Successive Precipitation Research Articles

Purification of guar gum for biological applications

Commercial guar gum (GG) was purified by four different methods and characterized by gel permeation chromatography (GPC), thermogravimetric analysis and the determination of monosaccharides composition, protein and copper content, turbidity, intrinsic viscosity and rheological parameters. The first method was based on enzymatic hydrolysis with porcine pancreatin. In the second method successive gum dissolution, centrifugation and precipitation with acetone and ethanol were carried out. Precipitation with Fehling solution was employed in the third method. In the fourth method, the gum was purified by method 2 and then by method 3. All methods led to a reduction in protein content, arabinose and glucose residues, considered as sugar contaminants, and also in intrinsic viscosity and molar mass. Total elimination of protein was only achieved by method 4. Using methods 3 and 4, the gum was contaminated with small amounts of Cu(II) from the Fehling solution. Methods 2 and 4 apparently provided purer guar gum. If the amount of protein is a crucial parameter in the biological application and the guar will be taken in low amounts, method 4 is recommended. Taking into account the purity, thermal stability, rheological parameters of the purified gum and also the cost and simplicity of the procedure, method 2 has wider biological application.

Effect of zirconium and yttrium hydroxide precipitation conditions on the fractal structure of the resulting xerogels and 0.97ZrO2 · 0.03Y2O3 powders

We have investigated the effect of the preparation procedure (successive or simultaneous precipitation of zirconium and yttrium hydroxides) on the fractal structure of the resulting xerogels and fluorite-structure oxide nanopowders. Small-angle x-ray scattering data indicate that the xerogels and oxide nanopowders have, respectively, three-and two-level fractal structures. Mass-fractal aggregation is shown to improve the properties of the precipitates (good filterability and the formation of soft powders easy to disaggregate).

Fibrous-clay mineral formation and soil evolution in Aridisols of northeastern Patagonia, Argentina

Recent studies of soil–landscape relationships in northeastern Patagonia identified fibrous-clay minerals in calcic and petrocalcic horizons developed on old fluvio-glacial plains called “Rodados Patagónicos” (RP). The objectives of this study were: i) to evaluate the occurrence of fibrous-clay minerals in the arid soil environment, and ii) to establish the relationship between the soil properties and degree of the calcic horizon development, including the age of the soils containing fibrous-clay minerals in extra-Andean Patagonia. The soil studied were Calciargids, Natrigypsids, and Petrocalcids, located at elevations of 50, 70, and 130 m a.s.l., respectively. The soils are polygenetic, where the clay mineralogy is related to the age of the pedogenetic periods that affected the formation of geomorphic surfaces. In the surface horizons, illite proved to be the dominant clay mineral and was slightly altered to interstratified illite–smectite and smectite. An older pedogenic episode was identified in argillic and calcic horizons, in which smectite was prevalent. The following soil-formation period was recorded in calcic and calcic-gypsic horizons appearing in the upper limit of the RP. In these horizons, palygorskite is the dominant clay mineral. Pedogenetic carbonate was qualified as low-Mg calcite, indicating that during its precipitation, the Mg 2+ activity increased in the soil solution, favoring the smectite → palygorskite transformation. The soil environment, favorable for this transformation, was the textural transition between the fine materials of sub-surface horizons and the coarsest deposit of RP, where temporary waterlogging occurred. The petrocalcic horizons, and their re-transported fragments, represent the oldest pedogenetic period, where sepiolite was the dominant clay mineral. During the calcretization processes, the sepiolite was precipitated from the soil solution following the formation of palygorskite. Fluorite was identified in the petrocalcic horizon, and its association with calcite and sepiolite indicated a successive precipitation of these minerals under alkaline conditions during evaporation processes.

Water-use strategy of three central Asian desert shrubs and their responses to rain pulse events

