FIG. 2.

Pichia in vivo water permeability assay. Comparison of absorbance with osmotic shock gradient (change in M sorbitol) for TIP3;1-G₃-H₆-expressing yeast and the control, parent yeast strain KM71H. Where indicated, the assay was performed in the presence of mercury ions (2 to 3 mM HgCl₂ with a 10-min preincubation prior to the osmotic shock). For this assay the osmotic shock gradient is defined as the molarity of sorbitol in the cell suspension prior to the osmotic shock, subtracted by the molarity of sorbitol in the suspension following the osmotic shock. Data are means ± standard deviations for the population (three to eight replicates). The response of each treatment group was normalized to the group average optical absorbance following an osmotic shock of 0 M sorbitol. Optical absorbance was measured ∼10 s following the osmotic shock.