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'Optical Activity' in keywords Facet   Publication Year 1983  [X]
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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    Henri Brunner, A.F M Mokhlesur RahmanRequires cookie*
 Title    Asymmetrische Katalysen, 13 [1] Chelat-Liganden und ihre Rhodium-Komplexe mit seitlichen Asymmetriezentren und ihre Anwendung in der enantioselektiven Katalyse Asymmetric Catalyses. 13 [1] Chelate Ligands and their Rhodium Complexes with Lateral Asymmetrie Centers and their Use in Enantioselective Catalysis  
 Abstract    The chelate ligands 1-3 with lateral asymmetric centers at the nitrogen atoms were prepared and characterized. In the Rh complexes 4 and 5 the asymmetric centers directly interact with those coordination positions where during enantioselective catalysis pro-chiral substrates are converted into optically active products. The compounds 4 and 5, as well as the in situ catalysts [Rh(COD)Cl]2/2 were used in the asymmetric hydrogenation of a-N[acetamino]cinnamic acid and in the asymmetric hydrosilylation of acetophenone with diphenylsilane. The low optical inductions obtained result from the catalyst loosing its chiral information during catalysis due to racemization or fragmentation. 
  Reference    Z. Naturforsch. 38b, 1332—1338 (1983); eingegangen am 16. Mai 1983 
  Published    1983 
  Keywords    Optical Activity, Asymmetrie Induction, Enantioselective Catalysis 
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 TEI-XML for    default:Reihe_B/38/ZNB-1983-38b-1332.pdf 
 Identifier    ZNB-1983-38b-1332 
 Volume    38