5(6)-FAM

Mixed isomer of 5 and 6-FAM. Fluorescein is one of the most popular green fluorescent reagents used for in situ labeling of peptides, proteins and nucleotides. It reacts with primary amines via carbodiimide activation of the carboxylic acid. Fluorescein has relatively high absorptivity, excellent fluorescence quantum yield, good water solubility, and an excitation maximum that closely matches the 488 nm spectral line of the argon-ion laser. The cell-impermeant 5,6-FAM can also be used as a nonfixable polar tracer to investigate fusion, lysis and gap-junctional communication and to detect changes in cell or liposome volume. It has also been used to prepare various small fluorescent molecules.