Ion mobility–mass spectrometry of supramolecular complexes and assemblies

Abstract

Despite their structural and functional differences, synthetic supramolecular assemblies share many similarities with biological ones, especially enzymes. The assemblies can be on the same length scales, 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 a protein's secondary and tertiary structure, such that the resulting dynamism makes structure elucidation challenging. In the case of 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 gasphase mobility as well as 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 Perspective describes IM-MS techniques and how they help us understand the structures of molecular self-assemblies, host-guest complexes and metallosupramolecular complexes.

Metal‐Organic Frameworks and Metal‐Organic Cages – A Perspective

“…[66] Ion mobility experiments make use of collisions with an inert carrier gas to reveal information on size and shape of assemblies; with MOCs with greater collision cross-sections undergoing more collisions and therefore having longer flight times/lower mobility. [67] This allows ion mobility MS to distinguish between isomeric species of the same m/z that often appear similar/the same in other analysis techniques. An interesting class of stimuli-responsive MOCs containing four dithienylethene photoswitchable units undergo reversible interconversion between closed ( Figure 3a) and open (Figure 3b) forms via a light-promoted 6π electrocyclization.…”

Thermodynamically driven self-assembly of pyridinearene to hexameric capsules

“…IM-MS has already demonstrated its power in structural analysis of different supramolecular systems. 12 In the ATD only a single wellresolved peak was observed. This implies that the corresponding [1 6 + G] 2+ ion has a relatively rigid well-defined structure.…”

Chemical mimicry of viral capsid self-assembly via corannulene-based pentatopic tectons

“…The unclear isotope patterns could result from the high molecular weight (~42 kDa) and high charge states. Traveling wave ion mobility mass spectrometry (TWIM-MS) 22 provided further structural information. The ESI-TWIM-MS spectrum of 4b (Fig.…”