Publication Date

April 2015


Francis Starr


Neuroscience and Behavior


English (United States)


Cell membranes, composed primarily of lipid bilayers, are dynamically active structures. While the relationship between heterogeneity of dynamics and biological function is being increasingly appreciated, the dynamical characteristics of lipid membranes remain a topic of vigorous debate. We use molecular simulations of simple, single-component lipid bilayers, as the first step in a systematic, bottom-up approach to establish a quantitative framework for membrane dynamics. We draw upon well-established methods from other strongly-interacting condensed materials to characterize dynamic heterogeneity in lipid bilayers. Consistent with experiments, our findings show significant changes in lipid dynamics between the liquid-disordered, liquid-ordered, and gel phases. Further, our simulations demonstrate that the gel and liquid-ordered phases exhibit hindered diffusion due to the transient trapping of lipids by their neighbors, similar to the dynamics seen in simple liquids approaching a glass transition. In both the gel and liquid-ordered phases, we find evidence for two mobility groups: (i) lipids that are transiently trapped by their neighbors, and (ii) lipids with displacements on the scale of the intermolecular spacing. Lipids dynamically exchange between these mobility groups. Most significantly, these distinct mobility groups are spatially segregated and form dynamic clusters. We provide a quantitative description of these dynamic lipid clusters and find that their time and size scales correspond to those argued to occur in lipid raft structures --- suggesting that this intrinsic lipid heterogeneity may provide a mechanism for complex cell and neuronal membrane organizations.



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