Non-Brownian diffusion in lipid membranes: Experiments and simulations.

Area of Science:

• Membrane biophysics
• Computational biophysics
• Cellular biology

Background:

• Cellular membrane dynamics and responses to particle binding are debated, particularly in crowded biological environments.
• Understanding diffusion in lipid bilayers is crucial for cellular function.

Purpose of the Study:

• To review recent single particle tracking experiments and supercomputing studies on lipid bilayer model membranes.
• To analyze anomalous diffusion in both protein-crowded and non-crowded membranes.
• To discuss the physical basis of anomalous diffusion, including ageing and deviations from Gaussian patterns.

Main Methods:

• Single particle tracking experiments in living cell plasma membranes.
• Supercomputing simulations of lipid bilayer model membranes (with and without protein crowding).
• Analysis of anomalous diffusion, ageing effects, scaling exponents, and displacement autocorrelation functions.

Main Results:

• Anomalous, non-Brownian diffusion is observed for lipids and proteins in crowded membranes.
• Simulations show transient anomalous diffusion in pure bilayers, becoming persistent with disorder (cholesterol, proteins) or gel phase transition.
• Experiments reveal anomalous diffusion of membrane proteins on macroscopic timescales, exhibiting ageing effects.

Conclusions:

• Disorder and phase transitions significantly impact the persistence of anomalous diffusion in lipid bilayers.
• Ageing and deviations from Gaussian diffusion patterns are key characteristics of anomalous diffusion in crowded biological membranes.
• Membrane compartmentalization and particle-membrane interactions influence membrane dynamics and response.