Photo-degradation behaviour of roseoflavin in some aqueous solutions

NASA Astrophysics Data System (ADS)

Tyagi, A.; Penzkofer, A.; Mathes, T.; Hegemann, P.

2010-03-01

An absorption and emission spectroscopic characterization of roseoflavin (8-dimethylamino-8-demethyl-riboflavin, RoF) in aqueous solutions was carried out. The studies were concentrated on roseoflavin in pH 8 phosphate buffer. Absorption cross-section spectra, fluorescence excitation spectra, fluorescence quantum distributions, fluorescence quantum yields and fluorescence lifetimes were determined. The fluorescence of RoF is quenched by photo-induced intra-molecular charge-transfer at room temperature. The photo-degradation of RoF in un-buffered water, in Tris-HCl buffer, and in phosphate buffer was studied. Phosphate buffer and to a smaller extent Tris buffer catalyse the RoF photo-degradation. Photo-excitation of the primary photoproduct, 8-methylamino-riboflavin (8-MNH-RF), enhanced the RoF degradation by triplet 8-MNH-RF - singlet RoF excitation transfer with subsequent triplet-state RoF degradation.

Studies on the electrochemical behavior of thiazolidine and its applications using a flow-through chronoamperometric sensor based on a gold electrode.

PubMed

Wang, Lai-Hao; Li, Wen-Jie

2011-09-06

The electrochemical behaviors of thiazolidine (tetrahydrothiazole) on gold and platinum electrodes were investigated in a Britton-Robinson buffer (pH 2.77-11.61), acetate buffer (pH 4.31), phosphate buffer solutions (pH 2.11 and 6.38) and methanol or acetonitrile containing various supporting electrolytes. Detection was based on a gold wire electrochemical signal obtained with a supporting electrolyte containing 20% methanol-1.0 mM of phosphate buffer (pH 6.87, potassium dihydrogen phosphate and dipotassium hydrogen phosphate) as the mobile phase. Comparison with results obtained with a commercial amperometric detector shows good agreement. Using the chronoamperometric sensor with the current at a constant potential, and measurements with suitable experimental parameters, a linear concentration from 0.05 to 16 mg L-1 was found. The limit of quantification (LOQ) of the method for thiazolidine was found to be 1 ng.

Proton transport by phosphate diffusion--a mechanism of facilitated CO2 transfer

PubMed Central

1976-01-01

We have measured CO2 fluxes across phosphate solutions at different carbonic anhydrase concentrations, bicarbonate concentration gradients, phosphate concentrations, and mobilities. Temperature was 22-25 degrees C, the pH of the phosphate solutions was 7.0-7.3. We found that under physiological conditions of pH and pCO2 a facilitated diffusion of CO2 occurs in addition to free diffusion when (a) sufficient carbonic anhydrase is present, and (b) a concentration gradient of HCO3- is established along with a pCO2 gradient, and (c) the phosphate buffer has a mobility comparable to that of bicarbonate. When the phosphate was immobilized by attaching 0.25-mm-long cellulose particles, no facilitation of CO2 diffusion was detectable. A mechanism of facilitated CO2 diffusion in phosphate solutions analogous to that in albumin solutions was proposed on the basis of these findings: bicarbonate diffusion together with a facilitated proton transport by phosphate diffusion. A mathematical model of this mechanism was formulated. The CO2 fluxed predicted by the model agree quantitatively with the experimentally determined fluxes. It is concluded that a highly effective proton transport mechanism acts in solutions of mobile phosphate buffers. By this mechanism; CO2 transfer may be increased up to fivefold and proton transfer may be increased to 10,000-fold. PMID:6619

Effect of Pressure-Induced Changes in the Ionization Equilibria of Buffers on Inactivation of Escherichia coli and Staphylococcus aureus by High Hydrostatic Pressure

PubMed Central

Gayán, Elisa; Condón, Santiago; Álvarez, Ignacio; Nabakabaya, Maria

2013-01-01

Survival rates of Escherichia coli and Staphylococcus aureus after high-pressure treatment in buffers that had large or small reaction volumes (ΔV°), and which therefore underwent large or small changes in pH under pressure, were compared. At a low buffer concentration of 0.005 M, survival was, as expected, better in MOPS (morpholinepropanesulfonic acid), HEPES, and Tris, whose ΔV° values are approximately 5.0 to 7.0 cm3 mol−1, than in phosphate or dimethyl glutarate (DMG), whose ΔV° values are about −25 cm3 mol−1. However, at a concentration of 0.1 M, survival was unexpectedly better in phosphate and DMG than in MOPS, HEPES, or Tris. This was because the baroprotective effect of phosphate and DMG increased much more rapidly with increasing concentration than it did with MOPS, HEPES, or Tris. Further comparisons of survival in solutions of salts expected to cause large electrostriction effects (Na2SO4 and CaCl2) and those causing lower electrostriction (NaCl and KCl) were made. The salts with divalent ions were protective at much lower concentrations than salts with monovalent ions. Buffers and salts both protected against transient membrane disruption in E. coli, but the molar concentrations necessary for membrane protection were much lower for phosphate and Na2SO4 than for HEPES and NaCl. Possible protective mechanisms discussed include effects of electrolytes on water compressibility and kosmotropic and specific ion effects. The results of this systematic study will be of considerable practical significance in studies of pressure inactivation of microbes under defined conditions but also raise important fundamental questions regarding the mechanisms of baroprotection by ionic solutes. PMID:23624471

Influence of calcium and phosphorus, lactose, and salt-to-moisture ratio on Cheddar cheese quality: pH buffering properties of cheese.

PubMed

Upreti, P; Bühlmann, P; Metzger, L E

2006-03-01

The pH buffering capacity of cheese is an important determinant of cheese pH. However, the effects of different constituents of cheese on its pH buffering capacity have not been fully clarified. The objective of this study was to characterize the chemical species and chemical equilibria that are responsible for the pH buffering properties of cheese. Eight cheeses with 2 levels of Ca and P (0.67 and 0.47% vs. 0.53 and 0.39%, respectively), residual lactose (2.4 vs. 0.78%), and salt-to-moisture ratio (6.4 vs. 4.8%) were manufactured. The pH-titration curves for these cheeses were obtained by titrating cheese:water (1:39 wt/wt) dispersions with 1 N HCl, and backtitrating with 1 N NaOH. To understand the role of different chemical equilibria and the respective chemical species in controlling the pH of cheese, pH buffering was modeled mathematically. The 36 chemical species that were found to be relevant for modeling can be classified as cations (Na+, Ca2+, Mg2+), anions (phosphate, citrate, lactate), protein-bound amino acids with a side-chain pKa in the range of 3 to 9 (glutamate, histidine, serine phosphate, aspartate), metal ion complexes (phosphate, citrate, and lactate complexes of Na+, Ca2+, and Mg2+), and calcium phosphate precipitates. A set of 36 corresponding equations was solved to give the concentrations of all chemical species as a function of pH, allowing the prediction of buffering curves. Changes in the calculated species concentrations allowed the identification of the chemical species and chemical equilibria that dominate the pH buffering properties of cheese in different pH ranges. The model indicates that pH buffering in the pH range from 4.5 to 5.5 is predominantly due to a precipitate of Ca and phosphate, and the protonation equilibrium involving the side chains of protein-bound glutamate. In the literature, the precipitate is often referred to as amorphous colloidal calcium phosphate. A comparison of experimental data and model predictions shows that the buffering properties of the precipitate can be explained, assuming that it consists of hydroxyapatite [Ca5(OH)(PO4)3] or Ca3(PO4)2. The pH buffering in the region from pH 3.5 to 4.5 is due to protonation of side-chain carboxylates of protein-bound glutamate, aspartate, and lactate, in order of decreasing significance. In addition, pH buffering between pH 5 to 8 in the backtitration results from the reprecipitation of calcium and phosphate either as CaHPO4 or Ca4H(PO4)3.

In Vivo Predictive Dissolution: Comparing the Effect of Bicarbonate and Phosphate Buffer on the Dissolution of Weak Acids and Weak Bases.

PubMed

Krieg, Brian J; Taghavi, Seyed Mohammad; Amidon, Gordon L; Amidon, Gregory E

2015-09-01

Bicarbonate is the main buffer in the small intestine and it is well known that buffer properties such as pKa can affect the dissolution rate of ionizable drugs. However, bicarbonate buffer is complicated to work with experimentally. Finding a suitable substitute for bicarbonate buffer may provide a way to perform more physiologically relevant dissolution tests. The dissolution of weak acid and weak base drugs was conducted in bicarbonate and phosphate buffer using rotating disk dissolution methodology. Experimental results were compared with the predicted results using the film model approach of (Mooney K, Mintun M, Himmelstein K, Stella V. 1981. J Pharm Sci 70(1):22-32) based on equilibrium assumptions as well as a model accounting for the slow hydration reaction, CO2 + H2 O → H2 CO3 . Assuming carbonic acid is irreversible in the dehydration direction: CO2 + H2 O ← H2 CO3 , the transport analysis can accurately predict rotating disk dissolution of weak acid and weak base drugs in bicarbonate buffer. The predictions show that matching the dissolution of weak acid and weak base drugs in phosphate and bicarbonate buffer is possible. The phosphate buffer concentration necessary to match physiologically relevant bicarbonate buffer [e.g., 10.5 mM (HCO3 (-) ), pH = 6.5] is typically in the range of 1-25 mM and is very dependent upon drug solubility and pKa . © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

Innovative Microsystems: Novel Nanostructures to Capture Circulating Breast Cancer Cells

DTIC Science & Technology

2009-05-01

temperature to promote a Schiff-base reaction. Recombinant protein G from E . coli (Zymed Lab Inc.) 50 μg/ml in Ca- and Mg-free phosphate-buffered...recombinant protein G from E . coli (Zymed Lab Inc.), at a concentration of 50 mg ml1 in 1 PBS, is incubated on the activated surface overnight at 4 C...reaction. Recombinant protein G from E . coli (Zymed Lab Inc.) 50 μg/ml in Ca- and Mg-free phosphate-buffered saline (CMF-PBS), is incubated on the

Behavior of soluble and immobilized acid phosphatase in hydro-organic media.

PubMed

Wan, H; Horvath, C

1975-11-20

The hydrolysis of p-nitrophenyl phosphate by wheat germ acid phosphatase (orthophosphoric monoester phosphohydrolase, EC 3.1.3.2) has been investigated in mixtures of aqueous buffers with acetone, dioxane and acetonitrile. The enzyme was either in free solution or immobilized on a pellicular support which consisted of a porous carbonaceous layer on solid glass beads. The highest enzyme activity was obtained in acetone and acetonitrile mixed with citrate buffer over a wide range of organic solvent concentration. In 50% (v/v) acetone both V and Km of the immobilized enzyme were about half of the values in the neat aqueous buffer, but the Ki for inorganic phosphate was unchanged. In 50% (v/v) mixtures of various solvents and citrate buffers of different pH, the enzymic activity was found to depend on the pH of the aqueous buffer component rather than the pH of the hydro-organic mixture as measured with the glass-calomel electrode. The relatively high rates of p-nitrophenol liberation in the presence of glucose even at high organic solvent concentrations suggest that transphosphorylation is facilitated at low water activity.

Laser Raman spectra of mono-, oligo- and polysaccharides in solution

NASA Astrophysics Data System (ADS)

Barrett, T. W.

We examined the Raman spectra of thirteen sugars—seven monosaccharides, two disaccharides, one trisaccharide and three polysaccharides—in the wavelength range 200—1700 cm -1 and (i) varied the phosphate buffered solution from pH 6.0 to 8.5 at constant ionic strength of 0.1 and (ii) varied HCl solutions from pH 0.8 to 5.0. As is to be expected with molecules containing COH groupings, all the molecular spectra are distinct. Of the thirteen sugars examined, only D-fructose 1,6-diphosphate (FDP) demonstrated spectral changes for the pH range 6.0—8.5 in phosphate buffer; but all exhibited band intensity enhancement in HCl at the lower pHs, but not band wavenumber changes. The results indicate that: (i) changes in the pH of the major intracellular buffer, phosphate, toward acidity, are able to hydrolyze the 1-phosphate group of FDP and the relative concentration of fructose 1-phosphate to fructose 6-phosphate is indicated by the intensity ratio of the 982 and 1080 cm -1 bands; (ii) it appears that all phosphate groups of FDP are hydrolyzed at pH 0.8 in HCl; and (iii) although conditions of extreme acidity are able to hydrolyze other sugars examined, there is no major degradation.

Interaction of two diclofenac acid salts with copolymers of ammoniomethacrylate: effect of additives and release profiles.

PubMed

Khalil, E; Sallam, A

1999-04-01

The copolymer of ammoniomethacrylate Eudragit RL (ERL) interacted with diclofenac acid salts (sodium and diethylamine salts) in aqueous solutions, forming a complex. Sorption experiments were done in aqueous solutions of either sodium lauryl sulfate (SLS), Tween 20, or Tween 80. The SLS competed strongly with the drug, even at low concentrations, and reduced significantly the amount of drug sorbed by ERL. Tweens at high concentrations exhibited two phase profiles: the sorption phase, which was short and during which drug concentration dropped sharply, and the release phase, during which the drug was released slowly over 24 hr and which was accompanied by dispersion of ERL particles into the colloidal dispersion. The interaction was dependent on temperature, ionic strength, and nature of the additives. The extent of interaction in water and phosphate buffer solutions was in the following order: water > pH 6 > pH 7-8. In-vitro dissolution studies of the dried complex were done over 24 hr. In water, the drug remained bound to the polymer. In aqueous surfactant solutions (SLS, Tween 20, and Tween 80) and phosphate buffer at pH 6.8, a linear relationship between drug concentration and the square root of time was obtained, indicating a matrix diffusion-controlled mechanism. However, 100% release was not reached, and resorption was observed in the phosphate buffer solution.

Albumin adsorption onto surfaces of urine collection and analysis containers☆

PubMed Central

Robinson, Mary K.; Caudill, Samuel P.; Koch, David D.; Ritchie, James; Hortin, Glen; Eckfeldt, John H.; Sandberg, Sverre; Williams, Desmond; Myers, Gary; Miller, W. Greg

2017-01-01

Background Adsorption of albumin onto urine collection and analysis containers may cause falsely low concentrations. Methods We added 125I-labeled human serum albumin to urine and to phosphate buffered solutions, incubated them with 22 plastic container materials and measured adsorption by liquid scintillation counting. Results Adsorption of urine albumin (UA) at 5–6 mg/l was <0.9%; and at 90 mg/l was <0.4%. Adsorption was generally less at pH 8 than pH 5 but only 3 cases had p <0.05. Adsorption from 11 unaltered urine samples with albumin 5–333 mg/l was <0.8%. Albumin adsorption for the material with greatest binding was extrapolated to the surface areas of 100 ml and 2 l collection containers, and to instrument sample cups and showed <1% change in concentration at 5 mg/l and <0.5% change at 20 mg/l or higher concentrations. Adsorption of albumin from phosphate buffered solutions (2–28%) was larger than that from urine. Conclusions Albumin adsorption differed among urine samples and plastic materials, but the total influence of adsorption was <1% for all materials and urine samples tested. Adsorption of albumin from phosphate buffered solutions was larger than that from urine and could be a limitation for preparations used as calibrators. PMID:24513540

Albumin adsorption onto surfaces of urine collection and analysis containers.

PubMed

Robinson, Mary K; Caudill, Samuel P; Koch, David D; Ritchie, James; Hortin, Glen; Eckfeldt, John H; Sandberg, Sverre; Williams, Desmond; Myers, Gary; Miller, W Greg

2014-04-20

Adsorption of albumin onto urine collection and analysis containers may cause falsely low concentrations. We added (125)I-labeled human serum albumin to urine and to phosphate buffered solutions, incubated them with 22 plastic container materials and measured adsorption by liquid scintillation counting. Adsorption of urine albumin (UA) at 5-6 mg/l was <0.9%; and at 90 mg/l was <0.4%. Adsorption was generally less at pH8 than pH5 but only 3 cases had p<0.05. Adsorption from 11 unaltered urine samples with albumin 5-333 mg/l was <0.8%. Albumin adsorption for the material with greatest binding was extrapolated to the surface areas of 100 ml and 2l collection containers, and to instrument sample cups and showed <1% change in concentration at 5 mg/l and <0.5% change at 20 mg/l or higher concentrations. Adsorption of albumin from phosphate buffered solutions (2-28%) was larger than that from urine. Albumin adsorption differed among urine samples and plastic materials, but the total influence of adsorption was <1% for all materials and urine samples tested. Adsorption of albumin from phosphate buffered solutions was larger than that from urine and could be a limitation for preparations used as calibrators. Copyright © 2014 Elsevier B.V. All rights reserved.

Effects of buffer composition and processing conditions on aggregation of bovine IgG during freeze-drying.

PubMed

Sarciaux, J M; Mansour, S; Hageman, M J; Nail, S L

1999-12-01

The objective of this study was to identify critical formulation and processing variables affecting aggregation of bovine IgG during freeze-drying when no lyoprotective solute is used. Parameters examined were phosphate buffer concentration and counterion (Na versus K phosphate), added salts, cooling rate, IgG concentration, residual moisture level, and presence of a surfactant. No soluble aggregates were detected in any formulation after either freezing/thawing or freeze-drying. No insoluble aggregates were detected in any formulation after freezing, but insoluble aggregate levels were always detectable after freeze-drying. The data are consistent with a mechanism of aggregate formation involving denaturation of IgG at the ice/freeze-concentrate interface which is reversible upon freeze-thawing, but becomes irreversible after freeze-drying and reconstitution. Rapid cooling (by quenching in liquid nitrogen) results in more and larger aggregates than slow cooling on the shelf of the freeze-dryer. This observation is consistent with surface area measurements and environmental electron microscopic data showing a higher surface area of freeze-dried solids after fast cooling. Annealing of rapidly cooled solutions results in significantly less aggregation in reconstituted freeze-dried solids than in nonannealed controls, with a corresponding decrease in specific surface area of the freeze-dried, annealed system. Increasing the concentration of IgG significantly improves the stability of IgG against freeze-drying-induced aggregation, which may be explained by a smaller percentage of the protein residing at the ice/freeze-concentrate interface as IgG concentration is increased. A sodium phosphate buffer system consistently results in more turbid reconstituted solids than a potassium phosphate buffer system at the same concentration, but this effect is not attributable to a pH shift during freezing. Added salts such as NaCl or KCl contribute markedly to insoluble aggregate formation. Both sodium and potassium chloride contribute more to turbidity of the reconstituted solid than either sodium or potassium phosphate buffers at similar ionic strength, with sodium chloride resulting in a substantially higher level of aggregates than potassium chloride. At a given cooling rate, the specific surface area of dried solids is approximately a factor of 2 higher for the formulation containing sodium chloride than the formulation containing potassium chloride. Turbidity is also influenced by the extent of secondary drying, which underscores the importance of minimizing secondary drying of this system. Including a surfactant such as polysorbate 80, either in the formulation or in the water used for reconstitution, decreased, but did not eliminate, insoluble aggregates. There was no correlation between pharmaceutically acceptability of the freeze-dried cake and insoluble aggregate levels in the reconstituted product.

Thermal stability of tagatose in solution.

PubMed

Luecke, Katherine J; Bell, Leonard N

2010-05-01

Tagatose, a monosaccharide similar to fructose, has been shown to behave as a prebiotic. To deliver this prebiotic benefit, tagatose must not degrade during the processing of foods and beverages. The objective of this study was to evaluate the thermal stability of tagatose in solutions. Tagatose solutions were prepared in 0.02 and 0.1 M phosphate and citrate buffers at pHs 3 and 7, which were then held at 60, 70, and 80 degrees C. Pseudo-1st-order rate constants for tagatose degradation were determined. In citrate and phosphate buffers at pH 3, minimal tagatose was lost and slight browning was observed. At pH 7, tagatose degradation rates were enhanced. Degradation was faster in phosphate buffer than citrate buffer. Higher buffer concentrations also increased the degradation rate constants. Enhanced browning accompanied tagatose degradation in all buffer solutions at pH 7. Using the activation energies for tagatose degradation, less than 0.5% and 0.02% tagatose would be lost under basic vat and HTST pasteurization conditions, respectively. Although tagatose does breakdown at elevated temperatures, the amount of tagatose lost during typical thermal processing conditions would be virtually negligible. Practical Application: Tagatose degradation occurs minimally during pasteurization, which may allow for its incorporation into beverages as a prebiotic.

Dominant oceanic bacteria secure phosphate using a large extracellular buffer

PubMed Central

Zubkov, Mikhail V.; Martin, Adrian P.; Hartmann, Manuela; Grob, Carolina; Scanlan, David J.

2015-01-01

The ubiquitous SAR11 and Prochlorococcus bacteria manage to maintain a sufficient supply of phosphate in phosphate-poor surface waters of the North Atlantic subtropical gyre. Furthermore, it seems that their phosphate uptake may counter-intuitively be lower in more productive tropical waters, as if their cellular demand for phosphate decreases there. By flow sorting 33P-phosphate-pulsed 32P-phosphate-chased cells, we demonstrate that both Prochlorococcus and SAR11 cells exploit an extracellular buffer of labile phosphate up to 5–40 times larger than the amount of phosphate required to replicate their chromosomes. Mathematical modelling is shown to support this conclusion. The fuller the buffer the slower the cellular uptake of phosphate, to the point that in phosphate-replete tropical waters, cells can saturate their buffer and their phosphate uptake becomes marginal. Hence, buffer stocking is a generic, growth-securing adaptation for SAR11 and Prochlorococcus bacteria, which lack internal reserves to reduce their dependency on bioavailable ambient phosphate. PMID:26198420

Aggravation of cold-induced injury in Vero-B4 cells by RPMI 1640 medium - identification of the responsible medium components.

PubMed

Pless-Petig, Gesine; Metzenmacher, Martin; Türk, Tobias R; Rauen, Ursula

2012-10-10

In modern biotechnology, there is a need for pausing cell lines by cold storage to adapt large-scale cell cultures to the variable demand for their products. We compared various cell culture media/solutions for cold storage of Vero-B4 kidney cells, a cell line widely used in biotechnology. Cold storage in RPMI 1640 medium, a recommended cell culture medium for Vero-B4 cells, surprisingly, strongly enhanced cold-induced cell injury in these cells in comparison to cold storage in Krebs-Henseleit buffer or other cell culture media (DMEM, L-15 and M199). Manufacturer, batch, medium supplements and the most likely components with concentrations outside the range of the other media/solutions (vitamin B12, inositol, biotin, p-aminobenzoic acid) did not cause this aggravation of cold-induced injury in RPMI 1640. However, a modified Krebs-Henseleit buffer with a low calcium concentration (0.42 mM), a high concentration of inorganic phosphate (5.6 mM), and glucose (11.1 mM; i.e. concentrations as in RPMI 1640) evoked a cell injury and loss of metabolic function corresponding to that observed in RPMI 1640. Deferoxamine improved cell survival and preserved metabolic function in modified Krebs-Henseleit buffer as well as in RPMI 1640. Similar Ca2+ and phosphate concentrations did not increase cold-induced cell injury in the kidney cell line LLC-PK1, porcine aortic endothelial cells or rat hepatocytes. However, more extreme conditions (Ca2+ was nominally absent and phosphate concentration raised to 25 mM as in the organ preservation solution University of Wisconsin solution) also increased cold-induced injury in rat hepatocytes and porcine aortic endothelial cells. These data suggest that the combination of low calcium and high phosphate concentrations in the presence of glucose enhances cold-induced, iron-dependent injury drastically in Vero-B4 cells, and that a tendency for this pathomechanism also exists in other cell types.

Simultaneous pollutant removal and electricity generation in denitrifying microbial fuel cell with boric acid-borate buffer solution.

PubMed

Chen, Gang; Zhang, Shaohui; Li, Meng; Wei, Yan

2015-01-01

A double-chamber denitrifying microbial fuel cell (MFC), using boric acid-borate buffer solution as an alternative to phosphate buffer solution, was set up to investigate the influence of buffer solution concentration, temperature and external resistance on electricity generation and pollutant removal efficiency. The result revealed that the denitrifying MFC with boric acid-borate buffer solution was successfully started up in 51 days, with a stable cell voltage of 205.1 ± 1.96 mV at an external resistance of 50 Ω. Higher concentration of buffer solution favored nitrogen removal and electricity generation. The maximum power density of 8.27 W/m(3) net cathodic chamber was obtained at a buffer solution concentration of 100 mmol/L. An increase in temperature benefitted electricity generation and nitrogen removal. A suitable temperature for this denitrifying MFC was suggested to be 25 °C. Decreasing the external resistance favored nitrogen removal and organic matter consumption by exoelectrogens.

Study of a hydraulic dicalcium phosphate dihydrate/calcium oxide-based cement for dental applications.

PubMed

el-Briak, Hasna; Durand, Denis; Nurit, Josiane; Munier, Sylvie; Pauvert, Bernard; Boudeville, Phillipe

2002-01-01

By mixing CaHPO(4) x 2H(2)O (DCPD) and CaO with water or sodium phosphate buffers as liquid phase, a calcium phosphate cement was obtained. Its physical and mechanical properties, such as compressive strength, initial and final setting times, cohesion time, dough time, swelling time, dimensional and thermal behavior, and injectability were investigated by varying different parameters such as liquid to powder (L/P) ratio (0.35-0.7 ml g(-1)), molar calcium to phosphate (Ca/P) ratio (1.67-2.5) and the pH (4, 7, and 9) and the concentration (0-1 M) of the sodium phosphate buffer. The best results were obtained with the pH 7 sodium phosphate buffer at the concentration of 0.75 M. With this liquid phase, physical and mechanical properties depended on the Ca/P and L/P ratios, varying from 3 to 11 MPa (compressive strength), 6 to 10 min (initial setting time), 11 to 15 min (final setting time), 15 to 30 min (swelling time), 7 to 20 min (time of 100% injectability). The dough or working time was over 16 min. This cement expanded during its setting (1.2-5 % according to Ca/P and L/P ratios); this would allow a tight filling. Given the mechanical and rheological properties of this new DCPD/CaO-based cement, its use as root canal sealing material can be considered as classical calcium hydroxide or ZnO/eugenol-based pastes, without or with a gutta-percha point. Copyright 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 447-453, 2002

Variation of power generation at different buffer types and conductivities in single chamber microbial fuel cells.

PubMed

Nam, Joo-Youn; Kim, Hyun-Woo; Lim, Kyeong-Ho; Shin, Hang-Sik; Logan, Bruce E

2010-01-15

Microbial fuel cells (MFCs) are operated with solutions containing various chemical species required for the growth of electrochemically active microorganisms including nutrients and vitamins, substrates, and chemical buffers. Many different buffers are used in laboratory media, but the effects of these buffers and their inherent electrolyte conductivities have not been examined relative to current generation in MFCs. We investigated the effect of several common buffers (phosphate, MES, HEPES, and PIPES) on power production in single chambered MFCs compared to a non-buffered control. At the same concentrations the buffers produced different solution conductivities which resulted in different ohmic resistances and power densities. Increasing the solution conductivities to the same values using NaCl produced comparable power densities for all buffers. Very large increases in conductivity resulted in a rapid voltage drop at high current densities. Our results suggest that solution conductivity at a specific pH for each buffer is more important in MFC studies than the buffer itself given relatively constant pH conditions. Based on our analysis of internal resistance and a set neutral pH, phosphate and PIPES are the most useful buffers of those examined here because pH was maintained close to the pK(a) of the buffer, maximizing the ability of the buffer to contribute to increase current generation at high power densities. Copyright 2009 Elsevier B.V. All rights reserved.

Quantification of the internal resistance distribution of microbial fuel cells.

PubMed

Fan, Yanzhen; Sharbrough, Evan; Liu, Hong

2008-11-01

Identifying the limiting factors in a microbial fuel cell (MFC) system requires qualifying the contribution of each component of an MFC to internal resistance. In this study, a new method was developed to calculate the internal resistance distribution of an MFC. Experiments were conducted to identify the limiting factors in single-chamber MFCs by varying the anode surface areas, cathode surface areas, and phosphate buffer concentrations. For the MFCs with equally sized electrodes (7 cm2) and 200 mM phosphate buffer, the anode contributed just 5.4% of the internal resistance, while the cathode and the electrolyte each contributed 47.3%, indicating that the anode was not the limiting factor in power generation. The limitation of the cathode was further revealed by the 780% higher area-specific resistance (284.4 omega cm2) than the 32.3 omega cm2 of the anode. The electrolyte limitation was also evidenced by the greatly increased contribution of electrolyte in internal resistance from 47.3 to 78.2% when the concentration of phosphate buffer was decreased from 200 to 50 mM. An anodic power density of 6860 mW/m2 was achieved at a current density of 2.62 mA/cm2 using the MFCs with an anode/cathode area ratio of 1/14 and 200 mM phosphate buffer. The method was also successfully applied to analyze the internal resistance distribution of the two chamber MFCs from a previously reported study. The comparison of the internal resistances of the two air cathode systems indicates that the much lower resistances, including anode, cathode, and membrane resistances, contributed to the much better performance of the single-chamber MFCs than the two-chamber system.

Countercurrent distribution of biological cells

NASA Technical Reports Server (NTRS)

1982-01-01

It is known that the addition of phosphate buffer to two polymer aqueous phase systems has a strong effect on the partition behavior of cells and other particles in such mixtures. The addition of sodium phosphate to aqueous poly(ethylene glycol) dextran phase systems causes a concentration-dependent shift in binodial on the phase diagram, progressively lowering the critical conditions for phase separation as the phosphate concentration is increased. Sodium chloride produces no significant shift in the critical point relative to the salt-free case. Accurate determinations of the phase diagram require measurements of the density of the phases; data is presented which allows this parameter to be calculated from polarimetric measurements of the dextran concentrations of both phases. Increasing polymer concentrations in the phase systems produce increasing preference of the phosphate for the dextran-rich bottom phase. Equilibrium dialysis experiments showed that poly(ethylene glycol) effectively rejected phosphate, and to a lesser extent chloride, but that dextran had little effect on the distribution of either salt. Increasing ionic strength via addition of 0.15 M NaCl to phase systems containing 0.01 M phosphate produces an increased concentration of phosphate ions in the bottom dextran-rich phase, the expected effect in this type of Donnan distribution.

Mixed microalgae consortia growth under higher concentration of CO2 from unfiltered coal fired flue gas: Fatty acid profiling and biodiesel production.

PubMed

Aslam, Ambreen; Thomas-Hall, Skye R; Manzoor, Maleeha; Jabeen, Faiza; Iqbal, Munawar; Uz Zaman, Qamar; Schenk, Peer M; Asif Tahir, M

2018-02-01

Biodiesel is produced by transesterification of fatty acid methyl esters (FAME) from oleaginous microalgae feedstock. Biodiesel fuel properties were studied and compared with biodiesel standards. Qualitative analysis of FAME was done while cultivating mixed microalgae consortia under three concentrations of coal fired flue gas (1%, 3.0% and 5.5% CO 2 ). Under 1% CO 2 concentration (flue gas), the FAME content was 280.3 μg/mL, whereas the lipid content was 14.03 μg/mL/D (day). Both FAMEs and lipid contents were low at other CO 2 concentrations (3.0 and 5.5%). However, mixed consortia in the presence of phosphate buffer and flue gas (PB + FG) showed higher saturated fatty acids (SFA) (36.28%) and unsaturated fatty acids (UFA) (63.72%) versus 5.5% CO 2 concentration, which might be responsible for oxidative stability of biodiesel. Subsequently, higher cetane number (52) and low iodine value (136.3 gI 2 /100 g) biodiesel produced from mixed consortia (PB + FG) under 5.5% CO 2 along with 50 mM phosphate buffer were found in accordance with European (EN 14214) standard. Results revealed that phosphate buffer significantly enhanced the biodiesel quality, but reduced the FAME yield. This study intended to develop an integrated approach for significant improvement in biodiesel quality under surplus phosphorus by utilizing waste flue gas (as CO 2 source) using microalgae. The CO 2 sequestration from industrial flue gas not only reduced greenhouse gases, but may also ensure the sustainable and eco-benign production of biodiesel. Copyright © 2018. Published by Elsevier B.V.

Ion sensitivity of large-area epitaxial graphene film on SiC substrate

NASA Astrophysics Data System (ADS)

Mitsuno, Takanori; Taniguchi, Yoshiaki; Ohno, Yasuhide; Nagase, Masao

2017-11-01

We investigated the intrinsic ion sensitivity of graphene field-effect transistors (FETs) fabricated by a resist-free stencil mask lithography process from a large-scale graphene film epitaxially grown on a SiC substrate. A pH-adjusted phosphate-buffered solution was used for the measurement to eliminate the interference of other ions on the graphene FET's ion sensitivity. The charge neutrality point shifted negligibly with changing pH for the pH-adjusted phosphate-buffered solution, whereas for the mixed buffer solution, it shifted toward the negative gate voltage owing to the decrease in the concentration of phthalate ions. This phenomenon is contrary to that observed in previous reports. Overall, our results indicate that the graphene film is intrinsically insensitive to ions except for those with functional groups that interact with the graphene surface.

Evaluation of the pH- and Thermal Stability of the Recombinant Green Fluorescent Protein (GFP) in the Presence of Sodium Chloride

NASA Astrophysics Data System (ADS)

Ishii, Marina; Kunimura, Juliana Sayuri; Jeng, Hélio Tallon; Vessoni Penna, Thereza Christina; Cholewa, Olivia

The thermal stability of recombinant green fluorescent protein (GFP) in sodium chloride (NaCl) solutions at different concentrations, pH, and temperatures was evaluated by assaying the loss of fluorescence intensity as a measure of denaturation. GFP, extracted from Escherichia coli cells by the three-phase partitioning method and purified through a butyl hydrophobic interaction chromatography (HIC) column, was diluted in water for injection (WFI) (pH 6.0-7.0) and in 10 mM buffer solutions (acetate, pH 5.0; phosphate, pH 7.0; and Tris-EDTA, pH 8.0) with 0.9-30% NaCl or without and incubated at 80-95°C. The extent of protein denaturation was expressed as a percentage of the calculated decimal reduction time (D-value). In acetate buffer (pH 4.84 ±0.12), the mean D-values for 90% reduction in GFP fluorescence ranged from 2.3 to 3.6 min, independent of NaCl concentration and temperature. GFP thermal stability diluted in WFI (pH 5.94±0.60) was half that observed in phosphate buffer (pH 6.08±0.60); but in both systems, D-values decreased linearly with increasing NaCl concentration, with D-values (at 80°C) ranging from 3.44, min (WFI) to 6.1 min (phosphate buffer), both with 30% NaCl. However, D-values in Tris-EDTA (pH 7.65±0.17) were directly dependent on the NaCl concentration and 5-10 times higher than D-values for GFP in WFI at 80°C. GFP pH-and thermal stability can be easily monitored by the convenient measure of fluorescence intensity and potentially be used as an indicator to monitor that processing times and temperatures were attained.

Electrochemical detection of copper ions leached from CuO nanoparticles in saline buffers and biological media using a gold wire working electrode

NASA Astrophysics Data System (ADS)

Baldisserri, Carlo; Costa, Anna Luisa

2016-04-01

We performed explorative cyclic voltammetry in phosphate-buffered saline buffers, Dulbecco's modified Eagle's medium (DMEM), and fetal bovine serum-added DMEM using Au wire as working electrode, both in the absence and in the presence of known nominal concentrations of Cu2+ ions or 15 nm CuO nanoparticles. Addition of either Cu2+ ions or aqueous suspension of CuO nanoparticles caused a single anodic peak to appear in the double-layer region of all three pristine media. The height of the anodic peak was found to increase in a monotonic fashion vs. Cu2+ concentration in Cu2+-added media, and versus time since CuO addition in CuO-added media. Stepwise addition of glycine to Cu2+-added phosphate-buffered saline buffer caused an increasing cathodic shift of the anodic peak accompanied by decreasing peak currents. Results indicate that preparing Cu2+-free suspensions of CuO nanoparticles in such media is difficult, owing to the presence of leached copper ions. The implications on results of experiments in which CuO nanoparticle-added biological media are used as cell culture substrates are discussed. Literature data on the interactions between Cu2+ ions, dissolved carbon dioxide in aqueous CuO suspensions, and amino acids present in such media are compared to our results.

Optimization of the elution buffer and concentration method for detecting hepatitis E virus in swine liver using a nested reverse transcription-polymerase chain reaction and real-time reverse transcription-polymerase chain reaction.

PubMed

Son, Na Ry; Seo, Dong Joo; Lee, Min Hwa; Seo, Sheungwoo; Wang, Xiaoyu; Lee, Bog-Hieu; Lee, Jeong-Su; Joo, In-Sun; Hwang, In-Gyun; Choi, Changsun

2014-09-01

The aim of this study was to develop an optimal technique for detecting hepatitis E virus (HEV) in swine livers. Here, three elution buffers and two concentration methods were compared with respect to enhancing recovery of HEV from swine liver samples. Real-time reverse transcription-polymerase chain reaction (RT-PCR) and nested RT-PCR were performed to detect HEV RNA. When phosphate-buffered saline (PBS, pH 7.4) was used to concentrate HEV in swine liver samples using ultrafiltration, real-time RT-PCR detected HEV in 6 of the 26 samples. When threonine buffer was used to concentrate HEV using polyethylene glycol (PEG) precipitation and ultrafiltration, real-time RT-PCR detected HEV in 1 and 3 of the 26 samples, respectively. When glycine buffer was used to concentrate HEV using ultrafiltration and PEG precipitation, real-time RT-PCR detected HEV in 1 and 3 samples of the 26 samples, respectively. When nested RT-PCR was used to detect HEV, all samples tested negative regardless of the type of elution buffer or concentration method used. Therefore, the combination of real-time RT-PCR and ultrafiltration with PBS buffer was the most sensitive and reliable method for detecting HEV in swine livers. Copyright © 2014 Elsevier B.V. All rights reserved.

Effect of Phosphate-Buffered Solution Corrosion on the Ratcheting Fatigue Behavior of a Duplex Mg-Li-Al Alloy

NASA Astrophysics Data System (ADS)

Yuan, Xin; Yu, Dunji; Gao, Li-Lan; Gao, Hong

2016-05-01

This work reports the uniaxial ratcheting and fatigue behavior of a duplex Mg-Li-Al alloy under the influence of phosphate-buffered solution corrosion. Microstructural observations reveal pitting and filament corrosion defects, which impair the load-bearing capacity of the alloy and cause stress concentration, thus leading to an accelerated accumulation of ratcheting strain and shortened fatigue life under the same nominal loading conditions. Comparing Smith model, Smith-Watson-Topper model, and Paul-Sivaprasad-Dhar model, a ratcheting fatigue life prediction model based on the Broberg damage rule and the Paul-Sivaprasad-Dhar model was proposed, and the model yielded a superior prediction for the studied magnesium alloy.

Influence of albumin on the electrochemical behaviour of Zr in phosphate buffered saline solutions.

PubMed

Wang, Lu-Ning; Huang, Xian-Qiu; Shinbine, Alyssa; Luo, Jing-Li

2013-02-01

The corrosion behaviour of Zr in phosphate buffered saline (PBS) solutions with various concentrations (0-4 g L(-1)) of albumin was studied by electrochemical techniques and surface analysis. Addition of albumin to PBS solutions moved the open circuit potential (OCP) to less nobler direction. OCP, polarization resistance and impedance increased and the corrosion current decreased over immersion duration. At early stages of immersion, the resistance was increased with the concentration of albumin because of the high adsorption kinetics of albumin on metal. After the long term immersion, the resistance in PBS without albumin was higher than PBS with albumin owing to the anodic dissolution effect of albumin on metal. According to the analysis of effective capacitances, a normal distribution of time-constants was proposed to estimate the surface film on Zr. A corrosion mechanism of Zr in PBS with different albumin was proposed based on electrochemical analysis.

Buffer capacity of biologics--from buffer salts to buffering by antibodies.

PubMed

Karow, Anne R; Bahrenburg, Sven; Garidel, Patrick

2013-01-01

Controlling pH is essential for a variety of biopharmaceutical process steps. The chemical stability of biologics such as monoclonal antibodies is pH-dependent and slightly acidic conditions are favorable for stability in a number of cases. Since control of pH is widely provided by added buffer salts, the current study summarizes the buffer characteristics of acetate, citrate, histidine, succinate, and phosphate buffers. Experimentally derived values largely coincide with values calculated from a model that had been proposed in 1922 by van Slyke. As high concentrated protein formulations become more and more prevalent for biologics, the self-buffering potential of proteins becomes of relevance. The current study provides information on buffer characteristics for pH ranges down to 4.0 and up to 8.0 and shows that a monoclonal antibody at 50 mg/mL exhibits similar buffer capacity as 6 mM citrate or 14 mM histidine (pH 5.0-6.0). Buffer capacity of antibody solutions scales linearly with protein concentration up to more than 200 mg/mL. At a protein concentration of 220 mg/mL, the buffer capacity resembles the buffer capacity of 30 mM citrate or 50 mM histidine (pH 5.0-6.0). The buffer capacity of monoclonal antibodies is practically identical at the process relevant temperatures 5, 25, and 40°C. Changes in ionic strength of ΔI=0.15, in contrast, can alter the buffer capacity up to 35%. In conclusion, due to efficient self-buffering by antibodies in the pH range of favored chemical stability, conventional buffer excipients could be dispensable for pH stabilization of high concentrated protein solutions. Copyright © 2013 American Institute of Chemical Engineers.

Influence of some mononucleotides and their corresponding nucleosides on the metabolism of carbohydrates in the isolated rat diaphragm muscle

PubMed Central

Beloff-Chain, Anne; Betto, P.; Bleszynski, W.; Catanzaro, Raffaella; Chain, E. B.; Dmitrovskii, A. A.; Longinotti, L.; Pocchiari, F.

1965-01-01

1. The influence of ATP on glucose metabolism was studied in the isolated rat diaphragm; it was shown that ATP increases the oxidation of glucose and the aerobic conversion of glucose into lactate, whereas it decreases glycogen synthesis. There was no influence of ATP on the anaerobic formation of lactate from glucose. 2. A maximum effect of ATP on the oxidation of glucose (about 160% increase) was obtained in the presence of 10mm-ATP; in the presence of 2mm-ATP the effect was about 65%, and was approximately constant from 10 to 90min. incubation period. 3. In a phosphate-free tris-buffered medium the oxidation of glucose was considerably decreased, but the percentage stimulation by ATP was about the same as in a phosphate-buffered medium. 4. ATP was shown to increase the oxidation of fructose, glucose 6-phosphate, glucose 1-phosphate, fructose 1,6-diphosphate and, to a much smaller extent, pyruvate. 5. ADP stimulated the oxidation of glucose to the same extent as ATP at a concentration of 2mm and the effect with AMP was only slightly less; IMP and adenosine had only a small stimulatory effect at this concentration, whereas inosine had no effect. PMID:16749165

Development and Optimization of HPLC Analysis of Metronidazole, Diloxanide, Spiramycin and Cliquinol in Pharmaceutical Dosage Forms Using Experimental Design.

PubMed

Elkhoudary, Mahmoud M; Abdel Salam, Randa A; Hadad, Ghada M

2016-11-01

A new simple, sensitive, rapid and accurate gradient reversed-phase high-performance liquid chromatography with photodiode array detector (RP-HPLC-DAD) was developed and validated for simultaneous analysis of Metronidazole (MNZ), Spiramycin (SPY), Diloxanidefuroate (DIX) and Cliquinol (CLQ) using statistical experimental design. Initially, a resolution V fractional factorial design was used in order to screen five independent factors: the column temperature (°C), pH, phosphate buffer concentration (mM), flow rate (ml/min) and the initial fraction of mobile phase B (%). pH, flow rate and initial fraction of mobile phase B were identified as significant, using analysis of variance. The optimum conditions of separation determined with the aid of central composite design were: (1) initial mobile phase concentration: phosphate buffer/methanol (50/50, v/v), (2) phosphate buffer concentration (50 mM), (3) pH (4.72), (4) column temperature 30°C and (5) mobile phase flow rate (0.8 ml min -1 ). Excellent linearity was observed for all of the standard calibration curves, and the correlation coefficients were above 0.9999. Limits of detection for all of the analyzed compounds ranged between 0.02 and 0.11 μg ml -1 ; limits of quantitation ranged between 0.06 and 0.33 μg ml -1 The proposed method showed good prediction ability. The optimized method was validated according to ICH guidelines. Three commercially available tablets were analyzed showing good % recovery and %RSD. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Phosphate and HEPES buffers potently affect the fibrillation and oligomerization mechanism of Alzheimer's A{beta} peptide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garvey, Megan; Tepper, Katharina; Haupt, Caroline

Highlights: {yields} Sodium phosphate buffer accelerated A{beta}(1-40) nucleation relative to HEPES. {yields} A{beta}(1-40) fibrils formed in the two buffers show only minor structural differences. {yields} NMR revealed that A{beta}(1-40) histidine residues mediate buffer dependent changes. -- Abstract: The oligomerization of A{beta} peptide into amyloid fibrils is a hallmark of Alzheimer's disease. Due to its biological relevance, phosphate is the most commonly used buffer system for studying the formation of A{beta} and other amyloid fibrils. Investigation into the characteristics and formation of amyloid fibrils frequently relies upon material formed in vitro, predominantly in phosphate buffers. Herein, we examine the effects onmore » the fibrillation and oligomerization mechanism of A{beta} peptide that occur due solely to the influence of phosphate buffer. We reveal that significant differences in amyloid fibrillation are observed due to fibrillation being initiated in phosphate or HEPES buffer (at physiological pH and temperature). Except for the differing buffer ions, all experimental parameters were kept constant. Fibril formation was assessed using fluorescently monitored kinetic studies, microscopy, X-ray fiber diffraction and infrared and nuclear magnetic resonance spectroscopies. Based on this set up, we herein reveal profound effects on the mechanism and speed of A{beta} fibrillation. The three histidine residues at positions 6, 13 and 14 of A{beta}(1-40) are instrumental in these mechanistic changes. We conclude that buffer plays a more significant role in fibril formation than has been generally acknowledged.« less

Reduction and conversion of 2,4,6-trinitrotoluene (TNT) by sulfide under simulated anaerobic conditions.

PubMed

Qiao, Hua; Wang, He-ling; Feng, Hua-jun; Yao, Jun; Shen, Dong-sheng; Tang, Zhi-jian

2010-07-15

To account for the fast disappearance of TNT in anaerobic fermentative liquid, we investigated TNT (TNT(0)=50 mg/L) reduction by Na(2)S at 30+/-1 degrees C in two types of buffer systems, a phosphate buffer (PB, system A) and a CH(3)COOH-NaHCO(3) buffer (system B). The effects of pH, sulfide concentration and buffer system on the conversion and reaction rate of TNT were investigated. The effect of different variables on the conversion of TNT decreased in the following order: Na(2)S concentration>pH>buffer system. A kinetics study showed that TNT reduction by Na(2)S occurred in two stages separated by a change point. The observed rate constants of the first stage K(obs-1) were 1 order of magnitude lower than those of the second stage. The TNT conversion rate increased and the time to reach the change point became shorter with increasing Na(2)S concentration and pH. A 5-fold increase in Na(2)S concentration above the theoretical stoichiometric concentration was optimum. Observed rate constants of the first stage K(obs-1) were proportional to the hydrosulfide ion concentration and the conversion rate of TNT was greater and faster in buffer system B than in system A. 2010 Elsevier B.V. All rights reserved.

Influence of the chloride ion concentration on the corrosion of high-purity Mg, ZE41 and AZ91 in buffered Hank's solution.

PubMed

Taltavull, C; Shi, Z; Torres, B; Rams, J; Atrens, A

2014-02-01

This research studied the influence of the chloride ion concentration on the corrosion behaviour of high-purity magnesium (Mg) and two Mg alloys in Hank's solution, using hydrogen evolution and weight loss. A buffer based on CO2 and NaHCO3 was used to maintain the pH constant. The corrosion behaviour was governed by a partially protective surface film, and film breakdown by the chloride ions. The carbonated calcium phosphate layer that formed in Hank's solution was important in determining the protective properties of the surface film.

Biodesulfurization of vanadium-bearing titanomagnetite concentrates and pH control of bioleaching solution

NASA Astrophysics Data System (ADS)

Liu, Xiao-rong; Jiang, Sheng-cai; Liu, Yan-jun; Li, Hui; Wang, Hua-jun

2013-10-01

Vanadium-bearing titanomagnetite concentrates were desulfurized with Acidithiobacillus ferrooxidans ( A. ferrooxidans). The sulfur content of the concentrates was reduced from 0.69wt% to 0.14wt% after bioleaching for 15 d with a 10% pulp density at 30°C. Maintaining a stable pH value during biodesulfurization was critical because of high acid consumption, resulting from a combination of nonoxidative and oxidative dissolution of pyrrhotite in acid solution. It is discovered that the citric acid-disodium hydrogen phosphate buffer of pH 2.0 can control the solution pH value smoothly in the optimal range of 2.0-3.0 for A. ferrooxidans growth. Using the buffer in the volume fraction range of 5.0%-15.0% stimulates A. ferrooxidans growth and improves the biodesulfurization efficiency. Compared with the buffer-free control case, the maximum increase of biodesulfurization rate is 29.7% using a 10.0vol% buffer. Bioleaching provides an alternative process for desulfurization of vanadium-bearing titanomagnetite ores.

Simple, sensitive, selective and validated spectrophotometric methods for the estimation of a biomarker trigonelline from polyherbal gels

NASA Astrophysics Data System (ADS)

Chopra, Shruti; Motwani, Sanjay K.; Ahmad, Farhan J.; Khar, Roop K.

2007-11-01

Simple, accurate, reproducible, selective, sensitive and cost effective UV-spectrophotometric methods were developed and validated for the estimation of trigonelline in bulk and pharmaceutical formulations. Trigonelline was estimated at 265 nm in deionised water and at 264 nm in phosphate buffer (pH 4.5). Beer's law was obeyed in the concentration ranges of 1-20 μg mL -1 ( r2 = 0.9999) in deionised water and 1-24 μg mL -1 ( r2 = 0.9999) in the phosphate buffer medium. The apparent molar absorptivity and Sandell's sensitivity coefficient were found to be 4.04 × 10 3 L mol -1 cm -1 and 0.0422 μg cm -2/0.001A in deionised water; and 3.05 × 10 3 L mol -1 cm -1 and 0.0567 μg cm -2/0.001A in phosphate buffer media, respectively. These methods were tested and validated for various parameters according to ICH guidelines. The detection and quantitation limits were found to be 0.12 and 0.37 μg mL -1 in deionised water and 0.13 and 0.40 μg mL -1 in phosphate buffer medium, respectively. The proposed methods were successfully applied for the determination of trigonelline in pharmaceutical formulations (vaginal tablets and bioadhesive vaginal gels). The results demonstrated that the procedure is accurate, precise, specific and reproducible (percent relative standard deviation <2%), while being simple and less time consuming and hence can be suitably applied for the estimation of trigonelline in different dosage forms and dissolution studies.

Oligoglyceric acid synthesis by autocondensation of glyceroyl thioester

NASA Technical Reports Server (NTRS)

Weber, A. L.

1986-01-01

The autocondensation of the glyceroyl thioester, S-glyceroyl-ethane-thiol, yielded olioglyceric acid. The rates of autocondensation and hydrolysis of the thioester increased from pH 6.5 to pH 7.5 in 2,6-lutidine and imidazole buffers. Autocondensation and hydrolysis were much more rapid in imidazole buffers as compared to 2,6-lutidine and phosphate buffers. The efficiency of ester bond synthesis was about 20% for 40 mM S-glyceroyl-ethane-thiol in 2,6-lutidine and imidazole buffers near neutral pH. The size and yield of the olioglyceric acid products increased when the concentration of the thioester was increased. The relationship of these results to prebiotic polymer synthesis is discussed.

On the Stability of DNA Origami Nanostructures in Low-Magnesium Buffers.

PubMed

Kielar, Charlotte; Xin, Yang; Shen, Boxuan; Kostiainen, Mauri A; Grundmeier, Guido; Linko, Veikko; Keller, Adrian

2018-05-25

DNA origami have great potential as functional platforms in various biomedical applications. Many applications, however, are incompatible with the high Mg2+ concentrations commonly believed to be a prerequisite for maintaining DNA origami integrity. Here, we investigate DNA origami stability in low-Mg2+ buffers. DNA origami stability is found to crucially depend on the availability of residual Mg2+ ions for screening electrostatic repulsion. The presence of EDTA and phosphate ions may thus facilitate DNA origami denaturation by displacing Mg2+ ions from the DNA backbone and reducing the strength of the Mg2+-DNA interaction, respectively. Most remarkably, these buffer dependencies are affected by DNA origami superstructure. However, by rationally selecting buffer components and considering superstructure-dependent effects, the structural integrity of a given DNA origami nanostructure can be maintained in conventional buffers even at Mg2+ concentrations in the low-μM range. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation and properties of BSA-loaded microspheres based on multi-(amino acid) copolymer for protein delivery

PubMed Central

Chen, Xingtao; Lv, Guoyu; Zhang, Jue; Tang, Songchao; Yan, Yonggang; Wu, Zhaoying; Su, Jiacan; Wei, Jie

2014-01-01

A multi-(amino acid) copolymer (MAC) based on ω-aminocaproic acid, γ-aminobutyric acid, L-alanine, L-lysine, L-glutamate, and hydroxyproline was synthetized, and MAC microspheres encapsulating bovine serum albumin (BSA) were prepared by a double-emulsion solvent extraction method. The experimental results show that various preparation parameters including surfactant ratio of Tween 80 to Span 80, surfactant concentration, benzyl alcohol in the external water phase, and polymer concentration had obvious effects on the particle size, morphology, and encapsulation efficiency of the BSA-loaded microspheres. The sizes of BSA-loaded microspheres ranged from 60.2 μm to 79.7 μm, showing different degrees of porous structure. The encapsulation efficiency of BSA-loaded microspheres also ranged from 38.8% to 50.8%. BSA release from microspheres showed the classic biphasic profile, which was governed by diffusion and polymer erosion. The initial burst release of BSA from microspheres at the first week followed by constant slow release for the next 7 weeks were observed. BSA-loaded microspheres could degrade gradually in phosphate buffered saline buffer with pH value maintained at around 7.1 during 8 weeks incubation, suggesting that microsphere degradation did not cause a dramatic pH drop in phosphate buffered saline buffer because no acidic degradation products were released from the microspheres. Therefore, the MAC microspheres might have great potential as carriers for protein delivery. PMID:24855351

Role of protein concentration and protein-saliva interactions in the astringency of whey proteins at low pH.

PubMed

Kelly, M; Vardhanabhuti, B; Luck, P; Drake, M A; Osborne, J; Foegeding, E A

2010-05-01

Whey protein beverages are adjusted to pH <4.5 to enhance clarity and stability, but this pH level is also associated with increased astringency. The goal of this investigation was to determine the effects of protein concentration on astringency and interactions between whey and salivary proteins. Whey protein beverages containing 0.25 to 13% (wt/wt) beta-lactoglobulin and 0.017% (wt/wt) sucralose at pH 2.6 to 4.2 were examined using descriptive sensory analysis. Controls were similar pH phosphate buffers at phosphate concentrations equivalent to the amount of phosphoric acid required to adjust the pH of the protein solution. Changes in astringency with protein concentration depended on pH. At pH 3.5, astringency significantly increased with protein concentration from 0.25 to 4% (wt/wt) and then remained constant from 4 to 13% (wt/wt). Conversely, at pH 2.6, astringency decreased with an increase in protein concentration [0.5-10% (wt/wt)]. This suggests a complex relationship that includes pH and buffering capacity of the beverages. Furthermore, saliva flow rates increased with increasing protein concentrations, showing that the physiological conditions in the mouth change with protein concentration. Maximum turbidity of whey protein-saliva mixtures was observed between pH 4.6 and 5.2. Both sensory evaluation and in vitro study of interactions between beta-LG and saliva indicate that astringency of whey proteins is a complex process determined by the extent of aggregation occurring in the mouth, which depends on the whey protein beverage pH and buffering capacity in addition to saliva flow rate. Copyright 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Anolyte recycling enhanced bioelectricity generation of the buffer-free single-chamber air-cathode microbial fuel cell.

PubMed

Ren, Yueping; Chen, Jinli; Shi, Yugang; Li, Xiufen; Yang, Na; Wang, Xinhua

2017-11-01

Anolyte acidification is an inevitable restriction for the bioelectricity generation of buffer-free microbial fuel cells (MFCs). In this work, acidification of the buffer-free KCl anolyte has been thoroughly eliminated through anolyte recycling. The accumulated HCO 3 - concentration in the recycled KCl anolyte was above 50mM, which played as natural buffer and elevated the anolyte pH to above 8. The maximum power density (P max ) increased from 322.9mWm -2 to 527.2mWm -2 , which is comparable with the phosphate buffered MFC. Besides Geobacter genus, the gradually increased anolyte pH and conductivity induced the growing of electrochemically active Geoalkalibacter genus, in the anode biofilm. Anolyte recycling is a feasible strategy to strengthen the self-buffering capacity of buffer-free MFCs, thoroughly eliminate the anolyte acidification and prominently enhance the electric power. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of source and particle size of supplemental phosphate on rumen function of steers fed high concentrate diets.

PubMed

Murphy, M R; Whetstone, H D; Davis, C L

1983-12-01

We examined effects of source and particle size of supplemental defluorinated rock phosphate, to meet phosphorus requirements, on rumen function of 195-kg Holstein steers fed high concentrate. Two sources and two particle sizes of each source were evaluated in a 5 X 5 Latin square with 14-day periods. There was no effect of source on ruminal mH [- log (mean (H+)]; however, ruminal mH was higher in animals fed supplements of larger particle size. This effect was also evident when rumen pH versus time curves were integrated below pH 6. Animals fed supplements of larger particle size had less area below pH 6 than those fed supplements of smaller size. Ruminal buffering capacity at pH 7 was affected by diet; however, orthogonal comparisons between treatment means were not significant. Neither source nor particle size of the supplement affected ruminal fluid osmolality, total volatile fatty acid concentration, or fecal starch. Water intake and ruminal dry matter on HyCal supplemented diets; however, there was also a trend toward increasing rumen fluid volume. The net effect was little change of dilution rate of ruminal fluid. This may explain why rumen fermentation was not affected greatly. Conventional phosphate supplements may have potential as rumen buffering agents, but higher levels of feeding should be studied.

Internal acid buffering in San Joaquin Valley fog drops and its influence on aerosol processing

NASA Astrophysics Data System (ADS)

Collett, Jeffrey L.; Hoag, Katherine J.; Rao, Xin; Pandis, Spyros N.

Although several chemical pathways exist for S(IV) oxidation in fogs and clouds, many are self-limiting: as sulfuric acid is produced and the drop pH declines, the rates of these pathways also decline. Some of the acid that is produced can be buffered by uptake of gaseous ammonia. Additional internal buffering can result from protonation of weak and strong bases present in solution. Acid titrations of high pH fog samples (median pH=6.49) collected in California's San Joaquin Valley reveal the presence of considerable internal acid buffering. In samples collected at a rural location, the observed internal buffering could be nearly accounted for based on concentrations of ammonia and bicarbonate present in solution. In samples collected in the cities of Fresno and Bakersfield, however, significant additional, unexplained buffering was present over a pH range extending from approximately four to seven. The additional buffering was found to be associated with dissolved compounds in the fogwater. It could not be accounted for by measured concentrations of low molecular weight ( C1- C3) carboxylic acids, S(IV), phosphate, or nitrophenols. The amount of unexplained buffering in individual fog samples was found to correlate strongly with the sum of sample acetate and formate concentrations, suggesting that unmeasured organic species may be important contributors. Simulation of a Bakersfield fog episode with and without the additional, unexplained buffering revealed a significant impact on the fog chemistry. When the additional buffering was included, the simulated fog pH remained 0.3-0.7 pH units higher and the amount of sulfate present after the fog evaporated was increased by 50%. Including the additional buffering in the model simulation did not affect fogwater nitrate concentrations and was found to slightly decrease ammonium concentrations. The magnitude of the buffering effect on aqueous sulfate production is sensitive to the amount of ozone present to oxidize S(IV) in these high pH fogs.

Electrochemical Behavior Assessment of As-Cast Mg-Y-RE-Zr Alloy in Phosphate Buffer Solutions (X Na3PO4 + Y Na2HPO4) Using Electrochemical Impedance Spectroscopy and Mott-Schottky Techniques

NASA Astrophysics Data System (ADS)

Fattah-alhosseini, Arash; Asgari, Hamed

2018-05-01

In the present study, electrochemical behavior of as-cast Mg-Y-RE-Zr alloy (RE: rare-earth alloying elements) was investigated using electrochemical tests in phosphate buffer solutions (X Na3PO4 + Y Na2HPO4). X-ray diffraction techniques and Scanning electron microscopy equipped with energy dispersive x-ray spectroscopy were used to investigate the microstructure and phases of the experimental alloy. Different electrochemical tests such as potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) and Mott-Schottky (M-S) analysis were carried out in order to study the electrochemical behavior of the experimental alloy in phosphate buffer solutions. The PDP curves and EIS measurements indicated that the passive behavior of the as-cast Mg-Y-RE-Zr alloy in phosphate buffer solutions was weakened by an increase in the pH, which is related to formation of an imperfect and less protective passive layer on the alloy surface. The presence of the insoluble zirconium particles along with high number of intermetallic phases of RE elements mainly Mg24Y5 in the magnesium matrix can deteriorate the corrosion performance of the alloy by disrupting the protective passive layer that is formed at pH values over 11. These insoluble zirconium particles embedded in the matrix can detrimentally influence the passivation. The M-S analysis revealed that the formed passive layers on Mg-Y-RE-Zr alloy behaved as an n-type semiconductor. An increase in donor concentration accompanying solutions of higher alkalinity is thought to result in the formation of a less resistive passive layer.

Mechanisms of Arsenic Hyperaccumulation in Pteris vittata. Uptake Kinetics, Interactions with Phosphate, and Arsenic Speciation1

PubMed Central

Wang, Junru; Zhao, Fang-Jie; Meharg, Andrew A.; Raab, Andrea; Feldmann, Joerg; McGrath, Steve P.

2002-01-01

The mechanisms of arsenic (As) hyperaccumulation in Pteris vittata, the first identified As hyperaccumulator, are unknown. We investigated the interactions of arsenate and phosphate on the uptake and distribution of As and phosphorus (P), and As speciation in P. vittata. In an 18-d hydroponic experiment with varying concentrations of arsenate and phosphate, P. vittata accumulated As in the fronds up to 27,000 mg As kg−1 dry weight, and the frond As to root As concentration ratio varied between 1.3 and 6.7. Increasing phosphate supply decreased As uptake markedly, with the effect being greater on root As concentration than on shoot As concentration. Increasing arsenate supply decreased the P concentration in the roots, but not in the fronds. Presence of phosphate in the uptake solution decreased arsenate influx markedly, whereas P starvation for 8 d increased the maximum net influx by 2.5-fold. The rate of arsenite uptake was 10% of that for arsenate in the absence of phosphate. Neither P starvation nor the presence of phosphate affected arsenite uptake. Within 8 h, 50% to 78% of the As taken up was distributed to the fronds, with a higher translocation efficiency for arsenite than for arsenate. In fronds, 49% to 94% of the As was extracted with a phosphate buffer (pH 5.6). Speciation analysis using high-performance liquid chromatography-inductively coupled plasma mass spectroscopy showed that >85% of the extracted As was in the form of arsenite, and the remaining mostly as arsenate. We conclude that arsenate is taken up by P. vittata via the phosphate transporters, reduced to arsenite, and sequestered in the fronds primarily as As(III). PMID:12428020

Optimizing buffering chemistry to maintain near neutral pH of broiler feed during pre-enrichment for Salmonella.

PubMed

Berrang, M E; Cosby, D E; Cox, N A; Cason, J A; Richardson, K E

2015-12-01

Salmonella is a human pathogen that can accompany live broilers to the slaughter plant, contaminating fully processed carcasses. Feed is one potential source of Salmonella to growing broilers. Monitoring feed for the presence of Salmonella is part of good agricultural practice. The first step in culturing feed for Salmonella (which may be at low numbers and sub-lethally stressed) is to add it to a pre-enrichment broth which is incubated for 24 h. During the course of pre-enrichment, extraneous bacteria metabolize carbohydrates in some feed and excrete acidic byproducts, causing the pH to drop dramatically. An acidic pre-enrichment pH can injure or kill Salmonella resulting in a failure to detect, even if it is present and available to infect chickens. The objective of this study was to test an array of buffering chemistries to prevent formation of an injurious acidic environment during pre-enrichment of feed in peptone water. Five grams of feed were added to 45 mL of peptone water buffered with carbonate, Tris pH 8, and phosphate buffering ingredients individually and in combination. Feed was subjected to a pre-enrichment at 35°C for 24 h; pH was measured at 0, 18, and 24 h. Standard phosphate buffering ingredients at concentrations up to 4 times the normal formulation were unable to fully prevent acidic conditions. Likewise, carbonate and Tris pH 8 were not fully effective. The combination of phosphate, carbonate, and Tris pH 8 was the most effective buffer tested. It is recommended that a highly buffered pre-enrichment broth be used to examine feed for the presence of Salmonella. Published by Oxford University Press on behalf of Poultry Science Association 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Spatial and Diel Variability in Photosynthetic and Photoprotective Pigments in Shallow Benthic Communities

DTIC Science & Technology

2002-09-30

phycocyanin analyses, the sediments were extracted repeatedly with a phosphate buffer. An ultrasonicator was used to extract pigments. Concentrations...species composition. While phycoerythrin concentrations varied around 20-fold, phycocyanin varied approximately 70-fold. The highest levels of...chlorophylls a and c, and phycocyanin were found in grapestone sediments and the lowest levels of chlorophylls a and c were found in ooid sands

Solubility of ammonium acid urate nephroliths from bottlenose dolphins (Tursiops truncatus).

PubMed

Argade, Sulabha; Smith, Cynthia R; Shaw, Timothy; Zupkas, Paul; Schmitt, Todd L; Venn-Watson, Stephanie; Sur, Roger L

2013-12-01

Nephrolithiasis has been identified in managed populations of bottlenose dolphins (Tursiops truncatus); most of these nephroliths are composed of 100% ammonium acid urate (AAU). Several therapies are being investigated to treat and prevent nephrolithiasis in dolphins including the alkalization of urine for dissolution of nephroliths. This study evaluates the solubility of AAU nephroliths in a phosphate buffer, pH range 6.0-8.0, and in a carbonate-bicarbonate buffer, pH range 9.0-10.8. AAU nephroliths were obtained from six dolphins and solubility studies were conducted using reverse-phase high performance liquid chromatography with ultraviolet detection at 290 nm. AAU nephroliths were much more soluble in a carbonate-bicarbonate buffer, pH range 9.0-10.8 compared to phosphate buffer pH range 6.0-8.0. In the pH range 6.0-8.0, the solubility was 45% lower in potassium phosphate buffer compared to sodium phosphate buffer. When citrate was used along with phosphate in the same pH range, the solubility was improved by 13%. At pH 7 and pH 8, 150 mM ionic strength buffer was optimum for dissolution. In summary, adjustment of urinary pH alone does not appear to be a useful way to treat AAU stones in bottlenose dolphins. Better understanding of the pathophysiology of AAU nephrolithiasis in dolphins is needed to optimize kidney stone prevention and treatment.

Improvement of Starch Digestion Using α-Amylase Entrapped in Pectin-Polyvinyl Alcohol Blend

PubMed Central

Cruz, Maurício; Fernandes, Kátia; Cysneiros, Cristine; Nassar, Reginaldo; Caramori, Samantha

2015-01-01

Polyvinyl alcohol (PVA) and pectin blends were used to entrap α-amylase (Termamyl) using glutaraldehyde as a cross-linker. The effect of glutaraldehyde concentration (0.25, 0.5, 0.75, 1.0, and 1.25%) on the activity of the immobilized enzyme and rate of enzyme released was tested during a 24 h period. Characteristics of the material, such as scanning electron microscopy (SEM), tensile strength (TS), elongation, and rate of dissolution in water (pH 5.7), ruminal buffering solution (pH 7.0), and reactor containing 0.1 mol L−1 sodium phosphate buffer (pH 6.5), were also analyzed. SEM results showed that the surfaces of the pectin/PVA/amylase films were highly irregular and rough. TS values increased as a function of glutaraldehyde concentration, whereas percentage of elongation (%E) decreased. Pectin/PVA/amylase films presented similar values of solubility in the tested solvents. The material obtained with 0.25% glutaraldehyde performed best with repeated use (active for 24 h), in a phosphate buffer reactor. By contrast, the material obtained with 1.25% glutaraldehyde presented higher performance during in vitro testing using an artificial rumen. The results suggest that pectin/PVA/amylase is a highly promising material for biotechnological applications. PMID:25949991

ELECTROPHORETIC MOBILITIES OF ESCHERICHIA COLI 0157:H7 AND WILD-TYPE ESCHERICHIA COLI STRAINS

EPA Science Inventory

The electrophoretic mobility (EPM) of a number of human-virulent and "wild-type" Escherichia coli strains in phosphate buffered water was measured. The impact of pH, ionic strength, cation type (valence) and concentration, and bacterial strain on the EPM was investigated. Resul...

Continuous analysis of phosphate in a Greenland shallow ice core

NASA Astrophysics Data System (ADS)

Kjær, Helle Astrid; Svensson, Anders; Bigler, Matthias; Vallelonga, Paul; Kettner, Ernesto; Dahl-Jensen, Dorthe

2010-05-01

Phosphate is an important and sometimes limiting nutrient for primary production in the oceans. Because of deforestation and the use of phosphate as a fertilizer changes in the phosphate cycle have occurred over the last centuries. On longer time scales, sea level changes are thought to have also caused changes in the phosphate cycle. Analyzing phosphate concentrations in ice cores may help to gain important knowledge about those processes. In the present study, we attach a phosphate detection line to an existing continuous flow analysis (CFA) setup for ice core analysis at the University of Copenhagen. The CFA system is optimized for high-resolution measurements of insoluble dust particles, electrolytic melt water conductivity, and the concentrations of ammonium and sodium. For the phosphate analysis we apply a continuous and highly sensitive absorption method that has been successfully applied to determine phosphate concentrations of sea water (Zhang and Chi, 2002). A line of melt water from the CFA melt head (1.01 ml per minute) is combined with a molybdate blue reagent and an ascorbic acid buffer. An uncompleted reaction takes place in five meters of heated mixing coils before the absorption measurement at a wavelength of 710 nanometer takes place in a 2 m long liquid waveguide cell (LWCC) with an inner volume of 0.5 ml. The method has a detection limit of around 0.1 ppb and we are currently investigating a possible interference from molybdate reacting with silicates that are present in low amounts in the ice. Preliminary analysis of early Holocene samples from the NGRIP ice core show phosphate concentration values of a few ppb. In this study, we will attempt to determine past levels of phosphate in a shallow Northern Greenland firn core with an annual layer thickness of about 20 cm ice equivalent. With a melt speed of 2.5 cm ice per minute our method should allow the resolution of any seasonal variability in phosphate concentrations.

Calcium phosphate/chitosan composite coating: Effect of different concentrations of Mg2+ in the m-SBF on its bioactivity

NASA Astrophysics Data System (ADS)

Zhang, Jie; Dai, Changsong; Wei, Jie; Wen, Zhaohui; Zhang, Shujuan; Lin, Lemin

2013-09-01

The purpose of this study was to investigate the effect of different concentration of Mg2+ in a modified simulated body fluid (m-SBF) on the bioactivity of calcium phosphate/chitosan composite coating. Calcium phosphate/chitosan composite coating was prepared on graphite substrate via electrophoretic deposition (EPD) followed by conversion in a phosphate buffer solution (PBS). The obtained samples were soaked in the m-SBF containing different concentration of Mg2+ for different times. And then, the composite coatings were assessed using X-ray diffractometer (XRD), Fourier-transformed infrared spectroscopy (FTIR), Raman spectra, and scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS). The soaking solution was evaluated by inductively coupled plasma optical emission spectrometer (ICP-OES) test. The analytical results showed that hydroxyapatite (HA) and bone-like apatite (HCA) grew on the surface of calcium phosphate/chitosan composite coating after incubation in different m-SBF. With Mg2+ concentration in m-SBF increased from 1× Mg to 10× Mg, HA in the composite coating first presented a dissolving process and then a precipitating one slowly, while HCA presented a growing trend, continuously. The increasing of Mg2+ concentration in the m-SBF inhibited the total growing process of HA and HCA as a whole. The structure of the composite coating changed from spherical into irregular morphology with the concentration of Mg2+ increasing from 1× Mg to 10× Mg. Over all, with the Mg2+ concentration increasing, the bioactivity of calcium phosphate/chitosan composite coating tended to decrease.

31P-Nuclear Magnetic Resonance Determination of Phosphate Compartmentation in Leaves of Reproductive Soybeans (Glycine max L.) as Affected by Phosphate Nutrition 1

PubMed Central

Lauer, Michael J.; Blevins, Dale G.; Sierzputowska-Gracz, Hanna

1989-01-01

Most leaf phosphorus is remobilized to the seed during reproductive development in soybean. We determined, using 31P-NMR, the effect phosphorus remobilization has on vacuolar inorganic phosphate pool size in soybean (Glycine max [L.] Merr.) leaves with respect to phosphorus nutrition and plant development. Phosphate compartmentation between cytoplasmic and vacuolar pools was observed and followed in intact tissue grown hydroponically, at the R2, R4, and R6 growth stages. As phosphorus in the nutrient solution decreased from 0.45 to 0.05 millimolar, the vacuolar phosphate peak became less prominent relative to cytoplasmic phosphate and hexose monophosphate peaks. At a nutrient phosphate concentration of 0.05 millimolar, the vacuolar phosphate peak was not detectable. At higher levels of nutrient phosphate, as plants progressed from the R2 to the R6 growth stage, the vacuolar phosphate peak was the first to disappear, suggesting that storage phosphate was remobilized to a greater extent than metabolic phosphate. Under suboptimal phosphate nutrition (≤ 0.20 millimolar), the hexose monophosphate and cytoplasmic phosphate peaks declined earlier in reproductive development than when phosphate was present in optimal amounts. Under low phosphate concentrations (0.05 millimolar) cytoplasmic phosphate was greatly reduced. Carbon metabolism was coincidently disrupted under low phosphate nutrition as shown by the appearance of large, prominent starch grains in the leaves. Cytoplasmic phosphate, and leaf carbon metabolism dependent on it, are buffered by vacuolar phosphate until late stages of reproductive growth. Images Figure 4 PMID:16666705

Formation of Fluorohydroxyapatite with Silver Diamine Fluoride

PubMed Central

Mei, M.L.; Nudelman, F.; Marzec, B.; Walker, J.M.; Lo, E.C.M.; Walls, A.W.; Chu, C.H.

2017-01-01

Silver diamine fluoride (SDF) is found to promote remineralization and harden the carious lesion. Hydroxyapatite crystallization is a crucial process in remineralization; however, the role of SDF in crystal formation is unknown. We designed an in vitro experiment with calcium phosphate with different SDF concentrations (0.38, 1.52, 2.66, 3.80 mg/mL) to investigate the effect of this additive on the nucleation and growth of apatite crystals. Two control groups were also prepared—calcium phosphate (CaCl2·2H2O + K2HPO4 in buffer solution) and SDF (Ag[NH3]2F in buffer solution). After incubation at 37 oC for 24 h, the shape and organization of the crystals were examined by bright-field transmission electron microscopy and electron diffraction. Unit cell parameters of the obtained crystals were determined with powder X-ray diffraction. The vibrational and rotational modes of phosphate groups were analyzed with Raman microscopy. The transmission electron microscopy and selected-area electron diffraction confirmed that all solids precipitated within the SDF groups were crystalline and that there was a positive correlation between the increased percentage of crystal size and the concentration of SDF. The powder X-ray diffraction patterns indicated that fluorohydroxyapatite and silver chloride were formed in all the SDF groups. Compared with calcium phosphate control, a contraction of the unit cell in the a-direction but not the c-direction in SDF groups was revealed, which suggested that small localized fluoride anions substituted the hydroxyl anions in hydroxyapatite crystals. This was further evidenced by the Raman spectra, which displayed up-field shift of the phosphate band in all the SDF groups and confirmed that the chemical environment of the phosphate functionalities indeed changed. The results suggested that SDF reacted with calcium and phosphate ions and produced fluorohydroxyapatite. This preferential precipitation of fluorohydroxyapatite with reduced solubility could be one of the main factors for arrest of caries lesions treated with SDF. PMID:28521107

Effects of pH and Temperature on the Stability of Fumonisins in Maize Products.

PubMed

Bryła, Marcin; Waśkiewicz, Agnieszka; Szymczyk, Krystyna; Jędrzejczak, Renata

2017-03-01

This paper is a study of the stability of fumonisins in dough based on maize flour prepared in a phosphate buffer with a pH of 3.5, 5.5 or 7.5 and baked at a temperature within the range of 100-250 °C. Buffers with various pH values were tested, since it is well-known that pH may significantly influence interactions of fumonisins with other substances. A standard analytical procedure was used to determine the concentration of free fumonisins. Hydrolysis in an alkaline medium was then applied to reveal the hidden forms, while the total fumonisins concentations was determined in another measurement. The total concentration of fumonisins was statistically higher in pH = 3.5 and pH = 5.5 than the concentration of free fumonisins; no similar difference was found at pH = 7.5. The applied phosphate buffer pH 7.5 may enhance solubility of fumonisins, which would increase extraction efficiency of free analytes, thereby decreasing the difference between concentrations of total and free fumonisins. Hydrolysed B₁ fumonisin (HFB₁) and partially hydrolysed B₁ fumonisin (isomers a and b: PHFB 1a and PHFB 1b , respectively) were the main investigated substances. For baking temperatures below 220 °C, fumonisins were slightly more stable for pH = 5.5 than for pH = 3.5 and pH = 7.5. In both of these latter cases, the concentration of partially hydrolysed fumonisins grew initially (up to 200 °C) with an increase in the baking temperature, and then dropped. Similar behaviour was observed for free HFB₁, which may suggest the following fumonisin degradation mechanism: initially, the tricarballylic acid (TCA) groups are removed from the molecules, and next, the HFB₁ molecules disintegrate.

Effects of pH and Temperature on the Stability of Fumonisins in Maize Products

PubMed Central

Bryła, Marcin; Waśkiewicz, Agnieszka; Szymczyk, Krystyna; Jędrzejczak, Renata

2017-01-01

This paper is a study of the stability of fumonisins in dough based on maize flour prepared in a phosphate buffer with a pH of 3.5, 5.5 or 7.5 and baked at a temperature within the range of 100–250 °C. Buffers with various pH values were tested, since it is well-known that pH may significantly influence interactions of fumonisins with other substances. A standard analytical procedure was used to determine the concentration of free fumonisins. Hydrolysis in an alkaline medium was then applied to reveal the hidden forms, while the total fumonisins concentations was determined in another measurement. The total concentration of fumonisins was statistically higher in pH = 3.5 and pH = 5.5 than the concentration of free fumonisins; no similar difference was found at pH = 7.5. The applied phosphate buffer pH 7.5 may enhance solubility of fumonisins, which would increase extraction efficiency of free analytes, thereby decreasing the difference between concentrations of total and free fumonisins. Hydrolysed B1 fumonisin (HFB1) and partially hydrolysed B1 fumonisin (isomers a and b: PHFB1a and PHFB1b, respectively) were the main investigated substances. For baking temperatures below 220 °C, fumonisins were slightly more stable for pH = 5.5 than for pH = 3.5 and pH = 7.5. In both of these latter cases, the concentration of partially hydrolysed fumonisins grew initially (up to 200 °C) with an increase in the baking temperature, and then dropped. Similar behaviour was observed for free HFB1, which may suggest the following fumonisin degradation mechanism: initially, the tricarballylic acid (TCA) groups are removed from the molecules, and next, the HFB1 molecules disintegrate. PMID:28257053

Partial Purification and Properties of an Alkaline α-Galactosidase from Mature Leaves of Cucurbita pepo1

PubMed Central

Gaudreault, Pierre-Richard; Webb, John A.

1983-01-01

A fourth molecular from of α-galactosidase, designated LIV, an alkaline α-galactosidase, was isolated from leaves of Cucurbita pepo and purified 165-fold. It was active over a narrow pH range with optimal hydrolysis of p-nitrophenyl-α-d-galactoside and stachyose at pH 7.5. The rate of stachyose hydrolysis was 10 times that of raffinose. Km determinations in McIlvaine buffer (200 millimolar Na2-phosphate, 100 millimolar citric acid, pH 7.5) for p-nitrophenyl-α-d-galactoside, stachyose, and raffinose were 1.40, 4.5, and 36.4 millimolar, respectively. LIV was partially inhibited by Ca2+, Mg2+, and Mn2+, more so by Ni2+, Zn2+, and Co2+, and highly so by Cu2+, Ag2+, Hg2+ and by p-chloromercuribenzoate. It was not inhibited by high concentrations of the substrate p-nitrophenyl-α-d-galactoside or by myo-inositol, but α-d-galactose was a strong inhibitor. As observed for most other forms of α-galactosidase, LIV only catalyzed the hydrolysis of glycosides possessing the α-d-galactose configuration at C1, C2, and C4, and did not hydrolyze p-nitrophenyl-α-d-fucoside (α-d-galactose substituted at C6). The enzyme was highly sensitive to buffers and chelating agents. Maximum hydrolytic activity for p-nitrophenyl-α-d-galactoside was obtained in McIlvaine buffer (pH 7.5). In 10 millimolar triethanolaminehydrochloride-NaOH (pH 7.5) or 10 millimolar Hepes-NaOH (pH 7.5), hydrolytic activity was virtually eliminated, but the addition of low concentrations of either ethylenediaminetetraacetate or citrate to these buffers restored activity almost completely. Partial restoration of activity was also observed, but at higher concentrations, with pyruvate and malate. Similar effects were found for stachyose hydrolysis, but in addition some inhibition of LIV in McIlvaine buffer, possibly due to the high phosphate concentration, was observed with this substrate. It is questionable whether the organic acid anions possess any regulatory control of LIVin vivo. It was possible that the results reflected the ability of these anions, and ethylene-diaminetetraacetate, to restore LIV activity through coordination with some toxic cation introduced as a buffer contaminant. Images Fig. 1 PMID:16662884

Influence of high-conductivity buffer composition on field-enhanced sample injection coupled to sweeping in CE.

