Physicochemical Properties Of Solutions Research Articles

Microfluidic DNA microarray analysis: A review

Microarray DNA hybridization techniques have been used widely from basic to applied molecular biology research. Generally, in a DNA microarray, different probe DNA molecules are immobilized on a solid support in groups and form an array of microspots. Then, hybridization to the microarray can be performed by applying sample DNA solutions in either the bulk or the microfluidic manner. Because the immobilized probe DNA binds and retains its complementary target DNA, detection is achieved through the read-out of the tagged markers on the sample target molecules. The recent microfluidic hybridization method shows the advantages of less sample usage and reduced incubation time. Here, sample solutions are confined in microfabricated channels and flow through the probe microarray area. The high surface-to-volume ratio in microchannels of nanolitre volume greatly enhanced the sensitivity as obtained with the bulk solution method. To generate nanolitre flows, different techniques have been developed, and this including electrokinetic control, vacuum suction and syringe pumping. The latter two are pressure-driven methods which are more flexible without the need of considering the physicochemical properties of solutions. Recently, centrifugal force is employed to drive liquid movement in microchannels. This method utilizes the body force from the liquid itself and there are no additional solution interface contacts such as from electrodes or syringes and tubing. Centrifugal force driven flow also features the ease of parallel hybridizations. In this review, we will summarize the recent advances in microfluidic microarray hybridization and compare the applications of various flow methods.

Effect of Ethylene Glycol and Its Derivatives on the Solubility Behavior of CaSO4·2H2O in the Aqueous NaCl System and Physicochemical Solution Properties at 35 °C

The effect of addition of ethylene glycol (EG), ethylene glycol monomethyl ether (EGMME), and ethylene glycol dimethyl ether (EGDME) on the solubility behavior of CaSO4·2H2O in aqueous NaCl solutio...

Effect of nonionic surfactant and acidity on chitosan nanofibers with different molecular weights

Blend solutions of chitosan (Cs) and poly(ethylene oxide) (PEO) at different acidities were electrospun to produce membranes of nanofibers with different diameters. The use of polysorbate surfactant Tween 20 to improve functionality of these nanofibers was studied. The procedure was as follows: 5% (w/v) of two high deacetylation degree Cs with different molecular weights (Mw = 148 kDa and 68 kDa) were dissolved in solutions with different acetic acid concentrations (10%, 50% and 90% (v/v)) then mixed with PEO. The influence of molecular weight and acidity on the morphology and physicochemical properties of solutions and formed nanofibers was also investigated. Results revealed that pure Cs dissolved in different acidities did not form fibers and instead it deposited as beads. Addition of PEO was necessary to electrospin all Cs solutions. Average fiber diameters and size distribution differ with acidity and molecular weight. Composite solutions of Cs, synthetic polymer PEO, and surfactant can be effectively electrospun. The presence of surfactant resulted in decrease of surface tension and in the formation of smooth or beaded fibers. This may be important for new applications since active nanofibers could serve as carriers of components such as drugs or additives.

Separation of phenols and their advanced oxidation intermediate products in aqueous solution by NF/RO membranes

The performance of nanofiltration and reverse osmosis membranes (NF-90 and TFC-HR) to retain the intermediate products of phenol chemical oxidation in aqueous solution was examined. Physical properties of the active layer of both membranes, such as roughness and hydrophobicity, were examined and pure water permeability was determined. Temporal evolution experiments of permeate relative flux and solute rejection were carried out for aqueous phenol, catechol, resorcinol, hydroquinone, malonic acid, oxalic acid, acetic acid, and formic acid. Physicochemical properties of solutes and membranes were used to analyse the filtration performance. NF-90 membrane exhibited lower relative fluxes for every solute than the corresponding to TFC-HR membrane. In addition, differences in flux decline between members of the same type of solute (aromatic and carboxylic) were also more evident for NF-90 membrane. At natural pH, rejection selectivity between phenolic solutes and dicarboxylic acids was higher for NF-90 membrane than for TFC-HR membrane. Except for oxalic acid, the sieving effect seems to be predominant over other mechanisms for the TFC-HR membrane; however, NF-90 rejection performance cannot be solely explained through steric hindrance interaction. In order to compare rejection selectivity between aromatic and carboxylic solutes of similar molecular weight at the same solution pH, performance of NF-90 membrane for dicarboxylic acids was investigated at solution pH higher than natural one. Experiments evidenced that selective separation between phenols and dicarboxylic acids can be achieved at solution pH around 5.

