Domain formation in membranes with quenched protein obstacles: Lateral heterogeneity and the connection to universality classes

Abstract

We show that lateral fluidity in membranes containing quenched protein obstacles belongs to the universality class of the two-dimensional random-field Ising model. The main feature of this class is the absence of a phase transition: there is no critical point and macroscopic domain formation does not occur. Instead there is only one phase. This phase is highly heterogeneous with a structure consisting of microdomains. The presence of quenched protein obstacles thus provides a mechanism to stabilize lipid rafts in equilibrium. Crucial for two-dimensional random-field Ising universality is that the obstacles are randomly distributed and have a preferred affinity to one of the lipid species. When these conditions are not met standard Ising or diluted Ising universality applies. In these cases a critical point does exist which then marks the onset toward macroscopic demixing.

Live Cell Plasma Membranes Do Not Exhibit a Miscibility Phase Transition over a Wide Range of Temperatures

“…23 The differential physical state, presumably tension, could be caused by the live cell plasma membrane's interaction with cortical actin 55,65 and may shift the plasma membrane to a point in the phase diagram where the miscibility transition temperature is lower. 66 However, an absolute magnitude of such tension in live cells may be insufficient to consider tension as the sole principle suppressing miscibility phase transition, 67 and template quenched second order miscibility transition, 39,60,63 as observed in our simulations, may deserve more attention. Perturbation by active processes, Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce t he published form of this manuscript, or allow others to do so, for U.S. Government purposes.…”

“…This means that, with a small perturbation, a second order miscibility transition can be quenched, 60 …”

Fluid–fluid demixing curves for colloid–polymer mixtures in a random colloidal matrix

“…If these conditions are not satisfied, standard Ising or randomly dilute Ising behavior is observed instead, see Refs. [51,52]. On the other hand, little is known on how demixing is influenced by the amount of disorder and by its nature (for a polymer matrix some results for the critical-point behavior as a function of the amount of disorder are reported in Ref.…”

Phase separation on the sphere: Patchy particles and self-assembly

“…It has been proposed in Refs. [3,4] that the quenched disorder found in real cells, provided by fixed cytoskeletal proteins, could be the key stabilizing mechanism.…”

“…If the heterogeneous domain structure on the cell surface is an equilibrium state, then some stabilizing mechanism is required; the line tension incurred by interfaces between domains would make inhomogeneous phases energetically unfavorable when compared to a fully phase-separated system. Computer simulation studies of simple model systems [3,4] have shown that the size, composition, and dynamics of membrane domains can be regulated by introducing randomly located, immobile objects. These obstacles, embedded within the two-dimensional fluid, serve to hinder macroscopic phase separation and act as a source of quenched disorder.…”