Figure 2
Representative chromatograms for ORN (B,D,F and H) and internal standard ORN–d6 (A,C,E and G) extracted at 133.112 and 139.148 Da corresponding to molecular ion of ORN and ORN–d6 respectively. Chromatograms are shown for ORN in arginase 1 calibrator 0 (C and D) and calibrator 4 (A and B), comprising 0.05 mg/mL arginase 1 HEK293T lysate, 0.05 M phosphate buffer, 3 mM ARG, 10 µL of 1200 µM ORN–d6 and 0 µM ORN (D) or 200 µM ORN (B). The corresponding internal standard chromatograms are shown in panels C and A. Similarly, chromatograms are shown for ORN in arginase 2 calibrator 0 (G and H) and calibrator 5 (E and F), comprising 0.1 mg/mL arginase 2 HEK293T lysate, 0.05 M phosphate buffer, 2 mM ARG, 10 µL of 300 µM ORN–d6 and 0 µM ORN (H) or 50 µM ORN (F). The corresponding internal standard chromatograms are shown in panels G and E. The small peak observed for ORN in calibrator 0 (D and H) arises from very low concentrations of endogenous ORN present in the HEK293T lysate.
