FIG. 3.

Visualization of the redox state in yeast and CHO-K1 cells. (A) Imaging of the FRET signal generated by wild-type (C probe) or mutant (A probe) Redoxfluor in S. cerevisiae in response to H₂O₂ (100 μM), ATZ (10 mM), or BSO (100 μM). Following the exposure of cells to H₂O₂ or ATZ, the cells were incubated in fresh (drug-free) medium and were monitored at the indicated times. Bar, 2 μm. (B) The FRET ratio imaging of C probe in CHO-K1 cells in response to H₂O₂ (100 μM) or ATZ (10 mM) (see Videos S1 and S2 in the supplemental material). The ATZ treatment of CHO-K1 cells expressing A probe did not show a C probe-like FRET response, although a slight FRET change due to the inherent redox-responsive nature of the fluorescent protein was observed. Bar, 10 μm. (C) From the microscopic analyses shown in panel B, the relative values of the FRET signal intensity of the C probe before and after H₂O₂ or ATZ treatment were plotted.