PromoCell’s Glutathione Detection Kit II provides a simple in vitro assay for detecting the GSH changes in apoptosis and other pathological processes. The assay utilizes a cell-permeable dye (monochlorobimane, MCB) that has a high affinity for glutathione. The unbound dye is almost nonfluorescent; whereas the dye fluoresces intensively blue (excitation = 380 nm; emission = 461 nm) when bound to reduced or oxidized glutathione (GSH-MCB). The reaction is catalyzed by glutathione S-transferase (GST). Thus, the decrease in glutathione level (e.g. in apoptotic cells) can be easily detected using a fluorometer or a 96-well fluorometric plate reader.