TCO-PEG24-NHS ester | CAS 2055646-26-7

TCO-PEG24-NHS ester is a polyethylene glycol (PEG)-spaced trans-cyclooctene (TCO) click chemistry reagent that couples an NHS ester reactive group for amine targeting. As a bioorthogonal handle compatible with inverse electron-demand Diels–Alder (IEDDA) chemistry, it is widely used to install TCO on proteins, peptides, and other primary-amine bearing biomolecules prior to subsequent labeling steps. The long PEG24 spacer improves conjugation flexibility and helps reduce steric constraints during downstream TCO-to-partner conjugation, making it a common reagent choice for building imaging probes, diagnostic reagents, and modular research conjugates.

1. Protein Conjugation Workflows

TCO-PEG24-NHS ester is used to functionalize antibodies, antibody fragments, enzymes, and other lysine-rich proteins through NHS ester reactivity with primary amines. The PEG24 spacer provides conformational flexibility that can improve accessibility of the TCO moiety for later IEDDA coupling, supporting efficient assembly of multi-component constructs such as protein–small molecule hybrids and protein–nanomaterial conjugates. This reagent is particularly common in workflows where researchers need a stable, site-randomized TCO display on biomolecules to enable modular downstream labeling with complementary click partners.

2. Molecular Imaging Probe Assembly

TCO-PEG24-NHS ester serves as a key intermediate for preparing imaging-oriented conjugates where a TCO-functional biomolecule is subsequently linked to a complementary imaging handle via IEDDA click chemistry. In molecular imaging and chemical biology labs, the PEG spacer helps maintain probe performance by reducing steric interference between the targeting biomolecule and the appended reporter component. Typical use cases include generating TCO-modified targeting ligands that can be rapidly combined with fluorophores, enrichment tags, or other reporter-bearing partners to create libraries of imaging reagents for assay development and instrument-compatible labeling strategies.

3. Diagnostic Reagent Development

TCO-PEG24-NHS ester is applied in the construction of diagnostic reagent components that require orthogonal, high-specificity conjugation chemistry. By installing TCO onto capture molecules such as affinity reagents, binding proteins, or other amine-containing components, teams can later perform click-based assembly with detection moieties and signal amplifiers in a controlled, modular manner. The PEG24 linker is frequently leveraged to improve conjugate handling and to support consistent presentation of the click-reactive TCO group for reproducible reagent build-outs used in assay prototyping and analytical method development.

4. Surface and Material Functionalization

TCO-PEG24-NHS ester is also used to introduce TCO functionality onto material surfaces and biomaterial interfaces that present accessible primary amines. Researchers employ NHS ester chemistry to tether the PEG-spaced TCO handle to amine-terminated polymers, coatings, and functionalized substrates, enabling subsequent IEDDA coupling to attach probes, affinity ligands, or reporter components. This approach supports the fabrication of click-assembled material platforms such as TCO-functional scaffolds for research assays, surface-based labeling tools, and modular materials where downstream conjugation is performed under conditions compatible with sensitive biomolecules.