PubMed

Anres, Philippe; Delaunay, Nathalie; Vial, Jérôme; Thormann, Wolfgang; Gareil, Pierre

2013-02-01

The aim of this work was to clarify the mechanism taking place in field-enhanced sample injection coupled to sweeping and micellar EKC (FESI-Sweep-MEKC), with the utilization of two acidic high-conductivity buffers (HCBs), phosphoric acid or sodium phosphate buffer, in view of maximizing sensitivity enhancements. Using cationic model compounds in acidic media, a chemometric approach and simulations with SIMUL5 were implemented. Experimental design first enabled to identify the significant factors and their potential interactions. Simulation demonstrates the formation of moving boundaries during sample injection, which originate at the initial sample/HCB and HCB/buffer discontinuities and gradually change the compositions of HCB and BGE. With sodium phosphate buffer, the HCB conductivity increased during the injection, leading to a more efficient preconcentration by staking (about 1.6 times) than with phosphoric acid alone, for which conductivity decreased during injection. For the same injection time at constant voltage, however, a lower amount of analytes was injected with sodium phosphate buffer than with phosphoric acid. Consequently sensitivity enhancements were lower for the whole FESI-Sweep-MEKC process. This is why, in order to maximize sensitivity enhancements, it is proposed to work with sodium phosphate buffer as HCB and to use constant current during sample injection. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stability of the Stevia-Derived Sweetener Rebaudioside A in Solution as Affected by Ultraviolet Light Exposure.

PubMed

Zhang, Jiewen; Bell, Leonard N

2017-04-01

Rebaudioside A is a natural noncaloric high-potency sweetener extracted from the leaves of Stevia rebaudiana. With rebaudioside A use increasing in foods, understanding the factors affecting its stability is necessary. This project evaluated the degradation rate constants of rebaudioside A in water, 0.1 M phosphate buffer, and 0.1 M citrate buffer at pH 3 and 7 as a function of ultraviolet (UV) light intensity (365 nm, 0 μW/cm 2 for dark conditions, 27 μW/cm 2 for low intensity, and 190 μW/cm 2 for high intensity) at 32.5 °C. Rebaudioside A stability was adversely affected by light exposure. The pseudo-1st-order degradation rate constants increased significantly (P < 0.05) with increasing light intensity in all solutions. Under dark conditions, rebaudioside A in phosphate buffers was more susceptible to breakdown than in water and citrate buffers at both pH levels. However, exposure to UV light resulted in rebaudioside A degradation occurring approximately 10 times faster in citrate than in phosphate buffers at both pH levels. The sensitivity of rebaudioside A to UV light was greater in citrate buffers than in water or phosphate buffers. The use of light-protective packaging for beverages containing rebaudioside A will improve its stability. © 2017 Institute of Food Technologists®.

Enantioselective determination of (R)-zopiclone and (S)-zopiclone (eszopiclone) in human hair by micropulverized extraction and chiral liquid chromatography/high resolution mass spectrometry.

PubMed

Miyaguchi, Hajime; Kuwayama, Kenji

2017-10-13

Zopiclone and its (S)-enantiomer (eszopiclone) are commonly prescribed for insomnia. Despite the high demand for enantioselective differentiation, the chiral analysis of zopiclone in hair has not been reported. In this study, a method for the enantioselective quantification of zopiclone in human hair was developed. The extraction medium and duration were optimized using real eszopiclone-positive hair samples. Specifically, micropulverized extraction with 3.0M ammonium phosphate buffer (pH 8.4) involving salting-out assisted liquid-liquid extraction with acetonitrile was utilized to minimize the degradation of zopiclone and for rapid and facile operation. On the other hand, recovery of the conventional solid-liquid extraction involved overnight soaking in 3.0M ammonium phosphate buffer (pH 8.4) was only 0.58±0.12% of the maximum recovery achieved by the present method due to the decomposition in the phosphate buffer. An excellent chiral separation (Rs=5.0) was achieved using a chiral stationary phase comprising cellulose tris(3,5-dichlorophenylcarbamate) and a volatile mobile phase of 10mM ammonium carbonate (pH 8.0)-acetonitrile (25:75, v/v). Detection was carried out using liquid chromatography/high resolution mass spectrometry (LC/HRMS) with electrospray ionization. A Q Exactive mass spectrometer equipped with a quadrupole-Orbitrap analyzer was used for detection. The concentration of 0.50pg/mg was defined as the lowest limit of quantification using 5mg of hair sample. Using the developed approach, the concentration of eszopiclone in hair after a single 2-mg dose was found to be 441pg/mg, which was higher than all the reported values regarding a single administration of zopiclone. After daily administration of racemic zopiclone (3.75mg/day), the concentrations of (R)-enantiomer and (S)-enantiomer in the black hair were 5.30-8.31ng/mg and 7.96-12.8ng/mg, respectively, and the concentration of the (S)-enantiomer was always higher than that of the (R)-enantiomer due to the enantioselective difference in the pharmacokinetics. Copyright © 2017 Elsevier B.V. All rights reserved.

Proteins contribute insignificantly to the intrinsic buffering capacity of yeast cytoplasm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poznanski, Jaroslaw; Szczesny, Pawel; Institute of Experimental Plant Biology and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw

Highlights: Black-Right-Pointing-Pointer We predicted buffering capacity of yeast proteome from protein abundance data. Black-Right-Pointing-Pointer We measured total buffering capacity of yeast cytoplasm. Black-Right-Pointing-Pointer We showed that proteins contribute insignificantly to buffering capacity. -- Abstract: Intracellular pH is maintained by a combination of the passive buffering of cytoplasmic dissociable compounds and several active systems. Over the years, a large portion of and possibly most of the cell's intrinsic (i.e., passive non-bicarbonate) buffering effect was attributed to proteins, both in higher organisms and in yeast. This attribution was not surprising, given that the concentration of proteins with multiple protonable/deprotonable groups in themore » cell exceeds the concentration of free protons by a few orders of magnitude. Using data from both high-throughput experiments and in vitro laboratory experiments, we tested this concept. We assessed the buffering capacity of the yeast proteome using protein abundance data and compared it to our own titration of yeast cytoplasm. We showed that the protein contribution is less than 1% of the total intracellular buffering capacity. As confirmed with NMR measurements, inorganic phosphates play a crucial role in the process. These findings also shed a new light on the role of proteomes in maintaining intracellular pH. The contribution of proteins to the intrinsic buffering capacity is negligible, and proteins might act only as a recipient of signals for changes in pH.« less

Quantification of the aggregation of magnetic nanoparticles with different polymeric coatings in cell culture medium

NASA Astrophysics Data System (ADS)

Eberbeck, D.; Kettering, M.; Bergemann, C.; Zirpel, P.; Hilger, I.; Trahms, L.

2010-10-01

The knowledge of the physico-chemical characteristics of magnetic nanoparticles (MNPs) is essential to enhance the efficacy of MNP-based therapeutic treatments (e.g. magnetic heating, magnetic drug targeting). According to the literature, the MNP uptake by cells may depend on the coating of MNPs, the surrounding medium as well as on the aggregation behaviour of the MNPs. Therefore, in this study, the aggregation behaviour of MNPs in various media was investigated. MNPs with different coatings were suspended in cell culture medium (CCM) containing fetal calf serum (FCS) and the distribution of the hydrodynamic sizes was measured by magnetorelaxometry (MRX). FCS as well as bovine serum albumin (BSA) buffer (phosphate buffered saline with 0.1% bovine serum albumin) may induce MNP aggregation. Its strength depends crucially on the type of coating. The degree of aggregation in CCM depends on its FCS content showing a clear, local maximum at FCS concentrations, where the IgG concentration (part of FCS) is of the order of the MNP number concentration. Thus, we attribute the observed aggregation behaviour to the mechanism of agglutination of MNPs by serum compartments as for example IgG. No aggregation was induced for MNPs coated with dextran, polyarabic acid or sodium phosphate, respectively, which were colloidally stable in CCM.

Effect of synovial fluid, phosphate-buffered saline solution, and water on the dissolution and corrosion properties of CoCrMo alloys as used in orthopedic implants.

PubMed

Lewis, A C; Kilburn, M R; Papageorgiou, I; Allen, G C; Case, C P

2005-06-15

The corrosion and dissolution of high- and low-carbon CoCrMo alloys, as used in orthopedic joint replacements, were studied by immersing samples in phosphate-buffered saline (PBS), water, and synovial fluid at 37 degrees C for up to 35 days. Bulk properties were analyzed with a fine ion beam microscope. Surface analyses by X-ray photoelectron spectroscopy and Auger electron spectroscopy showed surprisingly that synovial fluid produced a thin oxide/hydroxide layer. Release of ions into solution from the alloy also followed an unexpected pattern where synovial fluid, of all the samples, had the highest Cr concentration but the lowest Co concentration. The presence of carbide inclusions in the alloy did not affect the corrosion or the dissolution mechanisms, although the carbides were a significant feature on the metal surface. Only one mechanism was recognized as controlling the thickness of the oxide/hydroxide interface. The analysis of the dissolved metal showed two mechanisms at work: (1) a protein film caused ligand-induced dissolution, increasing the Cr concentration in synovial fluid, and was explained by the equilibrium constants; (2) corrosion at the interface increased the Co in PBS. The effect of prepassivating the samples (ASTM F-86-01) did not always have the desired effect of reducing dissolution. The release of Cr into PBS increased after prepassivation. The metal-synovial fluid interface did not contain calcium phosphate as a deposit, typically found where samples are exposed to calcium rich bodily fluids. (c) 2005 Wiley Periodicals, Inc.

A Chemist’s Perspective on the Role of Phosphorus at the Origins of Life

PubMed Central

Fernández-García, Christian; Coggins, Adam J.

2017-01-01

The central role that phosphates play in biological systems, suggests they also played an important role in the emergence of life on Earth. In recent years, numerous important advances have been made towards understanding the influence that phosphates may have had on prebiotic chemistry, and here, we highlight two important aspects of prebiotic phosphate chemistry. Firstly, we discuss prebiotic phosphorylation reactions; we specifically contrast aqueous electrophilic phosphorylation, and aqueous nucleophilic phosphorylation strategies, with dry-state phosphorylations that are mediated by dissociative phosphoryl-transfer. Secondly, we discuss the non-structural roles that phosphates can play in prebiotic chemistry. Here, we focus on the mechanisms by which phosphate has guided prebiotic reactivity through catalysis or buffering effects, to facilitating selective transformations in neutral water. Several prebiotic routes towards the synthesis of nucleotides, amino acids, and core metabolites, that have been facilitated or controlled by phosphate acting as a general acid–base catalyst, pH buffer, or a chemical buffer, are outlined. These facile and subtle mechanisms for incorporation and exploitation of phosphates to orchestrate selective, robust prebiotic chemistry, coupled with the central and universally conserved roles of phosphates in biochemistry, provide an increasingly clear message that understanding phosphate chemistry will be a key element in elucidating the origins of life on Earth. PMID:28703763

In vitro dissolution of proton-pump inhibitor products intended for paediatric and geriatric use in physiological bicarbonate buffer.

PubMed

Liu, Fang; Shokrollahi, Honaz

2015-05-15

Proton-pump inhibitor (PPI) products based on enteric coated multiparticulates are design to meet the needs of patients who cannot swallow tablets such as children and older adults. Enteric coated PPI preparations exhibit delays in in vivo absorption and onset of antisecretory effects, which is not reflected by the rapid in vitro dissolution in compendial pH 6.8 phosphate buffer commonly used for assessment of these products. A more representative and physiological medium, pH 6.8 mHanks bicarbonate buffer, was used in this study to evaluate the in vitro dissolution of enteric coated multiparticulate-based PPI products. Commercially available omeprazole, lansoprazole and esomeprazole products were subject to dissolution tests using USP-II apparatus in pH 4.5 phosphate buffer saline for 45 min (acid stage) followed by pH 6.8 phosphate buffer or pH 6.8 mHanks bicarbonate buffer. In pH 6.8 phosphate buffer, all nine tested products displayed rapid and comparable dissolution profiles meeting the pharmacopeia requirements for delayed release preparations. In pH 6.8 mHanks buffer, drug release was delayed and failed the pharmacopeia requirements from most enteric coated preparations. Despite that the same enteric polymer, methacrylic acid-ethyl acrylate copolymer (1:1), was applied to all commercial multiparticulate-based products, marked differences were observed between dissolution profiles of these preparations. The use of pH 6.8 physiological bicarbonate (mHanks) buffer can serve as a useful tool to provide realistic and discriminative in vitro release assessment of enteric coated PPI preparations and to assist rational formulation development of these products. Copyright © 2015 Elsevier B.V. All rights reserved.

Diurnal shifts in co-distributions of sulfide and iron(II) and profiles of phosphate and ammonium in the rhizosphere of Zostera capricorni

NASA Astrophysics Data System (ADS)

Pagès, Anaïs; Welsh, David T.; Robertson, David; Panther, Jared G.; Schäfer, Jörg; Tomlinson, Rodger B.; Teasdale, Peter R.

2012-12-01

High resolution, two dimensional distributions of porewater iron(II) and sulfide were measured, using colourimetric DET (diffusive equilibration in a thin film) and DGT (diffusive gradients in a thin film) techniques, respectively, in Zostera capricorni colonised sediments under both light and dark conditions. Low resolution depth profiles of ammonium and phosphate were measured using conventional DET and DGT methods, respectively. Porewater iron(II) and sulfide distributions showed a high degree of spatial heterogeneity under both light and dark conditions, and distributions were characterised by a complex mosaic of sediment zones dominated by either iron(II) or sulfide. However, there was a clear shift in overall redox conditions between light and dark conditions. During light deployments, iron(II) and sulfide concentrations were generally low throughout the rhizosphere, apart from a few distinct "hotspots" of high concentration. Whereas during dark deployments, high concentrations of iron(II) were sometimes measured in the near surface sediments and sulfide depth distributions migrated towards the sediment surface. Profiles of porewater ammonium and phosphate demonstrated an increase in ammonium concentrations under dark compared to light conditions. Surprisingly, despite the large changes in iron(II) distributions between light and dark conditions, phosphate profiles remained similar, indicating that adsorption/release of phosphate by iron(III) hydr(oxide) mineral formation and reduction was not a major factor regulating porewater phosphate concentrations in these sediments or that phosphate uptake by the seagrass roots persisted during the dark period. Overall, the results demonstrate that the photosynthetic activity of the seagrass played a significant role in regulating sulfide, iron(II) and ammonium concentrations in the rhizosphere, due to rates of radial oxygen loss and ammonium uptake by the roots and rhizomes being lower under dark compared to light conditions. This cyclic production and reduction of iron(III) hydr(oxides) in the rhizosphere may act as a buffering system preventing sulfide accumulation.

Precise method for the measurement of catalase activity in honey.

PubMed

Huidobro, José F; Sánchez, M Pilar; Muniategui, Soledad; Sancho, M Teresa

2005-01-01

An improved method is reported for the determination of catalase activity in honey. We tested different dialysis membranes, dialysis fluid compositions and amounts, dialysis temperatures, sample amounts, and dialysis times. The best results were obtained by dialysis of 7.50 g sample in a cellulose dialysis sack, using two 3 L portions of 0.015 M sodium phosphate buffer (pH 7.0) as the dialysis fluid at 4 degrees C for 22 h. As in previous methods, catalase activity was determined on the basis of the rate of disappearance of the substrate, H202, with the H202 determined spectrophotometrically at 400 nm in an assay system containing o-dianisidine and peroxidase. Trials indicated that the best solvent for the o-dianisidine was 0.2 M sodium phosphate buffer, pH 6.1; the best starting H202 concentration was 3 mM; the best HCl concentration for stopping the reaction was 6 N; and the best sample volume for catalase measurement was 7.0 mL. Precision values (relative standard deviations for analyses of 10 subsamples of each of 3 samples) were high, ranging from 0.48% for samples with high catalase activity to 1.98% for samples with low catalase activity.

Studies on aqueous two phase polymer systems useful for partitioning of biological materials

NASA Technical Reports Server (NTRS)

Brooks, D. E.; Bamberger, S.

1982-01-01

The two phase systems that result when aqueous solutions of dextran and poly(ethylene glycol) (PEG) are mixed above a critical concentration of a few percent provide a useful medium for the separation of biological cell subpopulations via partition between the top, PEG-rich phase and the liquid-liquid phase boundary. Interfacial tensions of such systems have been measured by the rotating drop technique and found to range between 0.1-100 micro-N/m. The tension was found to depend on the length of the tie line describing the system on a phase diagram, via a power law relationship which differed depending on the concentration of Na phosphate buffer present. The electrokinetic properties of drops of one phase suspended in the other were studied for a variety of systems. It was found that the droplet electrophoretic mobility increased monotonically with phosphate concentration and drop diameter but exhibited the opposite sign from that anticipated from phosphate partition measurements. It was possible to take advantage of these electrokinetic properties and dramatically enhance the speed of phase separation through application of relatively small electric fields.

Increasing the potency of an alhydrogel-formulated anthrax vaccine by minimizing antigen-adjuvant interactions.

PubMed

Watkinson, Allan; Soliakov, Andrei; Ganesan, Ashok; Hirst, Karie; Lebutt, Chris; Fleetwood, Kelly; Fusco, Peter C; Fuerst, Thomas R; Lakey, Jeremy H

2013-11-01

Aluminum salts are the most widely used vaccine adjuvants, and phosphate is known to modulate antigen-adjuvant interactions. Here we report an unexpected role for phosphate buffer in an anthrax vaccine (SparVax) containing recombinant protective antigen (rPA) and aluminum oxyhydroxide (AlOH) adjuvant (Alhydrogel). Phosphate ions bind to AlOH to produce an aluminum phosphate surface with a reduced rPA adsorption coefficient and binding capacity. However, these effects continued to increase as the free phosphate concentration increased, and the binding of rPA changed from endothermic to exothermic. Crucially, phosphate restored the thermostability of bound rPA so that it resembled the soluble form, even though it remained tightly bound to the surface. Batches of vaccine with either 0.25 mM (subsaturated) or 4 mM (saturated) phosphate were tested in a disease model at batch release, which showed that the latter was significantly more potent. Both formulations retained their potency for 3 years. The strongest aluminum adjuvant effects are thus likely to be via weakly attached or easily released native-state antigen proteins.

High-performance liquid chromatography method for the simultaneous determination of sulfamethoxazole and trimethoprim in bovine milk using an on-line clean-up column.

PubMed

Pereira, A V; Cass, Q B

2005-11-05

A bidimensional HPLC method for the simultaneous determination of sulfamethoxazole (SMX) and trimethoprim (TMP) in bovine milk has been developed and validated. After centrifugation, aliquots (150 microl) of milk samples were directly injected to a column-switching HPLC system. At the first step a RAM octyl-BSA column was employed to automatically remove proteins that otherwise would interfere with milk analysis. The mobile phase 0.01 M phosphate buffer pH 6.0:acetonitrile (95:5, v/v) was used in the first 5 min for the elution of milk proteins and then 0.01 M phosphate buffer pH 6.0:acetonitrile (83:17, v/v) for transfer SMX and TMP to the analytical column. The separation of SMX and TMP from one another and from other remaining milk components was performed on an octyl column using the mobile phase 0.01 M phosphate buffer pH 5.0:acetonitrile (82:18, v/v), which were detected by UV at 265 nm. The calibration graphs were linear in the concentration ranges of 25-800 ng/ml and 50-400 ng/ml for SMX and TMP, respectively. The intra- and inter-assay coefficients of variation were less than 15% for both drugs. The validated method was applied to the analysis of milk samples of twelve (two groups of six) cows after administration (intramuscular or subcutaneous) of a single recommended therapeutic dose of the SMX-TMP combination.

Determination of size distribution and encapsulation efficiency of liposome-encapsulated hemoglobin blood substitutes using asymmetric flow field-flow fractionation coupled with multi-angle static light scattering.

PubMed

Arifin, Dian R; Palmer, Andre F

2003-01-01

In this study, we investigated the size distribution, encapsulation efficiency, and oxygen affinity of liposome-encapsulated tetrameric hemoglobin (LEHb) dispersions and correlated the data with the variation in extruder membrane pore size, ionic strength of the extrusion buffer, and hemoglobin (Hb) concentration. Asymmetric flow field-flow fractionation (AFFF) in series with multi-angle static light scattering (MASLS) was used to study the LEHb size distribution. We also introduced a novel method to measure the encapsulation efficiency using a differential interferometric refractive index (DIR) detector coupled to the AFFF-MASLS system. This technique was nondestructive toward the sample and easy to implement. LEHbs were prepared by extrusion using a lipid combination of dimyristoyl-phosphatidylcholine, cholesterol, and dimyristoyl-phosphatidylglycerol in a 10:9:1 molar ratio. Five initial Hb concentrations (50, 100, 150, 200, and 300 mg Hb per mL of buffer) extruded through five different membrane pore diameters (400, 200, 100, 80, and 50 nm) were studied. Phosphate buffered saline (PBS) and phosphate buffer (PB) both at pH 7.3 were used as extrusion buffers. Despite the variation, extrusion through 400-nm pore diameter membranes produced LEHbs smaller than the pore size, extrusion through 200-nm membranes produced LEHbs with diameters close to the pore diameter, and extrusion through 100-, 80-, and 50-nm membranes produced LEHbs larger than the pore sizes. We found that the choice of extrusion buffer had the greatest effect on the LEHb size distribution compared to either Hb concentration or extruder membrane pore size. Extrusion in PBS produced larger LEHbs and more monodisperse LEHb dispersions. However, LEHbs extruded in PB generally had higher Hb encapsulation efficiencies and lower methemoglobin (metHb) levels. The choice of extrusion buffer also affected how the encapsulation efficiency correlated with Hb concentration, extruder pore size, and the metHb level. The most optimum encapsulation efficiency and amount of Hb entrapped were achieved at the highest Hb concentration and the largest pore size for both extrusion buffers (62.38% and 187.14 mg Hb/mL of LEHb dispersion extruded in PBS, and 69.98% and 209.94 mg Hb/mL of LEHb dispersion extruded in PB). All LEHbs displayed good oxygen-carrying properties as indicated by their P(50) and cooperativity coefficients. LEHbs extruded in PB had an average P(50) of 23.04 mmHg and an average Hill number of 2.29, and those extruded in PBS had average values of 27.25 mmHg and 2.49. These oxygen-binding properties indicate that LEHbs possess strong potential as artificial blood substitutes. In addition, the metHb levels in PB-LEHb dispersions are significantly low even in the absence of antioxidants such as N-acetyl-L-cysteine.

Phosphate-Catalyzed Hydrogen Peroxide Formation from Agar, Gellan, and κ-Carrageenan and Recovery of Microbial Cultivability via Catalase and Pyruvate.

PubMed

Kawasaki, Kosei; Kamagata, Yoichi

2017-11-01

Previously, we reported that when agar is autoclaved with phosphate buffer, hydrogen peroxide (H 2 O 2 ) is formed in the resulting medium (PT medium), and the colony count on the medium inoculated with environmental samples becomes much lower than that on a medium in which agar and phosphate are autoclaved separately (PS medium) (T. Tanaka et al., Appl Environ Microbiol 80:7659-7666, 2014, https://doi.org/10.1128/AEM.02741-14). However, the physicochemical mechanisms underlying this observation remain largely unknown. Here, we determined the factors affecting H 2 O 2 formation in agar. The H 2 O 2 formation was pH dependent: H 2 O 2 was formed at high concentrations in an alkaline or neutral phosphate buffer but not in an acidic buffer. Ammonium ions enhanced H 2 O 2 formation, implying the involvement of the Maillard reaction catalyzed by phosphate. We found that other gelling agents (e.g., gellan and κ-carrageenan) also produced H 2 O 2 after being autoclaved with phosphate. We then examined the cultivability of microorganisms from a fresh-water sample to test whether catalase and pyruvate, known as H 2 O 2 scavengers, are effective in yielding high colony counts. The colony count on PT medium was only 5.7% of that on PS medium. Catalase treatment effectively restored the colony count of PT medium (to 106% of that on PS medium). In contrast, pyruvate was not as effective as catalase: the colony count on sodium pyruvate-supplemented PT medium was 58% of that on PS medium. Given that both catalase and pyruvate can remove H 2 O 2 from PT medium, these observations indicate that although H 2 O 2 is the main cause of reduced colony count on PT medium, other unknown growth-inhibiting substances that cannot be removed by pyruvate (but can be by catalase) may also be involved. IMPORTANCE The majority of bacteria in natural environments are recalcitrant to laboratory culture techniques. Previously, we demonstrated that one reason for this is the formation of high H 2 O 2 levels in media prepared by autoclaving agar and phosphate buffer together (PT medium). In this study, we investigated the factors affecting H 2 O 2 formation from agar. H 2 O 2 formation is pH dependent, and ammonium ions promote this phosphate-catalyzed H 2 O 2 formation. Amendment of catalase or pyruvate, a well-known H 2 O 2 -scavenging agent, effectively eliminated H 2 O 2 Yet results suggest that growth-inhibiting factor(s) that cannot be eliminated by pyruvate (but can be by catalase) are present in PT medium. Copyright © 2017 American Society for Microbiology.

Phosphate-Catalyzed Hydrogen Peroxide Formation from Agar, Gellan, and κ-Carrageenan and Recovery of Microbial Cultivability via Catalase and Pyruvate

PubMed Central

Kamagata, Yoichi

2017-01-01

ABSTRACT Previously, we reported that when agar is autoclaved with phosphate buffer, hydrogen peroxide (H2O2) is formed in the resulting medium (PT medium), and the colony count on the medium inoculated with environmental samples becomes much lower than that on a medium in which agar and phosphate are autoclaved separately (PS medium) (T. Tanaka et al., Appl Environ Microbiol 80:7659–7666, 2014, https://doi.org/10.1128/AEM.02741-14). However, the physicochemical mechanisms underlying this observation remain largely unknown. Here, we determined the factors affecting H2O2 formation in agar. The H2O2 formation was pH dependent: H2O2 was formed at high concentrations in an alkaline or neutral phosphate buffer but not in an acidic buffer. Ammonium ions enhanced H2O2 formation, implying the involvement of the Maillard reaction catalyzed by phosphate. We found that other gelling agents (e.g., gellan and κ-carrageenan) also produced H2O2 after being autoclaved with phosphate. We then examined the cultivability of microorganisms from a fresh-water sample to test whether catalase and pyruvate, known as H2O2 scavengers, are effective in yielding high colony counts. The colony count on PT medium was only 5.7% of that on PS medium. Catalase treatment effectively restored the colony count of PT medium (to 106% of that on PS medium). In contrast, pyruvate was not as effective as catalase: the colony count on sodium pyruvate-supplemented PT medium was 58% of that on PS medium. Given that both catalase and pyruvate can remove H2O2 from PT medium, these observations indicate that although H2O2 is the main cause of reduced colony count on PT medium, other unknown growth-inhibiting substances that cannot be removed by pyruvate (but can be by catalase) may also be involved. IMPORTANCE The majority of bacteria in natural environments are recalcitrant to laboratory culture techniques. Previously, we demonstrated that one reason for this is the formation of high H2O2 levels in media prepared by autoclaving agar and phosphate buffer together (PT medium). In this study, we investigated the factors affecting H2O2 formation from agar. H2O2 formation is pH dependent, and ammonium ions promote this phosphate-catalyzed H2O2 formation. Amendment of catalase or pyruvate, a well-known H2O2-scavenging agent, effectively eliminated H2O2. Yet results suggest that growth-inhibiting factor(s) that cannot be eliminated by pyruvate (but can be by catalase) are present in PT medium. PMID:28821549

Solid-phase extraction of small biologically active peptides on cartridges and microelution 96-well plates from human urine.

PubMed

Semenistaya, Ekaterina; Zvereva, Irina; Krotov, Grigory; Rodchenkov, Grigory

2016-09-01

Currently liquid chromatography - mass spectrometry (LC-MS) analysis after solid-phase extraction (SPE) on weak cation-exchange cartridges is a method of choice for anti-doping analysis of small bioactive peptides such as growth hormone releasing peptides (GHRPs), desmoporessin, LHRH, and TB-500 short fragment. Dilution of urine samples with phosphate buffer for pH adjustment and SPE on weak cation exchange microelution plates was tested as a means to increase throughput of this analysis. Dilution using 200 mM phosphate buffer provides good buffering capacity without affecting the peptides recoveries. SPE on microelution plates was performed on Waters Positive Pressure-96 Processor with subsequent evaporation of eluates in nitrogen flow. Though the use of smaller sample volume decreases the pre-concentration factor and increases the limits of detection of 5 out of 17 detected peptides, the recovery, linearity, and reproducibility of the microelution extraction were comparable with cartridge SPE. The effectiveness of protocols was confirmed by analysis of urine samples containing ipamorelin, and GHRP-6 and its metabolites. SPE after urine sample dilution with buffer can be used for faster sample preparation. The use of microelution plates decreases consumption of solvents and allows processing of up to 96 samples simultaneously. Cartridge SPE with manual рН adjustment remains the best option for confirmation. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Chelatable trace zinc causes low, irreproducible KDAC8 activity.

PubMed

Toro, Tasha B; Edenfield, Samantha A; Hylton, Brandon J; Watt, Terry J

2018-01-01

Acetylation is an important regulatory mechanism in cells, and emphasis is being placed on identifying substrates and small molecule modulators of this post-translational modification. However, the reported in vitro activity of the lysine deacetylase KDAC8 is inconsistent across experimental setups, even with the same substrate, complicating progress in the field. We detected trace levels of zinc, a known inhibitor of KDAC8 when present in excess, even in high-quality buffer reagents, at concentrations that are sufficient to significantly inhibit the enzyme under common reaction conditions. We hypothesized that trace zinc in solution could account for the observed variability in KDAC8 activity. We demonstrate that addition of chelators, including BSA, EDTA, and citrate, and/or the use of a phosphate-based buffer instead of the more common tris-based buffer, eliminates the inhibition from low levels of zinc as well as the dependence of specific activity on enzyme concentration. This results in high KDAC8 activity that is consistent across buffer systems, even using low concentrations of enzyme. We report conditions that are suitable for several assays to increase both enzyme activity and reproducibility. Our results have significant implications for approaches used to identify substrates and small molecule modulators of KDAC8 and interpretation of existing data. Copyright © 2017 Elsevier Inc. All rights reserved.

Stopped-flow studies of the reaction of D-tartronate semialdehyde-2-phosphate with human neuronal enolase and yeast enolase 1.

PubMed

Brewer, John M; McKinnon, Jared S; Phillips, Robert S

2010-03-05

We determined the kinetics of the reaction of human neuronal enolase and yeast enolase 1 with the slowly-reacting chromophoric substrate D-tartronate semialdehyde phosphate (TSP), each in tris (tris (hydroxymethyl) aminomethane) and another buffer at several Mg2+ concentrations, 50 or 100 microM, 1 mM and 30 mM. All data were biphasic, and could be satisfactorily fit, assuming either two successive first-order reactions or two independent first-order reactions. Higher Mg2+ concentrations reduce the relative magnitude of the slower reaction. The results are interpreted in terms of a catalytically significant interaction between the two subunits of these enzymes. Copyright (c) 2010 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

An azine based sensor for selective detection of Cu2 + ions and its copper complex for sensing of phosphate ions in physiological conditions and in living cells

NASA Astrophysics Data System (ADS)

Tiwari, Karishma; Kumar, Sumit; Kumar, Vipan; Kaur, Jeevanjot; Arora, Saroj; Mahajan, Rakesh Kumar

2018-02-01

A simple and cost effective unsymmetrical azine based Schiff base, 5-diethylamino-2-[(2-hydroxy-benzylidene)hydrazonomethyl]-phenol (1) was synthesized which selectively detect Cu2 + ions in the presence of other competitive ions through ;naked eye; in physiological conditions (EtOH-buffer (1:1, v/v, HEPES 10 mM, pH = 7.4)). The presence of Cu2 + induce color change from light yellow green to yellow with the appearance of a new band at 450 nm in UV-Vis spectra of Schiff base 1. The fluorescence of Schiff base 1 (10 μM) was quenched completely in the presence of 2.7 equiv. of Cu2 + ions. Sub-micromolar limit of detection (LOD = 3.4 × 10- 7 M), efficient Stern-Volmer quenching constant (KSV = 1.8 × 105 L mol- 1) and strong binding constant (log Kb = 5.92) has been determined with the help of fluorescence titration profile. Further, 1 - Cu2 + complex was employed for the detection of phosphate ions (PO43 -, HPO42 - and H2PO4-) at micromolar concentrations in EtOH-buffer of pH 7.4 based on fluorescence recovery due to the binding of Cu2 + with phosphate ions. Solubility at low concentration in aqueous medium, longer excitation (406 nm) and emission wavelength (537 nm), and biocompatibility of Schiff base 1 formulates its use in live cell imaging.

Estimation of the Contribution of CYP2C8 and CYP3A4 in Repaglinide Metabolism by Human Liver Microsomes Under Various Buffer Conditions.

PubMed

Kudo, Toshiyuki; Goda, Hitomi; Yokosuka, Yuki; Tanaka, Ryo; Komatsu, Seina; Ito, Kiyomi

2017-09-01

We have previously reported that the microsomal activities of CYP2C8 and CYP3A4 largely depend on the buffer condition used in in vitro metabolic studies, with different patterns observed between the 2 isozymes. In the present study, therefore, the possibility of buffer condition dependence of the fraction metabolized by CYP2C8 (fm2C8) for repaglinide, a dual substrate of CYP2C8 and CYP3A4, was estimated using human liver microsomes under various buffer conditions. Montelukast and ketoconazole showed a potent and concentration-dependent inhibition of CYP2C8-mediated paclitaxel 6α-hydroxylation and CYP3A4-mediated triazolam α-hydroxylation, respectively, without dependence on the buffer condition. Repaglinide depletion was inhibited by both inhibitors, but the degree of inhibition depended on buffer conditions. Based on these results, the contribution of CYP2C8 in repaglinide metabolism was estimated to be larger than that of CYP3A4 under each buffer condition, and the fm2C8 value of 0.760, estimated in 50 mM phosphate buffer, was the closest to the value (0.801) estimated in our previous modeling analysis based on its concentration increase in a clinical drug interaction study. Researchers should be aware of the possibility of buffer condition affecting the estimated contribution of enzyme(s) in drug metabolism processes involving multiple enzymes. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Diluents for stabilization of tuberculin

PubMed Central

Magnusson, Mogens; Guld, Johannes; Magnus, Knut; Waaler, Hans

1958-01-01

Tuberculin is known to be adsorbed to containers and syringes. In the present paper, the adsorption which takes place in the ampoules has been studied in relation to the diluent for the tuberculin. Adsorption was most evident in dilutions prepared with saline or with phosphate buffer containing dextran. The inclusion in phosphate buffer diluent of small amounts of proteins or synthetic surface-active agents decreased or prevented adsorption. A boric-acid sodium-borate diluent containing gum arabic, previously recommended for the preparation of stabilized tuberculin dilutions, was found to be ineffective. The most suitable diluent for the preparation of stable tuberculin dilutions was a 0.05‰ solution of Tween 80 in phosphate-buffered saline; this diluent appeared to prevent adsorption under a variety of experimental conditions. The inclusion of Tween 80 in the diluent had little or no effect on the general storage stability of purified tuberculin. Sensitization experiments in guinea-pigs, rabbits and humans showed that no sensitization against Tween 80 need be feared when a 0.05‰ solution of Tween 80 in phosphate buffered saline is used in the preparation of tuberculin dilutions. PMID:13618720

Histological preparation of developing vestibular otoconia for scanning electron microscopy

NASA Technical Reports Server (NTRS)

Huss, D.; Dickman, J. D.

2003-01-01

The unique nature of vestibular otoconia as calcium carbonate biominerals makes them particularly susceptible to chemical deformation during histological processing. We fixed and stored otoconia from all three otolith endorgans of embryonic, hatchling and adult Japanese quail in glutaraldehyde containing either phosphate or non-phosphate buffers for varying lengths of time and processed them for scanning electron microscopy. Otoconia from all age groups and otolith endorgans processed in 0.1 M phosphate buffer (pH 7.4) showed abnormal surface morphology when compared to acetone fixed controls. Otoconia processed in 0.1 M sodium cacodylate or HEPES buffered artificial endolymph (pH 7.4) showed normal morphology that was similar to controls. The degree of otoconial deformation was directly related to the time exposed to phosphate buffer. Short duration exposure produced particulate deformations while longer exposures resulted in fused otoconia that formed solid sheets. Otoconial surface deformation and fusing was independent of the glutaraldehyde component of the histological processing. These findings should help vestibular researchers to develop appropriate histological processing protocols in future studies of otoconia.

Development of a nucleotide sugar purification method using a mixed mode column & mass spectrometry detection.

PubMed

Eastwood, Heather; Xia, Fang; Lo, Mei-Chu; Zhou, Jing; Jordan, John B; McCarter, John; Barnhart, Wesley W; Gahm, Kyung-Hyun

2015-11-10

Analysis of nucleotide sugars, nucleoside di- and triphosphates and sugar-phosphates is an essential step in the process of understanding enzymatic pathways. A facile and rapid separation method was developed to analyze these compounds present in an enzymatic reaction mixture utilized to produce nucleotide sugars. The Primesep SB column explored in this study utilizes hydrophobic interactions as well as electrostatic interactions with the phosphoric portion of the nucleotide sugars. Ammonium formate buffer was selected due to its compatibility with mass spectrometry. Negative ion mode mass spectrometry was adopted for detection of the sugar phosphate (fucose-1-phophate), as the compound is not amenable to UV detection. Various mobile phase conditions such as pH, buffer concentration and organic modifier were explored. The semi-preparative separation method was developed to prepare 30mg of the nucleotide sugar. (19)F NMR was utilized to determine purity of the purified fluorinated nucleotide sugar. The collected nucleotide sugar was found to be 99% pure. Published by Elsevier B.V.

Effect of buffer and antioxidant on stability of a mercaptopurine suspension.

PubMed

Aliabadi, Hamidreza Montazeri; Romanick, Marcel; Desai, Sunil; Lavasanifar, Afsaneh

2008-03-01

The stability of standard and modified mercaptopurine suspensions when stored at room temperature and under refrigerated conditions to test the feasibility of increasing shelf life was studied. A 50-mg/mL mercaptopurine suspension was compounded by adding simple syrup, cherry syrup, and sterile water for irrigation to triturated mercaptopurine tablets for the initial reference formulation. Three additional formulations were prepared by adding an antioxidant (ascorbic acid 10 mg), a buffer (sodium phosphate monobasic monohydrate 500 mg), and a combination of antioxidant and buffer to the reference formulation. Each compounded batch was divided into two parts and stored in amber bottles at room temperature (19-23 degrees C) or under refrigerated conditions (4-8 degrees C). Analysis through high-performance liquid chromatography determined mercaptopurine levels after three and seven days and weekly thereafter for at least two weeks after shelf life was reached under specified storage conditions. Solutions with at least 93% of the original mercaptopurine concentration and with no observable sign of aggregation or cake formation were considered stable. The reference suspension of mercaptopurine showed an acceptable physical and chemical stability of up to 5 weeks when stored at room temperature. The addition of ascorbic acid extended the shelf life of the compounded suspension to 11 weeks. However, the addition of sodium phosphate monobasic did not improve the stability of mercaptopurine in the suspension. The results showed a higher stability for all formulations after storage at room temperature compared with those stored in a refrigerator. A standard oral suspension of mercaptopurine contained an acceptable drug concentration for up to 5 weeks when stored at room temperature. The addition of ascorbic acid at a concentration of 0.1% w/v to the standard formulation increased the suspension's shelf life at room temperature to 11 weeks.

Final report of the key comparison APMP.QM-K9: APMP comparison on pH measurement of phosphate buffer

NASA Astrophysics Data System (ADS)

Hioki, Akiharu; Ohata, Masaki; Cherdchu, Chainarong; Tangpaisarnkul, Nongluck

2011-01-01

The APMP.QM-K9 was organised by TCQM of APMP to test the abilities of the national metrology institutes in the APMP region to measure a pH value of a phosphate buffer. This APMP comparison on pH measurement was proposed by the National Metrology Institute of Japan, NMIJ, and the National Institute of Metrology of Thailand, NIMT, in August 2009. After approval by TCQM, the comparison has been conducted by NMIJ and NIMT. The comparison is a key comparison following CCQM-K9, CCQM-K9.1 and CCQM-K9.2. The comparison material was a phosphate buffer of pH around 6.86 and the measurement temperatures were 15 °C, 25 °C and 37 °C. This is the first APMP key comparison on pH measurement and the third APMP comparison on pH measurement following APMP.QM-P06 (two phosphate buffers) in 2004 and APMP.QM-P09 (a phthalate buffer) in 2006. The results can be used further by any participant to support its CMC claim for a phosphate buffer. That claim will concern the pH method employed by the participant during this comparison and will cover the temperature(s) used or the full temperature range between 15 °C and 37 °C for the participant which measured pH values at the three temperatures. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Ex vivo evaluation of various instrumentation techniques and irrigants in reducing E. faecalis within root canals.

PubMed

Basmaci, F; Oztan, M D; Kiyan, M

2013-09-01

To evaluate ex vivo the effectiveness of single-file instrumentation techniques compared with serial Ni-Ti rotary instrumentation with several irrigation regimens in reducing E. faecalis within root canals. A total of 81 extracted human mandibular premolar teeth with a single root canal were infected with E. faecalis before and after canal preparation. Samples were divided randomly into 9 groups, as follows: group 1-A: sterile phosphate-buffered saline + Self-adjusting file, group 1-B: 5% sodium hypochlorite + 15% EDTA + Self-adjusting file, group 1-C: 5% sodium hypochlorite + 7% maleic acid + Self-adjusting file, group 2-A: sterile phosphate-buffered saline + Reciproc (R25), group 2-B: 5% sodium hypochlorite + 15% EDTA + Reciproc (R25), group 2-C: 5% sodium hypochlorite + 7% maleic acid + Reciproc (R25), group 3-A: sterile phosphate-buffered saline + ProTaper, group 3-B: 5% sodium hypochlorite + 15% EDTA + ProTaper, group 3-C: 5% sodium hypochlorite + 7% maleic acid + ProTaper. anova was used to analyse statistically the differences in terms of reduction in colony counts between the groups, and Dunn's post hoc test was used for multiple comparisons. All techniques and irrigation regimens significantly reduced the number of bacterial cells in the root canal (P < 0.001). Comparisons amongst the groups revealed significant differences between group 1A (sterile phosphate-buffered saline + Self-adjusting file)/group 1B (5% sodium hypochlorite + 15% EDTA + Self-adjusting file) (P = 0.031), group 1A (sterile phosphate-buffered saline + Self-adjusting file)/group 2C (5% sodium hypochlorite + 7% maleic acid + Reciproc) (P = 0.003), group 2A (sterile phosphate-buffered saline + Reciproc)/group 3B (5% sodium hypochlorite + 15% EDTA + ProTaper) (P = 0.036), group 3B (5% sodium hypochlorite + 15% EDTA + ProTaper)/group 1A (sterile phosphate-buffered saline + Self-adjusting file) (P < 0.001), and group 3C (5% sodium hypochlorite + 7% maleic acid + ProTaper)/group 1A (sterile phosphate-buffered saline + Self-adjusting file) (P = 0.033). No significant differences in terms of reduction in microbial counts were observed between single-file techniques (SAF and Reciproc) and serial Ni-Ti instrumentation technique (ProTaper) in combination with irrigants. © 2013 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Exposure to buffer solution alters tendon hydration and mechanics.

PubMed

Safa, Babak N; Meadows, Kyle D; Szczesny, Spencer E; Elliott, Dawn M

2017-08-16

A buffer solution is often used to maintain tissue hydration during mechanical testing. The most commonly used buffer solution is a physiological concentration of phosphate buffered saline (PBS); however, PBS increases the tissue's water content and decreases its tensile stiffness. In addition, solutes from the buffer can diffuse into the tissue and interact with its structure and mechanics. These bathing solution effects can confound the outcome and interpretation of mechanical tests. Potential bathing solution artifacts, including solute diffusion, and their effect on mechanical properties, are not well understood. The objective of this study was to measure the effects of long-term exposure of rat tail tendon fascicles to several concentrations (0.9-25%) of NaCl, sucrose, polyethylene glycol (PEG), and SPEG (NaCl+PEG) solutions on water content, solute diffusion, and mechanical properties. We found that with an increase in solute concentration the apparent water content decreased for all solution types. Solutes diffused into the tissue for NaCl and sucrose, however, no solute diffusion was observed for PEG or SPEG. The mechanical properties changed for both NaCl solutions, in particular after long-term (8h) incubation the modulus and equilibrium stress decreased compared to short-term (15min) for 25% NaCl, and the cross sectional area increased for 0.9% NaCl. However, the mechanical properties were unchanged for both PEG and SPEG except for minor alterations in stress relaxation parameters. This study shows that NaCl and sucrose buffer solutions are not suitable for long-term mechanical tests. We therefore propose using PEG or SPEG as alternative buffer solutions that after long-term incubation can maintain tissue hydration without solute diffusion and produce a consistent mechanical response. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fe(III) reduction-mediated phosphate removal as vivianite (Fe3(PO4)2⋅8H2O) in septic system wastewater.

PubMed

Azam, Hossain M; Finneran, Kevin T

2014-02-01

Phosphate is a water contaminant from fertilizers, soaps, and detergents that enters municipal and onsite wastewater from households, businesses, and other commercial operations. Phosphate is a limiting nutrient for algae, and is one of the molecules that promotes eutrophication of water bodies. Phosphate is especially problematic in onsite wastewater because there are few removal mechanisms under normal operating conditions; a system must be amended specifically with compounds to bond to or adsorb phosphate in the septic tank or within the leach field. Vivianite (Fe3(PO4)2⋅8H2O) is a stable mineral formed from ferrous iron and phosphate, often as the result of Fe(III) reducing microbial activity. What was unknown was the concentration of phosphate that could be removed by this process, and whether it was relevant to mixed microbial systems like septic tank wastewater. Data presented here demonstrate that significant concentrations of phosphate (12-14mM) were removed as vivianite in growing cultures of Geobacter metallireducens strain GS-15. Vivianite precipitates were identified on the cell surfaces and within multi cell clusters using TEM-EDX; the mineral phases were directly characterized using XRD. Phosphate was also removed in dilute and raw (undiluted) septic wastewater amended with different forms of Fe(III) including solid phase and soluble Fe(III). Vivianite precipitates were recovered and identified using XRD, along with siderite (ferrous carbonate), which was expected given that the systems were likely bicarbonate buffered. These data demonstrate that ferric iron amendments in septic wastewater increase phosphate removal as the mineral vivianite, and this may be a good strategy for phosphate attenuation in the septic tank portion of onsite wastewater systems. Copyright © 2013 Elsevier Ltd. All rights reserved.

Steady antibiotic release from biodegradable beads in the pleural cavity: an in vitro and in vivo study.

PubMed

Liu, Kuo-Sheng; Liu, Shih-Jung; Chen, Hsiao-Yun; Huang, Yao-Kuang; Peng, Yi-Jie; Wu, Ren-Chin; Ueng, Steve Wen-Neng

2012-05-01

Inadequate localized drug concentrations and systemic adverse effects are among the concerns when regional infections are treated with systemic antibiotics. We designed and fabricated a poly(D,L)-lactide-co-glycolide (PLGA)-based biodegradable drug delivery system and evaluated the release of antibiotics both in vitro and in vivo. PLGA copolymer and penicillin G sodium were mixed, compressed, and sintered to fabricate biodegradable antibiotic beads. The beads were placed in phosphate-buffered saline to test the characteristics of in vitro drug release. The beads then were introduced into the pleural cavities through chest tubes of six New Zealand white rabbits. Daily pleural effusion was collected to measure the antibiotic concentration and bacterial inhibitory characteristics. Forty percent of the penicillin was released in the first day in the in vitro study. The rest of the antibiotic was then gradually released in the following 30 days. All six animals survived the experiment. The initial surge of drug release was less significant in the pleural cavity than in the phosphate-buffered saline. The drug concentrations were well above the minimum inhibitory concentration breakpoint for penicillin susceptibility throughout the study period in both in vitro (30 days) and in vivo (14 days) studies. These preliminary findings demonstrated that the biodegradable PLGA antibiotic beads could achieve a fairly steady antibiotic release in the pleural cavity for at least 2 weeks. This drug delivery system may have the potential to serve as an adjuvant treatment of pleural cavity infection.

Kinetic behaviour of calf intestinal alkaline phosphatase with pNPP.

PubMed

Chaudhuri, Gouri; Chatterjee, Saswata; Venu-Babu, P; Ramasamy, K; Thilagaraj, W Richard

2013-02-01

The hydrolysis of p-nitrophenyl phosphate (pNPP) by calf intestinal alkaline phosphatase (CIAP) was investigated with respect to kinetic parameters such as V(max), K(m) and K(cat) under varying pH, buffers, substrate concentration, temperature and period of incubation. Highest activity was obtained with Tris-HCl at pH 11, while in the case of glycine-NaOH buffer the peak activity was recorded at pH 9.5. The enzyme showed the following kinetic characteristics with pNPP in 50 mM Tris-HCl at pH 11 and 100 mM glycine-NaOH at pH 9.5 at an incubation temperature of 37 degrees C: V(max), 3.12 and 1.6 micromoles min(-1) unit(-1); K(m), 7.6 x 10(-4) M and 4 x 10(-4) M; and K(cat), 82.98 s(-1) and 42.55 s(-1), respectively. CIAP displayed a high temperature optimum of 45 degrees C at pH 11. The kinetic behaviour of the enzyme under different parameters suggested that the enzyme might undergo subtle conformational changes in response to the buffers displaying unique characteristics. Bioprecipitation of Cu2+ from 50 ppm of CuCl2 solution was studied where 64.3% of precipitation was obtained. P(i) generated from CIAP-mediated hydrolysis of pNPP was found to bind with copper and precipitated as copper-phosphate. Thus, CIAP could be used as a test candidate in bioremediation of heavy metals from industrial wastes through generation of metal-phosphate complexes.

Structure-Function Relationship of Hydrophiidae Postsynaptic Neurotoxins

DTIC Science & Technology

1990-09-18

24 hr. Buffer F consisted of 10 mM sodium phosphate, pH 7.5. containing 0.02% (w/v) lauryl sulfate (SDS), and 0.04% (w/v) sodium cholate. The...subjected to gel filtration on Sephadex G-50-50 using 10 mM sodium phosphate buffer (pH 6.5) containing 0.1 M NaCl. Samples were dissolved in 3.5 ml buffer...sequencing. Isolation of Cobrotoxin. The venom from NaJa naia atra was subjected to Sephadex G50-50 gel filtration pre-equilibrated with 10 mM sodium

A segmental chronic pain syndrome in rats associated with intrathecal infusion of NMDA: evidence for selective action in the dorsal horn.

PubMed

Zochodne, D W; Murray, M; Nag, S; Riopelle, R J

1994-02-01

We explored the effects of chronic lumbar intrathecal NMDA infusion (mini-osmotic pumps) in Sprague-Dawley rats on motor and sensory axon integrity. Several different infusion protocols, each given over a 4 week period were examined: 0.15 M NMDA in phosphate buffered saline; phosphate buffered saline without NMDA; and 0.20 M magnesium sulfate plus 0.15 M NMDA; 0.35 M NMDA. In two additional protocols, 0.15 M NMDA or phosphate buffered saline were infused for a total of 8 weeks. Within 1-2 weeks of the onset of NMDA, but not phosphate buffered saline infusions, the rats exhibited irritability, circling, biting and excessive grooming resulting in loss of hair, and skin ulcerations from autotomy localized to lumbar and sacral innervated dermatomes. Co-infusion of NMDA with magnesium sulfate almost completely prevented these findings. The behavioural changes were not associated with abnormalities of sensory or motor conduction. Intrathecal infusion of NMDA induces a chronic "central" experimental pain disorder in rats, localized to the cord segment with the greatest exposure to the infusion, without involvement of peripheral sensory axons and sparing the axonal integrity of anterior horn cells.

The determination of calcium in phosphate, carbonate, and silicate rocks by flame photometer

USGS Publications Warehouse

Kramer, Henry

1956-01-01

A method has been developed for the determination of calcium in phosphate, carbonate, and silicate rocks using the Beckman flame photometer, with photomultiplier attachement. The sample is dissolved in hydrofluoric, nitric, and perchloric acids, the hydrofluoric and nitric acids are expelled, a radiation buffer consisting of aluminum, magnesium, iron, sodium, potassium, phosphoric acid, and nitric acid is added, and the solution is atomized in an oxy-hydrogen flame with an instrument setting of 554 mµ. Measurements are made by comparison against calcium standards, prepared in the same manner, in the 0 to 50 ppm range. The suppression of calcium emission by aluminum and phosphate was overcome by the addition of a large excess of magnesium. This addition almost completely restores the standard curve obtained from a solution of calcium nitrate. Interference was noted when the iron concentration in the aspirated solution (including the iron from the buffer) exceeded 100 ppm iron. Other common rock-forming elements did not interfere. The results obtained by this procedure are within ± 2 percent of the calcium oxide values obtained by other methods in the range 1 to 95 percent calcium oxide. In the 0 to 1 percent calcium oxide range the method compares favorably with standard methods.

Capillary electrophoretic enantioseparation of basic drugs using a new single-isomer cyclodextrin derivative and theoretical study of the chiral recognition mechanism.

PubMed

Liu, Yongjing; Deng, Miaoduo; Yu, Jia; Jiang, Zhen; Guo, Xingjie

2016-05-01

A novel single-isomer cyclodextrin derivative, heptakis {2,6-di-O-[3-(1,3-dicarboxyl propylamino)-2-hydroxypropyl]}-β-cyclodextrin (glutamic acid-β-cyclodextrin) was synthesized and used as a chiral selector in capillary electrophoresis for the enantioseparation of 12 basic drugs, including terbutaline, clorprenaline, tulobuterol, clenbuterol, procaterol, carvedilol, econazole, miconazole, homatropine methyl bromide, brompheniramine, chlorpheniramine and pheniramine. The primary factors affecting separation efficiency, which include the background electrolyte pH, the concentration of glutamic acid-β-cyclodextrin and phosphate buffer concentration, were investigated. Satisfactory enantioseparations were obtained using an uncoated fused-silica capillary of 50 cm (effective length 40 cm) × 50 μm id with 120 mM phosphate buffer (pH 2.5-4.0) containing 0.5-4.5 mM glutamic acid-β-cyclodextrin as background electrolyte. A voltage of 20 kV was applied and the capillary temperature was kept at 20°C. The results proved that glutamic acid-β-cyclodextrin was an effective chiral selector for studied 12 basic drugs. Moreover, the possible chiral recognition mechanism of brompheniramine, chlorpheniramine and pheniramine on glutamic acid-β-cyclodextrin was investigated using the semi-empirical Parametric Method 3. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An azine based sensor for selective detection of Cu2+ ions and its copper complex for sensing of phosphate ions in physiological conditions and in living cells.

PubMed

Tiwari, Karishma; Kumar, Sumit; Kumar, Vipan; Kaur, Jeevanjot; Arora, Saroj; Mahajan, Rakesh Kumar

2018-02-15

A simple and cost effective unsymmetrical azine based Schiff base, 5-diethylamino-2-[(2-hydroxy-benzylidene)hydrazonomethyl]-phenol (1) was synthesized which selectively detect Cu 2+ ions in the presence of other competitive ions through "naked eye" in physiological conditions (EtOH-buffer (1:1, v/v, HEPES 10mM, pH=7.4)). The presence of Cu 2+ induce color change from light yellow green to yellow with the appearance of a new band at 450nm in UV-Vis spectra of Schiff base 1. The fluorescence of Schiff base 1 (10μM) was quenched completely in the presence of 2.7 equiv. of Cu 2+ ions. Sub-micromolar limit of detection (LOD=3.4×10 -7 M), efficient Stern-Volmer quenching constant (K SV =1.8×10 5 Lmol -1 ) and strong binding constant (log K b =5.92) has been determined with the help of fluorescence titration profile. Further, 1-Cu 2+ complex was employed for the detection of phosphate ions (PO 4 3- , HPO 4 2- and H 2 PO 4 - ) at micromolar concentrations in EtOH-buffer of pH7.4 based on fluorescence recovery due to the binding of Cu 2+ with phosphate ions. Solubility at low concentration in aqueous medium, longer excitation (406nm) and emission wavelength (537nm), and biocompatibility of Schiff base 1 formulates its use in live cell imaging. Copyright © 2017 Elsevier B.V. All rights reserved.

Vtc5, a Novel Subunit of the Vacuolar Transporter Chaperone Complex, Regulates Polyphosphate Synthesis and Phosphate Homeostasis in Yeast*

PubMed Central

Desfougères, Yann; Gerasimaitė, R̄uta; Jessen, Henning Jacob

2016-01-01

SPX domains control phosphate homeostasis in eukaryotes. Ten genes in yeast encode SPX-containing proteins, among which YDR089W is the only one of unknown function. Here, we show that YDR089W encodes a novel subunit of the vacuole transporter chaperone (VTC) complex that produces inorganic polyphosphate (polyP). The polyP synthesis transfers inorganic phosphate (Pi) from the cytosol into the acidocalcisome- and lysosome-related vacuoles of yeast, where it can be released again. It was therefore proposed for buffer changes in cytosolic Pi concentration (Thomas, M. R., and O'Shea, E. K. (2005) Proc. Natl. Acad. Sci. U.S.A. 102, 9565–9570). Vtc5 physically interacts with the VTC complex and accelerates the accumulation of polyP synthesized by it. Deletion of VTC5 reduces polyP accumulation in vivo and in vitro. Its overexpression hyperactivates polyP production and triggers the phosphate starvation response via the PHO pathway. Because this Vtc5-induced starvation response can be reverted by shutting down polyP synthesis genetically or pharmacologically, we propose that polyP synthesis rather than Vtc5 itself is a regulator of the PHO pathway. Our observations suggest that polyP synthesis not only serves to establish a buffer for transient drops in cytosolic Pi levels but that it can actively decrease or increase the steady state of cytosolic Pi. PMID:27587415

Antitumour, antimicrobial and catalytic activity of gold nanoparticles synthesized by different pH propolis extracts

NASA Astrophysics Data System (ADS)

Gatea, Florentina; Teodor, Eugenia Dumitra; Seciu, Ana-Maria; Covaci, Ovidiu Ilie; Mănoiu, Sorin; Lazăr, Veronica; Radu, Gabriel Lucian

2015-07-01

The Romanian propolis was extracted in five different media, respectively, in water (pH 6.8), glycine buffer (pH 2.5), acetate buffer (pH 5), phosphate buffer (pH 7.4) and carbonate buffer (pH 9.2). The extracts presented different amounts of flavonoids and phenolic acids, increasing pH leading to higher concentrations of active compounds. Five variants of gold nanoparticles suspensions based on different pH Romanian propolis aqueous extracts were successfully synthesized. The obtained nanoparticles presented dimensions between 20 and 60 nm in dispersion form and around 18 nm in dried form, and different morphologies (spherical, hexagonal, triangular). Fourier transform infrared spectroscopy proved the attachment of organic compounds from propolis extracts to the colloidal gold suspensions and X-ray diffraction certified that the suspensions contain metallic gold. The obtained propolis gold nanoparticles do not exhibit any antibacterial or antifungal activity, but presented different catalytic activities and toxicity on tumour cells.

Magnesium Counteracts Vascular Calcification: Passive Interference or Active Modulation?

PubMed

Ter Braake, Anique D; Shanahan, Catherine M; de Baaij, Jeroen H F

2017-08-01

Over the last decade, an increasing number of studies report a close relationship between serum magnesium concentration and cardiovascular disease risk in the general population. In end-stage renal disease, an association was found between serum magnesium and survival. Hypomagnesemia was identified as a strong predictor for cardiovascular disease in these patients. A substantial body of in vitro and in vivo studies has identified a protective role for magnesium in vascular calcification. However, the precise mechanisms and its contribution to cardiovascular protection remain unclear. There are currently 2 leading hypotheses: first, magnesium may bind phosphate and delay calcium phosphate crystal growth in the circulation, thereby passively interfering with calcium phosphate deposition in the vessel wall. Second, magnesium may regulate vascular smooth muscle cell transdifferentiation toward an osteogenic phenotype by active cellular modulation of factors associated with calcification. Here, the data supporting these major hypotheses are reviewed. The literature supports both a passive inorganic phosphate-buffering role reducing hydroxyapatite formation and an active cell-mediated role, directly targeting vascular smooth muscle transdifferentiation. However, current evidence relies on basic experimental designs that are often insufficient to delineate the underlying mechanisms. The field requires more advanced experimental design, including determination of intracellular magnesium concentrations and the identification of the molecular players that regulate magnesium concentrations in vascular smooth muscle cells. © 2017 American Heart Association, Inc.

The effects of buffers and pH on the thermal stability, unfolding and substrate binding of RecA.

PubMed

Metrick, Michael A; Temple, Joshua E; MacDonald, Gina

2013-12-31

The Escherichia coli protein RecA is responsible for catalysis of the strand transfer reaction used in DNA repair and recombination. Previous studies in our lab have shown that high concentrations of salts stabilize RecA in a reverse-anionic Hofmeister series. Here we investigate how changes in pH and buffer alter the thermal unfolding and cofactor binding. RecA in 20mM HEPES, MES, Tris and phosphate buffers was studied in the pH range from 6.5 to 8.5 using circular dichroism (CD), infrared (IR) and fluorescence spectroscopies. The results show all of the buffers studied stabilize RecA up to 50°C above the Tris melting temperature and influence RecA's ability to nucleate on double-stranded DNA. Infrared and CD spectra of RecA in the different buffers do not show that secondary structural changes are associated with increased stability or decreased ability to nucleate on dsDNA. These results suggest the differences in stability arise from decreasing positive charge and/or buffer interactions. © 2013. Published by Elsevier B.V. All rights reserved.

Determination of total arsenic and arsenic(III) in phosphate fertilizers by hydride generation atomic absorption spectrometry after ultrasound-assisted extraction based on a control acid media.

PubMed

Rezende, Helen Cristine; Coelho, Nivia Maria Melo

2014-01-01

An ultrasound-assisted extraction procedure was developed for determination of inorganic arsenic (As) in phosphate fertilizer by hydride generation atomic absorption spectrometry. The variables that affect the hydride generation step were optimized, including the reducer, acid, sample flow rate, and concentrations of the acid and reducer. The determination of As(lll) was performed through the simple control of solution pH with a 0.5 M citric acid-sodium citrate buffer solution at pH 4.5, and total As was determined after a pre-reduction reaction with 1.0% (w/v) thiourea. Ultrasound-assisted acid extraction was performed, and the parameters sonication time and acid and Triton X-114 concentrations were optimized using a 23 factorial design and central composite design. LODs for As(lll) and total As were 0.029 and 0.022 microg/L, respectively. The accuracy of the method was confirmed with certified reference materials. The method was successfully applied in the determination of inorganic As in phosphate fertilizer samples.

Thermal inactivation of ileal loop-reactive Clostridium perfringens type A strains in phosphate buffer and beef gravy.

PubMed

Bradshaw, J G; Peeler, J T; Twedt, R M

1977-09-01

The thermal resistance of spore crops produced from each of two ileal loop-reactive strains of Clostridium perfringens type A was determined in two suspending vehicles consisting of 0.067 M (pH 7.0) phosphate buffer and a commercial beef gravy. D115.6 values obtained in buffer and enumerated after pretreatment with sodium ethylenediaminetetraacetate and recovery in plating medium containing lysozyme were two- to threefold greater than those obtained without this treatment. D115.6 values obtained with beef gravy were less than those obtained in buffer with or without lysozyme; however, the D98.9 and D104.4 values were 1.3 to 2 times greater than those obtained in buffer with lysozyme. The z values were within the ranges reported by previous investigators.

Thermal inactivation of ileal loop-reactive Clostridium perfringens type A strains in phosphate buffer and beef gravy.

PubMed Central

Bradshaw, J G; Peeler, J T; Twedt, R M

1977-01-01

The thermal resistance of spore crops produced from each of two ileal loop-reactive strains of Clostridium perfringens type A was determined in two suspending vehicles consisting of 0.067 M (pH 7.0) phosphate buffer and a commercial beef gravy. D115.6 values obtained in buffer and enumerated after pretreatment with sodium ethylenediaminetetraacetate and recovery in plating medium containing lysozyme were two- to threefold greater than those obtained without this treatment. D115.6 values obtained with beef gravy were less than those obtained in buffer with or without lysozyme; however, the D98.9 and D104.4 values were 1.3 to 2 times greater than those obtained in buffer with lysozyme. The z values were within the ranges reported by previous investigators. PMID:199113

Comparison of adhesive properties of water- and phosphate-buffer-washed cottonseed meals with cottonseed protein isolate on maple and poplar veneers

USDA-ARS?s Scientific Manuscript database

Water- and phosphate buffer (35 mM Na2HPO4/NaH2PO4, pH 7.5)-washed cottonseed meals (abbreviated as WCM and BCM, respectively) could be low-cost and environmentally friendly protein-based adhesives as their preparation does not involve corrosive alkali and acid solutions that are needed for cottonse...

Extending the applicability of pressurized hot water extraction to compounds exhibiting limited water solubility by pH control: curcumin from the turmeric rhizome.

PubMed

Euterpio, Maria Anna; Cavaliere, Chiara; Capriotti, Anna Laura; Crescenzi, Carlo

2011-11-01

Pressurized hot water extraction (PHWE, also known as subcritical water extraction) is commonly considered to be an environmentally friendly extraction technique that could potentially replace traditional methods that use organic solvents. Unfortunately, the applicability of this technique is often limited by the very low water solubility of the target compounds, even at high temperatures. In this paper, the scope for broadening the applicability of PHWE by adjusting the pH of the water used in the extraction is demonstrated in the extraction of curcumin (which exhibits very limited water solubility) from untreated turmeric (Curcuma longa L.) rhizomes. Although poor extraction yields were obtained, even at high temperatures when using degassed water or neutral phosphate buffer as the extraction medium, yields exceeding those obtained by Soxhlet extraction were achieved using highly acidic pH buffers due to curcumin protonation. The influence of the temperature, pH, and buffer concentration on the extraction yield were investigated in detail by means of a series of designed experiments. Optimized conditions for the extraction of curcumin from turmeric by PHWE were estimated at 197 °C using 62 g/L buffer concentration at pH 1.6. The relationships between these variables were subjected to statistical analysis using response surface methodology.

Effects of substrates and phosphate on INT (2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl tetrazolium chloride) and CTC (5-cyano-2,3-ditolyl tetrazolium chloride) reduction in Escherichia coli

NASA Technical Reports Server (NTRS)

Smith, J. J.; McFeters, G. A.

1996-01-01

The effects of substrates of primary aerobic dehydrogenases, and inorganic phosphate on aerobic INT and CTC reduction in Escherichia coli were examined. In general, INT produced less formazan than CTC, but INT (+) cell counts remained near values of CTC (+) cells. INT and CTC (+) cell numbers were higher than plate counts on R2A medium using succinate, formate, lactate, casamino acids, glucose, glycerol (INT only) and no substrate. Formate resulted in the greatest amount of INT and CTC formazan. Reduction of both INT and CTC was inhibited above 10 mmol l-1 phosphate, and this appeared to be related to decreased rates of O2 consumption. Formation of fluorescent CTC (+), but not INT (+) cells was also inhibited in a concentration dependent manner by phosphate above 10 mmol l-1. From light microscopic observations it appeared CTC formed increasing amounts of poorly or non-fluorescent formazan with increasing phosphate. Therefore, use of phosphate buffer in excess of 10 mmol l-1 may not be appropriate in CTC and INT reduction assays.

Overloaded elution band profiles of ionizable compounds in reversed-phase liquid chromatography: Influence of the competition between the neutral and the ionic species

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gritti, Fabrice; Guiochon, Georges A

2008-01-01

The parameters that affect the shape of the band profiles of acido-basic compounds under moderately overloaded conditions (sample size less than 500 nmol for a conventional column) in RPLC are discussed. Only analytes that have a single pK{sub a} are considered. In the buffer mobile phase used for their elution, their dissociation may, under certain conditions, cause a significant pH perturbation during the passage of the band. Two consecutive injections (3.3 and 10 {micro}L) of each one of three sample solutions (0.5, 5, and 50 mM) of ten compounds were injected on five C{sub 18}-bonded packing materials, including the 5more » {micro}m Xterra-C{sub 18} (121 {angstrom}), 5 {micro}m Gemini-C{sub 18} (110 {angstrom}), 5 {micro}m Luna-C{sub 18}(2) (93 {angstrom}), 3.5 {micro}m Extend-C{sub 18} (80 {angstrom}), and 2.7 {micro}m Halo-C{sub 18} (90 {angstrom}). The mobile phase was an aqueous solution of methanol buffered at a constant {sub W}{sup W}pH of 6, with a phosphate buffer. The total concentration of the phosphate groups was constant at 50 mM. The methanol concentration was adjusted to keep all the retention factors between 1 and 10. The compounds injected were phenol, caffeine, 3-phenyl 1-propanol, 2-phenyl butyric acid, amphetamine, aniline, benzylamine, p-toluidine, procainamidium chloride, and propranololium chloride. Depending on the relative values of the analyte pK{sub a} and the buffer solution pH, these analytes elute as the neutral, the cationic, or the anionic species. The influence of structural parameters such as the charge, the size, and the hydrophobicity of the analytes on the shape of its overloaded band profile is discussed. Simple but general rules predict these shapes. An original adsorption model is proposed that accounts for the unusual peak shapes observed when the analyte is partially dissociated in the buffer solution during its elution.« less

A phosphorus-free anolyte to enhance coulombic efficiency of microbial fuel cells

NASA Astrophysics Data System (ADS)

Tang, Xinhua; Li, Haoran; Du, Zhuwei; Ng, How Yong

2014-12-01

In this study, a phosphorus-free anolyte is prepared by using bicarbonate to replace phosphate buffer for application in two chamber microbial fuel cells (MFCs). Optical density test and Bradford protein assay shows that this phosphorus-free anolyte effectively inhibits the growth and reproduction of microorganisms suspended in the solution and greatly reduces the suspended cell mass. As a result, it considerably enhances the coulombic efficiency (CE) of MFCs. When the acetate concentration is 11 mM, the CE of the MFC using the pH 7 phosphate-containing anolyte is 9.7% and the CE with the pH 8.3 phosphate-containing anolyte is 9.1%, while the CE of the MFC using the phosphorus-free anolyte (pH 8.3) achieves 26.6%. This study demonstrates that this phosphorus-free anolyte holds the potential to enhance the feasibility for practical applications of MFCs.

Simultaneous HPLC analysis of pseudophedrine hydrochloride, codeine phosphate, and triprolidine hydrochloride in liquid dosage forms.

PubMed

Manassra, Adnan; Khamis, Mustafa; El-Dakiky, Magdy; Abdel-Qader, Zuhair; Al-Rimawi, Fuad

2010-03-11

An HPLC method using UV detection is proposed for the simultaneous determination of pseudophedrine hydrochloride, codeine phosphate, and triprolidine hydrochloride in liquid formulation. C18 column (250mmx4.0mm) is used as the stationary phase with a mixture of methanol:acetate buffer:acetonitrile (85:5:10, v/v) as the mobile phase. The factors affecting column separation of the analytes were studied. The calibration graphs exhibited a linear concentration range of 0.06-1.0mg/ml for pseudophedrine hydrochloride, 0.02-1.0mg/ml for codeine phosphate, and 0.0025-1.0mg/ml for triprolidine hydrochloride for a sample size of 5microl with correlation coefficients of better than 0.999 for all active ingredients studied. The results demonstrate that this method is reliable, reproducible and suitable for routine use with analysis time of less than 4min. Copyright 2009 Elsevier B.V. All rights reserved.

Study of a hydraulic DCPA/CaO-based cement for dental applications.

PubMed

El Briak, Hasna; Durand, Denis; Boudeville, Philippe

2008-02-01

A CPC was obtained by mixing calcium hydrogenphosphate (DCPA: CaHPO(4)) and calcium oxide with either water or sodium phosphate (NaP) buffers. Physical and mechanical properties such as compressive strength (CS), initial (I) and final (F) setting times, cohesion time (T(C)), dough time (T(D)), swelling time (T(S)), dimensional and thermal behavior, injectability (t(100%)), antimicrobial properties, setting reaction kinetics, and powder stability over time were investigated by varying different parameters such as liquid-to-powder (L/P) ratio (0.35 to 0.7 mL g(-1)), molar calcium-to-phosphate (Ca/P) ratio (1.67 to 3), the pH (4, 7 or 9) and the concentration (0 to 1 M) of the NaP buffer. The best results were obtained with the pH 7 NaP buffer at a concentration of 0.75 M. With this liquid phase, physical and mechanical properties depended on the Ca/P and L/P ratios, varying from 3 to 11 MPa (CS), 6 to 10 min (I), 11 to 15 min (F), 15 to 45 min (T(S)), 3 to 12 min (t(100%)), 16 min (T(D)). This cement expanded during its setting (2.5-7%), and is thus appropriate for tight filling. Finally the cement has antimicrobial activity from Ca/P = 2 and the whole properties were conserved after 8 months storage. Given the mechanical, rheological and antimicrobial properties of this new DCPA/CaO-based cement, its use as root canal sealing or pulp capping material may be considered as similar to calcium hydroxide or ZnO/eugenol-based pastes, without or with a gutta-percha point.

Opioid Abuse after TBI

DTIC Science & Technology

2015-09-01

hippocampal formation (Paxinos and Watson, 2005). The sections were mounted on 1% gelatin -coated slides and stored at -20°C until further histological... drying at room temperature overnight. Finally, sections were rinsed in xylene (2 times for 5 min) and coverslipped with DPX mounting media (Electron...0.1M phosphate buffered saline (3 x 5 min) and 0.1M phosphate buffer (3 x 5 min) and slides were allowed to dry for one hour before being

Optimization of microwave-assisted extraction of analgesic and anti-inflammatory drugs from human plasma and urine using response surface experimental designs.

PubMed

Fernández, Purificación; Fernández, Ana M; Bermejo, Ana M; Lorenzo, Rosa A; Carro, Antonia M

2013-04-01

The performance of microwave-assisted extraction and HPLC with photodiode array detection method for determination of six analgesic and anti-inflammatory drugs from plasma and urine, is described, optimized, and validated. Several parameters affecting the extraction technique were optimized using experimental designs. A four-factor (temperature, phosphate buffer pH 4.0 volume, extraction solvent volume, and time) hybrid experimental design was used for extraction optimization in plasma, and three-factor (temperature, extraction solvent volume, and time) Doehlert design was chosen to extraction optimization in urine. The use of desirability functions revealed the optimal extraction conditions as follows: 67°C, 4 mL phosphate buffer pH 4.0, 12 mL of ethyl acetate and 9 min, for plasma and the same volume of buffer and ethyl acetate, 115°C and 4 min for urine. Limits of detection ranged from 4 to 45 ng/mL in plasma and from 8 to 85 ng/mL in urine. The reproducibility evaluated at two concentration levels was less than 6.5% for both specimens. The recoveries were from 89 to 99% for plasma and from 83 to 99% for urine. The proposed method was successfully applied in plasma and urine samples obtained from analgesic users. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Formation kinetics of a novel product from photolysis of cytosine in phosphate-buffered solutions

NASA Astrophysics Data System (ADS)

Wenqing, Wang; Feng, Lin; Jilan, Wu

1999-01-01

For studying the role of phosphate in the origin of life and the effect of far-ultraviolet light induced photochemical damage to RNA, DNA and its components, it was found that the photolysis of nucleobases, nucleosides and nucleotides was strongly enhanced by phosphate under the irradiation of medium pressure mercury lamp (MPML). Ultraviolet irradiation (190-220 nm) of cytosine in 0.05 mol dm -3 phosphate buffered solution at pH 8-9 leads to the production of a novel compound C 4H 6N 3O 5P in the presence of oxygen. The main photoproduct has been isolated, purified and characterized by use of 1H- and 31P-NMR spectroscopy, elemental analysis, ultraviolet and infrared spectroscopy and electron impact mass spectrometry. Phosphate effect can be inhibited by amino acids. The formation mechanism of the photoproduct and the kinetics was studied.

Chemometrics-assisted spectrophotometric green method for correcting interferences in biowaiver studies: Application to assay and dissolution profiling study of donepezil hydrochloride tablets

NASA Astrophysics Data System (ADS)

Korany, Mohamed A.; Mahgoub, Hoda; Haggag, Rim S.; Ragab, Marwa A. A.; Elmallah, Osama A.

2018-06-01

A green, simple and cost effective chemometric UV-Vis spectrophotometric method has been developed and validated for correcting interferences that arise during conducting biowaiver studies. Chemometric manipulation has been done for enhancing the results of direct absorbance, resulting from very low concentrations (high incidence of background noise interference) of earlier points in the dissolution timing in case of dissolution profile using first and second derivative (D1 & D2) methods and their corresponding Fourier function convoluted methods (D1/FF& D2/FF). The method applied for biowaiver study of Donepezil Hydrochloride (DH) as a representative model was done by comparing two different dosage forms containing 5 mg DH per tablet as an application of a developed chemometric method for correcting interferences as well as for the assay and dissolution testing in its tablet dosage form. The results showed that first derivative technique can be used for enhancement of the data in case of low concentration range of DH (1-8 μg mL-1) in the three different pH dissolution media which were used to estimate the low drug concentrations dissolved at the early points in the biowaiver study. Furthermore, the results showed similarity in phosphate buffer pH 6.8 and dissimilarity in the other 2 pH media. The method was validated according to ICH guidelines and USP monograph for both assays (HCl of pH 1.2) and dissolution study in 3 pH media (HCl of pH 1.2, acetate buffer of pH 4.5 and phosphate buffer of pH 6.8). Finally, the assessment of the method greenness was done using two different assessment techniques: National Environmental Method Index label and Eco scale methods. Both techniques ascertained the greenness of the proposed method.

Chemometrics-assisted spectrophotometric green method for correcting interferences in biowaiver studies: Application to assay and dissolution profiling study of donepezil hydrochloride tablets.

PubMed

Korany, Mohamed A; Mahgoub, Hoda; Haggag, Rim S; Ragab, Marwa A A; Elmallah, Osama A

2018-06-15

A green, simple and cost effective chemometric UV-Vis spectrophotometric method has been developed and validated for correcting interferences that arise during conducting biowaiver studies. Chemometric manipulation has been done for enhancing the results of direct absorbance, resulting from very low concentrations (high incidence of background noise interference) of earlier points in the dissolution timing in case of dissolution profile using first and second derivative (D1 & D2) methods and their corresponding Fourier function convoluted methods (D1/FF& D2/FF). The method applied for biowaiver study of Donepezil Hydrochloride (DH) as a representative model was done by comparing two different dosage forms containing 5mg DH per tablet as an application of a developed chemometric method for correcting interferences as well as for the assay and dissolution testing in its tablet dosage form. The results showed that first derivative technique can be used for enhancement of the data in case of low concentration range of DH (1-8μgmL -1 ) in the three different pH dissolution media which were used to estimate the low drug concentrations dissolved at the early points in the biowaiver study. Furthermore, the results showed similarity in phosphate buffer pH6.8 and dissimilarity in the other 2pH media. The method was validated according to ICH guidelines and USP monograph for both assays (HCl of pH1.2) and dissolution study in 3pH media (HCl of pH1.2, acetate buffer of pH4.5 and phosphate buffer of pH6.8). Finally, the assessment of the method greenness was done using two different assessment techniques: National Environmental Method Index label and Eco scale methods. Both techniques ascertained the greenness of the proposed method. Copyright © 2018 Elsevier B.V. All rights reserved.

Interactive effects of redox intensity and phosphate availability on growth and nutrient relations of Cladium jamaicense (Cyperaceae)

USGS Publications Warehouse

Lissner, J.; Mendelssohn, I.A.; Lorenzen, B.; Brix, H.; McKee, K.L.; Miao, S.L.

2003-01-01

Expansion of Typha domingensis into areas previously dominated by Cladium jamaicense in the Florida Everglades has been linked to anthropogenic phosphorus (P) enrichment and increased hydroperiod. The principal stress factor for plants in flooded soils is biochemical reduction, the intensity of which is measured as redox potential (Eh). The objective of this study was to assess the growth response of C. jamaicense to Eh (-150, +150, and +600 mV) and P availability (10, 80, and 500 ??g P/L). Plants were grown hydroponically in a factorial experiment using titanium (Ti3+) citrate as an Eh buffer. Treatment effects on growth, biomass partitioning, and tissue nutrients were recorded. Growth approximately doubled in response to a 50-fold increase in P availability. Low redox significantly reduced growth and tissue P concentration. While plant P concentrations increased 20-fold between the 10 and 500 ??g P/L treatments, P concentrations were 50-100% higher at +600 mV than at -150 mV within each phosphate level. At high Eh, C. jamaicense appears well adapted to low nutrient environments because of its low P requirement and high retention of acquired E However, at low Eh the ability to acquire or conserve acquired P decreases and as a consequence, higher phosphate levels are required to sustain growth. Findings of this study indicate that young C. jamaicense exhibits low tolerance to strongly reducing conditions when phosphate is scarce.

Influence of Dissolution Media and Presence of Alcohol on the In Vitro Performance of Pharmaceutical Products Containing an Insoluble Drug.

