Electrostatic Interactions Control the Functionality of Bacterial Ice Nucleators,Journal of the American Chemical Society

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Electrostatic Interactions Control the Functionality of Bacterial Ice Nucleators
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-03-28 , DOI: 10.1021/jacs.9b13069
M. Lukas ₁ , R. Schwidetzky ₁ , A. T. Kunert ₂ , U. Pöschl ₂ , J. Fröhlich-Nowoisky ₂ , M. Bonn ₁ , K. Meister _{1,

3}

Affiliation

Bacterial ice-nucleating proteins (INPs) promote heterogeneous ice nucleation more efficiently than any other known material. Their potential applications include cryopreservation, agriculture, biomedicine and the modulation of precipitation patterns. The details of the working mechanism of bacterial ice nucleators remain elusive, but their high activity has been shown to involve the formation of large functional INP aggregates. Here we reveal the importance of electrostatic interactions for the activity of INPs from the bacterium Pseudomonas syringae by combining a high-throughput ice nucleation assay with surface-specific sum-frequency generation spectroscopy. We determined the charge state of non-viable P. syringae as a function of pH by monitoring the degree of alignment of the interfacial water molecules and the corresponding ice nucleation activity. The net charge strongly correlates with the ice nucleation activity of the larger INP aggregates, which is minimal at the isoelectric point. In contrast, the activity of INP monomers is less affected by pH changes. We conclude that electrostatic interactions play an essential role in the formation of the highly-efficient functionally aligned INP aggregates, providing a mechanism for promoting aggregation under conditions of stress that prompt the bacteria to nucleate ice.

中文翻译：

静电相互作用控制细菌冰核器的功能

细菌冰成核蛋白 (INP) 比任何其他已知材料更有效地促进异质冰成核。它们的潜在应用包括冷冻保存、农业、生物医学和降水模式的调节。细菌冰核器工作机制的细节仍然难以捉摸，但它们的高活性已被证明涉及大型功能性 INP 聚集体的形成。在这里，我们通过将高通量冰成核分析与表面特异性和频发生光谱相结合，揭示了静电相互作用对丁香假单胞菌 INP 活性的重要性。我们确定了非活性 P 的电荷状态。通过监测界面水分子的排列程度和相应的冰成核活性，将丁香作为 pH 值的函数。净电荷与较大 INP 聚集体的冰成核活动密切相关，在等电点处最小。相比之下，INP 单体的活性受 pH 变化的影响较小。我们得出结论，静电相互作用在高效功能对齐的 INP 聚集体的形成中起着至关重要的作用，提供了一种在促使细菌成核冰的压力条件下促进聚集的机制。

更新日期：2020-03-28

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