Used primarily in bioconjugation, Mal-PEG3-NHS ester is a bifunctional linker that connects biomolecules like proteins, peptides, and antibodies to other entities. The NHS ester group reacts efficiently with primary amine groups on biomolecules, while the maleimide group specifically targets thiol groups (e.g., on cysteine residues), enabling site-specific conjugation for targeted drug delivery and diagnostic imaging. The PEG3 spacer enhances the solubility and stability of conjugated molecules, making it valuable in therapeutic and research applications. Commonly employed in the development of antibody-drug conjugates (ADCs) and PEGylation processes to improve pharmacokinetics and reduce immunogenicity of therapeutic proteins.