Bilayer membrane bending stiffness by tether formation from mixed PC-PS lipid vesicles

Area of Science:

• Biophysics
• Materials Science
• Membrane Biophysics

Background:

• Lipid bilayer membranes are fundamental to cell structure and function.
• Measuring membrane bending stiffness is crucial for understanding membrane mechanics.
• A novel method using membrane tethers allows for precise bending stiffness measurements.

Purpose of the Study:

• To determine the bending stiffness of lipid bilayer membranes composed of mixtures of SOPC and POPS.
• To investigate the effect of membrane surface charge density on bending stiffness.
• To validate a theoretical relationship between aspiration pressure, tether radius, and tether force.

Main Methods:

• Formation of cylindrical membrane tethers from bilayer vesicles.
• Calculation of bending stiffness (B) using the formula B = f.Rt/2π, where f is axial force and Rt is tether radius.
• Testing three lipid mixtures: pure SOPC, SOPC with 2% POPS, and SOPC with 16% POPS.

Main Results:

• Bending stiffness values for the tested lipid mixtures were similar, ranging from 1.6-1.8 x 10⁻¹² ergs.
• The presence of negatively charged POPS did not significantly alter the bending stiffness.
• The measured forces closely matched theoretical predictions, with a ratio of 1.12 ± 0.17.

Conclusions:

• Membrane surface charge density has no significant effect on the intrinsic rigidity of lipid bilayers.
• The developed tether method provides reliable measurements of membrane bending stiffness.
• The findings support the understanding of lipid membrane mechanics and properties.