Exploring the interaction of copper-esculetin complex with ct-DNA: Insight from spectroscopic and docking studies

Abstract

Copper complex of esculetin, a dihydroxy coumarin, was synthesized with an aim to study the interaction with ct-DNA. The synthesized copper esculetin (Cu-esculetin) complex was characterized by common spectroscopic techniques like IR, HRMS and EPR. The interaction of Cu-esculetin complex with ct-DNA was studied by using steady state absorbance, fluorescence and circular dichroism spectrometer. From these photophysical changes it was indicated that Cu-esculetin complex binds to ct-DNA and the binding constant was estimated as 1.0 x 104 M−1. Competitive fluorescence displacement studies suggested that Cu-esculetin complex binds in the groove position of ct-DNA. The nature of groove binding was further supported by iodide quenching and viscosity study. In order to support the experimental observation, molecular docking studies were performed between Cu-esculetin complex and DNA. Docking studies revealed that the Cu-esculetin complex binds in to the minor groove of the DNA and then bends in such a way that it follows the curvature of the DNA groove. Apart from the hydrophobic interaction, H-bonding interaction and pi-anion interaction was also observed. The interaction strength was estimated as −4.96 kcal/mol. In summary, the above findings may provide useful information to assist in the design of new metal complexes having enhanced biological activity.