3,4-Dibromo-Mal-PEG4-NHS ester is a site specific Maleimide PEG linker with a dibromomaleimide group. NHS ester is reactive with amine containing moiety. The dibromomaleimide group allows for two points of substitution due to the two bromine atoms. Reagent grade, for research purpose. Please contact us for GMP-grade inquiries.