Overview of SAS-based ab initio modelling. The modelling process starts by selection of a suitable data range and determination of the corresponding p(r) function. The chosen ab initio modelling approach is repeated several times in order to explore the available solution space, and the generated models are grouped according to their structural similarity. The most probable and average models are selected on the basis of the clustering. Pairwise FSC functions of the structurally aligned bead or dummy residue models are computed. The average of all pairwise FSC functions is used to determine the variability estimate Δens as 2π/sens, where sens is the momentum transfer value at which the average FSC drops below 0.5. The corresponding resolution is estimated from the variability.