Plant water-use strategy is considered to be a function of the complex interactions between species of different functional types and the prevailing environmental conditions. The functional type of a plant’s root system is fundamental in determining the water-use strategy of desert shrubs and the physiological responses of the plant to an occasional rainfall event, or rain pulse. In this current study of Tamarix ramosissima Ledeb. Fl.Alt., Haloxylon ammodendron (C.A.Mey.) Bunge and Reaumuria soongorica (Pall.) Maxim., three dominant shrub species in the Gurbantonggut Desert (Central Asia), plant root systems were excavated in their native habitat to investigate their functional types and water-use strategies. We monitored leaf water potential, photosynthesis and transpiration rate during a 39-day interval between successive precipitation events during which time the upper soil water changed markedly. Plant apparent hydraulic conductance and water-use efficiency were calculated for the varying soil water conditions. Our results show that: 1) The three species of shrub belong to two functional groups: phreatophyte and non-phreatophyte; 2) The photosynthetic capacity and leaf-specific apparent hydraulic conductance of the three species was stable during the time that the water condition in the upper soil changed; 3) Transpiration, leaf water potential and water-use efficiency in Tamarix ramosissima Ledeb. Fl.Alt. were stable during the period of observation, but varied significantly for the other two species. Tamarix ramosissima Ledeb. Fl.Alt., as a phreatophyte, relies mostly on groundwater for survival; its physiological activity is not inhibited in any way by the deficiency in upper soil water. Non-phreatophyte Haloxylon ammodendron (C.A.Mey.) Bunge and Reaumuria soongorica (Pall.) Maxim. use precipitation-derived upper soil water for survival, and thus respond clearly to rain pulse events in terms of leaf water potential and transpiration. The observed similarity in leaf-specific photosynthesis capacity among all three species indicates that the two non-phreatophyte species are able to maintain normal photosynthesis within a wide range of plant water status. The observed stability in leaf-specific apparent hydraulic conductance indicates that the two non-phreatophyte species are able to maintain sufficient water supply to their foliage via, mostly likely, effective morphological adjustment at the scale of the individual plant.

Proteomic analysis of enamel matrix using a two‐dimensional protein fractionation system

Our objectives in this study were to perform separate proteomic analyses of porcine soft and hard enamel matrices, using the ProteomeLab PF-2D System, to compare the contents of the hard and soft enamel and to identify matrix constituents that are absent from the early maturation stage. Developing first permanent molars were dissected from 6-month-old pigs. Both immature and mature enamel samples were obtained by scraping the secretory-stage (soft) and maturation-stage (hard) enamel, respectively. Enamel matrix samples were sequentially extracted and fractionated with 50 mM phosphate buffer (pH 7.4) and then with 50 mM carbonate buffer (pH 10.8). The neutral enamel extract was separated into four fractions by successive ammonium sulfate precipitations. The alkaline enamel extract was separated into four fractions by ion-exchange chromatography. These eight extracts from both the soft and hard enamel were injected for chromatofocusing. Soft enamel fractions containing constituents absent from the hard enamel were further separated by reverse-phase high-performance liquid chromatography. The major soft enamel constituents absent from the hard enamel were acidic glycoproteins, corresponding to the 32-kDa enamelin, and the 29-, 27-, 15-, 13-, 8- and 6-kDa C-terminal fragments of ameloblastin. Loss of these glycoproteins is associated with a post-transition increase in enamel mineralization.

Chemotypes significance of lichenized fungi by structural characterization of heteropolysaccharides from the genera Parmotrema and Rimelia

Galactoglucomannans were isolated from the lichenized fungi of the genus Parmotrema ( Parmotrema austrosinense, Parmotrema delicatulum, Parmotrema mantiqueirense, Parmotrema schindlerii, and Parmotrema tinctorum and that of Rimelia ( Rimelia cetrata and Rimelia reticulata) via successive hot alkaline extraction and precipitation with Fehling solution. The structure of each polysaccharide was investigated using 13C NMR and HSQC-DEPT spectroscopy, methylation analysis, and HPSEC-MALLS. The galactoglucomannans had a (1 → 6)-linked main chain of α-Man p units, substituted preferentially at O-2 and O-4 by α-Gal p and β-Gal p nonreducing end-units, respectively. The C-1 region of the 13C NMR spectra of these heteropolysaccharides is typical of the lichen species, and is an additional tool in lichenized fungi classification.

Design of a 2-D Cementation Experiment in Porous Medium Using Numerical Simulation

The validation and qualification of reactive transport simulation tools has motivated the design and simulation, at a laboratory scale, of an experiment in which flow, advective/dispersive transport of solutes and physicochemical transformation affecting a porous medium are strongly coupled. Several possible experimental setups (or designs) have been evaluated using numerical simulation. The selected experimental design involves the successive precipitation and perforation of a clogging obstacle composed of calcium oxalate. Before an experiment can actually be conducted, this problem is proposed as a numerical benchmark for reactive transport codes and simulated using the coupled reactive transport code Hytec (CIG-Ecole des mines, France).

Mössbauer Study of Tetragonal ZrO2–Y2O3–Fe2O3Solid Solutions

Tetragonal Zr0.886Y0.057Fe0.057O2 – δ solid solutions prepared by calcining coprecipitated and successively precipitated hydroxide mixtures were studied by Mossbauer spectroscopy immediately after calcination and after long-term storage. The results indicate that the solid solutions prepared via coprecipitation and successive precipitation contain Fe3+ in two (octahedral coordination) and three (octahedral, fivefold, and tetrahedral coordinations) inequivalent sites, respectively. Partial Fe3+ substitution for Y3+ is shown to prevent or substantially slow down the low-temperature structural degradation of stabilized zirconia.

