NH2-PEG-NH2 (MW:5000) is a polyethylene glycol derivative containing two primary amine groups. These amine groups can rapidly react with activated carboxylic acids or carboxyl groups (such as NHS esters) to form stable amide bonds. The PEGylation of NH2-PEG-NH2 enhances solubility and stability while reducing the immunogenicity of peptides and proteins, making it primarily used for modifying proteins, peptides, and other substances.