title: Molecular rotor-based fluorescent probe for selective recognition of hybrid G-quadruplex and as a K+ sensor.
abstract: This work demonstrates the significant fluorescence enhancement of thioflavin T (ThT) when binding to G-quadruplexes possessing hybrid structures by using UV-vis absorption spectra, fluorescence spectra, and Tm experiments to confirm the binding events. ThT binding does not disturb native G-quadruplex structures preformed in Na(+) and K(+) solutions. The fluorescence enhancement is caused by the rotation restriction of benzothiazole (BZT) and dimethylaminobenzene (DMAB) rings in the ThT excited state upon its G-quadruplex binding. This molecular rotor mechanism as a means of fluorescence enhancement is confirmed using a nonrotor analogue of ThT. Hydroxylation and electrolyte experiments demonstrate that ThT stacks on the tetrad of the hybrid G-quadruplexes, whereas electrostatic forces contribute more to ThT binding for other G-quadruplex structures. By stacking on the tetrad, the ThT binding favors selective identification of DNA hybrid G-quadruplex structures with enhanced fluorescence and can serve as a conformation probe to monitor G-quadruplex structure conversion between hybrid and other structures. Using these properties, we developed a selective and label-free fluorescent K(+) sensor with a detection limit of 1 mM for K(+) in the presence of 100 mM Na(+). The coexistence of other metal ions produces a fluorescence response comparable to K(+) alone. We believe that ThT can potentially provide structure identification of hybrid G-quadruplexes and aid in the construction of G-quadruplex-based sensors.
authors.affiliation: Institute of Physical Chemistry, Zhejiang Normal University , Jinhua 321004, Zhejiang, People's Republic of China.
authors.forename: Lingling
authors.initials: L
authors.lastname: Liu
authors.forename: Yong
authors.initials: Y
authors.lastname: Shao
authors.forename: Jian
authors.initials: J
authors.lastname: Peng
authors.forename: Chaobiao
authors.initials: C
authors.lastname: Huang
authors.forename: Hua
authors.initials: H
authors.lastname: Liu
authors.forename: Lihua
authors.initials: L
authors.lastname: Zhang
mesh_terms: D001554:Benzene / Q000737:chemistry; D052160:Benzothiazoles / Q000737:chemistry; D005456:Fluorescent Dyes; D054856:G-Quadruplexes; D011188:Potassium / Q000032:analysis* / Q000737:chemistry*; D012399:Rotation; D013050:Spectrometry, Fluorescence; D013379:Substrate Specificity; D013844:Thiazoles / Q000737:chemistry*; D044366:Transition Temperature
chemical_list: D052160:Benzothiazoles; D005456:Fluorescent Dyes; D013844:Thiazoles; C009462:thioflavin T; C005465:benzothiazole; D001554:Benzene; D011188:Potassium