Low Concentrations Of Organic Solvents Research Articles

Sulfur Fluoride Exchange Enabled Polysufate Adsorbents: Flexible Group Embedded in Polymer Backbone Regulation Strategy for Organic Solvent Removal from Water.

Removal of organic solvents (such as chloroform, toluene, etc.) in trace amounts using adsorbents from water is a challenge due to their low removal efficiencies and poor selectivities. Herein, four polysulfates (P1-P4) with different flexible group embedded backbones were synthesized via a sulfur fluoride exchange (SuFEx) reaction, and their swelling behaviors in organic solvents were investigated. P1 with a flexible ethyl group on its backbone can selectively swell in aprotic organic solvents with medium and high polarities about 30-fold its original weight, which is much higher than that of P4 with rigid benzene on its backbone. Moreover, molecular dynamic (MD) simulation results showed that the swelling mechanism could be put down to the electrostatic and van der Waals forces between the polysulfates and organic solvents. Surprisingly, the polysulfates can be used to remove chloroform and toluene from water with removal efficiencies of up to 99.26 and 99.42%, respectively. Furthermore, the polysulfates also exhibited high selectivities and anti-interference performances toward chloroform in the presence of other pollutants and different acid/base environments. Our work provides a strategy to construct adsorbents with high efficiencies for removal of low concentrations of organic solvents from water.

Low concentrations of ethanol but not of dimethyl sulfoxide (DMSO) impair reciprocal retinal signal transduction.

The model of the isolated and superfused retina provides the opportunity to test drugs and toxins. Some chemicals have to be applied using low concentrations of organic solvents as carriers. Recently, E-/R-type (Cav2.3) and T-type (Cav3.2) voltage-gated Ca(2+) channels were identified as participating in reciprocal inhibitory retinal signaling. Their participation is apparent, when low concentrations of NiCl2 (15 μM) are applied during superfusion leading to an increase of the ERG b-wave amplitude, which is explained by a reduction of amacrine GABA-release onto bipolar neurons. During these investigations, differences were observed for the solvent carrier used. Recording of the transretinal receptor potentials from the isolated bovine retina. The pretreatment of bovine retina with 0.01 % (v/v) dimethylsulfoxide did not impair the NiCl2-mediated increase of the b-wave amplitude, which was 1.31-fold ± 0.03 of initial value (n = 4). However, pretreatment of the retina with the same concentration of ethanol impaired reciprocal signaling (0.96-fold ± 0.05, n = 4). Further, the implicit time of the b-wave was increased, suggesting that ethanol itself but not DMSO may antagonize GABA-receptors. Ethanol itself but not DMSO may block GABA receptors and cause an amplitude increase by itself, so that reciprocal signaling is impaired.

Effect of commonly used organic solvents on Aldehyde oxidase-mediated Vanillin, Phthalazine and Methotrexate oxidation in human, rat and mouse liver subcellular fractions

1. Aldehyde oxidase (AOX) is a cytosolic molybdoflavoprotein enzyme widely distributed across many tissues. In this study, we report the effect of commonly used organic solvents such as dimethyl sulfoxide (DMSO), acetonitrile (ACN), methanol and ethanol on AOX activity in human, rat and mouse liver S9 fractions using vanillin, phthalazine and methotrexate as probe substrates.2. Methanol was found to be the most potent solvent in inhibiting vanillic acid and 1-phthalazinone formation in comparison to DMSO, ACN and ethanol across the species tested, except 7-hydroxy methotrexate.3. Treatment with these solvents at approximate IC50 (% v/v) concentrations showed significant reduction in Clint and Vmax of the probe substrates and also resulted in different effects on Km across the species.4. Marked differences in the activity and affinity towards AOX were observed with different probe substrates with methotrexate showing least activity and affinity as compared to vanillin and phthalazine.5. Overall, AOX activity seemed to be more resilient to the presence of organic solvents at higher concentrations in human and rodent species. These results suggest that low concentrations of organic solvents are acceptable for in vitro incubations involving AOX-mediated metabolism.

