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PubMed2005

Rare-earth containing nanocrystal precipitation and up-conversion luminescence in oxyfluoride glasses.

Rare-earth ion doped oxyfluoride glass with a composition of 25SiO2 x 5GeO2 x 15AIO1.5 x 40PbF2 x 10PbO x (4.9 - x)GdF3 x 0.1HoF3 x xYbF3 (x = 0, 0.1,0.2, 0.5,1,2, 3, and 4) in molar ratio was developed. When the oxyfluoride glasses are heat-treated at the first crystallization temperature, the glasses give transparent glass-ceramics in which rare-earth-containing fluorite-type nanocrystals of about 17.2 nm in diameter uniformly precipitated in the glass matrix. Comparing with the glasses before heat treatment, the glass ceramics exhibit very strong up-conversion luminescence under 980-nm light excitation. Rare-earth-containing nanocrystals were also space selectively precipitated upon laser irradiation in an oxyfluoride glass; the size of precipitated nanocrystals can be controlled by laser power and scan speed. The intensity of the green up-conversion luminescence is strongly dependent on the precipitation of beta-PbF2 nanocrystals and the YbF3 concentration. The reasons for the highly efficient Ho3+ up-conversion luminescence are discussed.

Crystallization↗
PubMed1981

Evaluation of the polyethylene glycol precipitation method for the estimation of high-density lipoprotein cholesterol.

Treatment of fresh sera with polyethylene glycol 6000 at a final concentration of 100 g/l produced selective precipitation of low-density lipoproteins with only traces of contamination with high-density lipoproteins, as determined by electroimmunoassay using antisera to human alpha1-lipoprotein and human beta-lipoprotein. Supernatants collected for high-density lipoprotein-cholesterol estimation were free from low-density lipoproteins. Precipitates sedimented readily from specimens with high triglyceride contents, and secondary precipitation during enzymatic cholesterol determinations was absent. Values obtained by this method correlated well with those obtained by precipitation of low-density lipoproteins with heparin and manganous ions at concentrations optimal for discrete of lipoprotein classes (r = 0.975; p less than 0.001).

Chemical Precipitation↗
PubMed1992

Nephelometric determination of total protein in cerebrospinal fluid and urine using benzalkonium chloride as precipitation reagent.

Four different protein precipitants, namely trichloroacetic acid, sulphosalicylic acid, benzethonium chloride and benzalkonium chloride, were used to estimate the total protein concentration in cerebrospinal fluid and urine by nephelometry. Protein determinations for 50 cerebrospinal fluid samples and 100 urine samples were compared with values obtained by a trichloroacetic acid-Ponceau S spectrophotometric method. All methods were correlated well, but total protein results using acid precipitants were usually lower, while results obtained using benzethonium chloride were generally higher, than results obtained by the trichloroacetic acid-Ponceau S method. Anomalous results were obtained for some urine samples with benzethonium chloride, but not with benzalkonium chloride. Assays using benzalkonium chloride as precipitating reagent showed good precision and closest agreement with the trichloroacetic acid-Ponceau S dye-binding method. The use of benzalkonium chloride as precipitant is recommended for automated cerebrospinal fluid and urine protein estimations by nephelometry.

Benzalkonium Compounds↗
PubMed1992

Silica-induced precipitation of calcium phosphate in the presence of inhibitors of hydroxyapatite formation.

The promotion and the inhibition of hydroxyapatite formation by various substances were determined by measurement of the induction time of spontaneous precipitation (ti) from supersaturated solutions. Silica was found to decrease ti in Hepes-buffered (pH 7.2) supersaturated solutions with a wide range of calcium-to-phosphate ratios and concentrations. Also, in suspensions of the oral bacteria S. mutans or C. matruchotii in 1 mmol/L calcium, 7.5 mmol/L phosphate, and 50 mmol/L Hepes (pH 7.2), silica was capable of stimulating precipitation. Macromolecules derived from these bacteria by freezing and thawing appeared to be strong inhibitors of calcium phosphate precipitation. In the presence of silica, the effects of these bacterial inhibitors could be partially overcome, which supports the idea that silica in dental plaque is a promoter of calculus formation. In contrast, inhibition of calcium phosphate precipitation by a low-molecular-weight inhibitor, pyrophosphate, could not be counteracted by silica.

