N-Mal-N-bis(PEG4-amine) TFA salt is a branched PEG linker with a terminal maleimide group and two terminal amino groups. The maleimide group will react with a thiol group to form a covalent bond, enabling the connection of biomolecule with a thiol. The amino group is reactive with carboxylic acids, activated NHS esters, carbonyls (ketone, aldehyde) etc.