mPEG5-amine

mPEG5-amine is a methoxy-poly(ethylene glycol) primary amine linker designed to provide hydrophilicity, tunable solubility, and a convenient functional handle for bioconjugation workflows used in targeted protein degradation programs. Its ether-rich PEG backbone can help improve aqueous compatibility and reduce nonspecific interactions, while the terminal amine enables straightforward coupling to PROTAC-forming ligands or scaffold components. The following points describe its structure and practical reactivity for constructing PROTACs in detail below.

Structure: mPEG5-amine consists of a methoxy-terminated poly(ethylene glycol) chain capped with a terminal primary amine. The polymer contains repeating ether linkages, yielding a flexible, highly solvated scaffold. The presence of the amine provides a reactive nucleophilic site suitable for amide or urea-forming chemistry.

Reactivity: The terminal primary amine can be used for common PROTAC linker assembly routes, particularly nucleophilic acyl substitution to form amides with activated carboxylic acids (for example, using carbodiimides or activated ester intermediates) or for reductive amination with aldehyde-functional partners. Typical conditions employ polar aprotic or aqueous-organic solvent systems, mild bases, and temperature control to preserve sensitive ligands. Reaction efficiency is governed by amine nucleophilicity and the stability of the electrophile under coupling conditions.