Intraexperimental variability in the degree of protein tyrosine phosphorylation. A set of lysates from one of the three stimulation experiments in Fig 6 was reassayed on different occasions by anti-P(tyr) immunoblotting and ECL. Bands were analyzed and plotted as in Fig 6. The tyrosine-phosphorylated proteins indicated as p78 and p60 were analyzed in three replicate assays with the same lysate. Data shown for p137 and p96 represent only two of the assays, due to problems in the clear resolution of p137 and p96 in one of the assays.