Development and applications of a pesticide multiresidue analysis turn-key system utilizing UHPLC-Orbitrap mass spectrometry and post data processing

Significance of the Topic

Protein top down mass spectrometry is critical for detailed proteoform analysis, preserving intact sequence information and mapping post translational modifications. The availability of multiple dissociation modes enhances identification confidence and supports quality control workflows.

Study Objectives and Overview

This work evaluates four fragmentation techniques – collision induced dissociation, higher energy C trap dissociation, electron transfer dissociation, and ultraviolet photodissociation – on proteins ranging from 9 to 50 kilodaltons using a standard protein mixture. The goal is to define method strengths and limitations to guide top down proteomics development.

Methodology and Instrumentation

Instrument setup

• Thermo Scientific Orbitrap Fusion Lumos mass spectrometer employing CID HCD ETD and UVPD
• Dionex Ultimate 3000 UHPLC system with MabPac reversed phase column
• Pierce Intact Protein Standard Mix comprising proteins of 9 to 50 kilodaltons
• ProSightPC software for fragment ion assignment

Experimental approach included chromatographic separation over a 20 minute gradient, full scan MS at 15k resolution, targeted MS2 at 60k or 120k resolution, and varied collision energies or reaction times for each dissociation mode.

Main Results and Discussion

• CID and HCD produced b and y ions with controlled secondary fragmentation, delivering robust sequence coverage across the protein mass range by targeting weaker bonds.
• ETD preserved labile modifications and generated c and z ions, yet higher charge states of large proteins led to rapid over fragmentation and signal dilution; reduced anion concentration offered partial relief.
• UVPD yielded a broad array of ion types (a b c x y z), achieving high coverage for smaller proteins but generating complex spectra and baseline noise in larger proteoforms that challenge deconvolution algorithms.
• Combining all four dissociation modes significantly expanded cumulative sequence coverage and increased confidence in proteoform identification.

Benefits and Practical Applications

• A single platform offering multiple fragmentation strategies enables flexible top down proteomics workflows.
• Comprehensive intact protein analysis supports biopharmaceutical quality control and method validation.
• Standard protein mixtures serve as reliable benchmarks for method optimization and system performance monitoring.

Future Trends and Opportunities

• Implementing ion parking and novel ion manipulation schemes to refine ETD and UVPD fragmentation of large proteins.
• Enhancing deconvolution software to manage high complexity spectra from high molecular weight proteoforms.
• Exploring mixed mode dissociation techniques such as EThcD to combine benefits of multiple fragmentation pathways.
• Increasing transient averaging and faster chromatographic separations to extend capacity beyond 50 kilodaltons.

Conclusion

The integration of CID HCD ETD and UVPD on the Orbitrap Fusion Lumos provides a powerful toolkit for intact protein characterization, balancing sensitivity PTM retention and sequence coverage. Continued instrument and software innovations will further improve analysis of large proteoforms and complex samples.

Reference

• Syka JEP et al Peptide and protein sequence analysis by electron transfer dissociation mass spectrometry Proc Natl Acad Sci USA 2004 101 26 9528 9533
• Cannon JR et al Hybridizing ultraviolet photodissociation with electron transfer dissociation for intact protein characterization Anal Chem 2014 86 21 10970 10977
• McLuckey SA et al Ion parking during ion ion reactions in electrodynamic ion traps Anal Chem 2002 74 2 336 346