Synthesis, characterization and interaction studies of 2,7- naphthalenediol,2-[(4-Bromophenyl)]azo, with calf thymus deoxyribonucleic acid (ct-DNA)

In this study, at first, an azo dye, 2,7-naphthalenediol,2-[(4-Bromophenyl)azo (BPAND) as aligand has been synthesized by addition of p-Bromoaniline to the modified montomorilloniteK10 clay. This ligand was characterized using 1H-NMR, UV-Vis and IR spectroscopies.Subsequently, its interaction with calf thymus deoxyribonucleicacid,ct-DNA was investigated in5 mM phosphate buffer solution, pH=7 using UV-Vis absorption, thermal denaturation andviscosity measurement. From spectrophotometric titration experiments, the binding constant ofBPAND with ct-DNA was found to be (2.89±0.2)×107 M-1 at 25°C. In order to determinechanges in thermodynamic properties such as binding constant, Gibbs free energy, bindingenthalpy and binding entropy, this experiment was done at various temperatures. The enthalpyand entropy changes were -2.852±0.634 kJ/mol and -814.065 ±2.52 J/mol.K,respectively.Thermal denaturation experiments show the increasing of melting temperature of ct-DNA (about 0.06°C less than 0.6) due to binding of BPAND ligand. From these results, themechanism and the stoichiometry of binding were determined. The results revealed that thisinteraction is exothermic (negative enthalpy change) along with negative entropy change.Therefore, the driving force in these interactions is enthalpy and the process is enthalpy-drivenand suggests that the main driving force for the ct-DNA-BPAND complex formation is beingVan der Waals or hydrogen binding.

Keywords:

Deoxyribo nucleic acid , azo dye , thermodynamic , UV/Vis spectroscopy