Deutsches Elektronen-Synchrotron (DESY), D-22607 Hamburg, Germany.
Christian-Albrechts-Universität zu Kiel, Institute of Physical Chemistry, D-24118 Kiel, Germany.
Proc Natl Acad Sci U S A. 2023 Feb 28;120(9):e2214970120. doi: 10.1073/pnas.2214970120. Epub 2023 Feb 21.
Most biomolecular activity takes place in aqueous environments, and it is strongly influenced by the surrounding water molecules. The hydrogen bond networks that these water molecules form are likewise influenced by their interactions with the solutes, and thus, it is crucial to understand this reciprocal process. Glycoaldehyde (Gly), often considered the smallest sugar, represents a good template to explore the steps of solvation and determine how the organic molecule shapes the structure and hydrogen bond network of the solvating water cluster. Here, we report a broadband rotational spectroscopy study on the stepwise hydration of Gly with up to six water molecules. We reveal the preferred hydrogen bond networks formed when water molecules start to form three-dimensional (3D) topologies around an organic molecule. We observe that water self-aggregation prevails even in these early stages of microsolvation. These hydrogen bond networks manifest themselves through the insertion of the small sugar monomer in the pure water cluster in a way in which the oxygen atom framework and hydrogen bond network resemble those of the smallest three-dimensional pure water clusters. Of particular interest is the identification, in both the pentahydrate and hexahydrate, of the previously observed prismatic pure water heptamer motif. Our results show that some specific hydrogen bond networks are preferred and survive the solvation of a small organic molecule, mimicking those of pure water clusters. A many-body decomposition analysis of the interaction energy is also performed to rationalize the strength of a particular hydrogen bond, and it successfully confirms the experimental findings.
大多数生物分子的活性都发生在水相环境中，并强烈受到周围水分子的影响。这些水分子形成的氢键网络同样受到它们与溶质相互作用的影响，因此，理解这个相互作用的过程至关重要。甘油醛（Gly）通常被认为是最小的糖，它是一个很好的模板，可以用来探索溶剂化的步骤，并确定有机分子如何塑造溶剂化水团簇的结构和氢键网络。在这里，我们报告了对 Gly 与多达六个水分子逐步水合的宽带旋转光谱研究。我们揭示了当水分子开始围绕有机分子形成三维（3D）拓扑结构时形成的优先氢键网络。我们观察到，即使在这些微溶剂化的早期阶段，水分子的自聚集也占主导地位。这些氢键网络通过小分子单体在纯水中团簇中的插入表现出来，其氧原子骨架和氢键网络类似于最小的三维纯水中团簇的骨架和氢键网络。特别有趣的是，在五水合物和六水合物中，都鉴定出了以前观察到的棱柱形纯水中七聚体基元。我们的结果表明，一些特定的氢键网络是优先的，并在小分子有机分子的溶剂化过程中存活下来，模拟了纯水中团簇的氢键网络。还对相互作用能进行了多体分解分析，以合理化特定氢键的强度，并成功地证实了实验结果。
