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At least 919 records · Page 51Linked to original sources
PubMed2002

Preferential solvation of a dicyanate ester monomer and poly(sulfone) in different organic solvents by size-exclusion chromatography.

Preferential solvation parameters A in the ternary systems solvent (1) -monomer (2) -polymer (3) were determined as a tool to measure the compatibility between the cyanate ester monomer Arocy B10 and poly(sulfone), PSF, in the presence of three organic solvents: tetrahydrofuran, dimethylformamide and dicloromethane. The A parameter was measured by size-exclusion chromatography at different monomer-to-polymer ratios. The quantitative evaluation was rigorously made at polymer-diluted conditions. PSF was found to be preferentially solvated by the monomer. Concerning the solvent used, systems containing tetrahydrofuran showed the strongest solvation, the lowest A values being those obtained in dicloromethane. These results were in accordance with the intrinsic viscosity values of the PSF-solvent systems. The variation of A values with the Arocy B10 concentration is strongly dependent upon the nature of the solvent.

Chromatography, Gel↗
PubMed2002

Determination of oxanilic and sulfonic acid metabolites of acetochlor in soils by liquid chromatography-electrospray ionisation mass spectrometry.

An analytical method is presented that describes the extraction and quantification of oxanilic and sulfonic acid metabolites of the herbicide acetochlor in soil samples. Experiments were performed on 50 g of soil using a solvent extraction technique with an acetonitrile-water (60:40) mixture in an acidic medium. Analysis was carried out by reversed-phase liquid chromatography and detection by electrospray ionisation mass spectrometry in single ion monitoring and negative modes. Four different soil matrices were spiked in triplicate with standards of each degradation compound at three concentration levels between 2 and 80 microg/kg. The average recoveries range from 90 to 120% for both the metabolites, with relative standard deviations lower than 15%. The limits of quantification are about 1 and 2 microg/kg for the ethanesulfonic acid and the oxanilic acid metabolites, respectively. The method has been applied to soils and solids recovered from the deeper unsaturated zone of a small French catchment closely monitored as part of the European project "Pesticides in European Groundwaters: detailed study of Aquifers and Simulation of possible Evolution scenarios (PEGASE)".

Chromatography, Liquid↗
PubMed2003

Using second-order calibration to identify and quantify aromatic sulfonates in water by high-performance liquid chromatography in the presence of coeluting interferences.

We used the Generalized Rank Annihilation Method (GRAM), a second-order calibration method, to quantify aromatic sulfonates in water with high-performance liquid chromatography (HPLC) when interferences coeluted with the analytes of interest. With GRAM, we can quantify in only two chromatographic analyses, one for a calibration sample and one for the unknown sample. The calculated concentrations were not statistically different to those obtained when the chromatographic separation of the unknown sample was modified in order to completely separate the analyte from the interferences before univariate calibration. With GRAM, the concentrations are determined much more quickly because a complete resolution is not required.

Calibration↗
PubMed2003

Ion-exclusion chromatographic behavior of aliphatic carboxylic acids and benzenecarboxylic acids on a sulfonated styrene--divinylbenzene co-polymer resin column with sulfuric acid containing various alcohols as eluent.

The addition of C1-C7 alcohols (methanol, ethanol, propanol, butanol, heptanol, hexanol and heptanol) to dilute sulfuric acid as eluent in ion-exclusion chromatography using a highly sulfonated styrene-divinylbenzene co-polymer resin (TSKgel SCX) in the H+ form as the stationary phase was carried out for the simultaneous separations of both (a) C1-C7 aliphatic carboxylic acids (formic, acetic, propionic, isobutyric, butyric, isovaleric, valeric, 2-methylvaleric, isocaproic, caproic, 2,2-dimethyl-n-valeric, 2-methylhexanoic, 5-methylhexanoic and heptanoic acids) and (b) benzenecarboxylic acids (pyromellitic, hemimellitic, trimellitic, o-phthalic, m-phthalic, p-phthalic, benzoic and salicylic acids and phenol). Heptanol was the most effective modifier in ion-exclusion chromatography for the improvement of peak shapes and a reduction in retention volumes for higher aliphatic carboxylic acids and benzenecarboxylic acids. Excellent simultaneous separation and relatively highly sensitive conductimetric detection for these C1-C7 aliphatic carboxylic acids were achieved on the TSKgel SCX column (150 x 6 mm I.D.) in 30 min using 0.5 mM sulfuric acid containing 0.025% heptanol as eluent. Excellent simultaneous separation and highly sensitive UV detection at 200 nm for these benzenecarboxylic acids were also achieved on the TSKgel SCX column in 30 min using 5 mM sulfuric acid containing 0.075% heptanol as eluent.

