Properties of Hydration Shells of Protein Molecules at their Pressure‐ and Temperature‐Induced Native‐Denatured Transition

Properties of water at the surface of biomolecules are important for their conformational stability. The behaviour of hydrating water at protein transition (t) pressures Pt and temperatures Tt , with the points (Pt,Tt ) lying in the Native–Denatured (N-D) transition line, is studied. Hydration shells at the hydrophilic regions of protein molecules with surface charge density σ are investigated with the help of the equation of state of water in an open system. The local values of σ rather close to each other (σD ≈0.3 C m−2) are found for six different experimental lines of the N-D transition found in the literature. The values σD correspond to the crossings of the total pressure (Pt+Π) vs σ isotherms at different Tt (Π−electrostriction pressure). The pressures Pt and temperatures Tt appear to be related with some selected sites at the surfaces of the protein molecules.