Thermochemical parameters of minerals from oxygen-buffered hydrothermal equilibrium data: Method, application to annite and almandine

USGS Publications Warehouse

Zen, E.-A.

1973-01-01

Reversed univariant hydrothermal phase-equilibrium reactions, in which a redox reaction occurs and is controlled by oxygen buffers, can be used to extract thermochemical data on minerals. The dominant gaseous species present, even for relatively oxidizing buffers such as the QFM buffer, are H2O and H2; the main problem is to calculate the chemical potentials of these components in a binary mixture. The mixing of these two species in the gas phase was assumed by Eugster and Wones (1962) to be ideal; this assumption allows calculation of the chemical potentials of the two components in a binary gas mixture, using data in the literature. A simple-mixture model of nonideal mixing, such as that proposed by Shaw (1967), can also be combined with the equations of state for oxygen buffers to permit derivation of the chemical potentials of the two components. The two mixing models yield closely comparable results for the more oxidizing buffers such as the QFM buffer. For reducing buffers such as IQF, the nonideal-mixing correction can be significant and the Shaw model is better. The procedure of calculation of mineralogical thermochemical data, in reactions where hydrogen and H2O simultaneously appear, is applied to the experimental data on annite, given by Wones et al. (1971), and on almandine, given by Hsu (1968). For annite the results are: Standard entropy of formation from the elements, Sf0 (298, 1)=-283.35??2.2 gb/gf, S0 (298, 1) =+92.5 gb/gf. Gf0 (298, 1)=-1148.2??6 kcal, and Hf0 (298, 1)=-1232.7??7 kcal. For almandine, the calculation takes into account the mutual solution of FeAl2O4 (Hc) in magnetite and of Fe3O4 (Mt) in hercynite and the temperature dependence of this solid solution, as given by Turnock and Eugster (1962); the calculations assume a regular-solution model for this binary spinel system. The standard entropy of formation of almandine, Sf,A0 (298, 1) is -272.33??3 gb/gf. The third law entropy, S0 (298, 1) is +68.3??3 gb/gf, a value much less than the oxide-sum estimate but the deviation is nearly the same as that of grossularite, referring to a comparable set of oxide standard states. The Gibbs free energy Gf,A0 (298, 1) is -1192.36??4 kcal, and the enthalpy Hf,A0 (298, 1) is -1273.56??5 kcal. ?? 1973 Springer-Verlag.

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

Prefibrillar Formation Conditions of β-Lactoglobulin by Titration and Chaotropes Urea and KSCN Under Thermal Load

NASA Astrophysics Data System (ADS)

Babcock, Jeremiah; Valdez, Rolando; Brancaleon, Lorenzo

2009-10-01

The harmful growth of toxic oligomers in the formation of protein amyloid fibrils have been connected to degenerative diseases like Alzheimer's and Huntington's diseases. Understanding the fundamental mechanisms behind protein unfolding and subsequent fibrillogenesis may provide a way to stop the process from occurring. The purpose of this study was to identify favorable fibril growth conditions for a globular model protein β-lactoglobulin using the chaotropes urea and KSCN, along with titration of a pH 7.04 phosphate buffer solution at 40 ^oC over five days. Time-resolved and steady-state fluorescence was used to examine the shift in emission of the tryptophan amino acids over the applied denaturation ranges. BLG, a dimer in native form, monomerized and partially unfolded at 5 M Urea, 2 M KSCN and at pH 2 in phosphate buffer in vitro. Exposure of the solutions to continuous heat over time caused a increase in the lifetimes and red shift in the emission spectra, indicating the possible beginning of nucleation. The study has provided a base for continuation of the study of oligomerization and subsequent fibrillation of BLG, which may provide a fundamental mechanism of formation transferable to other proteins in vivo.

Morphological examination of the effects of defibrotide on experimentally induced bladder injury and its relation to interstitial cystitis.

PubMed

Aydin, H; Ercan, F; Cetinel, S; San, T

2001-08-01

This morphological study aims to investigate the effects of defibrotide, a deoxyribonucleic acid derivative drug with cytoprotective, immunosuppressive and vasorelaxant effects, on protamine sulfate induced bladder injury. Wistar albino female rats were catheterized and intravesically infused with phosphate buffered solution (control group) or, either protamine sulfate (bladder injury group) or protamine sulfate+defibrotide (bladder injury+defibrotide group) dissolved in phosphate buffered solution. The morphology of the urinary bladder was investigated using light and electron microscopy. The number of mast cells in the mucosa, mucosal alterations, intercellular junctions, surface topography and the glycosaminoglycan (GAG) layer as well as microvillus formation on the luminal surface were evaluated. In the bladder injury group, ulcerated areas, irregularity of the GAG layer, increased number of mast cells, vacuole formation, dilated perinuclear cistern, formation of pleomorphic and uniform microvilli and dilatations in the intercellular spaces in the urothelium were observed. In the bladder injury+defibrotide group a relatively normal urothelial topography, GAG layer and a few mast cells in the mucosa, some dilatations between the intercellular areas, less uniform microvilli, regular perinuclear cistern and tight junctions were observed. These results show that defibrotide can inhibit PS induced bladder damage.

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.

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.

Common stock solutions, buffers, and media.

PubMed

2001-05-01

This collection of recipes describes the preparation of buffers and reagents used in Current Protocols in Pharmacology for cell culture, manipulation of neural tissue, molecular biological methods, and neurophysiological/neurochemical measurements. RECIPES: Acid, concentrated stock solutions Ammonium hydroxide, concentrated stock solution EDTA (ethylenediaminetetraacetic acid), 0.5 M (pH 8.0) Ethidium bromide staining solution Fetal bovine serum (FBS) Gel loading buffer, 6× LB medium (Luria broth) and LB plates Potassium phosphate buffer, 0.1 M Sodium phosphate buffer, 0.1 M TE (Tris/EDTA) buffer Tris⋅Cl, 1 M.

Aggregation and Particle Formation of Therapeutic Proteins in Contact With a Novel Fluoropolymer Surface Versus Siliconized Surfaces: Effects of Agitation in Vials and in Prefilled Syringes.

PubMed

Teska, Brandon M; Brake, Jeffrey M; Tronto, Gregory S; Carpenter, John F

2016-07-01

We examined the effects of an accelerated agitation protocol on 2 protein therapeutics, intravenous immunoglobulin (IVIG) and Avastin (bevacizumab), in contact with a novel fluoropolymer surface and more typical siliconized surfaces. The fluoropolymer surface provides "solid-phase" lubrication for the syringe plunger-obviating the need for silicone oil lubrication in prefilled syringes. We tested the 2 surfaces in a vial system and in prefilled glass syringes. We also examined the effects of 2 buffers, phosphate-buffered saline (PBS) and 0.2-M glycine, with and without the addition of polysorbate 20, on agitation-induced aggregation of IVIG. Aggregation was monitored by measuring subvisible particle formation and soluble protein loss. In both vials and syringes, protein particle formation was much lower during agitation with the fluoropolymer surface than with the siliconized surface. Also, particle formation was greater in PBS than in glycine buffer, an effect attributed to lower colloidal stability of IVIG in PBS. Polysorbate 20 in the formulation greatly inhibited protein particle formation. Overall, the fluoropolymer plunger surface in an unsiliconized glass barrel was demonstrated to be a viable solution for eliminating silicone oil droplets from prefilled syringe formulations and providing a consistent system for rationale formulation development and simplified particle analysis. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Influence of cell culture medium composition on in vitro dissolution behavior of a fluoride-containing bioactive glass.

PubMed

Shah, Furqan A; Brauer, Delia S; Wilson, Rory M; Hill, Robert G; Hing, Karin A

2014-03-01

Bioactive glasses are used clinically for bone regeneration, and their bioactivity and cell compatibility are often characterized in vitro, using physiologically relevant test solutions. The aim of this study was to show the influence of varying medium characteristics (pH, composition, presence of proteins) on glass dissolution and apatite formation. The dissolution behavior of a fluoride-containing bioactive glass (BG) was investigated over a period of one week in Eagle's Minimal Essential Medium with Earle's Salts (MEM), supplemented with either, (a) acetate buffer, (b) 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer, (c) HEPES + carbonate, or (d) HEPES + carbonate + fetal bovine serum. Results show pronounced differences in pH, ion release, and apatite formation over 1 week: Despite its acidic pH (pH 5.8 after BG immersion, as compared to pH 7.4-8.3 for HEPES-containing media), apatite formation was fastest in acetate buffered (HEPES-free) MEM. Presence of carbonate resulted in formation of calcite (calcium carbonate). Presence of serum proteins, on the other hand, delayed apatite formation significantly. These results confirm that the composition and properties of a tissue culture medium are important factors during in vitro experiments and need to be taken into consideration when interpreting results from dissolution or cell culture studies. Copyright © 2013 Wiley Periodicals, Inc.

Analysis of the difference in color development in the dye-binding method due to the kind of buffer solution.

PubMed

Suzuki, Yuji

2006-06-01

In a dye-binding method using a pH indicator, color development has reportedly been affected by the kind of buffer solution used in the color reagent. This phenomenon was analyzed by using a calculation based on the assumption that the anion of the buffer solution also reacts with protein. Color development decreases with increases in the anion concentration of the buffer solution and in the equilibrium constant of the reaction between the anion and protein. The differences in color development due to the kind of buffer solution can be attributed to differences in the equilibrium constant of the reaction forming the anion-protein complex and to the concentration of the anion between the buffer solutions.

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

[Photometric determination of butyl "aeroflot" flotation agent (sodium dibutyl dithiophosphate) in the air of work zone and skin washings].

PubMed

Dorogova, V B; Kucheriavykh, E I; Sokolova, T V

1989-01-01

Photometric procedure of butyl "aeroflot" identification in the work zone air and in wash-out from workers' integument was developed, The procedure was based on the formation of yellow- and orange-dyed copper dibutyl dithiophosphate under butyl "aeroflot" interaction with copper sulphate with the subsequent photometry of dyed solutions for the wavelength of 420 nm in the 10-mm cell. Buffer solution with pH-9.2 was used as an absorbing solution for the workplace air sampling and integument wash-out.

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.

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.

Crystallization efficiencies of inorganic polyphosphate oligomers reacted with magnesium and calcium cations using anion-exchange chromatography with particulate formation-laser scattering detector.

PubMed

Ando, Masaki; Imadzu, Sakiyo; Kitagawa, Shinya; Ohtani, Hajime

2010-08-06

A particulate formation-laser scattering detector (PFLSD) was developed and used for evaluating the crystallization efficiency of inorganic polyphosphates (PPs) that reacted with either magnesium or calcium cations. As the solutions for reactive crystallization, 0.5 M ammonium buffer (pH 9.6) containing either 0.15 M MgCl(2) or 0.15 M CaCl(2) (MAP: magnesium ammonium phosphate and HAP: hydroxyapatite solution) were used. In the case of mono- and diphosphate (P1 and P2), the significant dependences of the particulate formation efficiency on various types of both P1/P2 and MAP/HAP reaction solutions were observed with the direct sample injection mode. The PFLSD was hyphenated with the anion-exchange chromatography and the dependence of the particulate formation efficiency on the polymerization degree (n(p)) of PP oligomers, separated chromatographically, was evaluated sequentially. The significant suppression of the particulate formation for PP oligomers was clearly confirmed, i.e., the MAP and HAP reaction solutions did not produce the particulates of the PP oligomers having an n(p) value of more than 3 and 5, respectively. As the overall tendency, the particulate formation efficiency in the case of the HAP solution was superior to that in the case of the MAP solution. Copyright 2010 Elsevier B.V. All rights reserved.

Finding the lost open-circuit voltage in polymer solar cells by UV-ozone treatment of the nickel acetate anode buffer layer.

PubMed

Wang, Fuzhi; Sun, Gang; Li, Cong; Liu, Jiyan; Hu, Siqian; Zheng, Hua; Tan, Zhan'ao; Li, Yongfang

2014-06-25

Efficient polymer solar cells (PSCs) with enhanced open-circuit voltage (Voc) are fabricated by introducing solution-processed and UV-ozone (UVO)-treated nickel acetate (O-NiAc) as an anode buffer layer. According to X-ray photoelectron spectroscopy data, NiAc partially decomposed to NiOOH during the UVO treatment. NiOOH is a dipole species, which leads to an increase in the work function (as confirmed by ultraviolet photoemission spectroscopy), thus benefitting the formation of ohmic contact between the anode and photoactive layer and leading to increased Voc. In addition, the UVO treatment improves the wettability between the substrate and solvent of the active layer, which facilitates the formation of an upper photoactive layer with better morphology. Further, the O-NiAc layer can decrease the series resistance (Rs) and increase the parallel resistance (Rp) of the devices, inducing enhanced Voc in comparison with the as-prepared NiAc-buffered control devices without UVO treatment. For PSCs based on the P3HT:PCBM system, Voc increases from 0.50 to 0.60 V after the NiAc buffer layer undergoes UVO treatment. Similarly, in the P3HT:ICBA system, the Voc value of the device with a UVO-treated NiAc buffer layer increases from 0.78 to 0.88 V, showing an enhanced power conversion efficiency of 6.64%.

Bioactivity of Sodium Free Fluoride Containing Glasses and Glass-Ceramics

PubMed Central

Chen, Xiaojing; Chen, Xiaohui; Brauer, Delia S.; Wilson, Rory M.; Hill, Robert G.; Karpukhina, Natalia

2014-01-01

The bioactivity of a series of fluoride-containing sodium-free calcium and strontium phosphosilicate glasses has been tested in vitro. Glasses with high fluoride content were partially crystallised to apatite and other fluoride-containing phases. The bioactivity study was carried out in Tris and SBF buffers, and apatite formation was monitored by XRD, FTIR and solid state NMR. Ion release in solutions has been measured using ICP-OES and fluoride-ion selective electrode. The results show that glasses with low amounts of fluoride that were initially amorphous degraded rapidly in Tris buffer and formed apatite as early as 3 h after immersion. The apatite was identified as fluorapatite by 19F MAS-NMR after 6 h of immersion. Glass degradation and apatite formation was significantly slower in SBF solution compared to Tris. On immersion of the partially crystallised glasses, the fraction of apatite increased at 3 h compared to the amount of apatite prior to the treatment. Thus, partial crystallisation of the glasses has not affected bioactivity significantly. Fast dissolution of the amorphous phase was also indicated. There was no difference in kinetics between Tris and SBF studies when the glass was partially crystallised to apatite before immersion. Two different mechanisms of apatite formation for amorphous or partially crystallised glasses are discussed. PMID:28788139

The photochemistry of manganese and the origin of banded iron formations

NASA Technical Reports Server (NTRS)

Anbar, A. D.; Holland, H. D.

1992-01-01

The origin of the deposition of superior-type Precambrian banded iron formations (BIFs) is investigated in experiments where the effect of UV radiation on dissolved manganese was studied to determine if the commonly accepted photochemical model for BIF formation is consistent with the distribution of Mn in BIFs. Solutions containing 0.56 M NaCl and about 180 microM MnCl2, with or without 3 to 200 microM FeCl2 were irradiated with filtered and unfiltered UV light for up to 8 hrs; the solutions were deaerated and buffered to a pH of 7, and the experiments were conducted under oxygen-free atmosphere. Data on the rate of manganese photooxidation confirmed that a photochemical model for the origin of oxide facies BIFs is consistent with field observations.

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.

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

Sundaramurthi, Prakash; Suryanarayanan, Raj

To effectively inhibit succinate buffer crystallization and the consequent pH changes in frozen solutions. Using differential scanning calorimetry (DSC) and X-ray diffractometry (XRD), the crystallization behavior of succinate buffer in the presence of either (i) a crystallizing (glycine, mannitol, trehalose) or (ii) a non-crystallizing cosolute (sucrose) was evaluated. Aqueous succinate buffer solutions, 50 or 200 mM, at pH values 4.0 or 6.0 were cooled from room temperature to -25 C at 0.5 C/min. The pH of the solution was measured as a function of temperature using a probe designed to function at low temperatures. The final lyophiles prepared from thesemore » solutions were characterized using synchrotron radiation. When the succinic acid solution buffered to pH 4.0, in the absence of a cosolute, was cooled, there was a pronounced shift in the freeze-concentrate pH. Glycine and mannitol, which have a tendency to crystallize in frozen solutions, remained amorphous when the initial pH was 6.0. Under this condition, they also inhibited buffer crystallization and prevented pH change. At pH 4.0 (50 mM initial concentration), glycine and mannitol crystallized and did not prevent pH change in frozen solutions. While sucrose, a non-crystallizing cosolute, did not completely prevent buffer crystallization, the extent of crystallization was reduced. Sucrose decomposition, based on XRD peaks attributable to {beta}-D-glucose, was observed in frozen buffer solutions with an initial pH of 4.0. Trehalose completely inhibited crystallization of the buffer components when the initial pH was 6.0 but not at pH 4.0. At the lower pH, the crystallization of both trehalose dihydrate and buffer components was evident. When retained amorphous, sucrose and trehalose effectively inhibited succinate buffer component crystallization and the consequent pH shift. However, when trehalose crystallized or sucrose degraded to yield a crystalline decomposition product, crystallization of buffer was observed. Similarly, glycine and mannitol, two widely used bulking agents, inhibited buffer component crystallization only when retained amorphous. In addition to stabilizing the active pharmaceutical ingredient, lyoprotectants may prevent solution pH shift by inhibiting buffer crystallization.« less

Comparison of behavior in muscle fiber regeneration after bupivacaine hydrochloride- and acid anhydride-induced myonecrosis.

PubMed

Akiyama, C; Kobayashi, S; Nonaka, I

1992-01-01

We compared the morphologic characteristics of muscle fiber necrosis and subsequent regeneration after injury induced by intramuscular injections of bupivacaine hydrochloride (BPVC) and a variety of solutions at acid and alkaline pH (acetic anhydride, citric acid buffer, and sodium carbonate buffer). After BPVC injection the necrotic muscle fibers were rapidly invaded by phagocytic cells, followed by active regeneration and very little fibrous scar formation. The regenerating muscle fibers increased rapidly in size and attained complete fiber type differentiation and regained their initial fiber diameter within 1 month. Both alkaline and acid solutions induced muscle fiber necrosis followed by regeneration. Fiber necrosis induced by alkaline buffers and acetic anhydride solutions above pH 5.0 produced changes quite similar to that induced by BPVC. However, injection with 0.1 M acetic anhydride at pH below 4.0 resulted in coagulative necrosis of the injured muscle with very little phagocytic infiltration with poor regenerative activity and dense fibrous tissue scarring. Thus, pH 4.0 appears to be the critical pH determining the type of muscle injury and subsequent poor phagocytic and regenerative activities. This model of acidic acetic anhydride injury may lead to the identification of factors which interfere with regeneration and cause fibrous tissue scarring in human muscular dystrophy.

Determination of methadone hydrochloride in a maintenance dosage formulation.

PubMed

Hoffmann, T J; Thompson, R D

1975-07-01

A colorimetric method for direct quantitative assay of methadone hydrochloride in liquid oral dosage forms is presented. The procedure involves the formation of a dye complex with bromothymol blue buffer solution. The resultant complex is extracted with benzene and measured spectrophotometrically. Duplicate tests on the formulation showed 99.2% of the labeled amount of methadone.

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.

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.

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

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.

Control of electrochemical reactions at the capillary electrophoresis outlet/electrospray emitter electrode under CE/ESI-MS through the application of redox buffers.

PubMed

Smith, A D; Moini, M

2001-01-15

It was found that combining capillary electrophoresis (CE) and electrospray ionization mass spectrometry (ESI-MS) overlays two controlled current techniques to form a three-electrode system (CE inlet, CE outlet/ES emitter, and MS inlet electrodes) in which the CE outlet electrode and the ES emitter electrode were shared between the CE and the ESI-MS circuits. Depending on the polarities and magnitudes of the voltages at the CE inlet, CE outlet/ES emitter, and MS inlet electrodes, the nature of the two redox reactions at the shared electrode was the same or different (both reduction, both oxidation, or one oxidation and the other reduction). Several redox buffers were introduced for controlling electrochemical reactions at the shared electrode. By reacting at this electrode, redox buffers were able to maintain electrode potentials below the onset of water electrolysis, thereby eliminating gas bubble formation and/or pH drift. The volume of the gas generated due to water electrolysis was used to quantitate water oxidation or reduction at this electrode. Two types of redox buffers were used. A reactive electrode with an oxidation potential below that of water was used as the electrode under anodic conditions. Also, a reactive compound with a redox potential below that of water was added to the CE and/or ESI running buffer. When the shared electrode was the anode of both CE and ESI-MS circuits, the use of iron or etched and sanded stainless steel (ss) wire, instead of platinum wire, suppressed bubble formation at the shared electrode. Under these conditions, corrosion of the Fe wire and formation of Fe2+ replaced oxidation of water, eliminating O2 gas bubble and H+ formation. When mixtures of peptides were analyzed, iron adducts of peptides were observed. For a fresh wire, however, the intensities of adduct ions were less than 3% of the protonated molecules. After a few days of operation, the intensities of the adduct ions increased to approximately 50%, due to rust formation on the Fe wire. On-column rinsing with a 40% solution of citric acid rejuvenated the Fe wire and reduced the adduct peak intensities to less than 3%. Unmodified ss wire did not quench bubble formation, which was attributed to its passivated surface. When Fe, ss, and Pt wires were used as the shared electrode under forward polarity CE and positive ESI mode, where the shared electrode acted as a cathode with respect to CE inlet and as an anode with respect to MS inlet, reduction of water at the cathodic end of the electrode and, in the case of ss and Pt wires, oxidation of water at the anodic end of the shared electrode produced a significant amount of bubbles. Under these conditions, however, a buffer containing 50 mM p-benzoquinone completely suppressed both cathodic reduction and anodic oxidation of water for CE currents up to 4 microA. Reduction of p-benzoquinone at the cathodic end of the shared electrode to hydroquinone, and oxidation of this hydroquinone at the anodic end of the electrode, replaced reduction and oxidation of water, eliminating bubble formation. A 0.1% acetic acid solution saturated with I2 was also found to suppress bubble formation at the cathode for CE currents up to 3 microA; however, strong iodine adduct ions were observed under CE/ESI-MS when a mixture of peptides was analyzed. The application of iron as an in-capillary electrode for the analysis of a peptide mixture and a protein digest demonstrated a high separation efficiency similar to when hydroquinone was used as a redox buffer.

Gossip-based solutions for discrete rendezvous in populations of communicating agents.

PubMed

Hollander, Christopher D; Wu, Annie S

2014-01-01

The objective of the rendezvous problem is to construct a method that enables a population of agents to agree on a spatial (and possibly temporal) meeting location. We introduce the buffered gossip algorithm as a general solution to the rendezvous problem in a discrete domain with direct communication between decentralized agents. We compare the performance of the buffered gossip algorithm against the well known uniform gossip algorithm. We believe that a buffered solution is preferable to an unbuffered solution, such as the uniform gossip algorithm, because the use of a buffer allows an agent to use multiple information sources when determining its desired rendezvous point, and that access to multiple information sources may improve agent decision making by reinforcing or contradicting an initial choice. To show that the buffered gossip algorithm is an actual solution for the rendezvous problem, we construct a theoretical proof of convergence and derive the conditions under which the buffered gossip algorithm is guaranteed to produce a consensus on rendezvous location. We use these results to verify that the uniform gossip algorithm also solves the rendezvous problem. We then use a multi-agent simulation to conduct a series of simulation experiments to compare the performance between the buffered and uniform gossip algorithms. Our results suggest that the buffered gossip algorithm can solve the rendezvous problem faster than the uniform gossip algorithm; however, the relative performance between these two solutions depends on the specific constraints of the problem and the parameters of the buffered gossip algorithm.

Gossip-Based Solutions for Discrete Rendezvous in Populations of Communicating Agents

PubMed Central

Hollander, Christopher D.; Wu, Annie S.

2014-01-01

The objective of the rendezvous problem is to construct a method that enables a population of agents to agree on a spatial (and possibly temporal) meeting location. We introduce the buffered gossip algorithm as a general solution to the rendezvous problem in a discrete domain with direct communication between decentralized agents. We compare the performance of the buffered gossip algorithm against the well known uniform gossip algorithm. We believe that a buffered solution is preferable to an unbuffered solution, such as the uniform gossip algorithm, because the use of a buffer allows an agent to use multiple information sources when determining its desired rendezvous point, and that access to multiple information sources may improve agent decision making by reinforcing or contradicting an initial choice. To show that the buffered gossip algorithm is an actual solution for the rendezvous problem, we construct a theoretical proof of convergence and derive the conditions under which the buffered gossip algorithm is guaranteed to produce a consensus on rendezvous location. We use these results to verify that the uniform gossip algorithm also solves the rendezvous problem. We then use a multi-agent simulation to conduct a series of simulation experiments to compare the performance between the buffered and uniform gossip algorithms. Our results suggest that the buffered gossip algorithm can solve the rendezvous problem faster than the uniform gossip algorithm; however, the relative performance between these two solutions depends on the specific constraints of the problem and the parameters of the buffered gossip algorithm. PMID:25397882

Quality by design in formulation and process development for a freeze-dried, small molecule parenteral product: a case study.

PubMed

Mockus, Linas N; Paul, Timothy W; Pease, Nathan A; Harper, Nancy J; Basu, Prabir K; Oslos, Elizabeth A; Sacha, Gregory A; Kuu, Wei Y; Hardwick, Lisa M; Karty, Jacquelyn J; Pikal, Michael J; Hee, Eun; Khan, Mansoor A; Nail, Steven L

2011-01-01

A case study has been developed to illustrate one way of incorporating a Quality by Design approach into formulation and process development for a small molecule, freeze-dried parenteral product. Sodium ethacrynate was chosen as the model compound. Principal degradation products of sodium ethacrynate result from hydrolysis of the unsaturated ketone in aqueous solution, and dimer formation from a Diels-Alder condensation in the freeze-dried solid state. When the drug crystallizes in a frozen solution, the eutectic melting temperature is above -5°C. Crystallization in the frozen system is affected by pH in the range of pH 6-8 and buffer concentration in the range of 5-50 mM, where higher pH and lower buffer concentration favor crystallization. Physical state of the drug is critical to solid state stability, given the relative instability of amorphous drug. Stability was shown to vary considerably over the ranges of pH and buffer concentration examined, and vial-to-vial variability in degree of crystallinity is a potential concern. The formulation design space was constructed in terms of pH and drug concentration, and assuming a constant 5 mM concentration of buffer. The process design space is constructed to take into account limitations on the process imposed by the product and by equipment capability.

Inhibition of Protein Carbamylation in Urea Solution Using Ammonium Containing Buffers

PubMed Central

Sun, Shisheng; Zhou, Jian-Ying; Yang, Weiming; Zhang, Hui

2013-01-01

Urea solution is one of the most commonly employed protein denaturants for protease digestion in proteomic studies. However, it has long been recognized that urea solution can cause carbamylation at the N-termini of proteins/peptides and at the side chain amino groups of lysine and arginine residues. Protein/peptide carbamylation blocks protease digestion and affects protein identification and quantification in mass spectrometry analysis by blocking peptide amino groups from isotopic/isobaric labeling and changing peptide charge states, retention times and masses. In addition, protein carbamylation during sample preparation makes it difficult to study in vivo protein carbamylation. In this study, we compared the peptide carbamylation in urea solutions of different buffers and found that ammonium containing buffers were the most effective buffers to inhibit protein carbamylation in urea solution. The possible mechanism of carbamylation inhibition by ammonium containing buffers is discussed, and a revised procedure for the protease digestion of proteins in urea and ammonium containing buffers was developed to facilitate its application in proteomic research. PMID:24161613

Buffers more than buffering agent: introducing a new class of stabilizers for the protein BSA.

