Hydration water in macromolecules of biological interest: An incoherent quasi elastic neutron scattering

We report a detailed dynamical study on a hydrated protein, Lysozyme compar ing its dynamical features with those obtained in the case of aqueous solut ions whose solute is a synthetic polymer, Poly(ethylene glycol), PEG600. Th e noteworthy feature of this kind of analysis is that it is yet reasonable to apply the same theoretical model to the experimental data, even if the c omplexity of the solute molecules, in passing from the polymer to the prote in,increases dramatically. The experimental measurements performed by Incoh erent Quasi Elastic Neutron Scattering technique (IQENS) were carried out b y using hydration conditions in H2O and D2O in order to clearly evaluate: t he different contributions of the protein/polymer matrix from that of hydra tion water. A clear slowing down in the dynamics of the latter with respect to the bulk water is revealed in both the cases. (C) 1999 Elsevier Science B.V. Ltd. All rights reserved.