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  • 11
    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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  • 12
    Electronic Resource
    Electronic Resource
    β-Turn conformations in crystal structures of model peptides containing α,α-Di-n-propylglycine and α,α-Di-n-butylglycine (1995)
    New York : Wiley-Blackwell
    Biopolymers 35 (1995), S. 1-9 
    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 conformations of three peptides containing the α,α-dialkylated residues. α,α-di-n-propylglycine (Dpg) and α,α-di-n-butylglycine (Dbg), have been established by x-ray diffraction. Boc-Ala-Dpg-Alu-OMe (I) and Boc-Ala-Dbg-Ala-OMe (III) adopt distorted type II β-turn conformations with Ala (1) and Dpg/Dbg (2) as the corner residues. In both peptides the conformational angles at the Dxg residue (I: φ = 66.2°, ψ = 19.3°; III: φ = 66.5°. ψ = 21.1°) deviate appreciably from ideal values for the i + 2 residue in a type II β-turn. In both peptides the observed (N…O) distances between the Boc CO and Ala (3) NH groups are far too long (1: 3.44 Å: III: 3.63 Å) for an intramolecular 4 → 1 hydrogen bond. Boc-Ala-Dpg-Ata-NHMe (II) crystallizes with two independent molecules in the asymmetric unit. Both molecules HA and HB adopt consecutive β-turn (type III-III in HA and type III-I in IIB) or incipient 310-helical structures, stabilized by two intramolecular 4 → 1 hydrogen bonds. In all four molecules the bond angle N-Cα-C′ (τ) at the Dxg residues are ≥ 110°. The observation of conformational angles in the helical region of φ,ψ space at these residues is consistent with theoretical predictions. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360350102
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  • 13
    Electronic Resource
    Electronic Resource
    α-Glutamyl oligopeptides: Preparation by the solid-phase method (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 157-167 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the oligomeric peptides (Glu)n-Phe(NO2)-Phe (up to n = 4) by the solid-phase method is reported. Fractionation by ion-exchange column chromatography of the crude materials cleaved from the resin and subsequent amino acid analysis revealed that the desired peptides were obtained, although contaminated by several by-products whose number depends on the length of peptide chain and on the experimental conditions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130110
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  • 14
    Electronic Resource
    Electronic Resource
    Structure in solution of protected homo-oligopeptides of L-valine, L-isoleucine, and L-phenylalanine: An infrared absorption study (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2225-2239 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monodisperesed, N-and C-Protected homo-oligopeptides [number (n) of resides from 2 to 5] of L-valine, L-isoleucine, and L-phenylalnine were studied by ir absorption spectroscopy between 1200 and 350 cm-1 at various solvents. The solvents and chain-length effects were examined for non-hydrogen-bonded peptide groups. The frequencies of the self-associated species are consistent with a model derived from the amide data. Self-association species are consistent with a model derived from the amide data. Self-association is favored by higher values of n = 2, the peptide is insoluble when more than two chains are bonded. For n = 3, 4, several chains may be associated by sliding along one another and remain soluble. For n = 2, the peptide is insoluble when more than two chains are bonded. For n = 3, 4, several chains may be associated by sliding along one another and remain slouble. For n = 5, the effect of n is to favour a model in which two chains exactly face each other so that the peptide precipitates at relatively low concentration.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170915
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  • 15
    Electronic Resource
    Electronic Resource
    Conformational preferences of side-chain protected amino acid residues and their impact in peptide synthesis (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 233-240 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the host-guest technique, tentative scales for the helix-inducing power and the β-structure-forming potential of various side-chain protected amino acid residues in trifluoro-ethanol are established mainly by CD measurements. The generally lower tendency for β-structure formation of the host-guest peptides compared to that of the host peptide is discussed. The influence of these conformational features on the solubility of the peptides is also pointed out.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360220132
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  • 16
    Electronic Resource
    Electronic Resource
    Vibrational circular dichroism of polypeptides. IV. Film studies of L-alanine homo-oligopeptides (1985)
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 1257-1263 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vibrational CD (VCD) and ir absorption data are reported for a series of films of Boc-(L-Ala)n-OMe homo-oligopeptides (n = 3-7) in the amide I and A regions. The data evidenced a sharp change between n = 3 and n = 4, which parallels the onset of β-structure formation, and another between n = 5 and n = 6, which parallels the full development of β-structure. This represents the first report of the application of VCD to oligopeptide conformation. The data resembled earlier reported film VCD studies of higher-molecular-weight polypeptides of known β-structure.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360240712
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  • 17
    Electronic Resource
    Electronic Resource
    Stereochemistry of peptides containing 1-aminocyclopentanecarboxylic acid (Acc5): Solution and solid-state conformations of Boc-Acc5-Acc5-NHMe (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1635-1644 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational analysis of a protected homodipeptide of 1-aminocyclopentanecarboxylic acid (Acc5) has been carried out. 1H-nmr studies establish a β-turn conformation for Boc-Acc5-Acc5-NHMe in chloroform and dimethylsulfoxide solutions involving the methylamide NH in an intramolecular hydrogen bond. Supportive evidence for the formation of an intramolecular hydrogen bond is obtained from ir studies. X-ray diffraction studies reveal a type III β-turn conformation in the solid state stabilized by a 4 → 1 hydrogen bond between the Boc CO and methylamide NH groups. The φ,ψ values for both Acc5 residues are close to those expected for an ideal 310-helical conformation (φ≃ ± 60°, ψ∼ ±30°).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250907
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  • 18
    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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  • 19
    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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  • 20
    Electronic Resource
    Electronic Resource
    Preferred conformation of peptides from Cα,α-symmetrically disubstituted glycines: Aromatic residues (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 637-641 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational preference of Cα,α-diphenylglycinc (Døg) and Cα,α-dibenzylglycine (Dbz) residues was assessed in selected derivatives and small peptides by conformational energy computations, ir absorption, 1H-nmr, and x-ray diffraction. Conformational energy computations on the two monopeptides strongly support the view that these Cα,α-symmetrically disubstituted glycines are conformationally restricted and that their minimum energy conformation falls in the fully extended (C5) region. The results of the theoretical analyses appear to be in agreement with the solution and crystal-state structural propensities of three derivatives and seven di-and tripeptides.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310608
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