Alcohols↗
PubMed2003

Ion-exclusion chromatographic separations of C1-C6 aliphatic carboxylic acids on a sulfonated styrene-divinylbenzene co-polymer resin column with 5-methylhexanoic acid as eluent.

The application of C7 aliphatic carboxylic acids (heptanoic, 2-methylhexanoic, 5-methylhexanoic and 2,2-dimethyl-n-valeric acids) as eluents in ion-exclusion chromatography with conductimetric detection for C1-C6 aliphatic carboxylic acids (formic, acetic, propionic, isobutyric, butyric, isovaleric, valeric, isocaproic and caproic acids) was carried out using a highly sulfonated styrene-divinylbenzene co-polymer resin (TSKgel SCX) in the H+ form as a stationary phase. When using 0.05 mM sulfuric acid at pH 4.0 as the eluent, peak shapes of hydrophobic carboxylic acids (isovaleric, valeric, isocaproic and caproic acids) were tailed strongly. In contrast, when using 1 mM these C7 carboxylic acids at pH ca. 4 as the eluents, although system peaks (vacant peaks) corresponding to these C7 carboxylic acids appeared, peak shapes of these hydrophobic acids were improved drastically. Excellent simultaneous separation and relatively high sensitive conductimetric detection for these C1-C6 aliphatic carboxylic acids were achieved in 25 min on the TSKgel SCX column (150 x 6 mm I.D.) using 1 mM 5-methylhexanoic acid at pH 4.0 as the eluent.

Benzoic Acid↗
PubMed2000

Retention behaviour of strong acid anions in ion-exclusion chromatography on sulfonate and carboxylate stationary phases.

Some factors influencing the retention of strong-acid anions on ion-exclusion columns were investigated using columns with sulfonate and carboxylate functional groups. The nature of the functional group on the resin, the eluent pH and the eluent ionic strength all significantly affected the retention and separation of these analytes. Retention was observed for all strong-acid anions over the eluent pH range 2.2-5.7 and increased with both decreasing eluent pH and increasing eluent ionic strength. Some separation of strong-acid anions was possible when using a resin with carboxylate functional groups. It has also been demonstrated that strong-acid anions are poor markers of column void volume for ion-exclusion chromatography. A more accurate value was obtained using the neutral polymeric material dextran blue. When using eluents of low ionic strength, poor or fronted peak shapes were observed. A mechanism for these observations is proposed that relates the shape to ionic strength changes across the peak. A system peak was encountered under most experimental conditions. The properties of this peak are discussed and a cause for the system peak postulated.

Acids↗
PubMed2002

Crystal structure of HslUV complexed with a vinyl sulfone inhibitor: corroboration of a proposed mechanism of allosteric activation of HslV by HslU.

On the basis of the structure of a HslUV complex, a mechanism of allosteric activation of the HslV protease, wherein binding of the HslU chaperone propagates a conformational change to the active site cleft of the protease, has been proposed. Here, the 3.1 A X-ray crystallographic structure of Haemophilus influenzae HslUV complexed with a vinyl sulfone inhibitor is described. The inhibitor, which reacts to form a covalent linkage to Thr1 of HslV, binds in an "antiparallel beta" manner, with hydrogen-bond interactions between the peptide backbone of the protease and that of the inhibitor, and with two leucinyl side chains of the inhibitor binding in the S1 and S3 specificity pockets of the protease. Comparison of the structure of the HslUV-inhibitor complex with that of HslV without inhibitor and in the absence of HslU reveals that backbone interactions would correctly position a substrate for cleavage in the HslUV complex, but not in the HslV protease alone, corroborating the proposed mechanism of allosteric activation. This activation mechanism differs from that of the eukaryotic proteasome, for which binding of activators opens a gated channel that controls access of substrates to the protease, but does not perturb the active site environment.

