N-(Aminooxy-PEG2)-N-bis(PEG3-propargyl) is a branched PEG derivative with two terminal propargyl groups and an Aminooxy group. The propargyl groups can be reacted with azide-bearing compounds or biomolecules via copper catalyzed azide-alkyne Click Chemistry to yield a stable triazole linkage. The aminooxy group can be used in bioconjugation. It reacts with an aldehyde to form an oxime bond. If a reductant is used, it will form a hydroxylamine linkage.