CryoEM: a crystals to single particles round-trip.

In the era of intense and steadily increasing attention to cryo electron microscopy (cryoEM) as a powerful tool in structural biology, particularly with regard to randomly oriented biological macromolecules, studies of 2D and small 3D crystals using cryoEM provide added value for addressing-specific questions. Size and shape demands are not as restrictive as for single particle specimens. Crystallization may stabilize whole or partly flexible molecules. Resolutions beyond 2Å, for 3D crystals even sub-Ångström structures, can be obtained allowing studies of chemical properties in detail. The electron dose can be kept low and reduce radiation damage for sensitive specimens. In contrast to X-ray crystallography, scattering of electrons will be directly related to the Coulomb potential and thus give information about charge distribution in biomolecules.