Interaction of Chelerythrine Choloride in Acid Buffer with Calf-thymus DNA

The binding of chelerythrine (CHE) iminium to calf-thymus (CT) DNA is characterized by hypochromism and bathochromism in the absorption band, enhancement of fluorescence intensity, increase in fluorescence polarization, and the perturbation of the CD spectra of DNA. These changes are characteristic of intercalation. Scatchard plots constructed from fluorescence titration data gave a binding constant of 5.77×105 and a binding site size of 3,4 base pairs at 25℃. The intercalative interaction is exothermic with a Van’t Hoff enthalpy of -33.7 kJ/mol. In addition, *G =-32.9 kJ/mol, and *S =-2.9 J/mol/K. The intercalation of CHE into the DNA helix is enthalpy-driven.