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Receptor R is over expressed in CHO cells and analysed for expression. 6 × 107 cells were incubated with its radioactive ligand (specific activity 100 counts per picomole). If the total counts present in cell pellet was 1000 cpm, the average number of receptors R per cell is (assume complete saturation of receptors with ligand and one ligand binds to one receptor)
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- 104
- 105
- 106
- 107
Correct Option: B
Number of ligands = total radioactivity/radioactivity in each ligand
= 1000 cpm/ 100 cpm/pmole
= 10 pmole
= 10 * 10–12 * 6.023 *10–12 * 6.023 * 1023 ligands
Thus, total ligands= 6.023 * 1012
Average number of receptors, R per cell = total receptor/number of cells
= 6.023 * 1012/6 * 107
= 105
