FastClick™ Biotin Azide contains both the CAG moiety of FastClick (for assisting click efficiency) and biotin hapten (as the detection tag) for developing biotin-based probes. It readily reacts with an alkyne-containing biomolecule under extremely mild conditions. Biotin is one of the most commonly used tags that finds a variety of utilities in biological detections similarly to other popular haptens such as 2,4-Dinitrophenol (DNP) and DIG etc. Biotin conjugates are widely used in fluorescence imaging, fluorescence in situ hybridization (FISH) and nucleic acid detections in combination with the fluorescence-labeled streptavidin, avidin or NeutrAvidin® or other biotin-binding protein conjugates. 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.