6-Fam (6-carboxyfluorescein) is one single isomer of the dye Fluorescein (Figure 1). It is usually coupled to DNA and RNA oligonucleotides via an amide bond and it has a good solubility in water. Spectral characteristics of 6-Fam are identical to those of FITC (Fluorescein-5,6-isothiocyanate), which consists of a reactive species of fluorescein bearing an isothiocyanate reactive group. 6-Fam can be successfully used with most fluorescent detection devices available in the market.
Figure 1. Structure of 5'-6-carboxyfluorescein (R = sequence).
metabion offers 6-Fam modifications in its DNA and RNA portfolio as a 5'-, 3'- or internal 6-Fam-dT modification:
Livak KJ., Flood SJ., Marmaro J., Giusti W., Deetz K. Oligonucleotides with fluorescent dyes at opposite ends provide a quenched probe system useful for detecting PCR product and nucleic acid hybridization. PCR Methods Appl. 1995 Jun;4(6):357-62.