Used in bioorthogonal chemistry for labeling biomolecules in live systems without interfering with natural biochemical processes. Its strained cyclooctyne group reacts rapidly with azides via copper-free click chemistry, making it ideal for imaging, protein labeling, and cell surface modification. The NHS ester enables covalent attachment to primary amines on proteins or other molecules, allowing construction of stable conjugates. Commonly applied in drug delivery systems, diagnostic probes, and real-time tracking of biomolecules in complex biological environments.