Grid selection strategy for high-resolution cryo-EM

Cryo-electron microscopy (cryo-EM) is a revolutionary technique to study the three-dimensional structure of macromolecules and theirs complexes at molecular resolution. The first step in preparing samples for cryo-EM is to select and optimize the right grid for the specimen. This screening process needs consideration in many aspects including concentration and stability of the specimen, compatibility with grid material and optimum ice thickness across the grid. Importantly, the best signal-to-noise ratio (SNR) for a micrograph is closely related to vitrifying the grid sample with the optimum imaging condition. Here we describe overall strategies for grid selection and optimization by understanding the properties of grids and a variety of techniques for grid treatment for high-resolution electron micrographs. This review also describes the utilization of various specimen supports including amorphous carbon, graphene and functionalized support films.