PubMed

Gupta, Bhupender S; Taha, Mohamed; Lee, Ming-Jer

2015-01-14

In this study, we have analyzed the influence of four biological buffers on the thermal stability of bovine serum albumin (BSA) using dynamic light scattering (DLS). The investigated buffers include 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES), 4-(2-hydroxyethyl)-1-piperazine-propanesulfonic acid (EPPS), 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid sodium salt (HEPES-Na), and 4-morpholinepropanesulfonic acid sodium salt (MOPS-Na). These buffers behave as a potential stabilizer for the native structure of BSA against thermal denaturation. The stabilization tendency follows the order of MOPS-Na > HEPES-Na > HEPES ≫ EPPS. To obtain an insight into the role of hydration layers and peptide backbone in the stabilization of BSA by these buffers, we have also explored the phase transition of a thermoresponsive polymer, poly(N-isopropylacrylamide (PNIPAM)), a model compound for protein, in aqueous solutions of HEPES, EPPS, HEPES-Na, and MOPS-Na buffers at different concentrations. It was found that the lower critical solution temperatures (LCST) of PNIPAM in the aqueous buffer solutions substantially decrease with increase in buffer concentration. The mechanism of interactions between these buffers and protein BSA was probed by various techniques, including UV-visible, fluorescence, and FTIR. The results of this series of studies reveal that the interactions are mainly governed by the influence of the buffers on the hydration layers surrounding the protein. We have also explored the possible binding sites of BSA with these buffers using a molecular docking technique. Moreover, the activities of an industrially important enzyme α-chymotrypsin (α-CT) in 0.05 M, 0.5 M, and 1.0 M of HEPES, EPPS, HEPES-Na, and MOPS-Na buffer solutions were analyzed at pH = 8.0 and T = 25 °C. Interestingly, the activities of α-CT were found to be enhanced in the aqueous solutions of these investigated buffers. Based upon the Jones-Dole viscosity parameters, the kosmotropic or chaotropic behaviors of the investigated buffers at 25 °C have been examined.

Rapid quantification of imidazolium-based ionic liquids by hydrophilic interaction liquid chromatography: Methodology and an investigation of the retention mechanisms.

PubMed

Hawkins, Cory A; Rud, Anna; Guthrie, Margaret L; Dietz, Mark L

2015-06-26

The separation of nine N,N'-dialkylimidazolium-based ionic liquids (ILs) by an isocratic hydrophilic interaction high-performance liquid chromatographic method using an unmodified silica column was investigated. The chosen analytical conditions using a 90:10 acetonitrile-ammonium formate buffer mobile phase on a high-purity, unmodified silica column were found to be efficient, robust, and sensitive for the determination of ILs in a variety of solutions. The retention window (k' = 2-11) was narrower than that of previous methods, resulting in a 7-min runtime for the nine IL homologues. The lower limit of quantification of the method, 2-3 μmol L(-1), was significantly lower than those reported previously for HPLC-UV methods. The effects of systematically modifying the IL cation alkyl chain length, column temperature, and mobile-phase water and buffer content on solute retention were examined. Cation exchange was identified as the dominant retention mechanism for most of the solutes, with a distinct (single methylene group) transition to a dominant partitioning mode at the highest solute polarity. Copyright © 2015 Elsevier B.V. All rights reserved.

Predicting the crystallization propensity of carboxylic acid buffers in frozen systems--relevance to freeze-drying.

PubMed

Sundaramurthi, Prakash; Suryanarayanan, Raj

2011-04-01

Selective crystallization of buffer components in frozen solutions is known to cause pronounced pH shifts. Our objective was to study the crystallization behavior and the consequent pH shift in frozen aqueous carboxylic acid buffers. Aqueous carboxylic acid buffers were cooled to -25°C and the pH of the solution was measured as a function of temperature. The thermal behavior of solutions during freezing and thawing was investigated by differential scanning calorimetry. The crystallized phases in frozen solution were identified by X-ray diffractometry. The malate buffer system was robust with no evidence of buffer component crystallization and hence negligible pH shift. In the citrate and tartarate systems, at initial pH

Electrodialysis operation with buffer solution

DOEpatents

Hryn, John N [Naperville, IL; Daniels, Edward J [Orland Park, IL; Krumdick, Greg K [Crete, IL

2009-12-15

A new method for improving the efficiency of electrodialysis (ED) cells and stacks, in particular those used in chemical synthesis. The process entails adding a buffer solution to the stack for subsequent depletion in the stack during electrolysis. The buffer solution is regenerated continuously after depletion. This buffer process serves to control the hydrogen ion or hydroxide ion concentration so as to protect the active sites of electrodialysis membranes. The process enables electrodialysis processing options for products that are sensitive to pH changes.

Mechanical characteristics of beta sheet-forming peptide hydrogels are dependent on peptide sequence, concentration and buffer composition

PubMed Central

Müller, Michael; König, Finja; Meyer, Nina; Gattlen, Jasmin; Pieles, Uwe; Peters, Kirsten; Kreikemeyer, Bernd; Mathes, Stephanie; Saxer, Sina

2018-01-01

Self-assembling peptide hydrogels can be modified regarding their biodegradability, their chemical and mechanical properties and their nanofibrillar structure. Thus, self-assembling peptide hydrogels might be suitable scaffolds for regenerative therapies and tissue engineering. Owing to the use of various peptide concentrations and buffer compositions, the self-assembling peptide hydrogels might be influenced regarding their mechanical characteristics. Therefore, the mechanical properties and stability of a set of self-assembling peptide hydrogels, consisting of 11 amino acids, made from four beta sheet self-assembling peptides in various peptide concentrations and buffer compositions were studied. The formed self-assembling peptide hydrogels exhibited stiffnesses ranging from 0.6 to 205 kPa. The hydrogel stiffness was mostly affected by peptide sequence followed by peptide concentration and buffer composition. All self-assembling peptide hydrogels examined provided a nanofibrillar network formation. A maximum self-assembling peptide hydrogel dissolution of 20% was observed for different buffer solutions after 7 days. The stability regarding enzymatic and bacterial digestion showed less degradation in comparison to the self-assembling peptide hydrogel dissolution rate in buffer. The tested set of self-assembling peptide hydrogels were able to form stable scaffolds and provided a broad spectrum of tissue-specific stiffnesses that are suitable for a regenerative therapy. PMID:29657766

Thermophysical properties of carboxylic and amino acid buffers at subzero temperatures: relevance to frozen state stabilization.

PubMed

Sundaramurthi, Prakash; Suryanarayanan, Raj

2011-06-02

Macromolecules and other thermolabile biologicals are often buffered and stored in frozen or dried (freeze-dried) state. Crystallization of buffer components in frozen aqueous solutions and the consequent pH shifts were studied in carboxylic (succinic, malic, citric, tartaric acid) and amino acid (glycine, histidine) buffers. Aqueous buffer solutions were cooled from room temperature (RT) to -25 °C and the pH of the solution was measured as a function of temperature. The thermal behavior of frozen solutions was investigated by differential scanning calorimetry (DSC), and the crystallized phases were identified by X-ray diffractometry (XRD). Based on the solubility of the neutral species of each buffer system over a range of temperatures, it was possible to estimate its degree of supersaturation at the subambient temperature of interest. This enabled us to predict its crystallization propensity in frozen systems. The experimental and the predicted rank orderings were in excellent agreement. The malate buffer system was robust with no evidence of buffer component crystallization and hence negligible pH shift. In the citrate and tartrate systems, at initial pH < pK(a)(2), only the most acidic buffer component (neutral form) crystallized on cooling, causing an increase in the freeze-concentrate pH. In glycine buffer solutions, when the initial pH was ∼3 units < isoelectric pH (pI = 5.9), β-glycine crystallization caused a small decrease in pH, while a similar effect but in the opposite direction was observed when the initial pH was ∼3 units > pI. In the histidine buffer system, depending on the initial pH, either histidine or histidine HCl crystallized.

Inhibition of protein carbamylation in urea solution using ammonium-containing buffers.

PubMed

Sun, Shisheng; Zhou, Jian-Ying; Yang, Weiming; Zhang, Hui

2014-02-01

Urea solution is one of the most commonly employed protein denaturants for protease digestion in proteomic studies. However, it has long been recognized that urea solution can cause carbamylation at the N termini of proteins/peptides and at the side chain amino groups of lysine and arginine residues. Protein/peptide carbamylation blocks protease digestion and affects protein identification and quantification in mass spectrometry analysis by blocking peptide amino groups from isotopic/isobaric labeling and changing peptide charge states, retention times, and masses. In addition, protein carbamylation during sample preparation makes it difficult to study in vivo protein carbamylation. In this study, we compared the peptide carbamylation in urea solutions of different buffers and found that ammonium-containing buffers were the most effective buffers to inhibit protein carbamylation in urea solution. The possible mechanism of carbamylation inhibition by ammonium-containing buffers is discussed, and a revised procedure for the protease digestion of proteins in urea and ammonium-containing buffers was developed to facilitate its application in proteomic research. Copyright © 2013 Elsevier Inc. All rights reserved.

Stable adducts of nerve agents sarin, soman and cyclosarin with TRIS, TES and related buffer compounds--characterization by LC-ESI-MS/MS and NMR and implications for analytical chemistry.

PubMed

Gäb, Jürgen; John, Harald; Melzer, Marco; Blum, Marc-Michael

2010-05-15

Buffering compounds like TRIS are frequently used in chemical, biochemical and biomedical applications to control pH in solution. One of the prerequisites of a buffer compound, in addition to sufficient buffering capacity and pH stability over time, is its non-reactivity with other constituents of the solution. This is especially important in the field of analytical chemistry where analytes are to be determined quantitatively. Investigating the enzymatic hydrolysis of G-type nerve agents sarin, soman and cyclosarin in buffered solution we have identified stable buffer adducts of TRIS, TES and other buffer compounds with the nerve agents. We identified the molecular structure of these adducts as phosphonic diesters using 1D (1)H-(31)P HSQC NMR and LC-ESI-MS/MS techniques. Reaction rates with TRIS and TES are fast enough to compete with spontaneous hydrolysis in aqueous solution and to yield substantial amounts (up to 20-40%) of buffer adduct over the course of several hours. A reaction mechanism is proposed in which the amino function of the buffer serves as an intramolecular proton acceptor rendering the buffer hydroxyl groups nucleophilic enough for attack on the phosphorus atom of the agents. Results show that similar buffer adducts are formed with a range of hydroxyl and amino function containing buffers including TES, BES, TRIS, BIS-TRIS, BIS-TRIS propane, Tricine, Bicine, HEPES and triethanol amine. It is recommended to use alternative buffers like MOPS, MES and CHES when working with G-type nerve agents especially at higher concentrations and over prolonged times. Copyright (c) 2010 Elsevier B.V. All rights reserved.

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.

High-performance liquid chromatographic analysis of methadone hydrochloride oral solution.

PubMed

Beasley, T H; Ziegler, H W

1977-12-01

A direct and rapid high-performance liquid chromatographic assay for methadone hydrochloride in a flavored oral solution dosage form is described. A syrup sample, one part diluted with three parts of water, is introduced onto a column packed with octadecylsilane bonded on 10 micrometer porous silica gel (reversed phase). A formic acid-ammonium formate-buffered mobile phase is linear programmed with acetonitrile. The absorbance is monitored continuously at 280 or 254 nm, using a flow-through, UV, double-beam photometer. An aqueous methadone hydrochloride solution is used for external standardization. The relative standard deviation was not more than 1.0%. Drug recovery from a syrup base was better than 99.8%.

Formation of Organized Protein Thin Films with External Electric Field.

PubMed

Ferreira, Cecília Fabiana da G; Camargo, Paulo C; Benelli, Elaine M

2015-10-01

The effect of an external electric field on the formation of protein GlnB-Hs films and on its buffer solution on siliconized glass slides has been analyzed by current versus electric field curves and atomic force microscopy (AFM). The Herbaspirillum seropedicae GlnB protein (GlnB-Hs) is a globular, soluble homotrimer (36 kDa) with its 3-D structure previously determined. Concentrations of 10 nM native denatured GlnB-Hs protein were deposited on siliconized glass slides under ambient conditions. Immediately after solution deposition a maximum electric field of 30 kV/m was applied with rates of 3 V/s. The measured currents were surface currents and were analyzed as transport current. Electric current started to flow only after a minimum electric field (critical value) for the systems analyzed. The AFM images showed films with a high degree of directional organization only when the proteins were present in the solution. These results showed that the applied electric field favored directional organization of the protein GlnB-Hs films and may contribute to understand the formation of protein films under applied electric fields.

Ultrasonication as a potential tool to predict solute crystallization in freeze-concentrates.

PubMed

Ragoonanan, Vishard; Suryanarayanan, Raj

2014-06-01

We hypothesize that ultrasonication can accelerate solute crystallization in freeze-concentrates. Our objective is to demonstrate ultrasonication as a potential predictive tool for evaluating physical stability of excipients in frozen solutions. The crystallization tendencies of lyoprotectants (trehalose, sucrose), carboxylic acid buffers (citric, tartaric, malic, and acetic) and an amino acid buffer (histidine HCl) were studied. Aqueous solutions of buffers, lyoprotectants and mixtures of the two were cooled from room temperature to -20°C and sonicated to induce solute crystallization. The crystallized phases were identified by X-ray diffractometry (laboratory or synchrotron source). Sonication accelerated crystallization of trehalose dihydrate in frozen trehalose solutions. Sonication also enhanced solute crystallization in tartaric (200 mM; pH 5), citric (200 mM pH 4) and malic (200 mM; pH 4) acid buffers. At lower buffer concentrations, longer annealing times following sonication were required to facilitate solute crystallization. The time for crystallization of histidine HCl progressively increased as a function of sucrose concentration. The insonation period required to effect crystallization also increased with sucrose concentration. Sonication can substantially accelerate solute crystallization in the freeze-concentrate. Ultrasonication may be useful in assessing the crystallization tendency of formulation constituents used in long term frozen storage and freeze-drying.

SODR Memory Control Buffer Control ASIC

NASA Technical Reports Server (NTRS)

Hodson, Robert F.

1994-01-01

The Spacecraft Optical Disk Recorder (SODR) is a state of the art mass storage system for future NASA missions requiring high transmission rates and a large capacity storage system. This report covers the design and development of an SODR memory buffer control applications specific integrated circuit (ASIC). The memory buffer control ASIC has two primary functions: (1) buffering data to prevent loss of data during disk access times, (2) converting data formats from a high performance parallel interface format to a small computer systems interface format. Ten 144 p in, 50 MHz CMOS ASIC's were designed, fabricated and tested to implement the memory buffer control function.

Ligand-enhanced electrokinetic remediation of metal-contaminated marine sediments with high acid buffering capacity.

PubMed

Masi, Matteo; Iannelli, Renato; Losito, Gabriella

2016-06-01

The suitability of electrokinetic remediation for removing heavy metals from dredged marine sediments with high acid buffering capacity was investigated. Laboratory-scale electrokinetic remediation experiments were carried out by applying two different voltage gradients to the sediment (0.5 and 0.8 V/cm) while circulating water or two different chelating agents at the electrode compartments. Tap water, 0.1 M citric acid and 0.1 M ethylenediaminetetraacetic acid (EDTA) solutions were used respectively. The investigated metals were Zn, Pb, V, Ni and Cu. In the unenhanced experiment, the acid front could not propagate due to the high acid buffering capacity of the sediments; the production of OH(-) ions at the cathode resulted in a high-pH environment causing the precipitation of CaCO3 and metal hydroxides. The use of citric acid prevented the formation of precipitates, but solubilisation and mobilisation of metal species were not sufficiently achieved. Metal removal was relevant when EDTA was used as the conditioning agent, and the electric potential was raised up to 0.8 V/cm. EDTA led to the formation of negatively charged complexes with metals which migrated towards the anode compartment by electromigration. This result shows that metal removal from sediments with high acid buffering capacity may be achieved by enhancing the electrokinetic process by EDTA addition when the acidification of the medium is not economically and/or environmentally sustainable.

High throughput analysis of red wine and grape phenolics-adaptation and validation of methyl cellulose precipitable tannin assay and modified Somers color assay to a rapid 96 well plate format.

PubMed

Mercurio, Meagan D; Dambergs, Robert G; Herderich, Markus J; Smith, Paul A

2007-06-13

The methyl cellulose precipitable (MCP) tannin assay and a modified version of the Somers and Evans color assay were adapted to high-throughput (HTP) analysis. To improve efficiency of the MCP tannin assay, a miniaturized 1 mL format and a HTP format using 96 well plates were developed. The Somers color assay was modified to allow the standardization of pH and ethanol concentrations of wine samples in a simple one-step dilution with a buffer solution, thus removing inconsistencies between wine matrices prior to analysis and allowing for its adaptation to a HTP format. Validation studies showed that all new formats were efficient, and results were reproducible and analogous to the original formats.

Direct extraction of genomic DNA from maize with aqueous ionic liquid buffer systems for applications in genetically modified organisms analysis.

PubMed

Gonzalez García, Eric; Ressmann, Anna K; Gaertner, Peter; Zirbs, Ronald; Mach, Robert L; Krska, Rudolf; Bica, Katharina; Brunner, Kurt

2014-12-01

To date, the extraction of genomic DNA is considered a bottleneck in the process of genetically modified organisms (GMOs) detection. Conventional DNA isolation methods are associated with long extraction times and multiple pipetting and centrifugation steps, which makes the entire procedure not only tedious and complicated but also prone to sample cross-contamination. In recent times, ionic liquids have emerged as innovative solvents for biomass processing, due to their outstanding properties for dissolution of biomass and biopolymers. In this study, a novel, easily applicable, and time-efficient method for the direct extraction of genomic DNA from biomass based on aqueous-ionic liquid solutions was developed. The straightforward protocol relies on extraction of maize in a 10 % solution of ionic liquids in aqueous phosphate buffer for 5 min at room temperature, followed by a denaturation step at 95 °C for 10 min and a simple filtration to remove residual biopolymers. A set of 22 ionic liquids was tested in a buffer system and 1-ethyl-3-methylimidazolium dimethylphosphate, as well as the environmentally benign choline formate, were identified as ideal candidates. With this strategy, the quality of the genomic DNA extracted was significantly improved and the extraction protocol was notably simplified compared with a well-established method.

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.

Electrolytic method to make alkali alcoholates using ion conducting alkali electrolyte/separator

DOEpatents

Joshi, Ashok V [Salt Lake City, UT; Balagopal, Shekar [Sandy, UT; Pendelton, Justin [Salt Lake City, UT

2011-12-13

Alkali alcoholates, also called alkali alkoxides, are produced from alkali metal salt solutions and alcohol using a three-compartment electrolytic cell. The electrolytic cell includes an anolyte compartment configured with an anode, a buffer compartment, and a catholyte compartment configured with a cathode. An alkali ion conducting solid electrolyte configured to selectively transport alkali ions is positioned between the anolyte compartment and the buffer compartment. An alkali ion permeable separator is positioned between the buffer compartment and the catholyte compartment. The catholyte solution may include an alkali alcoholate and alcohol. The anolyte solution may include at least one alkali salt. The buffer compartment solution may include a soluble alkali salt and an alkali alcoholate in alcohol.

The Temperature of Intracellular Ice Formation in Mouse Oocytes vs. the Unfrozen Fraction at that Temperature ⋆

PubMed Central

Mazur, Peter; Pinn, Irina L.; Kleinhans, F.W.

2009-01-01

We have previously reported [11] that intracellular ice formation (IIF) in mouse oocytes suspended in various concentrations of glycerol and ethylene glycol (EG) occurs at temperatures where the percentage of unfrozen water is about 6% and 12% respectively even though the IIF temperatures varied from −14° to −41°C. However, because of the way the solutions were prepared, the concentrations of salt and glycerol or EG in that unfrozen fraction at IIF were also rather tightly grouped. The experiments reported in the present paper were designed to separate the effects of the unfrozen fraction at IIF from that of the solute concentration in the unfrozen fraction. This separation makes use of two facts. One is that the concentration of solutes in the residual liquid at a given subzero temperature is fixed regardless of their concentration in the initial unfrozen solution. However, second, the fraction unfrozen at a given temperature is dependent on the initial solute concentration. Experimentally, oocytes were suspended in solutions of glycerol/buffered saline and EG/buffered saline of varying total solute concentration with the restriction that the mass ratio of glycerol and EG to salts are held constant. The oocytes were then cooled rapidly enough (20°C/min) to avoid significant osmotic shrinkage, and the temperature at which IIF occurred as noted. When this is done, we find, as previously that the fraction of water remaining unfrozen at the temperature of IIF remains nearly constant at 5 to 8% for both glycerol and EG even though the IIF temperatures vary from −14°C to −50°C. But unlike the previous results, the salt and CPA concentrations in the unfrozen fraction vary by a factor of three. The present procedure for preparing the solutions produces a potentially complicating factor; namely, the cell volumes vary substantially prior to freezing: Substantially greater than isotonic in some solution; substantially smaller in others. However, the data in toto demonstrate that cell volume is not a determining factor in the IIF temperature. PMID:17379206

The temperature of intracellular ice formation in mouse oocytes vs. the unfrozen fraction at that temperature.

PubMed

Mazur, Peter; Pinn, Irina L; Kleinhans, F W

2007-04-01

We have previously reported [Cryobiology 51 (2005) 29-53] that intracellular ice formation (IIF) in mouse oocytes suspended in various concentrations of glycerol and ethylene glycol (EG) occurs at temperatures where the percentage of unfrozen water is about 6% and 12%, respectively, even though the IIF temperatures varied from -14 to -41 degrees C. However, because of the way the solutions were prepared, the concentrations of salt and glycerol or EG in that unfrozen fraction at IIF were also rather tightly grouped. The experiments reported in the present paper were designed to separate the effects of the unfrozen fraction at IIF from that of the solute concentration in the unfrozen fraction. This separation makes use of two facts. One is that the concentration of solutes in the residual liquid at a given subzero temperature is fixed regardless of their concentration in the initial unfrozen solution. However, second, the fraction unfrozen at a given temperature is dependent on the initial solute concentration. Experimentally, oocytes were suspended in solutions of glycerol/buffered saline and EG/buffered saline of varying total solute concentration with the restriction that the mass ratios of glycerol and EG to salts are held constant. The oocytes were then cooled rapidly enough (20 degrees C/min) to avoid significant osmotic shrinkage, and the temperature at which IIF occurred was noted. When this is done, we find, as previously that the fraction of water remaining unfrozen at the temperature of IIF remains nearly constant at 5-8% for both glycerol and EG even though the IIF temperatures vary from -14 to -50 degrees C. But unlike the previous results, the salt and CPA concentrations in the unfrozen fraction vary by a factor of three. The present procedure for preparing the solutions produces a potentially complicating factor; namely, the cell volumes vary substantially prior to freezing: substantially greater than isotonic in some solutions; substantially smaller in others. However, the data in toto demonstrate that cell volume is not a determining factor in the IIF temperature.

The decomposition of peroxynitrite to nitroxyl anion (NO−) and singlet oxygen in aqueous solution

PubMed Central

Khan, Ahsan Ullah; Kovacic, Dianne; Kolbanovskiy, Alexander; Desai, Mehul; Frenkel, Krystyna; Geacintov, Nicholas E.

2000-01-01

The mechanism of decomposition of peroxynitrite (OONO−) in aqueous sodium phosphate buffer solution at neutral pH was investigated. The OONO− was synthesized by directly reacting nitric oxide with superoxide anion at pH 13. The hypothesis was explored that OONO−, after protonation at pH 7.0 to HOONO, decomposes into 1O2 and HNO according to a spin-conserved unimolecular mechanism. Small aliquots of the concentrated alkaline OONO− solution were added to a buffer solution (final pH 7.0–7.2), and the formation of 1O2 and NO− in high yields was observed. The 1O2 generated was trapped as the transannular peroxide (DPAO2) of 9,10-diphenylanthracene (DPA) dissolved in carbon tetrachloride. The nitroxyl anion (NO−) formed from HNO (pKa 4.5) was trapped as nitrosylhemoglobin (HbNO) in an aqueous methemoglobin (MetHb) solution. In the presence of 25 mM sodium bicarbonate, which is known to accelerate the rate of decomposition of OONO−, the amount of singlet oxygen trapped was reduced by a factor of ≈2 whereas the yield of trapping of NO− by methemoglobin remained unaffected. Because NO3− is known to be the ultimate decomposition product of OONO−, these results suggest that the nitrate anion is not formed by a direct isomerization of OONO−, but by an indirect route originating from NO−. PMID:10716721

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.

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

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

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

Formation of cage-like particles by poly(amino acid)-based block copolymers in aqueous solution.

PubMed Central

Cudd, A; Bhogal, M; O'Mullane, J; Goddard, P

1991-01-01

When dissolved in N,N-dimethylformamide and then dialyzed against phosphate-buffered saline, A-B-A block copolymers composed of poly [N5-(2-hydroxyethyl)-L-glutamine]-block-poly(gamma-benzyl-L-glutamate)- block-poly [N5-(2-hydroxyethyl)-L-glutamine] form particles. The particles are cage-like structures with average diameters of 300 nm (average polydispersity, 0.3-0.5). They are stable in aqueous solution at 4 degrees C for up to 3 weeks, at which time flocculation becomes apparent. Negative staining and freeze-fracture electron microscopy suggest that cage-like particles are formed by selective association of segregated micelle populations. A model of particle formation is presented in which B blocks form micelles in dimethylformamide. On dialysis against an aqueous solution, the extended A blocks then associate intermolecularly to form rod-shaped micelles, which connect the B block micelles. The result is a meshed cage-like particle. The implications of these observations on the aggregation behavior of polymeric surfactants in dilute solution are discussed. Images PMID:11607245

Role of Buffers in Protein Formulations.

PubMed

Zbacnik, Teddy J; Holcomb, Ryan E; Katayama, Derrick S; Murphy, Brian M; Payne, Robert W; Coccaro, Richard C; Evans, Gabriel J; Matsuura, James E; Henry, Charles S; Manning, Mark Cornell

2017-03-01

Buffers comprise an integral component of protein formulations. Not only do they function to regulate shifts in pH, they also can stabilize proteins by a variety of mechanisms. The ability of buffers to stabilize therapeutic proteins whether in liquid formulations, frozen solutions, or the solid state is highlighted in this review. Addition of buffers can result in increased conformational stability of proteins, whether by ligand binding or by an excluded solute mechanism. In addition, they can alter the colloidal stability of proteins and modulate interfacial damage. Buffers can also lead to destabilization of proteins, and the stability of buffers themselves is presented. Furthermore, the potential safety and toxicity issues of buffers are discussed, with a special emphasis on the influence of buffers on the perceived pain upon injection. Finally, the interaction of buffers with other excipients is examined. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Change in the Nd isotopic composition of the bottom water and detrital sediments on the Bering Slope over the last 500 kyrs with implications for the formation of the North Pacific Intermediate Water

NASA Astrophysics Data System (ADS)

Jang, K.; Huh, Y.; Han, Y.

