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  • 1
    Electronic Resource
    Electronic Resource
    Conformational Characterization of the 1-Aminocyclobutane-1-carboxylic Acid Residue in Model Peptides (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 3 (1997), S. 110-122 
    Details
    ISSN: 1075-2617
    Keywords: β-bend ; cyclic amino acid ; 310-helix ; peptide conformation ; X-ray diffraction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of N- and C-protected, monodispersed homo-oligopeptides (to the dodecamer level) from the small-ring alicyclic Cα,α-dialkylated glycine 1-aminocyclobutane-1-carboxylic acid (Ac4c) and two Ala/Ac4c tripeptides were synthesized by solution methods and fully characterized. The conformational preferences of all the model peptides were determined in deuterochloroform solution by FT-IR absorption and 1H-NMR. The molecular structures of the amino acid derivatives Z-Ac4c-OH and Z2-Ac4c-OH, the tripeptides Z-(Ac4c)3-OtBu, Z-Ac4c-(L-Ala)2-OMe and Z-L-Ala-Ac4c-L-Ala-OMe, and the tetrapeptide Z-(Ac4c)4-OtBu were determined in the crystal state by X-ray diffraction. The average geometry of the cyclobutyl moiety of the Ac4c residue was assessed and the τ(N-Cα-C′) bond angle was found to be significantly expanded from the regular tetrahedral value. The conformational data are strongly in favour of the conclusion that the Ac4c residue is an effective β-turn and helix former. A comparison with the structural propensities of α-aminoisobutyric acid, the prototype of Cα,α-dialkylated glycines, and the other extensively investigated members of the family of 1-aminocycloalkane-1-carboxylic acids (Acnc, with n=3, 5-8) is made and the implications for the use of the Ac4c residue in conformationally constrained peptide analogues are briefly examined. © 1997 European Peptide Society and John Wiley & Sons, Ltd
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Preferred conformation of peptides rich in Ac8c, a medium-ring alicyclic Cα,α-disubstituted glycine (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 2 (1996), S. 14-27 
    Details
    ISSN: 1075-2617
    Keywords: β-bend ; cyclic amino acid ; 310-helix ; peptide conformation ; X-ray diffraction ; Chemistry ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A complete series of terminally blocked, monodispersed homo-oligopeptides (to the pentamer level) from the sterically demanding, medium-ring alicyclic Cα,α-disubstituted glycine 1-aminocyclooctane-1-carb oxylic acid (Ac8c), and two Ala/Ac8c tripeptides, were synthesized by solution methods and fully characterized. The preferred conformation of all the oligopeptides was determined in deuterochloroform solution by IR absorption and 1H-NMR. The molecular structures of the amino acid derivative Z-Ac8c-OH, the dipeptide pBrBz- (Ac8c)2-OH and the tripeptide pBrBz-(Ac8c)3-OtBu were assessed in the crystal state by X-ray diffraction. Conformational energy computations were performed on the monopeptide Ac-Ac8c-NHMe. Taken together, the results obtained strongly support the view that the Ac8c residue is an effective β-turn and helix former. A comparison is also made with the conformational preferences of α-aminoisobutyric acid, the prototype of Cα, α-disubstituted glycines, and of the other members of the family of 1-aminocycloalkane-1-carboxylic acids (Acnc, with n=3, 5-7) investigated so far. The implications for the use of the Ac8c residue in peptide conformational design are considered.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/psc.43
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  • 3
    Electronic Resource
    Electronic Resource
    Conformational characterization of peptides rich in the cycloaliphatic Cα,α-disubstituted glycine 1-amino-cyclononane-1-carboxylic acid (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 3 (1997), S. 367-382 
    Details
    ISSN: 1075-2617
    Keywords: β-turn ; cyclic amino acid ; 310-helix ; peptide conformation ; X-ray diffraction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of N- and C-protected, monodispersed homo-oligopeptides (to the pentamer level) from the cycloaliphatic Cα,α,-dialkylated glycine 1-aminocyclononane-1-carboxylic acid (Ac9c) and two Ala/Ac9c tripeptides have been synthesized by solution methods and fully characterized. The conformational preferences of all the model peptides were determined in deuterochloroform solution by FT-IR absorption and 1H-NMR. The molecular structures of the amino acid derivatives mClAc-Ac9c-OH and Z-Ac9c-OtBu, the dipeptide pBrBz-(Ac9c)2-OtBu, the tetrapeptide Z-(Ac9c)4-OtBu, and the pentapeptide Z-( Ac9c)5-OtBu were determined in the crystal state by X-ray diffraction. Based on this information, the average geometry and the preferred conformation for the cyclononyl moiety of the Ac9c residue have been assessed. The backbone conformational data are strongly in favour of the conclusion that the Ac9c residue is a strong β-turn and helix former. A comparison with the structural propensity of α-aminoisobutyric acid, the prototype of Cα,α-dialkylated glycines, and the other extensively investigated members of the family of 1-aminocycloalkane-1-carboxylic acids (Acnc, with n=3-8) is made and the implications for the use of the Ac9c residue in conformationally constrained analogues of bioactive peptides are briefly examined. © 1997 European Peptide Society and John Wiley & Sons, Ltd.J. Pep. Sci. 3: 367-382No. of Figures: 10. No. of Tables: 6. No. of References: 62
