Agarose gel electrophoresis, absorption, fluorescence, viscosity, and circular dichroism (CD) have been used in exploring the interaction of terbium(III) complex, [Tb(bpy)2Cl3(OH2)] where bipy is 2,2'-bipyridine, with Fish salmon DNA. Agarose gel electrophoresis assay, along with absorption and fluorescence studies, reveal interaction between the corresponding complex and FS-DNA. Also, the binding constants (Kb) and the Stern-Volmer quenching constants (Ksv) of Tb(III) complex with FS-DNA were determined. The calculated thermodynamic parameters suggested that the binding of mentioned complex to FS-DNA was driven mainly by hydrophobic interactions. A comparative study of this complex with respect to the effect of iodide-induced quenching, ionic strength effect, and ethidium bromide exclusion assay reflects binding of explicit to the FS-DNA primarily in a groove fashion. CD and viscosity data also support the groove binding mode. Furthermore, Tb(III) complex have been simultaneously screened for their antibacterial and antifungal activities.

Keywords: 2,2′-bipyridine; DNA-binding; groove binding; spectroscopy; terbium(III) complex; thermodynamic parameters.