AVS 60th International Symposium and Exhibition
    Biomolecules at Aqueous Interfaces Focus Topic Monday Sessions
       Session BA+AI+AS+BI+IS+NL-MoM

Paper BA+AI+AS+BI+IS+NL-MoM10
A Molecular View of Water Interacting with Climate-active Ice Nucleating Proteins

Monday, October 28, 2013, 11:20 am, Room 203 A

Session: Biomolecules at Aqueous Interfaces
Presenter: T. Weidner, Max Planck Institute for Polymer Research, Germany
Authors: R. Pandey, Max Planck Institute for Polymer Research, Germany
J. Fröhlich, Max Planck Institute for Chemistry, Germany
U. Pöschl, Max Planck Institute for Chemistry, Germany
M. Bonn, Max Planck Institute for Polymer Research, Germany
T. Weidner, Max Planck Institute for Polymer Research, Germany
Correspondent: Click to Email
Specific bacteria, such as Pseudomonas syringae, effectively attack plants by using ice-nucleating proteins anchored to their outer cell surfaces. Ice nucleating proteins promote the local crystallization of ice at temperatures that would otherwise not allow ice formation. The frost damage caused by ice crystals then facilitates bacterial invasion of the affected plants. Ice nucleating proteins not only play an important role for agriculture, but are also very important for atmospheric processes: airborne ice-nucleating proteins have been shown to be among the most effective promoters of ice particle formation in the atmosphere. A recent survey of microorganisms in the troposphere biome by NASA has discovered massive emissions of biogenic ice nucleators from large forest areas like the amazon, which likely change precipitation patterns and may affect the global climate. To understand biogenic ice formation, a detailed molecular level picture of the mechanism by which ice-nucleating proteins interact with water molecules is important. Sum frequency generation (SFG) spectroscopy – owing to its inherent interface sensitivity – is ideally suited to determine the structure and dynamics of water molecules at interfaces. We have investigated the interaction a monolayer of the ice-nucleating protein inaZ with water using static and time-resolved SFG spectroscopy. When cooling the sample from room temperature to near-freezing temperatures (~5°C for D2O), inaZ significantly increases the structural order of water molecules in contact with inaZ proteins. This effect was not observed for liquid water surfaces without the protein or for protein monolayers which are not ice nucleators. SFG spectra in the CH and the amide I region also indicated a change of protein structure near the nucleation temperature. Femtosecond, time-resolved 2-dimensional SFG spectroscopy is used to quantify the heterogeneity of protein-bound water molecules and their structural dynamics.