Putting on the Squeeze: Solution NMR Investigations of Protein Structure and Hydration under High Pressure

Abstract

Ice-binding proteins (IBPs) depress the freezing point of body fluids below the melting point, resulting in a thermal hysteresis (TH) that prevents freezing of the organism. The potential of these proteins in the medical sector, in cryopreservation, in the frozen food industry, and in agriculture is enormous. We are investigating the mechanism by which IBPs interact with ice surfaces and inhibit ice growth and recrystallization. We have developed novel methods for these studies, including fluorescence microscopy techniques combined with temperature-controlled microfluidic devices. These techniques have enabled the replacement of the IBP solution surrounding an IBP-bound ice crystal by buffer, without losing the bound IBP or the TH activity. Our results show the irreversibility of the protein:ice interactions and the indirect dependence of TH activity on the protein concentration in solution. We found that the dynamics of the interactions with ice vary dramatically between different types of IBPs. From our results and other recent developments a new understanding of the mechanisms by which various IBPs act is emerging. This understanding is critical for the successful use of IBPs in cryobiological applications.