Influence of Hydration on the Dynamics of Lysozyme

¹ University of Akron
² NIST
³ Kent State University
⁴ Russian Academy of Sciences

^* To whom correspondence should be addressed. E-mail: alexei{at}uakron.edu.

Submitted on January 27, 2006
Revised on March 23, 2006
Accepted on 21 June 2006

	Abstract

Quasielastic neutron and light scattering techniques along with molecular dynamics simulations were employed to study the influence of hydration on internal dynamics of lysozyme. We identified three major relaxation processes that contribute to the observed dynamics in the picosecond - nanosecond time range: (i) fluctuations of methyl groups, (ii) fast picosecond relaxation and (iii) 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 increase first the fast relaxation process and then activates the slow relaxation process at h ~ 0.2. The quasielastic scattering intensity associated with the slow process increases sharply with an increase of hydration 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, while the dependence of the fast process seems to correlate with the hydration dependence of hydrogen exchange of lysozyme.

Key Words: Protein dynamics, light scattering, neutron scattering, role of hydration

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