| Abstract
| - Here, we use coarse grained molecular dynamics (MD) simulations to study the spontaneousaggregation of dipalmitoylphosphatidylcholine (DPPC) lipids into small unilamellar vesicles. We show thatthe aggregation process occurs on a nanosecond time scale, with bicelles and cuplike vesicles formed atintermediate stages. Formation of hemifused vesicles is also observed at higher lipid concentration. Witheither 25% dipalmitoylphosphatidylethanolamine (DPPE) or lysoPC mixed into the system, the final stagesof the aggregation process occur significantly faster. The structure of the spontaneously formed vesiclesis analyzed in detail. Microsecond simulations of isolated vesicles reveal significant differences in the packingof the lipids between the inner and outer monolayers, and between PC, PE, and lysoPC. Due to the smallsize of the vesicles they remain almost perfectly spherical, undergoing very limited shape fluctuations orbilayer undulations. The lipid lateral diffusion rate is found to be faster in the outer than in the inner monolayer.The water permeability coefficient of the pure DPPC vesicles is of the order of 10-3 cm s-1, in agreementwith experimental measurements.
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