Carboxyfluorescein-dPEG®₁₂-NHS ester




Carboxyfluorescein-dPEG®12-NHS ester, product number 10885, is a xanthene dye derivative that is water-soluble and amine-reactive due to a long single molecular weight, discrete PEG (dPEG®) spacer. In aqueous buffer containing 0.1M ethanolamine, pH 8.0, this dye has an excitation wavelength (λex) of 494 nm and an emission wavelength (λem) of 517 nm with a molar extinction coefficient (ε) of 61,480 M-1cm-1 at 494 nm.

Fluorescein and its derivatives are currently among the most popular dyes for labeling proteins and cells. Unfortunately, xanthene dyes like fluorescein are hydrophobic. Moreover, when these hydrophobic dyes are conjugated to biomolecules, care must be taken to avoid over-labeling. Extensive labeling with xanthene dyes causes them to quench due to dye-dye energy transfer instead of fluorescent emission. Moreover, excessive conjugation of hydrophobic molecules onto biomolecules often causes aggregation and precipitation of the bioconjugates.

PEGylation, the covalent attachment of polyethylene glycol (PEG) to molecules or surfaces, is renowned for imparting a hydrophilic character to hydrophobic molecules. PEGylation is the current “gold standard” for modification of biomolecules due to its ability to increase water solubility, extend in vivo circulation times of small molecules, and reduce or eliminate antigenicity of immunogenic molecules. However, traditional PEG compounds are disperse polymers (Đ ≥ 1.05) consisting of a mixture of different PEG chain lengths and molecular weights. This mixture greatly complicates purity and identity analyses for both the PEG and the PEG conjugates.

Quanta BioDesign’s single molecular weight PEG products are known as “discrete PEG” and are sold under the dPEG® trade name. By design, our products provide all the benefits of PEGylation while eliminating the intractable mixture of chain lengths and molecular weights found in traditional, disperse PEG products. By design, each of Quanta BioDesign’s dPEG® products contains a single length and molecular weight of PEG.

Carboxyfluorescein-dPEG®12-NHS ester consists of the 5(6) isomers of fluorescein that have been conjugated to a medium-length (40 atoms, 47.4 Å) dPEG®12 chain. The distal end of the dPEG®12 spacer is esterified with N-hydroxysuccinimide (NHS) for conjugation to free amines on proteins, peptides, or other molecules. The product has good solubility in aqueous media. Moreover, the flexible PEG spacer significantly reduces background noise in dye-based assays with fluorescein. This product is an excellent choice for studies or tests that require a fluorescein dye derivative.

If you need this product in larger quantities than our standard package sizes, our capabilities include the ability to scale any of our products to commercial scale. Please contact us for a quote on non-standard bulk orders.

Additional information

Weight .5 oz
Dimensions .75 × .75 × 2 in