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  • 1
    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
    Library Location Call Number Volume/Issue/Year Availability
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  • 2
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The decapeptides Boc-Aib-L-Val-Aib-Aib-(L-Val)3-Aib-L-Val-Aib-OMe and Boc-Aib-L-Leu-Aib-Aib-(L-Leu)3-Aib-L-Leu-Aib-OMe have been studied in CDCl3 and (CD3)2SO solutions by 270-MHz1 H-nmr. In CDCl3, the presence of eight intramolecularly hydrogen-bonded NH groups has been established, consistent with a 310-helical conformation, for both decapeptides. In (CD3)2SO, only seven solvent-shielded NH groups are observed, supporting either an α-helical conformation or a partially unfolded 310-helix. Ir studies provided supporting evidence for intramolecularly hydrogen-bonded structures in CHCl3, while CD studies suggest helical conformation in both decapeptides in various solvents. CD studies also support helical folding in the C-terminal hexapeptides. The central triplet of L-amino acids appears to destabilize 310-helical conformations in polar solvents like (CD3)2SO.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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