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PubMed2004

Selective extraction of iron(III) from aqueous nitrate solution in the presence of cobalt(II), copper(II) and nickel(II) ions using bis(delta2-2-imidazolinyl)-5,5'-dioxime.

The feasibility of using bis(delta2-2-imidazolinyl)-5,5'-dioxime (H2L) for the selective extraction of iron(III) from aqueous solutions was investigated by employing an solvent-extraction technique. The extraction of iron(III) from an aqueous nitrate solution in the presence of metal ions, such as cobalt(II), copper(II) and nickel(II), was carried out using H2L in binary and multicomponent mixtures. Iron(III) extraction has been studied as a function of the pH, equilibrium time and extractant concentration. From the extracted complex species in the organic phase, iron(III) was stripped with 2 M HNO3, and later determined using atomic-absorption spectrometry. The extraction was found to significantly depend on the aqueous solution pH. The extraction of iron(III) with H2L increases with the pH value, reaching a maximum in the zone of pH 2.0, remaining constant between 2 and 3.5 and subsequently decreasing. The quantitative extraction of iron(III) with 5 x 10(-30 M H2L in toluene is observed at pH 2.0. H2L was found to react with iron(III) to form ligand complex having a composition of 1:2 (Fe:H2L).

Journal Article↗
PubMed1973

Effects of selective extraction of histones on template activities of chromatin by use of exogenous DNA and RNA polymerases.

Exogenous DNA and RNA polymerases were used to measure the template activity of DNA in chromatin in isolated thymus nuclei from which lysinerich or arginine-rich histones were selectively extracted. Measurements were on nuclei containing 20-1200 mug of DNA per ml, the distinctions becoming clear at the higher concentrations. Experiments with RNA polymerase showed only moderate increases in template activity upon extraction of histone, although the removal of lysinerich histone had a greater effect than that of arginine-rich histone. DNA polymerase action on nuclei minus lysinerich histone achieved high results, exceeding even those on DNA itself.

Animals↗
PubMed2003

Selective extraction and characterization of a histidine-phosphorylated peptide using immobilized copper(II) ion affinity chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Phosphorylation is the predominant posttranslational modification involved in regulating enzymatic activity and mediating signal transduction in prokaryotic and eukaryotic cells. Selective enrichment of phosphorylated peptides prior to mass spectrometric analysis facilitates identification of phosphorylated proteins, determination of specific phosphorylated residues, and characterization of the conditions under which phosphorylation occurs. Such protocols have been established for peptides containing residues that form phosphoesters, such as serine and threonine, using immobilized metal-ion affinity chromatography. Despite the importance of histidine phosphorylation in two-component signal transduction pathways, similar protocols for peptides containing phosphorylated histidine (P-His) residues have proven elusive, due to the instability of these modifications and the propensity of unphosphorylated histidines to interact with immobilized metals ions. We describe a method for the selective extraction of a P-His-containing peptide using immobilized copper(II) ions and disposable metal-chelating pipet tips (ZipTipMC, Millipore). The method is contingent upon pH-dependent interactions between the phosphate group and immobilized copper(II) ions. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with postsource decay confirms the identity and phosphorylation state of the extracted peptide. Peptides containing unphosphorylated histidine residues or other phosphorylated amino acids are not retained, demonstrating the specificity of the method for P-His-containing peptides.

Cations, Divalent↗
PubMed2004

A new molecularly imprinted polymer for the selective extraction of naproxen from urine samples by solid-phase extraction.

A non-covalent molecularly imprinted polymer (MIP) was synthesised using naproxen (a non-steroidal, anti-inflammatory drug (NSAID)) as a template molecule. The MIP was chromatographically evaluated to confirm the imprinting effect, and was then applied as a selective sorbent in solid-phase extraction (SPE) to selectively extract naproxen. After this study, the MIP was used to extract naproxen from urine samples; it was demonstrated that by applying a selective washing step with acetonitrile (ACN) the compounds in the sample that were structurally related to naproxen could be eliminated.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2000

Selective extraction and purification of a mycobacterial outer membrane protein.

