Freeze Fracture Electron Microscopy

Freeze fracture electron microscopy i a technique lo reveal the surface features of hydrophobic interior of cell membrane. In this technique, the cells/tissues are first frozen in liquid freon at - 179°C. The frozen block is cut with a cold knife blade alongwith the planes of weakness, run through each cell. Generally, these planes occur between the two layers of lipid molecules of the membrane. The plane of fracture at these places exposes the interior of a plasma membrane (Figure shown below).

The newly exposed faces of a plasma membrane, the exoplasrnic fracture face (EF) and the protoplasmic fracture face (PF) are covered with a very thin layer of platinum by dissolving away the organic material. The freshly fractured membrane may be covered with platinum and carbon to dtain replicas (exact copies) of the surface and this is observed under a TEM. This technique demonstrates that intercellular junctions (where cells make contact with each other) are composed of specilaised membrane protein.