Bacterial Proteins↗
PubMedDate not supplied

Protein precipitation In Vitro as a measure of chemical-induced cytotoxicity: an EDIT sub-programme.

As a priority area of the Evaluation-Guided Development of In Vitro Toxicity and Toxicokinetic Tests (EDIT) programme, an in vitro protein precipitation (PP) assay was used on the 50 reference chemicals of the Multicentre Evaluation of In Vitro Cytotoxicity (MEIC) project, to confirm and extend the MEIC results. Dose-response curves were generated for only 30 of the chemicals, and the concentrations causing 10% (EC10) and 50% (EC50) protein precipitation versus the positive control were chosen as endpoints. The number of chemicals with a positive response increased to 46 when a new endpoint, the minimum effect concentration (MEC) that induces protein precipitation with respect to the negative control, was used. When the results were correlated with in vitro cytotoxicity in human cell lines, a similarly good correlation was found between the various endpoints of the PP assay at 5 hours and the 24-hour IC50 average cytotoxicity in human cell lines, even though the number of chemicals included in the correlation was larger for the MEC. Using the prediction error, the endpoint that gave the best correlation between the PP assay and human cell cytotoxicity was once more found to be the 5-hour MEC, and this was chosen for the PP assay. The sensitivity of the PP assay is lower than that of the in vitro cell-line cytotoxicity assay, possibly due to its shorter exposure period and because precipitation is the ultimate event in the sequence of a protein disturbance. It is expected that earlier denaturation steps would give better sensitivity. However, this simple, inexpensive and rapid assay could be useful in the early stages of testing chemicals.

Cell Line↗
PubMed2004

Polyethylene glycol-induced precipitation of interferon alpha-2a followed by vacuum drying: development of a novel process for obtaining a dry, stable powder.

Feasibility studies were performed on the development of a novel process based on polyethylene glycol (PEG)-induced precipitation of proteins followed by vacuum drying in the presence of sugars to obtain dry protein powders. Apparent solubility of interferon alpha-2a (IFNalpha2a) was determined in the presence of various PEGs and the effect of solution pH, ionic strength, and temperature was investigated. IFNalpha2a precipitate was dried at a shelf temperature of 25 degrees C at 100 mTorr either as it is or in the presence of mannitol and/or trehalose. The dried IFNalpha2a formulations were subjected to accelerated stability studies at 40 degrees C (3 months), and the stability was compared with that of a similar lyophilized formulation. The results indicated that more than 90% of the protein could be precipitated using 10% wt/vol PEG 1450 at pH 6.5 at a solution ionic strength of 71 mM. Vacuum drying of the precipitate only resulted in the formation of insoluble aggregates of IFNalpha2a; however, this was prevented by the addition of either mannitol or trehalose. The addition of excess mannitol resulted in low residual moisture content and better handling of the final dried product. Accelerated storage stability did not show any aggregation and showed less than 5% formation of oxidized IFNalpha2a in the dried formulation containing IFNalpha2a:trehalose:mannitol in a 1:10:100 wt/wt ratio upon storage at 40 degrees C for 3 months. The stability of this vacuum dried formulation was comparable with that of a similar lyophilized formulation.

Chemical Precipitation↗
PubMed1984

Determination of LDL cholesterol and LDL apolipoprotein B following precipitation of VLDL in blood serum with phosphotungstic acid/MgCl2.

A method is described for the selective precipitation of VLDL in blood serum using phosphotungstic acid/MgCl2. The method allows for the calculation of LDL apolipoprotein B as well as for the calculation of LDL cholesterol (following the additional determination of HDL cholesterol). Dependent on the triglyceride and the cholesterol content of the serum, three different procedures were developed using phosphotungstic acid and MgCl2 in different concentrations in the precipitation assay. Within the tested range of 3-10 mmol/l total cholesterol and 1-4 mmol/l triglyceride in blood serum the VLDL were nearly completely precipitated with negligible coprecipitation of LDL and HDL, but 40-50% coprecipitation of Lp(a). Regression analysis of the cholesterol values obtained by precipitation with phosphotungstic acid/MgCl2 (= serum cholesterol - LDL cholesterol), and the cholesterol values obtained by ultracentrifugation (d greater than 1.006 kg/l) revealed a good measure of agreement (r = 0.97, y = 0.93 X + 0.35, n = 76). An equally good measure of agreement was found for the corresponding apolipoprotein B values (r = 0.96, y = 1.03 X - 0.2, n = 61). In the determination of LDL cholesterol a variation coefficient of 4.3% (n = 20) was found in relation to the precision in the series, and a variation coefficient of 4.8% (n = 25) in relation to day to day precision.

