The Interaction Mechanism Of Amide Pesticides With Biomacromolecules

In this work,we explored the interaction mechanism of biomacromolecules（BSA/DNA）with amide pesticides such as boscalid,fenhexamid and sulfosulfuron using multispectroscopic methods and molecular docking,which provided a theoretical and experimental basis for the rational application of pesticides and evaluation of microscopic toxicity on pesticide.Firstly,fluorescence spectrometry was performed to determine the quenching mechanism of BSA with amide pesticides（boscalid,fenhexamid and sulfosulfuron）.The results showed that the quenching process of BSA induced by these pesticides were a static quenching.According to the competitive experiments,it can be found that boscalid and fenhexamid manily bound to the site II on BSA,respectively,whereas the sulfosulfuron mainly bound to the site I of BSA.In addition,there was one binding site on the BSA for boscalid/fenhexamid/sulfosulfuron binding.In the binding process,the van der Waals force and/or hydrogen bonding interaction were the main interactions based on thermodynamic parameter.The sucrose competitive experiment was reconfirmed that hydrogen bonding force existed in the binding process.Besides,synchronous fluorescence and three-dimensional fluorescence spectrometry illustrated that the hydrophobicity surrounding Tyr or Trp residues on BSA changed due to the pesticides binding.Finally,fourier transform infrared spectroscopy was measured and it could find that three pesticides could reduce theα-helix content and affect the secondary structure of BSA.Then,the interactions of DNA with amide pesticides（boscalid,fenhexamid and sulfosulfuron）were investicated by the UV spectroscopy,fluorescence spectroscopy and viscosity measurement.The results showed three pesticides interacted with DNA via the groove binding mode.Circular dichroism exhibited a slight change in the conformation of DNA during binding process.In addition,the combination ratio of boscalid,fenhexamid and sulfosulfuron with DNA was 1:1 and the binding constant were2.39×10³,2.45×10³,2.58×10³ M^-1,respectively,at 298 K.The thermodynamic parameters calculated from van’t Hoof plot indicated that van der Waals force and hydrogen bonding interaction were the main interacting forces in pesticides–DNA binding.Finally,the experiment results were futher confirmed by molecular docking.