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PubMed1983

Inhibition of an insect midgut trehalase by dioxane and delta-gluconolactone: enzyme pKa values and geometric relationships at the active site.

1. Inhibition of the Rhynchosciara americana midgut trehalase (alpha, alpha'-trehalose glucohydrolase, EC 3.2.1.28) by the competitive inhibitor dioxane have been studied. 2. Determinations of the Ki of dioxane at different pH provided the true pKa values of the prototropic groups of the trehalase active site (pKa 5.2 and 8.2), which are in agreement with those determined previously from kinetic and chemical modification data. 3. Dioxane only changes the enzyme pKa values if bound at the enzyme active site. 4. Gluconic acid does not inhibit the trehalase, in contrast to delta-gluconolactone which is a simple intersecting linear inhibitor. 5. Multiple inhibition analyses showed that delta-gluconolactone and Tris bind at the same site in the trehalase active center, whereas dioxane binds closer to delta-gluconolactone than to Tris. 6. The data support the assumption that dioxane binds at the middle portion of the trehalase active site.

Animals↗
PubMed2005

Chromosome breakage is primarily responsible for the micronuclei induced by 1,4-dioxane in the bone marrow and liver of young CD-1 mice.

1,4-Dioxane, a widely used industrial chemical and rodent hepatocarcinogen, has produced mixed, largely negative results in the mouse erythrocyte micronucleus assay. In contrast, a recent report has indicated that 1,4-dioxane induces micronuclei in mouse hepatocytes following in vivo treatment. The objective of this study was to confirm these earlier results and identify the origin of the induced micronuclei. Following an initial range-finding study, mice were administered 1,4-dioxane by gavage at doses ranging from 1500 to 3500 mg/kg. The test animals were also implanted with BrdU-releasing osmotic pumps to allow cell proliferation to be measured in the liver and to increase the sensitivity of the hepatocyte assay. Upon sacrifice, the frequency of micronuclei in the bone marrow erythrocytes and in the proliferating BrdU-labeled hepatocytes was determined. Significant dose-related increases in micronuclei were seen in both the liver and the bone-marrow with significant increases being detected at all the tested doses in the bone marrow and at the 2500 and 3500 mg/kg doses in the liver. Using CREST staining or pancentromeric FISH to determine the origin of the induced micronuclei, it was determined that 80-90% of the micronuclei in both tissues originated from chromosomal breakage. Small increases in centromere-containing micronuclei were also seen in the hepatocytes. Decreases in hepatocyte proliferation as well as in the ratio of bone marrow PCE:NCE were also observed. Based on these results, we conclude that at high doses: (i) dioxane exerts genotoxic effects in both the mouse bone marrow and liver; (ii) the induced micronuclei are formed primarily from chromosomal breakage; and (iii) dioxane can interfere with cell proliferation in both the liver and bone marrow.

Animals↗
PubMed2003

Enhanced sonochemical decomposition of 1,4-dioxane by ferrous iron.

The enhanced ultrasonic decomposition of 1,4-dioxane by the addition of ferrous iron (Fe(II)) was investigated at 205, 358, 618, and 1071 kHz. The total organic carbon (TOC) remaining was also determined at each frequency. Addition of Fe(II) improved the 1,4-dioxane decomposition rate and mineralization efficiency at all frequencies studied. A nearly four-fold increase of the rate constant was observed at the optimal Fe(II) concentration and a frequency of 205 kHz. In the presence and absence of the iron, the fastest overall degradation and mineralization of 1,4-dioxane took place at 358 kHz where 95% of the initial 1,4-dioxane was removed after 50 min. Finally, although reduced, the ultrasonic decomposition of 1,4-dioxane was still significant at all frequencies in the presence of the hydroxyl radical scavenger bicarbonate.

Dioxanes↗
PubMed1980

Specific solvent effects on the thermal denaturation of ribonuclease. Effect of dimethyl sulfoxide and p-dioxane on thermo dynamics of denaturation.