Apolipoproteins↗
PubMed2003

Crying as a precipitating factor for migraine and tension-type headache.

CONTEXT: Scarcely reported in the literature, crying seems to be an important precipitating factor for both migraine and tension-type headache in daily practice. OBJECTIVE: To evaluate the role of crying as a precipitating factor for migraine and tension-type headache. TYPE OF STUDY: Prospective evaluation. PARTICIPANTS: 163 workers or students from the Universidade Metropolitana de Santos, who presented at least one attack a month, for at least one year, of either migraine or tension-type headache. PROCEDURES: Interview by means of questionnaires and personal evaluations. Details of precipitating factors for the attacks were assessed. RESULTS: From the total group of 163 individuals, 90 (55.2%) considered crying to be a potential factor for triggering headache attacks. Of this group of 90 persons, 62 presented migraine (6 males, 56 females) and 28 presented tension-type headache (5 males, 23 females). Only stress, anxiety and menstrual periods rated higher or equal to crying as triggering factors for both types of headache. CONCLUSIONS: The physiology of crying is not well documented or understood. The act of crying seems to be an important precipitating factor for primary headaches and it should be studied further. The authors welcome comments on the matter and would like to work in collaboration with other groups interested in this subject.

Adolescent↗
PubMed2001

Precipitation and temperature effects on populations of Aedes albopictus (Diptera: Culicidae): implications for range expansion.

We investigated how temperature and precipitation regime encountered over the life cycle of Aedes albopictus (Skuse) affects populations. Caged populations of A. albopictus were maintained at 22, 26, and 30 degrees C. Cages were equipped with containers that served as sites for oviposition and larval development. All cages were assigned to one of three simulated precipitation regimes: (1) low fluctuation regime - water within the containers was allowed to evaporate to 90% of its maximum before being refilled, (2) high fluctuation regime - water was allowed to evaporate to 25% of its maximum before being refilled, and (3) drying regime - water was allowed to evaporate to complete container dryness before being refilled. Greater temperature and the absence of drying resulted in greater production of adults. Greater temperature in combination with drying were detrimental to adult production. These precipitation effects on adult production were absent at 22 degrees C. Greater temperatures and drying treatments yielded higher and lower eclosion rates, respectively and, both yielded greater mortality. Development time and size of adults decreased with increased temperatures, and drying produced larger adults. Greater temperatures resulted in greater egg mortality. These results suggest that populations occurring in warmer regions are likely to produce more adults as long as containers do not dry completely. Populations in cooler regions are likely to produce fewer adults with the variability of precipitation contributing less to variation in adult production. Predicted climate change in North America is likely to extend the northern distribution of A. albopictus and to limit further its establishment in arid regions.

Aedes↗
PubMed2002

Affinity precipitation separation of DNA binding protein using block conjugate composed of poly(N-isopropylacrylamide) grafted double-stranded DNA and double-stranded DNA containing a target sequence.

In this research, we synthesized a novel DNA-polymer conjugate and evaluated its application to an affinity precipitation separation of TATA-box binding protein (TBP), which is a representative general transcription factor. The conjugate was composed of two fractions. One was a double-stranded DNA modified by the grafting of poly(N-isopropylacrylamide) (PNIPAAm), which is known as a thermosensitive vinyl polymer. The other fraction is a native double-stranded DNA containing a specific base sequence (5'-TATAAA-3') called a TATA-box. These two fractions, which have EcoRI termini, were treated with T4 DNA ligase, and the block conjugate was obtained as a precipitate after two wash processes. When the resultant block conjugate was introduced into a sample solution containing TBP (0.26 microM) and bovine serum albumin (BSA) (0.39 microM), a rapid and selective precipitation separation of TBP under homogeneous conditions was achieved by controlling temperature. The purity of TBP in the precipitation fraction was estimated to be above 90%.

Acrylic Resins↗
PubMed1984

Separation of plasma high-density lipoprotein subclasses by a combined precipitation method using polyethylene glycol 6000 and dextran sulphate.