MspA forms water-filled channels in the mycolic acid layer of Mycobacterium smegmatis thereby allowing the diffusion of hydrophilic solutes through this permeability barrier into the periplasm. MspA is the first member of a new family of porins and is extremely stable against chemical and thermal denaturation. We developed a purification procedure based on selective extraction of MspA with detergents from whole cells of M. smegmatis at high temperatures. Anion-exchange and size-exclusion chromatography yielded about 230 microg apparently pure and highly active MspA per liter of culture. This was a 20-fold increased yield compared to previous purification protocols. Similar amounts of pure MspA were obtained with the detergents isotridecylpolyethyleneglycolether, lauryldimethylamine oxide, and octylpolyethylene oxide indicating that this purification procedure is not restricted to a specific detergent. This study will promote the structural and functional analysis of MspA and might be valuable for the isolation of porins from other mycolic acid-containing bacteria.

Chromatography, Ion Exchange↗
PubMed1995

Large-scale production of HIV-1 protease from Escherichia coli using selective extraction and membrane fractionation.

Human immunodeficiency virus type 1 (HIV-1) protease was expressed in Escherichia coli as a fusion protein with the N-terminal sequence of IGF-2. The protein accumulated in inclusion bodies as a 40:60 mixture of unprocessed fusion protein and processed protein. A simple purification procedure was developed that yielded 30-40 mg of active protease per liter of fermentation broth with a recovery of 30-40%. The purification process involved the selective extraction of HIV-1 protease from E. coli inclusion bodies with 50% acetic acid and fractional diafiltration to remove impurities and low-molecular-weight protease-related fragments. No chromatographic steps were employed, yet the HIV-1 protease produced by this procedure was greater than 95% pure by SDS-PAGE, reverse-phase HPLC, and N-terminal sequence analysis.

Acetates↗
PubMed1995

A specific enzyme immunoassay (EIA) with selective extraction for quantitation of a topical anti-inflammatory agent, SCH 40120, in human plasma.

SCH 40120 is a potent anti-inflammatory agent under development for the topical treatment of dermal inflammatory and allergic disorders such as atopic dermatitis, contact dermatitis and psoriasis. We have previously described a sensitive enzyme immunoassay (EIA) for SCH 40120 in unextracted human plasma to support clinical studies. However, severe cross-reaction with unknown metabolites was observed during validation using samples from rats dosed with 14C-SCH 40120. Therefore, a selective extraction procedure was developed to remove the unknown plasma metabolites of SCH 40120 prior to EIA quantitation. The modified EIA using extracted plasma was cross-validated with an LC method using plasma samples from dosed subjects (human and rat), thereby confirming the specificity of the assay. The EIA can reliably quantitate SCH 40120 in plasma samples from 100 pg ml-1 to 10 ng ml-1 with good linearity, accuracy and precision, and is suitable for pharmacokinetic studies in man.

Administration, Topical↗
PubMed2003

Optimization of the class-selective extraction of triazines from aqueous samples using a molecularly imprinted polymer by a comprehensive approach of the retention mechanism.

Direct, selective solid-phase extraction of triazines from aqueous samples is presented using a molecularly imprinted polymer (MIP) made with terbutylazine as template molecule. After optimization of the steps of the procedure, 14 triazines including degradation products were studied and satisfactory extraction recoveries were obtained except for thiotriazines. By comparing results obtained with the terbutylazine MIP and a similar non-imprinted polymer, it was determined that retention was achieved via specific interactions except for hydroxyterbutylazine. Selectivity of the extraction procedure was also verified by applying the MIP for the extraction of phenylureas that were not retained on it. The effects of the charge distribution and of molecular volume of the triazines (obtained by molecular modeling) on the selectivity of interactions between the analytes and the MIP were studied. However, when the optimized procedure was applied to real samples, low extraction recoveries were obtained due to strong matrix effects: ion-exchange occurs between the carboxylate groups of the MIP and the ionic species of the sample, that prevents subsequent specific interactions. By introducing an acid wash step, the procedure was successfully applied for the class-selective extraction of triazines from industrial effluent and surface water samples. Finally, increased extraction recoveries were achieved for the polar degradation products of triazines by using a mixed-phase composed of a polymeric sorbent and the MIP.

