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PubMed2002

Enhanced drug dissolution using evaporative precipitation into aqueous solution.

A new process, evaporative precipitation into aqueous solution (EPAS) has been developed to coat poorly water soluble drugs, in this case carbamazepine, with hydrophilic stabilizers to enhance dissolution rates. A heated organic solution of the drug in dichloromethane is sprayed though a fine nozzle into a heated aqueous solution. The rapid evaporation of the organic solvent produces high supersaturation and rapid precipitation of the drug in the form of a colloidal suspension that is stabilized by a variety of low molecular weight and polymeric surfactants. The stabilizer adsorbs to the drug surface and prevents particle growth and crystallization during the spray process. The suspensions are dried by spray drying or ultra-rapid freezing. The high dissolution rates are a consequence of the following advantages of the EPAS process: a small primary particle size, a hydrophilic coating on the particles that enhances wetting, and low crystallinity.

Anticonvulsants↗
PubMed2002

Rifampicin microparticles production by supercritical antisolvent precipitation.

Semi-continuous supercritical antisolvent (SAS) precipitation has been used to produce Rifampicin micro- and nanoparticles with controlled particle size (PS) and particle size distribution (PSD). SAS experiments were performed using different liquid solvents. The best micronization results have been obtained using dimethyl sulfoxide (DMSO); using this solvent and operating at 40 degrees C, we obtained nanoparticles with mean diameters ranging from 0.4 to 1 microm at a pressure of 120 bar or more, and microparticles with mean diameters ranging from 2.5 to 5 microm at pressures between 90 and 110 bar. The morphology of Rifampicin precipitates was different too. Nanoparticles connected in small aggregates were obtained at pressures higher than 120 bar, whereas, spherical single microparticles were obtained operating at lower pressures. We also investigated the effect of the concentration of Rifampicin in the liquid solution on particles diameter: we observed that, increasing the liquid concentration, the mean PS increased and the PSD enlarged. XRD and HPLC analysis on treated Rifampicin showed that particles are amorphous and no degradation occurred as a consequence of supercritical processing. We attempted an explanation of the different morphologies observed considering the modification of the high pressure vapor-liquid equilibria of the ternary system Rifampicin-DMSO-CO(2) with respect to the behavior of the binary system DMSO-CO(2).

Antibiotics, Antitubercular↗
PubMed2003

Effect of beta-sitosterol on precipitation of cholesterol from non-aqueous and aqueous solutions.

The aim of the present work was to study the solubility and phase behaviour of the beta-sitosterol-cholesterol mixed crystals in the presence and absence of water. Cholesterol, beta-sitosterol and 3:1, 1:1 and 1:3 mixtures of these were co-precipitated from acetone and acetone-water solutions. Precipitated crystals were analysed using powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), optical microscopy and Karl-Fischer titrimetry. The quantification of the sterols in solutions was preformed using GC-MS. The solubility of the sterols was mutually limiting. In the aqueous system, the solubility of both the sterols were significantly lower than in the absence of water, but the decrease in the solubility was considerably greater with the more hydrophobic beta-sitosterol. In the aqueous system, the total sterol solubility decreased with the increasing proportion of beta-sitosterol. The formation of new crystal structures, solid solutions of cholesterol and beta-sitosterol, was observed in non-aqueous as well as in aqueous environments except with the lowest cholesterol proportion in the system, in which case mixed crystals with eutectic behaviour were formed.

Acetone↗
PubMed2001

Plasma deproteinization by precipitation and filtration in the 96-well format.