Measurement and correlation of solute solubility in HFA-134a/ethanol systems

The goals of this study were to determine the solubility values of solid organic solutes in pure HFA-134a and in HFA-134a/ethanol cosolvent systems (0–20%, w/w), and to investigate the relationship between these solubilities and a solute's physico-chemical properties. A direct inject on-line HPLC method was used to determine the solubility of 21 solutes in HFA-134a/ethanol. The samples were allowed to equilibrate for at least 48 h. The filtered sample was injected directly on an analytical HPLC column through a manual injector interface, and analyzed at an appropriate solute wavelength via HPLC. The solutes display diverse physico-chemical properties and yielded solubility values that ranged over four orders of magnitude. In general, a linear–linear solubility relationship was observed as the fraction of ethanol increased. The effects on solubilization ranged from 1.3 to 99.4 times when 20% (w/w) ethanol was introduced, relative to pure HFA-134a. A regression equation utilizing a solute's hydrogen bonding potential resulted in a significant correlation to the slope obtained from a linear model for solubility in HFA-134a with 0–20% (w/w) ethanol, and may be useful for pre-formulation studies.

The limiting current density of copper electrodeposition on vertical electrode under the conditions of electrolyte natural convection

The problem of determining the limiting current density of copper electrodeposition on the vertical electrode under the conditions of electrolyte natural convection is solved numerically. The incomplete dissociation of copper sulfate and sulfuric acid by the second stage and the concentration dependences of physicochemical properties of solution are taken into consideration. The effect of incomplete dissociation of copper sulfate and sulfuric acid by the second stage on the ionic transport in the copper electrodeposition and on the limiting current density is estimated by comparing the results, which are calculated taking into account and ignoring the concentration dependences of dissociation constants, and also for the limiting cases of virtually complete dissociation of copper sulfate and sulfuric acid. It is shown that, in excess of supporting electrolyte, incomplete dissociation of copper sulfate and sulfuric acid only slightly affects the limiting current density: the limiting current density changes not more than by 10% with the variation of the dissociation constants by several orders of magnitude. At the moderate and small concentrations of supporting electrolyte, incomplete dissociation should be taken into account, because the error of limiting current density can exceed 50%.

Meso-Substituted Cationic Porphyrins of Biological Interest. Photophysical and Physicochemical Properties in Solution and Bound to Liposomes ¶

A series of cationic porphyrins with 1–4 positive charges are studied: mono(N-methyl-4-pyridyl)triphenylporphine chloride [Mono], cis(N-methyl-4-pyridyl)diphenylporphine chloride [Cis], tri(N-methyl-4-pyridyl)monophenylporphine chloride [Tri] and tetra(N-methyl-4-pyridyl)porphine chloride [Tetra]. Their photophysical properties are measured in small unilamellar vesicles and compared with those in homogeneous solution. Liposomes of l-α-dimyristoyl-phosphatidylcholine (100 nm diameter) and l-α-dipalmitoyl-phosphatidylcholine (50 nm diameter) in phosphate-buffered saline (pH = 7.4) or D2O 0.15 M NaCl were used. The effect of the medium microheterogeinity is discussed. The triplet quantum yields in liposomes for all the porphyrins are about 0.7, similar to the value obtained for Tetra in aqueous media. The singlet molecular oxygen quantum yields for the hydrophilic compounds Tri and Tetra are greater than those of the hydrophobic ones, Mono and Cis. Also, association constants (KL) of the dyes to liposomes and their localization within the membranes are determined from fluorescence and fluorescence polarization measurements, respectively. KL values are in the range of 104–105M−1 for all the compounds, indicating that hydrophobic and coulombic interactions between porphyrins and liposomes are responsible for the dye association. Fluorescence polarization experiments indicate that Mono and Cis can penetrate into the lipidic phase, and that Tri and Tetra are located near the polar heads of the lipidic molecules.

