mPEG-Epoxide is an activated polyethylene glycol (mPEG) derivative, which is achieved by converting the hydroxyl groups of mPEG into reactive epoxy groups. mPEG-Epoxide is a mild PEGylation reagent that reacts with amino groups in peptides and proteins to form stable secondary amine bonds. mPEG-Epoxide can be used in protein engineering and biomaterials research.