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Assay Method Information

Assay Name:  Binding Assay
Description:  Preparation of membranes containing recombinantly expressed sodium channels: Frozen recombinant cell pellets were thawed on ice and diluted to 4 times the cell pellet weight with ice cold 50 mM Tris HCl, pH 7.4 buffer. The cell suspensions were homogenized on ice using a motorized glass dounce homogeniser. Homogenates were further diluted 8.4 times with ice cold 50 mM Tris HCl, pH 7.4 buffer and then centrifuged at 200×g at 4° C. for 15 min. The supernatants were collected and centrifuged at 10000×g at 4° C. for 50 min. The pellets were then re-suspended in 100 mM NaCl, 20 mM Tris HCl, pH 7.4 buffer containing 1% v/v protease inhibitors (Calbiochem) and re-homogenized on ice. The homogenized membranes were then processed through a syringe equipped with a 26 gauge needle. Protein concentrations were determined by Bradford Assay and the membranes were stored at −80° C.Radioligand Binding Studies: Saturation experiments. A representative compound of formula (I) was tritiated. Three tritiums were incorporated in place of methyl hydrogens to generate [3H]compound. Binding of this radioligand was performed in 5 mL borosilicate glass test tubes at room temperature. Binding was initiated by adding membranes to increasing concentrations of [3H]compound in 100 mM NaCl, 20 mM Tris HCl, pH 7.4 buffer containing 0.01% w/v bovine serum albumin (BSA) for 18 h. Non-specific binding was determined in the presence of 1 μM unlabelled compound. After 18 h, the reactants were filtered through GF/C glass fiber filters presoaked in 0.5% w/v polyethylene imine. Filters were washed with 15 mL ice cold 100 mM NaCl, 20 mM Tris HCl, pH 7.4 buffer containing 0.25% BSA to separate bound from free ligand. [3H]compound bound to filters was quantified by liquid scintillation counting.Competitive binding experiments. Binding reactions were performed in 96-well polypropylene plates at room temperature for 18 h. In 360 μL, membranes were incubated with 100 pM [3H]compound and increasing concentrations of Test Compound. Non-specific binding was defined in the presence of 1 μM unlabelled compound. Reactions were transferred and filtered through 96-well glass fiber/C filter plates presoaked with 0.5% polyethylene imine. The filtered reactions were washed 5 times with 200 μL ice cold buffer containing 0.25% BSA. Bound radioactivity was determined by liquid scintillation counting.
Affinity data for this assay
 

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Last update November 1, 2007
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