Rationally Designed G-Quadruplex Selective "Turn-On" NIR Fluorescent Probe with Large Stokes Shift for Nucleic Acid...

Area of Science:

• Molecular Biology
• Biochemistry
• Chemical Biology

Background:

• Guanine-rich sequences form G-quadruplexes, crucial in cellular processes.
• Existing fluorescent probes lack selectivity, optimal spectral properties, or near-infrared (NIR) emission for cellular imaging.
• Developing selective NIR fluorescent probes is vital for G-quadruplex research.

Purpose of the Study:

• To design and synthesize novel NIR fluorescent probes for selective G-quadruplex detection.
• To evaluate the photophysical properties, selectivity, and cellular imaging capabilities of the designed probes.
• To investigate the binding mechanism of the lead compound with G-quadruplex structures.

Main Methods:

• Rational design and synthesis of quinolinium-based NIR fluorescent probes.
• Spectroscopic analysis (fluorescence emission, Stokes shift) and binding studies with various nucleic acid structures.
• Molecular docking simulations to elucidate binding modes.
• Live-cell fluorescence imaging in HeLa cells.

Main Results:

• Compound 4a exhibits far-red fluorescence (λmax = 680 nm) with a large Stokes shift (∼182 nm).
• 4a selectively binds to human telomeric G-quadruplexes, showing minimal interaction with single- and double-stranded DNA/RNA.
• Molecular docking reveals groove binding via π-π stacking and anion-π interactions.
• 4a demonstrates cell permeability, biocompatibility, and effective imaging of nuclear DNA and cytoplasmic RNA G-quadruplexes in live cells.

Conclusions:

• The designed NIR probe 4a possesses excellent photophysical properties and high selectivity for G-quadruplexes.
• 4a enables effective cellular imaging of G-quadruplexes without disturbing their structure or stability.
• This probe holds significant potential for advancing G-quadruplex biology research and cellular imaging applications.