Aptamer-Based K+ Sensor: Process of Aptamer Transforming into G-Quadruplex

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• 作者：Dongju Zhang ; Juan Han ; Yunchao Li ; Louzhen Fan ; Xiaohong Li
• 刊名：Journal of Physical Chemistry B
• 出版年：2016
• 出版时间：July 14, 2016
• 年：2016
• 卷：120
• 期：27
• 页码：6606-6611
• 全文大小：376K
• 年卷期：0
• ISSN：1520-5207

文摘

G-rich aptamers have been widely applied to develop various sensors for detecting proteins, small molecules, and cations, which is based on the target-induced conformational transfer from single strand to G-quadruplex. However, the transforming process is unclear. Here, with PW17 as an aptamer example, the forming process of G-quadruplex induced by K⁺ is investigated by circular dichroism spectroscopy, electrospray ionization mass spectroscopy, and native gel electrophoresis. The results demonstrate that PW17 undergoes a conformational transforming process from loose and unstable to compact and stable G-quadruplex, which is strictly K⁺ concentration-dependent. The process contains three stages: (1) K⁺ (<0.5 mM) could induce PW17 forming a loose and unstable G-quadruplex; (2) the compact and stable K⁺-stabilized G-quadruplex is almost formed when K⁺ is equal to or larger than 7 mM; and (3) when K⁺ ranges from 0.5 mM to 7 mM, the transformation of K⁺-stabilized PW17 from loose and unstable to compact and stable occurs. Interestingly, dimeric G-quadruplex through 5′-5′ stacking is involved in the forming process until completely formed at 40 mM K⁺. Moreover, the total process is thermodynamically controlled. With PW17 as a sensing probe and PPIX as a fluorescent probe for detection of K⁺, three linear fluorescent ranges are observed, which corresponds to the three forming stages of G-quadruplex. Clarifying the forming process provides a representative example to deeply understand and further design aptamer-based biosensers and logic devices.