Collective Transformation of Water between Hyperactive Antifreeze Proteins: RiAFPs

Abstract

We demonstrate, by molecular dynamics simulations, that water confined between a pair of insect hyperactive antifreeze proteins from the longhorn beetle Rhagium inquisitor is discontinuously expelled as the two proteins approach each other at a certain distance. The extensive striped hydrophobic–hydrophilic pattern on the surface, comprising arrays of threonine residues, enables water to form three independent ice channels through the assistance of hydroxyl groups, even at 300 K. The transformation is reminiscent of a freezing–melting transition rather than a drying transition and governs the stable protein–protein separation in the evaluation of the potential of mean force. The collectivity of water penetration or expulsion and the hysteresis in the time scale of ten nanoseconds predict a potential first-order phase transition at the limit of infinite size and provide a new framework for the water-mediated interaction between solutes.

How Size and Aggregation of Ice-Binding Proteins Control Their Ice Nucleation Efficiency

“…Indeed, the freezing efficiency of the concentrated solutions is comparable to the Δ T f = 6 K we predict for aggregation of Tm AFP to produce optimal coplanar dimers (Table S4) Our analysis indicates that the T het = 250 K attained by functionalization of surfaces with Tm AFP that expose their ice-binding surface to the solution require large aggregates, as we predict that coplanar trimers would nucleate, at best, at 247 K, and that the maximum ice nucleation temperature for an unlimited surface with Δγ bind = −55.1 mJ m −2 and τ = 10 pN is 264 K (Figure a). We conclude that aggregation can play a role in modulating the ice nucleation efficiency of antifreeze proteins, but also highlight that these small proteins have evolved to remain dispersed in solution, and are not prone to aggregate into the extended, probably coplanar ice-binding surfaces that endow bacterial INPs with their exceptional ice nucleation efficiency.…”

“…Interestingly, the Thet predicted for the trimer is close to the maximum Thet = 250 K attained by functionalization of surfaces with TmAFP that expose their ice-binding surface to the solution. 19 Our analysis indicates that aggregation can play a role in modulating the ice nucleation efficiency of antifreeze proteins, but also highlight that these small proteins have evolved to remain disperse in solution, and are not prone to aggregate 74 into the extended, probably coplanar ice-binding surfaces that endow bacterial INPs with their exceptional ice nucleation efficiency.…”

Ice Crystals

“…This finding suggests that the THF can promote water molecules from the planar pentagonal or hexagonal ring. On the other hand, Mochizuki and Matsumoto [5] presents an interesting paper related to the activities of antifreeze proteins. It is well-known that antifreeze proteins protect organisms living in subzero environments from freezing injury, which render them potential applications for cryopreservation of living cells, organs, and tissues.…”