Figure 1

Optimization of coriphosphine O staining concentration. Plasmodium falciparum NF54 asynchronous culture at ~13.0% parasitaemia, 2.5% haematocrit was stained with different concentrations of coriphosphine-O in separate wells shown column-wise as: (A1, A2, A3) for 100 nM; (B1, B2, B3) for 20 nM; (C1, C2, C3) for 5 nM and (D1, D2, D3) for 2.5 nM. The top row (A1, B1, C1, D1) is a histogram showing a test sample (in blue) with infected red blood cells (iRBCs) and a control sample (in red) of uninfected red blood cells (uRBCs). The CPO staining at 20 nM gave the closest total parasitaemia (12.8%) to the microscopy reading and the best separation between iRBCs and uRBCs. The middle row (A2, B2, C2, D2) is a dot plot (CPO versus FS Log) of CPO staining of the uRBC control sample for each concentration. The 20 nM concentration also gave the least background of non-specific staining of uRBCs. The bottom row (A3, B3, C3, D3) shows a dot plot (CPO versus FS Log) of the iRBC sample with the proportions of the various parasite stages indicated; S: schizonts; T: trophozoites; R: rings.