Tetrazine-Ph-PEG5-NHS ester | CAS 1682653-80-0

Tetrazine-Ph-PEG5-NHS ester is a PEGylated tetrazine reagent designed for bioorthogonal click chemistry, most commonly in inverse-electron-demand Diels–Alder reactions with strained trans-cyclooctenes (TCO) and related cyclooctene handles. The molecule couples a tetrazine warhead to a phenyl linker and a short, water-soluble PEG5 spacer, improving conjugation practicality and reducing steric constraints during labeling workflows. The NHS ester functionality enables straightforward attachment to primary amines on proteins, peptides, and other amine-bearing biomolecules, making this reagent widely used for preparing imaging probes, targeting conjugates, and modular research tools that rely on fast, selective tetrazine–cyclooctene ligation.

1. Protein Labeling Conjugates

Tetrazine-Ph-PEG5-NHS ester is used to functionalize amine-containing biomolecules such as antibodies, antibody fragments, enzymes, and carrier proteins with a tetrazine handle for subsequent cycloaddition-based assembly. In typical research workflows, NHS ester chemistry provides controlled installation of the reactive tetrazine moiety onto lysine residues, while the PEG5 spacer helps maintain accessibility of the tetrazine for downstream reaction with TCO-modified partners. This format is especially common in modular conjugation strategies where the tetrazine-labeled biomolecule is prepared first, then combined with a complementary cyclooctene-bearing reagent to generate defined conjugates for imaging, affinity reagents, or mechanistic studies in chemical biology.

2. Molecular Imaging Probe Assembly

Tetrazine-Ph-PEG5-NHS ester supports the construction of tetrazine-functional imaging probes by enabling amine-reactive incorporation of the tetrazine handle onto targeting scaffolds and probe-forming components. Researchers frequently employ this reagent to prepare probe intermediates that can be rapidly ligated to TCO-tagged imaging reporters, such as fluorophores, radiolabeling chelates, or other signal-bearing modules, using click chemistry as a late-stage conjugation step. The PEG5 element and phenyl spacer are relevant for probe design because they can improve solubility and reduce steric effects that otherwise limit efficient ligation, which is valuable when generating multi-component imaging reagents for microscopy, flow-based assays, or molecular imaging development.

3. Cell Surface Targeting Tools

Tetrazine-Ph-PEG5-NHS ester is applied in the preparation of cell-surface targeting and labeling tools where amine-reactive conjugation is used to install tetrazine functionality on targeting ligands. In common workflows, ligands bearing accessible primary amines are converted to tetrazine-modified versions via NHS ester chemistry, then used in combination with TCO-functional materials or reporter constructs to achieve selective surface labeling through click ligation. The PEG5 spacer can help preserve binding and interaction characteristics by providing a flexible tether that reduces interference between the tetrazine handle and the targeting moiety, supporting robust assembly of multivalent labeling reagents used in chemical biology and biomaterials research.

4. Biomaterials Surface Functionalization

Tetrazine-Ph-PEG5-NHS ester is also used to introduce tetrazine groups onto amine-functional biomaterial surfaces, enabling subsequent attachment of cyclooctene-bearing components through click chemistry. This approach is common in the fabrication of modular coatings, functionalized hydrogels, and affinity surfaces where pre-functionalization with an amine-reactive tetrazine precursor allows later installation of reporters, capture ligands, or responsive elements. The PEG5 spacer contributes to surface presentation by improving local mobility and accessibility of the tetrazine moiety, which can be important for achieving efficient ligation on heterogeneous material interfaces, particularly when assembling multi-step functional architectures for research-grade diagnostics and assay development.