Studies on the Binding Mode of Pinacyanol Chloride to Nucleic Acids

The interaction of pinacyanol chloride (PC) with nucleic acids has been investigated by a series of experiments. Extensive hypochromism, appreciable peak shifts, isosbestic points and new peaks of the product of binding to nucleic acids in the spectra were observed. They showed that the interaction between PC and nucleic adds occurred. The results from absorption spectra of DNA, DNA melting, electrophoresis and fluorescence polarization studies have indicated that PC binds to DNA in nonintercalative way. Consistent with the nonintercalation, the studies of fluorescence titration and absorption titration specified that the binding of PC to nucleic acids occurred by an outside stacking binding, in which nucleic acids served for acting templates. The fact that the new absorption peaks of bound PC at ca. 485 nm are just close to the absorption bands of H-aggregate of PC at high concentrations without DNA further supports the outside stacking binding mode. In addition, other evidence indicated that the interaction between PC and nucleic acids is not purely electrostatic.