Spectroscopic investigation of the interactions of carbofuran and amitrol herbicides with human serum albumin

In this study, various spectroscopic techniques including UV absorption, fluorescence and synchronous fluorescence spectroscopy were used to examine the interactions of carbofuran (CF) and amitrol (AMT) herbicides with human serum albumin (HSA). The results of spectroscopic experiments illustrated that CF was bound by HSA, on the other hand there was no interaction between HSA and AMT molecules. In HSA-CF system, static quenching mechanism was responsible for the fluorescence quenching of HSA. The Stern-Volmer constant and binding constant decreased with increasing temperature. This means that an increase in temperature reduces the stability of HSA-CF complex. In HSA-CF system, the number of binding site on protein was found to be one. From the thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) were calculated as −22.30 kJ mol−1 and −10.70 J mol−1 K−1, respectively, which indicated that the interaction forces between HSA and CF molecules were mainly hydrogen bonding and van der Waals forces. The conformational change in the protein structure was investigated by synchronous fluorescence spectroscopy. According to the results of synchronous fluorescence analysis, there was a change in the protein structure owing to the interaction of CF with HSA.