Studies on Thermodynamics Features of the Interaction between Imidacloprid and Bovine Serum Albumin

At different temperatures, the interactions between imidacloprid (IMI) and bovine serum albumin (BSA) were investigated with a fluorescence quenching spectrum, a synchronous fluorescence spectrum, a three-dimensional fluorescence spectrum and an ultraviolet-visible spectrum. The average values of bonding constants (K_LB: 3.424×10⁴ L·mol⁻¹), thermodynamic parameters (ΔH: 5.188 kJ·mol⁻¹, ΔG⁽:−26.36 kJ·mol⁻¹, ΔS: 103.9 J·K⁻¹·mol⁻¹) and the numbers of bonding sites (n: 1.156) could be obtained through Stern-Volmer, Lineweaver-Burk and thermodynamic equations. It was shown that the fluorescence of BSA could be quenched for its reactions with IMI to form a certain kind of new compound. The quenching belonged to a static fluorescence quenching, with a non-radiation energy transfer happening within a single molecule. The thermodynamic parameters agree with ΔH>0, ΔS>0 and ΔG^σ<0, suggesting that the binding power between IMI and BSA should be mainly a hydrophobic interaction.