Max Planck Institute for Polymer Research, 55128, Mainz, Germany.
Max Planck Institute for Chemistry, 55128, Mainz, Germany.
Chemistry. 2021 May 6;27(26):7402-7407. doi: 10.1002/chem.202004630. Epub 2021 Mar 16.
Ice nucleation-active bacteria are the most efficient ice nucleators known, enabling the crystallization of water at temperatures close to 0 °C, thereby overcoming the kinetically hindered phase transition process at these conditions. Using highly specialized ice-nucleating proteins (INPs), they can cause frost damage to plants and influence the formation of clouds and precipitation in the atmosphere. In nature, the bacteria are usually found in aqueous environments containing ions. The impact of ions on bacterial ice nucleation efficiency, however, has remained elusive. Here, we demonstrate that ions can profoundly influence the efficiency of bacterial ice nucleators in a manner that follows the Hofmeister series. Weakly hydrated ions inhibit bacterial ice nucleation whereas strongly hydrated ions apparently facilitate ice nucleation. Surface-specific sum-frequency generation spectroscopy and molecular dynamics simulations reveal that the different effects are due to specific interactions of the ions with the INPs on the surface of the bacteria. Our results demonstrate that heterogeneous ice nucleation facilitated by bacteria strongly depends upon the nature of the ions, and specific ion-protein interactions are essential for the complete description of heterogeneous ice nucleation by bacteria.
冰核活性细菌是已知最有效的冰核，能够在接近 0°C 的温度下使水结晶，从而克服这些条件下的动力学阻碍相变过程。它们利用高度专业化的冰核蛋白（INP），可能导致植物结霜，并影响大气中云的形成和降水。在自然界中，这些细菌通常存在于含有离子的水相环境中。然而，离子对细菌冰核活性效率的影响仍然难以捉摸。在这里，我们证明离子可以以遵循侯氏序列的方式深刻地影响细菌冰核的效率。弱水合离子抑制细菌冰核形成，而强水合离子显然促进冰核形成。基于表面的和频发生光谱和分子动力学模拟表明，不同的效果是由于离子与细菌表面的 INP 的特定相互作用造成的。我们的研究结果表明，细菌促进的异质冰核形成强烈依赖于离子的性质，并且特定的离子-蛋白质相互作用对于细菌异质冰核形成的完整描述是必不可少的。
