Network Structure Of Water Research Articles

Dynamics of human acetylcholinesterase bound to non-covalent and covalent inhibitors shedding light on changes to the water network structure.

We investigated the effects of non-covalent reversible and covalent irreversible inhibitors on human acetylcholinesterase and human butyrylcholinesterase. Remarkably a non-covalent inhibitor, Huperzine A, has almost no effect on the molecular dynamics of the protein, whereas the covalently binding nerve agent soman renders the molecular structure stiffer in its aged form. The modified movements were studied by incoherent neutron scattering on different time scales and they indicate a stabilization and stiffening of aged human acetylcholinesterase. It is not straightforward to understand the forces leading to this strong effect. In addition to the specific interactions of the adduct within the protein, some indications point towards an extensive water structure change for the aged conjugate as water Bragg peaks appeared at cryogenic temperature despite an identical initial hydration state for all samples. Such a change associated to an apparent increase in free water volume upon aging suggests higher ordering of the hydration shell that leads to the stiffening of protein. Thus, several additive contributions seem responsible for the improved flexibility or stiffening effect of the inhibitors rather than a single interaction.

Surface water network structure, landscape resistance to movement and flooding vital for maintaining ecological connectivity across Australia’s largest river basin

Context Landscape-scale research quantifying ecological connectivity is required to maintain the viability of populations in dynamic environments increasingly impacted by anthropogenic modification and environmental change.

Does urea alter the collective hydrogen-bond dynamics in water? A dielectric relaxation study in the terahertz-frequency region.

We report the ultrafast collective hydrogen-bond dynamics of water in the extended hydration layer of urea by using terahertz time-domain spectroscopy in the frequency region of 0.3-2.0 THz. The complex dielectric function has been fitted using a Debye relaxation model, and the timescales obtained are in the order of approximately 9 ps and 200 fs for bulk water; this exhibits a considerable acceleration beyond the 4 M urea concentration and indicates a possible disruption in the collective hydrogen-bonded water-network structure, which, in turn, provides an indirect support for the water "structure-breaking" ability of urea. With 5 M urea in the presence of different concentrations of trimethylamine-N-oxide (TMAO), it was found that these parameters essentially follow the trend observed for TMAO itself, which signifies that any possible disruption of the water structure by urea is outdone by the strong hydrogen-bonding ability of TMAO, which explains its ability to revive urea-denatured proteins to their respective native states.

International trade of scarce water

Recent analyses of the evolution and structure of trade in virtual water revealed that the number of trade connections and volume of virtual water trade have more than doubled over the past two decades, and that developed countries increasingly import water embodied in goods from the rest of the world to alleviate pressure on domestic water resources. At the same time, as demand continues to increase and climate change threatens to alter hydrological cycles, water scarcity is a growing problem. Does research into virtual water trade need to consider water scarcity and differentiate flows out of water-scarce regions from flows out of water-abundant regions? Previous studies sum and compare virtual water volumes originating in countries experiencing vastly different degrees of water scarcity. We therefore incorporate water scarcity into an assessment of global virtual water flows. We use input–output analysis to include indirect virtual water flows. We find that the structure of global virtual water networks changes significantly after adjusting for water scarcity.

Pressure Effect on the Reorientational Correlation Time of Water in Formamide–Water Mixtures at 25 °C

Abstract NMR spin–lattice relaxation times (T1) for nucleus D of D2O in deuterated formamide (FA-d3)–D2O mixtures were measured up to 80 mol % of FA-d3 at 25 °C under pressure up to 196.1 MPa. To discuss the pressure effect on the dynamic behavior of water molecules in the mixtures, the reorientational correlation times (τc) of D2O molecules were estimated from the quadrupole coupling equation. τc monotonously increased with increasing FA-d3 content at all pressures studied. However, τc apparently decreased with increasing pressure until 20 mol % of FA-d3, while over 40 mol % of FA-d3 the pressure coefficient of τc (∂τc/∂P) became positive and larger with increasing FA-d3 content. A negative pressure coefficient would indicate the existence of three-dimensional hydrogen-bonded network structure of water, and a positive one would be ascribed to the strengthening of dipole interactions and hydrogen bonds between FA-d3 and D2O by compression. In order to investigate the pressure effect on the reorientational dynamics of water molecules in detail, we performed molecular dynamics (MD) simulations paying attention to the pressure effect on hydrogen-bonding and dipole interactions.

