TCO-PEG2-Sulfo-NHS ester

TCO-PEG2-Sulfo-NHS ester is a bifunctional, water-compatible PROTAC linker designed to couple amine-bearing ligands to TCO-containing partners while maintaining solubility and efficient conjugation. Its PEG spacer supports favorable linker flexibility and reduced steric interference, which can improve assembly and performance of targeted protein degradation constructs. The sections below describe the molecule’s structure and the practical reactivity considerations for constructing PROTACs using this linker in a research setting.

Structure: The linker combines a TCO moiety with a short PEG spacer terminating in a sulfonated NHS ester. It contains an activated N-hydroxysuccinimide carbonate/ester functionality for acyl transfer, along with ether linkages in the PEG chain and a sulfonate group that enhances hydrophilicity.

Reactivity: The NHS ester reacts with primary amines to form stable amide bonds under mildly basic aqueous conditions commonly used for bioconjugation. Typical workflows involve dissolving the linker in buffered solvent, adding the amine-containing ligand, and controlling pH to favor NHS ester stability while enabling nucleophilic acyl substitution. The TCO group is suited for subsequent bioorthogonal ligation strategies (e.g., inverse-electron-demand cycloaddition) without requiring cytotoxic reagents.