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. Author manuscript; available in PMC: 2009 Jul 26.
Published in final edited form as: Biochem Soc Trans. 2008 Oct;36(Pt 5):1037–1044. doi: 10.1042/BST0361037

Figure 3.

Figure 3

LTQ tandem mass spectrum of the triply oxidized αB-crystallin peptide 57APSWFDTGLSEMR69. The b4 ion (m/z 474.2) is 218.1 bigger than the b3 ion (m/z 256.1), showing that the Trp residue contains two oxygen atoms (186.1 + 2 × 16). Similarly, the y2 ion (m/z 322.1) indicates that one oxygen atom has been added to the expected ion (m/z 306.1). Fragment ions that had undergone addition of oxygen to the Met residue (I) and/or the Trp residue (:) are marked.