Figure 2.

Neutral losses of 98, 80, and 116 Da in CID MS/MS spectra of diverse pHis peptides. Prominent neutral loss triplets (Δ98, Δ80, and Δ116 Da) were observed in the CID MS/MS spectra for (a) tryptic peptides from known pHis proteins (DhaM, PpsA) and chemically phosphorylated synthetic peptides, respectively, and (b) pHis peptides derived from chemically phosphorylated BSA. The Δ116, Δ98, and Δ80 Da product ion species are indicated in purple with each peak labeled with a green, red, or blue diamond, respectively. Precursor peptide sequences, charge state, and m/z values are shown to the right of each spectrum. MS/MS spectra showing the full recorded m/z range for these CID experiments are shown in Figure S1.