The effect of freezing rate on the cooperativity of antifreeze glycopeptides

1. 1. The glycopeptide antifreezes isolated from the serum of polar fishes depress the freezing point of the fishes' body fluids in a non-colligative manner. 2. 2. The high molecular weight glycopeptides exhibit freezing-point-depressing activity which is independent of the rate of freezing. 3. 3. The antifreeze activity of the low molecular weight glycopeptides is very sensitive to the freezing rate. 4. 4. When freezing points are determined on a freezing point osmometer, the small glycopeptides appear to potentiate the activity of the larger glycopeptides. 5. 5. When freezing points are measured by gradually cooling the sample in the presence of a seed ice crystal, the potentiation is not observed. 6. 6. The apparent potentiation observed in freezing point osmometer measurements appears to be an artifact which can be explained by the sensitivity of the antifreeze activity of the small glycopeptides the rate of freezing.