Used in bioconjugation and protein modification due to its ability to alkylate thiol groups in cysteine residues and amine groups in lysines. The bromoacetamide group (-CH₂Br) reacts with nucleophiles such as sulfhydryls (-SH) and amines (-NH₂), providing a stable thioether or alkylated amine bond, though reactivity is higher under slightly basic conditions. The mPEG₄ spacer enhances aqueous solubility, reduces protein aggregation, and improves pharmacokinetic properties.

Commonly applied in the development of antibody-drug conjugates (ADCs), peptide labeling, surface functionalization of nanoparticles, and PEGylation of biomolecules to increase stability in blood circulation and evade immune clearance. This reagent enables the creation of well-defined, homogeneous bioconjugates for therapeutic, diagnostic, and research applications in biopharmaceuticals and targeted drug delivery.