STUDIES ON THE PHYSICAL STATE OF WATER IN LIVING CELLS AND MODEL SYSTEMS .4. FREEZING AND THAWING POINT DEPRESSION OF WATER BY GELATIN, OXYGEN-CONTAINING POLYMERS AND UREA-DENATURED PROTEINS

  • 1 January 1983
    • journal article
    • research article
    • Vol. 15  (5) , 391-406
Abstract
Using a differential scanning calorimeter, the freezing and thawing behavior of solutions of 6 globular proteins (Hb, bovine serum albumin, .gamma.-globulin, .beta.-lactoglobulin, egg albumin and protamine sulfate); gelatin; and 3 synthetic polymers (polyvinylpyrrolidone (PVP), polyvinylmethylether (PVME) and poly(ethylene oxide) (PEO)) was studied. The native globular proteins in concentrations up to 50% produced no major change of the freezing temperature of the bulk phase water, or of the shape of the freezing peaks. The synthetic polymers caused a lowering of the freezing temperature and a widening of the freezing peaks; the peaks disappeared at the highest macromolecular concentration and exothermic peaks appeared during subsequent warming (warming exothermic peak or WEX). Gelatin behaved like the 3 polymers and so did the globular proteins after denaturation with urea but not after denaturation with sodium dodecyl sulfate (SDS). These different patterns of freezing and thawing of solutions of native globular proteins and of SDS-denatured globular proteins, on the one hand and of gelatin, PVP, PVME, PEO and urea-denatured globular proteins, on the other, parallels perfectly the different abilities of these groups of substances to reduce the solvency of the water for solutes, reported earlier. The major new conclusion from this study is that the presence of macromolecules to a concentration as high as 50% does not necessarily inhibit or even delay to any appreciable extent the freezing of the bulk phase water present. On the other hand, inhibition of ice-formation does occur in the presence of macromolecules (e.g., gelation, PVP) that cause multilayer polarization of the bulk phase water. This suggests that the bulk of water in living cells also exists in the state of polarized multilayers.