Influence of Hydration on the Dynamics of Lysozyme

Abstract

Quasielastic neutron and light-scattering techniques along with molecular dynamics simulations were employed to study the influence of hydration on the internal dynamics of lysozyme. We identified three major relaxation processes that contribute to the observed dynamics in the picosecond to nanosecond time range: 1), fluctuations of methyl groups; 2), fast picosecond relaxation; and 3), a slow relaxation process. A low-temperature onset of anharmonicity at T ; 100 K is ascribed to methyl-group dynamics that is not sensitive to hydration level. The increase of hydration level seems to first increase the fast relaxation process and then activate the slow relaxation process at h ; 0.2. The quasielastic scattering intensity associated with the slow process increases sharply with an increase of hydration to above h ; 0.2. Activation of the slow process is responsible for the dynamical transition at T ; 200 K. The dependence of the slow process on hydration correlates with the hydration dependence of the enzymatic activity of lysozyme, whereas the dependence of the fast process seems to correlate with the hydration dependence of hydrogen exchange of lysozyme.

Hydration water and peptide dynamics – two sides of a coin. A neutron scattering and adiabatic calorimetry study at low hydration and cryogenic temperatures

“…Further, the glass-like transition is suppressed in our dry peptide sample (Fig. 4), as has also been reported for dry proteins, 11,26 indicating that the solvent molecules are involved with the activation of diffusive anharmonic motions.…”

“…1 and 2) show three temperature dependence regions, in accordance with previous studies. 9,11,13 For the nominally dry peptide we did not observe a break in the temperature trend of hu 2 i values up to B240 K, as expected (Fig. 1, inset).…”

“…Thus the methyl group dynamics are expected to be faster, as compared to larger proteins. 9,11,33 Therefore, it cannot be ruled out that we can observe it within our timescale, with the instrument and conditions used. It can be argued, indeed, that they might not be observed in the same temperature range as in a globular protein.…”

“…Nevertheless, many aspects regarding its particular structure near the surface and inside biological macromolecules as well as its link to biological function are still under discussion. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Proteins are known to have a ''limiting hydration'' necessary for function, and thus there must exist a link between hydration and protein functional properties.…”

From shell to cell: neutron scattering studies of biological water dynamics and coupling to activity

“…The term 'slaving' has been used to express that water can impose its dynamical fingerprint on a protein 11,12 . Cryo-temperature dependent neutron scattering experiments revealed the solvent dependence of dynamical transitions in soluble proteins [13][14][15][16][17][18][19][20][21] and in RNA 22 and provided insights into the coupling between them. Molecular dynamics simulations suggested the onset of water translational diffusion to be at the origin of the dynamical transition 23,24 .…”