Bound Water Molecules Research Articles

Insight on the stability of methane hydrate in montmorillonite slits by molecular dynamics simulations

The extent of interactions between clay surfaces and water molecules and their impact on hydrate stability in clay reservoirs have been a source of debate. This study employs molecular dynamics simulations to investigate the stability of methane hydrates in montmorillonite slits at various temperatures, focusing on the surface influence scale, bound water molecule distribution characteristics, and binding strength. The results reveal that hydrates in close proximity to the clay surface exhibit lower stability and higher decomposition susceptibility due to the hydrophilic nature of the surface, which leads to water molecule aggregation, driving methane molecules away during decomposition. Furthermore, we compare the charged and neutral tetrahedral layer surfaces of montmorillonite and find that the quasi-liquid layer on the neutral tetrahedral layer surface is thinner, with persisting semicage structures within the vacancies of the Si-O rings. These variations in surface influence range and binding strength can be attributed to intermolecular Coulomb interactions and charge redistribution at the interface. These research findings provide valuable molecular insights into the microscopic characteristics and behavior of hydrates within clay slits.

Dielectric and Hydration Study of Aqueous Cellulose Derivative Solutions

Dielectric and hydration studies have been done on hydroxypropyl methyl cellulose (HPMC) (Molecular weight 1261 g/mole) in 15 centipoise (cPs) and 50 cPs and methyl cellulose (MC) (Molecular weight 454 g/mole) in 450 cPs and 4000 cPs aqueous solutions using a time domain reflectometry technique. The static dielectric constant, density, and hydration numbers were determined at various concentrations. The results revealed that the formation of bound water molecules around the cellulose derivative (CD) decreased with increasing concentrations of the CD. The higher value of the hydration number of the CD suggested that water-CD interactions were stronger in aqueous solutions of CD at the lower concentration of the solute; i.e., the CD-water interactions were progressively weaker as the CD concentration was increased.

Phase separation of multicomponent peptide mixtures into dehydrated clusters with hydrophilic cores

Phase separation of biomolecules underlies the formation and regulation of various membraneless condensates in cells. How condensates function reliably while surrounded by heterogeneous and dynamic mixtures of biomolecular components with specific and nonspecific interactions is yet to be understood. Studying multicomponent biomolecular mixtures with designer peptides has recently become an attractive avenue for learning about physicochemical principles governing cellular condensates. In this work, we employed long-timescale atomistic simulations of multicomponent tripeptide mixtures with all residue substitutions to illuminate the nature of direct and water-mediated interactions in a prototypical cellular condensate environment. We find that peptide mixtures form clusters with inverse hydrophobic order. Most multivalent and charged residues are localized in the cluster’s core, with a large fraction of nonaromatic hydrophobic residues remaining on the surface. This inverse hydrophobic order in peptide clusters is partly driven by the expulsion of nonspecifically bound water molecules following peptide cluster growth. The growth of clusters is also accompanied by the formation of increasing numbers of specific water-mediated interactions between polar and charged residues. While the present study focused on the condensation of short peptide motifs, the general findings and analysis techniques should be helpful for future studies on larger peptides and protein condensation.

Highly Strong, Tough, and Cryogenically Adaptive Hydrogel Ionic Conductors via Coordination Interactions.

Despite the promise of high flexibility and conformability of hydrogel ionic conductors, existing polymeric conductive hydrogels have long suffered from compromises in mechanical, electrical, and cryoadaptive properties due to monotonous functional improvement strategies, leading to lingering challenges. Here, we propose an all-in-one strategy for the preparation of poly(acrylic acid)/cellulose (PAA/Cel) hydrogel ionic conductors in a facile yet effective manner combining acrylic acid and salt-dissolved cellulose, in which abundant zinc ions simultaneously form strong coordination interactions with the two polymers, while free solute salts contribute to ionic conductivity and bind water molecules to prevent freezing. Therefore, the developed PAA/Cel hydrogel simultaneously achieved excellent mechanical, conductive, and cryogenically adaptive properties, with performances of 42.5 MPa for compressive strength, 1.6 MPa for tensile strength, 896.9% for stretchability, 9.2 MJ m-3 for toughness, 59.5 kJ m-2 for fracture energy, and 13.9 and 6.2 mS cm-1 for ionic conductivity at 25 and -70 °C, respectively. Enabled by these features, the resultant hydrogel ionic conductor is further demonstrated to be assembled as a self-powered electronic skin (e-skin) with high signal-to-noise ratio for use in monitoring movement and physiological signals regardless of cold temperatures, with hinting that could go beyond high-performance hydrogel ionic conductors.

