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Biophys J, November 1999, p. 2850-2855, Vol. 77, No. 5
*Physiology Department, School of Medical Sciences, University of Otago, Dunedin, New Zealand; #Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111 USA; and §Department of Chemistry and Institute for Molecular Design, University of Houston, Houston, Texas 77204 USA
Premelting at the surface of ice crystals is caused by
factors such as temperature, radius of curvature, and solute
composition. When polycrystalline ice samples are warmed from well
below the equilibrium melting point, surface melting may begin at
temperatures as low as 
15°C. However, it has been reported
(Bronshteyn and Steponkus, 1993. Biophys. J.
65:1853-1865) that when polycrystalline ice was warmed in a
differential scanning calorimetry (DSC) pan, melting began at about
50°C, this extreme behavior being attributed to short-range forces.
We show that there is no driving force for such premelting, and that
for pure water samples in DSC pans curvature effects will cause
premelting typically at just a few degrees below the equilibrium
melting point. We also show that the rate of warming affects the slope
of the DSC baseline and that this might be incorrectly interpreted as
an endotherm. The work has consequences for DSC operators who use water
as a standard in systems where subfreezing runs are important.
Biophys J, November 1999, p. 2850-2855, Vol. 77, No. 5
© 1999 by the Biophysical Society 0006-3495/99/11/2850/06 $2.00
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