INTEGRATION OF THEORY AND EXPERIMENT TO PROBE THE CHEMISTRY OF BIOLOGICAL MACROMOLECULES IN AQUEOUS AEROSOLS

With support from the Environmental Chemical Sciences Program in the Division of Chemistry, Professors Vicki Grassian and Rommie Amaro and their students will investigate the chemistry of biological macromolecules in aqueous aerosols, i.e. in small water droplets. Biological macromolecules, including proteins and environmental DNA, within aqueous aerosols get into the atmosphere through various pathways: from sea spray at the ocean surface, bursting of pollen grains, as well as from human emissions through breathing, sneezing and coughing.

Despite these known pathways, there remain many gaps in understanding the chemistry of biological macromolecules in aqueous aerosols. This project will fill some of these knowledge gaps by integrating laboratory experiments with computational simulations. Students will be engaged in this interdisciplinary topic from both perspectives.

The research team plans to participate in outreach activities to engage the broader public. Overall, these studies have implications for atmospheric chemistry, climate and human health.

This project utilizes an integrated, collaborative approach with a wide array of experimental tools, including spectroscopy, surface tension measurements, and mass spectrometry, along with explicitly solvated all-atom molecular dynamics simulations, to probe interfacial propensity and structure of proteins and environmental DNA (eDNA) within aqueous aerosols of different compositions. For DNA, quantitative measurements of eDNA melting, i.e. unwinding of the DNA helix, at the air/water interface in aqueous aerosols will be determined to see if it differs from bulk solutions.

These measurements will be coupled with molecular dynamics simulations to explain any differences. Additionally, experimental and theoretical studies of the reactivity of proteins and DNA with oxidants (e.g. ozone and nitrogen dioxide) and solar radiation will be carried out to determine how these perturbations impact and modify the surface propensity and structure of proteins and eDNA, as well as the melting temperature of eDNA in aqueous aerosols.

For proteins in aqueous aerosols, we will investigate the reactivity of lipase with oxidants to determine the impact on surface propensity and structure. For eDNA, double-stranded herring testes DNA with ~1000 base pairs will be used as well as shorter double stranded DNAmers, in particular, DNA double strands from the oligonucleotides with the sequence C(AT)nG (where n=2 or 4) and its complementary base pairing.

The DNAmers will be used for melting and reactivity studies. Experiments will inform simulation studies on what needs to be computed. While the experiments will guide this research, simulations will provide valuable insights and make predictions that can be tested experimentally, particularly about the behavior of biological macromolecules in aqueous aerosols, especially at the air-water interface.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.