Identification of Isomeric N‐Glycans by Conformer Distribution Fingerprinting using Ion Mobility Mass Spectrometry

Abstract

Glycans possess unparalleled structural complexity arising from chemically similar monosaccharide building blocks, configurations of anomeric linkages and different branching patterns, potentially giving rise to many isomers. This level of complexity is one of the main reasons that identification of exact glycan structures in biological samples still lags behind that of other biomolecules. Here, we introduce a methodology to identify isomeric N‐glycans by determining gas phase conformer distributions (CDs) by measuring arrival time distributions (ATDs) using drift‐tube ion mobility spectrometry‐mass spectrometry. Key to the approach is the use of a range of well‐defined synthetic glycans that made it possible to investigate conformer distributions in the gas phase of isomeric glycans in a systematic manner. In addition, we have computed CD fingerprints by molecular dynamics (MD) simulation, which compared well with experimentally determined CDs. It supports that ATDs resemble conformational populations in the gas phase and offer the prospect that such an approach can contribute to generating a library of CCS distributions (CCSDs) for structure identification.

Mass Spectrometry-Based Techniques to Elucidate the Sugar Code

“…A widespread approach to sample isolated carbohydrate ions is to employ empirical force fields. − While promising force fields have been parametrized for glycans, they were commonly not developed for sampling isolated charged molecules in the gas phase and are therefore often limited to the analysis of neutral carbohydrates in the condensed phase . Contrary to first-principles methods, force field methods do not have their origin in quantum mechanics but in Newtonian physics.…”

Advances in mass spectrometry‐based glycomics—An update covering the period 2017–2021

“…Another methodology introduced by Boons et al. [130] determines gas phase conformer distributions (CDs) to identify N ‐glycan isomers by measuring arrival time distributions (ATDs) based on drift‐tube IM‐MS. A series of synthetic biantennary glycan standards were prepared to investigate CDs in gas phase isomeric glycans.…”

“…Another methodology introduced by Boons et al [130] determines gas phase conformer distributions (CDs) to identify N-glycan isomers by measuring arrival time distributions (ATDs) based on drift-tube IM-MS. A series of synthetic biantennary glycan standards were prepared to investigate CDs in gas phase isomeric glycans. In addition, a database of CD fingerprints was computed, which can contribute to building a library of collision cross-section distributions (CCDs) for structure identification.…”

High sensitivity glycomics in biomedicine

“…Figure reused from (Hinneburg et al, 2019). AUC, area under the curve [Color figure can be viewed at wileyonlinelibrary.com] Toraño et al, 2021) or to detect variations in siteoccupancy (Guttman & Lee, 2016). While IMS does not directly improve the sensitivity of the analysis, it does provide valuable structural information compared to the conventional separation platforms such as CE or LC.…”