Label-free fluorescent probing of G-quadruplex formation and real-time monitoring of DNA folding by a quaternized tetraphenylethene salt with aggregation-induced emission characteristics.
Biosensing processes such as molecular beacons require non-trivial effort to covalently label or mark biomolecules. We report here a label-free DNA assay system with a simple dye with aggregation-induced emission (AIE) characteristics as the fluorescent bioprobe. 1,1,2,2-Tetrakis[4-(2-bromoethoxy)phenyl]ethene is nonemissive in solution but becomes highly emissive when aggregated. This AIE effect is caused by restriction of intramolecular rotation, as verified by a large increase in the emission intensity by increasing viscosity and decreasing temperature of the aqueous buffer solution of 1,1,2,2-tetrakis[4-(2-triethylammonioethoxy)phenyl]ethene tetrabromide (TTAPE). When TTAPE is bound to a guanine-rich DNA strand (G1) via electrostatic attraction, its intramolecular rotation is restricted and its emission is turned on. When a competitive cation is added to the G1 solution, TTAPE is detached and its emission is turned off. TTAPE works as a sensitive poststaining agent for poly(acrylamide) gel electrophoresis (PAGE) visualization of G1. The dye is highly affinitive to a secondary structure of G1 called the G-quadruplex. The bathochromic shift involved in the G1 folding process allows spectral discrimination of the G-quadruplex from other DNA structures. The strong affinity of TTAPE dye to the G-quadruplex structure is associated with a geometric fit aided by the electrostatic attraction. The distinct AIE feature of TTAPE enables real-time monitoring of folding process of G1 in the absence of any pre-attached fluorogenic labels on the DNA strand. TTAPE can be used as a K+ ion biosensor because of its specificity to K+-induced and -stabilized quadruplex structure.
Hong
Yuning
Y
Department of Chemistry, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China.
Häussler
Matthias
M
Lam
Jacky W Y
JW
Li
Zhen
Z
Sin
King Keung
KK
Dong
Yongqiang
Y
Tong
Hui
H
Liu
Jianzhao
J
Qin
Anjun
A
Renneberg
Reinhard
R
Tang
Ben Zhong
BZ
D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry*; D054856:G-Quadruplexes; D006801:Humans; D000644:Quaternary Ammonium Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D013194:Staining and Labeling; D055672:Static Electricity; D013267:Stilbenes / Q000138:chemical synthesis / Q000737:chemistry*; D016615:Telomere / Q000235:genetics; D013997:Time Factors
C531393:1,1,2,2-tetrakis(4-(2-triethylammonioethoxy)phenyl)ethene tetrabromide; D005456:Fluorescent Dyes; D000644:Quaternary Ammonium Compounds; D013267:Stilbenes; D004247:DNA