Difluorocarboxyfluorescein NHS Ester, 6-isomer

Difluorocarboxyfluorescein NHS Ester, 6-isomer is an amine-reactive fluorinated analog of fluorescein that overcomes some of the key limitations of fluorescein, including greater photostability and a lower pKa (pKa ~ 4.7 versus 6.4 for fluorescein), making its fluorescence essentially pH insensitive in the physiological pH range. Although the mixed isomers of Difluorocarboxyfluorescein NHS Ester, is a preferred, routinely used fluorescent dye for labeling proteins, peptides and nucleotides, purification of peptide and nucleotides labeled with 5 (6) isomers might be troublesome due to significant signal broadening in HPLC purification. Peptides and nucleotides labeled with a single isomer usually give better resolution in HPLC purification that is often required in the conjugation processes.