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. Author manuscript; available in PMC: 2008 Nov 1.
Published in final edited form as: Bioconjug Chem. 2007 Nov 21;18(6):2004–2017. doi: 10.1021/bc700257a

Figure 4. Nano-LC-MS/MS spectrum of the DCP-Bio1-labeled peptide of C165S AhpC containing an adduct at Cys46.

Figure 4

The covalent adduct with DCP-Bio1 was prepared from the R-SOH form of the AhpC mutant and digested with AspN in order to generate an 11-residue peptide. The AspN digest was separated by nano-HPLC coupled to a Thermo LTQ ion trap mass spectrometer. The analysis was performed in SIM mode where the DCP-Bio1-labeled peptide (m/z 811.77, +2 charge) was isolated for further fragmentation. Cleavage of the amide bond results in N-terminal fragments designated as “b” and C-terminal fragments designated as “y”. The masses of both sets of ions are consistent with DCP-Bio1 linked covalently to Cys46 (b6 − b5 = y6 − y5 = 497.1 m/z).