6-Carboxyfluorescein (6-FAM) is a fluorescent dye with an absorption wavelength of 495 nm and an emission wavelength of 517 nm. A carboxyfluorescein molecule is a fluorescein molecule with a carboxyl group added. They are commonly used as a tracer agents. It is used in the sequencing of nucleic acids and in the labeling of nucleotides.
Commercially available FAM is a mixture of two isomers, 5-FAM and 6-FAM, and the correct name is 5(6)-carboxyfluorescein.
The dyes are membrane-impermeant and can be loaded into cells by microinjection or scrape loading.[1] It can be incorporated into liposomes, and allows for the tracking of liposomes as they pass through the body. In addition, carboxyfluorescein has been used to track division of cells.[2] In vascular plants, 5(6)-carboxyfluorescein can be used as a symplastic tracer. It is able to move through the phloem due to its structural similarity to sucrose.[3] It is typically loaded into the leaves in order to gain access to the phloem.[4][5] This can be done by scraping, cutting, or weakening the leaf’s cuticle with an herbicide.
