Membrane elasticity in giant vesicles with fluid phase coexistence

Area of Science:

• Biophysics
• Cell Biology
• Membrane Biophysics

Background:

• Biological membranes possess compositional heterogeneities, known as rafts, with distinct compositions and functions.
• These heterogeneities are involved in dynamic transport processes.
• Membrane lipid phase coexistence can modulate these processes via differing mechanical properties and line tension.

Purpose of the Study:

• To compare theoretical predictions of vesicle shape with fluid phase coexistence to experimental geometries.
• To investigate the role of mechanical properties, specifically bending and Gaussian curvature moduli, in heterogeneous membranes.

Main Methods:

• Developed a shape theory for vesicles with fluid phase coexistence.
• Experimentally studied giant unilamellar vesicles exhibiting coexisting liquid-disordered (L(d)) and liquid-ordered (L(o)) phases.
• Compared theoretical predictions with observed vesicle geometries.

Main Results:

• Found a higher bending modulus for the L(o) phase compared to the L(d) phase.
• Determined a more negative Gaussian (Gauss) modulus for the L(o) phase than the L(d) phase.
• Observed that differences in Gaussian curvature moduli modulate experimental vesicle geometries.

Conclusions:

• The Gaussian modulus significantly influences membrane topological changes, such as vesicle fission and fusion.
• Differences in Gaussian curvature moduli between lipid phases are biologically relevant for heterogeneous membranes.
• Experimental results confirm theoretical predictions regarding the modulation of vesicle geometry by Gaussian curvature moduli differences.