[hyperchromic spectra of DNA complexes with phenosafranine and distamycin A]

Least squares have been applied to study the hyperchromic spectra of thermal denaturation of the complexes of DNA with distamycin A and phenosafranine. Respective components of hyperchromic spectra were found and used to describe the melting of A.T and G.C base pairs and the dissociation of the dye. The interaction of distamycin A with DNA is A.T-specific; this specificity is manifested by inversion of stability of A.T. and G.C base pairs in the course of thermal denaturation. In contrast interaction of phenosafranine with DNA shows only little A.T-specificity. The migration of the ligand is followed as a function of temperature, maximum concentration of the bound ligand is attained at 55-57 degrees for phenosafranine and 65-68 degrees for distamycin A.