Sub-ten-nanometer heterogeneity of solid supported lipid membranes determined by solution atomic force microscopy

Area of Science:

• Membrane biophysics
• Nanoscale science
• Atomic Force Microscopy

Background:

• Lipid-lipid interactions are key to membrane raft formation.
• Understanding nanoscopic organization in multicomponent lipid membranes is essential.

Purpose of the Study:

• To investigate nanoscopic structures and organization in multicomponent lipid membranes using solution atomic force microscopy (AFM).
• To explore the mechanisms controlling membrane heterogeneity size and structural transitions.
• To compare experimental findings with existing theoretical models and propose a new organizational principle.

Main Methods:

• Solution atomic force microscopy (AFM) was employed to study supported multicomponent lipid membranes.
• Three-component (POPC/bSM/Chol) and four-component (DOPC/POPC/bSM/Chol) lipid systems were analyzed.
• Systematic variation of lipid composition (DOPC/POPC ratio) was performed to observe transitions in membrane heterogeneity.

Main Results:

• Sub-ten-nanometer correlation lengths were observed, characterizing lateral membrane organization.
• Cholesterol concentration influenced height fluctuations but not correlation length.
• A continuous transition from macroscopic to nanoscopic membrane heterogeneity was observed with varying lipid composition.
• The structural transition occurred continuously in both lateral and normal directions.

Conclusions:

• Existing theoretical models (critical fluctuations, nanodomain) do not fully explain the observed nanoscopic structures.
• A novel nanoheterogeneity model is proposed to explain the organizational principle of nanoscopic structures in multicomponent lipid membranes.