[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. An increase of their content can cause a decrease in the denaturation enthalpy in accord with the water-bridge structure and due to the minimum enthalpy effect of stabilization of the triplets as compared to triplets of other type.