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  • 1
    Electronic Resource
    Electronic Resource
    Conformational Analysis of the cis- and trans-Isomers of FK506 by NMR and Molecular Dynamics (1991)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 74 (1991), S. 1027-1047 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The potent immunosuppressant drug FK506 (2) has been examined by 1H- and 13C-NMR spectroscopy and NOE-restrained molecular dynamics to elucidate the conformation in solution. A combination of two- and three-dimensional NMR techniques was used to completely assign the 1H- and 13C-NMR chemical shifts of the two configurational isomers resulting from the cis-trans isomerization about the single amide bond. Hetero- and homonuclear coupling constants were measured to assign the diastereotopic methylene protons at C(16), C(18), and C(23). Intramolecular H—H distances were defined from NOESY spectra recorded at -30° in CDCl3 and used as constraints in molecular-dynamics simulations. The conformational preferences of 2 in solution are discussed in light of the constitutional features recently proposed to be necessary for binding and activity.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19910740513
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and Solvent Effects on the Conformation of Hymenistatin 1 (1993)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 76 (1993), S. 1649-1666 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cyclic octapeptide cyclo(-Pro-Pro-Tyr-Val-ProLeu-Ile-Ile-) (1), isolated from the Hymeniacidon sponge, was synthesized and examined conformationally using NMR and molecular-dynamics simulations. Most structural parameters of synthetic 1 are in accord with those reported for the isolated material. Our study indicates some small but significant differences in the assignment of the 1H- and 13C-NMR resonances from those of the natural material. The Conformation was determind in both CHCl3 and DMSO using 1H-NMR and molecular-dynamics simulations. Both NOE's and coupling constants were used as experimental restraints during the simulations which utilized explicitly the same solvent as in the NMR study. The differences in the interaction of the solvent with 1 were examined, providing insight into the observed differenced in conformation. The dominant conformation contains a ßVIa turn about Ile8-Tyr3 including a Pro1-Pro2 cis-peptide bond and a ßI or ßII turn about Val4-Ile7 in CHCl3 and DMSO, respectively.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19930760422
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  • 3
    Electronic Resource
    Electronic Resource
    Moleküldynamikrechnungen für Peptide in Dimethylsulfoxid: Eliminierung von VakuumeffektenDiese Arbeit wurde von der Deutschen Forschungsgemeinschaft und dem Fonds der Chemischen Industrie gefördert. (1992)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 104 (1992), S. 213-214 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19921040226
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  • 4
    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.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Conformational studies of diastereomeric cyclic enkephalins by 1H-NMR and computer simulations (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 1573-1586 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report the solid-phase synthesis and conformational analysis of a 14-membered, cyclic enkephalin analog, H—Tyr—c[—D—A2bu—Gly—Phe—D—Leu—] (where A2bu represents α,γ-diaminobutyric acid). The results from the guinea pig ileum (GPI) and mouse vas deferens (MVD) assays show that the analog, though active, has little selectivity for the μ or δ opioid receptors. Conformational analysis is carried out using 1H-nmr and computer simulations, including molecular dynamics and energy minimizations. The results obtained here are compared with the findings of our studies carried out on the μ-receptor-selective diastereomer, H—Tyr—c[—D—A2bu—Gly—Phe—Leu—] [N. Mammi, M. Hassan, and M. Goodman (1985) J. Am. Chem. Soc. 107, 4008-4013]. This comparison allows for insight into the regiospecificity of these cyclic enkephalin analogs.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360260909
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  • 6
    Electronic Resource
    Electronic Resource
    Combined use of homo- and heteronuclear coupling constants as restraints in molecular dynamics simulations (1992)
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 1277-1282 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A penalty function for scalar coupling constants has been applied in molecular dynamics simulations as an experimental constraint. The function is based on the difference between the coupling constant calculated from the dihedral angle and the experimentally measured coupling constant. The method is illustrated on a model cyclic pentapeptide for which 3JHN-Hα and 3JHN-Cβ, both about the φ backbone dihedral angle, have been measured. The function is efficient in producing structures consistent with the scalar couplings, but removed from the conformation observed in solution. This arises from the lack of J restraints for the ψ dihedral angle. Simulation with both nuclear Overhauser effect (NOE) and J-coupling restraints illustrates small but significant differences from simulations using only NOEs. © 1992 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360321003
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  • 7
    Electronic Resource
    Electronic Resource
