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 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

New methods for isolation and fractionation by partition are described and compared with existing techniques. Substantially purer products were isolated by partition as compared to precipitation with hexadecylpyridinium chloride. The glycosaminoglycans isolated fron Furth murine mastocytoma tumor were found to consist of 78-80% heparin, 12-13% chondroitin sulfate, and 8-9% hyaluronate. Dermatan sulfate was not detected. Two heparin-like glycosaminoglycans could be isolated by partition fractionation in the phase system 1-butanol/aqueous NaCl containing hexadecylpyridinium chloride. The composition of one was typical of heparins. However, the other glycosaminoglycan contained only 0.47 moles N-sulfate/mole uronate, but had electrophoretic and partition properties characteristic of heparin.
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PMID:Isolation and characterization of glycosaminoglycans from the Furth murine mastocytoma. 41 10

Anaerobic sea or fresh water media with acetate and elemental sulfur yielded enrichments of a new type of strictly anaerobic, rod-shaped, laterally flagellated, Gram-negative bacterium. Three pure culture-strains from different sulfide-containing sea water sources were characterized in detail and are described as a new genus and species Desulfuromonas acetoxidans. The new bacterium is unable to ferment organic substances; it obtains energy for growth by anaerobic sulfur respiration. Acetate, ethanol or propanol can serve as carbon and energy source for growth; their oxidation to CO2 is stoichiometrically linked to the reduction of elemental sulfur to sulfide. Organic disulfide compounds, malate or fumarate are the only other electron acceptors used. Butanol and pyruvate are used in the presence of malate only; no other organic compounds are utilized. Biotin is required as a growth factor. The following dry weight yields per mole of substrate are obtained: in the presence of sulfur: 4.21 g on acetate, 9.77 g on ethanol; in the presence of malate: 16.5 g on acetate, 34.2 g on ethanol and 46.2 g on pyruvate. Accumulations of cells are pink; cell suspensions exhibit absorption spectra resembling those of c-type cytochromes (abs. max. at 419, 523 and 553 nm). Malate-ethanol grown cells contain a b-type cytochrome in addition. In the presence of acetate, ethanol or propanol, Desulfuromonas strains form robust growing syntrophic mixed cultures with phototrophic green sulfur bacteria.
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PMID:Desulfuromonas acetoxidans gen. nov. and sp. nov., a new anaerobic, sulfur-reducing, acetate-oxidizing bacterium. 101 37

The solubilities of a series of chemically related barbiturates, including some medically useful ones as well as phenobarbital, were determined at 25 degrees in the straight-chain alcohols methanol through butanol. The solubility values are given in both milligrams per milliliter and the mole fraction notation. The solubility in methanol was the highest and decreased nonlinearly for the solubility in 1-butanol. In several cases, mole fraction solubility gave shouldering or peaking as a function of the carbon number of the solvent. This series of barbiturates was broken down into two subsets of straight-chain and branched alkyl barbiturates, and solubility ratios in these subsets were considered.
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PMID:Solubility of straight-chain and branched alkyl barbiturates in straight-chain alcohols. 125 44

Spleen exonuclease, which degrades nucleic acids into single 3'-nucleotides, is used in the detection of DNA adducts by 32P-postlabeling. Contamination of the exonuclease with phosphatase activity can reduce the recovery of benzo[a]pyrene and N-hydroxy-2-naphthylamine DNA adducts by 32P-postlabeling. Four preparations of spleen exonuclease containing varying levels of phosphatase activity (< 1-62% of the unmodified 3'-nucleotides being dephosphorylated) were used to hydrolyze the DNA. The exonuclease with the lowest phosphatase activity produced a recovery of up to 9.60 mumol of benzo[a]pyrene adducts per mole of DNA. Recovery of benzo[a]pyrene adducts was reduced to 0.56 mumol of adduct per mole of DNA using the exonuclease with the highest phosphatase activity. Phosphatase in the exonucleases also dephosphorylated N-hydroxy-2-naphthylamine DNA adducts. Surprisingly, recovery of these DNA adducts was nearly 10 times greater using nuclease P1 than when using 1-butanol extraction for adduct enrichment, since arylamine DNA adducts have previously been reported to be poorly detected by 32P-postlabeling after nuclease P1 treatment. Our data indicate that the hydrolysis of DNA by spleen exonuclease may be an important source of variability in both qualitative and quantitative analysis of adducts by 32P-postlabeling.
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PMID:Phosphatase activity in commercial spleen exonuclease decreases the recovery of benzo[a]pyrene and N-hydroxy-2-naphthylamine DNA adducts by 32P-postlabeling. 805 38

