Fig. 4.

Reproducibility, linearity, and accuracy of K-score determination. (A) P31/Fuj cells were treated with 1 mm pV, an agent known to increase tyrosine phosphorylation, or left untreated. Cells were lysed and lysates mixed at the proportions shown. The resulting mixtures were processed for phosphoproteomic analysis and K-scores obtained from the data. The experiment was performed on three independent occasions, each analyzed in analytical triplicate. (B) Ranking of kinases based on K-scores as a function of pV-treated cells. Tyrosine kinases (shown as triangular data points) clearly increase their K-score-based ranks as a function of pV-treated extracts present in samples. (C and D) Reproducibility and linearity of K-scores for three representative kinases. The data show that K-scores can be obtained reproducibly, and such values are quantitative as the K-scores for tyrosine kinases were directly proportional to the fraction of pV-treated cells in the samples.