TCO TEG Phosphoramidite is a specialized reagent designed for the site-specific incorporation of a trans-cyclooctene (TCO) moiety into oligonucleotides during solid-phase synthesis. It features a strained TCO alkene linked via a tetra(ethylene glycol) spacer to a phosphoramidite group, allowing for efficient 5'-end modification of DNA or RNA strands. The TEG linker provides flexibility and hydrophilicity, minimizing steric hindrance and enhancing solubility in aqueous environments.

This reagent is particularly valuable for preparing oligonucleotides compatible with bioorthogonal labeling strategies. The TCO group enables fast and selective click reactions with tetrazine-functionalized probes, making it ideal for live-cell imaging, nucleic acid tracking, and therapeutic delivery.