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AAT Bioquest

XFD660 C5 Maleimide

Product key features

  • 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: Maleimide
  • Easy Conjugation: Efficiently labels thiol groups on proteins, antibodies, and oligonucleotides with stable thioether bonds
  • High Water-Solubility: Prevents aggregation and enhances signal clarity for advanced imaging and live-cell applications

Product description

XFD660, manufactured by AAT Bioquest, is a far-red fluorescent dye structurally equivalent to Alexa Fluor™ 660 (ThermoFisher). 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 maleimide derivative of XFD660 is widely used for labeling biomolecules with free thiol (SH) groups, including antibodies, proteins, thiol-modified oligonucleotides, and low molecular weight ligands. Maleimides react readily with sulfhydryl groups, forming stable thio-ether bonds between the dye and the biomolecule, facilitating robust and reliable labeling for diverse experimental applications.

Spectrum

Product family

NameExcitation (nm)Emission (nm)Extinction coefficient (cm -1 M -1)Quantum yieldCorrection Factor (260 nm)Correction Factor (280 nm)
XFD405 C5 maleimide40142135,000-0.230.70
XFD430 C5 maleimide43254015,000--0.28
XFD488 C5 Maleimide *Same Structure to Alexa Fluor™ 488 C5 Maleimide*499520710000.9210.300.11
XFD532 C5 Maleimide *Same Structure to Alexa Fluor™ 532 C5 Maleimide*534553810000.6110.240.09
XFD546 C5 maleimide5615721120000.7910.210.12
XFD568 C5 maleimide579603913000.6910.450.46
XFD594 C5 Maleimide *Same Structure to Alexa Fluor™ 594 C5 Maleimide*590618900000.6610.430.56
XFD633 C5 Maleimide632650159,000--0.55
XFD750 C5 maleimide7527762400000.1210.000.04
Page updated on May 19, 2025

Ordering information

Price
Unit size
Catalog Number70092
Quantity
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Additional ordering information

Telephone1-800-990-8053
Fax1-800-609-2943
Emailsales@aatbio.com
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ShippingStandard overnight for United States, inquire for international
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Physical properties

Molecular weight

1016.09

Solvent

DMSO

Spectral properties

Correction Factor (260 nm)

0.00

Correction Factor (280 nm)

0.10

Extinction coefficient (cm -1 M -1)

132000

Excitation (nm)

663

Emission (nm)

691

Storage, safety and handling

H-phraseH303, H313, H333
Hazard symbolXN
Intended useResearch Use Only (RUO)
R-phraseR20, R21, R22

Storage

Freeze (< -15 °C); Minimize light exposure
UNSPSC12171501
Schematic illustrating the maleimide–thiol reaction between a maleimide‐functionalized dye and a thiol‐modified biomolecule. This method is widely used for site‐specific conjugation to cysteine residues in proteins or to thiolated oligonucleotides. Maleimide–thiol coupling proceeds efficiently at or near physiological pH and results in a stable thioether bond.
Schematic illustrating the maleimide–thiol reaction between a maleimide‐functionalized dye and a thiol‐modified biomolecule. This method is widely used for site‐specific conjugation to cysteine residues in proteins or to thiolated oligonucleotides. Maleimide–thiol coupling proceeds efficiently at or near physiological pH and results in a stable thioether bond.
Schematic illustrating the maleimide–thiol reaction between a maleimide‐functionalized dye and a thiol‐modified biomolecule. This method is widely used for site‐specific conjugation to cysteine residues in proteins or to thiolated oligonucleotides. Maleimide–thiol coupling proceeds efficiently at or near physiological pH and results in a stable thioether bond.