992 resultados para Hahnemann, Samuel, 1755-1843.


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Aus: Mittheilungen aus d. Verein zur Abwehr des Antisemitismus

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​2-Aminopurine (​2AP) is a fluorescent isomer of ​adenine and has a fluorescence lifetime of ~11 ns in water. It is widely used in biochemical settings as a site-specific fluorescent probe of DNA and RNA structure and base-flipping and -folding. These assays assume that ​2AP is intrinsically strongly fluorescent. Here, we show this not to be the case, observing that gas-phase, jet-cooled ​2-aminopurine and ​9-methyl-2-aminopurine have very short fluorescence lifetimes (156 ps and 210 ps, respectively); they are, to all intents and purposes, non-fluorescent. We find that the lifetime of ​2-aminopurine increases dramatically when it is part of a hydrate cluster, 2AP·(H2O)n, where n = 1–3. Not only does it depend on the presence of water molecules, it also depends on the specific hydrogen-bonding site to which they attach and on the number of H2O molecules at that site. We selectively microhydrate ​2-aminopurine at its sugar-edge, cis-amino or trans-amino sites and see that its fluorescence lifetime increases by 4, 50 and 95 times (to 14.5 ns), respectively.

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von Tassilo Hoffmann

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door J. S. da Silva Rosa

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von [Abraham] Lewinsky

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hrsg. vom Verband d. Vereine f. Jüdische Geschichte u. Litteratur in Deutschland. Mit Beitr. von W. Bacher [u.a.]

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nach e. arabischen Handschrift mit dem Fragmente e. hebräischen Übers. kritisch hrsg. u. ins Dt. übertr. von Felix Kauffmann

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Mit Exlibris: Aus der Bibliothek A. Berliners ... der Frankfurter Stadtbibliothek geschenkt 1899