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  • 1990-1994  (14)
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  • 11
    Electronic Resource
    Electronic Resource
    Structural versatility of peptides from Cα,α-disubstituted glycines: Preferred conformation of the Cα,α-diphenylglycine residueThis paper is part 223 of the “Linear Oligopeptides” series; for part 222 see ref. 1. (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 1-11 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preferred conformation of the Cα,α-diphenylglycine residue was determined in simple derivatives and dipeptides. The dipeptides were synthesized by the 5(4H)-oxazolone (from the N-para-bromobenzoylated amino acid) method. This activated intermediate and a reaction by-product, para-bromobenzoylbenzhydrylamine, were characterized inter alia by x-ray diffraction. Conformational energy calculations on the Cα,α-diphenylglycine mono-peptide, Ac-Døg-NHMe, indicate that this Cα,α-symmetrically disubstituted residue is conformationally restricted and that its minimum energy conformation falls in the fully extended (C5) region. The results of the theoretical analysis are in agreement with the solution and crystal-state structural tendency of mClAc-Døg-OH, Z-Døg-OtBu, pBrBz-Døg-Gly-OMe and its tert-butyl ester analogue, determined by ir absorption, lH-nmr, and x-ray diffraction, and also described in this work. The implications for the use of the Døg residue in designing conformationally constrained analogues of bioactive peptides are briefly discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300103
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    Paper (German National Licenses)
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  • 12
    Electronic Resource
    Electronic Resource
    Crystal state conformation of three model monomer units for the β-bend ribbon structure (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 1669-1676 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular and crystal structures of three compounds, representing the repeating units of the β-bend ribbon (an approximate 310-helix, with an intramolecular hydrogen-bonding donor every two residues), have been determined by x-ray diffraction. They are Boc-Aib-Hib-NHBzl, Z-Aib-Hib-NHBzl, and Z-L-Hyp-Aib-NHMe (Aib, α-aminoisobutyric acid; Bzl, benzyl; Boc, t-butyloxycarbonyl; Hyp, hydroxyproline Hib, α-hydroxyisobutyric acid; Z, benzyloxycarbonyl). The two former compounds are folded in a β-bend conformation: type III (III′) for Boc-Aib-Hib-NHBzl, while type II (II′) for the Z analogue. Conversely, the structure of Z-L-Hyp-Aib-NHMe, although not far from a type II β-bend, is partially open.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360311402
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    Paper (German National Licenses)
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  • 13
    Electronic Resource
    Electronic Resource
    Structural versatility of peptides from Cα,α-disubstituted glycines: Preferred conformation of the chiral isovaline residue (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 1135-1148 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular structures of four protected isovaline- (Iva-) containing peptides to the pentamer level have been determined by x-ray diffraction. The peptides are t-Boc-Ala-(S)-Iva-Ala-OMe (t-Boc : tert-butyloxycarbonyl; OMe : methoxy) and its (R)-Iva diastereomer, and t-Boc-[Ala-(R)-Iva]2-Ala-OH and its (S)-Iva diastereomeric methyl ester analogue. The two tripeptides are folded in an open type II β-bend conformation. The fully developed right-handed 310-helix formed by the (R)-Iva pentapeptide, which includes an unusual intramolecular (acid) O—H⃛O=C(peptide) H bond, is partially unfolded (near the C-terminus) in the (S) -Iva pentapeptide. 1H-nmr and Fourier transform ir absorption studies suggest that in CDCl3 solution (a) the two tripeptides maintain a type II β-bend conformation of comparable stability and (b) both diastereomeric pentapeptide sequences adopt a fully developed 310-helix. A comparison with the preferred conformation of other extensively investigated Cα,α-disubstituted glycines is made and the implications for the use of the Iva residue in designing conformationally constrained analogues of bioactive peptides are briefly discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360311002
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    Paper (German National Licenses)
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  • 14
    Electronic Resource
    Electronic Resource
    Characterization at atomic resolution of peptide helical structures (1992)
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 453-456 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A survey of literature for the various types of helices experimentally observed in highresolution single crystal x-ray diffraction analyses of peptides has allowed to determine accurate conformational and helical parameters for the various secondary structures such as the α-helix, the 310-helix, the fully extended conformation (25-helix) and the β-bend ribbon spiral. For each of these structures the characteristic φ, ψ conformational parameters, n, the number of residues per turn, h, the height per residues and p, the pitch of the helix are described.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360320424
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    Paper (German National Licenses)
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