The Theory Study Of The Giant Vesicle Lateral Configuration Changes

Biological membranes are selective semipermeable membraneswhich composed of double phosphatide, protein and so on. Theyseparate the cells and the organelles from their surroundingenvironments, not only prevent the loss of cell contents, but alsokeep the cell chemical composition relative stability, their mainfunctions are energy conversion, material transport, informationrecognition and transfer, this play an important role in maintaininglife activities of cells. Base on the important significance of thebiomembrane, biomembrane research have been physical, chemical,biological and multidisciplinary cross a very active research field innearly a century. But because of the natural biomembrane liquidand its structure complexity, using the present experiment meansare difficult to achieve direct observations and the study of naturalbiomembrane internal structure and the self-organization. Based onthe above reasons, people uses a series of more simple componentand the structure, more facilitate experimental observation ofsynthetic membrane model to simulate and study biomembranestructure and the organizational behavior. Giant single vesicle asone of the most typical and widely used artificial membrane model,has the important research significance.In this paper, we detail study the change of different giant vesicle system configuration and energy system based on the real spaceself-consistent mean field theory. The main content of this articleas follows:In Chapter1, we briefly introduce biomembrane experimentalmodel and the research progress of biomembrane self-organizationin recent years, meantime, We also introduces the self-consistentfield theory (SCFT) in the application research of biomembrane.SCFT as a coarse graining model, can well reflect the biomembranephospholipid molecules amphipathy, effective shape and theflexibility of chain, etc.In Chapter2, simulate the process of a nanoparticle through asingle phospholipid giant vesicle, and discuss the impact of thephospholipid molecule concentration and the head-tail interactionon the system free energy. With the increase of the phospholipidmolecule concentration and the head-tail interaction, the systemfree energy also presents the increasing trend. In the process of thenanoparticle penetrate into the giant vesicle, the system freeenergy shows the tendency of increase after decrease. And thenchange the nanoparticle size and surface characteristic, throughthe analysis of the system energy, choose the best condition ofnanoparticle transport in membrane.In Chapter3, Through the simulation of a nanoparticle penetrateinto a giant vesicle formed by two kinds of phospholipid moleculeswith different effective shape, discuss the interaction betweenparticle and giant vesicle and the configuration changes of thebilayer membrane in the process. Analysis the impact of membranecomposition (the phospholipid concentration ratio and the same phospholipid head-tail interaction) on free energy of the system,then select the composition of membrane. Finally, change theparticle size and the surface properties, discuss the impact on thevarious system energy, and thus infer the optimum radius of theparticle size and surface field strength when transport in themembrane.In Chapter4, simulate the giant vesicles fusion formed by twokinds of phospholipid molecules. The vesicle configurationexperience the change process of hemifusion, fusion and vesiclebudding. Analysis whether the process is spontaneous from theperspective of energy, and the effect of vesicle fusion on thesystem energy. Firstly, fix the overall volume fraction of mixedphospholipids, By changing the phospholipids concentration ratioanalysis the energy difference of the membrane fusion, and selectthe phospholipids concentration ratio. Then discuss the effect ofthe same phospholipid molecules head-tail interaction on energydifference of the membrane fusion, and select the samephospholipid molecules head-tail interaction. Change the vesicleradius ratio, disscuss the effect on the system free energy, thebigger radius difference of giant vesicle, the bigger energydifference of the membrane fusion, this shows that the membranefusion is the more difficult to be happened.Finally, we summarize this thesis in Chapter5, and some per-spectives in further theoretical studies on the Giant vesiclesorganization are presented.