This compound is widely used in bioconjugation and chemical biology for labeling biomolecules. Its azido group allows for click chemistry reactions, particularly copper-catalyzed azide-alkyne cycloaddition (CuAAC), enabling the attachment of various probes or tags to proteins, peptides, or other biomolecules. The NHS ester group reacts efficiently with primary amines, making it suitable for modifying lysine residues or N-termini of proteins. The PEG3 spacer enhances water solubility and reduces steric hindrance, improving reaction efficiency. It is commonly applied in drug delivery systems, antibody-drug conjugates, and the development of diagnostic tools, facilitating precise and stable modifications in biological research and therapeutic applications.