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At least 163 records · Page 9Linked to original sources
PubMed1993

Exposure-excretion relationship of styrene and acetone in factory workers: a comparison of a lipophilic solvent and a hydrophilic solvent.

A factory survey was conducted in the second half of a working week on 41 exposed male workers, who were engaged in fiber-reinforced plastics work and exposed to the mixed vapors of styrene and acetone. Nonexposed workers, 20 men, were recruited from the same factory. Styrene and acetone in respiratory zone air were monitored for a 8-h shift with carbon cloth- and water-equipped personal diffusive samplers, respectively. Blood and urine samples were collected at the shift-end. Acetone and styrene concentrations in whole blood, serum and urine were measured by head-space gas chromatography, and phenylglyoxylic acid in urine by high-performance liquid chromatography. All biological exposure indicators analyzed correlated significantly with the intensity of exposure to the corresponding solvent during the shift. The slopes of the regression lines indicate that a very small fraction of styrene absorbed will be excreted into urine as styrene per se, and that styrene is quite effectively excreted into urine after metabolic conversion. In contrast, the slopes of regression lines for acetone suggest that acetone distributes both in the blood and urine quite evenly. When the distribution of the solvent in serum was compared with that in the whole blood, it was found that almost all of styrene in blood is present in the serum, whereas acetone distributed very evenly in the cellular and noncellular fractions of the blood.

Acetone↗
PubMed1987

The inhalation toxicity of two commercial dyes: solvent yellow 33 and solvent green 3.

The quinoline dye 2-(2'-quinolyl)-1,3-indandione or Solvent Yellow 33 (SY) and the anthraquinone dye 1,4-di-p-toluidinoanthraquinone or Solvent Green 3 (SG) are used in many manufactured products including military smoke grenades. During manufacturing, SY or a combination of both SY and SG can be released into the air, exposing factory workers by inhalation to these dye compounds. The potential inhalation toxicity of these compounds was tested by exposing F344/N rats to different concentrations of SY or SY/SG dye mixture (30:70 w/w) for 6 hr/day, 5 days/week for 4 or 13 weeks. In the 4-week studies, rats were exposed to SY aerosols at average concentrations of 10 +/- 5, 51 +/- 10, or 230 +/- 30 mg/m3 (means +/- SD) or SY/SG aerosols at average concentrations of 11 +/- 5, 49 +/- 11, or 210 +/- 50 mg/m3 (means +/- SD). Rats exposed to the highest concentration of SY or SY/SG had body weights that were approximately 8% or 7% less, respectively, than their controls after exposure. Rats exposed to the highest concentration of SY/SG for 4 weeks also had reduced pulmonary gas exchange efficiency, airflow obstruction, mild pulmonary inflammation, slight Type II pulmonary epithelial cell hyperplasia, and proliferation of vacuolated alveolar macrophages. In the 13-week studies, rats were exposed to SY aerosols at average concentrations of 1.0 +/- 0.2, 10.8 +/- 1.8, or 100 +/- 17 mg/m3 (means +/- SD) or SY/SG aerosols at average concentrations of 1.1 +/- 0.5, 10.2 +/- 3.1, or 101 +/- 23 mg/m3 (means +/- SD). Animals exposed to the highest concentration of SY or SY/SG for 13 weeks had body weights that were approximately 5 or 9% less, respectively, than their controls after exposure and had accumulation of vacuolated alveolar macrophages in lungs. Rats exposed to the highest concentration of SY/SG dye mixture for 13 weeks also had indications of mild pulmonary inflammation and slight Type II pulmonary epithelial cell hyperplasia. Very little SY was found in lungs after any exposures, indicating its clearance from lungs was at a rapid rate. However, significant amounts of the SG component of the SY/SG mixture were detected in lungs after each exposure. Lung clearance half-times of SG from the 13-week exposure were estimated to be approximately 280 days. In summary, neither test material appeared to be highly toxic following inhalation. However, the slightly higher toxicity observed for SY/SG over SY alone is probably related to the longer lung retention of the SG component of the dye mixture.

Administration, Inhalation↗
PubMed2003

Determination of coupled solvent mass in quartz crystal microbalance measurements using deuterated solvents.

