OVERCOMING PEAK CAPACITY LIMITATIONS IMPOSED BY HYDROGEN EXCHANGE QUENCH CONDITIONS

Significance of the Topic

Understanding protein dynamics is essential for structural biology, drug discovery and quality control. Hydrogen exchange mass spectrometry (HXMS) reveals conformational changes but suffers from limited chromatographic peak capacity under quench conditions, leading to co-eluting peptides and reduced data quality. Integrating ion mobility separation (IMS) addresses these limitations by resolving overlapping ions in the gas phase, enhancing peptide identification without compromising deuterium retention.

Aims and Study Overview

This study evaluated the effect of incorporating IMS into the HXMS workflow on sequence coverage, peak capacity and deuterium retention in complex protein mixtures, including a 90 kDa model protein and a 150 kDa antibody sample.

Methodology

• Continuous hydrogen exchange labeling at 0 °C, pH 2.5 with D₂O buffer
• Quench reaction followed by online pepsin digestion and RP-HPLC separation
• Mass spectrometry analyses with and without IMS using Waters SYNAPT G2
• Data processing via PLGS 2.5 and DynamX 2.0 software

Used Instrumentation

• Waters nanoACQUITY UPLC system with HDX technology
• Waters SYNAPT G2 mass spectrometer equipped with ESI source and argon-pressurized IMS cell

Results and Discussion

IMS integration markedly improved peak capacity in complex mixtures, resolving co-eluting peptides that are indistinguishable by LC or m/z alone. In a 1:28 molar mixture, sequence coverage increased from ~80% to ~95%. For a 90 kDa peptic digest, peptide counts rose from 271 to 315 with IMS while coverage remained at ~97–98%. Shorter LC gradients enabled by IMS preserved up to 0.65 Da more deuterium in antibody analyses. No significant perturbation of deuterium uptake was observed across labeling times, demonstrating IMS compatibility with quantitative HX measurements.

Practical Applications

• Enhanced mapping of protein dynamics and epitope interfaces
• Improved throughput and sensitivity in antibody characterization
• Reduced cycle time and increased confidence in deuterium uptake data

Future Trends and Opportunities

Advances in ion mobility technologies and software integration will further increase resolution and speed, enabling real-time conformational studies of large and heterogeneous protein assemblies. Emerging multi-dimensional separation strategies may combine IMS with advanced chromatographic and computational tools to drive deeper structural insights in biopharmaceutical research.

Conclusion

Incorporation of ion mobility into HXMS workflows overcomes chromatographic limitations by increasing peak capacity and peptide coverage without compromising deuterium retention or analysis time. This integration extends the applicability of HXMS to complex protein systems and enhances structural analysis capabilities.

References

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