Purification and physical-chemical characteristic of a novel antifreeze protein from wheat bran(wb AFP)

A novel antifreeze protein from wheat bran(wb AFP) was purified and the amino acid composition and the secondary structure were studied. This AFP was purified by four steps:crude extracted,ammonium sulfate precipitation, anion- exchange chromatography on a DEAE- cellulose- 26 column, and size- exclusion chromatography on a Sephadex G75 column. As a result,wb AFP was purified 449.99 fold,yielding a productivity of 4.17%. The molecular weight was 11.2 ku and the thermal hysteresis activity(THA) was 0.169 ℃ at a concentration of 5 mg/m L. The result of amino acid composition of wb AFP showed that it was glycine-rich(52.08 mol%) and had a relatively high hydrophilicity. Compared with several common antifreeze glycoproteins(AFGPs) it was inferred that wb AFP was related with cold-inducible protein. The secondary structure was determined by FT-IR spectra. The results were summarized as α-helix of 25.96%²6.52%,β-sheet of 21.69%²3.78%,β-turn of 35.31%³7.61% and random coil of 13.69%¹5.08%.