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Cryo-EM

Cryo-electron microscopy (Cryo-EM) is a technique that uses accelerated electrons as illumination source for biological samples. To minimize radiation damage, the sample is kept at cryogenic temperatures and the electron dose has to be low – resulting in noisy images. However, the enormous progress in hardware development and image processing over the past few years has made the technique available to solve near-atomic-resolution protein structures. And the technological progress is ongoing: With even better instruments and software the size and resolution limit will be pushed further down[1].
Today, Cryo-EM does not replace but rather complements X-ray crystallography as structural biology technique[2,3].

The surfactant Amphipol A8-35 stabilizes membrane proteins in a detergent-free aqueous solution and is therefore a useful additive for sample preparation in Cryo-EM.

Recommended Literature

[1] Glaeser (2016) How good can cryo-EM become? Nature Methods 13:28.
[2] Beniac et al. (2017) Structure of the Ebola virus glycoprotein spike within the virion envelope at 11 Å resolution. Sci. Rep. DOI: 10.1038/srep46374.
[3] Lokareddy et al. (2017) Portal protein functions akin to a DNA-sensor that couples genome-packaging to icosahedral capsid maturation. Nat. Commun. DOI: 10.1038/ncomms14310.