XFD555 Tetrazine

• Ex/Em: 553/568 nm
• Extinction coefficient: 155,000 cm^-1M^-1
• Reactive Group: Tetrazine
• Click Chemistry Conjugation: Provides rapid and copper-free labeling of TCO-modified biomolecules
• Bright & Stable: Exhibits intense fluorescence with resilience to photobleaching and pH variations from 4 to 10
• Hydrophilic: Minimizes aggregation, enhancing signal clarity for advanced imaging and live-cell studies

XFD555, manufactured by AAT Bioquest, is structurally identical to Alexa Fluor™ 555 (ThermoFisher). It is a bright orange-fluorescent dye with an excitation optimized for use with either the 488 nm line of the argon-ion laser or the 532 nm line of the frequency-doubled Nd:YAG laser. The high fluorescence quantum yield and high photostability of XFD555 allow for the detection of low-abundance biological structures with great sensitivity. XFD555 demonstrates good aqueous solubility and pH-insensitivity over a broad pH range (pH 4–10), ensuring stable fluorescence generation under varying experimental conditions. XFD555 dye molecules can be attached to proteins at high molar ratios without significant self-quenching, enabling brighter conjugates and more sensitive detection in imaging and flow cytometry.

XFD555 tetrazine is particularly useful for labeling TCO-modified biomolecules under copper-free conditions. It reacts with TCO-functionalized molecules, forming a stable conjugate via a dihydropyrazine moiety. This click reaction is favored over others due to its extremely fast kinetics and higher yields under mild reaction conditions, making it a popular choice for researchers.