Electron diffraction and three-dimensional crystallography for structural biology

Electron crystallography is increasingly becoming a viable alternative for structure elucidation of three-dimensional, multi-nanometre sized crystals of beam-sensitive organics and macromolecules. Because electrons interact with matter strongly, crystals cannot be much more than 200nm thick. Diffracted volumes are therefore small, leading to a poor signal-to-noise ratio (SNR) as beam damage limits the total electron dose. Data can be collected in diffraction - and imaging mode. Imaging has the advantage of providing spatial phase information but comes at a substantial cost in SNR. Highly sensitive hybrid pixel detectors push the limits of high-quality diffraction data acquisition even further. Data integration, structure solution and refinement are feasible with existing software after minor adaptations. We review the current state of electron diffraction for structural biology, including instrumentation, data acquisition and structure determination.