Abstract
Neutron Brillouin scattering and molecular dynamics simulations have been used to investigate protein hydration water density fluctuations as a function of pressure. Our results show significant differences between the pressure and density dependence of collective dynamics in bulk water and in concentrated protein solutions. Pressure-induced changes in the tetrahedral order of the water HB network have direct consequences for the high-frequency sound velocity and damping coefficients, which we find to be a sensitive probe for changes in the HB network structure as well as the wetting of biomolecular surfaces.
Highlights
Neutron Brillouin scattering and molecular dynamics simulations have been used to investigate protein hydration water density fluctuations as a function of pressure
To shed light on pressure effects on the structure of the protein hydration water hydrogen bond (HB) network and its correlation to a general slowdown of protein dynamics, we investigate here the collective dynamics of water in the presence of solvated proteins, combining coherent neutron scattering with computer simulations
Differences between collective dynamics in protein solutions, living cells, and bulk water at ambient pressure are statistically significant but small compared with pressure-induced changes
Summary
Neutron Brillouin scattering and molecular dynamics simulations have been used to investigate protein hydration water density fluctuations as a function of pressure. The applied pressure modifies the packing and order of the solvent at the protein surface, increases the protein hydration, and promotes the penetration of water in hydrophobic cavities [16, 17]. This induces swelling and eventually unfolding at pressures sufficient for denaturation [18]. The results showed that lysozyme maintains its globular structure up to at least 1,500 bar, while the density of the hydration shell slightly increases as a function of pressure This causes a moderate nonlinear change in the effective protein–protein interaction potential observed by SAXS measurements [20, 23]. Local dynamics described by mean square displacements of the protein protons [measured by quasi-elastic neutron scattering (QENS)]
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