Events
Biological and soft-matter physics
Spontaneous Curvature, Differential Stress, and Bending Modulus of Asymmetric Lipid Membranes
Prof. Markus Deserno
Department Of Physics, Carnegie Mellon University
Sun, 08 Mar 2020, 12:00
Sacta-Rashi Building for Physics (54), room 207
Abstract: Lipid bilayers can exhibit asymmetric states, in which the physical characteristics of one leaflet differ from those of the other. This most visibly manifests in a different lipid composition, but it can also involve opposing lateral stresses in each leaflet that combine to an overall vanishing membrane tension. In this talk I will explore the interplay between a compositional asymmetry and a nonvanishing differential stress using both simple theory and coarse-grained simulations. The elastic balance required by this asymmetry sometimes gives rise to phenomena that are unexpected: first, asymmetric flat bilayers, whose specific areas in each leaflet are matched to those of corresponding tensionless symmetric flat membranes, still exhibit a residual differential stress. And second, a sufficiently strong differential stress, but not compositional asymmetry alone, can increase the bending modulus of such membranes. I finally show how differential stress is affected by cholesterol—a lipid that can rapidly switch between the leaflets. Because cells keep most of their lipid bilayers in an asymmetric nonequilibrium steady state, I propose that biomembranes are elastically more complex than previously thought: besides a spontaneous curvature, they might also exhibit significant differential stress, which could strongly affect their curvature energetics.
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