The need for fast bioanalytical methods within the pharmaceutical sector is rapidly growing. Sample preparation is often the bottleneck step. A new approach to increasing sample throughput involves precipitated protein removal by filtration in the 96-well format, thereby eliminating the need for centrifugation and manual handling of individual tubes. The potential for such a new technique has been investigated for the determination of an iron chelator, a highly protein-bound compound (> or =99.5%) in plasma. An analog was used as internal standard. Acetonitrile and plasma were sequentially aspirated, separated by an air gap, using a manual electronic pipettor. They were then dispensed into the channel of an Empore filter PPT plate above the filter, and a slight vacuum was applied. The eluate was collected and diluted prior to injection. The compounds were then separated by reversed-phase chromatography and detected by UV at 295 nm. The chromatographic run time was 6 min. The mean recovery following protein precipitation was 78%, which shows that the technique can apply to a highly protein-bound compound. Replicate quality control samples were prepared in drug-free normal human plasma at four different concentrations. The mean accuracy ranged from 87 to 108% with the CV ranging from 3 to 8%. The described procedure is simple, fast and reproducible. It requires minimal equipment. The time required to prepare a plate manually is only about 20 min. The use of 12-channel repeater pipettors reduces the risk of error and improves productivity. Automation should be an aid to further increasing sample throughput when more than one plate a day is to be prepared.

Benzoates↗
PubMed1998

Two major proteins from locust plasma are involved in coagulation and are specifically precipitated by laminarin, a beta-1,3-glucan.

Incubation of plasma of the locust Locusta migratoria, with laminarin induced the precipitation of two major proteins with molecular masses of about 260,000 (P260) and 85,000 Da (P85). This precipitation was not observed when other polysaccharides, such as curdlan, dextran, chitin, cellulose or mannan were used. P260 and P85 were purified to homogeneity by a single step on heparin-sepharose chromatography. Since all attempts to separate P260 from P85, other than the use of sodium dodecyl sulfate, were unsuccessful, it is likely that these two molecules form a complex non-covalently associated. Treatment of P260-P85 complex with N-glycosidase F showed that P260 did not appear to be glycosylated whereas 6% of P85 molecular mass was due to N-linked carbohydrates. On the other hand, no change in molecular masses of P260 or P85 was observed once the complex had been treated with lipase. SDS-PAGE and Western blots of plasma and serum stained with blue Coomassie for proteins or with highly specific polysera to P260 or P85, respectively, showed that P260 was only present in plasma and P85 remained in both samples. This indicates that P260 is likely to be one of the most abundant plasma proteins directly involved in the coagulation process in Locusta migratoria. The addition of plasma or P260-P85 complex to a hemocyte lysate supernatant prior to its activation by laminarin induced a lower protease as well as phenoloxidase activity compared with the control. This reduction of activities was not observed in the presence of serum or when P260-P85 complex was added to a fully activated proPO system.

Amino Acid Sequence↗
PubMed1999

Protein precipitation: an expedient procedure for the routine analysis of the plasma metabolites of [123I]IBZM.

Plasma metabolite analysis of the single photon emission computed tomography (SPECT) D2/D3 receptor radiotracer (S)(-)-N-[(1-ethyl-2-pyrrolidinyl)methyl]-2-hydroxy-3-[123I]iodo-6-metho xybenzamide ([123I]IBZM) is needed for the equilibrium analysis of the SPECT data, in brain imaging studies involving bolus plus constant infusion paradigm. The purpose of these experiments was to find an appropriate procedure to expedite this analysis during routine determinations. The procedure was applied to the plasma analysis of 22 human subjects. Each plasma sample was subjected to acetonitrile protein precipitation. After separation of the pellet, the acetonitrile fraction contained 91% +/- 2% (n = 88) of the mixture of labeled metabolites and parent compound. The recovery coefficient of unmetabolized [123I]IBZM determined with an standard plasma sample was 95% +/- 2% (n = 22). The percent parent compound present in the extracted fraction, measured by high performance liquid chromatography, was 16% +/- 9% (n = 85) and the percent metabolites was 84% +/- 9% (n = 85). Free fraction determination (f1, fraction of radiotracer unbound to protein), was 4% +/- 0.8% (n = 22). Free fraction of parent was 15% +/- 8% (n = 85). The results indicate that acetonitrile protein precipitation is an adequate method for the analysis of the [123I]IBZM plasma metabolites.

