Lattice parameters as revealed by electron microscopy and a comparison between lipoprotein crystals from cyclostome eggs formed in vivo and in vitro

Electron diffraction of in vitro-grown lipoprotein crystals from cyclostome eggs (Ichthyomyzon unicuspis) has revealed lattice parameters (a = 19.4 nm, b = 8.9 nm, c = 8.9 nm, beta = 103.4 degrees; apparent symmetry C2 at 3 nm resolution) that were very close to those determined by X-ray diffraction in the same specimen and to others determined by the same electron microscope method in five cyclostome species (in-vivo crystals). Electron imaging has shown all investigated lipoprotein crystals to present similar views projected down the principal crystal axes. Electron diffraction of embedded and heavy-metal-treated lipoprotein crystals is a rapid procedure and a useful low-angle extension to X-ray diffraction.