Biotinylated glutathione ethyl ester (BioGEE) is a cell-permeant, biotinylated glutathione analog for the detection of glutathiolation. Under conditions of oxidative stress, cells may transiently incorporate glutathione into proteins. Stressed cells incubated in BioGEE will also incorporate this biotinylated glutathione derivative into proteins, facilitating the identification of oxidation-sensitive proteins. Once these cells are fixed and permeabilized, you can detect glutathiolation levels with a fluorescent streptavidin conjugate using either flow cytometry or fluorescence microscopy. Proteins glutathiolated with BioGEE can also be extracted and analyzed by mass spectrometry or by Western blotting methods in conjunction with fluorophore- or enzyme-labeled streptavidin conjugates.