Sensitivity and linearity of Qdot-RPPA. A. Qdot-RPPA could detect as low as 0.1pg of purified AKT. From top to bottom are 10 serial dilutions. From left to right represent 10 replicates. The Signal/Noise ratios are from 30 to 150 as indicated. B. The linearity of the intensity. X-axis indicates the exponent of 2-fold serial dilution and Y-axis represents the relative intensity normalized to the highest concentration. C. The corresponding Western blot showing the detection limit is 0.1ng, a 1000× difference in sensitivity. D. The signals of the Western blot were quantified from film and graphed as in B. The sigmoid curve indicates signal saturation and low dynamic range using Western blot.