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  • Chemistry  (3)
  • prediction of secondary structure  (1)
  • 1985-1989  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Design of analogues of parathyroid hormone: A conformational approach (1985)
    Springer
    The protein journal 4 (1985), S. 391-406 
    Details
    ISSN: 1573-4943
    Keywords: parathyroid hormone ; analogues ; prediction of secondary structure ; solid-phase peptide synthesis ; circular dichroism ; bioactivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An approach to the design of peptide-hormone analogues in which amino acid substitutions are based on predicted effects on secondary structure was investigated. The structural requirements for parathyroid-hormone (PTH) action are distinct from the determinants necessary for receptor binding alone without subsequent activation of adenylate cyclase. Two analogues of PTH containing substitutions in the principal binding domain of PTH, the region 25–34, were synthesized by the solid-phase method and evaluated for bioactivity. The sequence 25–34 was predicted to have nearly equal conformational potential for both α-helix and β-sheet using Chou and Fasman parameters. A previously studied analogue, [Tyr34]bPTH(1–34) amide, containing substitutions in this region, was more active than was bPTH-(1–34). The substitution of tyrosine for phenylalanine at position 34 in this analogue is predicted to promote β-sheet conformation. The analogues [Ile28, Tyr30, Tyr34]bPTH-(1–34) amide and [Arg32, Tyr34]bPTH-(1–34) amide each contain substitutions predicted to further enhance or stabilize β-sheet formation. The solution conformation of these analogues, determined by circular dichroism studies in an aqueous buffer and an organic solvent, indicated promotion of β-sheet secondary structural content in both analogues in a hydrophobic environment chosen to simulate that of the interaction of the peptide and the membrane receptor. In contrast, the native sequence lacks β-structure. Biological activity of these analogues in the rat renal adenylate cyclase assay in vitro and binding affinity in a radioreceptor assay were threefold those of unsubstituted PTH-(1–34). Peptide analogue design based on conformational prediction, rather than substitution of primary structure alone, offers an attractive alternative approach to the development of hormone analogues and antagonists.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01025179
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  • 2
    Electronic Resource
    Electronic Resource
    β-Turns in bridged proline-containing cyclic peptide models (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 1555-1572 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis, CD, ir spectroscopic, and conformational studies of a series of bridged cyclic peptides of the general formula, cyclo[NH-(CH2)n-CO-Gly-Pro-Y-Gly] (2a-d, Y = Gly or Ser(OBut), n = 4 or 2) is reported. As indicated by difference nuclear Overhauser enhancement and Fourier transform ir experiments, the tetrapeptide sequence of cyclo[NH-(CH2)4-CO-Gly-Pro-Gly-Gly] (2a) and cyclo[NH-(CH2)2-CO-Gly-Pro-Gly-Gly] (2b) adopts a 1 ← 4 hydrogenbonded type II β-turn conformation in solution, while cyclo[NH-(CH2)4-CO-Gly-Pro-Ser(OBut) -Gly] (2c) features a type I β-turn, fixed by 1 ← 4 and Oγ … NH intramolecular H bonds. In aqueous solution 2a and 2c show class B and class C CD spectra, respectively. This is the first case reported of a typical class C CD pattern in aqueous solution for a conformationally mobile system having a type I β-turn. Based on the comparison of the band intensities of the bridged models with those of linear and cyclic model systems reported earlier, a set of subspectra with reduced band intensities is suggested for use in the CD analysis of the conformation of polypeptides in solution.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360260908
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  • 3
    Electronic Resource
    Electronic Resource
    Studies on proline-containing tetrapeptide models of β-turnsDedicated to Elkan R. Blout on the occassion of his sixty-fifth birthday. (1985)
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 211-242 
    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 a series of protected tetrapeptides of the general formula Cbz-Gly-X2-Y3-Gly-OR (R = stearyl or methyl, X and/or Y = proline) is described. Detailed CD studies have been performed to evaluate the contribution of proline-containing β-turns to the CD spectra of proteins. The CD spectra of all the models are dominated by the chiral contribution of the proline residue. In polar, proton-donating solvents, a poly-proline II-like spectrum was observed in almost all cases. The tetrapeptide model Cbz-Gly-Gly-Pro-Gly-OStearyl, in acetonitrile shows a type C spectrum that has not been previously reported for linear peptides. The ir and nmr data on this model support the assumption of that of a type III β-turn, exhibiting a type C spectrum, participate in the conformational equilibrium. The most interesting finding of the CD studies is the observation of a type D spectrum (according to the classification of Woody [Woody, R. W. (1974) in Peptides, Polypeptides and Proteins, Blout, E. R. Bovey, F. A. Lotan, N. & Goodman, M. (Eds.), Wiley, New York]) for models Cbz-Gly-Pro-Asp(OBut)-Gly-OStearyl and Cbz-Gly-Pro-Ser(OBut)-Gly-OStearyl in cyclohexane. The results of the CD measurements ae discussed in correlation with ir and nmr data and with recent literature.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360240117
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  • 4
    Electronic Resource
    Electronic Resource
    β-Turns in serine-containing linear and cyclic models (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 1527-1553 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrapeptides, Cbz-Gly-X-Y-Gly-OSt (1-4) - as well as cyclic systems, cyclo[NH-(CH2)n-CO-Gly-Ser(OX)-Ser(OX)-Gly] (5 and 6; n = 4 and 2, X = But or H), have been synthesized in order to compare the CD spectrum of linear and cyclic β-turn models containing either a protected or a free hydroxyl of the serine residue. In extremely dilute cyclohexane solution the linear models Cbz-Gly-Ser-Y-Gly-OSt (1-3a) show class B spectra with very strong positive bands, contrary to other members of the series. Based on 200-MHz 1H nuclear overhauser enhancement and Fourier transform ir studies, Cbz-Gly-Ser-Ser(OBut)-Gly-OSt (3a) in dilute chloroform solution assumes a distorted type II β-turn conformation fixed by an extended system of intramolecular H bonds. As evidenced by 1H-nmr and FT-IR experiments, the cyclic model cyclo[NH-(CH2)4-CO-Gly-Ser(OBut)- Ser(OBut)-Gly] (5a) in a 1 : 1 mixture of (CD3)2SO-CDCl3 is also characterized by a type II β-turn encompassing the Ser3(OBut)-Gly4 sequence. In water, a class B pattern was measured for this model, in good agreement with theoretical and experimental studies that show that type II β-turns are generally characterized by class B spectra. In the protected and free OH cyclic models, cyclo[NH-(CH2)2-CO-Gly-Ser(OX)-Ser(OX)-Gly] (5b and 6b, X = But or H) distortions of the peptide backbone due to the loss of two CH2 groups result in the appearance of CD spectra characterized by a strong negative band near 200 nm, interpreted as a sign of the lack of β-turn structures in these models. This observation, together with other CD data discussed in this paper, clearly show that the CD of serine-containing β-turn sequences strongly depends on long-range backbone and local side-chain interactions.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360260907
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