Antifreeze proteins: computer simulation studies on the mechanism of ice growth inhibition

Abstract

Antifreeze proteins (AFPs), which are present in the bodily fluids of organisms inhabiting cold environments, function as inhibitors of ice growth by binding to certain planes of ice crystals. However, the exact mechanism of ice growth inhibition is still poorly understood as it is exceedingly difficult to experimentally analyze the molecular-scale growth kinetics of ice crystals at the planes to which the proteins bind. This review paper focuses on computer simulation studies on the mechanism of ice growth inhibition by AFPs. Recent molecular dynamics simulations of a growing ice-water interface to which protein is bound have indicated that, when the protein is stably bound to the interface, the growth rate of ice surrounding the protein decreases drastically, owing to depression of the ice melting point through the Gibbs-Thomson effect. The observed decrease in growth rate is expected to correspond to ice growth inhibition in real-world systems. In addition to presenting published simulation studies on the mechanism of ice growth inhibition by AFPs, this review also outlines the direction of future simulation studies in this field.

Coarse grained simulation reveals antifreeze properties of hyperactive antifreeze protein from Antarctic bacterium Colwellia sp.

“…AFPs exhibit ice inhibition mechanism by interacting through the gaps of ice cascade and preventing the ice crystals from linking to each other. 13,14 AFPs are classified based on their thermal hysteresis (TH) which defines their antifreeze activity under subfreezing temperature. [15][16][17] There are commonly two types of AFPs: moderate AFPs and hyperactive AFPs.…”

Dynamical mechanism of antifreeze proteins to prevent ice growth

“…However, a more careful inspection of AFPs shows a nonlinear dependence so that colligative effects are ruled out [11]. We propose a dynamical mechanism for freezing point depression by AFPs leading to a nonlinear dependence on the AFP density.…”

“…In other words more AFPs allow more ice nucleation but inhibit the cluster growth. [14,16,17] and insects [13] versus AFP concentration where (16) is used (lines) to fit the experimental data (points) of the collected data in [11]. The AFP-specific fitting parameter are given in the table.…”

“…The difference between the temperature below which the AFPs cannot stop ice nucleation and the melting temperature of ice crystals in solution is called thermal hysteresis. Experimental results illustrate a connection between protein structure and the thermal hysteresis activity on the one hand [10,11], and between the protein structure and the ice growth patterns on the other [8,12].…”

“…Molecular dynamic simulations [11,19] are limited by the computing power and running times. Moreover the interaction between AFPs and the liquid-solid interface is determined by the choice of the water model and the potential parameters [20][21][22][23][24][25][26][27][28].…”