Carbohydrates In Aqueous Solution Research Articles

Transferable united atom model for carbohydrates with explicit water: Glucose and sucrose

Understanding the role that molecular interactions have in aqueous solutions of carbohydrates is important in several technological applications, such as in the pharmaceutical industry. It is developed a force field for glucose and sucrose from a united atom model of methanol and ethanol parameterized with explicit water. The simulation results of liquid density, dielectric constant, surface tension, self-diffusion coefficient and shear-viscosity of glucose and sucrose in aqueous solutions are in excellent agreement with experimental data. The model improves the results of several all atoms models evaluated in this work. The surface tension increases with concentration of both carbohydrates because the molecules are dissolved within the liquid. It is also developed an all atoms model of glucose where dielectric constant is increased by changing the Lennard-Jones parameters. That model predicts that glucose is adsorbed at the liquid-vapor interface decreasing the surface tension as the concentration increases but the transport properties are not well reproduced. It is shown that the dielectric constant depends linearly on the molecular dipole moment of a mixture. The dihedral distribution on the hydroxymethyl group has a small effect on thermodynamic and transport properties. The systems are homogeneous and no evidence of phase separation is observed in the range of studied concentrations.

Relationships between Molecular Structure of Carbohydrates and Their Dynamic Hydration Shells Revealed by Terahertz Time-Domain Spectroscopy.

Despite more than a century of research on the hydration of biomolecules, the hydration of carbohydrates is insufficiently studied. An approach to studying dynamic hydration shells of carbohydrates in aqueous solutions based on terahertz time-domain spectroscopy assay is developed in the current work. Monosaccharides (glucose, galactose, galacturonic acid) and polysaccharides (dextran, amylopectin, polygalacturonic acid) solutions were studied. The contribution of the dissolved carbohydrates was subtracted from the measured dielectric permittivities of aqueous solutions based on the corresponding effective medium models. The obtained dielectric permittivities of the water phase were used to calculate the parameters describing intermolecular relaxation and oscillatory processes in water. It is established that all of the analyzed carbohydrates lead to the increase of the binding degree of water. Hydration shells of monosaccharides are characterized by elevated numbers of hydrogen bonds and their mean energies compared to undisturbed water, as well as by elevated numbers and the lifetime of free water molecules. The axial orientation of the OH(4) group of sugar facilitates a wider distribution of hydrogen bond energies in hydration shells compared to equatorial orientation. The presence of the carboxylic group affects water structure significantly. The hydration of polysaccharides is less apparent than that of monosaccharides, and it depends on the type of glycosidic bonds.

Chromatographic separation of mannitol from mixtures of other carbohydrates in aqueous solutions

The isolation of mannitol from natural sources, e.g. from plant extracts or broths, requires considerable time and effort. The separation of mannitol from aqueous solutions containing also glucose, fructose, and sucrose was tested using discontinuous preparative anion- and cation-exchange chromatography. The suitability of the application in the separation of carbohydrates and especially mannitol was tested under various conditions and using three different types of ion-exchangers. The effect of sorbent regeneration and modification on the separation was also examined using different concentrations and volumes of chemical agents. The fractions collected after the discontinuous chromatography were analysed on the content of mannitol by the high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) method. The successful isolation of pure mannitol fraction, using water as a mobile phase and a combination of sodium chloride and hydroxide for sorbent regeneration, was achieved only on anion-exchange chromatography.

Probing interactions and hydration behaviour of drug sodium salicylate in aqueous solutions of D-xylose/L-arabinose: Volumetric, acoustic and viscometric approaches

