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  • 1
    Electronic Resource
    Electronic Resource
    Structural versatility of peptides from Cα,αdialkylated glycines: Linear Ac3c homo-oligopeptides (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 175-184 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal-state molecular structures of five linear Ac3c homo-oligopeptides to the tetramer were determined by x-ray diffraction. The oligomers are H-(Ac3c)2-OMe, Fmoc-(Ac3c)2-OMe MeOH, Ac-(Ac3c)2-OMe, pBrBz-(Ac3c)3-OMe · H2O, and t-Boc-(Ac3c)4-OMe · 2H2O. The results indicate the propensity of the tri- and tetrapeptides to fold into type I β-bends and distorted 310-helices, respectively, in partial contrast to Aib, Ac5c, and Ac6c homo-peptides of comparable main-chain length, where regular type III β-bends and 310-helical structures were found. When the influence of the constraints produced by the intramolecular H bonds of the C10-type is absent, other less common structural features may be observed. The average geometry of the cyclopropyl group of the Ac3c residue is found to be asymmetric and the N—Cα—C′ bond angle significantly expanded from the regular tetrahedral value.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280119
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  • 2
    Electronic Resource
    Electronic Resource
    Cyclic β-alanyl-β-alanine containing peptides: A new molecular tool for β-turned peptides (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 189-196 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the present paper we describe the synthesis, purification, and single-crystal x-ray analysis of the cyclic tetrapeptide cyclo-(L-Pro-L-Phe-β-Ala-β-Ala). This compound contains the β-alanyl-β-alanine dipeptide as putative cyclization arm to force the remaining dipeptide-L-Pro-L-Phe- in a β-turned conformation. Thepeptide was synthesized by classical methods and cyclization of the free linear tetrapeptide was accomplished in reasonable yields in diluted methylene chloride solution. The compound crystallizes in space group P21 from hot water with two independent tetrapeptide molecules and seven solvent molecules in the unit cell. This compound shows in the solid state an intramolecular hydrogen bond between the CO group of the β-Ala4 and the NH group of the β-Ala3 residues stabilizing a type I β-turn conformation in which Pro1 and Phe2 occupy the relative position 2 and 3 of the turn, respectively. A rather complex network of 18 hydrogen bonds involving all the remaining CO and NH groups and the water molecules is present in the crystal.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300118
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  • 3
    Electronic Resource
    Electronic Resource
    Preferred conformation of peptides rich in alicyclic Cα,α-disubstituted glycines (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996), S. 519-522 
    Details
    ISSN: 0006-3525
    Keywords: conformational analysis, of peptides ; disubstituted glycines, peptides rich in ; Fourier transform ir absorption, of peptides ; 310-helical conformation, in peptides ; Cα-methylated α-amino acids, peptides rich in ; nmr, of peptides ; peptide conformation ; x-ray diffraction, of peptides ; β-turn conformation, in peptides ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational preferences of the alicyclic Cα,α-disubstituted glycines Acnc (1-amino-1-cycloalkane-carboxylic acid; n = 4, 7, 9, 12) were assessed in selected model compounds, including homopeptides and Ala (or Aib, α-aminoisobutyric acid)/Acnc peptides containing a small total number of residues, by Fourier transform ir absorption, 1H-nmr, and x-ray diffraction analyses. The results obtained indicate that β-turn and 310-helical structures are preferentially adopted by short peptides rich in these cycloaliphatic α-amino acids. © 1997 John Wiley & Sons, Inc. Biopoly 40: 519-522, 1996
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Conformations of bioactive peptides: Cyclolinopeptide ADedicated to the memory of Professor F. Weygand. (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 2099-2101 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360261209
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  • 5
    Electronic Resource
    Electronic Resource
    Structural versatility of peptides from Cα,α-dialkylated glycines. II. An IR absorption and 1H-nmr study of homo-oligopeptides from Cα,α-diethylglycine (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 373-379 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational preferences of the N-trifluoroacetylated homo-peptides of Cα,α-diethylglycine from monomer to pentamer in chloroform solution were determined by using ir absorption and 1H-nmr. Intramolecular hydrogen bonding was found to be the dominant factor for all NH groups. The likely absence of a conformational transition upon increasing main-chain length, and the remarkable stability to dilution, heating, and addition of perturbing agents, are additional relevant findings of this study. These results are in agreement with those of the fully extended, C5-conformation-forming homo-peptides from the higher homolog Cα,α-di-n-propylglycine, but contrast dramatically to those of the homo-peptides from the lower homolog Cα,α-dimethylglycine, which have been shown to adopt the 310-helical structure.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270303
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  • 6
    Electronic Resource
    Electronic Resource