A fast and cheap precipitation method for the separation of HDL subclasses been evaluated. It starts with precipitation of apo-B containing lipoproteins with PEG-6000 after which HDL2 is precipitated with dextran sulphate-Mg2+. A concentration of 0.72 g/l dextran sulphate was found to be suitable for the separation of HDL subclasses. HDL subclasses obtained by precipitation gave proper density profiles at density gradient centrifugations. The correlations between results obtained by this method and by sequential and density gradient centrifugation are good, r = 0.99 and 0.72, respectively.

Adult↗
PubMed1993

Separation and characteristics of glycoproteins in tears which inhibit coating and precipitation of protein.

Using a modified turbidimetric assay to determine the protein concentration in human tears by precipitation with trichloroacetic acid (TCA) we found lower protein concentrations if compared with other methods for protein determination. This implies that a factor in human tears is able to inhibit the precipitation of protein by TCA. Earlier a coating inhibitory factor in human tears was described which is able to prevent coating of a polyacrylate surface by proteins using a ELISA methodology. Because of the similarity in its behaviour towards protein we investigated whether the same factor could be responsible for both inhibitory effects. A pool of human tears was separated into various fractions using HPLC whereafter inhibitory activity in the turbidimetric and the coating assay could be found in the same fractions. Characterization of the inhibitory factor was performed by minigel-electrophoresis (SDS-PAGE), after which blotting and staining with a lectin (Jacalin) revealed two subunits of a glycoprotein with a molecular weight of 30 and 70 kD. The inhibitory factor also could be isolated if human tears were incubated for 30 min at 100 degrees C whereafter precipitated protein was removed by centrifugation. Inhibitory activity could be detected in the supernatant and an identical glycoprotein profile could be produced after staining with lectin (Jacalin). The results of this study suggest that a soluble glycoprotein serves as a coating and precipitation inhibitor in tears and may play an important role in the protein to protein interaction on the surface of the eye.

Chemical Precipitation↗
PubMed1981

Forming and removing stain precipitates on ultrathin sections.

Stain precipitates resulting from the use of lead or uranyl salts, or both, on ultrathin sections can be classified as belonging to one of three morphological types: I) extremely electron-dense particles caused by prolonged use of lead salts only, II) amorphous networks formed following double staining with either aqueous or alcoholic uranyl and lead salts, and III) crystalline needles sometimes resulting from double staining with alcoholic uranyl and lead salts. It has been found, however, that either acetic acid or aqueous uranyl acetate can be used to remove type I and type II precipitates from sections, and that oxalic acid and alcoholic uranyl solution will remove type II precipitates. Unfortunately, type III precipitates are unaffected by any agents tested so far.

Acetates↗
PubMed1989

Simple method of tocopherol determination in plasma lipoprotein fractions using a heparin-Ca precipitation technique.

A simple and convenient method using a heparin-Ca precipitation technique, which was devised for determination of serum lipoprotein fractions, was applied to the determination of tocopherol concentrations in individual lipoproteins. Three types of precipitates were prepared from 0.25 ml serum samples plus 0.1 ml of 5% heparin by mixing at 37 degrees C for 30 min with 5 ml of 0.054 M CaCl2 only, 0.054 M CaCl2 in 0.6% NaCl, or 0.054 M CaCl2 in 0.92% NaCl. These three precipitates consisted of chylomicron + VLDL (very low-density lipoprotein) + LDL (low density lipoprotein), chylomicron + VLDL, and chylomicron only, respectively. The tocopherol content of individual lipoproteins was calculated from the concentrations of tocopherol in these three precipitates, and the values obtained by using this technique were very close to those by a standard ultracentrifugation method. Thus, this simple method appears to be suitable for rapid tocopherol assay of a large number of samples.

Chemical Precipitation↗
PubMed1999

The content of delmopinol and characterization of the molecular weight pattern of salivary protein precipitates.

