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 signifi cantly enhanced resolution and reliability of structural models provided by the technique and made SAXS a useful complementary tool to high resolution methods. In particular, SAXS allows for rapid validation of high resolution crystallographic or theoretically predicted models, identifi cation of biologically active oligomers and visualization of missing fragments. Quaternary structure of complexes can be analyzed by rigid body movements/rotations of high resolution models of the individual subunits of domains. The basics of SAXS will be presented and illustrated by advanced applications to macromolecular solutions.