Conformational effects in protein electrospray-ionization mass spectrometry

Area of Science:

• Structural Biology
• Biophysics
• Analytical Chemistry

Background:

• Electrospray-ionization mass spectrometry (ESI-MS) is crucial for structural biology, but its protein ionization mechanism remains debated.
• Understanding conformational effects in ESI-MS is essential for accurate structural determination.
• Key parameters influencing protein ionization include solvent-accessible surface area (As) and apparent gas-phase basicity (GBapp).

Purpose of the Study:

• To review recent experimental and theoretical studies on the influence of As and GBapp on ESI-MS results.
• To explore the structural information obtainable from ESI-MS through these parameters.
• To present a unified model for protein ionization mechanisms in ESI-MS.

Main Methods:

• Review of recent experimental investigations.
• Analysis of theoretical studies and computational models.
• Examination of charge-state distribution (CSD) analysis in ESI-MS.

Main Results:

• Evidence supports a unified model for protein ionization in ESI-MS, applicable to both folded and unfolded proteins.
• Solvent-accessible surface area and apparent gas-phase basicity are critical factors controlling protein ionization extent.
• CSD analysis provides valuable structural information for diverse protein conformations.

Conclusions:

• A unified model for protein ionization in ESI-MS is supported by current evidence.
• ESI-MS, particularly CSD analysis, is a powerful tool for characterizing protein structures, including disordered ones.
• Further research into As and GBapp will refine ESI-MS applications in structural biology.