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  • Electronic Resource  (17)
  • Polymer and Materials Science  (17)
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  • Electronic Resource  (17)
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  • Polymer and Materials Science  (17)
  • Chemistry  (17)
  • 1
    Electronic Resource
    Electronic Resource
    13C nmr study of the helix-coil transition of poly-N5-(3-hydroxypropyl)-L-glutamine (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 765-768 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The helix-coil transition of poly-N5-(3-hydroxypropyl)-L-glutamine in methanol-water solutions has been observed using 13C nuclear magnetic resonance. Two signals appear in the α-CH region in the course of the transition; this is in contrast with previous proton magnetic resonance experiments carried out on this polymer in the same solvent system.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130411
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis of sequential polypeptides containing L-azetidine-2-carboxylic acid residues (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2211-2230 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and characterization of a series of sequential polypeptides with the repeating sequences Aze-Pro-Aze, Pro-Aze-Pro, Pro-Aze-Gly, Aze-Pro-Gly, Ala-Aze-Gly, Aze-Ala-Gly, and Pro-Pro-Gly are reported. The polymers were prepared by the active ester method, using the p-nitrophenyl, pentachlorophenyl, and N-hydroxysuccinimide esters as the polymerizable tripeptide derivatives. Except for poly(Ala-Aze-Gly) obtained via the N-hydroxysuccinimide ester, all polymers were isolated in good yields and have weight-average molecular weights in the range 10,000-30,000. The molecular weights have been determined by applying the calibrated gel chromatography system described by Fairweather et al. [J. Chromatogr. (1972) 67, 157] and by viscometry. All di- and tripeptide intermediates were chemically and optically pure.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360141016
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  • 3
    Electronic Resource
    Electronic Resource
    Conformational properties of the sequential polyproline analogs poly(Pro-Aze-Pro) and poly(Aze-Pro-Aze) (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1233-1242 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The lack of the positive band at around 226 nm in the CD spectra of poly(prolyl-azetidine-2-carbonyl-proline) in trifluoroethanol and of poly(azetidine-2-carbonyl-prolyl-azetidine-2-carboxylic) acid in F3EtOH and water, the hyperchromism of the absorption maximum at about 202 nm, and the extremely small intensity of the Cβ-Pro, Cγ-Pro, and Cβ-Aze signals for the cis peptide bonds in the 13C nmr spectrum of poly(Pro-Aze-Pro) in F3EtOH indicate that both polyproline analogs exist as disordered chains in this solvent, the trans peptide group being maintained. The disordering of the chains is attributed to an increase in the accessible range of ψ due to the reduced dimensions of the square ring of L-azetidine-2-carboxylic acid residue relative to the pyrrolidine ring of proline and to strong interactions of the haloalcohol with the peptide groups of the chains.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360150702
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  • 4
    Electronic Resource
    Electronic Resource
    1H-nmr studies of synthetic polypeptide models of Plasmodium falciparum circumsporozoite protein tandemly repeated sequence (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 225-246 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The major immunodominant region of the coating protein of Plasmodium falciparum sporozoites contains multiple tandem copies of the sequence Asn-Ala-Asn-Pro (NANP). Current efforts for the development of an antisporozoite vaccine are focused on the synthesis of polypeptides reproducing part of the circumsporozoite protein repeat sequence and, in an attempt to relate conformational properties and biological response, 1H-nmr one- and two-dimensional studies of the synthetic models (NANP)2NA and (NANP)6 were carried out in water and water/methanol mixtures, at 400 and 500 MHz. In water, (NANP)6 undergoes fast conformational averaging. At variance, in water/methanol, the molecule appears to adopt an extensive structure, but detailed analysis is impaired by high spectral degeneracy. Based on the results obtained with (NANP)2NA and from preliminary expermints in water/trifluoroethanol, an interpretation is suggested for the (NANP)6 data in water/methanol in terms of a mixed sequence of βI-turns and half-turns (or/and γI-turns) around the positions Ni-1-Pi-Ni+1.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360280124
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  • 5
    Electronic Resource
    Electronic Resource
    Conformational studies on the pyridoxal Schiff bases of polypeptides (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 897-908 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pyridoxal Schiff bases of the polypeptides poly(L-lysine), poly(L-ornithine), and poly(L-α,γ-diaminobutyric acid) were prepared and investigated in water/methanol by CD spectra and equilibrium dialysis experiments. Only the poly(L-α,γ-diaminobutyric acid) derivative is characterized by a relevant optical activity similar to that found in pyridoxal enzymes. The stereospecific interactions between the pyridoxylideneimine group and the polypeptide chain prevent the hydrolysis reaction of the aldimine bond.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170408
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  • 6
    Electronic Resource
    Electronic Resource
