Fluorogenic RNA aptamers-dye pairs. Above, schematic representations of two types of fluorogenic RNA aptamers based on their paired dyes: single dyes (A) and fluorophore-quencher conjugates (B). Yellow star, fluorophore; Gray rounded rectangle, quencher. Below, chemical structures of representative dyes. DFHBI, 3,5-difluoro-4-hydroxybenzylidene imidazolinone [8]; DFHBI-1T, DFHBI with a 1,1,1-trifluoroethyl substituent [9]; DFHO, 3,5-difluoro-4-hydroxybenzylidene imidazolinone-2-oxime [15]; TO, thiazole orange [18]; YO, oxazole yellow [20]; DIR, dimethylindole red [7]; OTB, oxazole thiazole blue [7]; SiR, silicon rhodamine [21]; HBC, (4-((2-hydroxyethyl)(methyl)amino)-benzylidene)-cyanophenyl-acetonitrile [22]; SR, Sulforhodamine B; DN, dinitroaniline; TMR, 5-carboxytetramethylrhodamine; MN, mononitroaniline [25,26]; BHQ, black hole quencher; Cbl, cobalamin [23].