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

Abstract

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

Link between the hydration enthalpy of lysozyme and the density of its hydration water: Electrostriction

“…This problem is resolved on the basis of the concept of subsystems of H 2 O molecules in the same physical conditions on the statistical ensemble of protein molecules and thoroughly discussed in ref. 13.…”

“…They induce inhomogeneity in the hydration shells through polarization of H 2 O dipoles and pulling of additional dipoles into the field, an effect occurring in open fluid systems. [11][12][13] The latter effect ultimately puts the H 2 O molecules (locally) closer together or, which is the same, makes the hydration shell at charged sites denser (electrostricted). The electric field performs work while polarizing the hydration water.…”

High-pressure small-angle neutron scattering studies of glucose isomerase conformation in solution

“…In the CRYSON program a hydration shell of a uniform thickness and density all over the protein surface is assumed. Theoretical studies (Merzel & Smith, 2005;Danielewicz-Ferchmin et al, 2006) however indicate that the hydration of proteins is not uniform: charged hydrophilic regions of the protein surface are strongly hydrated, while the hydration layer on the hydrophobic regions might be much thinner or non-existing.…”