m-PEG-Succinimidyl Amido Succinate (mPEG-SAS), MW 20K is a water-soluble amine-reactive PEG polymer. There is a C2 aliphatic amide bond between the PEG and the NHS ester. SAS has a longer hydrolytic half-life and is therefore more stable in aqueous buffers than many other types of NHS esters.
AxisPharm offers 5000+ PEG Linkers with high purity. Different kinds of PEG Reagents may be available by custom synthesis.