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  • 1
    Electronic Resource
    Electronic Resource
    The crystal and molecular structure of cyclo-[-(D-Val-Hyi-Val-D-Hyi)3-] (meso-valinomycin, C60H102N6O18) (1979)
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 2145-2166 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of the valinomycin analog, cyclo-[(-D-Val-Hyi-Val-D-Hyi-)3-] (meso-valinomycin, C60H102N6O18) has been determined by direct x-ray diffraction procedures. The crystals are triclinic, space group P1, number of molecules per unit cell Z = 1, and cell parameters a = 11.831, b = 13.815, c = 14.889 Å, α = 109.54°, β = 116.10°, γ = 98.89°. The atomic coordinates for the C,N,O atoms were refined in the anisotropic thermal motion approximation and for the H atoms in the isotropic approximation to R = 0.07.The structure is centrosymmetric and has a threefold axis of pseudosymmetry. The depsipeptide chain is in the form of a bracelet stabilized by six identical intramolecular 4 → 1 hydrogen bonds between the amide C=O and NH groups. The ester carbonyls are oriented towards the symmetry axis, their O atoms forming an ellipsoidal molecular cavity. The isopropyl side chains are located on the molecular periphery. The structure found differs considerably from the conformation of the crystalline naturally occurring antibiotic, valinomycin, but completely resembles that of valinomycin and meso-valinomycin in nonpolar solvents. In the crystal, meso-valinomycin molecules form stacks. The molecular cavities situated in the stacks one above the other along the pseudo-C3 axis form a continuous channel, the internal surface of which is lined by O atoms. The possible conformations of depsipeptides of the valinomycin series and their mode of action in membranes are discussed in the light of the data obtained.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1979.360180906
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  • 2
    Electronic Resource
    Electronic Resource
    The crystal and molecular structure of a valinomycin analogue cyclo[(D-Val-L-Lac-L-Ala-D-Hyi)2 (D-Val-L-Lac-L-Val-D-Hyi)] · H2O (C50H82N6O18 · H2O) (1997)
    New York : Wiley-Blackwell
    Biopolymers 42 (1997), S. 651-658 
    Details
    ISSN: 0006-3525
    Keywords: x-ray crystallography ; ionophore ; valinomycin analogue ; crystal and molecular structure ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal and molecular structure of the valinomycin analogue, cyclo [(D-Val-L-Lac-L-Ala-D-Hyi)2 (D-Val-L-Lac-L-Val-D-Hyi)] has been solved by x-ray direct methods using the “Shake and Bake” procedure. The crystals, grown from a mixture of octane/CH2Cl2, belong to space group P21 (Z = 4 ) with cell parameters a = 10.29, b = 32.08, c = 18.73 Å β = 97.05°, and contain two molecules per asymmetric unit. After anisotropic refinement the standard reliability factor was R1 = 0.058. The conformations of both independent molecules is similar to that observed for isoleucinomycin, cyclo [-(D-Ile-L-Lac-L-Ile-D-Hyi)3] [V. Z. Pletnev et al. (1980) Biopolymers, Vol. 19, pp. 1517-1534]. The structure has an asymmetric conformation stabilized by six intramolecular H bonds, five bonds being of the 4 → 1 type and one bond being of the 5 → 1 type. One water molecule is caged in the internal cavity of each cyclodepsipeptide. This conformation could represent an intermediate state between free and complexed forms of valinomycin. © 1997 John Wiley & Sons, Inc. Biopoly 42: 651-658, 1997
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular conformation of a D,L stereoisomeric analogue of valinomycin, cyclo[-(L-Val-L-Hyi-L-Val-D-Hyi)2-(D-Val-L-Hyi-L-Val-D-Hyi)-] (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 417-423 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of a synthetic analogue of valinomycin, cyclo[-(L-Val-L-Hyi-L-Val-D-Hyi)2-(D-Val-L-Hyi-L-Val-D-Hyi)-] ([L-Val1, L-Val5]meso-valinomycin), C60H102N6O18, has been determined. Crystals grown from petroleum ether are orthorhombic, space group P212121, with cell parameters a = 16.41(1), b = 18.76(1), c = 25.86(1) Å, and Z = 4. The atomic coordinates for nonhydrogen atoms, except those of terminal carbons on one side chain, were refined in the anisotropic thermal motion approximation. The coordinate parameters of the H atoms were incorporated into the structure factor calculations at geometrically expected positions. Values of the standard and weighted R factors after refinement are 0.074 and 0.083, respectively. The crystal structure of the molecule is asymmetric and adopts a conformation with four 4 → 1 type and one 6 → 1 type intramolecular hydrogen bonds between amide nitrogens and carbonyl oxygens. Valinomycin binds potassium more than 100 times strongly than the D,L Stereoisomeric analogue, as a result of a different spatial orientation of potentially interacting carbonyl groups.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310407
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  • 4
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of the depsipeptide ionophore Hexadecaisoleucinomycin, cyclo-[-(D-Ile-L-Lac-L-Ile-D-Hyi)4-] (C80H136N8O24) (1992)
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 819-827 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of a synthetic depsipeptide ionophore hexadecaisoleucinomycin, cyclo[-(D-Ile-L-Lac-L-Ile-D-Hyi)4-] (C80H136N8O24), has been determined by single crystal x-ray diffraction techniques. The crystals are orthorhombic, space group P212121, number of molecules per unit cell z = 4, and cell parameters a = 11.195, b = 17.853, c = 54.835 Å. The values of the standard ( R) and weighted ( Rw ) discrepancy factors after refinement are 0.122 and 0.135, respectively. The structure is characterized by an elongated bracelet form with a twofold axis of pseudosymmetry. It is stabilized by eight intramolecular 4 → 1 hydrogen bonds between the amide C=O and N—H groups. The ester carbonyls are directed toward the inside of the molecule, their oxygen atoms forming an ellipsoidal internal cavity. The side chains are located on the molecular periphery. The conformational states of hexadecaisoleucinomycin in solution are discussed in the light of the data obtained.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360320710
