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

Electron diffraction data from solution- and epitaxially-crystallized samples of 1,2-dihexadecyl-sn-glycerophosphocholine are used in an analysis of its molecular packing in the minimally hydrated crystal form. The molecular chain axes are found to be perpendicular to the bilayer plane and the chains pack in the hexagonal methylene subcell. Translational search of a model based on a known diacyl phosphatidylcholine crystal structure indicates that a crystallographic residual minimum corresponds to a headgroup packing distance similar to values found for the dipalmitoyl analog at low relative humidity. The bilayer packing for the ether-linked phosphatidylcholine is therefore similar to the one reported for a sphingomyelin.