The role of the mobile proton in fucose migration

Abstract

Fucose migration reactions represent a substantial challenge in the analysis of fucosylated glycan structures by mass spectrometry. In addition to the well-established observation of transposed fucose residues in glycan-dissociation product ions, recent experiments show that the rearrangement can also occur in intact glycan ions. These results suggest a low-energy barrier for migration of the fucose residue and broaden the relevance of fucose migration to include other types of mass spectrometry experiments, including ion mobility-mass spectrometry and ion spectroscopy. In this work, we utilize cold-ion infrared spectroscopy to provide further insight into glycan scrambling in intact glycan ions. Our results show that the mobility of the proton is a prerequisite for the migration reaction. For the prototypical fucosylated glycans Lewis x and blood group antigen H-2, the formation of adduct ions or the addition of functional groups with variable proton affinity yields significant differences in the infrared spectra. These changes correlate well with the promotion or inhibition of fucose migration through the presence or absence of a mobile proton. Electronic supplementary material The online version of this article (10.1007/s00216-019-01657-w) contains supplementary material, which is available to authorized users.

Separation of isomeric glycans by ion mobility spectrometry – the impact of fluorescent labelling

“…41 Metal adducts generally do not show fucose migration; protonated species on the other hand can rearrange when the proton is mobile and located at a certain position within the glycan. 35 The results of the isomer pairs LeA/BG H 1 and LeX/BG H 2 obtained here fully agree with those of previous reports. LeA/ BG H 1 as well as LeX/BG H 2 yield very similar CCSs as protonated ions and the ATDs overlap perfectly, which indicates migration into a similar structure.…”

“…19 Reducing end modifications have been studied extensively, namely the influence of fluorescent labels on retention in various chromatographic modes, [29][30][31] ionization efficiency in electrospray ionization (ESI), 32 fragmentation patterns in MS 33,34 and on rearrangement reactions of glycan ions. 35,36 On the other hand, very little is known about their influence on ion mobility separations. In the present study, we focus on the four most common reducing end modifications to study their influence on IMS separation (Fig.…”

“…36 However, more recent studies using cold-ion IR spectroscopy showed that fucose migration reactions have a rather low activation barrier and can therefore also occur without dissociation. 35,44 In this context, the type of adduct as well as the position of the charge was shown to be crucial. 41 Metal adducts generally do not show fucose migration; protonated species on the other hand can rearrange when the proton is mobile and located at a certain position within the glycan.…”

A Matrix-Assisted Laser Desorption/Ionization—Mass Spectrometry Assay for the Relative Quantitation of Antennary Fucosylated N-Glycans in Human Plasma

“…Core fucosylation was identified by the formation of the Y-ion of m/z 501.219 assigned as [Nacetylglucosamine(fucose)-GiRP] + . Core fucosylation also generates, to a lesser extent, the B-ion of m/z 512.198 assigned as [mannose-N-acetylglucosamine(fucose)+H] + caused by fucose rearrangement (Harvey et al, 2002;Chen and Flynn, 2007;Wuhrer et al, 2011;Lettow et al, 2019). This complicates the assessment of mixtures, especially relative quantitation by MS/MS.…”

Linkage Memory in Underivatized Protonated Carbohydrates

“…Protonated carbohydrates present additional challenges, as they can undergo rearrangement reactions, most notably migration of fucose during collision-induced dissociation (CID) 6 . This migration process is still under investigation [7][8][9] , and a general structural understanding of the even simple protonated carbohydrate systems is only now starting to emerge 10 . For intact glycoconjugates (i.e.…”