Dynamics of lipid domain formation: fluctuation analysis

Area of Science:

• Membrane biophysics
• Lipid self-assembly
• Fluorescence spectroscopy

Background:

• Lipid membranes exhibit complex phase behavior.
• Understanding lipid organization is crucial for membrane function.
• Subresolution heterogeneity in lipid phases remains poorly characterized.

Purpose of the Study:

• To investigate subresolution organizational fluctuations in lipid liquid-crystalline phases.
• To detect spatial heterogeneity in single lipid model systems.
• To analyze the impact of phase transitions on membrane organization.

Main Methods:

• Utilized scanning-fluctuation correlation spectroscopy.
• Employed the fluorescent probe Laurdan, sensitive to membrane water content.
• Calculated the pixel variance of the generalized polarization (GP) function.

Main Results:

• Detected spatial heterogeneity on the scale of few pixels (50 nm).
• Observed a peak in pixel variance at the lipid phase transition for pure lipid samples.
• Demonstrated abrupt changes in pixel variance at phase transitions, followed by a slow decrease.
• Found significant heterogeneity in the liquid phase even above the transition temperature.

Conclusions:

• The liquid phase of lipid membranes is heterogeneous at the microscale.
• Results suggest an underlying microscale structure with non-uniform water distribution.
• Simple lipid systems can generate and maintain stable structural and organizational heterogeneities.
• Identified domain-specific concentration of pixels with differing GP values.