title: Proton momentum distribution in a protein hydration shell.
abstract: The momentum distribution of protons in the hydration shell of a globular protein has been measured through deep inelastic neutron scattering at 180 and 290 K, below and above the crossover temperature Tc=1.23Tg, where Tg=219 K is the glass transition temperature. It is found that the mean kinetic energy of the water hydrogens shows no temperature dependence, but the measurements are accurate enough to indicate a sensible change of momentum distribution and effective potential felt by protons, compatible with the transition from a single to a double potential well. This could support the presence of tunneling effects even at room temperature, playing an important role in biological function.
authors.affiliation: Dipartimento di Fisica and Centro NAST, Università degli Studi di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Senesi
authors.forename: A
authors.initials: A
authors.lastname: Pietropaolo
authors.forename: A
authors.initials: A
authors.lastname: Bocedi
authors.forename: S E
authors.initials: SE
authors.lastname: Pagnotta
authors.forename: F
authors.initials: F
authors.lastname: Bruni
mesh_terms: D000465:Algorithms; D009502:Neutrons; D011506:Proteins / Q000737:chemistry*; D011522:Protons; D012542:Scattering, Radiation; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D011506:Proteins; D011522:Protons; D014867:Water