2015-12-01

The Bering Sea is a potential location for the formation of the North Pacific Intermediate/Deep Water (NPIW/NPDW) and may play an important role in the global heat distribution. We reconstructed the neodymium isotopic ratio (ɛNd) of authigenic Fe-Mn oxide coatings and detrital sediments on the Bering Slope (IODP Expedition 323 site U1345; water depth 1008 m) over the last 500 kyrs. The ɛNd is a quasi-conservative water mass tracer. We compared three different leaching techniques to assure that authigenic signals are captured without contamination from terrigenous sources: (1) leaching (3 hours) with 0.02 M hydroxylamine hydrochloride (HH) in 25% buffered acetic acid after decarbonation; sediment/solution (v/v) > 10, (2) leaching (1 hour) with 0.02 M HH in 25% buffered acetic acid without decarbonation; sediment/solution ~ 1, and (3) leaching (1 hour) with 0.005 M HH in 1.5% buffered acetic acid-0.003 M Na-EDTA without decarbonation; sediment/solution > 40. The low Al concentrations and less radiogenic ɛNdvalues indicated that method (2) is the most appropriate leaching process. The average ɛNd of the authigenic fraction over the last 500 kyrs is -3.3 ± 0.9 (1σ, n=38), with large temporal fluctuations. The ɛNd of authigenic and detrital fractions are well correlated (r2 ~ 0.66), suggesting that the bottom water composition in the Bering Sea was governed by terrigenous inflow from surrounding areas. Radiogenic ɛNd peaks (up to -1.9) seem to be influenced by radiogenic water inflow from the the Kamchatka or Aluetian arcs. The high bulk density and low b* values imply higher terrigenous versus biological contribution and enhanced sea ice formation. Subsequent brine formation would have triggered sinking of radiogenic surface water, forming the NPIW. On the other hand, non-radiogenic ɛNd troughs (down to -5.3) are observed at times of low bulk density and high b* values. We presume higher biological productivity which is supported by the high opal content at these intervals (Kanematsu et al., 2013). Sea level rise and boundary exchange with terrigenous sediment derived from N. America is a likely mechanism. This work was supported by the Basic Science Research Program through the NRF funded by Ministry of Science, ICT and Future Planning (No. 2014 0498836)

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.

Extinguishing visible photoluminescence of porous silicon stimulated by antigen-antibody immunocomplex formation

NASA Astrophysics Data System (ADS)

Starodub, Nickolaj F.; Fedorenko, Leonid L.; Starodub, Valentyna M.; Dikiy, S. P.; Svechnikov, Sergey V.

1997-02-01

The photoluminescence of the porous silicon obtained by special procedure with the usage of the chemical and laser beam treatment of silicon crystal was investigated in water, buffer and solution containing sodium chloride. It was demonstrated that the intensity of the photoluminescence did not practically change at the above mentioned conditions as well as after antigen or antibody immobilization on the porous silicon surface. But this parameter of the photoluminescence dramatically decreased in case of specific immune complex formation on the silicon surface. The level of the photoluminescence extinguishing depended on duration and intensity of immune reaction. It is proposed to use discovered effect for creation of the immunosensors based on the direct registration of immunocomplex formation.

Fluorescence and electron paramagnetic resonance studies of norfloxacin and N-donor mixed-ligand ternary copper(II) complexes: Stability and interaction with SDS micelles

NASA Astrophysics Data System (ADS)

Vignoli Muniz, Gabriel S.; Incio, Jimmy Llontop; Alves, Odivaldo C.; Krambrock, Klaus; Teixeira, Letícia R.; Louro, Sonia R. W.

2018-01-01

The stability of ternary copper(II) complexes of a heterocyclic ligand, L (L being 2,2‧-bipyridine (bipy) or 1,10-phenanthroline (phen)) and the fluorescent antibacterial agent norfloxacin (NFX) as the second ligand was studied at pH 7.4 and different ionic strengths. Fluorescence quenching upon titration of NFX with the binary complexes allowed to obtain stability constants for NFX binding, Kb, as a function of ionic strength. The Kb values vary by more than two orders of magnitude when buffer concentration varies from 0.5 to 100 mM. It was observed that previously synthesized ternary complexes dissociate in buffer according with the obtained stability constants. This shows that equimolar solutions of NFX and binary complexes are equivalent to solutions of synthesized ternary complexes. The interaction of the ternary copper complexes with anionic SDS (sodium dodecyl sulfate) micelles was studied by fluorescence and electron paramagnetic resonance (EPR). Titration of NFX-loaded SDS micelles with the complexes Cu:L allowed to determine the stability constants inside the micelles. Fluorescence quenching demonstrated that SDS micelles increase the stability constants by factors around 50. EPR spectra gave details of the copper(II) local environment, and demonstrated that the structure of the ternary complexes inside SDS micelles is different from that in buffer. Mononuclear ternary complexes formed inside the micelles, while in buffer most ternary complexes are binuclear. The results show that anionic membrane interfaces increase formation of copper fluoroquinolone complexes, which can influence bioavailability, membrane diffusion, and mechanism of action of the antibiotics.

Multiple, simultaneous, independent gradients for a versatile multidimensional liquid chromatography. Part II: Application 2: Computer controlled pH gradients in the presence of urea provide improved separation of proteins: Stability influenced anion and cation exchange chromatography.

PubMed

Hirsh, Allen G; Tsonev, Latchezar I

2017-04-28

This paper details the use of a method of creating controlled pH gradients (pISep) to improve the separation of protein isoforms on ion exchange (IEX) stationary phases in the presence of various isocratic levels of urea. The pISep technology enables the development of computer controlled pH gradients on both cationic (CEX) and anionic (AEX) IEX stationary phases over the very wide pH range from 2 to 12. In pISep, titration curves generated by proportional mixing of the acidic and basic pISep working buffers alone, or in the presence of non-buffering solutes such as the neutral salt NaCl (0-1M), polar organics such as urea (0-8M) or acetonitrile (0-80 Vol%), can be fitted with high fidelity using high order polynomials which, in turn allows construction of a mathematical manifold %A (% acidic pISep buffer) vs. pH vs. [non-buffering solute], permitting precise computer control of pH and the non-buffering solute concentration allowing formation of dual uncoupled liquid chromatographic (LC) gradients of arbitrary shape (Hirsh and Tsonev, 2012 [1]). The separation of protein isoforms examined in this paper by use of such pH gradients in the presence of urea demonstrates the fractionation power of a true single step two dimensional liquid chromatography which we denote as Stability-Influenced Ion Exchange Chromatography (SIIEX). We present evidence that SIIEX is capable of increasing the resolution of protein isoforms difficult to separate by ordinary pH gradient IEX, and potentially simplifying the development of laboratory and production purification strategies involving on-column simultaneous pH and urea unfolding or refolding of targeted proteins. We model some of the physics implied by the dynamics of the observed protein fractionations as a function of both urea concentration and pH assuming that urea-induced native state unfolding competes with native state electrostatic interaction binding to an IEX stationary phase. Implications for in vivo protein-membrane interactions are discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

Optimization of a model of red blood cells for the study of anti-oxidant drugs, in terms of concentration of oxidant and phosphate buffer.

PubMed

Bureau, A; Lahet, J-J; Lenfant, F; Bouyer, F; Petitjean, M; Chaillot, B; Freysz, M

2005-08-01

The aggression of erythrocytes by an oxidative stress induces hemolysis. This paper aims to valid a model of erythrocytes in terms of composition of the phosphate buffer solution and of concentration of a well-known oxidant, AAPH. Three compositions of phosphate buffer solution are mixed with three concentrations of oxidant. The influence of these two parameters on hemolysis is independently studied by a variance analysis and a Kruskal-Wallis test when ANOVA is not available. The hemolysis rate increases with time at fixed oxidant concentration, but is not influenced by the composition of the buffer solution. The highest hemolysis rate, 90%, was only measured within 2 h with the highest oxidant concentration. If we retain this concentration of oxidant, the lower concentration of the buffer can by eliminated by a significant less hemolysis and the highest concentration of the buffer can by chosen in regard of the better precision for a similar hemolysis compared to the mean buffer. We hope to study the effect of anti-oxidant agent with such a model of erythrocytes.

Method of junction formation for CIGS photovoltaic devices

DOEpatents

Delahoy, Alan E.

2006-03-28

Sulfur is used to improve the performance of CIGS devices prepared by the evaporation of a single source ZIS type compound to form a buffer layer on the CIGS. The sulfur may be evaporated, or contained in the ZIS type material, or both. Vacuum evaporation apparatus of many types useful in the practice of the invention are known in the art. Other methods of delivery, such as sputtering, or application of a thiourea solution, may be substituted for evaporation.

Method of junction formation for CIGS photovoltaic devices

DOEpatents

Delahoy, Alan E.

2010-01-26

Sulfur is used to improve the performance of CIGS devices prepared by the evaporation of a single source ZIS type compound to form a buffer layer on the CIGS. The sulfur may be evaporated, or contained in the ZIS type material, or both. Vacuum evaporation apparatus of many types useful in the practice of the invention are known in the art. Other methods of delivery, such as sputtering, or application of a thiourea solution, may be substituted for evaporation.

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

Influence of liquid medium and surface morphology on the response of QCM during immobilization and hybridization of short oligonucleotides.

PubMed

Ha, Tai Hwan; Kim, Sunhee; Lim, Geunbae; Kim, Kwan

2004-09-15

With the goal of developing a quartz crystal microbalance (QCM)-based DNA sensor, we have conducted an in situ QCM study along with fluorescence measurements using oligonucleotides (15-mer) as a model single-stranded DNA (ss-DNA) in two different aqueous buffer solutions; the sequence of 15-mer is a part of iduronate-2-sulphate exon whose mutation is known to cause Hunter syndrome, and the 15-mer is thiolated to be immobilized on the Au-coated quartz substrate. The fluorescence data indicate that the initial immobilization as well as the subsequent hybridization with a complementary strand is hardly dependent on the kind of buffer solution. In contrast, the mass increases deducible from the decrease of QCM frequency via the Sauerbrey equation are 2.7-6.2 and 3.0-4.4 times larger than the actual mass increases, as reflected in the fluorescence measurements, for the immobilization and the subsequent hybridization processes, respectively. Such an overestimation is attributed to the trapping of solvent as well as the formation of quite a rigid hydration layer associated with the higher viscosities and/or densities of the buffer solutions. Another noteworthy observation is the excessively large frequency change that occurs when the gold electrode is deposited in advance with Au nanoparticles. This clearly illustrates that the QCM detection of DNA hybridization is also affected greatly by the surface morphology of the electrode. These enlarged signals are altogether presumed to be advantageous when using a QCM system as an in situ probing device in DNA sensors.

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.

Combined Microfluidic-Eectric Diffused Mixing of Living Cells in Continuous Flow

NASA Astrophysics Data System (ADS)

Ming-Wen Wang,

2010-02-01

The mixing process is a crucially important stage in the operation of biological and chemical microfluidic devices. If the mixing is inadequate, reactants do not fully interact with each other, and the device may not operate properly. This paper describes a simplified microfluidic mixer (different from a chaotic mixer) which can uniformly mix a buffer solution with living cells by applying an AC electric charge. Diffusion of the living cells into the buffer solution occurs rapidly following the interface of the flow stream with the electric charge; no further agitating step is needed. To accomplish this, an asymmetric pair of electrodes was integrated at the inlets of the buffer solution and the cells fluid. When the buffer solution and the cells fluid were introduced into one flow path, they remained limited to that flow stream. When the electrodes were charged, however, the cells in a short distance were efficiently moved into the solution flow, and the original fluids were mixed. The mixing efficiency depends on the polarizability of the cells, and this in turn is governed by the dielectric properties of the cells, the medium, and the solvent. This micro device, capable of efficiently mixing living cells with a buffer solution, may potentially allow biological mixing to be done outside of hospitals, in facilities without biological analyzing instruments.

Ru(II)-polypyridyl surface functionalised gold nanoparticles as DNA targeting supramolecular structures and luminescent cellular imaging agents.

PubMed

Martínez-Calvo, Miguel; Orange, Kim N; Elmes, Robert B P; la Cour Poulsen, Bjørn; Williams, D Clive; Gunnlaugsson, Thorfinnur

2016-01-07

The development of Ru(II) functionalized gold nanoparticles 1–3·AuNP is described. These systems were found to be mono-disperse with a hydrodynamic radius of ca. 15 nm in water but gave rise to the formation of higher order structures in buffered solution. The interaction of 1–3·AuNP with DNA was also studied by spectroscopic and microscopic methods and suggested the formation of large self-assembly structures in solution. The uptake of 1–3·AuNP by cancer cells was studied using both confocal fluorescence as well as transmission electron microscopy (TEM), with the aim of investigating their potential as tools for cellular biology. These systems displaying a non-toxic profile with favourable photophysical properties may have application across various biological fields including diagnostics and therapeutics.

Redox buffered hydrofluoric acid etchant for the reduction of galvanic attack during release etching of MEMS devices having noble material films

DOEpatents

Hankins, Matthew G [Albuquerque, NM

2009-10-06

Etchant solutions comprising a redox buffer can be used during the release etch step to reduce damage to the structural layers of a MEMS device that has noble material films. A preferred redox buffer comprises a soluble thiophosphoric acid, ester, or salt that maintains the electrochemical potential of the etchant solution at a level that prevents oxidation of the structural material. Therefore, the redox buffer preferentially oxidizes in place of the structural material. The sacrificial redox buffer thereby protects the exposed structural layers while permitting the dissolution of sacrificial oxide layers during the release etch.

An evaluation of MES (2(N-Morpholino)ethanesulfonic acid) and Amberlite IRC-50 as pH buffers for nutrient solution studies

NASA Technical Reports Server (NTRS)

Bugbee, B. G.; Salisbury, F. B.

1985-01-01

All buffering agents used to stabilize pH in hydroponic research have disadvantages. Inorganic buffers are absorbed and may become phytotoxic. Solid carbonate salts temporarily mitigate decreasing pH but provide almost no protection against increasing pH, and they alter nutrient absorption. Exchange resins are more effective, but we find that they remove magnesium and manganese from solution. We have tested 2(N-Morpholino)ethanesulfonic acid (MES) as a buffering agent at concentrations of 1 and 10 mol m-3 (1 and 10 mM) with beans, corn, lettuce, tomatoes, and wheat. MES appears to be biologically inert and does not interact significantly with other solution ions. Relative growth rates among controls and MES treatments were nearly identical for each species during the trial period. The pH was stabilized by 1 mol m-3 MES. This buffer warrants further consideration in nutrient research.

The Determination of the pH of Standard Buffer Solution: A Laboratory Experiment.

ERIC Educational Resources Information Center

Harris, K. R.

1985-01-01

Describes an experiment which shows: (1) how measurements of the reaction electromotive force for the cell (Pt/glass/NaCl(aq,m),buffer/AgCl/Ag/Pt) can be utilized in determining the absolute pH of the buffer; and (2) the demonstration of the use of the Debye-Huckel model of an electrolyte solution in solving an important electrochemical problem.…

Characterization of solution-phase and gas-phase reactions in on-line electrochemistry-thermospray tandem mass spectrometry.

PubMed

Volk, K J; Yost, R A; Brajter-Toth, A

1989-07-14

Electrochemistry was used on-line with high-performance liquid chromatography-thermospray tandem mass spectrometry to provide insight into the solution-phase decomposition reactions of electrochemically generated oxidation products. Products formed during electrooxidation were monitored as the electrode potential was varied. The solution reactions which follow the initial electron transfer at the electrode are affected by the vaporizer tip temperature of the thermospray probe and the composition of the thermospray buffer. Either hydrolysis or ammonolysis reactions of the initial electrochemical oxidation products can occur with pH 7 ammonium acetate buffer. Both the electrochemically generated and the synthesized disulfide of 6-thiopurine decompose under thermospray conditions to produce 6-thiopurine and purine-6-sulfinate. Solution-phase studies indicate that nucleophilic and electrophilic substitution reactions with purine-6-sulfinate result in the formation of purine, adenine, and hypoxanthine. Products were identified and characterized by tandem mass spectrometry. This work shows the first example of high-performance liquid chromatography used on-line with electrochemistry to separate stable oxidation products prior to analysis by thermospray tandem mass spectrometry. In addition, solution-phase and gas-phase studies with methylamine show that the site of the nucleophilic and electrophilic reactions is probably inside the thermospray probe. Most importantly, these results also show that the on-line combination of electrochemistry with thermospray tandem mass spectrometry provides valuable information about redox and associated chemical reactions of biological molecules such as the structures of intermediates or products as well as providing insight into reaction pathways.

Improved interface growth and enhanced flux pinning in YBCO films deposited on an advanced IBAD-MgO based template

NASA Astrophysics Data System (ADS)

Khan, M. Z.; Zhao, Y.; Wu, X.; Malmivirta, M.; Huhtinen, H.; Paturi, P.

2018-02-01

The growth mechanism is studied from the flux pinning point of view in small-scale YBa2Cu3O6+x (YBCO) thin films deposited on a polycrystalline hastelloy with advanced IBAD-MgO based buffer layer architecture. When compared the situation with YBCO films grown on single crystal substrates, the most critical issues that affect the suitable defect formation and thus the optimal vortex pinning landscape, have been studied as a function of the growth temperature and the film thickness evolution. We can conclude that the best critical current property in a wide applied magnetic field range is observed in films grown at relatively low temperature and having intermediate thickness. These phenomena are linked to the combination of the improved interface growth, to the film thickness related crystalline relaxation and to the formation of linear array of edge dislocations that forms the low-angle grain boundaries through the entire film thickness and thus improve the vortex pinning properties. Hence, the optimized buffer layer structure proved to be particularly suitable for new coated conductor solutions.

[Involvement of carbonate/bicarbonate ions in the superoxide-generating reaction of adrenaline autoxidation].

PubMed

Sirota, T V

2015-01-01

An important role of carbonate/bicarbonate ions has been recognized in the superoxide generating reaction of adrenaline autooxidation in an alkaline buffer (a model of quinoid adrenaline oxidation in the body). It is suggested that these ions are directly involved not only in formation of superoxide anion radical (О(2)(-)) but also other radicals derived from the carbonate/bicarbonate buffer. Using various buffers it was shown that the rate of accumulation of adrenochrome, the end product of adrenaline oxidation, and the rate of О(2)(-)· formation depend on concentration of carbonate/bicarbonate ions in the buffer and that these ions significantly accelerate adrenaline autooxidation thus demonstrating prooxidant properties. The detectable amount of diformazan, the product of nitro blue tetrazolium (NBT) reduction, was significantly higher than the amount of adrenochrome formed; taking into consideration the literature data on О(2)(-)· detection by NBT it is suggested that adrenaline autooxidation is accompanied by one-electron reduction not only of oxygen dissolved in the buffer and responsible for superoxide formation but possible carbon dioxide also dissolved in the buffer as well as carbonate/bicarbonate buffer components leading to formation of corresponding radicals. The plots of the dependence of the inhibition of adrenochrome and diformazan formation on the superoxide dismutase concentration have shown that not only superoxide radicals are formed during adrenaline autooxidation. Since carbonate/bicarbonate ions are known to be universally present in the living nature, their involvement in free radical processes proceeding in the organism is discussed.

Single tag for total carbohydrate analysis.

PubMed

Anumula, Kalyan Rao

2014-07-15

Anthranilic acid (2-aminobenzoic acid, 2-AA) has the remarkable property of reacting rapidly with every type of reducing carbohydrate. Reactivity of 2-AA with carbohydrates in aqueous solutions surpasses all other tags reported to date. This unique capability is attributed to the strategically located -COOH which accelerates Schiff base formation. Monosaccharides, oligosaccharides (N-, O-, and lipid linked and glycans in secretory fluids), glycosaminoglycans, and polysaccharides can be easily labeled with 2-AA. With 2-AA, labeling is simple in aqueous solutions containing proteins, peptides, buffer salts, and other ingredients (e.g., PNGase F, glycosidase, and transferase reaction mixtures). In contrast, other tags require relatively pure glycans for labeling in anhydrous dimethyl sulfoxide-acetic acid medium. Acidic conditions are known to cause desialylation, thus requiring a great deal of attention to sample preparation. Simpler labeling is achieved with 2-AA within 30-60 min in mild acetate-borate buffered solution. 2-AA provides the highest sensitivity and resolution in chromatographic methods for carbohydrate analysis in a simple manner. Additionally, 2-AA is uniquely qualified for quantitative analysis by mass spectrometry in the negative mode. Analyses of 2-AA-labeled carbohydrates by electrophoresis and other techniques have been reported. Examples cited here demonstrate that 2-AA is the universal tag for total carbohydrate analysis. Copyright © 2014 Elsevier Inc. All rights reserved.

The effects of biological buffers TRIS, TAPS, TES on the stability of lysozyme.

PubMed

Pannuru, Pavani; Rani, Anjeeta; Venkatesu, Pannuru; Lee, Ming-Jer

2018-06-01

To explore the mechanism of lysozyme stabilization in buffer system, we have investigated the interactions between lysozyme and the biological buffers (TRIS, TAPS, and TES) using spectroscopic techniques, including ultraviolet-visible (UV-Vis), fluorescence, thermal fluorescence, dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) spectroscopy. From the series of spectroscopic studies, it is found that the native structure of the protein remains intact in the different concentrations (0.05, 0.1, 0.25, 0.5, and 1.0M) of the biological buffer aqueous solutions at pH7.0. Moreover, all these three investigated buffers are able to protect lysozyme against thermal denaturation, particularly in high concentration (1.0M) of the buffer aqueous solutions. Copyright © 2018 Elsevier B.V. All rights reserved.

A study of different buffers to maximize viability of an oral Shigella vaccine.

PubMed

Chandrasekaran, Lakshmi; Lal, Manjari; Van De Verg, Lillian L; Venkatesan, Malabi M

2015-11-17

Live, whole cell killed and subunit vaccines are being developed for diarrheal diseases caused by V. cholerae, Shigella species, ETEC, and Campylobacter. Some of these vaccines can be administered orally since this route best mimics natural infection. Live vaccines administered orally have to be protected from the harsh acidic gastric environment. Milk and bicarbonate solutions have been administered to neutralize the stomach acid. For many Shigella vaccine trials, 100-120 ml of a bicarbonate solution is ingested followed by the live vaccine candidate, which is delivered in 30 ml of bicarbonate, water or saline. It is not clear if maximum bacterial viability is achieved under these conditions. Also, volumes of neutralizing buffer that are optimal for adults may be unsuitable for children and infants. To address these questions, we performed studies to determine the viability and stability of a Shigella sonnei vaccine candidate, WRSS1, in a mixture of different volumes of five different buffer solutions added to hydrochloric acid to simulate gastric acidity. Among the buffers tested, bicarbonate solution, rotavirus buffer and CeraVacx were better at neutralizing acid and maintaining the viability of WRSS1. Also, a much smaller volume of the neutralizing buffer was sufficient to counteract stomach acid while maintaining bacterial viability. Published by Elsevier Ltd.

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.

THE KINETICS OF SAPONIFICATION OF IODOACETIC ACID BY SODIUM HYDROXIDE AND BY CERTAIN ALKALINE BUFFER SOLUTIONS.

PubMed

Brdicka, R

1936-07-20

1. The rate of the saponification of iodoacetic acid in sodium hydroxide and alkaline buffer solutions yielding glycollic acid was measured by means of Heyrovský's polarographic method. 2. From the bimolecular velocity constants, increasing with the ionic strength of the solution, the Brönsted factor, F, which characterizes the primary salt effect, was calculated. 3. In the borate buffer solutions the monomolecular constants of the saponification were determined which, at values above the pH of neutralization of boric acid, show a proportionality to the concentration of hydroxyl anions. Below the pH of neutralization of boric acid, they are proportional to the concentration of borate anions.

Formation and Properties of Multilayer Films Based on Polyethyleneimine and Bovine Serum Albumin

NASA Astrophysics Data System (ADS)

Kulikouskaya, V. I.; Lazouskaya, M. E.; Kraskouski, A. N.; Agabekov, V. E.

2018-01-01

(Polyethyleneimine/bovine serum albumin) n ((PEI/BSA) n) multilayer films ( n = 1-10) are produced via the layer-by-later deposition of polyelectrolytes. It is shown that thickness and morphology of the formed coatings can be controlled by varying the solution's ionic strength during alternating adsorption of the components. (PEI/BSA)10 multilayer systems that contain up to 0.6 mg of antiseptic miramistin per 1 cm2 of film were created. It is established that the kinetics of miramistin release from (PEI/BSA)10 films in phosphate buffers and physiological solutions obey the Korsmeyer-Peppas equation with a high degree of accuracy ( R 2 > 0.95).

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.

Acid neutralizing processes in an alpine watershed front range, Colorado, U.S.A.-1: Buffering capacity of dissolved organic carbon in soil solutions

USGS Publications Warehouse

Iggy, Litaor M.; Thurman, E.M.

1988-01-01

Soil interstitial waters in the Green Lakes Valley, Front Range, Colorado were studied to evaluate the capacity of the soil system to buffer acid deposition. In order to determine the contribution of humic substances to the buffering capacity of a given soil, dissolved organic carbon (DOC) and pH of the soil solutions were measured. The concentration of the organic anion, Ai-, derived from DOC at sample pH and the concentration of organic anion, Ax- at the equivalence point were calculated using carboxyl contents from isolated and purified humic material from soil solutions. Subtracting Ax- from Ai- yields the contribution of humic substances to the buffering capacity (Aequiv.-). Using this method, one can evaluate the relative contribution of inorganic and organic constituents to the acid neutralizing capacity (ANC) of the soil solutions. The relative contribution of organic acids to the overall ANC was found to be extremely important in the alpine wetland (52%) and the forest-tundra ecotone (40%), and somewhat less important in the alpine tundra sites (20%). A failure to recognize the importance of organic acids in soil solutions to the ANC will result in erroneous estimates of the buffering capacity in the alpine environment of the Front Range, Colorado. ?? 1988.

In vitro formation and thermal transition of novel hybrid fibrils from type I fish scale collagen and type I porcine collagen

NASA Astrophysics Data System (ADS)

Chen, Song; Ikoma, Toshiyuki; Ogawa, Nobuhiro; Migita, Satoshi; Kobayashi, Hisatoshi; Hanagata, Nobutaka

2010-06-01

Novel type I collagen hybrid fibrils were fabricated by neutralizing a mixture of type I fish scale collagen solution and type I porcine collagen solution with a phosphate buffer saline at 28 °C. Their structure was discussed in terms of the volume ratio of fish/porcine collagen solution. Scanning electron and atomic force micrographs showed that the diameter of collagen fibrils derived from the collagen mixture was larger than those derived from each collagen, and all resultant fibrils exhibited a typical D-periodic unit of ~67 nm, irrespective of volume ratio of both collagens. Differential scanning calorimetry revealed only one endothermic peak for the fibrils derived from collagen mixture or from each collagen solution, indicating that the resultant collagen fibrils were hybrids of type I fish scale collagen and type I porcine collagen.

