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1H NMR spectroscopy was used to investigate the stoichiometry and stability of the drug ketamine cation complexes with some crown ethers, such as 15-crown-5 (15C5), aza-15-crown-5 (A15C5), 18-crown-6 (18C6), aza-18-crown-6 (A18C6), diaza-18-crown-6 (DA18C6), dibenzyl-diaza-18-crown-6 (DBzDA18C6) and cryptant [2,2,2] (C222) in acetonitrile (AN), dimethylsulfoxide (DMSO) and methanol (MeOH) at 27 degrees C. In order to evaluate the formation constants of the ketamine cation complexes, the CH3 protons chemical shift (on the nitrogen atom of ketamine) was measured as function of ligand/ketamine mole ratio. The formation constant of resulting complexes were calculated by the computer fitting of chemical shift versus mole ratio data to appropriate equations. A significant chemical shift variation was not observed for 15C5 and 18C6. The stoichiometry of the mono aza and diaza ligands are 1:1 and 1:2 (ligand/ketamine), respectively. In all of the solvents studied, DA18C6 formed more stable complexes than other ligands. The solvent effect on the stability of these complexes is discussed.
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PMID:The interaction between ketamine and some crown ethers in common organic solvents studied by NMR: the effect of donating atoms and ligand structure. 1597 63

Raman spectra of propylamine (C3H7NH2) and its binary mixtures, C3H7NH2 + CH3OH with varying mole fractions of the reference system, C3H7NH2, C were recorded in two widely apart wavenumber regions, 3100-3600 cm(-1) and 1225-1325 cm(-1). In the former region, the two Raman bands at approximately 3305 and approximately 3326 cm(-1), obtained after the line shape analysis, which were assigned to symmetric nu(N-H) and anti-symmetric nu(N-H) stretching modes, respectively, show a downshift upon dilution. However, whereas the nu(N-H) anti-symmetric mode shows a shift of 18.6 cm(-1), the nu(N-H) symmetric mode shows a much smaller shift (5.7 cm(-1)) between neat liquid and high dilution, C = 0.1. This aspect has been explained using the optimized geometries calculated employing ab initio theory (MP2 level) for the neat C3H7NH2 and its different hydrogen-bonded complexes. The linewidth versus concentration plot for the nu(N-H) anti-symmetric stretching mode, however exhibits a distinct maxima at C = 0.4, which has been explained as a slight departure from the concentration fluctuation model. In the latter region, a symmetric peak is observed, which corresponds to nu(C-N) stretching mode, which shows an upshift upon dilution and an almost linear concentration dependence. This has also been explained in terms of the parameters obtained from the optimized geometries of the different hydrogen-bonded complexes.
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PMID:Investigation of nu(N-H) and nu(C-N) stretching modes of propylamine (C3H7NH2) in a binary system C3H7NH2 + CH3OH via concentration dependent Raman study and ab initio calculations. 1616 21

A novel analytical method for analysis of microbial quinones in activated sludge sample was developed with improved reliability compared to the conventional method. The operating conditions for the extraction of quinones from activated sludge sample with a methanol-chloroform mixture and hexane were optimized. A solid phase extraction method using the Sep-Pak Plus Silica, a small column packed with silica gel, was employed for the purification and separation of quinones instead of column chromatography and thin layer column chromatography used in the conventional method. The analytical operation was simplified and the analytical time was shortened by a half or two-thirds of that required for the conventional method. The recoveries of quinones were markedly increased from 30-60% with the conventional method to as high as 90-101% with the improved method, demonstrating that the reliability of the analytical results of the improved method is significantly higher than that of the conventional method. The quinone content value obtained using the improved method was twice as high as that obtained using the conventional method for the same activated sludge sample, but the quinone profiles expressed as the mole fraction of each quinone type were the same for each method.
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PMID:Development of a novel solid phase extraction method for the analysis of bacterial quinones in activated sludge with a higher reliability. 1623 85

