ButyrAldehyde-PEG-ButyrAldehyde(PEG-bis-Butyraldehyde,bALD-PEG-bALD), MW 20K, is a high-purity PEG polymer that Axispharm offers you. It contains two aldehyde groups, which can react with hydrazide or amine groups to form stable hydrazone or imine bonds, respectively.
AxisPharm offers 5000+ PEG Linkers with high purity. Different kinds of PEG Reagents may be available by custom synthesis.