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. 2010 Jul;38(Web Server issue):W540-4.
doi: 10.1093/nar/gkq461. Epub 2010 May 27.

FoXS: A Web Server for Rapid Computation and Fitting of SAXS Profiles

Free PMC article

FoXS: A Web Server for Rapid Computation and Fitting of SAXS Profiles

Dina Schneidman-Duhovny et al. Nucleic Acids Res. .
Free PMC article


Small angle X-ray scattering (SAXS) is an increasingly common technique for low-resolution structural characterization of molecules in solution. SAXS experiment determines the scattering intensity of a molecule as a function of spatial frequency, termed SAXS profile. SAXS profiles can contribute to many applications, such as comparing a conformation in solution with the corresponding X-ray structure, modeling a flexible or multi-modular protein, and assembling a macromolecular complex from its subunits. These applications require rapid computation of a SAXS profile from a molecular structure. FoXS (Fast X-Ray Scattering) is a rapid method for computing a SAXS profile of a given structure and for matching of the computed and experimental profiles. Here, we describe the interface and capabilities of the FoXS web server (


Figure 1.
Figure 1.
Snapshot of a FoXS output page. Computed profiles of two PDB files are compared to the experimental SAXS profile of malic enzyme (data from, PF1026). The first structure (pdb_model) includes a model of the unfolded His tag region (35 residues), while the second structure (2dvm) does not. The server was run with the default parameters and the hydration layer modeling was disabled. Plots on the left display the theoretical profiles and plots on the right display their fit to the experimental profile. The top two plots are for the structure with the modeled unfolded region (pdb_model), the middle two plots are for the original PDB file (2dvm), the bottom left plot overlay the profiles for the two input structures, and the bottom right plot shows their fit to the experimental profile. The structure with the modeled unfolded region shows a better fit to the experimental profile with the value of χ = 2.88, compared to χ = 6.33 for the original crystallographic structure. The user can follow the links to download the computed profiles and their fittings.

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