Viscometric studies on the stability of DNA-proflavine complex.

The binding of proflavine to native DNA increased its stability against thermal denaturation as measured by viscometric method. Up to a moderate ionic strength of 0.058 m , the melting temperature of the complex increased almost linearly with the increase of dye concentrations and a saturation was reached when one proflavine molecule was added per four to five DNA-Phosphates {DIP c^0 .2 ). The extent of stabilization (ATm) produced by dye binding decreased gradually with the increase of ionic strength and no stabilization effect was observed at an ionic strength of about 0.3 m . The maximum melting temperature attained by Proflavine binding was almost in­ dependent of the ionic strength of the medium. The same maximum value was reached as obtained simply by increasing the sodium ion concentration.