Aluminum Coprecipitates with Fe (hydr)oxides: Does Isomorphous Substitution of Al3plus for Fe3plus in Goethite Occur

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

E Bazilevskaya; D Archibald; M Aryanpour

2011-12-31

Iron (hydr)oxides are common in natural environments and typically contain large amounts of impurities, presumably the result of coprecipitation processes. Coprecipitation of Al with Fe (hydr)oxides occurs, for example, during alternating reduction-oxidation cycles that promote dissolution of Fe from Fe-containing phases and its re-precipitation as Fe-Al (hydr)oxides. We used chemical and spectroscopic analyses to study the formation and transformation of Al coprecipitates with Fe (hydr)oxides. In addition, periodic density functional theory (DFT) computations were performed to assess the structural and energetic effects of isolated or clustered Al atoms at 8 and 25 mol% Al substitution in the goethite structure. Coprecipitatesmore » were synthesized by raising the pH of dilute homogeneous solutions containing a range of Fe and Al concentrations (100% Fe to 100% Al) to 5. The formation of ferrihydrite in initial suspensions with {<=}20 mol% Al, and of ferrihydrite and gibbsite in initial suspensions with {>=}25 mol% Al was confirmed by infrared spectroscopic and synchrotron-based X-ray diffraction analyses. While base titrations showed a buffer region that corresponded to the hydrolysis of Fe in initial solutions with {<=}25 mol% Al, all of the Al present in these solutions was retained by the solid phases at pH 5, thus indicating Al coprecipitation with the primary Fe hydroxide precipitate. In contrast, two buffer regions were observed in solutions with 30 mol% Al (at pH {approx}2.25 for Fe{sup 3+} and at pH {approx}4 for Al{sup 3+}), suggesting the formation of Fe and Al (hydr)oxides as two separate phases. The Al content of initial coprecipitates influenced the extent of ferrihydrite transformation and of its transformation products as indicated by the presence of goethite, hematite and/or ferrihydrite in aged suspensions. DFT experiments showed that: (i) optimized unit cell parameters for Al-substituted goethites (8 and 25 Mol% Al) in clustered arrangement (i.e., the formation of diaspore-like clusters) were in good agreement with available experimental data whereas optimized unit cell parameters for isolated Al atoms were not, and (ii) Al-substituted goethites with Al in diaspore-like clusters resulted in more energetically favored structures. Combined experimental and DFT results are consistent with the coprecipitation of Al with Fe (hydr)oxides and with the formation of diaspore-like clusters, whereas DFT results suggest isomorphous Al for Fe substitution within goethite is unlike at 8 mol% Al substitution.« less

Sensitive determination of cadmium using solidified floating organic drop microextraction-slotted quartz tube-flame atomic absorption spectroscopy.

PubMed

Akkaya, Erhan; Chormey, Dotse Selali; Bakırdere, Sezgin

2017-09-20

In this study, solidified floating organic drop microextraction (SFODME) by 1-undecanol was combined with slotted quartz tube flame atomic absorption spectrometry (SQT-FAAS) for the determination of cadmium at trace levels. Formation of a complex with 4,4'-dimethyl-2,2'-bipyridine facilitated the extraction of cadmium from aqueous solutions. Several chemical variables were optimized in order to obtain high extraction outputs. Parameters such as concentration of the ligand, pH, and amount of buffer solution were optimized to enhance the formation of cadmium complex. The SFODME method was assisted by dispersion of extractor solvent into aqueous solutions using 2-propanol. Under the optimum extraction and instrumental conditions, the limit of detection and limit of quantitation values obtained for cadmium using the combined methods (SFODME-SQT-FAAS) were found to be 0.4 and 1.3 μg L -1 , respectively. Matrix effects on the method were also examined for tap water and wastewater, and spiked recovery results were found to be very satisfactory. Graphical Abstract SFODME-SQT-FAAS system for sensitive determination of cadmium.

Role of block copolymer-micelle nanocomposites in dye-bovine serum albumin binding: a combined experimental and molecular docking study.

PubMed

Manna, Anamika; Chakravorti, Sankar

2013-02-02

The role of a nanocomposite (NC), composed of intercalation of the diblock copolymer polyethylene-b-polyethylene glycol (PE-b-PEG) with the anionic surfactant sodium dodecyl sulphate (SDS), on the binding characteristics of bovine serum albumin (BSA) with a dye (1,8-naphthalimide, NAPMD) compared to the interaction between the same players in aqueous solution has been examined comprehensively in this paper. Static quenching due to complex formation in both NC medium and in buffer solution has been inferred on the basis of considerable changes in the absorption spectra of BSA on addition of NAPMD, of which the interaction is found to be stronger in NC medium. Temperature dependent fluorescence data also confirm an effective static quenching and stronger binding of NAPMD with BSA in NC medium. Peptide chain unfolding and denaturing of BSA in NC medium have been confirmed from steady state and time-resolved emission and circular dichroism data. This exposes both the tyrosine and tryptophan moieties as a unique case. Increased energy transfer between NAPMD and the tryptophan residue in the unfolded form of BSA helps in the appearance of tyrosine fluorescence in NC medium by quenching the tryptophan band. Ionization of the hydroxyl group in the aromatic ring of the tyrosine residue by the PEG group present in the NC medium produces a downshift of the tyrosine fluorescence band. The use of site selective markers confirms that NAPMD is near tryptophan in Sudlow's site I in NC medium and in buffer solution it is away from tryptophan in Sudlow's site II. The theoretical docking studies also vindicate the results of binding of NAPMD with BSA in site I or site II in NC and buffer media, as observed from different emission experiments including the site selective markers study.

Volumetric analysis of formation of the complex of G-quadruplex DNA with hemin using high pressure.

PubMed

Takahashi, Shuntaro; Bhowmik, Sudipta; Sugimoto, Naoki

2017-01-01

DNA guanine-quadruplexes (G-quadruplexes) complexed with the Fe-containing porphyrin, hemin (iron(III)-protoporphyrin IX), can catalyze oxidation reactions. This so-called DNAzyme has been widely used in the field of DNA nanotechnology. To improve DNAzyme properties, we sought to elucidate the interaction mechanism between G-quadruplex DNA and hemin. Here, we performed volumetric analyses of formation of the complex between an oligonucleotide with the sequence of human telomeric DNA (h-telo) and hemin. The G-quadruplex DNA alone and the G-quadruplex DNA-hemin complex were destabilized with increasing pressure in Na + buffer. The pressure required to destabilize the h-telo-hemin complex was less in K + -containing buffer than in buffer with Na + , which indicates that there was a smaller volumetric change upon h-telo formation in K + buffer than in Na + buffer. The calculated change in h-telo-hemin binding volume (∆V b ) in the Na + buffer was 2.5mLmol -1 , whereas it was -41.7 in mLmol -1 the K + buffer. The DNAzyme activity in the K + buffer was higher than that in the Na + buffer at atmospheric pressure. Interestingly, the pressure effect on the destabilization of the h-telo-hemin complex in the presence of poly(ethylene glycol)200 (PEG200) was repressed compared to that in the absence of PEG200. These results suggest that differences in volumetric parameters reflect different mechanisms of interaction between hemin and h-telo due to differences in both the fit of hemin into the h-telo structure and hydration. Thus, the pressure-based thermodynamic analysis provided important information about complex formation and could be a useful index to improve function of DNAzymes. Copyright © 2016 Elsevier Inc. All rights reserved.

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.

Making pH Tangible.

ERIC Educational Resources Information Center

McIntosh, Elizabeth; Moss, Robert

1995-01-01

Presents a laboratory exercise in which students test the pH of different substances, study the effect of a buffer on acidic solutions by comparing the behavior of buffered and unbuffered solutions upon the addition of acid, and compare common over-the-counter antacid remedies. (MKR)

Mass Spectrometry Based Mechanistic Insights into Formation of Tris Conjugates: Implications on Protein Biopharmaceutics

NASA Astrophysics Data System (ADS)

Kabadi, Pradeep G.; Sankaran, Praveen Kallamvalliillam; Palanivelu, Dinesh V.; Adhikary, Laxmi; Khedkar, Anand; Chatterjee, Amarnath

2016-10-01

We present here extensive mass spectrometric studies on the formation of a Tris conjugate with a therapeutic monoclonal antibody. The results not only demonstrate the reactive nature of the Tris molecule but also the sequence and reaction conditions that trigger this reactivity. The results corroborate the fact that proteins are, in general, prone to conjugation and/or adduct formation reactions and any modification due to this essentially leads to formation of impurities in a protein sample. Further, the results demonstrate that the conjugation reaction happens via a succinimide intermediate and has sequence specificity. Additionally, the data presented in this study also shows that the Tris formation is produced in-solution and is not an in-source phenomenon. We believe that the facts given here will open further avenues on exploration of Tris as a conjugating agent as well as ensure that the use of Tris or any ionic buffer in the process of producing a biopharmaceutical drug is monitored closely for the presence of such conjugate formation.

Geochemical evolution of solutions derived from experimental weathering of sulfide-bearing rocks

USGS Publications Warehouse

Munk, L.; Faure, G.; Koski, R.

2006-01-01

The chemical composition of natural waters is affected by the weathering of geologic materials at or near the surface of the Earth. Laboratory weathering experiments of whole-rock sulfide rocks from the Shoe-Basin Mine (SBM) and the Pennsylvania Mine (PM) from the Peru Creek Basin, Summit County, Colorado, indicate that the mineral composition of the sulfide rocks, changes in pH, the duration of the experiment, and the formation of sorbents such as Fe and Al oxyhydroxides affect the chemical composition of the resulting solution. Carbonate minerals in the rock from SBM provide buffering capacity to the solution, contribute to increases in the pH and enhance the formation of Fe and Al oxyhydroxides, which sorb cations from solution. The final solution pH obtained in the experiments was similar to those measured in the field (i.e., 2.8 for PM and 5.0 for SBM). At PM, acidic, metal-rich mine effluent is discharged into Peru Creek where it mixes with stream water. As a result, the pH of the effluent increases causing Fe and Al oxyhydroxide and schwertmannite to precipitate. The resulting solids sorb metal cations from the water thereby improving the quality of the water in Peru Creek. ?? 2006.

Assembly of Modified Ferritin Proteins on Carbon Nanotubes and its Electrocatalytic Activity for Oxygen Reduction

NASA Technical Reports Server (NTRS)

Kim, Jae-Woo; Lillehei, Peter T.; Park, Cheol

2012-01-01

Highly effective dispersions of carbon nanotubes (CNTs) can be made using a commercially available buffer solution. Buffer solutions of 3-(N-morpholino)-propanesulfonic acid (MOPS), which consists of a cyclic ring with nitrogen and oxygen heteroatoms, a charged group, and an alkyl chain greatly enhance the dispersibility and stability of CNTs in aqueous solutions. Additionally, the ability of biomolecules, especially cationized Pt-cored ferritins, to adhere onto the well-dispersed CNTs in the aqueous buffer solution is also improved. This was accomplished without the use of surfactant molecules, which are detrimental to the electrical, mechanical, and other physical properties of the resulting products. The assembled Pt-cored ferritin proteins on the CNTs were used as an electrocatalyst for oxygen reduction

THE KINETICS OF SAPONIFICATION OF IODOACETIC ACID BY SODIUM HYDROXIDE AND BY CERTAIN ALKALINE BUFFER SOLUTIONS

PubMed Central

Brdička, R.

1936-01-01

1. The rate of the saponification of iodoacetic acid in sodium hydroxide and alkaline buffer solutions yielding glycollic acid was measured by means of Heyrovský's polarographic method. 2. From the bimolecular velocity constants, increasing with the ionic strength of the solution, the Brönsted factor, F, which characterizes the primary salt effect, was calculated. 3. In the borate buffer solutions the monomolecular constants of the saponification were determined which, at values above the pH of neutralization of boric acid, show a proportionality to the concentration of hydroxyl anions. Below the pH of neutralization of boric acid, they are proportional to the concentration of borate anions. PMID:19872968

Role of cellular oxalate in oxalate clearance of patients with calcium oxalate monohydrate stone formation and normal controls.

PubMed

Oehlschläger, Sven; Fuessel, Susanne; Meye, Axel; Herrmann, Jana; Froehner, Michael; Albrecht, Steffen; Wirth, Manfred P

2009-03-01

To examine the cellular, plasma, and urinary oxalate and erythrocyte oxalate flux in patients with calcium oxalate monohydrate (COM) stone formation vs normal controls. Pathologic oxalate clearance in humans is mostly integrated in calcium oxalate stone formation. An underlying cause of deficient oxalate clearance could be defective transmembrane oxalate transport, which, in many tissues, is regulated by an anion exchanger (SLC26). We studied 2 groups: 40 normal controls and 41 patients with COM stone formation. Red blood cells were divided for cellular oxalate measurement and for resuspension in a buffered solution (pH 7.40); 0.1 mmol/L oxalate was added. The supernatant was measured for oxalate immediately and 1 hour after incubation. The plasma and urinary oxalate were analyzed in parallel. The mean cellular oxalate concentrations were significantly greater in the normal controls (5.25 +/- 0.47 micromol/L) than in those with COM stone formation (2.36 +/- 0.28 micromol/L; P < .01). The mean urinary oxalate concentrations were significantly greater in those with COM stone formation (0.31 +/- 0.02 mmol/L) than in the controls (0.24 +/- 0.02 mmol/L; P < .01). The cellular oxalate concentrations correlated significantly with the plasma (r = 0.49-0.63; P < .01) and urinary oxalate (r = -0.29-0.41; P < .03) concentrations in both groups. The plasma oxalate concentrations correlated significantly with the urinary oxalate concentrations (r = -0.30; P < .03) in the controls and with the erythrocyte oxalate flux (r = 0.25; P < .05) in those with COM stone formation. Our data implicate the presence of a cellular oxalate buffer to stabilize plasma and urinary oxalate concentrations in normal controls.

Aqueous solution dispersement of carbon nanotubes

NASA Technical Reports Server (NTRS)

Kim, Jae-Woo (Inventor); Park, Cheol (Inventor); Choi, Sang H. (Inventor); Lillehei, Peter T. (Inventor); Harrison, Joycelyn S. (Inventor)

2011-01-01

Carbon nanotubes (CNTs) are dispersed in an aqueous buffer solution consisting of at least 50 weight percent water and a remainder weight percent that includes a buffer material. The buffer material has a molecular structure defined by a first end, a second end, and a middle disposed between the first and second ends. The first end is a cyclic ring with nitrogen and oxygen heteroatomes, the middle is a hydrophobic alkyl chain, and the second end is a charged group.

Investigation of passive films formed on the surface of alloy 690 in borate buffer solution

NASA Astrophysics Data System (ADS)

Jinlong, Lv; Tongxiang, Liang; Chen, Wang; Wenli, Guo

2015-10-01

The passive film formed on the surface of the alloy 690 in borate buffer solution was studied by potentiodynamic curves and electrochemical impedance spectroscopy. With the increasing of the passivation potential, the corrosion resistance of the alloy 690 reduced. Moreover, the corrosion resistance of the passive film was the lowest in the vicinity of 0.6 VSCE. These results were supported by XPS and Mott-Schottky analyses. The corrosion resistance of the alloy 690 increased with the increasing of passivated potential in borate buffer solution with chloride ion. The chloride ion decreased corrosion resistance of the alloy 690 according to point defect model.

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.

Experimental Germ Tube Induction in Candida albicans: An Evaluation of the Effect of Sodium Bicarbonate on Morphogenesis and Comparison with Pooled Human Serum.

PubMed

Matare, Tapiwa; Nziramasanga, Pasipanodya; Gwanzura, Lovemore; Robertson, Valerie

2017-01-01

The potential of NaHCO 3 versus human serum to induce germ tube formation in Candida albicans was investigated. A total of 100 isolates were obtained from oral swabs of patients presenting with thrush. Approval for the study was granted by the Joint Research Ethics Committee (JREC/23/08). Confirmed C. albicans isolates by routine methods were tested for germ tube induction using 5 different concentrations of Tris-maleate buffered NaHCO 3 and Tris-maleate buffer control. Standard control strains included were C. albicans (ATCC 10231) and C. krusei (ATCC 6258). Microculture was done in 20  μ L inoculums on microscope slides for 3 hours at 37°C. The rate of germ tube formation at 10-minute intervals was determined on 100 isolates using the optimum 20 mM Tris-maleate buffered NaHCO 3 concentration. Parallel germ tube formation using human serum was done in test tubes. The optimum concentration of NaHCO 3 in Tris-maleate buffer for germ tube induction was 20 mM for 67% of isolates. Only 21% of isolates formed germ tubes in Tris-maleate buffer control. There was no significant difference in induction between human serum and Tris-maleate buffered NaHCO 3 . Tris-maleate buffered NaHCO 3 induced germ tube formation in C. albicans isolates at rates similar to human serum.

Robust media processing on programmable power-constrained systems

NASA Astrophysics Data System (ADS)

McVeigh, Jeff

2005-03-01

To achieve consumer-level quality, media systems must process continuous streams of audio and video data while maintaining exacting tolerances on sampling rate, jitter, synchronization, and latency. While it is relatively straightforward to design fixed-function hardware implementations to satisfy worst-case conditions, there is a growing trend to utilize programmable multi-tasking solutions for media applications. The flexibility of these systems enables support for multiple current and future media formats, which can reduce design costs and time-to-market. This paper provides practical engineering solutions to achieve robust media processing on such systems, with specific attention given to power-constrained platforms. The techniques covered in this article utilize the fundamental concepts of algorithm and software optimization, software/hardware partitioning, stream buffering, hierarchical prioritization, and system resource and power management. A novel enhancement to dynamically adjust processor voltage and frequency based on buffer fullness to reduce system power consumption is examined in detail. The application of these techniques is provided in a case study of a portable video player implementation based on a general-purpose processor running a non real-time operating system that achieves robust playback of synchronized H.264 video and MP3 audio from local storage and streaming over 802.11.

EQUALIZING THE ELECTRIC FIELD INTENSITY WITHIN CHICK BRAIN IMMERSED IN BUFFER SOLUTION AT DIFFERENT CARRIER FREQUENCIES

EPA Science Inventory

Presented here are the numerical relationships between incident power densities that produce the same average electric field intensity within a chick brain half immersed in buffered saline solution and exposed to a uniform electromagnetic field at carrier frequencies of 50, 147, ...

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

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.

Preparation of cellulose based microspheres by combining spray coagulating with spray drying.

PubMed

Wang, Qiao; Fu, Aiping; Li, Hongliang; Liu, Jingquan; Guo, Peizhi; Zhao, Xiu Song; Xia, Lin Hua

2014-10-13

Porous microspheres of regenerated cellulose with size in range of 1-2 μm and composite microspheres of chitosan coated cellulose with size of 1-3 μm were obtained through a two-step spray-assisted approach. The spray coagulating process must combine with a spray drying step to guarantee the formation of stable microspheres of cellulose. This approach exhibits the following two main virtues. First, the preparation was performed using aqueous solution of cellulose as precursor in the absence of organic solvent and surfactant; Second, neither crosslinking agent nor separated crosslinking process was required for formation of stable microspheres. Moreover, the spray drying step also provided us with the chance to encapsulate guests into the resultant cellulose microspheres. The potential application of the cellulose microspheres acting as drug delivery vector has been studied in two PBS (phosphate-buffered saline) solution with pH values at 4.0 and 7.4 to mimic the environments of stomach and intestine, respectively. Copyright © 2014 Elsevier Ltd. All rights reserved.

Synthesis, characterization, and electrochemical behavior of Au@Pd core shell nanoparticles

NASA Astrophysics Data System (ADS)

Wicaksono, W. P.; Ivandini, T. A.

2017-04-01

Au@Pd core shell nanoparticles (Au@Pd CSNPs) were successfully synthesized using a seed-mediated growth method. Firstly, a pale pink gold seed solution was used to produce a pale purple gold nanoparticles (AuNPs) core solution. Then, three series of Pd shell thickness using 20μ, 100 μL, and 500 μL of PdCl2 produced purple, brown, and deep brown of Au@Pd CSNPs respectively. A strong absorbance UV-Visible spectrum with peaks at 285 nm and 535 nm was identified for AuNPs formation. The disappearance of the peak at 535 nm was indicated the Au@Pd CSNPs formation. The electrochemical properties were examined in phosphate buffer pH 7 using cyclic voltammetry technique with boron-doped diamond (BDD) as working electrode showed a couple oxidation and reduction peak of gold at 0.67 V and at 0.33 V, respectively. The Au@Pd CNPs will be used for modification of BDD electrodes.

Corrosion inhibitor for aqueous ammonia absorption system

DOEpatents

Phillips, Benjamin A.; Whitlow, Eugene P.

1998-09-22

A method of inhibiting corrosion and the formation of hydrogen and thus improving absorption in an ammonia/water absorption refrigeration, air conditioning or heat pump system by maintaining the hydroxyl ion concentration of the aqueous ammonia working fluid within a selected range under anaerobic conditions at temperatures up to 425.degree. F. This hydroxyl ion concentration is maintained by introducing to the aqueous ammonia working fluid an inhibitor in an amount effective to produce a hydroxyl ion concentration corresponding to a normality of the inhibitor relative to the water content ranging from about 0.015 N to about 0.2 N at 25.degree. C. Also, working fluids for inhibiting the corrosion of carbon steel and resulting hydrogen formation and improving absorption in an ammonia/water absorption system under anaerobic conditions at up to 425.degree. F. The working fluids may be aqueous solutions of ammonia and a strong base or aqueous solutions of ammonia, a strong base, and a specified buffer.

Corrosion inhibitor for aqueous ammonia absorption system

DOEpatents

Phillips, B.A.; Whitlow, E.P.

1998-09-22

A method is described for inhibiting corrosion and the formation of hydrogen and thus improving absorption in an ammonia/water absorption refrigeration, air conditioning or heat pump system by maintaining the hydroxyl ion concentration of the aqueous ammonia working fluid within a selected range under anaerobic conditions at temperatures up to 425 F. This hydroxyl ion concentration is maintained by introducing to the aqueous ammonia working fluid an inhibitor in an amount effective to produce a hydroxyl ion concentration corresponding to a normality of the inhibitor relative to the water content ranging from about 0.015 N to about 0.2 N at 25 C. Also, working fluids for inhibiting the corrosion of carbon steel and resulting hydrogen formation and improving absorption in an ammonia/water absorption system under anaerobic conditions at up to 425 F. The working fluids may be aqueous solutions of ammonia and a strong base or aqueous solutions of ammonia, a strong base, and a specified buffer. 5 figs.

Formulation and stability of an extemporaneous 0.02% chlorhexidine digluconate ophthalmic solution.

PubMed

Lin, Shu-Chiao; Huang, Chih-Fen; Shen, Li-Jiuan; Wang, Hsueh-Ju; Lin, Chia-Yu; Wu, Fe-Lin Lin

2015-12-01

Acanthamoeba keratitis is difficult to treat because Acanthamoeba cysts are resistant to the majority of antimicrobial agents. Despite the efficacy of 0.02% chlorhexidine in treating Acanthamoeba keratitis, a lack of data in the literature regarding the formulation's stability limits its clinical use. The objective of this study was to develop an optimal extemporaneous 0.02% chlorhexidine digluconate ophthalmic formulation for patients in need. With available active pharmaceutical ingredients, 0.02% chlorhexidine digluconate sample solutions were prepared by diluting with BSS Plus Solution or acetate buffer. Influences of the buffer, type of container, and temperature under daily-open condition were assessed based on the changes of pH values and chlorhexidine concentrations of the test samples weekly. To determine the beyond-use date, the optimal samples were stored at 2-8°C or room temperature, and analyzed at time 0 and at Week 1, Week 2, Week 3, Week 4, Week 5, Week 8, Week 12, and Week 24. Despite chlorhexidine exhibiting better stability in acetate buffer than in BSS solution, its shelf-life was < 14 days when stored in a light-resistant low-density polyethylene container. The acetate-buffered 0.02% chlorhexidine digluconate solution stored in light-resistant high-density polyethylene eyedroppers did not exhibit significant changes in pH or strength at any time interval. The acetate-buffered 0.02% chlorhexidine digluconate ophthalmic solution stored in light-resistant high-density polyethylene eyedroppers demonstrated excellent stability at 2-25°C for 6 months after being sealed and for 1 month after opening. This finding will enable us to prepare 0.02% chlorhexidine digluconate ophthalmic solutions based on a doctor's prescription. Copyright © 2014. Published by Elsevier B.V.

Optimization of protein solution by a novel experimental design method using thermodynamic properties.

PubMed

Kim, Nam Ah; An, In Bok; Lee, Sang Yeol; Park, Eun-Seok; Jeong, Seong Hoon

2012-09-01

In this study, the structural stability of hen egg white lysozyme in solution at various pH levels and in different types of buffers, including acetate, phosphate, histidine, and Tris, was investigated by means of differential scanning calorimetry (DSC). Reasonable pH values were selected from the buffer ranges and were analyzed statistically through design of experiment (DoE). Four factors were used to characterize the thermograms: calorimetric enthalpy (ΔH), temperature at maximum heat flux (T( m )), van't Hoff enthalpy (ΔH( V )), and apparent activation energy of protein solution (E(app)). It was possible to calculate E(app) through mathematical elaboration from the Lumry-Eyring model by changing the scan rate. The transition temperature of protein solution, T( m ), increased when the scan rate was faster. When comparing the T( m ), ΔH( V ), ΔH, and E(app) of lysozyme in various pH ranges and buffers with different priorities, lysozyme in acetate buffer at pH 4.767 (scenario 9) to pH 4.969 (scenario 11) exhibited the highest thermodynamic stability. Through this experiment, we found a significant difference in the thermal stability of lysozyme in various pH ranges and buffers and also a new approach to investigate the physical stability of protein by DoE.

Physicochemical parameters influencing coaggregation between the freshwater bacteria Sphingomonas natatoria 2.1 and Micrococcus luteus 2.13.

PubMed

Min, K R; Zimmer, M N; Rickard, A H

2010-11-01

The aim of this study was to explore the physicochemical parameters that influence coaggregation between the freshwater bacteria Sphingomonas natatoria 2.1 and Micrococcus luteus 2.13. Using visual coaggregation assays, the effect of different buffers, solutions of differing ionic strength, pH, temperature, and viscosity on the degree of coaggregation was assessed. Coaggregation occurred maximally in distilled water but was inhibited when coaggregates were suspended in a commonly-used oral bacterial coaggregation buffer, saline solutions, and Tris-Cl buffers. Coaggregation was weakly expressed in standard laboratory buffers. The ionic strength of inorganic salt solutions required to inhibit coaggregation depended upon the inorganic salt being tested. Coaggregation occurred at a pH of 3-10, between 5 and 80°C and was inhibited in solutions with a viscosity of 22.5 centipoises at 20°C. Inhibition of coaggregation with NaCl impaired biofilm development. When developing buffers to test for coaggregation, the natural liquid environment should be considered. Coaggregation between S. natatoria 2.1 and M. luteus 2.13 is only affected by physicochemical conditions beyond those typically found in natural freshwater ecosystems. Such a robust ability to coaggregate may enhance the ability of S. natatoria 2.1 and M. luteus 2.13 to develop a niche in freshwater biofilms.

Nonclinical safety evaluation of boric acid and a novel borate-buffered contact lens multi-purpose solution, Biotrue™ multi-purpose solution.

PubMed

Lehmann, David M; Cavet, Megan E; Richardson, Mary E

2010-12-01

Multipurpose solutions (MPS) often contain low concentrations of boric acid as a buffering agent. Limited published literature has suggested that boric acid and borate-buffered MPS may alter the corneal epithelium; an effect attributed to cytotoxicity induced by boric acid. However, this claim has not been substantiated. We investigated the effect of treating cells with relevant concentrations of boric acid using two cytotoxicity assays, and also assessed the impact of boric acid on corneal epithelial barrier function by measuring TEER and immunostaining for tight junction protein ZO-1 in human corneal epithelial cells. Boric acid was also assessed in an in vivo ocular model when administered for 28 days. Additionally, we evaluated Biotrue multi-purpose solution, a novel borate-buffered MPS, alone and with contact lenses for ocular compatibility in vitro and in vivo. Boric acid passed both cytotoxicity assays and did not alter ZO-1 distribution or corneal TEER. Furthermore, boric acid was well-tolerated on-eye following repeated administration in a rabbit model. Finally, Biotrue multi-purpose solution demonstrated good ocular biocompatibility both in vitro and in vivo. This MPS was not cytotoxic and was compatible with the eye when administered alone and when evaluated with contact lenses. We demonstrate that boric acid and a borate-buffered MPS is compatible with the ocular environment. Our findings provide evidence that ocular effects reported for some borate-buffered MPS may be incorrectly attributed to boric acid and are more likely a function of the unique combination of ingredients in the MPS formulation tested. Copyright © 2010 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

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.

