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• Ex/Em: 633/647 nm
• Extinction Coefficient: 140,000 cm^-1M^-1
• Reactive Group: NHS ester
• Easy Conjugation: Efficiently labels primary amines on proteins, ligands, and amine-modified oligonucleotides
• Advanced Dye Properties: Excellent water solubility and structural match to Alexa Fluor™ 635
• Robust Signal Performance: Maintains high intensity and pH independence (pH 4-11) with exceptional photostability

XFD635, manufactured by AAT Bioquest, is a bright far red-fluorescent dye structurally identical to Alexa Fluor™ 635 (ThermoFisher). It is characterized by its intense brightness, high fluorescence quantum yield and photostability. The dye demonstrates excellent solubility in aqueous solutions and retains pH-independent fluorescence over a broad range (pH 4–11), ensuring consistent performance across diverse experimental conditions. Optimally excited by the 633 nm emission line of He-Ne lasers or the 635 nm diode laser, XFD635 is particularly well-suited for flow cytometry. Its robust and uniform labeling properties yield high signal intensity and reproducibility, making it an ideal choice for advanced fluorescence imaging, flow cytometry, and various fluorescence-based analytical techniques.

The N-hydroxysuccinimidyl (NHS) ester of XFD635 is a widely used reagent for the conjugation of this dye to proteins or antibodies. NHS esters react selectively and efficiently with primary amines (such as the side chains of lysine residues or aminosilane-coated surfaces) at pH 7-9, forming stable covalent amide bonds. This property makes XFD635 NHS ester an excellent choice for labeling proteins, amine-modified oligonucleotides, and other amine-containing molecules.