Fig. (3) Reversed phase liquid chromatography resolves the various modified forms of the 9-17 H3 peptide resulting from propionic anhydride derivatization and trypsin digestion. Each line represents an extracted ion chromatogram for peptide ions of a particular m/z value, namely at 535.304, 542.312, 521.307, and 528.315 m/z. The relative elution order for the unmodified and modified forms of the 9-17 peptide can be predicted on the basis on the number of propionyl, methyl, and acetyl groups.