Showing papers on "Solvent published in 1981"

Mechanism of protein stabilization by glycerol: preferential hydration in glycerol-water mixtures

Abstract: A densimetric investigation of the interactions between solvent components in glycerol-water mixtures (between 10 and 40 vol % glycerol) and seven proteins have been carried out in the acid pH region. All the proteins were found to be preferentially hydrated at all conditions used, i.e., addition of the proteins to the mixed solvent results in an increase in the chemical potential of glycerol. It is considered that this thermodynamically unfavorable interaction should tend to minimize the surface of contact between proteins and glycerol and in this way stabilize the native structure of globular proteins.

Extraction of tissue lipids with a solvent of low toxicity.

Abstract: Publisher Summary This chapter discusses the extraction of tissue lipids with a solvent of low toxicity. The extraction of lipids from tissues is invariably done with volatile organic solvents, most of which are sold with warnings against excessive inhalation. For each gram of tissue, add 18 ml of extraction solvent and homogenize thoroughly. The mixture should be a well-dispersed suspension. After 30–60 s of mixing, filter the mixture, preferably with a sintered-glass, Buchner funnel under pressure rather than with a vacuum. Materials containing above-average water content, such as plasma, should be extracted with a larger volume of extraction solvent to keep the water in solution. In the case of plasma and whole blood, it is best to add the material to the solvent in small portions with continuous vortexing, if a fine suspension of the nonlipid portion is to be produced. The washing step is a convenient way to reduce the volume of the lipid extract, a factor to consider in working on a large scale. It removes primarily the higher boiling component, and thereby facilitates subsequent evaporative removal of solvent. Removal of solvent from hexane-isopropanol extracts is readily done by vacuum evaporation, but a warmer bath than usual is recommended.

Dry column method for the quantitative extraction and simultaneous class separation of lipids from muscle tissue

Abstract: A method for lipid isolation is presented that is alternative to the traditional chloroform/methanol extraction methods. This new method allows lipid isolation by solvent elution of a dry column composed of a tissue sample, anhydrous sodium sulfate, and Celite 545 diatomaceous earth groud together. To isolate total lipids, the dry column is eluted with a mixture of dichloromethane/methanol (90∶10, v/v). Alternatively, the lipids may be isolated and simultaneously separated into neutral and polar fractions by a sequential elution procedure; neutral lipids free of polar lipids are eluted first with dichloromethane, followed by elution of polar lipids with the dichloromethane/methanol (90∶10) mixture. The two dry column methods-isocratic or sequential elution-were compared with the traditional chloroform/methanol methods by gravimetric, thin layer chromatographic and phosphorus analyses.

Mucous membrane-adhering film preparation and process for its preparation

Abstract: A mucous membrane-adhering film preparation wherein the film consists of two layers. One layer of the film consists of the pharmaceutical agents and water-soluble high polymer material. The other layer of the film material consists of poor water-soluble agents. The pharmaceutical agent and water-soluble high polymer material layer first layer and the poor water-soluble agents second layer are separately prepared in solvents. The first solution is coated on a base plate having a favorable releasing nature, and, by removing the solvent, the film is produced on the base plate, the second solvent is then coated on the first layer and by removing the solvent, the desired film having one poor water-soluble surface is produced.

Preferential Hydration of Bovine Serum Albumin in Polyhydric Alcohol-Water Mixtures

Abstract: The preferential solvent interaction with bovine serum albumin in aqueous solution of polyhydric alcohols (ethylene glycol, glycerol, xylitol, sorbitol, mannitol, and inositol) was investigated by a densimetric method with the application of multicomponent theory. This proteins was preferentially hydrated in all solvent systems examined: the extent depended on the number and the steric configuration of the hydroxyl groups of alcohols. The absolute interactions of these alcohols with the protein were estimated by assuming that the amount of hydration of protein at every solvent composition used is identical with that in pure water. The preferential hydration of the protein in 30% aqueous solutions of glycerol and sorbitol was found to decrease as the temperature was increased, indicating that the increase in chemical potential of protein on transferring it from water to both aqueous solvents is generated by a large positive enthalpy change, sufficient to compensate for the positive entropy change in the transfer process. On the basis of these results, and mechanism of stabilization of protein structure by these alcohols was discussed from the viewpoint of the solvation of protein.

