To confirm the suitability of our final tuning, an SID energyresolved mass spectrum (ERMS) plot was obtained for CRP 18+, the charge state used by Harvey et al. The ERMS plot in Figure features the dimer/trimer pair as the initial dominant SID product pathway, followed by monomer/tetramer. These pairs rise together in normalized intensity until dimer/trimer deviate due to secondary fragmentation of trimers to form monomer/dimer pairs and potentially dimer to monomer and tetramer to dimer-dimer or monomer-trimer, which also causes the monomer/tetramer pair to no longer track together. As the SID energy increases, monomer formation becomes the dominant SID pathway. These results clearly depict native-like SID fragmentation for the CRP pentamer, confirming that our tuning parameters (Figure ) are suitable for native-like analyses of protein complexes.