A Study on a Method for Evaluating Glycans in Biopharmaceuticals

Importance of the Topic

Glycan structures on therapeutic proteins influence efficacy, safety and immunogenicity. Reliable analysis of O-linked glycans is critical for quality control of biopharmaceuticals, yet conventional chemical release methods suffer from peeling side-reactions that obscure accurate profiling.

Objectives and Study Overview

This study aimed to develop a one-pot chemical method that simultaneously releases and labels O-glycans while suppressing peeling reactions. Fetuin was chosen as a model glycoprotein. Two alkali catalysts were compared: 28 % ammonia versus ammonium carbamate, both combined with 1-phenyl-3-methyl-5-pyrazolone (PMP) labeling in a single reaction vessel.

Methodology and Instrumentation

Releasing and labeling reagents were prepared in two versions: an ammonia-based PMP solution and an ammonium carbamate PMP solution. Fetuin samples were treated at 50 °C for 16 h, followed by liquid–liquid extraction and cleanup on C18 SPE cartridges. Labeled glycans were analyzed by:

• MALDI-TOF MS on a Shimadzu/Kratos MALDI-7090 with DHB matrix
• UHPLC-UV using Shimadzu Nexera, GlycanPac AXH-1 column, 0.1 % TFA and acetonitrile gradient, detection at 245 nm

Main Results and Discussion

MALDI-TOF spectra showed a substantial reduction in signals attributed to peeling products when using ammonium carbamate (final 2.5 M) compared with 28 % ammonia. LC profiling revealed peeling by-products comprising ~12 % of total peak area with ammonia, versus ~2 % with ammonium carbamate. However, overall release and labeling yield was lower under carbamate conditions, reflecting a trade-off between artifact suppression and efficiency.

Benefits and Practical Applications

The one-pot PMP labeling approach using ammonium carbamate minimizes peeling artifacts, improving the accuracy of O-glycan profiling for biopharmaceutical quality assessment. Reduced sample handling and combined release/labeling steps simplify workflows in analytical labs.

Future Trends and Potential Applications

Further optimization is needed to enhance labeling efficiency and detection sensitivity. Exploration of alternative catalysts, stronger UV-absorbing or fluorescent tags, and integration with high-sensitivity detectors may yield comprehensive, artifact-free glycan profiling for advanced QC and research applications.

Conclusion

This study demonstrates that one-pot PMP labeling with ammonium carbamate effectively suppresses peeling reactions in O-glycan analysis, reducing by-products to a few percent. Although yield is decreased, the method offers a promising route to more accurate glycan characterization in biopharmaceutical development.

Reference

• Honda S. et al. High-performance liquid chromatography of reducing carbohydrates as strongly ultraviolet-absorbing and electrochemically sensitive 1-phenyl-3-methyl-5-pyrazolone derivatives. Anal. Biochem. 1989, 180, 351–357.
• Wang C. et al. One-pot nonreductive O-glycan release and labeling with 1-phenyl-3-methyl-5-pyrazolone followed by ESI-MS analysis. Proteomics. 2011, 11, 4229–4242.