    Conformational characterization of a peptide mimetic of the third cytoplasmic loop of the G-protein coupled parathyroid hormone/parathyroid hormone related protein receptor (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996), S. 653-666 
    Details
    ISSN: 0006-3525
    Keywords: parathyroid hormone ; parathyroid hormone-related protein ; G-protein coupled receptors ; peptide conformations in micelles ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The third-cytoplasmic loop of the G-protein coupled receptor responsible for the activity of parathyroid hormone and parathyroid hormone-related protein has been structurally characterized in aqueous solution in the presence of sodium dodecylsulfate and dodecylphosphocholine micelles. The high-resolution conformation of the 29-amino acid peptide containing the sequence of the cytoplasmic loop was obtained by CD and nmr. The structure was refined using a two-step distance geometry based method that first includes the removal of all side chains to quickly locate the globular fold of the peptide. After a simulated annealing protocol, the side chains are added in a random fashion. The resulting conformation was further refined with nuclear Overhauser enhancement restrained molecular dynamics using a two-phase simulation cell consisting of carbon tetrachloride and water as a mimetic of the biphasic, hydrophobic/hydrophilic character of the micelles in which the experimental measurements were carried out. The topological orientation of the cycloplasmic loop within the micelle was determined by addition of 5-doxylstearate and monitoring the decrease of nmr signal intensities from the radical-induced relaxation. The conformation and relative orientation of the peptide provided insight into the mechanism by which the cytoplasmic portion of the receptor activates the heterotrimeric, guanine nucleotide-binding regulatory protein, one of the first steps in signal transduction. © 1997 John Wiley & Sons, Inc. Biopoly 40: 653-666, 1996
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Structure, dynamics, and topological orientation of the polyether, ionophore antibiotic monensin, in a micellar environment (1997)
    New York : Wiley-Blackwell
    Biopolymers 42 (1997), S. 759-769 
    Details
    ISSN: 0006-3525
    Keywords: antibiotic, conformation of antibiotic ; nmr structure refinement ; cation transport ; micelles ; structure in micelles ; spectroscopy in micelles ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure and dynamics of the ionophoric antibiotic monensin in the presence of micelles have been determined. The conformation of monensin was derived from 50 nuclear Overhauser enhancement (NOE) derived distance restraints and metric-matrix based distance geometry calculations. The conformation was further refined with extensive NOE restrained molecular dynamics simulations carried out in a biphasic simulation cell. From the addition of doxylstearate and monitoring of the induced relaxation of the nmr signals, the relative topological orientation of the molecule within the micelle was ascertained. The results indicate two dihedral angles that act as hinge regions allowing the molecule to adopt a wide range of conformations. Considering the biological activity of monensin, i.e., the capture and transport of cations across cell membranes, an open and closed form of monensin have been postulated. The identification of these hinge regions, which are only observed in the membrane-like environment of the detergent micelles, provides insight into the mechanism of action and can serve as targets for modification to alter the biological profile of monensin. © 1997 John Wiley & Sons, Inc. Biopoly 42: 759-769, 1997
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Vancomycin: Interactions with a model cell membrane (1997)
    New York : Wiley-Blackwell
    Biopolymers 42 (1997), S. 627-632 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Enkephalin analogues containing β-naphthylalanine at the fourth position (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 179-196 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: To examine the importance of the aromatic side chains of enkephalin on opiate activity, we report the synthesis and conformational analysis of a series of analogues related to enkephalin with β-naphthylalanine in place of phenylalanine at the fourth position. Three linear analogues (Tyr-D-Ala-Gly-(L and D)-β Nal(1)-Leu-NH2 and Tyr-D-Ala-Gly-β Nal(2)-Leu-NH2) were initially synthesized to examine the effect of the substitution on biological activity. The increased activity of these peptides at the μ-opiate receptor, compared to native Leu-enkephalin, prompted us to examine the more conformational constrained analogues, Tr-c[D-A2bu-Gly-(L and D)-β Nal(1)-Leu], incorporating a α,γ-diaminobutyric acid at the second position and cyclization to the carboxylic end of the leucine. These two cyclic analogues provide insight into the necessity for the L chirality of the aromatic residue at position 4. The Tyr-c[D-A2bu-Gly-L-β Nal(1)-Leu] analogue is highly potent and displays a slight preference for the μ receptor. The conformational analysis indicates that despite the high flexibility of the tyrosine side chain, the aromatic rings of the tyrosine and naphthylalanine are relatively distant from each other. The presence of two intramolecular hydrogen bonds help maintain the conformation of the 14-membered backbone ring that keeps the side chains directed away from each other. These findings are in agreement with our model of an extended structure required for μ selectivity and a folded form with close aromatic ring placement for δ selectivity.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290123
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