Biotin-PEG4-alkyne

Biotin-PEG4-alkyne is a bifunctional PEG-based linker designed for constructing PROTACs and other targeted degradation conjugates that benefit from aqueous compatibility and modular attachment chemistry. Its PEG spacer supports solubility and conformational flexibility, while the alkyne handle enables efficient bioorthogonal or click-type coupling to compatible partners. The biotin motif can also facilitate affinity-based handling or downstream workflows. Detailed structural and reactivity considerations are provided below.

Structure: The linker comprises a biotin-bearing moiety connected through a poly(ethylene glycol) chain to a terminal alkyne. It contains ether linkages characteristic of PEG, an amide-containing biotin scaffold, and a carbon–carbon triple bond at the coupling terminus. The flexible ether-rich backbone promotes water solubility and reduced steric bias.

Reactivity: The terminal alkyne is suitable for copper-catalyzed azide–alkyne cycloaddition or related alkyne-based conjugation strategies commonly used in PROTAC assembly. Typical approaches employ a compatible azide-bearing warhead or handle, with copper catalysts and appropriate ligands to control reactivity and minimize side reactions. Use polar, degassed solvents and maintain conditions that preserve sensitive functional groups on the recruited ligands.