PubMed

Friuli, Valeria; Bruni, Giovanna; Musitelli, Giorgio; Conte, Ubaldo; Maggi, Lauretta

2018-01-01

The purpose of this investigation is to determine how the dissolution media may influence the release rate of an insoluble drug in in vitro conditions. Some oral dosage forms containing ibuprofen, a molecule that shows pH-dependent solubility, are tested. They are evaluated in different media to simulate the gastrointestinal transit at paddle rotation speeds of 50 and 100 rpm. Moreover, the potential effect of different ethanol concentrations on drug release is tested. The dissolution profiles of the tablets show a similar behavior in water (pH 1.0) and phosphate buffer (pH 4.5) where the 2 doses are not completely dissolved. The soft capsules show a different behavior: a certain amount of ibuprofen, which is in solution inside the capsule, reprecipitates in water and in the pH 4.5 buffer. Instead, ibuprofen dissolves rapidly in the pH 6.8 buffer from all the formulations. In the water-ethanol solutions, the dissolution curves show a valuable increase in the drug dissolved at higher ethanol concentrations. Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Preparation of immunoglobulin Y from egg yolk using ammonium sulfate precipitation and ion exchange chromatography.

PubMed

Ko, K Y; Ahn, D U

2007-02-01

The objective of this study was to develop an economical, simple, and large-scale separation method for IgY from egg yolk. Egg yolk diluted with 9 volumes of cold water was centrifuged after adjusting the pH to 5.0. The supernatant was added with 0.01% charcoal or 0.01% carrageenan and centrifuged at 2,800 x g for 30 min. The supernatant was filtered through a Whatman no. 1 filter paper and then the filtrate was concentrated to 20% original volume using ultrafiltration. The concentrated solution was further purified using either cation exchange chromatography or ammonium sulfate precipitation. For the cation exchange chromatography method, the concentrated sample was loaded onto a column equilibrated with 20 mM citrate-phosphate buffer at pH 4.8 and eluted with 200 mM citrate-phosphate buffer at pH 6.4. For the ammonium sulfate precipitation method, the concentrated sample was twice precipitated with 40% ammonium sulfate solution at pH 9.0. The yield and purity of IgY were determined by ELISA and electrophoresis. The yield of IgY from the cation exchange chromatography method was 30 to 40%, whereas that of the ammonium sulfate precipitation was 70 to 80%. The purity of IgY from the ammonium sulfate method was higher than that of the cation exchange chromatography. The cation exchange chromatography could handle only a small amount of samples, whereas the ammonium sulfate precipitation could handle a large volume of samples. This suggests that ammonium sulfate precipitation was a more efficient and useful purification method than cation exchange chromatography for the large-scale preparation of IgY from egg yolk.

Catalysis of hydrolysis and nucleophilic substitution at the P-N bond of phosphoimidazolide-activated nucleotides in phosphate buffers

NASA Technical Reports Server (NTRS)

Kanavarioti, A.; Rosenbach, M. T.

1991-01-01

Phosphoimidazolide-activated derivatives of guanosine and cytidine 5'-monophosphates, henceforth called ImpN's, exhibit enhanced rates of degradation in the presence of aqueous inorganic phosphate in the range 4.0 < or = pH < or = 8.6. This degradation is been attributed to (i) nucleophilic substitution of the imidazolide and (ii) catalysis of the P-N bond hydrolysis by phosphate. The first reaction results in the formation of nucleoside 5'-diphosphate and the second in nucleoside 5'-monophosphate. Analysis of the observed rates as well as the product ratios as a function of pH and phosphate concentration allow distinction between various mechanistic possibilities. The results show that both H2PO4- and HPO4(2-) participate in both hydrolysis and nucleophilic substitution. Statistically corrected biomolecular rate constants indicate that the dianion is 4 times more effective as a general base than the monoanion, and 8 times more effective as nucleophile. The low Bronsted value beta = 0.15 calculated for these phosphate species, presumed to act as general bases in facilitating water attack, is consistent with the fact that catalysis of the hydrolysis of the P-N bond in ImpN's has not been detected before. The beta nuc = 0.35 calculated for water, H2PO4-, HPO4(2-), and hydroxide acting as nucleophiles indicates a more associative transition state for nucleotidyl (O2POR- with R = nucleoside) transfers than that observed for phosphoryl (PO3(2-)) transfers (beta nuc = 0.25). With respect to the stability/reactivity of ImpN's under prebiotic conditions, our study shows that these materials would not suffer additional degradation due to inorganic phosphate, assuming the concentrations of phosphate, Pi, on prebiotic Earth were similar to those in the present oceans ([Pi] approximately 2.25 micromoles).

40 CFR 180.920 - Inert ingredients used pre-harvest; exemptions from the requirement of a tolerance.

Code of Federal Regulations, 2012 CFR

2012-07-01

... di- and monohydrogen phosphate esters and the corresponding ammonium, calcium, magnesium, monoethanolamine, potassium, sodium, and zinc salts of the phosphate esters; minimum oxyethylene content is 2 moles.... 14433-76-2) Emulsifier, solvent, cosolvent Diammonium phosphate (CAS Reg. No. 7783-28-0) Buffer...

40 CFR 180.920 - Inert ingredients used pre-harvest; exemptions from the requirement of a tolerance.

Code of Federal Regulations, 2013 CFR

2013-07-01

... di- and monohydrogen phosphate esters and the corresponding ammonium, calcium, magnesium, monoethanolamine, potassium, sodium, and zinc salts of the phosphate esters; minimum oxyethylene content is 2 moles... phosphate (CAS Reg. No. 7783-28-0) Buffer, surfactant dibenzylidene sorbitol (32647-67-9) Thinning agent...

40 CFR 180.920 - Inert ingredients used pre-harvest; exemptions from the requirement of a tolerance.

Code of Federal Regulations, 2014 CFR

2014-07-01

... di- and monohydrogen phosphate esters and the corresponding ammonium, calcium, magnesium, monoethanolamine, potassium, sodium, and zinc salts of the phosphate esters; minimum oxyethylene content is 2 moles... phosphate (CAS Reg. No. 7783-28-0) Buffer, surfactant dibenzylidene sorbitol (32647-67-9) Thinning agent...

/sup 3/H)pirenzepine and (-)-(/sup 3/H)quinuclidinyl benzilate binding to rat cerebral cortical and cardiac muscarinic cholinergic sites. I. Characterization and regulation of agonist binding to putative muscarinic subtypes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watson, M.; Yamamura, H.I.; Roeske, W.R.

The binding and regulation of selected muscarinic agonists to putative subtypes in rat cerebral cortex and heart were studied. Parallel inhibition studies of (/sup 3/H)pirenzepine ((/sup 3/H)PZ) and (-)-(/sup 3/H)quinuclidinylbenzilate ((-)-(/sup 3/H)QNB)-labeled membranes were done with and without 30 microM guanyl-5'-yl imidodiphosphate (Gpp(NH)p) at 25 degrees C in 10 mM Na-K-phosphate buffer which enhances PZ binding affinity and in modified Krebs-phosphate buffer, which mimics physiological conditions. Classical agonists such as carbachol, oxotremorine and acetylcholine inhibited (-)-(/sup 3/H)QNB binding to membranes with shallow Hill values (nH less than 1), were better fit to a 2-state model, were Gpp(NH)p-regulated and showed lowermore » affinity in modified Krebs-phosphate buffer than in 10 mM Na-K-phosphate buffer. Some agonists were not significantly better fit to a 2-state model in (/sup 3/H)PZ-labeled cortical membranes, especially in 10 mM Na-K-phosphate buffer. Whereas putative M1 and M2 binding sites distinguished by PZ possessed multiple agonist affinity states, as judged by carbachol, and agonist binding to (/sup 3/H)PZ-labeled sites were Gpp(NH)p modulated, the partial agonist pilocarpine and nonclassical agonist McN-A-343 (3-(m-chlorophenylcarbamoyloxy)-2-butynyl trimethylammonium chloride) showed little Gpp(NH)p-induced shift in (/sup 3/H)PZ-labeled cortical membranes in physiological conditions. Agonist binding to (-)-(/sup 3/H)QNB-labeled putative M2 cardiac sites was more sensitive to Gpp(NH)p than (-)-(/sup 3/H)QNB-labeled cortical sites. Carbachol and acetylcholine showed significant selectivity for putative M2 sites.« less

Zearalenone reduction by commercial peroxidase enzyme and peroxidases from soybean bran and rice bran.

PubMed

Garcia, Sabrina O; Feltrin, Ana Carla P; Garda-Buffon, Jaqueline

2018-06-11

The peroxidase (POD) enzyme, obtained from different sources, has been described in the literature regarding its good results of reduction in concentration or degradation levels of mycotoxins, such as aflatoxin B1, deoxynivalenol and zearalenone. This study aimed at evaluating the action of commercial peroxidase and peroxidase from soybean bran (SB) and rice bran (RB) in zearalenone (ZEA) reduction in a model solution and the characterization of the mechanism of enzyme action. POD was extracted from SB and RB in phosphate buffer by orbital agitation. Evaluation of the action of commercial POD and POD from SB and RB in ZEA reduction was carried out in phosphate buffer and aqueous solution, respectively. Parameters of K M and V max were determined in the concentration range from 0.16 to 6 µg mL -1 . ZEA reduction was determined and the mechanism of enzyme action was characterized by Fourier transform infrared spectroscopy and high-pressure liquid chromatography-electrospray tandem mass spectrometry. Commercial POD and POD from RB and SB reduced ZEA concentration by 69.9, 47.4 and 30.6% in 24 h, respectively. K M values were 39.61 and 8.90 µM whereas V max values were 0.170 and 0.011 µM min -1 for commercial POD and POD from RB, respectively. The characterization of the mechanism of enzyme action showed the oxidoreductive action of commercial POD in the mycotoxin. The use of commercial POD and POD from agro-industrial by-products, such as SB and RB, could be a promising alternative for ZEA biodegradation.

A Study for Tooth Bleaching via Carbamide Peroxide-Loaded Hollow Calcium Phosphate Spheres.

PubMed

Qin, Tao; Mellgren, Torbjörn; Jefferies, Steven; Xia, Wei; Engqvist, Håkan

2016-12-26

The objective of this study was to investigate if a prolonged bleaching effect of carbamide peroxide-loaded hollow calcium phosphate spheres (HCPS) can be achieved. HCPS was synthesized via a hydrothermal reaction method. Carbamide peroxide (CP) was-loaded into HCPS by mixing with distilled water as solvent. We developed two bleaching gels containing CP-loaded HCPS: one gel with low HP concentration as at-home bleaching gel, and one with high HP concentration as in-office gel. Their bleaching effects on stained human permanent posterior teeth were investigated by measuring the color difference before and after bleaching. The effect of gels on rhodamine B degradation was also studied. To investigate the potential effect of remineralization of using HCPS, bleached teeth were soaked in phosphate buffer solution (PBS) containing calcium and magnesium ions. Both bleaching gels had a prolonged whitening effect, and showed a strong ability to degrade rhodamine B. After soaking in PBS for 3 days, remineralization was observed at the sites where HCPS attached to the teeth surface. CP-loaded HCPS could prolong the HP release behavior and improve the bleaching effect. HCPS was effective in increasing the whitening effect of carbamide peroxide and improving remineralization after bleaching process.

ELISA (Enzyme-linked Immunosorbent Assay) to Detect Humoral Antibodies Specific for Clostridium botulinum Type A Neurotoxin

DTIC Science & Technology

1985-11-19

10.6). Unbound toxoid was removed by washing three times with phosphate-buffered saline (pH 7.4) containing 0.05% Triton X-100 (Eastman Organic...MD) in phosphate-buffered saline was added. After a 90 min incubation period at 37*C, the excess conjugate was removed by washing each well three times...3. Cardella, M. A. 1964. Botulinum toxoids, p. 113-129. In K . H. Lewis and K . Cassel, Jr., (ed.), Botulism. U. S. Department of Health, Education

Analysis of Fatty Acid and Growth Profiles in Ten Shewanella spp. to Associate Phylogenetic Relationships

DTIC Science & Technology

2015-10-25

in a defined medium composed of half-strength Marine Broth adjusted to pH 6, 7, or 8 in a 50 mM phosphate buffer, both growth characteristics and...work had broad phylogenetic diversity (Fig. 1) and were isolated from mostly marine environments. S. putrefaciens was the only strain that was not...the defined medium that supported growth of most of the strains tested was marine broth diluted to half strength with 50 mM phosphate buffer (½-MB

Active Range Restoration via Caustic Hydrolysis of Explosively Contaminated Metal Parts

DTIC Science & Technology

2011-05-12

Ammonia, Formate – Sodium Cyanide  Low concentration (40 ppm)  Well established mitigation options • Primary Comp B off-gas components: – Ammonia, NOx...neutralized • In situ sodium cyanide treatment (D/H Reactor) – Hydrogen peroxide (H2O2) oxidizes CN- to CNO- • Analysis of liquid sample for sodium ... cyanide • pH neutralization and hydrolysate thickening – Phosphoric acid (H3PO4) forms buffer – Resulting sodium phosphate thickens to paste Lower

Reductive dechlorination of carbon tetrachloride using buffered alkaline ascorbic acid.

PubMed

Lin, Ya-Ting; Liang, Chenju

2015-10-01

Alkaline ascorbic acid (AA) was recently discovered as a novel in-situ chemical reduction (ISCR) reagent for remediating chlorinated solvents in the subsurface. For this ISCR process, the maintenance of an alkaline pH is essential. This study investigated the possibility of the reduction of carbon tetrachloride (CT) using alkaline AA solution buffered by phosphate and by NaOH. The results indicated that CT was reduced by AA, and chloroform (CF) was a major byproduct at a phosphate buffered pH of 12. However, CT was completely reduced by AA in 2M NaOH without CF formation. In the presence of iron/soil minerals, iron could be reduced by AA and Fe(2+) tends to precipitate on the mineral surface to accelerate CT degradation. A simultaneous transfer of hydrogenolysis and dichloroelimination would occur under phosphate buffered pH 12. This implies that a high alkaline environment is a crucial factor for maintaining the dominant pathway of two electron transfer from dianionic AA to dehydroascorbic acid, and to undergo dichloroelimination of CT. Moreover, threonic acid and oxalic acid were identified to be the major AA decomposition products in alkaline solutions. Copyright © 2015 Elsevier Ltd. All rights reserved.

The impact of reduced gastric acid secretion on dissolution of salts of weak bases in the fasted upper gastrointestinal lumen: Data in biorelevant media and in human aspirates.

PubMed

Litou, Chara; Vertzoni, Maria; Xu, Wei; Kesisoglou, Filippos; Reppas, Christos

2017-06-01

To propose media for simulating the intragastric environment under reduced gastric acid secretion in the fasted state at three levels of simulation of the gastric environment and evaluate their usefulness in evaluating the intragastric dissolution of salts of weak bases. To evaluate the importance of bicarbonate buffer in biorelevant in vitro dissolution testing when using Level II biorelevant media simulating the environment in the fasted upper small intestine, regardless of gastric acid secretions. Media for simulating the hypochlorhydric and achlorhydric conditions in stomach were proposed using phosphates, maleates and bicarbonates buffers. The impact of bicarbonates in Level II biorelevant media simulating the environment in upper small intestine was evaluated so that pH and bulk buffer capacity were maintained. Dissolution data were collected using two model compounds, pioglitazone hydrochloride and semifumarate cocrystal of Compound B, and the mini-paddle dissolution apparatus in biorelevant media and in human aspirates. Simulated gastric fluids proposed in this study were in line with pH, buffer capacity, pepsin content, total bile salt/lecithin content and osmolality of the fasted stomach under partial and under complete inhibition of gastric acid secretion. Fluids simulating the conditions under partial inhibition of acid secretion were useful in simulating concentrations of both model compounds in gastric aspirates. Bicarbonates in Level III biorelevant gastric media and in Level II biorelevant media simulating the composition in the upper intestinal lumen did not improve simulation of concentrations in human aspirates. Level III biorelevant media for simulating the intragastric environment under hypochlorhydric conditions were proposed and their usefulness in the evaluation of concentrations of two model salts of weak bases in gastric aspirates was shown. Level II biorelevant media for simulating the environment in upper intestinal lumen led to underestimation of concentrations in aspirates, even when bicarbonate buffer was used. Copyright © 2017 Elsevier B.V. All rights reserved.

Striking Effects of Storage Buffers on Apparent Half-Lives of the Activity of Pseudomonas aeruginosa Arylsulfatase.

PubMed

Li, Yuwei; Yang, Xiaolan; Wang, Deqiang; Hu, Xiaolei; Yuan, Mei; Pu, Jun; Zhan, Chang-Guo; Yang, Zhaoyong; Liao, Fei

2016-08-01

To obtain the label enzyme for enzyme-linked-immunoabsorbent-assay of two components each time in one well with conventional microplate readers, molecular engineering of Pseudomonas aeruginosa arylsulfatase (PAAS) is needed. To compare thermostability of PAAS/mutants of limited purity, effects of buffers on the half-activity time (t 0.5) at 37 °C were tested. At pH 7.4, PAAS showed non-exponential decreases of activity, with the apparent t 0.5 of ~6.0 days in 50 mM HEPES, but ~42 days in 10 mM sodium borate with >85 % activity after 15 days; protein concentrations in both buffers decreased at slower rates after there were significant decreases of activities. Additionally, the apparent t 0.5 of PAAS was ~14 days in 50 mM Tris-HCl, and ~21 days in 10 mM sodium phosphate. By sodium dodecyl-polyacrylamide gel electrophoresis, the purified PAAS gave single polypeptide; after storage for 14 days at 37 °C, there were many soluble and insoluble fragmented polypeptides in the HEPES buffer, but just one principal insoluble while negligible soluble fragmented polypeptides in the borate buffer. Of tested mutants in the neutral borate buffer, rates for activity decreases and polypeptide degradation were slower than in the HEPES buffer. Hence, dilute neutral borate buffers were favorable for examining thermostability of PAAS/mutants.

Plasma creatinine and creatine quantification by capillary electrophoresis diode array detector.

PubMed

Zinellu, Angelo; Caria, Marcello A; Tavera, Claudio; Sotgia, Salvatore; Chessa, Roberto; Deiana, Luca; Carru, Ciriaco

2005-07-15

Traditional clinical assays for nonprotein nitrogen compounds, such as creatine and creatinine, have focused on the use of enzymes or chemical reactions that allow measurement of each analyte separately. Most of these assays are mainly directed to urine quantification, so that their applicability on plasma samples is frequently hard to perform. This work describes a simple free zone capillary electrophoresis method for the simultaneous measurement of creatinine and creatine in human plasma. The effect of analytical parameters such as concentration and pH of Tris-phosphate running buffer and cartridge temperature on resolution, migration times, peak areas, and efficiency was investigated. Good separation was achieved using a 60.2-cm x 75-microm uncoated silica capillary, 75 mmol/L Tris-phosphate buffer, pH 2.25, at 15 degrees C, in less than 8 min. We compared the present method to a validated capillary electrophoresis assay, by measuring plasma creatinine in 120 normal subjects. The obtained data were compared by the Passing-Bablok regression and the Bland-Altman test. Moreover the performance of the developed method was assessed by measuring creatine and creatinine in 16 volunteers prior to and after a moderate physical exercise.

Anions in Electrothermal Supercharging of Proteins with Electrospray Ionization Follow a Reverse Hofmeister Series

PubMed Central

2015-01-01

The effects of different anions on the extent of electrothermal supercharging of proteins from aqueous ammonium and sodium salt solutions were investigated. Sulfate and hydrogen phosphate are the most effective anions at producing high charge state protein ions from buffered aqueous solution, whereas iodide and perchlorate are ineffective with electrothermal supercharging. The propensity for these anions to produce high charge state protein ions follows the following trend: sulfate > hydrogen phosphate > thiocyanate > bicarbonate > chloride > formate ≈ bromide > acetate > iodide > perchlorate. This trend correlates with the reverse Hofmeister series over a wide range of salt concentrations (1 mM to 2 M) and with several physical properties, including solvent surface tension, anion viscosity B-coefficient, and anion surface/bulk partitioning coefficient, all of which are related to the Hofmeister series. The effectiveness of electrothermal supercharging does not depend on bubble formation, either from thermal degradation of the buffer or from coalescence of dissolved gas. These results provide evidence that the effect of different ions in the formation of high charge state ions by electrothermal supercharging is largely a result of Hofmeister effects on protein stability leading to protein unfolding in the heated ESI droplet. PMID:24410546

Comparing human peritoneal fluid and phosphate-buffered saline for drug delivery: do we need bio-relevant media?

PubMed

Bhusal, Prabhat; Rahiri, Jamie Lee; Sua, Bruce; McDonald, Jessica E; Bansal, Mahima; Hanning, Sara; Sharma, Manisha; Chandramouli, Kaushik; Harrison, Jeff; Procter, Georgina; Andrews, Gavin; Jones, David S; Hill, Andrew G; Svirskis, Darren

2018-06-01

An understanding of biological fluids at the site of administration is important to predict the fate of drug delivery systems in vivo. Little is known about peritoneal fluid; therefore, we have investigated this biological fluid and compared it to phosphate-buffered saline, a synthetic media commonly used for in vitro evaluation of intraperitoneal drug delivery systems. Human peritoneal fluid samples were analysed for electrolyte, protein and lipid levels. In addition, physicochemical properties were measured alongside rheological parameters. Significant inter-patient variations were observed with regard to pH (p < 0.001), buffer capacity (p < 0.05), osmolality (p < 0.001) and surface tension (p < 0.05). All the investigated physicochemical properties of peritoneal fluid differed from phosphate-buffered saline (p < 0.001). Rheological examination of peritoneal fluid demonstrated non-Newtonian shear thinning behaviour and predominantly exhibited the characteristics of an entangled network. Inter-patient and inter-day variability in the viscosity of peritoneal fluid was observed. The solubility of the local anaesthetic lidocaine in peritoneal fluid was significantly higher (p < 0.05) when compared to phosphate-buffered saline. Interestingly, the dissolution rate of lidocaine was not significantly different between the synthetic and biological media. Importantly, and with relevance to intraperitoneal drug delivery systems, the sustained release of lidocaine from a thermosensitive gel formulation occurred at a significantly faster rate into peritoneal fluid. Collectively, these data demonstrate the variation between commonly used synthetic media and human peritoneal fluid. The differences in drug release rates observed illustrate the need for bio-relevant media, which ultimately would improve in vitro-in vivo correlation.

In vitro metabolic stability of moisture-sensitive rabeprazole in human liver microsomes and its modulation by pharmaceutical excipients.

PubMed

Ren, Shan; Park, Mi-Jin; Kim, Aera; Lee, Beom-Jin

2008-03-01

A reliable method to assess in vitro metabolic stability of rabeprazole and its modulation by Generally Recognized As Safe (GRAS)-listed pharmaceutical excipients was established in human liver microsomes. The metabolic stability of rabeprazole decreased as a function of incubation time, resulting in the formation of thioether rabeprazole via nonenzymatic degradation and enzymatic metabolism. Buffer type was also a determining factor for the degree of both nonenzymatic degradation and enzymatic metabolism. The net extent of enzymatic drug metabolism, obtained by calculating the difference in drug degradation between a microsome-present reaction system and a microsome-free solution, was about 9.20 +/- 0.67% in phosphate buffer and 2.27 +/- 1.76% in Tris buffer, respectively. Rabeprazole exhibited first-order kinetics in microsome-free solution but showed non-linear kinetics in the microsome-present reaction system. The maximal velocity, Vmax, in phosphate buffer was 5.07 microg mL(-1) h(-1) and the Michaelis-Menten constant, Km, was 10.39 microg mL(-1) by computer-fitting to the classical Michaelis-Menten equation for pattern of time-dependent change in the substrate concentration. The intact drug and its thioether form were well resolved and successfully identified by HPLC chromatography and liquid chromatography mass spectroscopy (LC/MS). The metabolic stability of rabeprazole was also modulated by the presence of pharmaceutical excipients. Among the five pharmaceutical excipients tested, poloxamer 188 and Gelucire 44/14 had potentially inhibitory effects on rabeprazole metabolism in human liver microsomes (p < 0.05). A greater understanding of metabolic stability and its modulation by pharmaceutical excipients would be useful for optimizing the bioavailability of rabeprazole at the early formulation stages.

Application of hanging drop technique to optimize human IgG formulations.

PubMed

Li, Guohua; Kasha, Purna C; Late, Sameer; Banga, Ajay K

2010-01-01

The purpose of this work is to assess the hanging drop technique in screening excipients to develop optimal formulations for human immunoglobulin G (IgG). A microdrop of human IgG and test solution hanging from a cover slide and undergoing vapour diffusion was monitored by a stereomicroscope. Aqueous solutions of IgG in the presence of different pH, salt concentrations and excipients were prepared and characterized. Low concentration of either sodium/potassium phosphate or McIlvaine buffer favoured the solubility of IgG. Addition of sucrose favoured the stability of this antibody while addition of NaCl caused more aggregation. Antimicrobial preservatives were also screened and a complex effect at different buffer conditions was observed. Dynamic light scattering, differential scanning calorimetry and size exclusion chromatography studies were performed to further validate the results. In conclusion, hanging drop is a very easy and effective approach to screen protein formulations in the early stage of formulation development.

Functional PEG–PAMAM-Tetraphosphonate Capped NaLnF4 Nanoparticles and their Colloidal Stability in Phosphate Buffer

PubMed Central

2015-01-01

Developing surface coatings for NaLnF4 nanoparticles (NPs) that provide long-term stability in solutions containing competitive ions such as phosphate remains challenging. An amine-functional polyamidoamine tetraphosphonate (NH2-PAMAM-4P) as a multidentate ligand for these NPs has been synthesized and characterized as a ligand for the surface of NaGdF4 and NaTbF4 nanoparticles. A two-step ligand exchange protocol was developed for introduction of the NH2-PAMAM-4P ligand on oleate-capped NaLnF4 NPs. The NPs were first treated with methoxy-poly(ethylene glycol)-monophosphoric acid (Mn = 750) in tetrahydrofuran. The mPEG750-OPO3-capped NPs were stable colloidal solutions in water, where they could be ligand-exchanged with NH2-PAMAM-4P. The surface amine groups on the NPs were available for derivatization to attach methoxy-PEG (Mn = 2000) and biotin-terminated PEG (Mn = 2000) chains. The surface coverage of ligands on the NPs was examined by thermal gravimetric analysis, and by a HABA analysis for biotin-containing NPs. Colloidal stability of the NPs was examined by dynamic light scattering. NaGdF4 and NaTbF4 NPs capped with mPEG2000–PAMAM-4P showed colloidal stability in DI water and in phosphate buffer (10 mM, pH 7.4). A direct comparison with NaTbF4 NPs capped with a mPEG2000-lysine-based tetradentate ligand that we reported previously (Langmuir2012, 28, 12861−1287022906305) showed that both ligands provided long-term stability in phosphate buffer, but that the lysine-based ligand provided better stability in phosphate-buffered saline. PMID:24898128

Functional PEG-PAMAM-tetraphosphonate capped NaLnF₄ nanoparticles and their colloidal stability in phosphate buffer.

PubMed

Zhao, Guangyao; Tong, Lemuel; Cao, Pengpeng; Nitz, Mark; Winnik, Mitchell A

2014-06-17

Developing surface coatings for NaLnF4 nanoparticles (NPs) that provide long-term stability in solutions containing competitive ions such as phosphate remains challenging. An amine-functional polyamidoamine tetraphosphonate (NH2-PAMAM-4P) as a multidentate ligand for these NPs has been synthesized and characterized as a ligand for the surface of NaGdF4 and NaTbF4 nanoparticles. A two-step ligand exchange protocol was developed for introduction of the NH2-PAMAM-4P ligand on oleate-capped NaLnF4 NPs. The NPs were first treated with methoxy-poly(ethylene glycol)-monophosphoric acid (M(n) = 750) in tetrahydrofuran. The mPEG750-OPO3-capped NPs were stable colloidal solutions in water, where they could be ligand-exchanged with NH2-PAMAM-4P. The surface amine groups on the NPs were available for derivatization to attach methoxy-PEG (M(n) = 2000) and biotin-terminated PEG (M(n) = 2000) chains. The surface coverage of ligands on the NPs was examined by thermal gravimetric analysis, and by a HABA analysis for biotin-containing NPs. Colloidal stability of the NPs was examined by dynamic light scattering. NaGdF4 and NaTbF4 NPs capped with mPEG2000-PAMAM-4P showed colloidal stability in DI water and in phosphate buffer (10 mM, pH 7.4). A direct comparison with NaTbF4 NPs capped with a mPEG2000-lysine-based tetradentate ligand that we reported previously (Langmuir 2012, 28, 12861-12870) showed that both ligands provided long-term stability in phosphate buffer, but that the lysine-based ligand provided better stability in phosphate-buffered saline.

Comparison of extraction buffers for the detection of fumonisin B(1) in corn by immunoassay and high-performance liquid chromatography.

PubMed

Kulisek, E S; Hazebroek, J P

2000-01-01

The Associatian of Official Analytical Chemists approved method for quantification of fumonisin B(1) (FB(1)) in corn meal or corn-based food products includes extraction into methanol (MeOH)/water (3:1, v/v). Disposal of the extraction medium can pose safety and environmental problems. To secure a rapid and inexpensive screen for FB(1) contamination, a sensitive competitive ELISA using a rabbit polyclonal antibody was developed. This assay was used in a comparative study measuring the extraction efficiency of FB(1) in aqueous or organic solvent buffers using 16 field corn samples. An aqueous phosphate buffer was found to be suitable for extracting FB(1), thus eliminating the need for organic solvents. HPLC and ELISA determinations compared well in fortified samples at known concentrations between 1 and 50 microg/mL of extract. Overestimation at levels >50 microg/mL were common. The characteristics and application of the ELISA for screening purposes are discussed.

Quantitative and qualitative optimization of allergen extraction from peanut and selected tree nuts. Part 2. Optimization of buffer and ionic strength using a full factorial experimental design.

PubMed

L'Hocine, Lamia; Pitre, Mélanie

2016-03-01

A full factorial design was used to assess the single and interactive effects of three non-denaturing aqueous (phosphate, borate, and carbonate) buffers at various ionic strengths (I) on allergen extractability from and immunoglobulin E (IgE) immunoreactivity of peanut, almond, hazelnut, and pistachio. The results indicated that the type and ionic strength of the buffer had different effects on protein recovery from the nuts under study. Substantial differences in protein profiles, abundance, and IgE-binding intensity with different combinations of pH and ionic strength were found. A significant interaction between pH and ionic strength was observed for pistachio and almond. The optimal buffer system conditions, which maximized the IgE-binding efficiency of allergens and provided satisfactory to superior protein recovery yield and profiles, were carbonate buffer at an ionic strength of I=0.075 for peanut, carbonate buffer at I=0.15 for almond, phosphate buffer at I=0.5 for hazelnut, and borate at I=0.15 for pistachio. The buffer type and its ionic strength could be manipulated to achieve the selective solubility of desired allergens. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Cytotoxic and inflammatory effects of contact lens solutions on human corneal epithelial cells in vitro.

PubMed

Oh, Sarah; McCanna, David J; Subbaraman, Lakshman N; Jones, Lyndon W

2018-06-01

To ascertain the effect that four contact lens (CL) multipurpose solutions (MPS) have on the viability and release of pro-inflammatory cytokines from human corneal epithelial cells (HCEC). HCEC were exposed to four different MPS at various concentrations for 18 hours. The cells were also exposed to phosphate buffer, borate buffer, and PHMB. The cell viability was evaluated using the alamarBlue assay. The release of pro-inflammatory cytokines was measured using a Multiplex electrochemiluminescent assay. MPS-A, MPS-B and MPS-C all reduced cell metabolic activity p < 0.05 from control with MPS-A showing the greatest cytotoxic effect (maximum reduction, 90.6%). In contrast, MPS-D showed no significant reductions in cytotoxicity except at the highest concentration tested (19% reduction at 20% MPS concentration). Of the four cytokines evaluated MPS-C showed a substantial increase in the release of IL-1β, IL-6, IL-8, and TNF-α at higher concentrations when compared to control p < 0.05. At the 20% concentration of MPS-A and MPS-B the release of IL-1 β increased p < 0.05 but the release of IL-6, IL-8, and TNF-α decreased. MPS-D did not cause a change in the release of cytokines IL-1β, IL-6, IL-8 and TNF-α p > 0.05. Exposing the cells to borate buffer and PHMB caused an increase in the release of TNF-α p < 0.05. This investigation demonstrates that at different concentration levels, several of the MPS tested showed a decrease in viability and an increase in the release of inflammatory cytokines from HCEC. The borate buffer component as well as PHMB appears to contribute to this pro-inflammatory reaction. Copyright © 2017 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

Micro solid-phase derivatization analysis of low-molecular mass aldehydes in treated water by micellar electrokinetic chromatography.

PubMed

Fernández-Molina, José María; Silva, Manuel

2014-03-01

A MEKC method was developed for the determination of aliphatic and aromatic low-molecular mass aldehydes (LMMAs) in treated water samples. The method involves the precapillary derivatization and extraction of the aldehydes on a Telos™ENV μ-SPE column impregnated with 2,4-dinitrophenylhydrazine . After elution of the hydrazones with ACN, the derivatives were analyzed using MEKC-DAD. Resolution of the MEKC procedure was studied by changing the pH and the concentration of the buffer, the type, and the concentration of surfactant, and the organic modifier content in the BGE. A running buffer consisting of a phosphate buffer (pH 7.2, 75 mM) with CTAB (50 mM) and ACN (30%) gave the best results. Linearity was established over the concentration range 0.5-500 μg/L and LODs from 65 to 775 ng/L; the interday precision was expressed as the RSD of the aldehydes ranging from 6.6 to 8.4%. Matrix effects were shown to be negligible by comparing the response factors obtained in ultrapure and treated waters. Aldehydes were readily determined at 1.1-8.4 μg/L levels in ozonated and chlorinated water samples, the method proposed being the first CE contribution developed for the systematic analysis of both aliphatic and aromatic LMMAs in water samples. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Catalase activity is stimulated by H2O2 in rich culture medium and is required for H2O2 resistance and adaptation in yeast☆

PubMed Central

Martins, Dorival; English, Ann M.

2014-01-01

Catalases are efficient scavengers of H2O2 and protect cells against H2O2 stress. Examination of the H2O2 stimulon in Saccharomyces cerevisiae revealed that the cytosolic catalase T (Ctt1) protein level increases 15-fold on H2O2 challenge in synthetic complete media although previous work revealed that deletion of the CCT1 or CTA1 genes (encoding peroxisomal/mitochondrial catalase A) does not increase the H2O2 sensitivity of yeast challenged in phosphate buffer (pH 7.4). This we attributed to our observation that catalase activity is depressed when yeast are challenged with H2O2 in nutrient-poor media. Hence, we performed a systematic comparison of catalase activity and cell viability of wild-type yeast and of the single catalase knockouts, ctt1∆ and cta1∆, following H2O2 challenge in nutrient-rich medium (YPD) and in phosphate buffer (pH 7.4). Ctt1 but not Cta1 activity is strongly induced by H2O2 when cells are challenged in YPD but suppressed when cells are challenged in buffer. Consistent with the activity results, exponentially growing ctt1∆ cells in YPD are more sensitive to H2O2 than wild-type or cta1∆ cells, whereas in buffer all three strains exhibit comparable H2O2 hypersensitivity. Furthermore, catalase activity is increased during adaptation to sublethal H2O2 concentrations in YPD but not in buffer. We conclude that induction of cytosolic Ctt1 activity is vital in protecting yeast against exogenous H2O2 but this activity is inhibited by H2O2 when cells are challenged in nutrient-free media. PMID:24563848

Light Scattering Characterization of Elastin-Like Polypeptide Trimer Micelles

NASA Astrophysics Data System (ADS)

Tsuper, Ilona; Terrano, Daniel; Maraschky, Adam; Holland, Nolan; Streletzky, Kiril

The elastin-like polypeptides (ELP) nanoparticles are composed of three-armed star polypeptides connected by a negatively charged foldon. Each of the three arms extending from the foldon domain includes 20 repeats of the (GVGVP) amino acid sequence. The ELP polymer chains are soluble at room temperature and become insoluble at the transition temperature (close to 50 ° C), forming micelles. The size and shape of the micelle are dependent on the temperature and the pH of the solution, and on the concentration of the phosphate buffered saline (PBS). The depolarized dynamic light scattering (DDLS) was employed to study the structure and dynamics of micelles at 62 ° C. The solution was maintained at an approximate pH level of 7.3 - 7.5, while varying PBS concentration. At low salt concentrations (<15 mM), the micelle radius was about 10nm but not very reproducible on account of unstable pH levels arising from low buffer concentrations. At intermediate salt concentrations (15 - 60 mM), the system formed spherically-shaped micelles, exhibiting a steady growth in the hydrodynamic radius (Rh) from 10 to 21 nm, with increasing PBS concentration. Interestingly, higher salt concentrations (>60 mM) displayed an apparent elongation of the micelles evident by a significant VH signal, along with a surge in the apparent Rh. A model of micelle growth (and potential elongation) with increase in salt concentration is considered.

Establishment and optimization of monoclonal antibody-based heterologous dcELISA for 19-nortestosterone residue in bovine edible tissue.

PubMed

Jiang, Jinqing; Zhang, Haitang; Li, Guangling; Yang, Xuefeng; Li, Renfeng; Wang, Ziliang; Wang, Jianhua

2012-04-01

This paper presents the generation of monoclonal antibodies (mAbs) with high specificity against 19-nortestosterone (NT) through cell fusion procedures, and the development of mAb-based heterologous direct competitive enzyme-linked immunoabsorbent assay (dcELISA) methods to detect NT residue using one of these hybridomas (clone 3B8-E6). Under optimal experimental conditions, this assay exhibited a working range of 0.004 to 19 ng/mL with IC₅₀ and limit of detection values of 0.28 and 0.002 ng/mL, respectively, when it was run in 0.01M phosphate-buffered saline (pH 7.4). Except for minor cross-reactivity with β-boldenone (6.9%) and trenbolone (1.2%), other interference to the assay was negligible (<0.05%). No significant differences (P > 0.05) were found for IC₅₀ values when the pH of the assay buffer ranged from 6 to 8 and phosphate ion concentration was less than 20 mM. The dcELISA can tolerate higher concentrations of methanol than other organic solvents tested. When applied to bovine sample, the correlation coefficients (R) of the dcELISA and GC-MS data were 0.9918 in muscle, 0.9834 in liver, and 0.9976 in kidney. Therefore, this assay has the potential to be incorporated into a quantitative monitoring program for the rapid screening of NT residue in food. © 2012 Institute of Food Technologists®

Evaluation of the erosive potential of soft drinks.

PubMed

de Carvalho Sales-Peres, Sílvia Helena; Magalhães, Ana Carolina; de Andrade Moreira Machado, Maria Aparecida; Buzalaf, Marília Afonso Rabelo

2007-01-01

This in vitro study evaluated the capability of different soft drinks (Coca-Cola(R)-C, Coca-Cola Light(R)-CL, Guaraná(R)-G, Pepsi Twist(R)-P and Sprite Light(R)-SL) to erode dental enamel, relating the percentage of superficial microhardness change (%SMHC) to concentrations of fluoride and phosphate, buffering capacity and pH of these drinks. The soft drinks were evaluated in respect to concentration of phosphate and fluoride spectrophotometrically using Fiske, Subarrow method and by specific electrode (Orion 9609), respectively. The pH and the buffering capacity were determined by glass electrode and by estimating of the volume of NaOH necessary to change the pH of the drink in one unit, respectively. One hundred specimens of bovine enamel were randomly assigned to 5 groups of 20 each. They were exposed to 4 cycles of demineralisation in the beverage and remineralisation in artificial saliva. The softening of enamel was evaluated by %SMHC. The mean %SMHC was: C=77.27%, CL= 72.45%, SL=78.43%, G=66.65% and P=67.95%. Comparing the %SMHC promoted by 5 soft drinks, SL = C > CL > P = G (P<.05). There was not significant correlation between %SMHC and the other variables tested for the five drinks (P>.05). The five soft drinks caused surface softening of enamel (erosion). In respect to the chemical variables tested, despite not statistically significant, the pH seems to have more influence on the erosive potential of these drinks. (Eur J Dent 2007;1:10-13).

Iron as a catalyst of human low-density lipoprotein oxidation: Critical factors involved in its oxidant properties.

PubMed

Lapenna, Domenico; Ciofani, Giuliano; Obletter, Gabriele

2017-05-01

Iron-induced human LDL oxidation, which is relevant to atherosclerosis, has not yet been properly investigated. We addressed such issue using iron(II) and (III) basically in the presence of phosphates, which are present in vivo and influence iron oxidative properties, at pH 4.5 and 7.4, representative, respectively, of the lysosomal and plasma environment. In 10mM phosphate buffered saline (PBS), iron(II) induces substantial LDL oxidation at pH 4.5 at low micromolar concentrations, while at pH 7.4 has low oxidative effects; iron(III) promotes small LDL oxidation only at pH 4.5. In 10mM sodium acetate/NaCl buffer, pH 4.5, iron-induced LDL oxidation is far higher than in PBS, highlighting the relevance of phosphates in the inhibitory modulation of iron-induced LDL oxidation. LDL oxidation is related to iron binding to the protein and lipid moiety of LDL, and requires the presence of iron(II) bound to LDL together with iron(III). Chemical modification of LDL carboxyl groups, which could bind iron especially at pH 4.5, decreases significantly iron binding to LDL and iron-induced LDL oxidation. Hydroxyl radical scavengers are ineffective on iron-induced LDL oxidation, which is inhibited by metal chelation, scavengers of alkoxyl/peroxyl radicals, or removal of LDL lipid hydroperoxides (LOOH). Overall, substantial human LDL oxidation is induced LOOH-dependently by iron(II) at pH 4.5 even in the presence of phosphates, suggesting the occurrence of iron(II)-induced LDL oxidation in vivo within lysosomes, where pH is about 4.5, iron(II) and phosphates coexist, plasma with its antioxidants is absent, and glutathione peroxidase is poorly expressed resulting in LOOH accumulation. Copyright © 2017 Elsevier GmbH. All rights reserved.

Partition coefficients of some purine derivatives and its application to pharmacokinetics.

PubMed

Chrzanowska, M; Sobiak, J; Kuehn, M; Dorawa, E; Hermann, T

2009-12-01

Metazathioprine (MAZA), a methylated derivative of azathioprine (AZA), demonstrated the greatest values of apparent and specific partition coefficients in n-octanol/phosphate buffer at pH 5.7 and pH 7.4 among purine derivatives such as 6-mercaptopurine (6-MP), 6-thioguanine (6-TG) and AZA. Introduction of a methyl group into the imidazole ring of AZA increases lipophilic properties of MAZA compared to AZA. Mass balance of purine derivatives in n-octanol and in phosphate buffer indicated their chemical stability in those media.

Inactivation of coliphage Q beta by potassium ferrate.

PubMed

Kazama, F

1994-05-15

The kinetics of inactivation of a bacteriophage by potassium ferrate were studied with the F-specific RNA-coliphage Q beta. Inactivation in phosphate buffer (pH 6, 7 and 8) containing ferrate could be described by Hom's model. The inactivation rate depended on the pH. However, the relative effects of ferrate concentration and exposure time on inactivation were not affected by a change in pH from 6 to 8. In a study of the mechanism by which ferrate inactivated the virus, the efficiency of viral inactivation after ferrate decomposed in buffer was assayed. Inactivation was still effective and still followed Hom's equation after the complete decomposition of ferrate ion; however, the efficiency of that inactivation disappeared when sodium thiosulfate was added, suggesting that long-lived oxidative intermediates capable of viral inactivation were generated during the decomposition of ferrate ions.

Control of brown stain: in Eastern white pine

Treesearch

Robert E. Stutz; Peter Koch; Millard L. Oldham

1961-01-01

Degrade caused by brown stain and blue stain in eastern white pine was virtually eliminated by the use of sap stain chemicals and sodium azide. Combinations of buffered sodium azide with both sodium pentachlorophenate plus borax and buffered ethyl mercury phosphate were effective.

The adsorption mechanism of nortryptiline on C18-bonded discovery

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gritti, Fabrice; Guiochon, Georges A

2005-08-01

The adsorption isotherms of an ionizable compound, nortriptyline, were accurately measured by frontal analysis (FA) on a C{sub 18}-Discovery column, first without buffer (in an aqueous solution of acetonitrile at 15%, v/v of ACN), then with a buffer (in 28%, v/v ACN solution). The buffers were aqueous solutions containing 20 mM of formic acid or a phosphate buffer at pH 2.70. The linear range of the isotherm could not be reached with the non-buffered mobile phase using a dynamic range larger than 40,000 (from 1.2 x 10{sup -3} g/L to 50 g/L). With a 20 mM buffer in the liquidmore » phase, the isotherm is linear for concentrations of nortriptyline inferior to 10{sup -3} g/L (or 3 {micro} mol/L). The adsorption energy distribution (AED) was calculated to determine the heterogeneity of the adsorption process. AED and FA were consistent and lead to a trimodal distribution. A tri-Moreau and a tri-Langmuir isotherm models accounted the best for the adsorption of nortriptyline without and with buffer, respectively. The nature of the buffer affects significantly the middle-energy sites while the properties of the lowest and highest of the three types of energy sites are almost unchanged. The desorption profiles of nortriptyline show some anomalies in relation with the formation of a complex multilayer adsorbed phase of acetonitrile whose excess isotherm was measured by the minor disturbance method. The C{sub 18}-Discovery column has about the same total saturation capacity, around 200 g of nortriptyline per liter of adsorbent (or 116 mg/g), with or without buffer. About 98-99% of the available surface consists in low energy sites. The coexistence of these different types of sites on the surface solves the McCalley's enigma, that the column efficiency begins to drop rapidly when the analyte concentration reaches values that are almost one hundred times lower than those that could be predicted from the isotherm data acquired under the same experimental conditions. Due to the presence of some relatively rare high energy sites, the largest part of the saturation capacity is not practically useful.« less

Piezoresistive cantilever array sensor for consolidated bioprocess monitoring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Seonghwan Sam; Rahman, Touhidur; Senesac, Larry R

2009-01-01

Cellulolytic microbes occur in diverse natural niches and are being screened for industrial modification and utility. A microbe for Consolidated bioprocessing (CBP) development can rapidly degrade pure cellulose and then ferment the resulting sugars into fuels. To identify and screen for novel microbes for CBP, we have developed a piezoresistive cantilever array sensor which is capable of simultaneous monitoring of glucose and ethanol concentration changes in a phosphate buffer solution. 4-mercaptophenylboronic acid (4-MPBA) and polyethyleneglycol (PEG)-thiol are employed to functionalize each piezoresistive cantilever for glucose and ethanol sensing, respectively. Successful concentration measurements of glucose and ethanol with minimal interferences aremore » obtained with our cantilever array sensor.« less

Developing procedures for the large-scale purification of human serum butyrylcholinesterase.

PubMed

Saxena, Ashima; Luo, Chunyuan; Doctor, Bhupendra P

2008-10-01

Human serum butyrylcholinesterase (Hu BChE) is the most viable candidate for the prophylactic treatment of organophosphate poisoning. A dose of 200 mg/70 kg is predicted to protect humans against 2x LD(50) of soman. Therefore, the aim of this study was to develop procedures for the purification of gram quantities of this enzyme from outdated human plasma or Cohn Fraction IV-4. The purification of Hu BChE was accomplished by batch adsorption on procainamide-Sepharose-CL-4B affinity gel followed by ion-exchange chromatography on a DEAE-Sepharose column. For the purification of enzyme from Cohn Fraction IV-4, it was resuspended in 25 mM sodium phosphate buffer, pH 8.0, and fat was removed by decantation, prior to batch adsorption on procainamide-Sepharose gel. In both cases, the procainamide gel was thoroughly washed with 25 mM sodium phosphate buffer, pH 8.0, containing 0.05 M NaCl, and the enzyme was eluted with the same buffer containing 0.1 M procainamide. The enzyme was dialyzed and the pH was adjusted to 4.0 before loading on the DEAE column equilibrated in sodium acetate buffer, pH 4.0. The column was thoroughly washed with 25 mM sodium phosphate buffer, pH 8.0 containing 0.05 M NaCl before elution with a gradient of 0.05-0.2M NaCl in the same buffer. The purity of the enzyme following these steps ranged from 20% to 40%. The purity of the enzyme increased to >90% by chromatography on an analytical procainamide affinity column. Results show that Cohn Fraction IV-4 is a much better source than plasma for the large-scale isolation of purified Hu BChE.

Dissolution enhancement of atorvastatin calcium by co-grinding technique.

PubMed

Prabhu, Priyanka; Patravale, Vandana

2016-08-01

Atorvastatin calcium (AC) is a BCS class II drug which shows poor bioavailability due to inadequate dissolution. Solid dispersions present a promising option to enhance the solubility of poorly soluble drugs. Co-grinding with hydrophilic excipients is an easy and economical technique to improve the solubility of poorly soluble drugs and is free from usage of organic solvents. The aim of the present study was to explore novel carrier VBP-1 (organosulphur compound) for formulating a solid dispersion by using a simple, commercially viable co-grinding technique to enhance the dissolution of AC and to develop an oral formulation of the same. Composition of the solid dispersion was optimized based on the release profile in pH 1.2 buffer. The optimized solid dispersion was further characterized for flow properties, DSC, FTIR spectroscopy, XRD, contact angle, SEM studies and release profile in phosphate buffer pH 6.8. The developed solid dispersion gave similar release profile as the innovator formulation (Lipitor® tablets) in both pH 1.2 buffer and phosphate buffer pH 6.8. The developed solid dispersion was formulated into hard gelatin capsules (size 3). The developed capsules were found to give similar release as the innovator formulation in both pH 1.2 buffer and phosphate buffer pH 6.8. The developed capsules were found to be stable for a period of 6 months. Anti-hyperlipidemic efficacy studies in rats showed higher reduction in cholesterol and triglyceride levels by the developed capsules in comparison to pure AC. In conclusion, novel carrier VBP-1 was successfully employed to enhance the dissolution of AC using co-grinding technique.

Increased rate of adenine incorporation into adenine nucleotide pool in erythrocytes of patients with chronic renal failure.

PubMed

Marlewski, M; Smolenski, R T; Szolkiewicz, M; Aleksandrowicz, Z; Rutkowski, B; Swierczynski, J

2000-11-01

Elevated purine nucleotide pool (mainly ATP) in erythrocytes of patients with chronic renal failure (CRF) is a known phenomenon, however the mechanism responsible for this abnormality is far from being clear. We hypothesize that the increased rate of adenine incorporation into adenine nucleotide pool is responsible for the elevated level of ATP in uremic erythrocytes. In chronically uremic patients we evaluated using HPLC technique: (a) plasma adenine concentration; (b) the rate of adenine incorporation into adenine nucleotide pool in uremic erythrocytes. Additionally, the effect of higher than physiological phosphate concentration (2.4 mM) and lower than physiological pH (7.1) on adenine incorporation into erythrocytes adenine nucleotide pool was investigated. Healthy volunteers with normal renal function served as control. The concentration of adenine in plasma of CRF patients was found to be significantly higher than in plasma of healthy subjects. In contrast, adenosine concentration was similar both in healthy humans and in CRF patients. In isolated erythrocytes of uremic patients (incubated in the medium pH 7.4, containing 1.2 mM inorganic phosphate) adenine was incorporated into adenine nucleotide pool at a rate approximately 2-fold higher than in erythrocytes from healthy subjects. The rate of adenosine incorporation into adenine nucleotide pool was similar in erythrocytes of both studied groups. Incubation of erythrocytes obtained from healthy subjects in the medium pH 7.4, containing 2.4 mM inorganic phosphate, caused the increase of adenine incorporation into adenine nucleotide pool by about 60%. Incubation of the cells in the pH 7.1 buffer containing 2. 4 mM inorganic phosphate increased the rate of adenine incorporation into adenylate approximately 2-fold as compared to erythrocytes incubated in the medium pH 7.4 containing 1.2 mM inorganic phosphate. Erythrocytes obtained from uremic patients and incubated in the pH 7.1 medium containing 2.4 mM phosphate incorporated adenine into adenine nucleotide pool at a rate similar to erythrocytes incubated in the medium pH 7.4 containing 1.2 mM phosphate. Erythrocytes obtained from either healthy subjects or from patients with CRF and incubated in the presence of higher than physiological concentration of inorganic phosphate (2.4 mM) and lower than physiological pH (7. 1) did not exhibit any increase in the rate of adenisine incorporation into adenine nucleotide pool. These results suggest that the increased rate of adenine incorporation into adenine nucleotide pool could be partially responsible for the increased concentration of ATP in uremic erythrocytes. Copyright 2000 S. Karger AG, Basel

Glucose buffer is suitable for blood group conversion with α-N acetylgalactosaminidase and α-galactosidase.

PubMed

Gao, Hong-Wei; Li, Su-Bo; Bao, Guo-Qiang; Zhang, Xue; Li, Hui; Wang, Ying-Li; Tan, Ying-Xia; Ji, Shou-Ping; Gong, Feng

2014-01-01

It is well known that the buffer plays a key role in the enzymatic reaction involved in blood group conversion. In previous study, we showed that a glycine buffer is suitable for A to O or B to O blood group conversion. In this study, we investigated the use of 5% glucose and other buffers for A to O or B to O blood group conversion by α-N-acetylgalactosaminidase or α-galactosidase. We compared the binding ability of α-N-acetylgalactosaminidase/α-galactosidase with red blood cells (RBC) in different reaction buffers, such as normal saline, phosphate-buffered saline (PBS), a disodium hydrogen phosphate-based buffer (PCS), and 5% commercial glucose solution. The doses of enzymes necessary for the A/B to O conversion in different reaction buffers were determined and compared. The enzymes' ability to bind to RBC was evaluated by western blotting, and routine blood typing and fluorescence activated cell sorting was used to evaluate B/A to O conversion efficiency. The A to O conversion efficiency in glucose buffer was similar to that in glycine buffer with the same dose (>0.06 mg/mL pRBC). B to O conversion efficiency in glucose buffer was also similar to that in glycine buffer with the same dose (>0.005 mg/mL pRBC). Most enzymes could bind with RBC in glycine or glucose buffer, but few enzymes could bind with RBC in PBS, PCS, or normal saline. These results indicate that 5% glucose solution provides a suitable condition for enzymolysis, especially for enzymes combining with RBC. Meanwhile, the conversion efficiency of A/B to O was similar in glucose buffer and glycine buffer. Moreover, 5% glucose solution has been used for years in venous transfusion, it is safe for humans and its cost is lower. Our results do, therefore, suggest that 5% glucose solution could become a novel suitable buffer for A/B to O blood group conversion.

Photophysical investigations of squaraine and cyanine dyes and their interaction with bovine serum albumin

NASA Astrophysics Data System (ADS)

Saikiran, M.; Sato, D.; Pandey, S. S.; Kato, T.

2016-04-01

A model far-red sensitive symmetrical squaraine dye (SQ-3) and unsymmetrical near infra-red sensitive cyanine dye (UCD-1) bearing direct-COOH functionalized indole ring were synthesized, characterized and subjected to photophysical investigations including their interaction with bovine serum albumin (BSA) as a model protein in phosphate buffer solution (PBS). Both of the dyes exhibit strong interaction with BSA in phosphate buffer with high apparent binding constant. A judicious tuning of hydrophobic main backbone with reactive functionality for associative interaction with active site of BSA has been found to be necessary for BSA detection in PBS.

Pediatric oral solutions with propranolol hydrochloride for extemporaneous compounding: the formulation and stability study.

PubMed

Klovrzová, Sylva; Zahálka, Lukáš; Matysová, Ludmila; Horák, Petr; Sklubalová, Zdenka

2013-02-01

The aim of this study is to formulate an extemporaneous pediatric oral solution of propranolol hydrochloride (PRO) 2 mg/ml for the therapy of infantile haemangioma or hypertension in a target age group of 1 month to school children and to evaluate its stability. A citric acid solution and/or a citrate-phosphate buffer solution, respectively, were used as the vehicles to achieve pH value of about 3, optimal for the stability of PRO. In order to mask the bitter taste of PRO, simple syrup was used as the sweetener. All solutions were stored in tightly closed brown glass bottles at 5 ± 3 °C and/or 25 ± 3 °C, respectively. The validated HPLC method was used to evaluate the concentration of PRO and a preservative, sodium benzoate, at time intervals of 0-180 days. All preparations were stable at both storage temperatures with pH values in the range of 2.8-3.2. According to pharmacopoeial requirements, the efficacy of sodium benzoate 0.05 % w/v was proved (Ph.Eur., 5.1.3). The preparation formulated with the citrate-phosphate buffer, in our experience, had better palatability than that formulated with the citric acid solution. propranolol hydrochloride pediatric preparation extemporaneous preparation solution stability testing HPLC.

Comparative Toxicity of Preservatives on Immortalized Corneal and Conjunctival Epithelial Cells

PubMed Central

Ahdoot, Michael; Marcus, Edward; Asbell, Penny A.

2009-01-01

Abstract Purpose Nearly all eye drops contain preservatives to decrease contamination. Nonpreservatives such as disodium-ethylene diamine tetra-acetate (EDTA) and phosphate-buffered saline are also regularly added as buffering agents. These components can add to the toxicity of eye drops and cause ocular surface disease. To evaluate the potential toxicity of these common components and their comparative effects on the ocular surface, a tissue culture model utilizing immortalized corneal and conjunctival epithelial cells was utilized. Methods Immortalized human conjunctival and corneal epithelial cells were grown. At confluency, medium was replaced with 100 μL of varying concentrations of preservatives: benzalkonium chloride (BAK), methyl paraben (MP), sodium perborate (SP), chlorobutanol (Cbl), and stabilized thimerosal (Thi); varying concentrations of buffer: EDTA; media (viable control); and formalin (dead control). After 1 h, solutions were replaced with 150 μL of MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazonium bromide). After 4 h, solutions decanted, 100 μL of acid isopropanol added, and the optical density determined at 572 nm to evaluate cell viability. Results Conjunctival and corneal cell toxicity was seen with all preservatives. Depending upon concentration, BAK exhibited from 56% to 89% toxicity. In comparison, Cbl exhibited from 50% to 86%, MP from 30% to 76%, SP from 23% to 59%, and Thi from 70% to 95%. EDTA with minimal toxicity (from 6% to 59%) was indistinguishable from SP. Conclusions Generally, the order of decreasing toxicity at the most commonly used concentrations: Thi (0.0025%) > BAK (0.025%) > Cbl (0.25%) > MP (0.01%) > SP (0.0025%) ≈ EDTA (0.01%). Even at low concentration, these agents will cause some degree of ocular tissue damage. PMID:19284328

Antihistamine effect on synaptosomal uptake of serotonin, norepinephrine and dopamine

NASA Technical Reports Server (NTRS)

Brown, P. A.; Vernikos, J.

1980-01-01

A study on the effects of five H1 and H2 antihistamines on the synaptosomal uptake of serotonin (5HT), norepinephrine (NE), and dopamine (DA) is presented. Brain homogenates from female rats were incubated in Krebs-Ringer phosphate buffer solution in the presence of one of three radioactive neurotransmitters, and one of the five antihistamines. Low concentrations of pyrilamine competitively inhibited 5HT uptake, had little effect on NE uptake, and no effect on DA uptake. Promethazine, diphenhydramine, metiamide, and cimetidine had no effect on 5HT or DA uptake at the same concentration. Diphenhydramine had a small inhibitory effect on NE uptake. It is concluded that pyrilamine is a selective and potent competitive inhibitor of 5HT uptake at concentrations between .05 and .5 micromolars.

Quality control of benserazide-levodopa and carbidopa-levodopa tablets by capillary zone electrophoresis.

PubMed

Fanali, S; Pucci, V; Sabbioni, C; Raggi, M A

2000-07-01

In modern practice, the treatment of Parkinson's disease and syndrome is carried out using pharmaceutical formulations containing a combination of levodopa and a decarboxylation inhibitor (carbidopa or benserazide). Two pharmaceutical formulations were quantified by capillary zone electrophoresis using two procedures which differed only in the kind of background electrolyte used. One procedure used a 25 mM phosphate buffer, pH 2.5, while the second one used a 25 mM borate buffer, pH 8.5. The electrophoretic analysis was carried out using an uncoated fused- silica capillary, a separation voltage of 20 kV with currents typically less than 60 microA, and spectrophotometric detection at 205 nm. Calibration curves were performed for levodopa (concentration range 1-100 microg/mL), for carbidopa and benserazide (1-50 microg/mL), and the plots of the peak area versus concentration were found to be linear with a correlation coefficient better than 0.9990. Satisfactory results were obtained when commercial tablets were analyzed in terms of accuracy (98-102%), repeatability (0.6-2.0%), and intermediate precision (1.1-2.6%).

Influence of vehicle properties and excipients on hydrolytic and photochemical stability of curcumin in preparations containing Pluronics: studies of curcumin and curcuminoids XLVIII.

PubMed

Singh, R; Kristensen, S; Tønnesen, H H

2013-03-01

The influence of vehicle properties and excipients on the hydrolytic and photochemical stability of curcumin in Pluronic preparations, and the interactions between curcumin and Pluronics was investigated. Curcumin was found to be degraded by general acid-base catalyzed hydrolytic degradation in alkaline preparations. The degradation rate of curcumin was higher in carbonate buffer than in phosphate buffer (pH 8.8), while it was higher in phosphate buffer than in citrate buffer (pH 7.8). At pH 8.0-8.8 the degradation rate of curcumin increased compared to preparations with pH <8.0. The stabilizing effect of the Pluronics against hydrolytic degradation of curcumin was only detectable at pH 8.0-8.8, and it was highest for F127 and lowest for P85, in phosphate buffer pH 8.8. An increase in the ionic strength increased the stabilization against hydrolytic degradation of curcumin by all Pluronics. Addition of ethanol decreased the hydrolytic stability of curcumin in all Pluronics. Addition of PEG 400 decreased the hydrolytic stability in preparation with either P123 or F127 while the degradation in preparations with P85 remained the same as in P85 preparations without PEG 400. Vehicle properties and excipients did not to any large degree influence the spectroscopic properties or the photostability of curcumin in Pluronic preparations. Photochemical half life of curcumin was in the minutes range. Spectrophotometric data indicate that Pluronic aggregates most likely solubilize curcumin through hydrophobic interactions, although hydrogen-bonding may also be involved.

Improved purification process for cholera toxin and its application to the quantification of residual toxin in cholera vaccines.

PubMed

Jang, Hyun; Kim, Hyo Seung; Kim, Jeong Ah; Seo, Jin Ho; Carbis, Rodney

2009-01-01

A simplified method for the purification of cholera toxin was developed. The 569B strain of Vibrio cholerae, a recognized hyper-producer of cholera toxin, was propagated in a bioreactor under conditions that promote the production of the toxin. The toxin was separated from the bacterial cells using 0.2-microm crossflow microfiltration, the clarified toxin was passed through the membrane into the permeate, and the bacterial cells were retained in the retentate. The 0.2-microm permeate was then concentrated 3-fold and diafiltered against 10 mM phosphate buffer, pH 7.6, using 30-kDa crossflow ultrafiltration. The concentrated toxin was loaded onto a cation exchange column, the toxin was bound to the column, and most of the impurities were passed unimpeded through the column. The toxin was eluted with a salt gradient of phosphate buffer, pH7.0, containing 1.0M NaCl. The peak containing the toxin was assayed for cholera toxin and protein and the purity was determined to be 92%. The toxin peak had a low endotoxin level of 3.1 EU/microg of toxin. The purified toxin was used to prepare antiserum against whole toxin, which was used in a G(M1) ganglioside-binding ELISA to determine residual levels of toxin in an oral inactivated whole-cell cholera vaccine. The G(M1) ganglioside-binding ELISA was shown to be very sensitive and capable of detecting as little as 1 ng/ml of cholera toxin.

Study on Biopharmaceutics Classification and Oral Bioavailability of a Novel Multikinase Inhibitor NCE for Cancer Therapy

PubMed Central

Yang, Yang; Fan, Chun-Mei; He, Xuan; Ren, Ke; Zhang, Jin-Kun; He, Ying-Ju; Yu, Luo-Ting; Zhao, Ying-Lan; Gong, Chang-Yang; Zheng, Yu; Song, Xiang-Rong; Zeng, Jun

2014-01-01

Specific biopharmaceutics classification investigation and study on phamacokinetic profile of a novel drug candidate (2-methylcarbamoyl-4-{4-[3- (trifluoromethyl) benzamido] phenoxy} pyridinium 4-methylbenzenesulfonate monohydrate, NCE) were carried out. Equilibrium solubility and intrinsic dissolution rate (IDR) of NCE were estimated in different phosphate buffers. Effective intestinal permeability (Peff) of NCE was determined using single-pass intestinal perfusion technique in rat duodenum, jejunum and ileum at three concentrations. Theophylline (high permeability) and ranitidine (low permeability) were also applied to access the permeability of NCE as reference compounds. The bioavailability after intragastrical and intravenous administration was measured in beagle dogs. The solubility of NCE in tested phosphate buffers was quite low with the maximum solubility of 81.73 μg/mL at pH 1.0. The intrinsic dissolution ratio of NCE was 1 × 10−4 mg·min−1·cm−2. The Peff value of NCE in all intestinal segments was more proximate to the high-permeability reference theophylline. Therefore, NCE was classified as class II drug according to Biopharmaceutics Classification System due to its low solubility and high intestinal permeability. In addition, concentration-dependent permeability was not observed in all the segments, indicating that there might be passive transportation for NCE. The absolute oral bioavailability of NCE in beagle dogs was 26.75%. Therefore, dissolution promotion will be crucial for oral formulation development and intravenous administration route will also be suggested for further NCE formulation development. All the data would provide a reference for biopharmaceutics classification research of other novel drug candidates. PMID:24776763

Study on biopharmaceutics classification and oral bioavailability of a novel multikinase inhibitor NCE for cancer therapy.

PubMed

Yang, Yang; Fan, Chun-Mei; He, Xuan; Ren, Ke; Zhang, Jin-Kun; He, Ying-Ju; Yu, Luo-Ting; Zhao, Ying-Lan; Gong, Chang-Yang; Zheng, Yu; Song, Xiang-Rong; Zeng, Jun

2014-04-25

Specific biopharmaceutics classification investigation and study on phamacokinetic profile of a novel drug candidate (2-methylcarbamoyl-4-{4-[3- (trifluoromethyl) benzamido] phenoxy} pyridinium 4-methylbenzenesulfonate monohydrate, NCE) were carried out. Equilibrium solubility and intrinsic dissolution rate (IDR) of NCE were estimated in different phosphate buffers. Effective intestinal permeability (P(eff)) of NCE was determined using single-pass intestinal perfusion technique in rat duodenum, jejunum and ileum at three concentrations. Theophylline (high permeability) and ranitidine (low permeability) were also applied to access the permeability of NCE as reference compounds. The bioavailability after intragastrical and intravenous administration was measured in beagle dogs. The solubility of NCE in tested phosphate buffers was quite low with the maximum solubility of 81.73 μg/mL at pH 1.0. The intrinsic dissolution ratio of NCE was 1 × 10⁻⁴ mg·min⁻¹·cm⁻². The P(eff) value of NCE in all intestinal segments was more proximate to the high-permeability reference theophylline. Therefore, NCE was classified as class II drug according to Biopharmaceutics Classification System due to its low solubility and high intestinal permeability. In addition, concentration-dependent permeability was not observed in all the segments, indicating that there might be passive transportation for NCE. The absolute oral bioavailability of NCE in beagle dogs was 26.75%. Therefore, dissolution promotion will be crucial for oral formulation development and intravenous administration route will also be suggested for further NCE formulation development. All the data would provide a reference for biopharmaceutics classification research of other novel drug candidates.

Evaluation of The Erosive Potential of Soft Drinks

PubMed Central

de Carvalho Sales-Peres, Sílvia Helena; Magalhães, Ana Carolina; de Andrade Moreira Machado, Maria Aparecida; Buzalaf, Marília Afonso Rabelo

2007-01-01

Objectives This in vitro study evaluated the capability of different soft drinks (Coca-Cola®-C, Coca-Cola Light®-CL, Guaraná®-G, Pepsi Twist®-P and Sprite Light®-SL) to erode dental enamel, relating the percentage of superficial microhardness change (%SMHC) to concentrations of fluoride and phosphate, buffering capacity and pH of these drinks. Methods The soft drinks were evaluated in respect to concentration of phosphate and fluoride spectrophotometrically using Fiske, Subarrow method and by specific electrode (Orion 9609), respectively. The pH and the buffering capacity were determined by glass electrode and by estimating of the volume of NaOH necessary to change the pH of the drink in one unit, respectively. One hundred specimens of bovine enamel were randomly assigned to 5 groups of 20 each. They were exposed to 4 cycles of demineralisation in the beverage and remineralisation in artificial saliva. The softening of enamel was evaluated by %SMHC. Results The mean %SMHC was: C=77.27%, CL= 72.45%, SL=78.43%, G=66.65% and P=67.95%. Comparing the %SMHC promoted by 5 soft drinks, SL = C > CL > P = G (P<.05). There was not significant correlation between %SMHC and the other variables tested for the five drinks (P>.05). Conclusions The five soft drinks caused surface softening of enamel (erosion). In respect to the chemical variables tested, despite not statistically significant, the pH seems to have more influence on the erosive potential of these drinks. (Eur J Dent 2007;1:10–13) PMID:19212490

An improved glycerol biosensor with an Au-FeS-NAD-glycerol-dehydrogenase anode.

PubMed

Mahadevan, Aishwarya; Fernando, Sandun

2017-06-15

An improved glycerol biosensor was developed via direct attachment of NAD + -glycerol dehydrogenase coenzyme-apoenzyme complex onto supporting gold electrodes, using novel inorganic iron (II) sulfide (FeS)-based single molecular wires. Sensing performance factors, i.e., sensitivity, a detection limit and response time of the FeS and conventional pyrroloquinoline quinone (PQQ)-based biosensor were evaluated by dynamic constant potential amperometry at 1.3V under non-buffered conditions. For glycerol concentrations ranging from 1 to 25mM, a 77% increase in sensitivity and a 53% decrease in detection limit were observed for the FeS-based biosensor when compared to the conventional PQQ-based counterpart. The electrochemical behavior of the FeS-based glycerol biosensor was analyzed at different concentrations of glycerol, accompanied by an investigation into the effects of applied potential and scan rate on the current response. Effects of enzyme stimulants ((NH 4 ) 2 SO 4 and MnCl 2 ·4H 2 O) concentrations and buffers/pH (potassium phosphate buffer pH 6-8, Tris buffer pH 8-10) on the current responses generated by the FeS-based glycerol biosensor were also studied. The optimal detection conditions were 0.03M (NH 4 ) 2 SO 4 and 0.3µm MnCl 2 ·4H 2 O in non-buffered aqueous electrolyte under stirring whereas under non-stirring, Tris buffer at pH 10 with 0.03M (NH 4 ) 2 SO 4 and 30µm MnCl 2 ·4H 2 O were found to be optimal detection conditions. Interference by glucose, fructose, ethanol, and acetic acid in glycerol detection was studied. The observations indicated a promising enhancement in glycerol detection using the novel FeS-based glycerol sensing electrode compared to the conventional PQQ-based one. These findings support the premise that FeS-based bioanodes are capable of biosensing glycerol successfully and may be applicable for other enzymatic biosensors. Copyright © 2016 Elsevier B.V. All rights reserved.

Controlled release of acidic drugs in compendial and physiological hydrogen carbonate buffer from polymer blend-coated oral solid dosage forms.

PubMed

Wulff, R; Rappen, G-M; Koziolek, M; Garbacz, G; Leopold, C S

2015-09-18

The objective of this study was to investigate the suitability of "Eudragit® RL/Eudragit® L55" (RL/L55) blend coatings for a pH-independent release of acidic drugs. A coating for ketoprofen and naproxen mini tablets was developed showing constant drug release rate under pharmacopeial two-stage test conditions for at least 300 min. To simulate drug release from the mini tablets coated with RL/L55 blends in the gastrointestinal (GI) tract, drug release profiles in Hanks buffer pH 6.8 were recorded and compared with drug release profiles in compendial media. RL/L55 blend coatings showed increased drug permeability in Hanks buffer pH 6.8 compared to phosphate buffer pH 6.8 due to its higher ion concentration. However, drug release rates of acidic drugs were lower in Hanks buffer pH 6.8 because of the lower buffer capacity resulting in reduced drug solubility. Further dissolution tests were performed in Hanks buffer using pH sequences simulating the physiological pH conditions in the GI tract. Drug release from mini tablets coated with an RL/L55 blend (8:1) was insensitive to pH changes of the medium within the pH range of 5.8-7.5. It was concluded that coatings of RL/L55 blends show a high potential for application in coated oral drug delivery systems with a special focus on pH-independent release of acidic drugs. Copyright © 2015 Elsevier B.V. All rights reserved.

Kinetic and Mechanistic Study of the pH-Dependent Activation (Epoxidation) of Prodrug Treosulfan Including the Reaction Inhibition in a Borate Buffer.

PubMed

Romański, Michał; Ratajczak, Whitney; Główka, Franciszek

2017-07-01

A prodrug treosulfan (T) undergoes a pH-dependent activation to epoxide derivatives. The process seems to involve an intramolecular Williamson reaction (IWR) but clear kinetic evidence is lacking. Moreover, a cis-diol system present in the T structure is expected to promote complexation with boric acid. As a result, the prodrug epoxidation would be inhibited; however, this phenomenon has not been investigated. In this article, the effect of pH on the kinetics of T conversion to its monoepoxide was studied from a mechanistic point of view. Also, the influence of boric acid on the reaction kinetics was examined. The rate constants observed for the activation of T (k obs ) in acetate, phosphate, and carbonate buffers satisfied the equation logk obs  = -7.48 + 0.96 pH. The reaction was inhibited in the excess of boric acid over T, and the k obs decreased with increasing borate buffer concentration. The experimental results were consistent with the inhibition model that included the formation of a tetrahedral, anionic T-boric acid monoester. To conclude, in nonborate buffers, the T activation to (2S,3S)-1,2-epoxybutane-3,4-diol 4-methanesulfonate follows IWR mechanism. A borate buffer changes the reaction kinetics and complicates kinetic analysis. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Comparing the acidities of aqueous, frozen, and freeze-dried phosphate buffers: Is there a "pH memory" effect?

PubMed

Vetráková, Ľubica; Vykoukal, Vít; Heger, Dominik

2017-09-15

The concept of "pH memory" has been established in the literature for the correlation between the pH of a pre-lyophilization solution and the ionization state of freeze-dried powder (lyophile). In this paper, the concept of "pH memory" is explored for the system of an aqueous solution, a frozen solution, and a lyophile. Sodium and potassium phosphate buffers in the pH range of 5-9 were frozen and lyophilized with sulfonephthalein indicators as acidity probes, and their Hammett acidity functions were compared to the initial pH of the aqueous solution. The results show that the acidities of the lyophiles are somewhat changed compared to the initial pHs, but the acidities in the frozen state differ more substantially. The Hammett acidity functions of the frozen buffers were found to be markedly dissimilar from the initial pH, especially in the sodium phosphate frozen at 233K, where an increase in the initial pH led to a decrease in the Hammett acidity function of the frozen state at a certain pH range. The large acidification observed after freezing the sodium phosphate buffer was not detected in the lyophiles after the sample had been dried; the phenomenon is explained considering the formed crystals analyzed by X-ray powder diffraction. The results suggest that monitoring the final acidity of a lyophile is not sufficient to predict all the acidity changes throughout the whole lyophilization process. The importance of well-controlled freezing and lyophilization conditions follows from the results of the research. Copyright © 2017 Elsevier B.V. All rights reserved.

Passive transport and binding of lead by human red blood cells.

PubMed

Simons, T J

1986-09-01

The uptake of Pb into human red blood cells has been studied using Pb buffers. Passive Pb movements can be studied conveniently when the cells are depleted of adenosine 5'-triphosphate (ATP), to eliminate active transport, and of inorganic phosphate, to prevent precipitation of lead phosphate. Pb can cross the membrane passively in either direction. Influx and efflux show similar properties. Passive Pb transport is strongly stimulated by HCO3-, and is reduced by replacing Cl- with ClO4-. It is inhibited by low concentrations of 4-acetamido-4'-isothiocyanostilbene-2,2'-disulphonic acid (SITS) and 4,4'-diisothiocyanostilbene-2.2'-disulphonic acid (DIDS), characteristic inhibitors of anion transport. Pb uptake is unaffected by varying the external concentrations of Na+, K+ and Ca2+. When Pb enters the cell, it binds mainly to haemoglobin. The ratio of bound Pb:free Pb2+ in the cytosol is estimated to be 6000:1. Pb binding to haemoglobin is unaffected by oxygenation. Binding to albumin is quantitatively similar to binding to haemoglobin. The implications of these results for the transport and binding of Pb in the blood are discussed.

Corrosion of dental amalgam and mercury vapor emission in vitro.

PubMed

Moberg, L E

1988-10-01

Amalgam specimens were immersed for 30 days in 1) water, 2) 0.9% NaCl in water, 3) 0.9% NaCl and 10 mM phosphate buffer in water, and 4) 0.9% NaCl, 7.7 mM phosphate, and 6.1 mM citric acid in water. The solutions were stored in stoppered glass tubes. Hg-drops were immersed in solutions 1, 2, and 3. The concentration of mercury vapor in the air above the solutions was measured once a day. After 30 days the amounts of Cu, Zn, Hg, and Ag in the solutions were analyzed by atomic absorption spectrophotometry. The results showed that 0.9% NaCl alone or in combination with the additives increased the amounts of elements released into the solutions. The concentration of Hg0 in the glass tubes increased with the amount of Hg in the solutions, with the exception of solution No. 3, from which significantly less Hg0 evaporated. The results indicate that the composition of the saliva, oral hygiene and dietary factors may be determinants of Hg0 emission from amalgams in the oral cavity.

Fibril growth kinetics link buffer conditions and topology of 3D collagen I networks.

PubMed

Kalbitzer, Liv; Pompe, Tilo

2018-02-01

Three-dimensional fibrillar networks reconstituted from collagen I are widely used as biomimetic scaffolds for in vitro and in vivo cell studies. Various physicochemical parameters of buffer conditions for in vitro fibril formation are well known, including pH-value, ion concentrations and temperature. However, there is a lack of a detailed understanding of reconstituting well-defined 3D network topologies, which is required to mimic specific properties of the native extracellular matrix. We screened a wide range of relevant physicochemical buffer conditions and characterized the topology of the reconstituted 3D networks in terms of mean pore size and fibril diameter. A congruent analysis of fibril formation kinetics by turbidimetry revealed the adjustment of the lateral growth phase of fibrils by buffer conditions to be key in the determination of pore size and fibril diameter of the networks. Although the kinetics of nucleation and linear growth phase were affected by buffer conditions as well, network topology was independent of those two growth phases. Overall, the results of our study provide necessary insights into how to engineer 3D collagen matrices with an independent control over topology parameters, in order to mimic in vivo tissues in in vitro experiments and tissue engineering applications. The study reports a comprehensive analysis of physicochemical conditions of buffer solutions to reconstitute defined 3D collagen I matrices. By a combined analysis of network topology, i.e., pore size and fibril diameter, and the kinetics of fibril formation we can reveal the dependence of 3D network topology on buffer conditions, such as pH-value, phosphate concentration and sodium chloride content. With those results we are now able to provide engineering strategies to independently tune the topology parameters of widely used 3D collagen scaffolds based on the buffer conditions. By that, we enable the straightforward mimicking of extracellular matrices of in vivo tissues for in vitro cell culture experiments and tissue engineering applications. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Voltammetric analysis of N-containing drugs using the hanging galinstan drop electrode (HGDE).

PubMed

Channaa, H; Surmann, P

2009-03-01

The electrochemical behaviour of several N-containing voltammetric active drugs such as 1,4-benzodiazepines (chlordiazepoxide, nitrazepam and diazepam) as well as one nitro-compound (nitrofurantoin) and one azo-compound (phenazopyridine) is described using a new kind of liquid electrode, the hanging galinstan drop electrode. Concentrations of 10(-5) - 10(-8) mol L(-1) are generally measurable. Differential pulse and adsorptive stripping voltammograms are recorded in different supporting electrolytes, like 0.1 M KNO3, acetate buffer solution pH = 4.6 and phosphate buffer solution pH = 7.0. The effects of varying the starting potentials, U(start) for DPV and accumulation times, t(acc) for AdSV are considered. Briefly, it is shown that the novel galinstan electrode is suitable for reducing several functional groups in organic substances, here presented for N-oxide-, azomethine-, nitro- and azo-groups.

Square-wave adsorptive stripping voltammetric determination of nanomolar levels of bezafibrate using a glassy carbon electrode modified with multi-walled carbon nanotubes within a dihexadecyl hydrogen phosphate film.

PubMed

Ardila, Jorge Armando; Oliveira, Geiser Gabriel; Medeiros, Roberta Antigo; Fatibello-Filho, Orlando

2014-04-07

A highly sensitive method for bezafibrate determination using a glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes within a dihexadecyl hydrogen phosphate film based on square-wave adsorptive stripping voltammetry (SWAdSV) is proposed. The electrochemical behaviour of bezafibrate has been studied by cyclic voltammetry, showing an irreversible anodic peak at a potential of 1.09 V in 0.1 mol L(-1) phosphate buffer solution (pH 2.0). A study of the scan rate showed that the oxidation of bezafibrate is an adsorptive-controlled process, involving the transfer of two electrons and two protons per molecule. The analytical curve was linear over a bezafibrate concentration range from 50 to 910 nmol L(-1), with a detection limit of 16 nmol L(-1). This analytical method was successfully applied for benzafibrate determination in pharmaceutical formulations, with results showing good agreement with those obtained using a comparative spectrophotometric method, and has the potential for field application.

Optimizing Fungal DNA Extraction Methods from Aerosol Filters

NASA Astrophysics Data System (ADS)

Jimenez, G.; Mescioglu, E.; Paytan, A.

