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The mechanism of flip-flops in a AOT lamella: A molecular dynamics study
SCIENCEDIRECT.COM
A long 5000 ns run was conducted on sodium dioctyl sulfosuccinate (AOT)/water lamellar system to understand the unusual behavior. During the simulation run, we track up to 24 AOT molecules translocated from upper leaflet (UL) to lower leaflet (LL) and vice-verse. AOT molecule takes ~2–17 ns in average to move from one leaflet to other. The potential energy barrier of AOT interlayer translocation calculated as sum of Lennard-Jones and electrostatic energies is estimated to be around ~100–120 kJ/mol and the free energy barrier about 90 kJ/mol. A long-scale simulation is accompanied with undulations and large curvation of bilayer. We argue that the transbilayer flip-flop process is a pore-mediated, i.e. the events are accompanied with water pores (defects) formation. On the other side, the size of “water tunnels” is also important, although the successful transbilayer flip-flop events are not depends on the size and lifetime of the water pores.
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