Several recent reports have provided evidence that interactions of small alcohols with lipid bilayer membranes are dominated by adsorption to the membrane-water interface. This mode of interaction is better modeled by binding models than solution theories. In the present study, alcohol-membrane interactions are examined by applying the 'solvent exchange model' [J.A. Schellmann, Biophys. Chem. 37 (1990) 121] to calorimetric measurements. Binding constants (in mole fraction units) for small alcohols to unilamellar liposomes of dimyristoyl phosphatidylcholine were found to be close to unity, and in contrast to partitioning coefficients they decrease through the sequence ethanol, 1-propanol, 1-butanol. Thus, the direct (intrinsic) affinity of the bilayer for these alcohols is lower the longer the acyl chain. A distinction between binding and partitioning is discussed, and it is demonstrated that a high concentration of solute in the bilayer (large partitioning coefficients) can be obtained even in cases of weak binding. Other results from the model suggest that the number of binding sites on the lipid bilayer interface is 1-3 times the number of lipid molecules and that the binding is endothermic with an enthalpy change of 10-15 kJ/mol. Close to the main phase transition of the lipid bilayer the results suggest the presence of two distinct classes of binding sites: 'normal' sites similar to those observed at higher temperatures, and a lower number of high-affinity sites with binding constants larger by one or two orders of magnitude. The occurrence of high-affinity sites is discussed with respect to fluctuating gel and fluid domains in bilayer membranes close to the main phase transition.
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PMID:Thermodynamics of alcohol-lipid bilayer interactions: application of a binding model. 1051 96

The total vapor pressures at 26 degreesC of binary (water-alcohol) and ternary (water-alcohol-vesicle) systems were measured for six short chain alcohols. The vesicles were unilamellar dipalmitoyl phosphatidylcholine (DMPC). The data was used to evaluate the effect of vesicles on the chemical potential of alcohols expressed as the preferential binding parameter of the alcohol-lipid interaction, gamma23. This quantity is a thermodynamic (model-free) measure of the net strength of membrane-alcohol interactions. For the smaller investigated alcohols (methanol, ethanol and 1-propanol) gamma23 was negative. This is indicative of so-called preferential hydration, a condition where the affinity of the membrane for water is higher than the affinity for the alcohol. For the longer alcohols (1-butanol, 1-pentanol, 1-hexanol) gamma23 was positive and increasing with increasing chain length. This demonstrates preferential binding, i.e. enrichment of alcohol in the membrane and a concomitant depletion of the solute in the aqueous bulk. The measured values of gamma23 were compared to the number of alcohol-membrane contacts specified by partitioning coefficients from the literature. It was found that for the small alcohols the number of alcohol-membrane contacts is much larger than the number of preferentially bound solutes. This discrepancy, which is theoretically expected in cases of very weak binding, becomes less pronounced with increasing alcohol chain length, and when the partitioning coefficient exceeds approximately 3 on the molal scale (10(2) in mole fraction units) it vanishes. Based on this, relationships between structural and thermodynamic interpretations of membrane partitioning are discussed.
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PMID:Binding of small alcohols to a lipid bilayer membrane: does the partitioning coefficient express the net affinity? 1124 45

Titration calorimetry has been used to study the effect of the addition of two primary alcohols, 1-butanol and 1-heptanol, to the aqueous phase on the thermal effects of micellization of benzyldimethyldodecylammonium bromide (BDDAB) as well as its adsorption onto nonporous Spherosil XO15M and onto porous aluminosilicate SiAl32d22 possessing uniformly sized mesopores. A linear decrease of the critical micelle concentration (CMC) of the cationic surfactant with the additive content was inferred from the specific conductivity measurements. All adsorption and calorimetry experiments were carried out at 298 K and at a fixed alcohol content (0.01 mol kg(-1)) either in deionized water or in a 0.01 mol kg(-1) NaBr solution. Dilution calorimetry measurements allowed determination of the cumulative molar enthalpy changes and a new analysis of these data was proposed to calculate easily the enthalpy of micellization per mole of BDDAB, Delta(mic)h, and the CMC value. The alcohol addition was shown to render the micellization phenomenon more exothermic, the effect being larger as the chain length of alcohol increased. These effects were attributed to the location of alcohol molecules between the surfactant units, their hydroxyl groups close to the surfactant head-groups, in competition with the surfactant counterions. The individual isotherms of alcohol and surfactant adsorption onto XO15M and SiAl32d22 were determined. The plots of the pseudo-differential molar enthalpy of displacement, Delta(dpl)h, against the surface coverage by the surfactant cation, Theta(BDDA+), were derived from the titration calorimetry data. The formation of surface-bound aggregates was thought to be a prerequisite for alcohol coadsorption at the solid-solution interface. At least two different types of adsolubilization sites were postulated, one of the sites being the same as in micelles and the other related to the contact area between the hydrophobic surfactant tails and the equilibrium bulk solution. Coadsorption (adsolubilization) of alcohol molecules at such sites was found to increase the exothermic contribution to the enthalpy of displacement per mole of the BDDA+ adsorbed.
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PMID:Effect of alcohol addition to the aqueous phase on the thermal effects of micellization of cationic benzyldimethyldodecylammonium bromide and its adsorption onto porous and nonporous silicas. 1502 84

