Figure 4.

MS analysis of HPLC-fractionated crude peptides that have been acid-eluted from viable LCL cells reveals three naturally processed LMP-2A peptides. HPLC fraction 45, derived from 4 × 10⁸ LCL cells of HLA-A2.1-positive donor IP1, was injected into the electrospray ionization source of a triple quadrupole mass spectrometer. Summation of the mass spectra obtained in the 880–1,100 m/z range is depicted. The (M+H)+ ions at m/z = 907, 978, and 1,036 were selected for collision-induced dissociation spectrum analysis based on theoretical concordance with LMP-2A-derived sequences and for fragmentation to generate sequence data. The deduced sequences of these peptides are indicated, where X represents an amino acid residue of indeterminant identity based on the fragmentation data.