Figure 5. Pseudo spectrum and molecular structure of (γ-)glutamyl-L-methionine.

The γ₁’’-fragment (on the very left) could be annotated thanks to the additional information provided by the ¹³C monoisotopic peaks; green: ¹²C monoisotopic peaks; magenta: ¹³C monoisotopic peaks; blue: associated heteroisotopic peaks; the “(ambiguous)” tag informs the user, that this neutral loss was calculated by mass decomposition and filtered for the correct number of carbon atoms, but still multiple sum formulae might explain the present mass difference.