(366j) Molecular Dynamics Simulations of Permeability in Gel Phase Mixed Lipid Bilayers

Lipid membranes are vital to all complex forms of life and can control the transport of material into cells and the body. While membrane composition and structure clearly play a role in determining if and how fast a solute can permeate across a membrane barrier, a better understanding of the relationship between membrane composition, structure, and permeability is needed to be able to improve, replicate, and control the barrier function of biological membranes. Although NMR spectroscopy and neutron scattering can measure global bilayer permeabilities, they cannot provide key molecular-level insight. Molecular simulations can uncover the physical mechanisms of permeation and provide a better understanding of the dependence of bilayer permeability on the local environment. Here, using atomistic molecular dynamics simulations, we investigate how chemical architecture of the bilayer molecules affects the structural properties, finding a complex balance between the size and hydrophilicity of the headgroups, relative length of lipid tails, and the attraction between tails. Furthermore, we focus on how these structural differences influence the passive permeation of water molecules through the bilayer structures, finding a strong dependence on the size and hydrophilicity of the headgroups, chain length, and side-branching.