Assay Method Information

Assay Name:  HTRF KinEASE-STK S2 kit
Description:  The kinase IC50 was determined by a commercialized CISBIO kinase detection kit, HTRF KinEASE-STK S2 kit (62ST2PEC). ROCK2 (01-119) employed in the reaction was purchased from Carna Biosciences.Before the assay, the following working solutions as needed were formulated with corresponding reagents according to the instruction of the kinase detection kit: 1×kinase buffer, 5×STK-S2 substrate working solution (1.5 μM) and 5×ATP working solution (1.5 μM), 5×ROCK2 kinase working solution, 4×Streptavidin-XL665 working solution, and 4×STK-Ab-Cryptate 2 detection solution. Then the assay was performed according to the following procedure.A solution of a compound at a concentration of 10000 nM was prepared with the 1×kinase buffer containing 2.5% DMSO. Gradient dilution of the solution of the compound was performed with the kinase buffer containing DMSO, so as to obtain solutions of a test compound at 9 different concentrations. In addition to wells of test compounds, a positive well (containing all the reagents except the compound) and a negative well (containing all the reagents except the test compound and kinase) were set. Except for the control wells (positive and negative wells), a solution of a test compound (4 μL) was added to each of the reaction wells, and a solution of 2.5% DMSO was added to the control wells. Then the substrate (2 μM, i.e., 2 μL 5×STK-S2 substrate working solution) was added to each of the reaction wells. The 5×ROCK2 kinase working solution (2 μL, containing 1.4 ng ROCK2 kinase) was added to each of the reaction wells except for the negative well, the volume of which was made up with the 1×kinase buffer (2 μL). The 5×ATP working solution (2 μL) was added to each of the reaction wells, and the mixtures were incubated at room temperature for 2 hours. After the kinase reaction was complete, the 4×Streptavidin-XL665 working solution was added to each of the reaction wells, the solutions were mixed, followed by immediate addition of the 4×STK-Ab-Cryptate 2 detection solution (5 μL), and the mixtures were incubated at room temperature for 1 hour. The fluorescence signal was read on ENVISION (Perkinelmer) (excitation wavelength: 320 nm, and emission wavelength: 665 nm and 615 nm). The inhibitory rate in each well was calculated based on the fluorescence intensity value: ER (Emission Ratio)=(fluorescence intensity at 665 nm/fluorescence intensity at 615 nm); inhibitory rate=(ERpositive−ERtest compound)/(ERpositive−ERnegative)*100%. Curves were plotted and fitted to obtain the median inhibitory concentration (IC50) of each test compound with the PRISM 5.0 software.
Affinity data for this assay
 

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