Assay Method Information
Assay Name:  Fluorescence Polarization Assay
Description:  Assays were performed at room temperature in 384-well microtiter plates with an incubation volume of 20.2 μL. Solutions of test compounds were prepared in DMSO and serially diluted with DMSO to yield 8 μL of each of 10 solutions differing by 3-fold in concentration, at 32 serial dilutions per plate. 100% inhibition is determined using a known PDE9 inhibitor, such as 1-(2-chlorophenyl)-6-[(2R)-3,3,3-trifluoro-2-methylpropyl]-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidine-4-one (BAY 73-6691), (6-[(3S,4S)-4-methyl-1-(pyrimidin-2-ylmethyl)pyrrolidin-3-yl]-1-(tetrahydro-2H-pyran-4-yl)-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one (PF-04447943). 0% of inhibition is determined by using DMSO (1% final concentrations). A Labcyte Echo 555 (Labcyte, Sunnyvale, CA) is used to dispense 200 nL from each well of the titration plate to the 384 well assay plate. Human PDE9A2 membrane preps were diluted to 1 ng/ml. FAM-labeled cGMP substrate (Molecular Devices, Sunnyvale, CA) was at a concentration of 100 nM (Km of PDE9 for cGMP is 70-170 nM) in the assay buffer (10 mM Tris HCl, pH 7.2, 10 mM MgCl2, 0.05% NaN3 0.01% Tween-20, and 1 mM DTT). PDE9 enzyme mix and compounds were mixed and incubated at room temperature for 30 min. Following which, FAMcGMP substrate was added, shaken and incubated for an additional 60 min at room temperature. The final concentration of human PDE9 membrane preparations were 0.5 ng/ml. The final concentration of FAM-cGMP was 50 nM. After the incubation period, the enzymatic reaction was stopped by addition of binding solution (IMAP-FP, Molecular Devices, comprised of 80% Solution A, 20% Solution B and a 1:600 dilution of binding reagent) to each well. The plates were shaken then incubated at room temperature for 1 h prior to determining the fluorescence polarization (mP) using a Perkin Elmer EnVision™ plate reader (Waltham, MA).
Affinity data for this assay
 
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