Fig 2. Divalent metal ions present in yeast nitrogen base inhibit DOX uptake into the cells.

The WT strain grown in YPD was washed, resuspended in either low YNB or standard YNB. Uptake assay was started by the addition of 800 μM of DOX and, at the same time, without and with increasing concentrations of the indicated salts (0 to 5 mM) to the cells in low YNB. Uptake reaction was stopped after 30 min and the intracellular accumulation of DOX was measured by FACS analysis. The results were the averages of three independent experiments.