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Why and how do antifreeze proteins bind ice? An experimental study on the solution and adsorption behaviour of antifreeze proteins

Final Report Summary - PRICE (Why and how do antifreeze proteins bind ice? An experimental study on the solution and adsorption behaviour of antifreeze proteins.)

Teaser
Cold-adapted species of fish, insects and plants can survive in the harsh climate of the polar regions due to biological ‘antifreeze’ in the form of antifreeze proteins (AFPs). The AFPs ensure that the organisms remain unfrozen and therefore survive as the proteins stick to small ice crystals to inhibit further growth.

Main text
Polar fish remain unfrozen in shallow waters at subzero temperatures due to antifreeze proteins (AFPs) circulating in their blood, which reduce the freezing point of bodily fluids and block ice recrystallization. How this works is not yet fully understood, but adsorption of AFPs onto nascent ice crystals is thought to be of prime importance.

The main aim of the PRICE project (entitled ‘Why and how do antifreeze proteins bind ice? An experimental study on the solution and adsorption behaviour of antifreeze proteins’) was to unravel the key mechanisms of action of AFPs.

Researchers expressed and characterised type I and III AFPs in the laboratory. They achieved this using recombinant expression in Escherichia coli (HPLC-12 QAE type III AFP) bacteria and solid-phase peptide synthesis (HPLC-g type I AFP) following established protocols.

The team further investigated the physico-chemical properties and activities of a wide variety of antifreeze proteins. Bulk association of several types of type I and III AFPs from winter flounder and ocean pout was studied using small-angle X-ray scattering. Furthermore, in collaboration with the Prof. Bakker laboratory at AMOLF in Amsterdam advanced spectroscopic tools were used to study the structure of the hydration layer and the solution structure of fish type III AFPs.

The PRICE project advances our current understanding of the natural cryoprotective ability of AFPs which can help reduce freeze damage in various products and processes such as the cold preservation of organs and food products.