N-(m-PEG4)-N'-(azide-PEG4)-Cy7

N-(m-PEG4)-N'-(azide-PEG4)-Cy7 is a bifunctional, PEG-based linker platform combining a near-infrared Cy7 scaffold with orthogonally addressable reactive handles. Its flexible polyethylene glycol spacers support solubility and reduce steric constraints, which is advantageous for building targeted protein degradation constructs. The azide functionality enables reliable bioorthogonal conjugation, supporting modular PROTAC assembly workflows. The following sections describe the structure and reactivity characteristics in detail.

Structure: The linker comprises a Cy7 chromophore connected through amide-linked PEG segments, incorporating m-PEG4 and azide-PEG4 motifs. It contains stable amide and ether linkages, with an azide group as a terminal functional handle. The PEG-rich framework confers high hydrophilicity and conformational flexibility.

Reactivity: The azide terminus is designed for copper-free or copper-catalyzed azide–alkyne cycloaddition, enabling efficient conjugation to complementary alkyne-bearing partners under mild conditions. Conjugation typically proceeds via formation of a triazole linkage, with reaction choice guided by substrate compatibility and desired kinetics. Suitable solvents are commonly polar aqueous mixtures or buffered systems, and conditions are selected to preserve Cy7 integrity and maintain linker solubility during PROTAC synthesis.