Probing lipid membrane bending mechanics using gold nanorod tracking.

Area of Science:

• Biophysics
• Soft Matter Physics
• Cell Biology

Background:

• Lipid bilayer membranes exhibit dynamic undulations driven by thermal fluctuations.
• Understanding membrane mechanics is crucial for cellular processes and biomaterial design.

Purpose of the Study:

• To investigate lipid membrane undulations and mechanical properties.
• To measure membrane viscosity, bending rigidity, tension, and interlayer friction.
• To explore the coupling between membrane physics and cellular actomyosin cortex.

Main Methods:

• Utilizing high-speed dark-field microscopy to track single gold nanorods (GNRs) adhered to membranes.
• Analyzing the time-varying orientation of GNRs to probe membrane dynamics.
• Applying measurements to both model lipid vesicles and living cell plasma membranes.

Main Results:

• GNR rotation is hindered by membrane undulations in a tension-dependent manner, validated by simulations.
• Quantified viscosity, bending rigidity, tension, and interlayer friction in lipid vesicles.
• Observed complex membrane physics and actomyosin coupling in living cells.

Conclusions:

• Single gold nanorod tracking is a powerful technique for characterizing lipid membrane mechanics.
• Membrane undulations and their mechanical properties are influenced by tension and coupled to cellular cytoskeleton.
• This method provides insights into the dynamic behavior of biological membranes in various contexts.