Collision-Induced Unfolding of High-m/z Native-like Protein Ions within a Trapped Ion Mobility Spectrometer

Native mass spectrometry (nMS) is a powerful tool for the rapid characterization of protein ions and protein-ligand com-plexes. By coupling nMS with ion mobility spectrometry (IMS), and collisional activation, insights into protein confor-mation and stability can be rapidly obtained. Originally incapable of this workflow, recent work enabled this collision-induced unfolding (CIU) process on commercially available Bruker timsTOF instruments. This early work, however, faced challenges in transmitting larger proteins and only sought to unfold small proteins up to 29 kDa. In this study, we continue the development of this technique and optimized instrument settings, enabling the transmission of proteins up to 8,000 Th, and successfully unfolded proteins such as dimers of superoxide dismutase and β-lactoglobulin, and oval-bumin on a timsTOF. When this TIMS activation technique is applied to large protein ions, however, limited unfolding was observed for bovine serum albumin and no unfolding was observed for immunoglobulin G.