Alcohol-water Media Research Articles

Modeling the Formation of Liposomes with Vinpocetine from Soy Lecithin Phospholipids by Molecular Dynamics

Introduction. Liposomal preparations have the following advantages: they protect body cells from the toxic effects of drugs; prolong the action of the drug introduced into the body; protect medicinal substances from degradation; promote the manifestation of targeted specificity due to selective penetration from blood into tissues; change the pharmacokinetics of drugs, increasing their pharmacological effectiveness; allow you to create a water-soluble form of a number of medicinal substances, thereby increasing their bioavailability. The development of liposomal forms of vinpocetine is highly relevant. Currently, when developing the composition of liposomal forms, molecular modeling methods are widely used, which are a convenient method for predicting both the properties of the membranes themselves and aspects of the interaction of membranes with small molecules or proteins.Aim. The aim of this study is to model the process of liposome assembly from soy lecithin phospholipids in the presence of vinpocetine by the molecular dynamics method; as well as predicting the distribution of vinpocetine between the internal cavity of the liposome, the phospholipid membrane, and the dispersion medium based on the simulation results.Materials and methods. To simulate the process of liposome formation, the method of coarse-grained molecular dynamics in a Martini 2.2 force field was used using the Gromacs 2016.4 program. The assembly of the simulated system - a solution of soy lecithin phospholipids in water was performed using the Internet service Charmm-GUI-> Inputgenerator-> Martinimaker-> Randombuilder.Results and discussion. The results of molecular modeling showed that the vinpocetine molecules did not penetrate into the liposome, but were adsorbed on its surface. This is due to the low solubility of vipocetin in the hydrophobic medium of the soy lecithin liposome membrane.Conclusion. It was shown that the minimum diameter of a liposome formed from purified soy lecithin is 15.3 nm. Vinpocetine does not penetrate into liposomes from purified soy lecithin, but is adsorbed on the outer surface of their membrane. The surface excess in this case, according to the results of modeling coarse-grained molecular dynamics at a temperature of 298 K in an alcohol-water medium, is 1.2 • 10-7 mol/m2.

Thermo-sensitive polymer nanospheres as a smart plugging agent for shale gas drilling operations

Emulsifier-free poly(methyl methacrylate–styrene) [P(MMA–St)] nanospheres with an average particle size of 100 nm were synthesized in an isopropyl alcohol–water medium by a solvothermal method. Then, through radical graft copolymerization of thermo-sensitive monomer N-isopropylacrylamide (NIPAm) and hydrophilic monomer acrylic acid (AA) onto the surface of P(MMA–St) nanospheres at 80 °C, a series of thermo-sensitive polymer nanospheres, named SD-SEAL with different lower critical solution temperatures (LCST), were prepared by adjusting the mole ratio of NIPAm to AA. The products were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, particle size distribution, and specific surface area analysis. The temperature-sensitive behavior was studied by light transmittance tests, while the sealing performance was investigated by pressure transmission tests with Lungmachi Formation shales. The experimental results showed that the synthesized nanoparticles are sensitive to temperature and had apparent LCST values which increased with an increase in hydrophilic monomer AA. When the temperature was higher than its LCST value, SD-SEAL played a dual role of physical plugging and chemical inhibition, slowed down pressure transmission, and reduced shale permeability remarkably. The plugged layer of shale was changed to being hydrophobic, which greatly improved the shale stability

A comparative study of the electro-osmotic behavior of cation and anion exchange membranes in alcohol-water media

Fuel flow coupled to the migration of ions is an important aspect of direct alcohol fuel cells, since it strongly affects the fuel cell performance. Solvent uptake and electro-osmotic transport in alcohol-water media have been investigated for different ion selective membranes. Cation and anion exchange membranes, and methanol and ethanol were used to assess the influence of the ion nature of the membrane and the type of alcohol. Current-voltage curves were also measured to determine the values of the limiting current density of each membrane system and analyze the influence of the concentration polarization effects on the measure of the electro-osmotic flow. The obtained results indicated that both the ionic nature and the type of alcohol affect the electro-osmotic transport. The membrane system with the anion exchange membrane and methanol-water solvent presented the lowest electro-osmotic permeability and a lower influence of the concentration polarization effects.

