Gas-Phase Behavior of Galactofuranosides upon Collisional Fragmentation: A Multistage High-Resolution Ion Mobility Study

Abstract

Carbohydrates are ubiquitous in nature but are among the least conserved biomolecules in life. These biopolymers pose a particular challenge to analytical chemists because of their high diversity and structural heterogeneity. In addition, they contain many isomerisms that complicate their structural characterization, notably by mass spectrometry. The tautomerism of the constitutive subunits is of particular interest. A given cyclized monosaccharide unit can take two forms: a most common 6membered ring (pyranose, p) and a more flexible 5-membered ring (furanose, f). The tautomers impact the biological properties of polysaccharides, resulting in interesting properties of the derived oligosaccharides. From an analytical point of view, the impact of tautomerism on the gas-phase behavior of ions has scarcely been described in the literature. In this work, we study the behavior of Galf-containing oligosaccharides, ionized as [M+Li] + species, under collisional dissociation (CID) conditions using high-resolution and multistage ion mobility (IMS) on a Cyclic IMS platform. In the first part of this work, we studied whether disaccharidic fragments released from Galf-containing (Gal) 1 (Man) 2 trisaccharides (and their Galp counterpart) would match the corresponding disaccharide standards, and�despite the fragments generally being a good match�we showed the possibility of Galf migrations and other unidentified alterations in the IMS profile. Next, we expanded on these unknown features using multistage IMS and molecular dynamics, unveiling the contributions of additional gas-phase conformers in the profile of fragments from a Galf-containing trisaccharide compared with the corresponding disaccharides.

Fingerprinting of Underivatized Monosaccharide Stereoisomers Using High-Resolution Ion Mobility Spectrometry and Its Implications for Carbohydrate Sequencing

“…More recently, we further demonstrated that it was generally possible to identify oligosaccharidic fragments by comparison with matching reference IMS profiles even for reputedly unstable structures like furanosideswith the exception of one very specific case where we observed an isomerization of the fragments. However, we proved that the isomerization in that specific case occurred during the fragmentation stage (but independently from the collision energy), and not during the drift of the ion in the IMS stage . Overall, our previous results indicate that mobility profiles of oligosaccharidic fragments are robust enough to envision a sequencing strategy based on those profiles.…”

Synthesis of galactomannan fragments to help NMR assignment of polysaccharides extracted from lichens

“…The strategy implemented in this study capitalized on recent works on the synthesis of the four possible regioisomers of Gal f -Man p and Gal p -Man p disaccharides. 20–22 In each case, the synthesis of a -family derivatives (Gal f family) and b -family compounds (Gal p one) followed a similar sequence of reactions.…”

Ring-Size Memory of Galactose-Containing MS/MS Fragments: Application to the Detection of Galactofuranose in Oligosaccharides and Their Sequencing

“…To access the ring-size information in larger oligosaccharides, the fragmentation approach could be envisioned, which requires the investigation of the impact of CID on the highly flexible furanose ring. We have recently reported promising IM-MS results on the fragmentation of galactose-containing trisaccharides, where the Gal-Man disaccharide fragment retained its structure in some conditions . To validate the sequencing approach, it is thus essential to generalize the conservation of the ring-size structural features upon CID fragmentation, particularly in monosaccharide fragments.…”