Stacking Interactions of nucleobases: NMR-Investigations I. Selfassociation of N6,N9-Dimethyladenine and N6-Dimethyl-N9-Ethyladenine |
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Authors: | W. Schimmack H. Sapper Dr. W. Lohmann |
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Affiliation: | (1) Abteilung für Biophysikalische Chemie, GSF, D-8042 Neuherberg;(2) Institut für Biophysik der UniversitÄt, D-63 Giessen, Fed. Rep. Germany |
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Abstract: | The selfassociation of N6,N9-dimethyladenine and N6-dimethyl-N9-ethyladenine has been studied by means of NMR technique. The thermodynamic quantities have been calculated using an isodesmic NMR model with three NMR parameters (the monomer shift M and two complex shifts 2 and 3).The dependence of the thermodynamic quantities on the NMR parameters is discussed. Special attention is given to the determination of Mand its temperature dependence.Calculations with 3=2·2 and Mtaken independently of temperature result in an average entropy S=–17.9±1.8 e.u. for N6,N9-dimethyladenine and S=–16.7±1.7 e.u. for N6-dimethyl-N9-ethyladenine and in an average enthalpy H=–7.2±0.6 kcal· mol–1 for both substances investigated.Part of the Ph.D. Theses of W. Schimmack and H. Sapper.Dedicated to Professor Dr. A. Schraub on the occasion of his 65th birthday. |
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Keywords: | Stacking selfassociation NMR Isodesmic Model Enthalpy |
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