organization of BChl c molecules is largely independent on the presence of the bulk of carotenoids as well as of at least half of the normal amount of the 5.7 kDa polypeptide. The Stark spectra of the chlorosomes, as characterized by a large difference polarizability for the ground- and excited states of the interacting BChl c molecules, were much more intense than those of individual pigments. It is proposed that this is caused by the strong overlap of BChl c molecules in the chlorosomes. In contrast to individual chlorophylls, BChl c in chlorosomes did not give rise to a significant difference permanent dipole moment for the ground- and excited states. This observation favors models for the BChl c organization which invoke the anti-parallel stacking of linear BChl c aggregates above those models in which linear BChl c aggregates are stacked in a parallel fashion. The difference between the Stark spectrum of carotenoid-deficient and WT chlorosomes indicates that the carotenoids are in the vicinity of the BChls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005903613179
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