Table 3. PTM Characterization of Herceptin (trastuzumab) Charge Variants by CEX mD-UPLC-MS/MS^a.

^aRelative quantification of the PTM Level from the Herceptin (trastuzumab) CEX fractions acidic, main, and basic obtained by MS/MS peptide mapping analysis with the mD-UPLC-MS/MS instrument. The calculation was performed using PMI-Byos (Byonic) software version 4.0-53 (Protein Metrics Inc.). For the calculation, the area under the curve (AUC) values of the extracted ion chromatograms (XIC) were used. The relative abundance of the modified peptide was calculated based on the XIC-AUC of the modified species divided by the total peak area of the unmodified and modified peptide. Afterward, the arithmetic mean (n = 2) and the standard deviation (SD) were calculated for the duplicates.