Figure 3  Serial dilution curve. (A) In the serial dilution plot the observed signal is plotted against the observed signal at the next dilution step. Dilution series which are very close or identical with the identity line indicate quality problems, as the dilution series fails to generate lowered signals. a and M are the intersection points at background level and saturation level, respectively; (B) Example of dilution curves from four samples with different initial concentrations. The dilution steps remain constant; (C) Simulated RPPA data generated with the Sips model as presented in Zhang et al. [23]; (D) Serial dilution curve for simulated data shown in (C). The continuous (blue) line corresponds to the serial dilution curve. The dashed (black) line represents the identity line. Scripts for plot generation were taken from [23].