N-(Azido-PEG3)-PEG4-t-butyl ester is a branched PEG linker with an azide group and a t-butyl ester group. The azide group reacts with alkyne or cyclooctyne in Click Chemistry reaction. The amino group is reactive with carboxylic acids, activated NHS esters, and carbonyls. Reagent grade, for research purpose. Please contact us for GMP-grade inquiries.