Differential scanning calorimetry has been used to study the thermal denaturation of ribonuclease in aqueous dimethyl sulfoxide and acqueous p-dioxane. A two-state reversible denaturation occurs in acqueous dimethyl sulfoxide. The denaturation is irreversible in aqueous p-dioxane. The transition temperatuire decreases in both organic solvents, with p-dioxane producing a considerably greater effect. The enthalpy of the denaturation initially increases with increasing dimethyl sulfoxide concentration and then decreases at high concentrations. Similar behavior is observed in the entropy in the dimethyl sulfoxide solutions. The enthalpy of the denaturation decreases markedly with low p-dioxane concentrations. Changes in pH due to presence of organic solvent cannot account for the changes in enthalpy of denaturation. Addition of organic solvent tends to increase the pH of the ribonuclease solution. Higher pH in aqueous solutions gives a high transition temperature, whereas addition of organic solvent results in the opposite bahavior. The relative changes in the two solvents systems suggest that specific solvent effects occur and that destablization of the native state relative to the denatured state is greater with p-dioxane than with dimethyl sulfoxide.

Animals↗
PubMed1998

Use of Fourier transform infrared (FTIR) spectroscopy to follow the adsorption of heptane and 1,4-dioxane vapors on a zinc oxide surface.

Vapor adsorption isotherms of two nonpolar model compounds, heptane and 1,4-dioxane, were determined for a very small particle size zinc oxide (ZnO) powder (median particle size approximately 23 nm) in the lower relative vapor pressure (P/Po) region. The ZnO samples for all adsorption measurements were dried at 400 degrees C for 4 h. A new method, which employed an FTIR spectrometer with a long path gas cell (IR path length of 3.0 m), was developed for the organic vapor adsorption measurements. The amount adsorbed was determined by mass balance. This method allows accurate quantification of organic vapors and is sensitive to very low P/Po values. The heptane and 1, 4-dioxane vapor adsorption isotherms appeared to exhibit the expected Type II behavior. The surface areas obtained for ZnO from BET analyses of the heptane and 1,4-dioxane vapor adsorption isotherms (36.9 and 30.3 m2/g) compared reasonably well to the surface area obtained from BET analysis of the nitrogen vapor adsorption isotherm (32.6 m2/g). The amount of vapor adsorbed by ZnO at P/Po equal to 0.1, in terms of number of moles, was observed to decrease in the order: water10 >> 1,4-dioxane > heptane. It was inferred that, while heptane was only adsorbed via a dipole-induced dipole interaction, 1,4-dioxane was physically adsorbed via an interaction dominated by the oxygen lone-pair orbital. Presumably, this interaction was more comparable to a weak dipole-dipole interaction. These results are consistent with the expected strengths of interaction.

Dioxanes↗
PubMed1979

Metabolism of dibenzo[1,4]dioxan by a Pseudomonas species.

Pseudomonas sp. N.C.I.B. 9816 strain 11, when grown on salicylate in the presence of dibenzo[1,4]dioxan, accumulated cis-1,2-dihydroxy-1,2-dihydrodibenzo[1,4]dioxan and 2-hydroxydibenzo[1,4]dioxan in the culture medium. Each metabolite was isolated in crystalline form and identified by a variety of conventional chemical techniques. Crude cell extracts prepared from the parental strain grown with naphthalene oxidized cis-1,2-dihydroxy-1,2-dihydrodibenzo[1,4]dioxan under both aerobic and anaerobic conditions to 1,2-dihydroxydibenzo[1,4]dioxan. Further degradation of this metabolite was not detected.

Chemical Phenomena↗
PubMed2005

Degradation of 1,4-dioxane and cyclic ethers by an isolated fungus.

By using 1,4-dioxane as the sole source of carbon, a 1,4-dioxane-degrading microorganism was isolated from soil. The fungus, termed strain A, was able to utilize 1,4-dioxane and many kinds of cyclic ethers as the sole source of carbon and was identified as Cordyceps sinensis from its 18S rRNA gene sequence. Ethylene glycol was identified as a degradation product of 1,4-dioxane by the use of deuterated 1,4-dioxane-d8 and gas chromatography-mass spectrometry analysis. A degradation pathway involving ethylene glycol, glycolic acid, and oxalic acid was proposed, followed by incorporation of the glycolic acid and/or oxalic acid via glyoxylic acid into the tricarboxylic acid cycle.

Biodegradation, Environmental↗
PubMedDate not supplied

[Toxicology of 1-4-dioxane].

