Used in bioconjugation processes to link proteins, peptides, or other biomolecules to polymers or surfaces. The maleimide group reacts selectively with thiol groups (-SH) on cysteine residues, forming stable thioether bonds. PEG spacer (PEG2) enhances solubility, reduces aggregation, and increases stability of conjugates. Commonly applied in drug delivery systems, antibody-drug conjugates (ADCs), and surface functionalization of nanoparticles or biosensors. The short PEG chain balances hydrophilicity and molecular size for efficient coupling in aqueous or mixed solvents.