Acetates↗
PubMed2003

kappa-Carrageenan as a carrier in affinity precipitation of yeast alcohol dehydrogenase.

kappa-Carrageenan is a non-toxic polymer from seaweeds, which becomes reversibly insoluble upon the addition of K(+). Its conjugate with the dye, Cibacron Blue 3GA, was used to purify alcohol dehydrogenase from crude yeast extract by affinity precipitation. Response surface methodology was used to optimize conditions for affinity precipitation of the enzyme with the polymer-dye conjugate. Recovery of 58% of the enzyme activity with 13.6-fold purification was obtained.

Alcohol Dehydrogenase↗
PubMed2000

Higher throughput bioanalysis by automation of a protein precipitation assay using a 96-well format with detection by LC-MS/MS.

Generic methodology for the automated preparation and analysis of drug levels in plasma samples within a drug discovery environment was achieved through the redesign of a protein precipitation assay to a microtiter (96-well) plate format and the application of robotic liquid handling for performance of all transfer and pipetting steps. Validation studies revealed that the application of robotics to sample preparation, in general, maintained the analytical accuracy and precision compared with preparing samples manually. The use of rapid gradient LC-MS/MS for analysis coupled with flow diversion of the solvent front allowed the introduction of protein-precipitated samples into the mass spectrometer without the necessity for source cleaning. The problem inherent in automatically pipetting plasma, caused by fibrinogen clots, was overcome by storing samples at -80 degrees C and thus precluding clot formation. The resulting methodology allowed sample preparation for a 96-well plate designed to accommodate 54 unknowns, duplicate 12-point calibration curves, and 6 sets of quality controls at three levels in approximately 2 h. This approach allowed an increase in throughput of sample preparation and analysis to >400 samples per day per LC-MS/MS instrument with minimal manual intervention. Overall, substantial time savings were realized, demonstrating that automation is an increasingly essential tool in a drug discovery bioanalytical environment.

Automation↗
PubMed2001

Amyloid-induced aggregation and precipitation of soluble proteins: an electrostatic contribution of the Alzheimer's beta(25-35) amyloid fibril.

Amyloid-induced aggregation and precipitation of soluble proteins were investigated in vitro using the amyloid fibrils of the beta(25--35) peptide, a cytotoxic fragment of the Alzheimer's beta-peptide at positions 25--35. The aggregation rate of firefly luciferase was found to be modulated by both a chaperone molecule DnaK and the beta(25--35) amyloid, but their effects were opposite in direction. The amyloid fibril drastically facilitated the luciferase aggregation, which may define a kind of anti-chaperone activity. The effect of the beta(25--35) amyloid to promote protein aggregation and precipitation was further demonstrated for a wide variety of target proteins. The amount of coprecipitation was well correlated with the predicted isoelectric point of the target proteins, indicating that the interaction between the beta(25--35) amyloid and the target was driven by an electrostatic force between them. This view was confirmed by the experiments using an electrically neutral mutant peptide, beta(25--35)KA. It was also found that clustering of the beta(25--35) peptide to form amyloid and the conformation of the target protein are additional factors that determine the strength of the amyloid-protein interaction. Spectroscopic and electron microscopic methods have revealed that the proteins coprecipitated with the beta(25--35) amyloid formed amorphous aggregates deposited together with the amyloid fibrils. The conformation of protein molecules left in the residual soluble fraction was also damaged in the amyloid-containing solution. As a summary, this study has proposed a scheme for events related to the nonspecific amyloid-protein interaction, which may play substantial roles in in vivo conditions.

Alzheimer Disease↗
PubMed1983

Quasi-elastic light-scattering studies of aqueous biliary lipid systems. Cholesterol solubilization and precipitation in model bile solutions.

