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. Author manuscript; available in PMC: 2017 Aug 14.
Published in final edited form as: Anal Chem. 2016 Oct 10;88(21):10504–10512. doi: 10.1021/acs.analchem.6b02553

Figure 2.

Figure 2

Schematic showing tandem mass spectra of unmodified and modified T3 peptides. a) Spectrum of the precursor ion for the unmodified T3 peptide [T3-S-H]3+. b) Spectrum of the precursor ion of a T3 peptide modified at Cys34 [T3-S-R]3+ to produce an adduct of added mass R. Note that the indicated pairs of b+-series are the same in both spectra while those of the y2+-series ions are offset by a mass represented by Δm/z = R/2 − MH. [The indicated signature ions were extracted from actual spectra obtained for the T3 peptide (a) and the T3 peptide modified with homocysteine (b)].