Transcreener Assays rely on homogenous immunodetection of nucleotides, which means robust, generic detection of entire families of drug targets. With the introduction of the Transcreener PDE (phosphodiesterase) Assay, BellBrook Labs extends its nucleotide detection capabilities to include AMP and GMP detection. Phosphodiesterases control a variety of cellular processes by hydrolyzing the second messenger signaling molecules cAMP and cGMP. The Transcreener PDE Assay is a far-red, competitive fluorescence polarization immunoassay based on the detection of the hydrolyzed substrates AMP or GMP. Enzyme reaction progress is indicated by a decrease in the fluorescence polarization signal. A simple two-step, endpoint test (see figure) accommodates cAMP/cGMP concentrations of 0.1 to 10 μM with a single reagent mix (up to 1 mM substrate has been used with Ab optimization).