An insight of spirooxindole-annulated thiopyran – DNA interaction: spectroscopic and docking approach of these biological materials

Abstract

The interaction of spirooxindole-annulated thiopyran (STP) with calf thymus DNA (CTDNA) has been studied here using spectroscopic and molecular modeling. A static mode of quenching has been observed from the fluorescence quenching mechanism of ethidium bromide (EB)–CTDNA by STP. A moderately strong binding affinity between STP and CTDNA has been observed (3.98, 2.51, 0.79 × 103 L mol−1 at 293, 303 and 313 K) from the fluorimetric data. Thermodynamic parameter, enthalpy change (ΔH) and entropy change (ΔS), suggested van der Walls force and hydrogen bonds played the main role in the binding of STP to CTDNA. Furthermore, circular dichroism (CD) revealed that STP did not disturb native conformation of CTDNA. As observed in the UV absorption and fluorescence spectroscopy the binding mode of STP with DNA was indicative of a non-intercalative binding, which was supposed to be a groove binding. Above mentioned results are found to be in consonance with molecular docking simulations and supports the STP–CTDNA binding with docking binding energy of -11.00 kcal/mol.