TCO-PEG4-acid | CAS 1802913-21-8

TCO-PEG4-acid is a trans-cyclooctene (TCO) functionalized polyethylene glycol carboxylic acid designed for strain-promoted inverse electron-demand Diels–Alder chemistry with tetrazines. The PEG4 spacer and terminal acid provide practical handles for aqueous conjugation workflows and for subsequent coupling to biomolecules, surfaces, or polymeric materials. As a click-chemistry reagent, TCO-PEG4-acid is widely used to prepare tetrazine-reactive probes for labeling, imaging, and modular construction of multicomponent molecular assemblies.

1. Tetrazine Probe Conjugation

TCO-PEG4-acid is commonly used as the TCO-bearing partner in tetrazine–TCO click labeling workflows, enabling rapid installation of functional payloads onto targeting ligands, affinity reagents, or imaging scaffolds. The PEG4 spacer supports aqueous compatibility and helps reduce steric constraints during conjugation, which is particularly useful when attaching bulky dyes, chelators, or reporter groups. The terminal carboxylic acid also supports downstream coupling strategies that integrate the TCO moiety into larger probe formats used in molecular imaging and chemical biology tool development.

2. Surface And Material Functionalization

TCO-PEG4-acid is well suited for creating tetrazine-reactive surfaces and material coatings where controlled presentation of reactive handles is required. Researchers incorporate the carboxylic acid functionality to enable attachment to polymer films, hydrogel matrices, and other functional supports, generating materials that can be patterned or selectively modified with tetrazine-functional components. This application is frequently used for building modular biosensing platforms, affinity capture surfaces, and research-grade biomaterials that benefit from orthogonal, fast click reactivity.

3. Multivalent Targeting Constructs

TCO-PEG4-acid is frequently employed to generate multivalent conjugates in which multiple reactive sites are presented to improve binding-site density for downstream assembly steps. By installing TCO groups through the PEG4 linker and carboxyl handle, teams can construct multicomponent architectures that are later coupled to tetrazine-functional partners such as fluorophores, affinity tags, or modular domains. This approach is widely adopted in chemical biology for building complex probe libraries and for creating well-defined reagent sets used in assay development and mechanistic studies.

4. Molecular Imaging Reagent Building

TCO-PEG4-acid is used as a key intermediate for preparing tetrazine-reactive imaging reagents, including fluorescent and other reporter-bearing constructs that require efficient, bioorthogonal conjugation. The PEG4 chain improves solubility and helps maintain accessibility of the TCO moiety when conjugated to larger reporter systems, supporting consistent labeling in aqueous experimental conditions. The carboxylic acid functionality enables integration into probe scaffolds that can be assembled into imaging-ready formats through tetrazine click chemistry.