Cross-Ring Fragmentation Patterns in the Tandem Mass Spectra of Underivatized Sialylated Oligosaccharides and Their Special Suitability for Spectrum Library Searching

Abstract

Reference spectral library searching, while widely used to identify compounds in other areas of mass spectrometry, is not commonly used in glycomics. Building on a study by Cotter and coworkers on analysis of sialylated oligosaccharides using atmospheric pressure-matrix-assisted laser-induced tandem mass spectrometry (MS/MS), we show that library search methods enable the automated differentiation of such sialylated oligosaccharide isomers using MS/MS derived from electrospray collision-induced dissociation in ion trap and beam-type fragmentation mass spectrometers. We compare MS/MS spectra of five sets of native sialylated oligosaccharide isomers and show a spectral library search method that can distinguish between these isomers using the precursor ion [M+2X-H]+, where X=Li, Na, or K. Sialic acid linkage (α2,3 vs. α2,6) is known to have a dramatic effect on the fragmentation of the sialylated compounds. We found that 2,4A3 cross-ring fragment at the terminal monosaccharide in sialyllactoses, sialyllactosamines, and sialyl pentasaccharides is highly abundant in the MS/MS spectra of [M+2X-H]+ species of α2,6-NeuAc glycans, while (2,4A3-H2O) fragment is highly abundant in α2,3-NeuAc moiety. The 2,4A3-H2O peak is specific to NeuAc-α2,3-Gal-β1,4-Y (Y=GlcNAc or Glc). To our knowledge, this observation was not reported previously. Theoretical calculations reveal major conformational differences between α2,6-NeuAc and α2,3-NeuAc structures that provide reasonable explanations for the observed fragmentation patterns. Other singly-charged ions ([M+X]+) do not show similar cross-ring cleavages. Implemented in a searchable library, these spectral differences provide a facile method to distinguish sialyl isomers without derivatization. We also found good spectral matching across instruments. MS/MS spectra and tools are available at http://chemdata.nist.gov/glycan/spectra. Graphical Abstract Electronic supplementary materialThe online version of this article (10.1007/s13361-018-2106-8) contains supplementary material, which is available to authorized users.

Identification of Plasma Lipidome Changes Associated with Low Dose Space-Type Radiation Exposure in a Murine Model

“…Subsequently, hierarchical clustering analysis was performed to visualize the differential expression of metabolites between the control and irradiated groups ( Figure 3, panel A). Out of 175 metabolites that were found to be dysregulated in the plasma of mice exposed to 0.1 Gy of 16 O, the identities of 51 metabolites and lipids were confirmed by matching MS/MS (Tandem-Mass Spectrometry) fragmentation spectra for each analyte against the NIST (National Institute of Standards and Technology) or METLIN (Scripps Institute, La Jolla, CA, USA) databases; this pipeline has been used by several research groups [18][19][20] (Supplementary Table S1). Exposure to 0.1 Gy of 16 O at 14 days and 90 days resulted in dysregulation of a large number of metabolites and lipids; however, a majority of these features could not be annotated using tandem mass spectrometry which remains a major bottleneck in this area of research.…”

How General Is Anomeric Retention during Collision-Induced Dissociation of Glycans?

“…Branching, bond position, and anomericity can be successfully determined by analyzing the fragments from relatively small glycans, [13][14][15][16][17][18][19][20] although the latter requires observing cross-ring fragments that preserve the anomeric configuration of the glycosidic bond. 10, [21][22] Nevertheless, tandem MS is typically unable to fully distinguish between all isomeric forms. Scheme 1 -Nomenclature for B/Y and C/Z fragments of glycans.…”

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

“…However, the ATDs of the glycan standards as [ M −2H] 2− and [ M −3H] 3− ions (Figure 5, marked in blue) are distinctive and can be employed to distinguish the various isomers without a need for demanding MS/MS fragmentation experiments. These differences likely arise from differences in conformational properties of α2,3‐ and α2,6‐linked sialosides [25] . The isomers 14 and 15 , which have an additional core Fuc, have close CCS values but can also be differentiated based on ATDs (Figure 4 C, D).…”

“…These differencesl ikely arise from differences in conformational properties of a2,3and a2,6-linked sialosides. [25] The isomers 14 and 15,w hich have an additional core Fuc, have close CCS values but can also be differentiated based on ATDs (Figure4C, D). Interestingly,t he CD of these compounds differ substantially from glycans 10 and 11 ( Figure 5), lacking the core Fuc, indicatingt he latter functionality exerts conformationalc ontrol.…”