Diffusely Charged Polymeric Zwitterions as Loosely Hydrated Marine Antifouling Coatings.

Polymeric zwitterions exhibit exceptional fouling resistance through the formation of a strongly hydrated surface of immobilized water molecules. While being extensively tested for their performance in biomedical, membrane, and, to a lesser extent, marine environments, few studies have investigated how the molecular design of the zwitterion may enhance its performance. Furthermore, while theories of zwitterion antifouling mechanisms exist for molecular-scale foulant species (e.g., proteins and small molecules), it remains unclear how molecular-scale mechanisms influence the micro- and macroscopic interactions of relevance for marine applications. The present study addresses these gaps through the use of a modular zwitterion chemistry platform, which is characterized by a combination of surface-sensitive sum frequency generation (SFG) vibrational spectroscopy and marine assays. Zwitterions with increasingly delocalized cations demonstrate improved fouling resistance against the green alga Ulva linza. SFG spectra correlate well with the assay results, suggesting that the more diffuse charges exhibit greater surface hydration with more bound water molecules. Hence, the number of bound interfacial water molecules appears to be more influential in determining the marine antifouling activities of zwitterionic polymers than the binding strength of individual water molecules at the interface.

Optimization of Deep Eutectic Solvents Enables Green and Efficient Cryopreservation.

Cryopreservation presents significant opportunities for biomedical applications including cell therapy, tissue engineering, and assisted reproduction. Dimethyl sulfoxide (DMSO), the most commonly used cryoprotectant (CPA), can be added to cells to prevent cryogenic damage. However, the toxicity of cryoprotectants restrains its further development in many areas with safety concerns such as clinical treatment. Therefore, the development of low-toxicity cryoprotectants is essential for medical research. This work reports deep eutectic solvents (DES) as naturally biocompatible osmoprotectants for green and efficient cryopreservation of human umbilical cord mesenchymal stem cells (HuMSC), which may be an ideal alternative to DMSO. The six types of DESs were explored for thermal properties, toxicity, and permeability in cells. Raman spectroscopy and viscosity studies showed that DES exhibited an improved hydrogen-bonding system as the temperature decreased. By optimizing the freezing process (cooling rate, incubation time, and loading procedure) of DES, the viability of mouse embryonic fibroblast cells (NIH-3T3) after thawing was significantly improved. The HuMSC were successfully preserved with no significant difference (p > 0.05) in cell viability (94.65%) after thawing compared with DMSO, which preserved the cell differentiation function and improved the cell proliferation rate. The mechanism of DES in cryopreservation was investigated, and it was found that DES could bind water molecules and effectively inhibit the growth of ice crystals during ice recrystallization, reducing mechanical damage to cells. This study highlights the excellent performance of DES as a low-toxicity CPA for stem cell preservation, which may be a significant advance for future clinical cell therapy.

Unlocking the Potential of Microwave Sterilization Technology in Ready-to-Eat Imitation Crab Meat Production.

Microwave sterilization is a novel potential sterilization technology to improve food quality. An industrial microwave sterilization system was used to sterilize imitation crab meat under thermal processing intensity F0 = 1, 2, 3. The characteristics of the microwave process, such as heating rate, processing time, and C100, were calculated. In addition, the quality of processed imitation crab meat was investigated. Compared with the conventional retort method, microwave sterilization significantly shortened the processing time of imitation crab meat by 63.71% to 72.45%. Under the same thermal processing intensity, microwave sterilization has demonstrated better results than retort sterilization in terms of water-holding capacity, color, and texture. Furthermore, microwave-treated imitation crab meat ingredients had a greater capacity to bind water molecules and obtained a more appropriate secondary protein structure. In addition, microwave technology can better preserve the unsaturated fatty acids (UFA) of imitation crab meat, which are 9.14%, 1.19%, and 0.32% higher than the traditional method at F0 = 1, 2, 3. The results would provide useful data for the subsequent research and development of ready-to-eat surimi products.

