Combined small-angle X-ray and neutron scattering restraints in molecular dynamics simulations

Small-angle X-ray and small-angle neutron scattering (SAXS/SANS) provide unique structural information on biomolecules and their complexes in solution. SANS may provide multiple independent data sets by means of contrast variation experiments, that is by measuring at different D2O concentrations and different perdeuteration conditions of the biomolecular complex. However, even the combined data from multiple SAXS/SANS sets is by far insufficient to define all degrees of freedom of a complex, leading to a significant risk of overfitting when refining biomolecular structures against SAXS/SANS data. Hence, to control against overfitting, the low-information SAXS/SANS data must be complemented by accurate physical models, and, if possible, refined models should be cross-validated against independent data not used during the refinement. We present a method for refining atomic biomolecular structures against multiple sets of SAXS and SANS data using all-atom molecular dynamics simulations. Using the protein cit...