Probing the interaction of pepsin with imidacloprid via DFT calculation, spectroscopic approaches and molecular docking

Abstract

The use of the pesticide imidacloprid can be hazardous to human health. In this work, the impacts of imidacloprid on the secondary structure of pepsin were investigated through spectroscopic techniques and simulation studies. One binding site for pepsin with strong affinity was evident from changes in the fluorescence emission spectra of pepsin in the presence of imidacloprid. Calculated thermodynamic parameters based on the van't Hoff relationship indicate the predominance of hydrophobic and hydrogen bonding interactions contributing to the imidacloprid-pepsin complex. Structural changes in pepsin were also evident from changes in the UV, FTIR, CD, three-dimensional fluorescence (3D), and synchronous fluorescence spectroscopy (SFS) of pepsin upon titration with imidacloprid. Furthermore, density functional theory (DFT) calculations and molecular docking studies revealed predominant binding of imidacloprid in the hydrophobic pocket of pepsin.