Fundamentals of Biological Ice Nucleation

ended

Ice active bacteria can promote the growth of ice more effectively than any other material known. Using specialized ice nucleating proteins (INPs), they attack plants by frost damage and, when airborne in the atmosphere, they drive ice nucleation within clouds and control global precipitation patterns. The control INPs exert over water phase transitions has relevance for disciplines as diverse as climatology, plant pathology, biomedicine and material science. Despite the apparent importance, the molecular mechanisms behind INP freezing have remained largely elusive. This lack of our knowledge can be traced back to the challenges in studying protein and water structure and dynamics at the very interface between monolayers of proteins and water. With F-BioIce my team and I want to reveal the molecular details of INP function. We ask the questions: What is the structural basis for protein control of freezing? What structural motifs do proteins use to interact with water, and what is the configuration of water molecules that INPs imprint into interfacial water layers? What is the role of structural dynamics and for surface freezing? We will develop new methods based on sum frequency generation (SFG) spectroscopy to determine mode of action by which INPs interact with and manipulate water. The INPs and water structure will be obtained by combining three rising methods in the field: SFG techniques that I have been spearheading, computer simulations and cryo-electron microscopy. We will study model water surfaces and, for the first time, realistic water aerosols interacting with INPs. These new strategies could lead to a paradigm shift in the entire field of ice nucleation and a search for similar processes in ice active fungi and pollen and abiotic ice nucleators – feldspar, silica and soot. The obtained information will provide critical input for climate models and revolutionary new freezing technologies for food preservation, cryomedicine and cloud seeding.