Difluorocarboxyfluorescein NHS Ester, 5-isomer

Unit Size
Price (USD)
Cat.#: 1222-5
Unit size: 5 mg
in stock
Cat.#: 1222-25
Unit size: 25 mg
in stock
Cat.#: 1222-100
Unit size: 100 mg
in stock

Difluorocarboxyfluorescein NHS Ester, 5-isomer (Oregon Green™ 488 Carboxylic Acid, Succinimidyl Ester, 5-isomer equivalent) 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.

Difluorocarboxyfluorescein dye structurally is identical to Oregon Green™ 488.

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Primary amine
Abs/Em Maxima
496/524 nm
Extinction coefficient
73,000 cm-1M-1
Spectrally similar dyes
Alexa Fluor® 488, DyLight® 488, Fluorescein
Molecular weight
Storage conditions
Shipping conditions
Ambient temperature


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