Extraction, separation and recovery of diterpene glycosides from Stevia rebaudiana plants

Abstract: A process for recovering diterpene glycosides from the Stevia rebaudiana plant includes the steps of sequentially extracting plant material with a first solvent of intermediate polarity to extract plant substances which tend to interfere with a liquid chromatographic separation of the glycosides, and then with a second solvent of high polarity to extract glycosides, and chromatographically separating the extracted glycosides by introducing them onto a liquid chromatography column having a packing of an oxygen-containing organic stationary phase covalently bonded through a silicon atom to an inorganic support, eluting them with a solvent of polarity higher than that of the first solvent but lower than that of the second solvent, and collecting individually eluate fractions rich in respective glycosides.

Flows of dilute hydrolyzed polyacrylamide solutions in porous media under various solvent conditions

Abstract: Experimental results on pressure losses of flows of dilute polymer solutions through porous media are summarized. The polymer products employed in this study consisted of partially hydrolyzed polyacrylamides (HPAM) with different degrees of hydrolysis. The effect of the hydrolysis on the pressure drop is investigated in a porous media test section designed to minimize polymer degradation. The investigations were carried out for various solvent conditions, and it is shown that the maximum increase in pressure drop is mainly dependent on the molecular weight of the polymers. The onset of the polymer action is measured for various fluid and solvent properties. Particular attention is given to measurements near θ-conditions. The results stress the importance of the solvent properties on the actions of the polymers and on the resultant pressure drop for porous media flows. The addition of salt ions to solutions of partially hydrolyzed polyacrylamides yields onset behavior previously observed for nonionic polymers. The differences measured between various solvent properties can be explained by the actual hydrodynamic molecule dimensions for a given molecular weight and polymer concentration. To quantify the influences of the solvent properties on the polymers, measurements were carried out in aqueous solutions for various pH values and therefore at various degrees of dissociation. The importance of separating polymer effects caused by their linear dimension in the solution from those that are introduced by and increase in solvent viscosity is shown. Measurements were performed to quantify the effects of solvent viscosity on the polymer action and to separate these effects from those due to changes in molecule dimensions. The implications of the present results are stressed in connection with applications of polymer solutions in tertiary oil recovery, and the positive features of the molecule actions on flow in such applications are described.

Comparison of methylene chloride and chloroform for the extraction of fats from food products

Abstract: Ten food products with a wide range of total fat, fatty acid and sterol content were obtained from a supermarket in the Washington, DC area. These food products were extraced by a new method, using methylene chloride/methanol as the extraction solvent. The results were compared to the Folch et al. procedure, in which chloroform/methanol is the extraction solvent. Total fat was determined, and fatty acid methyl esters and sterol butyrates were prepared and measured by gas liquid chromatography. An analysis of variance indicated that methylene chloride is as effective as chloroform, a suspected carcinogen, in the Folch et al. extraction of total fat, fatty acids and sterols from foods.

Recovery of fluorinated emulsifying acids from basic anion exchangers

Abstract: To elute fluorinated emulsifying acids, especially perfluoro-carboxylic acids, from basic anion exchangers a mixture of dilute mineral acid and polar organic solvents is used. The solvent should be miscible with water preferably to an extent of at least 40%. By this process the required amount of eluent and the time of elution can be reduced while simultaneously the amount of recovered emulsifying acid can be improved. The process is especially suitable for the recovery of fluorinated emulsifiers in the coagulation or concentration of fluoropolymer latices.