Graphene oxide incorporated PSU/SPEKEKK for potential application as proton exchange membranes in fuel cells

This study aims to develop a new PEM for fuel cell applications consisting of PSU/SPEKEKK/SGO membranes with improved physiochemical properties to surmount the low power generation of Nafion. The DFT calculations using NCI plots show that there are network interactions between PSU and SPEKEKK, established by the hydrogen bonding and vdW interactions. SGO was incorporated into the as-prepared PSU/SPEKEKK membrane. A solution casting method was employed to fabricate SGO-loaded composite membranes in the range of 0.1% to 1.5% (wt%). Structural evidence of the SGO and composite membranes was characterized by ATR-FTIR and FESEM, respectively. Adding SGO to PSU/SPEKEKK shows a significant increase in proton conductivity due to the presence of more protonated sites (SO3H) and water-mediated interactions for proton conduction. Of all the compositions considered, PSU/SPEKEKK/SGO-0.6-1.5% loading was found to have the highest proton conductivity, 0.03Scm−1. Although adding SGO to the composite membrane has reduced water absorption, the hydrophilic oxygenated functional groups in SGO, the bound water molecules, and the increased –SO3H groups have successfully improved the proton conductivity. The findings reveal that all composite membranes show excellent oxidative stabilities for 32 h in Fenton's reagent. To summarize, all composite membranes fabricated in this study show acceptable water uptake and swelling ratio, high oxidation, excellent thermal stability, and high proton conductivity.

The Effect of Hydrolyzed Pectin as a Sugar Substitute on The Physicochemical Properties of Pineapple Spread

Pineapple is a fruit that is widely produced in Indonesia. Pineapple can be processed into jam or fruit spread to extend its shelf life. However, jam contains high amount of sugar. High consumption of sugar in the diet can contribute to a high kilojoules diet or known as 'energy dense' and thus contribute to the development of health problems like obesity or diabetes. Sugar has important role in the jam. It binds water molecules to build spreadable product. Pectin can also bind water molecules and cannot be digested by human body but addition of pectin as sugar replacement cannot build spreadable product because pectin molecules is much longer than sucrose. Thus, depolymerization through hydrolysis is needed on pectin molecule. Therefore, the purpose of this research was to determine the effect of different hydrolyzed pectins as substitute for sucrose in a pineapple spread. The physicochemical properties of hydrolyzed pectin (viscosity and color value) and pineapple spreads made from the hydrolyzed pectin (color value, degree of brix, water activity, syneresis and spreadability) were investigated. The results showed that pectin treated with 0.05 M of HCl for 96 h produced the best pineapple spreads based on water activity and percentage of syneresis results. Moreover, pineapple spreads made from pectin treated with 0.05 M of HCl for 96 h has the most similar color and spreadability to the one with sucrose.

Thermodynamic hydration behaviour of glycine below room conditions using time domain reflectometry

The present work reports the concentration-dependent hydrophobicity of glycine below room temperature. The dynamics of aqueous glycine have been studied by means of dielectric relaxation spectroscopy using Time Domain Reflectometry (TDR) technique in the frequency region of 10 MHz–30 GHz. Complex permittivity spectra are obtained using TDR that allowed evaluation of the static dielectric constant (ε0) and average relaxation time (τ). As dielectric relaxation spectroscopy provides information on the average relaxation time (τ) related to the mechanism of hydrogen bond (HB) formation and breaking, therefore the concentration-temperature dependence of τ was used to evaluate and study hydration behaviour through dielectric parameters such as dipole moment (μ), correlation factor (g), and the dynamics of irrationally bound water molecules (Zib). Aqueous glycine relaxes in two different relaxation modes in the broad microwave frequency region from MHz to GHz. The low-frequency relaxation process (l-process) observed is associated with glycine relaxation, while the detected peak in the high-frequency relaxation process (h-process) is attributed to water associated with glycine. We have attempted a concentration-temperature-dependent hydrogen bonding mechanism in both relaxation processes, and the results were corroborated with thermodynamical parameters such as molar entropy of activation (∆Sj), molar enthalpy of activation (∆Hj), and molar free energy of activation (∆Fj).