2016-12-01

Fungi and fungal spores can be picked up from terrestrial ecosystems, transported long distances, and deposited into marine ecosystems. It is important to study dust-borne fungal communities, because they can stay viable and effect the ambient microbial populations, which are key players in biogeochemical cycles. One of the challenges of studying dust-borne fungal populations is that aerosol samples contain low biomass, making extracting good quality DNA very difficult. The aim of this project was to increase DNA yield by optimizing DNA extraction methods. We tested aerosol samples collected from Haifa, Israel (polycarbonate filter), Monterey Bay, CA (quartz filter) and Bermuda (quartz filter). Using the Qiagen DNeasy Plant Kit, we tested the effect of altering bead beating times and incubation times, adding three freeze and thaw steps, initially washing the filters with buffers for various lengths of time before using the kit, and adding a step with 30 minutes of sonication in 65C water. Adding three freeze/thaw steps, adding a sonication step, washing with a phosphate buffered saline overnight, and increasing incubation time to two hours, in that order, resulted in the highest increase in DNA for samples from Israel (polycarbonate). DNA yield of samples from Monterey (quart filter) increased about 5 times when washing with buffers overnight (phosphate buffered saline and potassium phophate buffer), adding a sonication step, and adding three freeze and thaw steps. Samples collected in Bermuda (quartz filter) had the highest increase in DNA yield from increasing incubation to 2 hours, increasing bead beating time to 6 minutes, and washing with buffers overnight (phosphate buffered saline and potassium phophate buffer). Our results show that DNA yield can be increased by altering various steps of the Qiagen DNeasy Plant Kit protocol, but different types of filters collected at different sites respond differently to alterations. These results can be used as preliminary results to continue developing fungi DNA extraction methods. Developing these methods will be important as dust storms are predicted to increase due to increased draughts and anthropogenic activity, and the fungal communities of these dust-storms are currently relatively understudied.

Vehicle influence on permeation through intact and compromised skin.

PubMed

Gujjar, Meera; Banga, Ajay K

2014-09-10

The purpose of this study was to compare the transdermal permeation of a model compound, diclofenac diethylamine, from a hydrophilic and lipophilic vehicle across in vitro models simulating compromised skin. Mineral oil served as a lipophilic vehicle while 10mM phosphate buffered saline served as a hydrophilic vehicle. Compromised skin was simulated by tape stripping, delipidization, or microneedle application and compared with intact skin as a control. Transepidermal water loss was measured to assess barrier function. Skin compromised with tape stripping and delipidization significantly (p<0.05) increased permeation of diclofenac diethylamine compared to intact and microneedle treated skin with phosphate buffered saline vehicle. A similar trend in permeation was observed with mineral oil as the vehicle. For both vehicles, permeation across skin increased in the same order and correlated with degree of barrier impairment as indicated by transepidermal water loss values: intact

Physical and chemical properties of pyropheophorbide-a methyl ester in ethanol, phosphate buffer and aqueous dispersion of small unilamellar dimyristoyl-L-alpha-phosphatidylcholine vesicles.

PubMed

Delanaye, Lisiane; Bahri, Mohamed Ali; Tfibel, Francis; Fontaine-Aupart, Marie-Pierre; Mouithys-Mickalad, Ange; Heine, Bélinda; Piette, Jacques; Hoebeke, Maryse

2006-03-01

The aggregation process of pyropheophorbide-a methyl ester (PPME), a second-generation photosensitizer, was investigated in various solvents. Absorption and fluorescence spectra showed that the photosensitizer was under a monomeric form in ethanol as well as in dimyristoyl-L-alpha-phosphatidylcholine liposomes while it was strongly aggregated in phosphate buffer. A quantitative determination of reactive oxygen species production by PPME in these solvents has been undertaken by electron spin resonance associated with spin trapping technique and absorption spectroscopy. In phosphate buffer, both electron spin resonance and absorption measurements led to the conclusion that singlet oxygen production was not detectable while hydroxyl radical production was very weak. In liposomes and ethanol, singlet oxygen and hydroxyl radical production increased highly; the singlet oxygen quantum yield was determined to be 0.2 in ethanol and 0.13 in liposomes. The hydroxyl radical production origin was also investigated. Singlet oxygen was formed from PPME triplet state deactivation in the presence of oxygen. Indeed, the triplet state formation quantum yield of PPME was found to be about 0.23 in ethanol, 0.15 in liposomes (too small to be measured in PBS).

Biochemical characteristics of glucose-6-phosphate dehydrogenase variants among the Malays of Singapore with report of a new non-deficient (GdSingapore) and three deficient variants.

PubMed

Saha, N; Hong, S H; Wong, H A; Jeyaseelan, K; Tay, J S

1991-12-01

Biochemical characteristics of one non-deficient fast G6PD variant (GdSingapore) and six different deficient variants (three new, two Mahidol, one each of Indonesian and Mediterranean) were studied among the Malays of Singapore. The GdSingapore variant had normal enzyme activity (82%) and fast electrophoretic mobilities (140% in TEB buffer, 160% in phosphate and 140% in Tris-HCl buffer systems respectively). This variant is further characterized by normal Km for G6P; utilization of analogues (Gal6P, 2dG6P; dAmNADP), heat stability and pH optimum. The other six deficient G6PD variants had normal electrophoretic mobility in TEB buffer with enzyme activities ranging from 1 to 12% of GdB+. The biochemical characteristics identity them to be 2 Mahidol, 1 Indonesian and 1 Mediterranean variants and three new deficient variants.

Analysis of three variables in sampling solutions used to assay bacteria of hands: type of solution, use of antiseptic neutralizers, and solution temperature.

PubMed Central

Larson, E L; Strom, M S; Evans, C A

1980-01-01

Tests were performed using the sterile bag technique to determine the effects of type of sampling solution, use of antiseptic neutralizers, and solution temperature on the detection and quantitation of bacteria on hands. Using paired hand cultures, three sampling solutions were compared: quarter-strength Ringer solution, a phosphate buffer containing Triton X-100, and the same buffer containing antiseptic neutralizers. The phosphate buffer containing Triton X-100 was significantly better than quarter-strength Ringer solution in mean bacterial yield; the neutralizer-containing sampling solution was slightly better than Triton X-100-containing solution, although differences were not significant at the P = 0.05 level. Temperature (6 or 23 degrees C) of the sampling solution showed no consistent effect on bacterial yield from hands tested with the fluid containing neutralizers. PMID:7012171

The effect of the type of HA on the degradation of PLGA/HA composites.

PubMed

Naik, Ashutosh; Shepherd, David V; Shepherd, Jennifer H; Best, Serena M; Cameron, Ruth E

2017-01-01

The aim of this study is to explore the importance of the potentially competing effects of buffering effects of the calcium phosphate filler and particle-mediated water sorption on the degradation products of poly(d,l lactide-co-glycolide (50:50))(PLGA)/hydroxyapatite(HA) composites. Further the influence of type of HA on the mechanical properties of the composites was investigated. Phase pure HA was synthesised via a reaction between aqueous solutions of calcium hydroxide and orthophosphoric acid. The powder produced was either used as produced (uncalcined) or calcined in air or calcined in a humidified argon atmosphere. An in-vitro degradation study was carried out in phosphate buffered saline (PBS). The results obtained indicated that the degradation rate of the composite might be better understood if both the buffering effects and the rate of water sorption by the composites are considered. Copyright © 2016 Elsevier B.V. All rights reserved.

Identification and Quantification of the Water Soluble Components of JP-4 and a Determination of Their Biological Effects upon Selected Freshwater Organisms.

DTIC Science & Technology

1982-12-23

assay Blanks and reaction mixtures were the same as in aminopy- rine demethylase assay except 0.5 ml of 153.64 mM aniline in 0.1 M phosphate buffer...replaced the 0.5 ml aminopyrine. (Final concentration of aniline in the reaction mixture was 25.61 mM). At the end of the 20 minute incubation period, the...with PB, 3MC, or PCB. Aniline hydroxylase activity did not change folowing PB treatment , however it did in- crease when 3MC or PCB were used as the

High sensitivity and high Q-factor nanoslotted parallel quadrabeam photonic crystal cavity for real-time and label-free sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Daquan; State Key Laboratory of Information Photonics and Optical Communications, School of Information and Communication Engineering, Beijing University of Posts and Telecommunications, Beijing 100876; School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138

We experimentally demonstrate a label-free sensor based on nanoslotted parallel quadrabeam photonic crystal cavity (NPQC). The NPQC possesses both high sensitivity and high Q-factor. We achieved sensitivity (S) of 451 nm/refractive index unit and Q-factor >7000 in water at telecom wavelength range, featuring a sensor figure of merit >2000, an order of magnitude improvement over the previous photonic crystal sensors. In addition, we measured the streptavidin-biotin binding affinity and detected 10 ag/mL concentrated streptavidin in the phosphate buffered saline solution.

Zinc oxide nano-rods based glucose biosensor devices fabrication

NASA Astrophysics Data System (ADS)

Wahab, H. A.; Salama, A. A.; El Saeid, A. A.; Willander, M.; Nur, O.; Battisha, I. K.

2018-06-01

ZnO is distinguished multifunctional material that has wide applications in biochemical sensor devices. For extracellular measurements, Zinc oxide nano-rods will be deposited on conducting plastic substrate with annealing temperature 150 °C (ZNRP150) and silver wire with annealing temperature 250 °C (ZNRW250), for the extracellular glucose concentration determination with functionalized ZNR-coated biosensors. It was performed in phosphate buffer saline (PBS) over the range from 1 μM to 10 mM and on human blood plasma. The prepared samples crystal structure and surface morphologies were characterized by XRD and field emission scanning electron microscope FESEM respectively.

Osmotic agents and buffers in peritoneal dialysis solution: monocyte cytokine release and in vitro cytotoxicity.

PubMed

Plum, J; Schoenicke, G; Grabensee, B

1997-09-01

Peritonitis remains a major problem in peritoneal dialysis. The incidence of peritonitis may be reduced by the use of more "biocompatible" peritoneal dialysis solutions that do not impair local host defense mechanisms, such as occurs with conventional lactate-buffered glucose solutions. In the present study, we investigated the use of bicarbonate and lactate as buffer systems and glucose, amino acids, and glucose polymer as osmotic agents on specific cellular functions of isolated fresh blood monocytes in vitro. The bicarbonate-buffered solutions had a physiologic pH (7.0 to 7.6). Lactate-buffered solutions were tested with a pH between 5.5 and 7.3. RPMI 1640 (Roswell Park Memorial Institute, supplied by Biochrom, Berlin, Germany) and phosphate-buffered saline were used as control mediums. The test solutions were incubated with 200,000 monocytes/mL for 45 minutes followed by a 1:1 mix with RPMI 1640 (with supplements) during a 24- or 4-hour tetrazolium bromide test (MTT test) recovery period. Constitutive and lipopolysaccharide (LPS)-stimulated release of interleukin-1beta (IL-1beta) and IL-6 in the supernatants as parameters of cellular host defense and lactate dehydrogenase concentrations and MTT-formazan production as parameters for cell cytotoxicity were measured. Significantly higher IL-6 and IL-1beta release was found in the bicarbonate-buffered solutions, both under basal conditions and after LPS stimulation, compared with the lactate-buffered solutions (LPS stimulation: 1% amino acids/34 mmol/L bicarbonate, IL-1beta: 1,166 +/- 192 pg/mL; 1.5% glucose/34 mmol/L bicarbonate, IL-1beta: 752 +/- 107 pg/mL; 1.5% glucose/35 mmol/L lactate/pH 5.5, IL-1beta: 174 +/- 51 pg/mL). Some of these differences could even be detected in spent dialysate after a 6-hour dwell in continuous ambulatory peritoneal dialysis patients (n = 10). A lower degree of cellular cytotoxicity (lactate dehydrogenase activity) and better-preserved metabolic activity (MTT test) also were found for the bicarbonate-buffered solutions. Amino acids (1%) proved to be comparable to glucose (1.5%) as an osmotic agent at a neutral pH with regard to LPS-stimulated cytokine release and cytotoxicity. The incubation with a glucose polymer solution (7.5% glucose polymer in phosphate-buffered saline, pH 7.3) resulted in a significantly lowered cytokine release (LPS stimulation: IL-1beta, 69 +/- 19 pg/mL) compared with the other solutions with neutral pH (P < 0.01). These results suggest that bicarbonate as a buffer provided better biocompatibility with regard to mononuclear cytokine release and viability compared with lactate. Amino acids and glucose were equivalent to these parameters at a physiologic pH. The glucose polymer solution, however, was associated with a marked depression of cytokine release.

The Role of Newly Discovered Exotoxin (S Toxin) in Pseudomonas aeruginosa Infections

DTIC Science & Technology

1979-08-01

sodium or potassium phosphate 6.0-8.0 N-2-hydroxyethylpiperazine-N’-2-ethanesulfonic acid (HEPES) 6.5-8.5 tris 7.0-9.5 sodium borate 7.5-9.5 sodium...was found to be variable with respect to whether sodium or potassium phosphate buffer was used. With sodium phosphate, virtually all the enzyme...activity bound was eluted between 20-100.2M phosphate at pH 6.8. With the potassium salt, elution occurs at 400-?00mM KP04. Since very little protein was

Human urine as test material in 1H NMR-based metabonomics: recommendations for sample preparation and storage.

PubMed

Lauridsen, Michael; Hansen, Steen H; Jaroszewski, Jerzy W; Cornett, Claus

2007-02-01

Metabonomic approaches are believed to have the capability of revolutionizing diagnosis of diseases and assessment of patient conditions after medical interventions. In order to ensure comparability of metabonomic 1H NMR data from different studies, we suggest validated sample preparation guidelines for human urine based on a stability study that evaluates effects of storage time and temperature, freeze-drying, and the presence of preservatives. The results indicated that human urine samples should be stored at or below -25 degrees C, as no changes in the 1H NMR fingerprints have been observed during storage at this temperature for 26 weeks. Formation of acetate, presumably due to microbial contamination, was occasionally observed in samples stored at 4 degrees C without addition of a preservative. Addition of a preserving agent is not mandatory provided that the samples are stored at -25 degrees C. Thus, no differences were observed between 1H NMR spectra of nonpreserved urines and urines with added sodium azide and stored at -25 degrees C, whereas the presence of sodium fluoride caused a shift of especially citrate resonances. Freeze-drying of urine and reconstitution in D2O at pH 7.4 resulted in the disappearance of the creatinine CH2 signal at delta 4.06 due to deuteration. A study evaluating the effects of phosphate buffer concentration on signal variability and assessment of the probability of citrate or creatinine resonances crossing bucket border (a boundary between adjacent integrated regions) led to the conclusion that a minimum buffer concentration of 0.3 M is adequate for normal urines used in this study. However, final buffer concentration of 1 M will be required for very concentrated urines.

Glucose buffer is suitable for blood group conversion with α-N acetylgalactosaminidase and α-galactosidase

PubMed Central

Gao, Hong-Wei; Li, Su-Bo; Bao, Guo-Qiang; Zhang, Xue; Li, Hui; Wang, Ying-Li; Tan, Ying-Xia; Ji, Shou-Ping; Gong, Feng

2014-01-01

Background It is well known that the buffer plays a key role in the enzymatic reaction involved in blood group conversion. In previous study, we showed that a glycine buffer is suitable for A to O or B to O blood group conversion. In this study, we investigated the use of 5% glucose and other buffers for A to O or B to O blood group conversion by α-N-acetylgalactosaminidase or α-galactosidase. Materials and methods We compared the binding ability of α-N-acetylgalactosaminidase/α-galactosidase with red blood cells (RBC) in different reaction buffers, such as normal saline, phosphate-buffered saline (PBS), a disodium hydrogen phosphate-based buffer (PCS), and 5% commercial glucose solution. The doses of enzymes necessary for the A/B to O conversion in different reaction buffers were determined and compared. The enzymes’ ability to bind to RBC was evaluated by western blotting, and routine blood typing and fluorescence activated cell sorting was used to evaluate B/A to O conversion efficiency. Results The A to O conversion efficiency in glucose buffer was similar to that in glycine buffer with the same dose (>0.06 mg/mL pRBC). B to O conversion efficiency in glucose buffer was also similar to that in glycine buffer with the same dose (>0.005 mg/mL pRBC). Most enzymes could bind with RBC in glycine or glucose buffer, but few enzymes could bind with RBC in PBS, PCS, or normal saline. Conclusion These results indicate that 5% glucose solution provides a suitable condition for enzymolysis, especially for enzymes combining with RBC. Meanwhile, the conversion efficiency of A/B to O was similar in glucose buffer and glycine buffer. Moreover, 5% glucose solution has been used for years in venous transfusion, it is safe for humans and its cost is lower. Our results do, therefore, suggest that 5% glucose solution could become a novel suitable buffer for A/B to O blood group conversion. PMID:24333060

On-line pH modification of carbonate eluents using an electrolytic potassium hydroxide generator for ion chromatography.

PubMed

Novic, Milko; Liu, Yan; Avdalovic, Nebojsa; Pihlar, Boris

2002-05-31

Classical gradient elution, based on the application of a gradient pump used for mixing two or more prepared eluent components in pre-determined concentrations, was replaced by a chromatography system equipped with an isocratic pump and an electrolytic KOH generator. The isocratic pump delivered a constant concentration eluent composed of pure hydrogencarbonate solution. Carbonate ions, the main component of carbonate/hydrogencarbonate-based eluents, were formed by titration of hydrogencarbonate with KOH formed on-line in the electrolytic KOH generator. By changing the concentration of electrolytically-generated KOH, the eluent composition could be changed from pure hydrogencarbonate to a carbonate/hydrogencarbonate buffer, and finally to a carbonate/hydroxide-based eluent. The described system was tested to achieve pH-based changes of retention behavior of phosphate under constant inflow eluent composition conditions.

A comparison of recovery of virus from wastewaters by beef extract-Celite, ferric chloride, and filter concentration procedures.

PubMed

Dahling, D R; Wright, B A

1988-12-01

An improved concentration method using sample volumes as large as 1500 ml has been developed to monitor for viruses in wastewaters. Non-precipitating dry beef extract powder is added to wastewater samples to give a 3% concentration and mixed until dissolved. This is followed by the addition of Celite as a virus adsorbent. By manipulating pH, viruses are eluted from the Celite in small volumes of phosphate buffer. This procedure was further tested without the aid of the Celite additives using a precipitating beef extract powder and substituting FeCl3 as an alternate reagent for the Celite. Comparison testing was also made with the currently recommended cartridge and disc filter procedures. In all cases, the non-precipitating beef extract-Celite method gave higher recovery rates in highly polluted waters.

Lethality of a Heat- and Phosphate-Catalyzed Glucose By-Product to Escherichia coli O157:H7 and Partial Protection Conferred by the rpoS Regulon

PubMed Central

Byrd, Jeffrey J.; Cheville, Ann M.; Bose, Jeffrey L.; Kaspar, Charles W.

1999-01-01

A by-product of glucose produced during sterilization (121°C, 15 lb/in2, 15 min) at neutral pH and in the presence of phosphate (i.e., phosphate-buffered saline) was bactericidal to Escherichia coli O157:H7 (ATCC 43895). Other six-carbon (fructose and galactose) and five-carbon (arabinose, ribose, and xylose) reducing sugars also produced a toxic by-product under the same conditions. Fructose and the five-carbon sugars yielded the most bactericidal activity. Glucose concentrations of 1% (wt/vol) resulted in a 99.9% decline in the CFU of stationary-phase cells per milliliter in 2 days at 25°C. An rpoS mutant (pRR10::rpoS) of strain 43895 (FRIK 816-3) was significantly (P < 0.001) more sensitive to the glucose-phosphate by-product than the parent strain, as glucose concentrations from 0.05 to 0.25% resulted in a 2- to 3-log10 reduction in CFU per milliliter in 2 days at 25°C. Likewise, log-phase cells of the wild-type strain, 43895, were significantly more sensitive (P < 0.001) to the glucose-phosphate by-product than were stationary-phase cells, which is consistent with the stability of rpoS and the regulation of rpoS-regulated genes. The bactericidal effect of the glucose-phosphate by-product was reduced when strains ATCC 43895 and FRIK 816-3 were incubated at a low temperature (4°C). Also, growth in glucose-free medium (i.e., nutrient broth) did not alleviate the sensitivity to the glucose-phosphate by-product and excludes the possibility of substrate-accelerated death as the cause of the bactericidal effect observed. The glucose-phosphate by-product was also bactericidal to Salmonella typhimurium, Shigella dysenteriae, and a Klebsiella sp. Attempts to identify the glucose-phosphate by-product were unsuccessful. These studies demonstrate the production of a glucose-phosphate by-product bactericidal to E. coli O157:H7 and the protective effects afforded by rpoS-regulated gene products. Additionally, the detection of sublethally injured bacteria may be compromised by the presence of this by-product in recovery media. PMID:10347019

Automatized sspKa measurements of dihydrogen phosphate and Tris(hydroxymethyl) aminomethane in acetonitrile/water mixtures from 20 to 60°C.

PubMed

Acquaviva, A; Tascon, M; Padró, J M; Gagliardi, L G; Castells, C B

2014-09-01

We measured pKa values of Tris(hydroxymethyl)aminomethane and dihydrogen phosphate; both are commonly used to prepare buffers for reverse-phase liquid chromatography (RPLC), in acetonitrile/water mixtures from 0% to 70% (v/v) (64.6% (w/w)) acetonitrile and at 20, 30, 40, 50, and 60°C. The procedure is based on potentiometric measurements of pH of buffer solutions of variable solvent compositions using a glass electrode and a novel automated system. The method consists in the controlled additions of small volumes of a thermostated solution from an automatic buret into another isothermal solution containing exactly the same buffer-component concentrations, but a different solvent composition. The continuous changes in the solvent composition induce changes in the potentials. Thus, only two sequences of additions are needed: increasing the amount of acetonitrile from pure water and decreasing the content of acetonitrile from 70% (v/v) (64.6% (w/w)). In the procedure with homemade apparatus, times for additions, stirring, homogenization, and data acquisition are entirely controlled by software programmed for this specific routine. This rapid, fully automated method was applied to acquire more than 40 potential data covering the whole composition range (at each temperature) in about two hours and allowed a systematic study of the effect of temperature and acetonitrile composition on acid-base equilibria of two widely used substances to control pH close to 7. The experimental pKa results were fitted to empirical functions between pKa and temperature and acetonitrile composition. These equations allowed predictions of pKa to estimate the pH of mixtures at any composition and temperature, which would be very useful, for instance, during chromatographic method development. Copyright © 2014 Elsevier B.V. All rights reserved.

A Phos-tag-based magnetic-bead method for rapid and selective separation of phosphorylated biomolecules.

PubMed

Tsunehiro, Masaya; Meki, Yuma; Matsuoka, Kanako; Kinoshita-Kikuta, Emiko; Kinoshita, Eiji; Koike, Tohru

2013-04-15

A simple and efficient method based on magnetic-bead technology has been developed for the separation of phosphorylated and nonphosphorylated low-molecular-weight biomolecules, such as nucleotides, phosphorylated amino acids, or phosphopeptides. The phosphate-binding site on the bead is an alkoxide-bridged dinuclear zinc(II) complex with 1,3-bis(pyridin-2-ylmethylamino)propan-2-olate (Phos-tag), which is linked to a hydrophilic cross-linked agarose coating on a magnetic core particle. All steps for the phosphate-affinity separation are conducted in buffers of neutral pH with 50 μL of the magnetic beads in a 1.5-mL microtube. The entire separation protocol for phosphomonoester-type compounds, from addition to elution, requires less than 12 min per sample if the buffers and the zinc(II)-bound Phos-tag magnetic beads have been prepared in advance. The phosphate-affinity magnetic beads are reusable at least 15 times without a decrease in their phosphate-binding ability and they are stable for three months in propan-2-ol. Copyright © 2013 Elsevier B.V. All rights reserved.

Cullin 5 Expression in the Rat: Cellular and Tissue Distribution, and Changes in Response to Water Deprivation and Hemorrhagic Shock

DTIC Science & Technology

2003-02-28

of Health p53 tumor suppressor PBS phosphate buffered saline PCO2 partial pressure of carbon dioxide PO2 partial pressure of oxygen PCR...buffered saline TTBS tween-20 tris buffered saline TonEBP tonicity-response enhancer binding protein TSNRP TriService Nursing Research Program...growth and metabolism (Hochstrasser, 1995; Deshaies, 1999). Although traditionally seen as no more than a means of eliminating no longer needed

The Effects of pH on the Growth and Aspect Ratio of Chicken Egg White Lysozyme Crystals Prepared in Different Buffers

NASA Technical Reports Server (NTRS)

Gibson, U. J.; Horrell, E. E.; Kou, Y.; Pusey, Marc

2000-01-01

We have measured the nucleation and aspect ratio of CEWL crystals grown by vapor diffusion in acetate, butyrate, carbonate, succinate, and phosphate buffers in a range of pH spanning the pK(sub a) of these buffers. The nucleation numbers drop off significantly in the vicinity of pK(sub a) for each of the buffers except the phosphate system, in which we used only the pH range around the second titration point(pK2). There is a concomitant increase in the sizes of the crystals. Some typical nucleation number results are shown. These data support and extend other observations. In addition, we have examined changes in aspect ratio which accompany the suppression of nucleation within each buffer system. The length of the face in the [001] direction was measured, and compared to the width of the (110) face in the [110] type directions. We find that while the aspect ratio of the crystals is affected by pH, it is dominated by a correlation with the size of the crystals. Small crystals are longer in the [0011 direction than crystals that are larger (higher pH within a buffer system). This relationship is found to hold independent of the choice of buffer. These results are consistent with those of Judge et al, who used a batch process which resulted in uniform sizing of crystals at each pH. In these experiments, we specifically avoid agitating the protein/salt buffer mixture when combining the two. This permits the formation of a range of sizes at a given pH. The results for a .05 M acetate 5% NaCl buffer are also shown. We will discuss these results in light of a growth model.

ROBUST: The ROle of BUffering capacities in STabilising coastal lagoon ecosystems

NASA Astrophysics Data System (ADS)

de Wit, Rutger; Stal, Lucas J.; Lomstein, Bente Aa.; Herbert, Rodney A.; van Gemerden, Hans; Viaroli, Pierluigi; Cecherelli, Victor-Ugo; Rodríguez-Valera, Francisco; Bartoli, Marco; Giordani, Gianmarco; Azzoni, Roberta; Schaub, Bart; Welsh, David T.; Donnelly, Andrew; Cifuentes, Ana; Antón, Josefa; Finster, Kai; Nielsen, Lise B.; Pedersen, Anne-Grethe Underlien; Neubauer, Anne Turi; Colangelo, Marina A.; Heijs, Sander K.

2001-12-01

"Buffer capacities" has been defined in ecology as a holistic concept (e.g., Integration of Ecosystem Theories: A Pattern, second ed. Kluwer, Dordrecht, 1997, 388pp), but we show that it can also be worked out in mechanistic studies. Our mechanistic approach highlights that "buffering capacities" can be depleted progressively, and, therefore, we make a distinction between current and potential "buffering capacities". We have applied this concept to understand the limited "local stability" in seagrass ecosystems and their vulnerability towards structural changes into macro-algal dominated communities. We explored the following processes and studied how they confer buffering capacities to the seagrass ecosystem: (i) net autotrophy is persistent in Zostera noltii meadows where plant assimilation acts as a sink for nutrients, this contrasted with the Ulva system that shifted back and forth between net autotrophy and net heterotrophy; (ii) the Z. noltii ecosystem possesses a certain albeit rather limited capacity to modify the balance between nitrogen fixation and denitrification, i.e., it was found that in situ nitrogen fixation always exceeded denitrification; (iii) the nitrogen demand of organoheterotrophic bacteria in the sediment results in nitrogen retention of N in the sediment and hence a buffer against release of nitrogen compounds from sediments, (iv) habitat diversification in seagrass meadows provides shelter for meiofauna and hence buffering against adverse conditions, (v) sedimentary iron provides a buffer against noxious sulfide (note: bacterial sulfide production is enhanced in anoxic sediment niches by increased organic matter loading). On the other hand, in the coastal system we studied, sedimentary iron appears less important as a redox-coupled buffer system against phosphate loading. This is because most inorganic phosphate is bound to calcium rather than to iron. In addition, our studies have highlighted the importance of plant-microbe interactions in the seagrass meadows.

Effect of degree of esterification of pectin and calcium amount on drug release from pectin-based matrix tablets.

PubMed

Sungthongjeen, Srisagul; Sriamornsak, Pornsak; Pitaksuteepong, Tasana; Somsiri, Atawit; Puttipipatkhachorn, Satit

2004-02-12

The aim of this work was to assess the effect of 2 formulation variables, the pectin type (with different degrees of esterification [DEs]) and the amount of calcium, on drug release from pectin-based matrix tablets. Pectin matrix tablets were prepared by blending indomethacin (a model drug), pectin powder, and various amounts of calcium acetate and then tableting by automatic hydraulic press machine. Differential scanning calorimetry, powder x-ray diffraction, and Fourier transformed-infrared spectroscopy studies of the compressed tablets revealed no drug-polymer interaction and the existence of drug with low crystallinity. The in-vitro release studies in phosphate buffer (United States Pharmacopeia) and tris buffer indicated that the lower the DE, the greater the time for 50% of drug release (T50). This finding is probably because of the increased binding capacity of pectin to calcium. However, when the calcium was excluded, the pectins with different DEs showed similar release pattern with insignificant difference of T50. When the amount of calcium acetate was increased from 0 to 12 mg/tablet, the drug release was significantly slower. However, a large amount of added calcium (ie, 24 mg/tablet) produced greater drug release because of the partial disintegration of tablets. The results were more pronounced in phosphate buffer, where the phosphate ions induced the precipitation of calcium phosphate. In conclusion, both pectin type and added calcium affect the drug release from the pectin-based matrix tablets.

Formation of surface reaction products on bioactive glass and their effects on the expression of the osteoblastic phenotype and the deposition of mineralized extracellular matrix.

PubMed

el-Ghannam, A; Ducheyne, P; Shapiro, I M

1997-02-01

The objective of the study was to examine the effect of alkali ion release, pH control and buffer capacity on the expression of the osteoblastic phenotype. In addition we determined the importance of modifications of the surface of porous bioactive glass (BG) on the activity of rat calvaria osteoblasts in vitro. We found that at a low tissue culture medium (TCM) volume to BG surface area (Vol/SA) ratio, the products of glass corrosion elevated the pH of the TCM to a value that adversely affected cellular activity; thus, the matrix synthesized by the cells was non-mineralized. On the other hand, when the Vol/SA was high and the buffer capacity of the medium was not exceeded, the cells generated a mineralized extracellular matrix. Addressing the second issue, we observed that modification of the composition of the BG surface markedly influenced osteoblast activity. BG that was coated with either a calcium phosphate-rich layer only or a serum protein layer changed the phenotypic characteristics of the osteoblasts. The presence of either of these surfaces lowered the alkaline phosphatase activity of the attached cells; this finding indicated that the osteoblast phenotype was not conserved. However, when the BG was coated with a bilayer of calcium phosphate and serum proteins, the alkaline phosphatase (AP) activity was elevated and the extracellular matrix contained characteristic bone markers. Our findings indicate that the calcium phosphate-rich layer promotes adsorption and concentration of proteins from the TCM, and it is utilized by the osteoblasts to form the mineralized extracellular matrix.

[Key factors in the control of electroosmosis with external radial electric field in CE].

PubMed

Zhu, Y; Chen, Y

1999-11-01

Direct control of electroosmosis flow (EOF) by external radial electric field was performed at room temperature using a home-made field-modulated capillary electrophoresis (CE) system. The EOF was monitored at 206 nm by using DMSO as a probe. To apply a radial electric field across the CE capillary wall, the capillary was cased with a wide column. Both of the concentric space and the capillary bore were then filled with an identical running buffer and applied with an axial electric field of 150 V/cm but starting from different levels. All of the tubes used were made of fused silica with polyimide over-coating (from the Yongnian Optical Fiber Work, Hebei, P. R. China). The size of the CE capillaries adopted was 25-100 microns i.d. (375 microns o.d.) x 28.5/45 cm (effective/total length), and that of the casing column 400 microns i.d. x 32 cm. To investigate the fundamentals of the external EOF control when using the flexible fused silica capillaries, various parameters have been inspected such as pH, buffer composition, additives and capillary wall feature etc.. As expected, to well control both of the magnitude and direction of the electroosmosis, the buffer pH should be kept below 4 and the buffer concentration below 50 mmol/L. However, buffers below 1 mmol/L should be avoided because such a diluted running buffer may result in poor CE separation. Weak electrolytes like citric acid, tartaric acid and acetic acid were found to be capable of generating better EOF control than the strong electrolytes such as phosphate and chlorides. This is possibly due to the formation of looser electric double layer with the weak rather than the strong electrolytes. Some wall coatings like calix arene and its derivatives can evidently improve the EOF control even at pH 5. This reveals an exciting way to expend the controllable pH range. In addition, narrow-bore capillaries were demonstrated to be better than wide-bore tubes. Other conditions such as buffer additives and capillary rinse procedure were shown to have only negligible influence on the control.

Deduction of a calcium ion circuit affecting rooster sperm in vitro.

PubMed

Froman, D P

2016-08-01

Four premises for rooster sperm preservation were outlined previously. Understanding mitochondrial Ca cycling in terms of whole-cell Ca flux was one premise. The present work tested the hypothesis that sperm mitochondria can be damaged by intracellular as well as extracellular Ca. Sperm were washed by centrifugation through 12% (wt/vol) Sperm were washed by centrifugation through 12%(at/vol) Accudenz to procure sperm at a physiological concentration within a chemically-defined suspension. Five solutions were tested. Each solution contained 30 m glucose, and had an osmolality of 320 mmol/kg and a pH of 7.4. Washed sperm were diluted to 2.0 × 10 sperm/mL. Each replicate sperm suspension was cooled to 10°C. Sperm mobility was measured after 1, 2, 4, 8, 12, and 24 h. Data were plotted as a function of time in each experiment. Function type was confirmed by lack of fit analysis. A parabola with a maximum at 3.7 h was observed when sperm were suspended in 205 m taurine buffered with 50 m-tris[hydroxyl-methyl]methyl-2-amino-ethanesulfonic acid (TES). This effect was attributed to a Ca flux from the nuclear envelope into mitochondria. An exponential decay was observed when TES-buffered taurine contained 2 m Ca. This effect was attributed to mitochondrial Ca overload induced by uptake of extracellular Ca. Exponential decay also was observed when TES-buffered taurine contained a Ca chelator. This effect was attributed to a Ca flux from the nuclear envelope through mitochondria and then into an extracellular Ca sink. This possibility was supported by the response of sperm to thapsigargin. Specifically, inhibition of sarcoendoplasmic reticulum Ca-ATPase compromised sperm mobility relative to a buffer control. Finally, a 60 m phosphate buffer containing 2 m citrate yielded a linear relationship in contrast to the TES-buffered solutions tested. Sperm mobility after 24 h of storage in the phosphate buffer was 92% of that observed for prewashed sperm. The linear response was attributed to weak chelators providing resistance within a Ca circuit and thereby preventing mitochondrial Ca overload. Fertility, however, was compromised when hens were inseminated with mobile sperm recovered after either 8 or 24 h of storage at 10°C. In conclusion, sperm cell Ca homeostasis was proven to be critical for maintaining sperm mobility in vitro, but mitochondrial Ca uptake is not the sole phenomenon that compromises sperm function during in vitro storage.

Biaxially textured composite substrates

DOEpatents

Groves, James R.; Foltyn, Stephen R.; Arendt, Paul N.

2005-04-26

An article including a substrate, a layer of a metal phosphate material such as an aluminum phosphate material upon the surface of the substrate, and a layer of an oriented cubic oxide material having a rock-salt-like structure upon the metal phosphate material layer is provided together with additional layers such as a HTS top-layer of YBCO directly upon a layer of a buffer material such as a SrTi.sub.x Ru.sub.1-x O.sub.3 layer.

The chemistry of the S-nitrosoglutathione/glutathione system

PubMed Central

Singh, S. P.; Wishnok, J. S.; Keshive, M.; Deen, W. M.; Tannenbaum, S. R.

1996-01-01

S-Nitrosothiols have generated considerable interest due to their ability to act as nitric oxide (NO) donors and due to their possible involvement in bioregulatory systems—e.g., NO transfer reactions. Elucidation of the reaction pathways involved in the modification of the thiol group by S-nitrosothiols is important for understanding the role of S-nitroso compounds in vivo. The modification of glutathione (GSH) in the presence of S-nitrosoglutathione (GSNO) was examined as a model reaction. Incubation of GSNO (1 mM) with GSH at various concentrations (1–10 mM) in phosphate buffer (pH 7.4) yielded oxidized glutathione, nitrite, nitrous oxide, and ammonia as end products. The product yields were dependent on the concentrations of GSH and oxygen. Transient signals corresponding to GSH conjugates, which increased by one mass unit when the reaction was carried out with 15N-labeled GSNO, were identified by electrospray ionization mass spectrometry. When morpholine was present in the reaction system, N-nitrosomorpholine was formed. Increasing concentrations of either phosphate or GSH led to lower yields of N-nitrosomorpholine. The inhibitory effect of phosphate may be due to reaction with the nitrosating agent, nitrous anhydride (N2O3), formed by oxidation of NO. This supports the release of NO during the reaction of GSNO with GSH. The products noted above account quantitatively for virtually all of the GSNO nitrogen consumed during the reaction, and it is now possible to construct a complete set of pathways for the complex transformations arising from GSNO + GSH. PMID:8962068

Comparative evaluation of the effects of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and xylitol-containing chewing gum on salivary flow rate, pH and buffering capacity in children: An in vivo study.

PubMed

Hegde, Rahul J; Thakkar, Janhavi B

2017-01-01

This study aimed to compare and evaluate the changes in the salivary flow rate, pH, and buffering capacity before and after chewing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and xylitol-containing chewing gums in children. Sixty children aged between 8 and 12 years were selected for the study. They were randomly divided into Group 1 (CPP-ACP chewing gum) and Group 2 (xylitol-containing chewing gum) comprising thirty children each. Unstimulated and stimulated saliva samples at 15 and 30 min interval were collected from all children. All the saliva samples were estimated for salivary flow rate, pH, and buffering capacity. Significant increase in salivary flow rate, pH, and buffering capacity from baseline to immediately after spitting the chewing gum was found in both the study groups. No significant difference was found between the two study groups with respect to salivary flow rate and pH. Intergroup comparison indicated a significant increase in salivary buffer capacity in Group 1 when compared to Group 2. Chewing gums containing CPP-ACP and xylitol can significantly increase the physiochemical properties of saliva. These physiochemical properties of saliva have a definite relation with caries activity in children.

Mechanisms altering airway smooth muscle cell Ca+ homeostasis in two asthma models.

PubMed

Kellner, Julia; Tantzscher, Juliane; Oelmez, Hamza; Edelmann, Martin; Fischer, Rainald; Huber, Rudolf Maria; Bergner, Albrecht

2008-01-01

Asthma is characterized by airway remodeling, altered mucus production and airway smooth muscle cell (ASMC) contraction causing extensive airway narrowing. In particular, alterations of ASMC contractility seem to be of crucial importance. The elevation of the cytoplasmic Ca(2+) concentration is a key event leading to ASMC contraction and changes in the agonist-induced Ca(2+) increase in ASMC have been reported in asthma. The aim of this study was to investigate mechanisms underlying these changes. Murine tracheal smooth muscle cells (MTSMC) from T-bet KO mice and human bronchial smooth muscle cells (HBSMC) incubated with IL-13 and IL-4 served as asthma models. Acetylcholine-induced changes in the cytoplasmic Ca(2+) concentration were recorded using fluorescence microscopy and the expression of Ca(2+) homeostasis regulating proteins was investigated with Western blot analysis. Acetylcholine-induced Ca(2+) transients were elevated in both asthma models. This correlated with an increased Ca(2+) content of the sarcoplasmic reticulum (SR). In MTSMC from T-bet KO mice, the expression of the SR Ca(2+) buffers calreticulin and calsequestrin was higher compared to wild-type mice. In HBSMC incubated with IL-13 or IL-4, the expression of ryanodine receptors, inositol-3-phosphate receptors and sarcoplasmic/endoplasmic reticulum Ca(2+) ATPases 2 was increased compared to HBSMC without incubation with interleukins. The enlarged acetylcholine-induced Ca(2+) transients could be reversed by blocking inositol-3-phosphate receptors. We conclude that in the murine asthma model the SR Ca(2+) buffer capacity is increased, while in the human asthma model the expression of SR Ca(2+) channels is altered. The investigation of the Ca(2+) homeostasis of ASMC has the potential to provide new therapeutical options in asthma. Copyright 2008 S. Karger AG, Basel.

Determination of residual cell culture media components by MEKC.

PubMed

Zhang, Junge; Chakraborty, Utpal; Foley, Joe P

2009-11-01

Folic acid, hypoxanthine, mycophenolic acid, nicotinic acid, riboflavin, and xanthine are widely used as cell culture media components in monoclonal antibody manufacturing. These components are subsequently removed during the downstream purification processes. This article describes a single MEKC method that can simultaneously determine all the listed compounds with acceptable LOD and LOQ. All the analytes were successfully separated by MEKC using running buffer containing 40 mM SDS, 20 mM sodium phosphate, and 20 mM sodium borate at pH 9.0. The MEKC method was compared to the corresponding CZE method using the same running buffer containing no SDS. The effect of SDS concentration on separation, the pH of the running buffer, and the detection wavelength were studied and optimal MEKC conditions were established. Good linearity was obtained with correlation coefficients of more than 0.99 for all analytes. Specificity, accuracy, and precision were also evaluated. The recovery was in the range of 89-112%. The precision results were in the range of 1.7-4.8%. The experimentally determined data demonstrated that the MEKC method is applicable to the determination of the six analytes in in-process samples from monoclonal antibody manufacturing processes.

The Preparation of Capsaicin-Chitosan Microspheres (CCMS) Enteric Coated Tablets

PubMed Central

Chen, Jian; Huang, Gui-Dong; Tan, Si-Rong; Guo, Jiao; Su, Zheng-Quan

2013-01-01

This study aimed to research the preparation and content determination of capsaicin-chitosan microspheres (CCMS) enteric coated tablets. The core tablets were prepared with the method of wet granulation. Nine formulae were designed to determine the optimal formula of the core tablet. Eudragit L100 was used to prepare the CCMS enteric-coated tablets. The effect of enteric coated formulation variables such as content of talc (10%, 25% and 40%), plasticisers (TEC and DBS), dosage of plasticiser (10%, 20% and 30%) and coating weight (2%, 3% and 5%) were evaluated for drug release characteristics. The in vitro release was studied using 0.1 N HCl and pH 6.8 phosphate buffer. Enteric coated tablets without ruptures or swelling behaviour over 2 h in 0.1 N HCl indicated that these tablets showed acid resistance. The accumulated release rate in phosphate buffer (pH 6.8) revealed that the prepared tablets were able to sustain drug release into the intestine and a first-order release was obtained for capsaicin. This research is the first report of the preparation and content determination of CCMS enteric coated tablets. The sustained release behavior of enteric coated formulations in pH 6.8 phosphate buffer demonstrated that it would be a potential drug delivery platform for sustained delivery of gastric irritant drugs. PMID:24351818

Simple and sensitive determination of five quinolones in food by liquid chromatography with fluorescence detection.

PubMed

Ramos, Macarena; Aranda, Angela; Garcia, Elena; Reuvers, Thea; Hooghuis, Henny

2003-06-15

A simple and sensitive high-performance liquid chromatographic (HPLC) method has been developed for the determination of five different quinolones: enrofloxacin, ciprofloxacin, sarafloxacin, oxolinic acid and flumequine in pork and salmon muscle. The method includes one extraction and clean-up step for the five quinolones together which are detected in two separated HPLC runs by means of their fluorescence. The proposed analytical method involves homogenizing of the tissue sample with 0.05 M phosphate buffer, pH 7.4 and clean-up by Discovery DS-18 cartridges. For chromatographic separation a Symmetry C(18) column is used in two different runs: (1) ciprofloxacin, enrofloxacin and sarafloxacin with acetonitrile-0.02 M phosphate buffer pH 3.0 (18:82) as mobile phase and the detector at excitation wavelength: 280 nm and emission wavelength 450 nm; and (2) oxolinic acid and flumequine with acetonitrile-0.02 M phosphate buffer pH 3.0 (34:66) as mobile phase and excitation wavelength: 312 nm and emission wavelength: 366 nm. Detection limit was as low as 5 ng g(-1), except for sarafloxacin which had a limit of 10 ng g(-1). Standard curves using blank muscle tissues spiked at different levels showed a good linear correlation coefficient, r(2) higher than 0.999 for all quinolones.

Determination of organophosphate diesters in urine samples by a high-sensitivity method based on ultra high pressure liquid chromatography-triple quadrupole-mass spectrometry.

PubMed

Su, Guanyong; Letcher, Robert J; Yu, Hongxia

2015-12-24

Organophosphate (OP) diesters in urine samples have potential use as biomarkers of organism exposure to environmentally relevant OP triester precursors and in particular OP triester flame retardants. This present study developed a quantitatively sensitive ultra high pressure liquid chromatography (UHPLC-MS) based method for urine and the determination of OP diesters (i.e. diphenyl phosphate (DPHP), bis(2-chloroethyl) phosphate (BCEP), bis(2-chloroisopropyl) phosphate (BDCIPP), di-n-butyl phosphate (DNBP), di(2-ethylhexyl) phosphate (DEHP), bis(1-chloro-2-propyl) phosphate (BCIPP), and bis(2-butoxyethyl) phosphate (BBOEP)). Fortified with the 7 OP diesters, 1mL of human urine sample was cleaned up using weak anion exchange solid phase extraction and eluted with high ionic strength ammonium acetate buffer. Subsequently, 4 non-chlorinated OP diesters were directly determined using UHPLC-electrospray(-)-triple quadrupole-MS (UHPLC-ESI(-)-QqQ-MS), and UHPLC-ESI(+)-QqQ-MS was used for determination of 3 chlorinated OP diesters after methylation using diazomethane. Recovery efficiencies of OP diesters ranged from 88 to 160% at three spiking levels (0.4, 2 and 10ng/mL urine). Matrix effects (MEs) and method limits of quantification (MLOQs) were 15-134% and 0.10-0.32ng/mL urine, respectively. Concentrations of OP diesters in n=12 urine samples (from 4 Canadian residents, 2014) varied as follows, nd-<0.28 (DNBP), nd-1.29 (DPHP), nd-<0.28 (DEHP), <0.16-12.33 (BCEP), nd-1.17 (BCDIPP) and nd-0.68ng/mL (BCIPP). Copyright © 2015. Published by Elsevier B.V.

Extraction of superoxide dismutase, catalase, and carbonic anhydrase from stroma-free red blood cell hemolysate for the preparation of the nanobiotechnological complex of polyhemoglobin-superoxide dismutase-catalase-carbonic anhydrase.

PubMed

Guo, C; Gynn, M; Chang, T M S

2015-06-01

We report a novel method to simultaneously extract superoxide dismutase (SOD), catalase (CAT), and carbonic anhydrase (CA) from the same sample of red blood cells (RBCs). This avoids the need to use expensive commercial enzymes, thus enabling a cost-effective process for large-scale production of a nanobiotechnological polyHb-SOD-CAT-CA complex, with enhancement of all three red blood cell functions. An optimal concentration of phosphate buffer for ethanol-chloroform treatment results in good recovery of CAT, SOD, and CA after extraction. Different concentrations of the enzymes can be used to enhance the activity of polyHb-SOD-CAT-CA to 2, 4, or 6 times that of RBC.

Separation of proteins by hydrophobic interaction chromatography at low salt concentration.

PubMed

Kato, Yoshio; Nakamura, Koji; Kitamura, Takashi; Moriyama, Hiroyuki; Hasegawa, Masazumi; Sasaki, Hiroo

2002-09-20

We investigated protein separation by hydrophobic interaction chromatography (HIC) at low salt concentration on the supports of various hydrophobicities. Hydrophobic proteins could be successfully separated with more than 90% recovery by gradient elution of ammonium sulfate from 0.3-0.5 M to 0 in 50 mM phosphate buffer (pH 6.8) by using supports whose hydrophobicities were properly adjusted individually for each protein. Satisfactory results were also obtained by isocratic elution without ammonium sulfate and gradient elution of ethanol from 0 to 10%. HIC at low salt concentration was compatible with other modes of liquid chromatography like ion-exchange chromatography. On the other hand, it was not successful to separate hydrophilic proteins at low salt concentration. Recoveries of hydrophilic proteins decreased before they were retained enough as support hydrophobicity increased. Therefore, it is inevitable to use a higher concentration of salt, e.g., 1-2 M ammonium sulfate, on hydrophilic or moderately hydrophobic support in order to retain hydrophilic proteins without decrease in recovery.

Tannate complexes of antihistaminic drug: sustained release and taste masking approaches.

PubMed

Rahman, Ziyaur; Zidan, Ahmed S; Berendt, Robert T; Khan, Mansoor A

2012-01-17

The aim of this investigation was to evaluate the complexation potential of brompheniramine maleate (BPM) and tannic acid (TA) for sustained release and taste masking effects. The complexes (1:1-1:7 TA to BPM ratio) were prepared by the solvent evaporation method using methanol, phosphate buffer pH 6.8 or 0.1N HCl as common solvents. The complexes were characterized microscopically by scanning electron microscopy (SEM), chemically by Fourier transform infrared (FTIR) and solid-state NMR (SSNMR), thermally by differential scanning calorimetry (DSC), for crystallinity by powder X-ray powder diffraction (PXRD), for organoleptic evaluation by electronic tongue (e-tongue), and for solubility in 0.1N HCl and phosphate buffer pH 6.8. The dissolution studies were carried out using the USP II method at 50 rpm in 500 ml of dissolution media (0.1N HCl or phosphate buffer pH 6.8). SEM images revealed that the morphology of complexes were completely different from the individual components, and all complexes had the same morphological characteristics, irrespective of the solvent used for their preparation, pH or ratio of BPM and TA. The FTIR spectra showed the presence of chemical interactions between the TA and BPM. DSC, PXRD and SSNMR indicated that the drug lost its crystalline nature by formation of the complex. Complexation has significantly reduced the solubility of BPM and sustained the drug release up to 24h in phosphate buffer pH 6.8 media. The bitter taste of the BPM was completely masked which was indicated by Euclidean distance values which was far from the drug but near to its placebo in the complexes in all ratios studied. The taste masked complexes can be potentially developed as suitable dosage forms for pediatric use. In summary, complexation of BPM and TA effectively sustained the dissolution and masked the bitter taste of drug for the development of suitable dosage forms for pediatric use. Published by Elsevier B.V.

Improved quantitative recovery of Listeria monocytogenes from stainless steel surfaces using a one-ply composite tissue.

PubMed

Vorst, Keith L; Todd, Ewen C D; Rysert, Elliot T

2004-10-01

Four sampling devices, a sterile environmental sponge (ES), a sterile cotton-tipped swab (CS), a sterile calcium alginate fiber-tipped swab (CAS), and a one-ply composite tissue (CT), were evaluated for quantitative recovery of Listeria monocytogenes from a food-grade stainless steel surface. Sterile 304-grade stainless steel plates (6 by 6 cm) were inoculated with approximately 106 CFU/cm2 L. monocytogenes strain Scott A and dried for 1 h. The ES and CT sampling devices were rehydrated in phosphate buffer solution. After plate swabbing, ES and CT were placed in 40 ml of phosphate buffer solution, stomached for 1 min and hand massaged for 30 s. Each CS and CAS device was rehydrated in 0.1% peptone before swabbing. After swabbing, CS and CAS were vortexed in 0.1% peptone for 1 min. Samples were spiral plated on modified Oxford agar with modified Oxford agar Rodac Contact plates used to recover any remaining cells from the stainless steel surface. Potential inhibition from CT was examined in both phosphate buffer solution and in a modified disc-diffusion assay. Recovery was 2.70, 1.34, and 0.62 log greater using CT compared with ES, CS, and CAS, respectively, with these differences statistically significant (P < 0.001) for ES and CT and for CAS, CS, and CT (P < 0.05). Rodac plates were typically overgrown following ES, positive after CS and CAS, and negative after CT sampling. CT was noninhibitory in both phosphate buffer solution and the modified disc-diffusion assay. Using scanning electron microscopy, Listeria cells were observed on stainless steel plates sampled with each sampling device except CT. The CT device, which is inexpensive and easy to use, represents a major improvement over other methods in quantifying L. monocytogenes on stainless steel surfaces and is likely applicable to enrichment of environmental samples.

Enantiomeric separation of fluoxetine and norfluoxetine in plasma and serum samples with high detection sensitivity capillary electrophoresis.

PubMed

Desiderio, C; Rudaz, S; Raggi, M A; Fanali, S

1999-11-01

A capillary electrophoresis method was optimized for the stereoselective analysis of the antidepressant drug fluoxetine and its main demethylated metabolite norfluoxetine using a cyclodextrin-modified sodium phosphate buffer at pH 2.5. The combination of a neutral and a negatively charged cyclodextrin, dimethylated-beta- and phosphated-gamma-respectively, provided the baseline enantiomeric separation of the two compounds. The very low concentrations of chiral selectors employed together with the use of a high sensitivity detection cell of special design (zeta-shaped) in a diode array UV detector allowed us to reach a limit of detection of 0.005 and 0.01 microg/mL for fluoxetine and norfluoxetine, respectively. Analysis of fluoxetine and norfluoxetine standard mixtures showed a reproducibility of migration times and peak area and linearity in the concentration range of 0.1-2.0 microg/mL. The optimized method was applied to the analysis of clinical serum and plasma samples of patients under depression therapy. In all the analyzed samples the enantiomeric forms of fluoxetine and norfluoxetine were easily identified. The fluoxetine and metabolite enantiomeric ratio confirmed the stereoselectivity of the metabolic process of the fluoxetine drug in accordance with the literature data.

Passive transport and binding of lead by human red blood cells.

PubMed Central

Simons, T J

1986-01-01

The uptake of Pb into human red blood cells has been studied using Pb buffers. Passive Pb movements can be studied conveniently when the cells are depleted of adenosine 5'-triphosphate (ATP), to eliminate active transport, and of inorganic phosphate, to prevent precipitation of lead phosphate. Pb can cross the membrane passively in either direction. Influx and efflux show similar properties. Passive Pb transport is strongly stimulated by HCO3-, and is reduced by replacing Cl- with ClO4-. It is inhibited by low concentrations of 4-acetamido-4'-isothiocyanostilbene-2,2'-disulphonic acid (SITS) and 4,4'-diisothiocyanostilbene-2.2'-disulphonic acid (DIDS), characteristic inhibitors of anion transport. Pb uptake is unaffected by varying the external concentrations of Na+, K+ and Ca2+. When Pb enters the cell, it binds mainly to haemoglobin. The ratio of bound Pb:free Pb2+ in the cytosol is estimated to be 6000:1. Pb binding to haemoglobin is unaffected by oxygenation. Binding to albumin is quantitatively similar to binding to haemoglobin. The implications of these results for the transport and binding of Pb in the blood are discussed. PMID:3795106

ISS Internal Active Thermal Control System (IATCS) Coolant Remediation Project

NASA Technical Reports Server (NTRS)

Morrison, Russell H.; Holt, Mike

2005-01-01

The IATCS coolant has experienced a number of anomalies in the time since the US Lab was first activated on Flight 5A in February 2001. These have included: 1) a decrease in coolant pH, 2) increases in inorganic carbon, 3) a reduction in phosphate buffer concentration, 4) an increase in dissolved nickel and precipitation of nickel salts, and 5) increases in microbial concentration. These anomalies represent some risk to the system, have been implicated in some hardware failures and are suspect in others. The ISS program has conducted extensive investigations of the causes and effects of these anomalies and has developed a comprehensive program to remediate the coolant chemistry of the on-orbit system as well as provide a robust and compatible coolant solution for the hardware yet to be delivered. The remediation steps include changes in the coolant chemistry specification, development of a suite of new antimicrobial additives, and development of devices for the removal of nickel and phosphate ions from the coolant. This paper presents an overview of the anomalies, their known and suspected system effects, their causes, and the actions being taken to remediate the coolant.

Heat pretreatment eliminates spurious butyrylcholinesterase enhancement of endotoxin levels in the kinetic chromogenic assay.

PubMed

Brawner, Andrew; Hinrichs, Steven H; Larson, Marilynn A; Lockridge, Oksana

2016-04-05

The kinetic chromogenic endotoxin assay measures the release of p-nitroaniline from the chromogenic peptide substrate Ac-IEAR-pNA. As part of our project to purify large quantities of human butyrylcholinesterase (HuBChE), we evaluated pure HuBChE for endotoxin levels. We found that HuBChE contributed up to 90% of the yellow p-nitroaniline product in a standard endotoxin assay through the catalytic hydrolysis of Ac-IEAR-pNA with a rate constant of 0.016 min(-1) and a Km of 2.9 mM in potassium phosphate buffer pH 7.0 at 24 °C. Thus, endotoxin concentrations for native BChE are artificially high in the kinetic chromogenic assay. Destruction of HuBChE catalytic activity by boiling yields endotoxin concentrations that more accurately reflect the endotoxin concentration in purified HuBChE preparations. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Non-thermal dielectric barrier discharge plasma induces angiogenesis through reactive oxygen species.

PubMed

Arjunan, Krishna P; Clyne, Alisa Morss

2011-01-01

Vascularization plays a key role in processes such as wound healing and tissue engineering. Non-thermal plasma, which primarily produces reactive oxygen species (ROS), recently emerged as an efficient tool in medical applications. Liquids and endothelial cells were treated with a non-thermal dielectric barrier discharge plasma. Plasma treatment of phosphate buffered saline (PBS) and serum-free medium increased ROS concentration in a dose-dependent manner, with a higher concentration in serum-free medium. ROS concentration in cells peaked 1 hour after treatment. 4.2 J/cm(2) increased cell proliferation, 2D and 3D migration, as well as tube formation. A fibroblast growth factor-2 (FGF-2) neutralizing antibody and ROS scavengers for hydrogen peroxide and hydroxyl radicals abrogated these angiogenic effects. Non-thermal plasma may be a potential tool for applying ROS in precise doses to enhance vascularization.

Assessment and kinetics of soil phosphatase in Brazilian Savanna systems.

PubMed

Ferreira, Adão S; Espíndola, Suéllen P; Campos, Maria Rita C

2016-05-31

The activity and kinetics of soil phosphatases are important indicators to evaluate soil quality in specific sites such as the Cerrado (Brazilian Savanna). This study aimed to determine the activity and kinetic parameters of soil phosphatase in Cerrado systems. Soil phosphatase activity was assessed in samples of native Cerrado (NC), no-tillage (NT), conventional tillage (CT) and pasture with Brachiaria brizantha (PBb) and evaluated with acetate buffer (AB), tris-HCl buffer (TB), modified universal buffer (MUB) and low MUB. The Michaelis-Menten equation and Eadie-Hofstee model were applied to obtain the kinetic parameters of soil phosphatase using different concentrations of p-nitrophenol phosphate (p-NPP). MUB showed the lowest soil phosphatase activity in all soils whereas AB in NC and NT presented the highest. Low MUB decreased interferences in the assessment of soil phosphatase activity when compared to MUB, suggesting that organic acids interfere on the soil phosphatase activity. In NC and NT, soil phosphatase activity performed with TB was similar to AB and low MUB. Km values from the Michaels-Menten equation were higher in NC than in NT, which indicate a lower affinity of phosphatase activity for the substrate in NC. Vmax values were also higher in NC than in NT. The Eadie-Hofstee model suggests that NC had more phosphatase isoforms than NT. The study showed that buffer type is of fundamental importance when assessing soil phosphatase activity in Cerrado soils.

Signal Amplification in Field Effect-Based Sandwich Enzyme-Linked Immunosensing by Tuned Buffer Concentration with Ionic Strength Adjuster.

PubMed

Kumar, Satyendra; Kumar, Narendra; Panda, Siddhartha

2016-04-01

Miniaturization of the sandwich enzyme-based immunosensor has several advantages but could result in lower signal strength due to lower enzyme loading. Hence, technologies for amplification of the signal are needed. Signal amplification in a field effect-based electrochemical immunosensor utilizing chip-based ELISA is presented in this work. First, the molarities of phosphate buffer saline (PBS) and concentrations of KCl as ionic strength adjuster were optimized to maximize the GOx glucose-based enzymatic reactions in a beaker for signal amplification measured by change in the voltage shift with an EIS device (using 20 μl of solution) and validated with a commercial pH meter (using 3 ml of solution). The PBS molarity of 100 μM with 25 mM KCl provided the maximum voltage shift. These optimized buffer conditions were further verified for GOx immobilized on silicon chips, and similar trends with decreased PBS molarity were obtained; however, the voltage shift values obtained on chip reaction were lower as compared to the reactions occurring in the beaker. The decreased voltage shift with immobilized enzyme on chip could be attributed to the increased Km (Michaelis-Menten constant) values in the immobilized GOx. Finally, a more than sixfold signal enhancement (from 8 to 47 mV) for the chip-based sandwich immunoassay was obtained by altering the PBS molarity from 10 to 100 μM with 25 mM KCl.

Kinetics and mechanism of bacterial inactivation by ultrasound waves and sonoprotective effect of milk components.

PubMed

Gera, N; Doores, S

2011-03-01

Inactivation of Escherichia coli and Listeria monocytogenes were investigated in buffer and milk upon treatment with ultrasound waves (USW). In addition, sonoprotective effect of milk components and ultrasound-induced changes in bacterial cells were investigated using scanning electron microscopy (SEM). Bacterial cells were added to phosphate buffer, whole milk, skim milk, or simulated milk ultrafiltrate (SMUF). To determine the sonoprotective effect of milk components, lactose (5%), casein (3%), or β lactoglobulin (0.3%) was added to SMUF. Samples were sonicated with 24 kHz pulse USW while maintaining the system temperature between 30 to 35 °C. Aliquots were drawn at set times during sonication and bacteria were enumerated by surface plating appropriate dilutions on selective and nonselective media plates. Escherichia coli exhibited significantly higher D values in whole (2.43 min) and skim milk (2.41 min) than phosphate buffer (2.19 min). Listeria monocytogenes also showed higher D values in whole (9.31 min) and skim milk (8.61 min) compared to phosphate buffer (7.63 min). Data suggest that milk exerts a sonoprotective effect on these bacteria. Escherichia coli exhibited a log-linear inactivation kinetics followed by tailing whereas L. monocytogenes showed 1st-order kinetics throughout. Among the milk components tested, presence of lactose in SMUF resulted in significantly higher D values than SMUF for both organisms suggesting that lactose was exerting a protective effect on bacteria. SEM images showed that USW caused mechanical damage to the cell wall and cell membrane of bacteria leading to their inactivation.

Erosion of water-based cements evaluated by volumetric and gravimetric methods.

PubMed

Nomoto, Rie; Uchida, Keiko; Momoi, Yasuko; McCabe, John F

2003-05-01

To compare the erosion of glass ionomer, zinc phosphate and polycarboxylate cements using volumetric and gravimetric methods. For the volumetric method, the eroded depth of cement placed in a cylindrical cavity in PMMA was measured using a dial gauge after immersion in an eroding solution. For the gravimetric method, the weight of the residue of a solution in which a cylindrical specimen had been immersed was measured. 0.02 M lactic acid solution (0.02 M acid) and 0.1 M lactic acid/sodium lactate buffer solution (0.1 M buffer) were used as eroding solutions. The pH of both solutions was 2.74 and the test period was 24 h. Ranking of eroded depth and weight of residue was polycarboxylate>zinc phosphate>glass ionomers. Differences in erosion were more clearly defined by differences in eroded depth than differences in weight of residue. In 0.02 M acid, the erosion of glass ionomer using the volumetric method was effected by the hygroscopic expansion. In 0.1 M buffer, the erosion for polycarboxylate and zinc phosphate using the volumetric method was much greater than that using the gravimetric method. This is explained by cryo-SEM images which show many holes in the surface of specimens after erosion. It appears that zinc oxide is dissolved leaving a spongy matrix which easily collapses under the force applied to the dial gauge during measurement. The volumetric method that employs eroded depth of cement using a 0.1 M buffer solution is able to quantify erosion and to make material comparisons.

Influence of diluent and sample processing methods on the recovery of the biocontrol agent Pantoea agglomerans CPA-2 from different fruit surfaces.

PubMed

Torres, R; Viñas, I; Usall, J; Remón, D; Teixidó, N

2012-08-01

Determining the populations of biocontrol agents applied as a postharvest treatment on fruit surfaces is fundamental to the assessment of the microorganisms' ability to colonise and persist on fruit. To obtain maximum recovery, we must develop a methodology that involves both diluent and processing methods and that does not affect the viability of the microorganisms. The effect of diluent composition was evaluated using three diluents: phosphate buffer, peptone saline and buffered peptone saline. An additional study was performed to compare three processing methods (shaking plus sonication, stomaching and shaking plus centrifugation) on the recovery efficiency of Pantoea agglomerans strain CPA-2 from apples, oranges, nectarines and peaches treated with this biocontrol agent. Overall, slight differences occurred among diluents, although the phosphate buffer maintained the most ideal pH for CPA-2 growth (between 5.2 and 6.2). Stomaching, using the phosphate buffer as diluent, was the best procedure for recovering and enumerating the biocontrol agent; this fact suggested that no lethal effects from naturally occurring antimicrobial compounds present on the fruit skins and/or produced when the tissues were disrupted affected the recovery of the CPA-2 cells, regardless of fruit type. The growth pattern of CPA-2 on fruits maintained at 20°C and under cold conditions was similar to that obtained in previous studies, which confirms the excellent adaptation of this strain to conditions commonly used for fruit storage. Copyright © 2012 Elsevier B.V. All rights reserved.

Anodic stripping voltammetry of nickel ions and nickel hydroxide nanoparticles at boron-doped diamond electrodes

NASA Astrophysics Data System (ADS)

Musyarofah, N. R. R.; Gunlazuardi, J.; Einaga, Y.; Ivandini, T. A.

2017-04-01

Anodic stripping voltammetry (ASV) of nickel ions in phosphate buffer solution (PBS) have been investigated at boron-doped diamond (BDD) electrodes. The deposition potential at 0.1 V (vs. Ag/AgCl) for 300 s in 0.1 M PBS pH 3 was found as the optimum condition. The condition was applied for the determination of nickel contained in nickel hydroxide nanoparticles. A linear calibration curve can be achieved of Ni(OH)2-NPs in the concentration range of x to x mM with an estimated limit of detection (LOD) of 5.73 × 10-6 mol/L.

An efficient buffer-mediated control between free radical substitution and proton-coupled electron transfer: dehalogenation of iodoethane by the α-hydroxyethyl radical in aqueous solution.

PubMed

Ljubić, Ivan; Matasović, Brunislav; Bonifačić, Marija

2013-11-07

A remarkable buffer-mediated control between free-radical substitution (FRS) and proton-coupled electron transfer (PCET) is demonstrated for the reaction between iodoethane and the α-hydroxyethyl radical in neutral aqueous solution in the presence of bicarbonate or phosphate buffer. The reaction is initiated by the γ-radiolysis of the water solvent, and the products, either the iodine atom (FRS) or anion (PCET), are analysed using ion chromatographic and spectrophotometric techniques. A detailed insight into the mechanism is gained by employing density functional theory (M06-2X), Møller-Plesset perturbation treatment to the second order (MP2), and multireference methods (CASSCF/CASPT2). Addition of a basic buffer anion is indispensable for the reaction to occur and the competition between the two channels depends subtly on its proton accepting affinity, with FRS being the dominant channel in the phosphate and PCET in the bicarbonate containing solutions. Unlike the former, the latter channel sustains a chain-like process which significantly enhances the dehalogenation. The present systems furnish an example of the novel PCET/FRS dichotomy, as well as insights into possibilities of its efficient control.

In vitro behaviour of three biocompatible glasses in composite implants.

PubMed

Varila, Leena; Lehtonen, Timo; Tuominen, Jukka; Hupa, Mikko; Hupa, Leena

2012-10-01

Poly(L,DL-lactide) composites containing filler particles of bioactive glasses 45S5 and S53P4 were compared with a composite containing a slowly dissolving glass S68. The in vitro reactivity of the composites was studied in simulated body fluid, Tris-buffered solution, and phosphate buffered saline. The high processing temperature induced thermal degradation giving cavities in the composites containing 45S5 and S53P4, while good adhesion of S68 to the polymer was observed. The cavities partly affected the in vitro reactivity of the composites. The degradation of the composites containing the bioactive glasses was faster in phosphate buffered saline than in the two other solutions. Hydroxyapatite precipitation suggesting bone tissue bonding capability was observed on these two composites in all three solutions. The slower dissolution of S68 glass particles and the limited hydroxyapatite precipitation suggested that this glass has potential as a reinforcing composition with the capability to guide bone tissue growth in biodegradable polymer composites.

Heat resistance of Alicyclobacillus acidocaldarius in water, various buffers, and orange juice.

PubMed

Palop, A; Alvarez, I; Raso, J; Condón, S

2000-10-01

The effect of the pH or the composition of the heating medium and of the sporulation temperature on the heat resistance of spores of a thermoacidophilic spore-forming microorganism isolated from a dairy beverage containing orange fruit concentrate was investigated. The species was identified as Alicyclobacillus acidocaldarius. The spores showed the same heat resistance in citrate-phosphate buffers of pH 4 and 7, in distilled water, and in orange juice at any of the temperatures tested (D120 degrees C = 0.1 min and z = 7 degrees C). A raise in 20 degrees C in the sporulation temperature (from 45 to 65 degrees C) increased the heat resistance eightfold (from D110 degrees C = 0.48 min when sporulated at 45 degrees C to 3.9 min when sporulated at 65 degrees C). The z-values remained constant for all sporulation temperatures. The spores of this strain of A. acidocaldarius were very heat resistant and could easily survive any heat treatment currently applied to pasteurize fruit juices.

Enantioseparation of dopa and related compounds by cyclodextrin-modified microemulsion electrokinetic chromatography.

PubMed

Borst, Claudia; Holzgrabe, Ulrike

2008-09-19

A chiral microemulsion electrokinetic chromatography method has been developed for the enantiomeric separation of 3,4-dihydroxyphenylalanine (dopa), its precursors phenylalanine and tyrosine, and the structurally related substance methyldopa. The separations were achieved using an oil-in-water microemulsion, which consisted of the oil-compound ethyl acetate, the surfactant sodium dodecylsulfate (SDS), the co-surfactant 1-butanol, the organic modifier propan-2-ol and 20mM phosphate buffer pH 2.5 or 2.0 as aqueous phase. For enantioseparation sulfated beta-cyclodextrin was added. The resolution of each racemate was optimized by varying the concentration of the buffer and all components of the microemulsion. Enantioseparation could be achieved for dl-dopa, dl-phenylalanine and dl-tyrosine within 13 min with a resolution of 4.3, 3.1 and 3.3, respectively, and for methyldopa in 17 min (Rs: 1.4). The established methods allowed the detection of dopa, phenylalanine, tyrosine and methyldopa with a limit at 0.5, 1.0, 0.2 and 2.0 microg/ml.

Toposelective electrochemical desorption of thiol SAMs from neighboring polycrystalline gold surfaces.

PubMed

Tencer, Michal; Berini, Pierre

2008-11-04

We describe a method for the selective desorption of thiol self-assembled monolayers from gold surfaces having micrometer-scale separations on a substrate. In an electrolyte solution, the electrical resistance between the adjacent areas can be much lower than the resistance between a surface and the counter electrode. Also, both reductive and oxidative thiol desorption may occur. Therefore, the potentials of the surfaces must be independently controlled with a multichannel potentiostat and operating windows for a given thiol/electrolyte system must be established. In this study operating windows were established for 1-dodecanethiol-based SAMs in phosphate buffer, phosphate-buffered saline, and sodium hydroxide solution, and selective SAM removal was successfully performed in a four-electrode configuration.

Basal buffer systems for a newly glycosylated recombinant human interferon-β with biophysical stability and DoE approaches.

PubMed

Kim, Nam Ah; Song, Kyoung; Lim, Dae Gon; Hada, Shavron; Shin, Young Kee; Shin, Sangmun; Jeong, Seong Hoon

2015-10-12

The purpose of this study was to develop a basal buffer system for a biobetter version of recombinant human interferon-β 1a (rhIFN-β 1a), termed R27T, to optimize its biophysical stability. The protein was pre-screened in solution as a function of pH (2-11) using differential scanning calorimetry (DSC) and dynamic light scattering (DLS). According to the result, its experimental pI and optimal pH range were 5.8 and 3.6-4.4, respectively. Design of experiment (DoE) approach was developed as a practical tool to aid formulation studies as a function of pH (2.9-5.7), buffer (phosphate, acetate, citrate, and histidine), and buffer concentration (20 mM and 50 mM). This method employed a weight-based procedure to interpret complex data sets and to investigate critical key factors representing protein stability. The factors used were Tm, enthalpy, and relative helix contents which were obtained by DSC and Fourier Transform Infrared spectroscopy (FT-IR). Although the weights changed by three responses, objective functions from a set of experimental designs based on four buffers were highest in 20 mM acetate buffer at pH 3.6 among all 19 scenarios tested. Size exclusion chromatography (SEC) was adopted to investigate accelerated storage stability in order to optimize the pH value with susceptible stability since the low pH was not patient-compliant. Interestingly, relative helix contents and storage stability (monomer remaining) increased with pH and was the highest at pH 4.0. On the other hand, relative helix contents and thermodynamic stability decreased at pH 4.2 and 4.4, suggesting protein aggregation issues. Therefore, the optimized basal buffer system for the novel biobetter was proposed to be 20 mM acetate buffer at pH 3.8±0.2. Copyright © 2015 Elsevier B.V. All rights reserved.

Fluorophotometric measurement of the buffering action of human tears in vivo.

PubMed

Yamada, M; Kawai, M; Mochizuki, H; Hata, Y; Mashima, Y

1998-10-01

The buffering action of human tears is thought to be important to keep its pH constant. We measured the change in pH in the precorneal tear film in vivo when the acidic solution is challenged, using a fluorophotometric technique. Twelve eyes from 6 healthy subjects were entered in this study. Each subject was pretreated with either one drop of 0.4% oxybuprocaine for once (light anesthesia), three times (deep anesthesia), or none (controls). The measurement was initiated by instilling 20 microl of 0.067 M phosphate buffer at pH 5.5 containing 2 mM bis-carboxyethyl-carboxyfluorescein free acid, a pH sensitive dye, into the subject's eye. The pH was determined by the ratio of fluorescent intensities at two excitation wavelengths (490 and 430 nm). pH recovery time (PHRT) as defined by the time required for pH to reach 95% of pH at equilibrium was used for the marker of tear buffering action. Tear turnover rate was also determined using the fluorescent decay curve at 430 nm, which was independent of pH, but dependent on dye concentration. Immediately after the instillation, the pH value in the tear film was around 6.0-6.5 in all cases. The tear film rapidly became more alkaline, reaching its normal value in 2.3 +/- 0.5 min in untreated eyes. The pretreatment with 0.4% oxybuprocaine retarded the neutralization process. A single regression analysis revealed that the PHRT had a significant negative correlation with the tear turnover rate (r = -0.78). Our results suggest that the neutralization process of tears largely depends on the tear turnover rate. The buffering action of tears in vivo consists of the tear turnover as well as its chemical buffering capacity.

Growth of calcium phosphates on magnesium substrates for corrosion control in biomedical applications via immersion techniques.

PubMed

Shadanbaz, Shaylin; Walker, Jemimah; Staiger, Mark P; Dias, George J; Pietak, Alexis

2013-01-01

Magnesium (Mg) has been suggested as a revolutionary biodegradable replacement for current permanent metals used in orthopedic applications. Current investigations concentrate on the control of the corrosion rate to match bone healing. Calcium phosphate coatings have been a recent focus of these investigations through various coating protocols. Within this investigation, an in situ crystallization technique was utilized as an inexpensive and relatively simple method to produce a brushite and monetite coating on pure Mg. Coatings were characterized using energy dispersive spectroscopy, glancing angle X-ray diffraction and field emission scanning electron microscopy. Corrosion protection properties of the coatings were assessed in physiological buffers, Earles balanced salt solution, minimum essential media, and minimum essential media containing serum albumin, over a 4-week period. Using this novel coating protocol, our findings indicate brushite and monetite coated Mg to have significant corrosive protective effects when compared with its uncoated counterpart whilst maintaining high coating substrate adhesion, homogeneity, and reproducibility. Copyright © 2012 Wiley Periodicals, Inc.

Buffer-free therapeutic antibody preparations provide a viable alternative to conventionally buffered solutions: from protein buffer capacity prediction to bioprocess applications.

PubMed

Bahrenburg, Sven; Karow, Anne R; Garidel, Patrick

2015-04-01

Protein therapeutics, including monoclonal antibodies (mAbs), have significant buffering capacity, particularly at concentrations>50 mg/mL. This report addresses pH-related issues critical to adoption of self-buffered monoclonal antibody formulations. We evaluated solution conditions with protein concentrations ranging from 50 to 250 mg/mL. Samples were both buffer-free and conventionally buffered with citrate. Samples were non-isotonic or adjusted for isotonicity with NaCl or trehalose. Studies included accelerated temperature stability tests, shaking stability studies, and pH changes in infusion media as protein concentrate is added. We present averaged buffering slopes of capacity that can be applied to any mAb and present a general method for calculating buffering capacity of buffer-free, highly concentrated antibody liquid formulations. In temperature stability tests, neither buffer-free nor conventionally buffered solution conditions showed significant pH changes. Conventionally buffered solutions showed significantly higher opalescence than buffer-free ones. In general, buffer-free solution conditions showed less aggregation than conventionally buffered solutions. Shaking stability tests showed no differences between buffer-free and conventionally buffered solutions. "In-use" preparation experiments showed that pH in infusion bag medium can rapidly approximate that of self-buffered protein concentrate as concentrate is added. In summary, the buffer capacity of proteins can be predicted and buffer-free therapeutic antibody preparations provide a viable alternative to conventionally buffered solutions. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Degradation of diethyl phthalate (DEP) by UV/persulfate: An experiment and simulation study of contributions by hydroxyl and sulfate radicals.

PubMed

Wang, Ziying; Shao, Yisheng; Gao, Naiyun; Lu, Xian; An, Na

2018-02-01

Degradation of diethyl phthalate (DEP) by ultraviolet/persulfate (UV/PS) process at different reaction conditions was evaluated. DEP can be degraded effectively via this process. Both tert-butyl (TBA) and methanol (MeOH) inhibited the degradation of DEP with MeOH having a stronger impact than TBA, suggesting sulfate radical () and hydroxyl radical (HO) both existed in the reaction systems studied. The second-order rate constants of DEP reacting with and HO were calculated to be (6.4±0.3)×10 7 M -1 s -1 and (3.7±0.1)×10 9 M -1 s -1 , respectively. To further access the potential degradation mechanism in this system, the pseudo-first-order rate constants (k o ) and the radical contributions were modeled using a simple steady-state kinetic model involving and HO. Generally, HO had a greater contribution to DEP degradation than . The k o of DEP increased as PS dosages increased when PS dosages were below 1.9 mM. However, it decreased with increasing initial DEP concentrations, which might be due to the radical scavenging effect of DEP. The k o values in acidic conditions were higher than those in alkaline solutions, which was probably caused by the increasing concentration of hydrogen phosphate (with higher scavenging effects than dihydrogen phosphate) from the phosphate buffer as pH values rose. Natural organic matter and bicarbonate dramatically suppressed the degradation of DEP by scavenging and HO. Additionally, the presence of chloride ion (Cl - ) promoted the degradation of DEP at low Cl - concentrations (0.25-1 mM). Finally, the proposed degradation pathways were illustrated. Copyright © 2017 Elsevier Ltd. All rights reserved.

Adsorption of Hydrophobin-Protein Mixtures at the Air-Water Interface: The Impact of pH and Electrolyte.

PubMed

Tucker, Ian M; Petkov, Jordan T; Penfold, Jeffrey; Thomas, Robert K; Cox, Andrew R; Hedges, Nick

2015-09-15

The adsorption of the proteins β-casein, β-lactoglobulin, and hydrophobin, and the protein mixtures of β-casein/hydrophobin and β-lactoglobulin/hydrophobin have been studied at the air-water interface by neutron reflectivity, NR. Changing the solution pH from 7 to 2.6 has relatively little impact on the adsorption of hydrophobin or β-lactoglobulin, but results in a substantial change in the structure of the adsorbed layer of β-casein. In β-lactoglobulin/hydrophobin mixtures, the adsorption is dominated by the hydrophobin adsorption, and is independent of the hydrophobin or β-lactoglobulin concentration and solution pH. At pH 2.6, the adsorption of the β-casein/hydrophobin mixtures is dominated by the hydrophobin adsorption over the range of β-casein concentrations studied. At pH 4 and 7, the adsorption of β-casein/hydrophobin mixtures is dominated by the hydrophobin adsorption at low β-casein concentrations. At higher β-casein concentrations, β-casein is adsorbed onto the surface monolayer of hydrophobin, and some interpenetration between the two proteins occurs. These results illustrate the importance of pH on the intermolecular interactions between the two proteins at the interface. This is further confirmed by the impact of PBS, phosphate buffered saline, buffer and CaCl2 on the coadsorption and surface structure. The results provide an important insight into the adsorption properties of protein mixtures and their application in foam and emulsion stabilization.

Inhibition of DNA synthesis in cultured lymphocytes and tumor cells by extracts of betel nut, tobacco, and miang leaf, plant substances associated with cancer of the ororespiratory epithelium.

PubMed

Yang, J A; Huber, S A; Lucas, Z J

1979-12-01

The high incidence of oropharyngeal, esophageal, and laryngeal cancers in certain parts of the world has been ascribed to conjugated tannins found in certain folk medicinal herbs. We extracted miang leaf and betel nut with phosphate-buffered saline (0.14 M NaCl, 0.15 M potassium phosphate buffer, pH 7.4) and found that the extracts inhibited [3H]thymidine incorporation by phytohemagglutinin-stimulated human lymphocytes and by rat mammary tumor and mouse L-cells in logarithmic growth. Pretreating the lymphocytes for 1 or 4 hr with the extracts inhibited phytohemagglutinin-induced thymidine incorporation 72 hr later. At concentrations of 2.5 volumes % or lower, miang and betel nut extracts inhibited thymidine incorporation by 40 to 98% without any apparent signs of toxicity as demonstrated by the 66Rb equilibrium assay. In addition, neither extract inhibited cytotoxicity of rat mammary tumor cells by immune syngeneic spleen cells. The molecular weights of the inhibitory factors were between 1,000 and 10,000 daltons as determined by ultrafiltration and were unaffected by boiling for 3 min or by treatment with alcohol and, therefore, are probably not proteins. This in vitro demonstration of inhibition of DNA synthesis by these plant extracts presumably enriched for conjugated tannins may relate to inhibition of growth of rats and chicks fed conjugated tanin-contaminated sorghum feed. The carcinogenic potential of either these extracts or conjugated tannins is not yet established.

