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

Figure 10

A scheme showing the structures of neutral loss fragments (upper branch) and signature ions (upper and lower branches) from the reaction of glutamate and putrescine. The neutral loss of 71 Da yields an observed signature ion at 129 Da, while the initial reaction yields the observed signature ion at 200 Da. Loss of CO and amine from the 200 Da adduct creates the observed signature ion at 155 Da.