Interference with xenobiotic metabolic activity by the commonly used vehicle solvents dimethylsulfoxide and methanol in zebrafish (Danio rerio) larvae but not Daphnia magna

Organic solvents, such as dimethylsulfoxide (DMSO) and methanol are widely used as vehicles to solubilise lipophilic test compounds in toxicity testing. However, the effects of such solvents upon innate detoxification processes in aquatic organisms are poorly understood. This study assessed the effect of solvent exposure upon cytochrome P450 (CYP)-mediated xenobiotic metabolism in Daphnia magna and zebrafish larvae (4d post fertilisation). Adult D. magna were demonstrated to have a low, but detectable, metabolism of ethoxyresorufin in vivo and this activity was not modulated by pre-exposure to DMSO or methanol (24h, up to 0.1% and 0.05% v/v, respectively). In contrast, the metabolism of ethoxyresorufin in zebrafish larvae was significantly reduced by both solvents (0.1% and 0.05% v/v, respectively) after 24h of exposure. In zebrafish, these observed decreases in activity towards ethoxyresorufin were accompanied by decreased expression of a variety of genes coding for drug metabolising enzymes (corresponding to CYP1, CYP2, CYP3 and UDP-glucuronyl transferase [UGT] family enzymes), measured by quantitative PCR. Reduction of gene expression and CYP1 enzyme activities by methanol (0.05% v/v) in zebrafish larvae was partially reversed by co-exposure with Aroclor 1254 (100μgL−1). Overall this study suggests that relatively low concentrations of organic solvents can impact upon the biotransformation of certain xenobiotics in zebrafish larvae, and that this warrants consideration when assessing compounds for metabolism and toxicity in this species.

Ultraviolet Resonance Raman Study of Lipid Mediated Peptide Folding

The interactions between proteins and biological membranes play an important role in many aspects of biochemistry. Thus, the ability to monitor the structural dynamics of membrane proteins is of great interest. In general, hydrophobic peptides are disordered and tend to aggregate in aqueous environments. For example, the amyloid-β (Aβ) peptide, a major component of the insoluble plaques associated with Alzheimer’s disease, is intrinsically disordered under physiological conditions. However, Aβ adopts α-helical structure in membrane mimicking environments. This is not surprising as the hydrophobic region derives from the transmembrane (TM) region of the amyloid precursor protein. More interesting is the fact that low concentrations of organic solvents or surfactants promote aggregation and formation of β-sheet structure. The ability to simultaneously monitor lipid association and study its effect on the secondary structure of amyloidogenic proteins would be of great interest. Recent studies have shown a significantly enhanced amide I mode in the deep-UV resonance Raman (dUVRR) spectra of transmembrane proteins is a marker for lipid association. Positively charged hydrophobic peptides, including the hydrophobic Aβ(25-40) fragment of Aβ, spontaneously insert into anionic lipid bilayers. The application of dUVRR spectroscopy to monitor lipid-association, insertion and folding of these peptides will be presented.

Accelerated Fibrillation of α-Synuclein Induced by the Combined Action of Macromolecular Crowding and Factors Inducing Partial Folding

To better model the characteristics of crowded intracellular environments, we examined the effect of several factors known to induce partial folding and accelerated fibrillation of alpha-synuclein in dilute solutions, on the fibrillation of this protein in a crowded milieu. We found that low pH, certain metals and pesticides, polyanions, polycations and low concentrations of organic solvents cause a significant acceleration of alpha-synuclein fibrillation in the presence of high concentrations of polyethylene glycol. This suggests that the fibril-promoting effects of factors inducing partial folding of alpha-synuclein and the fibril-stimulating effects of macromolecular crowding are relatively independent and thus might act additively or even synergistically.

Assessment of potential hazards during the process of house building in Estonia

The aim of this study was to evaluate new working conditions in the construction industry in Estonia. Three construction sites were investigated: a dwelling house at the stage of renovation, a warehouse at the stage of excavation and preparation work, and a hotel, where we examined the working conditions of the finishers. Microclimate: air temperature, relative humidity and air velocity were determined at every workplace. Full-shift personal exposure measurements of dust and gas exposure were performed among 97 construction workers in breathing zone air. The concentration of lead in the air was analysed by AAS. Vapours of benzene, styrene and toluene concentrations were determined by gas chromatography. The noise level was measured with the help of the sound-level meter at every workplace. All microclimatic indices were sometimes below or above exposure standards for indoor work. High levels of airborne dust and increased concentrations of lead were observed during repair work. Low concentrations of organic solvents in the air were determined when using paints and some synthetic substances. The noise level exceeded the permitted limit when an excavator and powerful electric appliances were used. A questionnaire determined the prevalence of subjectively experienced musculoskeletal strain in 30% of workers. The working conditions in the construction industry in Estonia are approaching European level. However, it is necessary to improve working conditions permanently by the use of new harmless materials, personal protective equipment, and through influencing worker health by permanent education and medical watch. We consider that questionnaires are very important in the control of the work environment, in subjective health assessments, and as a source of useful proposals to improve working conditions.

