The TopCount Microplate Scintillation Counter can be used to dramatically reduce costs and throughput when using the MultiScreen system. MultiScreen filtration plates manufactured by Millipore Corporation are available in a white, solvent-resistant plastic that is designed to prevent optical crosstalk between wells and to contain liquid cocktails. These plates provide optimum performance in the TopCount. After conducting set-up, incubation, and separation steps directly in the plate, it is snapped into a reflective adapter available from Packard Instrument Company. This permits the addition of volumes of LS cocktail sufficient to maximize counting efficiency for low energy isotopes such as 3H and 125I. LS cocktail is easily added to each well using automated equipment. This eliminates tedious punching and vial filling/ capping procedures, and permits the use of the microplate stacker and bar code sample identification systems on TopCount. With up to 12 simultaneously counting detectors, TopCount is capable of significantly increasing counting throughput.
Presented here are the results of several experiments which demonstrate the performance of the MultiScreen system on the TopCount Microplate Scintillation Counter.
Cellular Receptor Binding.
Competitive binding assays, typically done using cell harvesters and glass fiber filter media, are designed to assess the competition between a test compound and a labeled ligand for a cell surface receptor. A number of standard binding assays have been commercialized in kit form. For this experiment, we chose the Endothelin-1 kit (125I) available from DuPont-NEN Research Products, Boston, Massachusetts (Cat. No. NED- 009).
We used the white MultiScreen-HV plate (Millipore Cat. No. S