This bifunctional crosslinker, containing two N-hydroxysuccinimide (NHS) ester groups connected via a 3-aminopropanoate linker, is used in bioconjugation to covalently couple primary amines, such as lysine residues on proteins and peptides, to other biomolecules, labels, or surfaces. It enables the formation of stable amide bonds under mild, aqueous conditions with high specificity and reduced side reactions. Commonly applied in antibody labeling with fluorophores or haptens, protein immobilization on solid supports, preparation of biosensors and bioassays, and development of targeted drug delivery systems by conjugating therapeutics to specific carriers. Also useful in creating functionalized polymers and pharmaceutical intermediates for biomedical applications.