    Solution conformations of some azetidine cyclic peptidesThis is paper xxi of the series “Cyclic Peptides.” Paper XX of this series (Boni et al.) (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2401-2413 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1H-nmr spectra (270 MHz) of cyclic di- and tri-L-azatidine-2-carboxylic acid [cy-clo(L-Aze)2 and cyclo(L-Aze)3] were determined in CDCl3 and D2O and computer simulated. The spectral results were compared with those obtained with cyclo (L-Pro)2 and cyclo (L,-Pro)3. In CDCl3 and D2O solution, the four membered ring of cyclo (L-Aze)2 is puckered with the α-proton in a pseudo-axial position, and the φ angle is smaller in absolute value than -60°, as found for cyclo (L-Pro)2,. The puckering of the four-membered ring of cyclo(L,-Aze)3 in CDCl3 has the α-proton in a pseudo-equatorial position and φ angle larger in absolute value than -60°, in agreement with cyclo(L-Pro)3. In D2O, cyclo(L-Aze)3 was found to interconvert rapidly between different conformers. In the azetidine cyclic peptides studied, the range of values found for the φ angles was smaller than in the related proline cyclic peptides, indicating greater rigidity in the four-membered ring.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360171009
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis and circular dichroism characterization of L-azetidine-2-carboxylic acid cyclic peptidesThis is paper XX of the series “Cyclic Peptides.” For the previous paper in this series, see Baron et al. (1977) J. Am. Chem. Soc. 99, 8299-8306. (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 2385-2399 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several cyclic hemopeptides containing L-azetidine-2-carboxylix acid (Aze) - an imino acid homologous with proline but containing one less methylene group in its cyclic side chain - have been prepared. The peptides reported include (Aze)2, cyclo(Aze)3, and cyclo(Aze)6. The synthesis and spectral characterization of these cyclic peptides are described, and the results discussed in terms of the rigidity and steric constraints attributable to Aze-containing peptides. CD spectra of these materials in several solvents are reported and compared with those of proline analogs; the similarity between the CD spectra of cyclo(Aze)3 and cyclo (Pro)3, is noted.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360171008
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  • 8
    Electronic Resource
    Electronic Resource
    Far ultraviolet optical rotatory properties of poly-L-tryptophan. Part I (1968)
    New York : Wiley-Blackwell
    Biopolymers 6 (1968), S. 963-971 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A block copolymer [γ-Et-DL-Glu]m [L-Trp]n was prepared using N-carboxy anhydrides (NCA) of L-tryptohan and γ-ethyl DL-glutamate. The block copolymer, dissolved in trifluoroethanol (TFE)-dichloroacetic acid (DCA) mixtures, exhibited a sharp change in the specific rotation at 546 mμ when the solvent composition reached 70-75% DCA content. Optical rotatory dispersion (ORD) and circular dichroism (CD) measurement were carried out in TFE solution in the spectral range 180-350 mμ. Indole side-chain chromophores were found to be optically active in the polymer. On the other hand, these groups exhibit very small optical activity in the model compound C6H3—CH2—O—CO—(L-Trp)2—O—CH3. Indole groups therefore appear to be in a dissymmetric environment only in the polymer. From these data it was concluded that poly-L-Trp is in some type of helical conformation in TFE. Strong overlapping of CD bands from side-chain chromophores and peptides chromophores in the wavelength range 185-240 mμ does not allow definite conclusions to be drawn about the type of helical conformation which exists in poly-L-Trp in TFE solution.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1968.360060707
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  • 9
    Electronic Resource
    Electronic Resource
    Conformational studies on poly-L-tryptophan: Circular dichroism and X-ray diffraction studies (1968)
    New York : Wiley-Blackwell
    Biopolymers 6 (1968), S. 1477-1486 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Circular dichroism (CD) measurements were carried out on various copolymers of L-tryptophan and γ-ethyl L-glutamate in ethylene glycol monomethyl ether as the solvent. On increasing the L-tryptophan content of the copolymers a gradual change in the CD spectra was observed. The typical spectrum of the right-handedα-helix becomes more and more evident as the L-tryptophan content decreases. On the basis of these results we assumed that no conformational transition occurs on proceeding from pure poly (γ-ethyl L-glutamate) to pure poly-L-tryptophan in ethylene glycol monomethyl ether: therefore the conformation of poly-L-tryptophan should be that of a right-handed α-helix. Moreover we observed that the change in the CD spectra of the copolymers is gradual but not linear on increasing the tryptophan content. The deviations from linearity were attributed to interactions among side-chain chromophores whose contributions to the optical activity are not simply additive. An x-ray analysis carried out on oriented films of poly-L-tryptophan casted from solutions of the polymer in dimethylformamide shows conclusively that the solid-state conformation of the polymer is that, of an α-helix.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1968.360061010
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  • 10
    Electronic Resource
    Electronic Resource
    Enthalpy of helix-coil transition from heat of solutions. III. Poly-N-δ-carbobenzoxy-L-ornithine and poly-N-γ-carbobenzoxy-L-α,γ-aminobutyric acid (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 215-224 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The helix-to-coil transition in dichloroethane-dichloroacetic acid (DCE-DCA) mixtures for poly-N-δ-carbobenzoxy-L-ornithine (PCBO) and for poly-N-γ-carbobenzoxy-Lα,γ-aminobutyric acid (PCBBA) have been studied by ORD and the “heat of solution” method. The results provide strong evidence for the existence of a very specific side-chain/side-chain interaction in PCBBA, which is discussed on the basis of a detailed structural model. The main sources of enthalpy and entropy changes in helix-coil transitions of uncharged homopolypeptides in DCE-DCA mixtures are also discussed briefly.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1972.360110116
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