NONEQUILIBRIUM ANTIFREEZE PEPTIDES AND THE RECRYSTALLIZATION OF ICE

Evidence is presented that the nonequilibrium antifreeze peptide (AFP) from winter flounder has a special ability to inhibit recrystallizati on in ice only when an appreciable amount of liquid is present, as is the case when the system contains salts and the temperature is not too low. In this circumstance the AFP binds to the ice surface at the ice -solution interfaces in grain boundaries, preventing migration of the solution and effectively immobilizing the boundaries. In the absence o f liquid, recrystallization inhibition appears to be a common property of many peptides. This is consistent with the view that the special e ffects of AFPs require a structural fit onto ice, and therefore requir e the AFP molecules to have the mobility to achieve that fit. Since th e concentration of salt required to induce the special recrystallizati on inhibition effects of AFPs is lower (<10 mM) than that found normal ly in physiological fluids, AFPs could play a role in the survival of organisms by preventing damage due to recrystallization. The propositi on that mobility is needed for AFP molecules to produce their special influence upon ice growth argues against any special effects of AFPs i n devitrification. (C) 1995 Academic Press, Inc.