Research On The Migration And Biodegradation Of PCBs Based On 3D-QSAR And Molecular Docking

Polychlorinated biphenyls?PCBs?are one of the most widespread and persistent groups of persistent organic pollutants?POPs?in the environment and different from common organic pollutants due to their high stability,toxicity,environmental persistence,bioaccumulation,long-distance migration ability and other characteristics.PCBs' global mobility,long-term persistence and persistent have increased the difficulty of its degradation in the environment.Therefore,in this study,three-dimensional quantitative structure-activity relationship?3D-QSAR?and molecular docking are used to study the global migration and biodegradation of PCBs.For PCBs' global migration,two types of 3D-QSAR methods,comparative molecular field analysis?Co MFA?and comparative molecular similarity indices analysis?Co MSIA?,are used to establish 3D-QSAR models,predict the log K_OA values of 209 PCBs and to investigate the relationship between the structures of PCBs and their persistent migration ability.As a result,the two models show satisfactory fitting ability and acceptable predictive ability of the 209 PCBs.The two models mutually verify and prove that the electrostatic descriptors play a more significant role than steric descriptors and hydrophobic descriptors.However,hydrogen bond donor and acceptor fields contribute minimally to the log K_OA value of PCBs when steric,electrostatic and hydrophobic fields were introduced.In an electrostatic field,the introduction of electropositive groups in some positions of PCBs can significantly reduce the log K_OA values and migration ability.The correlation analysis of the relationship between the number of Cl atoms and the average log K_OA values of PCBs revealed that the log K_OA values gradually increased as the number of Cl atoms increases.Simultaneously,related studies on the detection of PCBs in the Arctic and Antarctic prove that higher log K_OA values indicate stronger PCBs migration ability.In addition,molecular docking method was employed to calculate the affinity energy between biphenyl dioxygenase?Bph A?,including 1ULJ,1WQL,2YFJ,2YFL,2GBX,2XSH,2E4 P,3GZX,and 3GZY,and 209 PCBs.Moreover,the relationship between the calculated affinity energy and the migration?K_OA?,persistence?t₁/2?,toxicity?IC50?,and bioaccumulation?BCF?of the PCBs was established by Pearson correlation analysis to reveal insight into the degradation of PCBs in the presence of Bph A.Two types of 3D-QSAR methods,CoMFA and Co MSIA,were used to prove the relationship between the free energy of binding and the PCB characteristics.As a result,firstly,the highest PCBs degradation rate for the 9 types of Bph A was 2GBX;secondly,the free energy of binding was highly significantly related to the molecular weight,K_OA,BCF,and t₁/2,respectively,but was not significantly related to IC50;thirdly,3D-QSAR models mutually verified and provided proof that the electrostatic descriptors played a more significant role than steric descriptors and h ydrophobic descriptors.This was consistent with the literature findings in which the electrostatic field was determined to be a primary factor governing the K_OA,t₁/2,and BCF,indicating that the influence of molecular structure on the free energy of bin ding,K_OA,t₁/2,and BCF was consistent;fourthly,in an electrostatic field,the introduction of electropositive groups in the 3-position of PCBs or electronegative groups in the 3?-position of PCBs significantly reduced the free energy of binding,molecular weight,K_OA,BCF,and t₁/2 values,indicating that the free energy of binding correlated with the molecular weight,K_OA,BCF,and t₁/2 of PCBs based on the internal structure of the molecules.The establishment of 3D-QSAR model and its satisfactory acceptable predictive ability are expected to be beneficial in predicting log K_OA values of PCBs and derivatives and in providing a theoretical foundation for further elucidation of the global migration behaviour of PCBs.Furthermore,reduction of the affinity energy improved the degradation ability of the PCBs and simultaneously decreased the K_OA,t₁/2,and BCF levels,thereby lowering the POPs behavior characteristics of PCBs in the environment.These results are expected to be beneficial in providing a theor etical foundation for further elucidation of the degradation and molecular modification of PCBs.