Toxic parameters of 1-4 dioxan were estimated to be for white rats during 4 hr inhalation LC16 = 40 mg/l LC50 = 46 (42.2 +/- 50.1) mg/l; LC84 = 52 mg/l; for white mice during 2 hr inhalation LC16 = 61 mg/l; LC50 = 65 (61.3 +/- 68.2) mg/l; LC84 = 69.5 mg/l. As a result of single and repeated application, 1-4 dioxan did not induce skin changes, it was rapidly absorbed into the blood, and led to acute poisoning and irritation of the eye mucosa. A 24 hr exposure of white rats to 1-4 dioxan at concentrations of 4 and 20 mg/m3 for 90 days brought about their delayed weight gain, increased activity of glutamate-aspartate and glutamate-alanine transminases, prolonged duration of narcotic sleep, elevated content of protein in the urine, decreased diuresis, changed content of chlorides and altered motor chronaxia. The above concentrations proved to be effective. 1-4 dioxan at a concentrations proved to be effective. 1-4 dioxan at a concentration of 0.5 mg/m3 produced slight threshold changes.

Animals↗
PubMed1997

Synthesis, Surface Properties, and Hydrolysis of Chemodegradable Anionic Surfactants: Diastereomerically Pure cis- and trans-2,5-Disubstituted-1,3-dioxanes

In our continuing systematic studies concerning the synthesis, surface properties, and hydrolysis of chemodegradable, diastereomerically pure surface active 2,5-disubstituted 1,3-dioxane derivatives, two new groups of anionic surfactants, sodium cis- and trans-(2-n-undecyl-1,3-dioxan-5-yl)methyl sulfates and sodium cis- and trans-3-[(2-n-undecyl-1,3-dioxan-5-yl)oxy]propanesulfonates, were synthesized and investigated. Surface properties of these surfactants, i.e., surface excess concentration, Gamma, surface area demand per molecule, A, effectiveness of surface tension reduction, Pi, critical micelle concentration, CMC, and standard free energies of adsorption, DeltaGads0, and of micellization, DeltaGmic0, were determined. It was shown that the trans-isomers, in which the configuration of the polar group is equatorial, are more surface active than the cis-isomers with axial configuration of the polar group at the C-5 carbon atom of the 1,3-dioxane ring. The surfactants under study undergo easy hydrolysis reaction in DCl/D2O solution with cleavage of the 1,3-dioxane ring to nonsurface active intermediates. The trans-isomers are hydrolyzed faster than cis-isomers.

Journal Article↗
PubMed1978

Bioassay of 1,4-dioxane for possible carcinogenicity.

A bioassay of 1,4-dioxane for possible carcinogenicity was conducted by administering the test chemical in the drinking water to Osborne-Mendel rats and B6C3F1 mice. Groups of 35 rats and 50 mice of each sex were administered 1,4-dioxane at concentrations of either 0.5% to 1.0% (v/v) in the drinking water. Because of variations in the intake of water, the doses of test chemical received by the high-dose groups were not precisely twice those received by the low-dose groups; in the male mice, the high dose was only slightly greater than the low dose. The rats were dosed for 110 weeks and the mice for 90 weeks. Matched controls consisted of 35 untreated rats and 50 untreated mice of each sex. All surviving rats were killed at 110-117 weeks and all surviving mice at 90-93-weeks. The mean body weights of the rats and mice were not consistently affected by the administration of dioxane. Survival rates of the dosed groups of rats and female mice were lower than those of corresponding control groups, but sufficient numbers of animals were at risk for development of late-appearing tumors. In rats, the incidence of squamous-cell carcinomas of the nasal turbinates was statistically significant in tests for dose-related trend in females (P=0.008) and for direct comparison of high-dose with matched-control males(P<0.001) and direct comparison of dosed with control females (P" 0.003) (males: controls 0/33, low-dose 12/33, high-dose 16/34; females: controls 0/34, low-dose 10/35, high-dose 8/35). In the females, but not in the males, the incidence of hepatocellular adenomas was significant (P" 0.001) in tests for dose-related trend and for direct comparison of both low- and high-dose groups with controls (controls 0/31, low-dose 10/33, high-dose 11/32). In both male and female mice, the incidence of hepatocellular carcinomas was statistically significant (P" 0.001), both in tests for dose-related trend and direct comparison of both dosed groups with controls (males: controls 2/49, low-dose 18/50, high-dose 24/47; females: controls 0/50, low-dose 12/48, high-dose 29/37). The incidences remained significant when hepatocellular adenomas were combined with hepatocellular carcinomas. It is concluded that under the conditions of this bioassay, 1,4-dioxane induced hepatocellular adenomas in female Osborne-Mendel rats. 1,4-Dioxane was carcinogenic in both sexes of rats, producing squamous-cell carcinomas of the nasal turbinates, and in both sexes of B6C3F1 mice, producing hepatocellular carcinomas.

