Maleimide Crosslinkers

Maleimide Crosslinkers

Published on 21/03/2023

Maleimides provide versatile options for connecting payloads to proteins and other biomolecules. Discover how our bifunctional thiol reactive crosslinkers can support your project. Read on!

Maleimides readily react with thiols in a Michael type addition to form succinimidyl thioethers. This reaction may be carried out in buffered aqueous solutions at pH 6.8 (useful range: 6.5-7.0) and usually completes within a few minutes. However, this reaction and linkage is reversible.

Schematic representation of the thioether formation between a thiol and a maleimide.

If increased stability of the conjugate is required, the resulting succinimide ring may be deliberately hydrolyzed. To this end, we are providing self-stabilizing crosslinkers with Boc-protected amines, which, after deprotection, may act as intramolecular nucleophiles to open the succinimide ring.

Hydrolysis of thiosuccinimides via an intrinsic catalytic nucleophilic amine. P = Payload.

Besides, we offer linkers with aryl moieties, which directly destabilize the succinimide after it has been formed, so that the ring then is quickly and irreversibly hydrolyzed.

Resonance promoted hydrolysis of thiosuccinimides. P = Payload.

Within our maleimido-crosslinker portfolio, we offer several kinds of additional reactive functions with various properties: reactivity towards amino groups, for use in Click Chemistry, for photoactivation, or to introduce new functional groups into your structure or biomolecule.

In the following, we are highlighting those additional functionalizations:

Succinimidyl esters (abbreviated as OSu or NHS) are a frequently used tool for coupling small molecules to peptides and proteins. These activated carboxyl groups react readily with amino groups in buffered aqueous solutions at pH 7.5 (useful range: 6.5-8.5). Iris Biotech is offering a wide selection of ready to use maleimide-succinimide crosslinkers with spacers of different properties and lengths between 6 and 16 atoms.

Pentafluorophenyl (PFP-) esters work like succinimidyl esters but are slightly less sensitive to undesired hydrolysis during the coupling process. As an example, Mal-L-Dap(Boc)-OPfp (MAA1080) introduces a spacer of five atoms.

Regarding Click Chemistry, we offer DBCO (dibenzoazacyclooctyne) and MeTz (methyltetrazine) functionalized maleimide crosslinkers suitable for copper-free conjugation in biological environments, as well as alkyne-functionalized ones for classical Click chemistry (see related products).

As photoactivatable crosslinker, we provide 4-(N-Maleimido)benzophenone (LS-3350), which can be activated upon irradiation with light of 350 nm.

Further functional groups may be introduced using maleimide-crosslinkers bearing amino, hydroxyl and carboxyl functions.

Besides “permanent” crosslinkers, our portfolio also includes cleavable linkers with a predetermined breaking point for targeted payload release, e.g. upon enzymatic activity, changes in pH or redox potential.

→ Browse our Brochure Linkerology® to discover the panoply of available linker technologies.
→ For more details about Click Chemistry or Photochemistry, download our booklets!
→ You cannot find what you are looking for? Get in contact for a Custom Synthesis and benefit of our expertise!


Reactivity and pH dependence of thiol conjugation to N-ethylmaleimide: detection of a conformational change in chalcone isomerase; R. A. Bednar; Biochemistry 1990; 29: 3684-3690.

Stabilization of cysteine-linked antibody drug conjugates with N-aryl maleimides; R. J. Christie, R. Fleming, B. Bezabeh, R. Woods, S. Mao, J. Harper, A. Joseph, Q. Wang, Z. Q. Xu, H. Wu, C. Gao,N. Dimasi; J Control Release 2015; 220: 660-70.

A versatile acid-labile linker for antibody–drug conjugates; M. C. Finniss, K. S. Chu, C. J. Bowerman, J. C. Luft, Z. A. Haroon,J. M. DeSimone; Med. Chem. Commun. 2014; 5: 1355-1358.

Long-term stabilization of maleimide-thiol conjugates; S. D. Fontaine, R. Reid, L. Robinson, G. W. Ashley,D. V. Santi; Bioconjug Chem 2015; 26: 145-52.

Bioconjugation - A versatile and essential research tool; G. Hermanson; Aldrichimica Acta 2017; 50: 43-57.

Chapter 3 - The Reactions of Bioconjugation; G. T. Hermanson; in Bioconjugate Techniques (Third Edition); edited by G. T. Hermanson; Academic Press; Boston 2013: 229-258

Cross-linking of rabbit skeletal muscle troponin with the photoactive reagent 4-maleimidobenzophenone: identification of residues in troponin I that are close to cysteine-98 of troponin C; J. Leszyk, J. H. Collins, P. C. Leavis,T. Tao; Biochemistry 1987; 26: 7042-7.

Self-hydrolyzing maleimides improve the stability and pharmacological properties of antibody-drug conjugates; R. P. Lyon, J. R. Setter, T. D. Bovee, S. O. Doronina, J. H. Hunter, M. E. Anderson, C. L. Balasubramanian, S. M. Duniho, C. I. Leiske, F. Li,P. D. Senter; Nature biotechnology 2014; 32: 1059-62.

pH Dependence of Succinimide-Ester-Based Protein Cross-Linking for Structural Mass Spectrometry Applications; E. Trabjerg, A. Keller,A. Leitner; ACS Measurement Science Au 2022; 2: 132-138.

