Physicochemical Properties Of Aqueous Solutions Research Articles

A tunable hydrogel for encapsulation and controlled release of bioactive proteins.

A N,N-dimethylacrylamide-based hydrogel (2) with the new cross-linker (ethylenedioxy) bis[2,2'-(N-acryloylamino)ethane] (1) has been prepared, and its physicochemical properties in aqueous solution were studied. Three different native proteins (lysozyme, bovine serum albumin, and rabbit IgG) were encapsulated within the polymeric matrix 2, and the kinetics of their release from the swollen hydrogel were determined. The rate of protein release exhibits a clear dependence on both the molecular weight of the protein and the amount of cross-linker utilized to prepare the hydrogel. This is reflected by the fact that the low molecular weight proteins are released at an increased rate versus higher molecular weight proteins. In addition a greater amount of protein is released from the hydrogels with a lower percentage of cross-linker. The polymerization procedure used in this study is sufficiently mild to safeguard the functional integrity of attendant biomolecules as determined by the retention of catalytic activity of encapsulated alpha-chymotrypsin and aldolase catalytic antibody 38C2. The potential utility of these hydrogels for the controlled release of bioactive agents in vivo is strengthened by both their lack of toxicity against human dermal fibroblasts and their lack of immunogenicity in mice.

Isolation and characterization of the exopolysaccharide produced by Streptococcus thermophilus SFi20

This paper reports isolation, structural characterization and some physico-chemical properties in aqueous solution of the exopolysaccharide (EPS) produced by Streptococcus thermophilus strain SFi20. The yield of the purified EPS was found to be reproducible and close to the average value of 143 mg/l. The chemical structure, previously suggested, has been confirmed on the basis of NMR data. Viscometric, chiro-optical and rheological measurements have been carried out with the aim of characterizing the conformational state of the polysaccharide in aqueous solution. All the data reported indicate that the EPS does not undergo a cooperative conformational transition under the investigated experimental conditions. Furthermore, the viscosity data and the viscoelastic behaviour suggest that the polymer is rather flexible and adopts a random coil conformation in aqueous solution.

Hydration of dioxaalkanes in aqueous solutions

The interactions between water and linear dioxaalkane molecules were investigated by water-heptane partition. Two homologous series: dimethoxyalkanes and diethoxyalkanes were studied, with the oxygen atoms separated by a number of methylene groups (changing from 1 to 5). Free energy and enthalpy of partition were calculated from partition constants and from their temperature dependence. Hydration of these amphiphilic solutes in the aqueous phase was evaluated. The separation between the oxygen atoms in the molecule affects hydrophilic-hydrophobic properties of dioxaalkanes. The effect is due not only to a different number of hydrophobic groups in the molecule, but also to different degrees of their hydrophobicity as well as of hydrophilicity of the oxygen atoms at different separations. The contribution from different parts of the molecules is, therefore, not additive and the group-contribution model cannot be used to describe physicochemical properties of aqueous solutions of dioxaalkanes without taking into account the structure of the solute molecules.

MEDIUM EFFECT ON THE SEPARATION FACTOR IN LIQUID-LIQUID EXTRACTION. APPLICATION TO THE SEPARATION OF TRTVALENT LANTHANIDE NITRATES BY TRI-N-BUTYLPHOSPHATE

ABSTRACT A physicochemical expression of the separation factor derived from the Mikulin-Sergievskii-Dannus' model is proposed to predict the medium effect on the separation of lanthanide nitrates by liquid-liquid extraction from nitrate media, using tri-n-butyphosphate (TBP) as extractant. The factors exerting an influence on the separation factor have been highlighted and discussed more deeply in this paper, mainly the water activity functions and the extraction equilibrium constant ratio of lanthanide nitrates. It has been shown that the water activity is a central variable to be controlled, particularly in concentrated aqueous solution. The present work is partly a review of the effects of aqueous media on the lanthanide separations and partly an analytical approach based on the physicochemical properties of aqueous solutions. Results of qualitative and quantitative predictions of changes in the separation factor with the aqueous solution composition are discussed. The proposed model provides a coherent explanation to the great number of experimental observations.

Reversible thermothickening of aqueous solutions of polycations from natural origin

This paper concerns our first set of experimental data on alkyl chitosans in acidic medium allowing to compare the roles of the degree of alkylation and that of the length of the alkyl chains on their physicochemical properties in aqueous solution. The balance between electrostatic repulsion (related to the fraction of -NH3+) and the hydrophobic attraction is discussed on the CC12 sample, a chitosan modified with a C12 aliphatic chain. A phase diagram is established separating the conditions for gel-like structure formation and phase separation. The roles of the net charge and that of the temperature on the formation of hydrophobic aggregates are examined.