    Conformation of diastereomeric peptide sequences: Structural analysis of Z-D-Val-Ac6c-Gly-L-Phe-OMe (1992)
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 1155-1161 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have recently undertaken a systematic structural analysis of fully protected tetrapeptides containing at the N- and C-terminus either homo- or heterochiral amino acids, spaced by an achiral dipeptide segment. The interest for this class of peptides derives from the observation that, on reverse-phase (HPLC), the homo- and heterochiral sequences have a markedly different retention times. The diastereomeric sequences, namely Z-(L/D)-Val-X-Y-L-Phe-OMe (X = Sar, Gly, Ac3c, Aib, Ac5c, Ac6c, Deg, Dpg, Dbu, Dip, Dph; Y = Sar, Gly, Ac3c, Aib, Ac6c, Ac6c) show different overall hydrophobicity attributed to a different three-dimensional structure that also depends on the X-Y segment. Therefore, following preliminary studies in solution, we report here the detailed x-ray analysis of the tetrapeptide Z-D-Val-Ac6c-Gly-L-Phe-OMe in order to understand the structural features governing the overall hydrophobicity of linear fully protected tetrapeptides. © 1992 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360320904
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  • 7
    Electronic Resource
    Electronic Resource
    Structural versatility of peptides from Cα,α-dialkylated glycines. I. A conformational energy computation and x-ray diffraction study of homo-peptides from Cα,α-diethylglycine (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 357-371 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational energy computations on a derivative and a homo-dipeptide of Cα,α-diethylglycine were performed. In both cases the N- and C-terminal groups are blocked as acetamido and methylamido moieties, respectively. It was found that the Cα,α-diethylglycine residues are conformationally restricted and that the minimum energy conformation corresponds to the fully extended C5 structure when the N—Cα—C′ bond angle is smaller than 108° (as experimentally observed). The results of the theoretical analysis are in agreement with the crystal-state structural propensity of the complete series of N-trifluoroacetylated homo-peptides of this Cα,α-dialkylated residue from monomer to pentamer, determined by x-ray diffraction and also described in this work. Interestingly, for the first time, a crystallographically planar peptide backbone was observed (in the protected tripeptide). A comparison with peptides of Cα,α-dimethylglycine, Cα-methyl, Cα-ethylglycine, and Cα,α-di-n-propylglycine indicates that the fully extended conformation becomes more stable than the helical structures when both amino acid side-chain Cβ atoms are substituted.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270302
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  • 8
    Electronic Resource
    Electronic Resource
    β-Alanine containing peptides: A novel molecular tool for the design of γ-turns (1992)
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 173-183 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the present paper we describe the synthesis, purification, single crystal x-ray analysis, and solution conformational characterization of the cyclic tetrapeptide cyclo- (L-Pro-γ-Ala-L-Pro-γ-Ala). This peptide was synthesized by classical solution methods and the cyclization of the free tetrapeptide was accomplished in good yields in diluted methylene chloride solution using N, N-dicyclohexyl-carbodiimide (DCCI). The compound crystallizes in the orthorombic space group P212121 from ethyl acetate. All peptide bonds are trans. The molecular conformation is stabilized by two intramolecular hydrogen bonds between the CO and NH groups of the two β-alanine residues. These hydrogen bonds take part in a C7 structure in which both proline residues occupy the 2 position of an inverse γ-turn. The two β-alanine residues have a typical folded conformation (around the Cα-Cβ bond) observed in other cyclic peptides containing this residue. A detailed 1H-nmr analysis in CD3CN solution has been carried out. The molecule assumes a twofold symmetry in solution with a molecular conformation consistent with that observed in the solid state.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360320207
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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    β-Alanine containing peptides: γ-Turns in cyclotetrapeptides (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 621-631 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the present paper we describe the synthesis, purification, single-crystal x-ray analysis, solution conformational characterization, and conformational energy calculations of the cyclic tetrapeptide cyclo- (β-Ala-L-Pro-β-Ala-L-Val). The peptide was synthesized by classical solution methods and the cyclization of the free tetrapeptide was accomplished in good yields in diluted methylene chloride solution using N,N-dicyclohexyl-carbodiimide. The compound crystallizes in the monoclinic space group P21 from ethanol with two independent molecules in the unit cell. All peptide bonds are trans. The nmr molecular conformation in the acetonitrile solution as well as that derived from the molecular dynamic simulation in vacuo is quite different from those observed in the solid state and is very similar to that previously observed for the parent compound cyclo-(β-Ala-L-Pro-β-Ala-L-Pro). © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360330411
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