Azido-PEG4-NHS ester is a very popular PEG reagent which containan azide group and an NHS ester. The hydrophilic PEG spacer increases solubility in aqueous media. The azide group can react with alkyne, BCN, DBCO via Click Chemistry to yield a stable triazole linkage. 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.