CF® dye with BCN reacts with azide to form 1,2,3-triazole by copper free 1,3-dipolar Huisgen cycloaddition. This copper-free bioorthogonal reaction allows staining the surface of live cells or cell extracts when there are concerns about native protein function loss with copper. CF®500-BCN has excitation/emission at 500/510 nm, and is designed for intracellular copper-free reaction with azide.