TCO-PEG4-TCO | CAS 2243569-23-3

TCO-PEG4-TCO is a bifunctional, PEG-linked trans-cyclooctene (TCO) click chemistry reagent designed for strain-promoted inverse electron-demand cycloaddition with tetrazines. The molecule contains two TCO moieties spaced by a flexible PEG4 linker, enabling multivalent labeling strategies and higher avidity in probe construction. This reagent is widely used in chemical biology and molecular imaging workflows where rapid, catalyst-free conjugation and tunable linker length are advantageous for building tetrazine-reactive imaging agents, affinity tools, and functional biomaterials.

1. Multivalent Tetrazine Probes

TCO-PEG4-TCO is commonly used to generate multivalent tetrazine-reactive probe formats, where two TCO handles allow controlled incorporation of tetrazine-bearing targeting ligands, reporters, or affinity tags. The PEG4 spacer helps reduce steric crowding during labeling, supporting more consistent conjugation outcomes when probes are assembled for fluorescence, luminescence, or other reporter-based detection platforms. Researchers frequently select this bifunctional scaffold when they want to increase effective binding through multivalency while keeping the conjugation chemistry fast and compatible with sensitive biomolecules.

2. Surface and Material Functionalization

TCO-PEG4-TCO is applied to functionalize polymeric and biomaterial surfaces that will subsequently be modified with tetrazine reagents, enabling stepwise assembly of reactive coatings and patterned interfaces. The dual TCO functionality supports crosslinking or multivalent attachment strategies on surfaces, improving the density of reactive sites available for downstream tetrazine coupling. In materials science and chemical biology, this approach is used to create modular platforms for immobilizing ligands, incorporating imaging reporters, or building responsive material architectures that rely on orthogonal, bioorthogonal click chemistry.

3. Protein and Biomolecule Labeling

TCO-PEG4-TCO is used as a PEG-based click handle for preparing tetrazine-compatible protein conjugates and biomolecule labeling reagents. The flexible linker and bifunctional TCO design make it suitable for introducing two reactive sites per construct, which can be beneficial when constructing dual-labeled reagents such as ratiometric probes, multi-epitope binders, or structured affinity reagents. Chemical biology groups often incorporate this reagent into workflows that require rapid conjugation under mild conditions, supporting efficient generation of labeled biomolecules for assay development and molecular tool creation.

4. Molecular Imaging Reagent Assembly

TCO-PEG4-TCO is frequently used in the assembly of molecular imaging reagent components, particularly where tetrazine-bearing reporters are coupled to generate well-defined, multivalent imaging probes. The dual TCO groups enable higher-order probe architectures that can improve signal generation through increased local reporter density and more robust probe presentation. Molecular imaging and diagnostic reagent development teams also value the PEG4 spacing for reducing steric effects, which supports reproducible conjugate formation when building imaging constructs from targeting moieties and reporter payloads that are introduced via tetrazine click chemistry.