A simple method is described for determining of the contribution of hydrodynamically coupled solvent to the adsorbed film mass determined in a quartz crystal microbalance (QCM) when operated in liquid. The method requires no additional apparatus and utilizes the change in QCM resonant frequency response between measurements made in non-deuterated and deuterated solvents. The mass of coupled water in a polymer film has been determined and is found to agree with that determined by XPS analysis of the dried polymer film.

Journal Article↗
PubMed1985

A double-quenching method for studying protein dynamics: separation of the fluorescence quenching parameters characteristic of solvent-exposed and solvent-masked fluorophors.

A novel experimental method, suitable for separate analysis of the quenching parameters characteristic of solvent-exposed and solvent-masked fluorophors of macromolecules, is described. The method is based on the modified Stern-Volmer analysis and requires simultaneous application of two kinds of quencher: one that can selectively quench the emission of exposed fluorophors (e.g., ionic quenchers) and another that is nonselective (e.g., oxygen or, in many cases, acrylamide), capable of quenching the fluorescence of both exposed and masked groups. In order to examine the accuracy of the model, a computer simulation was performed. The results showed that the errors are comparable to those arising from the conventional quenching experiments. The method is applicable to phosphorescence quenching as well and is extendable to time-resolved measurements (by replacing fluorescence intensities with lifetimes). The method was applied to resolve the quenching parameters of lysozyme fluorescence by the use of iodide as selective and acrylamide as nonselective quenchers. The determination of the acrylamide quenching constant associated with the internal fluorophor, Trp-108 (Kq = 3.5 M-1), permits specific studies on the dynamics of internal regions of the protein. The quenching constant determined for the more exposed residue Trp-62 (Kq = 1.6 M-1) provides local information about the surface independent of the electrostatic effects observed when an ionic quencher is used.

Animals↗
PubMed1999

Effect of Included Solvent Molecules on the Physical Properties of the Paramagnetic Charge Transfer Salts beta' '-(bedt-ttf)(4)[(H(3)O)Fe(C(2)O(4))(3)].Solvent (bedt-ttf = Bis(ethylenedithio)tetrathiafulvalene).

The new charge transfer salt, beta' '-(bedt-ttf)(4)[(H(3)O)Fe(C(2)O(4))(3)].C(5)H(5)N, I, (bedt-ttf = bis(ethylenedithio)tetrathiafulvalene) has a crystal structure closely similar to that of the reported salt beta' '-(bedt-ttf)(4)[(H(3)O)Fe(C(2)O(4))(3)].C(6)H(5)CN, II, which has a superconducting critical temperature of 8.6 K. However, variable temperature magnetic and transport experiments show that I has a metal to insulator transition at 116 K. The crystal structure of I has been determined above (150 K) and below (90 K) the metal to insulator transition and comparisons are made with the structure of II. The pyridine solvate crystallizes in the monoclinic space group C2/c with a = 10.267(2) Å, b = 19.845(4) Å, c = 34.907(7) Å, beta = 93.22(3) degrees, Z = 4 at 150 K and with a = 10.2557(15) Å, b = 19.818(28) Å, c = 34.801(49) Å, beta = 93.273(14) degrees, Z = 4 at 90 K. The structures of I and II both consist of layers of bedt-ttf with +0.5 formal charge per molecule and layers of approximately hexagonal symmetry containing H(3)O(+) and [Fe(C(2)O(4))(3)](3)(-). The solvent molecules occupy hexagonal cavities formed by the anionic layer. Changing the solvent molecule from C(6)H(5)CN to C(5)H(5)N induces disorder in the bedt-ttf layer which accounts for the dramatic difference in observed physical properties. For I, at 150 K, one-half of all the bedt-ttf molecules have identical conformations to all the molecules in II where both terminal ethylene groups of each bedt-ttf molecule are twisted and eclipsed with respect to the opposite end of the molecule. The remaining 50% of bedt-ttf molecules in I have disordered ethylene groups. The disorder persists at 90 K where it can be resolved into two conformations: twisted-twisted eclipsed and twisted-twisted staggered.

Journal Article↗
PubMed1996

Cell Envelope Changes in Solvent-Tolerant and Solvent-Sensitive Pseudomonas putida Strains following Exposure to o-Xylene.

