Synthetic antifreeze to improve aircraft and transplant safety

UK chemists and medics mimic natural ice protection mechanism with applications in engineering, medicine and food

Ice is a constant bugbear to many sectors. Its sharp-edged crystals interfere with the aerodynamics of aircraft, the smooth functioning of aircraft engines and wind turbines, and slice through the delicate cell structures of food and organs awaiting transplant as they are frozen to preserve them. But some animals and microbes that have evolved to live in the frigid regions of the Earth have developed ways to avoid these effects, and researchers at the University of Warwick have now synthesised antifreeze substances that mimic the proteins nature has developed to protect against ice.

Matthew Gibson

In a paper in the Journal of the American Chemical Society, Matthew Gibson and colleagues from the Warwick Department of Chemistry and Medical School explain that they were inspired by antifreeze proteins (AFPs) that are found in some species of Arctic fish and in extremophile bacteria from the Arctic and Antarctic.

antifreeze complex
The helical iron complexes have a similar structure to natural antifreeze proteins

The proteins themselves are expensive to make and have potential for toxicity and for causing allergic reactions, so the team’s approach was to try to mimic their shape. Many of them contain helical structures which exhibit some of the properties of surfactants; that is, some parts of the structure are hydrophilic-(water-attracting and oil-repelling), and other parts are hydrophobic (the opposite). Unlike surfactants, however, these proteins don’t tend to aggregate together because of the way the hydrophilic and hydrophobic regions are arranged around the helix; this anti-aggregation property is believed to be important to their ice inhibition characteristics.(See image to the right: The helical iron complexes have a similar structure to natural antifreeze proteins)

Gibson and colleagues synthesised compounds where organic structures spiral around iron atoms. “Some of these were found to be very potent at stopping ice growing, a rare property normally only associated with antifreeze proteins,” Gibson said. “The versatile synthetic and adaptable nature of these compounds will let us fine-tune the structure to both understand the ice/water interface and develop new inhibitors for (bio)technological applications.”

Some of these applications include protecting aircraft engines and wings and wind turbines from ice buildup or designing new types of wing or turbine blade, preserving transplant organs for longer or making ice cream smoother.