Molecular Dynamics Study On The Adsorption Behaviors Of Protein

The ocean is a huge treasure house with rich resources,and human beings gradually shift their development goals into the ocean.However,many of the problems have become the focus concerned by people when the ocean is developed at the same time.Marine bio-fouling is one of the issues concerned by researchers.Marine organisms would adhere to the solid surface through the secreted protein,and then develop into a biological community.The adhesion of marine organisms will not only increase the resistance to ships in sailing but also accelerate the corrosion of the ships,which would result in huge economic losses.Studies have shown that the initial stage of bio-fouling is the best stage of prevention,i.e.the adsorbed proces of protein.Although the application of antifouling coatings temporarily solves the problems caused by bio-fouling,some substances also have a certain impact on the environment.Therefore,the development of new substances to resist protein adsorption has become a hot spot in recent years.At present,many of the scientific research teams have researched on the antifouling materials,however,there is no uniform understanding for the antifouling mechanism of the materials,and the interaction between protein and materials could not be observed at the molecular level in experiments.In this thesis,molecular dynamics(MD)simulation was used to simulate the interaction between protein and materials from the microscopic level,and it is expected that the antifouling mechanism could be found.The MD method could also help us to design the new antifouling materials,and reduce the blindness and time-consuming of experiments.The contents of this paper are shown as below:1.The adsorption behaviors of mussel protein on the polydimethylsiloxane(PDMS)and perfluoroheptane self-assembled monolayers(C7F16-SAM)surfaces were studied by molecular dynamics simulation.After 20 ns simulations,the mussel protein was finally adsorbed on both membrane surfaces.In the later stage,the adsorbed process was analyzed by the protein characteristics,RMSF,interfacial residues,interactive energy,and potential of mean force.The simulated results showed that the interaction between the mussel protein and the hydrophobic C7F16-SAM membrane is larger,which could be reflected by the interactive energy between the protein and the membrane.However,two hydration layers near the hydrophilic PDMS membrane surface result in weak interaction between the protein and the membrane.2.The modified polymer is an important method to explore the new antifouling agents.The adsorption of mussel protein on the self-assembled monolayers with different terminal functional grops was studied by MD simulation.In this chapter,PDMS was modified by grafting the organic compounds containing methyl(-CH3)and carboxyl(-COOH)terminals,respectively.This was to study the effect of surface properties on the adsorption of mussel protein.The simulated results,which include the protein conformation,interfacial residues,non-bond interaction,potential of mean force,and the dynamics behaviors of water molecules in the hydration layer,were analyzed.The results demonstrated that there is a more stable interaction between mussel protein and CH3-SAM membrane;the mussel protein need to overcome the larger energy barrier which produced by the hydration layer when close to the COOH-SAM membrane.We also found that the adsorbed process of mussel protein on the film surfaces was a competitive result between the protein and the water.This is the antifouling mechanism of the materials.3.The optimal adsorbed direction ofprotein is always considered in many fields.Therefore,we take another method to eliminate the effects of different placement directions on protein adsorption.In this chapter,the adsorbed process of protein was carried out under unbalanced conditions,and hydrophobin was chosen as the target protein.The silica crystal was modified by grafting the organic compounds containing methyl(-CH3)and hydroxyl(-OH)terminals,respectively.The force parallel to the membrane surface was applied on the hydrophobin so that the protein could roll on the membrane,which eliminated the effect of the placement direction of protein on its adsorption.The analyzed contents contain the hydrophobin conformation,non-bond interaction,and the tensile force.The analyzed results showed that the hydrophobic surface still has a strong interaction with the hydrophobin under the unbalanced conditions.