Modification of technological properties of fish protein concentrates

Abstract: Fish protein concentrates are mixtures of cross-linked and aggregated molecules of different muscle proteins. The final conformation of the components of the mixtures is formed as a result of procedures applied to convert the raw materials into a product of desirable and stable sensory properties, containing less than 0.1% of lipids. To achieve this end usually extraction with hot organic solvents, mainly isopropyl alcohol and 1,2-dichloroethene, followed by air drying are employed. These conditions bring about denaturation of many of the proteins followed by aggregation of the molecules due to the interaction of reactive functional groups in extended polypeptide chains. In the final product a large proportion of hydrophobic groups is exposed to the solvent and the proteins exhibit an extremely low water affinity. Such concentrates, although valuable as protein supplements, have only limited suitability as active components of various processed foods, as they have poor technological value. They are insoluble or have a very low water dispersibility and swelling ability, do not form gels after heating, or have any significant fat-emulsifying capacity. Changing the dissociation or number of ionic groups of the molecules prior to extraction, e.g., by acidifying or acylating, can partially reduce the denaturing effect of heat and organic solvents and thus improve the functional properties of the product. An upgrading of the quality of concentrates produced by hot extraction can be achieved by partial enzymatic or chemical deaggregation, hydrolysis followed by the plastein reaction, or formation of suitable derivatives. The best results have been obtained by partial hydrolysis of acylated proteins or precipitation of the aggregated products using sodium hexametaphosphate. The functional properties of such products are comparable to those of vegetable protein isolates used as meat extenders. Various proteins of high technological value can be also obtained by enzymatic hydrolysis of the raw material, followed by separation of the lipids without organic solvent extraction. Such products, however, have a distinct odor and flavor and must be stabilized because of residual lipids.

Stable liquid polymeric precursor to silicon nitride and process

Abstract: Stable, viscous polymers of silicon, nitrogen and hydrogen are formed by reacting a halosilane with ammonia in the presence of a solvent comprising an aliphatic ether, a chloromethane or mixtures thereof. After the solvent has been removed from the reaction product, the polymer can be poured into a container of desired shape and then can be sintered to form a uniform silicon nitride product.

Conductive composite filaments and methods for producing said composite filaments

Abstract: Conductive composite filaments are disclosed that are formed by conjugate-spinning a conductive component composed of a thermoplastic polymer and/or a solvent soluble polymer and conductive metal oxide particles and a non-conductive component composed of a fiber-forming polymer.

Solvent extraction of alkali metal cations from aqueous solutions by highly lipophilic crown ether carboxylic acids

Abstract: Competitive solvent extractions of alkali metal cations from water into chloroform by 2-(sym-dibenzo-16-crown-5-oxy)-butanoic acid (5), 2-(sym-dibenzo-16-crown-5-oxy)hexanoic acid (6), 2-sym-dibenzo-16-crown-5-oxy)octanoic acid (7), 2-(syn-dibenzo-16-crown-5-oxy)decanoic acid (8), and 5-(sym-dibenzo-16-crown-5-oxy)pentanoic acid (9) are reported. For 6, 7, and 8 the complexing agents are sufficiently lipophillic that they remain totally in the organic phase when chloroform solutions of the crown ether carboxylic acids are contacted with highly alkaline aqueous alkali metal salt solutions.

Enthalpies of solvation in cyclohexane and in water for homologous aliphatic ketones and esters

Abstract: The standard enthalpies of solution at infinite dilution were determined for homologous aliphatic ketones and esters in water and in cyclohexane, using a rotating Calvet calorimeter, and solution concentrations about 5×10−4 mole fraction. Vaporization enthalpies, obtained for each compound with an effusion calorimetric cell, were added to calculate the solvation enthalpies. Their dependence on the number of carbon atoms in the chain is discussed in terms of the Friedman and Krishnan treatment. The effect of polarization of the functional groups is evaluated, and separation from the influence of chain length and the hydrophobic interactions of the methylenes is attempted. For the aqueous solutions, the rearrangement in the structure of the solvent around solute molecules is also considered in relation to deviations from linearity. Comparisons are made with solvation enthalpies obtained for ketones and esters with branched or cyclic substitutes.

Process for preparing arylamines

Abstract: The process of preparing a tertiary amine by the condensation of a mono- or di-tertiary amine and a mono- or di-iodoaryl compound. Conducting the condensation reaction in the presence of potassium hydroxide, and a copper catalyst, either in the absence of a solvent or with an inert saturated hydrocarbon solvent, in an inert atmosphere, at a temperature between from about 120° C. to about 190° C. for a period of time sufficient to at least substantially complete the reaction.