Forcing Nonamyloidogenic β-Synuclein To Fibrillate

The fibrillation and aggregation of alpha-synuclein is a key process in the formation of intracellular inclusions, Lewy bodies, in substantia nigral neurons and, potentially, in the pathology of Parkinson's disease and several other neurodegenerative disorders. Alpha-synuclein and its homologue beta-synuclein are both natively unfolded proteins that colocalize in presynaptic terminals of neurons in many regions of the brain, including those of dopamine-producing cells of the substantia nigra. Unlike its homologue, beta-synuclein does not form fibrils and has been shown to inhibit the fibrillation of alpha-synuclein. In this study, we demonstrate that fast and efficient aggregation and fibrillation of beta-synuclein can be induced in the presence of a variety of factors. Certain metals (Zn(2+), Pb(2+), and Cu(2+)) induce a partially folded conformation of beta-synuclein that triggers rapid fibrillation. In the presence of these metals, mixtures of alpha- and beta-synucleins exhibited rapid fibrillation. The metal-induced fibrillation of beta-synuclein was further accelerated by the addition of glycosaminoglycans or high concentrations of macromolecular crowding agents. Beta-synuclein also rapidly formed soluble oligomers and fibrils in the presence of pesticides, whereas the addition of low concentrations of organic solvents induced formation of amorphous aggregates. These new findings demonstrate the potential effect of environmental pollutants in generating an amyloidogenic, and potentially neurotoxic, conformation, in an otherwise benign protein.

Testing the role of solvent surface tension in protein ionization by electrospray

This work was aimed at probing the influence of solvent surface tension on protein ionization by electrospray. In particular, we were interested in testing the previously suggested hypothesis that the charge-state distributions (CSDs) of proteins in electrospray ionization mass spectrometry (ESI-MS) are controlled by the surface tension of the least volatile solvent component. In the attempt to minimize uncontrolled conformational effects, we used acid-sensitive proteins (cytochrome c and myoglobin) at low pH or highly stable proteins (ubiquitin and lysozyme) in the presence of low concentrations of organic solvents. A first set of experiments compared the effect of 1- and 2-propanol. These two alcohols have similar chemico-physical properties but values of vapor pressure below and above that of water, respectively. Both compounds have much lower surface tension than water. The solvents employed allowed testing of the influence of surface tension on protein spectra obtained from similarly denaturing solutions. The compared solvent conditions gave rise to very similar spectra for each tested protein. We then investigated the effect of the addition of dimethyl sulfoxide to acid-unfolded proteins. We observed enhanced ionization in the presence of acetic or formic acid, consistent with the previously described supercharging effect, but almost no shift of the CSD in the presence of HCl. Finally, we analyzed thermally denatured cytochrome c, to obtain reference spectra of the unfolded protein in high-surface-tension solutions. Also in this case, the CSD of the unfolded protein was shifted towards lower m/z values relative to low-surface-tension systems. In contrast to the other results reported here, this effect is consistent with an influence of solvent surface tension on CSD. The magnitude of the effect, however, is much smaller than predicted by the Rayleigh equation. The results presented here are not easy to reconcile with the hypothesis that the maximum charge state exhibited by proteins in ESI-MS reflects the Rayleigh-limit charge of the precursor droplet. The data are discussed with reference to models for the mechanism of electrospray ionization.

