Used in bioconjugation for attaching polyethylene glycol (PEG) chains to molecules containing ketone or aldehyde groups. The aminooxy group reacts selectively with carbonyls to form stable oxime linkages, making it ideal for modifying peptides, proteins, and antibodies to improve solubility, stability, and circulation time in pharmaceutical applications. Commonly applied in drug delivery systems, PEGylation strategies, and development of biocompatible materials. Also utilized in research settings for labeling and functionalizing biomolecules without the need for catalysts under mild reaction conditions.