Vibrational Dynamics and Couplings of the Hydrated RNA Backbone: A Two-Dimensional Infrared Study

Area of Science:

• Biophysics
• Spectroscopy
• Structural Biology

Background:

• The hydration shell and sugar-phosphate backbone structure of RNA differ significantly from those of DNA.
• Understanding these differences is crucial for comprehending RNA's biological functions.

Purpose of the Study:

• To elucidate the character, dynamics, and couplings of RNA backbone modes in an aqueous environment.
• To compare the hydration and structural dynamics of RNA with those of DNA.

Main Methods:

• Femtosecond two-dimensional infrared (2D-IR) spectroscopy was employed to study RNA in its aqueous environment.
• Molecular dynamics (MD) and quantum mechanical molecular mechanics (QM/MM) simulations were used for analysis.
• 2D-IR spectra of DNA oligomers served as a benchmark for comparison.

Main Results:

• RNA exhibits more backbone modes than DNA, with unique diagonal peak lineshapes.
• Complex coupling patterns in RNA spectra indicate significant phosphate-ribose interactions and local hydration.
• Water shell interactions cause spectral diffusion on a 300 fs timescale, affecting the phosphate group's symmetric stretching mode.

Conclusions:

• The aqueous structure of the RNA backbone and its hydration shell are distinct from hydrated DNA.
• Femtosecond 2D-IR spectroscopy effectively probes RNA backbone dynamics and hydration.
• These findings provide insights into RNA's structural behavior in solution.