Cryotechniques for electron microscopy: A minireview

Aim of this paper is to present a short overview about the state of the art of the so called cryotechniques for electron microscopy. These protocols have been developed and implemented starting in the 1980’s as alternatives, or better to say valid complements, to the standard protocols of chemical fixation routinely used for structural studies of biological samples by electron microscopy. The currently available and more commonly used protocols for rapid freezing such as: plunging, slamming, jet freezing, and high pressure freezing are illustrated and discussed shortly in the first section of this paper. The second section deals with processing of frozen samples summarizing the standard protocols of cryofracture, it then proceeds with the quick-freeze, deep-etch protocol, and ends mentioning briefly the technique for visualization of macromolecular structures after adsorption on mica, rapid freezing, freeze drying, and rotary shadowing. This paper ends with a section dedicated to cryo-electron microscopy: the most recent and high resolution protocol for observation of cell organelles and macromolecular assemblies in frozen hydrated conditions.