Heat capacity and thermodynamic characteristics of denaturation and glass transition of hydrated and anhydrous proteins.

Calorimetric measurements of absolute heat capacity have been performed for hydrated (11)S-globulin (0 < C(H(2)O) < 25%) and for lysozyme in a concentrated solution, both in the native and denatured states. The denaturation process is observed in hydrated and completely anhydrous proteins; it is accompanied by the appearance of heat capacity increment (Delta(N)(D)C(p)), as is the case for protein solutions. It has been shown that, depending on the temperature and water content, the hydrated denatured proteins can be in a highly elastic or glassy states.

[The role of vitrification in maintaining protein native structure during dehydration].

Concentration dependencies of maximum temperature (Td), thermal effect of denaturation (delta Qd) and also of glass transition temperature (Tg) were obtained in heat capacity investigation of five globular proteins with low water content. Special features of the observed Td and delta Qd dependencies, both general for polymers and specific for proteins, are discussed. The assumption is put forward that anomalously strong dependence of protein Tg on humidity, bringing together glass and denaturation transitions, results in the fact that denaturation process can be observed in completely dehydrated proteins.

[Heat capacity of hydrated and dehydrated globular proteins. The denaturing increment of heat capacity].

Absolute values of heat capacity for some hydrated globular proteins (11S globulin, ovalbumin, ribonuclease A, and lysozyme) have been studied by differential scanning calorimetry. It has been found that for proteins with bound water, as in the case of protein solutions, the heat capacity of denatured proteins is higher then prior to denaturation. Depending on temperature and humidity, the denatured proteins can be either in high-elastic or glass state.

[Denatured increments of heat capacity in globular proteins and its connection with vitrification processes].

Absolute values of heat capacity for some hydrated globular proteins have been studied by differential scanning calorimetry (DSC) method. It has been found that for the proteins with completely bound water, like in the case of protein solutions, the value of heat capacity of denatured proteins is higher than that prior to denaturation. Depending on temperature and humidity the denatured proteins can be either in high elastic or glass state.

[Structural transitions of bovine serum albumin detected during scanning calorimetry].

The calorimetry studies of temperature dependence of bovine serum albumin heat capacity for the temperature interval 20-150 degrees C and pH value varying from 4 to 9 were carried out. It is shown that in the pH range considered four types of denaturation curves differing in quantity and temperatures of endothermic pikes exist. The different types of the melting curves correspond to different types of protein domain structure.