Antibacterial Effects of Toothpastes Evaluated in an 
In Vitro Biofilm Model.

PubMed

Fernández, Eva; Sánchez, María Del Carmen; Llama-Palacios, Arancha; Sanz, Mariano; Herrera, David

To test the antibacterial effects of different toothpastes with the slurry method of toothpaste application in an in vitro oral biofilm model including relevant periodontal pathogens. Four commercially available toothpastes, two containing sodium fluoride (NaF) at different concentrations (1450 and 2500 ppm), two NaF with either triclosan or stannous fluoride, and a control phosphate-buffered saline (PBS) were used. Multispecies biofilms containing 6 species of oral bacteria were grown on hydroxyapatite disks for 72 h and then exposed for 2 min to the toothpaste slurries or phosphate buffer saline (PBS) by immersion, under continuous agitation at 37°C. Biofilms were then analysed by means of real-time polymerase chain reaction (PCR), combined with propidium monoazide (PMA). Statistical evaluation was performed using ANOVA and Student's t-test, with Bonferroni correction for multiple comparisons. The toothpastes containing NaF and stannous fluoride demonstrated superior antimicrobial activity for A. actinomycetencomitans, P. gingivalis and F. nucleatum when compared to those containing NaF and triclosan, 1450 ppm NaF or 2500 ppm NaF in this multispecies biofilm model. The proposed model for the evaluation of toothpastes in the form of slurries detected significant differences in the antimicrobial effects among the tested NaF-containing toothpastes, with the stannous fluoride-based formulation achieving better results than the other formulations. The use of toothpaste as slurries and real-time PCR with PMA is an adequate method for comparing the in vitro antimicrobial effect of different toothpastes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winterbourn, C.C.; Sutton, H.C.

O2- was produced by gamma irradiation of formate solutions, by the action of xanthine oxidase on hypoxanthine and O2, and by the action of ferredoxin reductase on NADPH and paraquat in the presence of O2. Its reaction with H2O2 and various iron chelates was studied. Oxidation of deoxyribose to thiobarbituric acid-reactive products that was appropriately inhibited by OH. scavengers, or formate oxidation to CO2, was used to detect OH(.). With each source of O2-, and by these criteria, Fe(EDTA) efficiently catalyzed this (Haber-Weiss) reaction, but little catalysis was detectable with iron bound to DTPA, citrate, ADP, ATP, or pyrophosphate, ormore » without chelator in phosphate buffer. O2- produced from xanthine oxidase, but not from the other sources, underwent another iron-dependent reaction with H2O2, to produce an oxidant that did not behave as free OH(.). It was formed in phosphate or bicarbonate buffer, and caused deoxyribose oxidation that was readily inhibited by mannitol or Tris, but not by benzoate, formate, or dimethyl sulfoxide. It did not oxidize formate to CO2. Addition of EDTA changed the pattern of inhibition to that expected for a reaction of OH(.). The other chelators all inhibited deoxyribose oxidation, provided their concentrations were high enough. The results are compatible with iron bound to xanthine oxidase catalyzing production of a strong oxidant (which is not free OH.) from H2O2 and O2- produced by the enzyme.« less

The characterisation and design improvement of a paper-based E.coli impedimetric sensor

NASA Astrophysics Data System (ADS)

Bezuidenhout, P.; Kumar, S.; Wiederoder, M.; Schoeman, J.; Land, K.; Joubert, T.-H.

2016-02-01

This paper describes the development and optimisation of a paper-based E. coli impedimetric biosensor for water quality monitoring. Impedimetric biosensing is advantageous because it is a highly sensitive, label-free, real-time method for the detection of biological species. An impedimetric biosensor measures the change in impedance caused by specific capture of a target on the sensor surface. Each biosensor consists of a pair of photo paper-based inkjet printed electrodes. An impedance analyser was used to measure the impedance at frequencies ranging from 1 kHz to 1 MHz at 1V. The parameters that were investigated to achieve enhanced sensor performance were buffer type, antibody attachment method, measurement frequency, electrode layout, and conductive material. A 0.04M PBS (phosphate buffered saline) solution achieves better results compared to a less conductive 0.04M PB (potassium phosphate dibasic) solution. The direct adsorption of anti-E. coli antibodies onto the sensor surface yielded better results than attaching the sensor to a lateral flow test. The resistive component had a greater impact on the detected impedance, therefore an optimal frequency of 1 MHz was identified. Geometrical electrode designs that maximise the resistive change between the electrodes were utilised. Both lower cost silver and bio-compatible gold ink were validated as electrode materials. The impedance change generated by the selective capture of E. coli K-12, ranging in concentration from 103 to 107 colony forming units per millilitre (cfu/ml), showed a detection limit of 105 cfu/ml.

Layer by layer assembled films between hemoglobin and multiwall carbon nanotubes for pH-switchable biosensing.

PubMed

Pan, Zhongqin; Liu, Xiaojun; Xie, Jing; Bao, Ning; He, Hong; Li, Xiaodong; Zeng, Jiang; Gu, Haiying

2015-05-01

Although pH-switchable behaviors have been reported based on multilayer films modified electrodes, their pH-switchable biosensing is still difficult due to the existence of the electroactive mediator. In this study, we report the pH-dependable determination of hydrogen peroxide (H2O2) based on a four-bilayer film fabricated through layer by layer assembly between hemoglobin (Hb) and multiwall carbon nanotubes (MWCNTs). We observed that response of electroactive probe Fe(CN)6(3-) at the multilayer films was very sensitive and reversible to pH values of phosphate buffer solutions phosphate buffer solution with cyclic voltammetry. The reduction peak height of Fe(CN)6(3-) at the multilayer film could reach ∼221μA at pH 3.0 while 0μA at pH 9.0. The linear range for the detection of H2O2 at pH 3.0 was from 12.5μM to 10.4mM, which was much wider than that at pH 9.0. Our results demonstrated that the detection of H2O2 with the proposed modified electrode is dependent on pH values of phosphate buffer solution. Moreover, the component of multilayer films has impacts on the performance of biosensors with pH-switchable behaviors. Copyright © 2015 Elsevier B.V. All rights reserved.

Influence of Temperature on the Colloidal Stability of Polymer-Coated Gold Nanoparticles in Cell Culture Media.

PubMed

Zyuzin, Mikhail V; Honold, Tobias; Carregal-Romero, Susana; Kantner, Karsten; Karg, Matthias; Parak, Wolfgang J

2016-04-06

The temperature-dependence of the hydrodynamic diameter and colloidal stability of gold-polymer core-shell particles with temperature-sensitive (poly(N-isopropylacrylamide)) and temperature-insensitive shells (polyallylaminine hydrochloride/polystyrensulfonate, poly(isobutylene-alt-maleic anhydride)-graft-dodecyl) are investigated in various aqueous media. The data demonstrate that for all nanoparticle agglomeration, i.e., increase in effective nanoparticle size, the presence of salts or proteins in the dispersion media has to be taken into account. Poly(N-isopropylacrylamide) coated nanoparticles show a reversible temperature-dependent increase in size above the volume phase transition of the polymer shell when they are dispersed in phosphate buffered saline or in media containing protein. In contrast, the nanoparticles coated with temperature-insensitive polymers show a time-dependent increase in size in phosphate buffered saline or in medium containing protein. This is due to time-dependent agglomeration, which is particularly strong in phosphate buffered saline, and induces a time-dependent, irreversible increase in the hydrodynamic diameter of the nanoparticles. This demonstrates that one has to distinguish between temperature- and time-induced agglomerations. Since the size of nanoparticles regulates their uptake by cells, temperature-dependent uptake of thermosensitive and non-thermosensitive nanoparticles by cells lines is compared. No temperature-specific difference between both types of nanoparticles could be observed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A calorimetric investigation of the interaction of the lac repressor with inducer.

PubMed

Donnér, J; Caruthers, M H; Gill, S J

1982-12-25

A calorimetric study has been made of the interaction between the lac repressor and isopropyl-1-thio-beta-D-galactopyranoside (IPTG). The buffer-corrected enthalpy of reaction at 25 degrees C was found to be -15.6, -24.7, -4.6 kJ/mol of bound IPTG at pH 7.0, pH 8.1, and pH 9.0, respectively. This large range of enthalpy values is in contrast to a maximum difference in the free energy of the reaction of only 1.5 kJ/mol of bound IPTG between these pH values. The reaction was found by calorimetric measurements in different buffers to be accompanied by an uptake of 0.29 mol of protons/mol of bound IPTG at pH 8.1. The pH dependency of the reaction enthalpy suggests differences in the extent of protonation of the binding site and the involvement of H bonding with IPTG. The lack of strong hydrophobic contributions in the IPTG binding process is revealed by the absence of any determinable heat capacity change for the reaction at pH 7.0. The presence of phosphate buffer significantly alters the enthalpy of IPTG binding at higher pH values, but has little effect upon the binding constant. This implies that highly negative phosphate species change the nature of the IPTG binding site without any displacement of phosphate upon IPTG binding.

Mode changes associated with oil droplet movement in solutions of gemini cationic surfactants.

PubMed

Banno, Taisuke; Miura, Shingo; Kuroha, Rie; Toyota, Taro

2013-06-25

Micrometer-sized self-propelled oil droplets in nonequilibrium systems have attracted much attention, since they form stable emulsions composed of oil, water, and surfactant which represent a primitive type of inanimate chemical machinery. In this work, we examined means of controlling the movement of oil droplets by studying the dynamics of n-heptyloxybenzaldehyde droplets in phosphate buffers containing alkanediyl-α,ω-bis(N-dodecyl-N,N-dimethylammonium bromide) (nG12) with either tetramethylene (4G12), octaethylene (8G12), or dodecamethylene (12G12) chains in the linker moiety. Significant differences in droplet dynamics were observed to be induced by changes in the linker structure of these gemini cationic surfactants. In a phosphate buffer containing 30 mM 4G12, self-propelled motion of droplets concurrent with the formation of molecular aggregates on their surfaces was observed, whereas the fusion of oil droplets was evident in both 8G12 and 12G12 solutions. We also determined that the surface activities and the extent of molecular self-assembly of the surfactants in phosphate buffer were strongly influenced by the alkyl chain length in the linker moiety. We therefore conclude that the surface activities of the gemini cationic surfactant have important effects on the oil-water interfacial tension of oil droplets and the formation of molecular aggregates and that both of these factors induce the unique movement of the droplets.

Improved Yield of High Molecular Weight DNA Coincides with Increased Microbial Diversity Access from Iron Oxide Cemented Sub-Surface Clay Environments

PubMed Central

Hurt, Richard A.; Robeson, Michael S.; Shakya, Migun; Moberly, James G.; Vishnivetskaya, Tatiana A.; Gu, Baohua; Elias, Dwayne A.

2014-01-01

Despite over three decades of progress, extraction of high molecular weight (HMW) DNA from high clay soils or iron oxide cemented clay has remained challenging. HMW DNA is desirable for next generation sequencing as it yields the most comprehensive coverage. Several DNA extraction procedures were compared from samples that exhibit strong nucleic acid adsorption. pH manipulation or use of alternative ion solutions offered no improvement in nucleic acid recovery. Lysis by liquid N2 grinding in concentrated guanidine followed by concentrated sodium phosphate extraction supported HMW DNA recovery from clays high in iron oxides. DNA recovered using 1 M sodium phosphate buffer (PB) as a competitive desorptive wash was 15.22±2.33 µg DNA/g clay, with most DNA consisting of >20 Kb fragments, compared to 2.46±0.25 µg DNA/g clay with the Powerlyzer system (MoBio). Increasing PB concentration in the lysis reagent coincided with increasing DNA fragment length during initial extraction. Rarefaction plots of 16S rRNA (V1–V3 region) pyrosequencing from A-horizon and clay soils showed an ∼80% and ∼400% larger accessed diversity compared to the Powerlyzer soil DNA system, respectively. The observed diversity from the Firmicutes showed the strongest increase with >3-fold more operational taxonomic units (OTU) recovered. PMID:25033199

Biosensing of DNA oxidative damage: a model of using glucose meter for non-glucose biomarker detection.

PubMed

Zhu, Xuena; Sarwar, Mehenur; Yue, Qiaoli; Chen, Chunying; Li, Chen-Zhong

2017-01-01

Non-glucose biomarker-DNA oxidative damage biomarker 8-hydroxy-2'-deoxyguanosine (8-OHdG) has been successfully detected using a smartphone-enabled glucose meter. Through a series of immune reactions and enzymatic reactions on a solid lateral flow platform, 8-OHdG concentration has been converted to a relative amount of glucose, and therefore can be detected by conventional glucose meter directly. The device was able to detect 8-OHdG concentrations in phosphate buffer saline as low as 1.73 ng mL -1 with a dynamic range of 1-200 ng mL -1 . Considering the inherent advantages of the personal glucose meter, the demonstration of this device, therefore, should provide new opportunities for the monitoring of a wide range of biomarkers and various target analytes in connection with different molecular recognition events.

Evaluation of ocular and general safety following repeated dosing of dexamethasone phosphate delivered by transscleral iontophoresis in rabbits.

PubMed

Patane, Michael A; Schubert, William; Sanford, Thomas; Gee, Raymond; Burgos, Melissa; Isom, William P; Ruiz-Perez, Begona

2013-10-01

To evaluate the toxicokinetics and tolerability (local ocular and general toxicity) of the anti-inflammatory agent, dexamethasone phosphate (a prodrug of dexamethasone) delivered to the eye in rabbits by transscleral iontophoresis. Female rabbits (n=6/group) received dexamethasone phosphate (40 mg/mL ophthalmic solution, EGP-437) transsclerally to the right eye (OD) using the Eyegate(®) II ocular iontophoresis delivery system once biweekly for 24 consecutive weeks at current doses of 10, 14, and 20 mA-min and current levels up to, and including -4 mA for 3.5-5 min. The study included 2 control groups (n=6/group): (1) a noniontophoresis control [an ocular applicator-loaded citrate buffer (placebo) without current] and (2) an iontophoresis control (a citrate buffer plus cathode iontophoresis at 20 mA-min, -4 mA for 5 min). Recoverability was evaluated 4 weeks following the last dose in 2 animals per group. The left eye (OS) was untreated and served as an internal control for each animal. Ocular and general safety of dexamethasone phosphate and dexamethasone were assessed. Other evaluations included toxicokinetics, ophthalmic examinations, intraocular pressure (IOP) measurements, electroretinographs, clinical observations, body weight, hematology and serum chemistry, gross necropsy, organ weight, and microscopic histopathology. The biweekly transscleral iontophoresis with either the citrate buffer or dexamethasone phosphate at cathodic doses up to, and including 20 mA-min and currents up to, and including -4 mA for 24 weeks was well-tolerated. Transient signs of conjunctival hyperemia and chemosis, mild corneal opacity, and fluorescein staining of the cornea were noted and attributed to expected ocular reactions to the temporary placement of the ocular applicator and application of iontophoresis. There were no dexamethasone phosphate-, dexamethasone-, or iontophoresis-related effects on IOP, electroretinography, or histopathology. Reductions in body weight gain, anemia, decreased leukocyte and lymphocyte counts, compromised liver function, enlarged liver, and reduced spleen weight were consistent with systemic corticosteroid-mediated pharmacology, repeated use of anesthesia, stress, and sedentariness, and unlikely to be related to iontophoresis application. The results of this investigation suggest that repeated transscleral iontophoresis with dexamethasone phosphate may be safe for use as a treatment for inflammatory ocular disorders that require prolonged and/or repeated corticosteroid therapy.

Corneal epithelial cell biocompatibility to silicone hydrogel and conventional hydrogel contact lens packaging solutions

PubMed Central

Tanti, N.C.; Jones, L.; Sheardown, H.

2010-01-01

Purpose Although all contact lenses (CLs) are applied initially to the eye directly from a packaging solution, little is known about the effects of these solutions on human corneal epithelial cells (HCECs). Due to the porous nature of CL materials, they have the potential to sorb components of the packaging solution during storage, which could then be subsequently released upon insertion of the CL on the eye. The purpose of this study was to investigate the effect of various packaging solutions on HCECs, using an in vitro model. Methods An in vitro assay was developed whereby various silicone hydrogels and conventional, poly-2-hydroxyethylmethacrylate  (polyHEMA)-based lens materials were removed directly from their packaging and then incubated for up to 24 h with HCECs. The effect of the retained and released packaging solution components on HCECs was assessed by measuring cell viability, adhesion phenotype, and apoptosis. Results Incubation of HCECs with CLs stored in borate-buffered packaging solutions resulted in a significant reduction in cell viability. Adherent cells incubated with these CLs also exhibited reduced levels of β1 and α3 integrin. Soaking borate-buffered packaged CLs in PBS before cell incubation resolved viability and integrin expression in all cases, with the exception of galyfilcon A and balafilcon A, from which a 20% reduction in cell viability was still observed. In comparison, CLs stored in phosphate-buffered packaging solutions had cellular viability and expression of integrins similar to control cells (cells incubated in the absence of a lens). When incubated with cells at a 10% concentration in serum-free medium, borate-buffered packaging solutions and borate-containing saline (Unisol 4) significantly reduced cell viability and integrin expression. Neither caspase activation nor annexin V binding was observed on cells following exposure to borate buffer solution. However, a significant decrease in reactive oxygen species was observed at 24 h. These latter results suggest that in vitro exposure to low concentration of borate/boric acid results in cell dysfunction, leading to necrosis rather than apoptosis. Conclusions Borate-buffered packaging solutions were shown to adversely affect the viability and integrin expression of HCECs in vitro. When used in ophthalmic packaging solutions, the antimicrobial properties of borate buffer may be outweighed by its relatively cytotoxic effects on cells. PMID:20169012

Corneal epithelial cell biocompatibility to silicone hydrogel and conventional hydrogel contact lens packaging solutions.

PubMed

Gorbet, M B; Tanti, N C; Jones, L; Sheardown, H

2010-02-19

Although all contact lenses (CLs) are applied initially to the eye directly from a packaging solution, little is known about the effects of these solutions on human corneal epithelial cells (HCECs). Due to the porous nature of CL materials, they have the potential to sorb components of the packaging solution during storage, which could then be subsequently released upon insertion of the CL on the eye. The purpose of this study was to investigate the effect of various packaging solutions on HCECs, using an in vitro model. An in vitro assay was developed whereby various silicone hydrogels and conventional, poly-2-hydroxyethylmethacrylate (polyHEMA)-based lens materials were removed directly from their packaging and then incubated for up to 24 h with HCECs. The effect of the retained and released packaging solution components on HCECs was assessed by measuring cell viability, adhesion phenotype, and apoptosis. Incubation of HCECs with CLs stored in borate-buffered packaging solutions resulted in a significant reduction in cell viability. Adherent cells incubated with these CLs also exhibited reduced levels of beta(1) and alpha(3) integrin. Soaking borate-buffered packaged CLs in PBS before cell incubation resolved viability and integrin expression in all cases, with the exception of galyfilcon A and balafilcon A, from which a 20% reduction in cell viability was still observed. In comparison, CLs stored in phosphate-buffered packaging solutions had cellular viability and expression of integrins similar to control cells (cells incubated in the absence of a lens). When incubated with cells at a 10% concentration in serum-free medium, borate-buffered packaging solutions and borate-containing saline (Unisol 4) significantly reduced cell viability and integrin expression. Neither caspase activation nor annexin V binding was observed on cells following exposure to borate buffer solution. However, a significant decrease in reactive oxygen species was observed at 24 h. These latter results suggest that in vitro exposure to low concentration of borate/boric acid results in cell dysfunction, leading to necrosis rather than apoptosis. Borate-buffered packaging solutions were shown to adversely affect the viability and integrin expression of HCECs in vitro. When used in ophthalmic packaging solutions, the antimicrobial properties of borate buffer may be outweighed by its relatively cytotoxic effects on cells.

Bioactive calcium phosphate-based glasses and ceramics and their biomedical applications: A review.

PubMed

Islam, Md Towhidul; Felfel, Reda M; Abou Neel, Ensanya A; Grant, David M; Ahmed, Ifty; Hossain, Kazi M Zakir

2017-01-01

An overview of the formation of calcium phosphate under in vitro environment on the surface of a range of bioactive materials (e.g. from silicate, borate, and phosphate glasses, glass-ceramics, bioceramics to metals) based on recent literature is presented in this review. The mechanism of bone-like calcium phosphate (i.e. hydroxyapatite) formation and the test protocols that are either already in use or currently being investigated for the evaluation of the bioactivity of biomaterials are discussed. This review also highlights the effect of chemical composition and surface charge of materials, types of medium (e.g. simulated body fluid, phosphate-buffered saline and cell culture medium) and test parameters on their bioactivity performance. Finally, a brief summary of the biomedical applications of these newly formed calcium phosphate (either in the form of amorphous or apatite) is presented.

Comparative studies in electrochemical degradation of sulfamethoxazole and diclofenac in water by using various electrodes and phosphate and sulfate supporting electrolytes.

PubMed

Sifuna, Fred W; Orata, Francis; Okello, Veronica; Jemutai-Kimosop, Selly

2016-09-18

In this study, the electro-oxidation capacities of Na2SO4 and potassium phosphate buffer supporting electrolytes were tested and compared for destruction of the sulfamethoxazole (SMX) and diclofenac (DCF) on platinum (Pt) electrode and graphite carbon electrode in aqueous medium. The suitability of pharmaceutical active compounds (PhACs) for electrochemical oxidation was tested by cyclic voltammetry (CV) technique performed in the potential range -1.5 to +1.5 V versus Ag/AgCl, which confirmed the electro-activity of the selected PhACs. The degradation and mineralization were monitored by ultraviolet (UV)-Vis spectrophotometry and HPLC. 0.1 M Na2SO4 supporting electrolyte was found to be more effective for mineralization of SMX and DCF, with efficiency of 15-30% more than the 0.1 M phosphate buffer supporting electrolyte on the platinum (Pt) and carbon electrodes. The Pt electrode showed better performance in the degradation of the two PhACs while under the same conditions than the carbon electrode for both 0.1 M Na2SO4 and 0.1 M potassium phosphate buffer supporting electrolytes. The SMX and DCF degradation kinetics best fitted the second-order reaction, with rate constants ranging between 0.000389 and 0.006 mol(2) L(-2) min(-1) and correlation coefficient (R(2)) above 0.987. The second-order degradation kinetics indicated that the rate-determining step in the degradation could be a chemical process, thus suggesting the active involvement of electrolyte radical species in the degradation of SMX and DCF. Results obtained from a real field sample showed a more than 98% removal of the PhACs from the wastewater by electrochemical degradation.

The effect of reaction conditions on formation of wet precipitated calcium phosphates

NASA Astrophysics Data System (ADS)

Huang, Chen; Cao, Peng

2015-03-01

The precipitation process discussed in the present study involves the addition of alkaline solutions to an acidic calcium phosphate suspension. Several parameters (pH, pH buffer reagent, ageing and stirring) were investigated. The synthesized powders were calcined at 1000°C for 1 h in air, in order to study the thermal stability and crystalline phase compositions. X-ray diffraction (XRD) and ESEM analysis were used for sample characterization. It is found that all these processing parameters affect the crystalline phases evolved and resultant microstructures. Phase evolution occurred at an elevated pH level. The pH buffer reagent would affect both the phase composition and microstructure. Ageing was essential for the phase maturation. Stirring accelerated the reaction process by providing a homogeneous medium for precipitation.

Structural characterization and dissolution profile of mycophenolic acid cocrystals.

PubMed

Zeng, Qing-Zhu; Ouyang, Jian; Zhang, Shuo; Zhang, Lei

2017-05-01

Three novel cocrystals of mycophenolic acid (MPA) with isonicotinamide (MPA-ISO), minoxidil (MPA-MIN) and 2,2'-dipyridylamine (MPA-DPA) as coformers have been prepared successfully by both slow evaporation and liquid-assisted grinding. The structures of these cocrystals show that all the three coformers form hydrogen bonds with the carboxylic acid group of MPA. The cocrystal MPA-ISO possesses remarkably improved solubility and dissolution rate, while two other cocrystals exhibit the opposite characteristics. The solids in the slurry with pH6.8 phosphate buffer and cocrystals remain as the incipient cocrystal after 24h. However, evidence of slight polymerization was shown in the slurry of pH6.8 phosphate buffer with MPA and MPA-ISO cocrystal. Copyright © 2017 Elsevier B.V. All rights reserved.

Program on Resorbable Radio Devices

DTIC Science & Technology

2014-05-05

radio circuit - + PDMS Copper Mg PBS Buffer 1© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com Transient, Biocompatible...way, ZnO provides an alternative to silicon [ 16 ] or organic semi- conductors [ 17–20 ] for physically transient forms of electronics and sensors...immersion in several different types of solutions, such as phosphate buffer saline (PBS, pH 4.0, Sigma- Figure 1 . Materials and designs for

Assessing the influence of media composition and ionic strength on drug release from commercial immediate-release and enteric-coated aspirin tablets.

PubMed

Karkossa, Frank; Klein, Sandra

2017-10-01

The objective of this test series was to elucidate the importance of selecting the right media composition for a biopredictive in-vitro dissolution screening of enteric-coated dosage forms. Drug release from immediate-release (IR) and enteric-coated (EC) aspirin formulations was assessed in phosphate-based and bicarbonate-based media with different pH, electrolyte composition and ionic strength. Drug release from aspirin IR tablets was unaffected by media composition. In contrast, drug release from EC aspirin formulations was affected by buffer species and ionic strength. In all media, drug release increased with increasing ionic strength, but in bicarbonate-based buffers was delayed when compared with that in phosphate-based buffers. Interestingly, the cation species in the dissolution medium had also a clear impact on drug release. Drug release profiles obtained in Blank CarbSIF, a new medium simulating pH and average ionic composition of small intestinal fluid, were different from those obtained in all other buffer compositions studied. Results from this study in which the impact of various media parameters on drug release of EC aspirin formulations was systematically screened clearly show that when developing predictive dissolution tests, it is important to simulate the ionic composition of intraluminal fluids as closely as possible. © 2017 Royal Pharmaceutical Society.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Streltsov, Victor A.; Titmuss, Stephen J.; Epa, V. Chandana

Neurodegeneration observed in Alzheimer disease (AD) is believed to be related to the toxicity from reactive oxygen species (ROS) produced in the brain by the amyloid-{beta} (A{beta}) protein bound primarily to copper ions. The evidence for an oxidative stress role of A{beta}-Cu redox chemistry is still incomplete. Details of the copper binding site in A{beta} may be critical to the etiology of AD. Here we present the structure determined by combining x-ray absorption spectroscopy (XAS) and density functional theory analysis of A{beta} peptides complexed with Cu{sup 2+} in solution under a range of buffer conditions. Phosphate-buffered saline buffer salt (NaCl)more » concentration does not affect the high-affinity copper binding mode but alters the second coordination sphere. The XAS spectra for truncated and full-length A{beta}-Cu{sup 2+} peptides are similar. The novel distorted six-coordinated (3N3O) geometry around copper in the A{beta}-Cu{sup 2+} complexes include three histidines: glutamic, or/and aspartic acid, and axial water. The structure of the high-affinity Cu{sup 2+} binding site is consistent with the hypothesis that the redox activity of the metal ion bound to A{beta} can lead to the formation of dityrosine-linked dimers found in AD.« less

The effect of EDTA, cations, and various buffers on the morphology of erythrocyte membranes: an electron-microscopic study.

PubMed

Pinteric, L; Manery, J F; Chaudry, I H; Madapallimattam, G

1975-05-01

Membranes of human erythrocytes were prepared by stepwise osmotic hemolysis in Ca2+-free solutions. Examination with the electron microscope after negative staining showed some short, conelike protuberances on the surface of about 20 percent of the ghosts, while 80 percent were round, intact spheres. After Ca2+ treatment, all membranes were round and intact. After exposure to ethylenediaminetetraacetic acid (EDTA) (1.0 mM, pH 7.4), the entire ghost surface was covered with long, thin extrusions called stromalytic forms (about 460 per cell). Their sizes, shapes, and fine structure are described. Exposure to ionic calcium (1.4 times 10-minus 4M) abolished the EDTA-induced stromalytic forms. A second exposure to EDTA reversed this Ca2+ effect. ATP, like EDTA, produced stromalytic forms. EDTA-induced stromalytic forms were also abolished by Zn2+, La3+, and Nd3+ at concentrations of 1-5 times 10-minus 4 M. Mg2+ at 10-minus 2 M was ineffective. Ghosts were prepared by graded lysis in various buffers. Those prepared in phosphate were the most stable and provided consistent EDTA effects and Ca2+ reversal. Ghosts in Tris-HCl showed breakdown unless salt was added. Moderately satisfactory ghosts were also obtained in Hepes-NaOH buffer and salt.

Fundamental and Applied Studies of Polymer Membranes

NASA Astrophysics Data System (ADS)

Imbrogno, Joseph

Four major areas have been studied in this research: 1) synthesizing novel monomers, e.g. chiral monomers, to produce new types of functionalized membranes for the biotechnology and pharmaceutical industries, 2) hydrophobic brush membranes for desalinating brackish water, sea water, and separating organics, 3) fundamental studies of water interactions at surfaces using sum frequency generation (SFG), and 4) discovering new surface chemistries that will control the growth and differentiation of stem cells. We have developed a novel synthesis method in order to increase the breadth of our high throughput screening library. This library was generated using maleimide chemistry to react a common methacrylate linker with a variety of different functions groups (R groups) in order to form new monomers that were grafted from the surface of PES ultrafiltration membranes. From this work, we discovered that the chirality of a membrane can affect performance when separating chiral feed streams. This effect was observed when filtering bovine serum albumin (BSA) and ovalbumin in a high salt phosphate buffered saline (PBS, 150 mM salt). The Phe grafted membranes showed a large difference in performance when filtering BSA with selectivity of 1.13 and 1.00 for (S) and (R) Phe, respectively. However, when filtering ovalbumin, the (S) and (R) modified surfaces showed selectivity of 2.06 and 2.31, respectively. The higher selectivity enantiomer switched for the two different proteins. Permeability when filtering BSA was 3.06 LMH kPa-1 and 4.31 LMH kPa -1 for (S)- and (R)- Phe, respectively, and 2.65 LMH kPa -1 and 2.10 LMH kPa-1 when filtering ovalbumin for (S)- and (R)- Phe, respectively. Additionally, these effects were no longer present when using a low salt phosphate buffer (PB, 10 mM salt). Since, to our knowledge, membrane chirality is not considered in current industrial systems, this discovery could have a large impact on the pharmaceutical and biotechnology industries. We have developed hydrophobic brush membranes that were able to selectively separate valuable organics (isobutanol) from water, while rejecting other undesirable species, such as enzymes, using pervaporation (PV). These membranes (grafted from nanofiltration (NF) support membranes) had a selectivity ˜1.5x higher than the current industrial standard, polydimethylsiloxane (PDMS), with alpha = 10.1 +/- 0.9 for our brush membranes and alpha = 6.7 +/- 0.1 for PDMS membranes. Since the mechanism of pervaporation is based on the solution diffusion (SD) model, these membranes may be used to desalinate water or fractionate gases since they are also based on the SD mechanism. We have discovered that hydrophobic brush membranes are able to reject monovalent salt ions. This type of membrane is analogous to carbon nanotubes (CNTs), which are believed to have extremely high water fluxes through them due to near frictionless flow caused by a lack of hydrogen bonding. Using these brush membranes we were able to achieve 42% monovalent (NaCl) salt rejection of simulated seawater (32,000 ppm salt). These membranes are easier to scale-up than current composite membranes produced using interfacial polymerization. We have been using SFG to study interfacial water on membrane surfaces. We believe that water interactions with the membrane surface and with the feed species, e.g. proteins, play a critical role during the fouling process. Relevant buffers, such as phosphate buffered saline (PBS) and phosphate buffer, contain ions that are known to restructure water at interfaces. Sum frequency generation spectroscopy (SFG) was used to characterize interfacial water structure at poly(ether sulfone) (PES) thin films in the presence of 0.01 M phosphate buffer (low salt) and 0.01 M phosphate buffered saline (high salt). Three model surfaces were studied: unmodified PES, hydrophobic alkane (C18) modified PES, and poly(ethylene glycol) (PEG) modified PES. In the presence of the low salt phosphate buffer (10 mM salt), phosphate anions were excluded from the PEG-modified PES film. This led to a charge separation between the phosphate anions and sodium cations, creating a surface potential which strongly ordered water molecules into the bulk. When using high salt PBS (138 mM salt) the sodium chloride ions screened this charge and reduced water ordering. Interestingly, this effect was the greatest for the PEG modified surface, with minor or no effects observed for the C18 modified PES and unmodified PES, respectively. Using our high throughput screening platform, we were able to determine that (N-[3-(dimethylamino)propyl] methacrylamide), DMAPMA, supported strong attachment and long-term self-renewal of mouse embryonic stem (ES) cells while preventing differentiation (maintaining pluripotency). After developing this platform, it was used to screen for a surface that could instead induce differentiation of bovine and human retinal pigment epithelium (RPE) cells while promoting cell growth. Several PEG based surfaces were able to induce cobblestone morphology of the RPE cells, which is indicative of differentiation. (Abstract shortened by UMI.).

[High performance liquid chromatogram (HPLC) determination of adenosine phosphates in rat myocardium].

PubMed

Miao, Yu; Wang, Cheng-long; Yin, Hui-jun; Shi, Da-zhuo; Chen, Ke-ji

2005-04-18

To establish method for the quantitative determination of adenosine phosphates in rat myocardium by optimized high performance liquid chromatogram (HPLC). ODS HYPERSIL C(18) column and a mobile phase of 50 mmol/L tribasic potassium phosphate buffer solution (pH 6.5), with UV detector at 254 nm were used. The average recovery rates of myocardial adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP) were 99%-107%, 96%-104% and 95%-119%, respectively; relative standard deviations (RSDs) of within-day and between-days were less than 1.5% and 5.1%, respectively. The method is simple, rapid and accurate, and can be used to analyse the adenosine phosphates in myocardium.

Establishment and optimization of NMR-based cell metabonomics study protocols for neonatal Sprague-Dawley rat cardiomyocytes.

PubMed

Zhang, Ming; Sun, Bo; Zhang, Qi; Gao, Rong; Liu, Qiao; Dong, Fangting; Fang, Haiqin; Peng, Shuangqing; Li, Famei; Yan, Xianzhong

2017-01-15

A quenching, harvesting, and extraction protocol was optimized for cardiomyocytes NMR metabonomics analysis in this study. Trypsin treatment and direct scraping cells in acetonitrile were compared for sample harvesting. The results showed trypsin treatment cause normalized concentration increasing of phosphocholine and metabolites leakage, since the trypsin-induced membrane broken and long term harvesting procedures. Then the intracellular metabolite extraction efficiency of methanol and acetonitrile were compared. As a result, washing twice with phosphate buffer, direct scraping cells and extracting with acetonitrile were chosen to prepare cardiomyocytes extracts samples for metabonomics studies. This optimized protocol is rapid, effective, and exhibits greater metabolite retention. Copyright © 2016 Elsevier Inc. All rights reserved.

Adaptation and major chromosomal changes in populations of Saccharomyces cerevisiae.

PubMed

Adams, J; Puskas-Rozsa, S; Simlar, J; Wilke, C M

1992-07-01

Thirteen independent populations of Saccharomyces cerevisiae (nine haploid and four diploid) were maintained in continuous culture for up to approximately 1000 generations, with growth limited by the concentration of organic phosphates in medium buffered at pH 6. Analysis of clones isolated from these populations showed that a number (17) of large-scale chromosomal-length variants and rearrangements were present in the populations at their termination. Nine of the 16 yeast chromosomes were involved in such changes. Few of the changes could be explained by copy-number increases in the structural loci for acid phosphatase. Several considerations concerning the nature and frequency of the chromosome-length variants observed lead us to conclude that they are selectively advantageous.

Development and study the performance of PBA cladding modified fiber optic intrinsic biosensor for urea detection

NASA Astrophysics Data System (ADS)

Botewad, S. N.; Pahurkar, V. G.; Muley, G. G.

2016-05-01

The fabrication and study of a cladding modified fiber optic intrinsic urea biosensor based on evanescent wave absorbance has been presented. The sensor was prepared using cladding modification technique by removing a small portion of cladding of an optical fiber and modifying with an active cladding of porous polyaniline-boric acid (PBA) matrix to immobilize enzyme-urease through cross-linking via glutaraldehyde. The nature of as-synthesized and deposited PBA film on fiber optic sensing element was studied by ultraviolet-visible (UV-vis) spectroscopy and X-ray diffraction (XRD) analysis. The performance of the developed sensor was studied for different urea concentrations in solutions prepared in phosphate buffer.

The Path of Carbon in Photosynthesis XIII. pH Effects in C{sup 14}O{sub 2} Fixation by Scenedesmus

DOE R&D Accomplishments Database

Ouellet, C.; Benson, A. A.

1951-10-23

The rates of photosynthesis and dark fixation of C{sup 14}O{sub 2} in Scenedesmus have been compared in dilute phosphate buffers of 1.6 to 11.4 pH; determination of C{sup 14} incorporation into the various products shows enhancement of uptake in an acid medium into sucrose, polysaccharides, alanine and serine, in an alkaline medium into malic asparctic acids. kinetic experiments at extreme pH values suggest that several paths are available for CO{sub 2} assimilation. A tentative correlation of the results with the pH optima of some enzymes and resultant effects upon concentrations of intermediates is presented.

The Debye-Huckel Approximation in Electroosmotic Flow in Micro- and Nano-channels

NASA Astrophysics Data System (ADS)

Conlisk, A. Terrence

2002-11-01

In this work we consider the electroosmotic flow in a rectangular channel. We consider a mixture of water or other neutral solvent and a salt compound such as sodium chloride and other buffers for which the ionic species are entirely dissociated. Results are produced for the case where the channel height is much greater than the electric double layer(EDL)(microchannel) and for the case where the channel height is of the order or slightly greater than the width of the EDL(nanochannel). At small cation, anion concentration differences the Debye-Huckel approximation is appropriate; at larger concentration differences, the Gouy-Chapman picture of the electric double emerges naturally. In the symmetric case for the electroosmotic flow so induced, the velocity field and the potential are similar. We specifically focus in this paper on the limits of the Debye-Huckel approximation for a simplified version of a phosphate buffered saline(PBS) mixture. The fluid is assumed to behave as a continuum and the volume flow rate is observed to vary linearly with channel height for electrically driven flow in contrast to pressure driven flow which varies as height cubed. This means that very large pressure drops are required to drive flows in small channels. However, useful volume flow rates may be obtained at a very low driving voltage.

Spermatozoa isolated from cat testes retain their structural integrity as well as a developmental potential after refrigeration for up to 7 days.

PubMed

Buarpung, Sirirak; Tharasanit, Theerawat; Thongkittidilok, Chommanart; Comizzoli, Pierre; Techakumphu, Mongkol

2015-10-01

The objective of this study was to compare the efficiency of preservation media for isolated feline testicular spermatozoa as well as the concentrations of bovine serum albumin (BSA) on: (1) the membrane (sperm membrane integrity (SMI)) and DNA integrity of spermatozoa; and (2) the developmental potential of spermatozoa after intracytoplasmic sperm injection (ICSI). Isolated cat spermatozoa were stored in HEPES-M199 medium (HM) or Dulbecco's phosphate-buffered saline (DPBS) at 4°C for up to 7 days. Results indicated that HM maintained a better SMI than DPBS throughout the storage periods (P > 0.05). When spermatozoa were stored in HM supplemented with BSA at different concentrations (4, 8 or 16 mg/ml), SMI obtained from HM containing 8 and 16 mg/ml BSA was higher than with 4 mg/ml BSA (P 0.05). In summary, cat spermatozoa immediately isolated from testicular tissue can be stored as a suspension in basic buffered medium at 4°C for up to 7 days. BSA supplementation into the medium improves membrane integrity of the spermatozoa during cold storage. Testicular spermatozoa stored in HM containing 16 mg/ml BSA retained full in vitro developmental potential after ICSI, similar to that of fresh controls even though DNA integrity had slightly declined.

Performance optimization in electric field gradient focusing.

PubMed

Sun, Xuefei; Farnsworth, Paul B; Tolley, H Dennis; Warnick, Karl F; Woolley, Adam T; Lee, Milton L

2009-01-02

Electric field gradient focusing (EFGF) is a technique used to simultaneously separate and concentrate biomacromolecules, such as proteins, based on the opposing forces of an electric field gradient and a hydrodynamic flow. Recently, we reported EFGF devices fabricated completely from copolymers functionalized with poly(ethylene glycol), which display excellent resistance to protein adsorption. However, the previous devices did not provide the predicted linear electric field gradient and stable current. To improve performance, Tris-HCl buffer that was previously doped in the hydrogel was replaced with a phosphate buffer containing a salt (i.e., potassium chloride, KCl) with high mobility ions. The new devices exhibited stable current, good reproducibility, and a linear electric field distribution in agreement with the shaped gradient region design due to improved ion transport in the hydrogel. The field gradient was calculated based on theory to be approximately 5.76 V/cm(2) for R-phycoerythrin when the applied voltage was 500 V. The effect of EFGF separation channel dimensions was also investigated; a narrower focused band was achieved in a smaller diameter channel. The relationship between the bandwidth and channel diameter is consistent with theory. Three model proteins were resolved in an EFGF channel of this design. The improved device demonstrated 14,000-fold concentration of a protein sample (from 2 ng/mL to 27 microg/mL).

An assay of optimal cytochrome c oxidase activity in fish gills.

PubMed

Hu, Yau-Chung; Chung, Meng-Han; Lee, Tsung-Han

2018-07-15

Cytochrome c oxidase (COX) catalyzes the terminal oxidation reaction in the electron transport chain (ETC) of aerobic respiratory systems. COX activity is an important indicator for the evaluation of energy production by aerobic respiration in various tissues. On the basis of the respiratory characteristics of muscle, we established an optimal method for the measurement of maximal COX activity. To validate the measurement of cytochrome c absorbance, different ionic buffer concentrations and tissue homogenate protein concentrations were used to investigate COX activity. The results showed that optimal COX activity is achieved when using 50-100 μg fish gill homogenate in conjunction with 75-100 mM potassium phosphate buffer. Furthermore, we compared branchial COX activities among three species of euryhaline teleost (Chanos chanos, Oreochromis mossambicus, and Oryzias dancena) to investigate differences in aerobic respiration of osmoregulatory organs. COX activities in the gills of these three euryhaline species were compared with COX subunit 4 (COX4) protein levels. COX4 protein abundance and COX activity patterns in the three species occurring in environments with various salinities increased when fish encountered salinity challenges. This COX activity assay therefore provides an effective and accurate means of assessing aerobic metabolism in fish. Copyright © 2018 Elsevier Inc. All rights reserved.

Predicting stability of DNA duplexes in solutions containing magnesium and monovalent cations.

PubMed

Owczarzy, Richard; Moreira, Bernardo G; You, Yong; Behlke, Mark A; Walder, Joseph A

2008-05-13

Accurate predictions of DNA stability in physiological and enzyme buffers are important for the design of many biological and biochemical assays. We therefore investigated the effects of magnesium, potassium, sodium, Tris ions, and deoxynucleoside triphosphates on melting profiles of duplex DNA oligomers and collected large melting data sets. An empirical correction function was developed that predicts melting temperatures, transition enthalpies, entropies, and free energies in buffers containing magnesium and monovalent cations. The new correction function significantly improves the accuracy of predictions and accounts for ion concentration, G-C base pair content, and length of the oligonucleotides. The competitive effects of potassium and magnesium ions were characterized. If the concentration ratio of [Mg (2+)] (0.5)/[Mon (+)] is less than 0.22 M (-1/2), monovalent ions (K (+), Na (+)) are dominant. Effects of magnesium ions dominate and determine duplex stability at higher ratios. Typical reaction conditions for PCR and DNA sequencing (1.5-5 mM magnesium and 20-100 mM monovalent cations) fall within this range. Conditions were identified where monovalent and divalent cations compete and their stability effects are more complex. When duplexes denature, some of the Mg (2+) ions associated with the DNA are released. The number of released magnesium ions per phosphate charge is sequence dependent and decreases surprisingly with increasing oligonucleotide length.

Final report of the key comparison APMP.QM-K91: APMP comparison on pH measurement of phthalate buffer

NASA Astrophysics Data System (ADS)

Hioki, Akiharu; Asakai, Toshiaki; Maksimov, Igor; Suzuki, Toshihiro; Miura, Tsutomu; Ketrin, Rosi; Nuryatini; Thanh, Ngo Huy; Truong Chinh, Nguyen; Vospelova, Alena; Bastkowski, Frank; Sander, Beatrice; Matzke, Jessica; Prokunin, Sergey; Frolov, Dmitry; Aprelev, Alexey; Dobrovolskiy, Vladimir; Uysal, Emrah; Liv, Lokman; Velina Lara-Manzano, Judith; Montero-Ruiz, Jazmin; Ortiz-Aparicio, JosÉ Luis; Ticona Canaza, Galia; Anuar Mohd Amin, Khirul; Abd Kadir, Haslina; Bakovets, Nickolay; Wong, Siu-Kay; Lam, Wai-Hing

2017-01-01

The APMP.QM-K91 was organised by TCQM of APMP to test the abilities of the national metrology institutes in the APMP region to measure a pH value of a phthalate buffer. This APMP comparison on pH measurement was proposed by the National Metrology Institute of Japan at the APMP-TCQM meeting held September 22-23, 2014. After approval by TCQM, the comparison has been conducted by NMIJ. The comparison is a key comparison following CCQM-K91. The comparison material was a phthalate buffer of pH around 4.0 and the measurement temperatures were 15 °C, 25 °C and 37 °C. This is the third APMP key comparison on pH measurement and the fifth APMP comparison on pH measurement following APMP.QM-P06 (two phosphate buffers) in 2004, APMP.QM-P09 (a phthalate buffer) in 2006, APMP.QM-K9/APMP.QM-P16 (a phosphate buffer) in 2010-2011 and APMP.QM-K19/APMP.QM-P25 (a borate buffer) in 2013-2014. The results can be used further by any participant to support its CMC claim at least for a phthalate buffer. That claim will concern the pH method employed by the participant during this comparison and will cover the used temperature(s) or the full temperature range between 15°C and 37 °C for the participant which measured pH values at the three temperatures. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Host plasma proteins on the surface of pathogenic Trichomonas vaginalis.

PubMed

Peterson, K M; Alderete, J F

1982-08-01

Sodium dodecyl sulfate-gel electrophoresis and fluorography and fluorography technology revealed that pathogenic Trichomonas vaginalis was able to acquire numerous loosely associated plasma proteins during incubation in normal human plasma. These proteins were readily removed by repeated washing of the parasite in phosphate-buffered saline. Plasma proteins avidly bound to the surface of T. vaginalis were also detected using a highly sensitive and specific agglutination assay with protein A-bearing Staphylococcus aureus pretreated with monospecific antiserum directed against individual human serum proteins. These avidly associated plasma proteins could not be removed by repeated washing in phosphate-buffered saline or by treatment of washed, live organisms with surface-modifying reagents such as trypsin and periodate. A combined radioimmunoprecipitation-gel electrophoresis-fluorography methodology indicated that parasite biosynthesis of hostlike macromolecules was not responsible for the observed agglutination and reinforced the idea of trichosomal acquisition of plasma components. Finally, incubation of trichomonads with plasma in various buffers at different pH values did not alter the agglutination patterns. These and other data suggest that specific membrane sites trichomonal binding of host proteins. The biological significance of our results is discussed.

Iodine susceptibility of pseudomonads grown attached to stainless steel surfaces

NASA Technical Reports Server (NTRS)

Pyle, B. H.; McFeters, G. A.

1990-01-01

Pseudomonads were adapted to grow in phosphate-buffered water and on stainless steel surfaces to study the iodine sensitivity of attached and planktonic cells. Cultures adapted to low nutrient growth were incubated at room temperature in a circulating reactor system with stainless steel coupons to allow biofilm formation on the metal surfaces. In some experiments, the reactor was partially emptied and refilled with buffer at each sampling time to simulate a "fill-and-draw" water system. Biofilms of attached bacteria, resuspended biofilm bacteria, and reactor suspension, were exposed to 1 mg l-1 iodine for 2 min. Attached bacterial populations which established on coupons within 3 to 5 days displayed a significant increase in resistance to iodine. Increased resistance was also observed for resuspended cells from the biofilm and planktonic bacteria in the system suspension. Generally, intact biofilms and resuspended biofilm cells were most resistant, followed by planktonic bacteria and phosphate buffer cultures. Thus, biofilm formation on stainless steel surfaces within water systems can result in significantly increased disinfection resistance of commonly-occurring water-borne bacteria that may enhance their ability to colonise water treatment and distribution systems.

Apoenzyme of aspartate aminotransferase isozymes in serum and its diagnostic usefullness for hepatic diseases.

PubMed

Kamei, S; Ohkubo, A; Yamanaka, M

1979-08-15

Aspartate aminotransferase in the sera of normal subjects and of patients with hepatic diseases has been immunologically separated into two isoenzymes, cytosolic aspartate aminotransferase and mitochondrial aspartate aminotransferase. The activity of the isoenzymes was measured in three different buffer solutions with or without pyridoxal 5'-phosphate. To attain maximal activation, the apoenzyme of mitochondrial fraction must be preincubated with pyridoxal 5'-phosphate longer than that of the cytosolic fraction in either of the three reaction mixtures. In most sera the activity of both isoenzymes increased substantially in the presence of pyridoxal 5'-phosphate regardless of the type of buffer solutions. Both the apoenzymatic activity and the ratio of apo- to holo-enzymatic activity of each of the isoenzymes varied among samples from the patients with hepatic diseases. However, significantly high ratios of apo- to holo-enzymatic activity of both isoenzymes were observed in the patients with hepatoma in contrast with those with other hepatic diseases. These findings suggest that the simultaneous measurement of both apo- and holo-enzyme activities of aspartate aminotransferase isoenzymes may be useful in the clinical assessment of hepatic diseases.

Visualising phase change in a brushite-based calcium phosphate ceramic

PubMed Central

Bannerman, A.; Williams, R. L.; Cox, S. C.; Grover, L. M.

2016-01-01

The resorption of brushite-based bone cements has been shown to be highly unpredictable, with strong dependence on a number of conditions. One of the major factors is phase transformation, with change to more stable phases such as hydroxyapatite affecting the rate of resorption. Despite its importance, the analysis of phase transformation has been largely undertaken using methods that only detect crystalline composition and give no information on the spatial distribution of the phases. In this study confocal Raman microscopy was used to map cross-sections of brushite cylinders aged in Phosphate Buffered Saline, Foetal Bovine Serum, Dulbecco’s – Minimum Essential Medium (with and without serum). Image maps showed the importance of ageing medium on the phase composition throughout the ceramic structure. When aged without serum, there was dissolution of the brushite phase concomitant to the deposition of octacalcium phosphate (OCP) around the periphery of the sample. The deposition of OCP was detectable within five days and reduced the rate of brushite dissolution from the material. The use of serum, even at a concentration of 10vol% prevented phase transformation. This paper demonstrates the value of confocal Raman microscopy in monitoring phase change in biocements; it also demonstrates the problems with assessing material degradation in non-serum containing media. PMID:27604149

DNA polymerases in the rat pituitary gland. Effect of oestrogens and sulpiride.

PubMed

Jahn, G A; Kalbermann, L E; Machiavelli, G; Szijan, I; Burdman, J A

1980-06-01

Changes in the activity of DNA polymerase and [3H]thymidine incorporation into the DNA of the anterior pituitary gland were studied in oestrogenized male and pregnant rats. The activities of DNA polymerases alpha and beta, extracted in Tris--HCl or in sodium phosphate buffer were characterized according to their optimum pH and sensitivity to N-ethyl-maleimide. In the Tris-soluble fraction DNA polymerase activity is almost exclusively alpha, while in the phosphate soluble fraction it is a mixture of alpha and beta. The administration of oestrogens to male rats increases [3H]thymidine incorporation and enhances the activity of DNA polymerases in the Tris-soluble fraction, while the activity of the phosphate-soluble enzyme does not change. Sulpiride administration results in a further increment of [3H]thymidine incorporation and of DNA polymerase activity in the Tris-soluble fraction. In pregnant rats sulpiride also produces an increment of DNA polymerase activity only in the Tris-soluble fraction. Thus, the activity of the Tris-soluble fraction from APG behaves as DNA polymerase alpha. This activity changes in parallel with [3H]thymidine incorporation into DNA which is an indication of cell proliferation in the gland. This is discussed with respect to a negative feedback mechanism between intracellular prolactin concentration and DNA synthesis in the APG.

Visualising phase change in a brushite-based calcium phosphate ceramic

NASA Astrophysics Data System (ADS)

Bannerman, A.; Williams, R. L.; Cox, S. C.; Grover, L. M.

2016-09-01

The resorption of brushite-based bone cements has been shown to be highly unpredictable, with strong dependence on a number of conditions. One of the major factors is phase transformation, with change to more stable phases such as hydroxyapatite affecting the rate of resorption. Despite its importance, the analysis of phase transformation has been largely undertaken using methods that only detect crystalline composition and give no information on the spatial distribution of the phases. In this study confocal Raman microscopy was used to map cross-sections of brushite cylinders aged in Phosphate Buffered Saline, Foetal Bovine Serum, Dulbecco’s - Minimum Essential Medium (with and without serum). Image maps showed the importance of ageing medium on the phase composition throughout the ceramic structure. When aged without serum, there was dissolution of the brushite phase concomitant to the deposition of octacalcium phosphate (OCP) around the periphery of the sample. The deposition of OCP was detectable within five days and reduced the rate of brushite dissolution from the material. The use of serum, even at a concentration of 10vol% prevented phase transformation. This paper demonstrates the value of confocal Raman microscopy in monitoring phase change in biocements; it also demonstrates the problems with assessing material degradation in non-serum containing media.

Induced binding of proteins by ammonium sulfate in affinity and ion-exchange column chromatography.

PubMed

Arakawa, Tsutomu; Tsumoto, Kouhei; Ejima, Daisuke; Kita, Yoshiko; Yonezawa, Yasushi; Tokunaga, Masao

2007-04-10

In general, proteins bind to affinity or ion-exchange columns at low salt concentrations, and the bound proteins are eluted by raising the salt concentration, changing the solvent pH, or adding competing ligands. Blue-Sepharose is often used to remove bovine serum albumin (BSA) from samples, but when we applied BSA to Blue-Sepharose in 20 mM phosphate, pH 7.0, 50%-60% of the protein flowed through the column; however, complete binding of BSA was achieved by the addition of 2 M ammonium sulfate (AS) to the column equilibration buffer and the sample. The bound protein was eluted by decreasing the AS concentration or by adding 1 M NaCl or arginine. AS at high concentrations resulted in binding of BSA even to an ion-exchange column, Q-Sepharose, at pH 7.0. Thus, although moderate salt concentrations elute proteins from Blue-Sepharose or ion-exchange columns, proteins can be bound to these columns under extreme salting-out conditions. Similar enhanced binding of proteins by AS was observed with an ATP-affinity column.

Development of soft extraction method for structural characterization of boreal forest soil proteins with MALDI-TOF/MS

NASA Astrophysics Data System (ADS)

Kanerva, Sanna; Ketola, Raimo A.; Kitunen, Veikko; Smolander, Aino; Kotiaho, Tapio

2010-05-01

Nitrogen (N) is usually the nutrient restricting productivity in boreal forests. Forest soils contain a great amount of nitrogen, but only a small part of it is in mineral form. Most part of soil N is bound in the structures of different organic compounds such as proteins, peptides, amino acids and more stabilized, refractory compounds. Due to the fact that soil organic N has a very important role in soil nutrient cycling and in plant nutrition, there is a need for more detailed knowledge of its chemistry in soil. Conventional methods to extract and analyze soil organic N are usually very destructive for structures of higher molecular weight organic compounds, such as proteins. The aim of this study was to characterize proteins extracted from boreal forest soil by "soft" extraction methods in order to maintain their molecular structure. The organic layer (F) from birch forest floor containing 78% of organic matter was sieved, freeze dried, pulverized, and extracted with a citrate or phosphate buffer (pH 6 or 8). Sequential extraction with the citrate or phosphate buffer and an SDS buffer (pH 6.8), slightly modified from the method of Chen et al. (2009, Proteomics 9: 4970-4973), was also done. Proteins were purified from the soil extract by extraction with buffered phenol and precipitated with methanol + 0.1M ammonium acetate at -20°C. Characterization of proteins was performed with matrix assisted laser desorption ionization - time-of-flight mass spectrometry (MALDI-TOF/MS) and the concentration of total proteins was measured using Bradford's method. Bovine serum albumin (BSA) was used as a positive control in the extractions and as a standard protein in Bradford's method. Our results showed that sequential extraction increased the amount of extracted proteins compared to the extractions without the SDS-buffer; however, it must be noted that the use of SDS-buffer very probably increased denaturization of proteins. Purification of proteins from crude soil extracts by phenol extraction was essential prior to measurement of total proteins; there seemed to be a lot of compounds in crude soil extracts that interfere with the analysis of total proteins, causing overestimation in protein concentration. pH of the buffer solution did not seem to be very crucial for the extractability of soil natural proteins, but at the higher pH, the amount of interfering compounds increased. However, the recovery of BSA added was clearly higher at the higher pH. When the protein precipitates were analyzed with MALDI-TOF/MS, a large curve, most likely formed from wide peaks of several compounds, indicate that most of the compounds in the precipitate were <15 kDa or ~20-50 kDa in molecular weight. It seems that in order to identify individual proteins from mass spectra, a separation of compounds with varying molecular weight is needed before the MALDI-TOF/MS analysis. Due to the fact that a relatively high amount of BSA added was not recovered by the extractions and that the intensity of the signals observed in mass spectra was low, it is questionable whether it is possible to extract soil natural proteins effectively from soils containing a high amount of organic matter without destructing the structures of proteins.

Phosphorus Amendment Efficacy for In Situ Remediation of ...

EPA Pesticide Factsheets

A validated method is needed to measure reductions of in vitro bioaccessible (IVBA) Pb in urban soil remediated with amendments. This study evaluated the effect of in vitro extraction solution pH and glycine buffer on bioaccesible Pb in P-treated soils. Two Pb-contaminated soils (790-1300 mg Pb kg-1), one from a garden and one from a city lot in Cleveland, OH, were incubated in a bench scale experiment for 1 yr. Six phosphate amendments, including bone meal, fish bone, poultry litter, monoammonium phosphate, diammonium phosphate, and triple superphosphate, were added to containers at two application rates. Lead IVBA was assessed using USEPA Method 1340 and three modified versions of this method. Modifications included using solutions with pH 1.5 and 2.5 as well as using solutions with and without 0.4 mol L-1 glycine. Soil amendments were effective in reducing IVBA Pb in these soils as measured by pH 1.5 with glycine buffer. The greatest reductions in IVBA Pb, from 5 to 26%, were found using pH 2.5 extractions. Lead mineral results showed several soil amendments promoted Pb phosphate formation, an indicator of remediation success. A significant negative linear relationship between reduction in IVBA Pb and Pb-phosphate formation was found only for pH 2.5 without glycine extraction solution. A modified USEPA Method 1340 without glycine and using pH 2.5 has the potential to predict P soil treatment efficacy and reductions in bioavailable Pb. Developing mana

Adsorption and bioactivity studies of albumin onto hydroxyapatite surface.

PubMed

Mavropoulos, Elena; Costa, Andréa M; Costa, Lilian T; Achete, Carlos A; Mello, Alexandre; Granjeiro, José M; Rossi, Alexandre M

2011-03-01

Bovine serum albumin (BSA) may have an inhibitory or promoter effect on hydroxyapatite (HA) nucleation when apatite is precipitated in a medium containing the protein. In this study we evaluated the influence of BSA on the precipitation of calcium phosphate phases (CP) from simulated body fluid (SBF) when the protein was previously bounded to HA surface. The kinetics of BSA immobilization onto hydroxyapatite surface was performed in different buffers and protein concentrations in order to adjust experimental conditions in which BSA was tightly linked to HA surface for long periods in SBF solution. It was shown that for BSA concentration higher than 0.1mg/mL the adsorption to HA surface followed Langmuir-Freundlich mechanisms, which confirmed the existence of cooperative protein-protein interactions on HA surface. Fourier Transformed Infrared Attenuated Total Reflectance Microscopy (FTIRM-ATR) evidenced changes in BSA conformational state in favor of less-ordered structure. Analyses from high resolution grazing incident X-ray diffraction using synchrotron radiation (GIXRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) showed that a poorly crystalline calcium phosphate was precipitated on the surface of HA discs coated with BSA, after the immersion in SBF for 4 days. The new bioactive layer had morphological characteristics similar to the one formed on the HA surface without protein. It was identified as a carbonated apatite with preferential crystal growth along apatite 002 direction. The GIXRD results also revealed that BSA layer bound to the surface inhibited the HA dissolution leading to a reduction on the formation of new calcium phosphate phase. 2010 Elsevier B.V. All rights reserved.

Increased degradation rate of nitrososureas in media containing carbonate.

PubMed

Seidegård, Janeric; Grönquist, Lena; Tuvesson, Helen; Gunnarsson, Per-Olov

2009-01-01

The stability of two nitrosoureas, tauromustine and lomustine, has been investigated in different media and buffers. All media tested, except Leibovitz's L-15 medium, significantly increased the degradation rate of the investigated nitrosoureas at pH 7.4. Sodium bicarbonate seems to be the cause of the observed increase of the degradation rate, since it provides the main buffering capacity of all the media except for Leibovitz's L-15 medium, which is based on phosphate buffer. Other ingredients in the media, such as amino acids, vitamins, and inorganic salts, or the ionic strength of a buffer, did not have any major effect on the degradation rate of the nitrosoureas. These results suggest that media containing carbonated buffer should be avoided when the anti-tumor effect of nitrosoureas is to be investigated in different cell cultures.

Buffers and Oscillations in Intracellular Ca2+ Dynamics

PubMed Central

Falcke, Martin

2003-01-01

I model the behavior of intracellular Ca2+ release with high buffer concentrations. The model uses a spatially discrete array of channel clusters. The channel subunit dynamics is a stochastic representation of the DeYoung-Keizer model. The calculations show that the concentration profile of fast buffer around an open channel is more localized than that of slow buffers. Slow buffers allow for release of larger amounts of Ca2+ from the endoplasmic reticulum and hence bind more Ca2+ than fast buffers with the same dissociation constant and concentration. I find oscillation-like behavior for high slow buffer concentration and low Ca2+ content of the endoplasmic reticulum. High concentration of slow buffer leads to oscillation-like behavior by repetitive wave nucleation for high Ca2+ content of the endoplasmic reticulum. Localization of Ca2+ release by slow buffer, as used in experiments, can be reproduced by the modeling approach. PMID:12524263

Functional Analysis of Human NF1 in Drosophila

DTIC Science & Technology

2007-01-01

adjusted to 1 mg/ml. Fifty microlitres of 2 assay buffer (50 mM Tris– acetate buffer at pH 7.5, 20 mM MgCl2, 2 mM dithiothreitol, 10 mM creatine phosphate...200 units/ml creatinine kinase, 0.1 mM cAMP at pH 7.5, 0.2 mg/ml bovine serum albumin, 0.02 mg/ml aprotinin, 0.02 mg/ml pepstatin and fresh 0.2 mg

A self-powered kinesin-microtubule system for smart cargo delivery

NASA Astrophysics Data System (ADS)

Jia, Yi; Dong, Weiguang; Feng, Xiyun; Li, Jieling; Li, Junbai

2014-11-01

A smart self-powered cargo delivery system that is composed of creatine phosphate kinase (CPK) microspheres, kinesins and microtubules is demonstrated. The CPK microsphere not only acts as an ATP generation and buffering system, but also as a carrier for cargo transport, thus realizing the easy loading and self-powered delivery of cargos at the same time.A smart self-powered cargo delivery system that is composed of creatine phosphate kinase (CPK) microspheres, kinesins and microtubules is demonstrated. The CPK microsphere not only acts as an ATP generation and buffering system, but also as a carrier for cargo transport, thus realizing the easy loading and self-powered delivery of cargos at the same time. Electronic supplementary information (ESI) available: Experimental details, Fig. S1-S4, and Mov. S1-S6. See DOI: 10.1039/c4nr04454a

Electrochemical Behavior of Pure Copper in Phosphate Buffer Solutions: A Comparison Between Micro- and Nano-Grained Copper

NASA Astrophysics Data System (ADS)

Imantalab, O.; Fattah-alhosseini, A.; Keshavarz, M. K.; Mazaheri, Y.

2016-02-01

In this work, electrochemical behavior of annealed (micro-) and nano-grained pure copper (fabricated by accumulative roll bonding process) in phosphate buffer solutions of various pH values ranging from 10.69 to 12.59 has been studied. Before any electrochemical measurements, evaluation of microstructure was obtained by optical microscope and transmission electron microscopy. To investigate the electrochemical behavior of the samples, the potentiodynamic polarization, Mott-Schottky analysis, and electrochemical impedance spectroscopy (EIS) were carried out. Potentiodynamic polarization plots and EIS measurements revealed that as a result of grain refinement, the passive behavior of the nano-grained sample was improved compared to that of annealed pure copper. Also, Mott-Schottky analysis indicated that the passive films behaved as p-type semiconductors and grain refinement did not change the semiconductor type of passive films.

Inactivation of avirulent Yersinia pestis in Butterfield's phosphate buffer and frankfurters by UVC (254 nm) and gamma radiation.

PubMed

Sommers, Christopher H; Cooke, Peter H

2009-04-01

Yersinia pestis is the causative agent of plague. Although rare, pharyngeal plague in humans has been associated with consumption or handling of meat prepared from infected animals. The risks of contracting plague from consumption of deliberately contaminated food are currently unknown. Gamma radiation is a penetrating form of electromagnetic radiation, and UVC radiation is used for decontamination of liquids or food surfaces. Gamma radiation D10-values (the radiation dose needed to inactivate 1 log unit pathogen) were 0.23 (+/-0.01) and 0.31 (+/-0.03) kGy for avirulent Y. pestis inoculated into Butterfield's phosphate buffer and onto frankfurter surfaces, respectively, at 0 degree C. A UVC radiation dose of 0.25 J/cm2 inactivated avirulent Y. pestis suspended in Butterfield's phosphate buffer. UVC radiation doses of 0.5 to 4.0 J/cm2 inactivated 0.97 to 1.20 log units of the Y. pestis surface inoculated onto frankfurters. A low gamma radiation dose of 1.6 kGy could provide a 5-log reduction and a UVC radiation dose of 1 to 4 J/cm2 would provide a 1-log reduction of Y. pestis surface inoculated onto frankfurters. Y. pestis was capable of growth on frankfurters during refrigerated storage (10 degrees C). Gamma radiation of frankfurters inhibited the growth of Y. pestis during refrigerated storage, and UVC radiation delayed the growth of Y. pestis.

Fracture toughness and fractography of dental cements, lining, build-up, and filling materials.

PubMed

Mueller, H J

1990-06-01

The plane strain fracture toughness (K1c) at 23 degrees C and the fractography of zinc phosphate and zinc polycarboxylate cements, buffered glass ionomer liner, amalgam alloy admixed glass ionomer build-up material, and glass ionomer, microfilled and conventionally filled bis-GMA resin composite filling materials were analyzed by elastic-plastic short-rod and scanning electron microscopy methodologies. Results indicated that significant differences occurred in their K1c's from the lowest to the highest in the following groups of materials, (i) buffered glass ionomer, (ii) zinc phosphate, glass ionomer, zinc polycarboxylate, and alloy mixed glass ionomer, (iii) microfilled resin, and (iv) conventionally filled resin. All materials except the microfilled resin, which fractured via crack jumping, fractured via smooth crack advance. Filler debonding without any crack inhibiting process was related to materials with low K1c values. The incorporation of either buffering compounds or alloy particles into glass ionomer had no beneficial effect upon fracture toughness. This was in contrast to microfilled and conventionally filled resins where either crack blunting or crack pinning processes, respectively, were likely involved with their increased K1c's. For microfilled resin, distinct radial zones positioned around the chevron apex and characterized by plastically deformed deposited material were related to distinct crack jumps that occurred in the load versus displacement behavior. Finally, for the two remaining materials of zinc phosphate and polycarboxylate, particle cleavage and matrix debonding for the former and shear yielding for the latter occurred.

Leishmanicidal activity of saponins isolated from the leaves of Eclipta prostrata and Gymnema sylvestre.

PubMed

Khanna, Venkatesan Gopiesh; Kannabiran, Krishnan; Getti, Giulia

2009-02-01

To evaluate the leishmanicidal activity of saponin, dasyscyphin C of Eclipta prostrata and sapogenin, gymnemagenol from Gymnema sylvestre leaves under in vitro conditions. Dasyscyphin C/Gymnemagenol were dissolved in phosphate buffered saline (PBS) and diluted with liquid medium to obtain concentrations ranging from 1000 to 15 mug /ml. The leishmanicidal activity against leishmanial parasites, Leishmania major, Leishmania aethiopica and Leishmania tropica promastigotes was studied by the MTS assay. The Dasyscyphin C isolated from E. prostrata showed good leishmanicidal activity at 1000mug/ml concentration, with the IC(50) value of 450mug/ml against L. major promastigote and the percentage of parasitic death was 73; whereas, gymnemagenol of G. sylvestre showed only 52% parasitic death at 1000 mug/ml concentration. The other Leishmania species, L. aethiopica and L. tropica promastigotes, were less sensitive to the saponins of E. prostrata and G. sylvestre. From this study, it can be concluded that the dasyscyphin C of E. prostrata has significant leishmanicidal activity against L. major promastigote.

Procedure for detecting and confirming pentobarbital residues in dog food by gas chromatography/mass spectrometry.

PubMed

Adam, L A; Reeves, V B

1998-01-01

The method described detects and confirms presence of pentobarbital residues in dry, extruded feeds at concentrations of 5-20 ppb. Dried feed is ground to a uniform powder and shaken overnight in methanol. A portion of the methanolic extract is evaporated, and the residue is reconstituted in phosphate-buffered saline. The aqueous extract is cleaned with a solid-phase extraction cartridge designed to extract barbiturate residues from biological matrixes. Dimethyl sulfoxide, tetramethylammonium hydroxide, and iodomethane are added to derivatize pentobarbital, 1,3-Dimethyl-pentobarbital is then acidified with dilute hydrochloric acid and extracted with isooctane. The organic layer is transferred and evaporated under a stream of nitrogen. The residue is reconstituted in a small volume of ethyl acetate for analysis by gas chromatography/mass spectrometry. The limit of detection is approximately 0.7 ppb. The method was validated with pentobarbital-fortified feed samples containing high concentrations of meat and bone meal.

Single-channel measurements of an N-acetylneuraminic acid-inducible outer membrane channel in Escherichia coli

PubMed Central

Giri, Janhavi; Tang, John M.; Wirth, Christophe; Peneff, Caroline M.

2012-01-01

NanC is an Escherichia coli outer membrane protein involved in sialic acid (Neu5Ac, i.e., N-acetylneuraminic acid) uptake. Expression of the NanC gene is induced and controlled by Neu5Ac. The transport mechanism of Neu5Ac is not known. The structure of NanC was recently solved (PDB code: 2WJQ) and includes a unique arrangement of positively charged (basic) side chains consistent with a role in acidic sugar transport. However, initial functional measurements of NanC failed to find its role in the transport of sialic acids, perhaps because of the ionic conditions used in the experiments. We show here that the ionic conditions generally preferred for measuring the function of outer-membrane porins are not appropriate for NanC. Single channels of NanC at pH 7.0 have: (1) conductance 100 pS to 800 pS in 100 mM KCl to 3 M KCl), (2) anion over cation selectivity (Vreversal = +16 mV in 250 mM KCl || 1 M KCl), and (3) two forms of voltage-dependent gating (channel closures above ±200 mV). Single-channel conductance decreases by 50% when HEPES concentration is increased from 100 μM to 100 mM in 250 mM KCl at pH 7.4, consistent with the two HEPES binding sites observed in the crystal structure. Studying alternative buffers, we find that phosphate interferes with the channel conductance. Single-channel conductance decreases by 19% when phosphate concentration is increased from 0 mM to 5 mM in 250 mM KCl at pH 8.0. Surprisingly, TRIS in the baths reacts with Ag|AgCl electrodes, producing artifacts even when the electrodes are on the far side of agar–KCl bridges. A suitable baseline solution for NanC is 250 mM KCl adjusted to pH 7.0 without buffer. PMID:22246445

Stability of buffer-free freeze-dried formulations: A feasibility study of a monoclonal antibody at high protein concentrations.

PubMed

Garidel, Patrick; Pevestorf, Benjamin; Bahrenburg, Sven

2015-11-01

We studied the stability of freeze-dried therapeutic protein formulations over a range of initial concentrations (from 40 to 160 mg/mL) and employed a variety of formulation strategies (including buffer-free freeze dried formulations, or BF-FDF). Highly concentrated, buffer-free liquid formulations of therapeutic monoclonal antibodies (mAbs) have been shown to be a viable alternative to conventionally buffered preparations. We considered whether it is feasible to use the buffer-free strategy in freeze-dried formulations, as an answer to some of the known drawbacks of conventional buffers. We therefore conducted an accelerated stability study (24 weeks at 40 °C) to assess the feasibility of stabilizing freeze-dried formulations without "classical" buffer components. Factors monitored included pH stability, protein integrity, and protein aggregation. Because the protein solutions are inherently self-buffering, and the system's buffer capacity scales with protein concentration, we included highly concentrated buffer-free freeze-dried formulations in the study. The tested formulations ranged from "fully formulated" (containing both conventional buffer and disaccharide stabilizers) to "buffer-free" (including formulations with only disaccharide lyoprotectant stabilizers) to "excipient-free" (with neither added buffers nor stabilizers). We evaluated the impacts of varying concentrations, buffering schemes, pHs, and lyoprotectant additives. At the end of 24 weeks, no change in pH was observed in any of the buffer-free formulations. Unbuffered formulations were found to have shorter reconstitution times and lower opalescence than buffered formulations. Protein stability was assessed by visual inspection, sub-visible particle analysis, protein monomer content, charge variants analysis, and hydrophobic interaction chromatography. All of these measures found the stability of buffer-free formulations that included a disaccharide stabilizer comparable to buffer-based formulations, especially at protein concentrations up to and including 115 mg/mL. Copyright © 2015 Elsevier B.V. All rights reserved.

Design of Phosphonium-Type Zwitterion as an Additive to Improve Saturated Water Content of Phase-Separated Ionic Liquid from Aqueous Phase toward Reversible Extraction of Proteins

PubMed Central

Ito, Yoritsugu; Kohno, Yuki; Nakamura, Nobuhumi; Ohno, Hiroyuki

2013-01-01

We designed phosphonium-type zwitterion (ZI) to control the saturated water content of separated ionic liquid (IL) phase in the hydrophobic IL/water biphasic systems. The saturated water content of separated IL phase, 1-butyl-3-methyimidazolium bis(trifluoromethanesulfonyl)imide, was considerably improved from 0.4 wt% to 62.8 wt% by adding N,N,N-tripentyl-4-sulfonyl-1-butanephosphonium-type ZI (P555C4S). In addition, the maximum water content decreased from 62.8 wt% to 34.1 wt% by increasing KH2PO4/K2HPO4 salt content in upper aqueous phosphate buffer phase. Horse heart cytochrome c (cyt.c) was dissolved selectively in IL phase by improving the water content of IL phase, and spectroscopic analysis revealed that the dissolved cyt.c retained its higher ordered structure. Furthermore, cyt. c dissolved in IL phase was re-extracted again from IL phase to aqueous phase by increasing the concentration of inorganic salts of the buffer solution. PMID:24013379

Integration of a Miniature Quartz Crystal Microbalance with a Microfluidic Chip for Amyloid Beta-Aβ42 Quantitation

PubMed Central

Tao, Wenyan; Xie, Qingji; Wang, Hairui; Ke, Shanming; Lin, Peng; Zeng, Xierong

2015-01-01

A miniature quartz crystal microbalance (mQCM) was integrated with a polydimethylsiloxane (PDMS) microfluidic device for on-chip determination of amyloid polypeptide–Aβ42. The integration techniques included photolithography and plasma coupling. Aβ42 antibody was immobilized on the mQCM surface using a cross-linker method, and the resonance frequency of mQCM shifted negatively due to antibody-antigen binding. A linear range from 0.1 µM to 3.2 µM was achieved. By using matrix elimination buffer, i.e., matrix phosphate buffer containing 500 µg/mL dextran and 0.5% Tween 20, Aβ42 could be successfully detected in the presence of 75% human serum. Additionally, high temperature treatments at 150 °C provided a valid method to recover mQCM, and PDMS-mQCM microfluidic device could be reused to some extent. Since the detectable Aβ42 concentration could be as low as 0.1 µM, which is close to cut-off value for Alzheimer patients, the PDMS-mQCM device could be applied in early Alzheimer’s disease diagnosis. PMID:26473864

Effect of tributyltin (TBT) in the metabolic activity of TBT-resistant and sensitive estuarine bacteria.

PubMed

Cruz, Andreia; Oliveira, Vanessa; Baptista, Inês; Almeida, Adelaide; Cunha, Angela; Suzuki, Satoru; Mendo, Sónia

2012-01-01

The effect of tributyltin (TBT) on growth and metabolic activity of three estuarine bacteria with different TBT resistance profiles was investigated in an organic-rich culture medium (TSB) and in phosphate buffered saline (PBS) buffer. Exposure to TBT was assessed by determining its effect on growth (OD(600 nm) measurement), bacterial productivity (leucine incorporation), viability (CFU counts), aggregation and cell size (from Live/Dead analysis), ATP and NADH concentrations. TBT exposure resulted in decrease of bacterial density, cell size, and metabolic activity. In addition, cell aggregates were observed in the TBT-treated cultures. TBT strongly affected bacterial cell metabolism and seemed to exert an effect on its equilibrium, interfering with cell activity. Also, TBT toxicity was lower when cells were grown in TSB than in PBS, suggesting that a nutrient-rich growth medium can protect cells from TBT toxicity. This study contributes to our understanding of the TBT-resistant cell behavior reflected in its physiology and metabolic activity. This information is of utmost importance for further studies of TBT bioremediation. Copyright © 2010 Wiley Periodicals, Inc.

Experimental design for a basic mixture on a fluorinated packing. The effect of composition of the mobile phase.

PubMed

Wang, Y; Harrison, M; Clark, B J

2006-02-10

An optimization methodology is introduced for investigating the separation and the retention behavior of analytes on a new fluorinated reversed-phase packing. Ten basic compounds were selected as test probes to study the predictive models developed by using SPSS and MATLAB software. A two-level orthogonal array design (OAD) was used to extract significant parameters. The significant factors were optimised using a central composite design to obtain the quadratic relationship between the dependent and the independent variables. Using this strategy, response surfaces were derived as the 3D and contour plots, and mathematical models were defined for the separation. The models had a satisfactory coefficient (R(2) > 0.97, n = 16). For the test compounds, the best separation condition was: MeCN/30 mM phosphate buffer pH 7.1(55.5:44.5, v/v) and 10 basic solutes were resolved in 22 min. The significant influence of the concentration of buffer shows that different mechanisms of separation for basic compounds on the fluorinated packing exist compared with a common ODS stationary phase.

Optimization and Validation of a Sensitive Method for HPLC-PDA Simultaneous Determination of Torasemide and Spironolactone in Human Plasma using Central Composite Design.

PubMed

Subramanian, Venkatesan; Nagappan, Kannappan; Sandeep Mannemala, Sai

2015-01-01

A sensitive, accurate, precise and rapid HPLC-PDA method was developed and validated for the simultaneous determination of torasemide and spironolactone in human plasma using Design of experiments. Central composite design was used to optimize the method using content of acetonitrile, concentration of buffer and pH of mobile phase as independent variables, while the retention factor of spironolactone, resolution between torasemide and phenobarbitone; and retention time of phenobarbitone were chosen as dependent variables. The chromatographic separation was achieved on Phenomenex C(18) column and the mobile phase comprising 20 mM potassium dihydrogen ortho phosphate buffer (pH-3.2) and acetonitrile in 82.5:17.5 v/v pumped at a flow rate of 1.0 mL min(-1). The method was validated according to USFDA guidelines in terms of selectivity, linearity, accuracy, precision, recovery and stability. The limit of quantitation values were 80 and 50 ng mL(-1) for torasemide and spironolactone respectively. Furthermore, the sensitivity and simplicity of the method suggests the validity of method for routine clinical studies.

[Determination of penicillin intermediate and three penicillins in milk by high performance capillary electrophoresis].

PubMed

Tian, Chunqiu; Tan, Huarong; Gao, Liping; Shen, Huqin; Qi, Kezong

2011-11-01

A high performance capillary electrophoresis (HPCE) method was developed for the simultaneous determination of penicillin intermediate and penicillins in milk, including 6-amino-penicillanic acid (6-APA), penicillin G (PEN), ampicillin (AMP) and amoxicillin (AMO). The main parameters including the ion concentration and pH value of running buffer, separation voltage and column temperature were optimized systematically by orthogonal test. The four penicillins (PENs) were baseline separated within 4.5 min with the running buffer of 40 mmol/L potassium dihydrogen phosphate-20 mmol/L borax solution (pH 7.8), separation voltage of 28 kV and column temperature of 30 degrees C. The calibration curves showed good linearity in the range of 1.56 - 100 mg/L, and the correlation coefficients (r2) were between 0.9979 and 0.9998. The average recoveries at three spiked levels were in the range of 84.91% - 96.72% with acceptable relative standard deviations (RSDs) of 1.11% - 9.11%. The method is simple, fast, accurate and suitable for the determination of penicillins in real samples.

