Used in bioconjugation to link proteins, peptides, or other biomolecules to surfaces or labels. Its maleimide group reacts selectively with thiol groups (-SH) on cysteine residues, while the NHS ester end binds to primary amines (-NH₂) on molecules like antibodies or fluorescent tags. Commonly used in preparing antibody-drug conjugates, immobilizing enzymes on biosensor surfaces, and labeling proteins for imaging or detection. Stable in aqueous solution for short periods, allowing efficient coupling under mild conditions. Preferred in creating targeted therapeutics and diagnostic probes due to its specific, controlled reactivity.