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  • conformation  (3)
  • Biochemistry  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Solution and solid state structure of an aib-containing cyclodecapeptide inhibiting the cholate uptake in hepatocytes (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996), S. 465-478 
    Details
    ISSN: 0006-3525
    Keywords: cyclic decapeptides ; cyclolinopeptide A ; x-ray ; nmr ; conformation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational analysis of synthetic cyclodecapeptide c(Pro-Phe-Phe-Aib-Leu)2 related to the cyclolinopeptide A, in the solid state and solution, has been carried out by x-ray diffraction and nmr spectroscopy. The structure of the monoclinic form obtained from methanol [a = 11.351(5) Å, b = 27.455(2) Å, c = 12.716(8) Å, β = 99.65(3)°; space group P21; Z = 2] shows the presence of six intramolecular NH···CO hydrogen bonds, with formation of four turns (three of type I and one of type III) and two C16 ring structures. All peptide units are trans. The solution structure, as found by nmr, indicates that, at room temperature, the peptide is conformationally homogeneous; the structure determined is perfectly symmetrical and topologically similar to that found in the solid state. The cyclodecapeptide exhibits similar biological activity to cyclolinopeptide A. © 1997 John Wiley & Sons, Inc. Biopoly 40: 465-478, 1996
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Conformational sampling of bioactive conformers: a low-temperature NMR study of 15N-Leu-enkephalin (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 253-265 
    Details
    ISSN: 1075-2617
    Keywords: Opioids ; enkephalin ; selectivity ; conformation ; NMR ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational studies of enkephalins are hampered by their high flexibility which leads to mixtures of quasi-isoenergetic conformers in solution and makes NOEs very difficult to detect in NMR spectra. In order to improve the quality of the NMR data, Leu-enkephalin was synthesized with 15N-labelled uniformly on all amide nitrogens and examined in a viscous solvent medium at low temperature. HMQC NOESY spectra of the labelled Leu-enkephalin in a DMSOd6/H2O mixture at 275 K do show numerous NOEs, but these are not consistent with a single conformer and are only sufficient to describe the conformational state as a mixture of several conformers. Here a different approach to the structure-activity relationships of enkephalins is presented: it is possible to analyse the NMR data in terms of limiting canonical structures (i.e. β- and γ-turns) and finally to select only those consistent with the requirements of δ selective agonists and antagonists. This strategy results in the prediction of a family of conformers that may be useful in the design of new δ selective opioid peptides. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    δ-Selective Opioid Peptides Containing a Single Aromatic Residue in the Message Domain: An NMR Conformational Analysis (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 2 (1996), S. 290-308 
    Details
    ISSN: 1075-2617
    Keywords: opioid peptides ; selectivity ; antagonism ; conformation ; NMR ; Chemistry ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sequence of deltorphin I, a δ-selective opioid agonist, has been systematically modified by inserting conformationally constrained Cα,α disubstituted apolar residues in the third position. As expected, substitution of Phe with Ac6c, Ac5c and Ac3c yields analogues with decreasing but sizeable affinity. Surprisingly, substitution with Aib yields an analogue with almost the same binding affinity of the parent compound but with a greatly increased selectivity. This is the first case of a potent and very selective opioid peptide containing a single aromatic residue in the message domain, that is, only Tyr1. Here we report a detailed conformational analysis of [Aib3]deltorphin I and [Ac6c3]deltorphin I in DMSO at room temperature and in a DMSO/water cryomixture at low temperature, based on NMR spectroscopy and energy calculations. The peptides are highly structured in both solvents, as indicated by the exceptional finding of a nearly zero temperature coefficient of Val5 NH resonance. NMR data cannot be explained on the basis of a single structure but it was possible to interpret all NMR data on the basis of a few structural families. The conformational averaging was analysed by means of an original computer program that yields qualitative and quantitative composition of the mixture. Comparison of the preferred solution conformations with two rigid δ-selective agonists shows that the shapes of [Aib3]deltorphin I and [Ac6c3]deltorphin I are consistent with those of rigid agonists and that the message domain of opioid peptides can be defined only in conformational terms.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/psc.56
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    Paper (German National Licenses)
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