On mechanisms of water nuclear magnetic relaxation in protein solutions

To describe water nuclear magnetic relaxation in protein solutions a new modification of two-state model has been advanced. It is assumed that the hydration water molecules take part in two type rotation motions: fast anisotropic and slow isotropic ones, each of them can be characterized by a single correlation time. A transition of water molecule from bound state into bulk water is considered as defect arousing and is described by defect diffusion model. The model advanced allows one to describe both frequency and temperature dependences of water spin-lattice relaxation times in protein solutions and to get an information on microdynamic parameters of hydration water molecules such as life time, fraction, hindrance of local motion, etc.