Icebinding

Icebinding refers to the activity of a class of proteins and peptides that bind to ice crystals and modify their growth. These ice-binding proteins (IBPs), including antifreeze proteins (AFPs) and ice-structuring proteins (ISPs), are produced by a range of cold-adapted organisms such as polar fishes, terrestrial and aquatic insects, certain plants, bacteria, and fungi. The principal function of IBPs is to increase an organism’s tolerance to freezing by interfering with ice crystal formation and enlargement.

IBPs bind to specific crystallographic planes of ice, creating growth barriers that slow or redirect crystal expansion. Many IBPs can also depress the non-equilibrium freezing point of the solution, producing thermal hysteresis that separates the melting point from the freezing point. In addition, IBPs exhibit ice recrystallization inhibition (IRI) activity, reducing the growth of larger ice crystals during freeze-thaw cycles, which helps minimize cellular damage.

Diversity among IBPs is high. Fish antifreeze glycoproteins (AFGPs) and other AFP families differ in structure and ice-binding surfaces, including alpha-helical, globular, and repetitive motifs. ISPs in plants and some insects, as well as bacterial and fungal IBPs, have evolved various folds and binding strategies but share the common property of ice-contact surfaces. The exact ice-binding mechanism can vary with temperature and solvent conditions.

Beyond basic biology, IBPs are of interest for biotechnology and cryobiology, including applications in cryopreservation, frost protection in crops, frozen food processing, and improvements in ice crystal control for industrial processes.