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The Oak Ridge National Laboratory is planning to build the Second Target Station (STS) at the Spallation Neutron Source (SNS). STS will host a suite of novel instruments that complement the First Target Station’s beamline capabilities by offering an increased flux for cold neutrons and a broader wavelength bandwidth. A novel neutron imaging beamline, named the Complex, Unique, and Powerful Imaging Instrument for Dynamics (CUPI2D), is among the first eight instruments that will be commissioned at STS as part of the construction project. CUPI2D is designed for a broad range of neutron imaging scientific applications, such as energy storage and conversion (batteries and fuel cells), materials science and engineering (additive manufacturing, superalloys, and archaeometry), nuclear materials (novel cladding materials, nuclear fuel, and moderators), cementitious materials, biology/medical/dental applications (regenerative medicine and cancer), and life sciences (plant–soil interactions and nutrient dynamics). The innovation of this instrument lies in the utilization of a high flux of wavelength-separated cold neutrons to perform real time in situ neutron grating interferometry and Bragg edge imaging—with a wavelength resolution of δλ/λ ≈ 0.3%—simultaneously when required, across a broad range of length and time scales. This manuscript briefly describes the science enabled at CUPI2D based on its unique capabilities. The preliminary beamline performance, a design concept, and future development requirements are also presented.

In-field material analysis is an important area of analysis, having the great advantage that the analytical measurement is performed at the site where the material is located, leading to faster and more informed decision making. This turns out to be very important for some very specific materials, such as high explosives or chemical/bio warfare agents, especially if the area to be inspected was thoroughly cleaned. The latter makes sample collection extremely difficult. However, regardless of how clean a surface is, trace amounts of the material of interest are still left behind. A combination of optical and acoustical methods that leads to improved detection efficiencies is presented. Surface-enhanced Raman spectroscopy (SERS) is a surface-sensitive technique that greatly enhances the Raman scattering by factors up to 1015, leading to detection down to the single molecule level. This technique requires very careful substrate preparation as well as very large spectroscopy equipment, which are not viable for infield analysis. In order to adapt SERS for in-field analysis, acoustic manipulation of metallic particles is used. Aggregation of particles on the surface of interest leads toa strong Raman enhancement factor, which will allow for much less sensitive handheld Raman instruments to be used in the field. Currently, preliminary results have achieved 103 enhancement, with much higher enhancement possible.

The structure of layer-by-layer (LbL) deposited nanofilm coatings consists of alternating polyethylenimine (PEI) and polystyrenesulfonate (PSS) films deposited on a single crystal quartz substrate. LbL-deposited nanofilms were investigated by neutron reflectomery (NR) in contact with water in the static and fluid shear stress conditions. The fluid shear stress was applied through a laminar flow of the liquid parallel to the quartz/polymer interface in a custom-built solid-liquid interface cell. The scattering length density profiles obtained from NR results of these polyelectrolyte multilayers (PEM), measured under different shear conditions, showed proportional decrease of volume fraction of water hydrating the polymers. For the highest shear rate applied (ca. 6800 s(-1)) the water volume fraction decreased by approximately 7%. The decrease of the volume fraction of water was homogeneous through the thickness of the film. Since there were not any significant changes in the total polymer thickness, it resulted in negative osmotic pressures in the film. The PEM films were compared with the behavior of thin films of thermoresponsive poly(N-isopropylacrylamide) (pNIPAM) deposited via spin-coating. The PEM and pNIPAM differ in their interactions with water molecules, and they showed opposite behaviors under the fluid shear stress. In both cases the polymer hydration was reversible upon the restoration of static conditions. A theoretical explanation is given to explain this difference in the effect of shear on hydration of polymeric thin films.

Neutron reflectometry was used to monitor structural variations in surface-supported dimyristoylphosphatidycholine (DMPC) bilayers induced by the addition of Triton X-100, a surfactant commonly used to aid solubilization of membrane proteins, and the coaddition of a membrane spanning nonionic amphiphilic triblock copolymer, (PEO117–PPO47–PEO117, Pluronic F98). Surfactant addition causes slight compression of the bilayer thickness and the creation of a distinct EO layer that increases the hydrophilic layer proximal to the supporting substrate (i.e., a water and EO gap between the lipid bilayer and quartz) to 6.8 ± 0.4 A. Addition of the triblock copolymer into the DMPC:Triton X-100 bilayer increases the complexity of (broadens) the lipid phase transition, further compresses the bilayer, and continues to expand the proximal hydrophilic layer thickness. The observed structural changes are temperature dependent with transmembrane polymer insertion achieved at 37 °C, leading to a compressed membrane thickness ...

