Structure And Function Research Of Antifreeze Proteins

Antifreeze proteins were first identified in Antarctic fishes as the causative agents of freezing point depression of blood serum. AFPs are known macroscopically not only to prevent the growth of the incipient ice crystals within a certain range of temperature of supercooling, but also to interfere with the growth morphology of ice crystal and, in noncolligative manner, to exhibit thermal hysteresis, which lowers the freezing temperature without affecting the melting temperature.This paper comprises mainly two parts: structure and function research for some antifreeze proteins. The correlations of amino acids for antifreeze proteins are studied by use of information theory in the part of structure research. Although it doesn't have short-range statistical correlation of amino acid, the deviation of the amino acid correlation for antifreeze proteins from independent sequence is more evident than the correlation for random chosen protein. The result may show that the amino acid sequence of antifreeze protein includes more abundant information. In addition, based on amino acid composition and secondary structure parameter No,N310,N6f the antifreeze proteins, the information clustering for antifreeze proteins has been studied by use of the method increment of diversity. The result shows that AFP II and insect AFP may belong to the same group. And the secondary structure of AFP IV is predicted by use of the single-peptide theory of Chou-Fasman and the theory of correlation between secondary structure of protein and neighbor amino acid.On the other hand, with the analysis of the structure properties for the interactionbetween the AFP IV and ice, the ratio of the number of ice molecules to the number of ice and water molecules is estimated in the interfacial region. The thermal hysteresis of AFPIV solution is calculated by use of the kinetic theory that is based on the Flory-Huggins lattice modal. By estimating the parameter of K and x , the thermal hysteresis of insect AFP solution is calculated in theoretically. The theoretical results are in accordance with experiments. These study may be useful for the further understanding of the relationship between the structure and function of antifreeze protein.