Crowding effects on diffusion in solutions and cells

Area of Science:

• Biophysics
• Cell Biology
• Physical Chemistry

Background:

• Molecular crowding is hypothesized to alter solute diffusion.
• Anomalous diffusion is predicted in simulations with obstacles or restricted transport.
• Understanding diffusion is crucial for cellular processes.

Purpose of the Study:

• To review the effects of molecular crowding on solute diffusion.
• To compare simulation predictions with experimental findings in various cellular environments.
• To clarify the prevalence of Brownian versus anomalous diffusion in cells.

Main Methods:

• Literature review of simulation studies on molecular crowding and diffusion.
• Analysis of experimental data on solute diffusion in solutions, aqueous compartments, and cell membranes.
• Evaluation of factors contributing to diffusion anomalies, such as obstacles and molecular interactions.

Main Results:

• Simulations predict anomalous diffusion in crowded environments.
• Experimental studies in solutions and cellular aqueous compartments predominantly show Brownian diffusion.
• Cell membranes exhibit both Brownian and anomalous diffusion, linked to lipid-protein and protein-protein interactions.

Conclusions:

• The concept of universally anomalous diffusion in cells due to molecular crowding is inaccurate.
• Diffusion slowing in cells is less significant than often assumed.
• Specific interactions within cell membranes are key drivers of anomalous diffusion.