Advances in Small and Wide‐Angle X ‐Ray Scattering from Proteins and Macromolecular Solutions

Abstract Small‐angle scattering of X‐rays (SAXS) is an established method for low‐resolution structural characterization of native biological macromolecules and soft matter objets in solution. Recent progress in instrumentation (most notably, high brilliance synchrotron sources) and novel data analysis methods significantly enhanced the capabilities of the technique for the structure research. SAXS allows one to study the overall static structure and conformational changes in response to variations in external conditions or ligand binding and is able of providing structural information about partially or completely disordered systems. Extending the data collection to wide‐angle X‐ray scattering (WAXS) allows one not only to resolve the overall size and shape of proteins and complexes but also to probe the fold and to analyze subtle structural transitions. In this article, we present the basic aspects of theory and instrumentation as well as the major modeling techniques used in data analysis and interpretation of macromolecular solutions. A brief account of small‐angle neutron scattering technique (SANS) is also presented showing its complementarity to SAXS. Selected applications of SAXS and WAXS to different types of macromolecular solutions are presented including the analysis of dynamic multicomponent equilibria, characterization of flexible systems, and time‐resolved studies.