m-dPEG®₃₇-NHS ester

Free amines react optimally at pH 7.2 – 7.5 in aqueous media with NHS esters. Furthermore, in aqueous media, the rate of hydrolysis of the ester to the carboxylic acid increases as the pH rises. Consequently, we do not recommend the storage of this product in water or aqueous buffer. Moreover, when dissolved in aqueous media, the product should be reacted immediately to minimize hydrolysis. Also, please note that reacting surface amines on biomolecules (e.g., proteins and peptides) with this neutral, methyl-capped dPEG^® spacer may alter the overall charge of the resulting conjugates.

m-dPEG^®₃₇-NHS ester, product number 10910, has been used successfully to modify silica shelled quantum dots used in imaging applications to make them water-soluble. Also, it has been employed to improve the pharmacokinetic (PK) and biodistribution (BD) properties of an antibody that targets an epitope that is found exclusively in adenocarcinomas. Carbon nanotubes and inorganic nanoparticles with amine-functionalized surfaces could also be modified to passivate the surface and make it hydrophilic. Moreover, proteins and other biomolecules conjugated to this product will have higher water solubility, reduced or eliminated antigenicity, and improved PK and BD properties. In-house studies by Quanta BioDesign indicated that proteins modified with this product would not aggregate.

m-dPEG^®₃₇-NHS ester, product number 10910, is just one member of a comprehensive line of methyl-terminated dPEG^® products. This line includes dPEG^® spacers containing 2 to 49 ethylene glycol units. These products are functionalized with NHS or with 2,3,5,6-tetrafluorophenol (TFP). TFP esters have proven to be superior to NHS esters for amine-reactive products. For more information on the outstanding 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 trade name dPEG^®. Because they are not disperse polymers, our products are distinctly different from traditional PEG products. However, dPEG^® products confer all of the benefits of conventional PEG products without the analytical headaches that dispersity causes. To learn more about dPEG^® products, please visit and peruse our page titled, “What is dPEG^®?“. Please also click on our Frequently Asked Questions page to get answers to the questions we answer most often.