Trans-Cyclooctene (TCO)-PEG3-Maleimide is a mid-length, sulfhydryl-reactive labeling reagent containing a 3-unit polyethylene glycol spacer arm for increased water-solubility.


  • Biocompatible – click reaction occurs efficiently under mild buffer conditions; requires no accessory reagents such as a copper catalyst or reducing agents (e.g. DTT)
  • Chemoselective – tetzines and trans-cyclooctene groups do not react or interfere with other functional groups found in biological samples but conjugate to one another with high efficiency
  • Unprecedented kinetics – inverse-electron demand Diels-Alder chemistry is the fastest bioorthogonal ligation available, delivering conjugates within 30 min at 1 mg/mL concentrations
  • Sulfhydryl-reactive – maleimide reacts rapidly with reduced cysteines and other molecules that contain reduced thiols (–SH groups), attaching the TCO moiety via a stable thioether bond
  • Highly stable – TCO functional group remains stable in aqueous buffered media (weeks at 4C, pH 7.5)
  • Extended PEG3 Spacer – reduces aggregation, minimizes steric hindrance, and enhances solubility

TCO-PEG3-Maleimide enables simple and efficient incorporation of TCO moiety onto antibodies, cysteine-containing peptides and other thiol-containing molecules. The hydrophilic polyethylene glycol (PEG) spacer arm imparts water solubility that is transferred to the labeled molecule, thus reducing aggregation of labeled proteins stored in solution. The PEG spacer arm provides a long and flexible connection that minimizes steric hindrance involved with ligation to complementary tetrazine-containing molecules.

Catalog Number Product DataSheet Size AVAILABILITY Price Qty
TCO-PEG3-Maleimide, 4 x 2 mg
4 x 2mg In stock
Regular Price:$186.00
On Sale:
TCO-PEG3-Maleimide, 10 mg
10mg In stock
Regular Price:$149.00
On Sale:
TCO-PEG3-Maleimide, 25 mg
25mg In stock
Regular Price:$270.00
On Sale:
TCO-PEG3-Maleimide, 100 mg
100mg In stock
Regular Price:$762.00
On Sale:

Product Type: Small Molecule
Name: Trans-Cyclooctene (TCO)-PEG3-Maleimide
Chemical Formula: C26H41N3O8
Molecular Weight: 523.62
Variant MPN: 1002
Purity: >90%, H NMR
Tested Applications: Protein-protein conjugation, protein-antibody conjugation, protein-small molecule conjugation, 18F radiolabeling, protein-oligonucleotide conjugation, surface modification
Solubility: DCM, Chloroform, DMSO, DMF
Storage: -20C.Desiccate
Shipped: Frozen - Dry Ice

  1. Blackman, M. L., et. al. (2008). "Tetrazine Ligation: Fast Bioconjugation Based on Inverse- Electron-Demand Diels-Alder Reactivity." J. Am. Chem. Soc., 130:13518-13519
  2. Devaraj, N. K., et. al. (2008) "Tetrazine-Based Cycloadditions: Application to Pretargeted Live Cell Imaging." Bioconjugate Chem., 19(12): 2297–2299.
  3. Devaraj, N. K., et. al. (2009) "Fast and Sensitive Pre-Targeted Labeling of Cancer Cells through a Tetrazine/trans-Cyclooctene Cycloaddition." Angew. Chem. Int. Ed., DOI: 10.1002/anie.200903233
  4. Haun, J.B., et. al. (2009) " Probing Intracellular Biomarkers and Mediators of Cell Activation Using Nanosensor and Bioorthogonal Chemistry" ACS Nano., 5:3204-321

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