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular structure of cyclo[-(D-Val-L-Hyi-L-Val-D-Hyi)2-] revealed by X-ray analysis (1992)
    New York : Wiley-Blackwell
    Biopolymers 32 (1992), S. 757-764 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of a synthetic analogue of valinomycin, cyclo [-(D-Val-L-Hyi-L-Val-D-Hyi)2-] (octa-meso-valinomycin) (I) (C40H68N4O12 · 1.5 · C4H8O2, Mr = 937.01 + 88.10), has been determined. Crystals grown from dioxane are monoclinic, space group P21/a, with cell parameters a = 21.487(8), b = 16.836(5), c = 16.089(4) Å, β = 111.70(4), and Z = 4. The atomic coordinates for nonhydrogen atoms were refined in the anisotropic thermal motion approximation. H atom positions were included in the structure factor calculations at their geometrically expected positions. Values of the standard and weighted R factors after refinement are 0.11 and 0.13, respectively. The conformation of the depsipeptide crystallized from dioxane is different from that crystallized from chloroform (II). The molecule adopts a rectangular shape with two type IV β-turns containing a hydrogen bond and possesses pseudorotational symmetry. The side chains are located on the molecular periphery. The orientation of the carbonyl groups of the molecule is not conducive for efficient metal-ion coordination and in the observed conformation cannot behave as an ionophore.In the crystal the molecules form infinite chains parallel to the c axis, and are stabilized by two intermolecular hydrogen bonds that are shorter and have better geometry than the intramolecular hydrogen bonds.A φ/Ψ plot for dodecadepsipeptides with a (DLLD)3 sequence has well-defined areas for Val and Hyi residues only in cases when the crystals have been grown from nonpolar or medium-polar solvents. The Φ/Ψ plot for octadepsipeptides crystallized from chloroform (II) shows this behavior also. There also is a correlation between the polarity of the solvent from which crystals of octa-meso-valinomycin or valinomycin analogues with a (DLLD) sequence of configuration have been grown and the number of the intramolecular hydrogen bonds that are formed. The more polar the solvent the fewer the number of intramolecular hydrogen bonds.Empirical energy calculations on octa-meso-valinomycin indicate that for isolated molecules, the energy of the bracelet form (II) is 4.7 kcal/mole lower than that of the rectangular form (I).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360320705
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  • 6
    Electronic Resource
    Electronic Resource
    The X-ray structure of the monoclinic crystal form of [D-Hyi2, L-Hyi4]meso-valinomycin (1997)
    New York : Wiley-Blackwell
    Biopolymers 42 (1997), S. 645-650 
    Details
    ISSN: 0006-3525
    Keywords: valinomycin analogue ; ionophore ; x-ray direct methods ; structure and function ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation and intermolecular association of [D-Hyi2, L-Hyi4]meso-valinomycin {cyclo[-D-Val-D-Hyi-L-Val-L-Hyi- (D-Val-L-Hyi-L-Val-D-Hyi)2-], C60H102N6O18} in a crystal form obtained from ethanol solution has been determined by x-ray crystallography. Two depsipeptides and one ethanol molecule per asymmetric unit crystallize in space group P21 (Z = 4); a - 14.579, b = 39.795, c = 13.928 Å, β = 116.90, R1 = 0.0757. The molecular conformation is very similar to that observed in the trigonal P32 crystal form obtained from acetone solution [V. Z. Pletnev et al. (1991) Biopolymers, Vol. 31, pp. 409-415]. Both independent molecules in the crystal adopt a similar distorted bracelet structure with a sterically inaccessible, partially formed, ion-binding center that is stabilized by six 4 → 1 type H bonds. The observed conformation accounts for the inability of the molecule to complex ions. Close examination of the three crystallographically independent molecules reveals that differences in the backbone conformation associated with solvent interaction are significantly larger than those associated with hydrophobic van der Waals interactions of crystal packing.© 1997 John Wiley & Sons, Inc. Biopoly 42: 645-650, 1997
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of the centrosymmetric meso-valinomycin analogue - cyclo (D-Val-D-Hyi-D-Val-L-Hyi-L-Val-D-Hyi-L-Val-L-Hyi-L-Val-D-Hyi-L-Val-L-Hyi) (C60H102N6O18) (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 615-621 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of cyclo (D-Val-D-Hyi-D-Val-L-Hyi-L-Val-D-Hyi-L-Val-L-Hyi-L-Val-D-Hyi-L-Val-L-Hyi)-2H2O has been solved by x-ray direct methods. The crystals (grown from a mixture of octane / CH2C12) are an orthorhombic, centrosymmetric space group Pbca, cell parameters a = 11.458(2). b = 25.613(3). c = 23.691(3) Å. Z = 4; therefore the molecule lies on a center of inversion in the cell. The atomic coordinates for the C, N, and O atoms were refined in the anisotropic thermal motion approximation (allowing for II-atom contribution to Fcal) to a standard R- factor value of 0.081. In contrast to meso-valinomycin, the analogue under study does not adopt an octahedral cage bracelet conformation. It has an unusual centrosymmetric elongated form with two type II terminal β-bends formed by N—H-C=O 4 → 1 type intramolecular H bonds. Two symmetry-related water molecules reside in the elongated molecular cavity of the centrosymmetric depsipeptide ring. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360360507
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