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'Circular D ichroism' in keywords Facet   section ZfN Section C  [X]
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1986 (1)
1980 (1)
1Author    Elisabeth Langer, H. Arald Lehner, Wolfhart Rüdiger, Barbara Zickendraht, -W EndelstadtRequires cookie*
 Title    Circular Dichroism of C-Phycoerythrin: A Conformational Analysis  
 Abstract    An extensive study o f the chiroptical properties o f C-phycoerythrin and the a-and ^-subunits in the spectral region from 700 -200 nm is presented. Based on the VIS-circular dichroism inherently chiral conform ations are proposed for the co­ valently linked chromophores. By means o f mean residue ellipticities and the experimental circular dichroism spectra in the region o f the n -* n* peptide transition the a-helix contents o f the apoproteins o f the ac-and ß-subunits are estimated to amount to 60% and 40%, respectively. The circular dichroism spectrum o f native C-phycoerythrin is congruent with a linear superposition o f the a-and /?-subspectra, in the whole spectral region studied. Since a-and /?-subunits are associated in native C-phycoery-thrin as revealed by sedim entation analysis the interactions between the subunits in the native chromoprotein are not accom panied by substantial conform ational changes. In the temperature range 0 ° -4 0 °C the thermally induced changes o f the chrom ophores in native C-phycoerythrin are not associated with changes o f the secondary structure o f the apoprotein. Unfolding occurs at 60 0 -7 0 °C but slowly leads to irreversible denaturation. Protein unfolding starts at 3 M urea. The random coil secondary structure o f the apoproteins is reached at 8 M urea. At this concentration the absorbance and the optical activity o f the chrom o­ phores are reduced by a factor 3 and 10, respectively. The conformational changes in the peptide with increasing denaturant concentration are not synchronous with those induced in the Chromo­ phore indicating that a m ultistep process is operative during unfolding. The C D results on dena­ turation are supplem ented by absorption and em ission spectroscopy. 
  Reference    Z. Naturforsch. 35c, 367 (1980); received February 5 1980 
  Published    1980 
  Keywords    Phycoerythrin, Subunits, Conformation o f Chrom ophores and Apoproteins, Circular D ichroism, Denaturation 
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 TEI-XML for    default:Reihe_C/35/ZNC-1980-35c-0367.pdf 
 Identifier    ZNC-1980-35c-0367 
 Volume    35 
2Author    R. Steiner, A. A. Ngerhofer+, H. ScheerRequires cookie*
 Title    The Photosynthetic Apparatus of Ectothiorhodospira halochloris 2. Accessibility of the Membrane Polypeptides to Partial Proteolysis and Antenna Polypeptide Assignments to Specific Chromophores  
 Abstract    E. halochloris thylakoids and spheroplasts were treated with trypsin, thermolysin or proteinase K to determ ine which proteins are exposed at the different m embrane surfaces. B ased on SD S polyacrylamide analysis, all 9 polypeptides are exposed on the cytoplasm ic side. O nly one (28 k D a) is accessible from the periplasmic side. This polypeptide is generally isolated as the H-subunit o f the reaction centers of photosynthetic bacteria, but is in the case o f E. halochloris rather isolated with the antenna (B 800/1020) (Steiner and Scheer, Biochim . Biophys. A cta 807, 278, 1983). Proteolysis is accom panied by a shift of the absorption band at longest w avelengths from 1020 to 960 nm (B 800/960), which upon standing is shifted further to 680 nm ("B " 800/680). The spectral changes are similar to the ones reported earlier for treatm ent with acid, and are also inducible with urea. The correlation o f SD S-P A G E and absorption spectroscopy show s, that the chrom ophores absorbing at 1020 nm are transformed sim ultaneously with the degradation o f the 6.5 kD a (— a) polypeptide. 
  Reference    Z. Naturforsch. 41c, 571 (1986); received January 9 1986 
  Published    1986 
  Keywords    Bacterial Photosynthesis, Ectothiorhodospira, M embrane T opology, A ntenna Polypeptides, F luorescence, Circular D ichroism, Energy Transfer 
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 TEI-XML for    default:Reihe_C/41/ZNC-1986-41c-0571.pdf 
 Identifier    ZNC-1986-41c-0571 
 Volume    41