Native ion mobility mass spectrometry (IMMS), is a rather new tool in structural biology. Complementary to the separation of the ions based on mass, they are also separated according to their physical size. Typically, ions with a larger cross section (volume) exhibit longer drift times in the gas-filled ion mobility chamber. Therefore, IMMS can reveal direct information regarding the shape and conformation of a protein complex. The Biomolecular Mass Spectrometry and Proteomics group at the Bijvoet Center has a Waters Synapt HD HDMS mass spectrometer for ion mobility analysis of proteins and protein complexes.