Isotopic Resolution of Protein Complexes up to 466 kDa Using Individual Ion Mass Spectrometry

Native mass spectrometry involves transferring large biomolecular complexes into the gas phase, enabling the characterization of their composition and stoichiometry. However, the overlap in distributions created by residual solvation, ionic adducts, and post-translational modifications creates a high degree of complexity that typically goes unresolved at masses above similar to 150 kDa. Therefore, native mass spectrometry would greatly benefit from higher resolution approaches for intact proteins and their complexes. By recording mass spectra of individual ions via charge detection mass spectrometry, we report isotopic resolution for pyruvate kinase (232 kDa) and beta-galactosidase (466 kDa), extending the limits of isotopic resolution for high mass and high m/z by >2.5-fold and >1.6-fold, respectively.

Automated summary

Native mass spectrometry allows characterization of biomolecular complexes in gas phase, but complexity due to solvation, adducts, and modifications is typically unresolved for masses over 150 kDa. Higher resolution approaches for intact proteins and complexes are needed. Charge detection mass spectrometry achieved isotopic resolution for pyruvate kinase (232 kDa) and beta-galactosidase (466 kDa), extending the limits of isotopic resolution for high mass and high m/z.