Browsing by Author "van Eijck, L"

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    Central atom size effect on the structure of group 14 tetratolyls
    (Wiley-VCH Verlag Berlin, 2009-07-06) Ng, MCC; Craig, DJ; Harper, JB; van Eijck, L; Stride, JA
    Size matters! The structure and dynamics of the tetratolyl Group 14 elements, which were probed by using high-resolution inelastic neutron scattering spectra, show a remarkable dependence on the size of the central atom. The para-methyl groups at the periphery of the molecules constitute the frontier intermolecular interactions of increasingly larger tetrahedra, which becomes critical at the molecular radius of the Si and Ge analogues. © 2009, Wiley-VCH Verlag Berlin
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    Dynamical coupling of intrinsically disordered proteins and their hydration water: comparison with folded soluble and membrane proteins
    (Cell Press, 2012-07-03) Gallat, FX; Laganowsky, A; Wood, K; Gabel, F; van Eijck, L; Wuttke, J; Moulin, M; Haertlein, M; Eisenberg, D; Colletier, JP; Zaccai, G; Weik, M
    Hydration water is vital for various macromolecular biological activities, such as specific ligand recognition, enzyme activity, response to receptor binding, and energy transduction. Without hydration water, proteins would not fold correctly and would lack the conformational flexibility that animates their three-dimensional structures. Motions in globular, soluble proteins are thought to be governed to a certain extent by hydration-water dynamics, yet it is not known whether this relationship holds true for other protein classes in general and whether, in turn, the structural nature of a protein also influences water motions. Here, we provide insight into the coupling between hydration-water dynamics and atomic motions in intrinsically disordered proteins (IDP), a largely unexplored class of proteins that, in contrast to folded proteins, lack a well-defined three-dimensional structure. We investigated the human IDP tau, which is involved in the pathogenic processes accompanying Alzheimer disease. Combining neutron scattering and protein perdeuteration, we found similar atomic mean-square displacements over a large temperature range for the tau protein and its hydration water, indicating intimate coupling between them. This is in contrast to the behavior of folded proteins of similar molecular weight, such as the globular, soluble maltose-binding protein and the membrane protein bacteriorhodopsin, which display moderate to weak coupling, respectively. The extracted mean square displacements also reveal a greater motional flexibility of IDP compared with globular, folded proteins and more restricted water motions on the IDP surface. The results provide evidence that protein and hydration-water motions mutually affect and shape each other, and that there is a gradient of coupling across different protein classes that may play a functional role in macromolecular activity in a cellular context. © 2012, Cell Press.
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    High/low-moment phase transition in hexagonal Mn-Fe-P-Si compounds
    (American Physical Society, 2012-07-30) Dung, NH; Zhang, L; Ou, ZQ; Zhao, L; van Eijck, L; Mulders, AM; Avdeev, M; Suard, E; van Dijk, NH; Brück, E
    Using high-resolution neutron diffraction measurements for Mn-rich hexagonal Mn-Fe-P-Si compounds, we show that the substitution of Mn for Fe on the 3f sites results in a linear decrease of the Fe/Mn(3f) magnetic moments, while the Mn(3g) magnetic moments remain constant. With increasing temperature, the Mn(3g) magnetic moments show almost no change, while the Fe/Mn(3f) moments decrease quickly when the transition temperature is approached. The reduction of the magnetic moments at the transition temperature and in the high-temperature range is discussed based on changes in interatomic distances and lattice parameters and high-temperature magnetic-susceptibility measurement. © 2012, American Physical Society.
