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Assay Method Information

Assay Name:  IMAP TR-FRET-based phosphodiesterase assay
Description:  An IMAP TR-FRET-based phosphodiesterase assay was developed using the PDE2A isoform. IMAP technology is based on high-affinity binding of phosphate by immobilized metal (MIII) coordination complexes on nanoparticles. The IMAP binding reagent recognizes phosphate groups on AMP or GMP generated from cAMP or cGMP in a PDE reaction. Cyclic nucleotides that carry a phosphodiester bond and not a free phosphate are not recognized by the binding reagent. The time resolved fluorescence resonance energy transfer (TR-FRET) is afforded by a Terbium (Tb)-Donor pre-bound to the nanoparticles. FRET occurs when the fluorescent-labeled AMP or GMP product of a PDE reaction binds and comes into close proximity to the Tb-Donor complex. Due to the long lifetime of Tb fluorescence, detection can be run in time-resolved mode to reduce or eliminate interference from auto-fluorescent compounds.The IMAP TR-FRET PDE2A assay was performed in 1536-well white plates. A total of 250 pg per well of FLAG-tagged PDE2A1 (amino acids 2-941) was dispensed in 2.5 μL IMAP assay buffer consisting of 10 mM Tris pH 7.2, 10 mM MgCl2, 1 mM DTT, and 0.1% fatty acid free BSA. 30 nL of compound was then added from 1 mM stocks in DMSO using a Kalypsys Pintool. Plates were incubated for 5 min at room temperature before dispensing 1.5 μL of 533 nM FAM-cAMP substrate for a final concentration of 200 nM. Following a brief centrifugation, plates were incubated for 30 min at room temperature. The assay was terminated by adding 5 μL IMAP binding reagent Tb complex to each well which was prepared according to manufacturer's recommendations (Molecular Devices). Plates were incubated an additional 90 minutes at room temperature and read on a Viewlux plate reader. All compounds were solvated at a concentration of 10 mM in DMSO and tested in 11-point half-log dose-response. Curve fitting and IC50 values were determined using a standard four parameter fit.
Affinity data for this assay
 

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Last update November 1, 2007
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