This heterobifunctional compound, Bromo-PEG5-azide, is widely used in bioconjugation and click chemistry applications. The bromo group enables nucleophilic substitution reactions, allowing attachment to thiol groups on cysteines in proteins or other nucleophilic sites on biomolecules. It serves as a linker molecule for attaching various functional groups to biomolecules, such as proteins, peptides, or nucleic acids. The azide group allows for efficient copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions, enabling the formation of stable triazole linkages. The PEG (polyethylene glycol) spacer enhances solubility and reduces steric hindrance, making it suitable for modifying biomolecules in aqueous environments. It is also utilized in drug delivery systems, where it helps in creating targeted and controlled-release formulations. Additionally, it finds applications in surface modification, polymer chemistry, and the development of biofunctional materials for research and therapeutic purposes.