Water provides the driving force for the assembly and stability of many cellular components. Despite its impact on biological functions, a nanoscale understanding of the relationship between its structure and dynamics under soft confinement has remained elusive. As expected, water in contact with biological membranes recovers its bulk density and dynamics at ∼1 nm from phospholipid headgroups but surprisingly enhances its intermediate range order (IRO) over a distance, at least, twice as large. Here, we explore how the IRO is related to the water’s hydrogen-bond network (HBN) and its coordination defects. We characterize the increased IRO by an alteration of the HBN up to more than eight coordination shells of hydration water. The HBN analysis emphasizes the existence of a bound–unbound water interface at ∼0.8 nm from the membrane. The unbound water has a distribution of defects intermediate between bound and bulk water, but with density and dynamics similar to bulk, while bound water has reduced thermal energy and many more HBN defects than low-temperature water. This observation could be fundamental for developing nanoscale models of biological interactions and for understanding how alteration of the water structure and topology, for example, due to changes in extracellular ions concentration, could affect diseases and signaling. More generally, it gives us a different perspective to study nanoconfined water.

中文翻译：

---

磷脂膜之间的纳米水域网络拓扑。

水为许多细胞组件的组装和稳定性提供了驱动力。尽管它对生物学功能有影响，但在软约束下对其结构与动力学之间关系的纳米尺度理解仍然难以捉摸。正如预期的那样，与生物膜接触的水在约1 nm处从磷脂头基中恢复了其堆积密度和动力学，但出人意料地在至少两倍大的距离上提高了其中间范围有序（IRO）。在这里，我们探索IRO与水的氢键网络（HBN）及其配位缺陷之间的关系。我们通过改变HBN直至多达八个以上的水合水来表征IRO增加。HBN分析强调离膜约0.8 nm处存在束缚-未束缚的水界面。未结合水的缺陷分布在结合水和散装水之间，但密度和动力学类似于散装水，而结合水比低温水具有更低的热能和更多的HBN缺陷。该观察对于开发生物相互作用的纳米尺度模型以及理解水结构和拓扑结构的变化（例如由于细胞外离子浓度的变化）如何影响疾病和信号传递可能是基础的。更一般而言，它为我们研究纳米受限水提供了不同的视角。该观察对于开发生物相互作用的纳米级模型以及理解水结构和拓扑结构的变化（例如由于细胞外离子浓度的变化）如何影响疾病和信号传递可能是基础的。更一般而言，它为我们研究纳米受限水提供了不同的视角。该观察对于开发生物相互作用的纳米级模型以及理解水结构和拓扑结构的变化（例如由于细胞外离子浓度的变化）如何影响疾病和信号传递可能是基础的。更一般而言，它为我们研究纳米受限水提供了不同的视角。