25 mM Tris/HCl, pH 8.0, 137 mM NaCl, 2.7 mM KCl, 1 mM MgCl2, and 0.1 mg/ml BSA, 20 µM BPS HDAC substrate 3 (Catalog #50037), and HDAC3/NcoR2. Incubation condition: 30 min at 37°C, followed by HDAC developer (Catalog #50030) for 15 min at room temperature. Fluorescence intensity is measured at ex360/em460.