WB (peptide competition) analysis of K562 cells stimulated with PMA (2-6) using GTX60928 PKC mu (phospho Ser742) antibody prior incubated with the non-phosphopeptide corresponding to the immunogen (Lane 3), a generic phosphoserine-containing peptide (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. The membrane treated with phosphatase (Lane 6) eliminates the signal further verifying that the antibody is phospho-specific.