Isolation and partial characterisation of acid phosphatase isozymes from dormant oilseed of Corylus avellana L.

The acid phosphatase (orthophosphoric-monoester phosphohydrolase, EC 3.1.3.2) complement from dormant hazel (Corylus avellana L.) seeds was found to exhibit significant electrophoretic heterogeneity partially attributable to the presence of distinct molecular forms. In axiferous tissue, total acid phosphatase activity increased in a biphasic fashion during chilling, a treatment necessary to alleviate seed dormancy. Three acid phosphatase isozymes were isolated from cotyledons of dormant hazel seeds by successive ammonium sulphate precipitation, size-exclusion, Concanavalin A affinity, cation- and anion-exchange chromatographies resulting in 75-, 389- and 191-fold purification (APase1, APase2, APase3, respectively). The three glycosylated isoforms were isolated to catalytic homogeneity as determined by electrophoretic, kinetic and heat-inactivation studies. The native acid phosphatase complement of hazel seeds had an apparent Mr of 81.5 +/- 3.5 kDa as estimated by size-exclusion chromatography, while the determined pI values were 5.1 (APase1), 6.9 (APase2) and 7.3 (APase3). The optimum pH for p-nitrophenyl phosphate hydrolysis was pH 3 (APase1), pH 5.6 (APase2) and pH 6 (APase3). The hazel isozymes hydrolysed a variety of phosphorylated substrates in a non-specific manner, exhibiting low Km and the highest specificity constant (Vmax/ Km) for pyrophosphate. They were not primary phytases since they could not initiate phytic acid hydrolysis, while APase2 and APase3 had significant phospho-tyrosine phosphatase activity. Inorganic phosphate was a competitive inhibitor, while activity was significantly impaired in the presence of vanadate and fluoride.

Purification and characterization of an isoflavone-conjugates-hydrolyzing beta-glucosidase from endophytic bacterium.

An isoflavone conjugates hydrolyzing beta-glucosidase (ICHG) from endophytic bacterium, Pseudomonas ZD-8 was purified to homogeneity by successive ammonium sulfate precipitation, gel filtration on SephadexG-100, DEAE-sephrose CL-6B and DEAE-Sephacel chromatography. The enzyme was a monomeric protein with an apparent molecular mass of 33 kDa as determined by SDS-PAGE and gel filtration. It was optimally active at pH 6.0 and 40 degrees C and had a specific activity of 1485 U mg of protein(-1) against genistin. The ICHG readily hydrolyzed rho-nitrophenyl-beta-glucoside, rho-nitrophenyl-beta-galactoside, genistin, daidzin, with Km values of 1.64, 1.87, 0.012, 0.014 mM, respectively. The ICHG showed a pronounced specificity for glucose in the 7-position of isoflavone and flavone conjugates and hydrolyzed effectively malonyl isoflavone glucosides as well as isoflavone glucosides with similar kinetics. Glucose and glucono-delta-lactone inhibited the enzyme competitively with Ki values of 84 mM and 23 mM, respectively. The enzyme did not require divalent cations for activity, and its activity was strongly inhibited by Hg2+, Ag+, rho-chloromercuribenzoate, iodoacetic acid, and N-ethylmaleimide while reducing agents such as beta-mercaptoethanol, dithiothreitol, dithioerythritol, glutathione slightly activated the enzyme.

Competitive Nucleation and Growth of {111} Ω with {001} GP Zones and θ′ in a Stress-Aged Al-Cu-Mg-Ag Alloy

The stress aging method was conducted for an Al-Cu-Mg-Ag polycrystalline alloy to study the competitive nucleation and growth behavior of GP zones, θ' and Ω precipitates concurrently existing on different {001} and {111} habit planes. After initial stress aging for 1 h, the preferential nucleation of GP zones against Q occurred irrespective of the stress direction applied to the grains. With increasing aging time, the density of Ω increased while the GP zones decreased in number to dissolve into the matrix, resulting from competitive nucleation due to the mutual constituent of Cu in GP zones and Q. With further stress aging, the growth of θ' plates was enhanced in comparison with the growth of Ω plates. The relative number density change between [001} and {111} precipitates was emphasized especially in grains with the stress direction along [001], which indicated that nucleation and growth of GP zones and θ' plates were highly sensitive to external stress compared with that of Ω. HREM observation found that low amounts of small Ω plates were nucleated during the initial stress aging indicating retarded Ω nucleation. Two-step aging (stress aging for 1 h followed by the stress-free aging) revealed that preferentially nucleated GP zone against Ω during the initial stress aging determined the successive precipitation sequence of the precipitation of Ω and θ'.

