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  • Conformational analysis  (4)
  • Benzene ring, distortion of  (2)
  • Monolayer cultures  (2)
  • 1
    Electronic Resource
    Electronic Resource
    The Conformational Behaviour of 10-Substituted Spiro[4.5]decanes (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 551-561 
    Details
    ISSN: 0009-2940
    Keywords: Conformational analysis ; Spiro[4.5]decanes ; Allylboration, transition state models ; Ketals, chiral, cleavage by Lewis acids ; Calculations, MNDO and SYBYL ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational behaviour of 10-X-substituted 1,4-dioxa-and 1,4,6-trioxaspiro[4.5]decanes 1 - 4 has been studied by 13C-, 19F- and 1H-NMR spectroscopy. Two X-ray analyses (of 2a,e) are presented, and their implications to cleavage reactions of chiral acetals are discussed. Participation of twist boat forms in the conformeric equilibrium of at least 1c has been made plausible by observing 13C,19F-NMR coupling constants. The ratios of axial to equatorial conformer in 1 - 4 have been calculated by molecular mechanics.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240322
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  • 2
    Electronic Resource
    Electronic Resource
    Structures of Tris(donor)-Tris(acceptor)-Substituted Benzenes, 2.Potassium Salts of Trinitrophloroglucinol (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 1727-1731 
    Details
    ISSN: 0009-2940
    Keywords: Conformational analysis ; Benzene, donor-acceptor-substituted ; Benzene ring, distortion of ; Hydrogen bonding, intramolecular ; Calculations, AM1 ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The X-ray crystallographic analysis of the mono-, di-, and tri-potassium salts 2b - d of trinitrophloroglucinol (2a) show their benzene rings to become considerably more distorted on successive deprotonation. A parallel increase in C - C, and a decrease in C - O and C - N bond lengths leading to a radialenetype structure is also observed. For 2b, two chemically different molecules are found in the crystal which differ in their hydrogen-bond pattern as well as in their average bond lengths and deviation of their benzene rings from planarity. AM1 calculations show that for 2b,d a multitude of structures, differing widely in the deviation of their benzene cores form planarity, can exist within a small energy range ( 〈 3 kcal/mol). The experimental and computational results are discussed in terms of a model that emphasizes “push-pull” interactions as the main cause for the distortions of the benzene rings in compounds of type 1 and 2.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240810
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  • 3
    Electronic Resource
    Electronic Resource
    Structures of Tris(donor)-Tris(acceptor)-Substituted Benzenes, 1. Steric, Polar and Hydrogen-Bonding Effects in TriaminotrinitrobenzenesDedicated to Professor Horst Prinzbach on the occasion of his 60th birthday. (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 1719-1725 
    Details
    ISSN: 0009-2940
    Keywords: Conformational analysis ; “Push-pull” interaction ; Benzene ring, deformation to boat and twist-boat forms ; Calculations, AM1 ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The X-ray analyses of three 1,3,5-tris(alkylamino)-2,4,6-trinitrobenzenes (alkyl = iPr, neopentyl, tBu; 1d - f) show their benzene rings to be highly distorted towards boat (1d iPrNH2) and twist-boat (1e,f) forms. The patterns found for intramolecular donor-acceptor interaction and hydrogen bonding depend on the conformation of the benzene core: boat structures have the “stern” amino group strongly donating to the “bow” nitro group in the para position and two stronger hydrogen bonds between the substituents on the “side” of the boat, whereas twist-boat structures have two amino groups strongly interacting with the nitro group in their common ortho position to which there are also two strong hydrogen bonds. 1d - f undergo conformational exchange on the 13C-NMR time scale at room temperature. Cooling to 220 K allows detection of all carbon signals and shows C1 symmetry to be present. AM1 calculations reproduce the distortions of 1d - f. Computations on several 2,4,6-tridonor-substituted 1,3,5-trinitrobenzenes indicate that the pronounced deviations from planarity in 1a - f originate largely from electronic effects.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240809
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  • 4
    Electronic Resource
    Electronic Resource
    Structures of tris(donor)-tris(acceptor)-substituted benzenes, 5. Organization and reorganization of the π system in a symmetric tris(alkylamino)trinitrobenzene: balance between cyanine and quinoid structuresDedicated to Prof. Dr. Reinhard W. Hoffmann on the occasion of his 60th birthday. (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2127-2131 
    Details
    ISSN: 0009-2940
