Probing Mobility-Selected Saccharide Isomers: Selective Ion–Molecule Reactions and Wavelength-Specific IR Activation

Abstract

Differential Ion Mobility Spectrometry (DIMS) provides orthogonal separation to mass spectrometry, and DIMS combined with the high sensitivity of a quadrupole ion-trap is shown to be useful for the separation and identification of saccharides. A comprehensive analysis of the separation of anomers (α- and β-methylated glucose) and epimers (α-methylated glucose and mannose) ionized with Li(+), Na(+), and K(+) is performed. DIMS separation is found to be better for saccharides cationized with the two latter species. The corresponding resolving power for the two glucose anomers with Na(+) is found to be very close to the corresponding drift-tube IMS value. The lithiated complexes are investigated further using a combination of infrared spectroscopy integrated to ion-trap mass spectrometry and quantum chemical calculations. Together with DIMS, consistent results are obtained. It is found that two competing structural motifs might be at play, depending on the subtle balance between the maximization of the coordination of the metal cation and the intrinsic conformational energetics of the saccharide, which is for a large part driven by hydrogen bonding. The comparison of simulated and observed spectra clearly shows that a band at ∼3400 cm(-1) is specific to a structural motif found in the lithiated glucose complexes, which could explain the trends observed in the DIMS spectra of the saccharide complexes. It is shown that DIMS-MS/MS using wavelength specific IR activation would provide a new orthogonal dimension to mass spectrometry.

Cryogenic Vibrational Spectroscopy Provides Unique Fingerprints for Glycan Identification

“…Along these lines, Hernandez et al [23] combined differential IMS (DIMS) with infrared multi-photon dissociation (IRMPD) spectroscopy to study mono-hydrated, methylated monosaccharides. While they demonstrated small differences in the IR spectrum of α and β anomers, the low resolution of DIMS is unlikely to be able to separate larger species.…”

Analyzing Glycopeptide Isomers by Combining Differential Mobility Spectrometry with Electron- and Collision-Based Tandem Mass Spectrometry

“…In recent years, FAIMS/DMS has been used to separate isomers of many forms, including structural isomers [15][16][17], sequence variant peptides [18], and tautomers [19][20][21]. Here, we describe the DMS separation of a set of glycopeptide isomers to enhance their characterization by either collisionor electron-based tandem mass spectrometry methods.…”

Recent advances in ion mobility–mass spectrometry for improved structural characterization of glycans and glycoconjugates

“…In addition to coupling IM with collision-based fragmentation methods, IM has recently been combined with a variety of fragmentation and spectroscopic techniques, including electron activated dissociation (ExD) [44], UV photodissociation [45,46], and cryogenic IR spectroscopy [47,48]. The combination of selected accumulation-trapped IM (SA-TIMS) with Fourier transform ion cyclotron resonance (FTICR) mass spectrometers makes it possible to perform ExD on mobility-selected ions [44].…”