Water-dimethyl Sulfoxide Solutions Research Articles

THERMODYNAMICS OF QUERCETIN SOLVATION IN WATER-DIMETHYLSULFOXIDE SOLVENT

The distribution coefficients of quercetin (QCT) in water-dimethylsulfoxide solvents with a content of dimethylsulfoxide from 0.0 to 0.5 mol. fr. were determined by the method of interfacial distribution of the substance between two immiscible phases: aqueous or water-dimethylsulfoxide solution and n-hexane at 298.2 K. The distribution coefficients are less than one, which indicates a better solvation of quercetin in water and a water-dimethylsulfoxide solvent than in hexane. Changes in the distribution coefficients of quercetin are not correlated with a gradual increase in the content of dimethylsulfoxide (DMSO) in the solvent. Using the obtained values of the distribution coefficients, we calculated the changes in the Gibbs energy of re-solvation of quercetin in water-dimethylsulfoxide solvents. The dependence of the Gibbs energy of QCT re-solvation on the solvent composition has an extreme form with a minimum in the range of DMSO concentrations corresponding to 0.3 mol. fr. A comparative analysis of the effect of a water-dimethylsulfoxide solvent on the change in Gibbs energy of re-solvation of quercetin, nicotinamide and nicotinic acid was carried out. In the case of both nicotinamide and nicotinic acid, an extreme change is observed in the Gibbs energy of re-solvation of particles with a maximum in the region with a low content of non-aqueous component XDMSO ≈ 0.1 mol. fr. The main contribution to the weakening of the solvation of nicotinamide and nicotinic acid is due to the enthalpy component, and with increasing concentration of dimethylsulfoxide there is an increase in the contribution of entropy to the change in the Gibbs energy transfer. An extreme change in the Gibbs energy transfer of quercetin suggests that the minimum on the dependence ∆trGº(QCT) = F(χDMSO) is also a consequence of a change in the prevailing thermodynamic factor in the solvate state of quercetin.

Stability Constants of Copper(II) Glycylglycinate Complexes in Water–Dimethylsulfoxide Solutions

Stability constants of normal and copper(II) bis-glycylglycinate complexes in water–dimethylsulfoxide solutions of variable composition are determined via potentiometry at a temperature of 298 K and an ionic strength of the solutions of 0.1 (NaClO4). The dissociation constants of the peptide group in copper(II) glycylglycinate in water–dimethylsulfoxide mixtures are calculated. It is found that the stability of copper(II) complexes with glycylglycinate ion grows along with the content of dimethylsulfoxide. Contributions from the resolvation of reagents in a water–dimethylsulfoxide solvent to the change in the Gibbs energy of copper(II) glycylglycinate formation are estimated.

Anomalous viscoelastic response of water-dimethyl sulfoxide solution and a molecular explanation of non-monotonic composition dependence of viscosity.

Amphiphilic molecules such as dimethyl sulfoxide (DMSO) and its aqueous binary mixtures exhibit pronounced nonideality in composition dependence of several static and dynamic properties. We carry out detailed molecular dynamics simulations to calculate various properties including viscosity of the mixture and combine the results with a mode coupling theory analysis to show that this nonideality can be attributed to local structures that are stable on a short time scale but transient on a long time scale to maintain the large scale homogeneity of the solution. Although the existence of such quasistable structures has been deciphered from spectroscopy, a detailed characterization does not exist. We calculate stress-stress autocorrelation functions (SACFs) of water-DMSO binary mixtures. We employ two different models of water, SPC/E and TIP4P/2005, to check the consistency of our results. Viscosity shows a pronounced nonmonotonic composition dependence. The calculated values are in good agreement with the experimental results. Fourier transform of SACF provides frequency-dependent viscosity. The frequency-dependent viscosity (that is, viscoelasticity) is also found to be strongly dependent on composition. Viscoelasticity exhibits sharp peaks due to intramolecular vibrational modes of DMSO, which are also seen in the density of states. We evaluate the wavenumber dependent dynamic structure factor and wavenumber dependent relaxation time. The latter also exhibits a sharp nonmonotonic composition dependence. The calculated dynamic structure factor is used in mode coupling theory expression of viscosity to obtain a semiquantitative understanding of anomalous composition dependence of viscosity. Both the self-diffusion coefficients and rotational correlation times of water and DMSO molecules exhibit nonmonotonic composition dependence.

