Membrane splitting in freeze-ethching. Covalently bound ferritin as a membrane marker.

The freeze-etch technique was used to observe red blood cell ghosts labeled on both surfaces with covalently bound ferritin. Ferritin molecules were never observed on fracture faces, thus indicating that fracture does not show membrane-surface detail. Subliming away the surrounding ice did expose the ferritin on the membrane surface. These results were consistent with the concept that membranes split during the fracture process of freeze-etching.