064 The dynamic nature of antifreeze protein activity

Abstract

Ice-binding proteins include antifreeze proteins (AFPs), ice nucleating proteins, ice adhesins, and ice recrystallization inhibition proteins. These proteins have great potential for controlling ice growth in various cryobiological and industrial applications. AFPs have been investigated for several decades. However, due to the unstable nature of ice crystals near their melting temperature, few experimental projects had addressed the kinetics of the AFP – ice interaction. When AFPs adsorb to ice they produce a thermal hysteresis (TH), which is the temperature gap between melting temperature of the ice in the solution of AFP, and the lowered temperature at which the crystal starts to grow. The basis for the relationship between TH and the concentration of AFP in solution is not known. We have used temperature-controlled microfluidic devices and fluorescently labeled AFPs to follow on the surface concentration of AFP on ice crystals. We find that the binding of the proteins to the ice surfaces is irreversible (”Superheating of ice crystals in antifreeze protein solutions” PNAS 2010 and ”Microfluidic experiments reveal that antifreeze proteins bound to ice crystals suffice to prevent their growth” PNAS 2013). Furthermore, we confirm that TH increases with the time that an ice crystal is expose to solutions that contain AFPs. We also find a direct connection between the surface concentrations of AFP and the measured TH. These experimental findings allow for testing different theoretical models regarding the mechanism of AFP’s ability to inhibit ice growth. Understanding the dynamic nature of AFP action will allow for rational design of their use in cryobiology applications. Source of funding: This research was funded by the Europe Research Council (ERC), the Israel Science Foundation (ISF), and the Canadian Institutes of Health Research (CIHR). Conflict of interest: None declared. ido.braslavsky@mail.huji.ac.il