Endothelial cells, master gatekeepers of the cardiovascular system, line its inner boundary from the heart to distant capillaries constantly exposed to blood flow. Interendothelial signaling and the monolayers adhesion to the underlying collagen-rich basal lamina are key in physiology and disease. Using neutron scattering, we report the first ever interfacial structure of endothelial monolayers under dynamic flow conditions mimicking the cardiovascular system. Endothelial adhesion (defined as the separation distance ℓ between the basal cell membrane and solid boundary) is explained using developed interfacial potentials and intramembrane segregation of specific adhesion proteins. Our method provides a powerful tool for the biophysical study of cellular layer adhesion strength in living tissues.

Neutron Reflectometry (NR) has long been used as a tool to study soft-condensed materials, including bio-related structures. For example, it has been applied to study model biomembranes to facilita...

Mixed carbohydrate systems are of special interest for the food and non-food industry as they offer a versatile range of unique and novel functional properties. However, intense research is required to understand the complex processes occurring in such systems on a molecular level and to be able to modify them aim-oriented. In food, characteristic properties are based on the physicochemical functions of the biopolymers added. Thus, small deformation tests and moisture analysis have been applied to study the impact of xanthan gum and two types of sugar on the viscoelastic properties, the sol–gel transition and the water holding capacity of 1% agarose hydrogels. Agarose gels are very elastic, turbid and prone to synaeresis, which impinges on their mouth feeling. Additions of xanthan gum revealed less elastic gels with an unaffected water holding capacity. Progressive addition of two different types of up to 40% of sugar yield an increase of the elasticity of agarose gels, whereby sugar concentrations of 60% partially result in a structural breakdown and thus a significant lower network structure but better water holding. In ternary systems, the effect of the sugar concentration and sugar type used is diminished by xanthan gum. The gelation mechanism of agarose gels with a distinct amount of co-solutes is presumably mainly affected by the water shortage evolved from the competition for it of all solutes present.

Neutron reflectivity (NR) and fluorescent microscopy (FM) were used to study the interactions of human (hIAPP) and rat (rIAPP) islet amyloid polypeptides with several formulations of supported model lipid bilayers at the solid-liquid interface. Aggregation and deposition of islet amyloid polypeptide is correlated with the pathology of many diseases, including Alzheimer's, Parkinson, and type II diabetes (T2DM). A central component of T2DM pathology is the deposition of fibrils in the endocrine pancreas, which is toxic to the insulin secreting β-cells. The molecular mechanism by which the cell death occurs is not yet understood, but existing evidence points toward interactions of IAPP oligomers with cellular membranes in a manner leading to loss of their integrity. Our NR and FM results showed that the human sequence variant, hIAPP, had little or no effect on bilayers composed of saturated-acyl chains like zwitterionic DPPC, anionic DPPG, and mixed 80:20 mol % DPPC:DPPG bilayers. In marked contrast, the bilayer structure and stability of anionic unsaturated DOPG were sensitive to protein interaction, and the bilayer was partly solubilized by hIAPP under the conditions used here. The rIAPP, which is considered less toxic, had no perturbing effects on any of the above membrane formulations. Understanding the conditions that result in membrane disruption by hIAPP can be crucial in developing counter strategies to fight T2DM and also physicochemically similar neurodegenerative diseases such as Alzheimer's.

Soy milk is a highly stable emulsion, the stability being mainly due to the presence of oleosomes or oil bodies, spherical structures filled with triacylglycerides (TAGs) and surrounded by a monolayer of phospholipids and proteins called oleosins. For oleosomes purified from raw soymilk, surface pressure investigations and Brewster angle microscopy have been performed to unveil their adsorption, rupture and structural changes over time at different subphase conditions (pH, ionic strength). Such investigations are important for (industrial) food applications of oleosomes, but are also useful for the understanding of the general behavior of proteins and phospholipids at interfaces. In addition a better comprehension of the highly stable oleosomes can lead to advancements in liposome manufacturing, e.g., for storage and transport applications. Although oleosomes have their origin in food systems, their unique stability and physical behavior show transferable characteristics which lead to a much better understanding of the description of any kind of emulsion. This study is one of the first steps toward the comparison of natural emulsification concepts based on different physical structures: e.g., the animals' low density lipoproteins, where apolipoproteins with phospholipids are located only at the interface and plant oleosomes with its oleosins, which are embedded in a phospholipid monolayer and reach deep inside the oil phase.

