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

TL;DR

This paper demonstrates that membranes with fixed protein obstacles exhibit a universal behavior akin to the 2D random-field Ising model, leading to stable micro-domains without macroscopic phase separation.

Contribution

It establishes the universality class of membrane heterogeneity with quenched obstacles and links it to the random-field Ising model, highlighting the absence of a phase transition.

Findings

Membranes with quenched obstacles follow the 2D random-field Ising universality class.

No critical point exists; only micro-domains form.

Standard Ising behavior occurs when obstacles are not randomly distributed or lack affinity.

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 micro-domains. 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 apply. In these cases, a critical point does exist, marking the onset toward macroscopic demixing.