Design and operation of a simple environmental chamber for rapid freezing fixation.

Rapid freezing is the most important step in sample preparation for freeze-fracture and other cryotechniques for electron microscopy. We present the design and operation of a simple environmental chamber coupled to a plunger-driven freezing device that has provided simple and reliable freezing from temperatures and humidities other than ambient. The chamber can be constructed and operated with equipment and techniques common to most electron microscopy labs. Temperature control of +/- 0.1 degree C and relative humidities of greater than 90% were provided over the range -5-60 degrees C. Typical electron micrographs showing well preserved structures comparable to jet-freezing are presented.