Analysis of the Ice Surface Structure after Binding of an Antifreeze Protein and its Correlation with the Gibbs-Thomson Equation

Antifreeze proteins (AFP) are able to adsorb to the ice crystal surface and to modulate the ice crystal growth and the recrystallization process due to the Gibbs-Thomson effect. The adsorption of AFP leads to the formation of a curved ice surface and it is generally believed that there is a critical ice crystal radius between the proteins on the ice surface, which determines the maximum thermal hysteresis. In this work, molecular dynamics simulations were performed to analyze the resulting structure of the ice crystal surface after adsorption of an AFP (spruce budworm AFP) and to determine the location of the critical radius.In contrast to earlier assumptions from literature, we were able to show that the critical radius is not directly between the adsorbed proteins. Furthermore, we have shown that the minimum temperature at which the system does not freeze is in very good agreement with the value calculated with the Gibbs-Thomson equation at the critical radius, provided that dynamic system conditions are taken into account. This proves that the Gibbs-Thomson effect is the basis of ice crystal growth inhibition and that MD simulations are useful for predicting melting point depression by AFP. ... mehrThe knowledge gained in this study will also be applied to other molecules and systems in the future.