The terminal propionic acid moiety can be coupled directly to free amines using EDC or another carbodiimide. Alternatively, converting the reactive end into an active ester permits conjugation of the transformed product to free amines. N-hydroxysuccinimide (NHS), 2,3,5,6-tetrafluorophenol (TFP), and 2,3,4,5,6-pentafluorophenol (PFP) typically are used for this purpose.
m-dPEG®25-amido-dPEG®24-acid, product number 11097, reacts with amine-functionalized surfaces (carbon nanotubes, nanoparticles made of silica or various metals, quantum dots, and similar types of products) or free amines on biomolecules. When used to coat surfaces or modify biomolecules, m-dPEG®25-amido-dPEG®24-acid reduces or eliminates non-specific binding and increases water solubility. Crucially, the elimination of non-specific binding may increase the signal-to-noise ratio in imaging applications and assays where this is a consideration. Please note that modifying the surface amines of biomolecules with this uncharged, methyl-capped dPEG® spacer may alter the overall charge of the resulting conjugates.
Many applications potentially, successfully could use m-dPEG®25-amido-dPEG®24-TFP ester to improve performance and function. Among those applications are:
- cell surface engineering;
- PK, BD, and immunogenicity profile improvements for biomolecules;
- imaging applications to reduce non-specific binding and background;
- dendrimer construction;
- nanoparticle, quantum dot, and carbon nanotube surface coating; and,
- prevention of protein aggregation.
m-dPEG®25-amido-dPEG®24-acid, product number 11097, is just one member of an extensive line of methyl-terminated dPEG® products. This line includes dPEG® spacers containing 2 to 49 ethylene glycol units. These products terminate with a carboxylic acid moiety. Activation of the carboxylic acid with NHS, TFP, or PFP is typically carried out before a subsequent reaction with free amines. Also, the carboxylic acid group may be coupled directly to free amines with a carbodiimide such as EDC. In addition to better hydrolytic stability, TFP esters have proven to be more reactive than NHS esters for amine-reactive products. For more information on the performance of TFP esters, please see our page TFP Esters Have More Hydrolytic Stability and Greater Reactivity than NHS Esters.
Quanta BioDesign, Ltd., makes and sells single molecular weight PEG linkers and spacers with discrete chain lengths under the dPEG® trade name. Our products are distinctly different from traditional PEG products in that they are not disperse polymers. However, they confer all of the benefits of conventional PEG products. To learn more about dPEG® products, please visit our “What is dPEG®?” page. Please also click this link to get answers to our most frequently asked questions.