Free-Radical-Mediated Glycan Isomer Differentiation

Abstract

The inherent structural complexity and diversity of glycans pose a major analytical challenge to their structural analysis. Radical chemistry has gained considerable momentum in the field of mass spectrometric biomolecule analysis, including proteomics, glycomics, and lipidomics. Herein, seven isomeric disaccharides and two isomeric tetrasaccharides with subtle structural differences are distinguished rapidly and accurately via one-step radical-induced dissociation. The free-radical-activated glycan-sequencing reagent (FRAGS) selectively conjugates to the unique reducing terminus of glycans in which a localized nascent free radical is generated upon collisional activation and simultaneously induces glycan fragmentation. Higher-energy collisional dissociation (HCD) and collision-induced dissociation (CID) are employed to provide complementary structural information for the identification and discrimination of glycan isomers by providing different fragmentation pathways to generate informative, structurally significant product ions. Furthermore, multiple-stage tandem mass spectrometry (MS 3 CID) provides supplementary and valuable structural information through the generation of characteristic parent-structure-dependent fragment ions.

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

“…Compared to the conventional 213 nm UVPD, the 266 nm fourth harmonic pulses induced RDD MS 3 spectra provided more difference in relative abundances of several fragments which could distinguish synthesized oligosaccharide isomers. More recently, a methylated free‐radical‐activated glycan sequencing reagent has been introduced to eradicate the glycan rearrangement in gas phase [169]. Although the potential of RDD has been brought to isomeric glycomic analysis, more investigations of this technique toward complex glycans from biological samples need to be performed in the future.…”

Charge transfer dissociation of a branched glycan with alkali and alkaline earth metal adducts

“…Alternative fragmentation techniques such as ultraviolet photodissociation (UVPD), 17 high‐energy CID, 18,19 electron transfer dissociation (ETD), 20,21 electron capture dissociation (ECD), 22 free radical‐activated glycan sequencing reagent (FRAGS), 23 electron detachment dissociation (EDD), 24,25 and negative electron transfer dissociation (NETD) 26,27 have also had success in generating cross‐ring cleavages in glycan analyses. These techniques have had varying degrees of success, but they do have some drawbacks.…”

Structural Characterization of Isomeric Oligogalacturonan Mixtures Using Ultrahigh-Performance Liquid Chromatography-Charge Transfer Dissociation Mass Spectrometry

“…28 FRAGS is capable of producing both glycosidic bonds and cross-ring cleavages without generating glycan rearrangements and internal and external residue losses upon collisional dissociation. 28,29 Charge transfer dissociation (CTD) is a novel ion activation method that provides such capabilities, and, despite its own drawbacks, CTD has shown promising results for oligosaccharides, peptides, proteins, and lipids. 8,30−32 Several groups helped lay the foundation for the development of CTD.…”

“…Free radical-activated glycan sequencing (FRAGS) of reagents is an alternative method inspired by the free radical-driven dissociation techniques . FRAGS is capable of producing both glycosidic bonds and cross-ring cleavages without generating glycan rearrangements and internal and external residue losses upon collisional dissociation. , Charge transfer dissociation (CTD) is a novel ion activation method that provides such capabilities, and, despite its own drawbacks, CTD has shown promising results for oligosaccharides, peptides, proteins, and lipids. ,− …”