Studies on the interaction mechanism for human serum albumin with hexythiazox

The interaction of human serum albumin (HSA) with hexythiazox (HEX) and the alterations of protein secondary structure in the presence of HEX were investigated by molecular docking, UV-vis absorption spectrometry, synchronous fluorescence spectrometry and three-dimensional fluorescence spectroscopy. Forecasting molecular docking results revealed that HEX could bind on site Ⅰ and site Ⅱ where it was easier to combine in HSA. The experiment results indicated that HEX had a strong ability to quench the intrinsic fluorescence of HSA through static quenching procedure. At the same time, HEX altered HSA surrounding microenvironment and led to change in the peptide chain structure of the protein. Binding affinity ( K A) and the amounts of binding sites ( n ) between HEX and HSA at 298 and 291 K were estimated as 7.35 × 103 mol/L, 0.82 and 1.02 × 104 mol/L, 0.86, respectively, which confirmed that HEX could only bind on site Ⅱ. The binding power between HEX and HSA involved mainly hydrogen bonds, van der Waals and hydrophobic forces, and an apparent distance between the Trp214 and HEX was 3.01 nm. The various informations of these studies help to understand toxicity of pesticide to humans and their bioaccumulative potential at the molecular level.