Azido-PEG3-SS-PEG3-azide

Azido-PEG3-SS-PEG3-azide is a bifunctional, reducible PEG-based linker designed for assembling PROTACs that require controlled connectivity between targeting ligands and E3-recruiting modules. Its azide termini enable modular “click” conjugation, while the central disulfide provides a redox-responsive handle that can support intracellular cleavage and altered linker behavior. The combination of flexible polyethylene glycol spacing and chemically orthogonal functional groups makes this linker well suited for constructing well-defined targeted protein degradation architectures.

Structure: The linker contains two terminal azide functional groups connected through polyethylene glycol segments, with a central disulfide (thioether-free) linkage. Its ether-rich PEG backbone provides conformational flexibility, while the azides serve as electrophile-compatible partners for azide–alkyne coupling. The disulfide introduces redox-sensitive S–S bonding that can be cleaved under reducing conditions.

Reactivity: PROTAC assembly can be performed via copper-catalyzed azide–alkyne cycloaddition or copper-free strain-promoted azide–alkyne cycloaddition, depending on the alkyne partner and desired selectivity. The disulfide core is generally stable under mild coupling conditions but should be handled to minimize premature reduction. Typical conjugation workflows use polar organic solvents or aqueous/organic mixtures compatible with click chemistry, with inert atmosphere and careful control of reducing agents to preserve linker integrity.