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. Author manuscript; available in PMC: 2023 Jul 25.
Published in final edited form as: Anal Biochem. 2022 Aug 9;655:114844. doi: 10.1016/j.ab.2022.114844

Fig. 2.

Fig. 2.

The MS/MS spectrum for the isopeptide crosslinked peptide AVNKVKDTPGLGK450VK/KGVDIE4391ISHR, where the subscripted residues indicate the site of the isopeptide crosslink. The parent ion is at m/z 896.85, +3 charged. Panel A shows the mass range from m/z 180 to 900. This includes a 5-amino acid, +1, b-ion sequence (AVNKV) from the N-terminal of the green peptide, a 3-amino acid, +1, b-ion sequence (KGV) from the N-terminal of the blue peptide, and a 3-amino acid, +3, ladder sequence (KGV) from the parent ion. Panel B shows the mass range m/z 1010 to 1260. This illustrates the first scenario for the mixed fragmentation. Structures of the proposed fragments are shown. Panel C also shows the mass range m/z 1010 to 1260. This illustrates the second scenario for the mixed fragmentation. Structures of the proposed fragments are shown. Unlabeled, red masses mostly represent loss of water, amine, or CO.