High pressure stabilization of collagen structure

Scanning microcalorimetry has been used to study heat denaturation of сollagen at high pressure. It has been demonstrated that an increase of the pressure by 200 MPa enlarges the structure stability by 6.8 °C. The pressure increase does not affect the cooperativity of transition and only slightly decreases its enthalpy. The changes of the partial specific volume of collagen as well as its isothermal compressibility and thermal expansibility during transition have been estimated. In contrast to denaturation of most globular proteins, denaturation of collagen proceeds with an increase of the partial specific volume at ambient pressure. Moreover, the absolute value of the collagen volume increment is distinctly greater than this in most globular proteins. The volume increment diminishes when the pressure increases due to the difference in the compressibility for folded and unfolded states. This effect is compensated to some extent by the differences in heat expansion. The volume increment alters its sign when the pressure reaches about 324 ± 20 MPa and the temperature of denaturation grows to 49.7 °C. Further pressure growing destabilizes the collagen structure.