Used as a bifunctional crosslinking agent in bioconjugation, with an NHS ester end that reacts selectively with primary amines to form stable amide bonds and a maleimide end that reacts with thiols to form stable thioether bonds. The PEG₅ hydrophilic spacer arm enhances solubility and reduces aggregation in aqueous environments. Commonly employed in the preparation of antibody-drug conjugates (ADCs), where the maleimide typically couples to cysteines on antibodies and the NHS ester to amine-containing payloads, as well as in the immobilization of biomolecules on thiol-reactive surfaces. Suitable for applications in drug delivery, diagnostics, and functional coatings.