This chemical is widely used in the field of bioconjugation and protein modification. It serves as a heterobifunctional PEG linker with a maleimide (pyrrole dione) group for selective coupling primarily with thiol groups (e.g., cysteines) in biomolecules, and a tert-butyl protected carboxylic ester at the distal end for further functionalization after deprotection. It enables attachment of functional groups, such as fluorescent dyes or drug molecules, to proteins or peptides. The polyethylene glycol (PEG₅) chain enhances solubility, flexibility, and reduces immunogenicity, making it suitable for applications in drug delivery systems. Additionally, it is utilized in the development of antibody-drug conjugates (ADCs), where it helps in creating stable and targeted therapeutic agents. Its use in research and pharmaceutical industries highlights its importance in advancing biomedical technologies.