Occupational Exposure to Low Concentrations of Organic Solvents in Shipyards

Occupational Exposure to Low Concentrations of Organic Solvents in Shipyards: Hironobu Katsuyama, et al. Department of Public Health, Kawasaki Medical School—Because shipbuilders have to use organic solvents in very confined spaces, they have a higher risk of inhaling the solvents than workers working in an open space. The working environment at 14 workplaces with very limited space was examined and biological monitoring was performed on 18 workers who worked in such places. Out of 14 workplaces, only 4 did not exceed the assessment criterion. Although exhaust ventilation fans and chemical cartridge respirators were used to avoid exposure to solvent vapor irrespective of the concentrations of solvents, biological samples revealed inhalation of solvent vapor. Urinary excretion of hippuric acid and methylhippuric acid varied from 0.07 to 0.92 g/ g Cr and 0.02 to 0.42 g/g Cr at the end of the shift, respectively. Concentration of toluene and xylene in the end‐exhaled air varied from <0.1 to 5.0 ppm and <0.1 to 10.6 ppm, respectively. The concentration of metabolites in urine and the concentration of solvent in the end‐exhaled air revealed a strong correlation in the case of xylene but not toluene. Because of the limitation of space, the mean concentration of solvents in the working environment is not always available in shipyards, which make it difficult to estimate the amounts inhaled by workers. Biological monitoring of the end‐exhaled air provides useful information to make it possible to avoid continuous and/or unexpected exposure of workers who have to work in a very limited space.

Blue-yellow deficiency in workers exposed to low concentrations of organic solvents.

To evaluate the effects of low concentrations of organic solvents on color vision. Color vision was examined in 24 workers exposed to mixtures of solvents and in 24 control subjects. Exposure to mixtures was below the threshold-limit values. Color vision ability was assessed using the Ishihara plates (to screen for congenital dyschromatopsia), the Farnsworth panel D-15 test, the Lanthony desaturated panel D-15 test, and the Standard Pseudoisochromatic Plates part 2 (SPP2 test). The comparatively less sensitive Farnsworth panel D-15 test failed to show any difference between the groups, but the Lanthony panel D-15 desaturated test as well as the SPP2 test showed a significant impairment in the exposed group. Errors were of the blue-yellow type. This study gives further evidence that even mixtures of organic solvents at concentrations below the threshold-limit values may impair color vision.

Clinical neuropsychological assessment of patients chronically exposed to organic solvents.

Investigations into the effects of short-term exposure to organic solvents revealed no harmful effects provided that the concentrations were relatively low. However, long-term exposure to low concentrations of organic solvents may affect physical and mental health. After long-term exposure to organic solvents, many workers make strong complaints about headaches, fatigue, forgetfulness, concentration and attention. There are, however, two problems which obstruct the recognition of the effects of long-term exposure: 1) in most cases medical assessment reveals no physical cause for the complaints (Morrow et al, 1990), and 2) until now, epidemiologic research with industrial workers has not produced clear evidence of the toxic effects of chronic exposure to organic solvents (Cherry et al. 1985; Triebig, 1988; Gade et al. 1988). The failure to recognize the complaints, however, causes the patients severe psychological problems. Sometimes they are forced to return to their work, often they are diagnosed as suffering from neurasthenia or dysthymia (DSMIIIR, 300.5, 309.82).

Method for characterization of selectivity in reversed-phase liquid chromatography : V. Calibration of the retention scale for chromatographic systems with low concentrations of organic solvents in the mobile phase

The method for the characterization and prediction of selectivity and absolute retention in reversedphase liquid chromatography based on two indices (a lipophilic and a polar one) has been previously applied to chromatographic systems with mobile phases containing 50% and more of one or two organic solvent(s). Because of a high retention, the homologues series of n-alkylbenzenes is not suitable for the direct calibration of the retention scale in mobile phases with lower concentrations of organic solvents, and the extrapolation of the calibration parameters based on the data for this series in mobile phases with low water content yields predicted retention data that are subject to significant errors. To circumvent this inconvenience and to expand the application possibilities of the above method to mobile phases with higher concentrations of water, three homologous series were tested as potential candidates for calibration standards: 3- n-alkyl-6-methyluracils, 3-alkoxycarbonyl-2-pyrazolines and alkan-2-ones. All three homologous series tested were found to be suitable substitutes for n-alkylbenzenes as calibration standards in mobile phases containing 25–50% methanol in water. The selection of suitable calibration standards for acetonitrile—water mobile phases is more difficult because of a curvature of the dependence of log k′ on the concentration of acetonitrile at low concentrations of this solvent in aqueous mobile phases. Here, the alkoxycarbonyl pyrazolines and alkan-2-ones proved useful as calibration standards in mobile phases containing 30–50% acetonitrile. The agreement between the predicted and experimental k′ was within 10% or better of the experimental k′.

