Higher 3D resolution of oligosaccharide structures can now be obtained using ion-mobility mass spectrometry

The team behind ion-mobility mass spectrometry.
From left: Dr Terry Nguyen-Khuong, Edward Pallister, Gavin Teo, Tay Shi Jie, Amelia Mak, Corrine Wan, Dr Ian Walsh and Dr Matthew Choo

Science

Glycans are chains of sugars that adorn proteins. Since these sugar chains can alter the functions of protein-based drugs, it is important to understand the nature of their structures. This has been a tremendous challenge because sugar chains can have very different 3D structures despite having the same mass. In this study, we demonstrated that ion-mobility mass spectrometry can distinguish structural differences in similar glycans, by breaking the glycans into smaller fragments and then measuring their shape. We are now one step closer to understanding how glycan structure can impact protein functions.

Societal Impact

A majority of protein-based drugs are glycosylated. Their safety, efficacy and clinical outcomes can be significantly affected by the oligosaccharides that decorate them. Uncovering the structural details of these oligosaccharides in high resolution helps researchers understand the functions and mechanisms of protein-based drugs, and improve corporate decisions regarding cost, time and efficiencies of quality control. Our work shows that ion-mobility mass spectrometry as an emerging technology can meet these needs and potentially be positioned as a standard in everyday analytical laboratories that support industry and clinics.

Technical Summary

Despite numerous approaches to characterizing glycans, there still remains the challenge of distinguishing isomeric glycan structures which have similar compositions. The emergence of ion-mobility spectrometry-mass spectrometry as an increasingly accessible analytical technology affords researchers and scientists the ability to distinguish glycan isomers. Whilst most approaches with ion mobility are focused on intact glycans, we dedicated this study to glycan fragments. Based on the collision cross section of glycan fragments, we can individually identify previously indistinguishable glycan isomers such as bisecting N-acetylglucosamine and tri-antennary glycans, galactose glycan arm extension and sialic acid extension, among others. The success of our approach is irrespective of what the glycan is conjugated to, such as a protein, peptide or fluorophore. By offering higher structural resolution using an increasingly accessible technique, our method allows deeper understanding of how glycan structures can affect the function and efficacy of their glyco-conjugates, and potentially advances quality control of therapeutic glycoproteins.

References

Pallister EG, Choo MSF, Walsh I, Tai JN, Tay SJ, Yang YS, Ng SK, Rudd PM, Flitsch SL, Nguyen-Khuong T. Utility of Ion-Mobility Spectrometry for Deducing Branching of Multiply Charged Glycans and Glycopeptides in a High-Throughput Positive ion LC-FLR-IMS-MS Workflow. Anal Chem. 2020 Dec 1;92(23):15323-15335. doi: 10.1021/acs.analchem.0c01954. Epub 2020 Nov 9. PMID: 33166117.