Structural Analysis of Native N-Glycans Released from Proteins Using a Novel Mixed-Mode Column and a Hybrid Quadrupole-Orbitrap Mass Spectrometer

Importance of the Topic

The structural characterization of N-glycans is essential for understanding protein function, cellular communication, and biopharmaceutical quality. Precise glycan profiling supports biosimilar comparability, drug safety assessment, and biomarker discovery.

Objectives and Study Overview

This study evaluates a novel mixed-mode GlycanPac AXH-1 column coupled with a Q Exactive hybrid quadrupole-Orbitrap mass spectrometer for detailed analysis of native (unlabeled) and 2AB labeled N-glycans released from bovine fetuin. The aim is to compare retention, separation selectivity, and structural elucidation capabilities for both workflows.

Methodology

Sample preparation involved enzymatic release of N-glycans with PNGase F, followed by HyperSep Hypercarb SPE cleanup for native glycans or 2AB fluorescent labeling and cleanup for tagged glycans. Separation was performed on a GlycanPac AXH-1 (2.1×150 mm, 1.9 µm) column using an acetonitrile/water and 80 mM ammonium formate (pH 4.4) gradient at 400 µL/min, 30 °C. MS detection employed negative-ion mode on a Q Exactive instrument (scan range 380–2000 m/z, 70,000 resolution) with data-dependent HCD MS/MS for structural assignment. Data were processed using ChromQuest, Xcalibur, and SimGlycan software.

Instrumentation Used

• Thermo Scientific Dionex UltiMate 3000 BioRS LC system with FLD3400RS fluorescence detector
• Thermo Scientific Q Exactive hybrid quadrupole-Orbitrap mass spectrometer
• Thermo Scientific Savant SPD131DDA SpeedVac Concentrator
• Labconco FreeZone benchtop lyophilizer
• Thermo Scientific 24-Port SPE vacuum manifold

Key Results and Discussion

The GlycanPac AXH-1 column exploits combined weak anion exchange and HILIC mechanisms to resolve 24 N-glycan species by charge state (neutral to penta-sialylated), size, and isomeric structure. Native glycans elute in a predictable order without labeling-induced shifts, while 2AB labeled profiles show altered peak intensities and charge distributions. MS/MS HCD spectra provided both glycosidic and cross-ring fragments, enabling confident annotation of monosaccharide composition and linkage patterns. Comparative analysis revealed that labeling can introduce artifact peaks and shift highly sialylated species to lower charge states, potentially obscuring true glycan heterogeneity.

Benefits and Practical Applications

• Label-free workflow reduces sample preparation time and avoids derivatization artifacts
• Enhanced selectivity for charged and neutral glycans facilitates comprehensive glycan profiling
• High-resolution MS/MS supports accurate structural assignment for QA/QC in biopharmaceutical development
• Flexibility to analyze both native and fluorescently labeled glycans on a single platform

Future Trends and Applications

Advancements may include automation of native glycan workflows, expansion to O-glycan and glycopeptide analysis, and integration with bioinformatics platforms for high-throughput glycomics. Emerging applications include personalized medicine, disease biomarker discovery, and online reaction monitoring.

Conclusion

The combination of GlycanPac AXH-1 mixed-mode chromatography and Q Exactive MS/MS provides a robust platform for native N-glycan structural analysis. Eliminating labeling preserves original glycan profiles, while high-resolution fragmentation ensures confident characterization. This approach is highly applicable to biopharmaceutical development, glycomics research, and quality control.

References

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