High performance liquid chromatography for the simultaneous analysis of penicillin residues in beef and milk using ion-paired extraction and binary water-acetonitrile mixture.

PubMed

Kukusamude, Chunyapuk; Burakham, Rodjana; Chailapakul, Orawon; Srijaranai, Supalax

2012-04-15

An ion-paired extraction (IPE) has been developed for the analysis of penicillin antibiotics (penicillin G, oxacillin and cloxacillin) in beef and milk samples using tetrabutylammonium bromide (TBABr) as ion-pairing agent and binary water-acetonitrile as extractant. The factors affecting the IPE efficiency were optimized including solution pH, volume of acetonitrile (ACN), concentration of TBABr and electrolyte salt (NH(4))(2)SO(4). The optimum IPE conditions were 10 mmol L(-1) phosphate buffer pH 8, 2 mL of ACN, 6 mmol L(-1) of TBABr and 2.5 mL of saturated ammonium sulfate. Under the HPLC condition: an Xbridge™ C18 reversed-phase column, isocratic elution of 5 mmol L(-1) phosphate buffer (pH 6.6) and acetonitrile (75:25, v/v) and a flow rate of 1 mL min(-1), with UV detection at 215 nm, the separation of three penicillins was achieved within 10 min. Under the selected optimum conditions, the enhancement of 21-53 folds compared to that without preconcentration and limits of detection (LODs) of 1-2 ng mL(-1) were obtained. Good reproducibility was achieved with RSD<2% for retention time and <5% for slope of calibration curves. The average recoveries higher than 85% were obtained. The proposed IPE-HPLC method has shown to be high efficient preconcentration and analysis method for penicillin residues in beef and milk with LOD lower than the maximum residue limits. Copyright © 2012 Elsevier B.V. All rights reserved.

Stability of Colistin and Colistin Methanesulfonate in Aqueous Media and Plasma as Determined by High-Performance Liquid Chromatography

PubMed Central

Li, Jian; Milne, Robert W.; Nation, Roger L.; Turnidge, John D.; Coulthard, Kingsley

2003-01-01

The stabilities of colistin and colistin methanesulfonate (CMS) in different aqueous media were studied by specific high-performance liquid chromatography (HPLC) methods. Colistin was stable in water at 4 and 37°C for up to 60 days and 120 h, respectively. However, degradation was observed when colistin was stored in isotonic phosphate buffer (0.067 M, pH 7.4) and human plasma at 37°C. The stability of CMS from three different sources in water was explored by strong-anion-exchange (SAX) HPLC for CMS and by measuring the concentrations of colistin formed from the hydrolysis of CMS. The peaks of CMS in SAX HPLC disappeared almost completely after 12 h at 37°C, but appeared to remain intact for up to 2 days at 4°C. Over the same period, there was no formation of colistin at 4°C. In water, phosphate buffer, and plasma, there was rapid formation of colistin within 24 to 48 h at 37°C from the three sources of CMS. The hydrolysis products were assumed to be a complex mixture of many different sulfomethyl derivatives, including colistin. The stability of a fourth source of CMS in Mueller-Hinton broth examined during 30 min at 37°C revealed no formation of colistin. Along with previous microbiological studies, this suggested that different sulfomethyl CMSs possess intrinsic antibacterial activity. These results will be helpful for understanding the pharmacokinetics and pharmacodynamics of colistin and CMS in humans and animals. PMID:12654671

Biodegradable and photocrosslinkable polyphosphoester hydrogel

PubMed Central

Li, Qiang; Wang, Jun; Shahani, Shilpa; Sun, Danny D.N.; Sharma, Blanka; Elisseeff, Jennifer H.; Leong, Kam W.

2008-01-01

A new biodegradable, photocrosslinkable and multifunctional macromer, poly(6-aminohexyl propylene phosphate) (PPE-HA)-ACRL, was synthesized by conjugation of acrylate groups to the side chains of PPE-HA. By controlling the synthetic conditions, different weight fractions of acrylate in the macromers were achieved as confirmed by 1H NMR. The hydrogels obtained from PPE-HA-ACRL through photocrosslinking were dominantly elastic. With increasing acrylate contents in the macromers, the hydrogels exhibited a lower swelling ratio and higher mechanical strength. The hydrogels with different crosslinking densities lost between 4.3% and 37.4% of their mass in 84 days when incubated in phosphate-buffered saline at 37 °C. No significant cytotoxicity of the macromers against bone marrow-derived mesenchymal stem cells from goat (GMSC) was observed at a concentration up to 10 mg/ml. Finally, GMSCs encapsulated in the photopolymerized gel maintained their viability when cultured in osteogenic medium for three weeks. Clear mineralization in the hydrogel scaffold was revealed by Von Kossa staining. This study suggests the potential of these biodegradable and photocrosslinkable as injectable tissue engineering scaffolds. PMID:16125222

[Determination of optical purity of alpha-phenylethylamine by high performance liquid chromatography with pre-column derivatization].

PubMed

Wang, Jinzhao; Zeng, Su; Wang, Danhua; Hu, Gongyun

2009-05-01

A simple pre-column derivatization-high performance liquid chromatographic (HPLC) method was established for the determination of optical purity of alpha-phenylethylamine. The enantiomers of alpha-phenylethylamine were derivatized with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate (GITC). The resulted diastereoisomers were separated on an Agilent Zorbax C18 column (250 mm x 4.6 mm, 5 microm) with a mobile phase of methanol-phosphate buffer (1.36 g/L aqueous solution of potassium dihydrogen phosphate, adjusted to pH 3.0 with concentrated phosphoric acid) (58:42, v/v). The flow rate was set at 1.0 mL/min and the detection wavelength was set at 241 nm. The method was linear from 0.15 - 15.0 mg/L for both enantiomers. The limit of detection and the limit of quantification were 0.05 mg/L and 0.15 mg/L, respectively. The relative standard deviations (RSDs) of inter- and intra-day determination were below 0.5%. The method is easy to handle, accurate, and suitable for the quality control of the optical purity of alpha-phenylethylamine.

INACTIVATION OF HEPATITIS A VIRUS AND MS2 BY OZONE AND OZONE-HYDROGEN PEROXIDE IN BUFFERED WATER

EPA Science Inventory

The comparative inactivation of highly purified hepatitis A virus (HAV) and MS2 by 1 mg H202/L, 2.0 and 0.4 mg 03/L, and 2.0 mg 03/L plus 0.6, 1.0, or 1.6 mg H202/L, at 3-10 degrees C, in 0.01 M phosphate buffer (pH 6-10) was determined. Both HAV and MS2 were completely inactivat...

Influence of mixtures of calcium-chelating salts on the physicochemical properties of casein micelles.

PubMed

Kaliappan, S; Lucey, J A

2011-09-01

Calcium-chelating salts (CCS), such as phosphates and citrates, are often added to milk systems to modify physical properties like heat stability. The objective of this study was to investigate the effect of binary CCS mixtures on the properties of casein (CN) micelles including the distribution of Ca between the soluble and CN-bound states. Six binary CCS mixtures were prepared from 4 different types of CCS [i.e., trisodium citrate (TSC), disodium phosphate (DSP), tetrasodium pyrophosphate (TSPP), and sodium hexameta phosphate (SHMP)] by combining 2 CCS at a time in 5 different proportions (8.3:91.7, 29.2:70.8, 50:50, 70.8:29.2, and 91.7:8.3). Different concentrations of these mixtures (0, 0.1, 0.3, 0.5, and 0.7% wt/wt) were added to milk protein concentrate solutions (5% wt/wt) at pH 5.8. The ability of CCS to disperse CN particles and its interaction with Ca were assessed from turbidity measurements, acid-base titration behavior, and the quantity of CN-bound Ca and inorganic phosphate (Pi). Turbidity and the buffering peak at pH ∼5.0 during acid titration decreased with an increasing concentration of CCS. This was due to the chelation of Ca and the dispersion of CN micelles. The presence of TSC in mixtures decreased the amount of CN-bound Ca and Pi; however, the presence of TSPP in mixtures increased CN-bound Ca and Pi. When DSP was present at high proportions in mixtures of CCS, the CN-bound Ca and Pi slightly increased. When SHMP was used in mixtures of CCS, CN-bound Ca and Pi increased with the use of a low proportion of SHMP but decreased when SHMP was used at high proportions in the mixture. Combinations of DSP-TSPP used in the proportions 29.2:70.8, 50:50, and 70.8:29.2 resulted in the gelation of milk protein concentrates when the total CCS concentration was ≥0.3%. These results indicated that the type of CCS present in a mixture modified CN properties by various mechanisms, including chelation of Ca, dispersion of CN micelles, and formation of new types of Ca-CCS complexes. The type of interaction between the newly formed Ca-CCS complexes and the dispersed CN depended on the proportion, concentration, and type of CCS present in the mixtures. This information is useful in understanding how mixtures of CCS affect CN properties. Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Report of the key comparison APMP.QM-K19. APMP comparison on pH measurement of borate buffer

NASA Astrophysics Data System (ADS)

Hioki, Akiharu; Asakai, Toshiaki; Maksimov, Igor; Suzuki, Toshihiro; Miura, Tsutomu; Obromsook, Krairerk; Tangpaisarnkul, Nongluck; Rodruangthum, Patumporn; Wong, Siu-Kay; Lam, Wai-Hing; Zakaria, Osman; Anuar Mohd. Amin, Khirul; Thanh, Ngo Huy; Máriássy, Michal; Vyskocil, Leos; Hankova, Zuzana; Fisicaro, Paola; Stoica, Daniela; Singh, Nahar; Soni, Daya; Ticona Canaza, Galia; Kutovoy, Viatcheslav; Barbieri Gonzaga, Fabiano; Dias, Júlio Cesar; Vospelova, Alena; Bakovets, Nickolay; Zhanasbayeva, Bibinur

2015-01-01

The APMP.QM-K19 was organised by TCQM of APMP to test the abilities of the national metrology institutes in the APMP region to measure a pH value of a borate buffer. This APMP comparison on pH measurement was proposed by the National Metrology Institute of Japan (NMIJ) and the National Institute of Metrology (Thailand) (NIMT) at the APMP-TCQM meeting held 26-27 November 2012. After approval by TCQM, the comparison has been conducted by NMIJ and NIMT. The comparison is a key comparison following CCQM-K19 and CCQM-K19.1. The comparison material was a borate buffer of pH around 9.2 and the measurement temperatures were 15 °C, 25 °C and 37 °C. This is the second APMP key comparison on pH measurement and the fourth APMP comparison on pH measurement following APMP.QM-P06 (two phosphate buffers) in 2004, APMP.QM-P09 (a phthalate buffer) in 2006 and APMP.QM-K9/APMP.QM-P16 (a phosphate buffer) in 2010-2011. The results can be used further by any participant to support its CMC claim at least for a borate buffer. That claim will concern the pH method employed by the participant during this comparison and will cover the used temperature(s) or the full temperature range between 15°C and 37 °C for the participant which measured pH values at the three temperatures. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Role of histidine-related compounds to intracellular buffering in fish skeletal muscle.

PubMed

Abe, H; Dobson, G P; Hoeger, U; Parkhouse, W S

1985-10-01

Histidine-related compounds (HRC) were analyzed in fish skeletal muscle as a means of identifying their precise role in intracellular buffering. Fish muscle was used because it contains two functionally and spatially distinct fiber types, red and white. Two fish species, rainbow trout (Salmo gairdneri) and the Pacific blue marlin (Makaira nigricans), were studied because these species demonstrate widely different activity patterns. Marlin red and white muscle buffer capacity was two times higher than trout with white muscle, buffering being two times greater than red in both species. Buffer capacity was highest in the 6.5-7.5 pH range for all tissues, which corresponded to their high anserine levels. The titrated HRC buffering was greater than the observed HRC buffering, which suggested that not all HRC were available to absorb protons. The HRC contribution to total cellular buffering varied from a high of 62% for marlin white to a low of 7% for trout red. The other principal buffers were found to be phosphate and protein with taurine contributing within red muscle in the 7.0-8.0 pH range. HRC were found to be dominant in skeletal muscle buffering by principally accounting for the buffering capacity differences found between the species and fiber types.

Determination of monosaccharides derivatized with 2-aminobenzoic Acid by capillary electrophoresis.

PubMed

Abo, Mitsuru; He, Li-Ping; Sato, Kae; Okubo, Akira

2013-01-01

Reducing monosaccharides were derivatized with 2-aminobenzoic acid (2-AA) through reductive amination using sodium cyanoborohydride as a reductant, and the derivatives were separated by capillary zone electrophoresis with UV detection using 50 mM sodium phosphate (pH 5.5) or 150 mM sodium borate-50 mM sodium phosphate (pH 7.0) running buffer. The derivatives of monosaccharides, which are major components of various carbohydrate materials, were completely separated within 25 min.

Effect of bioglass 45S5 addition on properties, microstructure and cellular response of tetracalcium phosphate/monetite cements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stulajterova, R., E-mail: rstulajterova@saske.sk

Tetracalcium phosphate/nanomonetite (TTCPMH) cement composites with 7.5 and 15 wt% addition of melt-derived 45S5 bioactive glass were prepared by mechanical homogenization of powder components and 2% NaH{sub 2}PO{sub 4} solution was used as a hardening liquid. The properties of composites with the acidic (Ca/P ratio equal 1.5) or basic (Ca/P ratio equal 1.67) TTCPMH component were compared. Addition of glass component caused rapid rise in pH of composites up to 10. In microstructure of basic cement composite, the large bioglass particles weakly bounded to surrounding cement matrix were found contrary to a more compact microstructure of acidic cement composites withmore » the high number of spherical silica particles. Both the significant refinement of hydroxyapatite particles and the change to needle-like morphology with rise in the content of bioglass were identified in hydroxyapatite coatings created during soaking of composites in phosphate buffered saline. In acidic cement mixtures, the increase of compressive strength with an amount of bioglass was found whereas the opposite tendency was revealed in the case of basic cement mixtures. The higher concentrations of ions were verified in solutions after immersion of acidic cement composites. The severe cytotoxicity of extracts and composite cement substrates containing 15 wt% of bioglass demonstrated adverse effects of both the ionic concentrations and unappropriate surface texture on proliferation of mesenchymal stem cells. The enhanced ALP activities of cells cultured on composite cements confirmed the positive effect of bioactive glass addition on differentiation of mesenchymal stem cells. - Highlights: • Novel B45S5 bioglass/tetracalcium phosphate/nanomonetite cement composites • Cement basicity negatively affected their microstructure. • Acid composite cements had higher compressive strengths than basic composites. • Fast differentiation of MSC to osteoblast line on composite with 7.5 wt% of bioglass • Severe cytotoxicity of 24 h extracts from composites with 15 wt% of bioglass.« less

Stretchable glucose biofuel cell with wirings made of multiwall carbon nanotubes

NASA Astrophysics Data System (ADS)

Fujimagari, Yusuke; Nishioka, Yasushiro

2015-12-01

In this study, we fabricated a flexible and stretchable glucose-biofuel cell with wirings made of multi wall carbon nanotube (MWCNTs) on a polydimethylsiloxane substrate. The biofuel cell investigated consists of a porous carbon anode (area of 30 mm2) modified by glucose oxidase and ferrocene, and a cathode (area of 30 mm2) modified by bilirubin oxidase. The anode and the cathode were connected with the MWCNT wirings. The maximum power of 0.31 μW at 76.6 mV, which corresponds to a power density of 1.04 μW/cm2, was realized by immersing the biofuel cell in a phosphate buffer solution with a glucose concentration of 100 mM, at room temperature.

Accelerated Hydrolysis of Aspirin Using Alternating Magnetic Fields

NASA Astrophysics Data System (ADS)

Reinscheid, Uwe M.

2009-08-01

The major problem of current drug-based therapy is selectivity. As in other areas of science, a combined approach might improve the situation decisively. The idea is to use the pro-drug principle together with an alternating magnetic field as physical stimulus, which can be applied in a spatially and temporarily controlled manner. As a proof of principle, the neutral hydrolysis of aspirin in physiological phosphate buffer of pH 7.5 at 40 °C was chosen. The sensor and actuator system is a commercially available gold nanoparticle (NP) suspension which is approved for animal usage, stable in high concentrations and reproducibly available. Applying the alternating magnetic field of a conventional NMR magnet system accelerated the hydrolysis of aspirin in solution.

Development of a new class of chemical and biological ultrasensors: Ribonuclease contamination and control

NASA Technical Reports Server (NTRS)

1984-01-01

In order to define ribonuclease contamination, an assay for ribonuclease having picogram level sensitivity was established. In this assay, polycytidylic acid is digested by ribonuclease leading to smaller fragments of poly C that remain soluble after treatment of the sample with perchloric acid and lanthanum acetate. An absorbance measurement at 260 nm of the supernatant from the centrifuged sample measures the ribonuclease. A standard curve is shown. Using this assay procedure, ribonuclease contamination was found to be significant in routine laboratory proteins, in particular, bovine serum albumin, lysozyme, catalase, and cytochrome C. This was confirmed by demonstrating a considerable reduction in this activity in the presence of phosphate buffer since phosphate inhibits ribonuclease. Ribonuclease contamination was not significantly encountered in routine laboratory glassware, plasticware, column surfaces, chromatographic particles, and buffer reagents, including airborne contamination. Some contamination could be introduced by fingerprints, however.

Flexible, Low-Cost Sensor Based on Electrolyte Gated Carbon Nanotube Field Effect Transistor for Organo-Phosphate Detection

PubMed Central

Bhatt, Vijay Deep; Joshi, Saumya; Becherer, Markus; Lugli, Paolo

2017-01-01

A flexible enzymatic acetylcholinesterase biosensor based on an electrolyte-gated carbon nanotube field effect transistor is demonstrated. The enzyme immobilization is done on a planar gold gate electrode using 3-mercapto propionic acid as the linker molecule. The sensor showed good sensing capability as a sensor for the neurotransmitter acetylcholine, with a sensitivity of 5.7 μA/decade, and demonstrated excellent specificity when tested against interfering analytes present in the body. As the flexible sensor is supposed to suffer mechanical deformations, the endurance of the sensor was measured by putting it under extensive mechanical stress. The enzymatic activity was inhibited by more than 70% when the phosphate-buffered saline (PBS) buffer was spiked with 5 mg/mL malathion (an organophosphate) solution. The biosensor was successfully challenged with tap water and strawberry juice, demonstrating its usefulness as an analytical tool for organophosphate detection. PMID:28524071

Microwave fixation versus formalin fixation of surgical and autopsy tissue.

PubMed

Login, G R

1978-05-01

Microwave irradiation of surgical and autopsy tissue penetrates, fixes, and hardens the tissue almost immediately (the fluid media used in the microwave consisted of saline, ten percent phosphate buffered formalin, and distilled water). Tissue sections from a representative sample of organs were tested. Comparable sections were simultaneously fixed in a phosphate buffered ten percent formalin bath in a vaccum oven as a control. Hematoxylin and eosin were used to stain the sections. Results equal to and superior to the control method were obtained. Saline microwave fixation was superior to formalin microwave fixation. Tissues placed in Zenker's solution and fixed in standard microwave oven (for approximately one minute) yielded results at least equal to conventional Zenker fixation (approximately two hours). No tissue hardening resulted from Zenker microwave fixation. A unique time versus temperature graph (microwave heating curve) reduces individual variation with this technique.

Synthesis of aldehyde-linked nucleotides and DNA and their bioconjugations with lysine and peptides through reductive amination.

PubMed

Raindlová, Veronika; Pohl, Radek; Hocek, Michal

2012-03-26

5-(5-Formylthienyl)-, 5-(4-formylphenyl)- and 5-(2-fluoro-5-formylphenyl)cytosine 2'-deoxyribonucleoside mono- (dC(R)MP) and triphosphates (dC(R)TP) were prepared by aqueous Suzuki-Miyaura cross-coupling of 5-iodocytosine nucleotides with the corresponding formylarylboronic acids. The dC(R)TPs were excellent substrates for DNA polymerases and were incorporated into DNA by primer extension or PCR. Reductive aminations of the model dC(R)MPs with lysine or lysine-containing tripeptide were studied and optimized. In aqueous phosphate buffer (pH 6.7) the yields of the reductive aminations with tripeptide III were up to 25 %. Bioconjugation of an aldehyde-containing DNA with a lysine-containing tripeptide was achieved through reductive amination in yields of up to 90 % in aqueous phosphate buffer. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Purification of peroxidase from Horseradish (Armoracia rusticana) roots.

PubMed

Lavery, Christopher B; Macinnis, Morgan C; Macdonald, M Jason; Williams, Joanna Bassey; Spencer, Colin A; Burke, Alicia A; Irwin, David J G; D'Cunha, Godwin B

2010-08-11

Peroxidase (EC 1.11.1.7) from horseradish ( Armoracia rusticana ) roots was purified using a simple, rapid, three-step procedure: ultrasonication, ammonium sulfate salt precipitation, and hydrophobic interaction chromatography on phenyl Sepharose CL-4B. The preparation gave an overall yield of 71%, 291-fold purification, and a high specific activity of 772 U mg(-1) protein. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the purified enzyme was homogeneous and had a molecular weight of approximately 40 kDa. The isolated enzyme had an isoelectric point of 8.8 and a Reinheitszahl value of 3.39 and was stable when stored in the presence of glycerol at -20 degrees C, with >95% retention of original enzyme activity for at least 6 months. Maximal activity of purified horseradish peroxidase (HRP) was obtained under different optimized conditions: substrate (guaiacol and H(2)O(2)) concentrations (0.5 and 0.3 mM, respectively), type of buffer (50 mM phosphate buffer), pH (7.0), time (1.0 min), and temperature of incubation (30 degrees C). In addition, the effect of HRP and H(2)O(2) in a neutral-buffered aqueous solution for the oxidation of phenol and 2-chlorophenol substrates was also studied. Different conditions including concentrations of phenol/2-chlorophenol, H(2)O(2), and enzyme, time, pH, and temperature were standardized for the maximal activity of HRP with these substrates; under these optimal conditions 89.6 and 91.4% oxidations of phenol and 2-chlorophenol were obtained, respectively. The data generated from this work could have direct implications in studies on the commercial production of this biotechnologically important enzyme and its stability in different media.

Analytical Quality by Design in pharmaceutical quality assurance: Development of a capillary electrophoresis method for the analysis of zolmitriptan and its impurities.

PubMed

Orlandini, Serena; Pasquini, Benedetta; Caprini, Claudia; Del Bubba, Massimo; Pinzauti, Sergio; Furlanetto, Sandra

2015-11-01

A fast and selective CE method for the determination of zolmitriptan (ZOL) and its five potential impurities has been developed applying the analytical Quality by Design principles. Voltage, temperature, buffer concentration, and pH were investigated as critical process parameters that can influence the critical quality attributes, represented by critical resolution values between peak pairs, analysis time, and peak efficiency of ZOL-dimer. A symmetric screening matrix was employed for investigating the knowledge space, and a Box-Behnken design was used to evaluate the main, interaction, and quadratic effects of the critical process parameters on the critical quality attributes. Contour plots were drawn highlighting important interactions between buffer concentration and pH, and the gained information was merged into the sweet spot plots. Design space (DS) was established by the combined use of response surface methodology and Monte Carlo simulations, introducing a probability concept and thus allowing the quality of the analytical performances to be assured in a defined domain. The working conditions (with the interval defining the DS) were as follows: BGE, 138 mM (115-150 mM) phosphate buffer pH 2.74 (2.54-2.94); temperature, 25°C (24-25°C); voltage, 30 kV. A control strategy was planned based on method robustness and system suitability criteria. The main advantages of applying the Quality by Design concept consisted of a great increase of knowledge of the analytical system, obtained throughout multivariate techniques, and of the achievement of analytical assurance of quality, derived by probability-based definition of DS. The developed method was finally validated and applied to the analysis of ZOL tablets. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Oxidation kinetics of guanine in DNA molecules adsorbed onto indium tin oxide electrodes.

PubMed

Armistead, P M; Thorp, H H

2001-02-01

Oligonucleotides containing the guanine nucleobase were adsorbed onto ITO electrodes from mixtures of DMF and acetate buffer. Chronocoulometry and chronoamperometry were performed on the modified electrodes in both phosphate buffer and buffer containing low concentrations of the inorganic complex Ru(bpy)3(2+) (bpy = 2,2' bipyridine), which catalyzes guanine oxidation. The charge and current evolution with and without the catalyst were compared to the charge and current evolution for electrodes that were treated with identical oligonucleotides that were substituted at every guanine with the electrochemically inert nucleobase hypoxanthine. Chronocoulometry over 2.5 s shows that roughly 2 electrons per guanine were transferred to the electrode in both the presence and absence of Ru(bpy)3(2+), although at a slower rate for the uncatalyzed process. Chronoamperograms measured over 250 ms can be fit to a double exponential decay, with the intensity of the fast component roughly 6-20 times greater than that of the slow component. First- and second-order rate constants for catalytic and direct guanine oxidation were determined from the fast component. The maximum catalytic enhancement for immobilized guanine was found to be i(cat)/i(d) = 4 at 25 microM Ru(bpy)3(2+). The second-order rate constant for the catalyzed reaction was 1.3 x 10(7) M(-1) s(-1), with an apparent dissociation constant of 8.8 microM. When compared to parallel studies in solution, a smaller value of the dissociation constant and a larger value of the second-order rate constant are observed, probably due to distortion of the immobilized DNA, an increase in the local negative charge due to the oxygen sites on the ITO surface, and redox cycling of the catalyst, which maintains the surface concentration of the active form.

Determination of bromhexine in plasma by reversed-phase liquid chromatography. Interference of lipoproteins on extraction.

PubMed

Johansson, M; Lenngren, S

1988-11-18

Extraction of the hydrophobic tertiary amine bromhexine from plasma using cyclohexane-heptafluorobutanol (99.5:0.5, v/v) was studied at different pH values. The extraction yield from buffer solutions was quantitative at pH greater than 4.1, but from plasma the extraction yield decreased with increasing pH. Furthermore, at pH 8.4 the extraction yield varied greatly (56-99%) in different human plasma. The addition of lipoproteins to phosphate buffer, at pH 8.1, decreased the extraction yields considerably. Quantitative extraction from plasma was obtained by using a very long extraction time at pH 8.4 or by decreasing the pH to 5.4. The chromatographic system consisted of a reversed-phase column (Nucleosil C18, 5 microns) with an acidic mobile phase (methanol-phosphate buffer, pH 2) containing an aliphatic tertiary amine. UV detection at 308 or 254 nm was used. The limit of quantitation was 5 ng/ml using 3.00 ml of plasma and detection at 254 nm. The intra-assay precision for bromhexine was better than 3.6% at 5 ng/ml.

Biomethylation and Volatilization of Arsenic by Model Protozoan Tetrahymena pyriformis under Different Phosphate Regimes

PubMed Central

Yin, Xixiang; Wang, Lihong; Zhang, Zhanchao; Fan, Guolan; Liu, Jianjun; Sun, Kaizhen; Sun, Guo-Xin

2017-01-01

Tetrahymena pyriformis, a freshwater protozoan, is common in aquatic systems. Arsenic detoxification through biotransformation by T. pyriformis is important but poorly understood. Arsenic metabolic pathways (including cellular accumulation, effluxion, biomethylation, and volatilization) of T. pyriformis were investigated at various phosphate concentrations. The total intracellular As concentration increased markedly as the external phosphate concentration decreased. The highest concentration was 168.8 mg·kg−1 dry weight, after exposure to As(V) for 20 h. Inorganic As was dominant at low phosphate concentrations (3, 6, and 15 mg·L−1), but the concentration was much lower at 30 mg·L−1 phosphate, and As(V) contributed only ~7% of total cellular As. Methylated As contributed 84% of total As at 30 mg·L−1 phosphate, and dimethylarsenate (DMAs(V)) was dominant, contributing up to 48% of total As. Cellular As effluxion was detected, including inorganic As(III), methylarsenate (MAs(V)) and DMAs(V). Volatile As was determined at various phosphate concentrations in the medium. All methylated As concentrations (intracellular, extracellular, and volatilized) had significant linear positive relationships with the initial phosphate concentration. To the best of our knowledge, this is the first study of As biotransformation by protozoa at different phosphate concentrations. PMID:28216593

Development and validation of a simple and robust method for arsenic speciation in human urine using HPLC/ICP-MS.

PubMed

Sen, Indranil; Zou, Wei; Alvaran, Josephine; Nguyen, Linda; Gajek, Ryszard; She, Jianwen

2015-01-01

In order to better distinguish the different toxic inorganic and organic forms of arsenic (As) exposure in individuals, we have developed and validated a simple and robust analytical method for determining the following six As species in human urine: arsenous (III) acid (As-III), As (V) acid, monomethylarsonic acid, dimethylarsinic acid, arsenobetaine (AsB), and arsenocholine. In this method, human urine is diluted using a pH 5.8 buffer, separation is performed using an anion exchange column with isocratic HPLC, and detection is achieved using inductively coupled plasma-MS. The method uses a single mobile phase consisting of low concentrations of both phosphate buffer (5 mM) and ammonium nitrate salt (5 mM) at pH 9.0; this minimizes the column equilibration time and overcomes challenges with separation between AsB and As-III. In addition, As-III oxidation is prevented by degassing the sample preparation buffer at pH 5.8, degassing the mobile phase online at pH 9.0, and by the use of low temperature (-70 °C) and flip-cap airtight tubes for long term storage of samples. The method was validated using externally provided reference samples. Results were in agreement with target values at varying concentrations and successfully passed external performance test criteria. Internal QC samples were prepared and repeatedly analyzed to assess the method's long-term precision, and further analyses were completed on anonymous donor urine to assess the quality of the method's baseline separation. Results from analyses of external reference samples agreed with target values at varying concentrations, and results from precision studies yielded absolute CV values of 3-14% and recovery from 82 to 115% for the six As species. Analysis of anonymous donor urine confirmed the well-resolved baseline separation capabilities of the method for real participant samples.

Effects of different carboxylic ester spacers on chemical stability, release characteristics, and anticancer activity of mono-PEGylated curcumin conjugates.

PubMed

Wichitnithad, Wisut; Nimmannit, Ubonthip; Callery, Patrick S; Rojsitthisak, Pornchai

2011-12-01

We investigated the effects of different carboxylic ester spacers of mono-PEGylated curcumin conjugates on chemical stability, release characteristics, and anticancer activity. Three novel conjugates were synthesized with succinic acid, glutaric acid, and methylcarboxylic acid as the respective spacers between curcumin and monomethoxy polyethylene glycol of molecular weight 2000 (mPEG(2000) ): mPEG(2000) -succinyl-curcumin (PSC), mPEG(2000) -glutaryl-curcumin (PGC), and mPEG(2000) -methylcarboxyl-curcumin (PMC), respectively. Hydrolysis of all conjugates in buffer and human plasma followed pseudo first-order kinetics. In phosphate buffer, the overall degradation rate constant and half-life values indicated an order of stability of PGC > PSC > PMC > curcumin. In human plasma, more than 90% of curcumin was released from the esters after incubation for 0.25, 1.5, and 2 h, respectively. All conjugates exhibited cytotoxicity against four human cancer cell lines: Caco-2 (colon), KB (oral cavity), MCF7 (breast), and NCI-H187 (lung) with half maximal inhibitory concentration (IC(50) ) values in the range of 1-6 µM, similar to that observed for curcumin itself. Our results suggest that mono-PEGylation of curcumin produces prodrugs that are stable in buffer at physiological pH, release curcumin readily in human plasma, and show anticancer activity. Copyright © 2011 Wiley-Liss, Inc.

ssDNA degradation along capillary electrophoresis process using a Tris buffer.

PubMed

Ric, Audrey; Ong-Meang, Varravaddheay; Poinsot, Verena; Martins-Froment, Nathalie; Chauvet, Fabien; Boutonnet, Audrey; Ginot, Frédéric; Ecochard, Vincent; Paquereau, Laurent; Couderc, François

2017-06-01

Tris-Acetate buffer is currently used in the selection and the characterization of ssDNA by capillary electrophoresis (CE). By applying high voltage, the migration of ionic species into the capillary generates a current that induces water electrolysis. This phenomenon is followed by the modification of the pH and the production of Tris derivatives. By injecting ten times by capillary electrophoresis ssDNA (50 nM), the whole oligonucleotide was degraded. In this paper, we will show that the Tris buffer in the running vials is modified along the electrophoretic process by electrochemical reactions. We also observed that the composition of the metal ions changes in the running buffer vials. This phenomenon, never described in CE, is important for fluorescent ssDNA analysis using Tris buffer. The oligonucleotides are degraded by electrochemically synthesized species (present in the running Tris vials) until it disappears, even if the separation buffer in the capillary is clean. To address these issues, we propose to use a sodium phosphate buffer that we demonstrate to be electrochemically inactive. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multiprobe Spectroscopic Inverstigation of Molecular-level Behavior within Aqueous 1-Butyl-3-methylimidazolium Tetrafluoroborate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarkar, Abhra; Ali, Maroof; Baker, Gary A

2009-01-01

In this work, an array of molecular-level solvent featuressincluding solute-solvent/solvent-solvent interactions, dipolarity, heterogeneity, dynamics, probe accessibility, and diffusionswere investigated across the entire composition of ambient mixtures containing the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim][BF4], and pH 7.0 phosphate buffer, based on results assembled for nine different molecular probes utilized in a range of spectroscopic modes. These studies uncovered interesting and unusual solvatochromic probe behavior within this benchmark mixture. Solvatochromic absorbance probessa watersoluble betaine dye (betaine dye 33), N,N-diethyl-4-nitroaniline, and 4-nitroanilineswere employed to determine ET (a blend of dipolarity/polarizability and hydrogen bond donor contributions) and the Kamlet-Taft indices * (dipolarity/polarizability), R (hydrogenmore » bond donor acidity), and (hydrogen bond acceptor basicity) characterizing the [bmim][BF4] + phosphate buffer system. These parameters each showed a marked deviation from ideality, suggesting selective solvation of the individual probe solutes by [bmim][BF4]. Similar conclusions were derived from the responses of the fluorescent polarity-sensitive probes pyrene and pyrene-1-carboxaldehyde. Importantly, the fluorescent microfluidity probe 1,3-bis(1-pyrenyl)propane senses a microviscosity within the mixture that significantly exceeds expectations derived from simple interpolation of the behavior in the neat solvents. On the basis of results from this probe, a correlation between microviscosity and bulk viscosity was established; pronounced solvent-solvent hydrogen-bonding interactions were implicit in this behavior. The greatest deviation from ideal additive behavior for the probes studied herein was consistently observed to occur in the buffer-rich regime. Nitromethane-based fluorescence quenching of pyrene within the [bmim][BF4] + phosphate buffer system showed unusual compliance with a sphere-of-action quenching model, a further manifestation of the microheterogeneity of the system. Fluorescence correlation spectroscopic results for both small (BODIPY FL) and macromolecular (Texas Red-10 kDa dextran conjugate) diffusional probes provide additional evidence in support of microphase segregation inherent to aqueous [bmim][BF4].« less

Bioactive calcium phosphate–based glasses and ceramics and their biomedical applications: A review

PubMed Central

Islam, Md Towhidul; Felfel, Reda M; Abou Neel, Ensanya A; Grant, David M; Ahmed, Ifty; Hossain, Kazi M Zakir

2017-01-01

An overview of the formation of calcium phosphate under in vitro environment on the surface of a range of bioactive materials (e.g. from silicate, borate, and phosphate glasses, glass-ceramics, bioceramics to metals) based on recent literature is presented in this review. The mechanism of bone-like calcium phosphate (i.e. hydroxyapatite) formation and the test protocols that are either already in use or currently being investigated for the evaluation of the bioactivity of biomaterials are discussed. This review also highlights the effect of chemical composition and surface charge of materials, types of medium (e.g. simulated body fluid, phosphate-buffered saline and cell culture medium) and test parameters on their bioactivity performance. Finally, a brief summary of the biomedical applications of these newly formed calcium phosphate (either in the form of amorphous or apatite) is presented. PMID:28794848

Hormone-Dependence of Sarin Lethality in Rats: Sex Differences and Stage of the Estrous Cycle

DTIC Science & Technology

2015-06-12

that causes numerous physiological events including miosis, salivation , respiratory failure, tremors, seizures, and death. Treatment regimens that...into 96-well plates. The reactions were initiated by the addition of 290 μL of 50 mM sodium phosphate buffer ( pH 8.0) containing one of the following...buffer containing 50mMHEPES pH 7.4 in a total volume of 280 μL. Treat- ed samples were loaded into a 96-microtiter plate well, and the reaction was

A Core Facility for the Study of Neurotoxins of Biological Origin

DTIC Science & Technology

1990-06-15

toxicity of 5 x 10-8 MLD/mg protein. Sodium 125 Iodine and the Bolton-Hunter Reagent - 1251odine were purchased from Amersham. Chloramine- T , glycine...tyrosine and all salts and buffers were from Sigma Chemical Co. and Fisher. Iodination procedures. The chloramine- T method was used essentially as...previously described. Tetanus toxin (100 ig) in sodium phosphate buffer (100 mM, pH 7.4) was mixed with chloramine- T (0.5 mM) and Na 1251 (1 mCi) for 30

[Isolation and determination of the seeds of Pachyrrhizus errosus protein by high performance gel filtration chromatography (GFC)].

PubMed

Wu, H; Hao, B; Tang, G; Lin, Y

1997-03-01

From the seeds of Pachyrrhizus errosus, three protein constituents, namel PE1, PE2 and PE3, have been isolated and purified by extraction with 5mmol/L phosphate saline (0.9% NaCl) buffer (PB) at pH 7.2, and S-Sepharose Fast Flow Column (2.6cm x 15cm) chromatography which eluted with 5mmol/L phosphate buffer (pH 7.0) containing 1mmol/L NaCl. Three proteins were burther separated on two connected Protein-Pak 60+Protein-Pak 125 [7.5mm x 39cm, 10microm] columns with mobile phase of 0.2mol/L phosphate buffer (pH 6.5). The flow rate was kept constant at 0.8mL/min by YSB-2 type high press pump. The effluent was monitored at a wavelength of 280nm on photodiode array detector. These three proteins are proved to be homogeneous by SDS-PAGE, IEF and HPGFC experiments, and all present the typical absorption spectra in ultraviolet region. The moleculer weights of the three proteins are approxiamtely 33000D, 14500D and 14000D respectively by SDS-PAGE. But as using HPGFC analysis, the MW value of PE2 is 28000D. This indicates PE2 may be composed of two chains joined by disulfide bond, which is further proved from the latter amino acid composition analysis. The isoelectric points of three proteins are 4.5, 6.5 and 7.5 respectively by using IEF. The amion acids compositions of the three proteins were determined with OPA post-column derivatization/fluorescence detection.

Two new glucose 6-phosphate dehydrogenase variants associated with congenital nonspherocytic hemolytic anemia found in Japan: GD(-) Tokushima and GD(-) Tokyo.

PubMed

Miwa, S; Ono, J; Nakashima, K; Abe, S; Kageoka, T

1976-01-01

Two new variants of glucose 6-phosphate dehydrogenase (G6PD) deficiency associated with chronic nonspherocytic hemolytic anemia were discovered in Japan. Gd(-) Tokushima was found in a 17-years-old male whose erythrocytes contained 4.4% of normal enzyme activity. Partially purified enzyme revealed a main band of normal electrophoretic mobility with additional two minor bands of different mobility; normal Km G6P, and Km NADP five-to sixfold higher than normal; normal utilization of 2-deoxy-G6P, galactose-6P, and deamino-NADP; marked thermal instability; a normal pH curve; and normal Ki NADPH. The hemolytic anemia was moderate to severe. Gd(-) Tokyo was characterized from a 15-year-old male who had chronic nonspherocytic hemolytic anemia of mild degree. The erythrocytes contained 3% of normal enzyme activity, and partially purified enzyme revealed slow electrophoretic mobility (90% of normal for both a tris-hydrochloride buffer system and a tris-EDTA-borate buffer system, and 70% of normal for a phosphate buffer system); normal Km G6P and Km NADP; normal utilization of 2-deoxy-G6P, galactose-6P, and deamino-NADP; greatly increased thermal instability; a normal pH curve; and normal Ki NADPH. These two variants are clearly different from hitherto described G6PD variants, including the Japanese variants Gd(-) Heian and Gd(-) Kyoto. The mothers of both Gd(-) Tokushima and Gd(-) Tokoyo were found to be heterozygote by an ascorbate-cyanide test.

A comparative study of the processes of generation of singlet oxygen upon irradiation of aqueous preparations on the basis of chlorin e6 and coproporphyrin III

NASA Astrophysics Data System (ADS)

Bagrov, I. V.; Belousova, I. M.; Gorelov, S. I.; Dobrun, M. V.; Kiselev, V. M.; Kislyakov, I. M.; Kris'ko, A. V.; Kris'ko, T. K.

2017-02-01

The photosensitizing ability of an agent based on chlorin e6 (Photoditazin), which is used for photodynamic diagnosis and therapy, is compared with that of a new preparation on the basis of coproporphyrin III in the environment of a phosphate buffer and a simulated biological environment (albumin solution). The efficiency of singlet-oxygen production was estimated by EPR spectroscopy and spectroscopy in the UV and visible ranges with the use of "chemical traps" of singlet oxygen. By irradiating drugs with LED emission centered at λmax = 520 nm, we determined the quantum yield of singlet-oxygen production in a buffer solution; the obtained values are 0.60 and 0.37 for chlorine and coproporphyrin, respectively. The steady-state concentration of singlet oxygen upon irradiation of solutions of the studied photosensitizers with concentrations of 12-43 μM and the density of radiation power within the 6-96 W/cm2 region was found to be in the region of 1010-1011 molecules/cm3. It is shown that the introduction into the solution of egg albumin (0.1%) reduces the sensitizing properties of the two drugs by two to three times, while the efficiencies of the preparations with respect to singlet-oxygen production become almost identical (0.19 and 0.17).

Desorption of Lipases Immobilized on Octyl-Agarose Beads and Coated with Ionic Polymers after Thermal Inactivation. Stronger Adsorption of Polymers/Unfolded Protein Composites.

PubMed

Virgen-Ortíz, Jose J; Pedrero, Sara G; Fernandez-Lopez, Laura; Lopez-Carrobles, Nerea; Gorines, Beatriz C; Otero, Cristina; Fernandez-Lafuente, Roberto

2017-01-05

Lipases from Candida antarctica (isoform B) and Rhizomucor miehei (CALB and RML) have been immobilized on octyl-agarose (OC) and further coated with polyethylenimine (PEI) and dextran sulfate (DS). The enzymes just immobilized on OC supports could be easily released from the support using 2% SDS at pH 7, both intact or after thermal inactivation (in fact, after inactivation most enzyme molecules were already desorbed). The coating with PEI and DS greatly reduced the enzyme release during thermal inactivation and improved enzyme stability. However, using OC-CALB/RML-PEI-DS, the full release of the immobilized enzyme to reuse the support required more drastic conditions: a pH value of 3, a buffer concentration over 2 M, and temperatures above 45 °C. However, even these conditions were not able to fully release the thermally inactivated enzyme molecules from the support, being necessary to increase the buffer concentration to 4 M sodium phosphate and decrease the pH to 2.5. The formation of unfolded protein/polymers composites seems to be responsible for this strong interaction between the octyl and some anionic groups of OC supports. The support could be reused five cycles using these conditions with similar loading capacity of the support and stability of the immobilized enzyme.

Enantioseparation of mandelic acid derivatives by high performance liquid chromatography with substituted β-cyclodextrin as chiral mobile phase additive and evaluation of inclusion complex formation

PubMed Central

Tong, Shengqiang; Zhang, Hu; Shen, Mangmang

2014-01-01

The enantioseparation of ten mandelic acid derivatives was performed by reverse phase high performance liquid chromatography with hydroxypropyl-β-cyclodextrin (HP-β-CD) or sulfobutyl ether-β-cyclodextrin (SBE-β-CD) as chiral mobile phase additives, in which inclusion complex formations between cyclodextrins and enantiomers were evaluated. The effects of various factors such as the composition of mobile phase, concentration of cyclodextrins and column temperature on retention and enantioselectivity were studied. The peak resolutions and retention time of the enantiomers were strongly affected by the pH, the organic modifier and the type of β-cyclodextrin in the mobile phase, while the concentration of buffer solution and temperature had a relatively low effect on resolutions. Enantioseparations were successfully achieved on a Shimpack CLC-ODS column (150×4.6 mm i.d., 5 μm). The mobile phase was a mixture of acetonitrile and 0.10 mol L-1 of phosphate buffer at pH 2.68 containing 20 mmol L-1 of HP-β-CD or SBE-β-CD. Semi-preparative enantioseparation of about 10 mg of α-cyclohexylmandelic acid and α-cyclopentylmandelic acid were established individually. Cyclodextrin-enantiomer complex stoichiometries as well as binding constants were investigated. Results showed that stoichiomertries for all the inclusion complex of cyclodextrin-enantiomers were 1:1. PMID:24893270

Immunochromatographic assay using gold nanoparticles for measuring salivary secretory IgA in dogs as a stress marker

NASA Astrophysics Data System (ADS)

Takahashi, Aki; Uchiyama, Shigeru; Kato, Yuya; Yuhi, Teruko; Ushijima, Hiromi; Takezaki, Makoto; Tominaga, Toshihiro; Moriyama, Yoshiko; Takeda, Kunio; Miyahara, Toshiro; Nagatani, Naoki

2009-06-01

The concentration of salivary secretory immunoglobulin A (sIgA) is a well-known stress marker for humans. The concentration of salivary sIgA in dogs has also been reported as a useful stress marker. In addition, salivary sIgA in dogs has been used to determine the adaptive ability of dogs for further training. There are conventional procedures based on enzyme-linked immunosorbent assay (ELISA) for measuring salivary sIgA in dogs. However, ELISA requires long assay time, complicated operations and is costly. In the present study, we developed an immunochromatographic assay for measuring salivary sIgA in dogs using a dilution buffer containing a non-ionic surfactant. We determined 2500-fold dilution as the optimum condition for dog saliva using a phosphate buffer (50 mM, pH 7.2) containing non-ionic surfactant (3 wt% Tween 20). The results obtained from the saliva samples of three dogs using immunochromatographic assay were compared with those obtained from ELISA. It was found that the immunochromatographic assay is applicable to judge the change in salivary sIgA in each dog. The immunochromatographic assay for salivary sIgA in dogs is a promising tool, which should soon become commercially available for predicting a dog's psychological condition and estimating adaptive ability for training as guide or police dogs.

Biosorption of mercury by the inactivated cells of Pseudomonas aeruginosa PU21 (Rip64)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, J.S.; Hong, J.

1994-10-01

Biomass of a mercury-resistance strain Pseudomonas aeruginosa PU21 (Rip64) and hydrogen-form cation exchange resin (AG 50W-X8) were investigated for their ability to adsorb mercury. The maximum adsorption capacity was approximately 180 mg Hg/g dry cell in deionized water and 400 mg Hg/g dry cell in sodium phosphate solution of pH 7.4, higher than the maximum mercury uptake capacity in the cation exchange resin. The mercury selectivity of the biomass over sodium ions was evaluated when 50 mM and 150 mM of Na[sup +] were present. Biosorption of mercury was also examined in sodium phosphate solution and phosphate-buffered saline solution containingmore » 50 mM and 150 mM of Na[sup +], respectively. It was found that the presence of Na[sup +] did not severely affect the biosorption of Hg[sup 2+], indicating a high mercury selectivity of the biomass over sodium ions. In contrast, the mercury uptake by the ion exchange resin was strongly inhibited by high sodium concentrations. The mercury biosorption was most favorable in sodium phosphate solution (pH 7.4), with a more than twofold increase in the maximum mercury uptake capacity. The pH was found to affect the adsorption of Hg[sup 2+] by the biomass and the optimal pH value was approximately 7.4. The adsorption of mercury on the biomass and the ion exchange resin appeared to follow the Langmuir or Freundlich adsorption isotherms.« less

Drug Release as a function of bioactivity, incubation regime, liquid, and initial load: Release of bortezomib from calcium phosphate-containing silica/collagen xerogels.

PubMed

Kruppke, Benjamin; Hose, Dirk; Schnettler, Reinhard; Seckinger, Anja; Rößler, Sina; Hanke, Thomas; Heinemann, Sascha

2018-04-01

The ability of silica-/collagen-based composite xerogels to act as drug delivery systems was evaluated by taking into account the initial drug concentration, bioactivity of the xerogels, liquid, and incubation regime. The proteasome inhibitor bortezomib was chosen as a model drug, used for the systemic treatment of multiple myeloma. Incubation during 14 days in phosphate-buffered saline (PBS) or simulated body fluid (SBF) showed a weak initial burst and was identified to be of first order with subsequent release being independent from the initial load of 0.1 or 0.2 mg bortezomib per 60 mg monolithic sample. Faster drug release occurred during incubation in SBF compared to PBS, and during static incubation without changing the liquid, compared to dynamic incubation with daily liquid changes. Drug-loaded xerogels with hydroxyapatite as a third component exhibited enhanced bioactivity retarding drug release, explained by formation of a surface calcium phosphate layer. The fastest release of 50% of the total drug load was observed for biphasic xerogels after 7 days during dynamic incubation in SBF. As a result, the presented concept is suitable for the intended combination of the advantageous bone substitution properties of xerogels and local application of drugs exemplified by bortezomib. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1165-1173, 2018. © 2017 Wiley Periodicals, Inc.

BIOKID: Randomized controlled trial comparing bicarbonate and lactate buffer in biocompatible peritoneal dialysis solutions in children [ISRCTN81137991

PubMed Central

Nau, Barbara; Schmitt, Claus P; Almeida, Margarida; Arbeiter, Klaus; Ardissino, Gianluigi; Bonzel, Klaus E; Edefonti, Alberto; Fischbach, Michel; Haluany, Karin; Misselwitz, Joachim; Kemper, Markus J; Rönnholm, Kai; Wygoda, Simone; Schaefer, Franz

2004-01-01

Background Peritoneal dialysis (PD) is the preferred dialysis modality in children. Its major drawback is the limited technique survival due to infections and progressive ultrafiltration failure. Conventional PD solutions exert marked acute and chronic toxicity to local tissues. Prolonged exposure is associated with severe histopathological alterations including vasculopathy, neoangiogenesis, submesothelial fibrosis and a gradual loss of the mesothelial cell layer. Recently, more biocompatible PD solutions containing reduced amounts of toxic glucose degradation products (GDPs) and buffered at neutral pH have been introduced into clinical practice. These solutions contain lactate, bicarbonate or a combination of both as buffer substance. Increasing evidence from clinical trials in adults and children suggests that the new PD fluids may allow for better long-term preservation of peritoneal morphology and function. However, the relative importance of the buffer in neutral-pH, low-GDP fluids is still unclear. In vitro, lactate is cytotoxic and vasoactive at the concentrations used in PD fluids. The BIOKID trial is designed to clarify the clinical significance of the buffer choice in biocompatible PD fluids. Methods/design The objective of the study is to test the hypothesis that bicarbonate based PD solutions may allow for a better preservation of peritoneal transport characteristics in children than solutions containing lactate buffer. Secondary objectives are to assess any impact of the buffer system on acid-base status, peritoneal tissue integrity and the incidence and severity of peritonitis. After a run-in period of 2 months during which a targeted cohort of 60 patients is treated with a conventional, lactate buffered, acidic, GDP containing PD fluid, patients will be stratified according to residual renal function and type of phosphate binding medication and randomized to receive either the lactate-containing Balance solution or the bicarbonate-buffered Bicavera® solution for a period of 10 months. Patients will be monitored by monthly physical and laboratory examinations. Peritoneal equilibration tests, 24-h dialysate and urine collections will be performed 4 times. Peritoneal biopsies will be obtained on occasion of intraabdominal surgery. Changes in small solute transport rates, markers of peritoneal tissue turnover in the effluent, acid-base status and peritonitis rates and severity will be analyzed. PMID:15485574

First characterization of extremely halophilic 2-deoxy-D-ribose-5-phosphate aldolase.

PubMed

Ohshida, Tatsuya; Hayashi, Junji; Satomura, Takenori; Kawakami, Ryushi; Ohshima, Toshihisa; Sakuraba, Haruhiko

2016-10-01

2-Deoxy-d-ribose-5-phosphate aldolase (DERA) catalyzes the aldol reaction between two aldehydes and is thought to be a potential biocatalyst for the production of a variety of stereo-specific materials. A gene encoding DERA from the extreme halophilic archaeon, Haloarcula japonica, was overexpressed in Escherichia coli. The gene product was successfully purified, using procedures based on the protein's halophilicity, and characterized. The expressed enzyme was stable in a buffer containing 2 M NaCl and exhibited high thermostability, retaining more than 90% of its activity after heating at 70 °C for 10 min. The enzyme was also tolerant to high concentrations of organic solvents, such as acetonitrile and dimethylsulfoxide. Moreover, H. japonica DERA was highly resistant to a high concentration of acetaldehyde and retained about 35% of its initial activity after 5-h' exposure to 300 mM acetaldehyde at 25 °C, the conditions under which E. coli DERA is completely inactivated. The enzyme exhibited much higher activity at 25 °C than the previously characterized hyperthermophilic DERAs (Sakuraba et al., 2007). Our results suggest that the extremely halophilic DERA has high potential to serve as a biocatalyst in organic syntheses. This is the first description of the biochemical characterization of a halophilic DERA. Copyright © 2016 Elsevier Inc. All rights reserved.

Coaxial atomic force microscope probes for dielectrophoresis of DNA under different buffer conditions

NASA Astrophysics Data System (ADS)

Tao, Yinglei; Kumar Wickramasinghe, H.

2017-02-01

We demonstrate a coaxial AFM nanoprobe device for dielectrophoretic (DEP) trapping of DNA molecules in Tris-EDTA (TE) and phosphate-buffered saline (PBS) buffers. The DEP properties of 20 nm polystyrene beads were studied with coaxial probes in media with different conductivities. Due to the special geometry of our DEP probe device, sufficiently high electric fields were generated at the probe end to focus DNA molecules with positive DEP. DEP trapping for both polystyrene beads and DNA molecules was quantitatively analyzed over the frequency range from 100 kHz to 50 MHz and compared with the Clausius-Mossotti theory. Finally, we discussed the negative effect of medium salinity during DEP trapping.

Simultaneous hydrogen and ethanol production from cascade utilization of mono-substrate in integrated dark and photo-fermentative reactor.

PubMed

Liu, Bing-Feng; Xie, Guo-Jun; Wang, Rui-Qing; Xing, De-Feng; Ding, Jie; Zhou, Xu; Ren, Hong-Yu; Ma, Chao; Ren, Nan-Qi

2015-01-01

Integrating hydrogen-producing bacteria with complementary capabilities, dark-fermentative bacteria (DFB) and photo-fermentative bacteria (PFB), is a promising way to completely recover bioenergy from waste biomass. However, the current coupled models always suffer from complicated pretreatment of the effluent from dark-fermentation or imbalance between dark and photo-fermentation, respectively. In this work, an integrated dark and photo-fermentative reactor (IDPFR) was developed to completely convert an organic substrate into bioenergy. In the IDPFR, Ethanoligenens harbinese B49 and Rhodopseudomonas faecalis RLD-53 were separated by a membrane into dark and photo chambers, while the acetate produced by E. harbinese B49 in the dark chamber could freely pass through the membrane into the photo chamber and serve as a carbon source for R. faecalis RLD-53. The hydrogen yield increased with increasing working volume of the photo chamber, and reached 3.38 mol H2/mol glucose at the dark-to-photo chamber ratio of 1:4. Hydrogen production by the IDPFR was also significantly affected by phosphate buffer concentration, glucose concentration, and ratio of dark-photo bacteria. The maximum hydrogen yield (4.96 mol H2/mol glucose) was obtained at a phosphate buffer concentration of 20 mmol/L, a glucose concentration of 8 g/L, and a ratio of dark to photo bacteria of 1:20. As the glucose and acetate were used up by E. harbinese B49 and R. faecalis RLD-53, ethanol produced by E. harbinese B49 was the sole end-product in the effluent from the IDPFR, and the ethanol concentration was 36.53 mmol/L with an ethanol yield of 0.82 mol ethanol/mol glucose. The results indicated that the IDPFR not only circumvented complex pretreatments on the effluent in the two-stage process, but also overcame the imbalance of growth and metabolic rate between DFB and PFB in the co-culture process, and effectively enhanced cooperation between E. harbinense B49 and R. faecalis RLD-53. Moreover, simultaneous hydrogen and ethanol production were achieved by coupling E. harbinese B49 and R. faecalis RLD-53 in the IDPFR. According to stoichiometry, the hydrogen and ethanol production efficiencies were 82.67% and 82.19%, respectively. Therefore, IDPFR was an effective strategy for coupling DFB and PFB to fulfill efficient energy recovery from waste biomass.

Dried venous blood samples for the detection and quantification of measles IgG using a commercial enzyme immunoassay.

PubMed Central

Riddell, Michaela A.; Byrnes, Graham B.; Leydon, Jennie A.; Kelly, Heath A.

2003-01-01

OBJECTIVES: To determine whether samples of dried venous blood (DVB) were an acceptable alternative to serum for detecting measles-specific IgG in a commercial enzyme immunoassay. METHODS: Paired samples of serum and DVB were collected from 98 suspected cases of measles and 1153 schoolchildren in Victoria, Australia. All samples were tested using the Dade Behring Enzygnost Anti-Measles-Virus/IgG immunoassay. DVB samples were eluted using either the sample buffer provided with the kit or 5% dry milk powder in phosphate-buffered saline-Tween 20. FINDINGS: DVB samples eluted by sample buffer showed significantly better linear correlation to the serum samples than did DVB samples eluted in 5% dry milk in phosphate-buffered saline-Tween 20. To improve the comparability of serum and DVB samples an adjustment factor of 1.28 was applied to the optical density (OD) values of DVB. This adjustment also enabled quantification of the titre of measles IgG in mIU/ml directly from the OD value using the alpha calculation as specified by the kit protocol. For DVB samples stored for less than six months at 4 degrees C, the assay showed an overall sensitivity of 98.4% and a specificity of 97.2% compared with the results of serum testing. CONCLUSION: These results illustrate the potential for DVB samples to be widely used with the Dade Behring enzyme immunoassay system for determining the immunity of the individual and the population to the measles virus. PMID:14758429

Chlorine transfer between glycine, taurine, and histamine: reaction rates and impact on cellular reactivity.

PubMed

Peskin, Alexander V; Midwinter, Robyn G; Harwood, David T; Winterbourn, Christine C

2005-02-01

Hypochlorous acid formed by activated neutrophils reacts with amines to produce chloramines. Chloramines vary in stability, reactivity, and cell permeability. We have examined whether chloramine exchange occurs between physiologically important amines or amino acids and if this affects interactions of chloramines with cells. We have demonstrated transchlorination reactions between histamine, glycine, and taurine chloramines by measuring chloramine decay rates with mixtures as well as by mass spectrometry. Kinetic analysis suggested the formation of an intermediate complex with a high Km. Apparent second-order rate constants, determined for concentrations

Chlorine transfer between glycine, taurine, and histamine: reaction rates and impact on cellular reactivity.

PubMed

Peskin, Alexander V; Midwinter, Robyn G; Harwood, David T; Winterbourn, Christine C

2004-11-15

Hypochlorous acid formed by activated neutrophils reacts with amines to produce chloramines. Chloramines vary in stability, reactivity, and cell permeability. We have examined whether chloramine exchange occurs between physiologically important amines or amino acids and if this affects interactions of chloramines with cells. We have demonstrated transchlorination reactions between histamine, glycine, and taurine chloramines by measuring chloramine decay rates with mixtures as well as by mass spectrometry. Kinetic analysis suggested the formation of an intermediate complex with a high K(m). Apparent second-order rate constants, determined for concentrations

Simplified procedure for encapsulating cytochrome c in silica aerogel nanoarchitectures while retaining gas-phase bioactivity.

PubMed

Harper-Leatherman, Amanda S; Iftikhar, Mariam; Ndoi, Adela; Scappaticci, Steven J; Lisi, George P; Buzard, Kaitlyn L; Garvey, Elizabeth M

2012-10-16

Cytochrome c (cyt. c) has been encapsulated in silica sol-gels and processed to form bioaerogels with gas-phase activity for nitric oxide through a simplified synthetic procedure. Previous reports demonstrated a need to adsorb cyt. c to metal nanoparticles prior to silica sol-gel encapsulation and processing to form aerogels. We report that cyt. c can be encapsulated in aerogels without added nanoparticles and retain structural stability and gas-phase activity for nitric oxide. While the UV-visible Soret absorbance and nitric oxide response indicate that cyt. c encapsulated with nanoparticles in aerogels remains slightly more stable and functional than cyt. c encapsulated alone, these properties are not very different in the two types of aerogels. From UV-visible and Soret circular dichroism results, we infer that cyt. c encapsulated alone self-organizes to reduce contact with the silica gel in a way that may bear at least some resemblance to the way cyt. c self-organizes into superstructures of protein within aerogels when nanoparticles are present. Both the buffer concentration and the cyt. c concentration of solutions used to synthesize the bioaerogels affect the structural integrity of the protein encapsulated alone within the dried aerogels. Optimized bioaerogels are formed when cyt. c is encapsulated from 40 mM phosphate buffered solutions, and when the loaded cyt. c concentration in the aerogel is in the range of 5 to 15 μM. Increased viability of cyt. c in aerogels is also observed when supercritical fluid used to produce aerogels is vented over relatively long times.

Polymer coated liposomes for dental drug delivery--interactions with parotid saliva and dental enamel.

PubMed

Nguyen, S; Hiorth, M; Rykke, M; Smistad, G

2013-09-27

The interactions between pectin coated liposomes and parotid saliva and dental enamel were studied to investigate their potential to mimic the protective biofilm formed naturally on tooth surfaces. Different pectin coated liposomes with respect to pectin type (LM-, HM- and AM-pectin) and concentration (0.05% and 0.2%) were prepared. Interactions between the pectin coated liposomes and parotid saliva were studied by turbidimetry and imaging by atomic force microscopy. The liposomes were adsorbed to hydroxyapatite (HA) and human dental enamel using phosphate buffer and parotid saliva as adsorption media. A continuous flow was imposed on the enamel surfaces for various time intervals to examine their retention on the dental enamel. The results were compared to uncoated, charged liposomes. No aggregation tendencies for the pectin coated liposomes and parotid saliva were revealed. This makes them promising as drug delivery systems to be used in the oral cavity. In phosphate buffer the adsorption to HA of pectin coated liposomes was significantly lower than the negative liposomes. The difference diminished in parotid saliva. Positive liposomes adsorbed better to the dental enamel than the pectin coated liposomes. However, when subjected to flow for 1h, no significant differences in the retention levels on the enamel were found between the formulations. For all formulations, more than 40% of the liposomes still remained on the enamel surfaces. At time point 20 min the retention of HM-pectin coated and positive liposomes were significantly higher. It was concluded that pectin coated liposomes can adsorb to HA as well as to the dental enamel. Their ability to retain on the enamel surfaces promotes the concept of using them as protective structures for the teeth. Copyright © 2013 Elsevier B.V. All rights reserved.

Phytosome-hyaluronic acid systems for ocular delivery of L-carnosine

PubMed Central

Abdelkader, Hamdy; Longman, Michael R; Alany, Raid G; Pierscionek, Barbara

2016-01-01

This study reports on L-carnosine phytosomes as an alternative for the prodrug N-acetyl-L-carnosine as a novel delivery system to the lens. L-carnosine was loaded into lipid-based phytosomes and hyaluronic acid (HA)-dispersed phytosomes. L-carnosine-phospholipid complexes (PC) of different molar ratios, 1:1 and 1:2, were prepared by the solvent evaporation method. These complexes were characterized with thermal and spectral analyses. PC were dispersed in either phosphate buffered saline pH 7.4 or HA (0.1% w/v) in phosphate buffered saline to form phytosomes PC1:1, PC1:2, and PC1:2 HA, respectively. These phytosomal formulations were studied for size, zeta potential, morphology, contact angle, spreading coefficient, viscosity, ex vivo transcorneal permeation, and cytotoxicity using primary human corneal cells. L-carnosine-phospholipid formed a complex at a 1:2 molar ratio and phytosomes were in the size range of 380–450 nm, polydispersity index of 0.12–0.2. The viscosity of PC1:2 HA increased by 2.4 to 5-fold compared with HA solution and PC 1:2, respectively; significantly lower surface tension, contact angle, and greater spreading ability for phytosomes were also recorded. Ex vivo transcorneal permeation parameters showed significantly controlled corneal permeation of L-carnosine with the novel carrier systems without any significant impact on primary human corneal cell viability. Ex vivo porcine lenses incubated in high sugar media without and with L-carnosine showed concentration-dependent marked inhibition of lens brunescence indicative of the potential for delaying changes that underlie cataractogenesis that may be linked to diabetic processes. PMID:27366062

Determination of chondroitin-6-sulphate by a competitive enzyme immunoassay using a biotinylated antigen.

PubMed

Kähnert, H; Brinkmann, T; Gässler, N; Kleesiek, K

1994-04-01

A competitive enzyme immunoassay was developed to determine chondroitin-6-sulphate in body fluids and cell cultures. The assay uses a monoclonal anti-chondroitin-6-sulphate antibody, immobilised to microtitre plates, and it involves a competitive binding reaction between chondroitin-6-sulphate in the samples and the biotinylated antigen. This assay enables the quantification of chondroitin-6-sulphate in the low concentration range of 16-120 micrograms/l. The intra-assay and inter-assay coefficients of variation are below 6.5% and 9.0%, respectively. More than 90% of chondroitin-6-sulphate was recovered when added to 0.1 mol/l phosphate-buffered saline, an albumin solution (40 g/l in phosphate-buffered saline) and cell culture medium (containing 100 ml/l foetal calf serum). Chondroitin-6-sulphate was also determined in sera of healthy male (n = 90) and female (n = 90) blood donors. The normal range was 55-169 micrograms/l. In men the mean value was estimated at 102.2 +/- 37.1 micrograms/l and in women at 98.7 +/- 26.4 micrograms/l. No age or sex dependence was observed. The urine excretion of chondroitin-6-sulphate in men (n = 16) was 44.5 +/- 21.1 mg/kg creatinine (mean +/- standard deviation) and in females (n = 10) 53.5 +/- 21.3 mg/kg creatinine. The clearance rate in men was 0.41 +/- 0.22 ml x min-1 and in women 0.38 +/- 0.15 ml x min-1. No sex dependence was found. Furthermore, the enzyme immunoassay was modified to measure the specific incorporation of a radioactively labelled precursor ([14C]galactosamine) into chondroitin-6-sulphate.(ABSTRACT TRUNCATED AT 250 WORDS)

Validation of dilution of plasma samples with phosphate buffered saline to eliminate the problem of small volumes associated with children infected with HIV-1 for viral load testing using Cobas AmpliPrep/COBAS TaqMan HIV-1 test, version 2.0 (CAP CTM HIV v2.0).

PubMed

Mine, Madisa; Nkoane, Tapologo; Sebetso, Gaseene; Sakyi, Bright; Makhaola, Kgomotso; Gaolathe, Tendani

2013-12-01

The sample requirement of 1 mL for the Roche COBAS AmpliPrep/COBAS TaqMan HIV-1 test, version 2.0 (CAP CTM HIV v2.0) limits its utility in measuring plasma HIV-1 RNA levels for small volume samples from children infected with HIV-1. Viral load monitoring is the standard of care for HIV-1-infected patients on antiretroviral therapy in Botswana. The study aimed to validate the dilution of small volume samples with phosphate buffered saline (1× PBS) when quantifying HIV-1 RNA in patient plasma. HIV RNA concentrations were determined in undiluted and diluted pairs of samples comprising panels of quality assessment standards (n=52) as well as patient samples (n=325). There was strong correlation (R(2)) of 0.98 and 0.95 within the dynamic range of the CAP CTM HIV v2.0 test between undiluted and diluted samples from quality assessment standards and patients, respectively. The difference between viral load measurements of diluted and undiluted pairs of quality assessment standards and patient samples using the Altman-Bland test showed that the 95% limits of agreement were between -0.40 Log 10 and 0.49 Log 10. This difference was within the 0.5 Log 10 which is generally considered as normal assay variation of plasma RNA levels. Dilution of samples with 1× PBS produced comparable viral load measurements to undiluted samples. Copyright © 2013 Elsevier B.V. All rights reserved.

A comparison of the biocompatibility of phosphate-buffered saline and dianeal 3.86% in the rat model of peritoneal dialysis.

PubMed

Wieczorowska-Tobis, K; Polubinska, A; Breborowicz, A; Oreopoulos, D G

2001-01-01

Phosphate-buffered saline (PBS), an isotonic solution with a physiologic pH can be considered an example of a biocompatible dialysis fluid. This study compared the biocompatibility of PBS with that of Dianeal 3.86% (Baxter Healthcare Corporation, Deerfield, IL, U.S.A.), using a model of peritoneal dialysis in the rat. In an acute experiment, after catheter implantation, rats were infused on day 1 with PBS, on day 5 with standard dialysis solution (Dianeal 3.86%), and on day 7 again with PBS. When rats were injected with Dianeal 3.86%, the inflammatory reaction was suppressed as compared with PBS. The cell count was lower with Dianeal (-85%, p < 0.001), the neutrophil:macrophage ratio in dialysate was 80% lower (p < 0.01), total protein concentration in the Dianeal dialysate was 73% lower (p < 0.01), and the dialysate nitrite level was 45% lower (p < 0.01). In a chronic experiment, after catheter implantation, rats were dialyzed for four weeks with PBS or with Dianeal 3.86%. At the end of the study, a 1-hour peritoneal equilibration test (PET) was performed. As evaluated on a semiquantitative scale, macroscopic changes in the peritoneum were more severe in rats exposed to PBS than in those exposed to Dianeal 3.86% (8.6 +/- 3.2 vs 5.2 +/- 2.6, p < 0.05). The thickness of the visceral peritoneum was comparable in both groups; but, in PBS-treated rats, the peritoneal interstitium contained more inflammatory cells and more new vessels. During the 1-hour PET, peritoneal permeability to water and solutes was comparable in the two groups. Despite a more physiologic composition, PBS is a less biocompatible peritoneal dialysis solutions than is standard, acidic, hypertonic dialysis solution.

A Sensitive Microplate Assay for Lipase Activity Measurement Using Olive Oil Emulsion Substrate: Modification of the Copper Soap Colorimetric Method.

PubMed

Mustafa, Ahmad; Karmali, Amin; Abdelmoez, Wael

2016-01-01

The present work involves a sensitive high-throughput microtiter plate based colorimetric assay for estimating lipase activity using cupric acetate pyridine reagent (CAPR). In the first approach, three factors two levels factorial design methodology was used to evaluate the interactive effect of different parameters on the sensitivity of the assay method. The optimization study revealed that the optimum CAPR concentration was 7.5% w/v, the optimum solvent was heptane and the optimum CAPR pH was 6. In the second approach, the optimized colorimetric microplate assay was used to measure lipase activity based on enzymatic hydrolysis of olive oil emulsion substrate at 37°C and 150 rpm. The emulsion substrates were formulated by using olive oil, triton X-100 (10% v/v in pH 8) and sodium phosphate buffer of pH 8 in ratio of 1:1:1 in the case of Candida sp. lipase. While in the case of immobilized lipozyme RMIM, The emulsion substrates were formulated by using olive oil, triton X-100 (1% v/v in pH 8) and sodium phosphate buffer of pH 8 in ratio of 2:1:1. Absorbance was measured at 655 nm. The stability of this assay (in terms of colored heptane phase absorbance readings) retained more than 92.5% after 24 h at 4°C compared to the absorbance readings measured at zero time. In comparison with other lipase assay methods, beside the developed sensitivity, the reproducibility and the lower limit of detection (LOD) of the proposed method, it permits analyzing of 96 samples at one time in a 96-well microplate. Furthermore, it consumes small quantities of chemicals and unit operations.

Viability of BCG suspensions, freshly prepared, stored, and light-exposed, estimated in different ways.

PubMed

CHRISTENSEN, P A; ROBINSON, M; WIDDICOMBE, M

1955-01-01

Tested by the roll-tube method, the inclusion in Dubos medium of oleic acid, Tween 80, or glucose hastens colony growth of tubercle bacilli (BCG), but the variability in counts between replicate bottles is large, and the mean count is low compared with that obtained in media free of these substances.The addition of glycerol hastens the development of colonies, and counts on glycerol medium may differ from those on glycerol-free medium. BCG suspensions stored at about 23 degrees C or exposed to skyshine or sunlight become glycerol-sensitive. Results obtained with glycerol medium may not, therefore, always be acceptable.The preparation and use in the roll-tube method of a simple medium is described. This consists of horse serum, M/15 phosphate buffer, and agar, and is preferable to more complex media as it tends to give higher viable counts and is easier to store and prepare.Stored at about 23 degrees C, the viability of BCG is better preserved in neutral phosphate buffer than in suspending fluids containing Sauton medium; no such difference is noticed with cold storage.Glutamic acid added in a concentration of 0.35% is without effect on the viability of suspensions stored in the cold, but under certain conditions it may have some preserving value at higher storage temperatures.Exposure to daylight in the laboratory, even for several hours, does not kill BCG or render it glycerol-sensitive. Exposure to intense skyshine does kill, but the mortality observed at the South African Institute for Medical Research is low compared with that recorded elsewhere. Possible explanations of this discrepancy are discussed.

Viability of BCG suspensions, freshly prepared, stored, and light-exposed, estimated in different ways

PubMed Central

Christensen, P. Agerholm; Robinson, Mary; Widdicombe, Margaret

1955-01-01

Tested by the roll-tube method, the inclusion in Dubos medium of oleic acid, Tween 80, or glucose hastens colony growth of tubercle bacilli (BCG), but the variability in counts between replicate bottles is large, and the mean count is low compared with that obtained in media free of these substances. The addition of glycerol hastens the development of colonies, and counts on glycerol medium may differ from those on glycerol-free medium. BCG suspensions stored at about 23°C or exposed to skyshine or sunlight become glycerol-sensitive. Results obtained with glycerol medium may not, therefore, always be acceptable. The preparation and use in the roll-tube method of a simple medium is described. This consists of horse serum, M/15 phosphate buffer, and agar, and is preferable to more complex media as it tends to give higher viable counts and is easier to store and prepare. Stored at about 23°C, the viability of BCG is better preserved in neutral phosphate buffer than in suspending fluids containing Sauton medium; no such difference is noticed with cold storage. Glutamic acid added in a concentration of 0.35% is without effect on the viability of suspensions stored in the cold, but under certain conditions it may have some preserving value at higher storage temperatures. Exposure to daylight in the laboratory, even for several hours, does not kill BCG or render it glycerol-sensitive. Exposure to intense skyshine does kill, but the mortality observed at the South African Institute for Medical Research is low compared with that recorded elsewhere. Possible explanations of this discrepancy are discussed. PMID:14379008

Phosphorus Amendment Efficacy for In Situ Remediation of Soil Lead Depends on the Bioaccessible Method.

PubMed

Obrycki, John F; Basta, Nicholas T; Scheckel, Kirk; Stevens, Brooke N; Minca, Kristen K

2016-01-01

A validated method is needed to measure reductions of in vitro bioaccessible (IVBA) Pb in urban soil remediated with amendments. This study evaluated the effect of in vitro extraction solution pH and glycine buffer on bioaccessible Pb in P-treated soils. Two Pb-contaminated soils (790-1300 mg Pb kg), one from a garden and one from a city lot in Cleveland, OH, were incubated in a bench scale experiment for 1 yr. Six phosphate amendments, including bone meal, fish bone, poultry litter, monoammonium phosphate, diammonium phosphate, and triple superphosphate, were added to containers at two application rates. Lead IVBA was assessed using USEPA Method 1340 and three modified versions of this method. Modifications included using solutions with pH 1.5 and 2.5 as well as using solutions with and without 0.4 mol L glycine. Soil amendments were ineffective in reducing IVBA Pb in these soils as measured by pH 1.5 with glycine buffer. The greatest reductions in IVBA Pb, from 5 to 26%, were found using pH 2.5 extractions. Lead mineral results showed several soil amendments promoted Pb phosphate formation, an indicator of remediation success. A significant negative linear relationship between reduction in IVBA Pb and Pb-phosphate formation was found only for pH 2.5 without glycine extraction solution. A modified USEPA Method 1340 without glycine and using pH 2.5 has the potential to predict P soil treatment efficacy and reductions in bioavailable Pb. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Increased serum phosphate concentrations in patients with advanced chronic kidney disease treated with diuretics.

PubMed

Caravaca, Francisco; García-Pino, Guadalupe; Martínez-Gallardo, Rocío; Ferreira-Morong, Flavio; Luna, Enrique; Alvarado, Raúl; Ruiz-Donoso, Enrique; Chávez, Edgar

2013-01-01

Serum phosphate concentrations usually show great variability in patients with advanced chronic kidney disease (ACKD) not on dialysis. Diuretics treatment can have an influence over the severity of mineral-bone metabolism alterations related to ACKD, but their effect on serum phosphate levels is less known. This study aims to determine whether diuretics are independently associated with serum phosphate levels, and to investigate the mechanisms by which diuretics may affect phosphate metabolism. 429 Caucasian patients with CKD not on dialysis were included in this cross-sectional study. In addition to conventional serum biochemical measures, the following parameters of renal phosphate excretion were assessed: 24-hours urinary phosphate excretion, tubular maximum phosphate reabsorption (TmP), and fractional excretion of phosphate (FEP). 58% of patients were on treatment with diuretics. Patients on diuretics showed significantly higher mean serum phosphate concentration (4.78 ± 1.23 vs. 4.24 ± 1.04 mg/dl; P<.0001), and higher TmP per GFR (2.77 ± 0.72 vs. 2.43 ± 0.78 mg/dl; P<.0001) than those not treated with diuretics. By multivariate linear and logistic regression, significant associations between diuretics and serum phosphate concentrations or hyperphosphataemia remained after adjustment for potential confounding variables. In patients with the highest phosphate load adjusted to kidney function, those treated with diuretics showed significantly lower FEP than those untreated with diuretics. Treatment with diuretics is associated with increased serum phosphate concentrations in patients with ACKD. Diuretics may indirectly interfere with the maximum renal compensatory capacity to excrete phosphate. Diuretics should be considered in the studies linking the relationship between serum phosphate concentrations and cardiovascular alterations in patients with CKD.

Long-term decrease in phosphate concentrations in the surface layer of the southern Japan Sea

NASA Astrophysics Data System (ADS)

Kodama, Taketoshi; Igeta, Yosuke; Kuga, Mizuki; Abe, Shoko

2016-10-01

To identify possible causes for the long-term trends in nutrient concentrations in the southern Japan Sea (JS), we studied nutrient concentrations that were obtained by the Japan Meteorological Agency. Our evaluation shows that phosphate concentrations declined in the surface layers in summer (0-20 and 21-50 m depth) and winter (0-20, 21-50, and 51-100 m depth) over the last 40 years, while no significant linear trend was observed for nitrate concentrations. The declining trend in the phosphate concentration was quantified as 1.8-3.3 nM yr-1. The increase in atmospheric nutrient deposition to the JS could not explain the decline in phosphate concentration. In addition, the mixed-layer depth during winter did not demonstrate any significant trend, and an increase in phosphate concentrations was not observed in any layers; therefore, the decrease in nutrient supply from deep JS water was not considered a major possible cause for the decline in the phosphate concentration. In contrast, the phosphate concentration in the surface of the southern JS during winter showed a significant positive correlation with the concentration in the 21-50 m depth layer of the saline East China Sea (ECS) water in the preceding summer, and the surface water of the southern JS was almost entirely replaced by water originating from the ECS during May-October. Therefore, it is concluded that the declining trend in the phosphate concentrations in the southern JS is caused by horizontal advection of ECS water.

Microfluidic in-channel multi-electrode platform for neurotransmitter sensing

NASA Astrophysics Data System (ADS)

Kara, A.; Mathault, J.; Reitz, A.; Boisvert, M.; Tessier, F.; Greener, J.; Miled, A.

2016-03-01

In this project we present a microfluidic platform with in-channel micro-electrodes for in situ screening of bio/chemical samples through a lab-on-chip system. We used a novel method to incorporate electrochemical sensors array (16x20) connected to a PCB, which opens the way for imaging applications. A 200 μm height microfluidic channel was bonded to electrochemical sensors. The micro-channel contains 3 inlets used to introduce phosphate buffer saline (PBS), ferrocynide and neurotransmitters. The flow rate was controlled through automated micro-pumps. A multiplexer was used to scan electrodes and perform individual cyclic voltammograms by a custom potentiostat. The behavior of the system was linear in terms of variation of current versus concentration. It was used to detect the neurotransmitters serotonin, dopamine and glutamate.

Preparation of glucose sensors using gold nanoparticles modified diamond electrode

NASA Astrophysics Data System (ADS)

Fachrurrazie; Ivandini, T. A.; Wibowo, W.

2017-04-01

A glucose sensor was successfully developed by immobilizing glucose oxidase (GOx) at boron-doped diamond (BDD) electrodes. Prior to GOx immobilization, the BDD was modified with gold nanoparticles (AuNPs). To immobilize AuNPs, the gold surface was modified to nitrogen termination. The characterization of the electrode surface was performed using an X-ray photoelectron spectroscopy and a scanning electron microscope, while the electrochemical properties of the enzyme electrode were characterized using cyclic voltammetry. Cyclic voltammograms of the prepared electrode for D-glucose in phosphate buffer solution pH 7 showed a new reduction peak at +0.16 V. The currents of the peak were linear in the concentration range of 0.1 M to 0.9 M, indicated that the GOx-AuNP-BDD can be applied for electrochemical glucose detection.

