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'Bilipeptides' in keywords
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1983 (2)
1Author    C. Schamagl, E. Köst-Reyes, S. Schneider, H.-P Köst, H. ScheerRequires cookie*
 Title    Circular Dichroism of Chromopeptides from Phycocyanin  
 Abstract    The circular dichroism of bilipeptides from Spirulina geitleri phycocyanin is strongly solvent and pH dependent. Maximum optical activity has been observed in aqueous solutions containing urea (8 M). In aqueous buffer, a sign reversal occurred upon the change from neutral to acidic pH; in methanolic solutions shows the optical activity a strong pH dependence both with respect to sign and magnitude. These findings have been rationalized by the presence o f chrom ophore-peptide interactions, which are minim ized in the presence of urea. M olecular orbital calculations indicate that the observed sign reversal is not necessarily due to a reversal o f the chirality o f the entire chromophore, but may also result from more localized conform ational changes. 
  Reference    Z. Naturforsch. 38c, 951—959 (1983); received June 22 1983 
  Published    1983 
  Keywords    Biliproteins, Bilipeptides, Conform ation, Optical Activity, Protein Interaction 
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 TEI-XML for    default:Reihe_C/38/ZNC-1983-38c-0951.pdf 
 Identifier    ZNC-1983-38c-0951 
 Volume    38 
2Author    Fritz Thümmler, W. Olfhart Rüdiger, Edmund Cmiel, Siegfried SchneiderRequires cookie*
 Title    Chromopeptides from Phytochrome and Phycocyanin. NM R Studies o f the Pfr and P r Chromophore of Phytochrome and EyZ Isomeric Chromophores of Phycocyanin  
 Abstract    Chromopeptides were prepared by pepsin digestion of C-phycocyanin isolated from the cyano­ bacterium Spirulina m axim a and o f phytochrom e isolated from seedlings o f Avena sativa L. The chromopeptides were characterized by am ino acid analysis. The Z Z Z configurated chrom ophore of the phycocyanin peptide was transformed into its Z Z E configurated isom er by the m ethod of Falk et al. (Mh. C hem ie 111, 159—175, 1980) which had previously been applied to biliverdins. The 500 MHz 'H N M R spectrum o f the Z Z E configurated chrom opeptides confirmed that its chromophore has the 15 E configuration. Irradiation yielded the Z Z Z configurated isom er for which the 'H N M R spectrum was also recorded. N ative phytochrom e was irradiated at 660 nm to yield the maximum am ount of the Pfr from (about 75% of total phytochrome). By digestion in the dark the previously described Pfr chrom opeptide was obtained. The 500 MHz 'H N M R spectrum was com pared with that o f the Z Z E phycocyanin peptide. It confirmed the 15 £ con­ figuration of the Pfr chrom opeptide. Irradiation yielded the 15 Z configurated Pr chrom opeptide. Comparison of the high resolution 'H N M R spectra o f Pfr and Pr chrom opeptides revealed that not only the chrom ophore resonances but also those of some amino acids are changed by the Pfr -*■ Pr chrom opeptide phototransform ation. The results are discussed in term s of chrom ophore amino acid interaction. 
  Reference    Z. Naturforsch. 38c, 359 (1983); received February 2 1983 
  Published    1983 
  Keywords    Bilipeptides, C-Phycocyanin, High Resolution N M R Spectra, Photoisom erization, Phytochrom e 
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 TEI-XML for    default:Reihe_C/38/ZNC-1983-38c-0359.pdf 
 Identifier    ZNC-1983-38c-0359 
 Volume    38