Aminooxy-PEG4-acid is widely utilized in bioconjugation chemistry for linking biomolecules, such as proteins, peptides, and antibodies, to other molecules or surfaces. Its aminooxy group reacts selectively with aldehydes or ketones to form stable oxime bonds, making it valuable in applications like drug delivery systems, where it helps attach therapeutic agents to targeting molecules. It is also used in the development of biosensors and diagnostic tools, enabling the immobilization of biomolecules onto solid supports. Additionally, its PEG spacer enhances solubility and reduces immunogenicity, making it suitable for improving the pharmacokinetic properties of bioconjugates in therapeutic and research applications.