MIXING ANTIFREEZE PROTEIN TYPES CHANGES ICE CRYSTAL MORPHOLOGY WITHOUT AFFECTING ANTIFREEZE ACTIVITY

All three fish antifreeze protein types (I, II and III) inhibit the gr owth of ice to form hexagonal bipyramidal ice crystals of characterist ic morphology. Mixtures of these different antifreezes produced ice cr ystals of hybrid shapes and dimensions, consistent with the different antifreeze types binding to the same ice surfaces. The activity of the mixtures mas independent of the proportions of the iso-active antifre eze protein stocks present, indicating that the different antifreezes neither attenuated nor potentiated each other's activity. We suggest t hat antifreeze protein molecules are independently active and do not r equire protein-protein interactions for ice-binding.