Variation in luciferase activity in drug-treated transgenic parasites. Plasmodium falciparum 3D7 parasites expressing firefly luciferase were incubated for 10 hours with chloroquine, DFMO , mefloquine, artemisinin , ritonavir or gramicidin in 96-well plates. At 2-hour intervals, luciferase activity in drug-exposed and solvent control cultures was determined with a luminescence based Bright-Glo® Luciferase Assay System reagent (Promega). At each time-point, luminescence is plotted as a percentage relative to that obtained with controls incubated with solvent alone, after background luminescence produced by uninfected red blood cells had been subtracted. Individual data-points are the mean relative luminescence values from three replicate wells and error bars indicate standard deviation.