Bi-objective optimization of a water network via benchmarking

This paper presents an approach to water system retrofitting by estimating both the economic and environmental impacts of a water network structure, using bi-objective optimization. The environmental impact is evaluated via benchmarking. By using benchmarking, the decision maker can have an insight, not only into the environmental impacts of certain designs belonging to Pareto optimal solutions, but also into the competitiveness of the design within a particular production sector. The economic criterion used is the total cost of the water network involving the freshwater cost, wastewater treatment cost, and the annual investment costs of storage tank, piping, and local treatment unit installation. A mixed-integer nonlinear programming (MINLP) model is used for water re-use and regeneration re-use within batch and semi-continuous processes. The Pareto fronts are generated using the classic and adaptive weighted-sum methods. The proposed approach was applied to an industrial case study within a brewery. The results obtained show that the benchmark could not be reached by process integration within the packaging area, therefore investment is needed regarding new technologies that lower freshwater consumption. Within the production area, however, the freshwater consumption could be reduced below the benchmark by water re-use and regeneration re-use, meaning that the brewery could achieve better performance than its competitors.

A new design method for water-using network of multiple contaminants with single internal water main

Abstract The internal water mains can simplify the structure of water networks, and reduce difficulty of control and operations of the systems. This paper presents a new method to design the networks of multiple contaminants with single internal water main. A conventional network without internal water main is obtained first by using the concentration potential method. An initial structure of the single internal water main can be developed based on the conventional network. The internal water main is formed by the sources with low concentration potential values. The final design can be obtained based on the initial network in a few iterations by adjusting the amount of the internal water main. The results of a few literature examples show that the designs obtained in this work are comparable to that obtained in the literature by using mathematical programming methods. The proposed method is simple and effective.

Water: A Responsive Small Molecule

Unique among small molecules, water forms a nearly tetrahedral yet flexible hydrogen-bond network. In addition to its flexibility, this network is dynamic: bonds are formed or broken on a picosecond time scale. These unique features make probing the local structure of water challenging. Despite the challenges, there is intense interest in developing a picture of the local water structure due to water's fundamental importance in many fields of chemistry. Understanding changes in the local network structure of water near solutes likely holds the key to unlock problems from analyzing parameters that determine the three dimensional structure of proteins to modeling the fate of volatile materials released into the atmosphere. Pictures of the local structure of water are heavily influenced by what is known about the structure of ice. In hexagonal I(h) ice, the most stable form of solid water under ordinary conditions, water has an equal number of donor and acceptor bonds; a kind of symmetry. This symmetric tetrahedral coordination is only approximately preserved in the liquid. The most obvious manifestation of this altered tetrahedral bonding is the greater density in the liquid compared with the solid. Formation of an interface or addition of solutes further modifies the local bonding in water. Because the O-H stretching frequency is sensitive to the environment, vibrational spectroscopy provides an excellent probe for the hydrogen-bond structure in water. In this Account, we examine both local interactions between water and small solutes and longer range interactions at the aqueous surface. Locally, the results suggest that water is not a symmetric donor or acceptor, but rather has a propensity to act as an acceptor. In interactions with hydrocarbons, action is centered at the water oxygen. For soluble inorganic salts, interaction is greater with the cation than the anion. The vibrational spectrum of the surface of salt solutions is altered compared with that of neat water. Studies of local salt-water interactions suggest that the picture of the local water structure and the ion distribution at the surface deduced from the surface vibrational spectrum should encompass both ions of the salt.

State of Water, Molecular Structure, and Cytotoxicity of Silk Hydrogels

A novel technique was developed to regulate the bulk water content of silk hydrogels by adjusting the concentrations of silk proteins, which is helpful to investigate the effects of the state of water in polymeric hydrogel on its biological functions, such as cytotoxicity. Gelation of the silk hydrogel was induced with ethanol and its gelation behavior was analyzed by rheometry. The silk hydrogels prepared at various silk concentrations were characterized with respect to their water content, molecular and network structures, state of water, mechanical properties, and cytotoxicity to human mesenchymal stem cells. The network structure of silk hydrogel was heterogeneous with β-sheet and fibrillar structures. The influence of the state of water in the silk hydrogel on the cytotoxicity was recognized by means of differential scanning calorimetry and cell proliferation assay, which revealed that the bound water will support cell-adhesion proteins in the cellular matrix to interact with the surface of the silk hydrogels.

