A freeze-etch electron microscopic study of liquid propane jet-frozen human erythrocyte membranes

Freeze-etch electron micrographs of haemolysing erythrocytes and isolated erythrocyte membranes frozen using a liquid propane jet-freezer reveal fracture faces very different from those seen after conventional freezing by dipping the specimens into partly solidified Freon 22. Instead of the rather smooth extracellular fracture faces found after conventional specimen freezing, extracellular fracture faces exhibiting large amounts of fibre-like structures are seen after liquid propane jet-freezing of these specimens. No such structures were found in normal red blood cells. When isolated erythrocyte membranes are frozen under conditions favouring spectrin-actin release, freeze-etch micrographs reveal an apparent continuity between the fibre-like structures on the extracellular fracture face and the long fibre-like structures which extent from the protoplasmic surface of the erythrocyte membrane. These results suggest that liquid propane jet-freezing is capable of revealing a structural difference between the membrane of haemolysing and nonhaemolysed red blood cells, and that this difference is related to the fibrous, peripheral proteins of the membrane.