Fig. 3.
MALDI-TOF peptide mass map of plasma and recombinant HCII. The ionization patterns of plasma HCII and recombinant HCII are shown in the top and bottom panels, respectively. Ionization of plasma HCII yields the QFPILLDFK peptide with m/z ratio 1120.63. The corresponding peptide in recombinant HCII is QFPILLDFR with m/z ratio of 1148.64, resulting from a polymorphism. An additional peptide is present, with m/z ratio 1131.62, and expected loss of 17 Da due to the cyclization of the N-terminal Q to pyroglutamate on the QFPILLDFR peptide.