Atomic diffusion in liquid gallium and gallium-nickel alloys probed by quasielastic neutron scattering and molecular dynamic simulations.

The atomic mobility in liquid pure gallium and a gallium-nickel alloy with 2 at% of nickel is studied experimentally by incoherent quasielastic neutron scattering. The integral diffusion coefficients for all-atom diffusion are derived from the experimental data at different temperatures. DFT-basedmolecular dynamics (MD) is used to find numerically the diffusion coefficient of liquid gallium at different temperatures, and numerical theory results well agree with the experimental findings at temperatures below 500 K.

Probing spin waves in CoO nanoparticles for magnonics applications.

The magnetic properties of spinel nanoparticles can be controlled by synthesizing particles of a specific shape and size. The synthesized nanorods, nanodots and cubic nanoparticles have different crystal planes selectively exposed on the surface. The surface effects on the static magnetic properties are well documented, while their influence on spin waves dispersion is still being debated.

Light-Induced Conformational Flexibility of the Orange Carotenoid Protein Studied by Quasielastic Neutron Scattering with Illumination.

The orange carotenoid protein plays a vital role in the photoprotection of cyanobacteria and exhibits a significant structural change upon photoactivation. A rarely considered aspect is the importance of internal protein dynamics in facilitating the structural transition to the active state. In this study, we use quasielastic neutron scattering under (in situ) blue light illumination for the first time to directly probe the protein dynamics of the orange carotenoid protein in the dark-adapted and active states.

Investigating H Adsorption in Isostructural Metal-Organic Frameworks M-CUK-1 (M = Co and Mg) through Experimental and Theoretical Studies.

A combined experimental and theoretical study of H adsorption was carried out in Co-CUK-1 and Mg-CUK-1, two isostructural metal-organic frameworks (MOFs) that consist of M ions (M = Co and Mg) coordinated to pyridine-2,4-dicarboxylate (pdc) and OH ligands. These MOFs possess saturated metal centers in distorted octahedral environments and narrow pore sizes and display high chemical and thermal stability. Previous experimental studies revealed that Co-CUK-1 exhibits a H uptake of 183 cm g at 77 K/1.

CSPEC: The cold chopper spectrometer of the ESS, a detailed overview prior to commissioning.

CSPEC is the cold chopper spectrometer of the European Spallation Source (ESS) and will come online with the ESS beam on the target. CSPEC will be the first cold chopper spectrometer on a long pulsed spallation source, which provides great opportunities in terms of signal to noise and novel measuring schemes. We provide a detailed overview of the instrument, scientific design considerations, and engineering requirements.

Quasielastic neutron scattering study on proton dynamics assisted by water and ammonia molecules confined in MIL-53.

Dynamics of water and other small molecules confined in nanoporous materials is one of the current topics in condensed matter physics. One popular host material is a benzenedicarboxylate-bridging metal (III) complex abbreviated to MIL-53, whose chemical formula is M(OH)[CH(CO)R] where M = Cr, Al, Fe and R = H, OH, NH, COOH. These materials absorb not only water but also ammonia molecules.

Self-diffusion in single component liquid metals: a case study of mercury.

We report the temperature dependent atomic dynamics in mercury investigated with quasi-elastic neutron scattering between 240 and 350 K. The self-diffusivity follows an Arrhenius behavior over the entire investigated temperature range, with an activation energy of 41.8 ± 1.

Diffusivelike Motions in a Solvent-Free Protein-Polymer Hybrid.

The interaction between proteins and hydration water stabilizes protein structure and promotes functional dynamics, with water translational motions enabling protein flexibility. Engineered solvent-free protein-polymer hybrids have been shown to preserve protein structure, function, and dynamics. Here, we used neutron scattering, protein and polymer perdeuteration, and molecular dynamics simulations to explore how a polymer dynamically replaces water.

Water Mobility in the Interfacial Liquid Layer of Ice/Clay Nanocomposites.

