A chance observation by researchers at Queen's University in Canada may end a decades-long controversy over the exact mechanism by which antifreeze proteins bind to the surface of ice crystals.
A chance observation by researchers at Queen's University in Canada may end a decades-long controversy over the exact mechanism by which antifreeze proteins bind to the surface of ice crystals.
"We got a nice picture of water molecules attached to the ice binding site of the protein," says Peter Davies, a professor in the Department of Biochemistry at Queen's University in Canada and a world expert in the study of antifreeze proteins. "In fact, we achieved a breakthrough at a discounted price."
Anticoagulant proteins (The term in Wikipedia) are a family of proteins that bind to the surface of ice crystals while preventing the growth and formation of the ice. Fish, insects, bacteria and plants that exist in sub-zero environments (degrees Celsius) all rely on these proteins for their survival. These proteins are also important in many areas of industry, including the ice cream and frozen yogurt industries that utilize these proteins in order to control the development of the ice crystals.
The implications of these findings go far beyond the preparation of low-fat and high-moisture ice creams that maintain a rich and creamy texture. Understanding the exact mechanism by which these proteins bind to the surface of ice crystals may allow researchers and industrialists to develop new, efficient and diverse proteins for the benefit of a number of applications ranging from increasing the resistance of crops to freezing to improving the ability to preserve organs and tissues for transplantation.
While determining the crystal structure of an antifreeze protein from an Antarctic bacterium, the researchers were lucky enough to observe an exposed ice-binding site of the protein - a valuable find in the field of crystallography of these proteins.
The ice-binding area in antifreeze proteins contains both hydrophobic (water-repelling) and hydrophilic (water-attracting) groups. Until now, the exact role of these opposing forces in ice binding has been unknown.
The researchers believe that although the presence of water-repellent regions seem counterintuitive for a protein that binds to ice, they hypothesize that the function of these regions is to force the water molecules located near the surface of the protein to gather in the form of an ice-like cage that simulates the structure of the water molecules present Because of the surface of the ice crystal. The hydrophilic regions on the surface of the protein anchor this cage structure to the protein through hydrogen bonds. The end result of this mechanism is that as long as the water molecules are anchored to this protein, it is unable to bind to ice.
