Equation (1) requires the evaluation of all the pairwise inter-atomic distances within the molecule of interest, thus resulting in N 2 calculations, where N is the number of the atoms involved, making it highly demanding for large biomolecules. This problem is exacerbated when multiple evaluations of the scattering profile are required, as in the case of MD simulations restrained by SAS data, resulting in severe performance degradation. A successful strategy to mitigate this computational burden is to coarse-grain the representation of the molecule . This simplification can be achieved by grouping the scattering behaviour of sets of atoms into larger beads, while preserving the overall scattering properties of the molecule. This is made possible by the intrinsically low-resolution nature of SAS data, which is more sensitive to the overall shape and size of the molecule rather than its atomic level details. Depending on the specific coarse-graining method used, both the criteria for assigning atoms to beads and the placement of their centre can vary significantly. In general, for a coarse-grained system, equation (1) becomes: