Evaluation of the binding effect and cytotoxicity assay of 2-Ethyle-5-(4-methylphenyl) pyrimido pyrazol ophthalazine trione on the calf thymus DNA: spectroscopic, calorimetric and molecular dynamics approaches.

With advances in new drug therapies, it is essential to understand the interactions between drugs and target molecules. In this study, we applied multiple spectroscopic techniques including: absorbance, fluorescence, circular dichroism spectroscopy, viscosity, thermal melting, calorimetric, and Molecular dynamics (MD) simulation in order to study the interaction of 2-Ethyle-5-(4-methylphenyl) pyrimido pyrazol ophthalazine trione (PPF) with calf thymus DNA (ct DNA) in the absence and presence of histone H1. PPF exhibits a high binding affinity toward ct DNA in binary and ternary systems. Besides, the result of binding constant was observed within the range of 104 M-1 , through the achieved fluorescence quenching data, while the values of enthalpy and entropy changes in regards to ct DNA-PPF and (ct DNA-H1) PPF complexes were measured to be -72.54 kJ.mol-1 , -161.14 J.mol-1 K-1 , -85.34 kJ.mol-1 , and -19.023 J.mol-1 K-1 , respectively. Furthermore, in accordance with circular dichroism spectra, the inducement of ct DNA structural alternation was observed during the binding of PPF and H1 in the forms of binary and ternary systems. The essential roles of hydrogen bonding and Vander Waals forces throughout the interaction were suggested by thermodynamic parameters. According to the obtained data, the interaction mode of ct DNA-PPF and (ct DNA-H1) PPF complexes are intercalations binding. Suggested by the MD simulation study, ct DNA-H1 complex caused a reduction in the stability of DNA structure in the presence and absence of ligand, which expresses the fact, that PPF as an intercalating agent can further distort the structure. The achieved information from this study will be quiet helpful in understanding the effects of PPF on the conformational state of ct DNA in the absence and presence of H1 molecule, which seems to be quite significant for clarifying the mechanisms of action and pharmacokinetics.