Migration of the proton in the strong O—H...O hydrogen bond in urea–phosphoric acid (1/1)

2001 ◽  
Vol 57 (3) ◽  
pp. 435-439 ◽  
Author(s):  
Chick C. Wilson
Keyword(s):  
Hydrogen Bond ◽  
Data Collection ◽  
Neutron Diffraction ◽  
Phosphoric Acid ◽  
Diffraction Data ◽  
Accurate Determination ◽  
Neutron Diffraction Data ◽  
Crystal Data ◽  
Collection Method

The structure of urea–phosphoric acid is reported at a large number of temperatures in the range 150–335 K from neutron diffraction data collected using a novel multiple single-crystal data collection method. The work focuses on the behaviour of the H atom involved in the short strong O—H...O hydrogen bond in this material. The position of this atom is shown to vary significantly, by around 0.035  Å, as a function of temperature, becoming effectively centred at the highest temperatures studied. This result, only accessible due to the accurate determination of H-atom parameters by neutron diffraction, has implications for the potential governing the hydrogen bond.

Single-crystal neutron diffraction of urea-phosphoric acid: evidence for H-atom migration in a short hydrogen bond between 150 K and 350 K

2001 ◽  
Vol 216 (6) ◽  
Author(s):  
C. C. Wilson ◽  
K. Shankland ◽  
N. Shankland
Keyword(s):  
Hydrogen Bond ◽  
Neutron Diffraction ◽  
Phosphoric Acid ◽  
Single Crystal ◽  
Diffraction Data ◽  
Neutron Diffraction Data ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
Short Hydrogen Bond ◽  
Atom Migration

AbstractThe structure of urea-phosphoric acid has been refined using single-crystal neutron diffraction data collected at seven temperatures in the range 150 K to 350 K. The structure is orthorhombic, space group

Design of a novel Peltier-based cooling device and its use in neutron diffraction data collection of perdeuterated yeast pyrophosphatase

2010 ◽  
Vol 43 (5) ◽  
pp. 1113-1120 ◽  
Author(s):  
Esko Oksanen ◽  
François Dauvergne ◽  
Adrian Goldman ◽  
Monika Budayova-Spano
Keyword(s):  
Data Collection ◽  
Neutron Diffraction ◽  
Diffraction Data ◽  
Catalytic Mechanism ◽  
Inorganic Pyrophosphatase ◽  
Neutron Diffraction Data ◽  
Cooling Device ◽  
Data Set ◽  
X Ray ◽  
X Ray Crystallography

H atoms play a central role in enzymatic mechanisms, but H-atom positions cannot generally be determined by X-ray crystallography. Neutron crystallography, on the other hand, can be used to determine H-atom positions but it is experimentally very challenging. Yeast inorganic pyrophosphatase (PPase) is an essential enzyme that has been studied extensively by X-ray crystallography, yet the details of the catalytic mechanism remain incompletely understood. The temperature instability of PPase crystals has in the past prevented the collection of a neutron diffraction data set. This paper reports how the crystal growth has been optimized in temperature-controlled conditions. To stabilize the crystals during neutron data collection a Peltier cooling device that minimizes the temperature gradient along the capillary has been developed. This device allowed the collection of a full neutron diffraction data set.

Real-time swelling-series method improves the accuracy of lamellar neutron-diffraction data

2000 ◽  
Vol 56 (1) ◽  
pp. 48-54 ◽  
Author(s):  
Malcolm J. M. Darkes ◽  
Jeremy P. Bradshaw
Keyword(s):  
Quantitative Analysis ◽  
Relative Humidity ◽  
Data Collection ◽  
Neutron Diffraction ◽  
Real Time ◽  
Diffraction Data ◽  
Series Method ◽  
Neutron Diffraction Data ◽  
Smooth Curves ◽  
Structure Factors

Neutron-diffraction data were collected from stacked bilayers of 1,2-dioleoyl-sn-glycero-phosphocholine under conditions of increasing relative humidity at both 0 and 8.06% 2H2O. Over the period of data collection, the d-repeat of both swelling-series samples increased. Each family of structure factors, representing each of the five orders of diffraction, are shown to lie on smooth curves, allowing structure factors of intermediate d-repeat to be determined. In the case of the 8.06% 2H2O data, but not the 0% 2H2O data, all observed structure factors lie on a single continuous transform. 8.06% 2H2O has a net neutron-scattering density of zero; its use in neutron-diffraction experiments presents a novel application of the so-called `minus fluid' approach, without mathematical manipulation. The data are used to demonstrate the increased accuracy inherent in this real-time swelling-series approach. A quantitative analysis of errors caused by differences in d-repeat in difference subtractions is presented.

Structure of Ce2Pt6Ga15: interplanar disorder from the Ce2Ga3 layers

1996 ◽  
Vol 52 (4) ◽  
pp. 580-585 ◽  
Author(s):  
G. H. Kwei ◽  
A. C. Lawson ◽  
A. C. Larson ◽  
B. Morosin ◽  
E. M. Larson ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Diffraction Data ◽  
Diffuse Scattering ◽  
Heavy Fermion ◽  
Neutron Diffraction Data ◽  
Crystal Data ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
A Cell

The structure of the heavy fermion compound Ce2Pt6Ga15 has been determined from neutron powder and X-ray/neutron single-crystal diffraction. Examination of symmetry equivalence among the single-crystal data, as well as the good fit of the powder data to the final structural arrangement, with all the atoms on symmetry sites, suggests that the correct space group is P63/mmc. The structure is unusual in that Ce layers have 1/3 of the Ce atoms replaced by groups of three Ga atoms; distances between atoms in these planes suggest this substitution must occur in a concerted fashion. The refined occupancies lead to a stoichiometry near Ce2Pt6Ga15, consistent with such an arrangement. In addition, single-crystal neutron diffraction data show columns of weak diffuse scattering along the <001> axes, suggesting disorder arising from a lack of registration of successive Ce2Ga3 layers (lying half a cell length or 8.27 Å apart along z) and a 3 × 3 × 1 supercell. This disorder is very likely responsible for the low resistance ratio of approximately unity measured for single-crystal samples.

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