The Physical and Chemical Nature of Ice Nucleating Macromolecules

HINRICH GROTHE, TU Wien, Institute of Materials Chemistry, Vienna, Austria

     Abstract Number: 266
     Working Group: Aerosol Physical Chemistry and Microphysics

Abstract
Biological aerosols are known as efficient heterogeneous ice nuclei. However, little is known about the physical and chemical specifica responsible for this effect. In 2012 Pummer et al. could show that it does not need a whole pollen grain but that water-soluble macromolecules can be separated from the original grain and the ice nucleation efficiency remains the same. On the basis of vibrational spectroscopy the same authors (Pummer et al 2013) concluded that polysaccharides are the crucial ice nucleating macromolecules (INM). Subsequently, several authors have tried to unravel the puzzle of the chemical nature of INM. Only recently, Failor et al. (2022) found that polyketide synthase and non-ribosomal peptide synthetase can be washed down from a Gram-positive bacterium acting as INM, while Burkart et al. (2021) washed down proteins from subpollen particles (SPP) which range from 77.4 µg mL−1 (highly concentrated INMs) to below 2.5 µg mL−1 (purified SPPs). Interestingly, INM were found on the surface of the whole tree and do not exclusive occur on pollen surfaces (Felgitsch et al. 2018). Additionally, INM were also detected in the aerosol phase next to the trees during precipitation events (Seifried et al. 2020).

This presentation will summarize all recent findings and will try to draw conclusions regarding chemistry and nucleation mechanism.

References
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