Sensitive Voltammetric Determination of Natural Flavonoid Quercetin on a Disposable Graphite Lead

PubMed Central

Vu, Dai Long; Žabčíková, Simona; Ertek, Bensu; Dilgin, Yusuf

2015-01-01

Summary In this paper, a pencil graphite electrode was pretreated using chronoamperometry technique in phosphate buffer solution (pH=7.0) for sensitive determination of quercetin. Oxidation of quercetin was investigated using pretreated pencil graphite electrode and anodic stripping differential pulse voltammetry. Under optimal conditions, the anodic current of quercetin exhibited linear response to its concentration in the range from 0.001 to 1.5 µmol/L with the limit of detection of 0.3·10–3 µmol/L. The proposed method was successfully applied for the determination of quercetin in cranberry and blackcurrant juices with recovery rate from 93.2 to 94.7%. Solid-phase extraction was found to be necessary prior to voltammetric determination of quercetin in fruit juice samples using pretreated pencil graphite electrode. PMID:27904372

A novel amperometric biosensor based on artichoke (Cynara scolymus L.) tissue homogenate immobilized in gelatin for hydrogen peroxide detection.

PubMed

Oztürk, G; Ertaş, F N; Akyilmaz, E; Dinçkaya, E; Tural, H

2004-01-01

A biosensor for specific determination of hydrogen peroxide was developed by using homogenized artichoke (Cynara scolymus L.) tissue in combination with a dissolved oxygen probe and applied in determination of hydrogen peroxide in milk samples. Artichoke tissue, which has catalase activity, was immobilized with gelatine by means of glutaraldehyde and fixed on a pretreated teflon membrane. The electrode response was maximum when 0.05 M phosphate buffer was used at pH 7.0 and at 30 degrees C. Upon addition of hydrogen peroxide, the electrode gives a linear response in a concentration range of 5.0-50 x 10(-5) M with a response time of 3 min. The method was also applied to the determination of hydrogen peroxide in milk samples.

Decomposition of L-valine under nonthermal dielectric barrier discharge plasma.

PubMed

Li, Yingying; Kojtari, Arben; Friedman, Gary; Brooks, Ari D; Fridman, Alex; Ji, Hai-Feng

2014-02-13

L-Valine solutions in water and phosphate buffer were treated with nonthermal plasma generated by using a dielectric barrier discharge (DBD) device and the products generated after plasma treatments were characterized by (1)H NMR and GC-MS. Our results demonstrate that L-valine is decomposed to acetone, formic acid, acetic acid, threo-methylaspartic acid, erythro-methlyaspartic acid, and pyruvic acid after direct exposure to DBD plasma. The concentrations of these compounds are time-dependent with plasma treatment. The mechanisms of L-valine under the DBD plasma are also proposed in this study. Acetone, pyruvic acid, and organic radicals (•)CHO, CH3COCH2OO(•) (acetonylperoxy), and CH3COC(OH)2OO(•) (1,1-dihydroxypropan-2-one peroxy) may be the determining chemicals in DNA damage.

On-line sample cleanup and enrichment chromatographic technique for the determination of ambroxol in human serum.

PubMed

Emara, Samy; Kamal, Maha; Abdel Kawi, Mohamed

2012-02-01

A sensitive and efficient on-line clean up and pre-concentration method has been developed using column-switching technique and protein-coated µ-Bondapak CN silica pre-column for quantification of ambroxol (AM) in human serum. The method is performed by direct injection of serum sample onto a protein-coated µ-Bondapak CN silica pre-column, where AM is pre-concentrated and retained, while proteins and very polar constituents are washed to waste using a phosphate buffer saline (pH 7.4). The retained analyte on the pre-column is directed onto a C(18) analytical column for separation, with a mobile phase consisting of a mixture of methanol and distilled deionized water (containing 1% triethylamine adjusted to pH 3.5 with ortho-phosphoric acid) in the ratio of 50:50 (v/v). Detection is performed at 254 nm. The calibration curve is linear over the concentration range of 12-120 ng/mL (r(2) = 0.9995). The recovery, selectivity, linearity, precision, and accuracy of the method are convenient for pharmacokinetic studies or routine assays.

Leishmanicidal activity of saponins isolated from the leaves of Eclipta prostrata and Gymnema sylvestre

PubMed Central

Khanna, Venkatesan Gopiesh; Kannabiran, Krishnan; Getti, Giulia

2009-01-01

Objective: To evaluate the leishmanicidal activity of saponin, dasyscyphin C of Eclipta prostrata and sapogenin, gymnemagenol from Gymnema sylvestre leaves under in vitro conditions. Materials and Methods: Dasyscyphin C/Gymnemagenol were dissolved in phosphate buffered saline (PBS) and diluted with liquid medium to obtain concentrations ranging from 1000 to 15 μg /ml. The leishmanicidal activity against leishmanial parasites, Leishmania major, Leishmania aethiopica and Leishmania tropica promastigotes was studied by the MTS assay. Result: The Dasyscyphin C isolated from E. prostrata showed good leishmanicidal activity at 1000μg/ml concentration, with the IC50 value of 450μg/ml against L. major promastigote and the percentage of parasitic death was 73; whereas, gymnemagenol of G. sylvestre showed only 52% parasitic death at 1000 μg/ml concentration. The other Leishmania species, L. aethiopica and L. tropica promastigotes, were less sensitive to the saponins of E. prostrata and G. sylvestre. Conclusion: From this study, it can be concluded that the dasyscyphin C of E. prostrata has significant leishmanicidal activity against L. major promastigote. PMID:20177579

The role of bound potassium ions in the hydrolysis of low concentrations of adenosine triphosphate by preparations of membrane fragments from ox brain cerebral cortex

PubMed Central

Goldfarb, P. S. G.; Rodnight, R.

1970-01-01

1. The intrinsic Na+, K+, Mg2+ and Ca2+ contents of a preparation of membrane fragments from ox brain were determined by emission flame photometry. 2. Centrifugal washing of the preparation with imidazole-buffered EDTA solutions decreased the bound Na+ from 90±20 to 24±12, the bound K+ from 27±3 to 7±2, the bound Mg2+ from 20±2 to 3±1 and the bound calcium from 8±1 to <1nmol/mg of protein. 3. The activities of the Na++K++Mg2+-stimulated adenosine triphosphatase and the Na+-dependent reaction forming bound phosphate were compared in the unwashed and washed preparations at an ATP concentration of 2.5μm (ATP/protein ratio 12.5pmol/μg). 4. The Na+-dependent hydrolysis of ATP as well as the plateau concentration of bound phosphate and the rate of dephosphorylation were decreased in the washed preparation. The time-course of formation and decline of bound phosphate was fully restored by the addition of 2.5μm-magnesium chloride and 2μm-potassium chloride. Addition of 2.5μm-magnesium chloride alone fully restored the plateau concentration of bound phosphate, but the rate of dephosphorylation was only slightly increased. Na+-dependent ATP hydrolysis was partly restored with 2.5μm-magnesium chloride; addition of K+ in the range 2–10μm-potassium chloride then further restored hydrolysis but not to the control rate. 5. Pretreatment of the washed preparation at 0°C with 0.5nmol of K+/mg of protein so that the final added K+ in the reaction mixture was 0.1μm restored the Na+-dependent hydrolysis of ATP and the time-course of the reaction forming bound phosphate. 6. The binding of [42K]potassium chloride by the washed membrane preparation was examined. Binding in a solution containing 10nmol of K+/mg of protein was linear over a period of 20min and was inhibited by Na+. Half-maximal inhibition of 42K+-binding required a 100-fold excess of sodium chloride. 7. It was concluded (a) that a significant fraction of the apparent Na+-dependent hydrolysis of ATP observed in the unwashed preparation is due to activation by bound K+ and Mg2+ of the Na++K++Mg2+-stimulated adenosine triphosphatase system and (b) that the enzyme system is able to bind K+ from a solution of 0.5μm-potassium chloride. PMID:4250237

Analysis of spiramycin by capillary electrophoresis.

PubMed

González-Hernández, R; Li, Y M; Van Schepdael, A; Roets, E; Hoogmartens, J

1999-09-01

The development and validation of an analytical method for the determination of spiramycin I in the presence of its related substances by capillary electrophoresis is shown. The separation, performed in a phosphate buffer (80 mM, pH 7.5) containing 12 mM cetyltrimethylammonium bromide (CTAB) and 20 mM sodium cholate, with a 50 microm ID and 44 cm long fused-silica capillary (36 cm effective length), applying a voltage of 12 kV (l approximately 80 microA), at 25 degrees C, is achieved in 15 min. Good selectivity among spiramycin I and its related substances was obtained. The influence of the buffer pH, and of the CTAB and sodium cholate concentrations was investigated. The method robustness, examined by means of a full-fraction factorial design, shows that it can be used within the limits set for the three parameters that were investigated. The method is linear (r = 0.9992) and precise (day-to-day corrected peak area repeatability, n = 18, relative standard deviation = 1.3%). The limits of detection and quantitation are 7 pg (0.025%) and 22 pg (0.08%), respectively, relative to a 2 mg/mL solution.

Chemical Modification of the Olfactory Receptor Epithelium of Vertebrate Species

DTIC Science & Technology

1990-06-28

Pre-column Derivatization Procedure: 1.0 mL of the Jeffamine solution was mixed with 1.0 mL of NaCN, 5.0 mL of phosphate buffer pH 9.5 followed by 1.0...running buffer. All the unprotonated components elute at the same time because their rate of elution is controlled only by the rate of electroosmotic ...elecarosomotic mobility under our experimental conditions. Using an average elution time of 22.2 min the measured electroosmotic mobility is 1.3 x 10-4 cm2

Initial-phase optimization for bioremediation of munition compound-contaminated soils.

PubMed Central

Funk, S B; Roberts, D J; Crawford, D L; Crawford, R L

1993-01-01

We examined the bioremediation of soils contaminated with the munition compounds 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine, and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazocine by a procedure that produced anaerobic conditions in the soils and promoted the biodegradation of nitroaromatic contaminants. This procedure consisted of flooding the soils with 50 mM phosphate buffer, adding starch as a supplemental carbon substrate, and incubating under static conditions. Aerobic heterotrophs, present naturally in the soil or added as an inoculum, quickly removed the oxygen from the static cultures, creating anaerobic conditions. Removal of parent TNT molecules from the soil cultures by the strictly anaerobic microflora occurred within 4 days. The reduced intermediates formed from TNT and hexahydro-1,3,5-trinitro-1,3,5-triazine were removed from the cultures within 24 days, completing the first stage of remediation. The procedure was effective over a range of incubation temperatures, 20 to 37 degrees C, and was improved when 25 mM ammonium was added to cultures buffered with 50 mM potassium phosphate. Ammonium phosphate buffer (50 mM), however, completely inhibited TNT reduction. The optimal pH for the first stage of remediation was between 6.5 and 7.0. When soils were incubated under aerobic conditions or under anaerobic conditions at alkaline pHs, the TNT biodegradation intermediates polymerized. Polymerization was not observed at neutral to slightly acidic pHs under anaerobic conditions. Completion of the first stage of remediation of munition compound-contaminated soils resulted in aqueous supernatants that contained no munition residues or aminoaromatic compounds. PMID:8357251

Knot Security of 5 Metric (USP 2) Sutures: Influence of Knotting Technique, Suture Material, and Incubation Time for 14 and 28 Days in Phosphate Buffered Saline and Inflamed Equine Peritoneal Fluid.

PubMed

Sanders, Ruth E; Kearney, Clodagh M; Buckley, Conor T; Jenner, Florien; Brama, Pieter A

2015-08-01

To evaluate knot security for 3 knot types created in 3 commonly used 5 metric suture materials incubated in physiological and pathological fluids. In vitro mechanical study. Knotted suture loops (n = 5/group). Loops of 3 different suture materials (glycolide/lactide copolymer; polyglactin 910; polydioxanone) were created around a 20 mm rod using 3 knot types (square [SQ], surgeon's [SK], and triple knot [TK]) and were tested to failure in distraction (6 mm/min) after tying (day 0) and after being incubated for 14 and 28 days in phosphate buffered saline (PBS) or inflamed peritoneal fluid. Failure load (N) and mode were recorded and compared. For polydioxanone, significant differences in force to knot failure were found between SQ and SK/TK but not between SK and TK. The force required to break all constructs increased after incubation in phosphate buffered saline (PBS). With glycolide/lactide copolymer no differences in force to knot failure were observed. With polyglactin 910, a significant difference between SQ and TK was observed, which was not seen between the other knot types. Incubation in inflamed peritoneal fluid caused a larger and more rapid decrease in force required to cause knot failure than incubation in PBS. Mechanical properties of suture materials have significant effects on knot security. For polydioxanone, SQ is insufficient to create a secure knot. Additional wraps above a SK confer extra stability in some materials, but this increase may not be clinically relevant or justifiable. Glycolide/lactide copolymer had excellent knot security. © Copyright 2015 by The American College of Veterinary Surgeons.

Regulation of the dissolved phosphate concentration of a mountainous stream, Kitakyushu, southwestern Japan.

PubMed

Koga, Masaaki; Yoshimura, Kazuhisa

2012-07-01

The phosphate concentration in mountainous stream water can be a measure of the forest condition, because its concentration will be low when the biomass in the forest is increasing and vice versa when the forest is declining. To investigate the seasonal change in the dissolved phosphate concentration of the mountainous stream water of the Yamakami River, Kitakyushu, from June 2009 to August 2010, and the regulation mechanism of the phosphate concentration, solid-phase spectrophotometry, which can be applicable to natural water without any pretreatment procedures, was employed for the determination of phosphate at μg P L(-1) levels in natural water. The phosphate concentrations in the mountainous stream waters at 6 sites ranged from 2.2 to 13 μg P L(-1), and those from the catchment area of the steady state forest were 5.3 ± 1.6 (±1 SD) μg P L(-1). Changes in the concentration were fairly small even during a storm runoff. The average phosphate concentration of rain was 2.8 ± 0.7 μg P L(-1), about half of the concentration in the stream water. The rate of runoff in forest areas is generally considered to be about 50% of the total precipitation. For a forest under a climax condition, the phosphate concentration is estimated to be regulated by the fallout and evapotranspiration (α = 0.05). At one of the sites, an upstream tributary, where a fairly big landslide occurred before July in 2009, the phosphate concentration was the highest, suggesting that the biomass may still be decreasing. For all of the six sites examined, a characteristic seasonal change in phosphate concentration was observed, reflecting the local budget between the biological decomposition of plant matter and the consumption by the biomass. The increase in the phosphate concentration during late spring and early summer may result from the extensive decomposition of plant litter mainly supplied in autumn and of plant matter relating to spring blooming such as fallen flowers, pollen and immature fruits. The proposed method using the phosphate concentration in surface stream waters without the period of the seasonal change mentioned above is expected to be very helpful in diagnosing the condition of forests.

Entrapment of ovalbumin into liposomes--factors affecting entrapment efficiency, liposome size, and zeta potential.

PubMed

Brgles, Marija; Jurasin, Darija; Sikirić, Maja Dutour; Frkanec, Ruza; Tomasić, Jelka

2008-01-01

Various amounts of Ovalbumin (OVA) were encapsulated into positively and negatively charged multilamellar liposomes, with the aim to investigate the entrapment efficiency in different buffers and to study their effects on the liposome size and zeta potential. Results showed that the entrapment efficiency of OVA in anionic liposomes was the same in 10 mM Phosphate Buffer (PB) as in Phosphate-Buffered Saline (PBS; PB + 0.15 M NaCl). Also, liposome size was approximately 1200 nm for all anionic liposomes incorporating OVA. The entrapment efficiency of OVA in cationic liposomes was highly dependent on ionic strength. The size of cationic liposomes was approximately 1200 nm in PBS, regardless of protein content, but increased with the amount of the incorporated protein in PB. Aggregation of cationic liposomes in PB was observed when the mass of the protein was 2.5 mg or greater. The zeta potential of anionic liposomes was negative and of cationic liposomes positive in the whole range of protein mass tested. These results show how different compositions of lipid and aqueous phases can be used to vary the entrapment efficiency, liposome size, and zeta potential--the factors that are of great importance for the use of liposomes as drug carriers.

In silico prediction of drug dissolution and absorption with variation in intestinal pH for BCS class II weak acid drugs: ibuprofen and ketoprofen.

PubMed

Tsume, Yasuhiro; Langguth, Peter; Garcia-Arieta, Alfredo; Amidon, Gordon L

2012-10-01

The FDA Biopharmaceutical Classification System guidance allows waivers for in vivo bioavailability and bioequivalence studies for immediate-release solid oral dosage forms only for BCS class I. Extensions of the in vivo biowaiver for a number of drugs in BCS class III and BCS class II have been proposed, in particular, BCS class II weak acids. However, a discrepancy between the in vivo BE results and in vitro dissolution results for BCS class II acids was recently observed. The objectives of this study were to determine the oral absorption of BCS class II weak acids via simulation software and to determine if the in vitro dissolution test with various dissolution media could be sufficient for in vitro bioequivalence studies of ibuprofen and ketoprofen as models of carboxylic acid drugs. The oral absorption of these BCS class II acids from the gastrointestinal tract was predicted by GastroPlus™. Ibuprofen did not satisfy the bioequivalence criteria at lower settings of intestinal pH of 6.0. Further the experimental dissolution of ibuprofen tablets in a low concentration phosphate buffer at pH 6.0 (the average buffer capacity 2.2 mmol l (-1) /pH) was dramatically reduced compared with the dissolution in SIF (the average buffer capacity 12.6 mmol l (-1) /pH). Thus these predictions for the oral absorption of BCS class II acids indicate that the absorption patterns depend largely on the intestinal pH and buffer strength and must be considered carefully for a bioequivalence test. Simulation software may be a very useful tool to aid the selection of dissolution media that may be useful in setting an in vitro bioequivalence dissolution standard. Copyright © 2012 John Wiley & Sons, Ltd.

In Silico Prediction of Drug Dissolution and Absorption with variation in Intestinal pH for BCS Class II Weak Acid Drugs: Ibuprofen and Ketoprofen§

PubMed Central

Tsume, Yasuhiro; Langguth, Peter; Garcia-Arieta, Alfredo; Amidon, Gordon L.

2012-01-01

The FDA Biopharmaceutical Classification System guidance allows waivers for in vivo bioavailability and bioequivalence studies for immediate-release solid oral dosage forms only for BCS class I. Extensions of the in vivo biowaiver for a number of drugs in BCS Class III and BCS class II have been proposed, particularly, BCS class II weak acids. However, a discrepancy between the in vivo- BE results and in vitro- dissolution results for a BCS class II acids was recently observed. The objectives of this study were to determine the oral absorption of BCS class II weak acids via simulation software and to determine if the in vitro dissolution test with various dissolution media could be sufficient for in vitro bioequivalence studies of ibuprofen and ketoprofen as models of carboxylic acid drugs. The oral absorption of these BCS class II acids from the gastrointestinal tract was predicted by GastroPlus™. Ibuprofen did not satisfy the bioequivalence criteria at lower settings of intestinal pH=6.0. Further the experimental dissolution of ibuprofen tablets in the low concentration phosphate buffer at pH 6.0 (the average buffer capacity 2.2 mmol L-1/pH) was dramatically reduced compared to the dissolution in SIF (the average buffer capacity 12.6 mmol L -1/pH). Thus these predictions for oral absorption of BCS class II acids indicate that the absorption patterns largely depend on the intestinal pH and buffer strength and must be carefully considered for a bioequivalence test. Simulation software may be very useful tool to aid the selection of dissolution media that may be useful in setting an in vitro bioequivalence dissolution standard. PMID:22815122

Adsorption stripping voltammetry of phenol at Nafion-modified glassy carbon electrode in the presence of surfactants.

PubMed

Yi, H; Wu, K; Hu, S; Cui, D

2001-12-24

In this paper, a new voltammetric method for the determination of phenol is described. In pH 8.00 phosphate buffer and in the presence of long-chain cationic surfactant-cetyltrimethylammonium bromide-phenol has a very sensitive oxidation peak at 0.47 V (vs. SCE) on the Nafion-modified glassy carbon electrode (GCE). The experimental parameters, such as supporting electrolyte and pH values, amounts of Nafion, varieties and concentration of surfactants, accumulation potential and time, as well as scan rate were optimized. The peak current is linear with the concentration of phenol in the range from 8x10(-9) to 1x10(-5) M, and the detection limit is 1x10(-9) M after being accumulated at -0.50 V (vs. SCE) for 3 min. Trace levels of phenol in water samples were determined by using this voltammetric method, the average recovery was calculated to be 99.56%.

Transdermal delivery of forskolin from emulsions differing in droplet size.

PubMed

Sikora, Elżbieta; Llinas, Meritxell; Garcia-Celma, Maria Jose; Escribano, Elvira; Solans, Conxita

2015-02-01

The skin permeation of forskolin, a diterpene isolated from Coleus forsholii, was studied using oil in water (O/W) emulsions as delivery formulations and also an oil solution for comparative purposes. Two forskolin-loaded emulsions of water/Brij 72:Symperonic A7/Miglyol 812:Isohexadecane, at 0.075 wt% forskolin concentration were prepared with the same composition and only differing in droplet size (0.38 μm and 10 μm). The emulsions showed high kinetic stability at 25 °C. In vitro study of forskolin penetration through human skin was carried out using the MicroettePlus(®) system. The concentration of the active in the receptor solution (i.e. ethanol/phosphate buffer 40/60, v/v) was analyzed by high performance liquid chromatography with UV detection. The obtained results showed that forskolin permeation from the emulsions and the oil solution, through human skin, was very high (up to 72.10%), and no effect of droplet size was observed. Copyright © 2015 Elsevier B.V. All rights reserved.

Analytical determination of virginiamycin drug residues in edible porcine tissues by LC-MS with confirmation by LC-MS/MS.

PubMed

Boison, Joe; Lee, Stephen; Gedir, Ron

2009-01-01

A liquid chromatographic-mass spectrometric (LC-MS) method was developed and validated for the determination and confirmation of virginiamycin (VMY) M1 residues in porcine liver, kidney, and muscle tissues at concentrations > or =2 ng/g. Porcine liver, kidney, or muscle tissue is homogenized with methanol-acetonitrile. After centrifugation, the supernatant is diluted with phosphate buffer and cleaned up on a C18 solid-phase extraction cartridge. VMY in the eluate is partitioned into chloroform and the aqueous upper layer is removed by aspiration. After evaporating the chloroform in the residual mixture to dryness, the dried extract is reconstituted in mobile phase and VMY is quantified by LC-MS. Any samples eliciting quantifiable levels of VMY M1 (i.e., at concentrations > or =2 ng/g) are subjected to confirmatory analysis by LC-MSIMS. VMY S1, a minor component of the VMY complex, is monitored but not quantified or confirmed.

Dependency of plasmon resonance sensitivity of colloidal gold nanoparticles on the identity of surrounding ionic media

NASA Astrophysics Data System (ADS)

Mehrdel, B.; Aziz, A. Abdul

2018-03-01

The plasmon resonance sensitivity of gold nanoparticles (AuNPs) in sodium chloride (NaCl) liquid in near-infrared to the visible spectral region was investigated. The correlation between NaCl concentration and refractive index was analyzed using concentration dependency and Lorenz-Lorenz methods. The first derivative method was applied to the measured absorption spectra to quantitatively evaluate the plasmon resonance sensitivity. To understand the influence of the identity of the surrounding medium on the plasmon resonance sensitivity, experiments were repeated by replacing NaCl with sodium hydroxide (NaOH), followed by phosphate buffered saline (PBS). Experimental results showed that NaCl is the most effective ionic surrounding medium, which gives prominent plasmon resonance response. AuNPs size can have a significant influence on the plasmon resonance sensitivity. For tiny AuNPs (∼10 nm AuNPs), the plasmon resonance is insensitive to the identity of the surrounding medium due to their low cross-section value.

Influence of D-Penicillamine on the Viscosity of Hyaluronic Acid Solutions

NASA Astrophysics Data System (ADS)

Liang, Jing; Krause, Wendy E.; Colby, Ralph H.

2006-03-01

Polyelectrolyte hyaluronic acid (HA, hyaluronan) is an important component in synovial fluid. Its presence results in highly viscoelastic solutions with excellent lubricating and shock-absorbing properties. In comparison to healthy synovial fluid, diseased fluid has a reduced viscosity. In osteoarthritis this reduction in viscosity results from a decline in both the molecular weight and concentration of hyaluronic acid HA. Initial results indicate that D-penicillamine affects the rheology of bovine synovial fluid, a model synovial fluid solution, and its components, including HA. In order to understand how D-penicillamine modifies the viscosity of these solutions, the rheological properties of sodium hyaluronate (NaHA) in phosphate-buffered saline (PBS) with D-penicillamine were studied as function of time, D-penicillamine concentration (0 -- 0.01 M), and storage conditions. Penicillamine has a complex, time dependent effect on the viscosity of NaHA solutions---reducing the zero shear rate viscosity of a 3 mg/mL NaHA in PBS by ca. 40% after 44 days.

Effect of pH adjustment, homogenization and diafiltration on physicochemical, reconstitution, functional and rheological properties of medium protein milk protein concentrates (MPC70).

PubMed

Meena, Ganga Sahay; Singh, Ashish Kumar; Gupta, Vijay Kumar; Borad, Sanket; Arora, Sumit; Tomar, Sudhir Kumar

2018-04-01

Poor solubility is the major limiting factor in commercial applications of milk protein concentrates (MPC) powders. Retentate treatments such as pH adjustment using disodium phosphate (Na 2 HPO 4 ), also responsible for calcium chelation with homogenization and; its diafiltration with 150 mM NaCl solution were hypothesized to improve the functional properties of treated MPC70 powders. These treatments significantly improved the solubility, heat stability, water binding, dispersibility, bulk density, flowability, buffer index, foaming and emulsifying capacity of treated powders over control. Rheological behaviour of reconstituted MPC solutions was best explained by Herschel Bulkley model. Compared to rough, large globular structures with dents in control; majorly intact, separate, smaller particles of smooth surface, without any aggregation were observed in SEM micrograph of treated powders. Applied treatments are easy, cost-effective and capable to improve functional properties of treated powders that could replace control MPC70 powder in various food applications where protein functionality is of prime importance.

A HPLC method for the quantification of butyramide and acetamide at ppb levels in hydrogeothermal waters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gracy Elias; Earl D. Mattson; Jessica E. Little

A quantitative analytical method to determine butyramide and acetamide concentrations at the low ppb levels in geothermal waters has been developed. The analytes are concentrated in a preparation step by evaporation and analyzed using HPLC-UV. Chromatographic separation is achieved isocratically with a RP C-18 column using a 30 mM phosphate buffer solution with 5 mM heptane sulfonic acid and methanol (98:2 ratio) as the mobile phase. Absorbance is measured at 200 nm. The limit of detection (LOD) for BA and AA were 2.0 {mu}g L{sup -1} and 2.5 {mu}g L{sup -1}, respectively. The limit of quantification (LOQ) for BA andmore » AA were 5.7 {mu}g L{sup -1} and 7.7 {mu}g L{sup -1}, respectively, at the detection wavelength of 200 nm. Attaining these levels of quantification better allows these amides to be used as thermally reactive tracers in low-temperature hydrogeothermal systems.« less

Cysteine Inhibits Mercury Methylation by Geobacter sulfurreducens PCA Mutant Δ omcBESTZ

DOE PAGES

Lin, Hui; Lu, Xia; Liang, Liyuan; ...

2015-04-21

For cysteine enhances Hg uptake and methylation by Geobacter sulfurreducens PCA wild type (WT) strain in short-term assays. The prevalence of this enhancement in other strains remains poorly understood. We examined the influence of cysteine concentration on time-dependent Hg(II) reduction, sorption and methylation by PCA-WT and its c-type cytochrome-deficient mutant ( omcBESTZ) in phosphate buffered saline. Without cysteine, the mutant methylated twice as much Hg(II) as the PCA-WT, whereas addition of cysteine inhibited Hg methylation, regardless of the reaction time. PCA-WT, but, exhibited both time-dependent and cysteine concentration-dependent methylation. In 144 hour assay, nearly complete sorption of the Hg(II) bymore » PCA-WT occurred in the presence of 1 mM cysteine, resulting in our highest observed methylmercury production. Moreover, the chemical speciation modeling and experimental data suggest that uncharged Hg(II) species are more readily taken up, and that this uptake is kinetic limiting, thereby affecting Hg methylation by both mutant and WT.« less

Amperometric Determination of Glucose at Parts per Million Levels with Immobilized Glucose Oxidase.

ERIC Educational Resources Information Center

Sittampalam, G.; Wilson, G. S.

1982-01-01

An experiment on the operation and utility of an amperometric immobilized enzyme electrode (or probe) is described, including advantages of the experiment, equipment, reagents, preparation of phosphate buffer, enzyme immobilization techniques, laboratory procedures, precautions, and discussion of experimental results. (SK)

Distribution of spotted fever group rickettsiae in select tissues of experimentally infected and field-collected Gulf Coast ticks.

PubMed

Edwards, Kristine T; Goddard, Jerome; Varela-Stokes, Andrea

2011-05-01

Salivary glands, midgut, Malpighian tubules, and ovaries were dissected from infected, colony-derived Amblyomma maculatum (Gulf Coast ticks) injected as nymphs with either Rickettsia parkeri (a spotted fever group rickettsia [SFGR]; treatment) or phosphate-buffered saline (negative control). For comparison, similar tissues were dissected from hemolymph-positive, field-collected ticks. Tissues were analyzed by indirect fluorescent antibody (IFA) tests. All phosphate-buffered saline-injected ticks were IFA negative, whereas SFGR were detected by IFA in 100% of the salivary glands and ovaries and 78 and 75% of midgut and Malpighian tubule samples, respectively, of R. parkeri-injected ticks. Nearly 22% (10/46) of the field-collected ticks were hemolymph positive. Of those, SFGR were detected by IFA in 80% of the salivary glands, 67% of the ovaries, and 60% in the midgut and Malpighian tubules. This is the first study to assess the distribution of SFGR in select tissues of A. maculatum ticks.

Chitosan adsorption on nanofibrillated cellulose with different aldehyde content and interaction with phosphate buffered saline.

PubMed

Ondaral, Sedat; Çelik, Elif; Kurtuluş, Orçun Çağlar; Aşıkuzun, Elif; Yakın, İsmail

2018-04-15

The chitosan adsorption on films prepared using nanofibrillated cellulose (NFC) with different content of aldehyde group was studied by means of Quartz Crystal Microbalance with Dissipation (QCM-D). Results showed that frequency change (Δf) was higher when the chitosan adsorbed on NFC film consisting more aldehyde group indicating the higher adsorption. The (Δf) and dissipation (ΔD) factors completely changed during adsorption of chitosan pre-treated with acetic acid: Δf increased and ΔD decreased, oppositely to un-treated chitosan adsorption. After acid treatment, molecular weight and crystallinity index of chitosan decreased addition to change in chemical structure. It was found that more phosphate buffered saline (PBS), as a model liquid for wound exudate, adsorbed to acid treated chitosan-NFC film, especially to film having more aldehyde groups. Comparing with bare NFC film, chitosan-NFC films adsorbed less PBS because chitosan crosslinked the NFC network and blocked the functional groups of NFC and thus, preventing swelling film. Copyright © 2017 Elsevier Ltd. All rights reserved.

A Janus cobalt-based catalytic material for electro-splitting of water

NASA Astrophysics Data System (ADS)

Cobo, Saioa; Heidkamp, Jonathan; Jacques, Pierre-André; Fize, Jennifer; Fourmond, Vincent; Guetaz, Laure; Jousselme, Bruno; Ivanova, Valentina; Dau, Holger; Palacin, Serge; Fontecave, Marc; Artero, Vincent

2012-09-01

The future of energy supply depends on innovative breakthroughs regarding the design of cheap, sustainable and efficient systems for the conversion and storage of renewable energy sources. The production of hydrogen through water splitting seems a promising and appealing solution. We found that a robust nanoparticulate electrocatalytic material, H2-CoCat, can be electrochemically prepared from cobalt salts in a phosphate buffer. This material consists of metallic cobalt coated with a cobalt-oxo/hydroxo-phosphate layer in contact with the electrolyte and mediates H2 evolution from neutral aqueous buffer at modest overpotentials. Remarkably, it can be converted on anodic equilibration into the previously described amorphous cobalt oxide film (O2-CoCat or CoPi) catalysing O2 evolution. The switch between the two catalytic forms is fully reversible and corresponds to a local interconversion between two morphologies and compositions at the surface of the electrode. After deposition, the noble-metal-free coating thus functions as a robust, bifunctional and switchable catalyst.

Effects of coating layer and release medium on release profile from coated capsules with Eudragit FS 30D: an in vitro and in vivo study.

PubMed

Moghimipour, Eskandar; Rezaei, Mohsen; Kouchak, Maryam; Fatahiasl, Jafar; Angali, Kambiz Ahmadi; Ramezani, Zahra; Amini, Mohsen; Dorkoosh, Farid Abedin; Handali, Somayeh

2018-05-01

The aim of the present research was to evaluate the impact of coating layers on release profile from enteric coated dosage forms. Capsules were coated with Eudragit FS 30D using dipping method. The drug profile was evaluated in both phosphate buffer and Hank's solutions. Utilization X-ray imaging, gastrointestinal transmission of enteric coated capsules was traced in rats. According to the results, no release of the drug was found at pH 1.2, and the extent of release drug in pH 6.8 medium was decreased by adding the coating layers. The results indicated single-layer coated capsules in phosphate buffer were significantly higher than that in Hank's solution. However, no significant difference was observed from capsules with three coating layers in two different dissolution media. X-ray imaging showed that enteric coated capsules were intact in the stomach and in the small intestine, while disintegrated in the colon.

Direct enantioseparation of catechin and epicatechin in tea drinks by 6-O-alpha-D-glucosyl-beta-cyclodextrin-modified micellar electrokinetic chromatography.

PubMed

Kodama, Shuji; Yamamoto, Atsushi; Matsunaga, Akinobu; Yanai, Hiroko

2004-08-01

Cyclodextrin-modified micellar electrokinetic chromatography was applied to the enantioseparation of catechin and epicatechin using 6-O-alpha-D-glucosyl-beta-cyclodextrin together with sodium dodecyl sulfate and borate-phosphate buffer. Factors affecting chiral resolution and migration time of catechin and epicatechin were studied. The optimum running conditions were found to be 200 mM borate-20 mM phosphate buffer (pH 6.4) containing 25 mM 6-O-alpha-D-glucosyl-beta-cyclodextrin and 240 mM sodium dodecyl sulfate with an effective voltage of +25 kV at 20 degrees C using direct detection at 210 nm. Under these conditions, the resolution (Rs) of racemic catechin and epicatechin were 4.15 and 1.92, respectively. With this system, catechin and epicatechin enantiomers along with other four catechins ((-)-catechin gallate, (-)-epicatechin gallate, (-)-epigallocatechin, (-)-epigallocatechin gallate) and caffeine in tea samples were analyzed successfully. The difference of migration time between catechin and epicatechin is discussed.

Acquired acid resistance of human enamel treated with laser (Er:YAG laser and Co2 laser) and acidulated phosphate fluoride treatment: An in vitro atomic emission spectrometry analysis

PubMed Central

Mathew, Anju; Reddy, N. Venugopal; Sugumaran, D. K.; Peter, Joby; Shameer, M.; Dauravu, Liju Marcely

2013-01-01

Background: Dental caries is essentially a process of diffusion and dissolution. If the aspect of dissolution can be curtailed some degree of prevention can be achieved. Aims: The present study was carried out to evaluate and compare the effect of Er:YAG laser and Co2 laser irradiation combined with acidulated phosphate fluoride treatment on in vitro acid resistance of human enamel. Design: An in vitro study was carried out on 30 human premolars to evaluate the enamel's acid resistance using an atomic emission spectrometry analysis. Materials and Methods: A total of 60 enamel specimens were prepared from 30 human premolars and were randomly assigned to 6 groups: (1) Untreated (control); (2) 1.23% acidulated phosphate fluoride (APF) gel application alone for 4 min; (3) Er:YAG laser treatment alone; (4) Co2 laser treatment alone; (5) Er:YAG laser + APF gel application; (6) Co2 laser + APF gel application. The specimens were then individually immersed in 5 ml of acetate buffer solution (0.1 mol/L, pH 4.5) and incubated at 37°C for 24 h, and the acid resistance was evaluated by determining the calcium ion concentration using the atomic emission spectrometry. Statistical Analysis: An ANOVA model was constructed (P value of 0.05), followed by Tukey's test for multiple pair wise comparisons of mean values. Results: Significant differences were found between the control group and the test groups (P < 0.001). Conclusions: Combining acidulated phosphate fluoride with either Er:YAG or Co2 laser had a synergistic effect in decreasing the enamel demineralization more than either fluoride treatment or laser treatment alone. PMID:24015004

Metal sites in 3,4-dihydroxy-2-butanone 4-phosphate synthase from Methanococcus jannaschii in complex with the substrate ribulose 5-phosphate.

PubMed

Steinbacher, Stefan; Schiffmann, Susanne; Bacher, Adelbert; Fischer, Markus

2004-07-01

The crystal structure of Methanococcus jannaschii 3,4-dihydroxy-2-butanone 4-phosphate synthase in complex with the substrate ribulose 5-phosphate at a dimetal centre has recently been determined at 1.7 A resolution. The enzyme converts ribulose 5-phosphate into 3,4-dihydroxy-2-butanone 4-phosphate, while its C4 atom is released as formate. The resulting four-carbon body supplies all eight C atoms for the xylene moiety of riboflavin. Three of the four hydroxyl groups of ribulose 5-phosphate were coordinated by the metal ions. Based on crystallographic refinement, the metals were assigned as zinc and calcium, which were present in the crystallization buffer. Neither metal supports the enzymatic reaction. In the present study, the correctness of this assignment is assessed using anomalous diffraction data collected at the high-energy side of the zinc absorption edge (lambda = 1.2823 A). Only the three tentative zinc ions give strong peaks in an anomalous difference Fourier map (>20sigma), whereas the four tentative calcium ions do not show anomalous signals above the noise level. These results confirm the initial assignment. In addition, the resolution was improved to 1.55 A.

Effect of mineral phosphates on growth and nitrogen fixation of diazotrophic cyanobacteria Anabaena variabilis and Westiellopsis prolifica.

PubMed

Yandigeri, Mahesh S; Yadav, Arvind K; Meena, Kamlesh Kumar; Pabbi, Sunil

2010-03-01

The nitrogen fixing cyanobacterial strains namely Anabaena variabilis (Nostocales, Nostocaceae) and Westiellopsis prolifica (Nostocales, Hapalosiphonaceae) were evaluated for their nitrogen fixation and growth potential in response to different concentrations (10, 20 and 30 mg P) of the alternate insoluble P-sources Mussorie Rock Phosphate and Tricalcium Phosphate. Distinct and significant intergeneric differences were observed with respect to nitrogen fixation measured as Acetylene Reduction Activity (ARA) and growth potential as soluble proteins, total carbohydrate content, dry weight and total chlorophyll content in response to different concentrations of Mussorie Rock Phosphate and Tricalcium Phosphate. Both the strains showed higher soluble protein content at 20 mg P (Mussorie Rock Phosphate) that increased with time of incubation in A. variabilis. Both cyanobacteria recorded maximum Acetylene Reduction Activity at 20 mg P (Tricalcium Phosphate) followed by activity in presence of soluble phosphate (K2HPO4). The mean activity at all concentrations of insoluble phosphate (Mussorie Rock Phosphate and Tricalcium Phosphate) was more than in the presence of soluble phosphate.

Spontaneous interfacial reaction between metallic copper and PBS to form cupric phosphate nanoflower and its enzyme hybrid with enhanced activity.

PubMed

He, Guangli; Hu, Weihua; Li, Chang Ming

2015-11-01

We herein report the spontaneous interfacial reaction between copper foil with 0.01 M phosphate buffered saline (PBS) to form free-standing cupric phosphate (Cu3(PO4)2) nanoflowers at ambient temperature. The underlying chemistry was thoroughly investigated and it is found that the formation of nanoflower is synergistically caused by dissolved oxygen, chlorine ions and phosphate ions. Enzyme-Cu3(PO4)2 hybrid nanoflower was further prepared successfully by using an enzyme-dissolving PBS solution and the enzymes in the hybrid exhibit enhanced biological activity. This work provides a facile route for large-scale synthesis of hierarchical inorganic and functional protein-inorganic hybrid architectures via a simple one-step solution-immersion reaction without using either template or surfactant, thus offering great potential for biosensing application among others. Copyright © 2015 Elsevier B.V. All rights reserved.

Concentrated flow paths in riparian buffer zones of southern Illinois

Treesearch

R.C. Pankau; J.E. Schoonover; K.W.J. Willard; P.J. Edwards

2012-01-01

Riparian buffers in agricultural landscapes should be designed to trap pollutants in overland flow by slowing, filtering, and infiltrating surface runoff entering the buffer via sheet flow. However, observational evidence suggests that concentrated flow is prevalent from agricultural fields. Over time sediment can accumulate in riparian buffers forming berms that...

Differential effect of buffering agents on the crystallization of gemcitabine hydrochloride in frozen solutions.

PubMed

Patel, Mehulkumar; Munjal, Bhushan; Bansal, Arvind K

2014-08-25

The purpose of this study was to evaluate the differential effect of buffering agents on the crystallization of gemcitabine hydrochloride (GHCl) in frozen solutions. Four buffering agents, viz. citric acid (CA), malic acid (MA), succinic acid (SA) and tartaric acid (TA) were selected and their effect on GHCl crystallization was monitored using standard DSC and low temperature XRD. Onset of GHCl crystallization during heating run in DSC was measured to compare the differential effect of buffering agents. Glass transition temperature (Tg'), unfrozen water content in the freeze concentrate and crystallization propensity of the buffering agents was also determined for mechanistic understanding of the underlying effects. CA and MA inhibited while SA facilitated crystallization of GHCl even at 25 mM concentration. Increasing the concentration enhanced their effect. However, TA inhibited GHCl crystallization at concentrations <100mM and facilitated it at concentrations ≥100 mM. Lyophilization of GHCl with either SA or TA yielded elegant cakes, while CA and MA caused collapse. Tg' failed to explain the inhibitory effects of CA, MA and TA as all buffering agents lowered the Tg' of the system. Differential effect of buffering agents on GHCl crystallization could be explained by consideration of two opposing factors: (i) their own crystallization tendency and (ii) unfrozen water content in the freeze concentrate. In conclusion, it was established that API crystallization in frozen solution is affected by the type and concentration of the buffering agents. Copyright © 2014 Elsevier B.V. All rights reserved.

Formulation and pharmacokinetics of diclofenac lipid nanoemulsions for parenteral application.

PubMed

Ramreddy, Srividya; Kandadi, Prabhakar; Veerabrahma, Kishan

2012-01-01

The objective of the present study was to formulate and determine the pharmacokinetics of stable o/w parenteral lipid nanoemulsions (LNEs) of diclofenac acid used to treat arthritic conditions. The LNEs of diclofenac acid with a mean size ranging from 200 to 240 nm and a zeta potential of -29.4 ± 1.04 mV (negatively charged LNEs) and 62.1 ± 3.5 (positively charged LNEs) emulsions were prepared by hot homogenization and ultrasonication process. The influence of formulation variables, such as the change in proportion of cholesterol, was studied, and optimized formulations were developed. The optimized formulations were relatively stable during centrifugal stress, dilution stress, and storage. The drug content and entrapment efficiency were determined using high-performance liquid chromatography. The in vitro drug release was carried out in phosphate-buffered saline pH 7.4 and cumulative amount of drug released was estimated using a UV-visible spectro-photometer. During in vivo pharmacokinetic studies in male Wistar rats, diclofenac serum concentration from LNEs was higher than that of Voveran injection and was detectable up to 12 h. Diclofenac in LNEs showed improved pharmacokinetic profile with increase in area under the curve, elimination half-life and mean residence time in comparison to Voveran. Our aim was to prepare and determine the pharmacokinetics of injectable lipid nanoemulsions of diclofenac acid for treating arthritic conditions by reducing the frequency of dosing and pain at site of injection. The nanoemulsions of diclofenac acid were prepared by homogenization and ultrasonication process. The sizes and charges of oil globules were determined. The effect of cholesterol on stability of emulsion was studied, and an optimized preparation was developed. The optimized formulations were stable during centrifugation, dilution, and storage. The total amount of drug in emulsion and percentage amount of drug present in emulsion globules were determined using high-performance liquid chromatography. The drug release from preparation was carried out in phosphate-buffered saline pH 7.4. The cumulative amount of drug released was estimated using a spectrophotometer. The time course of the released drug in rat serum was determined. Diclofenac concentrations from lipid nanoemulsions were higher than that of Voveran injection (solution form) in serum.

Evaluation of seven cosubstrates in the quantification of horseradish peroxidase enzyme by square wave voltammetry.

PubMed

Kergaravat, Silvina V; Pividori, Maria Isabel; Hernandez, Silvia R

2012-01-15

The electrochemical detection for horseradish peroxidase-cosubstrate-H(2)O(2) systems was optimized. o-Phenilendiamine, phenol, hydroquinone, pyrocatechol, p-chlorophenol, p-aminophenol and 3,3'-5,5'-tetramethylbenzidine were evaluated as cosubstrates of horseradish peroxidase (HRP) enzyme. Therefore, the reaction time, the addition sequence of the substrates, the cosubstrate:H(2)O(2) ratio and the electrochemical techniques were elected by one-factor optimization assays while the buffer pH, the enzymatic activity and cosubstrate and H(2)O(2) concentrations for each system were selected simultaneously by response surface methodology. Then, the calibration curves for seven horseradish peroxidase-cosubstrate-H(2)O(2) systems were built and the analytic parameters were analyzed. o-Phenilendiamine was selected as the best cosubstrate for the HRP enzyme. For this system the reaction time of 60s, the phosphate buffer pH 6.0, and the concentrations of 2.5×10(-4)molL(-1) o-phenilendiamine and of 1.25×10(-4)molL(-1) H(2)O(2) were chosen as the optimal conditions. In these conditions, the calibration curve of horseradish peroxidase by square wave voltammetry showed a linearity range from 9.5×10(-11) to 1.9×10(-8)molL(-1) and the limit of detection of 3.8×10(-11)molL(-1) with RSD% of 0.03% (n=3). Copyright © 2011 Elsevier B.V. All rights reserved.

Soil solution phosphorus turnover: derivation, interpretation, and insights from a global compilation of isotope exchange kinetic studies

NASA Astrophysics Data System (ADS)

Helfenstein, Julian; Jegminat, Jannes; McLaren, Timothy I.; Frossard, Emmanuel

2018-01-01

The exchange rate of inorganic phosphorus (P) between the soil solution and solid phase, also known as soil solution P turnover, is essential for describing the kinetics of bioavailable P. While soil solution P turnover (Km) can be determined by tracing radioisotopes in a soil-solution system, few studies have done so. We believe that this is due to a lack of understanding on how to derive Km from isotopic exchange kinetic (IEK) experiments, a common form of radioisotope dilution study. Here, we provide a derivation of calculating Km using parameters obtained from IEK experiments. We then calculated Km for 217 soils from published IEK experiments in terrestrial ecosystems, and also that of 18 long-term P fertilizer field experiments. Analysis of the global compilation data set revealed a negative relationship between concentrations of soil solution P and Km. Furthermore, Km buffered isotopically exchangeable P in soils with low concentrations of soil solution P. This finding was supported by an analysis of long-term P fertilizer field experiments, which revealed a negative relationship between Km and phosphate-buffering capacity. Our study highlights the importance of calculating Km for understanding the kinetics of P between the soil solid and solution phases where it is bioavailable. We argue that our derivation can also be used to calculate soil solution turnover of other environmentally relevant and strongly sorbing elements that can be traced with radioisotopes, such as zinc, cadmium, nickel, arsenic, and uranium.

Online sample concentration and analysis of drugs of abuse in human urine by micelle to solvent stacking in capillary zone electrophoresis.

PubMed

Aturki, Zeineb; Fanali, Salvatore; Rocco, Anna

2016-10-01

A sensitive and rapid CZE-UV method was developed to determine drugs and their metabolites' presence in human urine. Ten drugs of abuse were analyzed including four amphetamines, cocaine, cocaethylene, heroin, morphine, 6-monoacetylmorphine, and 4-methylmethcathinone. An MSS (micelle to solvent stacking) approach was evaluated to enhance method sensitivity. This method considers composition of the micellar sample solution matrix and the injection time. Several analytical conditions influencing the resolution of the drugs mixture as pH and buffer concentration, organic solvent content, were also investigated. The base-line separation of all studied analytes in the same run was achieved within 18 min in an uncoated fused silica capillary (50 μm id × 60 cm) using a background solution containing 50 mM phosphate buffer pH 2.5 and 30% ACN v/v. Other experimental parameters such as applied voltage and capillary temperature were set up at 20 kV and 20°C, respectively. LOD values ranging between 15 and 75 ng/mL for all studied compounds were obtained. From a comparison with conventional CZE, the proposed method provides an increase of sensitivity (39- to 55-fold enhancement factor). Under optimal MSS-CZE conditions, good linearity was achieved (R 2 ≤ 0.9998). The method was finally applied to the analysis of urine samples spiked with a standard mixture after a sample pretreatment, reaching satisfactory recovery values. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrochemical study of the interaction between dsDNA and copper(I) using carbon paste and hanging mercury drop electrode.

PubMed

Stanić, Z; Girousi, S

2008-06-30

The interaction of copper(I) with double-stranded (ds) calf thymus DNA was studied in solution and at the electrode surface by means of transfer voltammetry using a carbon paste electrode (CPE) as working electrode in 0.2 M acetate buffer solution (pH 5.0). As a result of the interaction of Cu(I) between the base pairs of the dsDNA, the characteristic peaks of dsDNA, due to the oxidation of guanine and adenine, increased and after a certain concentration of Cu(I) a new peak at +1.37 V appeared, probably due to the formation of a purine-Cu(I) complex (dsDNA-Cu(I) complex). Accordingly, the interaction of copper(I) with calf thymus dsDNA was studied in solution as well as at the electrode surface using hanging mercury drop electrode (HMDE) by means of alternating current voltammetry (AC voltammetry) in 0.3 M NaCl and 50 mM sodium phosphate buffer (pH 8.5) as supporting electrolyte. Its interaction with DNA is shown to be time dependent. Significant changes in the characteristic peaks of dsDNA were observed after addition of higher concentration of Cu(I) to a solution containing dsDNA, as a result of the interaction between Cu(I) and dsDNA. All the experimental results indicate that Cu(I) can bind to DNA by electrostatic binding and form an association complex.

Assessment of concentrated flow through riparian buffers

Treesearch

M.G. Dosskey; M.J. Helmers; D.E. Eisenhauer; T.G. Franti; K.D. Hoagland

2002-01-01

Concentrated flow of surface runoff from agricultural fields may limit the capability of riparian buffers to remove pollutants. This study was conducted on four farms in southeastern Nebraska to develop a method for assessing the extent of concentrated flow in riparian buffers and for evaluating the impact that it has on sediment-trapping efficiency. Field methods...

Biological Degradation of Tetrachloroethylene in Methanogenic Conditions

DTIC Science & Technology

1994-06-01

stock of neat PCE was not purged with N2-C0 2. Alcohol oxidase (from Pichia pasrori, phosphate-buffered 60 percent sucrose solution), peroxidase (Type...dechlorination of tetrachlorocthene in anaerobic aquifer microcosms by addition of short-chain organic acids or alcohols ," Appl. Environ. Microbiol. (58

Optimization and validation of a rapid method to determine citrate and inorganic phosphate in milk by capillary electrophoresis.

PubMed

Izco, J M; Tormo, M; Harris, A; Tong, P S; Jimenez-Flores, R

2003-01-01

Quantification of phosphate and citrate compounds is very important because their distribution between soluble and colloidal phases of milk and their interactions with milk proteins influence the stability and some functional properties of dairy products. The aim of this work was to optimize and validate a capillary electrophoresis method for the rapid determination of these compounds in milk. Various parameters affecting analysis have been optimized, including type, composition, and pH of the electrolyte, and sample extraction. Ethanol, acetonitrile, sulfuric acid, water at 50 degrees C or at room temperature were tested as sample buffers (SB). Water at room temperature yielded the best overall results and was chosen for further validation. The extraction time was checked and could be shortened to less than 1 min. Also, sample preparation was simplified to pipet 12 microl of milk into 1 ml of water containing 20 ppm of tartaric acid as an internal standard. The linearity of the method was excellent (R2 > 0.999) with CV values of response factors <3%. The detection limits for phosphate and citrate were 5.1 and 2.4 nM, respectively. The accuracy of the method was calculated for each compound (103.2 and 100.3%). In addition, citrate and phosphate content of several commercial milk samples were analyzed by this method, and the results deviated less than 5% from values obtained when analyzing the samples by official methods. To study the versatility of the technique, other dairy productssuch as cream cheese, yogurt, or Cheddar cheese were analyzed and accuracy was similar to milk in all products tested. The procedure is rapid and offers a very fast and simple sample preparation. Once the sample has arrived at the laboratory, less than 5 min (including handling, preparation, running, integration, and quantification) are necessary to determine the concentration of citric acid and inorganic phosphate. Because of the speed and accuracy of this method, it is promising as an analytical quantitative testing technique.

The role of hydroxo-bridged dinuclear species and the influence of "innocent" buffers in the reactivity of cis-[Co(III)(cyclen)(H₂O)₂]³⁺ and [Co(III)(tren)(H₂O)₂]³⁺ complexes with biologically relevant ligands at physiological pH.

PubMed

Basallote, Manuel G; Martínez, Manuel; Vázquez, Marta

2014-07-28

In view of the relevance of the reactivity of inert tetraamine Co(III) complexes having two substitutionally active cis positions capable of interact with biologically relevant ligands, the study of the reaction of cis-[Co(cyclen)(H2O)2](3+) and [Co(tren)(H2O)2](3+) with chlorides, inorganic phosphate and 5'-CMP (5'-cytidinemonophosphate) has been pursued at physiological pH. The results indicate that, in addition to the actuation of the expected labilising conjugate-base mechanism, the formation of mono and inert bis hydroxo-bridged species is relevant for understanding their speciation and reactivity. The reactivity pattern observed also indicates the key role played by the "innocent" buffers frequently used in most in vitro studies, which can make the results unreliable in many cases. The differences between the reactivity of inorganic and biologically relevant phosphates has also been found to be remarkable, with outer-sphere hydrogen bonding interactions being a dominant factor for the process. While for the inorganic phosphate substitution process the formation of μ-η(2)-OPO2O represents the termination of the reactivity monitored, for 5'-CMP only the formation of η(1)-OPO3 species is observed, which evolve with time to the final dead-end bis hydroxo-bridged complexes. The promoted hydrolysis of the 5'-CMP phosphate has not been observed in any of the processes studied.

Effects of a new bicarbonate/lactate-buffered neutral peritoneal dialysis fluid for peritoneal failure in patients undergoing peritoneal dialysis.

PubMed

Hoshino, Taro; Ishii, Hiroki; Kitano, Taisuke; Shindo, Mitsutoshi; Miyazawa, Haruhisa; Yamada, Hodaka; Ito, Kiyonori; Ueda, Yuichiro; Kaku, Yoshio; Hirai, Keiji; Mori, Honami; Ookawara, Susumu; Tabei, Kaoru; Morishita, Yoshiyuki

2016-02-01

The highly concentrated lactate in peritoneal dialysis fluid (PDF) has been considered to contribute to peritoneal failure in patients undergoing PD. A new PDF containing a lower lactate concentration, physiological bicarbonate concentration, and neutral pH (bicarbonate/lactate-buffered neutral PDF) was recently developed. We compared the clinical effects of this bicarbonate/lactate-buffered neutral PDF and a lactate-buffered neutral PDF. Patients undergoing PD were changed from a lactate-buffered neutral PDF to a bicarbonate/lactate-buffered neutral PDF. We then investigated the changes in peritoneal functions as estimated by a peritoneal equilibration test (PET) and the following surrogate markers of peritoneal membrane failure in the drained dialysate: fibrin degradation products (FDP), vascular endothelial growth factor (VEGF), cancer antigen 125 (CA125), interleukin-6 (IL-6), and transforming growth factor beta 1 (TGF-β1). Fourteen patients undergoing PD were enrolled. The PET results were not different before and after use of the bicarbonate/lactate-buffered neutral PDF. The FDP concentration significantly decreased from 15.60 ± 13.90 to 6.04 ± 3.49 μg/mL (p = 0.02) and the VEGF concentration significantly decreased from 37.83 ± 15.82 to 27.70 ± 3.80 pg/mL (p = 0.02), while the CA125 and IL-6 concentrations remained unchanged before and after use of the bicarbonate/lactate-buffered neutral PDF. TGF-β1 was not detected in most patients. The bicarbonate/lactate-buffered neutral PDF decreased the FDP and VEGF concentrations in the drained dialysate. These results suggest that the decreased lactate level achieved by administration of bicarbonate with a neutral pH in PDF may contribute to decreased peritoneal membrane failure in patients undergoing PD.

Effect of the addition CNTs on performance of CaP/chitosan/coating deposited on magnesium alloy by electrophoretic deposition.

PubMed

Zhang, Jie; Wen, Zhaohui; Zhao, Meng; Li, Guozhong; Dai, Changsong

2016-01-01

CaP/chitosan/carbon nanotubes (CNTs) coating on AZ91D magnesium alloy was prepared via electrophoretic deposition (EPD) followed by conversion in a phosphate buffer solution (PBS). The bonding between the layer and the substrate was studied by an automatic scratch instrument. The phase compositions and microstructures of the composite coatings were determined by using X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR), Raman spectroscopy and scanning electron microscope (SEM). The element concentration and gentamicin concentration were respectively determined by inductively coupled plasma optical emission spectrometer (ICP-OES) test and ultraviolet spectrophotometer (UV). The cell counting kit (CCK) assay was used to evaluate the cytotoxicity of samples to SaOS-2 cells. The results showed that a few CNTs with their original tubular morphology could be found in the CaP/chitosan coating and they were beneficial for the crystal growth of phosphate and improvement of the coating bonding when the addition amount of CNTs in 500 ml of electrophoretic solution was from 0.05 g to 0.125 g. The loading amount of gentamicin increased and the releasing speed of gentamicin decreased after CNTs was added into the CaP/chitosan coating for immersion loading and EPD loading. The cell viability of Mg based CaP/chitosan/CNTs was higher than that of Mg based CaP/chitosan from 16 days to 90 days. Copyright © 2015 Elsevier B.V. All rights reserved.

Improved Yield of High Molecular Weight DNA Coincides with Increased Microbial Diversity Access from Iron Oxide Cemented Sub-Surface Clay Environments

DOE PAGES

Hurt, Jr., Richard A.; Robeson II, Michael S.; Shakya, Migun; ...

2014-07-14

Despite more than three decades of progress, efficient nucleic acid extraction from microbial communities has remained difficult, particularly from clay environments. Lysis with concentrated guanidine followed by concentrated sodium phosphate extraction supported DNA and RNA recovery from high iron, low humus content clay. Alterating the extraction pH or using other ionic solutions (Na 2SO 4 and NH 4H 2PO 4) yielded no detectable nucleic acid. DNA recovered using a lysis solution with 500 mM phosphate buffer (PB) followed by a 1 M PB wash was 15.22±2.33 g DNA/g clay, with most DNA consisting of >20 Kb fragments, compared to 2.46±0.25more » g DNA/g clay with the Powerlyzer soil DNA system (MoBio). Increasing [PB] in the lysis reagent coincided with increasing DNA fragment length. Rarefaction plots based on16S rRNA (V1/V3 region) pyrosequencing libraries from A-horizon and clay soils showed an ~80% and ~400% larger accessed diversity compared to a previous grinding protocol or the Powerlyzer soil DNA system, respectively. The observed diversity from the Firmicutes showed the strongest increase with >3-fold more bacterial species recovered using this system. Additionally, some OTU's having more than 100 sequences in these libraries were absent in samples extracted using the PowerLyzer reagents or the previous lysis method.« less

Improved Yield of High Molecular Weight DNA Coincides with Increased Microbial Diversity Access from Iron Oxide Cemented Sub-Surface Clay Environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurt, Jr., Richard A.; Robeson II, Michael S.; Shakya, Migun

Despite more than three decades of progress, efficient nucleic acid extraction from microbial communities has remained difficult, particularly from clay environments. Lysis with concentrated guanidine followed by concentrated sodium phosphate extraction supported DNA and RNA recovery from high iron, low humus content clay. Alterating the extraction pH or using other ionic solutions (Na 2SO 4 and NH 4H 2PO 4) yielded no detectable nucleic acid. DNA recovered using a lysis solution with 500 mM phosphate buffer (PB) followed by a 1 M PB wash was 15.22±2.33 g DNA/g clay, with most DNA consisting of >20 Kb fragments, compared to 2.46±0.25more » g DNA/g clay with the Powerlyzer soil DNA system (MoBio). Increasing [PB] in the lysis reagent coincided with increasing DNA fragment length. Rarefaction plots based on16S rRNA (V1/V3 region) pyrosequencing libraries from A-horizon and clay soils showed an ~80% and ~400% larger accessed diversity compared to a previous grinding protocol or the Powerlyzer soil DNA system, respectively. The observed diversity from the Firmicutes showed the strongest increase with >3-fold more bacterial species recovered using this system. Additionally, some OTU's having more than 100 sequences in these libraries were absent in samples extracted using the PowerLyzer reagents or the previous lysis method.« less

Thermo-responsive methylcellulose hydrogels as temporary substrate for cell sheet biofabrication.

PubMed

Altomare, Lina; Cochis, Andrea; Carletta, Andrea; Rimondini, Lia; Farè, Silvia

2016-05-01

Methylcellulose (MC), a water-soluble polymer derived from cellulose, was investigated as a possible temporary substrate having thermo-responsive properties favorable for cell culturing. MC-based hydrogels were prepared by a dispersion technique, mixing MC powder (2, 4, 6, 8, 10, 12 % w/v) with selected salts (sodium sulphate, Na2SO4), sodium phosphate, calcium chloride, or phosphate buffered saline, to evaluate the influence of different compositions on the thermo-responsive behavior. The inversion test was used to determine the gelation temperatures of the different hydrogel compositions; thermo-mechanical properties and thermo-reversibility of the MC hydrogels were investigated by rheological analysis. Gelation temperatures and rheological behavior depended on the MC concentration and type and concentration of salt used in hydrogel preparation. In vitro cytotoxicity tests, performed using L929 mouse fibroblasts, showed no toxic release from all the tested hydrogels. Among the investigated compositions, the hydrogel composed of 8 % w/v MC with 0.05 M Na2SO4 had a thermo-reversibility temperature at 37 °C. For that reason, this formulation was thus considered to verify the possibility of inducing in vitro spontaneous detachment of cells previously seeded on the hydrogel surface. A continuous cell layer (cell sheet) was allowed to grow and then detached from the hydrogel surface without the use of enzymes, thanks to the thermo-responsive behavior of the MC hydrogel. Immunofluorescence observation confirmed that the detached cell sheet was composed of closely interacting cells.

The effects of temperature and salinity on phosphate levels in two euryhaline crustacean species

NASA Astrophysics Data System (ADS)

Spaargaren, D. H.; Richard, P.; Ceccaldi, H. J.

Total phoshate, inorganic phosphate and organic (phospholipid) phosphate concentrations were determined in the blood of Carcinus maenas and in whole-animal homogenates of Penaeus japonicus acclimatized to various salinities and a high or a low temperature. In the blood of Carcinus, total and inorganic P concentrations range between 1.0 and 4.5 mmol · l -1; the amount of phospholipids is negligeable. The higher values were found at more extreme salinities. Low temperature is associated with low phosphate concentrations, particularly at intermediate salinities. Total P concentrations in Penaeus homogenates range between 10 and 60 mmol · 1 -1; phospholipid concentrations range between zero and 50 mmol · 1 -1. The higher values are again found at the extreme salinities. Inorganic P concentrations are almost constant — ca 10 mmol · 1 -1. No apparent effect of temperature on phosphate concentrations was observed. The results show clearly that osmotic stress influences severely the phosphate metabolism of the two species studied. Both species are able to accumulate phosphate at all experimental temperature/salinity combinations used, even when deprived of food. At extreme salinities, large quantities of phosphate are accumulated and converted to organic P compounds, most likely as phospholipids associated with the cell membranes. These effects of osmotic conditions in phosphate metabolism may offer an explanation for the effect of Ca ++ on membrane permeability as the regulation of both ions may be strongly interrelated, often under hormonal control.

Formulation and synthesis of hydrogels having lower critical solution temperature near body temperature

NASA Astrophysics Data System (ADS)

Abidin, A. Z.; Graha, H. P. R.; Trirahayu, D. A.

2017-07-01

Copolymerization between bacterial cellulose nanocrystal (CN) and methyl cellulose (MC) was carried out using UV light to produce a biocompatible hydrogel at body temperature and liquid at room temperature. Viscosity and salt effect of the MC and copolymer solution at room temperature and its Lower Critical Solution Temperature (LCST) were evaluated. The analysis showed that the higher concentration of methyl cellulose and salt content in the solution produced lower LCST and higher solution viscosity. All samples of polymer solution with MC concentrations of 1 and 2% have a viscosity less than 5000 cP at room temperature. The solutions with MC concentration of 1, 2, and 3% have respectively LCST of 59, 58, and 57°C, while its copolymer solutions with CN concentration of 0.1, 0.3, and 0.5% have respectively LCST of 55, 51, and 41°C. The salt addition to the solution of MC-CN copolymer with concentrations of 1x and 1.5x Phosphat Buffered Saline (PBS) produces respectively LCST of 47 and 38°C. The results suggest that the copolymer solution of MC-CN could produce a lower LCST and the addition of salt could amplify the effect of LCST decrease that can be used to produce a biocompatible hydrogel with LCST as close as body temperature.

DEVELOPMENT OF BIOMARKER OF EXPOSURE TO VIRAL PATHOGENS

EPA Science Inventory

Interferon gamma (IFN-γ) was selected as a biomarker for a viral exposure study. Twelve-week-old BALB/c mice were intraperitoneally injected with 0.2ml of 104 PFU/ml of coxsackievirus B3 or B4 diluted in phosphate-buffered saline (PBS). Control mice were injected with PBS on...

Interferon Gamma as a Biomarker of Exposure to Enteric Viruses

EPA Science Inventory

Interferon gamma (IFN-γ) was selected as a biomarker for viral exposure. Twelve-week-old BALB/c mice were intraperitoneally injected with Coxsackievirus B3 or B4 diluted in phosphate-buffered saline (PBS). Control mice were injected with PBS only. Four months after viral infectio...

RELATIVE RATE CONSTANTS OF CONTAMINANT CANDIDATE LIST PESTICIDES WITH HYDROXYL RADICALS

EPA Science Inventory

The objective of this study was to establish the rate constants for the reactions of selected pesticides listed on the US EPA Contaminant Candidate List, with UV and hydroxyl radicals (·OH). Batch experiments were conducted in phosphate buffered solution at pH 7. All pestici...

Apoptosis and Tumor Progressionin Prostate Cancer

DTIC Science & Technology

2005-02-01

control. Proc Natl Acad Sci USA 94: 10057- 10062 . 5. Colombel M, Symmans F, et al. (1993): Detection of the apoptosis-suppressing oncoprotein bcl-2 in...hours prior to treatment. After treatment, cells were washed with phosphate buffered saline ( PBS ) and fixed in 500 [tL 0.2% glutaraldehyde in water for

Peak shapes of acids and bases under overloaded conditions in reversed-phase liquid chromatography, with weakly buffered mobile phases of various pH: A thermodynamic interpretation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gritti, Fabrice; Guiochon, Georges A

2009-01-01

We measured overloaded band profiles for a series of nine compounds (phenol, caffeine, 3-phenyl 1-propanol, 2-phenylbutyric acid, amphetamine, aniline, benzylamine, p-toluidine, and procainamidium chloride) on columns packed with four different C{sub 18}-bonded packing materials: XTerra-C{sub 18}, Gemini-C{sub 18}, Luna-C{sub 18}(2), and Halo-C{sub 18}, using buffered methanol-water mobile phases. The {sub W}{sup S}pH of the mobile phase was increased from 2.6 to 11.3. The buffer concentration (either phosphate, acetate, or carbonate buffers) was set constant at values below the maximum concentration of the sample in the band. The influence of the surface chemistry of the packing material on the retention andmore » the shape of the peaks was investigated. Adsorbents having a hybrid inorganic/organic structure tend to give peaks exhibiting moderate or little tailing. The retention and the shape of the band profiles can easily be interpreted at {sub W}{sup S}pHs that are well above or well below the {sub W}{sup S}pK{sub a} of the compound studied. In contrast, the peak shapes in the intermediary pH range (i.e., close to the compound {sub W}{sup S}pK{sub a}) have rarely been studied. These shapes reveal the complexity of the competitive adsorption behavior of couples of acido-basic conjugated compounds at {sub W}{sup S}pHs that are close to their {sub W}{sup S}pK{sub a}. They also reveal the role of the buffer capacity on the resulting peak shape. With increasing {sub W}{sup S}pH, the overloaded profiles are first langmuirian (isotherm type I) at low {sub W}{sup S}pHs, they become S-shaped (isotherm type II), then anti-langmuirian (isotherm type III), S-shaped again at intermediate {sub W}{sup S}pHs, and finally return to a langmuirian shape at high {sub W}{sup S}pHs. A new general adsorption isotherm model that takes into account the dissociation equilibrium of conjugated acidic and basic species in the bulk mobile phase accounts for these transient band shapes. An excellent agreement was achieved between experimental profiles and those calculated with a two-sites adsorption isotherm model at all {sub W}{sup S}pHs. The neutral species adsorbs strongly on a first type of sites that have a high density while the ionic species adsorb preferentially on a second type of sites that have a very low density. The evolution of the peak shape when the {sub W}{sup S}pH changes from acidic to basic is well explained by the weak buffer capacity of the mobile phase used compared to the concentration of the eluted compounds.« less

Direct, rapid, and label-free detection of enzyme-substrate interactions in physiological buffers using CMOS-compatible nanoribbon sensors.

PubMed

Mu, Luye; Droujinine, Ilia A; Rajan, Nitin K; Sawtelle, Sonya D; Reed, Mark A

2014-09-10

We demonstrate the versatility of Al2O3-passivated Si nanowire devices ("nanoribbons") in the analysis of enzyme-substrate interactions via the monitoring of pH change. Our approach is shown to be effective through the detection of urea in phosphate buffered saline (PBS), and penicillinase in PBS and urine, at limits of detection of <200 μM and 0.02 units/mL, respectively. The ability to extract accurate enzyme kinetics and the Michaelis-Menten constant (Km) from the acetylcholine-acetylcholinesterase reaction is also demonstrated.

Assessment of pancreas cells

NASA Technical Reports Server (NTRS)

Vanoss, C. J.

1978-01-01

Pancreatic islets were obtained from guinea pig pancreas by the collagenase method and kept alive in tissue culture prior to further studies. Pancreas cell morphology was studied by standard histochemical techniques using light microscopy. Preparative vertical electrophoresis-levitation of dispersed fetal guinea pig pancreas cells was conducted in phosphate buffer containing a heavy water (D20) gradient which does not cause clumping of cells or alter the osmolarity of the buffers. The faster migrating fractions tended to be enriched in beta-cell content. Alpha and delta cells were found to some degree in most fractions. A histogram showing the cell count distribution is included.

Content determination of aniracetam in aniracetam inclusion complex by HPLC.

PubMed

Li, Yongjian; Hu, Dejian; Sun, Yong

2009-01-01

We established a HPLC method for content determination of aniracetam in aniracetam inclusion complex. The chromato column was Agilent ODS (4.6mm x 150mm, 5 microm), the mobile phase was methanol-0.01 mol/L Potassium dihydrogen phosphate buffer solution (25:75, pH 3.0), with the flow rate of 1.0 ml/min, column temperature of 30 degrees and the detection wave at 280 nm, the sample size was 20microL. A good linear relationship was obtained between the peak areas and the concentrations of aniracetam in the range from 5- 80microg/ml (r=0.9998), the mean recovery was 100.1% (n=15), RSD=0.19%. This method is convenient, rapid, accurate, and brings about good recovery; it can be used for content determination of aniracetam in aniracetam inclusion complex.

Study on the inclusion behavior of p-sulfonatocalix[6]arene with propranolol by spectrofluorometry

NASA Astrophysics Data System (ADS)

Li, Hui; Song, Jin-Ping; Chao, Jian-Bin; Shuang, Shao-Min; Dong, Chuan

2012-11-01

The inclusion interaction between propranolol (PPL) and p-sulfonatocalix[6]arene (SCX6) was investigated by fluorescence and 1H NMR spectroscopy. Influences of pH, temperature, ionic strength and the concentration of SCX6 were examined in detail. In phosphate buffer solution with pH 7.5, the fluorescence of PPL dramatically quenched upon addition of SCX6 revealing the formation of inclusion complexes between PPL and SCX6. The stoichiometric ratio was verified to be 1:1 by the continuous variation method. The inclusion constant of PPL-SCX6 complexes was calculated as 2.2 × 104 L/mol by the nonlinear curve fitting method. 1H NMR titration spectra testified that the aliphatic chain of PPL may be partially penetrated into the hydrophobic cavity of SCX6. This was confirmed by molecular dynamics calculations.

Effects of creatine supplementation on exercise performance.

PubMed

Demant, T W; Rhodes, E C

1999-07-01

While creatine has been known to man since 1835, when a French scientist reported finding this constitutent of meat, its presence in athletics as a performance enhancer is relatively new. Amid claims of increased power and strength, decreased performance time and increased muscle mass, creatine is being hailed as a true ergogenic aid. Creatinine is synthesised from the amino acids glycine, arginine and methionine in the kidneys, liver and pancreas, and is predominantly found in skeletal muscle, where it exists in 2 forms. Approximately 40% is in the free creatine form (Crfree), while the remaining 60% is in the phosphorylated form, creatine phosphate (CP). The daily turnover rate of approximately 2 g per day is equally met via exogenous intake and endogenous synthesis. Although creatine concentration (Cr) is greater in fast twitch muscle fibres, slow twitch fibres have a greater resynthesis capability due to their increased aerobic capacity. There appears to be no significant difference between males and females in Cr, and training does not appear to effect Cr. The 4 roles in which creatine is involved during performance are temporal energy buffering, spatial energy buffering, proton buffering and glycolysis regulation. Creatine supplementation of 20 g per day for at least 3 days has resulted in significant increases in total Cr for some individuals but not others, suggesting that there are 'responders' and 'nonresponders'. These increases in total concentration among responders is greatest in individuals who have the lowest initial total Cr, such as vegetarians. Increased concentrations of both Crfree and CP are believed to aid performance by providing more short term energy, as well as increase the rate of resynthesis during rest intervals. Creatine supplementation does not appear to aid endurance and incremental type exercises, and may even be detrimental. Studies investigating the effects of creatine supplementation on short term, high intensity exercises have reported equivocal results, with approximately equal numbers reporting significant and nonsignificant results. The only side effect associated with creatine supplementation appears to be a small increase in body mass, which is due to either water retention or increased protein synthesis.

A Simple and Rapid Method for Standard Preparation of Gas Phase Extract of Cigarette Smoke

PubMed Central

Higashi, Tsunehito; Mai, Yosuke; Noya, Yoichi; Horinouchi, Takahiro; Terada, Koji; Hoshi, Akimasa; Nepal, Prabha; Harada, Takuya; Horiguchi, Mika; Hatate, Chizuru; Kuge, Yuji; Miwa, Soichi

2014-01-01

Cigarette smoke consists of tar and gas phase: the latter is toxicologically important because it can pass through lung alveolar epithelium to enter the circulation. Here we attempt to establish a standard method for preparation of gas phase extract of cigarette smoke (CSE). CSE was prepared by continuously sucking cigarette smoke through a Cambridge filter to remove tar, followed by bubbling it into phosphate-buffered saline (PBS). An increase in dry weight of the filter was defined as tar weight. Characteristically, concentrations of CSEs were represented as virtual tar concentrations, assuming that tar on the filter was dissolved in PBS. CSEs prepared from smaller numbers of cigarettes (original tar concentrations ≤15 mg/ml) showed similar concentration-response curves for cytotoxicity versus virtual tar concentrations, but with CSEs from larger numbers (tar ≥20 mg/ml), the curves were shifted rightward. Accordingly, the cytotoxic activity was detected in PBS of the second reservoir downstream of the first one with larger numbers of cigarettes. CSEs prepared from various cigarette brands showed comparable concentration-response curves for cytotoxicity. Two types of CSEs prepared by continuous and puff smoking protocols were similar regarding concentration-response curves for cytotoxicity, pharmacology of their cytotoxicity, and concentrations of cytotoxic compounds. These data show that concentrations of CSEs expressed by virtual tar concentrations can be a reference value to normalize their cytotoxicity, irrespective of numbers of combusted cigarettes, cigarette brands and smoking protocols, if original tar concentrations are ≤15 mg/ml. PMID:25229830

Modeling of the Modulation by Buffers of Ca2+ Release through Clusters of IP3 Receptors

PubMed Central

Zeller, S.; Rüdiger, S.; Engel, H.; Sneyd, J.; Warnecke, G.; Parker, I.; Falcke, M.

2009-01-01

Abstract Intracellular Ca2+ release is a versatile second messenger system. It is modeled here by reaction-diffusion equations for the free Ca2+ and Ca2+ buffers, with spatially discrete clusters of stochastic IP3 receptor channels (IP3Rs) controlling the release of Ca2+ from the endoplasmic reticulum. IP3Rs are activated by a small rise of the cytosolic Ca2+ concentration and inhibited by large concentrations. Buffering of cytosolic Ca2+ shapes global Ca2+ transients. Here we use a model to investigate the effect of buffers with slow and fast reaction rates on single release spikes. We find that, depending on their diffusion coefficient, fast buffers can either decouple clusters or delay inhibition. Slow buffers have little effect on Ca2+ release, but affect the time course of the signals from the fluorescent Ca2+ indicator mainly by competing for Ca2+. At low [IP3], fast buffers suppress fluorescence signals, slow buffers increase the contrast between bulk signals and signals at open clusters, and large concentrations of buffers, either fast or slow, decouple clusters. PMID:19686646

Effects of pH on contraction of rabbit fast and slow skeletal muscle fibers.

PubMed Central

Chase, P B; Kushmerick, M J

1988-01-01

We have investigated (a) effects of varying proton concentration on force and shortening velocity of glycerinated muscle fibers, (b) differences between these effects on fibers from psoas (fast) and soleus (slow) muscles, possibly due to differences in the actomyosin ATPase kinetic cycles, and (c) whether changes in intracellular pH explain altered contractility typically associated with prolonged excitation of fast, glycolytic muscle. The pH range was chosen to cover the physiological pH range (6.0-7.5) as well as pH 8.0, which has often been used for in vitro measurements of myosin ATPase activity. Steady-state isometric force increased monotonically (by about threefold) as pH was increased from pH 6.0; force in soleus (slow) fibers was less affected by pH than in psoas (fast) fibers. For both fiber types, the velocity of unloaded shortening was maximum near resting intracellular pH in vivo and was decreased at acid pH (by about one-half). At pH 6.0, force increased when the pH buffer concentration was decreased from 100 mM, as predicted by inadequate pH buffering and pH heterogeneity in the fiber. This heterogeneity was modeled by net proton consumption within the fiber, due to production by the actomyosin ATPase coupled to consumption by the creatine kinase reaction, with replenishment by diffusion of protons in equilibrium with a mobile buffer. Lactate anion had little mechanical effect. Inorganic phosphate (15 mM total) had an additive effect of depressing force that was similar at pH 7.1 and 6.0. By directly affecting the actomyosin interaction, decreased pH is at least partly responsible for the observed decreases in force and velocity in stimulated muscle with sufficient glycolytic capacity to decrease pH. Images FIGURE 1 PMID:2969265

Phosphate-dependent glutaminase in enterocyte mitochondria and its regulation by ammonium and other ions.

PubMed

Masola, B; Zvinavashe, E

2003-06-01

The effects of ammonium and other ions on phosphate dependent glutaminase (PDG) activity in intact rat enterocyte mitochondria were investigated. Sulphate and bicarbonate activated the enzyme in absence and presence of added phosphate. In presence of 10 mM phosphate, ammonium at concentrations <1 mM inhibited the enzyme. This inhibition was reversed by increased concentration of phosphate or sulphate. The inhibition of PDG by ammonium in presence of 10 mM phosphate was biphasic with respect to glutamine concentration, its effect being through a lowering of V(max) at glutamine concentration of

Effects of repeated 9 and 30-day exposure to extremely low-frequency electromagnetic fields on social recognition behavior and estrogen receptors expression in olfactory bulb of Wistar female rats.

PubMed

Bernal-Mondragón, C; Arriaga-Avila, V; Martínez-Abundis, E; Barrera-Mera, B; Mercado-Gómez, O; Guevara-Guzmán, R

2017-02-01

We investigated the short- and long-term effects of extremely low-frequency electromagnetic fields (EMF) on social recognition behavior and expression of α- and β-estrogen receptors (ER). Rats were exposed to 60-Hz electromagnetic fields for 9 or 30 days and tested for social recognition behavior. Immunohistochemistry and western blot assays were performed to evaluate α- and β-ER expression in the olfactory bulb of intact, ovariectomized (OVX), and ovariectomized+estradiol (E2) replacement (OVX+E2). Ovariectomization showed impairment of social recognition after 9 days of EMF exposure and a complete recovery after E2 replacement and so did those after 30 days. Short EMF exposure increased expression of β-ER in intact, but not in the others. Longer exposure produced a decrease in intact but an increase in OVX and OVX+E2. Our findings suggest a significant role for β-estrogen receptors and a lack of effect for α-estrogen receptors on a social recognition task. EMF: extremely low frequency electromagnetic fields; ERs: estrogen receptors; OB: olfactory bulb; OVX: ovariectomized; OVX + E 2 : ovariectomized + estradiol replacement; IEI: interexposure interval; β-ER: beta estrogen receptor; E 2 : replacement of estradiol; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; WB: Western blot; PBS: phosphate-buffer saline; PB: phosphate-buffer.

