mass spectrometry studies of complexes ion mobility mass spectrometry of complexes ion mobility mass spec orchard 2012-08-10T11:56:05Z IM-MS analysis is performed by first ionizing the protein complex of interest followed by ion mobility separation according to their cross-section-to-charge (Q/z) ratio. After separation, ions are sampled by a mass spectrometer and analyzed according to their mass-to-charge (m/z) ratio. Combined knowledge of both Q/z and m/z can be used to infer the size and shape of the complex. MI:1246 PSI-MI iM-MS