<p>A431 cells were treated with 5 mM H<sub>2</sub>O<sub>2</sub> for 30 minutes, 20 mM NAC for 18 hours, or sequential treatment with 20 mM NAC for 18 hours and then 5 mM H<sub>2</sub>O<sub>2</sub> for 30 minutes. Cell lysates were then fractionated by ultracentrifugation. The cytosolic fraction (S100) was analysed by Western blotting for the presence of endogenous RalA (upper panel), and quantitated by densitometry (central panel). Error bars represent the SEM (<i>n</i> = 3). The lower panel shows total cell protein stain of each of the samples represented in the upper panel.</p
