WB analysis of HEK293 cells overexpressing c-Raf alone (Lane 1) or immunoprecipitates prepared from cells co-transfected with c-Raf, Ras (V12), and Rac1 (Lane 2-6) using GTX24768 Raf1 (phospho Ser338/Tyr340) antibody prior incubated with the non-phosphopeptide corresponding to the phosphopeptide immunogen (Lane 3), a generic phosphoserine-containing peptide (Lane 4), a generic phosphotyrosine-containing peptide (Lane 5), or the phosphopeptide immunogen (Lane 6). The data show that only the immunogen phosphopeptide blocks the signal, demonstrating the specificity of the antibody.