Physicochemical investigations in systems of composition biosurfactant/sodium dodecyl sulfate/water around the critical micelle concentration

Some results of the investigation of the physicochemical properties of aqueous solutions of the synthetic surfactant sodium dodecyl sulfate (SDS) together with each of the two surfactants obtained from assimilating processes, sophorose lipid or rhamnose lipid, in the concentration range that involves micelle formation, are presented and discussed in this paper. The measurements of the solubilities, surface tensions, conductivities, pH values, and enthalpies of diluted mixtures of these solutions at 25°C were evaluated for this purpose. An improved method using a concentration gradient is proposed for precise conductivity and calorimetric measurements in the now conditions. The mathematical model for the description obtained from these experimental data was additionally developed. The results reveal that the low solubility of glycolipids in water may be considerably improved in the presence of SDS. The observed concentration dependence of all studied properties, suggest that formation of mixed micelles consisting of SDS and glycolipid monomers may occur. This aggregation takes place at a concentration of about one order of magnitude lower than the critical micelle concentration of SDS alone. The surfactant mixtures in solution exhibit non-ideal behaviour.

Response of laryngeal receptors to water solutions of different osmolality and ionic composition

Water-responsive laryngeal receptors with fibres in the superior laryngeal nerve were studied to characterize the specific physicochemical properties of aqueous solutions that activate these endings. The responses to water (37 degrees C) of 141 receptors were studied in 39 anaesthetized dogs breathing through a tracheostomy with the larynx functionally isolated. Of the 89 receptors stimulated by water, 53 were also challenged with isosmotic (275-315 mOsm) solutions of dextrose and sodium gluconate at 37 degrees C. Receptors that only responded to water (n = 31) with a long delay, long duration discharge were generally respiratory modulated. On the other hand, laryngeal receptors that responded to all test solutions (n = 22) with a short delay, short duration discharge were generally not respiratory modulated. We conclude that the former type of receptor responds to lower osmolality, whereas the latter responds to the lack of chloride ions in the test solutions. These two types of receptor may be responsible for the cough and bronchoconstriction induced by inhaled aerosols of different osmolalities and ionic compositions.

Preparation of latex particles by emulsion polymerization with amphoteric surfactants and interactions of latex particles thus prepared and pigments

The emulsion polymerization of styrene has been studied in the presence of an amphoteric surfactant such as N ϵ-lauroyl- N α, N α-dimethyl-lysine (DMLL) and N, N-dimethyl-n-laurylbetaine (LNB). The rate of polymerization and the concentration of latex particles generated are both proportional to the 0.6-power of the surfactant concentration. The particle size of the latices diminished as the concentration of the surfactant increased. The influence of the physicochemical properties of aqueous solutions of the surfactant on the emulsion polymerization at various pH values has also been discussed. Such properties significantly affect the characteristics of the latex particles formed at the various pH values studied. In order to elucidate the interaction between latex particles prepared in the presence of amphoteric surfactants and inorganic pigments, the zeta potentials and the turbidity of various mixed dispersions have been measured. It is shown that when the latex and pigment particles possess opposite charges, the mixed dispersions undergo heterocoagulation with redispersion occurring on increasing the number of latex particles in the system.

A set of textile auxiliaries for finishing Lanom fibre

The effect of TA on the physico-chemical properties of aqueous solutions has been investigated, as well as the electrophysical and frictional properties of Lanom fibre. It has been shown that the preparations Stearox 6 and composition 2 are effective for finishing Lanom fibre at a content of 0.3–0.6% on the fibre surface. Treatment with these TA assures the needed physico-mechanical and electrophysical properties, reduces the coefficient of friction by 17–26% as compared with that of the untreated fibre, and improves the ability of Lanom fibre to be processed.

The Physicochemical Properties of Aqueous Solutions of Sodium Alkanesulfonates. Apparent Molar Volumes, Viscosity B Coefficients, Heats of Solution, and Surface Tensions

Abstract The apparent molar volumes, viscosity B coefficients, heats of solution, and surface activity of sodium alkanesulfonates (RSO3Na, methyl to hexyl) in water were measured. The limiting apparent molar volumes at 25 °C increase with the number of carbon atoms in the alkyl chain; the increment per methylene group is about 16 cm3mol−1. The viscosity B coefficients of MeSO3Na and EtSO3Na increase with the temperature, while those of n-BuSO3Na decrease with an increase in the temperature. The changes in heat capacity for dissolution in water, ΔCpo, as calculated from the heats of solution at 15, 25, and 35 °C, were negative for MeSO3Na and EtSO3Na, while the ΔCpo values for n-PrSO3Na and higher homologs were positive. MeSO3Na raises the surface tension of water, while EtSO3Na and higher homologs reduce it. The structural changes in the solvent water upon the dissolution of sodium alkanesulfonates are discussed in comparison with those of sodium alkyl sulfates previously reported.

STUDIES OF URONIC ACID MATERIALS, PART 59: THE GUM EXUDATE FROM A CULTIVAR OFLEUCAENA LEUCOCEPHALA(LAM.) DE WIT

SUMMARY The gum exuded by a cultivar of Leucaena leucocephala growing in South India has been analysed. Its analytical parameters indicate that it is similar to gum arabic. The physico-chemical properties of aqueous solutions (good solubility, viscosity and colour) suggest that Leucaena gum would have useful commercial applications; its stability in acidic solutions is better than that of gum arabic.