40 CFR 63.9804 - What are my monitoring system installation, operation, and maintenance requirements?

Code of Federal Regulations, 2014 CFR

2014-07-01

... accuracy that is traceable to National Institute of Standards and Technology (NIST) standards. (ii) The... section. (i) Perform a single-point calibration using an NIST-certified buffer solution that is accurate... include a redundant pH sensor, perform a single point calibration using an NIST-certified buffer solution...

40 CFR 63.9804 - What are my monitoring system installation, operation, and maintenance requirements?

Code of Federal Regulations, 2013 CFR

2013-07-01

... accuracy that is traceable to National Institute of Standards and Technology (NIST) standards. (ii) The... section. (i) Perform a single-point calibration using an NIST-certified buffer solution that is accurate... include a redundant pH sensor, perform a single point calibration using an NIST-certified buffer solution...

A Pollutant Transformation Laboratory Exercise for Environmental Chemistry: The Reduction of Nitrobenzenes by Anaerobic Solutions of Humic Acid

ERIC Educational Resources Information Center

Dunnivant, Frank M.; Reynolds, Mark-Cody

2007-01-01

The laboratory experiment, which acts as a capstone, integrated lecture-laboratory exercise involving solution preparation, pH buffers, [E[subscript]H] (reduction potential) buffers, organic reaction mechanisms, reaction kinetics, and instrumental analysis is presented. The students completing the lecture and laboratory exercises could gain a…

Coefficient of Friction of Human Corneal Tissue.

PubMed

Wilson, Tawnya; Aeschlimann, Rudolf; Tosatti, Samuele; Toubouti, Youssef; Kakkassery, Joseph; Osborn Lorenz, Katherine

2015-09-01

A novel property evaluation methodology was used to determine the elusive value for the human corneal coefficient of friction (CoF). Using a microtribometer on 28 fresh human donor corneas with intact epithelia, the CoF was determined in 4 test solutions (≥5 corneas/solution): tear-mimicking solution (TMS) in borate-buffered saline (TMS-PS), TMS in phosphate-buffered saline (TMS-PBS), TMS with HEPES-buffered saline (TMS-HEPES), and tear-like fluid in PBS (TLF-PBS). Mean (SD) CoF values ranged from 0.006 to 0.015 and were 0.013 (0.010) in TMS-PS, 0.006 (0.003) in TMS-PBS, 0.014 (0.005) in TMS-HEPES, and 0.015 (0.009) in TLF-PBS. Statistically significant differences were shown for TMS-PBS versus TLF (P = 0.0424) and TMS-PBS versus TMS-HEPES (P = 0.0179), but not for TMS-PBS versus TMS-PS (P = 0.2389). Successful measurement of the fresh human corneal tissue CoF was demonstrated, with values differing in the evaluated buffer solutions, within this limited sample size.

Pyrroloquinoline quinone (PQQ) is reduced to pyrroloquinoline quinol (PQQH2) by vitamin C, and PQQH2 produced is recycled to PQQ by air oxidation in buffer solution at pH 7.4.

PubMed

Mukai, Kazuo; Ouchi, Aya; Nagaoka, Shin-ichi; Nakano, Masahiko; Ikemoto, Kazuto

2016-01-01

Measurements of the reaction of sodium salt of pyrroloquinoline quinone (PQQNa2) with vitamin C (Vit C) were performed in phosphate-buffered solution (pH 7.4) at 25 °C under nitrogen atmosphere, using UV-vis spectrophotometry. The absorption spectrum of PQQNa2 decreased in intensity due to the reaction with Vit C and was changed to that of pyrroloquinoline quinol (PQQH2, a reduced form of PQQ). One molecule of PQQ was reduced by two molecules of Vit C producing a molecule of PQQH2 in the buffer solution. PQQH2, thus produced, was recycled to PQQ due to air oxidation. PQQ and Vit C coexist in many biological systems, such as vegetables, fruits, as well as in human tissues. The results obtained suggest that PQQ is reduced by Vit C and functions as an antioxidant in biological systems, because it has been reported that PQQH2 shows very high free-radical scavenging and singlet-oxygen quenching activities in buffer solutions.

Direct Deposition of Gas Phase Generated Aerosol Gold Nanoparticles into Biological Fluids - Corona Formation and Particle Size Shifts

PubMed Central

Svensson, Christian R.; Messing, Maria E.; Lundqvist, Martin; Schollin, Alexander; Deppert, Knut; Pagels, Joakim H.; Rissler, Jenny; Cedervall, Tommy

2013-01-01

An ongoing discussion whether traditional toxicological methods are sufficient to evaluate the risks associated with nanoparticle inhalation has led to the emergence of Air-Liquid interface toxicology. As a step in this process, this study explores the evolution of particle characteristics as they move from the airborne state into physiological solution. Airborne gold nanoparticles (AuNP) are generated using an evaporation-condensation technique. Spherical and agglomerate AuNPs are deposited into physiological solutions of increasing biological complexity. The AuNP size is characterized in air as mobility diameter and in liquid as hydrodynamic diameter. AuNP:Protein aggregation in physiological solutions is determined using dynamic light scattering, particle tracking analysis, and UV absorption spectroscopy. AuNPs deposited into homocysteine buffer form large gold-aggregates. Spherical AuNPs deposited in solutions of albumin were trapped at the Air-Liquid interface but was readily suspended in the solutions with a size close to that of the airborne particles, indicating that AuNP:Protein complex formation is promoted. Deposition into serum and lung fluid resulted in larger complexes, reflecting the formation of a more complex protein corona. UV absorption spectroscopy indicated no further aggregation of the AuNPs after deposition in solution. The corona of the deposited AuNPs shows differences compared to AuNPs generated in suspension. Deposition of AuNPs from the aerosol phase into biological fluids offers a method to study the protein corona formed, upon inhalation and deposition in the lungs in a more realistic way compared to particle liquid suspensions. This is important since the protein corona together with key particle properties (e.g. size, shape and surface reactivity) to a large extent may determine the nanoparticle effects and possible translocation to other organs. PMID:24086363

Coassembly of Lysozyme and Amphiphilic Biomolecules Driven by Unimer-Aggregate Equilibrium.

PubMed

Tao, Yuanyuan; Ma, Xiaoteng; Cai, Yaqian; Liu, Li; Zhao, Hanying

2018-04-12

Synthesis and self-assembly of bioconjugates composed of proteins and synthetic molecules have been widely studied because of the potential applications in medicine, biotechnology, and nanotechnology. One of the challenging research studies in this area is to develop organic solvent-free approaches to the synthesis and self-assembly of amphiphilic bioconjugates. In this research, dialysis-assisted approach, a method based on unimer-aggregate equilibrium, was applied in the coassembly of lysozyme and conjugate of cholesterol and glutathione (Ch-GSH). In phosphate buffer solution, amphiphilic Ch-GSH conjugate self-assembles into vesicles, and the vesicle solution is dialyzed against lysozyme solution. Negatively charged Ch-GSH unimers produced in the unimer-vesicle exchange equilibrium, diffuse across the dialysis membrane and have electrostatic interaction with positively charged lysozyme, resulting in the formation of Ch-GSH-lysozyme bioconjugate. Above a critical concentration, the three-component bioconjugate molecules self-assemble into bioactive vesicles.

Electrochemical studies on zirconium and its biocompatible alloys Ti-50Zr at.% and Zr-2.5Nb wt.% in simulated physiologic media.

PubMed

Oliveira, Nilson T C; Biaggio, Sonia R; Rocha-Filho, Romeu C; Bocchi, Nerilso

2005-09-01

Different electrochemical studies were carried out for Zr and its biocompatible alloys Ti-50Zr at.% and Zr-2.5Nb wt.% in solutions simulating physiologic media, Ringer and PBS (phosphate buffered saline) solutions. The results from rest-potential measurements showed that the three materials are spontaneously passivated in both solutions and that the Ti-50Zr alloy has the greatest tendency for spontaneous oxide formation. Some corrosion parameters (such as the pitting and repassivation potentials) were obtained via cyclic voltammetry in both solutions, revealing that the Ti-50Zr has the best corrosion protection while Zr has the worst. On the other hand, the pre-anodization (up to 8 V vs. SCE) of the alloys in a 0.15 mol/L Na2SO4 solution led to a significant improvement in their protection against pitting corrosion when exposed to the Ringer solution. Elemental analyses by EDX showed that during pitting corrosion, there is no preferential corrosion of any of the alloying elements (Zr, Ti, Nb). Copyright (c) 2005 Wiley Periodicals, Inc.

In Vitro and in Vivo Evaluation of Native Glucagon and Glucagon Analog (MAR-D28) during Aging: Lack of Cytotoxicity and Preservation of Hyperglycemic Effect

PubMed Central

Ward, W Kenneth; Massoud, Ryan G; Szybala, Cory J; Engle, Julia M; El Youssef, Joseph; Carroll, Julie M; Roberts, Charles T; DiMarchi, Richard D

2010-01-01

Background For automated prevention of hypoglycemia, there is a need for glucagon (or an analog) to be sufficiently stable so that it can be indwelled in a portable pump for at least 3 days. However, under some conditions, solutions of glucagon can form amyloid fibrils. Currently, the usage instructions for commercially available glucagon allow only for its immediate use. Methods In NIH 3T3 fibroblasts, we tested amyloid formation and cytotoxicity of solutions of native glucagon and the glucagon analog MAR-D28 after aging under different conditions for 5 days. In addition, aged native glucagon was subjected to size-exclusion chromatography (SEC). We also studied whether subcutaneous aged Novo Nordisk GlucaGen® would have normal bioactivity in octreotide-treated, anesthetized, nondiabetic pigs. Results We found no evidence of cytotoxicity from native glucagon or MAR-D28 (up to 2.5 mg/ml) at a pH of 10 in a glycine solvent. We found a mild cytotoxicity for both compounds in Tris buffer at pH 8.5. A high concentration of the commercial glucagon preparation (GlucaGen) caused marked cytotoxicity, but low pH and/or a high osmolarity probably accounted primarily for this effect. With SEC, the decline in monomeric glucagon over time was much lower when aged in glycine (pH 10) than when aged in Tris (pH 8.5) or in citrate (pH 3). Congo red staining for amyloid was very low with the glycine preparation (pH 10). In the pig studies, the hyperglycemic effect of commercially available glucagon was preserved despite aging conditions associated with marked amyloid formation. Conclusions Under certain conditions, aqueous solutions of glucagon and MAR-D28 are stable for at least 5 days and are thus very likely to be safe in mammals. Glycine buffer at a pH of 10 appears to be optimal for avoiding cytotoxicity and amyloid fibril formation. PMID:21129325

Crystallization of calcium oxalate dihydrate in a buffered calcium-containing glucose solution by irradiation with non-equilibrium atmospheric pressure plasma

NASA Astrophysics Data System (ADS)

Kurake, Naoyuki; Tanaka, Hiromasa; Ishikawa, Kenji; Nakamura, Kae; Kajiyama, Hiroaki; Kikkawa, Fumitaka; Mizuno, Masaaki; Ikehara, Yuzuru; Hori, Masaru

2017-10-01

Oxalate was synthesized in the glucose solution by irradiation with non-equilibrium atmospheric pressure plasma (NEAPP), in which the NEAPP plume contacted the solution surface, via the generation of several intermediate organic products such as gluconic acid. A thermodynamically unstable phase of calcium oxalate dihydrate crystallized rapidly during incubation of a NEAPP-irradiated glucose solution that contained calcium ions and was buffered at neutral pH. Longer irradiation times increased the growth rate and the number of seed crystals.

Effects of hypertonic buffer composition on lymph node uptake and bioavailability of rituximab, after subcutaneous administration.

PubMed

Fathallah, Anas M; Turner, Michael R; Mager, Donald E; Balu-Iyer, Sathy V

2015-03-01

The subcutaneous administration of biologics is highly desirable; however, incomplete bioavailability after s.c. administration remains a major challenge. In this work we investigated the effects of excipient dependent hyperosmolarity on lymphatic uptake and plasma exposure of rituximab as a model protein. Using Swiss Webster (SW) mice as the animal model, we compared the effects of NaCl, mannitol and O-phospho-L-serine (OPLS) on the plasma concentration of rituximab over 5 days after s.c. administration. An increase was observed in plasma concentrations in animals administered rituximab in hypertonic buffer solutions, compared with isotonic buffer. Bioavailability, as estimated by our pharmacokinetic model, increased from 29% in isotonic buffer to 54% in hypertonic buffer containing NaCl, to almost complete bioavailability in hypertonic buffers containing high dose OPLS or mannitol. This improvement in plasma exposure is due to the improved lymphatic trafficking as evident from the increase in the fraction of dose trafficked through the lymph nodes in the presence of hypertonic buffers. The fraction of the dose trafficked through the lymphatics, as estimated by the model, increased from 0.05% in isotonic buffer to 13% in hypertonic buffer containing NaCl to about 30% for hypertonic buffers containing high dose OPLS and mannitol. The data suggest that hypertonic solutions may be a viable option for improving s.c. bioavailability. Copyright © 2014 John Wiley & Sons, Ltd.

Effects of hypertonic buffer composition on lymph node uptake and bioavailability of rituximab, after subcutaneous administration

PubMed Central

Fathallah, Anas M.; Turner, Michael R.; Balu-Iyer, Sathy V.

2015-01-01

Subcutaneous administration of biologics is highly desirable; however, incomplete bioavailability after sc administration remains a major challenge. In this work we investigated the effects of excipient dependent hyper-osmolarity on lymphatic uptake and plasma exposure of rituximab as a model protein. Using Swiss Webster (SW) mice as our animal model, we compared the effects of NaCl, mannitol and, O-Phospho-L-Serine (OPLS) on plasma concentration of rituximab over 5 days after sc administration. We observed an increase in plasma concentrations in animals administered rituximab in hypertonic buffer solutions, as compared to isotonic buffer. Bioavailability, as estimated by our pharmacokinetic model, increased from 29% in isotonic buffer to 54% in hypertonic buffer containing NaCl, to almost complete bioavailability in hypertonic buffers containing high dose OPLS or mannitol. This improvement in plasma exposure is due to improved lymphatic trafficking as evident from the increase in the fraction of dose trafficked through the lymph node in the presence of hypertonic buffers. The fraction of the dose trafficked through the lymphatic, as estimated by the model, increased from 0.05 % in isotonic buffer to 13% in hyper-tonic buffer containing NaCl to about 30% for hypertonic buffers containing high dose OPLS and mannitol. Our data suggests that hypertonic solutions may be a viable option to improve sc bioavailability. PMID:25377184

Berkeley Screen: a set of 96 solutions for general macromolecular crystallization

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

Pereira, Jose H.; McAndrew, Ryan P.; Tomaleri, Giovani P.

Using statistical analysis of the Biological Macromolecular Crystallization Database, combined with previous knowledge about crystallization reagents, a crystallization screen called the Berkeley Screen has been created. Correlating crystallization conditions and high-resolution protein structures, it is possible to better understand the influence that a particular solution has on protein crystal formation. Ions and small molecules such as buffers and precipitants used in crystallization experiments were identified in electron density maps, highlighting the role of these chemicals in protein crystal packing. The Berkeley Screen has been extensively used to crystallize target proteins from the Joint BioEnergy Institute and the Collaborative Crystallography programmore » at the Berkeley Center for Structural Biology, contributing to several Protein Data Bank entries and related publications. The Berkeley Screen provides the crystallographic community with an efficient set of solutions for general macromolecular crystallization trials, offering a valuable alternative to the existing commercially available screens. The Berkeley Screen provides an efficient set of solutions for general macromolecular crystallization trials.« less

Berkeley Screen: a set of 96 solutions for general macromolecular crystallization

DOE PAGES

Pereira, Jose H.; McAndrew, Ryan P.; Tomaleri, Giovani P.; ...

2017-09-05

Using statistical analysis of the Biological Macromolecular Crystallization Database, combined with previous knowledge about crystallization reagents, a crystallization screen called the Berkeley Screen has been created. Correlating crystallization conditions and high-resolution protein structures, it is possible to better understand the influence that a particular solution has on protein crystal formation. Ions and small molecules such as buffers and precipitants used in crystallization experiments were identified in electron density maps, highlighting the role of these chemicals in protein crystal packing. The Berkeley Screen has been extensively used to crystallize target proteins from the Joint BioEnergy Institute and the Collaborative Crystallography programmore » at the Berkeley Center for Structural Biology, contributing to several Protein Data Bank entries and related publications. The Berkeley Screen provides the crystallographic community with an efficient set of solutions for general macromolecular crystallization trials, offering a valuable alternative to the existing commercially available screens. The Berkeley Screen provides an efficient set of solutions for general macromolecular crystallization trials.« less

Hydrogen production in microbial reverse-electrodialysis electrolysis cells using a substrate without buffer solution.

PubMed

Song, Young-Hyun; Hidayat, Syarif; Kim, Han-Ki; Park, Joo-Yang

2016-06-01

The aim of this work was to use substrate without buffer solution in a microbial reverse-electrodialysis electrolysis cell (MREC) for hydrogen production under continuous flow condition (10 cell pairs of RED stacks, HRT=5, 7.5, and 15h). Decreasing in the HRT (increasing in the organic matter) made cell current stable and increased. Hydrogen gas was produced at a rate of 0.61m(3)-H2/m(3)-Van/d in H-MREC, with a COD removal efficiency of 81% (1.55g/L/d) and a Coulombic efficiency of 41%. This MREC system without buffer solution could successfully produce hydrogen gas at a consistent rate. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dynamics of diamond nanoparticles in solution and cells.

PubMed

Neugart, Felix; Zappe, Andrea; Jelezko, Fedor; Tietz, C; Boudou, Jean Paul; Krueger, Anke; Wrachtrup, Jörg

2007-12-01

The fluorescence and motional dynamics of single diamond nanocrystals in buffer solution and in living cells is investigated. Stable hydrosols of nanodiamonds in buffer solutions are investigated by fluorescence correlation spectroscopy. Measurement of the effective hydrodynamic radius yields particles of 48 nm diameter, which is in excellent agreement with atomic force microscopy measurements made on the same particles. Fluorescence correlation spectroscopy measurements indicate that nanocrystals easily form aggregates when the buffer pH is changed. This tendency is reduced when the surface of the diamonds is covered with surfactants. Upon incubation, cells spontaneously take up nanocrystals that uniformly distribute in cells. Most of the particles get immobilized within a few minutes. The binding of streptavidin to biotinylated aggregates of 4 nm diameter nanodiamonds is demonstrated.

Chemical micro-sensor

DOEpatents

Ruggiero, Anthony J.

2005-05-03

An integrated optical capillary electrophoresis system for analyzing an analyte. A modulated optical pump beam impinges on an capillary containing the analyte/buffer solution which is separated by electrophoresis. The thermally-induced change in the index of refraction of light in said electrophoresis capillary is monitored using an integrated micro-interferometer. The interferometer includes a first interferometer arm intersecting the electrophoresis capillary proximate the excitation beam and a second, reference interferometer arm. Changes in index of refraction in the analyte measured by interrogating the interferometer state using white light interferometry and a phase-generated carrier demodulation technique. Background thermo-optical activity in the buffer solution is cancelled by splitting the pump beam and exciting pure buffer solution in a second section of capillary where it crosses the reference arm of the interferometer.

Method for detecting coliform organisms

NASA Technical Reports Server (NTRS)

Nishioka, K.; Nibley, D. A.; Jeffers, E. L.; Brooks, R. L. (Inventor)

1983-01-01

A method and apparatus are disclosed for determining the concentration of coliform bacteria in a sample. The sample containing the coliform bacteria is cultured in a liquid growth medium. The cultured bacteria produce hydrogen and the hydrogen is vented to a second cell containing a buffer solution in which the hydrogen dissolves. By measuring the potential change in the buffer solution caused by the hydrogen, as a function of time, the initial concentration of bacteria in the sample is determined. Alternatively, the potential change in the buffer solution can be compared with the potential change in the liquid growth medium to verify that the potential change in the liquid growth medium is produced primarily by the hydrogen gas produced by the coliform bacteria.

Photoelectrodialytic cell

DOEpatents

Murphy, George W.

1983-01-01

A multicompartment photoelectrodialytic demineralization cell is provided with a buffer compartment interposed between the product compartment and a compartment containing an electrolyte solution. Semipermeable membranes separate the buffer compartment from the product and electrolyte compartments. The buffer compartment is flushed to prevent leakage of the electrolyte compartment from entering the product compartment.

SALICYLATE PROCESS FOR THORIUM SEPARATION FROM RARE EARTHS

DOEpatents

Cowan, G.A.

1959-08-25

The separation of thorium from rare earths is accomplished by forming an aqueous solution of salts of thorium and rare earths and sufficient acetate buffer to provide a pH of between 2 and 5, adding an ammonium salicylate to the aqueous buffered solution, contacting the resultant solution with a substantially water-immiscible organic solvent mixture of an ether and an ester, and separating the solvent extract phase containing thorium salicylate from the aqueous phase containing the rare earths.

Origins of interlayer formation and misfit dislocation displacement in the vicinity of InAs/GaAs quantum dots

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

Huang, S.; Kim, S. J.; Pan, X. Q.

We have examined the origins of interlayer formation and misfit dislocation (MD) displacement in the vicinity of InAs/GaAs quantum dots (QDs). For QDs formed by the Stranski-Krastanov mode, regularly spaced MDs nucleate at the interface between the QD and the GaAs buffer layer. In the droplet epitaxy case, both In island formation and In-induced “nano-drilling” of the GaAs buffer layer are observed during In deposition. Upon annealing under As flux, the In islands are converted to InAs QDs, with an InGaAs interlayer at the QD/buffer interface. Meanwhile, MDs nucleate at the QD/interlayer interface.

Continuous-flow electrophoresis: Membrane-associated deviations of buffer pH and conductivity

NASA Technical Reports Server (NTRS)

Smolka, A. J. K.; Mcguire, J. K.

1978-01-01

The deviations in buffer pH and conductivity which occur near the electrode membranes in continuous-flow electrophoresis were studied in the Beckman charged particle electrophoresis system and the Hanning FF-5 preparative electrophoresis instrument. The nature of the membranes separating the electrode compartments from the electrophoresis chamber, the electric field strength, and the flow rate of electrophoresis buffer were all found to influence the formation of the pH and conductivity gradients. Variations in electrode buffer flow rate and the time of electrophoresis were less important. The results obtained supported the hypothesis that a combination of Donnan membrane effects and the differing ionic mobilities in the electrophoresis buffer was responsible for the formation of the gradients. The significance of the results for the design and stable operation of continuous-flow electrophoresis apparatus was discussed.

Preparation and optimization of self-assembled chondroitin sulfate-nisin nanogel based on quality by design concept.

PubMed

Mohtashamian, Shahab; Boddohi, Soheil; Hosseinkhani, Saman

2018-02-01

Self-assembled nanogel was prepared by electrostatic complexation of two oppositely charged biological macromolecules, which were cationic nisin and anionic chondroitin sulfate (ChS). The critical factors affected the physical properties of ChS-nisin nanogel was screened and optimized by Plackett-Burman design (PB) and central composite design (CCD). The independent factors selected were: concentration ratio of nisin to ChS, injection rate of nisin solution, buffer solvent type, magnetic stirring rate, pH of initial buffer solution, centrifuge-cooling temperature, and centrifuge rotation speed. Among these factors, concentration ratio changed the entrapment efficiency and loading capacity significantly. In addition, the hydrodynamic diameter and loading capacity were significantly influenced by injection rate and pH of initial buffer solution. The optimized nanogel structure was obtained by concentration ratio of 6.4mg/mL nisin to 1mg/mL ChS, pH of buffer solution at 4.6, and nisin solution injection rate of 0.2mL/min. The observed values of dependent responses were close to predicted values confirmed by model from response surface methodology. The results obviously showed that quality by design concept (QbD) could be effectively applied to optimize the developed ChS-nisin nanogel. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

The role of the episodic buffer in working memory for language processing.

PubMed

Rudner, Mary; Rönnberg, Jerker

2008-03-01

A body of work has accumulated to show that the cognitive process of binding information from different mnemonic and sensory sources as well as in different linguistic modalities can be fractionated from general executive functions in working memory both functionally and neurally. This process has been defined in terms of the episodic buffer (Baddeley in Trends Cogn Sci 4(11):417-423, 2000). This paper considers behavioural, neuropsychological and neuroimaging data that elucidate the role of the episodic buffer in language processing. We argue that the episodic buffer seems to be truly multimodal in function and that while formation of unitary multidimensional representations in the episodic buffer seems to engage posterior neural networks, maintenance of such representations is supported by frontal networks. Although, the episodic buffer is not necessarily supported by executive processes and seems to be supported by different neural networks, it may operate in tandem with the central executive during effortful language processing. There is also evidence to suggest engagement of the phonological loop during buffer processing. The hippocampus seems to play a role in formation but not maintenance of representations in the episodic buffer of working memory.

Photoelectrodialytic cell

DOEpatents

Murphy, G.W.

1983-09-13

A multicompartment photoelectrodialytic demineralization cell is provided with a buffer compartment interposed between the product compartment and a compartment containing an electrolyte solution. Semipermeable membranes separate the buffer compartment from the product and electrolyte compartments. The buffer compartment is flushed to prevent leakage of the electrolyte compartment from entering the product compartment. 3 figs.

On the delay analysis of a TDMA channel with finite buffer capacity

NASA Technical Reports Server (NTRS)

Yan, T.-Y.

1982-01-01

The throughput performance of a TDMA channel with finite buffer capacity for transmitting data messages is considered. Each station has limited message buffer capacity and has Poisson message arrivals. Message arrivals will be blocked if the buffers are congested. Using the embedded Markov chain model, the solution procedure for the limiting system-size probabilities is presented in a recursive fashion. Numerical examples are given to demonstrate the tradeoffs between the blocking probabilities and the buffer sizing strategy.

40 CFR Appendix B to Subpart Nnn... - Free Formaldehyde Analysis of Insulation Resins by Hydroxylamine Hydrochloride

Code of Federal Regulations, 2011 CFR

2011-07-01

... 4.0 with pH 4.0 buffer and pH 7 with pH 7.0 buffer. 3.350-mL burette for 1.0 N sodium hydroxide. 3... hydrochloride solution, 100 grams per liter, pH adjusted to 4.00. 4.3Hydrochloric acid solution, 1.0 N and 0.1 N... magnetic stirrer. Confirm that the resin has dissolved. 5.4Adjust the resin/solvent solution to pH 4.0...

40 CFR Appendix B to Subpart Nnn... - Free Formaldehyde Analysis of Insulation Resins by Hydroxylamine Hydrochloride

Code of Federal Regulations, 2010 CFR

2010-07-01

... 4.0 with pH 4.0 buffer and pH 7 with pH 7.0 buffer. 3.350-mL burette for 1.0 N sodium hydroxide. 3... hydrochloride solution, 100 grams per liter, pH adjusted to 4.00. 4.3Hydrochloric acid solution, 1.0 N and 0.1 N... magnetic stirrer. Confirm that the resin has dissolved. 5.4Adjust the resin/solvent solution to pH 4.0...