Phosphoric acid addition effect on the microstructure and magnetic properties of iron-based soft magnetic composites

NASA Astrophysics Data System (ADS)

Hsiang, Hsing-I.; Fan, Liang-Fang; Hung, Jia-Jing

2018-02-01

The phosphoric acid addition effect on phosphate insulation coating microstructure was investigated in this study. The relationships between the phosphate insulation coating microstructure and temperature resistance, corrosion resistance and magnetic properties of iron-based soft magnetic composites (SMCs) were studied by using SEM, TEM/EDS and FTIR. It was observed that an iron phosphate/carbonyl iron core/shell structure is formed with carbonyl iron powder after phosphatizing treatment. The iron phosphate phase was identified as amorphous and its thickness increased from 30 nm to 60 nm as the phosphoric acid concentration was increased from 1 wt% to 2 wt%. When the phosphoric acid concentration was further increased to 5 wt%, the excess iron phosphate precipitates between the soft magnetic composite particles. The temperature and corrosion resistance and resistivity of the iron-based SMCs can be effectively improved using carbonyl iron powders after phosphatizing. The initial permeability of the iron-based SMCs decreased with increasing phosphoric acid concentration due to thicker insulation layer formation. However, the imaginary permeability below the domain wall displacement resonance frequency decreased with increasing phosphoric acid concentration. The DC-bias superposition characteristic can also be improved by increasing the phosphoric acid concentration. Iron-based SMCs with superior temperature and corrosion resistance, initial permeability, magnetic loss and DC-bias superposition characteristics can be obtained by controlling the phosphoric acid concentration during phosphatizing to adjust the iron phosphate precipitate thickness on the iron powder surface.

Measurement of radon concentration in super-Kamiokande's buffer gas

NASA Astrophysics Data System (ADS)

Nakano, Y.; Sekiya, H.; Tasaka, S.; Takeuchi, Y.; Wendell, R. A.; Matsubara, M.; Nakahata, M.

2017-09-01

To precisely measure radon concentrations in purified air supplied to the Super-Kamiokande detector as a buffer gas, we have developed a highly sensitive radon detector with an intrinsic background as low as 0 . 33 ± 0 . 07 mBq /m3. In this article, we discuss the construction and calibration of this detector as well as results of its application to the measurement and monitoring of the buffer gas layer above Super-Kamiokande. In March 2013, the chilled activated charcoal system used to remove radon in the input buffer gas was upgraded. After this improvement, a dramatic reduction in the radon concentration of the supply gas down to 0 . 08 ± 0 . 07 mBq /m3. Additionally, the Rn concentration of the in-situ buffer gas has been measured 28 . 8 ± 1 . 7 mBq /m3 using the new radon detector. Based on these measurements we have determined that the dominant source of Rn in the buffer gas arises from contamination from the Super-Kamiokande tank itself.

Effect of altered sink:source ratio on photosynthetic metabolism of source leaves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plaut, Z.; Mayoral, M.L.; Reinhold, L.

When seven crop species were grown under identical environmental conditions, decreased sink:source ratio led to a decreased photosynthetic rate within 1 to 3 days in Cucumis sativus L., Gossypium hirsutum L., and Raphanus sativus L., but not in Capsicum annuum L., Solanum melongena L., Phaseolus vulgaris L., or Ricinus communis L. The decrease was not associated with stomatal closure. In cotton and cucumbers, sink removal led to an increase in starch and sugar content, in glucose 6-phosphate and fructose 6-phosphate pools, and in the proportion of /sup 14/C detected in sugar phosphates and UDPglucose following /sup 14/CO/sub 2/ supply. Whenmore » mannose was supplied to leaf discs to sequester cytoplasmic inorganic phosphate, promotion of starch synthesis, and inhibition of CO/sub 2/ fixation, were observed in control discs, but not in discs from treated plants. Phosphate buffer reduced starch synthesis in the latter, but not the former discs. The findings suggest that sink removal led to a decreased ratio inorganic phosphate:phosphorylated compounds. In beans /sup 14/C in sugar phosphates increased following sink removal, but without sucrose accumulation, suggesting tighter feedback control of sugar level. Starch accumulated to higher levels than in the other plants, but CO/sub 2/ fixation rate was constant for several days.« less

Complement, Kinins, and Hereditary Angioedema: Mechanisms of Plasma Instability when C1 Inhibitor is Absent.

PubMed

Kaplan, Allen P; Joseph, Kusumam

2016-10-01

Plasma of patients with types I and II hereditary angioedema is unstable if incubated in a plastic (i.e., inert) vessel at 37 °C manifested by progressively increasing formation of bradykinin. There is also a persistent low level of C4 in 95 % of patients even when they are symptomatic. These phenomena are due to the properties of the C1r subcomponent of C1, factor XII, and the bimolecular complex of prekallikrein with high molecular weight kininogen (HK). Purified C1r auto-activates in physiologic buffers, activates C1s, which in turn depletes C4. This occurs when C1 inhibitor is deficient. The complex of prekallikrein-HK acquires an inducible active site not present in prekallikrein which in Tris-type buffers cleaves HK stoichiometrically to release bradykinin, or in phosphate buffer auto-activates to generate kallikrein and bradykinin. Thus immunologic depletion of C1 inhibitor from factor XII-deficient plasma (phosphate is the natural buffer) auto-activates on incubation to release bradykinin. Normal C1 inhibitor prevents this from occurring. During attacks of angioedema, if factor XII auto-activates on surfaces, the initial factor XIIa formed converts prekallikrein to kallikrein, and kallikrein cleaves HK to release bradykinin. Kallikrein also rapidly activates most remaining factor XII to factor XIIa. Additional cleavages convert factor XIIa to factor XIIf and factor XIIf activates C1r enzymatically so that C4 levels approach zero, and C2 is depleted. There is also a possibility that kallikrein is generated first as a result of activation of the prekallikrein-HK complex by heat shock protein 90 released from endothelial cells, followed by kallikrein activation of factor XII.

Dynamics and mitigation of six pesticides in a "Wet" forest buffer zone.

PubMed

Passeport, Elodie; Richard, Benjamin; Chaumont, Cédric; Margoum, Christelle; Liger, Lucie; Gril, Jean-Joël; Tournebize, Julien

2014-04-01

Pesticide pollution is one of the main current threats on water quality. This paper presents the potential and functioning principles of a "Wet" forest buffer zone for reducing concentrations and loads of glyphosate, isoproturon, metazachlor, azoxystrobin, epoxiconazole, and cyproconazole. A tracer injection experiment was conducted in the field in a forest buffer zone at Bray (France). A fine time-scale sampling enabled to illustrate that interactions between pesticides and forest buffer substrates (soil and organic-rich litter layer), had a retarding effect on molecule transfer. Low concentrations were observed for all pesticides at the forest buffer outlet thus demonstrating the efficiency of "Wet" forest buffer zone for pesticide dissipation. Pesticide masses injected in the forest buffer inlet directly determined concentration peaks observed at the outlet. Rapid and partially reversible adsorption was likely the major process affecting pesticide transfer for short retention times (a few hours to a few days). Remobilization of metazachlor, isoproturon, desmethylisoproturon, and AMPA was observed when non-contaminated water flows passed through the forest buffer. Our data suggest that pesticide sorption properties alone could not explain the complex reaction mechanisms that affected pesticide transfer in the forest buffer. Nevertheless, the thick layer of organic matter litter on the top of the forest soil was a key parameter, which enhanced partially reversible sorption of pesticide, thus retarded their transfer, decreased concentration peaks, and likely increased degradation of the pesticides. Consequently, to limit pesticide pollution transported by surface water, the use of already existing forest areas as buffer zones should be equally considered as the most commonly implemented grass buffer strips.

Effect of phosphate on U(VI) sorption to montmorillonite: Ternary complexation and precipitation barriers

NASA Astrophysics Data System (ADS)

Troyer, Lyndsay D.; Maillot, Fabien; Wang, Zheming; Wang, Zimeng; Mehta, Vrajesh S.; Giammar, Daniel E.; Catalano, Jeffrey G.

2016-02-01

Phosphate addition is a potential treatment method to lower the solubility of U(VI) in soil and groundwater systems by causing U(VI) phosphate precipitation as well as enhancing adsorption. Previous work has shown that iron oxide surfaces may facilitate the nucleation of U(VI) phosphate minerals and, that under weakly acidic conditions, phosphate also enhances U(VI) adsorption to such phases. Like iron oxides, clays are important reactive phases in the subsurface but little is known about the interaction of U(VI) and phosphate with these minerals. The effect of aqueous phosphate on U(VI) binding to Wyoming montmorillonite (SWy-2) in air-equilibrated systems was investigated. Equilibrium U(VI) uptake to montmorillonite was determined at pH 4, 6 and 8 at discrete initial phosphate concentrations between 0 and 100 μM. The observed behavior of U(VI) indicates a transition from adsorption to precipitation with increasing total uranium and phosphate concentrations at all pH values. At the highest phosphate concentration examined at each pH value, a barrier to U(VI) phosphate nucleation is observed. At lower concentrations, phosphate has no effect on macroscopic U(VI) adsorption. To assess the mechanisms of U(VI)-phosphate interactions on smectite surfaces, U(VI) speciation was investigated under selected conditions using laser-induced fluorescence spectroscopy (LIFS) and extended X-ray absorption fine-structure (EXAFS) spectroscopy. Samples above the precipitation threshold display EXAFS and LIFS spectral signatures consistent with the autunite family of U(VI) phosphate minerals. However, at lower U(VI) concentrations, changes in LIFS spectra upon phosphate addition suggest that U(VI)-phosphate ternary surface complexes form on the montmorillonite surface at pH 4 and 6 despite the lack of a macroscopic effect on adsorption. The speciation of solid-associated U(VI) below the precipitation threshold at pH 8 is dominated by U(VI)-carbonate surface complexes. This work reveals that ternary complexation may occur without a macroscopic signature, which is attributed to phosphate not appreciably binding to smectite in the absence of U(VI), with U(VI) surface complexes serving as the sole reactive surface sites for phosphate. This study shows that phosphate does not enhance U(VI) adsorption to smectite clay minerals, unlike oxide phases, and that a barrier to homogeneous nucleation of U(VI) phosphates was not affected by the presence of the smectite surface.

A photoacoustic tool for therapeutic drug monitoring of heparin (Conference Presentation)

NASA Astrophysics Data System (ADS)

Wang, Junxin; Hartanto, James; Jokerst, Jesse V.

2017-03-01

Heparin is used broadly in cardiac, pulmonary, surgical, and vascular medicine to treat thrombotic disorders with over 500 million doses per year globally. Despite this widespread use, it has a narrow therapeutic window and is one of the top three medication errors. The active partial thromboplastin time (PTT) monitors heparin, but this blood test suffers from long turnaround times, a variable reference range, and limited utility with low molecular weight heparin. Here, we describe an imaging technique that can monitor heparin concentration and activity in real time using photoacoustic spectroscopy via methylene blue as a simple and Federal Drug Agency-approved contrast agent. We found a strong correlation between heparin concentration and photoacoustic signal measured in phosphate buffered saline (PBS) and blood (R2>0.90). Clinically relevant concentrations were detected in blood with a heparin detection limit of 0.28 U/mL and a low molecular weight heparin (enoxaparin) detection limit of 72 μg/mL. We validated this imaging approach by correlation to the PTT (Pearson's r = 0.86; p<0.05) as well as with protamine sulfate treatment. To the best of our knowledge, this is the first report to use imaging data to monitor anticoagulation.

Quinoa starch granules as stabilizing particles for production of Pickering emulsions.

PubMed

Rayner, Marilyn; Sjöö, Malin; Timgren, Anna; Dejmek, Petr

2012-01-01

Intact starch granules isolated from quinoa (Chenopodium quinoa Willd.) were used to stabilize emulsion drops in so-called Pickering emulsions. Miglyol 812 was used as dispersed phase and a phosphate buffer (pH7) with different salt (NaCl) concentrations was used as the continuous phase. The starch granules were hydrophobically modified to different degrees by octenyl succinic anhydride (OSA) or by dry heat treatment at 120 degrees C in order to study the effect on the resulting emulsion drop size. The degree of OSA-modification had a low to moderate impact on drop size. The highest level of modification (4.66%) showed the largest mean drop size, and lowest amount of free starch, which could be an effect of a higher degree of aggregation of the starch granules and, thereby, also the emulsion drops stabilized by them. The heat treated starch granules had a poor stabilizing ability and only the starch heated for the longest time (150 min at 120 degrees C) had a better emulsifying capacity than the un-modified native starch granules. The effect of salt concentration was rather limited. However, an increased concentration of salt slightly increased the mean drop size and the elastic modulus.

Aqueous reactive species induced by a PCB surface micro-discharge air plasma device: a quantitative study

NASA Astrophysics Data System (ADS)

Chen, Chen; Li, Fanying; Chen, Hai-Lan; Kong, Michael G.

2017-11-01

This paper presents a quantitative investigation on aqueous reactive species induced by air plasma generated from a printed circuit board surface micro-discharge (SMD) device. Under the conditions amenable for proliferation of mammalian cells, concentrations of ten types of reactive oxygen and nitrogen species (RONS) in phosphate buffering solution (PBS) are measured by chemical fluorescent assays and electron spin resonance spectroscopy (ESR). Results show that concentrations of several detected RNS (NO2- , NO3- , peroxynitrites, and NO2\\centerdot ) are higher than those of ROS (H2O2, O2\\centerdot - , and 1O2) in the air plasma treated solution. Concentrations of NO3- can reach 150 times of H2O2 with 60 s plasma treatment. For short-lived species, the air plasma generates more copious peroxynitrite than other RONS including NO2\\centerdot , O2\\centerdot - , 1O2, and N{{O}\\centerdot } in PBS. In addition, the existence of reaction between H2O2 and NO2- /HNO2 to produce peroxynitrite is verified by the chemical scavenger experiments. The reaction relations between detected RONS are also discussed.

Glucose Synthesis in a Protein-Based Artificial Photosynthesis System.

PubMed

Lu, Hao; Yuan, Wenqiao; Zhou, Jack; Chong, Parkson Lee-Gau

2015-09-01

The objective of this study was to understand glucose synthesis of a protein-based artificial photosynthesis system affected by operating conditions, including the concentrations of reactants, reaction temperature, and illumination. Results from non-vesicle-based glyceraldehyde-3-phosphate (GAP) and glucose synthesis showed that the initial concentrations of ribulose-1,5-bisphosphate (RuBP) and adenosine triphosphate (ATP), lighting source, and temperature significantly affected glucose synthesis. Higher initial concentrations of RuBP and ATP significantly enhanced GAP synthesis, which was linearly correlated to glucose synthesis, confirming the proper functions of all catalyzing enzymes in the system. White fluorescent light inhibited artificial photosynthesis and reduced glucose synthesis by 79.2 % compared to in the dark. The reaction temperature of 40 °C was optimum, whereas lower or higher temperature reduced glucose synthesis. Glucose synthesis in the vesicle-based artificial photosynthesis system reconstituted with bacteriorhodopsin, F 0 F 1 ATP synthase, and polydimethylsiloxane-methyloxazoline-polydimethylsiloxane triblock copolymer was successfully demonstrated. This system efficiently utilized light-induced ATP to drive glucose synthesis, and 5.2 μg ml(-1) glucose was synthesized in 0.78-ml reaction buffer in 7 h. Light-dependent reactions were found to be the bottleneck of the studied artificial photosynthesis system.

Fasting suppresses T cell-mediated immunity in female Mongolian gerbils (Meriones unguiculatus).

PubMed

Xu, De-Li; Wang, De-Hua

2010-01-01

Immune defense is important for organisms' survival and fitness. Small mammals in temperate zone often face seasonal food shortages. Generally fasting can suppress immune function in laboratory rodents and little information is available for wild rodents. The present study tested the hypothesis that Mongolian gerbils (Meriones unguiculatus) could inhibit T cell-mediated immunity to adapt to acute fasting. Forty-two females were divided into the fed and fasted groups, in which the latter was deprived of food for 3days. After 66h fasting, half of the gerbils in each group were injected with phosphate buffered saline or phytohaemagglutinin (PHA) solution. T cell-mediated immunity assessed by PHA response was suppressed in the fasted gerbils compared with the fed gerbils. The fasted gerbils had lower body fat mass, wet and dry thymus mass, dry spleen mass, white blood cells, serum leptin and blood glucose concentrations, but higher corticosterone concentrations than those of the controls. Moreover, PHA response was positively correlated with body fat mass and serum leptin levels in the immunochallenged groups. Taken together, acute fasting leads to immunosuppression, which might be caused by low body fat mass and low serum leptin concentrations in female Mongolian gerbils.

Ultra high pressure homogenization (UHPH) inactivation of Bacillus amyloliquefaciens spores in phosphate buffered saline (PBS) and milk

PubMed Central

Dong, Peng; Georget, Erika S.; Aganovic, Kemal; Heinz, Volker; Mathys, Alexander

2015-01-01

Ultra high pressure homogenization (UHPH) opens up new areas for dynamic high pressure assisted thermal sterilization of liquids. Bacillus amyloliquefaciens spores are resistant to high isostatic pressure and temperature and were suggested as potential surrogate for high pressure thermal sterilization validation. B. amyloliquefaciens spores suspended in PBS buffer (0.01 M, pH 7.0), low fat milk (1.5%, pH 6.7), and whole milk (3.5%, pH 6.7) at initial concentration of ~106 CFU/mL were subjected to UHPH treatments at 200, 300, and 350 MPa with an inlet temperature at ~80°C. Thermal inactivation kinetics of B. amyloliquefaciens spores in PBS and milk were assessed with thin wall glass capillaries and modeled using first-order and Weibull models. The residence time during UHPH treatments was estimated to determine the contribution of temperature to spore inactivation by UHPH. No sublethal injury was detected after UHPH treatments using sodium chloride as selective component in the nutrient agar medium. The inactivation profiles of spores in PBS buffer and milk were compared and fat provided no clear protective effect for spores against treatments. Treatment at 200 MPa with valve temperatures lower than 125°C caused no reduction of spores. A reduction of 3.5 log10CFU/mL of B. amyloliquefaciens spores was achieved by treatment at 350 MPa with a valve temperature higher than 150°C. The modeled thermal inactivation and observed inactivation during UHPH treatments suggest that temperature could be the main lethal effect driving inactivation. PMID:26236296

Simultaneous determination of ochratoxin A and cyclopiazonic, mycophenolic, and tenuazonic acids in cornflakes by solid-phase microextraction coupled to high-performance liquid chromatography.

PubMed

Aresta, Antonella; Cioffi, Nicola; Palmisano, Francesco; Zambonin, Carlo G

2003-08-27

A solid-phase microextraction (SPME) method, coupled to liquid chromatography with diode array UV detection (LC-UV/DAD), for the simultaneous determination of cyclopiazonic acid, mycophenolic acid, tenuazonic acid, and ochratoxin A is described. Chromatographic separation was achieved on a propylamino-bonded silica gel stationary phase using acetonitrile/methanol/ammonium acetate buffer mixture (78:2:20, v/v/v) as mobile phase. SPME adsorption and desorption conditions were optimized using a silica fiber coated with a 60 microm thick polydimethylsiloxane/divinylbenzene film. Estimated limits of detection and limits of quantitation ranged from 3 to 12 ng/mL and from 7 to 29 ng/mL, respectively. The method has been applied to cornflake samples. Samples were subjected to a preliminary short sonication in MeOH/2% KHCO(3) (70:30, v/v); the mixture was evaporated to near dryness and reconstituted in 1.5 mL of 5 mM phosphate buffer (pH 3) for SPME followed by LC-UV/DAD. The overall procedure had recoveries (evaluated on samples spiked at 200 ng/g level) ranging from 74 +/- 4 to 103 +/- 9%. Samples naturally contaminated with cyclopiazonic and tenuazonic acids were found; estimated concentrations were 72 +/- 9 and 25 +/- 6 ng/g, respectively.

Buffering of Ocean Export Production by Flexible Elemental Stoichiometry of Particulate Organic Matter

NASA Astrophysics Data System (ADS)

Tanioka, Tatsuro; Matsumoto, Katsumi

2017-10-01

One of the most important factors that determine the ocean-atmosphere carbon partitioning is the sinking of particulate organic matter (POM) from the surface ocean to the deep ocean. The amount of carbon (C) removed from the surface ocean by this POM export production depends critically on the elemental ratio in POM of C to nitrogen (N) and phosphorus (P), two essential elements that limit productivity. Recent observations indicate that P:N:C in marine POM varies both spatially and temporally due to chemical, physical, and ecological dynamics. In a new approach to predicting a flexible P:C ratio, we developed a power law model with a stoichiometry sensitivity factor, which is able to relate P:C of POM to ambient phosphate concentration. The new factor is robust, measurable, and biogeochemically meaningful. Using the new stoichiometry sensitivity factor, we present a first-order estimate that P:C plasticity could buffer against a generally expected future reduction in global carbon export production by up to 5% under a future warming scenario compared to a fixed, Redfield P:C. Further, we demonstrate that our new stoichiometry model can be implemented successfully and easily in a global model to reproduce the large-scale P:N:C variability in the ocean.

Development and validation of a stability-indicating high performance liquid chromatographic assay for benoxinate.

PubMed

Chorny, Michael; Levy, Daniel; Schumacher, Ilana; Lichaa, Chaim; Gruzman, Boris; Livshits, Oleg; Lomnicky, Yossi

2003-04-24

Benoxinate is a local anaesthetic used for ophthalmic applications. The aim of this study was to develop a rapid and simple stability-indicating method for the determination of benoxinate formulated for ophthalmic use, evaluate its long-term stability and identify its major degradation product. Benoxinate was eluted on a 10 microm Spherisorb phenyl column, 250 x 3.2 mm, with a mobile phase consisting of acetonitrile-buffer (pH 3.5) (35:65, v/v), pumped at 0.8 ml min(-1) flow rate. The buffer was composed of sodium dihydrogen phosphate (50 mM), sodium hydrogen sulfate (2.5 mM) and 1-heptanesulfonic acid sodium salt (5 mM). The analyte was quantified spectrophotometrically at 308 nm. The chromatograms of benoxinate formulations obtained by this method showed benoxinate (t = 4.5 min) well resolved from its degradation product (t = 2.3 min), which was separately identified by means of HPLC-MS as 4-amino-3-butoxybenzoic acid. The assay was demonstrated to have high accuracy, precision and linearity. The method was implemented in investigating the long-term stability of benoxinate 0.4% ophthalmic solutions. The method was found to be simple, quick and selective in determining benoxinate concentrations in fresh and aged preparations.

Combining essential oils and olive extract for control of multi-drug resistant Salmonella enterica on organic leafy greens

USDA-ARS?s Scientific Manuscript database

We investigated the combined antimicrobial effects of plant essential oils and olive extract. Organic baby spinach, mature spinach, romaine lettuce, and iceberg lettuce were inoculated with the pathogen and then dip-treated in phosphate buffered saline (PBS) control, 3.0% hydrogen peroxide, a 0.1% ...

Inactivation of Hepatitis A Virus (HAV) by Chlorine and Iodine in Water

DTIC Science & Technology

1986-11-01

treatment practices utilizing chemical disinfection, primarily chlorination, are generally believed to * be effective in producing microbiologically safe...OCl) in 1 liter of HDFW. Stock solution was then diluted in tesi water (halogen demand-free, 0.01M phosphate buffer, pH 4.5, 7.0 or 9.5 in initial

Morphology of the female reproductive system and physiological age-grading of Megamelus scutellaris (Hemiptera: Delphacidae), a biological control agent of water hyacinth

USDA-ARS?s Scientific Manuscript database

The morphology of the female reproductive system in Megamelus scutellaris Berg (Hemiptera:Delphacidae), a biocontrol agent of Eichhornia crassipes (Mart.) Solms, was examined using standard light microscopy techniques. Ovaries extracted from individuals dissected in phosphate buffered saline were ex...

EFFECTS OF PH ON DECHLORINATION OF TRICHLOROETHYLENE BY ZERO-VALENT IRON

EPA Science Inventory

The reduction rates of trichloroethylene (TCE) using zero-valent iron (ZVI) and the rates of iron hydrolysis were characterized at pH values of 5 to 10. The reduction of TCE by ZVI was carried out in batch reactors filled with pH-buffered (phosphate based) solutions under anaerob...

Enumeration of sugars and sugar alcohols hydroxyl groups by aqueous-based acetylation and MALDI-TOF mass spectrometry

USDA-ARS?s Scientific Manuscript database

A method is described for enumerating hydroxyl groups on analytes in aqueous media is described, and applied to some common polyalcohols (erythritol, mannitol, and xylitol) and selected carbohydrates. The analytes were derivatized in water with vinyl acetate in presence of sodium phosphate buffer. ...

9 CFR 113.43 - Detection of chlamydial agents.

Code of Federal Regulations, 2014 CFR

2014-01-01

... in a filed Outline of Production. (a) The yolk sac of 6-day-old chicken embryos shall be injected. Three groups of 10 embryos shall be used sequentially. (1) The inoculum for each embryo in the first... embryos shall be harvested, pooled, homogenized as a 20 percent suspension in phosphate buffered saline...

9 CFR 113.43 - Detection of chlamydial agents.

Code of Federal Regulations, 2011 CFR

2011-01-01

... in a filed Outline of Production. (a) The yolk sac of 6-day-old chicken embryos shall be injected. Three groups of 10 embryos shall be used sequentially. (1) The inoculum for each embryo in the first... embryos shall be harvested, pooled, homogenized as a 20 percent suspension in phosphate buffered saline...

9 CFR 113.43 - Detection of chlamydial agents.

Code of Federal Regulations, 2013 CFR

2013-01-01

... in a filed Outline of Production. (a) The yolk sac of 6-day-old chicken embryos shall be injected. Three groups of 10 embryos shall be used sequentially. (1) The inoculum for each embryo in the first... embryos shall be harvested, pooled, homogenized as a 20 percent suspension in phosphate buffered saline...

9 CFR 113.43 - Detection of chlamydial agents.

Code of Federal Regulations, 2012 CFR

2012-01-01

... in a filed Outline of Production. (a) The yolk sac of 6-day-old chicken embryos shall be injected. Three groups of 10 embryos shall be used sequentially. (1) The inoculum for each embryo in the first... embryos shall be harvested, pooled, homogenized as a 20 percent suspension in phosphate buffered saline...

Discernment of lint trash in raw cotton using multivariate analysis of excitation-emission luminescence spectra

USDA-ARS?s Scientific Manuscript database

Excitation-Emission luminescence spectra of basic (pH 12.5) phosphate buffer solution extracts were used to distinguish among botanical components of trash within seed cotton. All components were separated from whole plants removed from a field in southern New Mexico. Unfolded Principal Component An...

Fission Yeast Model Study for Dissection of TSC Pathway

DTIC Science & Technology

2010-04-01

prepared as follows. A total of 1010 cells were incubated at 37! for 1 hr in spheroplasts buffer [50 mm citrate–phosphate (pH 5.6) and 1.2 m sorbitol ...potassium acetate, and 0.1 m sorbitol ] containing 0.4 mm phenylmethyl- sulfonyl fluoride and 13 protease inhibitor cocktail (Nacalai Tesque) and downed

Volunteer Challenge With Enterotoxigenic Escherichia coli That Express Intestinal Colonization Factor Fimbriae CS17 and CS19

DTIC Science & Technology

2011-07-01

for 18-20 h, bacteria were harvested in sterile saline, and the sus- pension was diluted in phosphate-buffered saline to the ap- propriate...Levine MM, Merson MM. Serologic differentiation between antitoxin responses to infection with Vibrio cholerae and enterotoxin-producing Escherichia coli

Biodegradable neural cell culture sheet made of poly(lactic-co-glycolic acid) thin film with micropatterns of Dulbecco’s phosphate-buffered saline (-) containing laminin layers

NASA Astrophysics Data System (ADS)

Nakamura, Yuki; Horiuchi, Shunpu; Nishioka, Yasushiro

2018-02-01

In the regenerative medicine field of nervous systems, techniques used to fabricate microstructures of neurons on flexible and biodegradable substrates have attracted attention. In this research, biodegradable and flexible neuron culture thin films that enable the selective axonal outgrowth of neurons were fabricated using poly(lactic-co-glycolic acid) (PLGA) thin films with micropatterns of Dulbecco’s phosphate-buffered saline (D-PBS) (-) containing laminin layers. The 100-µm-thick PLGA thin films were fabricated by diluting PLGA in acetone (5% w/w) and the solution was distributed onto a poly(dimethylsiloxane) (PDMS) mold. D-PBS (-) micropatterns containing laminin layers with widths of 10-150 µm were fabricated by micromolding in capillaries (MIMIC) and the microstencil method. Rat neurons were selectively cultured for 3 d on the laminin micropatterns; using the MIMIC method, the cells properly adhered to a pattern wider than 30 µm, while with the microstencil method, the necessary pattern width for proper adhesion was more than 50 µm.

Is nothing sacred?

USGS Publications Warehouse

Hoffman, G.L.

1980-01-01

N-sodium-N-chloro-rho-toluenesulfonamide (chloramine-T) effectively controls bacterial gill disease (BGD) in cultured fishes, BGD, a common disease of hatchery-reared salmonids, causes more fish losses than any other disease among these species, This study describes a liquid chromatographic (LC) method that is capable of direct, simultaneous analysis of chloramine-T and its primary degradation product, rho-toluenesulfonamide (rho-TSA), in water. The procedure involves reversed-phase (C-18) LC analysis with ion suppression, using 0.01 M phosphate buffer at pH 3. The mobile phase is phosphate buffer-acetonitrile (60 + 40) at 1 mL/min. Both chemicals can be detected with a UV spectrophotometer at 229 nm; the method is linear up to 40 mg, chloramine-T or rho-TSA/L. Mean recoveries were 96.4 +/- 6.1% for water samples fortified with 0.03 mg chloramine-T/L and 95.3 +/- 4.6% for water samples fortified with 0.005 mg rho-TSA/L. Limits of detection without sample enrichment for chloramine-T and rho-TSA are 0.01 mg/L and 0.001 mg/L, respectively.

Liquid chromatographic determination of chloramine-T and its primary degradation product, p-toluenesulfonamide, in water

USGS Publications Warehouse

Dawson, Verdel K.; Davis, Ruth A.

1997-01-01

N-sodium-N-chloro-rho-toluenesulfonamide (chloramine-T) effectively controls bacterial gill disease (BGD) in cultured fishes, BGD, a common disease of hatchery-reared salmonids, causes more fish losses than any other disease among these species. This study describes a liquid chromatographic (LC) method that is capable of direct, simultaneous analysis of chloramine-T and its primary degradation product, rho-toluenesulfonamide (rho-TSA), in water. The procedure involves reversed-phase (C-18) LC analysis with ion suppression, using 0.01 M phosphate buffer at pH 3. The mobile phase is phosphate buffer-acetonitrile (60 + 40) at 1 mL/min. Both chemicals can be detected with a UV spectrophotometer at 229 nm; the method is linear up to 40 mg, chloramine-T or rho-TSA/L. Mean recoveries were 96.4 +/- 6.1% for water samples fortified with 0.03 mg chloramine-T/L and 95.3 +/- 4.6% for water samples fortified with 0.005 mg rho-TSA/L. Limits of detection without sample enrichment for chloramine-T and rho-TSA are 0.01 mg/L and 0.001 mg/L, respectively.

Liquid chromatographic determination of chloramine-T and its primary degradation product, p-toluenesulfonamide, in water

USGS Publications Warehouse

Dawson, V.K.; Davis, R.A.

1997-01-01

N-sodium-N-chloro-rho-toluenesulfonamide (chloramine-T) effectively controls bacterial gill disease (BGD) in cultured fishes, BGD, a common disease of hatchery-reared salmonids, causes more fish losses than any other disease among these species, This study describes a liquid chromatographic (LC) method that is capable of direct, simultaneous analysis of chloramine-T and its primary degradation product, rho-toluenesulfonamide (rho-TSA), in water. The procedure involves reversed-phase (C-18) LC analysis with ion suppression, using 0.01 M phosphate buffer at pH 3. The mobile phase is phosphate buffer-acetonitrile (60 + 40) at 1 mL/min. Both chemicals can be detected with a UV spectrophotometer at 229 nm; the method is linear up to 40 mg, chloramine-T or rho-TSA/L. Mean recoveries were 96.4 +/- 6.1% for water samples fortified with 0.03 mg chloramine-T/L and 95.3 +/- 4.6% for water samples fortified with 0.005 mg rho-TSA/L. Limits of detection without sample enrichment for chloramine-T and rho-TSA are 0.01 mg/L and 0.001 mg/L, respectively.

Development of Cell Analysis Software for Cultivated Corneal Endothelial Cells.

PubMed

Okumura, Naoki; Ishida, Naoya; Kakutani, Kazuya; Hongo, Akane; Hiwa, Satoru; Hiroyasu, Tomoyuki; Koizumi, Noriko

2017-11-01

To develop analysis software for cultured human corneal endothelial cells (HCECs). Software was designed to recognize cell borders and to provide parameters such as cell density, coefficient of variation, and polygonality of cultured HCECs based on phase contrast images. Cultured HCECs with high or low cell density were incubated with Ca-free and Mg-free phosphate-buffered saline for 10 minutes to reveal the cell borders and were then analyzed with software (n = 50). Phase contrast images showed that cell borders were not distinctly outlined, but these borders became more distinctly outlined after phosphate-buffered saline treatment and were recognized by cell analysis software. The cell density value provided by software was similar to that obtained using manual cell counting by an experienced researcher. Morphometric parameters, such as the coefficient of variation and polygonality, were also produced by software, and these values were significantly correlated with cell density (Pearson correlation coefficients -0.62 and 0.63, respectively). The software described here provides morphometric information from phase contrast images, and it enables subjective and noninvasive quality assessment for tissue engineering therapy of the corneal endothelium.

Immunological relatedness among Candida albicans and other pathogenic Candida species.

PubMed Central

Hector, R F; Lyon, F L; Domer, J E

1981-01-01

Membrane-mitochondrial (butanol-hot phosphate-buffered saline) and cytosol (soluble cytoplasmic substances) extracts from seven pathogenic species of Candida were used in in vivo and in vitro immunological assays to study antigenic similarities among the strains with respect to C. albicans. Mice were sensitized with C. albicans serotype A for footpad testing or to provide cells for lymphocyte stimulation assays, and guinea pigs were immunized with whole cells or butanol-hot phosphate-buffered saline extracts of C. albicans to obtain antisera for immunodiffusion assays. When extracts from each of the seven species were used in the assays, they consistently segregated, as determined by statistical or subjective analyses, into three groups. Extracts of C. albicans serotype A or B and C. stellatoidea were the most immunologically reactive in all assays, indicating close similarities between those two species, whereas extracts of C. tropicalis and C. parapsilosis elicited only moderate responses. Extracts from C. krusei, C. guilliermondii, and C. pseudotropicalis were hypo- or nonreactive in the assays, indicating a low level of antigenic relatedness to C. albicans. Images PMID:7037643

Development of gastro intestinal sustained release tablet formulation containing acryl-EZE and pH-dependent swelling HPMC K 15 M.

PubMed

Lamoudi, Lynda; Chaumeil, Jean Claude; Daoud, Kamel

2012-05-01

The aim of this study was to evaluate physical properties and release from matrix tablets containing different ratios of HPMC 15 M and Acryl-EZE. A further aim is to assess their suitability for pH dependent controlled release. Matrix tablets containing HPMC 15 M and Acryl-EZE were manufactured using a fluidized bed. The release from this matrix using Sodium Diclofenac (SD) as model drug is studied in two dissolution media (0.1 N HCl or pH = 6.8 phosphate buffer solution); the release rate, mechanism, and pH dependence were characterized by fitting four kinetic models and by using a similarity factor analysis. The obtained results revealed that the presence of Acryl-EZE in the matrix tablets is effective in protecting the dosage forms from release in acid environments such as gastric fluid. In pH = 6.8 phosphate buffer, the drug release rate and mechanism of release from all matrices is mainly controlled by HPMC 15 M. The model of Korsmeyer-Peppas was found to fit experimental dissolution results.

Clarification of the recovery mechanism of Escherichia coli after hydrostatic pressure treatment

NASA Astrophysics Data System (ADS)

Ohshima, Shuto; Nomura, Kazuki; Iwahashi, Hitoshi

2013-06-01

High hydrostatic pressure (HP) technology has gained more attention as a non-thermal food pasteurization technology. Recently, a limitation of the HP technology was reported by Koseki and Yamamoto [Recovery of Escherichia coli ATCC 25922 in phosphate buffered saline after treatment with high hydrostatic pressure. Int. J. Food Microbiol. 2006;110:108-111], who completely recovered Escherichia coli species after HP treatment. We investigated the recovery mechanism of E. coli after HP treatment. The cells were treated with 200-300 MPa at 0-25°C for 24 h. The HP-treated E. coli was recovered in phosphate-buffered saline (PBS) during 120 h of incubation at 25°C, confirming the results reported by them. However, E. coli did not grow in PBS but grew with inactivated cells in PBS. In addition, the results of our "population size experiments" demonstrated that the recovery of E. coli cells depended on both the degree of pressure and the population size. These results suggest that some portion of cells recovered from the damage and then grew by using inactivated cells.

Corrosion behavior of pristine and added MgB2 in Phosphate Buffered Saline Solution

NASA Astrophysics Data System (ADS)

Batalu, D.; Bojin, D.; Ghiban, B.; Aldica, G.; Badica, P.

2012-09-01

We have obtained by Spark Plasma Sintering (SPS), dense samples of MgB2 added with Ho2O3. Starting composition was (MgB2)0.975(HoO1.5)0.025 and we used addition powders with an average particle size below and above 100 nm. For Mg, pristine and added MgB2 samples we measured potentiodynamic polarization curves in Phosphate Buffered Saline (PBS) solution media at room temperature. MgB2 based composites show corrosion/ degradation effects. This behavior is in principle similar to Mg based alloys in the same media. Our work suggests that the different morphologies and phase compositions of the SPS-ed samples influence the interaction with corrosion medium; hence additions can play an important role in controlling the corrosion rate. Pristine MgB2 show a significant improvement of the corrosion resistance, if compared with Mg. The best corrosion resistance is obtained for pristine MgB2, followed by MgB2 with nano-Ho2O3 and μ-Ho2O3 additions.

Assessing the utility of bipolar membranes for use in photoelectrochemical water-splitting cells.

PubMed

Vargas-Barbosa, Nella M; Geise, Geoffrey M; Hickner, Michael A; Mallouk, Thomas E

2014-11-01

Membranes are important in water-splitting solar cells because they prevent crossover of hydrogen and oxygen. Here, bipolar membranes (BPMs) were tested as separators in water electrolysis cells. Steady-state membrane and solution resistances, electrode overpotentials, and pH gradients were measured at current densities relevant to solar photoelectrolysis. Under forward bias conditions, electrodialysis of phosphate buffer ions creates a pH gradient across a BPM. Under reverse bias, the BPM can maintain a constant buffer pH on both sides of the cell, but a large membrane potential develops. Thus, the BPM does not present a viable solution for electrolysis in buffered electrolytes. However, the membrane potential is minimized when the anode and cathode compartments of the cell contain strongly basic and acidic electrolytes, respectively. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hemolytic and antimicrobial activities differ among saponin-rich extracts from guar, quillaja, yucca, and soybean.

PubMed

Hassan, Sherif M; Byrd, James A; Cartwright, Aubry L; Bailey, Chris A

2010-10-01

Hemolytic and antibacterial activities of eight serial concentrations ranged from 5-666 microg/mL of saponin-rich extracts from guar meal (GM), quillaja, yucca, and soybean were tested in 96-well plates and read by enzyme-linked immunosorbent assay plate-well as 650 nm. Hemolytic assay used a 1% suspension of chicken red blood cells with water and phosphate buffered saline as positive and negative controls, respectively. Antibacterial activity against Staphylococcus aureus, Salmonella typhimurium, and Escherichia coli were evaluated using ampicillin and bacteria without saponin-rich extract as positive and negative controls, respectively. The 100% MeOH GM and commercial quillaja saponin-rich extracts were significantly the highest in both hemolytic and antibacterial activities against all bacteria at the same concentration tested. Soybean saponin-rich extract had no antibacterial activity against any of the bacteria at the concentrations tested while yucca saponin-rich extract had no antibacterial activity against the gram-negative bacteria at the concentrations tested. GM and quillaja saponin-rich extracts were hemolytic, while yucca and soybean saponin-rich extracts were not hemolytic at the concentrations tested. No saponin-rich extract source had antibacterial activity against S. typhimurium or E. coli at the concentrations tested. Both GM and quillaja saponin-rich extracts exhibited antibacterial activity against S. aureus. Saponin-rich extracts from different plant sources have different hemolytic and antibacterial activities.

Gellan gum microspheres crosslinked with trivalent ion: effect of polymer and crosslinker concentrations on drug release and mucoadhesive properties.

PubMed

Boni, Fernanda Isadora; Prezotti, Fabíola Garavello; Cury, Beatriz Stringhetti Ferreira

2016-08-01

Gellan gum microspheres were obtained by ionotropic gelation technique, using the trivalent ion Al(3+). The percentage of entrapment efficiency ranged from 48.76 to 87.52% and 2(2) randomized full factorial design demonstrated that both the increase of polymer concentration and the decrease of crosslinker concentration presented a positive effect in the amount of encapsulated drug. Microspheres size and circularity ranged from 700.17 to 938.32 μm and from 0.641 to 0.796 μm, respectively. The increase of polymer concentration (1-2%) and crosslinker concentration (3-5%) led to the enlargement of particle size and circularity. However, the association of increased crosslinker concentration and reduced polymer content made the particles more irregular. In vitro and ex vivo tests evidenced the high mucoadhesiveness of microspheres. The high liquid uptake ability of the microspheres was demonstrated and the pH variation did not affect this parameter. Drug release was pH dependent, with low release rates in acid pH (42.40% and 44.93%) and a burst effect in phosphate buffer pH (7.4). The Weibull model had the best correlation with the drug release data, demonstrating that the release process was driven by a complex mechanism involving the erosion and swelling of the matrix or by non-Fickian diffusion.

INTERACTIONS AMONG PHOSPHATE AMENDMENTS, MICROBES AND URANIUM MOBILITY IN CONTAMINATED SEDIMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knox, A

2007-08-30

The use of sequestering agents for the transformation of radionuclides in low concentrations in contaminated soils/sediments offers considerable potential for long-term environmental cleanup. This study evaluated the influence of four phosphate amendments and two microbial amendments on U availability. The synchrotron X-ray fluorescence mapping of the untreated U-contaminated sediment showed that U was closely associated with Mn. All tested phosphate amendments reduced aqueous U concentration more than 90%, likely due to formation of insoluble phosphate precipitates. The addition of A. piechaudii and P. putida alone were found to reduce U concentrations 63% and 31% respectively. Uranium sorption in phosphate treatmentsmore » was significantly reduced in the presence of microbes. However, increased microbial activity in the treated sediment led to reduction of phosphate effectiveness. The average U concentration in 1 M MgCl{sub 2} extract from U amended sediment was 437 {micro}g/kg, but in the same sediment without microbes (autoclaved sediment), the extractable U concentration was only 103 {micro}g/kg. When the autoclaved amended sediment was treated with autoclaved biological apatite, U concentration in the 1 M MgCl{sub 2} extract was {approx}0 {micro}g/kg. Together these tests suggest that microbes may enhance U leaching and reduce phosphate amendment remedial effectiveness.« less

The effect of pH and buffer concentration on anode biofilms of Thermincola ferriacetica.

PubMed

Lusk, Bradley G; Parameswaran, Prathap; Popat, Sudeep C; Rittmann, Bruce E; Torres, Cesar I

2016-12-01

We assessed the effects of pH and buffer concentration on current production and growth of biofilms of Thermincola ferriacetica - a thermophilic, Gram-positive, anode-respiring bacterium (ARB) - grown on anodes poised at a potential of -0.06V vs. SHE in microbial electrolysis cells (MECs) at 60°C. T. ferriacetica generated current in the pH range of 5.2 to 8.3 with acetate as the electron donor and 50mM bicarbonate buffer. Maximum current density was reduced by ~80% at pH5.2 and ~14% at 7.0 compared to pH8.3. Increasing bicarbonate buffer concentrations from 10mM to 100mM resulted in an increase in the current density by 40±6%, from 6.8±1.1 to 11.2±2.7Am(-2), supporting that more buffer alleviated pH depression within T. ferriacetica biofilms. Confocal laser scanning microscopy (CLSM) images indicated that higher bicarbonate buffer concentrations resulted in larger live biofilm thicknesses: from 68±20μm at 10mM bicarbonate to >150μm at 100mM, supporting that buffer availability was a strong influence on biofilm thickness. In comparison to mesophilic Geobacter sulfurreducens biofilms, the faster transport rates at higher temperature and the ability to grow at relatively lower pH allowed T. ferriacetica to produce higher current densities with lower buffer concentrations. Published by Elsevier B.V.

A construction of novel iron-foam-based calcium phosphate/chitosan coating biodegradable scaffold material.

PubMed

Wen, Zhaohui; Zhang, Liming; Chen, Chao; Liu, Yibo; Wu, Changjun; Dai, Changsong

2013-04-01

Slow corrosion rate and poor bioactivity restrict iron-based implants in biomedical application. In this study, we design a new iron-foam-based calcium phosphate/chitosan coating biodegradable composites offering a priority mechanical and bioactive property for bone tissue engineering through electrophoretic deposition (EPD) followed by a conversion process into a phosphate buffer solution (PBS). Tensile test results showed that the mechanical property of iron foam could be regulated through altering the construction of polyurethane foam. The priority coatings were deposited from 40% nano hydroxyapatite (nHA)/ethanol suspension mixed with 60% nHA/chitosan-acetic acid aqueous solution. In vitro immersion test showed that oxidation-iron foam as the matrix decreased the amount of iron implanted and had not influence on the bioactivity of this implant, obviously. So, this method could also be a promising method for the preparation of a new calcium phosphate/chitosan coating on foam construction. Copyright © 2012. Published by Elsevier B.V.

ATP-stabilized amorphous calcium carbonate nanospheres and their application in protein adsorption.

PubMed

Qi, Chao; Zhu, Ying-Jie; Lu, Bing-Qiang; Zhao, Xin-Yu; Zhao, Jing; Chen, Feng; Wu, Jin

2014-05-28

Calcium carbonate is a common substance found in rocks worldwide, and is the main biomineral formed in shells of marine organisms and snails, pearls and eggshells. Amorphous calcium carbonate (ACC) is the least stable polymorph of calcium carbonate, which is so unstable under normal conditions that it is difficult to be prepared in vitro because it rapidly crystallizes to form one of the more stable polymorphs in aqueous solution. Herein, we report the successful synthesis of highly stable ACC nanospheres in vitro using adenosine 5'-triphosphate disodium salt (ATP) as a stabilizer. The effect of ATP on the stability of ACC nanospheres is investigated. Our experiments show that ATP plays an unique role in the stabilization of ACC nanospheres in aqueous solution. Moreover, the as-prepared ACC nanospheres are highly stable in phosphate buffered saline for a relatively long period of time (12 days) even under relatively high concentrations of calcium and phosphate ions. The cytotoxicity tests show that the as-prepared highly stable ACC nanospheres have excellent biocompatibility. The highly stable ACC nanospheres have high protein adsorption capacity, implying that they are promising for applications in biomedical fields such as drug delivery and protein adsorption. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Voltammetric Determination of the Herbicide Linuron Using a Tricresyl Phosphate-Based Carbon Paste Electrode

PubMed Central

Đorđević, Jelena; Papp, Zsigmond; Guzsvány, Valéria; Švancara, Ivan; Trtić-Petrović, Tatjana; Purenović, Milovan; Vytřas, Karel

2012-01-01

This paper summarises the results of voltammetric studies on the herbicide 3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea (Linuron), using a carbon paste electrode containing tricresyl phosphate (TCP-CPE) as liquid binder. The principal experimental conditions, such as the pH effect, investigated in Britton-Robinson buffer solutions (pH 2.0–7.0), the peak characteristics for the analyte of interest, or instrumental parameters for the differential pulse voltammetric mode were optimized for the method. As found out, the best electroanalytical performance of the TCP-CPE was achieved at pH 2.0, whereby the oxidation peak of Linuron appeared at ca. +1.3 V vs. SCE. The analytical procedure developed offers good linearity in the concentration range of 1.25–44.20 μg mL−1 (1.77 × 10−4–5.05 × 10−6 mol L−1), showing—for the first time—the applicability of the TCP-CPE for anodic oxidations in direct voltammetry (without accumulation). The method was then verified by determining Linuron in a spiked river water sample and a commercial formulation and the results obtained agreed well with those obtained by the reference HPLC/UV determination. PMID:22368461

[Simultaneous determination of scopolamine hydrobromide, atropine sulfate, ephedrine hydrochloride and pseudoephedrine hydrochloride in Zhichuanling oral liquid with HPLC].

PubMed

Zhang, Yu-Lin; Li, Yu-Ping

2013-10-01

To establish an HPLC method for determining the contents of scopolamine hydrobromide, atropine sulfate, ephedrine hydrochloride and pseudoephedrine hydrochloride in Zhichuanling oral liquid. Agela Durashell RP-C18 (4. 6 mm x250 mm, 5 microm) was adopted, with acetonitrile-sodium phosphate buffer solution (0. 07 mol L-1 sodium phosphate solution with 17.5 mmol L-1 sodium dodecylsulfate adjusted to pH 6.0 with phosphoric acid solution) (30:70) as the mobile phase. The flow rate was 0. 9 mL min -1, the detection wavelength was 207 nm, and the column temperature was 25 degree C. Scopolamine hydrobromide, atropine sulfate, ephedrine hlvdrochloride and pseudoephedrine hydrochloride showed good linear relations with peak areas within the concentration range of 0. 021 21-1. 060 5 pg (r =0. 999 3) , 0. 011 14-0. 557 microg (r = 0. 999 6) , 0. 200 56-10. 028 microg (r =0. 999 7) and 0.070 33-3. 516 5 gg (r =0. 999 6), respectively, with the average recoveries of 101.9% , 99. 80%, 100. 3%, 100. 2% (n=6). The method was so quick, simple, highly reproducible and specific that it could be used as one of quality control methods of Zhichuanling oral liquid.

Effects on transport of rapidly penetrating, competing substrates: activation and inhibition of the choline carrier in erythrocytes by imidazole.

PubMed

Devés, R; Krupka, R M

1987-01-01

The properties of the choline transport system are fundamentally altered in saline solution containing 5 mM imidazole buffer instead of 5 mM phosphate: (i) The system no longer exhibits accelerated exchange. (ii) Choline in the external compartment fails to increase the rate of inactivation of the carrier by N-ethylmaleimide. (iii) Depending on the relative concentrations of choline and imidazole, transport may be activated or inhibited. The maximum rates are increased more than fivefold by imidazole, but at moderate substrate concentrations activation is observed with low concentrations of imidazole and inhibition with high concentrations. (iv) The imidazole effect is asymmetric, there being a greater tendency to activate exit than entry. All this behavior is predicted by the carrier model if imidazole is a substrate of the choline carrier having a high maximum transport rate but a relatively low affinity, and if imidazole rapidly enters the cell by simple diffusion, so that it can add to carrier sites on both sides of the membrane. Addition at the cis side inhibits, and at the trans side activates. According to the carrier model, asymmetry is a necessary consequence of the potassium ion gradient in red cells, potassium ion being another substrate of the choline system.

Percutaneous absorption of sunscreen agents from liquid paraffin: self-association of octyl salicylate and effects on skin flux.

PubMed

Jiang, R; Roberts, M S; Prankerd, R J; Benson, H A

1997-07-01

This study provides an investigation of the availability of octyl salicylate (OS), a common sunscreen agent, from liquid paraffin and the effect of OS on skin permeability. A model membrane system to isolate the vehicle effect from membrane permeability has been developed. Partitioning of OS between liquid paraffin and aqueous receptor phases was conducted. Partition coefficients increased with increase in OS concentration. A range of OS concentrations in liquid paraffin was diffused across human epidermis and synthetic membranes into 4% bovine serum albumin in phosphate-buffered saline and 50% ethanol. Absorption profiles of OS obtained from silicone and low-density polyethylene (LDPE) membranes were similar to each other but higher than for the high-density polyethylene [HDPE (3 times)] membrane and human epidermis (15 times). The steady state fluxes and apparent permeability coefficients (Kp') obtained from the diffusion studies showed the same trends with all membranes, except for the HDPE membrane which showed greater increase in flux and Kp' at concentrations above 30%. IR spectra showed that several bands of OS were shifted with concentrations, and the molecular models further suggested that the main contribution to the self-association is from non-1,4 van der Waals interactions.

Biochemical differences in the mass and activity tests of lipoprotein-associated phospholipase A2 explain the discordance in results between the two assay methods.

PubMed

Zhuo, Shaoqiu; Wolfert, Robert L; Yuan, Chong

2017-12-01

There are two platforms for the detection of Lp-PLA 2 in sera or plasmas: by its enzymatic activity (PLAC® activity test) and by its mass concentration (PLAC® mass test). It has been long recognized that these two platforms are not correlated well. The underlying cause for this is therefore investigated by the biochemical characterization of the two PLAC tests. Human sera with and without the treatment by detergent were fractionated by using a Superose-6 column in phosphate buffered saline and the phospholipid associated Lp-PLA 2 was assessed by both PLAC mass and activity tests. The Lp-PLA 2 values of the two PLAC tests were compared under such conditions. Fractionation of sera and plasmas indicates that the association of Lp-PLA 2 with phospholipids, especially LDL and other large size phospholipid vesicles, may block the detection of the enzyme by antibodies in the immunoassay format under the conditions of the PLAC mass test. Inclusion of high concentration (>CMC, critical micelle concentration) of detergents in the assay buffer of PLAC mass test dissociates Lp-PLA 2 from phospholipid vesicles and results in the full detection of all Lp-PLA 2 in sera or plasmas for concentration. Such assay modification significantly improves the correlation between the PLAC mass and PLAC activity tests. PLAC mass test only detects a small portion of the total Lp-PLA 2 , mainly the Lp-PLA 2 associated with HDL. This is the main cause of the discordance and poor correlation between the PLAC mass and activity tests. Our results demonstrate the PLAC activity test is more accurate in assessing the total level of circulating Lp-PLA 2 . Copyright © 2017 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.

Formate binding near the redox-active tyrosineD in photosystem II: consequences on the properties of tyrD.

PubMed

Hienerwadel, Rainer; Gourion-Arsiquaud, Samuel; Ballottari, Matteo; Bassi, Roberto; Diner, Bruce A; Berthomieu, Catherine

2005-06-01

Formate and phosphate affect substantially the rate of tyrosine D (TyrD) oxidation and the stability of the radical TyrD* in Photosystem II [Hienerwadel R, Boussac A, Breton J and Berthomieu C (1996) Biochemistry 35: 15447-15460]. This observation prompted us to analyze the influence of formate and phosphate on the environment of TyrD using FTIR spectroscopy. The nu (CO) IR mode of TyrD* at 1503 cm-1 remains unchanged whatever the buffer used at pH 6 and whether formate is present or not in the sample. Similarly, the main IR mode of reduced TyrD remains at approximately 1250 cm-1 in all tested conditions. We thus conclude that formate does not modify the hydrogen-bonded interactions of TyrD and TyrD* with neighbouring D2His189 and D2Gln164. In the TyrD-state, an IR mode of formate significantly different from that observed in solution, is detected using 13C-formate, showing that formate forms a strong electrostatic interaction within PS II. The presence of formate affects also IR bands that may be assigned to an arginine side chain. Upon TyrD* formation, formate does not protonate but its binding interaction weakens. A proton uptake by Mes or phosphate buffer is detected, which is not observed when BisTris is used as a buffer. In these latter conditions, IR bands characteristic of the protonation of a carboxylate group of the protein are detected instead. The present IR data and the recent structural model of the TyrD environment proposed by Ferreira KN, Iverson TM, Maghlaoui K, Barber J and Iwata S [(2004) Science 303: 1831-1838], suggest that the proton released upon TyrD* formation is shared within a hydrogen bonding network including D2Arg294, and CP47Glu364 and that perturbation of this network by formate - possibly binding near D2Arg294 - substantially affects the properties of TyrD.

Non-linear hydroxyl radical formation rate in dispersions containing mixtures of pyrite and chalcopyrite particles

NASA Astrophysics Data System (ADS)

Kaur, Jasmeet; Schoonen, Martin A.

2017-06-01

The formation of hydroxyl radicals was studied in mixed pyrite-chalcopyrite dispersions in water using the conversion rate of adenine as a proxy for hydroxyl radical formation rate. Experiments were conducted as a function of pH, presence of phosphate buffer, surface loading, and pyrite-to-chalcopyrite ratio. The results indicate that hydroxyl radical formation rate in mixed systems is non-linear with respect to the rates in the pure endmember dispersions. The only exception is a set of experiments in which phosphate buffer is used. In the presence of phosphate buffer, the hydroxyl radical formation is suppressed in mixtures and the rate is close to that predicted based on the reaction kinetics of the pure endmembers. The non-linear hydroxyl radical formation in dispersions containing mixtures of pyrite and chalcopyrite is likely the result of two complementary processes. One is the fact that pyrite and chalcopyrite form a galvanic couple. In this arrangement, chalcopyrite oxidation is accelerated, while pyrite passes electrons withdrawn from chalcopyrite to molecular oxygen, the oxidant. The incomplete reduction of molecular oxygen leads to the formation of hydrogen peroxide and hydroxyl radical. The galvanic coupling appears to be augmented by the fact that chalcopyrite generates a significant amount of hydrogen peroxide upon dispersal in water. This hydrogen peroxide is then available for conversion to hydroxyl radical, which appears to be facilitated by pyrite as chalcopyrite itself produces only minor amounts of hydroxyl radical. In essence, pyrite is a ;co-factor; that facilitates the conversion of hydrogen peroxide to hydroxyl radical. This conversion reaction is a surface-mediated reaction. Given that hydroxyl radical is one of the most reactive species in nature, the formation of hydroxyl radicals in aqueous systems containing chalcopyrite and pyrite has implications for the stability of organic molecules, biomolecules, the viability of microbes, and exposure to dust containing the two metal sulfides may present a health burden.

Tris-sucrose buffer system: a new specially designed medium for extracellular invertase production by immobilized cells of isolated yeast Cryptococcus laurentii MT-61.

PubMed

Aydogan, Mehmet Nuri; Taskin, Mesut; Canli, Ozden; Arslan, Nazli Pinar; Ortucu, Serkan

2014-01-01

The aims of the present study were to isolate new yeasts with high extracellular (exo) invertase activity and to investigate the usability of buffer systems as invertase production media by immobilized yeast cells. Among 70 yeast isolates, Cryptococcus laurentii MT-61 had the highest exo-invertase activity. Immobilization of yeast cells was performed using sodium alginate. Higher exo-invertase activity for immobilized cells was achieved in tris-sucrose buffer system (TSBS) compared to sodium acetate buffer system and potassium phosphate buffer system. TSBS was prepared by dissolving 30 g of sucrose in 1 L of tris buffer solution. The optimum pH, temperature, and incubation time for invertase production with immobilized cells were determined as 8.0, 35 °C and 36 h in TSBS, respectively. Under optimized conditions, maximum exo-invertase activity was found to be 28.4 U/mL in sterile and nonsterile TSBS. Immobilized cells could be reused in 14 and 12 successive cycles in sterile and nonsterile TSBS without any loss in the maximum invertase activity, respectively. This is the first report which showed that immobilized microbial cells could be used as a biocatalyst for exo-invertase production in buffer system. As an additional contribution, a new yeast strain with high invertase activity was isolated.

Release of Ciprofloxacin-HCl and Dexamethasone Phosphate by Hyaluronic Acid Containing Silicone Polymers.

PubMed

Nguyen, Darrene; Hui, Alex; Weeks, Andrea; Heynen, Miriam; Joyce, Elizabeth; Sheardown, Heather; Jones, Lyndon

2012-04-19

The purpose of this study was to determine the effect of the covalent incorporation of hyaluronic acid (HA) into conventional hydrogel and hydrogels containing silicone as models for contact lens materials on the uptake and release of the fluoroquinolone antibiotic ciprofloxacin and the anti-inflammatory steroid dexamethasone phosphate. A 3 mg/mL ciprofloxacin solution (0.3% w/v) and a 1 mg/mL dexamethasone phosphate solution (0.1%) was prepared in borate buffered saline. Three hydrogel material samples (pHEMA; pHEMA TRIS; DMAA TRIS) were prepared with and without the covalent incorporation of HA of molecular weight (MW) 35 or 132 kDa. Hydrogel discs were punched from a sheet of material with a uniform diameter of 5 mm. Uptake kinetics were evaluated at room temperature by soaking the discs for 24 h. Release kinetics were evaluated by placing the drug-loaded discs in saline at 34 °C in a shaking water bath. At various time points over 6-7 days, aliquots of the release medium were assayed for drug amounts. The majority of the materials tested released sufficient drug to be clinically relevant in an ophthalmic application, reaching desired concentrations for antibiotic or anti-inflammatory activity in solution. Overall, the silicone-based hydrogels (pHEMA TRIS and DMAA TRIS), released lower amounts of drug than the conventional pHEMA material (p < 0.001). Materials with HA MW132 released more ciprofloxacin compared to materials with HA MW35 and lenses without HA (p < 0.02). Some HA-based materials were still releasing the drug after 6 days.

Microbial Characterization of Internal Active Thermal Control System (IATCS) Hardware Surfaces after Five Years of Operation in the International Space Station

NASA Technical Reports Server (NTRS)

Roman, Monsi C.; Weir, Natalee E.; Wilson, Mark E.; Pyle, Barry H.

2006-01-01

A flex hose assembly containing aqueous coolant from the International Space Station (ISS) Internal Active Thermal Control System (IATCS) consisting of a 2 foot section of Teflon hose and quick disconnects (QDs) and a Special Performance Checkout Unit (SPCU) heat exchanger containing separate channels of IATCS coolant and iodinated water used to cool spacesuits and Extravehicular Mobility Units (EMUS) were returned for destructive analyses on Shuttle return to flight mission STS-114. The original aqueous IATCS coolant used in Node 1, the Laboratory Module, and the Airlock consisted of water, borate (pH buffer), phosphate (corrosion control), and silver sulfate (microbiological control) at a pH of 9.5 +/- 0.5. Chemical changes occurred after on-orbit implementation including a decrease to pH 8.4 due to the diffusion of carbon dioxide through the Teflon hoses, an increase in nickel ions due to general corrosion of heat exchanger braze coatings, a decrease in phosphate concentration due to precipitation of nickel phosphate, and the rapid disappearance of silver ions due to deposition on hardware surfaces. Also associated with the coolant chemistry changes was an increase in planktonic microorganisms from less than 100 colony forming units (CFU) per 100 ml to approximately 1 million CFU per 100 ml. Attachment and growth of microorganisms to the system surfaces (biofilm) was suspected due to the levels of planktonic microorganisms in the coolant. Biofilms can reduce coolant flow, reduce heat transfer, amplify degradation of system materials initiated by chemical corrosion, and enhance mineral scale formation.

Innovative self-powered submersible microbial electrolysis cell (SMEC) for biohydrogen production from anaerobic reactors.

PubMed

Zhang, Yifeng; Angelidaki, Irini

2012-05-15

A self-powered submersible microbial electrolysis cell (SMEC), in which a specially designed anode chamber and external electricity supply were not needed, was developed for in situ biohydrogen production from anaerobic reactors. In batch experiments, the hydrogen production rate reached 17.8 mL/L/d at the initial acetate concentration of 410 mg/L (5 mM), while the cathodic hydrogen recovery ( [Formula: see text] ) and overall systemic coulombic efficiency (CE(os)) were 93% and 28%, respectively, and the systemic hydrogen yield ( [Formula: see text] ) peaked at 1.27 mol-H(2)/mol-acetate. The hydrogen production increased along with acetate and buffer concentration. The highest hydrogen production rate of 32.2 mL/L/d and [Formula: see text] of 1.43 mol-H(2)/mol-acetate were achieved at 1640 mg/L (20 mM) acetate and 100 mM phosphate buffer. Further evaluation of the reactor under single electricity-generating or hydrogen-producing mode indicated that further improvement of voltage output and reduction of electron losses were essential for efficient hydrogen generation. In addition, alternate exchanging the electricity-assisting and hydrogen-producing function between the two cell units of the SMEC was found to be an effective approach to inhibit methanogens. Furthermore, 16S rRNA genes analysis showed that this special operation strategy resulted same microbial community structures in the anodic biofilms of the two cell units. The simple, compact and in situ applicable SMEC offers new opportunities for reactor design for a microbial electricity-assisted biohydrogen production system. Copyright © 2012 Elsevier Ltd. All rights reserved.

Role of saliva in the caries experience and calculus formation of young patients undergoing hemodialysis.

PubMed

Andrade, Marcia Rejane Thomas Canabarro; Salazar, Sabrina Loren Almeida; de Sá, Leandro Figueira Reis; Portela, Maristela; Ferreira-Pereira, Antonio; Soares, Rosangela Maria Araújo; Leão, Anna Thereza Thomé; Primo, Laura Guimarães

2015-11-01

The aims of this study were to investigate the caries experience, periodontal status, oral hygiene habits, and salivary parameters of children and adolescents undergoing hemodialysis (HD) and to compare them with their healthy counterparts. Fifty-two HD patients were matched for age, sex, ethnicity, and social class with 52 healthy subjects for analysis of the number of decayed, missing and filled teeth, plaque and gingival index, dental calculus accumulation, measurements of pocket depth, clinical attachment level, gingival recession, and bleeding on probing. Stimulated saliva samples were collected to assess salivary flow rate, pH and buffer capacity, and salivary concentrations of calcium, phosphate, and urea by colorimetric method. HD patients had lower dental caries (p = 0.004), greater plaque and calculus accumulation (p = 0.001), and reported flossing less often than the controls (p = 0.013). Regarding salivary analysis, HD patients showed significantly higher values of pH, buffer capacity, and salivary urea concentration when compared to the controls (p = 0.001). HD patients had lower caries experience, higher accumulation of dental plaque, and calculus deposition than their healthy counterparts, probably due to the differences found in their salivary biochemical parameters. A significant number of children and adolescents undergoing hemodialysis are candidates for kidney transplantation and should receive complete pre-transplant dental exams and dental treatment. Our results open the way for the development of an individualized dental protocol for these patients with preventive measures and treatment of the poor oral health in HD patients.

Characterization of complexes between phenethylamine enantiomers and β-cyclodextrin derivatives by capillary electrophoresis-Determination of binding constants and complex mobilities.

PubMed

Wahl, Joachim; Furuishi, Takayuki; Yonemochi, Etsuo; Meinel, Lorenz; Holzgrabe, Ulrike

2017-04-01

To optimize chiral separation conditions and to improve the knowledge of enantioseparation, it is important to know the binding constants K between analytes and cyclodextrins and the electrophoretic mobilities of the temporarily formed analyte-cyclodextrin-complexes. K values for complexes between eight phenethylamine enantiomers, namely ephedrine, pseudoephedrine, methylephedrine and norephedrine, and four different β-cyclodextrin derivatives were determined by affinity capillary electrophoresis. The binding constants were calculated from the electrophoretic mobility values of the phenethylamine enantiomers at increasing concentrations of cyclodextrins in running buffer. Three different linear plotting methods (x-reciprocal, y-reciprocal, double reciprocal) and nonlinear regression were used for the determination of binding constants with β-cyclodextrin, (2-hydroxypropyl)-β-cyclodextrin, methyl-β-cyclodextrin and 6-O-α-maltosyl-β-cyclodextrin. The cyclodextrin concentration in a 50 mM phosphate buffer pH 3.0 was varied from 0 to 12 mM. To investigate the influence of the binding constant values on the enantioseparation the observed electrophoretic selectivities were compared with the obtained K values and the calculated enantiomer-cyclodextrin-complex mobilities. The different electrophoretic mobilities of the temporarily formed complexes were crucial factors for the migration order and enantioseparation of ephedrine derivatives. To verify the apparent binding constants determined by capillary electrophoresis, a titration process using ephedrine enantiomers and β-cyclodextrin was carried out. Furthermore, the isothermal titration calorimetry measurements gave information about the thermal properties of the complexes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrophoretic analysis of the major polypeptides of human erythrocyte membranes prepared by low and high osmolarity haemolysis.

PubMed

Zail, S S; Hoek, V D

1975-04-16

Human erythrocyte membranes were prepared in three ways: washing in hypotonic Tris buffer, pH 7.6, by lysis in isotonic Tris buffer pH 7.6 after incubation at 37 degrees C for 2 hours and by ultrasonication in an isotonic medium, pH 7.6. Analysis of the major polypeptides of the erythrocyte membranes by sodium dodecylsulphate polyacrylamide gel electrophoresis revealed a selective depletion of a major polypeptide representing glyceraldehyde-3-phosphate dehydrogenase in the membranes prepared by high osmolarity lysis. The pattern of seperation of the remaining polypeptides was identical in the 3 different membrane preparations.

Elution kinetics, antimicrobial activity, and mechanical properties of 11 different antibiotic loaded acrylic bone cement.

PubMed

Gálvez-López, Ruben; Peña-Monje, Alejandro; Antelo-Lorenzo, Ramón; Guardia-Olmedo, Juan; Moliz, Juan; Hernández-Quero, José; Parra-Ruiz, Jorge

2014-01-01

Antibiotic-loaded acrylic bone cements (ALABC) spacers are routinely used in the treatment of prosthetic joint infections. The objectives of our study were to evaluate different ALABC for elution kinetics, thermal stability, and mechanical properties. A 10 or 20% mixture (w/w) beads of medium viscosity bone cement (DePuy, Inc) and vancomycin (VAN), gentamycin (GM), daptomycin (DAP), moxifloxacin (MOX), rifampicin (RIF), cefotaxime (CTX), cefepime (FEP), amoxicillin clavulanate (AmC), ampicillin (AMP), meropenem (MER), and ertapenem (ERT) were formed and placed into wells filled with phosphate-buffered saline. Antibiotic concentrations were determined using high-performance liquid chromatography. Antimicrobial activity was tested against Micrococcus luteus ATCC 9341 or Escherichia coli ATCC 25922. AmC, AMP, and FEP concentration rapidly decreased after day 2, being almost undetectable at day 4. Sustained and high elution rates were observed with VAN, GM, MOX, and RIF for the 30-day duration of the experiment. DAP, MER, ERT, and CTX elution rates constantly decreased from day 4. All antibiotics tested retained antimicrobial activity proving thermal stability. Mechanical properties of ALABC were maintained except when RIF was used. © 2013.

Effect of inflammatory challenge on hypothalamic neurons expressing orexinergic and melanin-concentrating hormone.

PubMed

Palomba, Maria; Seke Etet, Paul Faustin; Veronesi, Carlo

2014-06-06

Neurons containing the hypothalamic peptides orexin-A (hypocretin 1) and melanin-concentrating hormone (MCH) have been reported numerous roles in the regulation of the sleep-wake cycle, energy balance and feeding behavior. We investigated the response of these cells to repeated administration of low doses of endotoxin lipopolysaccharide (LPS) in mice. Adult male C57/6J mice where intraperitoneally (i.p.) injected with either LPS or phosphate-buffered saline (PBS) weekly for either 4 or 8 weeks, and afterwards were sacrificed at different time intervals from last injection. A significant drop in orexin-containing neuron number, but not in numbers of MCH or neuronal nuclear antigen (NeuN)-immunoreactive neurons, was observed after 8 weeks of LPS treatment, as compared to PBS treatment. Orexin expression entirely returned to control levels 30 days after the last LPS injection in mice treated for 8 weeks. These data strongly suggest the occurrence of selective alterations of orexinergic system, reversible over time, following repeated and intermittent systemic inflammatory challenge in mice. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Photodegradation of Dicloran in Freshwater and Seawater.

PubMed

Vebrosky, Emily N; Saranjampour, Parichehr; Crosby, Donald G; Armbrust, Kevin L

2018-03-21

Dicloran appears to be a model pesticide for investigating photodegradation processes in surface waters. Photodegradation processes are particularly relevant to this compound as it is applied to crops grown in proximity to freshwater and marine ecosystems. The photodegradation of dicloran under simulated sunlight was measured in distilled water, artificial seawater, phosphate buffer, and filter-sterilized estuarine water to determine its half-life, degradation rate, and photodegradation products. The half-life was approximately 7.5 h in all media. There was no significant difference in the rate of degradation between distilled water and artificial seawater for dicloran. For the intermediate products, a higher concentration of 2-chloro-1,4-benzoquinone was measured in artificial seawater versus distilled water, while a slightly higher concentration of 1,4-benzoquinone was measured in distilled water versus artificial seawater. The detection of chloride and nitrate ions after 2 h of light exposure suggests photonucleophilic substitution contributes to the degradation process. Differences in product distributions between water types suggest that salinity impacts on chemical degradation may need to be addressed in chemical exposure assessments.

Palladium nanoparticles deposited on graphene and its electrochemical performance for glucose sensing

NASA Astrophysics Data System (ADS)

Mijowska, Ewa; Onyszko, Magdalena; Urbas, Karolina; Aleksandrzak, Malgorzata; Shi, Xiaoze; Moszyński, Dariusz; Penkala, Krzysztof; Podolski, Jacek; El Fray, Mirosława

2015-11-01

This paper reports on the fabrication and characterization of glucose oxidase (GOx) immobilized onto a glassy carbon electrode (GCE) modified with reduced graphene oxide/palladium nanocomposite (RGO-Pd). Characterization tools showed well dispersed uniform Pd nanoparticles on a partly reduced graphene oxide surface. Cyclic voltammetry demonstrated successful immobilization of GOx on RGO-Pd modified GCE (GCE-RGO-Pd) using covalent bonding of GOx with RGO-Pd (RGO-Pd-GOx). Therefore, it was used as an electrochemical biosensor of glucose. RGO-Pd-GOx exhibited good electrocatalysis toward glucose in different glucose concentrations (from 2 to 10 mM, which includes the blood glucose levels of both normal and diabetic persons) with O2 saturated phosphate buffer solution (PBS) at pH 7.4. The system showed a linear increase in current at potential -0.085 V in the concentration range examined, with a correlation coefficient of 0.996. The sensitivity of the biosensor was 41.3 μA cm-2 mM-1, suggesting that RGO-Pd-GOx-modified GCE could be a potential candidate as a glucose sensor.

Electrochemical biosensor based on glucose oxidase encapsulated within enzymatically synthesized poly(1,10-phenanthroline-5,6-dione).

PubMed

Ciftci, Hakan; Oztekin, Yasemin; Tamer, Ugur; Ramanaviciene, Almira; Ramanavicius, Arunas

2014-11-01

This study is focused on the investigation of electrocatalytic effect of glucose oxidase (GOx) immobilized on the graphite rod (GR) electrode. The enzyme modified electrode was prepared by encapsulation of immobilized GOx within enzymatically formed poly(1,10-phenanthroline-5,6-dione) (pPD) film. The electrochemical responses of such enzymatic electrode (pPD/GOx/GR) vs. different glucose concentrations were examined chronoamperometrically in acetate-phosphate buffer solution (A-PBS), pH 6.0, under aerobic or anaerobic conditions. Amperometric signals of the pPD/GOx/GR electrode exhibited well-defined hyperbolic dependence upon glucose concentration. Amperometric signals at 100mM of glucose were 41.17 and 32.27 μA under aerobic and anaerobic conditions, respectively. Amperometric signals of the pPD/GOx/GR electrode decreased by 6% within seven days. The pPD/GOx/GR electrode showed excellent selectivity in the presence of dopamine and uric acid. Furthermore it had a good reproducibility and repeatability with standard deviation of 9.4% and 8.0%, respectively. Copyright © 2014 Elsevier B.V. All rights reserved.

Novel RuCoSe as non-platinum catalysts for oxygen reduction reaction in microbial fuel cells

NASA Astrophysics Data System (ADS)

Rozenfeld, Shmuel; Schechter, Michal; Teller, Hanan; Cahan, Rivka; Schechter, Alex

2017-09-01

Microbial electrochemical cells (MECs) are explored for the conversion of acetate directly to electrical energy. This device utilizes a Geobacter sulfurreducens anode and a novel RuCoSe air cathode. RuCoSe synthesized in selected compositions by a borohydride reduction method produces amorphous structures of powdered agglomerates. Oxygen reduction reaction (ORR) was measured in a phosphate buffer solution pH 7 using a rotating disc electrode (RDE), from which the kinetic current (ik) was measured as a function of potential and composition. The results show that ik of RuxCoySe catalysts increases in the range of XRu = 0.25 > x > 0.7 and y < 0.15 for all tested potentials. A poisoning study of RuCoSe and Pt catalysts in a high concentration acetate solution shows improved tolerance of RuCoSe to this fuel at acetate concentration ≥500 mM. MEC discharge plots under physiological conditions show that ∼ RuCo2Se (sample S3) has a peak power density of 750 mW cm-2 which is comparable with Pt 900 mW cm-2.

Integrated polymer-based Mach-Zehnder interferometer label-free streptavidin biosensor compatible with injection molding.

PubMed

Bruck, R; Melnik, E; Muellner, P; Hainberger, R; Lämmerhofer, M

2011-05-15

We report the development of a Mach-Zehnder interferometer biosensor based on a high index contrast polymer material system and the demonstration of label-free online measurement of biotin-streptavidin binding on the sensor surface. The surface of the polyimide waveguide core layer was functionalized with 3-mercaptopropyl trimethoxy silane and malemide tagged biotin. Several concentrations of Chromeon 642-streptavidin dissolved in phosphate buffered saline solution were rinsed over the functionalized sensor surface by means of a fluidic system and the biotin-streptavidin binding process was observed in the output signal of the interferometer at a wavelength of 1310 nm. Despite the large wavelength and the comparatively low surface sensitivity of the sensor system due to the low index contrast in polymer material systems compared to inorganic material systems, we were able to resolve streptavidin concentrations of down to 0.1 μg/ml. The polymer-based optical sensor design is fully compatible with cost-efficient mass production technologies such as injection molding and spin coating, which makes it an attractive alternative to inorganic optical sensors. Copyright © 2011 Elsevier B.V. All rights reserved.

Gelatin and galactomannan-based scaffolds: Characterization and potential for tissue engineering applications.

PubMed

Siqueira, Nataly M; Paiva, Bruno; Camassola, Melissa; Rosenthal-Kim, Emily Q; Garcia, Ketlin C; dos Santos, Francisco P; Soares, Rosane M D

2015-11-20

In this work, we produced gelatin films containing different concentrations of galactomannan by casting solutions. The films were crosslinked by immersion in 30mM solution of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC). The crosslinking of gelatin-containing films was confirmed by the reduction of free amine band intensity (3400-3200cm(-1)) in the GEL IR, as well as by the evaluation of its behavior when immersed in phosphate-buffer solution. The crosslinking of galactomannan film was confirmed by the formation of new ether bonds, as observed by increasing intensity of the band at 1148cm(-1), and the reduction of OH band intensity (3600-3200cm(-1)). The presence of galactomannan and the crosslinking mediated by EDC were responsible to improve elasticity in the gelatin-based films. The samples did not show cytotoxicity during 24h or 48h. In addition, rat mesenchymal stem cells adhered to the films regardless of galactomannan concentration. The results indicated that the gelatin/galactomannan films are potential biomaterials for use as scaffolds for tissue engineering. Copyright © 2015 Elsevier Ltd. All rights reserved.

Electrochemical Detection of Anti-Breast-Cancer Agents in Human Serum by Cytochrome P450-Coated Carbon Nanotubes

PubMed Central

Baj-Rossi, Camilla; De Micheli, Giovanni; Carrara, Sandro

2012-01-01

We report on the electrochemical detection of anti-cancer drugs in human serum with sensitivity values in the range of 8–925 nA/μM. Multi-walled carbon nanotubes were functionalized with three different cytochrome P450 isoforms (CYP1A2, CYP2B6, and CYP3A4). A model used to effectively describe the cytochrome P450 deposition onto carbon nanotubes was confirmed by Monte Carlo simulations. Voltammetric measurements were performed in phosphate buffer saline (PBS) as well as in human serum, giving well-defined current responses upon addition of increasing concentrations of anti-cancer drugs. The results assert the capability to measure concentration of drugs in the pharmacological ranges in human serum. Another important result is the possibility to detect pairs of drugs present in the same sample, which is highly required in case of therapies with high side-effects risk and in anti-cancer pharmacological treatments based on mixtures of different drugs. Our technology holds potentials for inexpensive multi-panel drug-monitoring in personalized therapy. PMID:22778656

Screening of extraction methods for glycoproteins from jellyfish ( Rhopilema esculentum) oral-arms by high performance liquid chromatography

NASA Astrophysics Data System (ADS)

Ren, Guoyan; Li, Bafang; Zhao, Xue; Zhuang, Yongliang; Yan, Mingyan; Hou, Hu; Zhang, Xiukun; Chen, Li

2009-03-01

In order to select an optimum extraction method for the target glycoprotein (TGP) from jellyfish ( Rhopilema esculentum) oral-arms, a high performance liquid chromatography (HPLC)-assay for the determination of the TGP was developed. Purified target glycoprotein was taken as a standard glycoprotein. The results showed that the calibration curves for peak area plotted against concentration for TGP were linear ( r = 0.9984, y = 4.5895 x+47.601) over concentrations ranging from 50 to 400 mgL-1. The mean extraction recovery was 97.84% (CV2.60%). The fractions containing TGP were isolated from jellyfish ( R. esculentum) oral-arms by four extraction methods: 1) water extraction (WE), 2) phosphate buffer solution (PBS) extraction (PE), 3) ultrasound-assisted water extraction (UA-WE), 4) ultrasound-assisted PBS extraction (UA-PE). The lyophilized extract was dissolved in Milli-Q water and analyzed directly on a short TSK-GEL G4000PWXL (7.8 mm×300 mm) column. Our results indicated that the UA-PE method was the optimum extraction method selected by HPLC.