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    Hydrogen in porous tetrahydrofuran clathrate hydrate
    (Wiley-VCH Verlag Berlin, 2008-06-23) Mulder, FM; Wagemaker, M; van Eijck, L; Kearley, GJ
    The lack of practical methods for hydrogen storage is still a major bottleneck in the realization of an energy economy based on hydrogen as energy carrier.([1]) Storage within solid-state clathrate hydrates,([2-4]) and in the clathrote hydrate of tetrohydrofuran (THF), has been recently reported.([5,6]) In the latter case, stabilization by THF is claimed to reduce the operation pressure by several orders of magnitude close to room temperature. Here, we apply in situ neutron diffraction to show that-in contrast to previous reports([5,6]) - hydrogen (deuterium) occupies the small cages of the clathrote hydrate only to 30% (at 274 K and 90.5 bar). Such a D-2 load is equivalent to 0.27 wt. % of stored H-2. In addition, we show that a surplus of D2O results in the formation of additional D2O ice Ih instead of in the production of sub-stoichiometric clathrate that is stabilized by loaded hydrogen (as was reported in ref. [6]). Structure-refinement studies show that [D-8]THF is dynamically disordered, while it fills each of the large cages of [D-8]THF center dot 17D(2)O stoichiometrically. Our results show that the clathrate hydrate takes up hydrogen rapidly at pressures between 60 and 90 bar (at about 270 K). At temperatures above approximate to 220 K, the H-storage characteristics of the clathrate hydrate have similarities with those of surface-adsorption materials, such as nanoporous zeolites and metal-organic frameworks,([7,8]) but at lower temperatures, the adsorption rates slow down because of reduced D-2 diffusion between the small cages. © 2008, Wiley-VCH Verlag Berlin
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    Localized relaxational dynamics of succinonitrile
    (American Chemical Society, 2009-08-20) van Eijck, L; Best, AS; Long, S; Fernandez-Alonso, F; MacFarlane, D; Forsyth, M; Kearley, GJ
    Succinonitrile (N C-CH2-CH2-C N) is a good ionic conductor, when doped with an ionic compound, at room temperature, where it is in its plastic crystalline phase (Long et al. Solid State Ionics 2003, 161. 105: Alarco et al. Nat. Mater. 2004, 3, 476). We report on the relaxational dynamics of the plastic phase near the two first-order phase transitions and on the effect of dissolving a salt in the plastic matrix by quasi-elastic neutron scattering. At 240 K, the three observed relaxations are localized and we can describe their dynamics (iota approximate to 1.7, 17, and 140 ps) to a certain extent from a model using a single molecule that was proposed by Bee et al. allowing for all conformations in its unit cell (space group IM3M). The extent of the localized motion as observed is however larger than that predicted by the model and suggests that the isomerization of succinonitrile is correlated with a jump to the nearest neighbor site ill the unit cell. The salt containing system is known to be it good ionic conductor, and our results show that the effect of the ions on the succinonitrile matrix is homogeneous. Because the isomerizations and rotations are governed by intermolecular interactions, the dissolved ions have ail effect over ail extended range. Due to the addition of the salt, the dynamics of one of the components (iota approximate to 17 ps) shows more diffusive character at 300 K. The calculated upper limit of the corresponding diffusion constant of succinonitrile in the electrolyte is a factor 30 higher than what is reported for the ions. Our results suggest that the succinonitrile diffusion is caused by nearest neighbor jumps that are localized on the observed length and time scales. © 2009, American Chemical Society
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    Neutron diffraction study on the magnetic structure of Fe2P-based Mn0.66Fe1.29P1-xSix melt-spun ribbons
    (Elsevier Science BV., 2013-08-01) Ou, ZQ; Zhang, L; Dung, NH; van Eijck, L; Mulders, AM; Avdeev, M; van Dijk, NH; Brück, E
    We report on the magnetic and structural properties of Mn0.66Fe1.29P1−xSix melt-spun ribbons with 0.34≤x≤0.42 that are promising candidates for high-temperature magnetocaloric applications. A magnetic moment of up to 4.57 μB/f.u. for x=0.34 indicates high magnetic density in the system, which is certainly advantageous for the magnetocaloric effects. Introducing site disorder at the 3g site by replacing 1/3 of Fe with Mn appears to enhance the magnetic interaction, while the strong magnetoelastic coupling is maintained. This site disorder also shows a stabilizing effect on the hexagonal crystal structure, which is maintained to a high Si content. The moment alignment within the crystallographic unit cell is also affected when the Si content is increased from x=0.34 to 0.42 in the Mn0.66Fe1.29P1−xSix compounds as the canting angle with respect to the c-direction increases. © 2013, Elsevier Ltd.
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    Protein surface and core dynamics show concerted hydration-dependent activation
    (Wiley-V C H Verlag GMBH, 2013-01-01) Wood, K; Gallat, FX; Otten, R; van Heel, AJ; Lethier, M; van Eijck, L; Moulin, M; Haertlein, M; Weik, M; Mulder, FAA
    By specifically labeling leucine/valine methyl groups and lysine side chains “inside” and “outside” dynamics of proteins on the nanosecond timescale are compared using neutron scattering (see picture). Surprisingly, both groups display similar dynamics as a function of temperature, and the buried hydrophobic core is sensitive to hydration and undergoes a dynamical transition. © 2013, Wiley-VCH Verlag GmbH & Co. KGaA