Macromolecular electron microscopy in the era of structural genomics.

Macromolecular machines carry out many cellular functions. Cryo-electron microscopy (cryo-EM) is emerging as a powerful method for studying the structure, assembly and dynamics of such macromolecules, and their interactions with substrates. With resolutions still improving, 'single-particle' analyses are already depicting secondary structure. Moreover, cryo-EM can be combined in several ways with X-ray diffraction to enhance the resolution of cryo-EM and the applicability of crystallography. Electron tomography holds promise for visualizing machines at work inside cells.