FDG [Fluorescein di-ß-D-galactopyranoside] - 5 mg

Fluorescein di-β?D-galactopyranoside (FDG) is one of the most sensitive fluorogenic substrates available for detecting β?galactosidase. The colorless and nonfluorescent FDG is hydrolyzed to highly fluorescent fluorescein, which exhibits excellent spectral properties (Ex/Em=492/520 nm) that match the optimal detection window of most fluorescence instruments. Galactosidase-catalyzed hydrolysis of FDG can be followed by fluorescence increase around 520 nm. Alternatively, FDG can also be used to detect β?galactosidase in a chromogenic mode since the enzymatic product (fluorescein) exhibits a large extinction coefficient (close to 100,000 cm-1mol-1). In general, fluorescence-based measurements can be several orders of magnitude more sensitive than absorption-based measurements. FDG has been widely used for identifying lacZ-positive cells with fluorescence microscopy and flow cytometry. FDG is also used to detect β?galactosidase expression in live cells. Fluorescence-based assays employing FDG are also reported to be 100 to 1000-fold more sensitive than radioisotope-based ELISAs.

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