The basic idea behind small angle X-ray solution scattering is simple: shine a beam of X-rays on a droplet of protein solution and measure how much the rays get deflected.
What parameters can BioSAXS determine?
radius of gyration (typically 2% accuracy)
molecular weight (typically 10% accuracy)
maximum intra-particle distance
low-resolution electron density
degree of folding, denaturation, or disorder
comparisons with models
interparticle interaction potentials
What are people able to do with BioSAXS data?
determining physiological oligomeric state
validating proposed models of complexes
building complexes from monomers or known fragments
studying protein-protein interaction under different solution conditions
modeling missing loops and domains
refining homology models
categorizing discrete folded and unfolded states
finding volume fractions in mixtures
Will BioSAXS work on my samples?
In crystallography, poor crystals and overlapping spots are a frequent cause of failure. BioSAXS can have problems too. Just because it does not require crystals does not guarantee success. In crystallography, it is easier to detect bad data: you can't index or integrate the diffraction spots. With BioSAXS, however, you can process bad data with very few indications that anything is wrong. It is therefore very important to understand how to recognize bad data and to diagnose the possible causes.
