Detailed Analysis of the Ice Surface after Binding of an Insect Antifreeze Protein and Correlation with the Gibbs–Thomson Equation

Abstract

Antifreeze proteins (AFPs) are able to influence the ice crystal growth and the recrystallization process due to the Gibbs−Thomson effect. The binding of the AFP leads to the formation of a curved ice surface and it is generally assumed that there is a critical radius between the proteins on the ice surface that determines the maximal thermal hysteresis. Up to now, this critical radius has not yet been proven beyond doubt or only in poor agreement with the Gibbs− Thomson equation. Using molecular dynamics (MD) simulations, the resulting three-dimensional surface structure is analyzed and the location of the critical radius is identified. Our results demonstrate that the correct analysis of the geometry of the ice surface is extremely important and cannot be guessed upfront a simulation. In contrary to earlier expectations from the literature, we could show that the critical radius is not located directly between the adsorbed proteins. In addition, we showed that the minimum temperature at which the system does not freeze is in very good agreement with the value calculated with the Gibbs−Thomson equation at the critical radius, as long as dynamic system conditions are taken into account. This proves on the one hand that the Gibbs−Thomson effect is the basis of thermal hysteresis and that MD simulations are suitable for the prediction of the melting point depression.

Ice Recrystallization Inhibition by Amino Acids: The Curious Case of Alpha- and Beta-Alanine

“…Hence, this process readily occurs under these conditions, in contrast to larger molecules such as AFPs and polymers, for which overgrowth is considered a rare event at similar levels of supercooling. 41,42 Having established this difference between αand β-alanine, we suggest that inhibition and overgrown outcomes might be linked, because once the molecule becomes overgrown, the ice front can advance unimpeded and any inhibitory capacity is lost. In contrast, when the (α/β-)alanine molecule is not overgrown, it is still able to disrupt the growth of ice at or near the interface.…”

“…Hence, this process readily occurs under these conditions, in contrast to larger molecules such as AFPs and polymers, for which overgrowth is considered a rare event at similar levels of supercooling. 41 , 42 …”

A gel lattice alters the phase state of a solvent

“…24–26 Similar effects were observed in, for example, a water–glass system 27 and even in a non-porous water–protein system. 28 Therefore, if some changes in the properties of the solvent take place in the neighborhood of the TFAAA gel lattice, the properties of such a special phase can be probed with differential scanning calorimetry.…”

Modulating the Pore Architecture of Ice-Templated Dextran Microparticles Using Molecular Weight and Concentration

“…In constitutional undercooling, the accumulation of solute near the freezing front increases the undercooling due to freezing point depression, leading to a destabilizing influence on the freezing front shape, as the nucleation barrier is subsequently locally lowered . Knowledge on the dynamics of solution ice growth is of fundamental importance in their application, e.g., protein–ice interactions play a crucial role in ice-binding proteins’ ability to control ice crystal growth. − Although SFD has been applied to the micronization of pharmaceutical and food products, the quantitative description of morphology formation in SFD particles is still challenging and poorly understood. , …”