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. Author manuscript; available in PMC: 2015 Feb 1.
Published in final edited form as: Mol Microbiol. 2014 Jan 9;91(4):649–664. doi: 10.1111/mmi.12491

Fig. 4.

Fig. 4

Mass spectrometric analyses of AerR and AerR mutant proteins. The deconvoluted spectrum of full length protein LC-ESI-MS spectrum of (A) 6 M urea treated WT AerR protein; (B) 0.04M HCl treated WT AerR protein; (C) 6 M urea treated AerR H10A protein; (D) 0.04 M HCl treated AerR H10A protein. (E) ~ (G) are LC-ESI-MS/MS analyses of a B12 containing peptide (residues 6~16: VELEHGSTGCL) obtained by pepsin digestion. (E) Extracted ion chromatogram (EIC) of the triply-charged peptide containing B12 at m/z 824.7 (* indicates the peak of interest); the corresponding UV-Vis spectrum of this peptide is shown in the inset. (F) High-resolution mass spectrum of this B12 containing peptide ion at m/z 824.7 (2 ppm mass error). (G) Collision induced dissociation (CID) spectrum of this peptide ion at m/z 824.7. (E) and (G) were obtained using the Bruker HCT ion trap MS instrument whereas (F) was obtained using the Thermo LTQ-Orbitrap MS instrument. (H) Structure and CID fragmentation of the pepsin-generated WT AerR peptide containing B12 attached to His10. The experimental data for this peptide are shown in Fig. 4E-G.