Inelastic incoherent neutron scattering measurements of intact cells and tissues and detection of interfacial water

We have previously used inelastic incoherent neutron scattering spectroscopy to investigate the properties of aqueous suspensions of biomolecules as a function of hydration. These experiments led to the identification of signals corresponding to interfacial (hydration) water at low water content. A prediction from these studies was that in the crowded environment inside living cells, a significant proportion of the water would be interfacial, with profound implications for biological function. Here we describe the first inelastic incoherent neutron scattering spectroscopy studies of living cells and tissues. We find that the interfacial water signal is similar to that observed for water interacting with purified biomolecules and other solutes, i.e., it is strongly perturbed in the librational and translational intermolecular optical regions of the spectrum at 20-150 meV. The ratio of interfacial water compared to total water in cells (approximately 30%) is in line with previous experimental data for hydration water and calculations based on simple assumptions.     

Inelastic neutron scattering study of water in hydrated LTA-type zeolites

The vibrational dynamics of water molecules encapsulated in synthetic Na-A and Mg-exchanged A zeolites were studied versus temperature by inelastic neutron scattering (INS) measurements (30-1200 cm(-1)) as a function of the induced ion-exchange percentage by using the indirect geometry tof spectrometer TOSCA at the ISIS pulse neutron facility (RAL, UK). The experimental INS spectra were compared with those of ice Ih to characterize the structural changes induced by confinement on the H2O hydrogen-bonded network. We observed, after increasing the Mg2+ content, a tendency of water molecules to restore the bulklike arrangements together with more hindered dynamics. These results are confirmed by the analysis of the evaluated one-phonon amplitude-weighted proton vibrational density of states aimed, in particular, to follow the evolution of the water molecules librational mode region.     

Dynamics of water in a molecular sieve by quasielastic neutron scattering

We have investigated the dynamics of water confined in a molecular sieve, with a cylindrical pore diameter of 10 A, by means of quasielastic neutron scattering (QENS). Both the incoherent and coherent intermediate scattering functions I(Q,t) were determined by time-of-flight QENS and the neutron spin-echo technique, respectively. The results show that I(Q,t) is considerably more stretched in time with a slightly larger average relaxation time in the case of coherent scattering. From the Q dependence of I(Q,t) it is clear that the observed dynamics is almost of an ordinary translational nature. A comparison with previous dielectric measurements suggests a possible merging of the alpha and beta relaxations of the confined water at T=185 K, although the alpha relaxation cannot be directly observed at lower temperatures due to the severe confinement. The present results are discussed in relation to previous results for water confined in a Na-vermiculite clay, where the average relaxation time from spin-echo measurements was found to be slower than in the present system (particularly at low temperatures).     

A technique for improved detection limit in indirect neutron activation determination of boron

Using vanadium as the activable element, an indirect cyclic neutron activation technique for determination of boron in aqueous solutions has been developed. Experimental arrangement consisted of a 5 Ci Pu?Be based neutron irradiator and a 7.5 cm × 7.5 cm NaI/Tl/ detector. Recycling of vanadium between the irradiation source and the detector produced improved detection limit and sensitivity.     

Dynamics of surface water in ZrO2 studied by quasielastic neutron scattering

A quasielastic neutron scattering experiment has revealed the dynamics of surface water in a high surface area zirconium oxide in the temperature range of 300-360 K. The characteristic times of the rotational (picoseconds) and translational (tens of picoseconds) components of diffusion motion are well separated. The rotational correlation time shows an Arrhenius-type behavior with an activation energy of 4.48 kJ/mol, which is lower compared to bulk water. The rotational diffusion at room temperature is slower by about a factor of 2 compared to bulk water, whereas the translational diffusion slows down by a factor of 40. In contrast to bulk water, the translational correlation time exhibits an Arrhenius-type temperature dependence with an activation energy of 11.38 kJ/mol. Comparison of different models for jump diffusion processes suggests that water molecules perform two-dimensional jumps at a well-defined, almost temperature-independent distance of 4.21-4.32 A. Such a large jump distance indicates a low molecular density of the layer of diffusing molecules. We argue that undissociated water molecules on an average form two hydrations layers on top of the surface layer of hydroxyl groups, and all the layers have similar molecular density. Quasielastic neutron scattering experiment assesses the dynamics of the outermost hydration layer, whereas slower motion of the water molecules in the inner hydration layer contributes to the elastic signal.     

A small angle neutron scattering study of the sodium di-n-pentyl phosphate micelles in water

Small angle neutron scattering has been used to elucidate the size and shape of a micelle in the sodium di-n-pentyl phosphate (DPP)-water system. The results are summarized as follows. For the DPP micelle, the aggregation number (n) depends on the concentration (n=12, at 7.0 wt% andn=15 at 10.0 wt%). The minimum micelle is spherical and has an aggregation numbern=7. For the DPP-micellar system, it can be assumed that micellar growth and variation from the spherical to probate shape occurs with an increase in concentration above the CMC.     

