Gas-Phase Dopant-Induced Conformational Changes Monitored with Transversal Modulation Ion Mobility Spectrometry

Area of Science:

• Analytical Chemistry
• Biophysical Chemistry
• Physical Chemistry

Background:

• Ion Mobility Spectrometry (IMS) is a powerful technique for analyzing biomolecules in the gas phase.
• Understanding protein structure and conformational changes is crucial in various biological and medical fields.
• Existing IMS techniques have limitations in resolving complex protein dynamics.

Purpose of the Study:

• To evaluate the potential of a Transversal Modulation Ion Mobility Spectrometry (TMIMS) instrument for protein analysis.
• To investigate the use of dopants in tandem IMS-IMS for probing protein structure.
• To characterize the conformational behavior of proteins under different doping conditions.

Main Methods:

• Utilized a Transversal Modulation Ion Mobility Spectrometry (TMIMS) instrument.
• Measured the Collision Cross Section (CCS) of cytochrome c.
• Performed tandem IMS-IMS experiments using dry and vapor-doped gases (hexane, alcohols).
• Analyzed dopant-induced shifts in CCS to infer structural changes.

Main Results:

• TMIMS accurately measured the CCS of cytochrome c, consistent with literature values.
• Tandem IMS-IMS with various dopants revealed distinct protein structural responses.
• Hexane induced a significant CCS shift, indicating hydrophobic part exposure.
• Alcohols showed dual behavior: specific vapor uptake followed by unspecific uptake.
• The +8 charge state of a molten globule protein exhibited a dopant-induced conformational transition from folded to unfolded states.

Conclusions:

• TMIMS is a capable instrument for detailed protein analysis.
• Tandem IMS-IMS with chemical dopants provides insights into gas-phase protein structure and conformational dynamics.
• Dopant-induced conformational changes, particularly with alcohols, can be effectively studied using TMIMS.