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  • 1
    ISSN: 1432-1327
    Keywords: Key words Paradigm ; Deoxyribonucleic acid ; Electron transfer ; Chemistry at a distance ; Molecular wire
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: It is typical of the present time, that two practically unknown chemists, one from a veterinary college and the other from an agricultural institute, pass judgement on the loftiest problems of Chemistry, those which will probably never be solved, particularly the question of the position of atoms in space, and they undertake such a paradigm with an impudence and assurance that absolutely astonish the true scientist H. Kolbe [1] New paradigms and new truths in science are not usually adopted because opponents are eventually convinced of their persuasive character, but, more often, because opponents gradually die; the new paradigms are readily adopted by the new generation of students as the laws of nature, just as the dead opponents accepted the old paradigm M. Planck [2]
    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 25 (1987), S. 259-269 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The quenching of pyrene fluorescence by nitromethane, Tl+, Cu2+, I-, and 4-dimethylaminopyridine (DMAP) in aqueous solutions of a pyrene substituted poly(acrylic acid) (1) was influenced by the “polyelectrolyte effect” of 1. The efficiency of quenching in solutions of 1 was measured in terms of the Stern-Volmer constants for dynamic and static quenching which were obtained from comparison of the intensity and lifetime of pyrene fluorescence in solutions of 1 and a monomer model compound. The efficiency of quenching in solutions of 1 was always greater at high pH (9) in comparison to that at low pH (4). The ionization of carboxylic groups in 1 caused an expansion of the polymer mainchain and concomitant exposure of the pyrene molecules to the aqueous phase and quencher. The polyanion domain of 1 favored the condensation of cationic quenchers and could account for very efficient quenching in case of Cu2+ and Tl+. A very efficient quenching of pyrene fluorescence in solutions of 1 by DMAP at high pH was attributed to the hydrophobic interactions of DMAP and pyrene moiety. The iodide ions were less efficient quenchers of pyrene fluorescence due to electrostatic repulsion from the polyanion. The efficiency of quenching by nitromethane was not significantly affected by ionization of the carboxylic groups in 1.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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