N-(TCO)-N-bis(PEG4-NHS ester) is a branched click chemistry reagent with a terminal TCO group and two terminal NHS esters. This reagent can react with tetrazine-containing molecule to form a stable covalent bond . The inverse-electron demand Diels-Alder cycloaddition reaction of TCO with tetrazines is the fastest bioorthogonal reaction with exceptional selectivity. The NHS ester can be used to label the primary amines (-NH2) of proteins, amine-modified oligonucleotides, and other amine-containing molecules. Reagent grade, for research purpose. Please contact us for GMP-grade inquiries.