Solvent-tolerant and -sensitive Pseudomonas putida strains were studied to determine their cell envelope changes following exposure to o-xylene. Both strains produced trans-unsaturated fatty acids. The tolerant strain showed an increase in total fatty acids, an increase in saturated fatty acids, and modified lipopolysaccharide. It is suggested that these envelope modifications aid in survival at high concentrations of organic solvents.

Journal Article↗
PubMed2001

Definition of a solvent system for spherical crystallization of salbutamol sulfate by quasi-emulsion solvent diffusion (QESD) method.

In this paper we describe how the spherical crystallization process by QESD method can be applied to a water-soluble drug, salbutamol sulfate. The type of solvent, antisolvent, and emulsifier and the concentration of emulsifier to be used for the production of spherical particles with a size range 80-500 microm are determined. Furthermore, the solvent/antisolvent ratio and the temperature difference between them (Delta T) are studied. It was observed that, in the case of salbutamol sulfate, the Delta T value has no influence on the formation of spherical particles. A very large metastable zone of salbutamol sulfate in water could explain this phenomenon. Finally, the influence of emulsifier concentration and of maturation time on the size of spherical particles is studied. The results show that these two parameters must be fixed to control the size of the recovered particles.

Acetates↗
PubMed1976

Solubility of nonelectrolytes in polar solvents IV: nonpolar drugs in mixed solvents.

The molecular and group surface area approach to solubility is shown to be applicable to mixed aqueous solvent systems. An equation is derived which is consistent with the exponential increase in the aqueous solubility of nonpolar drugs that frequently accompanies the addition of a cosolvent. This equation predicts that: (a) the ability of a drug to be solubilized by a cosolvent is proportional to its hydrophobic surface area per molecule, and (b) the ability of a cosolvent to solubilize any drug is inversely proportional to its interfacial tension against a reference liquid hydrocarbon. These predictions are experimentally verified with solubility studies of several alkyl p-aminobenzoates in propylene glycol-water mixtures and of hexyl p-aminobenzoate in mixtures of water the ethanol, methanol, ethylene glycol, propylene glycol, glycerin, and formamide.

Aminobenzoates↗
PubMed1981

Thermochemical investigations of nearly ideal binary solvents. VII: Monomer and dimer models for solubility of benzoic acid in simple binary and ternary solvents.

Solubilities are reported for benzoic acid at 25.0 degrees in binary mixtures of carbon tetrachloride with cyclohexane, n-hexane, or n-heptane and of cyclohexane with n-hexane or n-heptane and in ternary mixtures of carbon tetrachloride-cyclohexane-n-hexane and carbon tetrachloride-cyclohexane-n-heptane. Solubilities also are reported for benzoic acid in some binary solvents at 30.0 degrees and for m-toluic acid in binary mixtures of cyclohexane and n-hexane at 25.0 degrees. The results are compared to the predictions of equations developed previously for solubility in systems of purely nonspecific interactions, with the benzoic acids considered as either monomeric or dimeric molecules in solution. The dimer model gave more accurate predictions, with a maximum deviation of 4.4% between observed and predicted solubilities in all systems studied. Solubility maxima were predicted and observed for benzoic and m-toluic acids in cyclohexane-n-hexane and for benzoic acid in cyclohexane-n-heptane. The application of these solubility relationships to liquid-liquid partition coefficients is discussed.

Benzoates↗
PubMed1987

Thermochemical investigations of associated solutions: 5. Calculation of solute-solvent equilibrium constants from solubility in mixtures containing two complexing solvents.

Solubilities are reported for carbazole in binary dibutyl ether plus 1-chlorohexane mixtures at 25 degrees C. Results of these measurements are compared with solution models developed for solubility in systems containing specific solute-solvent interactions. A simple stoichiometric complexation model based on a 1:1 carbazole:dibutyl ether complex could describe the measured solubility to within an average absolute deviation of 1.7%. The calculated equilibrium constant, though, was about one-half of values previously determined from carbazole solubilities in several binary dibutyl ether plus alkane mixtures. A more sophisticated solution model, derived by assuming both 1:1 carbazole: dibutyl ether and carbazole:chlorohexane complexes, could describe the solubilities to within 2.4%. This latter model enables the carbazole-chlorohexane association constant to be calculated from experimental carbazole solubilities and a priori knowledge of the carbazole-dibutyl ether equilibrium constant.

