[A microcalorimetric study of collagen hydrated water in a temperature range 20-100 degrees C].

A new method for determining bound water was developed, which is based on precise measurements of the enthalpy of water evaporation from a sample using differential scanning calorimetry.

[Collagen denaturation enthalpy--nonlinear function of 4-hydroxyproline].

The results of calorimetric measurements of denaturation of collagens with different imino acid content are reported. In contrast to the existing point of view that denaturation enthalpy is a linear function of 4-oxyproline content, a nonlinear dependence was revealed. It is suggested that the reason for the observed nonlinearity is triplets of the (Gly-Pro-Hyp) type.

[Enthalpic denaturation of collagen satisfies the general relation of the change in Delta H(d) from Delta C(p) for proteins at zero hydroxyproline level].

One of the noticeable peculiarities of thermodynamics of collagen is an anomalous high magnitude of the enthalpy of denaturation delta Hd at a very low thermostability. Taking into account recent ideas about the role of hydrophobic interactions in determination of the thermodynamic function of protein denaturation, it is shown that the high magnitude of delta Hd of collagen in comparison with those of globular proteins can be explained by two factors: a significant contribution of residues of 4-hydroxyproline and small magnitude of hydrophobic interactions.

[Temperature dependence of the kinetics of renaturation of partially denatured collagen].

By the method of optical activity it has been studied the temperature dependence of the triple helical refolding process of partially denatured collagen from the skin and swim bladder of the mirror carp, and also that of the rat skin. It is shown that reducing the renaturation temperature the triple helical refolding rate increases and is in perfect agreement with the earlier observed fact [1,2]. The temperature coefficient of the reaction rate in the investigated region of temperatures remains constant, this fact ought to point to the zero value of activity energy of cis-trans isomerization process since renaturation goes on without nucleation stage.