Nondestructive observation of state of water in concrete using dielectric spectroscopy

We present a method of observing the relaxation process reflecting the motion of water molecules masked by the contribution of electrical conduction. By using this method, we can observe the Cole–Cole-type relaxation process reflecting the motion of the bound water molecules in cement-based materials. The relaxation time and strength of this process increase with curing time, and both parameters saturate to a constant value. The curing time dependence of compressive strength can be described by a logarithmic function, and the change in compressive strength correlates strongly with the change in relaxation time. In the analysis using the τ-β CC diagram, the trajectory of the τ-β CC diagram shifts to the lower right as the curing progresses, and the feature of the trajectory of the τ-β CC diagram depends on the difference in the wetting environment. Our results indicate that the state of water retained in the pore structure can be used as a probe to obtain information on the curing progress of concrete.

Poly[di-aqua-[μ-1,4-bis-(pyridin-4-ylmeth-yl)pip-era-zine][μ-4-(carboxyl-atoeth-yl)benzoato]nickel(II)

The title compound, [Ni(C10H8O4)(C16H20N4)(H2O)2]n, contains NiII cations octa-hedrally surrounded within an [O4N2] coordination set. The cations are linked by 4-(carb-oxy-eth-yl)benzoate (ceb) and 1,4-bis-(pyridin-4-ylmeth-yl)piperazine (bpmp) ligands into tri-periodic diamondoid (dia) networks. The fivefold inter-penetrated dia networks are held into the crystal structure by means of O-H⋯O hydrogen bonding between bound water mol-ecules and unligated carboxyl-ate O atoms of the ceb ligands.

Neutron studies of diffusion processes near a singular point in a dilute aqueous solution of ethanol

The problem considered in this work relates to the physics of liquids. Rather, to the physics of dynamic processes in liquids. The method of quasielastic scattering of slow neutrons was used to study the dynamics of molecules of the water-ethanol system as a function of concentration at a temperature of 8 °C and as a function of temperature at a concentration of X = 0.04 molar particles (mol. particl.). The overall coefficient of self-diffusion of molecules D, its single-particle Ds-p and collective Dcoll components, as well as the time of settled life of a molecule in a vibrational state t, are determined. The region of small concentrations was studied in detail, where in the vicinity of concentrations X = 0.04 mol. particl. and X = 0.2 mol. particl. two minima are found in the coefficients D and Ds-p. Time t at these concentrations increases significantly. This indicates a significant decrease in the intensity of the activation mechanism of molecular diffusion at these concentrations, which is quite possibly caused by the binding of water and ethanol molecules into complexes (clusters). Similarly, a deep minimum was found in the D and Ds-p coefficients near the temperature of 4 °С. Time t at this temperature also increases. That is, at a temperature of 4 °C, the intensity of the activation mechanism of the diffusion of solution molecules decreases. Therefore, at a concentration of X = 0.04 mol. particl. and at a temperature of 4°C, a special point exists in the water-ethanol system. However, its position does not coincide with the data on scattering light.

Methyl-Functionalized Al-Based MOF ZJU-620(Al): A Potential Physisorbent for Carbon Dioxide Capture.