Carbazoles↗
PubMed1991

Compatibility of organic solvents with the Microscreen prophage-induction assay: solvent--mutagen interactions.

The following solvents did not induce prophage lambda in the Escherichia coli WP2s(lambda) Microscreen assay: acetone, benzene, chloroform, ethanol, n-hexane, isopropanol, methanol, toluene, and a mixture of the three isomers of xylene. Dimethyl sulfoxide was genotoxic in the presence and absence of S9, and methylene chloride was weakly genotoxic in the presence of S9. The genotoxic potencies of 2-aminoanthracene and 2-nitrofluorene were reduced when dissolved in DMSO or methanol compared to their potencies when dissolved in acetone.

Anthracenes↗
PubMed1994

High resolution structures of the 4-4-20 Fab-fluorescein complex in two solvent systems: effects of solvent on structure and antigen-binding affinity.

Three-dimensional structures were determined for three crystal forms of the antigen binding fragment (Fab) of anti-fluorescein antibody 4-4-20 in complex with fluorescein. These included 1) a triclinic (P1) form crystallized in 47% (v/v) 2-methyl-2,4-pentanediol (MPD); 2) a triclinic (P1) form crystallized in 16% (w/v) poly(ethylene glycol), molecular weight 3350 (PEG); and 3) a monoclinic (P21) form crystallized in 16% PEG. Solvent molecules were added to the three models and the structures were refined to their diffraction limits (1.75-A, 1.78-A, and 2.49-A resolution for the MPD, triclinic PEG, and monoclinic PEG forms, respectively). Comparisons of these structures were interesting because 4-4-20 exhibited a lower antigen-binding affinity in 47% MPD (Ka = 1.3 x 10(8) M-1) than in either 16% PEG (Ka = 2.9 x 10(9) M-1) or phosphate-buffered saline (Ka = 1.8 x 10(10) M-1). Even though the solution behavior of the antibody was significantly different in MPD and PEG, the crystal structures were remarkably similar. In all three structures, the fluorescein-combining site was an aromatic slot formed by tyrosines L32, H96, and H97 and tryptophans L96 and H33. In addition, several active site constituents formed an electrostatic network with the ligand. These included a salt link between arginine L34 and one of fluorescein's enolate oxygen atoms, a hydrogen bond between histidine L27d and the second enolic group, a hydrogen bond between tyrosine L32 and the phenylcarboxylate group, and two medium range (approximately 5 A) electrostatic interactions with lysine L50 and arginine H52. The only major difference between the triclinic MPD and PEG structures was the degree of hydration of the antigen-combining site. Three water molecules participated in the above electrostatic network in the MPD structure, while eight were involved in the PEG structure. Based on this observation, we believe that 4-4-20 exhibits a lower affinity in MPD due to the depletion of the hydration shell of the antigen-combining site.

Amino Acid Sequence↗
PubMed2002

Solvent effects in tandem mass spectrometry: mechanistic studies indicating how a change in solvent conditions and pH can dramatically alter CID spectra.

Dramatically different CID (collision-induced dissociation) spectra are obtained when the complex [Zn(dien-glucose)](+) is electrosprayed from acidic and basic solutions. To understand this peculiar phenomenon, an in-depth mechanistic study was performed on one of the product ions that is present when the initial complex is diluted in basic solution but absent when the complex is diluted with acidic solution. On the basis of the results of this study, the differences in the CID spectra can be rationalized by the fact that the complex electrosprayed from basic solution was kinetically trapped, with the deprotonation site distal from the metal center. Under acidic conditions, the deprotonation site is at a hydroxyl group coordinated to the metal ion. A variety of experiments support this hypothesis. The studies herein underscore the importance of using identical solvent conditions when comparing sets of CID spectra. The data also highlight a very interesting phenomenon involving deprotonation of a hydroxyl group, which was several atoms away from the Zn(II) metal center.

Glucose↗
PubMed2000

Spo0A directly controls the switch from acid to solvent production in solvent-forming clostridia.

