A new family of bioorthogonally applicable fluorogenic labels.

Synthetic procedures for the construction of fluorogenic azido-labels were developed. Photophysical properties were elaborated by experimental and theoretical investigations. Of the newly synthesized fluorogenic and bioorthogonally applicable dyes two were selected on the basis of their fluorogenic performance and further subjected to in vitro and in vivo studies. Both tags exhibited excellent fluorogenic properties as in aqueous medium, the azide form of the selected dyes is virtually non-fluorescent, while their "clicked" triazole congeners showed intense fluorescence. One of these labels showed a very large Stokes shift. To the best of our knowledge this is the first reported case of mega-Stokes type of fluorogenic labels. These studies have justified that these two fluorogenic tags are remarkably suitable for bioorthogonal tagging schemes. The developed synthetic approach together with the theoretical screen of possible fluorogenic tags will enable the generation of libraries of such tags in the future.