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Entropic Tension in Crowded Membranes

Figure 2

Excluded-area interactions and channel gating.

(A) Gating of a channel (red) crowded by a single crowder (gray) of radius in the constant area ensemble, where the total surface area is fixed by the outer walls (dashed). (B) In the constant tension ensemble with applied tension , the total area increases as the channel opens, so that the total lipid area is conserved. For disk-shaped particles of finite size, the free area available for each center of mass is limited by the minimum distance between two centers of mass. This effect can be illustrated by exclusion zones of width around each protein. In the constant tension ensemble, the reduced area for the crowders is due to larger exclusion zone in the open compare to the closed state. In the high density regime (C), the exclusion zones overlap, which complicates the analysis. We use scaled-particle theory to analyze this case.

doi: https://doi.org/10.1371/journal.pcbi.1002431.g002