Sulfuric Acid Technology for Processing of Eudialyte Concentrate

Sulfuric acid decomposition of eudialyte was studied, and a technological process including two-stage treatment with sulfuric acid, separation and washing of an insoluble residue, successive hydrolytic precipitation of zirconium and iron-manganese concentrates from solution, and recovery of rare-earth elements from the insoluble residue by leaching, was considered. It was found that zirconium(IV) is recovered from a complex carbonate precipitate in the form of a basic sulfate.

Structural characterization of a galactomannan from the cyanolichen Leptogium azureum

A galactomannan was isolated from the cyanolichen Leptogium azureum via successive alkaline extraction and precipitation with Fehling solution. The structure of the polysaccharide was investigated using NMR spectroscopy, methylation analysis, Smith degradation, and HPSEC-MALLS. As galactomannans from other lichens species, the polymer obtained presents a (1→6)-linked main chain of α-mannopyranose, substituted preferentially at O-2 by α-Man p or β-Gal p non-reducing ends. As observed in previous investigations, the C-1 region of the 13C-NMR of these heteropolysaccharides are typical of some lichens species, and can be used as fingerprints in chemotaxonomy. However, in despite of the general structure in common, the substitution level of this structure and their content of mannose is higher than of the others galactomannans obtained of lichenized fungi contained the green alga of the genus Trebouxia.

Binding of Zona Binding Inhibitory Factor-1 (ZIF-1) from Human Follicular Fluid on Spermatozoa

Previous studies showed that zona binding inhibitory factor-1 (ZIF-1) was the glycoprotein mainly responsible for the spermatozoa zona binding inhibitory activity of human follicular fluid. ZIF-1 has a number of properties similar to glycodelin-A. A binding kinetics experiment in the present study demonstrated the presence of two binding sites of ZIF-1 on human spermatozoa. These binding sites were saturable, reversible, and bound to (125)I-ZIF-1 in a time-, concentration-, and temperature-dependent manner. Glycodelin-A shared one common binding site with ZIF-1 on spermatozoa, and it could displace only 70% of the (125)I-ZIF-1 bound on human spermatozoa. ZIF-1 and glycodelin-A formed complexes with the soluble extract of human spermatozoa. Coincubation of solubilized zona pellucida proteins reduced the binding of ZIF-1 to two complexes of the extract, suggesting that the ZIF-1 binding sites and zona pellucida protein receptors on human spermatozoa were closely related. ZIF-1, but not glycodelin-A, significantly suppressed progesterone-induced acrosome reaction of human spermatozoa. The carbohydrate moieties derived from ZIF-1 reduced the binding of native ZIF-1 on human spermatozoa as well as the zona binding inhibitory activity of the glycoprotein, although the intensity of the effects are lower when compared with the native protein. These effects are not due to the action of the molecules on the motility, viability, and acrosomal status of the treated spermatozoa. Deglycosylated ZIF-1 had no inhibitory effect on both ZIF-1 binding and zona binding capacity of spermatozoa. We concluded that the carbohydrate part of ZIF-1 was critical for the functioning of the glycoprotein.

The presence of partially 3- O-methylated mannogalactan from the fruit bodies of edible basidiomycetes Pleurotus ostreatus ‘ florida’ Berk. and Pleurotus ostreatoroseus Sing

The partially 3- O-methylated mannogalactans were isolated from the fruiting bodies of edible basidiomycetes Pleurotus ostreatus ‘ florida’ Berk. and Pleurotus ostreatoroseus Sing. They were obtained via successive aqueous extraction, freeze thawing, and precipitation with Fehling solution and then investigated using 13C- and 1H-nuclear magnetic resonance spectroscopy (including COSY, TOCSY and HMQC techniques), methylation analysis and Smith degradation. The main chain consisted of (1→6)-linked α- D-galactopyranosyl residues containing 3- O-Me-α- D-galactopyranoses, a part of these units being substituted in the position O-2 with β- D-mannopyranose residues. The heteropolysaccharides found were similar with differences only in the levels of the 3- O-Me-α- D-galactopyranoses residues. The presence of partially 3- O-methylated mannogalactan appears to be typical of Pleurotus spp.