Chromatography, High Pressure Liquid↗
PubMed1971

Selective extraction of isolated mitotic apparatus. Evidence that typical microtubule protein is extracted by organic mercurial.

Mitotic apparatus isolated from sea urchin eggs has been treated with meralluride sodium under conditions otherwise resembling those of its isolation. The treatment causes a selective morphological disappearance of microtubules while extracting a major protein fraction, probably consisting of two closely related proteins, which constitutes about 10% of mitotic apparatus protein. Extraction of other cell particulates under similar conditions yields much less of this protein. The extracted protein closely resembles outer doublet microtubule protein from sea urchin sperm tail in properties considered typical of microtubule proteins: precipitation by calcium ion and vinblastine, electrophoretic mobility in both acid and basic polyacrylamide gels, sedimentation coefficient, molecular weight, and, according to a preliminary determination, amino acid composition. An antiserum against a preparation of sperm tail outer doublet microtubules cross-reacts with the extract from mitotic apparatus. On the basis of these findings it appears that microtubule protein is selectively extracted from isolated mitotic apparatus by treatment with meralluride, and is a typical microtubule protein.

Amino Acids↗
PubMed1979

Glycophorin-enriched vesicles obtained by a selective extraction of human erythrocyte membranes with a non-ionic detergent.

A method is described for isolating glycophorin-enriched vesicles from human erythrocytes by extracting membranes that were incubated for 30 min at 37 degrees C at pH 4.5 and washed at low and high ionic strength with the nonionic detergent Triton X-100. The extracts were 11.8 +/- 2.4 fold enriched in glycophorin and contained 325 +/- 69 microgram sialic acid/mg protein, which represented 61 +/- 16% of the total sialic acid. Upon removal of Triton X-100 one third of the total glycophorin forms glycophorin-enriched vesicles with coextracted, endogenous lipids as shown sedimintation, dextran-density gradient centrifugation, and electron microscopy. Addition of exogenous lipids increased the fraction of glycophorin-enriched vesicles up to 87%. The incorporation of glycophorin in the membrane was shown by hemagglutination inhibition assays using anti-M sera and by the accessibility of glycophorin to trypsin. Freeze-fractured vesicles did not reveal intramembranous particles. The selectivity of the extraction procedure is not simply due to chemical constraints introduced by disulfide cross-linkage of protein component 3, because only 20% of this protein undergo disulfide cross-linking. The selective extraction of glycophorin implies that glycophorin is segregated from protein component 3 and thus from intramembranous particles when erythrocyte membranes have been incubated at pH 4.5. This segregation may precede aggregation of intramembranous particles.

Cell Fractionation↗
PubMed1992

Sulfated proteoglycans of rabbit aorta: selective extraction and alternative method for glycosaminoglycan moiety analysis.

Three different solutions containing urea, guanidine hydrochloride, or a detergent mixture were used to extract proteoglycan molecules (PG) metabolically labeled with 35S from normal rabbit aortic tissue. The size distribution of whole sulfated PG and the glycosaminoglycan (GAG) compositions in the three extracts were compared and found to be characteristically determined by the type of solution used for extraction. The spectrum of sulfated PG isolated by each solution was maintained at consecutive extractions of the tissue, even if this was used after another type of solution. The extracts obtained by using the urea- or guanidine-containing solutions contained similar, rather balanced populations of large and small PG, while the detergent-containing buffer was found to preferentially extract smaller, heparan sulfate-rich aortic PG. The selectivity of various extracting solutions could be exploited to obtain preparations enriched in certain types of sulfated PG. On the other hand, one could obtain a larger variety of 35S-labeled PG from the tissue by consecutively using two solutions with different capacities of extraction. The distribution of GAG moieties among PG populations, separated by size chromatography, was investigated by one of the commonly used methods and by a new method. The standard method is based on comparison of the chromatographic profiles of the extract before and after enzymatic digestions, requiring several chromatographic runs for a sample. In the alternative method proposed, the fractions obtained after a single chromatographic separation are adsorbed onto a support membrane. Processing of the whole membrane by GAG-specific, enzymatic treatments allows simultaneous assessment of GAG types in each fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Sol-gel immunosorbents doped with polyclonal antibodies for the selective extraction of malathion and triazines from aqueous samples.

