Electron diffraction nears atom-level resolution

Science : An advancement in cryoelectron microscopy (cryo-EM) has produced images that reveal high-resolution details of a molecule bonded to a protein. Cryo-EM had previously been limited to a resolution of 0.5 nm, but recent progress had lowered that to 0.3 nm, still shy of the 0.2-nm resolution achieved by x-ray crystallography and nuclear magnetic resonance imaging. Now Sriram Subramaniam of the National Cancer Institute and his colleagues have reached a resolution of 0.22 nm. The achievement combines improved image analysis algorithms with better isolation of the target molecules. Cryo-EM works by measuring the reflection of electrons off of molecules that have been frozen in place with liquid nitrogen. The randomness of the reflections creates a multitude of blurry images that have to be combined to produce a final clear picture. Subramaniam’s team was able to use the improvements to spot water molecules attached to a protein.