Popular green fluorescent cell-permeable dye. Covalently couples via its succinimidyl group to intracellular molecules. The amine-reactive succinimidyl ester of 5-FAM acid is a common fluorescent derivatization reagent for covalently labeling peptides, proteins and nucleotides. Due to this covalent coupling reaction it can be retained within cells for extremely long periods and due to this stable linkage, once incorporated within cells the dye is not transferred to adjacent cells. Yields carboxyamides which are more resistant to hydrolysis than fluorescein conjugates prepared with FITC. Better retained in cells than fluorescein. Used in fluorescent small molecule preparations. Spectral data: lambdaex 494 nm| lambdaem 520 nm (Buffer pH 9.0).