Determining Collisional Cross Sections from Ion Decay with Individual Ion Mass Spectrometry

Area of Science:

• Analytical Chemistry
• Biophysical Chemistry
• Mass Spectrometry

Background:

• Collision cross section (CCS) measurements via ion mobility spectrometry (IMS) offer valuable insights into gas-phase protein structure, complementing mass analysis.
• Existing methods for CCS determination on Fourier transform mass spectrometry (FT-MS) platforms rely on signal decay during detection, often requiring specialized equipment.

Purpose of the Study:

• To develop and validate a method for simultaneous determination of charge, mass, and CCS for proteins and protein complexes using FT-MS.
• To demonstrate the utility of individual ion mass spectrometry (I²MS) for structural characterization without a dedicated IMS instrument.

Main Methods:

• Utilized individual ion mass spectrometry (I²MS) for charge detection and measurement of ion lifetimes during FT-MS detection.
• Tracked ion lifetimes across the entire FT-MS detection event for whole ion populations.
• Applied signal decay analysis during detection on FT-MS platforms.

Main Results:

• Successfully demonstrated simultaneous determination of charge, mass, and CCS for a range of proteins and complexes.
• Covered a mass range from approximately 8 to 232 kDa.
• Showcased the capability of I²MS to provide structural information complementary to traditional mass spectrometry.

Conclusions:

• I²MS on FT-MS platforms provides a powerful, label-free approach for gas-phase protein structural analysis.
• This method eliminates the need for dedicated IMS instrumentation, making CCS measurements more accessible.
• The simultaneous determination of multiple ion properties advances the characterization of biomolecular structures.