Proton momentum distribution in a protein hydration shell.
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.
Senesi
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Dipartimento di Fisica and Centro NAST, Università degli Studi di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy.
Pietropaolo
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Bocedi
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Pagnotta
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Bruni
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D000465:Algorithms; D009502:Neutrons; D011506:Proteins / Q000737:chemistry*; D011522:Protons; D012542:Scattering, Radiation; D013696:Temperature; D014867:Water / Q000737:chemistry
D011506:Proteins; D011522:Protons; D014867:Water