Additional evidence that suggests minimal to no quaternary structure rearrangement is found in the monomer product's average charge. As depicted in Figure , the average charge remains steady as a function of cone voltage. This was somewhat surprising, since isCA could have caused the monomeric subunits to elongate in a way that more charge could be placed on the monomers during SID, even if the SID trend was not disrupted. This apparently did not happen. To confirm this, the mobiligrams at each cone voltage were compared to each other and no difference in mobility arrival time was observed as a function of cone voltage. Given the fact that isCA was limited to low voltages when coupled to SID, it is unsurprising that no quaternary structure rearrangement was observed for PhosB. Figure . A) 15+ TRAP isCA∆ -SIDC (1050 eV) plot for a few indicated SID products, the remainder of which are found in Figure ; the overlay is the TRAP 15+ CIx plot; B) SID monomer product average charge state, which shows no statistically significant trend. C) SID product comparison at 1050 eV of SID energy for the 15+ at two distinct cone voltages, and the 21+ at a low cone voltage. The left inset is the calibrated CCS for the indicated precursor charge states and their cone voltage settings. The CCS for the 15+ at high cone voltage and the 21+ are highly similar, suggesting they both feature a compact structure. The right inset structure depicts the TRAP bst 11mer (PDB 1GTN), with the tryptophan ligands removed.