At solid/ice interfaces, a premelting layer is formed at temperatures below the melting point of bulk water. However, the structural and dynamic properties within the premelting layer have been a topic of intense debate. Herein, we determined the translational diffusion coefficient D of water in ice/clay nanocomposites serving as model systems for permafrost by quasi-elastic neutron scattering.

Dynamics of porous and amorphous magnesium borohydride to understand solid state Mg-ion-conductors.

Rechargeable solid-state magnesium batteries are considered for high energy density storage and usage in mobile applications as well as to store energy from intermittent energy sources, triggering intense research for suitable electrode and electrolyte materials. Recently, magnesium borohydride, Mg(BH), was found to be an effective precursor for solid-state Mg-ion conductors. During the mechanochemical synthesis of these Mg-ion conductors, amorphous Mg(BH) is typically formed and it was postulated that this amorphous phase promotes the conductivity.

Complex molecular dynamics of a symmetric model discotic liquid crystal revealed by broadband dielectric, thermal and neutron spectroscopy.

The molecular dynamics of the triphenylene-based discotic liquid crystal HAT6 is investigated by broadband dielectric spectroscopy, advanced dynamical calorimetry and neutron scattering. Differential scanning calorimetry in combination with X-ray scattering reveals that HAT6 has a plastic crystalline phase at low temperatures, a hexagonally ordered liquid crystalline phase at higher temperatures and undergoes a clearing transition at even higher temperatures. The dielectric spectra show several relaxation processes: a localized γ-relaxation at lower temperatures and a so called α2-relaxation at higher temperatures.

Strong Adverse Contribution of Conformational Dynamics to Streptavidin-Biotin Binding.

Molecular dynamics plays an important role for the biological function of proteins. For protein ligand interactions, changes of conformational entropy of protein and hydration layer are relevant for the binding process. Quasielastic neutron scattering (QENS) was used to investigate differences in protein dynamics and conformational entropy of ligand-bound and ligand-free streptavidin.

Solution Structure and Conformational Flexibility in the Active State of the Orange Carotenoid Protein. Part II: Quasielastic Neutron Scattering.

Orange carotenoid proteins (OCPs), which are protecting cyanobacterial light-harvesting antennae from photodamage, undergo a pronounced structural change upon light absorption. In addition, the active state is anticipated to boost a significantly higher molecular flexibility similar to a "molten globule" state. Here, we used quasielastic neutron scattering to directly characterize the vibrational and conformational molecular dynamics of OCP in its ground and active states, respectively, on the picosecond time scale.

A quasielastic and inelastic neutron scattering study of the alkaline and alkaline-earth borohydrides LiBH and Mg(BH) and the mixture LiBH + Mg(BH).

Quasielastic neutron scattering was used to investigate the low energy transfer dynamics of the complex borohydrides Mg(BH4)2 in the α- and β-modifications, LiBH4 in the low and high temperature crystal structure, and an 1 : 1 molar mixture of LiBH4 + α-Mg(BH4)2. All investigated compounds show a rich dynamic behaviour below an energy range of ΔE = 10 meV with the superposition of rotational dynamics of the constituent [BH4]- anions and low lying lattice modes. For Mg(BH4)2, the rotational diffusion of the [BH4] units was found to be much more activated in the metastable β-polymorph compared to the α-phase, and the low lying lattice modes are even softer in the former crystal structure.

Homogeneous and heterogeneous dynamics in native and denatured bovine serum albumin.

A characteristic property of unfolded and disordered proteins is their high molecular flexibility, which enables the exploration of a large conformational space. We present neutron scattering experiments on the dynamics of denatured and native folded bovine serum albumin (BSA) in solution. Global protein diffusion and internal macromolecular dynamics were measured using quasielastic neutron time-of-flight and backscattering spectroscopy on the picosecond to nanosecond time- and Ångstrom length-scale.

Anomalies in the low frequency vibrational density of states for a polymer with intrinsic microporosity - the Boson peak of PIM-1.

Polymers with intrinsic microporosity are promising candidates for the active separation layer in gas separation membranes. Here, the vibrational density of states (VDOS) for PIM-1, the prototypical polymer with intrinsic microporosity, is investigated by means of inelastic neutron scattering. The results are compared to data measured for a more conventional high-performance polyimide used in gas separation membranes (Matrimid).

