Ion Mobility and Surface Collisions: Submicrometer Capillaries Can Produce Native-like Protein Complexes

Area of Science:

• Biophysical Chemistry
• Analytical Chemistry
• Mass Spectrometry

Background:

• Submicrometer capillaries in nanoelectrospray ionization (nESI) reduce salt adducts, enhancing mass spectrometer resolution.
• Potential protein structural changes due to increased surface interactions in submicrometer capillaries are a concern.

Purpose of the Study:

• To compare the impact of micrometer and submicrometer capillaries on the native structures of protein complexes.
• To evaluate potential structural perturbations during ionization using different capillary sizes.

Main Methods:

• Native mass spectrometry (MS) of streptavidin, concanavalin A, and C-reactive protein.
• Ion mobility mass spectrometry (IM-MS) to assess collision cross sections.
• Surface-induced dissociation (SID) to compare dissociation behaviors.

Main Results:

• Submicrometer capillaries did not induce significantly higher charge states, indicating no major protein expansion.
• No significant differences in collision cross sections were observed between capillary types via IM-MS.
• Similar dissociation patterns were observed for protein complexes ionized with both capillary sizes.

Conclusions:

• Submicrometer capillaries do not cause significant structural changes in protein complexes under charge-reducing conditions.
• These capillaries are viable for native MS, offering improved resolution without structural compromise.
• Reproducible fabrication and clogging issues for larger complexes require consideration.