Mass Spectrometry of Putrescine, Spermidine, and Spermine Covalently Attached to Francisella tularensis Universal Stress Protein and Bovine Albumin

Figure 11

A scheme showing the structures of neutral loss fragments (upper branch) and signature ions (upper and lower branches) for the reaction of glutamine-spermidine adduct. The neutral loss of 71 Da from the initial adduct at 257 Da yields the observed signature ion at 186 Da. The observed signature ion at 212 Da is due to loss of CO and amine from the 257 Da adduct.