4-Nitrophenyl 2,3,4,6-tetra-O-acetyl-b-D-thioglucopyranoside is a fluorescent dye that is used in recording and registration. It has been shown to be a very sensitive reporter of protein interactions in living cells. This dye binds to proteins via the hydroxyl groups on its sugar moiety, and has been shown to bind to a variety of proteins such as myosin light chain kinase and phosphatidylinositol 4-kinase. The fluorescent properties of this dye make it useful for tracking protein localization in the cell.