Mono and binuclear Ag(I), Cu(II), Zn(II) and Hg(II) complexes of a new azo-azomethine as ligand: Synthesis, potentiometric, spectral and thermal studies

New azo-azomethine dyes were prepared by reaction of p-aminobenzoic acid, o-anisidine, o-nitroaniline, and p-bromoaniline with salicylaldehyde respectively to form azo compounds and then condensation by urea to form 4-(R-arylazo 2-salicylaldene)-urea azo-azomethine derivatives (I a–d). The complexes of these ligands with Ag(I), Cu(II), Zn(II) and Hg(II) metal ions were prepared. The structure of the free ligands and their complexes were characterized by using elemental analysis (C, H, N), 1H NMR, IR and UV–Vis-spectra. The proton dissociation constants of the ligands and the stability constant of their complexes have been determined potentiometrically in 40% (v/v) alcohol–water medium as well as the stoichiometry of complexes were determined conductometrically. The data reveal that the stoichiometries for all complexes were prepared in molar ratios (1:1) and (1:2) (M:L). The electrolytic and nonelectrolytic natures of the complexes were assigned based on molar conductance measurements. The thermogravimetric (TG), and differential thermal analyses (DTA) were studied in nitrogen atmosphere with heating rate 10 °C/min. The kinetic and thermodynamic parameters for thermal decomposition of complexes have been calculated by graphical method using Coats–Redfern (CR) method.

Kinetics and Oxidation of Substituted Benzyl Alcohols by Phenyliodoso Acetate

Oxidation of benzyl alcohol and some meta‐ and para‐ substituted alcohols by phenyliodoso acetate (PIA) in t‐butyl alcohol–water medium (50:50) leads to the formation of corresponding benzaldehyde. The stoichiometry of the reaction was found to be 1:1. The reaction was first order each in substrate and oxidant concentrations. This reaction was studied at four different temperatures and the activation parameters were calculated. Correlation analysis was carried out using Taft’s and Swain’s dual substituent parameter (DSP) equation. The rate data of meta‐ compounds showed good correlation with (F,R) values, para‐substituted benzyl alcohols showed good correlation with σIσR+ A suitable mechanism has been proposed.

Unconventional metal organic frameworks: porous cross-linked phosphonates

The past decade has witnessed an exponential growth of metal organic framework compounds (MOFs). The defining character of these compounds is their porosity. However, in many cases no effort was made to show evidence that a stable porous structure has been achieved and that the pores may be accessed. In the present paper we describe recent work on porous pillared zirconium diphosphonates, and the newer and in many respects different characteristics of tin(iv) phosphonates. The Sn(IV) monophosphonates form spherical globules that exhibit very high surface areas. The surface area arises from their nano-sized particles that pack in a "house of cards" arrangement. Also, it is shown that the 1,4-monophenyldiphosphonic acid forms highly porous (250-400 m2 g(-1)) materials with Sn(IV) when prepared in alcohol-water media. This is not the case with analogous Zr(IV) compounds. The many variations in the syntheses of both the zirconium and tin aryl- and alkyldiphosphonate pillars and their combinations with spacers such as methyl- and monophenylphosphonic acid have created a variety of highly porous materials that are stable to 400 degrees C in air, highly stable in acid media, do not collapse when de-solvated, and can be post and presynthesis altered to include functional groups. Several new directions taken by other researchers are also described. However, it is emphasized in this presentation that the cross-linked compounds form particles that precipitate rapidly into nanoparticles that exhibit only short range order. Therefore, they differ from the more conventional MOFs in that they are not amenable to structure solution by X-ray or neutron diffraction techniques. Rather, they must be understood on the basis of modeling and indirect data from EM, NMR, and additional spectroscopic and textural studies.

