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. Author manuscript; available in PMC: 2014 Apr 10.
Published in final edited form as: Chem Rev. 2013 Feb 26;113(4):2343–2394. doi: 10.1021/cr3003533

Figure 8.

Figure 8

Two quantitative strategies based on chemical reaction. The representative peptide is doubly charged, and consisting of 15 molecules of averagine, a hypothetical amino acid. Averagine has a molecular formula of C4.9384 H7.7583 N1.3577 O1.4773 S0.0417, which is derived from statistical occurrence of amino acids in the protein identification resource protein database. a, b, c: Dimethyl labeling. The quantification is calculated based on the ion intensities in MS1. The MS2 is only used to identify the peptide sequence (c). This given peptide has slight isotopic peak overlap between the three groups (b), the overlapped areas will become more significant for longer peptides. d, e, f, g: 6-plex TMT labeling. The quantification is calculated based on the report ion intensities in MS2 (g). The MS2 is used for both peptide sequence identification (f) and quantification (g). The mixed peptide groups have the same m/z in MS1 (e).