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Assay Method Information

Assay Name:  HTRF FRET Assay
Description:  A homogeneous time-resolved FRET assay can be used to determine IC50 values for inhibitors of the soluble human BACE1 catalytic domain. This assay monitors the increase of 620 nm fluorescence that resulted from BACE1 cleavage of an APPswedish APPswe mutant peptide FRET substrate (QSY7-EISEVNLDAEFC-Europium-amide). This substrate contains an N-terminal QSY7 moiety that serves as a quencher of the C-terminal Europium fluorophore (620 nm Em). In the absence of enzyme activity, 620 nm fluorescence is low in the assay and increased linearly over 3 hours in the presence of uninhibited BACE1 enzyme Inhibition of BACE1 cleavage of the QSY7-APPswe-Eu substrate by inhibitors is manifested as a suppression of 620 nm fluorescence.Varying concentrations of inhibitors at 3 the final desired concentration in a volume of 10 ul are preincubated with purified human BACE1 catalytic domain (3 nM in 10 μl) for 30 minutes at 30 C. in reaction buffer containing 20 mM Na-Acetate pH 5.0, 10% glycerol, 0.1% Brij-35 and 7.5% DSMO. Reactions are initiated by addition of 10 μl of 600 nM QSY7-APPswe-Eu substrate (200 nM final) to give a final reaction volume of 30 μl in a 384 well Nunc HTRF plate. The reactions are incubated at 30 C. for 1.5 hours. The 620 nm fluorescence is then read on a Rubystar HTRF plate reader (BMG Labtechnologies) using a 50 millisecond delay followed by a 400 millisecond acquisition time window.
Affinity data for this assay
 

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Last update November 1, 2007
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