Mesoporous hydroxyapatites prepared in ethanol–water media: Structure and surface properties

Porous calcium hydroxyapatite Ca 10(PO 4) 6(OH) 2 (HAp) has been prepared from calcium hydroxide and NH 4H 2PO 4 solutions in alcohol–water media at various temperatures. The resulting powders have been characterized using X-ray diffraction, FT-IR spectroscopy, TG/TD analyses, nitrogen porosimetry, dynamic light scattering, complex impedance method and scanning electron microscopy. The temperature of the reaction and the use of ethanol as the solvent significantly alter the HAp morphology and particle size. The as-precipitated materials are mainly amorphous but they can become highly crystalline after heat-treatment at 800 °C, while still retaining high specific surface area. A correlation between structural and surface properties has been established.

Aggregation kinetics of latex microspheres in alcohol–water media

We report zeta potential and aggregation kinetics data on colloidal latex particles immersed in water–alcohol media. Zeta potential values show absolute maxima for volume fractions of alcohol of 0.10 and 0.05 for ethanol and 1-propanol, respectively. For methanol, no maximum of the absolute value of the zeta potential was found. Aggregation kinetics was studied by means of a single-cluster optical sizing equipment and for alcohol volume fractions ranging from 0 to 0.1. The aggregation processes are induced by adding different potassium bromide concentrations to the samples. We expected to find a slowdown of the overall aggregation kinetics for ethanol and 1-propanol, and no significant effect for methanol, as compared with pure water data. That is, we expected the zeta potential to govern the overall aggregation rate. However, we obtained a general enhancement of the aggregation kinetics for methanol and 1-propanol and a general slowdown of the aggregation rate for ethanol. In addition, aggregation data under ethanol show a slower kinetics for large electrolyte concentration than that obtained for intermediate electrolyte concentration. We think that these anomalous behaviors are linked to layering, changes in hydrophobicity of particle surfaces due to alcohol adsorption, complex ion–water–alcohol–surface structuring, and competition between alcohol–surface adsorption and alcohol–alcohol clustering.

Synthesis of leaf-like Ag 2S nanosheets by hydrothermal method in water–alcohol homogenous medium

Special Ag 2S leaf-like nanosheets were successfully synthesized in NH 3–CS 2 system by hydrothermal route in an alcohol–water medium. Changing the reaction medium from water, alcohol–water to alcohol, the morphology changed from big irregular nanosheets + microspheres, leaf-like nanosheets + nanoparitcles to big microspheres. It is found that alcohol–water homogenous condition and sulfur source of NH 3–CS 2 are the key issues to construct this unique morphology.

Studies on the oxidation reaction of tyrosine (Tyr) with H 2O 2 catalyzed by horseradish peroxidase (HRP) in alcohol–water medium by spectrofluorimetry and differential spectrophotometry

An oxidation reaction of tyrosine (Tyr) with H 2O 2 catalyzed by horseradish peroxidase (HRP) was studied by spectrofluorimetry and differential spectrophotometry in the alcohol(methanol, ethanol, 1-propanol and isopropanol)–water mutual solubility system. Compared with the enzymatic-catalyzed reaction in the water medium, the fluorescence intensities of the product weakened, even extinguished. Because the addition of alcohols made the conformation of HRP change, the catalytic reaction shifted to the side of polymerization and the polymer (A n H 2, n ≥ 3) exhibited no fluorescence. The four alcohols cannot deactivate HRP. Moreover isopropanol activated HRP remarkably.

Stability constants of some bivalent metal ions with naphthofuran-2-carbohydrazide Schiff base

The stability constants of 1 : 1 and 1 : 2 metal complexes formed between Th I V , UO I I 2 , Cu I I , Pb I I , Co I I , Ni I I , Zn I I , Cd I I , Ba I I , Ca I I and Mg I I metal ions with Schiff bases NHPC, NHMePC, NHMeOPC and NHClPC were determined by potentiometric titration technique. Calvin-Bjerrum pH titration method as modified by Irving-Rossotti was used to calculate the pK I I I I L , log K M M L and log K M L M L 2 , values in 60 : 40% (v/v) alcohol-water medium at 30 ′ 0.1C temperature and at constant ionic strength of 0.1 M NaCIO 4 . The correlation between log K values and some of the fundamental properties of the metal ions are discussed. The negative ΔG° values indicate that complex formation is spontaneous one.

