The Effect Of Type Ⅰ Antifreeze Proteins On The Equilibrium Structure Of Interfacial Layer Of Ice Crystal

Antifreeze Proteins (AFPs) is a kind of specific proteins which can inhibit the growth of ice crystals. It is recognized that AFPs can lower the freezing temperature of solution and the melting point of solution almost without changing. It is a non-colligative effect. The difference between melting and freezing temperature of the AFP solution is called'thermal hysteresis'. Many groups in molecular biology, bio-physics and bio-chemical field focus on the research on special anti-freezing properties of antifreeze proteins. Different types of antifreeze proteins(AFPs) have been isolated from organisms of ocean fishes, terrestrial insects, plants, bacteria and fungi, the gene sequences and structures of these antifreeze proteins were also determined. The results of experiment show that AFPs can bind on ice surface, the shape and the growth habits of ice crystals are different in AFPs solution and pure water with same driving force. It is a result of affinity of AFP molecular to the ice surface. The recognition of the ice surface is a key point in the functions of AFPs. According to the theory of ice crystal growth, with the given driving force, the growth morphology of ice crystals is determined by the mechanisms and kinetics of the interface, and the mechanisms and kinetics of the interface depend on the microstructure of ice crystal interface. So it suggests that the structure of ice crystal surface can be changed by AFPs. Based on the thermodynamic properties of ice crystal growth in aqueous solution and using multilayer model, Gibbs function of interfacial layer of ice crystal in pure water and antifreeze protein solution are obtained respectively. Equilibrium structure of interfacial layer of ice crystal in three kinds of typeâ… antifreeze protein solution are analyzed by using the Gibbs function. The effect on the shape of ice crystal that caused by change of equilibrium structure of interfacial layer of ice crystal is discussed. It is a theoretical evidence for understanding the experiment results that growth habits and shape of ice crystals are different in antifreeze protein solution and pure water.