A Novel, High-Accuracy Glucose-Unit Based N-glycan Retention Library and Peak Assignment Tool for Compound Identification in LC or LC/MS Data

Importance of the Topic

Glycosylation is a crucial post-translational modification affecting the stability, half-life and efficacy of protein biotherapeutics. Monitoring glycan profiles is essential in pharmaceutical quality control, yet complex branching and isomerism pose challenges for routine analysis. Normalizing retention times to glucose unit values simplifies glycan identification and reduces reliance on laborious enzymatic digestions or MSn experiments.

Objectives and Study Overview

This study introduces a high-accuracy glucose-unit-based N-glycan retention library and a web-based peak assignment tool for LC and LC/MS data. The main goals are:

• To develop a retention time prediction model for common N-glycans labeled with InstantPC and 2-AB
• To build an internal calibration library covering 115 InstantPC and 105 2-AB labeled glycans
• To implement a refinement algorithm using experimental glycan RTs for enhanced assignment specificity

Methodology and Instrumentation

Glycans were enzymatically released from cetuximab and labeled with InstantPC. Calibration used two glucose ladders (InstantPC maltodextrin and 2-AB homopolymer) run in parallel. Chromatographic separation employed an Agilent AdvanceBio Amide HILIC column at 60 °C with standardized gradients. Analysis was performed on an Agilent 1290 Bio Infinity II LC/FLD system coupled via tee splitter to a 6545XT AdvanceBio LC/Q-TOF. Fluorescence detection was set to each label’s optimal excitation and emission wavelengths.

Main Results and Discussion

Predicted retention times matched observed values with errors under 2%, dropping below 1% when using the refinement feature. The tool successfully resolved isomeric peaks, and MS data provided orthogonal confirmation when multiple candidates fell within the prediction tolerance. Annotated cetuximab N-glycan profiles corresponded closely to expected structures, demonstrating the tool’s robustness in complex matrices.

Benefits and Practical Applications

• Reduces the need for time-consuming exoglycosidase digestions and extensive MSn workflows
• Enhances confidence in glycan assignments, supporting routine QA/QC in biopharmaceutical labs
• Compatible with any LC system using the AdvanceBio Amide HILIC column, enabling broad adoption

Future Trends and Opportunities

Potential extensions include expanding the GU library to cover additional glycan types, integrating machine-learning models for adaptive retention prediction, and incorporating other labeling chemistries. Cloud-based calibration sharing and real-time instrument alignment could further streamline glycan analysis workflows.

Conclusion

The developed GU-based retention library and web application provide a user-friendly, high-accuracy solution for rapid N-glycan identification in LC and LC/MS analyses. The combination of GU calibration, retention prediction and optional refinement supports reliable assignments, reducing analytical burden and accelerating glycan profiling.

References

1. Zhou Q and Qui H The mechanistic impact of N-glycosylation on stability pharmacokinetics and immunogenicity of therapeutic proteins Journal of Pharmaceutical Sciences 2019 108 1366–1377
2. Guile GR et al A rapid high-resolution high-performance liquid chromatographic method for separating glycan mixtures and analyzing oligosaccharide profiles Analytical Biochemistry 1996 240 210–226
3. Gautam S et al Glucose unit index GUI of permethylated glycans for effective identification of glycans and glycan isomers Analyst 2020 145 6656–6667
4. Robinson R et al Improved Hydrophilic Interaction Liquid Chromatography for LC/FLD/MS Analysis of Released N-Glycans Agilent Technologies Application Note 5994-6916EN 2023