Protein structures are usually done from 2-dimensional crystals (sheets or helices), polyhedrons such as viral capsids, or dispersed proteins. Electrons can be used in these situations, whereas X-rays cannot, because electrons interact more strongly with atoms than X-rays do.
Electron crystallography is a method to determine the arrangement of atoms in solids using a transmission electron microscope (TEM). The method was invented by Aaron Klug, who won the Nobel Prize in Chemistry for this, and his studies on virus structures and transfer RNA, in 1982.
The first electron crystallographic protein structure to be solved was bacteriorhodopsin in 1990. Since then, several other high-resolution structures have been done by electron crystallography, including the light-harvesting complex, and the bacterial flagellum.
- Klug A. 1978/79. Image analysis and reconstruction in the electron microscopy of biological macromolecules. Chemica Scripta 14. 245-256
- Kühlbrandt W, Wang DN, Fujiyoshi Y. 1994. Atomic model of plant light-harvesting complex by electron crystallography. Nature 367 p61.4 PMID 8107845
- Yonekura K, Maki-Yonekura S, Namba K. 2003. Complete atomic model of the bacterial flagellar filament by electron cryomicroscopy. Nature 424, p643 PMID 12904785