AFDye™ 488 Picolyl Azide (Alexa Fluor® 488 Picolyl Azide equivalent) is an advanced fluorescent probe that incorporates a copper-chelating motif to raise the effective concentration of Cu(I) at the reaction site. The rate of the CuAAC reaction depends on the concentrations of all reagents, including copper, therefore raising the effective copper concentration at the reaction site can dramatically increase the rate of reaction without the need to increase the concentration of azide reagent or copper.
In addition, the use of picolyl azides instead of conventional azides allows for at least a tenfold reduction in the concentration of the copper catalyst without sacrificing the efficiency of labeling.
In summary, the introduction of a picolyl moiety into an azide probe leads to a substantial increase in the sensitivity of alkyne detection. This is of special value for the detection of low abundance targets or where significant increase in signal intensity is desired.