Polyubiquitination is a critical protein post-translational modification involved in a variety of processes in eukaryotic cells Understanding the molecular basis for selective recognition of the polyubiquitin signals by cellular receptors requires knowledge of the three-dimensional structures polyubiquitin chains adopt. We aim at determining conformational ensembles of polyubiquitin chains by combining experimental data from NMR and small-angle scattering with computer modeling. I will discuss and illustrate how integrating information derived from NMR and SANS measurements with modeling capabilities provided by SASSIE enabled us to paint a portrait of polyubiquitins as flexible conformational ensembles. I will also discuss our efforts to integrate into SASSIE new capabilities for ensemble and NMR data analysis.