Single-crystal neutron diffraction studies of hydrogen-bonded systems: Two recent examples from IPNS

Koetzle, Thomas F.; Piccoli, Paula M. B.; Schultz, Arthur J.

doi:10.1016/j.nima.2008.11.126

Cited by 7 publications

(6 citation statements)

References 15 publications

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“…As already mentioned before, all neutron beam lines for both elastic and inelastic scattering experiments at spallation neutron sources use the TOF technique to resolve diffraction patterns from different Miller indexes [62,63] or to record inelastic spectra at differenthω and q [64,65]. In what follows, we will briefly describe direct and inverse geometry instruments, eventually focusing our discussion on the inverse geometry spectrometers, where eV neutron scattering is widely and more effectively performed for condensed matter investigations [21,66].…”

Section: Instrumentation For Ev Neutron Scatteringmentioning

confidence: 99%

Electron volt neutron spectrometers

Pietropaolo

Senesi

2011

Physics Reports

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The advent of pulsed neutron sources has made available intense fluxes of epithermal neutrons (500 meV ≤ E≤100 eV). The possibility to open new investigations on condensed matter with eV neutron scattering techniques, is related to the development of methods, concepts and devices that drive, or are inspired by, emerging studies at this energy scale. Electron volt spectrometers have undergone continuous improvements since the construction of the first prototype instruments, but in the last decade major breakthroughs have been accomplished in terms of resolution and counting statistics, leading, for example, to the direct measurement of the proton 3-D Born-Oppenheimer potential in any material, or to quantitatively probe nuclear quantum effects in hydrogen bonded systems. This paper reports on the most effective methods and concepts for energy analysis and detection, as well as devices for the optimization of electron volt spectrometers for different applications. This is set in the context of the progress made up to date in instrument development. Starting from early stages of development of the technique, particular emphasis will be given to the Vesuvio eV spectrometer at the ISIS neutron source, the first spectrometer where extensive scientific, as well as research and development programmes have been carried out. The potential offered by this type of instrumentation, from single particle excitations to momentum distribution studies, is then put in perspective into the emerging fields of eV spectroscopy applied to cultural heritages and neutron irradiation effects in electronics

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Section: Instrumentation For Ev Neutron Scatteringmentioning

confidence: 99%

Electron volt neutron spectrometers

Pietropaolo

Senesi

2011

Physics Reports

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“…The process of generating neutrons is highly energy intensive, resulting in relatively weak neutron beam fluxes when contrasted to X-ray beam fluxes at synchrotron sources 13 . To ensure sufficient signal-to-noise ratios during data collection, it is necessary to grow crystals of suitable size and quality 14 .…”

Section: Introductionmentioning

confidence: 99%

Neutron Crystallography Data Collection and Processing for Modelling Hydrogen Atoms in Protein Structures

Schröder

Meilleur

2020

JoVE

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Neutron crystallography is a structural technique that allows determination of hydrogen atom positions within biological macromolecules, yielding mechanistically important information about protonation and hydration states while not inducing radiation damage. X-ray diffraction, in contrast, provides only limited information on the position of light atoms and the X-ray beam rapidly induces radiation damage of photosensitive cofactors and metal centers. Presented here is the workflow employed for the IMAGINE and MaNDi beamlines at Oak Ridge National Laboratory (ORNL) to obtain a neutron diffraction structure once a protein crystal of suitable size (> 0.1 mm 3 ) has been grown. We demonstrate mounting of hydrogenated protein crystals in quartz capillaries for neutron diffraction data collection. Also presented is the vapor exchange process of the mounted crystals with D 2 O-containing buffer to ensure replacement of hydrogen atoms at exchangeable sites with deuterium. The incorporation of deuterium reduces the background arising from the incoherent scattering of hydrogen atoms and prevents density cancellation caused by their negative coherent scattering length.Sample alignment and room temperature data collection strategies are illustrated using quasi-Laue data collection at IMAGINE at the High Flux Isotope Reactor (HFIR). Furthermore, crystal mounting and rapid freezing in liquid nitrogen for cryo-data collection to trap labile reaction intermediates is demonstrated at the MaNDi time-offlight instrument at the Spallation Neutron Source (SNS). Preparation of the model coordinate and diffraction data files and visualization of the neutron scattering length density (SLD) maps will also be addressed. Structure refinement against neutron dataonly or against joint X-ray/neutron data to obtain an all-atom structure of the protein of interest will finally be discussed. The process of determining a neutron structure will be demonstrated using crystals of the lytic polysaccharide monooxygenase Neurospora crassa LPMO9D, a copper-containing metalloprotein involved in the degradation of recalcitrant polysaccharides via oxidative cleavage of the glycosidic bond.

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“…Short strong hydrogen bonds in which a proton bridges donor and acceptor atoms have been a continuing topic of research as model systems for proton transfer, − with particular interest in their structure and dynamics. Here, we present an accurate description of the dynamics of proton transfer in one such system, namely, tetraacetylethane (TAE) (CH 3 CO) 2 CHCH(COCH 3 ) 2 , by bringing together time-average structure and thermal parameters from neutron-diffraction crystallography, vibrational spectroscopy from inelastic neutron scattering (INS), and density functional theory (DFT) calculations.…”

Section: Introductionmentioning

confidence: 99%

“…The general picture that emerges from past studies on these mainly nonsymmetric systems is that as the temperature increases the time-average position of the proton moves away from the donor toward a midposition and may even be transferred permanently (on time average) to the acceptor . Similarly, crystallography has shown that in TAE, despite the symmetry of the molecule, there is a tendency for the bridging proton to be closer to one of the O atoms even at room temperature, , where we henceforth denote the O atoms as O1 and O2, with the preferred O atom for the bridging proton as O1. On increasing the temperature further, the proton is found to migrate toward a position that is closer to the midpoint between the donor and the acceptor.…”

Section: Introductionmentioning

confidence: 99%

Methyl Dynamics Flattens Barrier to Proton Transfer in Crystalline Tetraacetylethane

et al. 2012

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We analyze the interplay between proton transfer in the hydrogen-bond bridge, O···H···O, and lattice dynamics in the model system tetraacetylethane (TAE) (CH(3)CO)(2)CH═CH(COCH(3))(2) using density functional theory. Lattice dynamics calculations and molecular dynamics simulations are validated against neutron scattering data. Hindrance to the cooperative reorientation of neighboring methyl groups at low temperatures gives a preferred O atom for the bridging proton. The amplitude of methyl torsions becomes larger with increasing temperature, so that the free-energy minimum for the proton becomes flat over 0.2 Å. For the isolated molecule, however, we show an almost temperature-independent symmetric double-well potential persists. This difference arises from the much higher barriers to methyl torsion in the crystal that make the region of torsional phase space that is most crucial for symmetrization poorly accessible. Consequently, the proton-transfer potential remains asymmetric though flat at the base, even at room temperature in the solid.

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Single-crystal neutron diffraction studies of hydrogen-bonded systems: Two recent examples from IPNS

Cited by 7 publications

References 15 publications

Electron volt neutron spectrometers

Electron volt neutron spectrometers

Neutron Crystallography Data Collection and Processing for Modelling Hydrogen Atoms in Protein Structures

Methyl Dynamics Flattens Barrier to Proton Transfer in Crystalline Tetraacetylethane

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