Interaction of anthelmintic drug (thiabendazole) with DNA: Spectroscopic and molecular modeling studies

Abstract

The interaction between thiabendazole (TBZ) and calf-thymus DNA (ct-DNA) was studied by experimental and molecular modeling methods. The intrinsic fluorescence of TBZ was quenched in the presence of ct-DNA. In competition experiments, TBZ could displace Hoechst 33258 (a minor groove binder to DNA), whereas it was unable to replace ethidium bromide (an intercalator). Potassium iodide could quench the fluorescence of TBZ, which indicated the nonintercalative mode of binding of TBZ to ct-DNA. UV absorbance of TBZ shows hyperchromic effect on the addition of DNA to the solution with negligible shift in wavelength. Salt effect studies showed the non-electrostatic nature of binding of TBZ to DNA. The viscosity of ct-DNA solution was almost unchanged on addition of TBZ. Circular dichroism (CD) spectra of DNA showed small changes in the presence of TBZ which is in agreement with groove binding mode of interaction. Moreover, from molecular modeling methods, a docked structure with minimum energy was obtained in which TBZ was located in minor grooves of ct-DNA.