Fluorescence properties of 9,10-diphenylanthracene-modified DNA hairpins: Influence of salt-induced B–Z transition and thermal fluctuations

We developed new fluorescent DNA hairpins having 9,10-diphenylanthracene (DPA) units. Both DNA1 (one DPA) and DNA2 (two DPAs) showed a salt-induced B–Z transition in 5 M NaCl. Interestingly, DNA2 exhibited a significant twofold increase in fluorescence intensity when heated to 80 °C under high-salt conditions. The unique “turn-on” response is likely due to the structural relaxation of the DPA stacking arrangement in the Z-form. In contrast, DNA1 showed no such enhancement. Furthermore, the fluorescence response of DNA2 was highly reversible and stable. Our findings suggest that DNA2 is a promising candidate for developing sensitive fluorescent thermo-sensors.