Bromo-PEG3-acetic acid is widely used in bioconjugation and pharmaceutical research due to its bifunctional structure. The bromo group acts as a reactive alkylating agent, enabling covalent attachment to nucleophiles such as thiols or amines in biomolecules. The PEG3 (triethylene glycol) spacer provides water solubility, reduces aggregation, and increases the flexibility and biocompatibility of the linked molecules. The terminal acetic acid group allows further activation and coupling to amines via standard carbodiimide chemistry. This compound is particularly valuable in the synthesis of antibody-drug conjugates (ADCs), targeted therapies, and PROTACs, where controlled spacing and stable linkages are critical. It is also used in the development of PEGylated compounds to improve pharmacokinetic properties. Additionally, its modular reactivity makes it a useful building block in click chemistry and solid-phase synthesis.