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  • Articles  (29)
  • Polymer and Materials Science  (22)
  • 310-helix  (4)
  • General Chemistry  (3)
  • Chemistry and Pharmacology  (29)
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  • Articles  (29)
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  • Chemistry and Pharmacology  (29)
  • 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.
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  • 2
    Electronic Resource
    Electronic Resource
    Solid State and Solution Conformation of 6-[4-[N-tert-ButoxycarbonylN-(N′-ethyl)propanamide]imidazolyl]-6-deoxycyclomaltoheptaose: Evidence of Self-Inclusion of the Boc Group within the β-Cyclodextrin Cavity (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1065-1076 
    Details
    ISSN: 1434-193X
    Keywords: Cyclodextrins ; Inclusion compounds ; Carcinine ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A new modified β-cyclodextrin (β-CD) derivative 1 that was functionalized in position 6 with Boc-Carcinine was synthesised and its crystal structure was determined. The structure reveals a “sleeping swan”-like shape, the covalently bonded Boc-Carcinine moiety forming a folded structure with the Boc group inserted within the hydrophobic cavity of the β-cyclodextrin. The conformation of the Carcinine moiety is determined by the inclusion of the Boc group and is further stabilised by three intramolecular hydrogen bonds, two between the amide N1-H group, the carbonyl C′1=O1 group and a primary hydroxylic group of the glucose unit 5, one between the carbonyl C′0=O0 group and the primary hydroxylic group of the glucose unit 2. The β-CD macrocycle differs only slightly from unmodified β-CDs, maintaining an approximate sevenfold symmetry. The solution structure of the new β-CD derivative was investigated by NMR spectroscopy and circular dichroism (c.d.) spectroscopy. In addition to a complete (1H and 13C) assignment of the pendant Boc-Carcinine group, the NMR study allowed the assignment of all the proton resonances associated with the β-CD macrocycle. Furthermore, NMR and c.d. results indicated that the self-inclusion of the Boc group within the β-CD cavity is retained in aqueous solution. In order to estimate the strength of this self-inclusion complex a series of competition experiments with the external guest 1-adamantanol was carried out using c.d. spectroscopy.
    Additional Material: 9 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Conformational Analysis by NMR and Distance-Geometry Techniques of Deltorphin Analogs (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2279-2287 
    Details
    ISSN: 1434-193X
    Keywords: Receptor selectivity ; Agonist activity ; Distance geometry ; Conformation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: To identify the peptide conformation that is preferentially recognized by the receptor, we have synthetized by solid-phase method a series of deltorphin I analogs with increasing selectivity for δ- and μ-opioid receptor. Structure-selectivity relationship of these peptides were evaluated on the basis of receptor-binding properties and conformational features, computed by two-dimensional NMR spectra and distance-geometry techniques. These compounds in solution are present with a large number of conformers with no defined secondary structural elements. The analysis of the average properties of these compounds indicate the presence of some distinct conformational preferences that can be related to the observed opioid receptor selectivities. Selectivity for the δ- and μ-opioid receptors can be ascribed to the spatial arrangement of the aromatic moieties. In addition, substitutions in position 2 and 4 are important for the correct arrangement and must be taken into account in the design of δ-opioid receptor-selective ligands.
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Inversion of 310-helix screw sense in a (D-αMe)Leu homotetrapeptide induced by a guest D-(αMe)val residue (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 1 (1995), S. 396-402 
    Details
    ISSN: 1075-2617
    Keywords: (αMe) amino acids ; CD spectroscopy ; 310-helix ; peptide 3D-structure ; X-ray structure ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The terminally blocked tetrapeptide pBrBz-[D-(αMe)Leu]2-D-(αMe)Val-D-(αMe)Leu-OtBu is folded in the crystal state in a left-handed 310-helical structure stabilized by two consecutive 1 ← 4 C=O⃛H—N intramolecular H-bonds, as determined by X-ray diffraction analysis. A CD study strongly supports the view that this conformation is also that largely prevailing in MeOH solution. A comparison with the published conformation of pBrBz-[D-(αMe)Leu]4-OtBu indicates that incorporation of a single internal β-branched (αMe)Val guest residue into the host homo-tetrapeptide from the γ-branched (αMe)Leu residue is responsible for a dramatic structural perturbation, i.e. an inversion of the 310 screw sense from right to left-handed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/psc.310010607
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  • 5
    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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  • 6
    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.