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Structural aspects of small peptides. A circular dichroism study of monodisperse protected homo-oligomers derived from L-alanine (1975)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 176 (1975), S. 2547-2558 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Konformation einer Reihe von molekulareinheitlichen, chemisch und optisch reinen geschützten L-Alanin-Homo-Oligomeren mit der allgemeinen Formel BOC—(L-Ala)n—OCH3 (n=2-7) wurden in Lösung mit Hilfe der CD-Methode untersucht. Es wurde gefunden, daß diese Peptide in einem hauptsächlich β-assoziierten statistischen Knäuel oder in partiell α-helicalen Konformationen auftreten können, abhängig vom Molekulargewicht, Lösungsmittel, Temperatur und Oligomerenkonzentration. Die β-Struktur, die im Bereich 5≤n≤7 in 2,2,2-Trifluoräthanol (TFE), TFE-Wasser 20:80 (V/V), Methanol und Äthanol auftrat, konnte durch Verdünnung oder Temperaturerhöhung zerstört werden. In verdünnter TFE-Lösung wurde die Tendenz des Heptameren zur Kettenfaltung gefunden. In 1,1,1,3,3,3-Hexafluorpropan-2-ol und Hexafluoraceton-ses-quihydrat treten alle Oligomeren jedoch ausschließlich in einer ungeordneten Konformation auf.
    Notes: The conformational properties in solution of a series of monodisperse, chemically and optically pure protected L-alanine homo-oligomers, having the general formula BOC—(L-Ala)n—OCH3 (n = 2-7), were investigated using essentially the CD technique. This study demonstrates that these peptides may exist in predominantly β-associated, statistical coil, or partially α-helical conformations depending upon molecular weight, solvent, temperature, and oligomer concentration. The β-structure, which appears in the range 5≤n≤7 in 2,2,2-trifluoroethanol (TFE), TFE-water 20:80 (v/v), methanol, and ethanol could be destroyed by dilution or by increasing the temperature. In diluted TFE solutions, the tendency of the heptamer to form folded species could be detected. In 1,1,1,3,3,3-hexafluoropropan-2-ol and hexafluoroacetone sesquihydrate, however, all oligomers exist essentially in an unordered conformation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1975.021760907
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  • 5
    Electronic Resource
    Electronic Resource
    Structural aspects of small peptides. Synthesis and characterization of protected homo-oligomers derived from L-alanine (1975)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 176 (1975), S. 2535-2545 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Eine Reihe von geschützten L-Alanin-Homo-Oligomeren vom Dimeren bis zum Heptameren wurde durch die Dicyclohexylcarbodiimid- und Azidkupplung dargestellt. Als N-Schutzgruppe wurde der tert-Butoxycarbonylrest und als C-Schutzgruppe die Methylestergruppe verwendet. Die so synthetisierten molekulareinheitlichen Oligomeren wurden charakterisiert und erwiesen sich als chemisch rein. Die polarimetrische Untersuchung in einem denaturierenden Lösungsmittel zeigte, daß alle Reaktionen unter vollständiger Erhaltung der Konfiguration erfolgten. Außerdem wurde die Abhängigkeit der experimentell gefundenen Werte der Molekularrotation der innenständigen L-Alaninreste bei 589 nm im statistischen Knäuel von der Struktur der Endgruppen und dem Lösungsmittel besonders herausgestellt.
    Notes: A series of protected L-alanine homo-oligomers from dimer to heptamer was prepared by the dicyclohexylcarbodiimide and acyl azide coupling methods. In the course of the synthetic approach tert-butoxycarbonyl as the N-protecting and methyl ester as the C-protecting end groups were employed. The monodisperse oligomers prepared in this manner were characterized and found to be chemically pure. A polarimetric investigation in a structure disrupting solvent also indicated that all reactions proceeded with complete retention of the configuration. In addition, the dependence of the experimental molar rotation values at 589 nm of L-alanine internal residues in a polypeptide in a statistical coil conformation on the end groups of the molecule and the solvent is emphasized.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1975.021760906
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  • 6
    Electronic Resource
    Electronic Resource
    Linear oligopeptides, 29.Part 28: cf.1. Infrared conformational analysis of homo-oligopeptides in the solid state and in solution (1976)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 177 (1976), S. 1477-1492 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die IR-Spektren von 8 Reihen von molekulareinheitlichen, chemisch und optisch reinen, geschützten linearen Homo-Oligopeptiden mit der allgemeinen Formel Boc(—L—X)n—OMe (mit X = Ala, Nva, Val, Leu, Ile, Phe, Met, Cys(Me) und n = 2-7) wurden durch IR-Absorptionsspektroskopie im festen Zustand und in Lösung untersucht. Die Messungen im festen Zustand ergaben, daß alle Pentameren und höheren Oligomeren hauptsächlich eine β-Form einnehmen. Trimere und Tetramere bestehen danach aus Mischungen von β- und ungeordneten Strukturen, während in den Dimeren die ungeordnete Struktur vorherrscht. Das Auftreten der ungewöhnlichen intermolekularen parallelen βKonformation wird für HCl·H(—L—X)7—OMe (mit X = Val, Ile, Phe) vorgeschlagen. Außerdem wurde die Absorption im Gebiet der N—H-Valenzschwingung in Abhängigkeit von der Konzentration in Deuterochloroform bestimmt. Diese Konformationsanalyse in Lösung zeigte, daß ein hoher Gehah an Strukturen mit intramolekularen Wasserstoffbrücken in allen Homo-Tetrameren vorliegt, mit Ausnahme der Derivate mit β-verzweigten Aminosäureresten (Valin, Isoleucin). Der Effekt eines Schwefelatoms und eines aromatischen Rings in der Seitenkette (S-Methplcystein - Methionin - und Phenylalanin-Peptide) auf die Stabilitlt der gefalteten Formen wird ebenfalls diskutiert.
