title: Collective dynamics of protein hydration water by brillouin neutron spectroscopy.
abstract: By a detailed experimental study of THz dynamics in the ribonuclease protein, we could detect the propagation of coherent collective density fluctuations within the protein hydration shell. The emerging picture indicates the presence of both a dispersing mode, traveling with a speed greater than 3000 m/s, and a nondispersing one, characterized by an almost constant energy of 6-7 meV. In agreement with molecular dynamics simulations [Phys. Rev. Lett. 2002, 89, 275501], the features of the dispersion curves closely resemble those observed in pure liquid water [Phys. Rev. E: Stat. Phys., Plasmas, Fluids, Relat. Interdiscip. Top. 2004, 69, 061203]. On the contrary, the observed damping factors are much larger than in bulk water, with the dispersing mode becoming overdamped at Q = 0.6 A(-1) already. Such novel experimental findings are discussed as a dynamic signature of the disordering effect induced by the protein surface on the local structure of water.
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Perugia, Via Pascoli I-06123 Perugia, Italy. andrea.orecchini@pg.infn.it
authors.forename: Andrea
authors.initials: A
authors.lastname: Orecchini
authors.forename: Alessandro
authors.initials: A
authors.lastname: Paciaroni
authors.forename: Alessio
authors.initials: A
authors.lastname: De Francesco
authors.forename: Caterina
authors.initials: C
authors.lastname: Petrillo
authors.forename: Francesco
authors.initials: F
authors.lastname: Sacchetti
mesh_terms: D003198:Computer Simulation; D008958:Models, Molecular; D015394:Molecular Structure; D009502:Neutrons; D012259:Ribonuclease, Pancreatic / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods*; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D012259:Ribonuclease, Pancreatic