Dynamical mechanism of antifreeze proteins to prevent ice growth

TL;DR

This paper introduces a dynamical model using Ginzburg-Landau theory to explain how antifreeze proteins inhibit ice growth by phase separation, clustering, and lowering interfacial energy, aligning with experimental observations.

Contribution

It presents a novel dynamical mechanism and a theoretical model explaining AFP action on ice growth, incorporating phase separation and hysteresis effects.

Findings

AFP accelerates pre-ice clustering

AFP reduces ice grain growth and critical nuclei size

The model aligns with experimental freezing point depression data

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.