Surface tensions (sigma) for [1,3-dioxolane+methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and 1-pentanol] and excess molar volumes (v(E)) for [1,3-dioxolane+methanol, ethanol, 1-propanol, 2-propanol, and 2-butanol] at the temperature 298.15 K and normal atmospheric pressure have been determined as a function of mole fractions. The magnitude of these experimental quantities is discussed in terms of the nature and type of intermolecular interactions in binary mixtures. In order to analyze the surface tension behavior, the extended Langmuir (EL) model was used and the results obtained for the systems containing 1,3-dioxolane were compared with those of other formerly published series: [1,4-dioxane+alkanes] and [1,4-dioxane+alcohols].
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PMID:Surface tension and density of mixtures of 1,3-dioxolane+alkanols at 298.15 K: analysis under the extended Langmuir model. 1502 9

Phase diagrams of pseudo-quaternary systems of cetyltrimethylammonium bromide (CTAB)/polyoxyethylene(20)cetyl ether (Brij-58)/water/1-butanol (or 1-pentanol)/n-heptane (or n-decane) at fixed omega (=[water]/[surfactant]) of 55.6 were constructed at different temperatures (293, 303, 313, and 323 K) and different mole fraction compositions of Brij-58 (X(Brij-58)=0, 0.5, and 1.0 in CTAB + Brij-58 mixture). Pure CTAB stabilized systems produced larger single-phase domains than pure Brij-58 stabilized systems. Increasing temperature increased the single-phase domain in the Brij-58 stabilized systems, whereas the domain decreased in the CTAB stabilized systems. For mixed surfactant systems (with X(Brij)=0.5) negligible influence of temperature in the studied range of 293 to 323 K on the phase behavior was observed. Interfacial compositions of the mixed microemulsion systems at different temperature and different compositions were evaluated by the dilution method. The n(a)(i) (number of moles of alcohol at the interface) and n(a)(o) (number of moles of alcohol in the oil phase) determined from dilution experiments were found to decrease and increase respectively for CTAB stabilized systems, whereas an opposite trend was witnessed for Brij-58 stabilized systems. The energetics of transfer of cosurfactants from oil to the interface were found to be exothermic and endothermic for CTAB and Brij-58 stabilized systems, respectively. At equimolar composition of CTAB and Brij-58, the phase diagrams were temperature insensitive, so that the enthalpy of the aforesaid transfer process was zero.
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PMID:Phase behavior, interfacial composition and thermodynamic properties of mixed surfactant (CTAB and Brij-58) derived w/o microemulsions with 1-butanol and 1-pentanol as cosurfactants and n-heptane and n-decane as oils. 1667 63

Ambient pressure (solid + liquid) equilibria (SLE) and (liquid + liquid) equilibria (LLE) of binary systems--ionic liquid (IL) tetra- n-butylphosphonium p-toluenesulfonate + 1-alcohol (1-butanol, 1-hexanol, 1-octanol, 1-decanol, or 1-dodecanol), benzene, or n-alkylbenzene (toluene, ethylbenzene, n-propylbenzene)-have been determined by using dynamic method in a broad range of mole fractions and temperatures from 250 to 335 K. For binaries containing alcohol, simple eutectic diagrams were observed with complete miscibility in the liquid phase. Only in the case of system [IL + n-propylbenzene] was mutual immiscibility with an upper critical solution temperature (UCST) with low solubility of the IL in the alcohol and high solubility of the alcohol in the IL detected. The basic thermal properties of pure IL, i.e., melting and glass-transition temperatures as well as enthalpy of melting, have been measured with differential scanning microcalorimetry technique (DSC). Well-known UNIQUAC, Wilson, NRTL, NRTL1, and NRTL2 equations have been fitted to obtain experimental data sets. For the system containing immiscibility gap [IL + n-propylbenzene], parameters of the equations have been derived only from SLE data. As a measure of goodness of correlations, root-mean square deviations of temperature have been used. These experimental results were compared to the previously measured binary systems with tetra- n-butylphosphonium methanesulfonate. Changing anion from methanesulfonate to p-toluenesulfonate decreases solubilities in systems with alcohols and increases the solubilities in binary systems with benzene and alkylbenzenes.
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PMID:Phase equilibria study in binary systems (tetra-n-butylphosphonium tosylate ionic liquid + 1-alcohol, or benzene, or n-alkylbenzene). 1869 11


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