Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan.
NTT Device Technology Labs, NTT Corporation, Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198, Japan.
J Chem Phys. 2017 Mar 14;146(10):105102. doi: 10.1063/1.4978232.
Modification of the water hydrogen bond network imposed by disaccharides is known to serve as a bioprotective agent in living organisms, though its comprehensive understanding is still yet to be reached. In this study, aiming to characterize the dynamical slowing down and destructuring effect of disaccharides, we performed broadband dielectric spectroscopy, ranging from 0.5 GHz to 12 THz, of sucrose and trehalose aqueous solutions. The destructuring effect was examined in two ways (the hydrogen bond fragmentation and disordering) and our result showed that both sucrose and trehalose exhibit an obvious destructuring effect with a similar strength, by fragmenting hydrogen bonds and distorting the tetrahedral-like structure of water. This observation strongly supports a chaotropic (structure-breaking) aspect of disaccharides on the water structure. At the same time, hydration water was found to exhibit slower dynamics and a greater reorientational cooperativity than bulk water because of the strengthened hydrogen bonds. These results lead to the conclusion that strong disaccharide-water hydrogen bonds structurally incompatible with native water-water bonds lead to the rigid but destructured hydrogen bond network around disaccharides. Another important finding in this study is that the greater dynamical slowing down of trehalose was found compared with that of sucrose, at variance with the destructuring effect where no solute dependent difference was observed. This discovery suggests that the exceptionally greater bioprotective impact especially of trehalose among disaccharides is mainly associated with the dynamical slowing down (rather than the destructuring effect).
双糖对水氢键网络的修饰被认为是生物体内的一种生物保护剂，尽管人们对其还没有全面的了解。在这项研究中，我们旨在通过宽频介电谱（从 0.5GHz 到 12THz）来研究双糖的动态减缓和去结构化效应，对蔗糖和海藻糖水溶液进行了研究。我们用两种方法（氢键的断裂和无序）来研究去结构化效应，结果表明，蔗糖和海藻糖都表现出明显的去结构化效应，它们通过断裂氢键和扭曲水的四面体结构来破坏氢键的有序性。这一观察结果强烈支持了双糖对水结构具有亲（破坏结构）的特性。同时，由于氢键的增强，水合水的动力学比体相水慢，重新取向协同性更大。这些结果得出的结论是，与天然水-水键结构不相容的强双糖-水氢键导致了双糖周围刚性但去结构化的氢键网络。本研究的另一个重要发现是，与去结构化效应不同，海藻糖的动力学减缓比蔗糖更为明显，而在去结构化效应中，没有观察到溶质依赖性差异。这一发现表明，双糖中特别是海藻糖具有异常大的生物保护作用，主要与动力学减缓（而不是去结构化效应）有关。
