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. Author manuscript; available in PMC: 2016 Nov 17.
Published in final edited form as: Anal Chem. 2015 Nov 5;87(22):11448–11454. doi: 10.1021/acs.analchem.5b03009

Figure 3. Extracted ion chromatograms of isobaric peptides.

Figure 3

(A) Extracted ion chromatogram of the histone H3 peptide aa 18–26 with 1 acetyl group. The top panel displays the chromatogram of the monoisotopic precursor mass (in blue) and its respective first and second isotope (violet and brown, respectively). The panels below display the extracted ion chromatogram of the unique fragment ions for the peptide H3K18ac (middle) and H3K23ac (bottom). The figure demonstrates that the two peptides co-elute, but they can be distinguished based on their MS/MS chromatogram. (B) Extracted LC-MS chromatogram of the unmodified histone H3 peptide aa 9–17, which has the same mass as K9me1K14ac. The two signals present at the full MS scan level (top) can be discriminated by extracting their unique fragment ions (middle and bottom). (C) Ion chromatogram of the histone H2A peptide aa 4–11 with 1 acetyl group, which includes the two modified forms K5ac (middle) and K9ac (bottom).

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