Growth Inhibition Mechanism of an Ice–Water Interface by a Mutant of Winter Flounder Antifreeze Protein: A Molecular Dynamics Study

Molecular dynamics (MD) simulations of a growing ice-water interface of a pyramidal {2021} plane in the presence of a mutant of winter flounder antifreeze protein (AFP) were conducted. Simulation results indicated that the AFP was partially surrounded by ice grown at the pyramidal interface. The AFP stably bound to the interface only when AFP hydrophobic residues bound to ice. Simulation results also indicated a drastic decrease in the growth velocity of the ice surrounding the stably bound AFP, in agreement with ice growth inhibition processes that have been observed in real systems. We confirmed that the decrease in the growth velocity of ice was attributable to the melting point depression caused by the Gibbs-Thomson effect. Simulation results suggested that the growth of ice surrounding the AFP is needed to promote stable AFP binding to the interface and subsequent ice growth inhibition. MD simulations of a growing ice-water interface of a prismatic {10_10} plane were also conducted. Neither the stable binding of the AFP to the interface nor the decrease in the growth velocity occurred for the prismatic plane. These results agree with the fact that AFPs inhibit the growth of ice only on the pyramidal planes in real systems.