Viscometric technique has been used to estimate the relative contributions of strong and weak binding modes towards thermal stabilization of the Proflavine-DNA complex. Variation of the ratio of the specific viscosity of the dye-bound DNA to that of the DNA solution (η′sp/η sp) with different dye to DNA-phosphate ratios (D/P) shows that the saturation is attained at D/P value of about 0.2. This effect is more pronounced at lower ionic strengths. Heat-induced helix-coil transition curves at different D/P values at a fixed ionic strength of the buffer reveal a gradual shift towards higher temperature with the increase of D/P and levelling off at D/P of about 0.22. It is suggested that only the strong binding mode causes thermal stabilization of the DNA double helix and the double helix having all the possible intercalating sites saturated by the dye molecules attains the most stable configuration.
© 1946 – 2014: Verlag der Zeitschrift für Naturforschung
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.