FoXS, FoXSDock and MultiFoXS: Single-state and multi-state structural modeling of proteins and their complexes based on SAXS profiles

Nucleic Acids Res. 2016 Jul 8;44(W1):W424-9. doi: 10.1093/nar/gkw389. Epub 2016 May 5.


Small Angle X-ray Scattering (SAXS) is an increasingly common and useful technique for structural characterization of molecules in solution. A SAXS experiment determines the scattering intensity of a molecule as a function of spatial frequency, termed SAXS profile. Here, we describe three web servers for modeling atomic structures based on SAXS profiles. FoXS (Fast X-Ray Scattering) rapidly computes a SAXS profile of a given atomistic model and fits it to an experimental profile. FoXSDock docks two rigid protein structures based on a SAXS profile of their complex. MultiFoXS computes a population-weighted ensemble starting from a single input structure by fitting to a SAXS profile of the protein in solution. We describe the interfaces and capabilities of the servers (, followed by demonstrating their application on Interleukin-33 (IL-33) and its primary receptor ST2.

MeSH terms

  • Interleukin-1 Receptor-Like 1 Protein / chemistry
  • Interleukin-33 / chemistry
  • Internet
  • Models, Molecular*
  • Multiprotein Complexes / chemistry*
  • Proteins / chemistry*
  • Scattering, Small Angle*
  • Software*
  • X-Ray Diffraction*


  • Interleukin-1 Receptor-Like 1 Protein
  • Interleukin-33
  • Multiprotein Complexes
  • Proteins