Journal Article↗
PubMed1987

Solubility in binary solvent systems: 8. Estimation of binary alkane plus p-dioxane solvent nonideality from measured anthracene solubilities.

Experimental solubilities are reported for anthracene in binary solvent mixtures containing p-dioxane with n-hexane, cyclohexane, n-heptane, methylcyclohexane, n-octane, cyclooctane, and isooctane at 25 degrees C. Results of these measurements, used in conjunction with the nearly ideal binary solvent (NIBS) model, enabled excess Gibbs free energies, delta GBCfh, of the seven binary solvent mixtures to be estimated. Estimated values for p-dioxane plus cyclohexane, p-dioxane plus n-heptane, and p-dioxane plus methylcyclohexane mixtures are in reasonable agreement with published values based on vapor pressure measurements.

Alkanes↗
PubMed2000

Studies on the protonation constants and solvation of alpha-amino acids in dioxan-water mixtures.

To gain more information about the effect of solvent on alpha-amino acids, the stoichiometric protonation constants of 10 alpha-amino acids (glycine, DL-alanine, DL-valine, L-leucine, L-isoleucine, DL-phenylalanine, L-serine, L-threonine, L-asparagine, and L-glutamine) in different dioxan-water mixtures have been determined potentiometrically using a combined pH electrode system calibrated in concentration units of hydrogen ion at 25 degrees C with an ionic strength of 0.10 M. For all amino acids studied, it was observed that the log K(1) values relating to the protonation equilibria of the anionic form are almost unaltered by the change in solvent composition. However, the log K(2) values corresponding to the formation equilibria of cationic form increase with the increase in dioxan content. The variation of these constants is discussed on the basis of specific solute-solvent interactions and structural changes of amino acids from water to dioxan-water media. The zwitterionic to neutral form ratio of these acids in dioxan-water mixtures is also discussed.

Amino Acids↗
PubMed1990

Is 1,4-dioxane a genotoxic carcinogen?

Female Sprague-Dawley rats were given 0, 168, 840, 2550 or 4200 mg/kg of 1,4-dioxane 21 and 4 h before sacrifice. Hepatic DNA damage (by the alkaline elution technique), ornithine decarboxylase activity (ODC), reduced glutathione content, cytochrome P-450 content and serum alanine aminotransferase activity (ALT) were determined. Treatment with 1,4-dioxane increased hepatic DNA damage and cytochrome P-450 content at doses of 2550 and 4200 mg/kg. Large increases in the activity of hepatic ODC were observed at 840, 2550 and 4200 mg/kg of 1,4-dioxane. Thus the data suggest that 1,4-dioxane is a weak genotoxic carcinogen in addition to being a strong promoter of carcinogenesis (a non-genotoxic carcinogen).

Animals↗
PubMed1977

Rapid method for the simultaneous determination of 1,4-dioxan and its major metabolite, beta-hydroxyethoxyacetic acid, concentrations in plasma and urine.

1,4-Dioxan and its principle metabolite, beta-hydroxyethoxyacetic acid (HEAA), are determined by gas chromatography-mass spectrometry (GC-MS) on a 3% OV-17 column using selected ion monitoring, following the methylation of HEAA directly in plasma or urine without extraction. The recoveries of dioxan from plasma and urine are 98 and 94%, respectively, and the recoveries of HEAA from plasma and urine are 86 and 94%, respectively. The detection limits of 1,4-dioxan in plasma and urine are 0.07 ppm, and the detection limits of HEAA in plasma and urine are 0.5 and 0.1 ppm, respectively. Separate simultaneous measurements of 1,4-dioxan and HEAA methyl ester concentrations in urine and plasma are obtained after the methylation via GC-MS without additional preparation of the samples.

Acetates↗
PubMed1997

Rapid determination of 1,4-dioxane in water by solid-phase extraction and gas chromatography-mass spectrometry.

