Water freezing and ice formation are fundamental processes for life on Earth. Ice active bacteria are the most efficient ice nucleators known. These specialized bacteria catalyse liquid-solid phase transitions of water at high subzero temperatures using ice-nucleating proteins (INPs). Despite the critical and well-recognized importance of ice bacteria on local and global precipitation, frost damage in agriculture and their potential for biomimetic freezing applications, the molecular mechanisms behind protein-driven ice formation remain largely elusive. In this project, I want to study the function of INPs at the molecular level using tools provided by recent advances of ultrafast vibrational spectroscopy. Supported by experienced scientists in the host group, I will develop a novel two-colour two-dimensional sum frequency generation (2D SFG) approach that will enable me to address the fundamental aspects of protein and water structure, molecular motion and energy flow. First, I will elucidate the secondary structure and conformation of a new model bacterial INP at a lipid membrane-water interface. Then, I will follow ultrafast energy transfer from interfacial water layers to the surrounding media to test the hypothesis that INPs can remove latent heat of nucleation from the nucleation site. Finally, I will study the effect of inter-protein distance and aggregation on the ultrafast energy transfer. The project will be supported with molecular dynamics simulations, protein engineering and cryo-electron microscopy by collaborators. My experience in non-linear optical spectroscopy combined with the excellent scientific environment in the host group will make it possible now to gain new insights into the mechanism of biological ice formation that were not accessible previously. The findings will be of interest for an interdisciplinary audience, and could provide input for next generation climate models and freezing technologies.
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