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. Author manuscript; available in PMC: 2017 Feb 27.
Published in final edited form as: Anal Chem. 2017 Feb 9;89(4):2636–2644. doi: 10.1021/acs.analchem.6b05003

Figure 3.

Figure 3

Click addition of FLI-tag to a peptide-steroid adduct. A) Scheme illustrating non-specific photolabeling of peptide YGGFLRF with a diazirine and alkyne-containing neurosteroid (yellow oval). Irradiation of the sample resulted in a loss of N2 and covalent attachment of the ligand to YGGFLRF. FLI tag (red box) was attached via Cu(I) catalyzed click chemistry. B) MS1 (z=3) pair of the peptide-steroid-FLI-tag adduct. C) An overlay of light (black) and heavy (red) MS2 spectra for MS1 features in figure 3b. The most abundant features are loss of adduct, adduct, and reporter ions. A few (relatively low intensity) y ions were also identified. D) MS1 pair of the z=2 peptide-adduct. E) Overlay of light (black) and heavy (red) MS2 spectra for MS1 features in figure 3d. The most abundant features are adduct and loss of adduct. Site-defining y and b ions were also identified and had a relative increase in intensity compared to higher charge states. Reporter ions were minor features and are not labeled.