Dimeric G-Quadruplex: An Effective Nucleic Acid Scaffold for Lighting Up Thioflavin T

Area of Science:

• Biochemistry
• Molecular Biology
• Biophysics

Background:

• Higher-order quadruplex (G4) structures, including G4 dimers, are emerging as significant players in biological processes.
• The interaction between G4 structures and fluorescent dyes like thioflavin T (ThT) is crucial for developing sensitive detection methods.

Purpose of the Study:

• To investigate the formation and properties of a stable G4 dimer from tandem PW17 DNA sequences.
• To evaluate the potential of the G4 dimer/ThT complex as a superior fluorescence indicator for biosensing applications.

Main Methods:

• Accidental discovery and characterization of a stable G4 dimer from two tandem PW17 sequences.
• Comparative fluorescence intensity measurements of G4 dimer/ThT versus G4 monomer/ThT.
• Assessment of fluorescence stability in varying ionic conditions (Na+, K+).
• Development of a label-free DNA probe and a rolling circle amplification-based biosensing strategy utilizing the G4 dimer/ThT system.

Main Results:

• Two tandem PW17 sequences spontaneously form a stable G4 dimer.
• The G4 dimer significantly enhances ThT fluorescence intensity (approximately ninefold) compared to the G4 monomer.
• The G4 dimer/ThT system demonstrates enhanced fluorescence stability across different Na+ and K+ concentrations.
• A functional label-free DNA probe and a biosensing strategy were successfully developed using the G4 dimer/ThT indicator.

Conclusions:

• Dimeric G4 structures serve as effective scaffolds for enhancing ThT fluorescence.
• The G4 dimer/ThT system offers a promising platform for sensitive, label-free bioassays.
• This finding opens new avenues for nucleic acid-based fluorescence detection and diagnostics.