AAT Bioquest

FastClick™ XFD405 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 weight843.90
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™ XFD405 Alkyne


See also: Click Chemistry
Molecular weight
FastClick™ XFD405 Azide contains both the CAG moiety of FastClick (for assisting click efficiency) and Alexa Fluor® 405 fluorophore (as the fluorescence tag) for developing Alexa Fluor® 405-based fluorescent probes. Alexa Fluor® 405 is a commonly used blue fluorophore for labeling proteins, nucleic acids, or other biomolecules. It has moderate photostability and excitation that matches the 405 nm laser line. Its conjugates are used for imaging and flow cytometry applications. It has an excitation wavelength of 405 nm and an emission wavelength of 421 nm. It is water soluble pyrene 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. Two important characteristics make click chemistry attractive for assembling biomolecules. First, click reactions are bio-orthogonal, thus the click chemistry-functionalized biomolecules would not react with the natural biomolecules that lack a clickable functional group. Second, the reactions proceed with ease under mild conditions, such as at room temperature and in aqueous media.


Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of FastClick™ XFD405 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 mM118.497 µL592.487 µL1.185 mL5.925 mL11.85 mL
5 mM23.699 µL118.497 µL236.995 µL1.185 mL2.37 mL
10 mM11.85 µL59.249 µL118.497 µL592.487 µL1.185 mL

Molarity calculator

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Mass (Calculate)Molecular weightVolume (Calculate)Concentration (Calculate)Moles

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™ XFD555 Azide5535681500000.110.080.08
FastClick™ XFD647 Azide6506712390000.3310.000.03
FastClick™ XFD750 Azide7527762400000.1210.000.04



View all 6 references: Citation Explorer
Effects of Viscosity and Refractive Index on the Emission and Diffusion Properties of Alexa Fluor 405 Using Fluorescence Correlation and Lifetime Spectroscopies.
Authors: van Zanten, Camila and Melnikau, Dzmitry and Ryder, Alan G
Journal: Journal of fluorescence (2021): 835-845
Egg autofluorescence and options for detecting peanut agglutinin binding for the identification of Haemonchus contortus eggs in fecal samples.
Authors: Abbas, Ibrahim and Hildreth, Michael
Journal: Veterinary parasitology (2019): 69-74
Author Correction: A dynamic three-step mechanism drives the HIV-1 pre-fusion reaction.
Authors: Iliopoulou, Maro and Nolan, Rory and Alvarez, Luis and Watanabe, Yasunori and Coomer, Charles A and Jakobsdottir, G Maria and Bowden, Thomas A and Padilla-Parra, Sergi
Journal: Nature structural & molecular biology (2019): 526
Identification of novel cell-impermeant fluorescent substrates for testing the function and drug interaction of Organic Anion-Transporting Polypeptides, OATP1B1/1B3 and 2B1.
Authors: Patik, Izabel and Székely, Virág and Német, Orsolya and Szepesi, Áron and Kucsma, Nóra and Várady, György and Szakács, Gergely and Bakos, Éva and Özvegy-Laczka, Csilla
Journal: Scientific reports (2018): 2630
Energy transfer between a biological labelling dye and gold nanorods.
Authors: Racknor, Chris and Singh, Mahi R and Zhang, Yinan and Birch, David J S and Chen, Yu
Journal: Methods and applications in fluorescence (2013): 015002
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Journal: Cytometry. Part A : the journal of the International Society for Analytical Cytology (2006): 1153-60