Inelastic neutron scattering studies of the interaction between water and some amino acids

The interaction between water and some of amino acids (glycine, L-glutamine, L-threonine, L-cysteine and L-serine) was studied by inelastic incoherent neutron scattering (IINS). The vibrational spectra of dry amino acids and amino acids with a water content (e.g., 1 mol water/1 mol amino acid) were recorded. Comparing the difference spectra obtained by subtracting the spectrum of dry sample from those of wet sample with the spectra of ice Ih, we obtained that the difference spectrum for serine changed greatly from normal ice spectrum; but on the other hand, the difference spectra for the other amino acids such as glycine, glutamine, threonine, and cysteine changed slightly. The results demonstrate that serine has stronger hydrophilic character than glycine, glutamine, threonine, and cysteine. This is the first time the hydrophilic or hydrophobic character of amino acids was studied by using inelastic neutron scattering techniques, which provides important information for theoretical modeling and force field refinement for the interaction between water and the amino acids studied here.     

An anion exchange technique for separation of Na and K for neutron activation analysis of W-Ti alloy

Anthropogenic radioactivity is being measured in near-real time by an international monitoring system designed to verify the Comprehensive Nuclear Test Ban Treaty. Airborne radioactivity measurements are conducted in-situ by stations that are linked to a central data processing and analysis facility. Aerosols are separated by high-volume air sampling with high-efficiency particulate filters. Radio-xenon is separated from other gases through cryogenic methods. Gamma-spectrometry is performed by high purity germanium detectors and the raw spectral data is immediately transmitted to the central facility via Internet, satellite, or modem. These highly sensitive sensors, combined with the automated data processing at the central facility, result in a system capable of measuring environmental radioactivity on the microbeequerel scale where the data is available to scientists within minutes of the field measurement. During the past year, anthropogenic radioactivity has been measured at approximately half of the stations in the current network. Sources of these measured radionuclides include nuclear power plant emissions, Chernobyl resuspension, and isotope production facilities. The ability to thoroughly characterize site-specific radionuclides, which contribute to the radioactivity of the ambient environment, will be necessary to reduce the number of false positive events. This is especially true of anthropogenic radionuclides that could lead to ambiguous analysis.     

A small-angle neutron scattering study of the ethyl (n-octyl) phosphate micelles in water

Summary Mixed-double chain anionic surfactants, barium- and lithium-salts of ethyl(n-octyl) phosphate (EOP), which are asymmetric in the molecular shape, and a series of identical chain di-n-alkyl phosphate lithium salts have been synthezized. The limiting partial molar volume of a PO ₄ ^– group (23.43±0.41 cm³ mol^–1) for use in small-angle neutron scattering analysis was determined by density measurements of a series of identical chain di-n-alkyl phosphate lithium salts. For lithium EOP-D₂O system, a critical micellar concentration (2.3 wt%) was determined by³¹P NMR spectra. The micellar shape and size in the EOP-water binary system has been investigated by using small-angle neutron scattering (SANS) spectra. It has been found that the micelles of barium EOP in water have the shape of a prolate spheroid and aggregation numbers (n) equal to 48 at 23°C and 52 at 50°C. For the lithium EOP-micellar system, it has been found that the minimum micelle with an aggregation numbern=21 is spherical and micellar growth and variation from the spherical to the prolate shape might occur with an increase in concen tration above the CMC.     

A membrane separation technique for optimizing sample preparation of MALDI-TOF MS detection

Here, we report a new method based on the combination of membrane separation technology and nanomaterial to rapid detection of peptides and protein with MALDI-TOF MS. This method shows advantages as it can inhibit the heterogeneous of sample spot and enhance the target molecular signal intensity.     

Superhydrophobic polymer multilayers for the filtration- and absorption-based separation of oil/water mixtures

We report layer-by-layer approaches to the design of superhydrophobic and superoleophilic substrates for the filtration- or absorption-based separation of bulk oil from oil/water mixtures. Fabrication of covalently cross-linked, nanoporous polymer multilayers on mesh substrates yielded superhydrophobic and superoleophilic porous media that allow oil to pass, but completely prevent the passage of bulk water. This approach can be used to promote the filtration of oil/water mixtures, and these film-coated substrates can be bent and physically manipulated without affecting oil- and water-wetting properties. Fabrication on three-dimensional macroporous polymer pads yielded flexible objects that float on water and absorb oil at contaminated air/water interfaces. This approach permits oil to be recovered by squeezing or rinsing with solvent and the reuse of these materials without decreases in performance. These pads can also absorb oil from simulated seawater, brine, and other media representative of marine or industrial contexts where oil contamination can occur. Our results address issues associated with the design of polymer-based coatings for the separation, removal, and collection of oil from oil-contaminated water. With further development, this approach could provide low-energy alternatives to conventional remediation methods or yield new strategies that can be implemented in ways that are impractical using current technologies. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3127–3136     

Controllable wettability of laser treated aluminum mesh for on-demand oil/water separation

Oil/water separation has attracted more attention with the dramatic increasing of oil spill accidents and arbitrarily discharged oily industrial water. However, many reported materials with controllable wettability for on-demand oil/water separation of both heavy and light oil/water mixtures involve complicated devices and dangerous fabrication processes. Herein, we propose a simple, environmentally friendly and high-efficient method to fabricate Al mesh with controllable wettability. Heavy oil can be separated with a high efficiency of 99% in oil-removing mode. For light oil, the separation efficiency can also reach up to 99% in water-removing mode. Additionally, surface wettability of the mesh can be conversed from superhydrophobicity to superhydrophilicity by atmospheric pressure plasma jet (APPJ) and heating, thereby realizing continuous bidirectional separation. Therefore, this work provides a facile, green, and efficient way for on-demand oil/water separation and finds a promising solution for oil pollution problems.     

