Ice Growth Habits in Solutions Containing Insect Thermal Hysteresis Proteins Compared to Those with Fish Antifreeze Proteins.

BACKGROUND: The details of the mechanism of action of ice binding proteins (IBPs) have been intensively studied and hotly debated for some decades. OBJECTIVE: To outline the inherent differences between the manifested growth of single ice crystals grown in the presence of fish antifreeze proteins and those grown with insect thermal hysteresis proteins. MATERIALS AND METHODS: Observations of single ice crystals taking the shape of hexagonal bipyramids using a nanolitre osmometer and grown in the presence of so called antifreeze glycopeptides from the Antarctic fish species Dissostichus maswoni, are compared with those seen with insect thermal hysteresis proteins from Tenebrio molitor, grown in a Ramsay chamber, which grow as lemon-shaped crystals. RESULTS: The difference in growth allows us to infer methods of action of each class of protein. Further, below the thermal hysteresis gap, or non-equilibrium freezing point, the explosive growth seen with fish antifreeze proteins is demonstrated but is yet to be fully explored. CONCLUSION: Ice growth behaviour can be used to indicate or infer the crystal faces to which the molecules may have adsorbed.