The solute–solute and solute–solvent interactions of drug sodium salicylate in aqueous-carbohydrate solutions are investigated using experimentally measured densities, ρ, ultrasonic speeds, u and viscosities, η of the drug sodium salicylate in water and in aqueous−D-xylose/L-arabinose (5% and 10% D-xylose/L-arabinose in water, w/w) solvents at temperatures (293.15, 298.15, 303.15, 308.15, 313.15 and 318.15) K and at atmospheric pressure. The ρ, u and η data were used to calculate the apparent molar volumes, Vϕ, limiting apparent molar volumes, Vϕ°, limiting apparent molar expansibilities, Eϕ°, apparent molar compressibilities, Ks,ϕ, limiting apparent molar compressibilities, Ks,ϕ° along with the transfer volumes, Vϕ,tr° and transfer compressibilities, Ks,ϕ,tr°. Furthermore, Falkenhagen coefficient A, Jones-Dole coefficient B, free energy of activation of viscous flow per mole of solvent, Δμ1°# and per mole of solute, Δμ2°#, enthalpies, ΔH°# and entropies, ΔS°#of activation of viscous flow were obtained from the viscosity data. The observed trends in these properties as function of temperature and composition were analysed in terms of molecular interactions amongst the solute and solvent molecules. The results are discussed in terms of hydrophilic-hydrophilic and hydrophilic-hydrophobic interactions in these systems along with the structure breaking/making ability of the drug.

Aqueous solutions of carbohydrates are new choices of green solvents for highly efficient exfoliation of two-dimensional nanomaterials

Abstract Deep eutectic solvents (DESs) have found great interest among researchers due to their green nature and lower costs compared to organic solvents and ionic liquids. Water, an essential component of most DESs, poses paramount impacts on the properties of these solvents. In the present study, we found that water can modulate the molecular arrangement of the solvent and affect the synthesis efficiency of both MoS2 and graphene nanosheets considerably. Using a low-cost mechanical exfoliation approach and response surface methodology, we achieved the synthesis yield of 87% for MoS2 nanosheets. We also succeeded in the production of few-layer graphene with the average lateral dimension of 3.5 μm. We further showed that it is possible to dilute DESs by water and still retain the synthesis yield at reasonably high levels. In this way, the total cost of the exfoliation process reduces, particularly when it is aimed to synthesize large scales of two-dimensional nanomaterials.

Поляриметрия как метод изучения структуры водных растворов углеводов: корреляция с другими методами

Поляриметрия как метод изучения структуры водных растворов углеводов: корреляция с другими методами

Molecular interactions of drug semicarbazide hydrochloride in aqueous-D-xylose/L-arabinose solutions at different temperatures: Volumetric, acoustic and viscometric study

The interactions of drug semicarbazide hydrochloride in water and in aqueous-carbohydrate (D-xylose/L-arabinose) solutions from their physicochemical behaviour are studied. Density, ρ, ultrasonic speed, u and viscosity, η of the drug semicarbazide hydrochloride in water and in aqueous-D-xylose/L-arabinose (5 wt% and 10 wt% of D-xylose/L-arabinose in water, w/w) solvents were measured as functions of concentrations at temperatures, T = (293.15 – 318.15) K and at atmospheric pressure, p = 101 kPa. The measured data have been utilized to calculate various properties like the apparent molar volume, Vφ from density measurements while apparent molar compressibility, Ks,ϕ, acoustic impedance, Z and intermolecular free length, Lf from ultrasonic speed measurements. The values obtained from these parameters indicate strong solute–solvent interactions within the solutions. The viscosity data have been analyzed using Jones-Dole equation and coefficients A and B were evaluated. The temperature derivative of B-coefficient, dB/dT together with activation parameters of viscous flow have also been determined. The results are discussed in terms of hydrophilic-hydrophilic and hydrophilic-hydrophobic interactions in these systems along with the structure breaking/making ability of the drug.

Study on the interactions of drug isoniazid in aqueous-D-xylose/L-arabinose solutions at different temperatures using volumetric, acoustic and viscometric approaches

