In many cases our data comes from heterogeneous samples. Heterogeneity can be both compositional and conformational. Interpretation of data collected on heterogeneous sample requires a multi-state model. A multi-state model is a model that specifies two or more co-existing structural states and values for other parameters, such as the weights of each state.

IMP includes a command line tool multi_foxs for enumeration and scoring of multi-state models against SAXS profiles. There is also a web interface available, which functions similarly. See the MultiFoXS tutorial for a demonstration.