Spectrophotometric Evaluation of L-Lysine Concentrations in Water–Organic Solutions

In this work, the conditions of spectrophotometric evaluation of the ninhydrin assay for L-lysine in a water dimethyl sulfoxide solution were investigated. The absorption spectrum of the L-lysine–ninhydrin reaction product exhibited two maxima at 420 and 500 nm. It was shown that pH of the reaction medium affected the intensity of the product color. The stability of the ninhydrin reaction products was the highest at pH 8–9. The phase proportion of the water–organic solution had little effect on the optical density of the product. The absorption spectra of the ninhydrin reaction products of L-lysine derivatives: Nα-boc-lysine and Ne-z-lysine, indicated that it was the α amino group of lysine that participated in the reaction.

Isopoly Tungstate Anions in Water–Dimethyl Sulfoxide Solutions

The formation of isopoly tungstate anions (IPTAs) in water–dimethyl sulfoxide (DMSO) solutions was studied by potentiometric titration, followed by mathematical modeling, and electronic absorption spectroscopy. Logarithmic equilibrium constants and Gibbs free energies were calculated for IPTA formation from $$\rm{WO}_4^{2-}$$ and Н+ in the $$\rm{WO}_4^{2-}$$ –H+(DMSO = dimethyl sulfoxide) system for various solution acidities Z=v(H+)/v( $$\rm{WO}_4^{2-}$$ ). A scheme was suggested for IPTA interconversions at various DMSO contents in solution. Dimethyl sulfoxide was found to have a stabilizing effect on [W7O24]6– and [W10O32]4– anions. The distribution diagrams and the calculated thermodynamic parameters of IPTA formation were used to determine optimal conditions for preparing decatungstates from water–DMSO solutions, which consisted in using sodium tungstate solutions acidified to Z = 1.60 and containing ϕ(DMSO) = 40%.

Декавольфрамат никеля [Ni(C2H6SO)5(H2O)]2[W10O32]: Синтез из водно-диметилсульфоксидного раствора, определение кристаллической структуры, ИК- и КР-спектроскопический анализ, микроморфология поверхности

Декавольфрамат никеля [Ni(C2H6SO)5(H2O)]2[W10O32]: Синтез из водно-диметилсульфоксидного раствора, определение кристаллической структуры, ИК- и КР-спектроскопический анализ, микроморфология поверхности

Diffusive Transport in Pores. Tortuosity and Molecular Interaction with the Pore Wall

The self-diffusion of neat water, dimethyl sulfoxide (DMSO), octanol, and the molecular components in a water–DMSO solution was measured by 1H and 2H NMR diffusion experiments for those fluids imbibed into controlled pore glasses (CPG). Their highly interconnected structure is scaled by pore size and shows invariant pore topology independent of the size. The nominal pore diameter of the explored CPGs varied from 7.5 to 72.9 nm. Hence, the about micrometer mean-square diffusional displacement during the explored diffusion times was much larger than the individual pore size, and the experiment yielded the average diffusion coefficient. Great care was taken to establish the actual pore volumes of the CPGs. Transverse relaxation experiments processed by inverse Laplace transformation were performed to verify that the liquids explored filled exactly the available pore volume. Relative to the respective diffusion coefficients obtained in bulk phases, we observe a reduction in the diffusion coefficient that is independent of pore size for the larger pores and becomes stronger toward the smaller pores. Geometric tortuosity governs the behavior at larger pore sizes, while the interaction with pore walls becomes the dominant factor at our smallest pore diameter. Deviation from the trends predicted by the Renkin equation indicates that the interaction with the pore wall is not a just simple steric one but is in part dependent on the specific features of the molecules explored here.

Surface modification of superabsorbing hydrogels through a feasible esterification reaction: Toward tunable superabsorbent for hygienic applications

ABSTRACTImproved superabsorbent polymers (SAPs) were prepared by feasible esterification reactions to prohibit gel blockage and develop swollen gel strength leading to enhanced saline absorbency under load (AUL). Thus, water–dimethylsulfoxide solutions containing benzyl chloride and 1,2-dichloroethane were used to modify SAP particle surface through tetramethylguanidine-promoted reactions. Attenuated total reflection-Fourier transform infrared spectroscopy was used to verify the modification. Influence of the modification reaction variables on free swelling (in water and saline), AUL, absorption rate, contact angle, water retention capability, gel blockage prohibition, gel content, and rheological properties were investigated. This modification approach was considered as a good candidate to scale up the production of SAPs for hygienic applications.

