HDAC assay buffer is an essential reagent for signal generation in HDAC assays performed with any of BPS Bioscience's HDAC fluorimetric substrates or assay kits. An appropriate fluorimetric substrate, comprising an acetylated lysine side chain, is first incubated with a sample containing HDAC activity (nuclear or cellular extract, purified enzyme, bead-bound immunocomplex, etc.) in HDAC assay buffer. Deacetylation of the substrate sensitizes it so that, in a second step, treatment with the HDAC assay developer produces a fluorophore. Trichostatin A is included asan 'inhibitor stop' for class I and II HDACs.