    Keywords: Conformational analysis ; Benzene, donor-acceptor-substituted ; Benzene ring, distortion of ; Cyanine concept ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The π system of 1a may adopt markedly different electronic structures with concomitant strong conformational preferences for the six-membered ring. Neutral 1a can exist either in a quinoid boat form or as a twist boat, formally resulting from the coupling of an anionic with a cationic trimethinecyanine. Deprotonation gives a rigid quinoid boat structure; protonation occurs at a ring atom to form an equally rigid cyanine.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260924
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  • 5
    Electronic Resource
    Electronic Resource
    Morphological changes induced by sodium bromide in murine neuroblastoma cells in vitro (1982)
    Springer
    Cell & tissue research 222 (1982), S. 379-388 
    Details
    ISSN: 1432-0878
    Keywords: Neuroblastoma ; Monolayer cultures ; Sodium bromide ; Membrane dynamics ; Specialized contacts ; Synaptogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Sodium bromide was applied in vitro to mouse neuroblastoma cells of different ages for short and long periods (2h to 10 days). The changes observed light-and-electron microscopically were similar to those described earlier after GABA treatment. Coated vesicles proliferated and originated by pinching off from the Golgi complex and from the rough endoplasmic reticulum. Numerous coated vesicles were continuous with the plasma membrane, especially near zones in which electron-dense material aggregated at the inner aspect of the plasmalemma. Small invaginations, similar in ultrastructure to coated vesicles, were also formed. It is unclear whether the coated vesicles or the dense plasmalemma invaginations contribute to the “undercoating” by fusing with the adjacent electron-dense plasma membrane. There was a distinct increase in the number and area of specialized contacts (intermediate junctions and zonulae adhaerentes) between cells and their processes. A floccular or filamentous electron-dense substance varying in amount and appearance was occasionally seen between the contacting membranes. Varicosities of terminal swellings of cell processes contained vesicles of variable size, shape and density, and also profiles of the smooth endoplasmic reticulum. Under the influence of sodium bromide, similar to the effect of GABA, mitochondria appeared within the varicosities, and primitive contacts (intermediate junctions) were formed between the terminal swellings and potential postsynaptic elements, which were absent in controls. Additionally, dense-core vesicles proliferated and aggregated at the cell periphery. They were often arranged linearly below the plasma membranes of perikarya and processes, and surrounded by a highly electron-dense substance. The similarity of the present findings to those obtained after GABA treatment and their relation to synaptogenesis are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213219
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of GABA-Administration on murine neuroblastoma cells in culture (1981)
    Springer
    Cell & tissue research 218 (1981), S. 567-579 
    Details
    ISSN: 1432-0878
    Keywords: Neuroblastoma cells, murine ; Monolayer cultures ; GABA ; Increased membrane dynamics ; Specialized contact formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary (Gamma aminobutyric acid) GABA was applied to cultures of mouse neuroblastoma cells of different ages at concentrations ranging from 10-4 to 10-6 M. The cultures were exposed to GABA either in short term experiments for 2 h to 2 days or for longer periods by adding the substance twice within 10 days at 5-day intervals. The following effects were observed: (1) There was a strong proliferation of coated vesicles, appearing to derive from the Golgi complex and the rough endoplasmic reticulum (RER), and also showing all intermediate stages of fusion and pinching off from the plasma membranes. (2) In numerous areas, electron-dense material aggregated at the inner aspect of the plasma membrane and around small invaginations of the plasmalemma. (3) The number and area of specialized contacts increased between cells and their processes. (4) Similar to cultures free of GABA, varicosities and terminal swellings of the cells and their processes were filled with small round vesicles, 40–60 nm in diameter, or with smooth, very large, empty-appearing vesicular inclusions, or with flat pleiomorphic vesicles. In addition, mitochondria and some formations of the smooth endoplasmic reticulum (SER) appeared, and primitive contacts (symmetrical densities) were formed. (5) Dense-cored vesicles were found peripherally and linearly arranged, surrounded by an electron-dense substance. (6) Electron-dense material of unknown origin was seen between cells or their processes near the peripherally arranged dense-cored vesicles. Exogenous GABA may play a specific role in the early stages of synaptogenesis, since it showed a positive effect on the neuroblastoma cells, which in the absence of GABA are only capable of forming primitive or immature presynaptic elements. The significance of the peripheral accumulation of dense-cored vesicles, accompanied by an amorphous, electron-dense substance occurring both intra- and extracellularly is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210116
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