The equilibrium structure of the RNA sugar–phosphate backbone and its hydration shell is distinctly different from hydrated DNA. Applying femtosecond two-dimensional infrared (2D-IR) spectroscopy in a range from 950 to 1300 cm^–1, we elucidate the character, dynamics, and couplings of backbone modes of a double-stranded RNA A-helix geometry in its aqueous environment. The 2D-IR spectra display a greater number of backbone modes than for DNA, with distinctly different lineshapes of diagonal peaks. Phosphate–ribose interactions and local hydration structures are reflected in the complex coupling pattern of RNA modes. Interactions with the fluctuating water shell give rise to spectral diffusion on a 300 fs time scale, leading to a quasi-homogeneous line shape of the symmetric (PO₂)⁻ stretching mode of the strongly hydrated phosphate groups. The RNA results are benchmarked by 2D-IR spectra of DNA oligomers in water and analyzed by molecular dynamics and quantum mechanical molecular mechanics simulations.

中文翻译：

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水合RNA骨架的振动动力学和耦合：二维红外研究

RNA糖磷酸骨架的平衡结构及其水合壳与水合DNA明显不同。在950至1300 cm ^–1范围内应用飞秒二维红外（2D-IR）光谱，我们阐明了在水环境中双链RNA A螺旋几何结构的骨架模式的特征，动力学和耦合。2D-IR光谱显示出比DNA更大的主链模式，对角峰的线形明显不同。磷酸核糖相互作用和局部水合结构反映在RNA模式的复杂偶联模式中。与波动的水壳的相互作用会在300 fs的时间尺度上引起光谱扩散，从而导致对称（PO ₂）的准均匀线形⁻强水合磷酸酯基团的拉伸方式。RNA结果以水中DNA寡聚物的2D-IR光谱为基准，并通过分子动力学和量子力学分子力学模拟进行分析。