Suberoylanilide hydroxamic acid (SAHA) is a class I and class II histone deacetylase (HDAC) inhibitor that binds directly to the catalytic site of the enzyme thereby blocking substrate access. [1] coumarin-Suberoylanilide hydroxamic acid (c-SAHA) is a SAHA derivative where the anilino cap" group is replaced by 7-amino-4-methylcoumarin to produce a fluorescent probe that competitively binds HDAC. [2] The fluorescence excitation and emission maxima of free c-SAHA is 325 and 400 nm