Isopiestic determination of water binding by fish antifreeze glycoproteins

The effectiveness of water binding of antifreeze glycoproteins relative to hemoglobin, cytochrome c and polyvinylpyrrolidone was determined by analyzing results obtained in an isopiestic study at 25 degrees C. The net weight of water which moved from a protein/NaCl aqueous sample to a saturated NaCl reference solution increased in the order: antifreeze glycoprotein, hemoglobin, polyvinylpyrrolidone and cytochrome c. Since the glycoproteins were least effective in transporting water we conclude that, of the proteins studied, the glycoprotein was most effective in binding water under equilibrium conditions at 25 degrees C.