We have employed quasi-elastic light-scattering methods to characterize micellar aggregates and microprecipitates formed in aqueous solutions containing sodium taurocholate (TC), egg lecithin (L), and cholesterol (Ch). Particle size and polydispersity were studied as functions of Ch mole fraction (XCh = 0-15%), L/TC molar ratio (0-1.6), temperature (5-85 degrees C), and total lipid concentration (3 and 10 g/dL in 0.15 M NaCl). For XCh values below the established solubilization limits (XChmax) [Carey, M. C., & Small, D. M. (1978) J. Clin. Invest. 61, 998], added Ch has little influence on the size of simple TC micelles (type 1 systems), on the coexistence of simple and mixed TC-L micelles (type 2 systems), or on the growth of "mixed disc" TC-L micelles (type 3 systems). For supersaturated systems (XCh/XChmax greater than 1), 10 g/dL type 1 systems (L/TC = 0) exist as metastable micellar solutions even at XCh/XChmax = 5.3. Metastability is decreased in type 2 systems (0 less than L/TC less than 0.6), and "labile" microprecipitation occurs when XCh/XChmax exceeds approximately 1.6. In 10 g/dL mixtures, the microprecipitates initially range in size from 500 to 20000 A and later coalesce to form a buoyant macroscopic precipitate phase. In 3 g/dL mixtures, the microprecipitates are smaller (200-400 A) and remain as a stable, noncoalesced microdispersion. Transmission electron microscopy of the microprecipitates formed at both concentrations indicates a globular noncrystalline structure, and lipid analysis reveals the presence of cholesterol and lecithin in a molar ratio (Ch/L) of approximately 2/1, suggesting that the microprecipitates represent a metastable cholesterol-rich liquid-crystalline phase. In supersaturated type 3 systems (0.6 less than L/TC less than 2.0), the precipitate phase is a lecithin-rich liquid-crystalline phase which likewise coalesces in a 10 g/dL system but forms stable vesicle (liposomal) structures (600-800 A radius) in 3 g/dL systems. In conjunction with these experimental data, we present a quantitative thermodynamic analysis of Ch solubilization in model bile systems from which rigorous deductions of the free energy and enthalpy change for solubilization of cholesterol monohydrate in type 1 and type 2 systems are obtained. In addition, we employ homogeneous nucleation theory to analyze the origin of the metastable/labile limit in supersaturated systems and to deduce the interfacial tension between microprecipitates and solution. On the basis of these experimental data and theoretical analyses, we offer new hypotheses on the structure and physiology of bile and the pathogenesis of Ch gallstones. In particular, it is suggested that the "stable" microprecipitates observed in 3 g/dL type 2 systems may provide a secondary vehicle (in addition to micelles) for cholesterol transport in supersaturated hepatic bile.

Bile↗
PubMed1977

Purification using polyethylenimine precipitation and low molecular weight subunit analyses of calf thymus and wheat germ DNA-dependent RNA polymerase II.

DNA-dependent RNA polymerase II from calf thymus has been successfully purified using polythylenimine precipitation. Thus, 5-6 mg of nearly homogeneous homogeneous trna polymerase II (greater than 96% pure) can be prepared from 1 kg of calf thymus with three chromatography steps following extraction and precipitation of the enzyme from the polyethylenimine pellet. This procedure eliminates the high salt extraction of chromatin previously used in purification of this enzyme and makes possible the large scale preparation of mammalian RNA polymerase II. Calf thymus polymerase II prepared by this method is greater than 90% form IIb and consists of ten different subunits having the following molecular weights: 180 000; 145 000; 36 000; 25 000; 20 000; 18 500; 16 000; 15 000; 12 000; 11 500. The homologous enzyme isolated from wheat germ is greater than 90% form IIa and contains subunits of the following molecular weights: 206 000; 145 000; 44 000-47 000; 24 500; 21 000; 19 000; 17 000; 14 000; 13 500. The wheat germ and calf thymus enzymes exhibit similar subunits structures, but the molecular weights of individual subunits are clearly different between the enzymes. Wheat germ RNA polymerase II is 50% inhibited by 0.271 microng/mL of alpha-amanitin, a level 30-fold higher than that found for calf thymus RNA polymerase II. These enzymes are further distinguished by the absence of antigenic cross reactivity.

Animals↗
PubMedDate not supplied

Selective flocculation and precipitation for the improvement of virus-like particle recovery from yeast homogenate.

