Freeze etching biological method

An alternative method is the freeze-etching technique [24, 25], which consists of producing platinum shadowed replicas of fractures created in rapidly frozen biological systems or lyotropic liquid crystals. The fracture orientation is somewhat haphazard, but occurs preferentially within the paraffinic level of the bilayers. These methods offer the possibility of viewing bilayers directly and preparing stereoviews. Beautiful pictures of liquid crystalline DNA, both cholesteric and hexagonal, have been obtained, but individual molecules are not easily resolved. However, the director distribution can be deduced from the images [26],... 

An excellent review of freeze fracturing is found in a chapter by McNutt [362]. The method has been described for preparation of biological membranes. An older, improved version of the method was described by Steere [363] and Moor et al. [364], while a review of the method and application to membranes was described by Branton [365]. The method involves cementing a 1-2 mm piece of the material onto a copper disk with gum arabic dissolved in 20% glycerin and then transferring the material to liquid Freon 22 (chlorodifluoromethane). The specimen is fractured with a cold knife in a vacuum evaporator, and it may be etched prior to replication. A replica can be cast on the surface of the hydrated... 

---