5-FAM

5-FAM is the amine-reactive purified single isomer of 5,6-carboxyfluorescein and is used for labeling peptides, proteins and nucleotides through the interaction of carboxylic acid with primary amines. It has been used to develop a variety of green fluorescent reagents and small fluorescent molecules due to its relatively high absorbance characteristics, excellent fluorescence quantum yield, and good water solubility. The probe has also found application in studies of liposome-cell, cell-cell, and liposome-liposome interactions and in related studies on lipid bilayer structures. Spectral data: λex = 494nm; λem = 518nm. Carboxyfluorescein is better retained in cells than is fluorescein, its pKa of ~6.5 is lower than the cytosolic pH of most cells (pH ~6.8-7.4). Carboxyfluorescein is commonly employed as a polar tracer.