Special features of phosphatidylcholine vesicles as seen in cryo-transmission electron microscopy.

Vesicles of egg yolk phosphatidylcholine (EYPC) were studied by cryo-transmission electron microscopy. The electron micrographs indicate that, despite the rapidity of cooling, membrane undulations are flattened and some vesicles change their shapes before the samples freeze. These artefacts are attributed to the action of the lateral tension that results from the membrane area contraction associated with the temperature drop. Other micrographs represent grainy membranes and angular vesicles. We regard them as the first direct evidence for the superstructure and optically invisible roughness which were recently postulated for these membranes.