Small-angle scattering techniques for biomolecular structure and dynamics

Abstract

Small-angle scattering (SAS) techniques provide useful information, typically around the mesoscale (1?100 nm), but they could bring the information to 1000 nm for certain instrumental arrangements. Contrary to microscopies, a direct image is not obtained in SAS techniques. The scattered light, X-ray, neutron radiation is analyzed to deduce the structure. Light scattering from homogeneous media (gas, solid, or liquid) is because of electron density fluctuations. The contrast in X-ray scattering results from the differences in the electron densities and, for neutron beams, arises from the differences in the nature of the atomic nucleus. The X-rays and neutrons can sample similar structural dimensions because of their comparable wavelengths. From another pointof view, although electrons surrounding the atomic nuclei are the target of light and X-ray interaction, the neutrons are scattered by the nucleus itself. Although experiments and data treatment of SAS techniques are different, the fundamental theories and models are quite similar. The main difference is the mechanism by which the incident radiation interacts with the matter.