Fullerene Containing Polymers: A Review on Their Synthesis and Supramolecular Behavior in Solution

Due to the theoretical importance and potential applications of fullerene, numerous fullerene derivatives have been developed to enhance its solubility and processability. This article provides an overview on fullerene containing polymers, from synthesis to their physicochemical properties in solution. Due to the unique chemical structure of fullerene, different fullerene containing polymeric architecture can be synthesized through various kinds of conjugating techniques, where fullerene can be located either on the backbone or the branch chain. Recently, the successful development of azido coupling and atom transfer radical addition (ATRA) makes it possible to synthesize "controlled" and well-defined fullerene containing polymers. Experimental results indicated that fullerene containing polymers not only increase the solubility of fullerene in solution, but also retain the conjugating properties of fullerene molecules. By blocking well-defined functional polymers onto fullerene molecules, different types of stimuli-responsive amphiphilic systems can be achieved. However, the large bulk volume and high hydrophobicity of fullerene gives rise to the large aggregates with different morphologies produced in solution, which can be tuned by changing external stimuli, such as pH, temperature, salt, and co-solvents. Interestingly, fullerene containing anionic polymers could induce the formation nano-scale fractal pattern, but not fullerene containing cationic polymers, which is evident from morphological studies.

The effect of water solubility of solutes on their flux through human skin in vitro: An extended Flynn database fitted to the Roberts–Sloan equation

The edited Flynn database ( n = 62) for determining the effect of the physicochemical properties of solutes on their skin absorption has been extended ( n = 114) to give a database for which solubilities of the solutes in water, S AQ, and their maximum fluxes from water through human skin in vitro, J MAQ, are known or can be calculated. Besides the six major contributors to the original and edited Flynn database, nine more contributors have been included in the extended database to give 15 contributors. As in the edited Flynn database, data for solutes that were significantly ionized or for experiments using different thicknesses of skin were not excluded from the extended database so that the diversity of the original database was maintained. The extended database was fit to five equations where the independent variables were solubility in octanol ( S OCT), in water ( S AQ) or molecular weight (MW) and combinations of those three variables; and the dependent variable was J MAQ. The best fit was obtained from the Roberts–Sloan (RS) equation: log J MAQ = x + y log S OCT + (1 − y) log S AQ − z MW, x = −2.574, y = 0.586, z = 0.00440, r 2 = 0.887, S.D. = 0.399, F = 139. This result is comparable to the best fit published using permeability coefficients, P, as the dependent variable, but gives greater insight into the factors affecting permeation. J MAQ is more important clinically because it described how much is permeating per unit area and time, while P is in the units of speed (cm h −1). Because of the dependence of J MAQ on S AQ, the selection of new drugs with improved topical delivery should include considerations of their S AQ in their design.

The effect of water solubility of solutes on their flux through human skin in vitro

The Flynn database ( n = 97) for determining the effect of the physicochemical properties of solutes on their skin absorption has been edited to give a database for which the solubilities of the solutes in water, S AQ, and their maximum fluxes from water through human skin in vitro, J MAQ, are known or can be calculated ( n = 76). Data from the six major contributors to the original Flynn database have been included. Data for solutes, which were significantly ionized or for experiments using different thicknesses of skin were not excluded so that the edited database is as diverse as the original. The edited database was fit to five equations where the independent variables were solubility in octanol ( S OCT) in water ( S AQ) or molecular weight (MW), and combinations of those three variables; and the dependent variable was J MAQ. The best fit was obtained from the Roberts–Sloan (RS) equation: log J MAQ = x + y log S OCT + (1 − y) log S AQ − z MW, x = −3.00, y = 0.73, z = 0.0048, r 2 = 0.934, S.D. = 0.37 and F = 274. This result is important because J (amount/area time) is the more clinically useful descriptor of permeation compared to P (distance/time); and because the identification of S AQ as a significant variable in predicting flux changes the design parameters for optimizing topical delivery of drugs from solubility in lipids (or partition coefficients between OCT and AQ, K OCT:AQ) and MW, to solubility in lipids, S OCT, and in water, S AQ, as well as MW.

Gadocoletic Acid Trisodium Salt (B22956/1)

