Figure 1.

Illustrations of various calibration approaches for targeted protein quantification and the study design of the comparative study. (A) The three options of internal standard (I.S.) methods used for targeted protein quantification. Full length stable-isotope-labeled (SIL) protein I.S. is added to the sample before any preparation; SIL-extended-peptide I.S. is added right before digestion, and SIL-peptide I.S. is spiked into the digest mixture after digestion. (B) Scheme of the comparison. The peptide- and extended-peptide-level calibrations and two hybrid calibrations were compared against the protein-level calibration (the Gold Standard), for quantitative performances in both protein-spiked QC samples and a full rat PK study. (C) The calibrators and I.S. employed for each calibration approach for quantification of the anti-HCV mAb in plasma. For each calibration approach, two sets of calibration curves (one for each SP) were independently established and then used for quantification.