Binding affinity of pyrano[3, 2-f]quinoline and DNA: spectroscopic and docking approach

The interaction between pyrano[3, 2-f]quinoline (PQ) and calf thymus DNA (CTDNA) using spectroscopic and molecular modeling approach has been presented here. Apparent association constant (1.05×10⁵ L/mol) calculated from UV-vis specta, indicates a moderate complex formation between CTDNA and PQ. The quenching phenomena as obtained from emission spectra of ethidium bromide (EB)-CTDNA by PQ was found to be a dynamic one and the binding constants found to be 8.64, 9.25, 11.17, 12.03 × 10⁴ L/mol at 293, 300, 308, and 315 K. Thermodynamic parameter enthalpy change (ΔH) and entropy change (ΔS), indicates weak force like van der Walls force and hydrogen bonds having the key role in this binding process. The results of circular dichroism (CD) demonstrate that PQ has not induced characteristic changed in CTDNA. Results achieved from UV absorption and fluorescence spectroscopy indicating the binding mode of PQ with DNA seems to be a nonintercalative binding. The theoretical results as originating from molecular modeling showed that PQ possibly will bind into the hydrophobic region of DNA having docking binding energy = -10.03 kcal/mol and the obtained results are in consonance with the inferences obtained from experimental data. This result is important for the better understanding of pharmaceutical aspects of binding affinity of PQ and CTDNA.