Paradoxical effects on ice nucleation are intrinsic to a small winter flounder antifreeze protein.

Antifreeze proteins (AFPs) bind to ice in solutions, resulting in non-colligative freezing point depression; however, their effects on ice nucleation are not well understood. The predominant plasma AFP of winter flounder (Pseudopleuronectes americanus) is AFP6, which is an amphiphilic alpha helix. In this study, AFP6 and modified constructs were produced as fusion proteins in Escherichia coli, subjected to proteolysis when required and purified prior to use.

Interaction of curcumin with a winter flounder alpha-helical antifreeze protein.

The winter flounder, Pseudopleuronectes americanus, synthesizes a variety of alpha-helical antifreeze proteins (AFPs) that adhere to ice and inhibit its growth. The best studied of these is AFP6, which is a 37-residue protein abundant in the flounder blood plasma during winter. Curcumin from the turmeric plant (Curcuma longa) was found to interact with AFP6 in aqueous solutions, resulting in measurable changes in the curcumin, but not in the protein.