Reversible Photo-switching of G-Quadruplex by Backbone-Inserted Azobenzene

Introduction: Taking the typical human telomeric G-quadruplex (G4) sequence as a reference, we designed four photoresponsive DNA sequences by inserting azobenzene moieties into a planar interlayer and the end surfaces of the G4 structure. Methods: The photo-responsive G4 molecules were investigated by melting curve, FRET, CD, and gel electrophoresis. Results and Discussion: The measurements showed that the photo-responsive G4 molecules took the stable four-strand structure under visible light, but after UV light irradiation, the G4 structures tended to be disentangled. When azobenzene molecules were inserted at the end surfaces of the G4 structure, the Tm difference of the photo-responsive G4 between visible light and UV light reached more than 30 ºC. Conclusion: In a temperature range from 20 to 53 ºC, the reversible transformation of the G4 structure can be realized solely by light irradiation.