General base catalysis vs. medium effects in the hydrolysis of an RNA modelElectronic supplementary information (ESI) available: tables of primary kinetic data and derived rate constants. See http://www.rsc.org/suppdata/p2/b1/b109325h
| Autor: | Anthony J. Kirby, Robert E. Marriott |
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| Rok vydání: | 2002 |
| Předmět: | |
| Zdroj: | Journal of the Chemical Society, Perkin Transactions 2. :422-427 |
| ISSN: | 1364-5471 1472-779X |
| Popis: | The interpretation of buffer catalysis data is always subject to a degree of uncertainty, because changing the concentration of the catalyst necessarily changes the medium. The history of the imidazole-catalysed reactions of ribonucleotide derivatives is a classic illustration of the potential problems, which are complicated further by significant sensitivity to ionic strength and specific salt effects. Results are reported for the hydrolysis of 4-nitrophenoxymethyl uridine 3′-phosphate, which releases the chromophoric p-nitrophenolate on cleavage of the P–OCH2OAr bond. In the case of catalysis by imidazole, a bell-shaped dependence on the buffer ratio is explained in terms of a solvent effect on the background, hydroxide-catalysed reaction. Results for six other amine bases with pKa = 7 ± 1 show that, in this system, non-linear behaviour is the norm rather than the exception. |
| Databáze: | OpenAIRE |
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