The Deformation Of Bilayer Membrane Driven By External Or Internal Forces

The deformation and response behavior of biomembrane are the physical basis for the realization of cell function and biological activity on the micro scale.It can be driven by active force,such as the process of endocytosis and exocytosis,or driven by passive force,such as the cell doformation under shear fluid force.In this paper,the deformation behaviors of bilayer membrane driven by external or internal forces are studied based on self-consistent field theory(SCFT),external potential dynamics(EPD)and self-assembly of block copolymers.Based on SCFT,the budding and fracture behaviors of bilayer membrane is investigated,and the dynamic regulation mechanism of asymmetric phospholipid components on the deformation and fracture toughness of bilayer membrane is analyzed.The bilayer membrnae can be highly curved under external tension,and form a negative curvature structure.Besides,the hydrophilic groups of phospholipid components in the membrane are likely to gather at the positions with negative curvature,which will increase the stress in this area and eventually lead to the fracture of the bilayer membrane.The doping of asymmetric phospholipid can affect the elastic modulus of bilayer mmebrane.The elastic modulu of bilayer membrane is larger with longer hydrophilic chain of doping asymmetric phospholipid,and its easyer for bilayer to break with longer hydrophilic block.Taking the growth of lipid droplet in the bilayer membrane as a research model,an active dynamic model is established based on self consistent field theory(SCFT)and external potential dynamics(EPD),and the membrane deformation process driven by internal force is explored.we can continuously synthesize neutral lipids at the fixed point in the bilayer membrane using the active dynamic model.Driven by internal chemical potential and pressure,bilayer membrane components and neutral lipid evolve continuously and form a lens structure which grows in two directions:expending the contact line and increasing surface area.The thickness of the bilayer membrane become thinner as the growth of lens structure,and finally break at the contact line of lens.According to its growth characteristics,we analyzed the packing density of phospholipids.Its packing density is lowered due to the loading of surface tension and line tension comparing with that of free membrane.And we find that the growth of lipid droplte is a three-period dynamic process which is regulated by surface tension and line tension.In recent years,the study of biomembrane deformation is a hot topic in the field of life science,and the corresponding research is mainly based on experiments.In this paper,we use simulation method to reveal the micro physical mechanism of life process and provide theoretical guidance for biological experiments...