Molecular docking and biophysical studies on the interaction between thiram and human hemoglobin

Thiram is a dithiocarbamate compound that is widely used as a fungicide and ectoparasiticide in agricultural fields. It is also used in industry as an accelerator and chelating agent, and commercially as a sunscreen and bactericide. Studies have shown that thiram is harmful to animals and human health. Here, we have studied the interaction of human hemoglobin (Hb) with thiram by UV-visible absorption and fluorescence spectroscopy, Fourier transform infrared spectroscopy (FT-IR), circular dichroism (CD) and molecular docking techniques. Thiram quenched the fluorescence emission of Hb by the static quenching mechanism. Analysis of thermodynamic parameters showed that van der Waals forces and hydrogen bonds were mainly involved in the interaction between Hb and thiram. The results obtained from FT-IR, CD and synchronous fluorescence spectroscopy revealed that binding of thiram induced changes in the conformation and microenvironment of Hb. Thiram inhibited the peroxidase activity of Hb in a concentration-dependent manner, which further confirmed its binding to Hb. The experimentally calculated free energy change for Hb-thiram complex was approximately equal to theoretical docking energy value. In-silico docking predicted the presence of one thiram binding site in Hb, which is in agreement with the findings of spectroscopic experiments. Our results provide insight into the binding mechanism between Hb and thiram, which in turn will serve as the basis for assessing the effect of thiram on other cellular proteins. (C) 2022 Elsevier B.V. All rights reserved.