CHEMICAL SOLUTION DEPOSITION BASED OXIDE BUFFERS AND YBCO COATED CONDUCTORS

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

Paranthaman, Mariappan Parans

We have reviewed briefly the growth of buffer and high temperature superconducting oxide thin films using a chemical solution deposition (CSD) method. In the Rolling-Assisted Biaxially Textured Substrates (RABiTS) process, developed at Oak Ridge National Laboratory, utilizes the thermo mechanical processing to obtain the flexible, biaxially oriented copper, nickel or nickel-alloy substrates. Buffers and Rare Earth Barium Copper Oxide (REBCO) superconductors have been deposited epitaxially on the textured nickel alloy substrates. The starting substrate serves as a template for the REBCO layer, which has substantially fewer weak links. Buffer layers play a major role in fabricating the second generation REBCOmore » wire technology. The main purpose of the buffer layers is to provide a smooth, continuous and chemically inert surface for the growth of the REBCO film, while transferring the texture from the substrate to the superconductor layer. To achieve this, the buffer layers need to be epitaxial to the substrate, i.e. they have to nucleate and grow in the same bi-axial texture provided by the textured metal foil. The most commonly used RABiTS multi-layer architectures consist of a starting template of biaxially textured Ni-5 at.% W (Ni-W) substrate with a seed (first) layer of Yttrium Oxide (Y2O3), a barrier (second) layer of Yttria Stabilized Zirconia (YSZ), and a Cerium Oxide (CeO2) cap (third) layer. These three buffer layers are generally deposited using physical vapor deposition (PVD) techniques such as reactive sputtering. On top of the PVD template, REBCO film is then grown by a chemical solution deposition. This article reviews in detail about the list of oxide buffers and superconductor REBCO films grown epitaxially on single crystal and/or biaxially textured Ni-W substrates using a CSD method.« less

In vitro corrosion of magnesium alloy AZ31 — a synergetic influence of glucose and Tris

NASA Astrophysics Data System (ADS)

Li, Ling-Yu; Liu, Bin; Zeng, Rong-Chang; Li, Shuo-Qi; Zhang, Fen; Zou, Yu-Hong; Jiang, Hongwei George; Chen, Xiao-Bo; Guan, Shao-Kang; Liu, Qing-Yun

2018-05-01

Biodegradable Mg alloys have generated great interest for biomedical applications. Accurate predictions of in vivo degradation of Mg alloys through cost-effective in vivo evaluations require the latter to be conducted in an environment close to that of physiological scenarios. However, the roles of glucose and buffering agents in regulating the in vivo degradation performance of Mg alloys has not been elucidated. Herein, degradation behavior of AZ31 alloy is investigated by hydrogen evolution measurements, pH monitoring and electrochemical tests. Results indicate that glucose plays a content-dependent role in degradation of AZ31 alloy in buffer-free saline solution. The presence of a low concentration of glucose, i.e. 1.0 g/L, decreases the corrosion rate of Mg alloy AZ31, whereas the presence of 2.0 and 3.0 g/L glucose accelerates the corrosion rate during long term immersion in saline solution. In terms of Tris-buffered saline solution, the addition of glucose increases pH value and promotes pitting corrosion or general corrosion of AZ31 alloy. This study provides a novel perspective to understand the bio-corrosion of Mg alloys in buffering agents and glucose containing solutions.

In vitro corrosion of magnesium alloy AZ31 — a synergetic influence of glucose and Tris

NASA Astrophysics Data System (ADS)

Li, Ling-Yu; Liu, Bin; Zeng, Rong-Chang; Li, Shuo-Qi; Zhang, Fen; Zou, Yu-Hong; Jiang, Hongwei George; Chen, Xiao-Bo; Guan, Shao-Kang; Liu, Qing-Yun

2018-06-01

Biodegradable Mg alloys have generated great interest for biomedical applications. Accurate predictions of in vivo degradation of Mg alloys through cost-effective in vivo evaluations require the latter to be conducted in an environment close to that of physiological scenarios. However, the roles of glucose and buffering agents in regulating the in vivo degradation performance of Mg alloys has not been elucidated. Herein, degradation behavior of AZ31 alloy is investigated by hydrogen evolution measurements, pH monitoring and electrochemical tests. Results indicate that glucose plays a content-dependent role in degradation of AZ31 alloy in buffer-free saline solution. The presence of a low concentration of glucose, i.e. 1.0 g/L, decreases the corrosion rate of Mg alloy AZ31, whereas the presence of 2.0 and 3.0 g/L glucose accelerates the corrosion rate during long term immersion in saline solution. In terms of Tris-buffered saline solution, the addition of glucose increases pH value and promotes pitting corrosion or general corrosion of AZ31 alloy. This study provides a novel perspective to understand the bio-corrosion of Mg alloys in buffering agents and glucose containing solutions.

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.

Bicarbonate- versus lactate-buffered solutions for acute continuous haemodiafiltration or haemofiltration.

PubMed

Tian, Jin Hui; Ma, Bin; Yang, KeHu; Liu, Yali; Tan, Jiying; Liu, Tian Xi

2015-03-05

Acute kidney injury (AKI) is a severe loss of kidney function that results in patients' inability to appropriately excrete nitrogenous wastes and creatinine. Continuous haemodiafiltration (HDF) or haemofiltration (HF) are commonly used renal replacement therapies for people with AKI. Buffered dialysates and solutions used in HDF or HF have varying effects on acid-base physiology and several electrolytes. The benefits and harms of bicarbonate- versus lactate-buffered HDF or HF solutions for treating patients with AKI remain unclear. To assess the benefits and harms of bicarbonate- versus lactate-buffered solutions for HDF or HF for treating people with AKI. We searched the Cochrane Renal Group's Specialised Register to 6 January 2015 through contact with the Trials' Search Co-ordinator using search terms relevant to this review. We also searched the Chinese Biomedical Literature Database. All randomised controlled trials (RCT) and quasi-RCTs that reported comparisons of bicarbonate-buffered solutions with lactate-buffered solutions for AKI were selected for inclusion irrespective of publication status or language. Two authors independently assessed titles and abstracts, and where necessary the full text of studies, to determine which satisfied our inclusion criteria. Data were extracted by two authors who independently assessed studies for eligibility and quality using a standardised data extraction form. Methodological quality was assessed using the Cochrane risk of bias tool. Results were expressed as risk ratio (RR) or mean difference (MD) with 95% confidence intervals (CI). We identified four studies (171 patients) that met our inclusion criteria. Overall, study quality was suboptimal. There were significant reporting omissions related to methodological issues and potential harms. Outcome measures were not defined or reported adequately. The studies were small and lacked follow-up phases.Serum lactate levels were significantly lower in patients treated with bicarbonate-buffered solutions (4 studies, 171 participants: MD -1.09 mmol/L, 95% CI -1.30 to -0.87; I(2) = 0%). There were no differences in mortality (3 studies, 163 participants: RR 0.76, 95% CI 0.50 to 1.15; I(2) = 0%); serum bicarbonate levels (3 studies, 163 participants: MD 0.27 mmol/L, 95% CI -1.45 to 1.99; I(2) = 78%), serum creatinine (2 studies, 137 participants: MD -22.81 µmol/L, 95% CI -129.61 to 83.99; I(2) = 73%), serum base excess (3 studies, 145 participants: MD 0.80, 95% CI -0.91 to 2.50; I(2) = 38%), serum pH (4 studies, 171 participants: MD 0.01, 95% CI -0.02 to 0.03; I(2) = 70%) or carbon dioxide partial pressure (3 studies, 151 participants: MD -1.04, 95% CI -3.84 to 1.76; I(2) = 83%). A single study reported fewer cardiovascular events (RR 0.39, 95% CI 0.20 to 0.79), higher mean arterial pressure (10.25 mm Hg, 95% CI 6.68 to 13.82) and less hypotensive events (RR 0.44, 95% CI 0.26 to 0.75) in patients receiving bicarbonate-buffered solutions. One study reported no significant difference in central venous pressure (MD 2.00 cm H2O, 95% CI -0.7 to, 4.77). Total length of hospital and ICU stay and relapse were not reported by any of the included studies. There were no significant different between bicarbonate- and lactate-buffered solutions for mortality, serum bicarbonate levels, serum creatinine, serum base excess, serum pH, carbon dioxide partial pressure, central venous pressure and serum electrolytes. Patients treated with bicarbonate-buffered solutions may experience fewer cardiovascular events, lower serum lactate levels, higher mean arterial pressure and less hypotensive events. With the exception of mortality, we were not able to assess the main primary outcomes of this review - length of time in ICU, total length of hospital stay and relapse.

Free flow cell electrophoresis using zwitterionic buffer

NASA Technical Reports Server (NTRS)

Rodkey, R. Scott

1990-01-01

Studies of a zwitterionic buffer formulated for cell electrophoresis were done using the McDonnell-Douglas Continuous Flow Electrophoresis System. Standard buffers were analyzed for their stability in the electrical field and the results showed that both buffers tested were inherently unstable. Further, titration studies showed that the standards buffers buffered poorly at the pH employed for electrophoresis. The zwitterionic buffer buffered well at its nominal pH and was shown to be stable in the electrical field. Comparative studies of the buffer with standard cell separation buffers using formalin fixed rabbit and goose red blood cells showed that the zwitterionic buffer gave better resolution of the fixed cells. Studies with viable hybridoma cells showed that buffer Q supported cell viability equal to Hank's Balanced Salt Solution and that hybridoma cells in different stages of the growth cycle demonstrated reproducible differences in electrophoretic mobility.

Highly sensitive and selective detection of Al(III) ions in aqueous buffered solution with fluorescent peptide-based sensor.

PubMed

In, Byunggyu; Hwang, Gi Won; Lee, Keun-Hyeung

2016-09-15

A fluorescent sensor based on a tripeptide (SerGluGlu) with a dansyl fluorophore detected selectively Al(III) among 16 metal ions in aqueous buffered solutions without any organic cosolvent. The peptide-based sensor showed a highly sensitive turn on response to aluminium ion with high binding affinity (1.84×10(4)M(-1)) in aqueous buffered solutions. The detection limit (230nM, 5.98ppb) of the peptide-based sensor was much lower than the maximum allowable level (7.41μM) of aluminium ions in drinking water demanded by EPA. The binding mode of the peptide sensor with aluminium ions was characterized using ESI mass spectrometry, NMR titration, and pH titration experiments. Copyright © 2016 Elsevier Ltd. All rights reserved.

Detoxification of Chemical Warfare Agents Using a Zr6 -Based Metal-Organic Framework/Polymer Mixture.

PubMed

Moon, Su-Young; Proussaloglou, Emmanuel; Peterson, Gregory W; DeCoste, Jared B; Hall, Morgan G; Howarth, Ashlee J; Hupp, Joseph T; Farha, Omar K

2016-10-10

Owing to their high surface area, periodic distribution of metal sites, and water stability, zirconium-based metal-organic frameworks (Zr 6 -MOFs) have shown promising activity for the hydrolysis of nerve agents GD and VX, as well as the simulant, dimethyl 4-nitrophenylphosphate (DMNP), in buffered solutions. A hurdle to using MOFs for this application is the current need for a buffer solution. Here the destruction of the simulant DMNP, as well as the chemical warfare agents (GD and VX) through hydrolysis using a MOF catalyst mixed with a non-volatile, water-insoluble, heterogeneous buffer is reported. The hydrolysis of the simulant and nerve agents in the presence of the heterogeneous buffer was fast and effective. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Eu(III)-Sensitized Luminescence Probe for Determination of Tolnaftate in Pharmaceuticals and Biological Fluids.

PubMed

Alarfaj, Nawal A; El-Tohamy, Maha F

2016-01-01

A highly selective, sensitive, accurate, and reproducible luminescence procedure for determination of antifungal drug tolnaftate was developed. The introduced method was based on the formation of Europa Universalis III (Eu(III))-tolnaftate complex using sodium sulfite as a deoxygenated agent in the presence of acetate buffer (pH = 6) and micellar solution of anionic surfactant sodium dodecyl sulfate. The optimum conditions (effect of pH, buffer, surfactant, Eu(III), and sodium sulfite concentrations) for the luminescence signal were investigated and optimized. The luminescence signals were recorded at λex = 270 nm and λem = 460 nm. The method has a good linear response (0.2-130 μg/mL(-1)) between the luminescence intensity and the concentrations of the drug (r = 0.999), with a LOD 0.07 μg/mL(-1) and LOQ 0.2 μg/mL(-1). The luminescence signals of Eu (III)-tolnaftate-sodium dodecyl sulfate were found to be 200-fold more sensitive without the presence of micelle solution. The interferences of some additives, metals, amino acids, sugars, and other related pharmacological action drugs were examined and no interference was recorded. The proposed method was used for quick and simple determination of tolnaftate in its pharmaceuticals and biological fluids.

Structural Characterization of Apomyoglobin Self-Associated Species in Aqueous Buffer and Urea Solution

PubMed Central

Chow, Charles; Kurt, Neşe; Murphy, Regina M.; Cavagnero, Silvia

2006-01-01

The biophysical characterization of nonfunctional protein aggregates at physiologically relevant temperatures is much needed to gain deeper insights into the kinetic and thermodynamic relationships between protein folding and misfolding. Dynamic and static laser light scattering have been employed for the detection and detailed characterization of apomyoglobin (apoMb) soluble aggregates populated at room temperature upon dissolving the purified protein in buffer at pH 6.0, both in the presence and absence of high concentrations of urea. Unlike the β-sheet self-associated aggregates previously reported for this protein at high temperatures, the soluble aggregates detected here have either α-helical or random coil secondary structure, depending on solvent and solution conditions. Hydrodynamic diameters range from 80 to 130 nm, with semiflexible chain-like morphology. The combined use of low pH and high urea concentration leads to structural unfolding and complete elimination of the large aggregates. Even upon starting from this virtually monomeric unfolded state, however, protein refolding leads to the formation of severely self-associated species with native-like secondary structure. Under these conditions, kinetic apoMb refolding proceeds via two parallel routes: one leading to native monomer, and the other leading to a misfolded and heavily self-associated state bearing native-like secondary structure. PMID:16214860

Effect of pH and the role of organic matter in the adsorption of isoproturon on soils.

PubMed

Ertli, Tímea; Marton, Aurél; Földényi, Rita

2004-11-01

Equilibrium measurements were carried out with the herbicide isoproturon on natural adsorbents (brown forest-, chernozem-, sandy soils and quartz) in different buffered media (pH 5, 7, 8 phosphate buffer). Adsorption isotherms were fitted by a multi-step adsorption equation providing numerical information used in the environmental propagation models and risk assessment works. In the adsorption of the slightly polar isoproturon the dissolved organic matter of the soil and the pH play an important role. At molecular level, results are interpreted by taking into consideration the hydrophobic interaction and the formation of hydrogen bonds between the surface and the solute. The observed adsorption behavior indicates that the organic matter content of the soils and its soluble fulvic acid, alkaline soluble humic acid and insoluble humin fractions were considerable different. The chernozem soil containing the highest amount of insoluble organic fraction proved to be a very efficient adsorbent. The brown forest and the sandy soils exhibit rather similar adsorbent properties but at pH 7 the latter containing more fulvic acid adsorbs less isoproturon due to the enhanced solubility of the soil organic matter. In alkaline conditions the negatively charged solute and the surface repel each other and the hydrophobic interactions are also weaker than in neutral media.

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.

Continuous processing of recombinant proteins: integration of refolding and purification using simulated moving bed size-exclusion chromatography with buffer recycling.

PubMed

Wellhoefer, Martin; Sprinzl, Wolfgang; Hahn, Rainer; Jungbauer, Alois

2014-04-11

Continuous processing of recombinant proteins was accomplished by combining continuous matrix-assisted refolding and purification by tandem simulated moving bed (SMB) size-exclusion chromatography (SEC). Recombinant proteins, N(pro) fusion proteins from inclusion bodies were dissolved with NaOH and refolded in the SMB system with a closed-loop set-up with refolding buffer as the desorbent buffer and buffer recycling of the refolding buffer of the raffinate by tangential flow filtration. For further purification of the refolded proteins, a second SMB operation also based on SEC was added. The whole system could be operated isocratically with refolding buffer as the desorbent buffer, and buffer recycling could also be applied in the purification step. Thus, a significant reduction in buffer consumption was achieved. The system was evaluated with two proteins, the N(pro) fusion pep6His and N(pro) fusion MCP-1. Refolding solution, which contained residual N(pro) fusion peptide, the cleaved autoprotease N(pro), and the cleaved target peptide was used as feed solution. Full separation of the cleaved target peptide from residual proteins was achieved at a purity and recovery in the raffinate and extract, respectively, of approximately 100%. In addition, more than 99% of the refolding buffer of the raffinate was recycled. A comparison of throughput, productivity, and buffer consumption of the integrated continuous process with two batch processes demonstrated that up to 60-fold higher throughput, up to 180-fold higher productivity, and at least 28-fold lower buffer consumption can be obtained by the integrated continuous process, which compensates for the higher complexity. Copyright © 2014 Elsevier B.V. All rights reserved.

Vermiculite's strong buffer capacity renders it unsuitable for studies of acidity on soybean (Glycine max L.) nodulation and growth.

PubMed

Indrasumunar, Arief; Gresshoff, Peter M

2013-11-14

Vermiculite is the most common soil-free growing substrate used for plants in horticultural and scientific studies due to its high water holding capacity. However, some studies are not suitable to be conducted in it. The described experiments aimed to test the suitability of vermiculite to study the effect of acidity on nodulation and growth of soybean (Glycine max L.). Two different nutrient solutions (Broughton & Dilworth, and modified Herridge nutrient solutions) with or without MES buffer addition were used to irrigate soybean grown on vermiculite growth substrates. The pH of nutrient solutions was adjusted to either pH 4.0 or 7.0 prior its use. The nodulation and vegetative growth of soybean plants were assessed at 3 and 4 weeks after inoculation. The unsuitability of presumably inert vermiculite as a physical plant growth substrate for studying the effects of acidity on soybean nodulation and plant growth was illustrated. Nodulation and growth of soybean grown in vermiculite were not affected by irrigation with pH-adjusted nutrient solution either at pH 4.0 or 7.0. This was reasonably caused by the ability of vermiculite to neutralise (buffer) the pH of the supplied nutrient solution (pH 2.0-7.0). Due to its buffering capacity, vermiculite cannot be used as growth support to study the effect of acidity on nodulation and plant growth.

Hydrolysis of the quinone methide of butylated hydroxytoluene in aqueous solutions.

PubMed

Willcockson, Maren Gulsrud; Toteva, Maria M; Stella, Valentino J

2013-10-01

Butylated hydroxytoluene or BHT is an antioxidant commonly used in pharmaceutical formulations. BHT upon oxidation forms a quinone methide (QM). QM is a highly reactive electrophilic species that can undergo nucleophilic addition. Here, the kinetic reactivity of QM with water at various apparent pH values in a 50% (v/v) water-acetonitrile solution at constant ionic strength of I = 0.5 (NaCl)4 , was studied. The hydrolysis of QM in the presence of added acid, base, sodium chloride, and phosphate buffer resulted in the formation of only one product--the corresponding 3,5-di-tert-butyl-4-hydroxybenzyl alcohol (BA). The rate of BA formation was catalyzed by the addition of acid and base, but not chloride and phosphate species. Nucleophilic excipients, used in the pharmaceutical formulation, or nucleophilic groups on active pharmaceutical ingredient molecule may form adducts with QM, the immediate oxidative product of BHT degradation, thus having implications for drug product impurity profiles. Because of these considerations, BHT should be used with caution in formulations containing drugs or excipients capable of acting as nucleophiles. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.

Tetragonal Chicken Egg White Lysozyme Solubility in Sodium Chloride Solutions

NASA Technical Reports Server (NTRS)

Forsythe, Elizabeth L.; Judge, Russell A.; Pusey, Marc L.

1998-01-01

The solubility of chicken egg white lysozyme, crystallized in the tetragonal form was measured in sodium chloride solutions from 1.6 to 30.7 C, using a miniature column solubility apparatus. Sodium chloride solution concentrations ranged from 1 to 7% (w/v). The solutions were buffered with 0.1 M sodium acetate buffer with the solubility being measured at pH values in 0.2 pH unit increments in the range pH 4.0 to 5.4, with data also included at pH 4.5. Lysozyme solubility was found to increase with increases in temperature and decreasing salt concentration. Solution pH has a varied and unpredictable effect on solubility.

Simply enhancing throughput of free-flow electrophoresis via organic-aqueous environment for purification of weak polarity solute of phenazine-1-carboxylic acid in fermentation of Pseudomonas sp. M18.

PubMed

Yang, Jing-Hua; Shao, Jing; Wang, Hou-Yu; Dong, Jing-Yu; Fan, Liu-Yin; Cao, Cheng-Xi; Xu, Yu-Quan

2012-09-01

Herein, a simple novel free-flow electrophoresis (FFE) method was developed via introduction of organic solvent into the electrolyte system, increasing the solute solubility and throughput of the sample. As a proof of concept, phenazine-1-carboxylic acid (PCA) from Pseudomonas sp. M18 was selected as a model solute for the demonstration on feasibility of novel FFE method on account of its faint solubility in aqueous circumstance. In the developed method, the organic solvent was added into not only the sample buffer to improve the solubility of the solute, but also the background buffer to construct a uniform aqueous-organic circumstance. These factors of organic solvent percentage and types as well as pH value of background buffer were investigated for the purification of PCA in the FFE device via CE. The experiments revealed that the percentage and the types of organic solvent exerted major influence on the purification of PCA. Under the optimized conditions (30 mM phosphate buffer in 60:40 (v/v) water-methanol at an apparent pH 7.0, 3.26 mL/min background flux, 10-min residence time of injected sample, and 400 V), PCA could be continuously purified from its impurities. The flux of sample injection was 10.05 μL/min, and the recovery was up to 93.7%. An 11.9-fold improvement of throughput was found with a carrier buffer containing 40% (v/v) methanol, compared with the pure aqueous phase. The developed procedure is of evident significance for the purification of weak polarity solute via FFE. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced efficiency of inverted polymer solar cells by using solution-processed TiOx/CsOx cathode buffer layer.

PubMed

Zhou, Xiaodong; Fan, Xi; Sun, Xianke; Zhang, Yunli; Zhu, Ziqiang

2015-01-01

In this work, a double-buffer film of TiOx coated with CsOx (TiOx/CsOx) was solution prepared to be applied in poly(3-hexylthiophene):indene-C60 bisadduct (P3HT:ICBA) and P3HT:[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) inverted polymer solar cells (PSCs). Compared with TiOx films and CsOx films, the TiOx/CsOx double-buffer film exhibited a favorable energy-level alignment among TiOx, CsOx, and the electron acceptor of PCBM or ICBA a better surface morphology; and an enhanced wetting and adhesion property with a contact angle of 21.0°, leading to a higher electron mobility of 5.52 × 10(-3) cm(2) V(-1)·s(-1). Moreover, the P3HT:ICBA and P3HT:PCBM photovoltaic devices with the double-buffer film showed the best power conversion efficiency up to 5.65% and 3.76%, respectively. Our results not only present that the double-buffer film is superior than the single film of TiOx and CsOx, but also imply that the solution-processed film has a potential to be generally used in roll-to-roll processed organic photovoltaic devices.

Vein Graft Preservation Solutions, Patency, and Outcomes After Coronary Artery Bypass Graft Surgery

PubMed Central

Harskamp, Ralf E.; Alexander, John H.; Schulte, Phillip J.; Brophy, Colleen M.; Mack, Michael J.; Peterson, Eric D.; Williams, Judson B.; Gibson, C. Michael; Califf, Robert M.; Kouchoukos, Nicholas T.; Harrington, Robert A.; Ferguson, T. Bruce; Lopes, Renato D.

2015-01-01

IMPORTANCE In vitro and animal model data suggest that intraoperative preservation solutions may influence endothelial function and vein graft failure (VGF) after coronary artery bypass graft (CABG) surgery. Clinical studies to validate these findings are lacking. OBJECTIVE To evaluate the effect of vein graft preservation solutions on VGF and clinical outcomes in patients undergoing CABG surgery. DESIGN, SETTING, AND PARTICIPANTS Data from the Project of Ex-Vivo Vein Graft Engineering via Transfection IV (PREVENT IV) study, a phase 3, multicenter, randomized, double-blind, placebo-controlled trial that enrolled 3014 patients at 107 US sites from August 1, 2002, through October 22, 2003, were used. Eligibility criteria for the trial included CABG surgery for coronary artery disease with at least 2 planned vein grafts. INTERVENTIONS Preservation of vein grafts in saline, blood, or buffered saline solutions. MAIN OUTCOMES AND MEASURES One-year angiographic VGF and 5-year rates of death, myocardial infarction, and subsequent revascularization. RESULTS Most patients had grafts preserved in saline (1339 [44.4%]), followed by blood (971 [32.2%]) and buffered saline (507 [16.8%]). Baseline characteristics were similar among groups. One-year VGF rates were much lower in the buffered saline group than in the saline group (patient-level odds ratio [OR], 0.59 [95% CI, 0.45-0.78; P < .001]; graft-level OR, 0.63 [95% CI, 0.49-0.79; P < .001]) or the blood group (patient-level OR, 0.62 [95% CI, 0.46-0.83; P = .001]; graft-level OR, 0.63 [95% CI, 0.48-0.81; P < .001]). Use of buffered saline solution also tended to be associated with a lower 5-year risk for death, myocardial infarction, or subsequent revascularization compared with saline (hazard ratio, 0.81 [95% CI, 0.64-1.02; P = .08]) and blood (0.81 [0.63-1.03; P = .09]) solutions. CONCLUSIONS AND RELEVANCE Patients undergoing CABG whose vein grafts were preserved in a buffered saline solution had lower VGF rates and trends toward better long-term clinical outcomes compared with patients whose grafts were preserved in saline- or blood-based solutions. PMID:25073921

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.

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

Solution-processed MoS(x) as an efficient anode buffer layer in organic solar cells.

PubMed

Li, Xiaodong; Zhang, Wenjun; Wu, Yulei; Min, Chao; Fang, Junfeng

2013-09-25

We reported a facile solution-processed method to fabricate a MoSx anode buffer layer through thermal decomposition of (NH4)2MoS4. Organic solar cells (OSCs) based on in situ growth MoSx as the anode buffer layer showed impressive improvements, and the power conversion efficiency was higher than that of conventional PEDOT:PSS-based device. The MoSx films obtained at different temperatures and the corresponding device performance were systematically studied. The results indicated that both MoS3 and MoS2 were beneficial to the device performance. MoS3 could result in higher Voc, while MoS2 could lead to higher Jsc. Our results proved that, apart from MoO3, molybdenum sulfides and Mo(4+) were also promising candidates for the anode buffer materials in OSCs.

Calculated and measured [Ca(2+)] in buffers used to calibrate Ca(2+) macroelectrodes.

PubMed

McGuigan, John A S; Stumpff, Friederike

2013-05-01

The ionized concentration of calcium in physiological buffers ([Ca(2+)]) is normally calculated using either tabulated constants or software programs. To investigate the accuracy of such calculations, the [Ca(2+)] in EGTA [ethylene glycol-bis(β-aminoethylether)-N,N,N|,N|-tetraacetic acid], BAPTA [1,2-bis(o-aminophenoxy) ethane-N,N,N|,N|-tetraacetic acid], HEDTA [N-(2-hydroxyethyl)-ethylenediamine-N,N|,N|-triacetic acid], and NTA [N,N-bis(carboxymethyl)glycine] buffers was estimated using the ligand optimization method, and these measured values were compared with calculated values. All measurements overlapped in the pCa range of 3.51 (NTA) to 8.12 (EGTA). In all four buffer solutions, there was no correlation between measured and calculated values; the calculated values differed among themselves by factors varying from 1.3 (NTA) to 6.9 (EGTA). Independent measurements of EGTA purity and the apparent dissociation constants for HEDTA and NTA were not significantly different from the values estimated by the ligand optimization method, further substantiating the method. Using two calibration solutions of pCa 2.0 and 3.01 and seven buffers in the pCa range of 4.0-7.5, calibration of a Ca(2+) electrode over the pCa range of 2.0-7.5 became a routine procedure. It is proposed that such Ca(2+) calibration/buffer solutions be internationally defined and made commercially available to allow the precise measurement of [Ca(2+)] in biology. Copyright © 2013 Elsevier Inc. All rights reserved.