International audience; Tethered bilayer lipid membranes have been used as a model system to mimic the interactions between the whey protein β-lactoglobulin and a lipid interface. The approach allowed for a detailed study of the lipid-protein interactions, the results being of possible importance in food and cosmetic applications. For such applications, lipid-protein interactions and the interfacial behavior are vital factors in controlling and manipulating process conditions such as emulsion stabilization and gelification. Lipid composition as well as the structural properties of the protein governed their interactions, which were probed by a combination of surface plasmon spectroscopy, neutron reflectivity, and electrochemical impedance spectroscopy. Comparison of results obtained using native and a partially unfolded protein indicated that the protein preferentially forms loosely packed layers at the lipid interface.

The structural stability of Al layers in contact with 3.5 wt.% NaCl water solution was investigated at a temperature of 25 °C and hydrostatic pressures from 1 to 600 atm using neutron reflectometry. A pressure–temperature (P–T) Neutron Reflectometry (NR) cell developed at Los Alamos National Laboratory (LANL) was used to understand the behavior of thin (∼900 A) aluminum layers in contact with saline liquid. Experimental results suggest that in the preliminary stages of corrosion the influence of pressure accelerates the mechanism of interactions of the oxide film with Cl− and H2O with lower speed compared to results found in the literature.

Soy milk is a highly stable emulsion mainly due to the presence of oleosomes, which are oil bodies and function as lipid storage organelles in plants, e.g., in seeds. Oleosomes are micelle-like structures with an outer phospholipid monolayer, an interior filled with triacylglycerides (TAGs), and oleosins anchored hairpin-like into the structure with their hydrophilic parts remaining outside the oleosomes, completely covering their surface (K. Hsieh and A. H. C. Huang, Plant Physiol., 2004, 136, 3427-3434). Oleosins are alkaline proteins of 15–26 kDa (K. Hsieh and A. H. C. Huang, Plant Physiol., 2004, 136, 3427–3434) which are expressed during seed development and maturation and play a major role in the stability of oil bodies. Additionally, the oil bodies of seeds seem to have the highest impact on coalescence, probably due to the required protection against environmental stress during dormancy and germination compared to, e.g., vertebrates' lipoproteins. Surface pressure investigations and Brewster angle microscopy of oleosomes purified from raw soy milk were executed to reveal their diffusion to the air–water interface, rupture, adsorption and structural modification over time at different subphase conditions. Destroying the surface portions of the oleosins by tryptic digestion induced coalescence of oleosomes (J. Tzen and A. Huang, J. Cell. Biol., 1992, 117, 327–335) and revealed severe changes in their adsorption kinetics. Such investigations will help to determine the effects behind oleosome stability and are necessary for a better understanding of the principal function of oleosins and their interactions with phospholipids.

Because of its high sensitivity for light elements and the scattering contrast manipulation via isotopic substitutions, neutron reflectometry (NR) is an excellent tool for studying the structure of soft-condensed material. These materials include model biophysical systems as well as in situ living tissue at the solid–liquid interface. The penetrability of neutrons makes NR suitable for probing thin films with thicknesses of 5–5000 Å at various buried, for example, solid–liquid, interfaces [J. Daillant and A. Gibaud, Lect. Notes Phys. 770, 133 (2009); G. Fragneto-Cusani, J. Phys.: Condens. Matter 13, 4973 (2001); J. Penfold, Curr. Opin. Colloid Interface Sci. 7, 139 (2002)]. Over the past two decades, NR has evolved to become a key tool in the characterization of biological and biomimetic thin films. In the current report, the authors would like to highlight some of our recent accomplishments in utilizing NR to study highly complex systems, including in-situ experiments. Such studies will result in a much better understanding of complex biological problems, have significant medical impact by suggesting innovative treatment, and advance the development of highly functionalized biomimetic materials.

