Alternate dissociation pathways identified in charge-reduced protein complex ions

Area of Science:

• Proteomics
• Biophysical Chemistry
• Analytical Chemistry

Background:

• Tandem mass spectrometry (MS) is crucial for analyzing large protein complexes.
• Understanding protein complex dissociation mechanisms enhances MS utility.
• Human transthyretin serves as a model system for studying protein complex behavior.

Purpose of the Study:

• To systematically analyze the charge state-dependent dissociation of human transthyretin tetramers.
• To investigate the mechanisms governing protein complex decay under collision-induced dissociation (CID).
• To explore charge state modulation as a tool for controlling gas-phase dissociation.

Main Methods:

• Noncovalent complex formation of human transthyretin.
• Charge reduction using crown ether to generate specific charge states (15+ to 7+).
• Tandem MS and ion mobility spectrometry for analyzing dissociated fragments and intact complexes.

Main Results:

• Identified three distinct charge-dependent dissociation regimes.
• Observed asymmetric monomer ejection, folded monomer expulsion, and C-terminal peptide release.
• Demonstrated charge state influences the dissociation pathway and structural outcome.

Conclusions:

• Charge state modulation effectively directs gas-phase dissociation and unfolding of protein complexes.
• Provides insights into the fundamental mechanisms of protein complex fragmentation.
• Advances the application of tandem MS for detailed structural analysis of biomolecular assemblies.