FAM is the short version for Fluorescein – the prevalent fluorescent label. Fluorescein is a yellow dye that absorbs blue light (absorption maximum 485 nm) and emits blue to green light (515 nm) [which looks yellowish to the human eye]. Additional synonyms are FL, FLU or FITC (isothiocyanate reagent compatible for coupling on oligo synthesizers).

FAM can be read by most sequencing instruments (ABI 310 and others).

FAM can be read by all Real-Time PCR instruments and is therefore a preferred reporter dye.

For TaqMan® Probes, customers prefer the combination of 5’-FAM and 3’-TAMRA quencher or another non-fluorescent (dark) Quencher like 3'-Dabcyl, BlackBerry Quencher (BBQ) or Black-Hole-Quencher-1 or -2 (BHQ-1/2).

For Molecular Beacons or Scorpion Primers, a Dabcyl Quencher is used, in case of a scorpion primer as an internal dT-Dabcyl Quencher.

FRET systems use FAM (FL) as a Donor dye.

FAM can be used for in-situ hybridization (FISH). But because of its instability to light exposure and the natural fluorescent background of biological probes in the range of 480-530 nm, FAM has mostly been replaced by more stable dyes like Oregon Green or Cy dyes (Cy3 and Cy5).

Alternatively, Fluorescein can also be used for immune detection instead of Digoxigenin and Biotin.

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