Developing Al-based metal-organic frameworks (MOFs) with moisture-resistance ability is a challenge for carbon dioxide (CO2) capture. Methyl-functionalized Al-based MOF ZJU-620(Al), with excellent chemical-thermal stability and specific surface area of 1347 m2/g, observed here, is a potential adsorbent for CO2 capture with good recyclability and large capacity up to 4.25 mmol/g at 298 K and 1 atm. CO2 molecules are largely trapped on two types of sites. One (site I) is near the AlO6 clusters, and another (site II) is between two parallel benzene rings with a distance of 6.64 Å. ZJU-620(Al) can be used for CO2/N2 (15/85) separation with the excellent selectivity up to 107.20 at 273 K and 31.93 at 298 K, and the separation factor of 13.68. It is also with excellent moisture-resistance ability due to 5% breakthrough time (outlet concentration reached the 5% of inlet concentration) without reduction at 80% relative humidity than under dry conditions. Water molecules occupy a small amount of CO2 adsorption site I, but they almost do not occupy the CO2 adsorption site II due to hydrophobic methyl-functional ligands. Moreover, CO2 can be adsorbed on the ZJU-620(Al) surface through C═O···H binding of water molecules with high affinity. Thus, ZJU-620(Al) is a candidate adsorbent for CO2 capture and separation especially under humidity conditions.

Effects of garlic peptides on rheology, moisture, microstructure, gluten distribution, and baking properties of dough

The effects of different proportions of Garlic Peptides (GPs) on wheat dough were investigated to improve the dough quality. The pasting, rheological properties, water migration and distribution, microstructure, protein polymerization, and baking behaviors of GPs on the dough were determined. Pasting results showed that GPs inhibited starch swelling and gelatinization, improved the gas production capacity of yeast, and promoted dough fermentation. Rheological properties showed that GPs had a moderate weakening effect on dough, thus reducing the viscoelasticity of dough. Meanwhile, GPs could effectively bind water molecules and inhibit the water migration. Moreover, GPs could change the gluten distribution in the dough, facilitating the development of gluten networks. In addition, baking characteristics showed that GPs helped produce bread with uniform internal structure and soft texture. Therefore, this study emphasized the potential role of GPs and showed the theoretical basis of interactions in peptides-dough systems.

Altered structure indicating reduced barrier function of lesional compared to non-lesional psoriatic skin-A non-invasive in vivo study of the human stratum corneum with confocal Raman micro-spectroscopy.

Psoriasis, one of the most common skin diseases affecting roughly 2%-3% of the world population, is associated with a reduced skin barrier function (SBF) that might play an important role in its pathophysiology. The SBF is provided primarily by the stratum corneum (SC) of the skin. Previous studies have revealed a higher trans-epidermal water loss, lower hydration, abnormal concentration and composition of intercellular lipids, as well as alterations in secondary keratin structure in the psoriatic SC. We compared on molecular level lesional psoriatic skin (LPS) with non-lesional psoriatic skin (nLPS) from 19 patients non-invasively in vivo, using confocal Raman micro-spectroscopy. By analysing the corresponding Raman spectra, we determined SBF-defining parameters of the SC depth-dependently. Our results revealed a lower total lipid concentration, a shift of lamellar lipid organisation towards more gauche-conformers and an increase of the less dense hexagonal lateral packing of the intercellular lipids in LPS. Furthermore, we observed lower natural moisturising factor concentration, lower total water as well as a strong tendency towards less strongly bound and more weakly bound water molecules in LPS. Finally, we detected a less stable secondary keratin structure with increased β-sheets, in contrast to the tertiary structure, showing a higher degree of folded keratin in LPS. These findings clearly suggest structural differences indicating a reduced SBF in LPS, and are discussed in juxtaposition to preceding outcomes for psoriatic and healthy skin. Understanding the alterations of the psoriatic SC provides insights into the exact pathophysiology of psoriasis and paves the way for optimal future treatments.

