IQENS FROM HYDRATED LYSOZYME

We present quasi-elastic incoherent neutron scattering data on wet lys ozyme powders at water contents (grams of water/grams of protein) of h = 0.20 and 0.45, corresponding to hydration levels below and above th e full monolayer coverage of the protein surface. The data were collec ted under H2O and D2O hydration condition; using the IRIS spectrometer with a resolution of 11 mu eV(full-width). From spectra for the D2O h ydrated sample we obtain information on the protein dynamics. These sp ectra are used to separate from the H2O hydrated sample the contributi on due to the hydration water. We show that at low hydration the dynam ics of water is very slow and on the same time scale as that of the pr otein dynamics, while at higher hydration the water molecules show a f aster dynamics. The results support the idea that there are clusters o f hydration water. (C) 1998 Elsevier Science B.V. All rights reserved.