Used in bioconjugation for labeling biomolecules such as proteins, peptides, and antibodies without the need for copper catalysts. Enables efficient and selective coupling with azide-containing molecules through strain-promoted alkyne-azide cycloaddition (SPAAC), commonly applied in live cell imaging, surface functionalization, and development of antibody-drug conjugates. Stable under physiological conditions, making it suitable for in vitro and in vivo applications. Ideal for site-specific modification due to fast reaction kinetics and high biocompatibility.