Systematic measurements of interleaflet friction in supported bilayers

Area of Science:

• Biophysics
• Materials Science

Background:

• Lipid bilayers comprise two leaflets that slide past each other under stress.
• Interleaflet friction quantifies this leaflet sliding resistance, but previous measurements vary widely.

Purpose of the Study:

• To systematically measure interleaflet friction in supported lipid membranes using a novel microfluidic technique.
• To investigate the effects of lipid saturation and cholesterol on interleaflet friction.
• To explore shear-induced phase transitions in lipid bilayers.

Main Methods:

• Utilized a microfluidic device to apply fluid shear stress to supported lipid membranes.
• Measured the coefficient of interleaflet friction (b) by observing leaflet sliding.
• Systematically varied lipid composition (saturated vs. unsaturated) and cholesterol content.

Main Results:

• The microfluidic technique provided reproducible measurements of interleaflet friction.
• Interleaflet friction differed significantly between membranes with saturated and unsaturated lipids.
• Cholesterol addition substantially increased interleaflet friction in both saturated and unsaturated membranes.
• Fluid shear stress was found to reversibly induce gel phase in lipid bilayers near their transition temperature.

Conclusions:

• The developed microfluidic method accurately quantifies interleaflet friction in lipid bilayers.
• Lipid unsaturation and cholesterol content are critical factors modulating membrane mechanical properties.
• Shear stress can dynamically alter lipid bilayer phase behavior, with implications for membrane function.