Max Planck Institute for Polymer Research, 55128 Mainz, Germany.
Max Planck Institute for Chemistry, 55128 Mainz, Germany.
J Phys Chem Lett. 2021 Nov 11;12(44):10783-10787. doi: 10.1021/acs.jpclett.1c03118. Epub 2021 Nov 1.
Ice-nucleating proteins (INPs) from are among the most active ice nucleators known, enabling ice formation at temperatures close to the melting point of water. The working mechanisms of INPs remain elusive, but their ice nucleation activity has been proposed to depend on the ability to form large INP aggregates. Here, we provide experimental evidence that INPs alone are not sufficient to achieve maximum freezing efficiency and that intact membranes are critical. Ice nucleation measurements of phospholipids and lipopolysaccharides show that these membrane components are not part of the active nucleation site but rather enable INP assembly. Substantially improved ice nucleation by INP assemblies is observed for deuterated water, indicating stabilization of assemblies by the stronger hydrogen bonds of DO. Together, these results show that the degree of order/disorder and the assembly size are critically important in determining the extent to which bacterial INPs can facilitate ice nucleation.
来自 的冰核蛋白（INP）是已知最活跃的冰核之一，能够在接近水的冰点的温度下促进冰的形成。INP 的工作机制仍不清楚，但据推测其冰核活性取决于形成大的 INP 聚集体的能力。在这里，我们提供了实验证据表明，单独的 INP 不足以实现最大的冷冻效率，完整的膜是至关重要的。对磷脂和脂多糖的冰核测量表明，这些膜成分不是活性成核部位的一部分，而是能够促进 INP 组装。对于氘化水，观察到 INP 组装体的冰核形成得到了显著改善，表明 DO 的更强氢键稳定了组装体。这些结果表明，有序/无序程度和组装体大小对于确定细菌 INP 促进冰核形成的程度至关重要。
