Water Dynamics in Biological Systems investigated using Neutron Scattering Techniques

Living systems can not survive in absence of the water environments which play a fundamental role in living functions. Thus in the scienti?c community many studies were and are addressed to characterize water and its dynamics properties in biological systems. However, a clear description of water in such systems has been not reached yet. In fact, the investigations performed with di?erent techniques - those based on Nuclear Magnetic Resonance or those based on Neutron Scattering - look at di?erent di?usive motions and interactions water-biomolecules, leading controversial results and hence generating many debates between scientists. In this thesis we support the idea that two water populations are present in systems such as ?phantoms?, cells and tissues, suggesting that this is a general property for bio- logical systems. Such populations are de?ned as the ?fast water? and the ?slow water? components which are characterized by dynamics properties similar to bulk water and by slower dynamics, respectively. The samples are investigated mainly using Quasi Elastic Neutron Scattering (QENS) technique which has access to atomic scale and looks at tens of picosecond/nanosecond di?usive processes. A theoretical model previously tested is used to analyze the QENS data. The strategy to analyze the data is improved in the project by using data sets from two energy resolutions - idea existing, but e?ectively implemented in this work - and introducing the con?dence limit investigation to check the true min- ima. The investigated samples are (1) sucrose in aqueous solution at 10, 20 and 30% of mass fraction percentage at 300K; (2) E. coli samples at 300, 310, and 320K, yeast and Glioma-9L at 300K; (3) right and left cerebral hemispheres and right and left cerebellum from bovine brain tissues at 300K. Successfully, the results con?rm the existence of the two predicted fast and slow water populations in biological systems. Moreover, results from phantom systems and E. coli fully validate, as expected, the theoretical approach used. Interestingly, results from Glioma-9L (tumoral cells) show faster di?usion properties for slow water component with respect to the other cells here investigated. On the other hand, results from bovine brain tissues highlight that cerebral hemispheres seem less dynamic with respect to the cerebellum. Moreover, left-right asymmetry is found in slow water component in cerebral hemispheres, while asymmetry in cerebellum is not, if any, evident.