Phase separation in model lipid membranes investigated with cryogenic electron microscopy

Area of Science:

• Membrane biophysics
• Lipid self-assembly
• Cryo-electron microscopy

Background:

• Cell membranes exhibit lateral heterogeneity due to distinct lipid phases.
• Understanding lipid domain formation is crucial for cell function and lipid raft phenomena.
• Existing ensemble-averaged techniques obscure individual vesicle variability.

Purpose of the Study:

• To present a novel method for investigating membrane heterogeneity using cryo-electron microscopy (cryo-EM).
• To enable direct visualization and analysis of individual liposomes.
• To provide insights into lipid raft formation and function.

Main Methods:

• Utilizing phase contrast cryo-electron microscopy (cryo-EM) to image liposomes.
• Analyzing differences in thickness and molecular density between ordered and disordered lipid phases.
• Performing spatially resolved thickness and intensity measurements for phase state assessment.

Main Results:

• Cryo-EM successfully visualizes individual vesicles, revealing heterogeneity obscured by ensemble methods.
• The method leverages inherent lipid phase properties for contrast, eliminating the need for extrinsic probes.
• Spatially resolved analyses provide quantitative data on membrane phase states.

Conclusions:

• The developed cryo-EM method offers direct visualization of membrane nanodomain structure.
• This technique overcomes limitations of ensemble-averaged biophysical methods.
• It facilitates a deeper understanding of lipid raft phenomena in synthetic and biological membranes.