Study of buffer substrate and Arenga wood fiber size on hydroponic Kailan (Brassica alboglabra)

NASA Astrophysics Data System (ADS)

Harjoko, D.; Anggraheny, M. D.; Arniputri, R. B.

2018-03-01

Kailan is a kind of vegetable that has high economic value, however its prospect is not well developed. One of obstacles in Kailan cultivation is the limitation of fertile soil, that can be solved by using hydroponic substrate. Considering its amount and potential, the fiber waste of Arenga wood was selected as substrate candidate. For that, this research aims to study the growth and yield of Kailan with different soaking treatment using buffer solution and size of Arenga wood fiber in the hydroponic substrate. Research was conducted at Green House Laboratory, Faculty of Agriculture Sebelas Maret University Surakarta from February to May 2017. The treatments were soaking buffer solution with EC 1.2 mScm-1; 1.4 mScm-1; and 1.6 mScm-1 and the size of Arenga fiber <1 cm, 1-2 cm and 2-3 cm. In this experiment, sand media was used as control. Result show that, soaking in 1.6 mScm-1 EC buffer solution with Arenga fiber size lower than 3 cm gives higher root volume compared to other treatments combination.

Controlling the stoichiometry and strand polarity of a tetramolecular G-quadruplex structure by using a DNA origami frame

PubMed Central

Rajendran, Arivazhagan; Endo, Masayuki; Hidaka, Kumi; Lan Thao Tran, Phong; Mergny, Jean-Louis; Sugiyama, Hiroshi

2013-01-01

Guanine-rich oligonucleotides often show a strong tendency to form supramolecular architecture, the so-called G-quadruplex structure. Because of the biological significance, it is now considered to be one of the most important conformations of DNA. Here, we describe the direct visualization and single-molecule analysis of the formation of a tetramolecular G-quadruplex in KCl solution. The conformational changes were carried out by incorporating two duplex DNAs, with G–G mismatch repeats in the middle, inside a DNA origami frame and monitoring the topology change of the strands. In the absence of KCl, incorporated duplexes had no interaction and laid parallel to each other. Addition of KCl induced the formation of a G-quadruplex structure by stably binding the duplexes to each other in the middle. Such a quadruplex formation allowed the DNA synapsis without disturbing the duplex regions of the participating sequences, and resulted in an X-shaped structure that was monitored by atomic force microscopy. Further, the G-quadruplex formation in KCl solution and its disruption in KCl-free buffer were analyzed in real-time. The orientation of the G-quadruplex is often difficult to control and investigate using traditional biochemical methods. However, our method using DNA origami could successfully control the strand orientations, topology and stoichiometry of the G-quadruplex. PMID:23863846

Aqueous corrosion of phosphide minerals from iron meteorites: a highly reactive source of prebiotic phosphorus on the surface of the early Earth.

PubMed

Pasek, Matthew A; Lauretta, Dante S

2005-08-01

We present the results of an experimental study of aqueous corrosion of Fe-phosphide under conditions relevant to the early Earth. The results strongly suggest that iron meteorites were an important source of reactive phosphorus (P), a requirement for the formation of P-based life. We further demonstrate that iron meteorites were an abundant source of phosphide minerals early in Earth history. Phosphide corrosion was studied in five different solutions: deionized water, deionized water buffered with sodium bicarbonate, deionized water with dissolved magnesium and calcium chlorides, deionized water containing ethanol and acetic acid, and deionized water containing the chlorides, ethanol, and acetic acid. Experiments were performed in the presence of both air and pure Ar gas to evaluate the effect of atmospheric chemistry. Phosphide corrosion in deionized water results in a metastable mixture of mixed-valence, P-bearing ions including pyrophosphate and triphosphate, key components for metabolism in modern life. In a pH-buffered solution of NaHCO(3), the condensed and reduced species diphosphonate is an abundant corrosion product. Corrosion in ethanol- and acetic acid-containing solutions yields additional P-bearing organic molecules, including acetyl phosphonate and a cyclic triphosphorus molecule. Phosphonate is a major corrosion product of all experiments and is the only P-bearing molecule that persists in solutions with high concentrations of magnesium and calcium chlorides, which suggests that phosphonate may have been a primitive oceanic source of P. The stability and reactivity of phosphonate and hypophosphite in solution were investigated to elucidate reaction mechanisms and the role of mineral catalysts on P-solution chemistry. Phosphonate oxidation is rapid in the presence of Fe metal but negligible in the presence of magnetite and in the control sample. The rate of hypophosphite oxidation is independent of reaction substrate.

The Maintenance of Cross-Domain Associations in the Episodic Buffer

ERIC Educational Resources Information Center

Langerock, Naomi; Vergauwe, Evie; Barrouillet, Pierre

2014-01-01

The episodic buffer has been described as a structure of working memory capable of maintaining multimodal information in an integrated format. Although the role of the episodic buffer in binding features into objects has received considerable attention, several of its characteristics have remained rather underexplored. This is the case for its…

Buffered hydrochloric acid: a modern method of treating metabolic alkalosis.

PubMed

Finkle, D; Dean, R E

1981-03-01

Twenty-one patients with metabolic alkalosis were treated successfully with intravenous hydrochloric acid (HCl) buffered in an amino acid solution (TPN). No complications of HCl were seen. TPN was used to meet energy needs and provide a buffering effect through the interaction of HCl and amino acids. Buffered HCl therapy should be considered as the initial treatment in patients with metabolic alkalosis associated with congestive heart failure, renal failure, hepatic failure, cerebral edema, or refractory metabolic alkalosis.

Buffer salt effects in off-line coupling of capillary electrophoresis and mass spectrometry.

PubMed

Marák, Jozef; Stanová, Andrea

2014-05-01

In this work, the impact of buffer salts/matrix effects on the signal in direct injection MS with an electrospray interface (DI-ESI-MS) following pITP fractionation of the sample was studied. A range of buffers frequently used in CE analyses (pH 3-10) was prepared containing 10, 50, and 90% v/v of ACN, respectively. The sets of calibration solutions of cetirizine (an antihistaminic drug with an amphiprotic character) within a 0.05-2.0 mg/L concentration range were prepared in different buffers. The greatest enhancements in the MS signal (in terms of change in the slope of the calibration line) were obtained for the beta-alanine buffer (pH 3.5) in positive ionization and for the borate buffer (pH 9.2) in negative ionization, respectively. The procedure was successfully applied to the analysis of buserelin (a peptidic drug). The slope of the calibration line for solutions containing the beta-alanine buffer with 50% of ACN was 4 times higher than for water or urine, respectively. This study clearly demonstrates that the buffer salt/matrix effects in an offline combination of pITP and DI-ESI-MS can also play a positive role, as they can enhance the signal in MS. A similar influence of the above effects can also be presumed in the CE techniques combined on-line with ESI-MS.

Oligomeric stability of Rapana venosa hemocyanin (RvH) and its structural subunits.

PubMed

Dolashka-Angelova, Pavlina; Schwarz, Heinz; Dolashki, Aleksandar; Stevanovic, Stefan; Fecker, Miriam; Saeed, Muhammad; Voelter, Wolfgang

2003-03-21

The two structural subunits RvH1 and RvH2 were separated after overnight dialysis of Rapana venosa Hc against 130 mM Gly/NaOH buffer, pH 9.6, on an ion exchange column Hiload 26/10 Sepharose Q using a fast performance liquid chromatography (FPLC) system. The reassociation characteristics of these two RvH isoforms and the native molecule were studied in buffers with different pH values and concentrations of Ca(2+) and Mg(2+). Reassociation of mixed RvH subunits was performed over a period of several days using a stabilizing buffer (SB) of pH 7.0 containing different concentrations of Ca(2+) and Mg(2+) ions. After 2 days of dialysis, an RvH subunit mixture of didecamers and multidecamers was observed in the presence of 100 mM CaCl(2) and MgCl(2), though RvH1 and RvH2 are biochemically and immunologically different and have also different dissociation properties. The reassociation, performed at pH 9.6 with 2 mM CaCl(2) and MgCl(2) at 4 degrees C over a period of one to several weeks, led to the formation of decameric oligomers, while didecamers formed predominantly in the SB at pH 7.0. Higher concentrations of calcium and magnesium ions led to a more rapid reassociation of RvH1 resulting in long stable multidecamers and helical tubules, which were stable and slowly dissociated into shorter multidecamers and decamers at higher pH values. The reassociation of the RvH2 structural subunit in the same buffers processed slowly and yielded didecamers, shorter tubule polymers and long multidecamers which are less stable at higher pH values. The stability of RvH isoforms under varying ionic conditions is compared with the stability of keyhole limpet (KLH, Megathura crenulata) hemocyanin (KLH) and Haliotis tuberculata hemocyanin (HtH) isoforms. The process of dissociation and reassociation is connected with changes of the fluorescence intensity at 600 nm, which can be explained by differences in opalescence of the solutions of these two isoforms. The solutions of longer tubule polymers and multidecamers of RvH1 show a higher opalescence compared to the solutions of shorter helical tubules and multidecamers of RvH2.

[Study on stability of curcumine, demethoxycurcumin and bisdemethoxycurcumin].

PubMed

Han, Gang; Cui, Jing-jing; Bi, Rui; Zhao, Lin-lin; Zhang, Wei-guo

2008-11-01

To investigate the stability of curcumin, demethoxycurcumin and bisdemethoxycurcumin in different buffer solution. To determine concentration of curcumin by HPLC when added curcumin, demethoxycurcumin and bisdemethoxycurcumin into the buffer solution the equation of degradation was established. The sequence of stability are bisdemethoxycurcumin > or = demethoxycurcumin > or =curcumin at the same condition. The demethoxycurcumin can stabilize curcumin more strong than the others. The demethoxycurcumin is a nature stabilizing agent for curcumin.

Strategies for the depyrogenation of contaminated immunoglobulin G solutions by histidine-immobilized hollow fiber membrane.

PubMed

Legallais, C; Anspach, F B; Bueno, S M; Haupt, K; Vijayalakshmi, M A

1997-03-28

The depyrogenation of different IgG solutions using the histidine-linked hollow fiber membrane developed in our laboratory is presented here. Three strategies for endotoxin (ET) removal were investigated according to the immobilized histidine's ability to bind different immunoglobulins: (1) ET removal from 1 mg/ml non histidine-binding mouse monoclonal IgG1 (MabCD4) solution was achieved in the presence of acetate buffer (pH 5.0) without any protein loss. (2) For contaminated human IgG, combined adsorption of ET and IgG in the presence of MOPS of Tris buffer was tested, followed by differential elution using increasing salt concentrations. This attempt was not successful since ET were quantitatively found in the IgG elution fraction. (3) Alternatively, it was proposed to adsorb selectively ET in the presence of acetate buffer (pH 5.0) under non binding conditions for human IgG. Human IgG could then be purified if necessary with the same membrane in the presence of MOPS buffer (pH 6.5). With a 1 m2 histidine-PEVA module under these operating conditions, it is estimated that the depyrogenation of 3 l of 1 mg/ml IgG (human or murine) solution containing 80 EU/ml of ET should be possible.

Kinetics of Contact Formation and End-to-End Distance Distributions of Swollen Disordered Peptides

PubMed Central

Soranno, Andrea; Longhi, Renato; Bellini, Tommaso; Buscaglia, Marco

2009-01-01

Unstructured polypeptide chains are subject to various degrees of swelling or compaction depending on the combination of solvent condition and amino acid sequence. Highly denatured proteins generally behave like random-coils with excluded volume repulsion, whereas in aqueous buffer more compact conformations have been observed for the low-populated unfolded state of globular proteins as well as for naturally disordered sequences. To quantitatively account for the different mechanisms inducing the swelling of polypeptides, we have examined three 14-residues peptides in aqueous buffer and in denaturant solutions, including the well characterized AGQ repeat as a reference and two variants, in which we have successively introduced charged side chains and removed the glycines. Quenching of the triplet state of tryptophan by close contact with cysteine has been used in conjunction with Förster resonance energy transfer to study the equilibrium and kinetic properties of the peptide chains. The experiments enable accessing end-to-end root mean-square distance, probability of end-to-end contact formation and intrachain diffusion coefficient. The data can be coherently interpreted on the basis of a simple chain model with backbone angles obtained from a library of coil segments of proteins and hard sphere repulsion at each Cα position. In buffered water, we find that introducing charges in a glycine-rich sequence induces a mild chain swelling and a significant speed-up of the intrachain dynamics, whereas the removal of the glycines results in almost a two-fold increase of the chain volume and a drastic slowing down. In denaturants we observe a pronounced swelling of all the chains, with significant differences between the effect of urea and guanidinium chloride. PMID:19217868

Common stock solutions, buffers, and media.

PubMed

2001-05-01

This section describes the preparation of buffers and reagents used in this manual for cell culture, manipulation of tissue, and cell biological methods. Also discussed are special considerations for PCR experiments and for working with RNA.

Aqueous photolysis of niclosamide

USGS Publications Warehouse

Graebing, P.W.; Chib, J.S.; Hubert, T.D.; Gingerich, W.H.

2004-01-01

The photodegradation of [14C]niclosamide was studied in sterile, pH 5, 7, and 9 buffered aqueous solutions under artificial sunlight at 25.0 A? 1.0 A?C. Photolysis in pH 5 buffer is 4.3 times faster than in pH 9 buffer and 1.5 times faster than in pH 7 buffer. In the dark controls, niclosamide degraded only in the pH 5 buffer. After 360 h of continuous irradiation in pH 9 buffer, the chromatographic pattern of the degradates was the same regardless of which ring contained the radiolabel. An HPLC method was developed that confirmed these degradates to be carbon dioxide and two- and four-carbon aliphatic acids formed by cleavage of both aromatic rings. Carbon dioxide was the major degradate, comprising 40% of the initial radioactivity in the 360 h samples from both labels. The other degradates formed were oxalic acid, maleic acid, glyoxylic acid, and glyoxal. In addition, in the chloronitroaniline-labeled irradiated test solution, 2-chloro-4-nitroaniline was observed and identified after 48 h of irradiation but was not detected thereafter. No other aromatic compounds were isolated or observed in either labeled test system.

Determination of Novel Strategies for Hastening Corneal Wound Healing and Reducing Tissue Inflammation

DTIC Science & Technology

2011-10-01

blocking buffer, 5% fat -free milk in 0.1% Tris-buffered solution/Tween-20, for 1 hour at room temperature and then probed overnight at 5°C with...and blotting onto Immun-Blot PVDF membrane (Bio-Rad, Hercules, CA). Membranes were blocked with blocking buffer, 5% fat -free milk in 1x PBS buffer...distribution unlimited 13. SUPPLEMENTARY NOTES The aim of this study is to uncover novel transient receptor potential protein vanilloid-1 (TRPV1

High-performance porous polylactide stereocomplex crystallite scaffolds prepared by solution blending and salt leaching.

PubMed

Xie, Yan; Lan, Xiao-Rong; Bao, Rui-Ying; Lei, Yang; Cao, Zhi-Qiang; Yang, Ming-Bo; Yang, Wei; Wang, Yun-Bing

2018-09-01

Biodegradable stereocomplex crystallite polylactide (SC-PLA) porous scaffolds with well-defined pore structures, high heat resistance, mechanical strength, and solvent resistance together with good biocompatibility, were obtained through solution casting of mixed poly(l-lactide) and poly(d-lactide) solution and subsequent leaching of sodium chloride particles. The pore structure of the SC-PLA scaffolds can be perfectly maintained after a high-pressure sterilization treatment at 121 °C, owing to the extensive formation of stereocomplex crystallites in the scaffolds. In vivo pilot study demonstrates that the fibroblasts of rats can infiltrate into the SC-PLA scaffolds well through the open pores. Degradation tests in phosphate-buffered saline solution reveal that the structure of SC-PLA scaffolds was quite stable due to the enhanced hydrolysis-resistance and improved mechanical properties of the scaffolds. These results reveal that SC-PLA scaffolds with good biocompatibility are potentially to be used as implanted biomaterials for the regeneration and restoration of tissues or organs. Copyright © 2018 Elsevier B.V. All rights reserved.

A dynamic system for the simulation of fasting luminal pH-gradients using hydrogen carbonate buffers for dissolution testing of ionisable compounds.

PubMed

Garbacz, Grzegorz; Kołodziej, Bartosz; Koziolek, Mirko; Weitschies, Werner; Klein, Sandra

2014-01-23

The hydrogen carbonate buffer is considered as the most biorelevant buffer system for the simulation of intestinal conditions and covers the physiological pH range of the luminal fluids from pH 5.5 to about pH 8.4. The pH value of a hydrogen carbonate buffer is the result of a complex and dynamic interplay of the concentration of hydrogen carbonate ions, carbonic acid, the concentration of dissolved and solvated carbon dioxide and its partial pressure above the solution. The complex equilibrium between the different ions results in a thermodynamic instability of hydrogen carbonate solutions. In order to use hydrogen carbonate buffers with pH gradients in the physiological range and with the dynamics observed in vivo without changing the ionic strength of the solution, we developed a device (pHysio-grad®) that provides both acidification of the dissolution medium by microcomputer controlled carbon dioxide influx and alkalisation by degassing. This enables a continuous pH control and adjustment during dissolution of ionisable compounds. The results of the pH adjustment indicate that the system can compensate even rapid pH changes after addition of a basic or acidic moiety in amounts corresponding up to 90% of the overall buffer capacity. The results of the dissolution tests performed for a model formulation containing ionizable compounds (Nexium 20mg mups) indicate that both the simulated fasting intraluminal pH-profiles and the buffer species can significantly affect the dissolution process by changing the lag time prior to initial drug release and the release rate of the model compound. A prediction of the in vivo release behaviour of this formulation is thus most likely strongly related to the test conditions such as pH and buffer species. Copyright © 2013 Elsevier B.V. All rights reserved.

Protein-Water and Protein-Buffer Interactions in the Aqueous Solution of an Intrinsically Unstructured Plant Dehydrin: NMR Intensity and DSC Aspects

PubMed Central

Tompa, P.; Bánki, P.; Bokor, M.; Kamasa, P.; Kovács, D.; Lasanda, G.; Tompa, K.

2006-01-01

Proton NMR intensity and differential scanning calorimetry measurements were carried out on an intrinsically unstructured late embryogenesis abundant protein, ERD10, the globular BSA, and various buffer solutions to characterize water and ion binding of proteins by this novel combination of experimental approaches. By quantifying the number of hydration water molecules, the results demonstrate the interaction between the protein and NaCl and between buffer and NaCl on a microscopic level. The findings overall provide direct evidence that the intrinsically unstructured ERD10 not only has a high hydration capacity but can also bind a large amount of charged solute ions. In accord, the dehydration stress function of this protein probably results from its simultaneous action of retaining water in the drying cells and preventing an adverse increase in ionic strength, thus countering deleterious effects such as protein denaturation. PMID:16798808

Three-Stream, Bicarbonate-Based Hemodialysis Solution Delivery System Revisited: With an Emphasis on Some Aspects of Acid-Base Principles.

PubMed

Lew, Susie Q; Kohn, Orly F; Cheng, Yuk-Lun; Kjellstrand, Carl M; Ing, Todd S

2017-06-01

Hemodialysis patients can acquire buffer base (i.e., bicarbonate and buffer base equivalents of certain organic anions) from the acid and base concentrates of a three-stream, dual-concentrate, bicarbonate-based, dialysis solution delivery machine. The differences between dialysis fluid concentrate systems containing acetic acid versus sodium diacetate in the amount of potential buffering power were reviewed. Any organic anion such as acetate, citrate, or lactate (unless when combined with hydrogen) delivered to the body has the potential of being converted to bicarbonate. The prescribing physician aware of the role that organic anions in the concentrates can play in providing buffering power to the final dialysis fluid, will have a better knowledge of the amount of bicarbonate and bicarbonate precursors delivered to the patient. © 2017 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Quantitative Correlation between Viscosity of Concentrated MAb Solutions and Particle Size Parameters Obtained from Small-Angle X-ray Scattering.

PubMed

Fukuda, Masakazu; Moriyama, Chifumi; Yamazaki, Tadao; Imaeda, Yoshimi; Koga, Akiko

2015-12-01

To investigate the relationship between viscosity of concentrated MAb solutions and particle size parameters obtained from small-angle X-ray scattering (SAXS). The viscosity of three MAb solutions (MAb1, MAb2, and MAb3; 40-200 mg/mL) was measured by electromagnetically spinning viscometer. The protein interactions of MAb solutions (at 60 mg/mL) was evaluated by SAXS. The phase behavior of 60 mg/mL MAb solutions in a low-salt buffer was observed after 1 week storage at 25°C. The MAb1 solutions exhibited the highest viscosity among the three MAbs in the buffer containing 50 mM NaCl. Viscosity of MAb1 solutions decreased with increasing temperature, increasing salt concentration, and addition of amino acids. Viscosity of MAb1 solutions was lowest in the buffer containing histidine, arginine, and aspartic acid. Particle size parameters obtained from SAXS measurements correlated very well with the viscosity of MAb solutions at 200 mg/mL. MAb1 exhibited liquid-liquid phase separation at a low salt concentration. Simultaneous addition of basic and acidic amino acids effectively suppressed intermolecular attractive interactions and decreased viscosity of MAb1 solutions. SAXS can be performed using a small volume of samples; therefore, the particle size parameters obtained from SAXS at intermediate protein concentration could be used to screen for low viscosity antibodies in the early development stage.

Expanding pH screening space using multiple droplets with secondary buffers for protein crystallization

NASA Astrophysics Data System (ADS)

Zhang, Chen-Yan; Dong, Chen; Lu, Xiao-Li; Wang, Bei; He, Tian-Yuan; Yang, Rui-Zeng; Lin, Hua-Long; Yang, Xue-Zhou; Yin, Da-Chuan

2017-04-01

We have proposed a rational strategy for selecting a suitable pH of protein solution based on protein biochemical properties. However, it is difficult to use this strategy for biochemical properties unknown proteins. In this paper, a simpler and faster pH buffer strategy was proposed. An additional pH-controlling buffer was added to crystallization droplet mixed with protein solution and commercial crystallization reagents to adjust its pH. The results revealed that protein crystallization success rates were enhanced by this strategy due to expansion of the pH screening space, which was closely related with protein solubility. Thus, the possibility of reaching supersaturation was increased by using this strategy.

Effect of gel formation on the dissolution behavior of clarithromycin tablets.

PubMed

Inukai, Koki; Takiyama, Kei; Noguchi, Shuji; Iwao, Yasunori; Itai, Shigeru

2017-04-15

Clarithromycin (CAM) is a macrolide antibiotic that is widely used at clinical sites. We found that release of CAM is suppressed when tablets of CAM were exposed to an external solvent containing carboxylate buffers such as citrate. The suppressed release of CAM can be attributed to the formation of gels on the tablet surfaces, which inhibits penetration of the solvent into the tablet and thus disintegration of the tablets. Delayed disintegration of the tablets was also observed for commercial tablets. This suggests that taking CAM and carboxylates at the same time might be avoided. The crystal structure of CAM citrate reveals that molecular chains of CAM are cross-linked by hydrogen bond between citrate groups in the crystal. The crystal structure indicates that cross-linked CAM chains of the three-dimensional mesh structure might also be formed in high concentration CAM solutions in the presence of carboxylates, resulting in gel formation. Copyright © 2017 Elsevier B.V. All rights reserved.

Injections of Algesic Solutions into Muscle Activate the Lateral Reticular Formation: A Nociceptive Relay of the Spinoreticulothalamic Tract

PubMed Central

Panneton, W. Michael; Gan, Qi; Ariel, Michael

2015-01-01

Although musculoskeletal pain disorders are common clinically, the central processing of muscle pain is little understood. The present study reports on central neurons activated by injections of algesic solutions into the gastrocnemius muscle of the rat, and their subsequent localization by c-Fos immunohistochemistry in the spinal cord and brainstem. An injection (300μl) of an algesic solution (6% hypertonic saline, pH 4.0 acetate buffer, or 0.05% capsaicin) was made into the gastrocnemius muscle and the distribution of immunolabeled neurons compared to that obtained after control injections of phosphate buffered saline [pH 7.0]. Most labeled neurons in the spinal cord were found in laminae IV-V, VI, VII and X, comparing favorably with other studies, with fewer labeled neurons in laminae I and II. This finding is consistent with the diffuse pain perception due to noxious stimuli to muscles mediated by sensory fibers to deep spinal neurons as compared to more restricted pain localization during noxious stimuli to skin mediated by sensory fibers to superficial laminae. Numerous neurons were immunolabeled in the brainstem, predominantly in the lateral reticular formation (LRF). Labeled neurons were found bilaterally in the caudalmost ventrolateral medulla, where neurons responsive to noxious stimulation of cutaneous and visceral structures lie. Immunolabeled neurons in the LRF continued rostrally and dorsally along the intermediate reticular nucleus in the medulla, including the subnucleus reticularis dorsalis caudally and the parvicellular reticular nucleus more rostrally, and through the pons medial and lateral to the motor trigeminal nucleus, including the subcoerulear network. Immunolabeled neurons, many of them catecholaminergic, were found bilaterally in the nucleus tractus solitarii, the gracile nucleus, the A1 area, the CVLM and RVLM, the superior salivatory nucleus, the nucleus locus coeruleus, the A5 area, and the nucleus raphe magnus in the pons. The external lateral and superior lateral subnuclei of the parabrachial nuclear complex were consistently labeled in experimental data, but they also were labeled in many control cases. The internal lateral subnucleus of the parabrachial complex was labeled moderately. Few immunolabeled neurons were found in the medial reticular formation, however, but the rostroventromedial medulla was labeled consistently. These data are discussed in terms of an interoceptive, multisynaptic spinoreticulothalamic path, with its large receptive fields and role in the motivational-affective components of pain perceptions. PMID:26154308

Injections of Algesic Solutions into Muscle Activate the Lateral Reticular Formation: A Nociceptive Relay of the Spinoreticulothalamic Tract.

