Certain plants and animals protect themselves against temperatures below freezing with antifreeze proteins. How the larva of the beetle Dendroides canadensis manages to withstand temperatures down to -30 degrees Celsius is reported by an international team of researchers led by Prof. Dr. Martina Havenith from the Department of Physical Chemistry II at the Ruhr-Universitt in the journal PNAS. Together with American colleagues, the RUB-researchers showed that interactions between the antifreeze proteins and water molecules contribute significantly to protection against the cold. Previously, it was assumed that the effect was only achieved through direct contact of the protein with ice crystals. The team obtained the results through a combination of terahertz spectroscopy and molecular dynamics simulations.
Protein-ice interaction: locally and over longer distances
The structure of the fire beetle antifreeze proteins resembles a triangular prism. The ice binding surface of the "prism" contains many exposed side chains, as fragments of the amino acid threonine protrude from the surface here. These side chains bind ice crystals. Up until now, it was assumed that the antifreeze proteins only interact locally with nano ice crystals and thus prevent the formation of larger ice crystals. The international group of researchers showed, however, that this interaction also takes place between proteins and ice crystals over longer distances via water molecules, which also contributes to the freeze-protection.
The dynamics of the water molecules is important for the freeze-protection
Close to the ice binding surface, the scientists observed a much slower movement of the water molecules, which differed significantly from the water movements on the non-ice-binding sides of the protein and of free water. The lower the temperature, the slower the water moved. "We suspect that the calmer water movement on the bindin
|Contact: Martina Havenith|