FIG. 2.

Redox titration of Redoxfluor with reduced and oxidized glutathione in vitro. (A) Spectrophotometric analysis of C probe and A probe at 37°C in titration buffer containing different ratios of GSH/GSSG corresponding to the designated electropotential (E₀′) gradient. The excitation wavelength was 405 or 434 nm. (B) mPEG-maleimide modification of Redoxfluor. Under the same titration conditions as those described for panel A, the purified Redoxfluor was incubated with mPEG-maleimide and subjected to immunoblot analysis. The arrows indicate the signals corresponding to the nonmodified form of the protein. The asterisks indicate signals corresponding to modified forms of the probe protein.