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MPS-Acid (QBD-10323)



MPS-Acid, product number QBD-10323, is 3-maleimidopropanoic acid, a thiol-reactive crosslinker for linking sulfhydryl groups with free amines. Although it is not a dPEG® product, MPS-Acid is a building block for Vector Laboratories’ complete line of Maleimide-dPEG®x products. As a crosslinker, the spacer is from the reactive site of the maleimide to the carbonyl carbon of the propanoic acid.

The maleimido group reacts with sulfhydryl groups to form thiol ether bonds. In the range of pH 6.5 – 7.5, the thiol-maleimide reaction is chemoselective. Above pH 7.5, the maleimide group can also react with free amine groups. Consequently, high pH buffers should be avoided when using this product.

This product can be functionalized with an active ester such as N-hydroxysuccinimide (NHS); 2,3,5,6-tetrafluorophenol (TFP); or 2,3,4,5,6-pentafluorophenol (PFP) in order to react with free amines. Alternatively, the acid moiety can be coupled directly to free amines using a water-soluble carbodiimide such as 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC).


Unit Size100 mg, 1000 mg
Molecular Weight169.13; single compound
Chemical formulaC₇H₇NO₄
Purity> 98%
SpacersSpacer is 6 atoms and 6.0 Å
Typical solubility properties (for additional information contact Customer Support)Acetonitrile, DMAC, DMSO or water.
Storage and handling-20°C; Always let come to room temperature before opening; be careful to limit exposure to moisture and restore under an inert atmosphere; stock solutions can be prepared with dry solvent and kept for several days (freeze when not in use). dPEG® pegylation compounds are generally hygroscopic and should be treated as such. This will be less noticeable with liquids, but the solids will become tacky and difficult to manipulate, if care is not taken to minimize air exposure.


Greg T. Hermanson, Bioconjugate Techniques, 3rd Edition, Elsevier, Waltham, MA 02451, 2013, ISBN 978-0-12-382239-0; See Chapter 18, Discrete PEG Reagents, pp. 787-821, for a full overview of the dPEG® products.

Applicable patents and legal notices are available at legal notices.

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