General correlation between warfarin IC₅₀and VKORC1 levels. (A) Quantification of cellular VKORC1 levels. Endogenous VKOR and VKOR transfection in various amounts (top) and purified VKORC1 protein in various amounts (bottom). Anti-VKORC1 antibody was used for the western blots, which were developed simultaneously to allow direct comparison and quantification. (B) In-cell ELISA quantification of the protein level of transfected VKORC1. (C) Warfarin inhibition curves with different amounts of transfected VKORC1. (D) Correlation between warfarin IC₅₀ (from panel C) and VKORC1 protein level. ELISA reading of the protein level is converted from DNA transfection amount (from panel B). Error bars are estimated from the inhibition curves.