Thioflavin T as an Efficient Inducer and Selective Fluorescent Sensor for the Human Telomeric G-Quadruplex DNA

Abstract

The quest for a G-quadruplex specific fluorescent sensor among other DNA forms under physiological salt conditions has been addressed in this article. We demonstrate for the first time the application of a water-soluble fluorogenic dye, Thioflavin T (ThT), in a dual role of exclusively inducing quadruplex folding in the 22AG human telomeric DNA, both in the presence and absence of Tris buffer/salt, and sensing the same through its fluorescence light-up having emission enhancement of the order of 2100-fold in the visible region. Appropriate conditions allow an apparent switch over of the parallel quadruplex structure in 22AG-ThT (50 mM Tris, pH 7.2) solution to the antiparallel form just by the addition of K(+) ions in the range 10-50 mM. Moreover, addition of ThT cooperatively stabilizes the K(+) induced antiparallel quadruplexes by a ΔT(m) ∼11 °C. The distinction of ThT as a quadruplex inducer has been contrasted with the erstwhile used structurally related dye, Thiazole Orange (TO), which did not induce any quadruplex folding in the 22AG strand in the absence of salt. The striking fluorescence light-up in ThT on binding to the human telomeric G-quadruplex is shown to be highly specific compared to the less than 250-fold enhancement observed with other single/double strand DNA forms. This work has implication in designing new generation dyes based on the ThT scaffold, which are highly selective for telomeric DNA, for potential diagnostic, therapeutic, and ion-sensing applications.

Dinickel–Salphen Complexes as Binders of Human Telomeric Dimeric G‐Quadruplexes

“…Though no significant changes were observed in the presence of complexes 2 a and 2 b , the addition of 1 and 2 c caused a marked increase of the intensity of the positive peak at approximately 265 nm (associated with the parallel conformation), and a decreased intensity of the positive peak at approximately 295 nm (associated with the antiparallel conformation). These results suggest that complexes 2 c and 1 promote the formation of parallel quadruplex in K + buffer 30, 34, 43…”

Amplified Fluorescent Detection of Mercuric Ions by Conjugation of the ThT-induced G-Quadruplex Based Hybridization Chain Reaction

“…Thus, H1 and H2 are cross-opened autonomously and selfassembled into long-chain DNA incorporated with multiple G-quadruplexes, and the formation of the long-chain DNA incorporated with multiple G-quadruplexes depends on the concentration of Hg 2+ . Because thioflavin T (ThT) can be bound to G-quadruplexe and its fluorescence intensity become enhanced, 40 the long-chain DNA with multiple G-quadruplexes will make the fluorescence intensity of ThT increase greatly. Based on this, the concentration of Hg 2+ can be detected by monitoring the fluorescence changes of the solution.…”

“…One of the hairpins was opened by the released initiator probe, which triggered a successive cross-opening of two hairpins based the strand displacement principle, resulting in the formation of long-chain DNA with multiple G-quadruplex. Thioflavin T (ThT), a commercially available dye which could be selectively bound to the G-quadruplex structure with the result of fluorescence enhancement, 40,41 was employed as the fluorophore to design a label-free THMS-HCR-based fluorescence sensor. Because the T-T base pair can only be stabilized by Hg…”

Sensing of Intracellular Environments by Fluorescence Lifetime Imaging of Exogenous Fluorophores

“…1G), which is used to detect the amyloid structure, also specifically binds to G-quadruplex DNA, and its fluorescence lifetime has a tendency to increase with increasing magnitude of the interaction between ThT and G-quadruplex. 57 The increase in the fluorescence lifetime may come from the steric hindrance of a G-quadruplex structure that reduces the rate of the non-radiative relaxation of ThT. The fluorescence lifetime of 3,6-bis(1-methyl-4-vinylpyridinium) carbazole diiodide (BMVC), synthesized for detecting G-quadruplex DNA, was also suggested to detect the presence of G-quadruplex structures.…”