Question

All the questions refer to an experimental drug (RDRPkill), designed to treat COVID-19. The drug is a specific inhibitor of the coronavirus specific RNA-directed RNA-polymerase.
Although it does not dissolve in pure water, RDRPkill is soluble in 10% (w/v) ethanol or pure dimethyl sulfoxide (DMSO).
It is supplied in vials that generally contain 5 mg of powder. Liquid is transferred in and out of these vials by puncturing the rubber seal at the top with a syringe.

3. An experiment requires an incubation to be carried out with 1 μM of RDRPkill. The incubation will be carried out in a total volume of 500 μL of culture medium. What volume of each of the stock solutions below (a – d) would you need to add to the incubation to give 1 μM of RDRPkill?
a. 1mM
b. 0.5% (w/v)

c. 20 μg/dL

d. 10 μg/mL
e. Due to the toxicity of the solvent, the volume added cannot exceed 0.1% (v/v) in the final 500 μL of culture.

Which of the stock solutions above COULD actually be used for this incubation?

Answer 1