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MAL-dPEG®₄-Lys(-5(6)-Carboxyfluorescein)-NH-m-dPEG®₂₄ (QBD-11577)



MAL-dPEG®4-Lys(5(6)-carboxyfluorescein)-NH-m-dPEG®24, product number QBD-11577, is one of Vector Laboratories’ unique, patented class of modular, designable payload delivery reagents called Sidewinder™. Sidewinder™ products are built on a discrete PEG (dPEG®) backbone for use in antibody-drug conjugates (ADCs) and related constructs. The payload (cytotoxin, dye, small molecule) loads onto the chain’s sidearm. The distal end’s methoxy-terminated dPEG®24 spacer protects payloads and modifies performance.

The maleimide reactive group of MAL-dPEG®4-Lys(5(6)-carboxyfluorescein)-NH-m-dPEG®24, product number QBD-11577 reacts with free thiols on the biomolecule through the thiol-maleimide reaction (a Michael addition reaction). The sidearm is functionalized with 5(6)-carboxyfluorescein (ex/em = 493/517) and can be used to track cell trafficking and internalization of a conjugated molecule such as an antibody or antibody fragment.

Sidewinder™ products are designed to facilitate the creation of stable, high-DAR ADCs. Published research has shown that putting a hydrophobic payload (e.g., a cytotoxin) close to the antibody surface and protecting it with a SuperHydrophilic™ dPEG® construct is better by many measures of efficacy than putting the payload at the distal end of the linker. This molecule can also be used to modify and optimize BD, cell trafficking and internalization, serum half-life, and immunogenicity.

The dPEG® linkers and spacers in the Sidewinder™ construct are uniform, single molecular-weight PEGs with discrete chain lengths. This differs from traditional, non-uniform polymer PEG linkers and spacers, which have a dispersed range of PEG chain lengths, each with a unique molecular weight. In contrast to dispersed polymer PEGs, dPEG® products are high-purity compounds with reproducible purity profiles.

Sidewinder™ molecules are also fully designable. MAL-dPEG®4-Lys(5(6)-carboxyfluorescein)-NH-m-dPEG®24 can be modified to change the spacer lengths, add more sidearm attachment points, add different sidearm attachment points to carry payloads with different reactivities, change the maleimide attachment group to a different reactive group, and many more customizations. Please inquire about your specific needs.


Unit Size5 mg
Molecular Weight1973.20; single compound
Chemical formulaC₉₄H₁₄₉N₅O₃₉
Purity> 95%
SpacersdPEG® Spacer is 99 atoms and 113.3 Å
Typical solubility properties (for additional information contact Customer Support)Methylene Chloride or Dimethylformamide
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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