Inversion recovery, three-dimensional, gradient-recalled echo magnetic resonance coronary angiography (IR-3D-GRE-MRCA), performed after administration of an intravascular T1-relaxing agent with prolonged permanence in the blood, is one of the most promising approaches to noninvasive magnetic resonance imaging (MRI) of the coronaries. The aim of the present study was the evaluation of the physicochemical properties in solution, pharmacokinetics, elimination from the body, protein binding, and signal enhancement characteristics of gadocoletic acid trisodium salt (B22956/1), a candidate gadolinium-based MRI contrast agent for coronary angiography. The pharmacokinetics and elimination from the body of gadocoletate ion, the contrastographically active component of gadocoletic acid trisodium salt, was evaluated after intravenous administration in rats and monkeys, using for assays high-performance liquid chromatography, x-ray fluorescence, and inductively coupled plasma atomic emission spectrometry. The binding of the gadocoletate ion to animal and human serum albumin was studied by means of ultrafiltration. The imaging properties of blood outside coronary arteries after contrast agent administration were evaluated in cynomolgus monkeys (Macaca fascicularis) by measuring aortic signal-to-noise and contrast-to-noise ratios in lower body angiograms. The suitability of gadocoletic acid trisodium salt for achieving contrast-enhanced magnetic resonance coronary angiography (ceMRCA) was tested in Yucatan micropigs with an IR-3D-GRE sequence. All in vivo relaxation rate measurement and images were obtained using a 1.5 T Siemens Symphony scanner. The fractional binding of gadocoletate ion at a concentration of 0.5 mM to serum albumin at the physiological concentration was 95%, 92%, 88%, and 86% for human, monkey, pig, and rat, respectively. In rats and monkeys, gadocoletate ion was excreted unmetabolized through the biliary and urinary routes. It was recovered with feces depending on the injected dose in percentages from 18% to 97%, providing evidence for a saturable biliary pathway. Plasma pharmacokinetics showed the complete elimination of gadocoletate ion within 24 hours after administration. In the monkey, the gadocoletate ion showed the pharmacokinetic behavior of a compound with partial vascular confinement and long plasma half-life, which may be ascribed to elevated binding to serum albumin. These properties manifested themselves in lower body angiograms with excellent image contrast between vessels and muscle. The slowly decaying aortic blood signal-to-noise and contrast-to-noise ratios over a 15-minute period is expected to allow 3-dimensional coronary angiography. The potential of gadocoletic acid trisodium salt for ceMRCA was also demonstrated in Yucatan micropigs. Elevated blood signal intensity and almost total myocardial signal suppression was maintained for almost 1 hour after administration, ie, for much longer than expected to be necessary for coronary angiography. During the whole period high resolution images of the right coronary artery could be obtained. On the basis of the pharmacokinetic profile and imaging characteristics, gadocoletic acid trisodium salt shows promise as a MR contrast agent for coronary angiography.

Quadruplex-Forming Oligonucleotides as Tools in Anticancer Therapy and Aptamers Design: Energetic Aspects

Recent investigations on the G-quadruplex motif propose a new strategy for the making of antitumour drugs. Quadruplex-drug complexes have been suggested to inhibit telomerase activity; further, aptamers based on the quadruplex motif have been proved useful as tools aimed at binding and inhibiting particular proteins, thus serving as pharmaceutically active agents. However, the design of new aptamers is difficult because many factors affecting their activity and stability have not still been clarified. The knowledge of the energetics of quadruplex formation is a crucial point in view of their potential therapeutic utilization both as targets as well as therapeutic agents. In this review the energetic aspects of both quadruplex assembly and quadruplex-ligand interactions are discussed together with a summary of recent studies on physico-chemical properties in solution of quadruplex structures obtained from synthetic aptamers, including PNA-DNA chimeras.

Physicochemical properties of solutions of bis(2,3,5,6-tetraoxo-4-nitropyridinate) dianions. Crystal structures of sodium 2,3,5,6-tetraoxo-4-nitropyridinate trihydrate and sodium ammonium bis(2,3,5,6-tetraoxo-4-nitropyridinate) monohydrate

Ammonium 2,3,5,6-tetraoxo-4-nitropyridinate was shown to exist as stable dimers and act as a weak electrolyte in both a crystalline state and aqueous solutions. In a strongly alkaline medium, ammonium cations were successively replaced by sodium cations. The molecular and crystal structures of sodium 2,3,5,6-tetraoxo-4-nitropyridinate trihydrate and sodium ammonium bis(2,3,5,6-tetraoxo-4-nitropyridinate) monohydrate were established, and their spectroscopic characteristics were determined.

Single Bubble Sonoluminescence–A Chemist's Overview

The phenomenon of sonoluminescence has been known for over 60 years but it is only over the last few years that a better understanding of its origins has emerged. In part the discovery of single bubble sonoluminescence, just over 10 years ago, has been a major contributor to the theoretical advances that have been made to account for the event. This Minireview is from the perspective of a physical chemist and considers the progress that has been made in understanding the role of solutes in affecting the sonoluminescence from a solution exposed to ultrasound. The physicochemical properties of solutes that are important in controlling both single bubble and multibubble sonoluminescence are discussed.

Effect of potentiated solutions on mercury(II) signal in inversion voltammetry.

