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. Author manuscript; available in PMC: 2016 Oct 6.
Published in final edited form as: Anal Chem. 2015 Sep 4;87(19):9855–9863. doi: 10.1021/acs.analchem.5b02307

Figure 1.

Figure 1

CMT approach generates multiples reporter ion series for increased quantitative information. (A) Chemical structure of TMT (Proteome Sciences, plc), a commercial isobaric labeling reagent and the reporter ion generated upon TMT fragmentation. (B) CMT isobaric labeling reagents fragment at more than one position (denoted by red lines) under both CID and HCD conditions. In contrast to TMT, CMT reagents generate multiple reporter ions, first fragmenting into a primary reporter ion series with a range of molecular masses beginning at 171.14919 Da, which can further fragment into a secondary reporter ion series with molecular masses beginning at 126.09134 Da. (C) CMT secondary reporter ion formation occurs via cyclization of the primary reporter ion region and subsequent loss of dimethylamine. (D) The generation of unique primary/secondary reporter ion pairs enables increased multiplexing by enabling the coding of both the number of heavy isotopes in the reporter region of the reagent, and their position within the reporter region such that unique reporter ion pairs distinguish each reagent.