BP Fluor 555 azide is a water-soluble, bright orange fluorescent dye with an excitation wavelength ideal for 532 nm or 555 nm laser lines and can be visualized using TRITC (tetramethylrhodamine) filter sets. The dye's conjugates with antibodies, peptides, and proteins exhibit stability across a pH range of 4 to 10. AF 555 conjugates are notably effective for detecting low-abundance targets. BP Fluor 555 azide reacts with terminal alkynes via copper-catalyzed click reactions (CuAAC) and can also undergo copper-free 'click chemistry' with strained cyclooctynes, forming stable triazoles without the need for copper catalysts or high temperatures. The dye’s brightness and photostability make it especially suitable for direct imaging of low-abundance targets.