Thioflavin T (ThT) was once regarded to be a specific fluorescent probe for the human telomeric G-quadruplex, but more other kinds of DNA were found that can also bind to ThT in recent years. Herein, we focus on G-rich parallel-stranded DNA and utilize fluorescence, absorbance, circular dichroism, and surface plasmon resonance spectroscopy to investigate its interaction with ThT. Pyrene label and molecular modeling are applied to unveil the binding mechanism. We find a new class of non-G-quadruplex G-rich parallel-stranded (ps) DNA with the sequence of TG(GA)n can bind to ThT and increase the fluorescence with an enhancement ability superior to G-quadruplex. The optimal binding specificity for ThT is conferred by two parts. The first part is composed of two bases TG at the 5′ end, which is a critical domain and plays an important role in the formation of the binding site for ThT. The second part is the rest alternative d(GA) bases, which forms the ps homoduplex and cooperates with the TG bases at the 5′ end to bind the ThT.

中文翻译：

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通过平行链TG（GA）n DNA同质双链体点亮硫黄素T

硫黄素T（ThT）曾经被认为是人类端粒G-四链体的特异性荧光探针，但近年来发现了更多其他种类的DNA也可以与ThT结合。在这里，我们专注于富含G的平行链DNA，并利用荧光，吸光度，圆二色性和表面等离振子共振光谱法研究其与ThT的相互作用。P标记和分子模型被用于揭示结合机理。我们发现了一类新的非G四链体富含G的平行链（ps）DNA，其序列为TG（GA）n可以与ThT结合并以优于G-四链体的增强能力增强荧光。对ThT的最佳结合特异性由两部分赋予。第一部分在5'端由两个碱基TG组成，这是一个关键域，在ThT结合位点的形成中起着重要作用。第二部分是其余的替代性d（GA）碱基，它形成ps同源双链体，并在5'端与TG碱基配合以结合ThT。