Molecular packing of a crystalline ether-linked phosphatidylcholine: an electron diffraction study

Area of Science:

• Lipid crystallography
• Molecular biophysics
• Structural biology

Background:

• Understanding lipid packing is crucial for cell membrane structure and function.
• 1,2-dihexadecyl-sn-glycerophosphocholine is an ether-linked phospholipid with implications in biological systems.
• Minimally hydrated crystal forms offer insights into lipid behavior under specific conditions.

Purpose of the Study:

• To determine the molecular packing arrangement of 1,2-dihexadecyl-sn-glycerophosphocholine in a minimally hydrated crystal state.
• To compare its packing with known diacyl phosphatidylcholines and related lipids.
• To elucidate the structural basis of its bilayer organization.

Main Methods:

• Electron diffraction analysis of solution- and epitaxially-crystallized samples.
• Crystallographic model building and translational search.
• Comparison with existing crystal structures of related phospholipids.

Main Results:

• Molecular chain axes are oriented perpendicular to the bilayer plane.
• Lipid chains exhibit hexagonal packing within the methylene subcell.
• Headgroup packing distances are comparable to the dipalmitoyl analog at low humidity.

Conclusions:

• The bilayer packing of this ether-linked phosphatidylcholine resembles that of sphingomyelin.
• The study provides detailed structural insights into ether-linked phospholipid organization.
• Findings contribute to the understanding of lipid polymorphism and membrane biophysics.