Direction: Absence of cellulosic cell wall, high β-carotene content and GRAS status make Dunaliella salina a good model system for producing edible vaccines. 109 Cells of D. salina were electroporated with a high expression DNA vector containing an antigenic gene.
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The antigen is expressed as transmemb-rane protein with a single epitope on its extracellular domain. The cells that survived (assume 100% transfection and expression of protein) were incubated with a radio labeled Fab fragment (specific activity: 100 cpm/picomole) against this epitope. After washing, the cell pellet has1000 cpm. The average number of epitopes present on a single recombinant alga are
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- 6 × 109
- 1 × 109
- 6 × 103
- 1 × 106
Correct Option: A
103 cpm in pellet is due to Fab binding to epitope present on recombinant living cells/algae
| Total Fab or epitope = | ||
| Specific activity |
| = | ||
| 102 cpm (picomole)-1 |
| = | = 10 × 10-12 mole | |
| 102 |
= 10 picomole
These 10 picomole epitopes are present on 103 cells (assuming) 100% transfection and expression of protein).
| Average number of epitopes on single recombinant alga = | = 10-14 mole | |
| 103 |
= 6.023 × 1023 × 10–14
= 6 × 109
