Interaction of calf thymus DNA with N,N'-Bis(3,4-dihydroxybenzylidene)-1,2-diaminobenzene ligands

In the present study, at first, N,N'-bis(3,4-dihydroxyhenzylidene)-1,2-diaminobenzene (BDBDAB), has been synthesized by combination of 1,2-diaminobenzene and 3,4-dihydroxybenzaldehyde in a solvent system. These ligand containing ortho-quinone functional groups were characterized using UV-VIS and IR spectroscopies. Subsequently, the interaction between native calf thymus deoxyribonucleic acid (ct-DNA) and BDBDAB was investigated in 10 mM Tris-HCl buffer solution, pH 7.2, using UV-visible absorption and fluorescence spectroscopies, thermal denaturation technique, viscosity measurement, and cyclic voltametry. From spectrophotometric titration experiments, the binding constants of BDBDAB with double stranded DNA were found to be (0.9 +/- 0.1) x 10(4) M-1. The magnitude of the interaction between the ligands and DNA can be quantified by using the Stern-Volmer equation. From the plot of I (0)/I versus [DNA]/[BDBDAB] the quenching constants (K (SV)) were obtained and found to be 5.6 +/- 0.2. Thermal denaturation experiments represent the increasing of melting temperature of DNA (about 3.2A degrees C) due to binding of BDBDAB. There is no increasing of viscosity was observed in addition of BDBDAB to DNA. The electroactivity of the quinone moiety in N,N'-bis(3,4-dihydroxybenzylidene)-1,2-diaminobenzene bound to DNA could be employed as cyclic voltametry to obtain binding constant. These results suggest that interaction with the grooves could be the principal mode of binding of BDBDAB to double stranded ct-DNA.