m-PEG-Succinimidyl Glutarate (mPEG-SG) is a degradable PEG linker, usually a white solid, with a C4 aliphatic ester bond between PEG and NHS ester, and the hydroxyl end is activated to a SG group, which can be combined with The free amino bond of active drugs can be widely used in medical research, drug release, biomedical polymers, peptide synthesis carriers and other fields.