Neutron reflectometry (NR) was used to examine various live cells' adhesion to quartz substrates under different environmental conditions, including flow stress. To the best of our knowledge, these measurements represent the first successful visualization and quantization of the interface between live cells and a substrate with sub-nanometer resolution.In our first experiments, we examined live mouse fibroblast cells as opposed to past experiments using supported lipids, proteins, or peptide layers with no associated cells. We continued the NR studies of cell adhesion by investigating endothelial monolayers and glioblastoma cells under dynamic flow conditions. We demonstrated that neutron reflectometry is a powerful tool to study the strength of cellular layer adhesion in living tissues, which is a key factor in understanding the physiology of cell interactions and conditions leading to abnormal or disease circumstances. Continuative measurements, such as investigating changes in tumor cell — surface contact of various glioblastomas, could impact advancements in tumor treatments. In principle, this can help us to identify changes that correlate with tumor invasiveness. Pursuit of these studies can have significant medical impact on the understanding of complex biological problems and their effective treatment, e.g. for the development of targeted anti-invasive therapies.

A robust and simple method for the preparation of pH-responsive lipid membranes is reported. Polymeric cushions to support a lipid bilayer were obtained by performing layer-by-layer deposition of a polycation (polyethylene imine [PEI]) and a polyanion (polystyrene sulfonate [PSS]) on quartz, with PEI as a capping layer. Subsequently, a model membrane was obtained by depositing a DPPE bilayer using Langmuir–Blodgett and Langmuir–Schafer technique. Structural characterization using Neutron Reflectivity revealed that the separation distance between the polymeric cushion and the DPPE bilayer can be reversibly adjusted by varying the pH of the aqueous environment. These observations were further supported by Electrochemical Impedance Spectroscopy measurements. Molecular dynamics simulations suggest that coulombic forces play a key role in affecting the separation distances between the polymeric support and the lipid bilayer. Similar pH-dependent behavior was also recorded for a DPPC bilayer. We believe that this novel system offers great potential for fundamental biophysical studies of membrane properties decoupled from the underlying solid support.

Using Neutron Reflectometry (NR), polyelectrolyte multilayer (PEM) films made by layer-by-layer (LbL) deposition of a strong polycation (polyethylene imine [PEI]) and a polyanion (polystyrene sulfonate [PSS]) have been characterized. PEI terminated samples with a total of 5, 7, and 9 layers were deposited on a quartz substrate and studied under three different environmental conditions (i.e., dry air, 100% relative humidity, and bulk water). We were able to model all the measurements at three different contrast conditions using one simple, physically reasonable and consistent model, which led to a firm understanding of the structure of the systems. The PEM thickness was found to vary linearly with the number of layers deposited. Thin film structures formed using the LbL method were constituted of two distinctive regions, i.e., the bottom and top strata. When measured in dry air and D2O vapors, the ∼30 to 50 A thick bottom stratum was found to consist of loosely packed polymers (i.e. 30% polymer by volume). This region could have resulted from an island type of deposition during the initial stages of LbL assembly. In contrast, the thickness of the top strata, which consisted of densely packed polymers (i.e. 100% polymer by volume when measured in dry air), was found to vary linearly with the number of layers deposited. Upon exposure to D2O saturated vapors, it was observed that the top and bottom strata absorbed significant quantities of heavy water, accompanied with PEM swelling. We estimated that in this case, the top strata comprise ca. 57% (v/v) polymer and 43% (v/v) D2O for 7- and 9-layered samples. No further swelling of the PEM samples was observed when they were exposed to bulk D2O. Nevertheless, the entire polymeric system underwent a rearrangement leading towards the homogenization of the multilayered structure, suggested by the decreased scattering contrast between the top and bottom strata. We also performed studies to assess the cytocompatibility of 7-layered PEM structures. Two different cell types, fibroblasts (3T3) and human embryo kidney cells (HEK-293), were seeded on the polyelectrolyte multilayer, and the cell coverage was monitored by optical microscopy at varying times. Our observations confirmed that cells adhered and spread on PEM substrates, which showed no sign of immediate toxicity. Therefore, such multilayers proved to be a suitable support for 3T3 and HEK-293 cell growth.

Tethered bilayer lipid membranes can be used as model platforms to host membrane proteins or membrane-active peptides, which can act as transducers in sensing applications. Here we present the synthesis and characterization of a valinomycin derivative, a depsipeptide that has been functionalized to serve as a redox probe in a lipid bilayer. In addition, we discuss the influence of the molecular structure of the lipid bilayer on its ability to host proteins. By using electrical impedance techniques as well as neutron scattering experiments, a clear correlation between the packing density of the lipids forming the membrane and its ability to host membrane proteins could be shown.