Morphology Of Lipid Aggregates On Clay Minerals And Connections To Macroscopic Wettability

Assembly of the lipid fraction of soil organic matter on mineral surfaces may stabilize lipids against microbial attack and the consequent redistribution of carbon. However, such assembly is a poorly understood phenomenon that reflects underlying lipid-lipid and lipid-substrate interactions, both of which are expected to be sensitive to hydration/dehydration cycles and have the potential for significant environmental impacts. Therefore, the goal of this project is to explore the range of lipid behavior on particulate mineral surfaces, including the distribution of lipids throughout clay films and nanometer-scale topography of the aggregates themselves. We have conducted atomic force microscopy and fluorescence microscopy experiments to determine the microscale features of phospholipid-montmorillonite films, such as the lipid distribution and film topography. We have additionally performed molecular dynamics simulations of phospholipid-montmorillonite interaction to gain molecular-level data on lipid aggregate conformation and free energy of lipid-mineral binding. Lipid head group and melting temperature were found to influence lipid distribution and aggregate behavior. For example, lipids that are solid at room temperature are not distributed evenly throughout the film as are liquid lipids. Film characteristics were then quantified and compared to measurements of wettability to determine if lipid distribution and aggregate characteristics influenced macroscopic wettability.