We studied the effects of homeopathically potentiated substances in ultralow doses on physicochemical properties of solutions. Inverse voltammetric signals during Hg(II) oxidation-reduction in the presence of potentiated water, lithium chloride, and mercury nitrate were studied by alternating-current inversion voltammetry. Potentiated substances modified oxidation-reduction processes in the electrochemical system. Potentiated solutions of Hg(II) increased the effective concentration (activity) of mercury ions. The effect was most significant in the presence of mercury nitrate in homeopathic dilutions C6+C12+C24. Our results indicate that potentiated substances specifically modulate kinetic and thermodynamic characteristics of solutions containing the same compounds.

Concentration transition from water-electrolyte to electrolyte-water solvents and ionic clusters in solutions

A general model of structural and molecular-kinetic changes in transition from dilute electrolyte solutions to aqueous melts of crystal hydrates and salts is suggested. The model corresponds to the scheme: ions and complexes in the water structure→ ionic and ion-water clusters→ polymeric melt structures. The structural transition is caused by a decrease in electrostatic hydration effects and an abrupt decrease in the dielectric permittivity of electrolyte solutions beyond the concentration range of the first structural region where the water structure persists. The appearance of cluster nanostructures is considered to be a common property of highly concentrated solutions of electrolytes. Analysis of concentration structural changes is based on X-ray diffraction and spectroscopic data. Microwave dielectric properties and other physicochemical properties of solutions (electric conductivity, viscosity, density, etc.), as well as phase equilibria in water-salt systems are interpreted in terms of the concepts developed.

Physicochemical properties of solutions of sodium alginate extracted from brown algae Laminaria digitata

The rheological properties of sodium alginate solutions were studied as influenced by the concentration of alginic acid, pH of the medium, and temperature. The probable structural and conformational transformations induced on varying these parameters were suggested. The effect of cations and anions of varied nature on the viscous characteristics of these solutions was discussed.

Physicochemical Properties of Solutions of Amides in H2O and in D2O

Excess volume, partial molar volumes, viscosity, and ultrasound velocity in H2O and D2O solutions of formamide (FM), acetamide (AM), dimethylformamide (DMF), and dimethylacetamide (DMA) were studied at 20°C. The change in the excess volume of the various amide solutions on substitution of D2O for H2O varies both in magnitude and direction. On the other hand, the isotope effect on the ultrasound velocity behaves similarly in all cases. Its magnitude is greatest for pure water and then decreases monotonically with increasing amide concentration. Although the behavior of the concentration dependence of viscosity is similar to that for ultrasound velocity, the isotope effect on the viscosity behaves in a different way. For methyl-substitued amides, a maximum isotope effect is observed at amide mole fraction 0.2, but the isotope effect for FM and AM increases monotonically with increasing amide concentration. The differences in the behavior of amides in aqueous solution are discussed in terms of their interactions with water.

Evaluation of the retention dependence on the physicochemical properties of solutes in reversed-phase liquid chromatographic linear gradient elution based on linear solvation energy relationships

This paper describes the results of the evaluation of retention dependence on the physicochemical properties of solutes in linear gradient elution by reversed-phase liquid chromatography (RPLC) based on linear solvation energy relationships (LSERs). Retention time data on Inertsil ODS(3) column by linear gradient elution were collected for both acetonitrile–water and methanol–water binary mobile phases under various gradient steepness. Based on the LSERs, the retention times were linearly correlated with the physicochemical properties (size, dipolarity, and hydrogen bond donor–acceptor acidity and basicity) of solutes. As predicted by LSERs, very acceptable linear relationships are observed for both mobile phases. While the magnitudes of the coefficients are modified by the gradient steepness, their signs are consistent with those obtained by isocratic elution. As obtained for isocratic elution, the dominant factors to retention in linear gradient elution of RPLC are the solutes’ size and hydrogen bond acceptor basicity. The conclusions of the study allow us to predict retention in chromatographic method development by gradient elution.

Anodic behavior of tungsten in water—organic solutions of sodium chloride

The anodic behavior of tungsten in water-amino alcohol solutions of sodium chloride is studied potentiostatically and potentiodynamically on a rotating disk electrode. The introduction of monoethanol amine (MEA) into an aqueous NaCl solution leads to anodic activation of tungsten. From the dependence of the current density on the disk electrode rotation rate, it is determined that the anodic dissolution obeys the diffusion kinetics equations. The delivery of MEA molecules to the electrode is the slow stage of the reaction. The dissolution rate and the tungsten surface quality after the treatment are the highest at 6 M MEA. The effect of physicochemical properties of solutions on the anodic reaction is shown