Cold denaturation of proteins

By taking advantage of the phase behavior of water, high pressure can significantly lower the freezing point of an aqueous protein solution. In this way, using high-resolution, high-pressure NMR techniques, one can investigate not only pressure denaturation but also cold denaturation of proteins. After an overview of compression effects on dynamic and hydrodynamic behavior of water and heavy water at subzero temperatures, the main part of this contribution is devoted to selected results from recent pressure and cold denaturation NMR studies of Ribonuclease A. The cold denatured state of Ribonuclease A contains partial secondary structures in contract to its thermally denatured state which contains little or no stable hydrogen bond structures. It was interesting to find that the pattern of protection factors for the pressure and cold denatured states of Ribonuclease A obtained by hydrogen exchange experiments parallels the pattern of protection factors for the folding intermediate of Ribonuclease A reported by Udgoaonkar and Baldwin on the basis of their pulsed hydrogen experiments.