Applications: To determine the structure of cells and their surface at 2 nm resolution. This technique is especially suited to the study of membrane structure and membrane proteins. Precious information about the surface of cells can be obtained.
Method: The sample (tissue, cells, liposomes ...) is cryo-protected and vitrified at high pressure or in liquid propane, inserted into the vacuum chamber of the instrument and broken (freeze-fracture) with a knife at -125°C. The partial sublimation of ice at -105°C (freeze-etching) reveals the surface of the sample. The fractured and etched surfaces are replicated with 1 nm platinum/carbon. The replica is transferred to am EM grid for TEM examination.
Advantages: Sample preservation, high contrast. Small membrane proteins can be visualized.
Disadvantages: Only the external surfaces and the regions where the fracture occur are visualized.
Sample requirements:10 to 50 μl of a highly concentrated sample suspension.