ATP-Dependent Proteases↗
PubMed2002

Ozonation of naphthalene sulfonic acids in aqueous solutions. Part I: elimination of COD, TOC and increase of their biodegradability.

Ozonation of 11 naphthalene sulfonic acids (NSA) in the aqueous solution was studied by bubbling at 31 degrees C at an ozone dose rate of 5.56 mg min(-1) l(-1). COD, TOC and BOD5 of these compounds were tested. It was found that COD and TOC can be removed effectively by ozonation as expected. More than 40% COD of compounds No. I (2-amino-1-NSA), No. 5 (1-hydroxy-7-amino-5-NSA), No. 6 (6-hydroxy-1-NSA), No. 8 (6-amino-1,4-naphthalene disulfonic acid) and No. 11 (I -hydroxy-6-amino-3-NSA) has been eliminated at an ozone dosage of 5.56 mg min(-1) l(-1) for 2 h. Although TOC removal was very different, a good biodegradability was reached for NSAs with an average ozone consumption of 3.0 mgl(-1) for a TOC0 concentration of 100 mg(-1). Ozonation and biotreatment should be good alternatives for these compounds, especially after 20% TOC reduction and TOC removal were more sensitive in predicting an increase in biodegradability during ozonation, than that of COD. NSAs are similar in their behavior with reference to ozone consumption. In order to obtain a good biodegradability of NSAs at a TOC0 concentration of 100 mgl(-1), an ozone consumption between 2.0 and 4.0 mg mg(-1) ACOD is needed for this setup and 3.0 mg O3 mg(-1) TOC0 requirement may be more practical in predicting the biological behavior of naphthalene compounds.

Biodegradation, Environmental↗
PubMed2002

Anticoagulant mechanism of sulfonated polyisoprenes.

The influence of sulfonated polyisoprene (SPIP) on coagulation factors and human blood cells was investigated to elucidate and compare its anticoagulant mechanism with that of heparin. While the number of red cells was unaffected, the number of platelets decreased dramatically in the presence of SPIP due to aggregation. Using a synthetic peptide substrate to assay thrombin activity in the presence of its natural inhibitor, antithrombin (AT), we observed no stimulation by SPIP of AT-mediated inhibition. Nevertheless, thrombin cleavage of its natural substrate fibrinogen to fibrin peptide A was slightly inhibited. SPIP altered the electrophoretic mobility of fibrinogen and completely inhibited fibrinogen from clotting. We detected no significant influence of SPIP on factors II, VII, IX, and X, while factor XI and factors V and VIII were only slightly affected. Therefore, the main mechanism of SPIP's anticoagulant activity appears to be a strong interaction with fibrinogen and fibrin monomer, first, to prevent proteolytic conversion of the former to the latter and second, to inhibit polymerization of the fibrin monomer, once formed.

Anticoagulants↗
PubMed2003

Enhanced blood compatibility of polymers grafted by sulfonated PEO via a negative cilia concept.