The spo0A genes of Clostridium beijerinckii NCIMB 8052 and Clostridium cellulolyticum ATCC 35319 were isolated and characterized. The C-terminal DNA-binding domains of the predicted products of spo0A from these two organisms, as well as 16 other taxonomically diverse species of Bacillus and Clostridium, show extensive amino acid sequence conservation (56% identity, 65% similarity over 104 residues). A 12-amino-acid motif (SRVERAIRHAIE) that forms the putative DNA recognition helix is particularly highly conserved, suggesting a common DNA target. Insertional inactivation of spo0A in C. beijerinckii blocked the formation of solvents (as well as spores and granulose). Sequences resembling Spo0A-binding motifs (TGNCGAA) are found in the promoter regions of several of the genes whose expression is modulated at the onset of solventogenesis in Clostridium acetobutylicum and C. beijerinckii. These include the upregulated adc gene, encoding acetoacetate decarboxylase (EC 4.1.1. 4), and the downregulated ptb gene, encoding phosphotransbutyrylase (EC 2.3.1.c). In vitro gel retardation experiments using C. acetobutylicum adc and C. beijerinckii ptb promoter fragments and recombinant Bacillus subtilis and C. beijerinckii Spo0A suggested that adc and ptb are directly controlled by Spo0A. The binding affinity was reduced when the 0A boxes were destroyed, and enhanced when they were modified to conform precisely to the consensus sequence. In vivo analysis of wild-type and mutagenized promoters transcriptionally fused to the gusA reporter gene in C. beijerinckii validated this hypothesis. Post-exponential phase expression from the mutagenized adc promoter was substantially reduced, whereas expression from the mutagenized ptb promoter was not shut down at the end of exponential growth.

Acids↗
PubMed1998

Extraction of lignite coal fly ash for polynuclear aromatic hydrocarbons: modified and unmodified supercritical fluid extraction, enhanced-fluidity solvents, and accelerated solvent extraction.

A comparison among modified and unmodified supercritical fluid extraction (SFE), enhanced-fluidity liquid extraction, and accelerated solvent extraction (ASE) techniques was made for the extraction of polynuclear aromatic hydrocarbons (PAHs) from an aged, spiked lignite coal fly ash. All of the attempted extraction conditions allowed the extraction of the PAHs to some degree, but no single extraction technique proved to be superior for all of the PAHs used. Three groups of PAHs with similar extraction efficiencies were identified. The group with the lowest molecular weights was best recovered using a 90% CO2-10% methanol mixture at 70 degrees C and 238 atm. The group of medium-molecular-weight PAHs was recovered equally well using any of three extraction conditions: SFE (100% CO2, 90 degrees C, and 238 atm), enhanced-fluidity liquid mixture (60% CO2-40% methanol, 70 degrees C, and 238 atm), and a methanol ASE mixture. The group of high-molecular-weight PAHs seemed to be equally well recovered with all of the attempted extraction conditions, but the enhanced-fluidity conditions (60% CO2-40% methanol, 70 degrees C, and 238 atm) had extraction recoveries (> 85%) with the lowest standard deviations (approximately 5%).

Carbon↗
PubMed1998

Extraction of bituminous coal fly ash for polynuclear aromatic hydrocarbons: evaluation of modified and unmodified supercritical fluid extraction, enhanced fluidity solvents, and accelerated solvent extraction.

A comparison among supercritical fluid extraction (SFE), modified SFE, enhanced-fluidity extraction, and accelerated solvent extraction (ASE) techniques was made for the extraction of polynuclear aromatic hydrocarbons (PAHs) from an aged, spiked bituminous coal fly ash. Non-ASE extraction techniques used in this study could not recover PAHs with molecular weights greater than that of pyrene. ASE techniques using methylene chloride (with and without a static step) and toluene were able to recover most of the PAHs studied. None of the ASE techniques could quantitatively extract the low-molecular-weight PAHs from the bituminous fly ash. The medium-molecular-weight PAHs were best recovered with toluene ASE. The high-molecular-weight PAHs were best recovered with the toluene ASE technique (> 80%), but the overall precision of these measurements was low. Methylene chloride ASE with a static step recovered the high-molecular-weight PAHs with the next highest efficiency (approximately 55%) and had standard deviations less than 10% (longer extraction times [> 30 min] with the methylene chloride would increase the recoveries of these analytes.) A comparison of the results from this study with those of a previous study using lignite coal fly ash illustrates the difficulty in developing and adapting analyte-specific extraction methods for analytes that are adsorbed on different matrices.

Carbon↗