The purification of an intracellular product from a complex mixture of contaminants after cell disruption is a common problem in processes downstream of fermentation systems. This is particularly challenging for the recovery of particulate (80 nm in diameter) multimeric protein products, named virus-like particles (VLPs), from cell debris and other intracellular components. Selective flocculation for debris removal followed by selective precipitation of the target protein can be used as a preclarification step to aid purification. In this paper, selective borax flocculation of cell debris in yeast homogenate, followed by selective poly(ethylene glycol) precipitation of VLPs are defined with a view to demonstrating their potential in aiding the initial clarification stages of the purification sequence. The translation from laboratory scale to pilot scale operation is addressed, demonstrating the challenge of scale-up of solid-liquid separation stages for biological particle processing.

Borates↗
PubMed2003

Mineralogical characterization of arsenic in uranium mine tailings precipitated from iron-rich hydrometallurgical solutions.

Arsenic-rich uranium mine tailings from the Rabbit Lake in-pit tailings management facility (RLITMF) in northern Saskatchewan, Canada, were investigated to determine the mineralogy and long-term stability of secondary arsenic precipitates formed from iron-rich hydrometallurgical solutions. Total arsenic and iron concentrations in six iron-rich samples of the mine tailings ranged from 56 to 6,000 microg/g and from 12 600 to 30 200 microg/g, respectively (Fe/As molar ratios of 5.3-303). On the basis of stability field diagrams generated from pH, Eh, and temperature measurements on tailings samples (mean values of 9.79, +162 mV, and 2.8 degrees C, respectively), it was concluded that arsenic and iron in the tailings were stable as As5+ and Fe3+. Synchrotron-based X-ray absorption spectroscopic studies of tailings samples, fresh mill precipitates, and reference compounds showed that the arsenic in iron-rich areas of the tailings existed as the stable As5+ and was adsorbed to 2-line ferrihydrite through inner-sphere bidentate linkages. Furthermore, under the conditions in the RLITMF, the 2-line ferrihydrite did not undergo any measurable conversion to more crystalline goethite or hematite, even in tailings discharged to the RLITMF 10 yr prior to sampling.

Arsenic↗
PubMed2003

Electrostatic precipitator collection efficiency and trace element emissions from co-combustion of biomass and recovered fuel in fluidized-bed combustion.

Particle and trace element emissions from energy production have continuously been subject to tightening regulations. At the same time, not enough is known on the effect of different combustion processes and different fuels and fuel mixtures on the particle characteristics and particle removal device operation. In this investigation, electrostatic precipitator fractional collection efficiency and trace metal emissions were determined experimentally at a 66 MW biomass-fueled bubbling fluidized-bed combustion plant. The measurements were carried out at the inlet and outlet of the two-field electrostatic precipitator (ESP) at the flue gas temperature of 130-150 degrees C. Two fuel mixtures were investigated: biomass fuel containing 70% wood residue and 30% peat and biomass with recovered fuel containing 70% wood residue, 18% peat, and 12% recovered fuel. The particle mass concentration at the ESP inlet was 510-1400 mg/Nm3. Particle emission at the ESP outlet was 2.3-6.4 mg/Nm3. Total ESP collection efficiency was 99.2-99.8%. Collection efficiency had a minimum in particle size range of 0.1-2 microm. In this size range, collection efficiency was 96-97%. The emission of the trace metals As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb, Tl, and V was well below the regulation values set by EU directive for waste incineration and co-incineration.

Air Pollutants↗
PubMed2004

In situ metal precipitation in a zinc-contaminated, aerobic sandy aquifer by means of biological sulfate reduction.

The applicability of in situ metal precipitation (ISMP) based on bacterial sulfate reduction (BSR) with molasses as carbon source was tested for the immobilization of a zinc plume in an aquifer with highly unsuitable initial conditions (high Eh, low pH, low organic matter content, and low sulfate concentrations), using deep wells for substrate injection. Batch experiments revealed an optimal molasses concentration range of 1-5 g/L and demonstrated the necessity of adding a specific growth medium to the groundwater. Without this growth medium, even sulfate, nitrogen, phosphorus, and potassium addition combined with pH optimization could not trigger biological sulfate reduction. In column experiments, precipitation of ZnS(s) was induced biologically as well as chemically (by adding Na2S). In both systems, zinc concentrations dropped from about 30 mg/L to below 0.02 mg/L. After termination of substrate addition the biological system showed continuation of BSR for at least 2 months, suggesting the insensitivity of the sulfate reducing system for short stagnations of nutrient supply, whereas in the chemical system an immediate increase of Zn concentrations was observed. A pilot experiment conducted in situ at the zinc-contaminated site showed a reduction of zinc concentrations from around 40 mg/L to below 0.01 mg/L. Termination of substrate supply did not result in an immediate stagnation of the BSR process, but continuation of BSR was observed for at least 5 weeks.

