TCO-PEG6-amine

TCO-PEG6-amine is a polyethylene glycol–based PROTAC linker bearing a trans-cyclooctene (TCO) reactive handle and a terminal amine for straightforward conjugation. Its flexible PEG spacer supports productive ternary complex formation by improving linker solubility and conformational adaptability, while the TCO group enables rapid bioorthogonal ligation strategies commonly used in targeted protein degradation workflows. The structure and reactivity considerations for constructing PROTACs using this linker are described in detail below.

Structure: The molecule combines a PEG chain that provides hydrophilicity and conformational flexibility with a trans-cyclooctene moiety suitable for strain-promoted addition chemistry. A terminal primary amine offers a reactive functional group for amide or urea bond formation, while ether linkages dominate the backbone.

Reactivity: TCO-containing linkers are typically employed in bioorthogonal conjugation schemes that rely on strain-driven reactivity, often proceeding under aqueous conditions compatible with biomolecule stability. The terminal amine enables coupling to activated carboxylic acids (e.g., via carbodiimide-mediated activation) to form amide linkages, or to isocyanate/activated derivatives for alternative bond types. Mild, oxygen-tolerant handling and avoidance of strongly nucleophilic or reducing conditions are generally used to preserve TCO reactivity during PROTAC assembly.