Stability of proteins at subzero temperatures: Thermodynamics and some ecological consequences

Abstract

The thermal stability of proteins is limited by two temperatures at which cooperative transitions are observed which either render the protein inactive or cause it to change its function. The thermodynamic features of the cold-induced transition are analysed in detail and its ecological significance is briefly discussed. It is shown that the common assumption of the the temperature independence of the heat capacity change associated with the transition, coupled with extrapolations of heat denaturation data to subzero temperatures is unrealistic and does not provide correct estimates of cold-induced transition temperatures. Now that techniques exist for direct studies of proteins in undercooled solutions, down to -40°C, such methods are to be preferred over the use of cryosolvents, chaotropes and pH-destabi1ization, as means of bringing the cold-induced transition into a temperature range where it can be more conveniently investigated. © 1991, IUPAC