Voltammetric and Spectroscopic Investigation of the Interaction Between 1,4-Benzodiazepines and Bovine Serum Albumin

Abstract

The interaction of diazepam (DZ) and chlordiazepoxide hydrochloride (CPZ) with bovine serum albumin (BSA) was investigated by the application of cyclic and square wave voltammetry. The electrochemical behavior of DZ and CPZ in the absence and in the presence of BSA was studied using a Sonogel–Carbon electrode modified with 5 % bentonite. In the presence of BSA, the reductive peak current of DZ or CPZ was decreased apparently without any significant changes in peak potentials and the appearance of no new reduction or oxidation peaks. Electrochemical parameters such as formal potential (E°), standard rate constant (k s) and charge transfer coefficient (α) were calculated and compared in the absence and presence of BSA. The results showed that the interaction of DZ or CPZ with BSA resulted in formation of an electro-inactive bio-complex. The equilibrium constant (β s) and binding ratio (m) of the bio-complexes were calculated. UV–Vis spectrophotometry and Fourier transform infrared (FT-IR) techniques were used to assess the structural effects of DZ and CPZ binding on BSA. The formation of DZ–BSA and CPZ–BSA bio-complexes was proved and the binding constant was calculated from the UV–Vis measurements. There is little difference between the binding constant values calculated using the voltammetric and UV–Vis spectrophotometric techniques. The formation of DZ–BSA and CPZ–BSA bio-complexes was confirmed by recording the changes in both intensity and position of FT-IR spectral bands of BSA, DZ, CPZ and their bio-complexes DZ–BSA and CPZ–BSA.