Lipoamide-PEG3-Mal contains a lipoic acid group and a terminal maleimide group. Lipoic acid contains two sulfur atoms (at C6 and C8) connected by a disulfide bond and is thus considered to be oxidized although either sulfur atom can exist in higher oxidation states. The maleimide group will react with a thiol group to form a covalent bond, enabling the connection of biomolecule with a thiol. The hydrophilic PEG linker increases the water solubility of the compound.