Abstract
In this study, we examined the effects that antifreeze proteins have on the supercooling and ice-nucleating abilities of aqueous solutions. Very little information on such nucleation currently exists. Using an automated lag time apparatus and a new analysis, we show several dilution series of Type I antifreeze proteins. Our results indicate that, above a concentration of ∼8 mg/ml, ice nucleation is enhanced rather than hindered. We discuss this unexpected result and present a new hypothesis outlining three components of polar fish blood that we believe affect its solution properties in certain situations.
Highlights
In addition to inhibiting the growth of macroscopic ice crystals in the fish’s intestinal tract, it is speculated that an important function of antifreeze molecules may be peptides (AFPs) activity is to depress the rate or efficiency of ice nucleation in the supercooled blood, tissues and other body fluids
Franks et al [6] found that AFGP is not able to depress the homogeneous nucleation temperature any more than polyvinylpyrrolidone, a synthetic polymer lacking hysteretic activity. This suggests that the AFGP molecules cannot inhibit the embryonic clusters and exhibit hysteretic activity only when macroscopic ice is present and the Kelvin effect [7] is invoked
By sorting the nucleation temperatures from each Manhattan plot and plotting the fraction of runs unfrozen as a function of temperature, referred to as a “survival curve” (Fig. 3), the inherent spread of nucleation temperatures of any given sample can be analyzed
Summary
We examined the effects that antifreeze proteins have on the supercooling and ice-nucleating abilities of aqueous solutions. Depending on the fish species, these antifreeze molecules may be peptides (AFPs) or glycopeptides (AFGPs), for which the kinetic effects on the growth of ice are well documented [1,2,3]. Wilson and Leader [9] found that the addition of AFGP molecules to solutions containing ice-nucleating proteins lowers Thet by ϳ2 °C. Du et al [14] studied ice nucleation inhibition in microsized water droplets with added Type III AFP molecules. A dilution series was carried out for various concentrations of AFP in NaCl, including zero AFP
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