The effects of trimethylamine N‐oxide (TMAO) on guanidinium chloride and hydrogen‐bonded networks of water are explored in this joint Raman spectroscopic and quantum chemical study. Both TMAO and guanidinium are osmolytes that affect the stability of proteins, as TMAO is known to stabilize and counteract the destabilizing effects of guanidinium. While guanidinium is very similar in chemical structure to urea, the exact mechanisms of the molecular interactions between guanidinium, TMAO, and proteins continue to be investigated. Herein, we use Raman spectroscopy to elucidate the physical interactions between TMAO and guanidinium in aqueous solutions to better understand how these important osmolytes interact with each other and affect adjacent hydrogen‐bonding networks of water. Comparing experiment to theory yields good agreement and allows for the identification and tracking of different vibrational modes. It was determined that adding TMAO into an aqueous solution of guanidinium induces a blue shift (shift to higher energy) in guanidinium's H‐N‐H bending modes, which is indicative of direct interactions between the two osmolytes and similar to the earlier results observed for TMAO interacting with urea.

中文翻译：

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拉曼光谱和量子化学研究三甲胺N-氧化物对水合胍和氢键水网络的影响

在这项拉曼光谱和量子化学联合研究中，探讨了三甲胺N-氧化物（TMAO）对氯化胍和氢键化水网络的影响。TMAO和胍盐都是影响蛋白质稳定性的渗透剂，因为已知TMAO可以稳定并抵消胍盐的去稳定作用。尽管胍盐在化学结构上与尿素非常相似，但仍在研究胍盐，TMAO和蛋白质之间的分子相互作用的确切机理。在本文中，我们使用拉曼光谱法阐明了水溶液中TMAO和胍盐之间的物理相互作用，以更好地了解这些重要的渗透物如何相互影响并影响相邻的氢键网络。将实验与理论进行比较可以很好地达成共识，并可以识别和跟踪不同的振动模式。已确定将TMAO添加到胍盐的水溶液中会导致胍盐的H-N-H弯曲模式发生蓝移（转变为更高的能量），这表明两种渗透物之间存在直接相互作用，与早期观察到的结果相似TMAO与尿素相互作用。