DBCO-PEG-NHS (MW 2000) is a heterobifunctional PEG derivative containing a dibenzocyclooctyne (DBCO) unit for copper-free click chemistry with azides and an N-hydroxysuccinimide (NHS) ester for reaction with primary amines on proteins or peptides. The compound is an essential tool for constructing bio-orthogonal conjugation platforms, aiming to efficiently anchor ligands to nanocarriers or surfaces via a stable PEG spacer while reducing steric hindrance.