Aerobiosis↗
PubMed2003

Modeling precipitation and sorption of elements during mixing of river water and porewater in the Coeur d'Alene River basin.

Reddish brown flocs form along the edge of the Coeur d'Alene River when porewater drains into river water during the annual lowering of water level in the basin. The precipitates are efficient scavengers of dissolved elements and have characteristics that may make metals associated with them bioavailable. This work characterizes the geochemistry of the porewater and models the formation and composition of the flocs. Porewater is slightly acidic, has suboxic to anoxic characteristics, tends to have higher alkalinity, and contains elevated concentrations of many constituents relative to river water. Laboratory mixing experiments involving porewater and river water were done to produce the precipitates. Thermodynamic predictions using PHREEQC indicate that predicted amounts of ferrihydrite and gibbsite agree with removal of Fe and Al. Predictions of element removal by adsorption onto ferrihydrite are consistent with observed removal using a combination of surface complexation constants for the generalized two-layer model (As and Se), alternative surface constants derived from experiments at high sorbate-to-sorbent ratios (Cd, Co, Cu, Ni, Pb, and Zn), and adjusted surface constants to fit experimental data (Cr, Mo, and Sb). This new set of surface complexation constants needs further testing in other contaminated systems.

Chemical Precipitation↗
PubMed2004

X-ray absorption spectroscopic evidence for the formation of Pb(II) inner-sphere adsorption complexes and precipitates at the calcite-water interface.

Combined batch sorption and in situ X-ray absorption spectroscopy provide direct assessment of the mechanisms for Pb(II) sorption atthe calcite--water interface under low-temperature conditions. At low metal concentration, 1 microM initial Pb, X-ray absorption fine structure data indicate the formation of Pb mononuclear inner-sphere complexes at the surface. A first-shell Pb-O bond length of 2.34 A is consistent with nearest oxygen neighbors in 3- or 4-fold coordination with a distorted trigonal pyramidal or square pyramidal geometry with a stereochemically active electron lone pair. For high initial Pb concentrations, 20 and 60 microM Pb, precipitation of hydrocerussite and cerussite secondary phases dominates Pb partitioning. At 5 and 10 microM initial Pb, the sorption mechanism is dual in nature with persistence of the mononuclear adsorption complex combined with precipitation of a cerussite phase occurring prior to saturation of theoretically available surface sites. The formation of inner-sphere complexes implies strong metal interactions with the surface-the mechanistic reason for the affinity of Pb for calcite as observed in macroscopic studies. The geometry of the adsorbed complex can influence Pb coprecipitation, as a change to octahedral coordination is required for incorporation into calcite. The results provide the basis for predictions of Pb sequestration by calcite in natural systems.

Adsorption↗
PubMed2004

Characterizing dependence of pesticide load in surface water on precipitation and pesticide use for the Sacramento River watershed.

Transport of pesticides by surface runoff during rainfall events is a major process contributing to pesticide contamination in rivers. This study presents an empirical regression model that relates pesticide loading over time in the Sacramento River with the precipitation and pesticide use in the Sacramento River watershed. The model closely simulated loading dynamics of diazinon, simazine, and diuron during 1991-1994 and 1997-2000 winter storm seasons. The coefficients of determination for regression ranged from 0.168 to 0.907, all were significant at <0.001. The results of this study provide strong evidence that precipitation and pesticide use are the two major environmental variables dictating the dynamics of pesticide transport into surface water in a watershed. The capability of the statistical model to provide time-series estimates on pesticide loading in rivers is unique and may be useful fortotal maximum daily load (TMDL) assessments.

Agriculture↗