MAL-dPEG®6-TFP ester, product number 10556, is a crosslinking reagent built around a polyethylene glycol (PEG) cross-bridge. This product joins free amines to free thiols (sulfhydryl groups). Sulfhydryl groups react with the maleimide via a Michael addition reaction. The amines form amide bonds with the crosslinker by nucleophilic substitution of the 2,3,5,6-tetrafluorophenyl (TFP) ester of the terminal propionic acid group. The maleimido and TFP functional groups of the crosslinker sit at either end of a short, discrete-length chain of PEG (hence, dPEG®). The monodisperse, single molecular weight dPEG® spacer is 28 atoms (32.1 Å) long.
The conjugation of free amines to sulfhydryl groups is one of the most popular, most useful crosslinking reactions in bioconjugate chemistry,. These reactions require heterobifunctional reagents capable of bridging the two groups. Typical crosslinkers are hydrophobic. Quanta BioDesign’s amphiphilic dPEG® PEGylation reagents are monodisperse, single molecular weight PEG compounds with discrete chain lengths.
Conventional hydrophobic crosslinking reagents frequently trigger aggregation and precipitation of the conjugates made from them. These problems do not happen with our water-soluble, non-immunogenic dPEG® crosslinkers. Furthermore, hydrophobic crosslinkers contribute to non-specific interactions in assays. Our dPEG® PEGylation reagents greatly reduce and often eliminate non-specific interactions due to hydrophobicity.
Traditional PEGylation reagents are made from dispersed polymers. These polymeric reagents are intractably complex mixtures of different sizes and molecular weights of PEG chains. This complexity creates difficulties in the analysis of conjugates. Quanta BioDesign’s dPEG® products have no dispersity (Ð = 1; that is, they are monodisperse PEGs). Each dPEG® product consists of a discrete chain of PEG with a single molecular weight. The uniform nature of our dPEG® products eliminates one of the most vexing analytical difficulties faced by users of traditional polymer PEG products.
Nevertheless, our customers enjoy all the benefits of PEG, minus the headaches that PEG polymers cause. For more information about our dPEG® products, please see our “What is dPEG®?” page. Also, click here for answers to our most frequently asked questions.
TFP Esters are Superior to NHS esters
TFP esters are more stable in aqueous buffers than N-hydroxysuccinimidyl (NHS) esters. Moreover, TFP esters have higher reactivity with free amines than NHS esters. NHS esters hydrolyze readily in water or aqueous buffer. As the pH increases, the hydrolysis rate of the NHS ester increases. In 2017, a study by J. Wang, et al., on the performance of fluorophenyl esters concluded, “With regards to PEGylation, the TFP ester performed better than NHS ester.”In-house research at Quanta BioDesign confirms the superior performance of TFP esters over NHS esters.
How to Use MAL-dPEG®6-TFP ester
TFP esters react under the same conditions as NHS esters. However, the optimal pH range for TFP esters (7.5 – 8.0) is slightly higher than for NHS esters (7.0 – 7.5).5 Amide bond formation between the TFP-activated propionic acid group of MAL-dPEG®6-TFP ester and a free amine will be slightly slower at a suboptimal pH compared to the reaction rate within the optimum pH range.
The maleimide end of MAL-dPEG®6-TFP ester, product number 10556, reacts optimally with a sulfhydryl at pH 6.5 – 7.5. Conduct the conjugation at the lowest reasonable pH within this range. Above pH 7.5, free amines compete with free thiols at the maleimide reaction site, which may confound the data. Moreover, at higher pH values, the maleimide ring may open to form unreactive maleamic acid. For details about maleimide-thiol reaction chemistry, please click here.
Uses of MAL-dPEG®6-TFP ester
MAL-dPEG®6-TFP ester, product number 10556, can be used the same way and in the same applications as the equivalent NHS esters. Possible uses for this product include the following:
Adding flexibility and water solubility to a peptide;
Building supramolecular constructs;
Coating nanoparticle surfaces;
Conjugating the TFP ester end of the molecule to a liposomal surface and then using the free maleimide end of the molecule to attach a small molecule drug, peptide, or antibody for targeted delivery of a diagnostic or therapeutic package.
Constructing antibody-drug conjugates (ADCs);
Increasing the water solubility and hydrodynamic volume of hydrophobic biomolecules; and,
Tethering antibodies to atomic force microscopy (AFM) probes.
How can you use this product in your next product development project?
Bulk Scale Synthesis of MAL-dPEG®6-TFP ester is 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.
Hydrophobic crosslinkers create more problems than they solve. Traditional disperse polymer PEG crosslinkers add unnecessary analytical complexity to conjugates that incorporate them.
So, stop using inferior products!
Start using single molecular weight dPEG® crosslinkers and discover the dPEG® difference. To get started, please click the “Add to Cart” button now to order MAL-dPEG®6-TFP ester, product number 10556.
 Hermanson, G. T. Chapter 6, Heterobifunctional Crosslinkers. In Bioconjugate Techniques, 3rd ed.; Academic Press: New York, NY, 2013; pp 299–340, specifically page 300. Many scientists engaged in bioconjugation work consider Greg Hermanson’s book to be the definitive reference on the subject. Click here now to read a review of Greg’s book and to purchase it.
 Hermanson, G. T. Chapter 18, PEGylation and Synthetic Polymer Modification. In Bioconjugate Techniques, 3rd ed.; Academic Press: New York, NY, 2013; pp 787–838, specifically page 794.
 Hermanson, G. T. Chapter 3, The Reactions of Bioconjugation. In Bioconjugate Techniques; Academic Press: New York, NY, 2013; pp 229–258, specifically page 239.