Influence of water clustering on the dynamics of hydration water at the surface of a lysozyme

¹ University of Dortmund
² University of Washington

^* To whom correspondence should be addressed. E-mail: brov{at}heineken.chemie.uni-dortmund.de.

Submitted on March 12, 2007
Revised on May 7, 2007
Accepted on 20 June 2007

	Abstract

Dynamics of hydration water at the surface of a lysozyme molecule is studied by computer simulations at various hydration levels in relation with water clustering and percolation transition. Increase of the translational mobility of water molecules at the surface of a rigid lysozyme molecule upon hydration is governed by the water-water interactions. Lysozyme dynamics strongly affect translational motions of water and this dynamic coupling is maximal at hydration levels, corresponding to the formation of a spanning water network. Anomalous diffusion of hydration water does not depend on hydration level up to monolayer coverage and reflects spatial disorder. Rotational dynamics of water molecules show stretched exponential decay at low hydrations. With increasing hydration, we observe appearance of weakly bound water molecules with bulk-like rotational dynamics, whose fraction achieves 20 to 25 % at the percolation threshold.

Key Words: anomalous diffusion, clustering and percolation, hydration water, lysozyme, protein hydration

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