In our laboratory sulfonated PEO (PEO-SO(3)) was designed as a "negative cilia model" to investigate a synergistic effect of PEO and negatively charged SO(3) groups. PEO-SO(3) itself exhibited a heparin-like anticoagulant activity of 14% of free heparin. Polyurethane grafted with PEO-SO(3) (PU-PEO-SO(3)) increased the albumin adsorption to a great extent but suppressed other proteins, while PU-PEO decreased the adsorption of all the proteins. The platelet adhesion was decreased on PU-PEO but least on PU-PEO-SO(3) to demonstrate an additional effect of SO(3) groups. The enhanced blood compatibility of PU-PEO-SO(3) in the ex vivo rabbit and in vivo canine implanting tests was confirmed. Furthermore, PU-PEO-SO(3) exhibited an improved biostability and suppressed calcification in addition to the enhanced antithrombogenicity. The in vivo antithrombogenicity and biostability were improved in the order of PU PU-PEO>PU-PEO-SO(3) in spite of the possible attraction between negative SO(3) groups and positive calcium ions. The bioprosthetic tissue (BT) was grafted with H(2)N-PEO-SO(3) via glutaraldehyde (GA) residues after conventional GA fixation. BT-PEO-SO(3) also displayed the decreased calcification by in vivo animal models. The application of PEO-SO(3) was extended by designing amphiphilic copolymers containing PEO-SO(3) moiety and hydrophobic long alkyl groups as anchors. The superior effect of PEO-SO(3) groups on thromboresistance compared to PEO was confirmed also in the case of copolymers coated or blended with other polymers and the systems coupled by UV irradiation, photoreaction or gold/sulfur or silane coupling technology, and therefore it might be very useful for the medical devices.

Adsorption↗
PubMed2001

Dipeptide vinyl sulfones suitable for intracellular inhibition of dipeptidyl peptidase I.

In granules of hematopoetic cells, dipeptidyl peptidase I (DPPI) processes inactive proenzymes into active enzymes, e.g., lymphocyte progranzyme A. Our goal was to develop irreversible inhibitors of intracellular DPPI. First, we identified inhibitors with aqueous stability. Then we determined which inhibitors were nontoxic, could enter cells and inactivate intracellular DPPI. We screened nine dipeptide vinyl sulfone (VS) inhibitors (kobs/[I] > 72 M-1 s-1) and found six that were nontoxic. Four affected intracellular DPPI at < 25 microM. These compounds contained only uncharged amino acid residues; the two less reactive compounds contained charged Glu residues. The best one, Leu-Phe-VS-CH3, inactivated DPPI in cells with an ID50 of approximately 5 microM. This inhibitor was not the best inhibitor of purified DPPI. Longer aqueous stabilities were important predictors of cellular efficacy. Leu-Phe-VS-CH3 had a half life of 97 min at the pH of the extracellular medium (7.5) and 1302 min at pH 5.5 (the intracellular environment of DPPI). This VS had no direct effect on granzyme activities. In contrast, the diazomethyl ketone inhibitor Gly-Phe-CHN2 inhibited chymase activity. Several good intracellular DPPI VS inhibitors lacked reactivity with cathepsins B, H and L. In conclusion, we have identified DPPI inhibitors suitable for cellular applications.

Animals↗
PubMed2003

Comparison of polyvinylidene fluoride and polyether sulfone membranes in filtering viral suspensions.

Low-protein-binding membranes with a pore size of 0.22 microm are used to filter aqueous solutions containing viruses. Virus adsorption to the membranes is avoided if they are made of polyvinylidene fluoride (PVDF) or if they are made of cellulose esters saturated with beef extract. Recently, a new kind of membrane filter made of polyether sulfone (PES) has become available commercially. The manufacturers claim that such membranes allow the filtration of greater volumes of sample than those made of PVDF. We compared the filtration rate and volume that could be filtered before clogging for these two membranes. The bacteriophage and enterovirus counts were then compared in sewage after filtration through the two membranes. There were no differences in virus recovery after filtration, but PES membranes allowed a higher filtration rate and clogged more slowly. The use of PES membranes is recommended.

Bacteriophages↗
PubMed2003

Sorption and mass fluxes of sulfonated naphthalene formaldehyde condensates in aquifers.

