PDF(Pubmed)
Abstract：
Ice-nucleating proteins (INpro) trigger the freezing of supercooled water droplets relevant to atmospheric, biological, and technological applications. The high ice nucleation activity of INpro isolated from the bacteria Pseudomonas syringae could be linked to the aggregation of proteins at the bacterial membrane or at the air-water interface (AWI) of droplets. Here, we imaged freezing onsets, providing direct evidence of these proposed mechanisms. High-speed cryo-microscopy identified the onset location of freezing in droplets between two protein-repellent glass slides. INpro from sterilized P. syringae (Snomax) statistically favored nucleation at the AWI of the droplets. Removing cellular fragments by filtration or adding surfactants increased the frequency of nucleation events at the AWI. On the other hand, cultivated intact bacteria cells or lipid-free droplets nucleated ice without an affinity to the AWI. Overall, we provide visual evidence that INpro from P. syringae trigger freezing at hydrophobic interfaces, such as the AWI or the bacterial membrane, with important mechanistic implications for applications of INpro.
摘要：
冰核蛋白（INpro）触发与大气相关的过冷水滴的冻结，生物，和技术应用。从细菌丁香假单胞菌中分离出的INpro的高冰核活性可能与蛋白质在细菌膜或液滴的空气-水界面（AWI）上的聚集有关。这里,我们拍摄了冻结的开始，提供这些拟议机制的直接证据。高速低温显微镜检查确定了两个蛋白质排斥玻璃载玻片之间的液滴中冻结的开始位置。来自灭菌的丁香假单胞菌(Snomax)的INpro在统计学上有利于液滴的AWI处的成核。通过过滤或添加表面活性剂去除细胞碎片增加了AWI处成核事件的频率。另一方面,培养的完整细菌细胞或无脂液滴成核冰，对AWI没有亲和力。总的来说,我们提供了视觉证据，表明丁香假单胞菌的INpro在疏水界面引发冻结，如AWI或细菌膜，对INpro的应用具有重要的机械意义。
