Fluorescein is a bright fluorophore that is utilized in a wide range of applications and is especially popular for oligonucleotide labeling. Most syntheses directly incorporate fluorescein using the phosphoramidite approach, and this NHS ester provides the option for post-deprotection labeling. When paired with a 5’-amino-modifier C6 (10-1906, 10-1907, 10-1916 or 10-1947), the resulting product would be identical to that generated with 5’-Fluorescein Phosphoramidite (10-5901).
Coupling: For labeling 0.2 µmoles of an amino-modified oligonucleotide, dissolve 2.4 mg of the Fluorescein NHS Ester in 100 µL DMSO (or DMF). Dissolve the amino-modified oligonucleotide in 200 µL 0.25 M carbonate/bicarbonate buffer (pH 9). Add 20 µL of the NHS Ester solution and vortex. Let react for 60 min at room temperature and desalt.