Some physico-chemical properties of aqueous solutions of N α-acyl-L-histidine

The critical micelle concentrations of aqueous solutions of N α-acyl-L-histidine have been determined by the spectral shift method with Rhodamine 6G and by the light scattering method. With the spectral shift method critical micelle concentrations of 40, 9.0, 1.0, 0.11, and 0.012 mM were obtained for N α-acyl-L-histidine containing saturated acids of 8, 10, 12, 14, and 16 carbons respectively, at 45°C and pH 8.6 in the absence of added salt. For the homologs containing 10, 12, and 14 carbon acids, critical micelle concentration of 9.0, 1.0, and 0.11 mM were determined by the light scattering method. The light scattering studies yield micelle weights of 60, 66, and 84 thousand for the C-10, C-12, and C-14 homologs, respectively. N α-acyl-L-histidine is an unusual surfactant in that the hydrophilic portion of the molecule is relatively large and contains both an ionic group (carboxylate group) and a nonionic group (imidazole side-chain). The bulky hydrophilic group of N α-acyl-L-histidine causes this molecule to exhibit physico-chemical behavior which is not typical of that exhibited by most ionic surfactants. In particular, the dependence of the critical micelle concentration on the acyl chain length and on the concentration of added salt is atypical. Chemical shift measurements (by NMR) on the C-2 and C-5 protons of imidazole in micellar N α-dodecanoyl-L-histidine indicate that the imidazole group is, indeed, positioned at the water-micelle interface.

Some physico-chemical properties and sorption ability of benzylated polyethyleneimines in aqueous solutions

An investigation has been made on the change in the physico-chemical properties of aqueous solutions of branched and linear polyethyleneimine (a high mol. wt catalyst for hydrolysis of nitrophenyl esters) occurring on its being alkylated by benzyl chloride. The first result of alkylation is benzyldiethylamine fragments in PEI. Provided that the degree of conversion is below 0–3, the reaction is second order. Then the rate constant decreases, probably due to a decrease in the steric factor. Alkylation diminishes p K a 's of nitrogen atoms of PEI. Accumulation of benzyl groups in PEI results in a marked contraction of its macromolecules in aqueous solutions and enhances the sorption ability with respect to n-nitroanilides. The free energy of sorption is −4 · 1 to − 5·5 kcal/mole.

Physicochemical properties of aqueous solutions of fluorinated surfactants

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhysicochemical properties of aqueous solutions of fluorinated surfactantsKozo Shinoda, Masakatsu Hato, and Takao HayashiCite this: J. Phys. Chem. 1972, 76, 6, 909–914Publication Date (Print):March 1, 1972Publication History Published online1 May 2002Published inissue 1 March 1972https://doi.org/10.1021/j100650a021RIGHTS & PERMISSIONSArticle Views1688Altmetric-Citations339LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (627 KB) Supporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Synthesis and physicochemical properties in aqueous solution of the sequential polypeptide poly(Tyr-Ala-Glu).

AbstractA polypeptide having the repealing sequence (Tyr‐Ala‐Glu)n was synthesized by the polymerization of the N‐hydroxysuccinimide ester of O‐benzyl‐L‐tyrosyl‐L‐alanyl‐γ‐benzyl‐L‐glutamate, followed by the removal of the benzyl groups by means of hydrogen bromide. The main fraction obtained on gel filtration had an average molecular weight of over 60, 000, corresponding to over 500 amino acid residues per polypcptide chain. The polymer is soluble in water above pH 5.5, and precipitates on lowering the pH. The x‐ray powder photographs show features of an α‐helical structure. The dependence of the ultraviolet absorption spectrum, the optical rotatory dispersion, and the fluorescence of poly(Tyr‐Ala‐Glu) on pH, in salt‐free as well as in salt‐containing aqueous solutions, was compared with the corresponding properties of a copolymer containing equimolar proportions of tyrosine, alanine, and glutamic acid in a random sequence. From these measurements it was concluded that poly(Tyr‐Ala‐Glu ) has a helical con formation at low pH and a random coil conformation at high pH, the transition taking place at pH 6 in the absence of salt and pH II in the presence of salt. Thus, in the range pH 7 to l0. random coil‐to‐helix transition can be achieved by merely increasing the ionic strength. A model is proposed for the structure of the helical poly peptide which accounts for the Stability of the helical conformation by assuming hydrogen bonding between the carboxylate group of the ith glutamic acid residue and the hydroxyl group of the (i + 4 )th tyrosine residue. The complex ORD of helical poly(Tyr‐Ala‐Glu) is explained as being due to a superposition of the ORD of an α‐helix and that of a regular array of phenolic ehroniopholes originating from the immobilization of the aromatic rings in the specific structure of the polymer.