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-Universität 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 binding surface of the protein facilitates the docking of the nano ice crystals," Martina Havenith speculated. In accordance with this, the researchers found little change in the movement of the water molecules in an inactive mutant of the antifreeze protein.
More efficient than in fish
The antifreeze proteins of the fire-coloured beetle are ten to one hundred times more active than those of Arctic and Antarctic fish that need to protect themselves against temperatures of -1.9 degrees Celsius. The insects achieve this high antifreeze activity through the combination of the two strategies: direct interaction between proteins and ice and interaction via water molecules.
Observing the role of the solvent
"The special role of water in natural antifreeze is an excellent example demonstrating that when looking at the function of a biomolecule, you not only have to consider its 3D structure, but also its entire environment - especially the solvent; in this case water," Prof. Havenith said. This topic is the focus of the cluster of excellence RESOLV, which was launched on the 1st November 2012 at the RUB and whose spokesperson is Martina Havenith. The current studies were funded by the Volkswagen Foundation.
Ruhr-University Bochum: http://www.ruhr-uni-bochum.de
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
Claims that Ai Hin was faking pregnancy to get better treatment have been debunked by leading panda expert
The recent release of Susan Greenfields new book and the film Lucy, both of which are dependent on tired misconceptions or dubious theories about the brain, suggest one worrying conclusion: we are running out of myths about the brain. So here are some new ones, to keep things mysterious
These are the siphonophores, some 180 known species of gelatinous strings that can grow to 100 feet long, making them some of the longest critters on the planet. But instead of growing as a single body like virtually every other animal, siphonophores clone themselves thousands of times over into half a dozen different types of specialized cloned bodies, all strung together to work as a team---a very deadly team at that.
Researchers who study memory have had a thrilling couple of years. Some have erased memories in people with electroshock therapy, for example. Others have figured out, in mice, how to create false memories and even turn bad memories into good ones.
Hunting bats don't just listen out for male frogs' mating calls: they can also use echolocation to detect when the frogs inflate their throat sacs
A crèche of 30 dinosaur infants looked over by an older animal shows that even terrible lizards needed a night away from the kids
Families have identifiable collections of microbes that travel with them. It can take just 24 hours for the microbes to take over a new house
When rabbits were domesticated, around 100 regions of their genome changed to make them less fearful, but the variations are not fixed
Scientists never understood what became of the Paleo-Eskimos who once peopled the north. Now they know—and there's new reason to miss them
NOAA whittles down initial list of 66 species to be covered by Endangered Species Act