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Biophys J. 2011 Apr 6;100(7):1668-77. doi: 10.1016/j.bpj.2011.02.029.

Minimal model of plasma membrane heterogeneity requires coupling cortical actin to criticality.

Author information

1
Department of Physics, Cornell University, Ithaca, New York, USA.

Abstract

We present a minimal model of plasma membrane heterogeneity that combines criticality with connectivity to cortical cytoskeleton. The development of this model was motivated by recent observations of micron-sized critical fluctuations in plasma membrane vesicles that are detached from their cortical cytoskeleton. We incorporate criticality using a conserved order parameter Ising model coupled to a simple actin cytoskeleton interacting through point-like pinning sites. Using this minimal model, we recapitulate several experimental observations of plasma membrane raft heterogeneity. Small (r ∼ 20 nm) and dynamic fluctuations at physiological temperatures arise from criticality. Including connectivity to the cortical cytoskeleton disrupts large fluctuations, prevents macroscopic phase separation at low temperatures (T ≤ 22°C), and provides a template for long-lived fluctuations at physiological temperature (T = 37°C). Cytoskeleton-stabilized fluctuations produce significant barriers to the diffusion of some membrane components in a manner that is weakly dependent on the number of pinning sites and strongly dependent on criticality. More generally, we demonstrate that critical fluctuations provide a physical mechanism for organizing and spatially segregating membrane components by providing channels for interaction over large distances.

PMID:
21463580
PMCID:
PMC3072667
DOI:
10.1016/j.bpj.2011.02.029
[Indexed for MEDLINE]
Free PMC Article

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