(E)-TCO-PEG4-NHS ester | CAS 1621096-79-4

(E)-TCO-PEG4-NHS ester is a strained trans-cyclooctene (TCO) click chemistry reagent bearing a PEG4 spacer and an NHS ester for efficient conjugation to primary amines on biomolecules and surfaces. As a widely used component for bioorthogonal labeling, it enables rapid strain-promoted inverse electron-demand Diels–Alder (SPIEDAC) reactions with tetrazine partners in imaging and assay workflows. The combination of TCO reactivity, PEG-mediated solubility, and NHS-driven amide formation makes it a practical reagent for preparing TCO-functional probes, conjugates, and materials used across chemical biology and molecular imaging research.

1. Antibody And Protein Labeling

(E)-TCO-PEG4-NHS ester is commonly used to functionalize antibodies, antibody fragments, and other amine-containing proteins to generate TCO-bearing bioconjugates for downstream tetrazine-based click labeling. Researchers employ this reagent when they need stable attachment of the strained alkene handle while maintaining aqueous compatibility and minimizing aggregation, with the PEG4 spacer helping preserve conjugate behavior during labeling and purification. TCO-functional proteins prepared from (E)-TCO-PEG4-NHS ester are frequently used to build modular probe sets, where a tetrazine-tagged fluorophore, affinity ligand, or reporter is introduced at a later stage to streamline multicolor or multistep experimental designs.

2. Cell Surface Receptor Targeting

(E)-TCO-PEG4-NHS ester is used to install TCO groups onto cell-surface proteins and other extracellular amine-rich targets in labeling workflows that rely on tetrazine ligation. In chemical biology and biomaterials labs, the reagent is valued for enabling rapid, catalyst-free coupling of a tetrazine partner after TCO installation, supporting sequential labeling strategies that reduce cross-reactivity between probes. The PEG4 linker improves handling and labeling consistency, while the NHS ester chemistry supports attachment to accessible amines on proteins displayed at the cell interface, enabling preparation of cell-associated materials for imaging, binding studies, and probe optimization experiments.

3. Molecular Imaging Probe Construction

(E)-TCO-PEG4-NHS ester serves as a key intermediate for constructing imaging probes that use tetrazine click chemistry to attach reporters such as fluorophores, quencher pairs, or imaging moieties to a targeting scaffold. Supplier and research workflows often rely on this reagent because it provides a convenient way to generate TCO-functional targeting conjugates (e.g., protein or polymer carriers) that can be rapidly decorated with tetrazine-bearing imaging components under mild conditions. The PEG4 spacing helps maintain solubility and reduces nonspecific interactions during probe assembly, which is particularly useful when preparing conjugates intended for repeated labeling and comparative imaging optimization in molecular imaging development.

4. Surface Coatings And Biomaterials

(E)-TCO-PEG4-NHS ester is widely adopted for functionalizing polymer surfaces, hydrogel materials, and biomaterial scaffolds that present primary amines, enabling subsequent tetrazine-mediated attachment of fluorescent or affinity tags. Biomaterials researchers use the NHS ester functionality to covalently anchor TCO handles onto material surfaces, while the PEG4 spacer supports uniform presentation of reactive groups and improved wetting in aqueous environments. This approach supports modular fabrication of click-reactive coatings, sensor interfaces, and immobilized probe platforms where tetrazine reagents can be introduced in a controlled, late-stage step to tune labeling density, multicomponent patterning, or assay readout configurations.