We present molecular-dynamics (MD) computer simulation results for the local structures, hydrogen (H)-bond distribution, and dynamical properties of methanol (MeOH) and dimethylsulfoxide (DMSO) binary mixtures at ambient conditions over the entire composition range. The simulated heat of mixing and site-site pair distribution functions suggest that the intermolecular structures of the pure liquids are not markedly altered upon mixing. Nevertheless, H-bonding statistics show that aggregates of the type 1DMSO:1MeOH are formed and represent the predominant form of molecular association in these mixtures. Only a small fraction (10%) of DMSO molecules in MeOH-rich mixtures (85% in mole) forms H-bonding trimers of type 1DMSO:2MeOH. No evidence of other types of interspecies association is found. The self-diffusion coefficient for DMSO (MeOH) increases (decreases) upon mixing. The characteristic reorientation time tau1 of both species increases in the mixture, but the composition dependence is weak. The frequency spectrum of MeOH reorientational time-correlation function shows significant redshifts of the principal librational band as DMSO is added to the system, whereas the librational band of DMSO shows small alterations upon mixing. Our results are discussed in the light of previous simulation analyses for a similar system, DMSO-water mixtures, and compared with available experimental results.
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PMID:Molecular-dynamics simulations of dimethylsulfoxide-methanol mixtures. 1625 62

Surface tensions (sigma) for {1,4-dioxane + methanol, ethanol, or 1-propanol} at the temperature 298.15 K and normal atmospheric pressure have been determined as a function of mole fractions. The experimental results have been analyzed using the ideal and Langmuir models and in the light of the well-documented bulk properties of these systems, which reflect hydrogen bonding between the alcohol and 1,4-dioxane molecules. For {1,4-dioxane + ethanol} surface tensions were also measured at other temperatures between 288.15 and 308.15 K, and these data were used to calculate the surface entropy and enthalpy per unit area.
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PMID:Thermodynamic analysis of surface formation of {1,4-dioxane + 1-alkanol} mixtures. 1629 Aug 48

The effects of temperature, solvents, and cultural conditions on the fermentative physiology of an ethanol-tolerant (56 g/liter at 60 degrees C) and parent strain of Clostridium thermohydrosulfuricum were compared. An ethanol-tolerant mutant was selected by successive transfer of the parent strain into media with progressively higher ethanol concentrations. Physiological differences noted in the mutant included enhanced growth, tolerance to various solvents, and alterations in the substrate range and the fermentation end product ratio. Ethanol tolerance was temperature dependent in the mutant but not in the parent strain. The mutant grew with ethanol concentrations up to 8.0% (wt/vol) at 45 degrees C, but only up to 3.3% (wt/vol) at 68 degrees C. Low ethanol concentration (0.2 to 1.6% [wt/vol]) progressively inhibited the parent strain to where glucose was not fermented at 2.0% (wt/vol) ethanol. Both strains grew and produced alcohols on glucose complex medium at 60 degrees C in the presence of either 5% methanol or acetone, and these solvents when added at low concentration stimulated fermentative metabolism. The mutant produced ethanol at high concentrations and displayed an ethanol/glucose ratio (mole/mole) of 1.0 in media where initial ethanol concentrations were </=4.0% (wt/vol), whereas when ethanol concentration was changed from 0.1% to 1.6% (wt/vol), the ethanol/glucose ratio for the parent strain changed from 1.6 to 0.6. These data indicate that C. thermohydrosulfuricum strains are tolerant of solvents and that low ethanol tolerance is not a result of disruption of membrane fluidity or glycolytic enzyme activity.
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PMID:Ethanol Production by Thermophilic Bacteria: Physiological Comparison of Solvent Effects on Parent and Alcohol-Tolerant Strains of Clostridium thermohydrosulfuricum. 1634 85

Ab initio molecular dynamics simulations are employed to study the structural and proton transport properties of methanol-water mixtures. Structural characteristics analyzed at two different methanol mole fractions (X(M) = 0.25 and X(M) = 0.5) reveal enhanced structuring of water as the methanol mole fraction increases in agreement with recent neutron diffraction experiments. The simulations reveal the existence of separate hydrogen-bonded water and methanol networks, also in agreement with the neutron diffraction data. The addition of a single proton to the X(M) = 0.5 mixture leads to an anomalous structural or Grotthuss-type diffusion mechanism of the charge defect in which water-to-water, methanol-to-water, and water-to-methanol proton transfer reactions play the dominant role with methanol-to-methanol transfers being much less significant. Unlike in bulk water, where coordination number fluctuations drive the proton transport process, suppression of the coordination number of waters in the first solvation shell of the defect diminish the importance of coordination number fluctuations as a driving force in the structural diffusion process. The charge defect is found to reside preferentially at the interface between water and methanol networks. The length of the ab initio molecular dynamics run (approximately 120 ps), allowed the diffusion constant of the charge defect to be computed, yielding a value of D = 4.2 x 10(-5) cm2/s when deuterium masses are assigned to all protons in the system. The relation of this value to excess proton diffusion in bulk water is discussed. Finally, a kinetic theory is introduced to identify the relevant time scales in the proton transfer/transport process.
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PMID:Ab initio molecular dynamics simulation of the structure and proton transport dynamics of methanol-water solutions. 1649 28

