FITC (6-Isomer) (3' modification)
There are two derivatives of the dye fluorescein: FITC and 6-Fam. Both forms differ only in the structures of their linkers to the oligonucleotide.
FITC, fluorescein isothiocyanate, can be used as label for direct fluorescence imaging. But it also serves as haptene-label that can be visualized with immuno-detection linked either to chemiluminiscence or colour formation.
The fluorescein label is available as 6-Fam or FITC, that differ only in the linkage of the fluorescein moiety to the oligonucleotide.