In the case of biological macromolecules such as proteins, the advantage of SAXS over crystallography is that a crystalline sample is not needed.
[6] Nuclear magnetic resonance spectroscopy methods encounter problems with macromolecules of higher molecular mass (> 30–40 kDa).
However, owing to the random orientation of dissolved or partially ordered molecules, the spatial averaging leads to a loss of information in SAXS compared to crystallography.
The major problem that must be overcome in SAXS instrumentation is the separation of the weak scattered intensity from the strong main beam.
In principle the problem could be overcome by focusing the beam, but this is not easy when dealing with X-rays and was previously not done except on synchrotrons where large bent mirrors can be used.
Thus measuring times with line-collimation SAXS instruments are much shorter compared to point-collimation and are in the range of minutes.
The resulting smearing can be easily removed using model-free algorithms or deconvolution methods based on Fourier transformation, but only if the system is isotropic.
Line collimation is of great benefit for any isotropic nanostructured materials, e.g. proteins, surfactants, particle dispersion and emulsions.