Cryo-electron Microscopy

Cryo-electron microscopy (cryo-EM), or electron cryomicroscopy, is a form of transmission electron microscopy (EM) where the sample is studied at cryogenic temperatures (generally liquid nitrogen temperatures). Cryo-EM is developing popularity in structural biology.

The popularity of cryoelectron microscopy stems from the fact that it allows the observation of specimens that have not been stained or fixed in any way, showing them in their native environment, in contrast to X-ray crystallography, which generally requires placing the samples in non-physiological environments, which can occasionally lead to functionally irrelevant conformational changes. In practice, the resolution of cryo-electron microscopy maps is not high enough to allow for unambiguous model construction on the basis of EM maps only, and models obtained by protein crystallography are used to interpret the cryo-EM maps. However, the resolution of cryo-EM maps is improving steadily, and some virus structures obtained by cryo-EM are already at a resolution that can be interpreted in terms of an atomic model.

A version of electron cryomicroscopy is cryo-electron tomography (CET) where a 3D reconstruction of a sample is created from tilted 2D images.