A highly sensitive and accurate gas chromatography-mass spectrometry method for rapidly quantitative analysis of dioxane in water samples is described. Dioxane in water sample was extracted by hexane-methylene chloride (80:20, v/v) then transferred to a C18 solid-phase extraction (SPE) cartridge and eluted by acetonitrile. An aliquot of this solution was analyzed by gas chromatography-mass spectrometry with electron impact ionization and selected ion monitoring (dioxane m/z 88) mode. The quantitative limit was set to be 0.05 microgram/ml with an injection volume of 2 microliters and a sample volume of 1 ml. The isotopically labelled [2H8]dioxane (m/z 96) was used as internal standard. Analysis time is approximately 6 min. The results for various kinds of SPE cartridges in this method are also discussed.

Carcinogens, Environmental↗
PubMed1997

Two-photon excitation of dioxane: time-resolved measurements of excited state complex formation with water.

We observed emission from the non-aromatic hydrocarbon 1,4-dioxane upon illumination with ps pulses at 380 nm. The emission intensity depended quadratically on incident power at 380 nm, indicating a two-photon process. In the absence of water the intensity decay was close to a single exponential, but displayed some evidence of an excited state process. In the presence of 1% water the emission spectra shifted dramatically to long wavelength. Water also resulted in wavelength-dependent intensity decays with negative pre-exponential factors on the long wavelength side of the emission, demonstrating the presence of an excited state reaction. At this water concentration the results are consistent with a two-state model due to emission from dioxane and a dioxane and a dioxane-water complex.

Dioxanes↗
PubMed2006

Endoperoxide derivatives from marine organisms: 1,2-dioxanes of the plakortin family as novel antimalarial agents.

Plakortin (1) is a remarkably simple 1,2-dioxane derivative, extracted from the marine sponge Plakortis simplex, showing a submicromolar activity against chloroquine-resistant strains of Plasmodium falciparum. Using plakortin as a novel antimalarial hit, we have prepared a series of semisynthetic derivatives in order to gain insights into the structural requirements of simple 1,2-dioxanes for exhibiting antimalarial activity. Their synthesis, spectroscopic and computational analysis, and in vitro antimalarial activity are herein reported. Results obtained, besides confirming the crucial role of the cycloperoxide functionality, revealed other structural features critical for antimalarial activity, namely the "Western" alkyl side chain, the dioxane ring conformation, and the absolute configuration of the stereogenic carbons on the 1,2-dioxane ring, when affecting the bioactive ring conformation.

Animals↗
PubMed2006

Computer simulation of the linear and nonlinear optical susceptibilities of p-nitroaniline in cyclohexane, 1,4-dioxane, and tetrahydrofuran in quadrupolar approximation. II. Local field effects and optical susceptibilitities.

This is the second part of a study to elucidate the local field effects on the nonlinear optical properties of p-nitroaniline (pNA) in three solvents of different multipolar character, that is, cyclohexane (CH), 1,4-dioxane (DI), and tetrahydrofuran (THF), employing a discrete description of the solutions. By the use of liquid structure information from molecular dynamics simulations and molecular properties computed by high-level ab initio methods, the local field and local field gradients on p-nitroaniline and the solvent molecules are computed in quadrupolar approximation. To validate the simulations and the induction model, static and dynamic (non)linear properties of the pure solvents are also computed. With the exception of the static dielectric constant of pure THF, a good agreement between computed and experimental refractive indices, dielectric constants, and third harmonic generation signals is obtained for the solvents. For the solutions, it is found that multipole moments up to two orders higher than quadrupole have a negligible influence on the local fields on pNA, if a simple distribution model is employed for the electric properties of pNA. Quadrupole effects are found to be nonnegligible in all three solvents but are especially pronounced in the 1,4-dioxane solvent, in which the local fields are similar to those in THF, although the dielectric constant of DI is 2.2 and that of the simulated THF is 5.4. The electric-field-induced second harmonic generation (EFISH) signal and the hyper-Rayleigh scattering signal of pNA in the solutions computed with the local field are in good to fair agreement with available experimental results. This confirms the effect of the "dioxane anomaly" also on nonlinear optical properties. Predictions based on an ellipsoidal Onsager model as applied by experimentalists are in very good agreement with the discrete model predictions. This is in contrast to a recent discrete reaction field calculation of pNA in 1,4-dioxane, which found that the predicted first hyperpolarizability of pNA deviated strongly from the predictions obtained using Onsager-Lorentz local field factors.

Aniline Compounds↗