title: 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 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.
authors.affiliation: Münster University of Applied Science, Stegerwaldstrasse 39, 48565 Steinfurt, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Kutschan
authors.affiliation: Münster University of Applied Science, Stegerwaldstrasse 39, 48565 Steinfurt, Germany and International Institute of Physics (IIP), Federal University of Rio Grande do Norte, Av. Odilon Gomes de Lima 1722, 59078-400 Natal, Brazil and Max-Planck-Institute for the Physics of Complex Systems, 01187 Dresden, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Morawetz
authors.affiliation: Alfred Wegener Institut, Am Handelshafen 12, D-27570 Bremerhaven, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Thoms
mesh_terms: D021301:Antifreeze Proteins / Q000737:chemistry*; D004058:Diffusion; D005615:Freezing; D007053:Ice; D016014:Linear Models; D008956:Models, Chemical; D013997:Time Factors; D044366:Transition Temperature
chemical_list: D021301:Antifreeze Proteins; D007053:Ice