Inactivation of Ice Nucleating
Activity of Silver
Iodide by Antifreeze Proteins and Synthetic Polymers
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Abstract
Antifreeze proteins (AFPs) and poly(vinyl alcohol) (PVA)
are known
as anti-ice nucleating agents (anti-INAs), which inhibit ice nucleation
initiated by ice nucleating agents (INAs). Although the effectiveness
of anti-INAs depends on the type of INA, most previous studies on
anti-INAs used only a few types of biological INAs as targets to inactivate.
In this study, the effects of fish AFPs (AFP I and AFP III) and PVA
on the ice nucleating activity of silver iodide (AgI) were measured
by using emulsified solutions. Results showed that AgI was inactivated
not only by AFPs and PVA but also by two other polymers previously
not considered as anti-INAs, namely, poly(vinylpyrrolidone) and poly(ethylene
glycol). Even in the presence of AgI, a non-negligible fraction, typically
more than 10%, of emulsified droplets of these anti-INA solutions
at 1.0 mg mL<sup>–1</sup> was supercooled to about −37
°C, which corresponds to ice nucleation temperature measured
in the absence of AgI