WB (peptide competition) analysis of NIH3T3 cells treated with 50ng/mL PDGF for 15 minutes (Lane 2-5) using GTX25615 MEK1 (phospho Thr386) antibody with the non-phosphopeptide corresponding to the phosphopeptide immunogen (Lane 3), a generic phosphothreonine-containing peptide (Lane 4), or the phosphopeptide immunogen (Lane 5) control. The data show that only the immunogen phosphopeptide blocks the signal, demonstrating the specificity of the antibody.