Transparent, conductive gold nanowire networks assembled from soluble Au thiocyanate

Extremely long gold nanowires spontaneously assemble in a water-dimethylsulfoxide (DMSO) solution of Au(SCN)4(-). The Au nanowires were crystalline, exhibited a very high aspect ratio, and, importantly, were produced without co-addition of reducing agents. Transparent conductive films were formed by surface deposition of the nanowires and plasma treatment.

Thermodynamic Study of Poly(vinyl pyrrolidone) in Water/Dimethyl Sulfoxide Solutions by Viscometry

In this work, the intrinsic viscosities of poly(vinyl pyrrolidone) with a molar mass of 58 kg⋅mol−1 were measured in water–dimethyl sulfoxide solutions at temperatures from (298.15 to 318.15) K. The expansion factors of the polymer chains were calculated from the intrinsic viscosity data. The thermodynamic parameters (entropy of dilution parameter, the heat of dilution parameter, theta temperature, polymer–solvent interaction parameter and second osmotic virial coefficient) were derived by the temperature dependence of the polymer chain expansion factor. The thermodynamic parameters indicate that mixtures of water/dimethyl sulfoxide become poorer solvents for poly(vinyl pyrrolidone) as the temperature is increased. Also, the thermodynamic parameters indicate that water/dimethyl sulfoxide mixtures become better solvents for poly(vinyl pyrrolidone) by increasing the volume fractions of dimethyl sulfoxide.

Thermochemical characteristics of nicotinamide protolytic equilibria in water-dimethylsulfoxide mixtures

The heat effects of nicotinamide protonation in water-dimethylsulfoxide (DMSO) solutions over the concentration range 0–0.75 DMSO mole fractions were determined calorimetrically at 25.00 ± 0.01°C and ionic strength 0.25 (NaClO4). Changes in the enthalpy of protonation as the content of DMSO increased were found to be described by an S-shaped curve. This curve shape was caused by the dynamics of reagent solvation contributions as the concentration of DMSO grew with the predominance of the nicotinamide solvation contribution.

Effect of solvation on the thermodynamics of the formation of molecular complexes of 18-crown-6 ether with glycine in water-dimethylsulfoxide solutions

Complexation of the 18-crown-6 ether (18C6) with glycine (Gly) in mixed H2O-DMSO solvents with the composition of 0.1, 0.2, and 0.25 mole fraction of DMSO (T = 298.15 K) was studied calorimetrically. Thermodynamic characteristics of the reaction of the formation of the molecular Gly18C6 complex (ΔrG°, ΔrH°, TΔrS°) were calculated from the calorimetric data. It was established that the change in the stability of the Gly18C6 complex is mainly determined by the predominance of the enthalpy component of the Gibbs energy over the entropy component. It was shown during the analysis of the enthalpy contributions of the reagents to the enthalpy of the reaction of the formation of Gly18C6 that the change in the enthalpy of the reaction upon a change the solvent composition was due to changes in the solvation state of 18C6.

Constants of acid-base equilibria of glycylglycine in water-dimethyl sulfoxide solutions at 298 K

Constants of acid-base equilibria of glycylglycine were obtained by potentiometry at a temperature of 298 K and an ionic strength of 0.1 M (NaClO4) in water-dimethyl sulfoxide solutions. It was determined that upon an increase in the content of the organic component in solution, the dissociation constant of the glycylglycinium ion declines stepwise. It was concluded that the pK of the dissociation of glycylglycine versus the composition of a mixed solvent is of a critical character with a minimum in the water-organic solvent composition range of 0.1 to 0.3 molar fractions of DMSO. It is suggested that upon an increase in the concentration of DMSO, the zwitter-ion form of glycylglycine transitions to the molecular form.

