Structure analysis of biological macromolecules by small-angle X-ray scattering

Abstract

Small-angle X-ray scattering (SAXS) is a low resolution (1-2 nm) structural method, which is applicable to macromolecules in solution providing information about the overall structure and structural transitions. The method covers an extremely broad range of sizes (from a few kDa to hundreds MDa) and experimental conditions (temperature, pH, salinity, ligand addition etc.). Recent progress in instrumentation and novel data analysis methods significantly enhanced resolution and reliability of structural models provided by the technique and made SAXS a useful complementary tool to high resolution methods. Modern SAXS allows for rapid validation of crystallographic or theoretically predicted models, identification of biologically active oligomers and visualization of missing fragments in high resolution structures. Quaternary structure of complexes can be analyzed by rigid body movements/rotations of high resolution models of the individual subunits of domains. Recent developments made it possible also to quantitatively characterize flexible macromolecular systems, including intrinsically unfolded proteins. The basics of SAXS will be presented and illustrated by advanced applications to macromolecular solutions. © 2013 Springer Science+Business Media Dordrecht.