Figure 6.

Shown are expanded regions of charge-deconvoluted UVPD mass spectra of (A) monoubiquitin (based on UVPD of the 10+ precursor) and (B) unmodified Sic60-DHFR (based on UVPD of the 23+ precursor) demonstrating little ion overlap. Panels (C) and (D) show comparisons of the expanded isotopic envelopes of the a₄₇ ion from monoubiquitin and the combination of the Y₄₇ and y₄₇ ions from Sic60-DHFR (expanded peaks are shaded in gray in panels (A) and (B)). The majority of matched ions were matched at <2 ppm and none were matched at >10 ppm. For reference, the mass difference shown between two adjacent peaks in panels (C) and (D) is >50 ppm, thus confirming the ability to readily differentiate ubiquitin-derived and DHFR-derived ions.