Aptamer-Based K(+) Sensor: Process of Aptamer Transforming into G-Quadruplex.
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.
Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University , Beijing 100875, China.
Dongju
D
Zhang
Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University , Beijing 100875, China.
Juan
J
Han
Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University , Beijing 100875, China.
Yunchao
Y
Li
Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University , Beijing 100875, China.
Louzhen
L
Fan
Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University , Beijing 100875, China.
Xiaohong
X
Li
D052157:Aptamers, Nucleotide / Q000737:chemistry*; D002942:Circular Dichroism; D005456:Fluorescent Dyes / Q000737:chemistry; D054856:G-Quadruplexes; D044367:Phase Transition; D011188:Potassium / Q000032:analysis*; D013050:Spectrometry, Fluorescence; D021241:Spectrometry, Mass, Electrospray Ionization
D052157:Aptamers, Nucleotide; D005456:Fluorescent Dyes; D011188:Potassium