Capillary electrophoresis in aqueous–organic media: Ionic strength effects and limitations of the Hubbard–Onsager dielectric friction model

The mobilities of three aromatic sulfonates, ranging in charge from −1 to −3, were investigated by capillary electrophoresis using buffers containing 0 to 75% ethanol or 2-propanol. Absolute mobilities were determined by extrapolation of the effective mobilities to zero ionic strength according to the Pitts’ equation. For all buffers studied, ions of higher charge experienced larger ionic strength effects. The resulting ionic strength-induced selectivity alterations were more dramatic when organic solvents were present in the media. Furthermore, for different organic modifier types and contents, the magnitude of the ionic strength effect was governed to a large extent by the 1/( ηε 1/2) dependence in the electrophoretic effect of the Pitts’ equation. Addition of ethanol or 2-propanol to the electrophoretic media resulted in changes in the absolute mobilities of the ions. These solvent-induced mobility changes are attributed to dielectric friction. As predicted by the Hubbard–Onsager model, dielectric friction increased with increasing organic content and with increasing analyte charge. As a result, dramatic changes in the relative absolute mobilities were observed, such as a reversal in migration order between sulfonates of −1 and −3 charge in 75% 2-propanol. Within the alcohols, the Hubbard–Onsager model was successful at predicting the relative mobility trends upon changing solvent. However, the relative trends observed between acetonitrile–water and alcohol–water media were not consistent with the model. This may be explained by the continuum nature of the model, whereby the different ion–solvent interactions characteristic to each solvent class are not taken into account.

Synthesis and evaluation of conducting polypyrrole/Al 2O 3 nanocomposites in aqueous and non-aqueous medium

The polymerization of pyrrole (PY) in aqueous or alcohol/water mixed medium in presence of FeCl 3 and nanodimensional Al 2O 3 resulted in the formation of conducting nanocomposites of polypyrrole (PPY)/Al 2O 3. The incorporation of PPY in the composites was endorsed by FT-IR studies. The extent of PPY loading in the composites decreased with increasing amount of Al 2O 3 in the initial feed at a fixed PY and FeCl 3 amount, respectively. For alcohol–water systems, the extent of PPY loading in the composites decreased with increasing alcohol concentration in the mixture with fixed amount of Al 2O 3, FeCl 3 and PY, respectively. SEM and TEM studies revealed interesting morphological features for the composites prepared under various conditions and confirmed the formation of monodispersed composite particles of diameters in the nanometer range. TG analyses revealed the enhanced thermal stabilities of the nanocomposites relative to the base polymer. The dc conductivities of the PPY/Al 2O 3 nanocomposites were in the order of (63±3 to 33±5)×10 −2 S/cm, and the values increasing with decreasing Al 2O 3 loading in the nanocomposites in aqueous medium but in case of alcohol–water medium, dc conductivities increases with increasing alcohol content in the medium. Some of these nanocomposites could be obtained as stable dispersion during synthesis.

Potentiometric determination of formation constants of metal ion complexes with 4-hydrazinobenzofuro[3,2-d]pyrimidine Schiff base

Solution equilibrium studies on the complex formation of bivalent Mg, Co, Ni, Zn, Cd, Hg and Cu with the Schiff base derived from condensation of 4-hydrazinobenzofuro[3,2-d]pyrimidine with 5-methylsalicylaldehyde by pH-titration technique at 30 ′ 1° at a constant ionic strength, 0.1 M (NaClO 4 ) in 70 : 30% (v/v) alcohol-water medium, indicate the order : Cu > Co > Ni > Zn > Hg > Cd > Mg of stability constants of the complexes.