Effect of Temperature on the Structural and Thermodynamic Properties of Aqueous Dimethyl Sulfoxide

The structural and thermodynamic properties of aqueous dimethyl sulfoxide (DMSO) at a mole fraction of 0.002 were investigated using referenced interaction site model theory at different temperatures. The results reveal that the water network structure is enhanced by the presence of DMSO. The increased fluctuation in the potential of mean force suggests that the water-induced force is repulsive. In addition, the increased entropy of solvation and free energy of solvation imply that the randomness of the solution increases with an increase in temperature. The increased interaction energy and excess chemical potential reveal that the solution deviates from an ideal solution. Furthermore, the increased cavity reorganization energy shows that the system structure reorganizes easily at high temperature.

Collective dynamics of hydrated β-lactogloblin by inelastic x-ray scattering

Inelastic x-ray scattering measurements of hydrated β-lactoglobulin (β-lg) were performed to investigate the collective dynamics of hydration water and hydrated protein on a picosecond time scale. Samples with different hydration levels h [=mass of water (g)/mass of protein (g)] of 0 (dry), 0.5, and 1.0 were measured at ambient temperature. The observed dynamical structure factor S(Q,ω)/S(Q) was analyzed by a model composed of a Lorentzian for the central peak and a damped harmonic oscillator (DHO) for the side peak. The dispersion relation between the excitation energy in the DHO model and the momentum transfer Q was obtained for the hydrated β-lg at both hydration levels, but no DHO excitation was found for the dry β-lg. The high-frequency sound velocity was similar to that previously observed in pure water. The ratio of the high-frequency sound velocity of hydrated β-lg to the adiabatic one of hydrated lysozyme (h=0.41) was estimated as ∼1.6 for h=0.5. The value is significantly smaller than that (∼2) of pure water that has the tetrahedral network structure. The present finding thus suggests that the tetrahedral network structure of water around the β-lg is partially disrupted by the perturbation from protein surface. These results are consistent with those reported from Brillouin neutron spectroscopy and molecular dynamics simulation studies of hydrated ribonuclease A.

Structure of Water in the Vicinity of Amphoteric Polymers as Revealed by Vibrational Spectroscopy

The water incorporated in a thin film of amphoteric terpolymers composed of various ratios of methacrylic acid (MA), N-[3-(dimethylamino)propyl]methacrylamide (DMAPMA) and n-butyl methacrylate was analyzed using the band shapes of the O–H stretching in the infrared spectra. At an early stage of sorption of water into the polymer film, the O–H stretching band for the water incorporated in the film with comparative contents of MA and DMAPMA residues was similar to that for bulk water. These results clearly indicate that the amphoteric polymers with comparative contents of cationic and anionic groups do not significantly disturb the hydrogen-bonded network structure of water, probably due to the counteraction of the electrostatic hydration effect by the proximity between the anionic and cationic side groups. The number of platelets adhered to the film with comparative contents of MA and DMAPMA residues was relatively the smallest among the examined terpolymer films, which suggested a correlation between the mildness of the charge-balanced polymeric materials to the structure of incorporated water and their blood-compatibilities. In addition, the structure and hydrogen bonding of water in an aqueous solution of co-polymers composed of various ratios of MA and DMAPMA or [3-(methacryloylamino)propyl]trimethylammonium chloride (MAPTAC) were also analyzed using the contours of the O–H stretching in the polarized Raman spectra. The number of hydrogen bonds disrupted due to the presence of one monomer residue (N corr value) for PolyMA was largely positive, and with an increase in the content of the DMAPMA or MAPTAC residues, the N corr value became smaller, and after passing a minimum (which was still slightly positive) at a roughly equivalent molar ratio, the N corr value increased again. This is in a significant contrast with the largely positive N corr values for the homo-polymers (PolyMA, PolyDMAPMA and PolyMAPTAC), and other ordinary polyelectrolytes. The effect of the charge-balanced co-polymer on the hydrogen-bonded network structure of vicinal water observed by Raman spectroscopy was in accordance with that of the charge-balanced terpolymer film observed by infrared spectroscopy.

