ORNL_SAS: software for calculation of small-angle scattering intensities of proteins and protein complexes

The program ORNL_SAS calculates solution small-angle X-ray and neutron scattering intensity profiles from a wide variety of structures, including atomic-resolution models of proteins and protein complexes, low-resolution models defined in any manner, or combinations of both. ORNL_SAS is capable of simultaneously generating multiple intensity profiles, such as a contrast-variation series, and evaluating the quality of the fit of the model profiles to experimental data in a single run of the program. The capabilities of the widely applicable approach make it possible to use ORNL_SAS as the intensity calculation engine of model-building applications for small-angle scattering data.