Neutron Protein Crystallography: Beyond the Folding Structure Available to Purchase

Neutron diffraction provides an experimental method of directly locating hydrogen atoms in proteins, a technique complementary to ultra‐high‐resolution X‐ray diffraction. A neutron diffractometers for biological macromolecules has been constructed in Japan, and it has been used to determine the crystal structures of proteins up to resolution limits of 1.5–2.5 Å. Results relating to hydrogen positions and hydration patterns in proteins have been obtained from these studies. Examples include the geometrical details of hydrogen bonds, the role of hydrogen atoms in enzymatic activity, $CH3$ configuration, H/D exchange in proteins and oligonucleotides, and the dynamical behavior of hydration structures, all of which have been extracted from these structural results and reviewed.