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Why is DMSO used as the vehicle in the rapamycin experiments of Gao et al. (2010)?Edit

DMSO is used because rapamycin is soluble in DMSO and methanol.

What is the EC50 of rapamycin in this kind of experiment?Edit

The EC50 of rapamycin varies from cell type to cell type and from experiment to experiment.

Zhu et al. (2009) tell us that rapamycin even smooth muscle cells in veins and arteries have different EC50s.

But Zhu does explain how to calculate the EC50 for any particular experiment:

The concentrations of rapamycin which produce 50% of the maximal antiproliferative effect (EC50) and induce 50% of the maximal lethal (toxic) effect (LC50) were obtained by fitting the respective concentration-effect data to the following sigmoid Emax equation (or Hill equation) using the nonlinear regression function in SigmaPlot.
E = Emax . Cn / ECn50 + Cn         (10)

Where E is the percentage of antiproliferative or toxic effect at concentration C relative to the maximal antiproliferative or toxic effect Emax (100); EC50 is the concentration of drug that produces 50% of the maximal antiproliferative or toxic effect; n is the shape factor. Therapeutic index is calculated as the ratio of LC50 to EC50.

What is the half-life of rapamycin in culture?Edit

The half-life of rapamycin is 57–63 hours.