Direct imaging of paracrystalline phospholipid structure in the electron microscope

Area of Science:

• Materials Science
• Biophysics
• Crystallography

Background:

• Phospholipids are key amphiphilic molecules in biological systems.
• Epitaxial crystallization is a technique used to grow crystalline materials on a substrate.
• Electron microscopy allows for high-resolution imaging of materials.

Purpose of the Study:

• To directly resolve the lamellar structure of crystallized phospholipid 1,2-dihexadecyl sn glycerophosphoethanolamine.
• To investigate the presence of defects and undulations within the phospholipid crystal lattice.
• To correlate observed structural features with potential biological properties and experimental challenges.

Main Methods:

• Epitaxial crystallization of 1,2-dihexadecyl sn glycerophosphoethanolamine.
• Direct imaging of unstained crystals using transmission electron microscopy (TEM).
• Analysis of lattice images to identify structural features and defects.

Main Results:

• Direct resolution of 55.6 A lamellae in unstained phospholipid crystals at room temperature.
• Observation of line dislocations and lenticular cracks within the crystal lattice.
• Identification of undulating lattice structures with a periodicity of 0.1-0.5 micron.

Conclusions:

• The direct visualization of phospholipid lamellae provides unprecedented structural detail.
• The observed undulations and defects may influence the biological properties of the phospholipid.
• These structural features can explain difficulties encountered in X-ray and electron diffraction studies.