Relaxational dynamics of water molecules at protein surface

Relaxational dynamics of water molecules at the surface of a C-phycocyanin protein is studied by high resolution quasi-elastic neutron scattering. The neutron quasi-elastic spectra are well described by the alpha-relaxation p rocess of mode coupling theory of supercooled liquids. The relaxation times of interfacial water exhibit a power law dependence on the wave vector Q. The average diffusion coefficient is 10 times lower than that of bulk water . This confirms that there is a retardation of water molecules at the prote in surface which is in good agreement with the results of water at the surf ace of hydrophilic model systems. (C) 2000 Elsevier Science B.V. All rights reserved.