– 2-Bromo-4′-hydroxyacetophenone(PTP Inhibitor I) is a cell-permeable, protein tyrosine phosphatase (PTP) inhibitor that covalently blocks the catalytic domain of the Src homology region 2 domain-containing phosphatase (SHP-1(ΔSH2)) with a Ki value of 43 μM and PTP1B with a Ki value of 42 μM [1]. SHP-1 and PTP1B both have known roles in regulating insulin signaling as well as myeloid and lymphoid cell differentiation, making inhibitors of these phosphatases of interest in diabetes, cancer, allergy, and inflammation research [2].