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  • 1
    ISSN: 1432-2048
    Keywords: Dinitroaniline ; Rosa ; Herbicide ; Microtubule ; Oryzalin ; Haemanthus ; Taxol ; tubulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of oryzalin, a dinitroaniline herbicide, on chromosome behavior and on cellular microtubules (MTs) were examined by light microscopy and immunogold staining, respectively, in endosperm cells from Haemanthus katherinae Bak. Brief treatments with 1.0·10-8 M oryzalin reduced markedly the migration rate of anaphase chromosomes and 1.0·10-7 M oryzalin stopped migration abruptly. Oryzalin (1.0·10-7 M) depolymerized MTs and prevented the polymerization of new MTs at all stages of the mitotic cycle. The chromosome condensation cycle was unaffected by oryzalin. Endothelial cells from the heart of Xenopus leavis showed no chromosomal or microtubular rearrangements after oryzalin treatment. The inhibition by oryzalin of the polymerization of tubulin isolated from cultured cells of Rosa sp. cv. Paul's scarlet was examined in vitro by turbidimetry, electron microscopy and polymer sedimentation analysis. Oryzalin inhibited the rapid phase of taxol-induced polymerization of rose MTs at 24°C with an apparent inhibition constant (K i ) of 2.59·106 M. Shorter and fewer MTs were formed with increasing oryzalin concentrations, and maximum inhibition of taxol-induced polymerization occurred at approx. 1:1 molar ratios of oryzalin and tubulin. Oryzalin partially depolymerized taxol-stabilized rose MTs. Ligand-binding experiments with [14C]oryzalin demonstrated the formation of a tubulin-oryzalin complex that was time- and pH-dependent. The tubulin-oryzalin interaction (24°C, pH 7.1) had an apparent affinity constant (K app) of 1.19·105 M-1. Oryzalin did not inhibit taxol-induced polymerization of bovinebrain MTs and no appreciable binding of oryzalin to brain tubulin or other proteins was detected. The results demonstrate pharmacological differences between plant and animal tubulins and indicate that the most sensitive mode of action of the dinitroaniline herbicides is the direct poisoning of MT dynamics in cells of higher plants.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 1741-1746 
    ISSN: 0887-624X
    Keywords: electrically conducting polymers ; 3,3′-dimethoxy-2,2′-bithiophene ; 3-methoxythiophene ; synthesis ; polymerization ; electrochemistry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new electroactive polymer, namely poly(3,3′-dimethoxy-2,2′-bithiophene) has been prepared by voltammetric polymerization of 3,3′-dimethoxy-2,2′-bithiophene. Due to a different coupling pattern (equivalent to “head-to-head,” and “tail-to-tail” coupled alkoxythiophene rings), poly(3,3′-dimethoxy-2,2′-bithiophene) exhibits different voltammetric properties than the corresponding “head-to-tail” coupled polymer, i.e., poly(3-methoxythiophene). Poly(3,3′-dimethoxy-2,2′-bithiophene) gives very sharp oxidation and reduction peaks indicating an abrupt insulator to conductor transition. This hypothesis was corroborated by the studies of relative resistance as a function of electrode potential. Sharper and better-defined redox peaks may indicate better stereoregularity of poly(3,3′-dimethoxy-2,2′-bithiophene) as compared to poly(3-methoxythiophene) since in this compound the 5,5′-coupling positions are geometrically equivalent and no coupling defects are expected. © 1992 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 1761-1765 
    ISSN: 0887-624X
    Keywords: polythiophenes ; soluble ; steric hindrance ; UV spectroscopy ; nuclear magnetic resonance ; high resolution in solid state ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 4
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Interaction of carbon compounds with transition metal surfaces results, under appropriate conditions, in the formation of a number of carbon-containing species of different character. In the present work, the pattern recognition method (the k-nearest neighbour rule) together with AES was applied to study the carbonaceous residues after adsorption of acetylene and ethylene at the surface of polycrystalline nickel and platinum. The above method identifies the residues by comparison to different samples of polyacetylenes. Identification is based on analysis of the KLL Auger spectra shape recorded for carbon atoms. As hypothetical oligomers, polyacetylenes with different conjugation lengths were chosen (7-105 Å). The applied method confirmed that ethylene and acetylene oligomerize at the nickel surface. Carbonaceous residues were recognized as the polyacetylenes with the longest conjugation lengths (105 Å). At the platinum surface the oligomerization process was also observed, but to a much smaller extent (average conjugation length equal to 15 Å).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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