Department of Physics and Astronomy, University of Leeds, Leeds, UK.
ISIS Facility, STFC Rutherford Appleton Laboratory, Didcot, UK.
Phys Chem Chem Phys. 2020 Mar 4;22(9):4924-4937. doi: 10.1039/c9cp06324b.
The presence of magnesium perchlorate (Mg(ClO4)2) as the dominant ionic compound in the Martian regolith and the recent discovery of a subsurface lake on Mars suggests that beneath the Martian surface may lie an aqueous environment suitable for life, rich in chaotropic ions. Closer to Earth, terrestrial organisms use osmolytes, such as trimethylamine N-oxide (TMAO), to overcome the biologically damaging effects of pressure. While previous studies have revealed that Mg(ClO4)2 acts to modify water structure as if it has been pressurized, little is known about the competing effects of chaotropes and kosmotropes. Here we ask whether TMAO can help to preserve the hydrogen bond network of water against the pressurising effect of Mg(ClO4)2? We address this question using neutron scattering, computational modelling using Empirical Potential Structure Refinement (EPSR) analysis, and a new approach to quantifying hydrogen bond conformations and energies. We find that the addition of 1.0 M TMAO to 0.2 M Mg(ClO4)2 or to 2.7 M Mg(ClO4)2 is capable of partially restoring the hydrogen bond network of water, and the fraction of water molecules in energetically unfavourable conformations. This suggests that terrestrial protecting osmolytes could provide a protective mechanism to the extremes found in Martian environments for biological systems.
高氯酸镁（Mg(ClO4)2）作为火星土壤中主要的离子化合物的存在，以及最近在火星上发现的一个地下湖泊，表明火星表面以下可能存在适合生命存在的水相环境，富含离液离子。在地球附近，陆地生物使用渗透剂，如三甲胺 N-氧化物（TMAO），来克服压力对生物的破坏性影响。虽然之前的研究表明，Mg(ClO4)2 可以改变水的结构，使其看起来受到了压力的影响，但对于离液剂和向液剂的竞争作用知之甚少。在这里，我们想知道 TMAO 是否可以帮助保护水的氢键网络免受 Mg(ClO4)2 的加压影响？我们使用中子散射、使用经验势结构细化 (EPSR) 分析的计算建模以及一种新的方法来量化氢键构象和能量，来回答这个问题。我们发现，向 0.2 M Mg(ClO4)2 或 2.7 M Mg(ClO4)2 中添加 1.0 M TMAO 能够部分恢复水的氢键网络，以及处于不利能量构象的水分子比例。这表明陆地保护渗透剂可以为火星环境中的生物系统提供一种保护机制，以应对极端条件。
