Department of Chemistry and Biochemistry, University of Mississippi, University, Mississippi 38677, USA.
J Phys Chem B. 2011 Jun 16;115(23):7699-707. doi: 10.1021/jp203840w. Epub 2011 May 20.
The effects of hydration on vibrational normal modes of trimethylamine N-oxide (TMAO) are investigated by Raman spectroscopy and electronic structure computations. Microsolvated networks of water are observed to induce either red or blue shifts in the normal modes of TMAO with increasing water concentration and to also exhibit distinct spectral signatures. By taking advantage of the selective and gradual nature of the water-induced shifts and using comparisons to theoretical predictions, the assignments of TMAO's normal modes are re-examined and the structure of the hydrogen-bonded network in the vicinity of TMAO is elucidated. Agreement between experiment and theory suggests that the oxygen atom in TMAO accepts on average at least three hydrogen bonds from neighboring water molecules and that water molecules are likely not directly interacting with TMAO's methyl groups.
通过拉曼光谱和电子结构计算研究了水合作用对三甲胺 N-氧化物（TMAO）振动正则模式的影响。观察到随着水浓度的增加，水的微溶网络会导致 TMAO 的正则模式发生红移或蓝移，并表现出明显的光谱特征。通过利用水诱导位移的选择性和逐渐性，并与理论预测进行比较，重新检查了 TMAO 正则模式的分配，并阐明了 TMAO 附近氢键网络的结构。实验与理论之间的一致性表明，TMAO 的氧原子平均至少接受来自邻近水分子的三个氢键，并且水分子不太可能直接与 TMAO 的甲基相互作用。
