Figure 9.

Example of a higher-order native top-down MS approach used for the characterization of membrane proteins such as pMMO. Nanodiscs embedded with pMMO were subjected to CID in the source region for ejection of the protein complex from the nanodisc, resulting in the stabilization of the pMMO protomer species (MS¹). Increasing collisional activation breaks up the protomer into individual pMMO subunits (MS²). Further collisional activation in the HCD cell of the Orbitrap-UHMR enables backbone fragmentation of each subunit (MS³). From ref (235). CC BY 4.0.