We begin by analyzing an asymmetric bilayer with leaflets derived from simulations of symmetric Lo and Ld bilayers. In this paper, we report on all-atom molecular dynamics simulations (a total of 4.1 μs) of symmetric and asymmetric bilayer systems composed of more » liquid-ordered (Lo) or liquid-disordered (Ld) leaflets, based on the nanodomain-forming POPC/DSPC/cholesterol system. This raises the question of how the phase behavior in one bilayer leaflet may affect the apposing leaflet and how one begins to construct asymmetric model systems to investigate these interleaflet interactions. Leaflet compositional asymmetry and lateral lipid organization are just two of the ways in which membrane structure appears to be more complex than initially postulated by the fluid mosaic model. Spatial organization within lipid bilayers is an important feature for a range of biological processes. Our results are explained on the basis of the interdigitation between bilayer leaflets and how interdigitation is related to other structural = , It is demonstrated that the structural properties of bilayers with asymmetric tail lengths depend strongly on the bilayer composition, while the composition has less influence on mixed-component bilayers with nearly symmetric tail lengths.

Although tail tilt is the primary mechanism for single-component bilayers to balance tail attraction and headgroup repulsion, our results demonstrate that the lipid mixtures studied adjust this balance via an offset between the depths of the different molecular species in the bilayer this behavior is found to depend both on composition and on the length of alcohol molecules relative to the length of DSPC tails. Several bilayer properties, including area per lipid, tilt angle, chain interdigitation, and headgroup offset, are studied for each system and compared, revealing important structural implications depending upon headgroup size and chain length. The structural properties of two-component gel-phase bilayers of distearylphosphatidylcholine (DSPC) and alcohol molecules with different compositions and chain lengths (12–24 carbons long) are studied via molecular dynamics simulations.

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