Microcrystal electron diffraction promises a revolution in study of proteins, small molecules

They say seeing is believing but our understanding of chemical systems predominantly depends on second-hand observations and measurements. A colour change can suggest that a reaction has occurred, NMR peaks show how atoms in a structure are connected and enantiomeric excess measurements indicate the proportion of different enantiomers. But, chemists don’t usually see the molecules themselves.

Crystallography is one of the few exceptions, turning those secondary measurements into a conclusive 3D structure. Single crystal x-ray diffraction – the most widely used of these techniques – has been known for more than 100 years and is the gold standard of structure identification across both chemistry and biology. When x-rays are fired at a crystal sample, its regular internal structure scatters light systematically and, by recording this diffraction pattern and working backwards, it’s possible to calculate the 3D structure of the molecule.