mPEG6-NHS ester

This mPEG6-NHS ester is a polyethylene glycol (PEG)-based activated ester designed for efficient conjugation in targeted protein degradation workflows. Its NHS-activated carbonate/ester functionality enables rapid formation of stable amide linkages with primary amines, facilitating the construction of PROTACs and related bifunctional degraders. The PEG spacer improves aqueous compatibility and can help tune linker flexibility and solubility, supporting reliable synthesis and subsequent biochemical evaluation; detailed structural and reactivity considerations are provided below.

Structure: The molecule comprises a methoxy-terminated PEG chain bearing an N-hydroxysuccinimide ester, providing an activated carboxylate for acyl transfer. It features ether linkages along the PEG backbone, with an NHS leaving group and an ester carbonyl suitable for nucleophilic substitution. The PEG segment confers hydrophilicity and steric spacing.

Reactivity: The NHS ester reacts with primary amines to form amides via acyl substitution, typically under mildly basic conditions that preserve amine nucleophilicity while maintaining ester reactivity. Common approaches use aqueous or mixed aqueous buffers with controlled pH, with the amine-bearing PROTAC warhead or ligand added to the activated linker. No special catalysts are required; however, fresh activation and avoidance of competing nucleophiles (e.g., primary amines in buffers) are important.