Sol-gel immunosorbents (IS) prepared by encapsulation of polyclonal antibodies in silica were packed in cartridges and evaluated for selective immunoaffinity extraction (IAE) of malathion and triazines from aqueous samples. Encapsulated atrazine antibodies highly cross-reacted with simazine and propazine but did not recognize prometon and prometryn. No cross-reactivity of malathion antibodies was observed with the closely related metabolites oxomalathion and isomalathion. Mean IS binding capacities per milligram of entrapped antibody were 0.33 nmol of malathion and 0.47 nmol of atrazine (approximately 100 ng each). This capacity remained constant for at least 10 weeks, and the cartridge reusability was excellent (>60 IAE runs); also, high preconcentration factors were feasible because the breakthrough of analytes from IS cartridges did not occur up to the 250 mL sample volumes, provided that the capacity was not surpassed. Simple and rapid methods for determination of malathion or three triazines in surface water were developed using off-line IAE and HPLC-UV. The application to 50 mL dam water samples spiked at approximately 1 ng/mL of pesticides resulted in recoveries of approximately 90% and RSD < 5% (n=7). LODs for this sample volume (direct injection of IS eluates) were in the range of 0.15-0.50 ng/mL. Lower LODs (0.03-0.1 ng/mL) were achieved by online analysis of whole eluates previously loaded in RP precolumns.

Antibodies↗
PubMed2002

A self-assembled, redox-responsive receptor for the selective extraction of LiCl from water.

There is considerable interest in synthetic ionophores with high affinity and selectivity for Li(+). But so far, compounds that selectively bind Li(+) in the presence of other alkali and alkaline earth metal ions are rare and current approaches toward this goal are often accompanied with substantial synthetic efforts. Here we describe a trinuclear ruthenium metallamacrocyclic complex (1) that was obtained by self-assembly of ruthenium halfsandwich complexes and 3-hydroxy-2-pyridone ligands. This complex was shown to be an extremely potent receptor for LiCl with an affinity high enough to extract LiCl from water. The selectivity of this receptor is exceptional: even in the presence of a large excess of Na(+), K(+), Cs(+), Ca(2+), and Mg(2+), Li(+) was extracted exclusively. The Li(+)/Na(+) selectivity ratio was determined to be higher than 1,000:1. Compared with other synthetic ionophores, the receptor 1 offers two additional advantages: (i) the synthesis can be accomplished in one step by using simple starting materials; and (ii) the presence of lithium ions can be detected electrochemically. Complex 1 is therefore a very attractive candidate for the construction of a Li(+)-specific chemosensor.

Chemistry↗
PubMed2003

Selective extraction of functional components derived from herb in plasma by using a molecularly imprinted polymer based on 2,2-bis(hydroxymethyl)butanol trimethacrylate.

To make molecularly imprinted polymer (MIP) solid-phase extraction (SPE) capable of direct clean-up of aqueous biological samples, an anti-quercetin MIP with evident hydrophobic matrix was synthesized using acrylamide (AA) as the functional monomer and 2,2-bis(hydroxymethyl)butanol trimethacrylate (TRIM) as the crosslinker. The affinity and selectivity were evaluated by liquid chromatography, and the binding sites and the dissolution constants were measured by frontal chromatography. Compared with the AA-co-ethyleneglycol dimethacrylate (EDMA) MIP, the anti-quercetin AA-co-TRIM MIP exhibited stronger binding and possessed improved column efficacy. A linear plot of the peak area versus sample size (in the range of 0.4-2.2 microg) was obtained, which made it promising for the MIP columns to be directly used for analysis. Before MIP-SPE of the sample of plasma, several washing solvents were tested and it was shown that the careful choice of the right washing solvent is the key step to successful sample extraction. The anti-quercetin AA-co-TRIM polymer selectively extracted quercetin, the effective component in the plasma of rats fed the hydrolyzed extract of Gingko biloba L. The recovery (67%) for MIP-SPE was calculated using spiked plasma. The results of the present work showed that the properties of MIP could be improved by modifying the polymerization and that MIP-SPE could be used for direct clean-up of biological samples for the analysis of functional components in vivo originating from an extract of medicinal herbs.

