DBCO-dPEG®12-carboxyfluorescein, product number 11812, permits fluorescein labeling of peptides, proteins, and other molecules using strain-promoted azide-alkyne cycloaddition (SPAAC). This compound combines 5(6)-carboxyfluorescein with dibenzylcyclooctyne (DBCO) through a single molecular weight, discrete PEG (dPEG®) spacer. The carboxyfluorescein label has an excitation wavelength (λex) of 498 nanometers (nm), and an emission wavelength (λem) of 528 nm. The molar absorptivity (ε) is 7.96×104 M-1 cm-1 at pH 8.0 and 498 nm.

About Fluorescein and DBCO

Fluorescein and its derivatives are among the most popular dyes in use today for labeling proteins and cells. Unfortunately, these dyes are hydrophobic. Moreover, care must be taken to avoid over-labeling. Extensive labeling with xanthene dyes can result in quenching caused by dye-dye energy transfer instead of fluorescent emission. Furthermore, putting too many hydrophobic moieties on a biomolecule causes aggregation and precipitation of the bioconjugates.

DBCO is an increasingly popular choice for SPAAC chemistry, also known as “copper-free click chemistry.” The highly strained cyclooctyne ring reacts readily with azides to form a stable triazole ring. Additionally, copper(I) is not needed to catalyze the reaction, making SPAAC chemistry preferable when working with live cells that can be poisoned by copper(I). Although the DBCO can react with free sulfhydryl groups under some conditions, it is highly selective for azides. Because azides must be introduced artificially into proteins, DBCO is considered a bioorthogonal click chemistry reagent.

PEGylation and Quanta BioDesign’s dPEG® Products

PEGylation is the process of covalently attaching a polyethylene glycol (PEG) molecule to another molecule, such as a peptide, protein, or drug. PEG is amphiphilic, meaning that it dissolves in both water and many organic solvents. Attaching PEG to a hydrophobic molecule causes the conjugate molecule to be water-soluble. The degree of water solubility depends in part on the length of the PEG chain, because a typical PEG molecule can hydrogen bond three water molecules per ethylene oxide unit in the chain.

Traditional PEGylation reagents are disperse polymers (Đ = 1.05 – 1.20). The polymeric processes by which traditional PEG is made do not permit full control of the synthesis. Dispersity creates difficult challenges in characterizing and analyzing conjugates, especially biological conjugates, because of the complex mixture of chain lengths and molecular weights in a “pure” sample of a disperse polymer. In contrast, Quanta BioDesign’s dPEG® products are designed to have no dispersity (Đ = 1); that is, they are monodisperse. In any dPEG® product, there is a single PEG chain length with a single molecular weight. Thus, using dPEG® products greatly simplifies analysis and characterization of conjugates!

Using DBCO-dPEG®12-carboxyfluorescein

The introduction of a dPEG® spacer between carboxyfluorescein and DBCO imparts water solubility to DBCO-dPEG®12-carboxyfluorescein. Also, the hydrophilic dPEG® introduces flexibility and increases the conjugate’s hydrodynamic volume through hydrogen bonding with water. Furthermore, the 47.6Å spacer keeps the carboxyfluorescein group away from the surface of the molecule to which it is conjugated.

DBCO-dPEG®12-carboxyfluorescein provides a highly selective, flexible, water-soluble way to label proteins, peptides, and cells with carboxyfluorescein using a bio-orthogonal reagent designed to simplify analysis and characterization of the conjugate.

Bulk Quantities are Available

If you need bulk product in a larger package size than our standard sizes, please contact us for a quote. Our commercial capabilities permit us to manufacture this product at any scale that you need.

Buy It Now!

Quanta BioDesign’s dPEG® products are different from traditional PEGylation reagents. When used correctly, dPEG® products make a difference in every application compared to both hydrophobic and conventional (disperse) PEGylation products. We call this “the dPEG® difference.”

To discover the dPEG® difference for yourself, click the “Add to Cart” button now. Get ready for a pleasant surprise.


Additional information

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

You may also like…