Molecular Dynamics Study On The Toxicity Of Nitrogen Dioxide,sulfur Dioxide,ozone And Short-chain Chlorinated Paraffin To Membrane

Air pollution has become a profound scientific and social issue,which has a major impact on the living environment.The composition of the atmosphere includes not only particulate matter,but also gaseous common pollutants such as nitrogen dioxide?NO₂?,ozone?O₃?and sulfur dioxide?SO₂?.NO₂,O₃ and SO₂ in the air are the main toxic components of indoor and outdoor environmental pollution caused by smoke,fossil fuel combustion,and emissions from automobiles and other internal combustion engines.Therefore,the toxicity studies of NO₂,O₃ and SO₂ have gradually attracted people's attention.NO₂ O₃ and SO₂ could cause oxidative damage to lung cells and closely relate to the asthma and lung cancer.In addition,there are many new persistent organic pollutants in the atmosphere,such as Short Chain Chlorinated Paraffins?SCCPs?.SCCPs could decrease the cell viability and lead to metabolic damage to lipids,amino acids,and nucleotides.In recent years,SCCPs has been reported to be associated with various diseases including lung cancer.However,the environmental toxicological effects of NO₂,O₃,SO₂ and SCCPs,especially the interaction mechanism with membrane,are still lacking in-depth research.In the first part of the work,we simulated the interaction of NO₂,O₃,and SO₂molecules with dipalmitoylphosphatidylcholine?DPPC?bilayers based on molecular dynamics calculations.The results showed that NO₂,O₃ and SO₂ molecules could enter the lipid layer from the aqueous phase.With the increase of the concentration of NO₂,O₃ and SO₂ molecules,the thickness of the phospholipid bilayer and the lipid average area increased and further increased lipid order parameters,which caused a downward trend of the fluidity of the membrane and the damage of membrane.The above results illustrated that NO₂,O₃ and SO₂ could damage the DPPC bilayers structure by affecting the physical properties,and the increase of their concentrations could exacerbate membrane damage.In the second part of the work,we further explored the potential membrane damage of the mixture system of NO₂,O₃ and SO₂ on the DPPC bilayers based on the conclusions of the first part of the work.The phospholipid bilayer thickness,lipid average area,phospholipid bilayer membrane potential and lipid order parameters of the phospholipid bilayer were calculated by molecular dynamics simulation.In addition,there was a higher influence on the structural changes of the phospholipid bilayer compared with the NO₂,O₃ and SO₂ single molecular systems in the first part of the work,which were more significant of the decreasing trend of membrane fluidity.The result further showed that there was a more significant damage effect on membrane of the mixture systems with NO₂,O₃ and SO₂ coexisting.In the third part of the work,we studied the damage of new persistent organic pollutants SCCPs to membrane by combining E.coli experiments and molecular dynamics simulations..The analysis of the surface hydrophobicity of E.coli showed that the surface hydrophobicity of E.coli had a decreasing trend with the increasing concentration of SCCPs.The analysis of?-galactosidase activity showed that the addition of SCCPs could cause the leakage of?-galactosidase and the damage of membrane.The SCCPs systems with different concentrations on the phospholipid bilayer were simulated based on molecular dynamics simulations.The analysis results showed that the structure of phospholipid bilayer changed significantly and the fluidity of the membrane showed a downward trend with the increase of the concentration of SCCPs.E.coli membrane damage experiments and molecular dynamics simulations showed that SCCPs could cause damage to the membrane structure.The results of the research also provided reliable data support and scientific basis for subsequent SCCPs toxicity assessment.