Histone deacetylases (HDACs) catalyze the hydrolytic removal of acetyl groups from histone lysine residues resulting in chromatin condensation and transcriptional repression of chromosomal DNA. Thus, HDAC inhibition allows the conformation of DNA to be relaxed and transcriptional activation to ensue. Changes in the transcription of key genes have linked HDAC inhibitors to blocking angiogenesis and cell cycling, and promoting apoptosis and differentiation. Cayman’s HDAC1 Inhibitor Screening Assay Kit provides a fast, fluorescence-based method for screening HDAC1 inhibitors. The procedure requires only two easy steps, both performed in the same microplate. The fluorescent reaction product is easily analyzed using a fluorometer with excitation wavelengths of 340-360 nm and emission wavelengths of 440-465 nm. Sufficient purified HDAC1 is provided for 100 tests.