Lastly, the inset of Figure is the CCS distribution for the same three precursor ion conditions (charge states 15+ at cone 10 and 160V, and charge state 21+ at cone 10V). Because we are comparing two different charge states, we felt it appropriate to calibrate TRAP's CCS. We did so using IMSCal, and a CCS database composed of protein complexes under native and charge-reducing conditions. The calibrants selected included: alcohol dehydrogenase, c-reactive protein, and streptavidin, which were prepared as described for other proteins complexes above. These calibrants were sprayed from 200 mM ammonium acetate and 160/40 mM ammonium acetate/TEAA.