Fig. 5.

Sequence confirmation of phosphorylated ligands. The identity of each reported phosphopeptide was confirmed by fragmentation of the corresponding synthetic peptide. A, experimental MS2 spectrum of a molecular species at m/z = 523.74 fragmented during LC-MS analysis of the B*40:02-bound peptidome. B, MS2 spectrum of the synthetic peptide S[pS]YGNIRAV. C, the retention time of each phosphorylated peptide in the IMAC fraction (Rt - IMAC) is plotted against the retention time of the corresponding synthetic peptide (Rt - Syn.) in an independent LC-MS run. The data fit a linear function (R² = 0.9991).