In the case of organisms living in freezing habitats, a particularly potent antifreeze protein is able to dominate the preponderance that ice has over water and “persuades” water molecules to behave in ways that benefit the protein.
Antifreeze proteins are known to have evolved to inhibit ice growth in organisms living at sub-zero temperatures, but there is no full understanding of the underlying mechanisms involved. This has led an international team of scientists to study closely the molecular structure of the antifreeze protein in order to understand how it works.
The team moved to the coldest places on the planet, including the Arctic and Antarctic, to collect antifreeze proteins from different sources. After evaluating several alternatives, the researchers focused their efforts on studying the most active antifreeze protein on record, which comes from a northern European beetle called Rhagium mordax.
Researcher Konrad Meister, a professor at the Max Planck Institute for Polymer Research in Germany and co-author of the study, explained:
Antifreeze proteins have one side that has a unique structure, the so-called ice binding side of the protein, which is distinguished by being very flat, slightly hydrophobic and has no loaded residue. But how this side is used to interact with ice is obviously very difficult to understand if you can’t directly measure an ice protein interface.
Now, for the first time, these unique biomolecules have been adsorbed into ice in the laboratory to take a closer look at the mechanisms that guide interaction when antifreeze proteins come in contact with ice.
Using vibration sum frequency generation spectroscopy, the researchers evidenced that the corrugated structure of the protein, which holds the water channels in place, causes that when these proteins come into contact with ice, rather than freezing, the water molecules are altered to have a different hydrogen bond structure and orientation.
The researchers state that this finding is key to understanding the function or working mechanism of antifreeze proteins.
In addition to broadening our knowledge on the subject, explain the authors of the study, having this knowledge could open new ways for the development of synthetic versions to help thaw aircraft, preserve organs and prevent crystals from forming in the freezer, among other applications.