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  • General Chemistry  (3)
  • conformation  (3)
  • molecular dynamics  (2)
  • 1
    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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  • 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 behaviour of Cα,α-diphenylglycine: folded vs. extended structures in DφG-containing tripeptides (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 4 (1998), S. 21-32 
    Details
    ISSN: 1075-2617
    Keywords: Cα,α-disubstituted amino acids ; crystal structure ; molecular dynamics ; conformation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structures of three fully protected tripeptides containing the Dφg residue (Cα,α-diphenylglycine) in the central position are reported, namely Z-Gly-Dφg-Gly-OMe (a), Z-Gly-Dφg-Aib-OMe (b) and Z-Aib-Dφg-Aib-OMe (c). The molecular conformations are quite unusual because the Dφg residue adopts a folded conformation in the 310-helical region when the following residue adopts a folded conformation of opposite handedness (peptidesbandc). In contrast, the Dφg residue adopts the more frequently observed fully extended conformation when the following residue adopts a semi-extended conformation (peptidea). These findings are in agreement with the theoretical calculations on Ac-Dφg-Aib-NHCH3 and Ac-Aib-Dφg-NHCH3 also reported in this work. © 1998 European Peptide Society and John Wiley & Sons, Ltd.
    Additional Material: 9 Ill.
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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.
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  • 5
    Electronic Resource
    Electronic Resource
    Solution and solid state structure of an aib-containing cyclodecapeptide inhibiting the cholate uptake in hepatocytes (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996), S. 465-478 
    Details
    ISSN: 0006-3525
    Keywords: cyclic decapeptides ; cyclolinopeptide A ; x-ray ; nmr ; conformation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational analysis of synthetic cyclodecapeptide c(Pro-Phe-Phe-Aib-Leu)2 related to the cyclolinopeptide A, in the solid state and solution, has been carried out by x-ray diffraction and nmr spectroscopy. The structure of the monoclinic form obtained from methanol [a = 11.351(5) Å, b = 27.455(2) Å, c = 12.716(8) Å, β = 99.65(3)°; space group P21; Z = 2] shows the presence of six intramolecular NH···CO hydrogen bonds, with formation of four turns (three of type I and one of type III) and two C16 ring structures. All peptide units are trans. The solution structure, as found by nmr, indicates that, at room temperature, the peptide is conformationally homogeneous; the structure determined is perfectly symmetrical and topologically similar to that found in the solid state. The cyclodecapeptide exhibits similar biological activity to cyclolinopeptide A. © 1997 John Wiley & Sons, Inc. Biopoly 40: 465-478, 1996
    Additional Material: 7 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Solution conformational preferences of a peptidic analogue of a natural macrolide (1997)
    New York : Wiley-Blackwell
    Biopolymers 42 (1997), S. 349-361 
    Details
    ISSN: 0006-3525
    Keywords: cyclic peptides ; molecular dynamics ; nmr ; conformation ; FK506 ; FK506 binding proteins ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational behavior in solution of a cyclic peptide with sequence cyclo-(Pro1-Pro2-Dab3 (cHexA)ψ[N7HCO]-Leu4ψ[NHCO]-Suc5-Gly6-) has been throughly investigated with the combined use of nmr and molecular dynamic techniques. The compound, which has been modeled to mimic the FK506 macrolide bound to the FK506 binding protein structure, can be considered as a peptidic analogue of the FK506 system.The synthesis was carried out on a phenylacetoamidomethyl resin using an appropriate protocol for the peptide chain elongation. The conformational properties of the cyclic hexapeptide were studied in DMSO and water. The nmr data in DMSO and restrained molecular dynamics simulations show the presence of two contiguous cis peptide bonds involving the -Gly-Pro-Pro- segment. This segment in water exhibits conformational heterogeneity presenting at least two distinct conformational families, characterized the first by cis-cis and the second by a trans-cis Gly-Pro-Pro configuration; the trans-cis isomer was fully characterized. © 1997 John Wiley & Sons, Inc. Biopoly 42: 349-361, 1997
    Additional Material: 6 Ill.
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