Predicting protein plasticity with molecular dynamics (MD) calculations requires experimental assessment. Using small-angle X-ray scattering (SAXS) we compare scattering profiles computed from MD structures with experimental profiles from Cu-Zn superoxide dismutase (SOD1) in its metal- loaded and metal-free form. Forty-nanosecond MD calculations provide a sizeable pool of conformational states yielding a neat agreement with experiments for the metal- loaded enzyme and an exploration of flexible polypeptide segments in the metal- free dimer. This flexibility leads to a discrepancy between SAXS and MD which can be resolved proficiently by partial protein metallation highlighting the potential of this approach for examining overall conformational protein dynamics. (C) 2009 Elsevier B.V. All rights reserved.