MS/MS of the 47+ Charge State of the Intact 19S Lid
(A) Applying a voltage of 100 V to the collision cell generates product ions from the loss of only Rpn9 and/or Rpn12. Peaks between 12,500–17,000 m/z correspond to the loss of Rpn9 (blue squares), while the series at 10,000–12,000 m/z correspond to the loss of Rpn12 (red squares). The low intensity charge series at 17,000–18,000 m/z indicate the loss of both Rpn9 and Rpn12 (magenta squares). At low m/z 1,000–2,400 series of peaks are assigned to individual Rpn9 (blue circles) and Rpn12 (red circles). The data indicate the Rpn9 and Rpn12 have a relatively small contact surface with the other subunits, which implies that they are exposed.
(B) Increasing the voltage to 120 V induces the dissociation of Rpn6 in addition to Rpn9 and Rpn12. The highly charged Rpn6 series is centered at ~ 2,200 m/z (green circles), while the remaining stripped complex is observed between 13,000 to 18,000 m/z (green squares). In summary, Rpn9 and Rpn12 are easily dissociated from the lid complex (blue). An increase in the collision cell voltage also induces dissociation of Rpn6 (purple).