DNA base-pair flipping with fluorescent perylenediimide pincers

Area of Science:

• Molecular Biology
• Supramolecular Chemistry
• Biophysical Chemistry

Background:

• DNA hairpins are crucial nucleic acid structures with diverse biological roles.
• Perylenediimide (PDI) molecules serve as versatile chromophores and base pair surrogates in synthetic DNA.
• Understanding the photophysical properties and structural behavior of modified DNA is essential for developing novel molecular tools.

Purpose of the Study:

• To synthesize and characterize DNA hairpins containing two perylenediimide (PDI) base pair surrogates.
• To investigate the structural and electronic properties of these modified DNA hairpins using spectroscopic and computational methods.
• To determine the thermodynamic stability of PDI stacking in comparison to natural base pairs.

Main Methods:

• Synthesis of DNA hairpins with PDI base pair surrogates at various positions.
• Spectroscopic analysis including electronic absorption, fluorescence, and circular dichroism (CD).
• Molecular modeling to predict and analyze the geometry of PDI stacking.

Main Results:

• DNA hairpins with adjacent PDI chromophores exhibit a slipped, pi-stacked geometry.
• Spectra indicate isolated PDIs when separated by GC base pairs, but complex behavior with AT base pairs.
• PDI stacking free energy is greater than a single AT base pair and comparable to GC base pairs.

Conclusions:

• The geometry and electronic properties of PDI-containing DNA hairpins are influenced by the PDI arrangement and intervening base pairs.
• PDI stacking is thermodynamically favorable, comparable to natural base pairs, suggesting potential applications in DNA nanotechnology.
• The study provides insights into the interplay between chromophore stacking and DNA structural dynamics.