To evaluate the performance of the modified instrument (Figure ), several model protein complexes, including 53 kDa streptavidin (SA), 64 kDa homotetrameric avidin (AV), 103 kDa concanavalin A (Con A), 147 kDa alcohol dehydrogenase (ADH), 58 kDa cholera toxin B (CTB), 115 kDa C-reactive protein (CRP), 90 kDa his-tagged toyocamycin nitrile hydratase (His-TNH), 801 kDa wild-type GroEL, and 3 MDa T=3 and 4 MDa T=4 HBV capsids, were chosen and are discussed below. HRas*GTP-SOS-HRas complex was used to evaluate TIMS-Q-SID performance. Extending the Mass-to-charge Ratio Range for Protein Complex Ion Mobility Analysis. Initially, the TIMS-Q-TOF instrument was configured with a concave TIMS cartridge (Figure ) operating at 830 kHz RF, which can trap ions up to 6,000 m/z. In the work described here, the TIMS cartridge was changed to a convex electrode geometry (inset of Figure and Figure ) coupled with a 425 kHz RF frequency TIMS driver to enhance the trapping efficiency for species up to 38,000 m/z. The performance of the TIMS cartridge with convex electrodes was verified with selected model protein complexes, which ranged in m a s s f r o m 5 0 -8 0 1 k D a ( 4 , 5 0 0 -1 8 , 5 0 0 m / z ) .