Amino-PEG4-Azide is widely used in bioconjugation and chemical biology due to its unique properties. The azide group enables click chemistry reactions, particularly copper-catalyzed azide-alkyne cycloaddition (CuAAC), which is highly efficient and selective for labeling biomolecules. This makes it valuable for attaching fluorescent dyes, drugs, or other functional groups to proteins, peptides, or nucleic acids. Additionally, the PEG4 spacer enhances solubility and reduces steric hindrance, improving the performance of the conjugate in biological systems. It is also employed in the development of antibody-drug conjugates (ADCs) and targeted drug delivery systems, where precise and stable linking is essential. Furthermore, it finds applications in surface modification, polymer chemistry, and materials science for creating functionalized surfaces or polymers with specific properties.