It was suggested that this lack of correlation could be due to factors not being taken into account by this first model (overlapping binding sites and compound chirality); a pharmacophore model explains aspects of the geometry of the interaction but not the details of the thermodynamics of the protein-small molecule contacts. Fig. Poor correlation was seen between the first model's predictions and experimental data. While there is excellent correlation between in vitro parasite killing potency and the ability to dysregulate parasite ion homeostasis ("PfATP4") activity, the majority of the model predictions did not correlate well with the experimental data. The compounds were tested for their effects on Na + regulation in saponin-isolated parasites (Dd2 strain) at 1 M and for their effects on parasite pH at 5 M; 'Yes': indicates that the compound gave rise to an increase in Na + concentration similar in magnitude to that of 50 nM cipargamin and a cytosolic alkalinisation, 'No': indicates that the compound did not affect the resting Na + concentration or pH, 'Moderate': indicates that the compound gave rise to an increase in pH, as well as an increase Na + concentration that was less than that observed on addition of 50 nM cipargamin.