Abstract
Abstract The dependence of the PMR spectra of three purine nucleosides (inosine, adenosine and deoxyadenosine) on temperature, concentration and addition of benzene (0.12 molal) has been investigated in aqueous solution. The interaction of benzene with the nucleosides is deduced from the spectra. Enthalpies of self association have been determined as 2.2± 0.1 kcal·mole-1 for dA and I. The corresponding values obtained for hetero association with benzene are 2.7 ± 0.2 kcal·mole-1 for dA and 2.3± 0.2 kcal·mole-1 for I. The formation of edge to face complexes is concluded. Additional evidence for this type of hetero association has been obtained from the concentration and solvent dependence of the nuclear Overhauser enhancements (NOE) of solutions of the nucleosides. The enhancement factors of aqueous solutions of dA and I depend on the concentrations of the nucleosides. In solutions containing I the NOE found previously in DMSO and the NOE observed in D2O differ significantly 1. The results obtained can be explained by a change of the average glycosyl torsion angle of approximately 10° to 15° in the two solvents.
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