Volumetric, acoustic and viscometric properties of drug isoniazid in water and aqueous solutions of carbohydrates, D-xylose and L-arabinose (5% and 10% D-xylose/L-arabinose in water, w/w) were studied at various temperatures, T = (293.15–318.15) K and at atmospheric temperature. The apparent molar volumes, Vϕ and apparent molar compressibilities, Ks,ϕ were calculated from the experimentally measured densities and ultrasonic speeds. Limiting apparent molar volumes, Vϕ°, limiting apparent molar compressibilities, Ks,ϕ°, limiting molar expansibilities, Eϕ° and their corresponding transfer volumes, Vϕ,tr° and transfer compressibilities, Ks,ϕ,tr° of drug isoniazid from water to aqueous carbohydrate solutions were also evaluated. Falkenhagen Coefficients, A, Jones-Dole coefficients, B, variation of B with temperature, dB/dT, free energies of activation of viscous flow per mole of solvent, Δμ1°# and per mole of solute, Δμ2°#, enthalpies, ΔH°# and entropies, ΔS°# of activation of viscous flow were calculated from the viscosity measurements. The negative sign of dB/dT indicated the structure making ability of the drug isoniazid. The results obtained have been discussed in terms of solute-solvent interactions in order to understand the solvation behaviour of isoniazid in these aqueous-carbohydrate solutions.

Solute-solute and solute-solvent interactions of drug sodium salicylate in aqueous-glucose/sucrose solutions at temperatures from 293.15 to 318.15 K: A physicochemical study

Physical properties like ultrasonic speed and compressibility give us an idea about the type of interactions prevailing in the solutions. Keeping this in view, we have measured the densities, ρ, ultrasonic speeds, u and viscosities, η of the drug sodium salicylate in water and in aqueous−D-glucose/d-sucrose (5 wt% and 10 wt% glucose/sucrose in water) solvents at different temperatures (293.15, 298.15, 303.15, 308.15, 313.15 and 318.15) K and at atmospheric pressure. These experimental values have been used to calculate apparent molar volumes, Vϕ and apparent molar compressibilities, Ks,ϕ, limiting apparent molar volumes, Vϕ° and limiting apparent molar compressibilities, Ks,ϕ°. The transfer volumes, Vϕ,tr° and transfer compressibilities, Ks,ϕ,tr° of sodium salicylate from water to aqueous carbohydrate solutions were also calculated. The co-sphere model has been used to interpret the transfer molar properties. Using the η data, the viscosity A and B coefficients have been calculated. The variation of viscosity B coefficient with respect to temperature, i.e., dB/dT have been investigated, the sign of which is indicative of the structure making/breaking ability of the drug in these media. The free energy of activation of viscous flow per mole of solvent, Δμ1°# and per mole of solute, Δμ2°#, enthalpies, ΔHο# and entropy, ΔSο# of activation of viscous flow, were also obtained from the viscosity data. The results obtained are discussed in terms of solute-solute and solute-solvent interactions prevailing in these solutions.

Optimizing Nonbonded Interactions of the OPLS Force Field for Aqueous Solutions of Carbohydrates: How to Capture Both Thermodynamics and Dynamics.

Knowledge on thermodynamic and transport properties of aqueous solutions of carbohydrates is of great interest for process and product design in the food, pharmaceutical, and biotechnological industries. Molecular simulation is a powerful tool to calculate these properties, but current classical force fields cannot provide accurate estimates for all properties of interest. The poor performance of the force fields is mainly observed for concentrated solutions, where solute–solute interactions are overestimated. In this study, we propose a method to refine force fields, such that solute–solute interactions are more accurately described. The OPLS force field combined with the SPC/Fw water model is used as a basis. We scale the nonbonded interaction parameters of sucrose, a disaccharide. The scaling factors are chosen in such a way that experimental thermodynamic and transport properties of aqueous solutions of sucrose are accurately reproduced. Using a scaling factor of 0.8 for Lennard-Jones energy parameters (ϵ) and a scaling factor of 0.95 for partial atomic charges (q), we find excellent agreement between experiments and computed liquid densities, thermodynamic factors, shear viscosities, self-diffusion coefficients, and Fick (mutual) diffusion coefficients. The transferability of these optimum scaling factors to other carbohydrates is verified by computing thermodynamic and transport properties of aqueous solutions of d-glucose, a monosaccharide. The good agreement between computed properties and experiments suggests that the scaled interaction parameters are transferable to other carbohydrates, especially for concentrated solutions.

