TCO-PEG3-acid | CAS 2141981-86-2

TCO-PEG3-acid is a strained trans-cyclooctene (TCO) click-chemistry reagent bearing a short PEG3 linker and a terminal carboxylic acid, designed for conjugation workflows where subsequent tetrazine-mediated ligation is used. Its PEG spacer improves aqueous handling and reduces steric effects when decorating biomolecules, surfaces, or polymeric materials. The carboxylic acid enables straightforward incorporation into carrier systems and material platforms that benefit from TCO presentation for downstream bioorthogonal labeling and imaging reagent construction.

1. Tetrazine Ligation Labeling

TCO-PEG3-acid is widely used as a TCO handle for tetrazine-reactive click labeling of probes, affinity reagents, and engineered binding constructs. Researchers incorporate the carboxyl-functional PEG spacer to promote efficient presentation of the strained alkene in aqueous buffers, supporting robust conjugation to tetrazine-bearing partners used for fluorescence, affinity capture, or signal amplification workflows. This reagent format is particularly useful when the downstream labeling step must be performed under mild, bioorthogonal conditions to preserve the functionality of sensitive targeting ligands or reporter moieties.

2. Surface And Material Functionalization

TCO-PEG3-acid supports the preparation of TCO-functional surfaces and biomaterials where tetrazine-tagged components are later assembled for modular material construction. The terminal carboxylic acid facilitates attachment to carboxyl-reactive or amide-forming surface chemistries, enabling controlled TCO density on coatings, assay substrates, and polymer scaffolds. Such platforms are commonly used in materials science and chemical biology to create stepwise assembly pipelines, where the tetrazine partner can be exchanged to generate different readouts or binding functionalities without reworking the base material.

3. Bioconjugation Of PEGylated Carriers

TCO-PEG3-acid is frequently selected for conjugation to PEGylated carriers and macromolecular scaffolds that require a defined linker length between the reactive TCO group and the parent construct. The PEG3 spacer helps maintain solubility and reduces local crowding around the strained alkene, which is important when decorating proteins, peptides, or polymer backbones used as research tools. The carboxylic acid functionality also makes it compatible with common conjugation strategies that generate stable, tethered TCO-bearing constructs for subsequent tetrazine-mediated attachment of imaging or detection reagents.

4. Molecular Imaging Probe Assembly

TCO-PEG3-acid is used to build modular molecular imaging probe systems by introducing TCO into probe scaffolds that are subsequently coupled to tetrazine-functional imaging reporters. The PEG3 linker and acid handle support conjugation to probe carriers and targeting motifs, enabling consistent probe architecture and improved aqueous compatibility during labeling and formulation. This approach is favored in chemical biology and molecular imaging development because it allows rapid interchange of tetrazine-bearing reporters to tailor probe characteristics for different experimental imaging modalities and assay formats.