Animals↗
PubMed2001

Selective extraction of blood plasma exchangeable copper for isotope studies of dietary copper absorption.

Measuring mineral absorption by fecal monitoring is labor-intensive and relies on good volunteer compliance. Blood indicators of absorption could be advantageous and we have developed a method for selective extraction-of recently absorbed (exchangeable) copper based on dialysis of plasma with histidine and subsequent copper extraction using Chelex resin. The potential for measuring copper absorption by transient enrichment of exchangeable copper with the stable isotope 65Cu from an ingested tracer, was also investigated. This method was compared with that of the fecal monitoring technique in a human volunteer, who consumed a 6 mg dose of 65Cu with inhibitors of copper absorption. Holmium was used as a non-absorbable rare-earth marker of unabsorbed tracer excretion, allowing estimation of re-secreted 65Cu (44 microg d(-1)), and hence calculation of true tracer absorption, which was only 10.8%. Monitoring plasma tracer kinetics showed potential for estimation of copper absorption without the need for fecal copper analysis.

Chelating Agents↗
PubMedDate not supplied

Selective extraction and determination of multiclass pesticide residues in post-harvest French beans by low-pressure gas chromatography/tandem mass spectrometry.

A selective and reliable extraction procedure was developed and validated to determine multiclass pesticide residues in lyophilized agricultural plants by low-pressure gas chromatography coupled with tandem mass spectrometry. The method is based on a rapid and simple extraction of the lyophilized sample with dichloromethane. The results were compared with those obtained by using fresh and naturally dried samples. Slightly better recoveries and precision values were obtained for the lyophilized samples. The application of the proposed methodology was tested by analyzing French bean plants from an agricultural area of Almería (Spain). The availability of this methodology, which is capable of detecting a high number of analytes in a single analysis, has priority in analyses for a large number of pesticides used on individual commodities.

Crops, Agricultural↗
PubMed2002

Phase transfer of monosaccharides through noncovalent interactions: selective extraction of glucose by a lipophilic cage receptor.

We have previously shown that macrotricyclic host 1a is a powerful receptor for glucopyranosyl units in the nonpolar medium of chloroform. However, the solubility properties of 1a did not permit studies of the extraction of carbohydrates from aqueous solution. This paper describes the synthesis of the new variant 1b, furnished with a highly lipophilic exterior array of 12 benzyloxy substituents. In homogeneous solution, 1b behaves much as 1a, binding n-octyl beta-d-glucoside with K(a) = 720 M(-1) in CD(3)OH/CDCl(3) (8:92). In two-phase experiments, the improved solubility of 1b allows carbohydrate extraction to be observed. Three hexoses (glucose, galactose, and mannose), two pentoses (ribose and xylose), and the two methyl glucosides are all extracted substantially into chloroform from 1 M aqueous solutions. Among the hexoses, 1b shows notable affinity and selectivity for glucose, extracting detectable amounts even from 0.1 M aqueous solutions.

Cadmium Chloride↗
PubMed1984

Selective extraction by 1-butanol of surface glycoprotein antigens from human melanoma cells.

The butanol extraction method has previously been used to achieve selective release of tumor-specific transplantation antigens from mouse sarcoma cells. In this study we investigated the feasibility of this method for extracting four surface glycoprotein antigens (87K, 95-150K, HLA-DR, and HLA-A,B,C) from cultured human melanoma cells. Of the four antigens examined, only 95-150K and HLA-DR antigens could readily be detected in material extracted by 2%, 3%, or 5% butanol. The 3% butanol was found to be most effective in releasing these two antigens. Treatment of melanoma cells with less than or equal to 3% butanol did not decrease the viability of extracted cells as judged by either Trypan Blue dye exclusion or plating efficiency. Thus the noncytolytic butanol extraction method offers a promising approach to the isolation of certain glycoproteins such as 95-150K and HLA-DR from viable human melanoma cells for further purification and structural analysis.

1-Butanol↗