The aims of this investigation were: a) To quantify the amount of radiolabelled delmopinol in precipitates formed in a mixture of saliva and delmopinol at two concentrations, b) To analyze the precipitates by polyacrylamide gel electrophoresis. Unstimulated whole saliva was collected from 5 individuals and the samples were clarified by centrifugation. In a first series of experiments radiolabelled delmopinol hydrochloride at the final concentrations of 1.6 mM and 6.4 mM was incubated with the saliva samples and centrifuged. The supernatants and the pellets were immediately transferred to scintillation vials and radiolabelled delmopinol was detected by using scintillation counting. In a second series of experiments, similar saliva-delmopinol mixtures were centrifuged and the supernatants and pellets were prepared for electrophoresis. Videodensitometry was used to quantify the relative density of stained protein in the pellet samples within four ranges of molecular weight (10-21.5, 21.5-26, 26-45, 45-300 kDa). The results of this study showed that the amounts of labeled delmopinol found in the precipitates were higher at 6.4 mM delmopinol than at 1.6 mM. The amount of salivary protein precipitated by delmopinol was found to depend on delmopinol concentration as well as salivary composition. Delmopinol interactions to salivary proteins could influence protein availability on oral cavity surfaces.

Adult↗
PubMed2000

Laboratory scaledown of protein purification processes involving fractional precipitation and centrifugal recovery.

The ability to predict the performance of large-scale processes is central to the rapid development of successful operations at the pilot and industrial scale. In this article, we examine the operation, at laboratory scale, of precipitation reactors and centrifuges for protein precipitate recovery and dewatering and how they might best mimic large-scale reactors and centrifuges, in this case, a pilot-scale batch stirred-tank reactor and a multichamber-bowl centrifuge. Novel approaches to bench-top centrifuge operation are provided, in particular with a view to delivery of material for subsequent high-resolution purification, which would be obtained at full pilot scale. Results are presented in terms of properties of the protein precipitates, the fraction of solids recovered, and the extent of dewatering achieved. Good agreement was obtained at bench scale (a 1000-fold scale down factor) for all of these parameters for pilot-scale, batch-feed operation. In addition, the methodology developed allows identification of the extent of break-up that occurs in continuous-feed centrifuges when processing shear-sensitive materials such as the protein precipitates studied here.

Alcohol Dehydrogenase↗
PubMed1999

Urine protein electrophoresis of renal transplant recipients using room temperature precipitation technique.

Proteinuria is one of the markers of renal diseases. Its quantitative measurements alone limited diagnostic conclusions. To determine the extent of precipitated proteinuria as a tool for diagnosis, I used the precipitated urine protein without any effect of any chemical and heat for protein precipitation utilizing an approach which was developed previously (Ahmed Mukhtar, 1997 & 1998). Two samples of urine (5 c.c each) from two different occasions were collected from 8 renal transplant recipients with and 7 normal healthy persons without any history of renal involvement. The samples were dried at room temperature without adding any chemical for 24 hours and precipitated urine was diluted in 0.3-0.5 ml distilled water. Then were run on Bekman apparatus Paragon Electrophoresis System and scanned for electrophoresis bands for the following proteins in BDF hospital: albumin, alpha 1, alpha 2, beta, and gamma. The pattern of electrophoresis graph and bands were different in the urine of patients compared to the urine of healthy persons. There were alterations in alpha 1 and beta proteins in the urine of renal transplant recipients. This technique illustrates a feasible approach to estimate the protein alteration in renal transplant recipients, and this pilot study could be used as a tool for further studies.

Chemical Precipitation↗
PubMed2001

Struvite precipitation potential for nutrient recovery from anaerobically treated wastes.

Geochemical equilibrium speciation modeling was used to determine optimum conditions for precipitation of magnesium ammonium phosphate, or struvite, for the recovery of nutrients from anaerobically digested wastes. Despite a wide range of pH values with the potential to precipitate struvite, the optimum pH was determined to be 9.0. Bench experiments conducted on effluent from an anaerobic sequencing batch reactor (ASBR) treating swine wastes achieved a maximum of 88% ammonia removal at a pH of 9.5 with added magnesium and phosphate to achieve an ammonium: magnesium: phosphate molar ratio of 1:1.25:1. Struvite precipitation was performed on a continuous basis in a pilot-scale ASBR treating swine wastes. Through the addition of supplemental magnesium and phosphate, the ammonia concentration was reduced from 1500 mg/L as nitrogen to less than 10 mg/L. The supenatant from the struvite precipitation clarifier was recycled to the feed of the ASBR without adverse impact, simulating on-farm effluent reuse as flush water.

Agriculture↗