Biotin-PEG4-allyl

Biotin-PEG4-allyl is a PEG-based, biotin-functional linker designed for modular PROTAC construction, enabling efficient conjugation to biotin-binding handles and subsequent attachment to protein-targeting ligands. Its ether-rich, flexible PEG architecture supports productive ternary complex formation by reducing steric constraints, while the allyl terminus provides a chemically addressable site for coupling strategies commonly used in targeted protein degradation workflows. The following points describe the structure and practical reactivity considerations in detail below.

Structure: The linker combines a biotin moiety with a polyethylene glycol chain and an allyl functional group, featuring ether linkages along the PEG backbone and an alkene at the terminal allyl site. This architecture yields high conformational flexibility, good aqueous compatibility, and a chemically stable scaffold suitable for bioconjugation chemistry.

Reactivity: The allyl handle supports allyl-based conjugation approaches such as thiol–ene or related radical-mediated additions, and it can be used as a reactive electrophile/partner depending on the chosen coupling partner. Typical PROTAC linker assembly employs inert-atmosphere handling when radical chemistry is used, with appropriate radical initiators, mild organic solvents, and controlled temperature to preserve sensitive ligands. Reaction design should account for PEG solubility and biotin integrity during coupling and purification.