Statistical Analysis of Differential Potentiometric Precipitation Titration Data for a Mixture of Three Heterovalent Ions Using Linear Characteristics

A computer-based method is proposed for data processing in the successive potentiometric precipitation titration of a three-component mixture of differently charged ions. It is based on a piecewise transformation of the titration curve into linear regression characteristics, the parameters of which determine the successive equivalence points and the solubility products of the precipitates formed in the course of titration to the accuracy of least-squares estimates. To implement the calculation algorithm, a DIFTITR2 program written in Turbo Pascal was developed. The method was tested on the titration of an artificial solution containing a mixture of Cd(II), Hg(II), and Te(IV) with diethyldithiocarbamate, using a chalcogenide Cd-selective or a glassy-carbon indicator electrode, and was used for the analysis of the main components in a semiconductor material, namely, a solid solution of mercury and cadmium tellurides. For concentrations of test ions in the model solution from 7.5 × 10–3 to 3 × 10–4 M, the RSD value varies from 0.01 to 0.3; the determination error does not exceed 6%. The RSD value for the semiconductor alloy lies in the range of from 0.002 to 0.01.

Effect of Preparation Conditions on the Phase Composition of ZrO2–Al2O3–CeO2 Powders

Data are presented on the phase composition of ZrO2–Al2O3–CeO2 powders containing 10, 30, and 70 mol %, prepared via coprecipitation and successive precipitation. The precipitation procedure is shown to have a strong effect on the phase composition of the heat-treated powders and the state (inter- or intracrystalline) of the T-ZrO2 phase, thereby changing its stability. At an Al2O3 content of 30 mol %, the M-ZrO2 content is independent of the precipitation procedure.

Aqueous sulphur dioxide leaching of Cu, Ni, Co, Zn and Fe from smelter slag in absence of oxygen

AbstractSmelter slag and sulphur dioxide are waste products of non‐ferrous pyrometallurgical processes. Dissolution behaviour of Co, Cu, Fe, Ni and Zn from smelter slag in aqueous sulphur dioxide was studied. Experiments were carried out in batch mode, under near ambient conditions. Under the conditions studied, 81% Co, 60% Fe, 35% Ni and 68% Zn extraction were achieved within 3 h, while Cu behaved very differently. The initial dissolution of Cu was rapid, but subsequent precipitation lowered its overall extraction. The precipitation of Cu was more temperature sensitive than its dissolution. At 65°C all the dissolved Cu was precipitated in 2.5 h. The successive precipitation was explained based on the solution chemistry of the Cu‐Fe‐S(IV) system. Dissolution kinetics of the other metals were evaluated using the shrinking core model. Diffusion through the product/ash layer appeared to be the rate controlling step. SEM‐EDS analysis was used to characterize the slag and to confirm the existence of a product/ash layer after leaching.

Synthesis of [32P]Phosphoramidate for Use as a Low Molecular Weight Phosphodonor Reagent

Phosphoramidate serves as a useful phosphodonor reagent in protein and peptide phosphorylation, notably in studying two-component signal transduction systems in which low molecular weight phosphodonors can substitute for the phosphodonor function of histidine protein kinases in in vitro phosphorylation studies of response regulator proteins. A convenient method for the synthesis of radiolabeled phosphoramidate has not been developed, and this has limited its broader use. Here we report the synthesis of radiolabeled ammonium hydrogen phosphoramidate [(NH4)H32PO3NH2] which is achieved by activation of [32P]orthophosphate with ethyl isocyanate followed by aminolysis with ammonium hydroxide to form the desired phosphoramidate. The procedure is conveniently carried out in a microfuge tube and requires only two successive precipitation steps to obtain pure ammonium hydrogen phosphoramidate. Molar yields of 15–30% and specific activities of 10–20 Ci/mol are readily achieved. Phosphorylation of microgram quantities of response regulator proteins CheY, CheB, and DrrA is shown. Low level, but detectable, nonspecific phosphorylation was observed for reactions near ambient temperatures when substrate response regulators lacking the active site aspartate but containing histidine residues are used. More significant levels of nonspecific phosphorylation were observed for reactions at elevated temperatures when using a nonresponse regulator control protein (RNase A).

Effect of precipitation conditions on the phase composition, particle morphology, and properties of iron(III,II) hydroxide precipitates

The phase composition and particle shape of amorphous iron hydroxide-iron oxide precipitates were correlated with the oxidation state of iron in the starting solution, Fe2O3 : FeO ratio, and precipitation procedure (coprecipitation or successive precipitation) using Mossbauer spectroscopy, atomic absorption, lowtemperature nitrogen BET, and electron microscopy data. A correlation was established between the amount of iron(II) in the starting solution, the amount of the metastable phase γ-Fe2O3 in the precipitate, particle shape, and the activity of the final heat-treatment products—α-Fe2O3 and mixed oxides of iron.