Highly ordered pyrene π-stacks on an RNA duplex display static excimer fluorescence.

Area of Science:

• Biochemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Oligonucleotides are crucial in biological processes and nanotechnology.
• Pyrene derivatives are useful fluorescent probes and building blocks for supramolecular assemblies.

Purpose of the Study:

• To investigate the binding and fluorescence properties of RNA sequences modified with varying numbers of pyrene units.
• To understand the self-assembly mechanism and photophysical characteristics of pyrene-RNA conjugates.

Main Methods:

• Synthesis of pyrene-modified RNA oligonucleotides with pyrene attached via a one-carbon linker at the 2'-O-position.
• Hybridization studies to form RNA duplexes.
• Spectroscopic analyses including UV-Vis absorption, Circular Dichroism (CD), and fluorescence spectroscopy.
• Thermal stability measurements (melting temperature).

Main Results:

• Formation of pyrene-modified RNA duplexes with normal thermal stability.
• Assembly of pyrene units into inter-strand arrays driven by π-stacking interactions, evidenced by hypochromic effects and exciton-coupled circular dichroism (ECCD) signals.
• Observation of strong, structureless excimer fluorescence characteristic of static excimers.
• Demonstration that the number of attached pyrene units regulates the spatial configuration of the pyrene assemblies.

Conclusions:

• Pyrene-modified RNA can self-assemble into ordered inter-strand arrays upon hybridization.
• The observed static excimer fluorescence provides insights into the ground-state interactions of the pyrene moieties.
• The degree of pyrene modification influences the supramolecular organization and photophysical properties of the resulting assemblies.