Problems of solubility of hydrolysis lignin

Interaction of hydrolysis lignin with polyacrylonitrile in water-dimethyl sulfoxide solution in the presence of an activator was studied, and the properties of the products were examined.

Copolymerization of sodium 2-acrylamido-2-methylpropanesulfonate with sodium acrylate in water-dimethyl sulfoxide solutions

The solvent effect on the kinetic features of the synthesis and molecular characteristics of the copolymers in homogeneous radical copolymerization of sodium 2-acrylamido-2-methylpropanesulfonate with sodium acrylate in water and water-dimethyl sulfoxide mixtures (75: 25, 50: 50, 25: 75) at pH 9 and 60°C in the presence of potassium persulfate was studied

Fluorescent analysis of the structural changes of human serum albumin induced by low temperatures in water-dimethyl sulfoxide solutions

Structural changes in human serum albumin (HSA) induced by low temperatures in water-dimethyl sulfoxide (DMSO) solutions were studied by fluorescent spectroscopy. The emission, synchronous, and isopotential synchronous spectra (3D spectra) of the HSA were analyzed. It was shown that protein does not undergo drastic structural changes in the fast freezing/defrosting mode in solutions of up to 20% DMSO but becomes more compact.

The effect of solvated ions on the thermal denaturation of human serum albumin in water-dimethylsulfoxide solutions

The effects of solvated ions on the thermal denaturation of human serum albumin (HAS) in water-dimethylsulfoxide (DMSO) solutions were studied by the method of electron absorption spectroscopy. It was shown that depending on the DMSO concentration, electrolytes (LiCl, LiNO3, LiClO4, NaCl, and NaNO3) contained in these solutions were characterized by different anion and cation solvation degrees: unlike cations, anions were only negligibly solvated, which affected HAS thermal denaturation. Electrostatic interactions between anions and positively charged amino acid residues supporting protein denaturation subsided in the line Cl- > NO3- > ClO4-.

Effects of solvent on the redox properties of cytochrome c: cyclic voltammetry and 1H NMR experiments in mixed water-dimethylsulfoxide solutions

Bovine heart cytochrome c (cyt c) was studied through cyclic voltammetry, 1H NMR and circular dichroism measurements in mixed water-dimethylsulfoxide (DMSO) solutions containing up to 50% DMSO by volume, under different conditions of temperature and pH. The effect of DMSO on the reduction potential of native cyt c was found to be determined mainly the he decrease in dielectric constant of the medium. No appreciable specific DMSO-protein interactions were detected. Instead, DMSO affects to some extent the conformation of alkaline cyt c and notably, stabilizes both redox states of this form to the detriment of the native form. In particular, DMSO lowers the p K a of the native to alkaline transition for oxidized cyt c and increases the electrochemical reversibility of the voltammetric wave of the alkaline form. DMSO-induced changes in the reduction entropy for native and alkaline cyt c were also determined and interpreted tentatively in terms of solvation properties of the heme and structural features of the protein environment.

Comparative study of the structure of microlayering water-dioxane and water-dimethylsulfoxide solutions

The infrared absorption spectra of water in the water-dioxane and water-dimethylsulfoxide systems have been investigated in a wide range of concentrations. Absorption bands of differen: forms of water present in solution have been identified. The state of internal water in aqueous microregions in both systems is characterized by increased stability. It is proposed that the specific state of the internal water of microregions is the motive force of the microlayering process hindering its ransition into ordinary macrolayering. Consecutive microlayering stages at varying concentrations of the nonelectrolyte are considered. The behavior of protein molecules in different microlayering solverts has been studied.

Site-specificities in the interactions of Cu(II) with aldopentopyranoses in dimethyl sulfoxide

Interactions of Cu(II) with aldopentoses having different C3 and C4 hydroxy configuration, D-arabinose, D-xylose, and their methyl glycosides, in water-dimethyl sulfoxide (dmso) solutions were studied by 13C NMR with specific line broadening techniques and electronic and ESR spectrometries. When monosaccharides had the arabinopyranose-type ring configuration, site-specific interaction involving C3 and C4 hydroxy groups was observed in dmso, and Cu(II) was shown to suffer tetragonal distortion upon coordination of monosaccharides. Anomer- and site-specificity of the interaction between monosaccharides and Cu(II) were sensitive to the nature of the solvent.