Improved profiling of sialylated N-linked glycans by ion chromatography-Orbitrap mass spectrometry

Significance of the topic

The detailed profiling of sialylated N-linked glycans is crucial for quality control of glycoprotein therapeutics. High-resolution separation combined with structural identification ensures consistent batch production and supports the development of novel biopharmaceuticals.

Objectives and study overview

This study aims to optimize high-performance anion-exchange chromatography (HPAE) with Orbitrap mass spectrometry to improve separation and characterization of released N-linked glycans. Four glycoprotein standards (bovine fetuin, bovine thyroglobulin, bovine fibrinogen, human alpha-1-acid glycoprotein) were used to assess the impact of hydroxide concentration and temperature on glycan resolution.

Methodology and instrumentation

• Enzymatic digestion: PNGase F release of N-linked glycans from denatured proteins.
• Chromatography: Dionex CarboPac PA200 column with varying NaOH (100–150 mM) gradients and column temperatures (25–35 °C).
• Detection: High-performance anion-exchange with pulsed amperometric detection (HPAE-PAD) coupled to Q Exactive Orbitrap mass spectrometer via an electrolytic desalting device (Dionex ERD 500).
• Data analysis: SimGlycan and Thermo Chromeleon software for peak identification and MS/MS annotation.

Key results and discussion

Higher NaOH concentration enhanced overall resolution, particularly for sialylated isomers, while lower concentration improved separation of certain structural features such as fucosylation and sialic acid linkage variants. Temperature reduction further increased peak sharpness. Unexpected elution order reversals were observed for specific disialylated glycans under high hydroxide conditions, illustrating the sensitivity of retention to glycan composition.

Benefits and practical applications

This optimized HPAE-Orbitrap workflow enables rapid, derivatization-free profiling of therapeutic glycoproteins, supports batch-to-batch consistency monitoring, and expedites glycan database creation.

Future trends and applications

Emerging opportunities include automation of gradient optimization for diverse glycan libraries, integration with advanced bioinformatics for high-throughput glycomics, and application to novel biotherapeutic formats such as glyco-engineered antibodies and fusion proteins.

Conclusion

Adjusting hydroxide concentration and temperature in HPAE-PAD combined with Orbitrap MS significantly improves the resolution and structural elucidation of N-linked glycans, facilitating robust glycoprotein analysis for pharmaceutical development.

Reference

1. Spiro RG. Glycobiology, 2002, 12(4):43R–56R.
2. Shental-Bechor D, Levy Y. PNAS, 2008, 105(24):8256–61.
3. Brandley BK, Schnaar RL. J. Leukocyte Biol., 1986, 40(1):97–111.
4. Thermo Scientific Application Update 72829, 2019.
5. Hermentin P et al. Anal. Biochem., 1992, 203(2):281–289.
6. Grey C et al. J. Chromatogr. B, 2009, 877:1827–1832.
7. Thermo Scientific Technical Note 71.
8. Thermo Scientific Technical Note 72478.
9. Cooper G, Rohrer J. Anal. Biochem., 1995, 226:182–184.
10. Thermo Scientific Application Note 595, 2019.
11. Rohrer J. Glycobiology, 1995, 5(4):359–360.
12. Basa L, Spellman M. J. Chromatogr. A, 1990, 499:205–220.