Neurodegenerative diseases are commonly associated with the accumulation of intracellular or extracellular protein aggregates and are characterized by the misfolding of a specific protein or proteins, i. e. alpha-synuclein in Parkinson¿s disease, beta-amyloid in Alzheimer¿s disease and huntingtin in Huntington¿s disease. In vivo alpha-synuclein assemblies in several aggregated forms: oligomeric, prefibrillar and fibrillar. Even if these different forms can be produced in vitro, the nature of the proteic aggregates causing the neuronal death is still debated. We propose to use IRIS to characterize the relaxational and diffusive properties of alpha-synuclein at 293K, 323K and 363K in H2O and D2O solutions. The diffusive dynamics of fibrillar and soluble species of alpha-synuclein will be compared and investigated also in the presence of trehalose, a bioprotectant disaccharide.