Hydrogen-bond network and local structure of liquid water: An atoms-in-molecules perspective

The nearly linear relationship between hydrogen-bond strength at the CCSD(T)/Aug-cc-pVTZ level and the electron density at the bond critical point in the atoms-in-molecules theory provides a practical means of calculating the hydrogen-bond strength in liquid water. A statistical analysis of the hydrogen-bonds obtained from Car-Parrinello molecular dynamics simulations shows that the strengths of hydrogen bonds in liquid water conform to a Gaussian distribution. Considering supercooled (250 K) water to have a fully coordinated (icelike) local tetrahedral configuration, we show that the local structure of liquid water is partly distorted tetrahedral in normal liquid water and even in superheated water.

Topological building blocks of hydrogen bond network in water

Basic three-dimensional units of the network, called fragments, are introduced to characterize the hydrogen bond (HB) network structure of water. Topological differences among normal liquid water, water at low temperature, and water under high pressure are elucidated by their fragment statistics. Water at low temperature has almost defect-free network and is filled with stable fragments with small distortion. It is found that there exists a certain way on how fragments mutually aggregate. Well-formed aggregates heterogeneously constitute very stable network structures. HB network rearrangements occur scarcely inside these aggregated domains but take place in their surface areas. The heterogeneity of HB structure and rearrangement in water is thus explained in terms of the fragment structure and its rearrangements. The fragment analysis thus elucidates the intermediate-range order in water HB network.

Molecular Dynamics Simulation of Nanostructural Organization in Ionic Liquid/Water Mixtures

Molecular dynamics simulations have been carried out to investigate nanostructural organization in mixtures of 1-octyl-3-methylimidazolium nitrate ionic liquid and water at multiple water concentrations. Evolution of the polar network, water network, and micelle structures is visualized and analyzed via partial radial distribution functions. The calculated static partial structure factors show that within the range of water contents examined, polar networks, water networks, and micelles possess an approximately invariant characteristic length at around 20 A. Furthermore, the above calculations point out that, as the amount of water increases, the polar network is continuously broken up (screened) by the intruding water, while the structural organization of the water network and the micelle exhibits a turnover. At the turnover point, the most ordered micelle (cation-cation) structure and water (water-anion-water) network are formed. Thereafter, the structural organization abates drastically, and only loose micelle structure exists due to the dominant water-water interactions. The simulated turnover of structural organization agrees with the sharpest peak in the experimentally obtained structure factor in aqueous solutions of similar ionic liquids; the simulated water structure reveals that water can form liquidlike associated aggregates due to the planar symmetry and strong basicity of NO(3)-, in agreement with experiment. The turnover of structural organization of micelles results from the persistent competition between the hydrophobic interactions of the nonpolar groups and the breakup of the charged polar network with increasing water content, whereas the turnover of the water network results from the competition between the water-water and water-anion interactions.

Raman spectroscopic study of the structure of water in aqueous solutions of amphoteric polymers

Methacrylic acid (MA) and [3-(methacryloylamino)propyl]trimethylammonium chloride (MAPTAC) were polymerized to give amphoteric copolymers with various compositions. The structure and H-bonding of water in an aqueous solution of the copolymer were analyzed using the contours of the O-H stretching in the polarized Raman spectra. For comparison, the H-bonded network structure of aqueous solutions of homopolymers (polyMA and polyMAPTAC) was also examined. From the relative intensity of the collective band (C value) corresponding to a long range coupling of the O-H stretching in the aqueous polymer solutions, the number of H-bonds disrupted due to the presence of one monomer residue of the polymers (Ncorr) was determined. The Ncorr value for polyMA was largely positive, and with an increase in the content of the MAPTAC residue, the Ncorr value became smaller, and after passing a minimum (which was still slightly positive) at a roughly equivalent molar ratio, the Ncorr value increased again. This is in significant contrast with the larger positive Ncorr values for the homopolymers (both polyMA and polyMAPTAC), and other ordinary polyelectrolytes such as sodium polyethylenesulfonate, poly-L-lysine hydrobromide and sodium polyacrylate. Furthermore, the Ncorr value for the copolymer (MA ratio MAPTAC = 56:44) became much smaller by the neutralization of MA residues in the copolymer with sodium hydroxide, and comparable to those for neutral polymers such as poly(ethylene glycol) and poly(N-vinylpyrrolidone) and zwitterionic polymers such as poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) and poly[3-sulfo-N,N-dimethyl-N-(3'-methacryloylaminopropyl)propanaminium inner salt]. The present results clearly indicate that the amphoteric polymers with comparative contents of cationic and anionic groups do not significantly disturb the H-bonded network structure of water, probably due to the counteraction of the electrostatic hydration effect by the proximity between the anionic and cationic side groups.

