Tandem mass tags. Tags A, B, and C in Figure 22-41 with nominal m/z 116 m/z 116 reporter ions are members of a set of 1212 tags accessible by certain synthetic pathways.

a. Explain the functions of the amine-reactive group, the balance COCO group, and the reporter in the structure at the top left of Figure 22-41.

b. Ions selected by Q1 in a tandem mass spectrometer all have nominal m/z 146. m/z 146. Which chemical bond of a labeled peptide breaks to give m/z 146?m/z 146? Why is it necessary for all mass tags to produce a fragment with the same nominal mass (m/z 146) (m/z 146) at the Q1 stage of analysis?

c. The published set of mass tags with the general structure in Figure 22-41 has two reporters with nominal m/z 115, m/z 115, three with nominal m/z 116,m/z 116, three with nominal m/z 117,m/z 117, and four with nominal m/z 118. m/z 118. Draw one isotopologue of the m/z 146 m/z 146 ion C8H16NO+ C₈H₁₆NO⁺ that produces a reporter with m/z 115,m/z 115, one that produces m/z 117,m/z 117, and one that produces m/z 118.m/z 118. The top left structure in Figure 22-41 shows which sites could be labeled with 2H,²H 13C,¹³C, 15N,¹⁵N, or 180.18O.

Figure 22-41

Transcribed Image Text:

Structure of tandem mass tag Amine-reactive group Reporter 115-118 u * H₂C H₂C ** CH3 * CH3 Balance 28-31 B Collision-induced H₂C dissociation in Q2 High resolution separation in Q3 15 OCH3 OCH 3 CH3 H₂N-Peptide Tag A 13CH₂ C6¹CH₁6¹5N m/z 116.129 Peptide labeled with tandem mass tag H₂C H₂C. CH3 1 CH3 H3¹³C || 13CH3 NH I Peptide Tag B CH₂ C₂¹3C₂H16N m/z 116.135 lon formed prior to Q1 mass separator CH3 S CH₂ CH16NO m/2 146 Mass spectrometer ionization H₂C DH₂C DH₂C Tag C -CH₂ C₂H₁4D₂N m/z 116.140 QE