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Assay Method Information

Assay Name:  Time-Resolved Fluorescence Resonance Energy Transfer (TR-FRET) Assay
Description:  For the assay, 50 nl of a 100-fold concentrated solution of the respective test substance in DMSO were pipetted into a black low-volume 384-well microtitre plate (Greiner Bio-One, Frickenhausen, Germany) 2 μl of a solution of the Tie2 fusion protein in assay buffer [50 mM HEPES/HCl pH 7, mM MgCl2, 2.5 mM MnCl2, 1 mM dithiothreitol, 0.01% (v/v) Nonidet P-40, 0.1% (w/v) bovine serum albumin (BSA), 1× Complete EDTA-free protease inhibitor mixture (Roche)] were added, and the mixture was incubated for 15 min to allow pre-binding of the substance to the enzyme prior to the kinase reaction. The kinase reaction was then started by adding 3 μl of a solution of adenosine triphosphate (ATP, 1.67 mM→final concentration in 5 μl assay volume=1 mM) and substrate (1.67 μM→final concentration in 5 μl assay volume=1 μM) in assay buffer, and the resulting mixture was incubated for a reaction time of 60 min at 22° C. The concentration of the Tie2 fusion protein was adapted to the respective activity of the enzyme and adjusted such that the assay was carried out in the linear range. Typical concentrations were in the range of 30 ng/ml. The reaction was stopped by addition of 5 μl of a solution of TR-FRET detection reagents [200 nM streptavidin-XL665 and 2 nM PT66-Eu chelate, a europium chelate-labelled anti-phosphotyrosine antibody (Perkin-Elmer); alternatively, it is also possible to use PT66-Tb cryptate (Cisbio Bioassays, Codolet, France)] in aqueous EDTA solution [90 mM EDTA, 0.28% (w/v) bovine serum albumin (BSA) in 50 mM HEPES pH 7.5]. The resulting mixture was incubated at 22° C. for 1 h to allow formation of the complex of the biotinylated phosphorylated substrate and the detection reagents. The amount of phosphorylated substrate was then determined by measuring the resonance energy transfer from PT66-Eu chelate to streptavidin-XL665. To this end, the fluorescence emissions at 620 nm and 665 nm after excitation at 350 nm were measured in a TR-FRET measuring instrument (for example Viewlux, Perkin-Elmer).
Affinity data for this assay
 

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Last update November 1, 2007
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