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Formation Mechanism and Properties of Polyelectrolyte Multilayer-Supported Lipid Bilayers: A Coarse-Grained Molecular Dynamics Study
journal contribution
posted on 2017-03-31, 00:00 authored by Caixia Wen, Mingwei Wan, Xiaoxu Li, Qiang He, Lianghui Gao, Weihai FangPolyelectrolyte multilayer
(PEM)-supported lipid bilayers (SLBs)
that connect with functional proteins are popular models for cell
membranes and are usually obtained via vesicle adsorption and spreading.
However, the exact mechanism by which SLBs are formed is not fully
understood. In this study, we employ coarse-grained molecular dynamics
simulations to investigate the pathways by which vesicles undergo
spreading upon the deposition on PEM-cushioned substrates. The substrates
consist of positive chitosan (CHI)/negative alginate (ALG) multilayers.
We find that an isolated vesicle tends to completely disintegrate
upon deposition, forming a well-ordered lipid bilayer at appropriate
polymer ionic strengths by a mechanism described as “parachute”
model. Lipids from the vesicle’s outer leaflet are predominantly
oriented toward the bulk after the formation of the SLB. The PEM cushion
provides adsorption energy of 26.9 kJ mol–1 per
lipid for the SLBs. The process by which SLBs are formed is almost
independent of the number of layers of CHI/ALG in the PEM cushion.
Additional simulations on vesicle clusters also demonstrate that the
formation of SLBs can be catalyzed by either neighboring vesicles
or preexisting bilayer edges on the support. Moreover, our simulations
show that SLBs created on PEM supports preserve the lateral mobility
and the symmetric density profile of the phospholipids, as in a freestanding
bilayer.