Analysis Of Pollution Load Of Heavily Polluted River And Theoretical Study On The Mechanism Of Cysteine Dioxygenase Catalytic Reaction

The treatment of black-odor river water is an important policy measure in the field of national environmental protection.However,due to the long-term engineering perspective only,the lack of systematic governance thinking has resulted in a large amount of capital investment and has not achieved good results.The Yong'an River is a typical heavily polluted river in Wujin District,Changzhou City,Jiangsu Province The surface water quality is generally of Class V.Among the 10 sections from upstream to downstream,the Class V section accounts for 70%.The water quality of the whole area is beyond the nutritional standard.As an important river entering theTai Lake,its pollution load takes up a very high proportion.The regional pollution sources are complex,the water environment capacity is low,and the black and odor of the branch is serious,which seriously affects the living environment quality and health and safety of the residents along the coast.Based on the investigation of point source,area source and internal source in Yong'an River Basin,this study carried out analysis and load calculation,studied load distribution rules,and simulated the relationship between load distribution and water quality through WASP water quality simulation software.This provides a scientific basis for the prevention and control of regional water pollution,the state-controlled or provincial-controlled cross-sections are stably reaching the standard.At the same time it canreduce the load into the Tai Lake and improve the water qualityAt the same time,in order to explore the application of biological enzymes in the treatment of black-odor river water body,especially the possibility of degradation of odor substances.We have done some work in the field of quantitative calculation of biological enzymes,and preliminary studied the catalytic reaction mechanism of cysteine dioxygenase(CDO)to break the C-F bond.CDO is a vital enzyme that can regulate the balance of cysteine in living organism and play a decisive role in human sulfur metabolism.However,the detailed catalytic process is still obscure.Here the catalytic mechanism of CDO toward 3,5-difluoro-l-tyrosine was studied with the aid of combined quantum mechanics/molecular mechanics(QM/MM)method.The results show that the catalytic process involves four elementary steps:H-abstraction,C-S bond formation,F-transfer,C-F bond cleavage.The C-F bond cleavage is the rate-determining step with an energy barrier of 18.8 kcal/mol,which is in reasonable consistent with the experimentally determined rate constant(0.77 s-1,corresponds to 17.6 kcal/mol).Possible intersystem crossing events were observed and discussed.In addition,the electrostatic influence of active site residues was investigated and residues Asp87,Phel61 were highlighted as potential targets for future mutations for efficient C-F bond cleavage.This research can also provide reliable theoretical support for the design of catalysts to effectively alleviate the environmental problems caused by fluorine-containing compounds.