Novel Silyl Ether-Based Acid-Cleavable Antibody-MMAE Conjugates with Appropriate Stability and Efficacy; Y. Wang, S. Fan, D. Xiao, F. Xie, W. Li, W. Zhong,X. Zhou; Cancers (Basel) 2019; 11: 957.

Discovery of Peptidomimetic Antibody-Drug Conjugate Linkers with Enhanced Protease Specificity; B. Wei, J. Gunzner-Toste, H. Yao, T. Wang, J. Wang, Z. Xu, J. Chen, J. Wai, J. Nonomiya, S. P. Tsai, J. Chuh, K. R. Kozak, Y. Liu, S. F. Yu, J. Lau, G. Li, G. D. Phillips, D. Leipold, A. Kamath, D. Su, K. Xu, C. Eigenbrot, S. Steinbacher, R. Ohri, H. Raab, L. R. Staben, G. Zhao, J. A. Flygare, T. H. Pillow, V. Verma, L. A. Masterson, P. W. Howard,B. Safina; J Med Chem 2018; 61: 989-1000.

Characterization of Ring-Opening Reaction of Succinimide Linkers in ADCs; K. Zheng, Y. Chen, J. Wang, L. Zheng, M. Hutchinson, J. Persson,J. Ji; J Pharm Sci 2019; 108: 133-141.

Related Products
    1. Structure image for Mal-AMCHC-OSu

      Product code: MAA1000

      Startet von 87,50 $

    2. Structure image for Mal-beta-Ala-OSu

      Product code: MAA1020

      Startet von 312,50 $

    3. Structure image for TCEP*HCl

      Product code: LS-3405

      Startet von 237,50 $

    4. Structure image for Mal-L-Dap(Boc)-OH*DCHA

      Product code: MAA1040

      Startet von 100,00 $

    5. Structure image for Mal-D-Dap(Boc)-OH*DCHA

      Product code: MAA1060

      Startet von 112,50 $

    6. Structure image for Sulfo-SMCC

      Product code: MAA1050

      Startet von 312,50 $

    7. Structure image for Z-DEVD-Rh110-p

      Product code: LS-3550

      Startet von 1.375,00 $

    8. Structure image for MeTz-PEG(4)-mal

      Product code: RL-2340

      Startet von 262,50 $

    9. Structure image for DBCO-mal

      Product code: RL-2490

      Startet von 300,00 $

    10. Structure image for DBCO-PEG(4)-mal

      Product code: RL-2500

      Startet von 225,00 $

    11. Structure image for 3-Mal-Bz-NHS

      Product code: RL-2600

      Startet von auf Anfrage

    12. Structure image for 3-Mal-MBz-NHS

      Product code: RL-2610

      Startet von auf Anfrage

    13. Structure image for 4-Mal-Bz-NHS

      Product code: RL-2620

      Startet von auf Anfrage

    14. Structure image for 4-Mal-MBz-NHS

      Product code: RL-2630

      Startet von auf Anfrage

    15. Structure image for Mal-Bu-NHS

      Product code: RL-2640

      Startet von auf Anfrage

    16. Structure image for Mal-cHxHx-NHS

      Product code: RL-2650

      Startet von 218,75 $

    17. Structure image for Mal-Hx-NHS

      Product code: RL-2660

      Startet von 75,00 $

    18. Structure image for Mal-Pen-NHS

      Product code: RL-2670

      Startet von auf Anfrage

    19. Structure image for Mal-PhBu-NHS

      Product code: RL-2680

      Startet von auf Anfrage

    20. Structure image for Mal-PrHx-NHS

      Product code: RL-2690

      Startet von auf Anfrage

    21. Structure image for DBCO-PEG(24)-MAL

      Product code: PEG6780

      Startet von 468,75 $

    22. Structure image for Mal-NH2*HCl

      Product code: RL-2780

      Startet von 93,75 $

    23. Structure image for Mal-Et-OH

      Product code: RL-3000

      Startet von 343,75 $

    24. Structure image for Mal-L-Dap(Boc)-OPfp

      Product code: MAA1080

      Startet von 118,75 $

    25. Structure image for Mal-cyclobutane-1,1-dicarboxamide-Cit-PAB

      Product code: ADC1460

      Startet von auf Anfrage

    26. Structure image for Mal-cyclobutane-1,1-dicarboxamide-Ala-PAB

      Product code: ADC1560

      Startet von auf Anfrage

    27. Structure image for Mal-cyclobutane-1,1-dicarboxamide-Ala-PAB-PNP

      Product code: ADC1570

      Startet von auf Anfrage

    28. Structure image for Mal-N-Boc-Aeg-NHS

      Product code: RL-3430

      Startet von 243,75 $

    29. Structure image for Mal-CH2CH2-N(Me)-CH2-COOH

      Product code: RL-3400

      Startet von auf Anfrage

    30. Structure image for Mal-AMCHC-N-Propargylamide

      Product code: MAA1100

      Startet von 150,00 $

    31. Structure image for Mal-PEG(2)-DipSi-PHB-PNP

      Product code: ADC1640

      Startet von auf Anfrage

    32. Structure image for Mal-Pen-O-DipSi-PHB-PNP

      Product code: ADC1650

      Startet von auf Anfrage

    33. Structure image for MC-Val-Ala-PAB-Cl

      Product code: ADC1700

      Startet von 625,00 $

    34. Structure image for DBCO-PEG(36)-MAL

      Product code: PEG6785

      Startet von auf Anfrage