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SPDP-dPEG®₄-NHS ester (QBD-10374)



SPDP-dPEG®4-NHS ester, product number QBD-10374, is Vector Laboratories’ water-soluble version of the immensely popular, but unfortunately hydrophobic, SPDP crosslinker. SPDP-dPEG®4-NHS ester is a heterobifunctional crosslinker. The N-hydroxysuccinimidyl (NHS) ester end of the molecule reacts with free amines. The opposite end is a 3-(2-pyridyldithio)-propionate functional group that reacts with sulfhydryl groups in thiol-containing molecules to form disulfide bonds. Between the two functional groups is a short (20 atoms), amphiphilic, single molecular weight, discrete polyethylene glycol (dPEG®) spacer.

Among the most popular heterobifunctional crosslinking reagents used in bioconjugate chemistry are those compounds that conjugate molecules containing free amine groups with molecules that contain sulfhydryl groups. SPDP (N-succinimidyl 3-(2-pyridyldithio)-propionate) is one of the most popular versions of this type of crosslinker. Unfortunately, SPDP and its popular varieties (LC-SPDP and Sulfo-LC-SPDP) are hydrophobic molecules. When conjugated to biomolecules, care must be taken not to modify the target molecules too much, because this can precipitate the conjugate products.

By contrast, SPDP-dPEG®4-NHS ester, product number QBD-10374, is used like SPDP and its related hydrophobic products. However, precautions against overly modifying the target molecule are not necessary. The water-soluble dPEG® product will not cause the resulting conjugates to precipitate due to excessive hydrophobicity.


Unit Size100 mg, 1000 mg
Molecular Weight559.65; single compound
Chemical formulaC₂₃H₃₃N₃O₉S₂
Purity> 97%
SpacersdPEG® Spacer is 20 atoms and 23.1 Å
Typical solubility properties (for additional information contact Customer Support)Methylene chloride, Acetonitrile, DMAC or DMSO.
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, 2nd Edition, Elsevier Inc., Burlington, MA 01803, April, 2008 (ISBN-13: 978-0-12-370501-3; ISBN-10: 0-12-370501-0); See pp. 276-335 for general description and use of heterobifunctional crosslinkers, and the specific sample protocol for SPDP and LC-SPDP on pp. 286-288. See Greg’s extensive index on pp. 1192-1193 for references to a number and range of applications and their respective protocols.

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.

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Applicable patents and legal notices are available at legal notices.

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