Dynamic processes in biological membrane mimics revealed by quasielastic neutron scattering.

Neutron scattering is a powerful tool to study relaxation processes in biological membrane mimics in space and time. Combining different inelastic and quasielastic neutron scattering techniques, a large dynamic range can be covered: from atomic to mesoscopic lengths and from femto- to some hundreds of nanoseconds in time. This allows studies on e.

Solvent Dynamics in Solutions of PNIPAM in Water/Methanol Mixtures-A Quasi-Elastic Neutron Scattering Study.

The solvent dynamics of concentrated solutions of poly(N-isopropylacrylamide) (PNIPAM, 25 wt %) in water/methanol mixtures (85:15 v/v) are measured with the aim of shedding light onto the cononsolvency effect. Quasi-elastic neutron scattering (QENS) with contrast variation has been carried out at temperatures below and above the cloud point by using in the first set of experiments the mixture H2O:d-MeOD (d-MeOD denotes fully deuterated methanol) as a solvent and in the second set of experiments the mixture D2O:MeOH (MeOH denotes methanol). As a reference, bulk H2O, bulk MeOH and the mixtures H2O:d-MeOD and D2O:MeOH (both 85:15 v/v) have been investigated as well.

Hydrogen dynamics in β-Mg(BH4)2 on the picosecond timescale.

A quasielastic neutron scattering study on β-Mg(BH4)2 has been performed to investigate the hydrogen dynamics on the picosecond time-scale. Both vibrational and rotational motions of the [BH4](-) tetrahedra contribute to the signal at low energy transfers. A comprehensive analysis of the elastic and quasielastic incoherent structure factors allowed the separation of different parts.

Water response to ganglioside GM1 surface remodelling.

Background: Gangliosides are biological glycolipids participating in rafts, structural and functional domains of cell membranes. Their headgroups are able to assume different conformations when packed on the surface of an aggregate, more lying or standing. Switching between different conformations is possible, and is a collective event.

Photoactivation Reduces Side-Chain Dynamics of a LOV Photoreceptor.

We used neutron-scattering experiments to probe the conformational dynamics of the light, oxygen, voltage (LOV) photoreceptor PpSB1-LOV from Pseudomonas putida in both the dark and light states. Global protein diffusion and internal macromolecular dynamics were measured using incoherent neutron time-of-flight and backscattering spectroscopy on the picosecond to nanosecond timescales. Global protein diffusion of PpSB1-LOV is not influenced by photoactivation.

Alzheimer's peptide amyloid-β, fragment 22-40, perturbs lipid dynamics.

The peptide amyloid-β (Aβ) interacts with membranes of cells in the human brain and is associated with Alzheimer's disease (AD). The intercalation of Aβ in membranes alters membrane properties, including the structure and lipid dynamics. Any change in the membrane lipid dynamics will affect essential membrane processes, such as energy conversion, signal transduction and amyloid precursor protein (APP) processing, and may result in the observed neurotoxicity associated with the disease.

Extension of the LOPLS-AA Force Field for Alcohols, Esters, and Monoolein Bilayers and its Validation by Neutron Scattering Experiments.

The recently presented LOPLS-AA all-atom force field for long hydrocarbon chains, based on the OPLS-AA force field, was extended to alcohols, esters, and glyceryl monooleate (GMO) lipids as a model lipid. Dihedral angles were fitted against high level ab initio calculations, and ester charges were increased to improve their hydration properties. Additionally, the ester Lennard-Jones parameters were readjusted to reproduce experimental liquid bulk properties, densities, and heats of vaporization.

Dynamics of tetrahydrofuran as minority component in a mixture with poly(2-(dimethylamino)ethyl methacrylate): A neutron scattering and dielectric spectroscopy investigation.

We have investigated a mixture of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and tetrahydrofuran (THF) (70 wt. % PDMAEMA/30 wt. % THF) by combining dielectric spectroscopy and quasielastic neutron scattering (QENS) on a labelled sample, focusing on the dynamics of the THF molecules.