Resolving individual atoms of protein complex by cryo-electron microscopy

Breakthroughs in single-particle cryo-electron microscopy (cryo-EM) technology have made near-atomic resolution structure determination possible. Cryo-EM has resolved over four thousand structures at near-atomic resolutions (2–4 Å). It is rapidly becoming the method of choice for structure determination of membrane proteins, large assemblies, and multi-protein complexes partly because it does not require a crystal and partly because it can accommodate specimens with heterogeneous composition and/or conformation. This powerful technique is now capable of resolving protein complexes to better than 2 Å resolution3 and has been used to solve 3.7 Å resolution structure of RNA as small as ~40 kilodaltons.