DNA and RNA "traffic lights": synthetic wavelength-shifting fluorescent probes based on nucleic acid base substitutes for molecular imaging.

The DNA base substitute approach by the (S)-3-amino-1,2-propanediol linker allows placing two fluorophores in a precise way inside a given DNA framework. The double helical architecture around the fluorophores, especially the DNA-induced twist, is crucial for the desired photophysical interactions. Excitonic, excimer, and energy transfer interactions yield fluorescent DNA and RNA probes with dual emission color readout.

RNA "traffic lights": an analytical tool to monitor siRNA integrity.

The combination of thiazole orange and thiazole red as an internal energy transfer-based fluorophore pair in oligonucleotides provides an outstanding analytical tool to follow DNA/RNA hybridization through a distinct fluorescence color change from red to green. Herein, we demonstrate that this concept can be applied to small interfering RNA (siRNA) to monitor RNA integrity in living cells in real time with a remarkable dynamic range and excellent contrast ratios in cellular media. Furthermore, we show that our siRNA-sensors still possess their gene silencing function toward the knockdown of enhanced green fluorescent protein in CHO-K1 cells.

Energy-transfer-based wavelength-shifting DNA probes with "clickable" cyanine dyes.

The insertion of cyanine dye azides as energy donor dyes via postsynthetic "click"-type cycloaddition chemistry with e.g. a new thiazole orange azide combined with thiazole red yields dual emitting DNA probes with good fluorescence readout properties.

"DNA traffic lights": concept of wavelength-shifting DNA probes and application in an aptasensor.

Add it and see it: The concept of "DNA traffic lights" for wavelength-shifting DNA probes has a great potential in the application of biosensors, for example, in DNA aptamers. A visual color change in the DNA aptasensor fluorescence from green to red occurs after specific target binding.