A CG DPPC model developed by Marrink et al. (Ref. 55). Four major atoms correspond to one CG bead.
Scheme of the aggregation structure of lipids: (a) Initial DPPC small ball (512 lipids), where solid surface and thin line are the head groups and the tail groups, respectively; (b) randomly distributed DPPC molecules; (c) DPPC multilayer structure.
A scheme of the interaction of DPPC with water in the tail-tail zone: The hydrophilic head groups join together to prohibit the invasion of water.
A scheme of the interaction of DPPC with water in the head-head zone. The hydrophobic tail groups join together and the head-head zone splits to form a channel for water’s pervasion.
Morphology evolution (middle section) of two samples (S1 and S2, corresponding to disk and vesicle, respectively) in group 9 of Table I (392 DPPC molecules, water is not shown). The head groups and tail groups are depicted using different color for distinction. Images are rendered using VMD package (Ref. 62) (a) 0 ns, (b) 8 ns, (c) 104 ns, (d) 240 ns, and (e) 800 ns.
The dependences on the time of energy changes in two samples (S1 and S2, corresponding to disk and vesicle, respectively) in Fig. 5: Upper panel is the energy evolution of the total system (including DPPCs and water); lower panel represents the energy curve of DPPCs without water. The energy is the sum of kinetic and potential energy. The arrow line with time labeled as 104 ns is the peak energy point corresponding to the cuplike intermediate structure.
The average lipid number in the inner and outer layers of an equilibrium vesicle with different vesicle sizes (dot). The linear relationship with the total number of DPPCs is shown by fitting straight lines.
(a) The RDF curve of three characteristic groups (head group, end group, and the hydrophobic chain-tail group) with respect to the mass center of the vesicle (392 DPPCs). (b) Dependence of the vesicle area on the total amount of DPPC in the vesicle, where the radius is defined as the distance between the center of mass and the peak point of end group distribution in RDF.
Illustration of morphology change by lamellar bending. The curved lamella at the origin point is regarded as a partial spherical surface with curvature radius and with angle between the surface edge direction and the minus direction of the axis. Figure shows a slice along the coordinate plane.
Upper panel: The curves of with different surface areas . Here the dark points label the peak energy of each curve, one of which is in bold to be shown more clearly. The left side represents the lamellar morphology, and the right side represents the vesicle. Lower panel: Illustration of two different evolution pathways from an initial lipid ball.
The dependences on the droplet size of (a) vesicle appearance probabilities and (b) the energy difference between disks and vesicles. The droplet size, which is equal to about 362 when the energy of a vesicle is equal to that of a disk, is close to the value (about 388) at (crossing dash lines).
Overview of the DPPC-water system and the results of the simulation.
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