By analyzing the returning light beam's frequency components, Weidner and his colleagues found a surprisingly dramatic result: as the temperature approached zero degrees Celcius the water molecules at the ice-nucleating protein surface suddenly became more ordered and the molecular motions become sluggish. They also found that thermal energy was very efficiently removed from the surrounding water. The results indicate that ice nucleating proteins might have a specific mechanism for heat removal and ordering water that is activated at low temperatures, Weidner said.
"We were very surprised by these results," Weidner added. "When we first saw the dramatic increase of water order with lower temperatures we believed it was an artifact." The movements of the water molecules near the ice-nucleating protein was very different than the way water had interacted with the many other proteins, lipids, carbohydrates, and other biomolecules the team had studied.
Recent studies have shown that large numbers of bacterial ice-nucleating proteins become airborne over areas like the Amazon rainforest and can spread around the globe. The proteins are among the most effective promoters of ice particle formation in the atmosphere, and have the potential to significantly influence weather patterns. Learning how P. syringae triggers frost could help teach researchers how ice particle formation occurs in the upper atmosphere.
"Understanding at the microscopic level down to the interaction of specific protein sites with water molecules the mechanism of protein-induced atmospheric ice formation will help us understand biogenic impacts on atmospheric processes and the climate," Weidner said. For a more detailed picture of protein-water interactions it will also be important to combine their spectroscopic results with computer models, he said.
|Contact: Catherine Meyers|
American Institute of Physics