metal mirror freezing (slam freezing)

Metal mirror freezing (slam freezing) is one of rapid freeze fixation techniques. This technique punches and rapidly freezes a biological specimen against a metal block cooled by a coolant such as liquid nitrogen.  In many cases, high-thermal-conductivity, high-purity copper with gold plating is used for a metal block.  To increase a temperature drop efficiency of the specimen, the surface of the metal block is prepared into a flat mirror-surface.  This technique can be performed using a relatively inexpensive device, but provides a smaller freezing depth suitable for TEM observation (about 20 µm) than the suitable depth produced by high pressure freezing.  This technique is mainly used to fix tissues.  Specimen preparation for TEM observation of the frozen specimen is carried out by one of the following three procedures.  (1) Applying freeze sectioning to the specimen, (2) Applying resin embedding and ultrathin sectioning to the specimen after the specimen is subject to freeze substitution and is returned to room temperature, and (3) Making a replica of the specimen by freeze fracturing. 

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