In this report, the Cerenkov counting performance of the TopCount is documented for linearity, volume effects, efficiency, background and well-to-well crosstalk, as well as the applicability of this technique for liquid and filter/membrane counting. A protein kinase C assay was done to demonstrate the utility of this technique in a common application.
The Cerenkov counting mode was used on the TopCount with a factory set region of interest especially suited for highest sensitivity. Where appropriate, samples were also Cerenkov counted on the Packard Tri-Carb 2500TR LSC for comparison to TopCount. The microplates were sealed with TopSeal-A, a self-adhesive sealer. 32P-ATP (Amersham #PB.10204) was the radioisotope used in all experiments. A stock solution containing 49,000 DPM/μL was used for all experiments.
96- and 24-Well Microplates
Counting efficiency, crosstalk, and background data were acquired for counting in white 96- and 24-well OptiPlates. The 96- and 24-well OptiPlate performance was evaluated using 200 μL and 1.0 mL, respectively, of water per well as the medium. Activity was added to the wells such that a spiked well was surrounded by eight neighboring blank wells containing only water 2 in order to evaluate well-to-well crosstalk. The crosstalk pattern was performed in triplicate for 96-well f