Water State in Hemoglobin Solutions: Microwave Dielectric Spectroscopy Study

In this review, we discuss the dielectric relaxation of water in the Hemoglobin (Hb) aqueous solutions in different states (MetHb, OxyHb, and DeoxyHb)). The interpretation of the results was performed by the 3D trajectory approach, which considers dielectric parameters of water relaxation and protein concentration. It has been shown that the interaction of amino acid dipole residues, located on the surface of a protein macromolecule, with water dipoles determines the protein hydration. In addition, ions of the buffer, in which proteins are dissolved, are also hydrated. The transition from a dipole-ion interaction of water molecules to a dipole-dipole interaction of water with an increase in protein concentration is observed. We proposed a new approach to calculate hemoglobin hydration shells. The theoretical model defines the change in the ratio between the content of free and bound water molecules (BWM) as a function of MetHb concentration in ion-free and ion-containing aqueous solutions. It considers the number of positive and negative charges at the surface of the protein molecule, the number of BWMs in its hydration shells, and the partition of water molecules bound to MetHb and the inorganic ions. The theoretical evaluation of the ratio of free-to-bound water reveals that, in the absence of ions, MetHb binds about 1400 water molecules, which is in good agreement with experimental data. At MetHb concentrations close to physiological, Hb is dominating in binding water over the inorganic ions, and the amount of BWM remains at the level of ~20% of total cytosol water as the concentration of Hb increases above 15 g/dL. These results suggest that in the physiological concentration diapason (29 - 35g/dL), molecules of MetHb are so close together that their hydration shells interact and shrink from four to one layer of water molecules. In contrast, Hb molecules aggregate to neutralize their surface charges mutually.

Synthesis of pH-dependent Ni(II) coordination complexes with Schiff base and their structural characterization

This article describes the study of two Nickel (Ni(II)) complexes based on Schiff base at pH 7.0 and pH 9.0 respectively and characterized using various characterization techniques. The reaction of C7H9N3S2 with NiCl2·6H2O at pH 7.0 resulted in the C1 complex. However, when the same reaction was performed at pH 9.0, C2 complex was obtained. The magnetic behavior (µ) of both complexes was found to be 2.92 (C1) and 2.96B.M. (C2) respectively, which showed that both complexes were paramagnetic and in octahedral shape. In a similar fashion, the electrical conductance of (181.0 Ohm-1cm2 mole-1 for (C1) and (179 Ohm−1 cm2 mole-1 for (C1) suggested that the compound was found in the 1:2 (Metal: Ligand) electrolytically nature in their coordination mode. In the electronic spectrum study, it is clearly shown that both the Ni(II) complexes (9500–10415, 14200–14940, and 23500–24000 cm−1) were octahedral. The broad band at 3350–3600 cm−1 in the IR data of C1 indicates the νOH mode of vibration of the bounded water molecules. Whereas, the 610 cm−1 band is unchanged in the C1 but found red-shifted (600 cm−1) in C2 complex. This indicates that the sulfur of the thiophene unit is not involved in the bonding coordination to metal in C1 but has coordinated with the metal C2 complex.

Poly[[(μ-aqua)[μ4-4-(carboxyl-atometh-yl)ben-zo-ato]cobalt(II)] hemi[1,4-bis-(pyridin-4-ylmeth-yl)piper-azine] hemihydrate

In the title com-pound, {[Co(C9H6O4)(H2O)]·0.5C16H20N4·0.5H2O}n, two-di-men-sional coordination polymer slabs are held together in the three-dimensional crystal structure by means of O-H⋯N hydrogen bonding between bound water mol-ecules and pyridyl N atoms of cocrystallized 1,4-bis-(pyridin-4-yl-meth-yl)piperazine mol-ecules.

A bridging model of a water-triggered shape-memory effect in an amorphous polymer undergoing multiple glass transitions

Hydrothermally-driven shape memory polymers (SMPs) have been extensively studied due to their advantage of having multiple response capabilities. In these SMPs,bound water reduces their glass transition temperatures (T g) by plasticizing the soft segments to achieve a water-triggered shape-memory effect (SME). However, the effect of bound water on hard segments, which has a synergistic effect on the T g and water-triggered SME of the soft ones, remains largely unexplored. In this study, we propose a new model to explore the working principles and hydrothermally-driven shape memory behaviors of amorphous SMPs. The bound water molecules are first divided into bridging and non-bridging bound water, and then a bridging effect is proposed to convert hard segments into soft ones, thus affecting the T g and water-triggered shape memory behavior in SMPs. An extended Gordon–Taylor model is formulated to identify the effects of bound water weight fraction and T g. Furthermore, a constitutive relationship between strain and relaxation time has been developed to describe the effects of temperature and bound water weight fraction on the hydrothermally-driven shape memory behaviors. Finally, the effectiveness of the proposed models is verified using the experimental results of amorphous SMPs reported in the literature.