Raman spectroscopic study on the structure of water in aqueous solution of [formula omitted]-amino acids

The structure and hydrogen bonding of water in an aqueous solution of various α , ω -amino acids were analyzed using the contours of the O H stretching in the polarized Raman spectra. From the relative intensity of the collective band ( C value) corresponding to a long-range coupling of the O H stretching in the aqueous amino acid solutions, the number of hydrogen bonds disrupted due to the presence of one amino acid molecule ( N corr value) was evaluated. The N corr value for glycine was slightly positive, whereas with an increase in the number of methylene groups between ammonium and carboxylate groups, the N corr value gradually increased. These results suggest that the species with proximal anionic and cationic groups do not disturb the hydrogen-bonded network structure of water significantly, probably due to the counteraction of the electrostatic hydration effect attributable to the anionic and cationic groups.

Design of Water Network with Internal Mains for Multi-contaminant Wastewater Regeneration Recycle

Water networks incorporating a regeneration recycle can minimize freshwater consumption and wastewater discharge, to the extent of approaching the inherent minimum value. Based on the water network structure provided with internal water mains, this paper addresses the design methodology for water recycling with regeneration, and extends prior work to cases involving multi-contaminant systems. In such a structure water is supplied to each water-using process from freshwater main, regenerated water main, or regeneration water main according to water quality. How to determine the contaminant concentrations in the regeneration water main is the key in such a water network design. The regeneration concentrations should be the lowest compatible with the freshwater consumption of the system equal to its inherent minimum value. The corresponding design methodology focuses on how to determine which main to use as the water source and how much the water flow rate is to be for each water-using process, on the basis of mass balance and the inlet contaminant concentration condition of that process. Finally, an example is given to illustrate the design method.

Raman spectroscopic study on the structure of water in aqueous solution of zwitterionic surfactants

The structure and hydrogen bonding of water in aqueous solutions of various surfactants were analyzed using the contours of the OH stretching in the polarized Raman spectra. From the relative intensity of the collective band ( C value) corresponding to a long-range coupling of the OH stretching in the aqueous surfactant solutions, the number of hydrogen bonds disrupted due to the presence of one surfactant molecule ( N corr value) was evaluated. The N corr value for decylsulfobetaine was slightly negative, whereas those for ordinary ionic surfactants such as sodium dodecylsulfate and dodecyltrimethylammonium chloride were large positive values. Furthermore, the N corr for carboxybetaine surfactant was a small positive value. These results suggest that zwitterionic surfactants do not disturb the hydrogen-bonded network structure of water significantly, probably due to the counteraction of the electrostriction effect by the proximity between the anionic and cationic groups.

Dipolar Hydration Anomaly in the Temperature Dependence: Carbonyl and Nitrile Solutes Studied by 13C NMR Chemical Shifts

The 13C chemical shifts δ of carbonyl (13CO) and nitrile (13C⋮N) compounds in aqueous solutions were measured as functions of temperature to study the hydration structure around dipolar solutes. The δ values showed an anomalous maximum in the temperature dependence; at −9 °C for urea, at 23 °C for diethyl ketone, at 24 °C for cyanamide, at 32 °C for acetone, at 63 °C for acetaldehyde, and at 96 °C for acetonitrile. No such anomaly was observed in any other organic solvents. The presence of the maximum is due to the competition of two factors, solute−solvent and solvent−solvent interactions. One is the electrostatic hydrogen bond between the solute and water, and the other is the hydrogen bond network characteristic of solvent water. When the network structure of water is collectively stabilized with decreasing temperature, the effective water−water interaction becomes stronger than the solute−water interaction, giving the maximum in the temperature dependence of δ. The temperature of the maximum chemical shift Tmax δ was found to be sensitive to the solute polarity. The solute dependence of Tmax δ was explained in terms of the solute dipole moment μ obtained from ab initio calculations: the larger the μ, the lower the Tmax δ.