Marine aerosols are produced at the ocean surface through bubble bursting and impact our climate by scattering solar radiation, nucleating clouds, and interacting with trace atmospheric gases. The aerosol surface thus plays an important role in marine aerosol atmospheric chemistry. Unfortunately, experimental single particle analysis techniques are difficult to use and fail to access the resolution, surface structure, and complexity at the surface. To overcome these limitations, molecular dynamics (MD) simulations can be used to understand how a chemical system evolves over time at the atomic level. The surfaces of marine aerosols are known experimentally to be coated by a mixture of fatty acids organized into a lipid monolayer. Recently, active enzymes such as lipases and proteases, secreted by marine bacteria, have also been discovered in nascent marine aerosols. This work uses all-atom MD to probe the dynamics of the fatty acid and protein components in the aerosol. First, simulations of randomly dispersed fatty acids are monitored to understand how carbon chain length and surface pressure affect fatty acid self-assembly into 3-dimensional lipid structures, and how those structures partition at the air-aqueous interface. Second, the enzyme <i>Burkholderia cepacia </i>lipase is added to the fatty acid mixture to study how the self-assembly dynamics are impacted by the presence of biological material. Finally, the diffusion of fatty acids at the interface is measured to understand how surface dynamics are affected by lipid orientation, composition, grouping, and surface pressure. These simulations, combined with experimental data, will allow us to draw conclusions about the partitioning of bioorganic material throughout the particle and the relationship between surface structure and aerosol chemistry.

Partitioning, diffusion, and self-assembly dynamics of protein and fatty acid mixtures in marine aerosols

2019 Fall National Meeting

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