A neutron scattering study of the structure and water partitioning of selectively deuterated copolymer micelles

We present a scattering study of a selectively deuterated micelle-forming diblock copolymer. The copolymer comprises a partially deuterated polystyrene (d,h-PS) block and an imidazolium-functionalized PS (IL) block. In toluene solutions, the copolymers assemble into elongated micelles where the IL block forms the micelle core. Through dynamic light scattering (DLS) measurements, we obtain the overall size of the micelles. In our small-angle neutron scattering (SANS) studies, we use contrast matching to characterize the IL core and the PS shell of the micelles independently. The PS block forming the micelle shell exhibits either a starlike or brushlike conformation depending upon the size of the core to which it is tethered. We find the IL block to be in an extended conformation, driving the formation of slightly elongated and relatively stiff micelle cores. The elongated micelle core cross-sectional radius and length depend linearly on the length of the IL block. We find that the micelles can sequester a few water molecules for each IL repeat unit; the addition of water slightly increases the cross section of the elongated micelles.     

A simple salt-enhanced surface-tension technique for detection of trace surfactants in water

A simple, relatively inexpensive DuNoy tensiometer can be used to detect small amounts of surfactants in water (at the μg l^-1 level in many cases). The surfactant must be salted-out to produce the desired effect. Addition of salt to pure water produces a reproducible increase in surface tension, whereas addition of salt to a water sample containing traces of surfactant produces a distinct, reproducible decrease. For pure surfactant solutions, calibration curves can be constructed for quantitative work.     

Measurement of the diffusivity of benzene in microporous silica by quasi-elastic neutron scattering and NMR pulsed-field gradient technique

The diffusivity of benzene in a microporous silica powder has been measured by neutron scattering and NMR techniques. The measurements have been performed on un-supported silica but the powder has the same characteristics as the active layer of a real membrane. Self-diffusion coefficients of the order of 10^–10 m²s^–1 are found at 300 K by both techniques so that the model of Knudsen diffusion is not valid for benzene in this microporous material. Due to the presence of small pores, the diffusion of benzene in the membrane-material approaches the diffusion regime usually observed in zeolites. Furthermore, the diffusivity of benzene follows an Arrhenius law with an activation energy of 11 kJ mol^–1.     

Structural features of molecular-colloidal solutions of C60 fullerenes in water by small-angle neutron scattering

Highly stable and reproducible molecular-colloidal water solutions of C60 fullerenes (FWS) obtained by transferring fullerenes from an organic solution into an aqueous phase with the help of ultrasonic treatment are investigated by means of small-angle neutron scattering (SANS). A polydispersity in the size of detected particles up to 84 nm is revealed. These particles are slightly anisotropic and have a characteristic size of approximately 70 nm. Along with it, there are some indications that a significant part of fullerenes composes particles with the size of the order of 1 nm. The contrast variation based on mixtures of light and heavy water shows that the mean scattering length density of the particles is close to that of the packed fullerene associates as well as that the characteristic size of possible fluctuations of the scattering length density within the particles does not exceed 2 nm. A smooth surface resulting in the Porod law for the scattering is detected. A number of models discussed in the literature are considered with respect to the SANS data.     

Preferential hydration of lysozyme in water/glycerol mixtures: a small-angle neutron scattering study

In solution small-angle neutron scattering has been used to study the solvation properties of lysozyme dissolved in water/glycerol mixtures. To detect the characteristics of the protein-solvent interface, 35 different experimental conditions (i.e., protein concentration, water/glycerol fraction in the solvent, content of deuterated compounds) have been considered and a suitable software has been developed to fit simultaneously the whole set of scattering data. The average composition of the solvent in the close vicinity of the protein surface at each experimental condition has been derived. In all the investigated conditions, glycerol resulted especially excluded from the protein surface, confirming that lysozyme is preferentially hydrated. By considering a thermodynamic hydration model based on an equilibrium exchange between water and glycerol from the solvation layer to the bulk, the preferential binding coefficient and the excess solvation number have been estimated. Results were compared with data previously derived for ribonuclease A in the same mixed solvent: even if the investigated solvent compositions were very different, the agreement between data is noticeable, suggesting that a unique mechanism presides over the preferential hydration process. Moreover, the curve describing the excess solvation number as a function of the solvent composition shows the occurrence of a region of maximal hydration, which probably accounts for the changes in protein stability detected in the presence of cosolvents.