Conformationally Locked 5-Benzylidene-4Н-Imidazolthion as Fluorogenic Dye
We report novel conformationally locked 5-(4-(diethylamino)benzylidene)-2,3-dimethyl-3,5-dihydro-4<i>H</i>-imidazole-4-thion. Derivatives of conformationally locked chromophores of the fluorescent protein containing sulfur instead of oxygen in the imidazolone fragment are characterized by red-shifted spectra and higher extinction coefficient relative to the corresponding derivative containing an oxygen atom. That compound can be used as fluorogenic dyes for lipocalin-based fluorogen-activating proteins in fluorescent microscopy.