Studies on the physical state of water in living cells and model systems. V. The warming exothermic reaction of frozen aqueous solution of polyvinylpyrrolidone, poly(ethylene oxide), and urea-denatured proteins.

The warming exothermic peaks (WEX) first described by Luyet and coworkers in solutions of ethylene glycol, glycerol, and polyvinylpyrrolidone(PVP) was interpreted on the basis of a devitrification phenomenon, in which rapid cooling converts normal water to amorphous ice, which devitrifies on warming to the state of normal Ice I. Our present studies of the WEX phenomenon in aqueous solutions of urea-denatured proteins, PVP, PVME, and two types of poly(ethylene oxide) led us to a different conclusion: WEX is the result of a transformation of chilled water in the state of polarized multilayers to Ice I. Among the evidence for this is the fact that WEX of the polymer-water system is indifferent to the rate of cooling between 320 degrees/min. and 1.25 degrees/min. and that polymer-water systems cooled to -70 degrees C remain viscous liquids and not (solid) vitreous ice. The transformation from water dominated by PVP, PVME, and urea-denatured proteins to Ice I can occur rapidly during warming or more slowly when the chilled polymer-water systems are kept at 223 degrees K. To effect this transformation the polymers themselves must undergo movements which tend to be retarded most by the presence of bulky side chains, as in urea-denatured proteins, and least in polymers with no side chains (e.g., Polyox WSR-N750).