Proton Momentum Distribution in a Protein Hydration Shell

Senesi, R.; Pietropaolo, A.; Bocedi, Alessio; Pagnotta, Sara; Bruni, Fabio

doi:10.1103/physrevlett.98.138102

Cited by 49 publications

(56 citation statements)

References 35 publications

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“…As anticipated, the 4p 2 np measured in two supercooled states shows a low-momentum narrowing along with a shoulder at about p 17 A ÿ1 , while no such feature is visible for the two stable phases. It has been shown that secondary peaks in the radial momentum distribution indicate quantum delocalization, or coherent interference of the proton over the two sites of a doublewell potential [15,26,27]. In other words, assuming that each water proton is shared by a covalent bound oxygen and a H-bonded one, the proton will be coherent over two separated sites along the H-bond direction.…”

Section: =2mentioning

confidence: 99%

Excess of Proton Mean Kinetic Energy in Supercooled Water

et al. 2008

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We find, by means of a deep inelastic neutron scattering experiment, a significant excess of proton mean kinetic energy hE k i in supercooled water, compared with that measured in stable liquid and solid phases.The measured values of hE k i at moderate degrees of supercooling do not fit the predicted linear increase with temperature observed for the water stable phases. This anomalous behavior is confirmed by the shape of the measured momentum distribution, thus supporting a likely occurrence of ground-state quantum delocalization of a proton between the O atoms of two neighboring molecules. These results strongly suggest a transition from a single-well to a double-well potential felt by the delocalized proton, with a reduced first neighbor O-O distance, in the supercooled state, as compared to ambient condition. The anomalous properties of water have attracted great attention from the scientific community for a long time and are still a topic of intense research. These remarkable properties, most pronounced in the supercooled metastable state [1], can be ascribed to water's unique structure, consisting of a random and fluctuating three-dimensional network of hydrogen bonds [2]. Despite the combined effort of powerful molecular dynamics simulation and novel experimental methods, a complete description of water is still missing. Therefore, this apparently simple liquid still represents a challenging puzzle [3][4][5]. These issues have received great interest in recent years thanks to possibilities opened by novel experimental techniques, detailed theoretical predictions, and computer simulation methods. In particular, the development of pulsed neutron sources has allowed the remarkable advance of the deep inelastic neutron scattering (DINS) technique [6,7]. DINS is based on measurements at high energy, @!, and high momentum, @q, transfers, thus providing a probe of both the short-time (t 10 ÿ15 s) dynamics and local (r 1 A) environment of the atoms in materials [6,7]. The high energy and momentum transfers achieved allow us to describe the scattering process within the framework of the impulse approximation (IA) [7][8][9]. The scattering cross section is then expressed in terms of the single particle momentum distribution, np, whose variance is related to the mean kinetic energy hE k i. In the case of water protons, for instance, the np and hE k i provide a richness of information about the potential surface that the proton experiences, including the effects of hydrogen bonding. This complements microscopic structural studies and allows a direct comparison with quantum Monte Carlo simulations [10,11]. These possibilities make the DINS technique a unique and well established tool to investigate the hydrogen bonding of water under various conditions [12 -16].Here we report on an experimental determination of the proton np and hE k i for a sample of bulk moderately supercooled water. This experiment was performed on a large sample of bulk water, thus avoiding the perturbation introduced by a confining substrate, oft...

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Section: =2mentioning

confidence: 99%

Excess of Proton Mean Kinetic Energy in Supercooled Water

et al. 2008

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“…In recent years, several DINS experiments have addressed the study of bulk water in stable liquid, 7 solid, 8 and supercooled liquid 13,14 phases and in confined geometry. [15][16][17][18] In parallel, novel simulation techniques have been employed to calculate the n(p) using open path integral simulations 19 implemented with first principles molecular dynamics 20 within the path integral Car-Parrinello molecular dynamics (PICPMD) framework. 21 The path integral simulation has access to the three dimensional n( p), and thus provides complementary information to the spherically averaged n(p) obtained via DINS a) Author to whom correspondence should be addressed.…”

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confidence: 99%

Spherical momentum distribution of the protons in hexagonal ice from modeling of inelastic neutron scattering data

Flammini

Pietropaolo

Senesi

et al. 2012

The Journal of Chemical Physics

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107

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Adiabatic and non-adiabatic quantum dynamics calculation of O(1D) + D2 OD + D reaction J. Chem. Phys. 135, 234301 (2011) New ab initio coupled potential energy surfaces for the Br(2P3/2, 2P1/2) + H2 reaction J. Chem. Phys. 135, 164311 (2011) Reaction between graphene and hydrogen under oblique injection J. Appl. Phys. 110, 084320 (2011) An experimental and computational study of the reaction of ground-state sulfur atoms with carbon disulfide J. Chem. Phys. 135, 144306 (2011) The dissociative chemisorption of methane on Ni(100): Reaction path description of mode-selective chemistry J. Chem. Phys. 135, 114701 (2011) Additional information on J. Chem. Phys. The spherical momentum distribution of the protons in ice is extracted from a high resolution deep inelastic neutron scattering experiment. Following a recent path integral Car-Parrinello molecular dynamics study, data were successfully interpreted in terms of an anisotropic Gaussian model, with a statistical accuracy comparable to that of the model independent scheme used previously, but providing more detailed information on the three dimensional potential energy surface experienced by the proton. A recently proposed theoretical concept is also employed to directly calculate the mean force from the experimental neutron Compton profile, and to evaluate the accuracy required to unambiguously resolve and extract the effective proton potential from the experimental data.

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“…In as much as 20Å is the characteristic distance between elements of biological cells, the energetics of the interactions between these elements, and hence some of the properties of water that make life possible, are determined by this state, not the molecular state. It has already been demonstrated that changes in the zero-point motion of the protons can produce binding of water molecules to dry dna 22 , and that the protons in a partial layer of water on the surface of lysozyme has a delocalized momentum distribution similar to those described here [23][24] . Simulations based on empirical potential models of water cannot be expected to give these properties correctly.…”

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confidence: 76%