Homogeneous isotope equilibrium of tritium in aqueous solutions of carbohydrates: glucose

Information on equilibrium of tritium exchange reactions in homogeneous liquid systems is important for radiobiology. Developed methods of quasi-equilibrium evaporation and vacuum distillation have been applied to study distribution of tritium in glucose aqueous solutions at moderate temperatures. The results show that both glucose hydroxyls and hydrate water molecules are enriched with tritium. Equilibrium water vapor over glucose solutions contains more tritium than equilibrium vapor over pure water. The distribution is quite insensitive to temperature variations between 20 and 70 °C. The reasoning by analogy results in high possibility of concentrating tritium in sugar parts of DNA and RNA molecules. It supposes to refine the models used in estimating tritium damage for cell nuclei.

Highly Efficient Hydrogenation of Levulinic Acid into γ-Valerolactone using an Iron Pincer Complex.

The search for nonprecious-metal-based catalysts for the synthesis of γ-valerolactone (GVL) through hydrogenation of levulinic acid and its derivatives in an efficient fashion is of great interest and importance, as GVL is an important a sustainable liquid. We herein report a pincer iron complex that can efficiently catalyze the hydrogenation of levulinic acid and methyl levulinate into GVL, achieving a turnover number of up to 23 000 and a turnover frequency of 1917 h-1 . This iron-based catalyst also enabled the formation of GVL from various biomass-derived carbohydrates in aqueous solution, thus paving a new way toward a renewable chemical industry.

Vapor Pressure Osmometry Studies of Aqueous Ionic Liquid–Carbohydrate Systems

Precise vapor pressure osmometry (VPO) measurements at 308.15 K were conducted for solutions of three ILs, 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), 1-butyl-3-methylimidazolium bromide ([Bmim][Br]), and 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim][HSO4]), in aqueous solutions of three carbohydrates, sucrose, maltose, and maltitol, as well as for solutions of the carbohydrates in aqueous solutions of these ILs. Because of the unfavorable IL–carbohydrate interactions, all the investigated IL + carbohydrates aqueous systems show the soluting-out effect and vapor–liquid equilibria behavior of these systems in the monophasic region show the negative deviation from the semi-ideal behavior (aw + 1 [Bmim][HSO4] ≫ [Bmim][Br]. In the case of [Bmim][BF4]/carbohydrate aqueous systems, which have a phase se...

Direct Observation of Carbohydrate Hydroxyl Protons in Hydrogen Bonds with a Protein.

Hydroxyl proton resonances of uniformly 13C-labeled Manα(1-2)Manα(1-2)ManαOMe (Man3) bound to cyanovirin-N (CV-N) were detected at ambient temperature in aqueous solution by NMR spectroscopy. The directions of the hydroxyl groups were determined on the basis of NOEs, and a previously unknown hydrogen-bonding network between Man3 and CV-N was discovered. This is the first report on detecting hydroxyl protons of a protein-bound carbohydrate in aqueous solution by NMR. Approaches such as those presented here may open the door for accurately determining intermolecular hydrogen bonds in carbohydrate-protein complexes.

Evaluation of the effect of ionic-liquids as soluting-out agents on the solubility of carbohydrates in aqueous solutions

In order to study the soluting-effect of ionic liquids on carbohydrates in aqueous solutions and to better understanding of its molecular mechanism, systematic investigations on the vapor–liquid (VLE) equilibria and solid–liquid equilibria (SLE) of ternary ionic liquid + carbohydrate + water systems were carried out at various temperatures. The ionic liquids 1-butyl-3-methylimidazolium bromide ([Bmim][Br]) and 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim][HSO4]) with different hydrophilicity and seven carbohydrates including monosaccharides (L-(+)-arabinose, D-(+)-xylose, D-(+)-glucose and D-(−)-fructose), disaccharides (maltose and sucrose), and a polyol (maltitol) were selected. The water activity data showed that the hydrophilicity of the investigated solutes obey the following order: [Bmim][HSO4] > [Bmim][Br] ≥ carbohydrates. In these systems, the more hydrophilic solutes [Bmim][Br] and [Bmim][HSO4] acted as soluting-out agent and precipitated the sugars from the aqueous solutions. The negative deviations of the constant water activity lines from the linear isopiestic relation for [Bmim][HSO4]/carbohydrate systems were somewhat larger than [Bmim][Br]/carbohydrate systems. The order of these deviations was agreement with the obtained soluting-out coefficients, ks, from the SLE experiments.

