Engineering interlocked G-wire assembly by systematic modulation of G-triad•G Interface connections

Area of Science:

• Supramolecular Chemistry
• Biophysical Chemistry
• Nanotechnology

Background:

• G-quadruplex (G4) structures are formed by guanine-rich sequences and have potential applications in nanotechnology.
• The assembly of complex G4 architectures, such as interlocked G4 wires, is influenced by sequence composition and G-tract characteristics.
• Understanding the role of G-tract position is crucial for controlling the formation and properties of G4-based nanostructures.

Purpose of the Study:

• To systematically investigate how the position of long G-tracts within heterogeneous G-tract sequences affects the assembly of interlocked G-quadruplex (G4) architectures.
• To elucidate the relationship between G-tract features, assembly pathways, and the resulting photophysical properties of G4 nanostructures.
• To identify strategies for enhancing the yield and controlling the assembly of interlocked G4 wires.

Main Methods:

• Systematic investigation of G-quadruplex assembly using heterogeneous G-tract sequences with varying long G-tract positions.
• Analysis of G4 architecture formation, including end-stacking modes (5'-5' vs. 5'-3') and interface stacking (5-ring vs. 5/6-ring).
• Characterization of G4 structures using fluorescence spectroscopy to determine emission wavelengths associated with different assembly pathways.
• Evaluation of N-cyanoimidazole-driven end-ligation for enhancing G4-wire yield.

Main Results:

• Assembly into interlocked G4 dimers (5'-5' stacking) was observed only for sequences with a 5'-terminal long G-tract and a 3'-terminal thymine.
• Most other sequences formed interlocked G4 wires via 5'-3' end-stacking, with assembly pathways dependent on the G-tract's role in forming intramolecular G-tetrads.
• Pathway I (5-ring interface) resulted in 330 nm emission, while Pathway II (5/6-ring interface) yielded 385 nm emission; central G-tracts showed pathway plasticity.
• N-cyanoimidazole-driven end-ligation significantly improved the yield of interlocked G4 wires.

Conclusions:

• The position of the long G-tract is a critical determinant for the assembly pathway and resulting architecture of interlocked G4 structures.
• Specific G-tract configurations and ionic environments can direct the formation of distinct G4-wire stacking modes and fluorescence properties.
• This study provides valuable insights and practical methods for the rational design, regulation, and optimization of G4-based nanostructures.