FIG. 4.

Cytotoxicity of nucleoside analogs in HeLa cells. Cytotoxicity was measured using an Alamar blue-based assay as described in Materials and Methods. Cells were incubated in the presence of the nucleoside of interest, and Alamar blue reagent was added 6 h prior to measuring absorbance (A) 24 (A) or 48 (B) h postexposure. Data were normalized such that 100% viability was set equal to the percentage of Alamar blue reagent reduced by untreated cells. Data are presented as the means and standard deviations from three independent wells. For each series, the bars represent, from left to right, 0, 0.05, 0.1, 0.5, 1, and 2 mM treatments.