    Notes: The IR spectra of eight series of monodisperse, chemically and optically pure, protected linear homo-oligopeptides having the general formula Boc(—L—X)n—OMe, where X = Ala, Nva, Val, Leu, Ile, Phe, Met, Cys(Me), and n = 2-7, were investigated by IR absorption spectroscopy in the solid state and in solution. The measurement in the solid state indicate that all pentamers and higher oligomers assume essentially a β-form; trimers and tetramers present evidence of mixtures of β- and unordered structures, while in dimers the unordered structure is largely predominant. The occurrence of the unusual intermolecular β-parallel conformation was suggested for HCl·H(—L—X)7—OMe, where X = Val, Ile, and Phe. Further, the absorbance in the N—H stretching region was determined as a function of concentration in deuterochloroform. This conformational analysis in solution showed that a high content of intramolecularly hydrogen-bonded forms exist in all homo-tetramers with the exception of those derived from the β-branched amino acid residues, valine and isoleucine. The effect of the presence of a sulfur atom or an aromatic ring in the amino acid side chain (S-methyl cysteine, methionine, and phenylalanine peptides) on the stability of the folded forms is also discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1976.021770519
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  • 7
    Electronic Resource
    Electronic Resource
    Conformational studies on polypeptides containing L-alanine and ω-amino acids (1978)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 179 (1978), S. 2707-2718 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis and the conformational studies of the following sequential polypeptides are reported: poly(alanyl-3-aminopropanoic acid), poly(alanyl-4-aminobutanoic acid), poly(alanyl-5-aminopentanoic acid), and poly(alanyl-6-aminohexanoic acid). These compounds were examined in the solid state by X-ray diffraction and in solution by circular dichroism spectroscopy. X-ray diffraction patterns indicate that all copolymers assume an antiparallel pleated-sheet conformation. The results in solution suggest that the synthetic polypeptides, in 2,2,2-trifluoroethanol (TFE)/methanol exhibit a β-conformation. The addition of water to a solution of copolymers in TFE destabilize this ordered structure except in the case of poly(alanyl-6-aminohexanoic acid).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1978.021791113
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  • 8
    Electronic Resource
    Electronic Resource
    Linear oligopeptides, 70Part 69: Cf.1.. Study of the relationship between conformation and nature of the side chain: Homologous series derived from α-amino acid residues with linear hydrocarbon side chains (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 3149-3162 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of N- and C-protected L-α-aminobutyric acid homo-oligopeptides from dipeptide through heptapeptide was synthesized by the dicyclohexylcarbodiimide and acyl azide coupling methods. The monodisperse peptides were characterized and found to be chemically and optically pure. By means of infrared absorption and circular dichroism in the vacuum ultraviolet (150 nm) the occurrence of the intermolecular β-conformation in the higher oligopeptides in the solid state was ascertained. In solvents of low polarity at high dilution the amount of intramolecularly hydrogen-bonded folded structure formation was established as a function of peptide chain length. Unordered and intermolecular β-structures were found in alcohols and in water/2,2,2-trifluoroethanol mixtures. The results obtained are compared with those already published of other homologous peptide series derived from L-α-amino acid residues with linear hydrocarbon side chains, namely alanine, norvaline, and norleucine. Analogies and differences with the series from β- and γ-branched residues are also discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1981.021821121
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  • 9
    Electronic Resource
    Electronic Resource
    Solid state investigation on the homo-oligopeptide Boc—(L-Ala)6—OCH3 by X-rays (1978)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 179 (1978), S. 2803-2806 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1978.021791126
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  • 10
    Electronic Resource
    Electronic Resource
    Conformational properties of homo-oligo(L-leucine)s in solution. Comparison with isoleucines (1974)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 175 (1974), S. 1665-1668 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1974.021750525
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