Direct imaging of paracrystalline phospholipid structure in the electron microscope.

A long chain amphiphilic molecule--the phospholipid 1,2-dihexadecyl sn glycerophosphoethanolamine--has been crystallized epitaxially so that the interlamellar molecular periodicity is parallel to the substrate and hence normal to the electron beam in the electron microscope. This has permitted the direct resolution of the 55.6 A lamellae in unstained crystals at room temperature. The lattice images have shown the presence of line dislocations and lenticular cracks in the crystals. Of significance to their biological properties is that the lattice is undulating with a periodicity of 0.1-0.5 micron. This would also account for the difficulties encountered by X-ray and electron diffraction techniques when examining these crystals.