To What Extent Is Water Responsible for the Maintenance of the Life for Warm-Blooded Organisms?

In this work, attention is mainly focused on those properties of water which are essentially changed in the physiological temperature range of warm-blooded organisms. Studying in detail the half-width of the diffusion peak in the quasi-elastic incoherent neutron scattering, the behavior of the entropy and the kinematic shear viscosity, it is shown that the character of the translational and rotational thermal motions in water radically change near T(H) ~ 315 K, which can be interpreted as the temperature of the smeared dynamic phase transition. These results for bulk pure water are completed by the analysis of the isothermic compressibility and the NMR-spectra for water-glycerol solutions. It was noted that the non-monotone temperature dependence of the isothermic compressibility (β(T)) takes also place for the water-glycerol solutions until the concentration of glycerol does not exceed 30 mol%. At that, the minimum of β(T) shifts at left when the concentration increases. All these facts give us some reasons to assume that the properties of the intracellular and extracellular fluids are close to ones for pure water. Namely therefore, we suppose that the upper temperature limit for the life of warm-blooded organisms [T(D) = (315 ± 3) K] is tightly connected with the temperature of the dynamic phase transition in water. This supposition is equivalent to the assertion that the denaturation of proteins at T ≥ T(H) is mainly provoked by the rebuilding of the H-bond network in the intracellular and extracellular fluids, which takes place at T ≥ T(H). A question why the heavy water cannot be a matrix for the intracellular and extracellular fluids is considered. The lower physiological pH limit for the life of warm-blooded organisms is discussed.