Temperature-dependent aggregation of bio-surfactants in aqueous solutions of galactose and lactose: Volumetric and viscometric approach

Abstract Modulation in the aggregation behavior of bio-surfactants (bile salts), sodium cholate (NaC) and sodium deoxycholate (NaDC) in aqueous solutions of carbohydrates (galactose and lactose) have been investigated by measuring the density (ρ), speed of sound (u) and viscosity (η) of the mixtures at different temperatures 293.15, 298.15, 303.15, 308.15 and 313.15 K. The density and speed of sound data have been used to calculate various volumetric and compressibility parameters such as apparent molar volume (Vφ), isentropic compressibility (κs), apparent molar adiabatic compression (κs, φ) to get a better insight into the micellization mechanism of bile salts. Further, the viscosity data have been studied in the light of relative viscosity (ηr) and viscous relaxation time (τ). Some derived parameters such as free volume (Vf), internal pressure (πi) and molar cohesive energy (MCE) of NaC and NaDC in aqueous solution of saccharides have also been calculated from viscosity data in conjunction with density and speed of sound values. All the calculated and derived parameters provide qualitative information regarding the nature of interactions i.e. solute–solute, solute–solvent and solvent–solvent in the solution.

Thermodynamic study of the soluting effect in aqueous ionic liquid - monosaccharide solutions by the vapor pressure osmometry

In this work, to study vapor-liquid equilibria of several ternary ionic liquid+carbohydrate+water and binary ionic liquid+water systems, water activity measurements have been made using the vapor pressure osmometry (VPO) technique at 308.15K. Three imidazolium-based ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), 1-butyl-3-methylimidazolium bromide ([Bmim][Br]), and 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim][HSO4]) and four monosaccharide carbohydrates l-(+)-arabinose, d-(+)-xylose, d-(+)-glucose, and d-(−)-fructose were selected. The hydrophilicities of the investigated ILs follow the order: [Bmim][HSO4]>[Bmim][Br]≫[Bmim][BF4]. Our results showed that the unfavorable IL-carbohydrate interactions can be lead to reducing the water activity and vapor pressure of ternary solution relative to the semi-ideal solution model (Δaw<0 and ∆p−(∆p°IL+∆p°C)<0). For the systems that had extreme negative departure from the semi-ideal behavior ([Bmim][BF4]/carbohydrate) aqueous biphasic system (ABS) is formed in the concentrations higher than the critical values. For these systems, magnitudes of the negative departures from the semi-ideal behavior were in agreement with the soluting-out strength of the monosaccharides that follow the order: d-(+)-glucose>d-(−)-fructose>l-(+)-arabinose>d-(+)-xylose. Aqueous [Bmim][Br]/carbohydrate and [Bmim][HSO4]/carbohydrate systems with smaller negative departure from the semi-ideal behavior are unable to form the ABS and the soluting-out effect of these ILs on aqueous carbohydrate solutions is appeared in the form of precipitation of sugars from the aqueous solutions. In these systems, for a certain carbohydrate the magnitude of the departure from the semi-ideal behavior increased from [Bmim][Br] to [Bmim][HSO4] which is in agreement with the hydrophilicity of the ILs.

