XFD660 NHS Ester

• Ex/Em: 663/691 nm
• Extinction coefficient: 132,000 cm^-1M^-1
• Superior Fluorescence Performance: High quantum yield, exceptional photostability, and pH-independent fluorescence across pH 4–11.
• Reactive Group: NHS ester
• Easy Conjugation: Efficiently labels primary amines on proteins, ligands, and amine-modified oligonucleotides
• High Water-Solubility: Prevents aggregation and enhances signal clarity for advanced imaging and live-cell applications

XFD660, manufactured by AAT Bioquest, is a far-red fluorescent dye structurally similar to Alexa Fluor™ 660 (Thermo Fisher). The dye demonstrates high fluorescence quantum yield, photostability, and aqueous solubility, with pH-independent fluorescence across a broad range (pH 4–11), providing consistent performance across diverse experimental conditions.

XFD660 is optimized for red laser excitation and is compatible with flow cytometers equipped with spectral detection systems. It provides robust and uniform labeling with high signal intensity and reproducibility, making it ideal for fluorescence imaging, flow cytometry, and other analytical techniques. XFD660 demonstrates versatility in labeling a wide range of targets, including cell surface, intracellular, and intranuclear antigens. Its spectral properties position it between XFD647 and XFD700, making it a valuable intermediate fluorophore for constructing complex multicolor panels and enabling precise experimental designs in advanced research workflows.

The N-hydroxysuccinimidyl (NHS) ester of XFD660 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 XFD660 NHS ester an excellent choice for labeling proteins, amine-modified oligonucleotides, and other amine-containing molecules.