Ion mobility–mass spectrometry of supramolecular complexes and assemblies

Despite their structural and functional differences, synthetic supramolecular assemblies share many similarities with biological assemblies, especially enzymes. The assemblies can be on the same length scale, and their structures and guest binding are typically governed by non-covalent interactions. Thus, only relatively weak interactions define the shape of a synthetic supramolecule or the secondary and tertiary structure of a protein, such that the resulting dynamism makes structure elucidation challenging. For biomolecules such as peptides, proteins, glycans and lipids this has often been tackled using ion mobility–mass spectrometry (IM-MS), whereby analyte ions are separated according to their gas-phase mobility and their mass-to-charge ratio. IM-MS is an established method in omics, separation sciences and small-molecule structural chemistry, but has only recently grown in popularity for the study of synthetic supramolecular assemblies in the gas phase. This Review describes IM-MS techniques and how they can help us understand the structures of molecular self-assemblies, host–guest complexes and metallosupramolecular complexes.