G-triplexes are G-rich oligonucleotides composed of three G-tracts and have absorbed much attention due to their potential biological functions and attractive performance in biosensing. Through the optimization of loop compositions, DNA lengths, and 5′-flanking bases of G-rich sequences, a new stable G-triplex sequence with 14 bases (G3-F15) was discovered to dramatically activate the fluorescence of Thioflavin T (ThT), a water-soluble fluorogenic dye. The fluorescence enhancement of ThT after binding with G3-F15 reached 3200 times, which was the strongest one by far among all of the G-rich sequences. The conformations of G3-F15 and G3-F15/ThT were studied by circular dichroism. The thermal stability measurements indicated that G3-F15 was a highly stable G-triplex structure. The conformations of G3-F15 and G3-F15/ThT in the presence of different metal cations were studied thoroughly by fluorescent spectroscopy, circular dichroism, and nuclear magnetic resonance. Furthermore, using the G3-F15/ThT complex as a fluorescent probe, a robust and simple turn-on fluorescent sensor for uracil-DNA glycosylase activity was developed. This study proposes a new systematic strategy to explore new functional G-rich sequences and their ligands, which will promote their applications in diagnosis, therapy, and biosensing.

中文翻译：

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新型 G-Triplex DNA 显着激活硫黄素 T 的荧光，并作为尿嘧啶-DNA 糖基化酶活性检测的开启荧光传感器

G-三链体是由三个G-束组成的富含G的寡核苷酸，由于其潜在的生物学功能和在生物传感方面的诱人性能而备受关注。通过优化环组成、DNA 长度和富含 G 序列的 5' 侧翼碱基，发现了一种新的稳定的 14 个碱基 G-三链体序列 (G3-F15)，可以显着激活硫磺素 T (ThT) 的荧光，一种水溶性荧光染料。 ThT与G3-F15结合后的荧光增强达到3200倍，是迄今为止所有富含G的序列中最强的。通过圆二色性研究了G3-F15和G3-F15/ThT的构象。热稳定性测量表明G3-F15是高度稳定的G-三链体结构。通过荧光光谱、圆二色性和核磁共振对G3-F15和G3-F15/ThT在不同金属阳离子存在下的构象进行了深入研究。此外，使用 G3-F15/ThT 复合物作为荧光探针，开发了一种强大且简单的尿嘧啶-DNA 糖基化酶活性开启荧光传感器。本研究提出了一种新的系统策略来探索新的功能性富含G序列及其配体，这将促进它们在诊断、治疗和生物传感中的应用。