Cellulose ethers with a block-like distribution of the substituents by structure-selective derivatization of cellulose

Native cellulose, especially ground cotton linters, was step-by-step carboxymethylated in alcohol-water medium at low concentrations of NaOH. Using the 13C cross-polarization/magic angle spinning n.m.r. method, it has been found that, under these conditions, initially the non-crystalline regions were selectively etherified; only at higher degrees of substitution were the crystalline regions gradually integrated in the reaction. Therefore, already at relatively low degrees of substitution, the hydrolysates of such cellulose ethers contained higher quantities of di- and trisubstituted glucose units than those of cellulose samples etherified by the conventional method to a comparable degree of substitution. The experimental results confirm the concept of reacting structural fractions proposed for the alkalization of cellulose and indicate the formation of cellulose ethers with a block-like distribution of the substituents along the molecular chains.

Effects of activation and inhibition by oxygen of the photocatalytic evolution of hydrogen from alcohol-water media

Acceleration by oxygen of the photocatalytic evolution of H2 from an H2O-C2H5OH mixture has been detected. A mechanism of the process is proposed that includes formation of CH3CHOH radicals on a semiconductor photocatalyst, their reaction with O2, and fragmentation of radical products with formation of H atoms, which dehydrogenate C2H5OH, forming additional amounts of H2.

Spray Drying of Metal Alkoxide Sol for Strontium Titanate Ceramics

Conditions for obtaining a stable sol in an isopropyl alcohol–water medium containing titanium isopropoxide and strontium nitrate, and acetic acid as a modifier, have been described. Spray drying of the sol results in submicrometer spherical agglomerates which on further thermal decomposition yield submicrometer particles of strontium titanate at temperatures as low as 500°C. The thermal decomposition characteristics of the spray‐dried precursor and the development of strontium titanate phase have been discussed. Calcined precursor powder possesses a specific surface area of 12m2/g, a comp action density of 57%, and a sintered density of > 98%. The optimum sintering temperature of such a powder was 1450°C, which resulted in a sintered grain size around 1.5 μm. Further, such a sintered sample had a dielectric constant of 260 and a loss factor of 0.008 at 1 kHz. This method appears to be very convenient with respect to handling of stable sols and thus avoids the usual difficulties regarding extended gelation as well as inhomogeneous precipitation.

Electrochemically induced processes of formation of phosphoric acid derivatives. 3. Electrosynthesis from white phosphorus in alcohol-water solutions

It has been established that the process of splitting of the P-P bonds of the white phosphorus molecules is initiated by cathode-generated nucleophiles (HO−, RO−), while functionalization of the P-H bond formed in phosphoric oligomers occurs under the action only of alcohol. The primary product after splitting of all the P-P bonds in phosphoric oligomers is dialkylphosphite (in alcohol-water media), or trialkylphosphite (in absolute alcohol), in the course of electrolysis being transformed into trialkylphosphate. Formation of esters of pyrophosphoric acid with reduced protogenic character of the medium was examined. It is proposed that under these conditions nucleophilic reagents of the type (〉P)c-O− form and participate in splitting of the P-P bonds.

Mechanism of electron transfer in dinitrogen fixation in the system Ti(III)−Mo(III)

Mo(III) and N2 together inhibit H2 evolution in the dinitrogen fixing system Ti(III)−Mo(III) in alcohol-water media. It is concluded that the formation of a Mo2N2 complex changes the collective properties of Ti(III) hydroxide. The catalytic action of Mo(III) in N2 reduction is explained by the possibility of electron transfer to the Mo2N2 complex from a number of Ti(III) atoms situated around the catalyst complex.

Mechanism of electron transfer in dinitrogen fixation in the system Ti(III)−Mo(III)

Mo(III) and N2 together inhibit H2 evolution in the dinitrogen fixing system Ti(III)−Mo(III) in alcohol-water media. It is concluded that the formation of a Mo2N2 complex changes the collective properties of Ti(III) hydroxide. The catalytic action of Mo(III) in N2 reduction is explained by the possibility of electron transfer to the Mo2N2 complex from a number of Ti(III) atoms situated around the catalyst complex.