Department of Theory & Bio-systems, Max Planck Institute for Colloids and Interfaces, Science Park, Potsdam 14476, Germany.
Purdue University, Department of Chemistry, West Lafayette, Indiana 47907, United States.
J Phys Chem B. 2021 Dec 16;125(49):13552-13564. doi: 10.1021/acs.jpcb.1c08601. Epub 2021 Dec 7.
The interplay between the local hydration shell structure, the length of hydrophobic solutes, and their identity (perfluorinated or not) remains poorly understood. We address this issue by combining Raman-multivariate curve resolution (Raman-MCR) spectroscopy, simulation, and quantum-mechanical calculations to quantify the thermodynamics and the first principle interactions behind the formation of defects in the hydration shell of alkyl-diol and perfluoroalkyl-diol chains. The hydration shell of the fluorinated diols contains substantially more defects than that of the nonfluorinated diols; these defects are water hydroxy groups that do not donate hydrogen bonds and which either point to the solute (radial-dangling OH) or not (nonradial-dangling OH). The number of radial-dangling OH defects per carbon decreases for longer chains and toward the interior of the fluorinated diols, mainly due to less favorable electrostatics and exchange interactions; nonradial-dangling OH defects per carbon increase with chain length. In contrast, the hydration shell of the nonfluorinated diols only contains radial-dangling defects, which become more abundant toward the center of the chain and for larger chains, predominantly because of more favorable dispersion interactions. These results have implications for how the folding of macromolecules, ligand binding to biomacromolecules, and chemical reactions at water-oil interfaces could be modified through the introduction of fluorinated groups or solvents.
局部水合壳结构、疏水溶质长度及其特性（全氟或非全氟）之间的相互作用仍未得到很好的理解。我们通过结合拉曼多变量曲线解析（Raman-MCR）光谱、模拟和量子力学计算来解决这个问题，以量化烷基二醇和全氟烷基二醇链水合壳中缺陷形成的热力学和第一性原理相互作用。氟化二醇的水合壳包含的缺陷比非氟化二醇多得多；这些缺陷是不提供氢键的水分子羟基，它们要么指向溶质（径向悬垂 OH），要么不指向溶质（非径向悬垂 OH）。每根碳原子的径向悬垂 OH 缺陷数量随链长的增加而减少，并且向氟化二醇的内部减少，主要是由于静电和交换相互作用不太有利；每根碳原子的非径向悬垂 OH 缺陷数量随链长的增加而增加。相比之下，非氟化二醇的水合壳仅包含径向悬垂缺陷，这些缺陷在链的中心和较大的链中变得更加丰富，主要是由于更有利的色散相互作用。这些结果对于如何通过引入氟基团或溶剂来改变大分子的折叠、配体与生物大分子的结合以及油水界面的化学反应具有重要意义。