Determining detection limits of aqueous anions using electrochemical impedance spectroscopy

BackgroundPulsed amperometric detection is a relatively new method for detection of ions and especially non-electrolytes such as carbohydrates in aqueous solutions. Pulsed amperometric detection relies on a redox reaction while electrochemical impedance simply measures the real and capacitive resistant of the solution. There is a correlation between the real impedance of a solution and the ionic strength of the solution.MethodThis work explores measuring real impedance of pure water as a function of temperature from 25.0 to 60.0 °C to determine the relationship between impedance and temperature. Maintaining temperature at 25.0 °C, solutions of sodium chloride, potassium carbonate, sodium sulfate acetate and bicarbonate have been measured using impedance spectroscopy.ResultsRegression analysis shows that measuring anions using impedance spectroscopy and simple stainless steel cylinders that detection limits at the parts per trillion (ppt) level are possible. There was no statistical difference when comparing impedance values of the same concentration of acetate and chloride in solution, showing real impedance is not dependent on ion size. However, ions with higher charge do result in lower impedance measurements.ConclusionsThis work establishes the use of simple, small, robust stainless steel cylinders and impedance measurements following separation for the identification and quantification of ions in solution.

Soluting-out effect of carbohydrates on the surface active ionic liquid 1-decyl-3-methylimidazolium bromide in aqueous solutions

Herein, with the aim of shedding light on the effect of non-ionic co-solute (carbohydrate) stereochemistry on the aggregation and surface behaviour of ionic liquid-based surfactant 1-decyl-3-methylimidazolium bromide ([C10mim][Br]) in aqueous solution, we studied the surface tension, electrical conductivity, volumetric and compressibility properties for the aqueous solutions of [C10mim][Br] in the presence of different sugars containing pentose monosaccharides (xylose, ribose and arabinose), hexose monosaccharides (glucose, and mannose), disaccharides (sucrose and lactose) and trisaccharide (raffinose) at different temperatures. From the electrical conductivity measurements, the values of the degree of ionization of the counter ion on the micelles (α) and thermodynamic properties of micellization (ΔGm) for [C10mim][Br] in aqueous carbohydrate solutions were obtained. The various parameters such as apparent molar volume (Vϕ), isentropic compressibility (κs), apparent molar isentropic compressibility (Kϕ) and the change of apparent molar properties upon micellization (ΔVϕ,m and ΔKϕ,m) were derived from the experimental density and speed of sound data. The surface tension measurements provided a series of parameters, including surface tension at the cmc (γcmc), effectiveness of surface tension reduction (Πcmc), maximum surface excess concentration (Γmax) and minimum surface area per molecule (Amin) at interface of air/solution for the investigated surfactant in the presence of different sugars at 298.15K. All the investigated carbohydrates have soluting-out effect (favouring the micelle formation) and their abilities to reduce the cmc of [C10mim][Br] in aqueous solutions increase with an increase in the hydrophilicity of the carbohydrate.

Soluting-in and soluting-out of water-soluble polymers in aqueous carbohydrate solutions studied by vapor pressure osmometry

Abstract Precise vapor pressure osmometry measurements at 308.15 K have been performed for ternary systems of carbohydrate in aqueous 0.2 w/w polymer solutions. The polymers are polyethylene glycol 400 (PEG400), polyethylene glycol 10,000 (PEG10000) and polypropylene glycol 400 (PPG400), and the carbohydrates are xylose, xylitol, glucose, fructose, sucrose and raffinose. In order to study the soluting-out and soluting-in effects occurring in the polymer-carbohydrate aqueous systems, deviations of vapor-liquid equilibria behavior of these systems from the semi-ideal state have been evaluated. In the case of PPG + carbohydrates aqueous systems, because of unfavorable PPG-carbohydrate interactions, the solutes exclude themselves from the vicinity of each other and therefore aqueous biphasic systems are entropically formed above a critical concentration. The monophasic and biphasic regions of these systems show, respectively, negative and positive deviations from the semi-ideal behavior, which become more negative and more positive with increasing hydrophilicity of the carbohydrates. However, in the case of PEG + carbohydrate aqueous systems, which are completely miscible, because of favorable PEG-carbohydrate interactions, the interaction of each solute with water molecules becomes weaker in the presence of the other solute. These systems show positive deviations from the semi-ideal behavior. By increasing the PEG molar mass and decreasing the hydrophilicity of carbohydrates, the carbohydrate-PEG interactions increase and then the positive deviations from the semi-ideal state increase.