TCO-PEG4-NHS ester | CAS 1613439-69-2

TCO-PEG4-NHS ester is a strained-alkene trans-cyclooctene (TCO) click chemistry reagent equipped with a PEG4 spacer and an N-hydroxysuccinimide (NHS) ester for efficient amide formation with primary amines. As a key component of widely used bioorthogonal TCO-based click conjugation workflows, it enables rapid installation of TCO handles onto proteins, peptides, and other amine-bearing biomolecules prior to subsequent inverse-electron-demand Diels–Alder ligation. The PEG4 linker improves conjugation practicality and helps manage steric effects during downstream labeling, making this reagent a common choice for preparing imaging probes, targeting constructs, and modular research reagents.

1. Protein Conjugation Workflows

TCO-PEG4-NHS ester is commonly used to functionalize antibodies, antibody fragments, enzymes, and other amine-rich proteins with TCO groups for later click coupling to complementary partners. The NHS ester chemistry supports straightforward labeling of lysine residues under standard bioconjugation conditions, while the PEG4 spacer helps maintain accessibility of the TCO moiety for efficient secondary ligation. This approach is widely adopted in chemical biology and molecular imaging labs that build modular probe libraries, where controlling the density and distribution of clickable handles is important for reproducible conjugate performance in assays and imaging experiments.

2. Targeting Ligand Labeling

TCO-PEG4-NHS ester is frequently selected for decorating targeting ligands such as peptides and engineered binding domains that contain accessible primary amines. By introducing TCO handles at the ligand stage, researchers can streamline later assembly of multicomponent constructs, including ligand–reporter hybrids and ligand–material conjugates. The PEG4 linker provides a flexible distance element that can reduce steric hindrance between the targeting moiety and the eventual click partner, supporting consistent labeling outcomes across different ligand scaffolds used in imaging reagent development and platform-style assay construction.

3. Surface and Material Functionalization

TCO-PEG4-NHS ester is used to introduce TCO functionality onto amine-terminated surfaces and biomaterial scaffolds, enabling subsequent click-based attachment of dyes, affinity tags, or other functional components. In biomaterials science workflows, NHS ester reactivity is leveraged to couple TCO-bearing PEG linkers to amine-containing coatings, polymer films, or hydrogel matrices, creating clickable interfaces for downstream modular assembly. This strategy supports the fabrication of functional materials used in research settings, such as TCO-encoded surfaces for rapid immobilization of complementary cyclopentadiene-bearing reagents and for constructing multivalent surface architectures.

4. Modular Probe and Assay Building

TCO-PEG4-NHS ester is a go-to reagent for preparing TCO-functional building blocks used in modular probe design, including fluorescent or affinity-based constructs assembled via click chemistry. The PEG4 spacer and NHS ester handle enable efficient incorporation of TCO into diverse amine-bearing components, which is particularly valuable when building combinatorial reagent sets where the same click handle must be installed consistently across multiple targets. Chemical biology teams use TCO-PEG4-NHS ester to standardize reagent preparation for downstream conjugation steps, supporting reproducible workflows for assay development and molecular imaging reagent optimization.