Small-angle scattering and neutron contrast variation for studying bio-molecular complexes.

Structural molecular biology over the past several decades has progressed from studies of the individual proteins, subunits, and domains that accomplish specific biochemistry to seeking to understand the dynamic bio-molecular complexes and assemblies that are responsible for biological function. This progress has led to an expansion of the structural analysis "tool box" to include methods that complement the mainstay techniques of the field: X-ray crystallography, nuclear magnetic resonance (NMR), and cryo-electron microscopy. Small-angle scattering of X-rays or neutrons is one such complementary technique that provides information on the size and shape of scattering particles in solution. This low-resolution structural information can be a powerful complement to high-resolution structural data, especially for the study of bio-molecular interactions with ligands or each other. Further, exploitation of the different neutron-scattering properties of the stable isotopes of hydrogen ((1)H and (2)H) can be used to enrich the information available from the small-angle scattering data, especially for bio-molecular complexes.