Sulfonated naphthalene formaldehyde condensates (SNFC) and their monomeric analogues were used as superplasticizers for cement suspension injections at two tunnel construction sites that are in direct contact with groundwater. Because in one case the aquifer is an important drinking water resource, the behavior of SNFC in the groundwater was carefully investigated. Chemical analyses showed that SNFC leached to the groundwater in concentrations of up to 58 microg/l of total SNFC at a distance of about 60 m down-gradient from the construction site. Of the individual SNFC components, only monomers and oligomers with up to four units could be detected in the groundwater. Oligomers with more than four units did not leach from the cement paste. The leached oligomers were transported in the groundwater at different velocities, which can be explained by sorption experiments. Mass fluxes of SNFC used at the tunnel construction sites were evaluated. Most SNFC were immobilized in the cement, but 5% (w/w) of the applied SNFC were found to leach into the aquifer. This corresponds to a total amount of leached SNFC of approximately 100 kg, of which about 80% are biodegraded in the aquifer and 20% (20 kg) still remain in the groundwater.

Biodegradation, Environmental↗
PubMed2003

New styryl sulfones as anticancer agents.

New styryl sulfone compounds have been synthesized and evaluated for their anti-proliferative activity. Among the compounds synthesized, one compound (7k) has shown 51% tumor growth inhibition in mice implanted with HT-29 human carcinoma at 400 mg kg(-1) orally.

Animals↗
PubMed2001

Direct electrochemistry of hemoglobin in layer-by-layer films with poly(vinyl sulfonate) grown on pyrolytic graphite electrodes.

Stable layer-by-layer electroactive films were grown on pyrolytic graphite (PG) electrodes by alternate adsorption of layers of polyanionic poly(vinyl sulfonate) (PVS) and positively charged hemoglobin (Hb) from their aqueous solutions. Cyclic voltammetry (CV) of [PVS/Hb]n films showed a pair of well-defined and nearly reversible peaks at about - 0.28 V vs. SCE at pH 5.5, characteristic of Hb heme Fe(III)/Fe(II) redox couple. The process of (PVS/Hb) bilayer growth was monitored and confirmed by CV, X-ray photoelectron spectroscopy (XPS) and UV-Vis spectroscopy. While the amount of Hb adsorbed in each bilayer was the same, the amount of electroactive Hb in each bilayer decreased dramatically with increase of the number of bilayer, and electroactivity was just extended to 8 [PVS/Hb] bilayers. CVs of [PVS/Hb]8 films maintained stable in buffers containing no Hb. Positions of Soret band of Hb in [PVS/Hb]n films grown on transparent glass slides suggest that Hb in the films keeps its secondary structure similar to its native state in a wide pH range. Trichloroacetic acid and nitrite were catalytically reduced by [PVS/Hb]8 films with significant lowering of the electrode potential required.

Catalysis↗
PubMed1999

Desulfonation of a colitis inducer 2,4,6-trinitrobenzene sulfonic acid produces sulfite radical.

2,4,6-Trinitrobenzene sulfonic acid (TNBS) has been used in vivo to induce colitis. With the nitroreductase of intestinal cells, TNBS underwent redox cycling to produce TNBS-nitro and superoxide radical anions which are thought to be involved in initial oxidative reactions that lead to colonic injury. In this study, we demonstrated that the TNBS desulfonative reaction with tissue amino acids produces sulfite which is subsequently oxidized to sulfite radical. Sulfite radical was measured using a spin trapping methodology. Sulfite radical adducts of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) or 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO) were detected in a mixture of TNBS and lysine, xanthine oxidase, red blood cells, colonic mucosal or submucosal muscle tissues. TNBS alone did not produce sulfite radical, indicating that its formation required the presence of amino acids. Because sulfite radical is the precursor of highly reactive sulfiteperoxyl and sulfate radicals, our data imply that these sulfite-derived free radicals may also contribute to oxidative reactions leading to colonic injury in TNBS-induced colitis.

Animals↗
PubMed2002

Separation of N-alkyl phenothiazine sulfones by HPTLC using an optimum mobile phase.

In high performance thin layer chromatography some form of optimization is necessary if complete separation of all components is required. The selection of mobile phase composition is one of the most important components of an optimization strategies. The aim of this paper is the separation of the N-alkyl phenothiazine sulfones by high performance thin layer chromatography using an optimum mobile phase system. The optimum composition of mobile phase (toluene-ethyl ether-chloroform, 30:50:20, v/v) are given by the maximum of objective function (F(obj)=10.6110).

Algorithms↗