Surface-Induced Dissociation of Protein Complexes Selected by Trapped Ion Mobility Spectrometry

Native mass spectrometry, particularly in conjunction with gas-phase ion mobility spectrometry measurements, has proven useful as a structural biology tool for evaluating the stoichiometry, conformation, and topology of protein complexes. Here, we demonstrate the combination of trapped ion mobility spectrometry (TIMS) and surface-induced dissociation (SID) on a Bruker SolariX XR 15 T FT-ICR mass spectrometer for structural analysis of protein complexes. We successfully performed SID on mobility-selected protein complexes, including streptavidin tetramer and cholera toxin B with bound ligand. Additionally, TIMS-SID was employed on a mixture of peptides bradykinin desR1 and desR9 to mobility separate and identify the individual peptides. Importantly, results show that native-like conformations can be maintained throughout the TIMS analysis. The TIMS-SID spectra are analogous to SID spectra acquired using quadrupole mass selection, indicating little measurable, if any, structural rearrangement during mobility selection. Mobility parking was used on the ion or mobility of interest and 50 to 200 SID mass spectra were averaged. High quality TIMS-SID spectra were acquired over a period of 2-10 minutes, comparable to or slightly longer than SID coupled with ion mobility on various instrument platforms in our laboratory. The ultrahigh resolving power of the 15 T FT-ICR allowed for the identification and relative quantification of overlapping SID fragments with the same nominal m/z based on isotope patterns and shows promise as a platform to probe small mass differences, such as protein-ligand binding or post-translational modifications. These results represent the potential of TIMS-SID-MS for the analysis of both protein complexes and peptides.