AAT Bioquest

FastClick™ XFD555 Azide

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The reaction (Green Bar) of FastClick Cy5 Azide with coumarin alkyne occurs under extremely mild conditions (e.g., [Azide] = 0.02 mM, [Alkyne] = 0.02 mM, [CuSO4] = 0.02 mM, [Sodium Ascorbate] = 5 mM, in 100 mM HEPES) under which the common Cy5 azide does not effectively react with the coumarin alkyne substrate.
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Physical properties
Molecular weight1159.25
Spectral properties
Correction Factor (260 nm)0.08
Correction Factor (280 nm)0.08
Extinction coefficient (cm -1 M -1)150000
Excitation (nm)553
Emission (nm)568
Quantum yield0.11
Storage, safety and handling
H-phraseH303, H313, H333
Hazard symbolXN
Intended useResearch Use Only (RUO)
R-phraseR20, R21, R22
StorageFreeze (< -15 °C); Minimize light exposure
Alternative formats
FastClick™ XFD555 Alkyne


See also: Click Chemistry
Molecular weight
Correction Factor (260 nm)
Correction Factor (280 nm)
Extinction coefficient (cm -1 M -1)
Excitation (nm)
Emission (nm)
Quantum yield
FastClick™ XFD555 Azide contains both the CAG moiety of FastClick (for assisting click efficiency) and Alexa Fluor® 555 fluorophore (as the fluorescence tag) for developing Alexa Fluor® 555-based fluorescent probes. Alexa Fluor® 555 is a commonly used orange-red fluorophore for labeling proteins, nucleic acids, or other biomolecules. It has moderate photostability and excitation that matches the common 555 nm laser line that is equipped with almost most of the major fluorescence instruments. Its conjugates are widely used for imaging and flow cytometry applications in combination with the widely available Cy3 filter set. It is a water-soluble Cy3 derivative that has pH-insensitive fluorescence from pH 4 to pH 10. Alexa Fluor® is a trademark of ThermoFisher Scientific. FastClick™ reagents have been developed by the scientists of AAT Bioquest for enhancing the yield and reaction speed of copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. They contain a copper-chelating ligand that significantly stabilizes the Cu(I) oxidation state and thus accelerates the click reaction. They do not require the use of an external copper-chelator (such as the common THPTA or BTTAA). The high concentration of copper chelators is known to have a detrimental effect on DNA/RNA, thus causing biocompatibility issues. The introduction of a copper-chelating moiety at the reporter molecule allows for a dramatic raise of the effective Cu(I) concentration at the reaction site and thus accelerates the reaction. Under extremely mild conditions the FastClick™ azides and alkynes react much faster in high yield compared to the corresponding conventional CuAAC reactions. Click chemistry was developed by K. Barry Sharpless as a robust and specific method of ligating two molecules together.


Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of FastClick™ XFD555 Azide to given concentration. Note that volume is only for preparing stock solution. Refer to sample experimental protocol for appropriate experimental/physiological buffers.

0.1 mg0.5 mg1 mg5 mg10 mg
1 mM86.263 µL431.313 µL862.627 µL4.313 mL8.626 mL
5 mM17.253 µL86.263 µL172.525 µL862.627 µL1.725 mL
10 mM8.626 µL43.131 µL86.263 µL431.313 µL862.627 µL

Molarity calculator

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Spectral properties

Correction Factor (260 nm)0.08
Correction Factor (280 nm)0.08
Extinction coefficient (cm -1 M -1)150000
Excitation (nm)553
Emission (nm)568
Quantum yield0.11

Product Family

NameExcitation (nm)Emission (nm)Extinction coefficient (cm -1 M -1)Quantum yieldCorrection Factor (260 nm)Correction Factor (280 nm)
FastClick™ Cy3 Azide55556915000010.1510.070.073
FastClick™ Cy5 Azide65167025000010.271, 0.420.020.03
FastClick™ Cy7 Azide7567792500000.30.050.036
FastClick™ XFD350 Azide34344119000-0.250.19
FastClick™ XFD488 Azide499520710000.9210.300.11
FastClick™ XFD647 Azide6506712390000.3310.000.03
FastClick™ XFD750 Azide7527762400000.1210.000.04



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