Hydroxy-PEG3-NHS

Hydroxy-PEG3-NHS is a polyethylene glycol (PEG)-based NHS ester linker designed for efficient conjugation in PROTAC workflows. Its PEG spacer improves solubility and provides a flexible, hydrophilic connection between targeting ligands and E3-recruiting or binding modules. The NHS-activated ester enables robust amide-bond formation under standard bioconjugation conditions, supporting modular synthesis and optimization of targeted protein degraders. The structural and reactivity considerations are described in detail below.

Structure: The linker comprises a PEG chain terminated by a hydroxyl group and an N-hydroxysuccinimide ester, enabling formation of stable amide linkages. It contains an NHS leaving group, an ether-rich backbone, and flexible C–O and C–C connectivity that supports conformational mobility and aqueous compatibility.

Reactivity: Hydroxy-PEG3-NHS reacts with primary amines to form amide bonds via nucleophilic acyl substitution, with NHS serving as the leaving group. Suitable conditions typically use mildly basic aqueous or mixed solvent systems that maintain amine nucleophilicity while limiting hydrolysis. Common coupling approaches employ buffered solutions and controlled temperatures, often without additional catalysts, and require timely addition of the amine-containing partner to maximize coupling efficiency.