Effect of Syk inhibitors on growth inhibition and band 3 phosphorylation; stage-dependent sensitivity of parasite to R406 treatment. (A) Parasite growth inhibition (% growth inhibition) and the levels of band 3 phosphorylation at different concentrations of R406 expressed as a percentage of the band 3 maximal phosphorylation levels measured in untreated cultures (% phosphorylation). Parasitemia was measured at the second cycle of growth, and band 3 phosphorylation was measured 36 hours postinfection. (B) Relative activity of R406 (1.0 µM) added at 12, 24, 36, 40, and 48 hours postinfection. Values are expressed as percentage of the maximal R406 activity (treatment time 24 hours postinfection) measured as % activity. Data are the average of 5 experiments ± SD.