Azido-PEG3-Sulfone-PEG4-Boc is widely used in bioconjugation and chemical biology research. Its azido group enables click chemistry reactions, particularly copper-catalyzed azide-alkyne cycloaddition (CuAAC), making it valuable for labeling biomolecules like proteins, peptides, and nucleic acids. The sulfone group serves as a reactive handle for thiol-specific modifications, allowing precise attachment to cysteine residues in proteins. The PEG (polyethylene glycol) spacers enhance solubility and reduce steric hindrance, improving reaction efficiency in aqueous environments. Additionally, the Boc (tert-butyloxycarbonyl) protecting group provides stability during synthesis and can be selectively removed under acidic conditions, enabling further functionalization. This compound is particularly useful in drug delivery systems, surface functionalization, and the development of bioconjugates for therapeutic and diagnostic applications.