Dynamical mechanism of antifreeze proteins to prevent ice growth

Abstract

The fascinating ability of algae, insects and fishes to survive at temperatures below normal freezing is realized by antifreeze proteins (AFPs). These are surface-active molecules and interact with the diffusive water/ice interface thus preventing complete solidification. We propose a new dynamical mechanism on how these proteins inhibit the freezing of water. We apply a Ginzburg-Landau type approach to describe the phase separation in the two-component system (ice, AFP). The free energy density involves two fields: one for the ice phase with a low AFP concentration, and one for liquid water with a high AFP concentration. The time evolution of the ice reveals microstructures resulting from phase separation in the presence of AFPs. We observed a faster clustering of pre-ice structure connected to a locking of grain size by the action of AFP, which is an essentially dynamical process. The adsorption of additional water molecules is inhibited and the further growth of ice grains stopped. The interfacial energy between ice and water is lowered allowing the AFPs to form smaller critical ice nuclei. Similar to a hysteresis in magnetic materials we observe a thermodynamic hysteresis leading to a nonlinear density dependence of the freezing point depression in agreement with the experiments.

Growth suppression of ice crystal basal face in the presence of a moderate ice-binding protein does not confer hyperactivity

“…Note that some previous studies (28,40) reported the possibility that IBPs may decrease the free energies of ice-water interfaces, resulting in faster growth kinetics and more pronounced morphological instability. In this study, the effect of fcIBP11 on the free energy of ice-water interfaces remains uncertain.…”

Thermal hysteresis activity of antifreeze proteins: A model based on fractional statistics theory of adsorption

“…A similar effect was reported by DeLuca et al [13], who reported that an increment in the AFP activity is observed when the type III AFP is linked to other proteins and thus its size is increased. From a theoretical point of view, several models have been proposed relating thermal hysteresis activity with the portion of ice surface occupied by AFPs [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. These approaches stimulate the researchers to develop more refined theoretical solutions for the adsorption thermodynamics of complex adsorbates (in this case, proteins of different sizes and shapes).…”

Antifreeze proteins and homogeneous nucleation: On the physical determinants impeding ice crystal growth

“…This would suggest that AFPs avoid the growth of a post-critical ice nucleus rather than impeding the formation of an ice nucleus. Nevertheless, despite a growing body of the literature on ice-binding proteins, [6][7][8][9]11,12,[14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] a complete study on the antifreeze effect of the AFP concentration on the ice growth is still missing.…”