Chemical nano-imaging of ice nucleating particles for understanding heterogeneous ice formation in atmospheric clouds
EMSL Project ID
60192
Abstract
Ice nucleation in atmospheric clouds can determine the phase of water in the clouds and affect the radiative properties, lifetime and precipitation behavior. While pure water droplets can remain liquid as low as 235 K, ice nucleating particles, particularly biological ice nuclei (IN) can initiate freezing within a few degrees of 273 K. Despite the importance of ice-nucleating particles in mixed-phase clouds, the microscopic mechanisms of heterogeneous ice nucleation remain poorly understood. Experimental measurement has remained difficult due to the combined nanometer length scales, scarcity of nucleation sites, and low energies of interaction. Here we propose a multimodal approach to measure water-protein interactions at the surface of biological IN using EMSL capabilities including in-liquid IR s-SNOM, E-SEM, and vibrational SFG. In our recently completed user proposal, 51057, we have successfully developed the capabilities of in-liquid IR s-SNOM instrument, including showing the necessary sensitivity for vibrational spectroscopy of membrane proteins and vibrational spectroscopy of the surrounding liquid water medium. In this proposal, we will apply those capabilities to understanding protein-water interactions including identifying nucleation-active sites on known IN and mapping chemical identity across the cell membrane. We will also measure ordering of the liquid water in the nanoscale region surrounding IN bacteria in order to identify protein-induced ordering of the liquid above the freezing point of water. This work will focus on IN particles including the bacteria pseudomonas syringae and ambient environment biological aerosols. We compare surface proteins and structuring of water in the aqueous surroundings for IN-active particles with measurements of oxidation deactivated IN. Drop-freeze assay measurements performed by the Perring lab at Colgate University will quantify the IN activity of samples. We will map chemical identity of biostructures across the cell membrane using in-liquid IR s-SNOM. We will measure structural ordering of interfacial water using a combination of in-liquid IR s-SNOM, vibrational SFG, and ATR IR spectroscopy. Finally, we will characterize individual freezing events using E-SEM. Our results will provide fundamental and quantitative insight into the intermolecular interactions between proteins and the surrounding water medium that govern ice nucleation. Our methods will be readily generalizable and portable to investigation of a wide range of protein-solvent, protein-lipid, and protein-protein interactions relevant to catalysis, cell-signaling, and environmental applications.
Project Details
Project type
Exploratory Research
Start Date
2021-12-01
End Date
2023-10-01
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members