Molecular spectroscopy evidence of berberine binding to DNA: comparative binding and thermodynamic profile of intercalation

Berberine (BH) is an important traditional medicinal herb endowed with diverse pharmacological and biological activities. In this work, the binding characteristics and molecular mechanism of the interaction between the BH and herring sperm DNA were explored by UV-vis absorbance and fluorescence spectroscopy. In the mechanism discussion, fluorescence quenching, absorption spectra, competition experiment, and iodide quenching experiment studies hinted at an intercalative mode of binding for BH to DNA. Fluorescence studies revealed the binding constant (K) of BH-DNA was ～10(4) L·mol(-1). The effects of temperature, chemical denaturants, thermal denaturation, and pH were studied to show the factors of the interaction and provided further support for the intercalative binding mode. The results of thermodynamic parameters ΔG, ΔH, and ΔS at different temperatures indicated that the hydrogen bonds and van der Waals interactions played major roles in the reaction, and the effect of ionic strength indicated that electrostatic attraction between the BH and DNA was also a component of the interaction.