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. Author manuscript; available in PMC: 2012 Oct 1.
Published in final edited form as: J Am Soc Mass Spectrom. 2011 Jul 9;22(10):1784–1793. doi: 10.1007/s13361-011-0196-7

Figure 1.

Figure 1

Elevated electrostatic potentials of the Z-spray ion source can induce gas-phase migration of deuterium in a selectively labeled peptide during ETD. (a) Full ETD spectrum of triply protonated peptide P1. Close-up spectra of the c3 fragment ion (left), the c4 fragment ion (middle), and the intact reduced species RS+ (right) of labeled (b)–(c) and unlabeled (d) peptide P1, recorded with a sample cone voltage of 45 V (b) and 25 V (c)–(d). The occurrence of gas-phase scrambling is directly detected by the mass shift in c3 and c4 fragment ions in ETD spectra recorded using a cone voltage of 45 V. The shift in mass observed in (b) corresponds to complete (100%) scrambling of all labile sites in peptide P1 prior to ETD.