Removal of organic vapors from air by selective membrane permeation

Many industrial processes such as printing, metal cleaning or painting produce waste air streams containing low concentrations of organic solvents, such as acetone, toluene, perchloroethane, xylene, etc. The total value of the solvent lost with the waste air is considerable. In addition, these solvents represent a significant pollution problem, and in recent years several procedures for recovering solvents from air, such as carbon adsorption, incineration, etc. have been introduced in the industry. All of them show some draw-backs in terms of efficiency, reliability and costs. In this paper a membrane process is described, which provides an attractive alternative to the conventional methods. In a basic study the permeabilities of acetone, toluene, xylene, dichloroethane and dichloromethane through a homogeneous polydimethylsiloxane (PDMS) membrane have been determined using a pressure difference between 400 and 1000 mbar as driving force. The selectivity of the membrane for the various solvents and their dependence on the solvent concentration in a mixture with nitrogen were studied. The selectivities of the PDMS membrane for the solvent/nitrogen mixtures were in the range of S = 70-160, depending on the solvent and its concentration in the feed mixture. Based on these data a pilot plant process has been designed in which a solvent is recovered from a waste air stream and the depleted air is recycled into the waste air producing process. The solvent which has permeated the membrane is recovered as a liquid by condensation. Thus, complete recycling of air and solvents is possible. In a cost analysis it has been demonstrated that the membrane process is indeed an attractive alternative to conventional air cleaning techniques.

Immobilization of Metapyrocatechase and Its Properties in Comparison with the Soluble Enzyme1

Metapyrocatechase [catechol : oxygen 2,3-oxidoreductase, EC 1.13.11.2] was immobilized with cyanogen bromide-activated agarose with a coupling yield of 78% of the protein added. The immobilized enzyme showed a specific activity of 77 mumol/min/mg protein, which is about 30% of that of the native enzyme. The immobilization enhanced the stability of the enzyme against inactivation by heat, acid or alkaline pH, and various denaturing agents. However, like the native enzyme, the immobilized enzyme was rapidly inactivated by oxidants such as oxygen or hydrogen peroxide, and the inactivation was completely prevented in the presence of low concentrations of organic solvents. The pH profile for the activity and the substrate specificity were slightly changed by the immobilization.

Interaction of human Clq with insoluble immunoglobulin aggregates

A system of interaction between 125I-Clq and IgG aggregates insolubilized by glutaraldehyde, which was designed as a model for studying the initial event in activation of the complement sequence, is described. Binding of Clq was shown to be rapid, specific, reversible and saturable, with an average dissociation constant in the order of 1 × 10 −8 M. The binding data produced non-linear Scatchard plots. The binding was favored at an ionic strength below μ = 0.15. a pH range of 5.5–8.5. and was sensitive to low concentrations of organic solvents. Among many compounds which interfered with Clq-IgG aggregate interaction, an anionic compound, suramin, was shown to be a good inhibitor of Clq binding with a sigmoidal inhibition curve and with a K D of Clq-suramin complex in the order of 5 × 10 −5 M. Dissociation of radiolabeled Clq by succinylation caused a loss of binding activity but the succinylated Clq retained the capacity to inhibit 125I-Clq binding to IgG aggregates. The characteristic radioiodination pattern of Clq subunits was shown to be significantly changed when iodination was carried out on the IgG aggregates-bound Clq in such a fashion as to imply an IgG aggregates-induced conformational change in Clq, suggesting the usefulness of this system in exploring the possible mechanism underlying immune-complex mediated Cl activation.

Action of pancreatic lipase on monomeric tripropionin in the presence of water-miscible organic compounds

The addition of low concentrations of some water-miscible organic compounds (dioxane, acetonitrile, tert.-butanol, formamide) to an aqueous system induces a substantial increase of the activity of pancreatic lipase (EC 3.1.1.3) towards monomeric tripropionin. This effect is due to a rise of the maximum velocity ( V) of the reaction. K m becomes less favorable upon solvent addition with the result that, for all substrate concentrations lower than the saturating value, lipase activity passes by a maximum in a relatively narrow solvent concentration range. The fact that lipase is able to attack tripropionin monomers in organic solvent-water systems is confirmed by the complete disparation of the triglyceride after a 40% hydrolysis. The main product of the reaction is dipropionin. The finding that lipase can display a strong activity in the complete absence of substrate aggregates and interfaces is discussed in the light of current concepts concerning the mechanism of action of this enzyme. Hydrophobic interfaces and low concentrations of organic solvents have been reported to modify the structure of liquid water. The assumption is made that the modification favors the action of lipase on tripropionin monomers through a transconformation of the enzyme molecule or any other process.