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  • 7
    Electronic Resource
    Electronic Resource
    A Modified Cyclodextrin with a Fully Encapsulated Dansyl Group: Self-Inclusion in the Solid State and in Solution (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 373-381 
    Details
    ISSN: 0947-6539
    Keywords: crystal structure ; cyclodextrins ; dansyl derivatives ; fluorescent sensors ; self-inclusion ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A monofunctionalized β-cyclodextrin containing a dansyl moiety, 6- deoxy- 6 - N - ( N′- (5- dimethylamino - 1 - naphthalenesulfonyl)diaminoethane) - β-cyclodextrin (CD-en-DNS, 2), was synthesized and its crystal structure determined. It was shown that the dansyl group is fully encapsulated within the cyclodextrin cavity, with the dimethylamino and sulfonyl groups emerging from opposite sides. The shape of the cavity is considerably flattened, since O(4)-O(4) distances parallel to the naphtalene ring were found to be longer than the others. The conformation of the diaminoethane linker was found to be determined by the inclusion of the dansyl group and by a hydrogen bond between the sulfonamide NH and one of the O(6)-H groups on the cyclodextrin rim. The self-inclusion features of the aromatic moiety were found to be consistent with the solution data: 1H NMR ROESY spectra suggested that the orientation of the dansyl moiety observed in the solid state was retained in aqueous solution; the circular dichroism spectrum was consistent with an axial complexation model. Fluorescence spectra showed that the inclusion of the dansyl group in the cyclodextrin cavity considerably increases the quantum yield: time-resolved fluorescence experiments showed the presence of a long-lifetime component (16.1 ns), which was attributed to the included fluorophore. The ability of 2 to act as a fluorescence sensor was evaluated by the addition of several guests of different shape: fluorescence intensity was lowered, especially upon addition of adamantanecarboxylic acid. All the data obtained were consistent with the model of the in-out movement of the dansyl group from the self-included conformation observed in the solid state to a position more exposed to the bulk solvent. Copper(II) was shown to enhance the difference in the fluorescence of 2 in the presence of guests by additional static quenching.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020404
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  • 8
    Electronic Resource
    Electronic Resource
    Bicyclic peptides: Solid state conformation of cyclo(Glu-Leu-Pro-Gly-Lys-Leu-Pro-Gly)cyclo(1γ-5∊)Gly (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 509-516 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solid state conformational analysis of the ionophoric homodetic bicyclic cyclo(Glu-Leu-Pro-Gly-Lys-Leu-Pro-Gly)cyclo(1γ-5∊)Gly (BCP3) has been carried out by x-ray diffraction. It crystallizes with 4.5 molecules of water per peptide molecule in the monoclinic system, space group P21, with a = 11.425 Å, b = 16.616 Å, c = 13.931 Å, β = 109.24°, and Z = 2. The structure has been determined by direct methods and refined to an R factor of 0.061 for 2448 observed reflections. The structure characterized by all trans peptide bonds is stabilized by three intramolecular hydrogen bonds: a type II β-turn, a mixed type I-type III β-turn, and a pseudo γ-turn, which involves the side chain C=O and the main-chain N—H groups of the Glu1 residue. The resulting globular molecule presents a rather hydrophilic surface with most of the C=O groups available to hydration of the solvent molecules, which are linked through hydrogen bonds of the N—H … O or O—H … O types in a complicated H-bonding scheme. The conformation observed in the solid state is rather different from the conformation proposed in solution for both the free and the Ca2+-complexed BCP3 molecule.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300504
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  • 9
    Electronic Resource
    Electronic Resource
    Ion binding of cyclolinopeptide A: An nmr and CD conformational study (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 761-767 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: CD and nmr techniques have been used to study, in acetonitrile solution, the ion-complexing capability of Cyclolinopeptide A (CLA), a cyclic nonapeptide of sequence \documentclass{article}\pagestyle{empty}\begin{document}$$ cyclo{\rm - }\left({{\rm Pro - Pro - Phe - Phe - Leu - Ile - Ile - Leu - Val}} \right) $$\end{document} endowed with remarkable cytoprotective ability in vitro, and the conformation of the Ba2+/ CLA complex.At room temperature, CLA in acetonitrile shows a proton nmr spectrum characteristic of the coexistence of many different conformers in intermediate exchange. The backbone contains a cis Pro-Pro bond, with all other peptide bonds in the transconformation.CLA binds Ba2+ more tightly than the other cations studied, namely K+, Na+, Mg2+, and Ca2+; CD data are indicative of the presence of both 1 : 2 (sandwich) and 1 : 1 (equimolar) type complexes, depending on the Ba2+ ion concentration, whereas nmr data are consistent with an equimolar form.The relevant conformational features of the equimolar Ba2+/CLA complex are that the backbone contains all transpeptide bonds, a type I 6 → 3 β-turn and a 3 → 1 γ-turn (or a distorted 3 → 9 β-turn). The global shape of the complexed peptide can be described as a bowl, with the concave (polar) side hosting Ba2+ and the convex side predominantly apolar.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310621
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  • 10
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation in vacuo and in solution of cyclolinopeptide A: A conformational study (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 1017-1024 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation of cyclolinopeptide A [c-(Pro-Pro-Phe-Phe-Leu-Ile-Ile-Leu-Val)], a naturally occurring peptide with remarkable cytoprotective activity, has been investigated by means of molecular dynamics simulations in various molecular environments. Structural and dynamical properties have been analyzed and compared with those experimentally determined. A detailed analysis of hydrogen bonds is reported.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310811
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