A Rationale for Mesoscopic Domain Formation in Biomembranes

Area of Science:

• Soft condensed matter physics
• Biophysics
• Cell biology

Background:

• Cell plasma membranes exhibit complex structures with functional domains.
• Lipid and protein compositions define these domains.
• Patterned morphologies are observed in model systems like supported membranes and lipid vesicles.

Purpose of the Study:

• To classify diverse mechanisms driving mesophase separation in biomembranes.
• To distinguish between equilibrium and out-of-equilibrium mechanisms.
• To identify biologically relevant mechanisms by comparing theory, simulations, and experiments.

Main Methods:

• Review of existing literature on biomembrane mesophase separation.
• Classification based on equilibrium thermodynamics and out-of-equilibrium processes (e.g., active membrane recycling).
• Focus on up-down symmetry breaking mechanisms in equilibrium, including spontaneous and explicit symmetry breaking.

Main Results:

• Mesophase separation in biomembranes arises from various mechanisms.
• Equilibrium mechanisms often involve up-down symmetry breaking between bilayer leaflets.
• Out-of-equilibrium mechanisms, such as active membrane recycling, also contribute.

Conclusions:

• Symmetry breaking is a key mechanism in biomembrane mesophase formation.
• Both equilibrium and non-equilibrium processes are crucial for understanding membrane organization.
• Confronting theoretical predictions with experimental data helps validate biological mechanisms.