Simulation Study About The Interaction Of Biomolecules With Surfaces

Protein,the material basis of life,is an important biological molecule.The studies about the interaction of proteins with environment and their interfacial behaviors are important to the understanding of a variety of biological processes and the investigation of the biological effects of nanomaterials.We employ two computational simulation methods and construct multi-scale model systems to study several important aspects about interfacial behaviors of protein(adsorption,desorption,etc.)and illustrate the underlying mechanisms,especially the impacts of interfacial water molecules.Besides,we observe some scaling relations of the interfacial behaviors of biomolecules.In the Chapter 3 and 4,we use molecular dynamics simulation to investigate the interactions of human serum albumin with the amine-terminated self-assembled monolayers coated gold surface.The response of the protein interfacial behavior to solution pH,especially the spontaneous desorption,is studied.When the solution pH is relatively low,the protein can adsorb to the surface via salt bridges.While the increase of the solution pH reduces the binding affinity of the protein,which engenders the lateral diffusion of the protein and the increase of interlayer water molecules.When the solution pH is further increased,the enhanced lateral diffusion of the protein and the growth of interlayer water disrupt the formation of salt bridges between the protein and the surface,and the protein progressively dissociates from the surface.The spontaneous desorption process of the protein and the corresponding mechanisms illustrated in this work may be helpful to develop an antifouling surface and enhance the biosafety of nanomaterials.We characterize the spontaneous desorption process and the corresponding mechanism of protein for the first time,which fills up the lacuna of the research about the spontaneous protein desorption.And this work is featured on the back cover of the Physical Chemistry Chemical Physics.During the spontaneous desorption process of the non-specifically bound protein,it is found that the interlayer water molecule plays a pivotal role.Therefore,regulating the behavior of interfacial water molecules is important to induce the desorption of non-specifically bound protein.In the Chapter 5,we construct model system with different hydrophobicity using self-assembled monolayers,and investigate the effect of the ratio of hydrophilic groups to hydrophobic groups to the dynamic behaviors of interfacial water molecules by molecular dynamics simulation.It is found that with increasing proportion of hydrophilic groups in the mixed surface,the diffusion coefficient of water molecules near the surface drops dramatically.This is attributed to the fact that the hydrophilic group in the mixed system can affect the majority of the interfacial water molecules through hydrogen-bonded interactions.In the Chapter 6,we use two parallel surface to mimic the confined environment in the cell,and investigate the impacts of surface attraction on the dynamic behaviors of a chain molecule by Monte Carlo simulation.When the surface attraction is weak(lower than the critical adsorption point),the slit height-dependent behaviors of diffusion relaxation time r and rotational relaxation time ?R of the chain is ??H-? and ?R?H-??and both exponents increase with increasing surface attraction.When the surface attraction is larger than the critical adsorption point,the two scaling laws are destroyed.The study about the dynamic properties of confined chains is important for the development of devices that exploit confinement to manipulate biomolecules.