NA-23 AND LI-7 NMR SPIN-LATTICE RELAXATION MEASUREMENTS IN THE STUDY OF INTERCALATION IN DNA

Sodium-23 spin-lattice relaxation rate (the reciprocal relaxation time) measurements have been used to study the intercalation of 9-aminoacridine in calf thymus DNA. The results are analyzed by a two state model based on the counterion condensation theory and a theory for the quadrupolar relaxation of counterions in polyelectrolyte solutions. It is shown that change of the solvent from H2O to D2O has a negligible effect on the intercalation process. Furthermore, an attempt is made to analyze the dependence of the Li-7 spin-lattice relation rate on intercalation of 9-aminoacridine in LiDNA. It is shown that both quadrupolar and dipolar mechanisms contribute to the bound Li-7 relation rate, and that both these contributions are reduced upon intercalation of 9-aminoacridine.