Circular Dichroic Probe of the Competition for Drug and Dye Between Anionic Polymers DNA and Heparin. I

Abstract The changes in the absorption and CD spectra of daunomycin caused by DNA and heparin (Hep) are characteristically different for the two biopolymers. These changes have been utilized to study the competition for the drug between DNA and Hep. The results show that DNA can totally take away the drug bound to Hep; the intercalating ability of DNA being the decisive factor. The spectrophotometric and dichroic probes also show that the same intercalating ability helps DNA to strip off acridine orange bound to Hep, a much stronger polyelectrolytic chromotrope than DNA. It is essential that the concentration of DNA be at least four times the concentration of the ligand to overcome the competition with Hep.