The solvatochromic parameters (ET(N), normalized polarity parameter; pi*, dipolarity/polarizability; beta, hydrogen-bond acceptor basicity; alpha, hydrogen-bond donor acidity) were determined for binary solvent mixtures of 1-(1-butyl)-3-methylimidazolium tetrafluoroborate ([bmim]BF4) with water, methanol, and ethanol at 25 degrees C over the whole range of mole fractions. In nonaqueous solutions, the value of the mixture increases with mole the fraction of [bmim]BF4 and then decreases gradually to the value of pure [bmim]BF4. Positive deviation from ideal behavior was observed for the solvent parameters ET(N), pi*, and alpha, whereas the deviation of the beta parameter is negative. The applicability of the combined nearly ideal binary solvent/Redlich-Kister equation for the correlation of various solvatochromic parameters with solvent composition was proved too for the first time. This equation provides a simple computational model to correlate and/or predict various solvatochromic parameters for many binary solvent systems. The correlation between the calculated and the experimental values of various parameters was in accordance with this model. Solute-solvent and solvent-solvent interactions have been applied for interpretation of the results.
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PMID:Solvatochromic parameters for binary mixtures of 1-(1-butyl)-3-methylimidazolium tetrafluoroborate with some protic molecular solvents. 1657 Oct 25

The free solution mobilities of curved and normal 199-bp DNA fragments have been measured in buffer solutions containing various quantities of the organic cosolvents methanol, ethanol, 2-propanol, 2-methyl-2,4-pentanediol (MPD), ethylene glycol, and ACN, using CE. The curved fragment, taken from the VP1 gene of SV40, contains five unevenly spaced A- and T-tracts in a centrally located "curvature module"; the A- and T-tracts have been mutated to other sequences in the normal 199-bp fragment. The free solution mobility of the curved 199-bp fragment is significantly lower than that of its normal counterpart in aqueous solutions [Stellwagen, E., Lu, Y. J., Stellwagen, N. C., Nucleic Acids Res. 2005, 33, 4425-4432]. The mobilities of both the curved and normal fragments decrease with increasing cosolvent concentration, due to the effect of the cosolvent on the viscosity and dielectric constant of the solution. The mobility differences between the curved and normal 199-bp fragments and the mobility ratios decrease approximately linearly with the increasing mole fraction of cosolvent in the solution. Hence, MPD and other organic cosolvents affect DNA electrophoretic mobility by a common mechanism, most likely the preferential hydration of the DNA surface that occurs in aqueous cosolvents. The gradual loss of the anomalously slow mobility of the curved 199-bp fragment with increasing cosolvent concentration, combined with other data in the literature, suggests that preferential hydration gradually widens the narrow A-tract minor groove, releasing site-bound counterions in the minor groove and shifting the conformation toward that of normal DNA.
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PMID:Effect of organic cosolvents on the free solution mobility of curved and normal DNA molecules. 1660 31

The metabolism of [(14)CH(3)]2-(2,4-dichlorophenoxy)isobutyric acid (DIB) was studied in plants and cell suspension cultures of Lycopersicon esculentum Mill. sp. ;Lukullus'. Both plants and cells in suspension culture showed a rapid uptake of DIB from nutrient media. The metabolites, isolated by extraction with methanol and separated by chromatographic methods, were identified by enzymic, chemical, and spectrometric methods. Two conjugates of the carboxyl with 2 and 3 moles glucose per mole DIB and, to a smaller extent, its beta-d-glucopyranosyl ester, were formed in both intact plants and cell suspension cultures, but there were quantitative differences.
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PMID:Comparative Investigations on the Metabolism of 2-(2,4-Dichlorophenoxy)Isobutyric Acid in Plants and Cell Suspension Cultures of Lycopersicon esculentum. 1666 86


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