PubMed

Panneton, W Michael; Gan, Qi; Ariel, Michael

2015-01-01

Although musculoskeletal pain disorders are common clinically, the central processing of muscle pain is little understood. The present study reports on central neurons activated by injections of algesic solutions into the gastrocnemius muscle of the rat, and their subsequent localization by c-Fos immunohistochemistry in the spinal cord and brainstem. An injection (300 μl) of an algesic solution (6% hypertonic saline, pH 4.0 acetate buffer, or 0.05% capsaicin) was made into the gastrocnemius muscle and the distribution of immunolabeled neurons compared to that obtained after control injections of phosphate buffered saline [pH 7.0]. Most labeled neurons in the spinal cord were found in laminae IV-V, VI, VII and X, comparing favorably with other studies, with fewer labeled neurons in laminae I and II. This finding is consistent with the diffuse pain perception due to noxious stimuli to muscles mediated by sensory fibers to deep spinal neurons as compared to more restricted pain localization during noxious stimuli to skin mediated by sensory fibers to superficial laminae. Numerous neurons were immunolabeled in the brainstem, predominantly in the lateral reticular formation (LRF). Labeled neurons were found bilaterally in the caudalmost ventrolateral medulla, where neurons responsive to noxious stimulation of cutaneous and visceral structures lie. Immunolabeled neurons in the LRF continued rostrally and dorsally along the intermediate reticular nucleus in the medulla, including the subnucleus reticularis dorsalis caudally and the parvicellular reticular nucleus more rostrally, and through the pons medial and lateral to the motor trigeminal nucleus, including the subcoerulear network. Immunolabeled neurons, many of them catecholaminergic, were found bilaterally in the nucleus tractus solitarii, the gracile nucleus, the A1 area, the CVLM and RVLM, the superior salivatory nucleus, the nucleus locus coeruleus, the A5 area, and the nucleus raphe magnus in the pons. The external lateral and superior lateral subnuclei of the parabrachial nuclear complex were consistently labeled in experimental data, but they also were labeled in many control cases. The internal lateral subnucleus of the parabrachial complex was labeled moderately. Few immunolabeled neurons were found in the medial reticular formation, however, but the rostroventromedial medulla was labeled consistently. These data are discussed in terms of an interoceptive, multisynaptic spinoreticulothalamic path, with its large receptive fields and role in the motivational-affective components of pain perceptions.

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.

Effect of the Protein Corona on Antibody-Antigen Binding in Nanoparticle Sandwich Immunoassays.

PubMed

de Puig, Helena; Bosch, Irene; Carré-Camps, Marc; Hamad-Schifferli, Kimberly

2017-01-18

We investigated the effect of the protein corona on the function of nanoparticle (NP) antibody (Ab) conjugates in dipstick sandwich immunoassays. Ab specific for Zika virus nonstructural protein 1 (NS1) were conjugated to gold NPs, and another anti-NS1 Ab was immobilized onto the nitrocellulose membrane. Sandwich immunoassay formation was influenced by whether the strip was run in corona forming conditions, i.e., in human serum. Strips run in buffer or pure solutions of bovine serum albumin exhibited false positives, but those run in human serum did not. Serum pretreatment of the nitrocellulose also eliminated false positives. Corona formation around the NP-Ab in serum was faster than the immunoassay time scale. Langmuir binding analysis determined how the immobilized Ab affinity for the NP-Ab/NS1 was impacted by corona formation conditions, quantified as an effective dissociation constant, K D eff . Results show that corona formation mediates the specificity and sensitivity of the antibody-antigen interaction of Zika biomarkers in immunoassays, and plays a critical but beneficial role.

Correlated Fluorescence-Atomic Force Microscopy Studies of the Clathrin Mediated Endocytosis in SKMEL Cells

NASA Astrophysics Data System (ADS)

Smith, Steve; Hor, Amy; Luu, Anh; Kang, Lin; Scott, Brandon; Bailey, Elizabeth; Hoppe, Adam

Clathrin-mediated endocytosis is one of the central pathways for cargo transport into cells, and plays a major role in the maintenance of cellular functions, such as intercellular signaling, nutrient intake, and turnover of plasma membrane in cells. The clathrin-mediated endocytosis process involves invagination and formation of clathrin-coated vesicles. However, the biophysical mechanisms of vesicle formation are still debated. We investigate clathrin vesicle formation mechanisms through the utilization of tapping-mode atomic force microscopy for high resolution topographical imaging in neutral buffer solution of unroofed cells exposing the inner membrane, combined with fluorescence imaging to definitively label intracellular constituents with specific fluorescent fusion proteins (actin filaments labeled with green phalloidin-antibody and clathrin coated vesicles with the fusion protein Tq2) in SKMEL (Human Melanoma) cells. Results from our work are compared against dynamical polarized total internal fluorescence (TIRF), super-resolution photo-activated localization microscopy (PALM) and transmission electron microscopy (TEM) to draw conclusions regarding the prominent model of vesicle formation in clathrin-mediated endocytosis. Funding provided by NSF MPS/DMR/BMAT award # 1206908.

Delivery of resveratrol, a red wine polyphenol, from solutions and hydrogels via the skin.

PubMed

Hung, Chi-Feng; Lin, Yin-Ku; Huang, Zih-Rou; Fang, Jia-You

2008-05-01

Resveratrol, the main active polyphenol in red wine, has been demonstrated to show benefits against skin disorders. The bioavailability of orally administered resveratrol is insufficient to permit high enough drug concentrations for systemic therapy. In this study, we examined the feasibility of the topical/transdermal delivery of resveratrol. The effects of vehicles on the in vitro permeation and skin deposition from saturated solutions such as aqueous buffers and soybean oil were investigated. The general trend for the delivery from solutions was: pH 6 buffer=pH 8 buffer>10% glycerol formal in pH 6 buffer>pH 9.9 buffer>pH 10.8 buffer>soybean oil. A linear relationship was established between the permeability coefficient (K(p)) and drug accumulation in the skin reservoir. Viable epidermis/dermis served as the predominant barrier for non-ionic resveratrol permeation. On the other hand, both the stratum corneum (SC) and viable skin acted as barriers to anionic resveratrol. Several prototype hydrogel systems were also studied as resveratrol vehicles. The viscosity but not the polarity of the hydrogels controlled resveratrol permeation/deposition. Piceatannol, a derivative of resveratrol with high pharmacological activity, showed 11.6-fold lower skin permeation compared to resveratrol. The safety profiles of resveratrol suggested that the hydrogel caused no SC disruption or skin erythema. It was concluded that delivery via a skin route may be a potent way to achieve the therapeutic effects of resveratrol. This is the first report to establish the permeation profiles for topically applied resveratrol.

Stabilization of a supersaturated solution of mefenamic acid from a solid dispersion with EUDRAGIT(®) EPO.

PubMed

Kojima, Taro; Higashi, Kenjirou; Suzuki, Toyofumi; Tomono, Kazuo; Moribe, Kunikazu; Yamamoto, Keiji

2012-10-01

The stabilization mechanism of a supersaturated solution of mefenamic acid (MFA) from a solid dispersion with EUDRAGIT(®) EPO (EPO) was investigated. The solid dispersions were prepared by cryogenic grinding method. Powder X-ray diffractometry, in vitro dissolution test, in vivo oral absorption study, infrared spectroscopy, and solid- and solution-state NMR spectroscopies were used to characterize the solid dispersions. Dissolution tests in acetate buffer (pH 5.5) revealed that solid dispersion showed > 200-fold higher concentration of MFA. Supersaturated solution was stable over 1 month and exhibited improved oral bioavailability of MFA in rats, with a 7.8-fold higher area under the plasma concentration-versus-time curve. Solid-state (1)H spin-lattice relaxation time (T(1)) measurement showed that MFA was almost monomolecularly dispersed in the EPO polymer matrix. Intermolecular interaction between MFA and EPO was indicated by solid-state infrared and (13)C-T(1) measurements. Solution-state (1)H-NMR measurement demonstrated that MFA existed in monomolecular state in supersaturated solution. (1)H-T(1) and difference nuclear Overhauser effect measurements indicated that cross relaxation occurred between MFA and EPO due to the small distance between them. The formation and high stability of the supersaturated solution were attributable to the specifically formed intermolecular interactions between MFA and EPO.

Enantioselective separation of chiral aromatic amino acids with surface functionalized magnetic nanoparticles.

PubMed

Ghosh, Sudipa; Fang, Tan Hui; Uddin, M S; Hidajat, K

2013-05-01

Chiral resolution aromatic amino acids, DL-tryptophan (DL-Trp), DL-phenylalanine (DL-Phe), DL-tyrosine (DL-Tyr) from phosphate buffer solution was achieved in present study employing the concept of selective adsorption by surface functionalized magnetic nanoparticles (MNPs). Surfaces of magnetic nanoparticles were functionalized with silica and carboxymethyl-β-cyclodextrin (CMCD) to investigate their adsorption resolution characteristics. Resolution of enantiomers from racemic mixture was quantified in terms of enantiomeric excess using chromatographic method. The MNPs selectively adsorbed L-enantiomers of DL-Trp, DL-Phe, and DL-Tyr from racemic mixture and enantiomeric excesses (e.e.) were determined as 94%, 73% and 58%, respectively. FTIR studies demonstrated that hydrophobic portion of enantiomer penetrated into hydrophobic cavity of cyclodextrin molecules to form inclusion complex. Furthermore, adsorption site was explored using XPS and it was revealed that amino group at chiral center of the amino acid molecule formed hydrogen bond with secondary hydroxyl group of CMCD molecule and favorability of hydrogen bond formation resulted in selective adsorption of L-enantiomer. Finally, stability constant (K) and Gibbs free energy change (-ΔG°) for inclusion complexation of CMCD with L-/D-enantiomers of amino acids were determined using spectroflurometry in aqueous buffer solution. Higher binding constants were obtained for inclusion complexation of CMCD with L-enantiomers compared to D-enantiomers which stimulated enantioselective properties of CMCD functionalized magnetite silica nanoparticles. Copyright © 2013 Elsevier B.V. All rights reserved.

Closed-form solutions of performability. [modeling of a degradable buffer/multiprocessor system

NASA Technical Reports Server (NTRS)

Meyer, J. F.

1981-01-01

Methods which yield closed form performability solutions for continuous valued variables are developed. The models are similar to those employed in performance modeling (i.e., Markovian queueing models) but are extended so as to account for variations in structure due to faults. In particular, the modeling of a degradable buffer/multiprocessor system is considered whose performance Y is the (normalized) average throughput rate realized during a bounded interval of time. To avoid known difficulties associated with exact transient solutions, an approximate decomposition of the model is employed permitting certain submodels to be solved in equilibrium. These solutions are then incorporated in a model with fewer transient states and by solving the latter, a closed form solution of the system's performability is obtained. In conclusion, some applications of this solution are discussed and illustrated, including an example of design optimization.

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®.

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.

Biocompatibility of a bicarbonate-buffered amino-acid-based solution for peritoneal dialysis.

PubMed

Bender, Thorsten O; Witowski, Janusz; Aufricht, Christoph; Endemann, Michaela; Frei, Ulrich; Passlick-Deetjen, Jutta; Jörres, Achim

2008-09-01

Amino-acid-based peritoneal dialysis (PD) fluids have been developed to improve the nutritional status of PD patients. As they may potentially exacerbate acidosis, an amino-acid-containing solution buffered with bicarbonate (Aminobic) has been proposed to effectively maintain acid-base balance. The aim of this study was to evaluate the mesothelial biocompatibility profile of this solution in comparison with a conventional low-glucose-based fluid. Omentum-derived human peritoneal mesothelial cells (HPMC) were preexposed to test PD solutions for up to 120 min, then allowed to recover in control medium for 24 h, and assessed for heat-shock response, viability, and basal and stimulated cytokine [interleukin (IL)-6] and prostaglandin (PGE(2)) release. Acute exposure of HPMC to conventional low-glucose-based PD solution resulted in a time-dependent increase in heat-shock protein (HSP-72) expression, impaired viability, and reduced ability to release IL-6 in response to stimulation. In contrast, in cells treated with Aminobic, the expression of HSP-72 was significantly lower, and viability and cytokine-producing capacity were preserved and did not differ from those seen in control cells. In addition, exposure to Aminobic increased basal release of IL-6 and PGE(2). These data point to a favorable biocompatibility profile of the amino-acid-based bicarbonate-buffered PD solution toward HPMC.

Investigations Concerning Hydrolysis and Stabilization of Antiradiation Compounds

DTIC Science & Technology

1982-01-01

Stability of Unencapsulated WR 2721 31 V. DISCUSSION 35 A. Microencapsulation 35 1. Microspheres 35 2. Microcapsules 35 B. Hydrolytic Stability of...in 1.5 hours at 370C in buffered solutions of pH 1.0 or 3.0. 3^ The more promising microspheres and microcapsules released the WR 2721 within two...hours at pH 7.5 in buffered solutions. 4) Analytical procedures were developed for: "♦ WR 2721 (directly) in microcapsules using an HPLC

Formation of Fe/mg Smectite Under Acidic Conditions from Synthetic Adirondack Basaltic Glass: an Analog to Fe/mg Smectite Formation on Mars

NASA Technical Reports Server (NTRS)

Sutter, B.; Peretyazhko, T.; Morris, R. V.; Ming, D. W.

2014-01-01

Smectite has been detected as layered material hundreds of meters thick, in intracrater depositional fans, in plains sediments, and deposits at depth on Mars. If early Mars hosted a dense CO2 atmosphere, then extensive carbonate should have formed in the neutral/alkaline conditions expected for smectite formation. However, large carbonate deposits on Mars have not been discovered. Instead of neutral to moderately alkaline conditions, early Mars may have experienced mildly acidic conditions that allowed for Fe/Mg smectite formation but prevented widespread carbonate formation. The objective of this work is to demonstrate that Fe(II)/Mg saponite and nontronite can form in mildly acidic solutions (e.g., pH 4). Synthetic basaltic glass (< 53 microns) of Adirondack rock class composition was exposed to pH 4 (acetic acid buffer) and N2 purged (anoxic) solutions amended with 0 and 10 mM Mg or Fe(II). Basaltic glass in these solutions was heated to 200 C in batch reactors for 1, 7, and 14 days. X-ray diffraction analysis of reacted materials detected the presence of phyllosilicates as indicated by a approx. 15.03-15.23Angstroms (001) peak. Smectite was confirmed as the phyllosilicate after treatments with glycerol and KCl and heating to 550 C. Trioctahedral saponite was confirmed by the presence of a 4.58 to 4.63 Angstroms (02l) and 1.54Angstroms (060) peaks. Saponite concentration was highest, as indicated by XRD peak intensity, in the 10 mM Mg treatment followed by the 0 mM and then 10 mM Fe(II) treatments. This order of sapontite concentration suggests that Fe(II) additions may have a role in slowing the kinetics of saponite formation relative to the other treatments. Nontronite synthesis was attempted by exposing Adirondack basaltic glass to pH 4 oxic solutions (without N2 purge) at 200 C for 14 days. X-ray diffraction analysis indicated that mixtures of trioctahedral (saponite) and dioctahedral (nontronite) may have formed in these experiments based on the 02l and 060 peaks. Moessbauer analysis coupled with future experiments are planned to verify if nontronite can be formed under mildly acidic and oxic conditions. Results of this work demonstrate that acidic conditions could have occurred on an early Mars, which allowed for smectite formation but inhibited carbonate formation.

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

Formation of the thioester, N,S-diacetylcysteine, from acetaldehyde and N,N'-diacetylcystine in aqueous solution with ultraviolet light

NASA Technical Reports Server (NTRS)

Weber, A. L.

1981-01-01

The thioester, N,S-diacetylcysteine, is formed during the illumination of phosphate buffered (pH 7.0) aqueous solutions of acetaldehyde and N,N'-diacetylcystine with ultraviolet light. The yield of N,S-diacetylcysteine relative to N-acetylcysteine and unidentified products progressively increases as ultraviolet light below 239 nm, 253 nm and 281 nm is cut off with optical filters. When ultraviolet light below 320 nm is removed with an optical filter, there is no detectable reaction. Illumination of 0.025 M N,N'-diacetylcystine with 0.5 M and 1.0 M acetaldehyde with filtered ultraviolet light gives, respectively, 20% and 80% yields of N,S-diacetylcysteine. In the reaction with 1.0 M acetaldehyde, N-acetylcysteine forms early in the reaction and later decreases with its conversion to N,S-diacetylcysteine. The prebiotic significance of these reactions is discussed.

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.

Simultaneous determination of bromhexine hydrochloride and methyl and propyl p-hydroxybenzoate and determination of dextromethorphan hydrobromide in cough-cold syrup by high-performance liquid chromatography.

PubMed

Rauha, J P; Salomies, H; Aalto, M

1996-11-01

Liquid chromatographic methods were developed for the determination of bromhexine hydrochloride, methyl p-hydroxybenzoate and propyl p-hydroxybenzoate (method A) and dextromethorphan hydrobromide (method B) in cough-cold syrup formulations. Reversed-phase analytical columns (150 mm x 3.9 mm i.d.) were used with (A) C18 and (B) phenyl as stationary phases and mixtures of (A) acetonitrile and aqueous 15 mM triethylamine solution (43:57) and (B) methanol and aqueous 3% ammonium formate buffer solution (53:47) as mobile phases at a flow rate of 1.0 ml min-1. Both aqueous components were adjusted to pH 3.9. UV detection of analytes was at (A) 245 nm and (B) 278 nm. In both methods, the time required for an HPLC run giving good separations and recoveries was less than 8 min.

One-pot non-enzymatic formation of firefly luciferin in a neutral buffer from p-benzoquinone and cysteine

PubMed Central

Kanie, Shusei; Nishikawa, Toshio; Ojika, Makoto; Oba, Yuichi

2016-01-01

Firefly luciferin, the substrate for the bioluminescence reaction of luminous beetles, possesses a benzothiazole ring, which is rare in nature. Here, we demonstrate a novel one-pot reaction to give firefly luciferin in a neutral buffer from p-benzoquinone and cysteine without any synthetic reagents or enzymes. The formation of firefly luciferin was low in yield in various neutral buffers, whereas it was inhibited or completely prevented in acidic or basic buffers, in organic solvents, or under a nitrogen atmosphere. Labelling analysis of the firefly luciferin using stable isotopic cysteines showed that the benzothiazole ring was formed via the decarboxylation and carbon-sulfur bond rearrangement of cysteine. These findings imply that the biosynthesis of firefly luciferin can be developed/evolved from the non-enzymatic production of firefly luciferin using common primary biosynthetic units, p-benzoquinone and cysteine. PMID:27098929

One-pot non-enzymatic formation of firefly luciferin in a neutral buffer from p-benzoquinone and cysteine.

PubMed

Kanie, Shusei; Nishikawa, Toshio; Ojika, Makoto; Oba, Yuichi

2016-04-21

Firefly luciferin, the substrate for the bioluminescence reaction of luminous beetles, possesses a benzothiazole ring, which is rare in nature. Here, we demonstrate a novel one-pot reaction to give firefly luciferin in a neutral buffer from p-benzoquinone and cysteine without any synthetic reagents or enzymes. The formation of firefly luciferin was low in yield in various neutral buffers, whereas it was inhibited or completely prevented in acidic or basic buffers, in organic solvents, or under a nitrogen atmosphere. Labelling analysis of the firefly luciferin using stable isotopic cysteines showed that the benzothiazole ring was formed via the decarboxylation and carbon-sulfur bond rearrangement of cysteine. These findings imply that the biosynthesis of firefly luciferin can be developed/evolved from the non-enzymatic production of firefly luciferin using common primary biosynthetic units, p-benzoquinone and cysteine.

Formation of hydroxyl radical from San Joaquin Valley particles extracted in a cell-free solution

NASA Astrophysics Data System (ADS)

Shen, H.; Anastasio, C.

2011-06-01

Previous studies have suggested that the adverse health effects from ambient particulate matter (PM) are linked to the formation of reactive oxygen species (ROS) by PM. While hydroxyl radical (•OH) is the most reactive of the ROS species, there are few quantitative studies of •OH generation from PM. Here we report on •OH formation from PM collected at an urban (Fresno) and rural (Westside) site in the San Joaquin Valley (SJV) of California. We quantified •OH in PM extracts using a cell-free, phosphate-buffered saline (PBS) solution with or without 50 μM ascorbate (Asc). The results show that generally the urban Fresno PM generates much more •OH than the rural Westside PM. The presence of Asc at a physiologically relevant concentration in the extraction solution greatly enhances •OH formation from all the samples. Fine PM (PM2.5) generally makes more •OH than the corresponding coarse PM (PMcf, i.e., 2.5 to 10 μm) normalized by air volume collected, while the coarse PM typically generates more •OH normalized by PM mass. •OH production by SJV PM is reduced on average by (97 ± 6) % when the transition metal chelator desferoxamine (DSF) is added to the extraction solution, indicating a dominant role of transition metals. By measuring calibration curves of •OH generation from copper and iron, and quantifying copper and iron concentrations in our particle extracts, we find that PBS-soluble copper is primarily responsible for •OH production by the SJV PM, while iron often makes a significant contribution. Extrapolating our results to expected burdens of PM-derived •OH in human lung lining fluid suggests that typical daily PM exposures in the San Joaquin Valley are unlikely to result in a high amount of pulmonary •OH, although high PM events could produce much higher levels of •OH, which might lead to cytotoxicity.

Confocal raman microscopy as a non-invasive tool to investigate the phase composition of frozen complex cryopreservation media.

PubMed

Kreiner-Møller, A; Stracke, F; Zimmermann, H

2013-01-01

Various cryoprotective agents (CPA) are added to cell media in order to avoid cell injury during cryo preservation. The resulting complex environment of the preserved cell, consisting of crystalline and liquid phases can however not be investigated non-invasively by established methods in cryobiology. This study shows how scanning confocal Raman microscopy can non-invasively extract information on chemical composition, phase domain and distribution at cryogenic temperatures. The formation of the salt hydrate, hydrohalite NaCl∙H2O, in solutions comprised of phosphate buffered saline (PBS) and dimethyl sulphoxide (DMSO) is studied in particular. Scanning confocal Raman microscopy can be used to unambiguously identify hydrohalite in a medium containing DMSO and saline. The confocal Raman microscopy imaging along with differential scanning calorimetric measurements further show that the hydrohalite is formed without eutectic formation. This method also allows for discrimination between closely packed hydrohalite crystals that are oriented differently.

Nanophase iron phosphate, iron arsenate, iron vanadate, and iron molybdate minerals synthesized within the protein cage of ferritin.

PubMed

Polanams, Jup; Ray, Alisha D; Watt, Richard K

2005-05-02

Nanoparticles of iron phosphate, iron arsenate, iron molybdate, and iron vanadate were synthesized within the 8 nm interior of ferritin. The synthesis involved reacting Fe(II) with ferritin in a buffered solution at pH 7.4 in the presence of phosphate, arsenate, vanadate, or molybdate. O2 was used as the oxidant to deposit the Fe(III) mineral inside ferritin. The rate of iron incorporation into ferritin was stimulated when oxo-anions were present. The simultaneous deposition of both iron and the oxo-anion was confirmed by elemental analysis and energy-dispersive X-ray analysis. The ferritin samples containing iron and one of the oxo-anions possessed different UV/vis spectra depending on the anion used during mineral formation. TEM analysis showed mineral cores with approximately 8 nm mineral particles consistent with the formation of mineral phases inside ferritin.

Investigation of Al Coated Mg for Biomedical Applications

NASA Astrophysics Data System (ADS)

Elmrabet, Nabila; Roe, Martin; Neate, Nigel; Grant, David M.; Brown, Paul D.

The corrosion resistant properties of 1-2 μm thick Al coatings deposited by radio frequency magnetron sputtering on polished Mg surfaces, within Ar and Ar/H2 environments, have been appraised. The coatings were heat-treated at 300°C for 5 h to induce the formation of bioinert Al2O3, and samples were corroded within phosphate buffered saline solution at 37°C to mimic the biological environment. Both the as-deposited and heat-treated coatings were found to delay the onset of corrosion, but showed higher initial corrosion rates, once established, as compared with polished Mg surfaces. Slightly improved performance of the coatings was achieved through the addition of H2 to the system which acted to inhibit Al-Mg alloying and MgO formation. However, localized accelerated corrosion associated with substrate polishing damage emphasized the need for improved process control and coating uniformity.

Programmable pH buffers

DOEpatents

Gough, Dara Van; Huber, Dale L.; Bunker, Bruce C.; Roberts, Mark E.

2017-01-24

A programmable pH buffer comprises a copolymer that changes pK.sub.a at a lower critical solution temperature (LCST) in water. The copolymer comprises a thermally programmable polymer that undergoes a hydrophobic-to-hydrophilic phase change at the LCST and an electrolytic polymer that exhibits acid-base properties that are responsive to the phase change. The programmable pH buffer can be used to sequester CO.sub.2 into water.

Junction formation of Cu3BiS3 investigated by Kelvin probe force microscopy and surface photovoltage measurements

PubMed Central

Mesa, Fredy; Chamorro, William; Vallejo, William; Baier, Robert; Dittrich, Thomas; Grimm, Alexander; Lux-Steiner, Martha C

2012-01-01

Summary Recently, the compound semiconductor Cu3BiS3 has been demonstrated to have a band gap of ~1.4 eV, well suited for photovoltaic energy harvesting. The preparation of polycrystalline thin films was successfully realized and now the junction formation to the n-type window needs to be developed. We present an investigation of the Cu3BiS3 absorber layer and the junction formation with CdS, ZnS and In2S3 buffer layers. Kelvin probe force microscopy shows the granular structure of the buffer layers with small grains of 20–100 nm, and a considerably smaller work-function distribution for In2S3 compared to that of CdS and ZnS. For In2S3 and CdS buffer layers the KPFM experiments indicate negatively charged Cu3BiS3 grain boundaries resulting from the deposition of the buffer layer. Macroscopic measurements of the surface photovoltage at variable excitation wavelength indicate the influence of defect states below the band gap on charge separation and a surface-defect passivation by the In2S3 buffer layer. Our findings indicate that Cu3BiS3 may become an interesting absorber material for thin-film solar cells; however, for photovoltaic application the band bending at the charge-selective contact has to be increased. PMID:22497001

Junction formation of Cu(3)BiS(3) investigated by Kelvin probe force microscopy and surface photovoltage measurements.

PubMed

Mesa, Fredy; Chamorro, William; Vallejo, William; Baier, Robert; Dittrich, Thomas; Grimm, Alexander; Lux-Steiner, Martha C; Sadewasser, Sascha

2012-01-01

Recently, the compound semiconductor Cu(3)BiS(3) has been demonstrated to have a band gap of ~1.4 eV, well suited for photovoltaic energy harvesting. The preparation of polycrystalline thin films was successfully realized and now the junction formation to the n-type window needs to be developed. We present an investigation of the Cu(3)BiS(3) absorber layer and the junction formation with CdS, ZnS and In(2)S(3) buffer layers. Kelvin probe force microscopy shows the granular structure of the buffer layers with small grains of 20-100 nm, and a considerably smaller work-function distribution for In(2)S(3) compared to that of CdS and ZnS. For In(2)S(3) and CdS buffer layers the KPFM experiments indicate negatively charged Cu(3)BiS(3) grain boundaries resulting from the deposition of the buffer layer. Macroscopic measurements of the surface photovoltage at variable excitation wavelength indicate the influence of defect states below the band gap on charge separation and a surface-defect passivation by the In(2)S(3) buffer layer. Our findings indicate that Cu(3)BiS(3) may become an interesting absorber material for thin-film solar cells; however, for photovoltaic application the band bending at the charge-selective contact has to be increased.

The application of animal models to study the biocompatibility of bicarbonate-buffered peritoneal dialysis solutions.

PubMed

ter Wee, P M; Beelen, R H J; van den Born, J

2003-12-01

The application of animal models to study the biocompatibility of bicarbonate-buffered peritoneal dialysis solutions. Patients treated with peritoneal dialysis (PD) are at risk for development of ultrafiltration failure and peritonitis. These two significant complications can result in the termination of PD treatment. The relative unphysiologic composition of the currently used standard peritoneal dialysis fluids (PDF) is considered to be a major cause for the development of morphologic changes of the peritoneal membrane, ultimately resulting in ultrafiltration failure and probably contributing to changes in local defense mechanisms with the associated increased risk of peritonitis. In recent years, a major research focus has become the development of new and improved PD solutions. This has resulted in the development of an amino-acid-based PDF, a glucose polymer-based PDF, and several bicarbonate-buffered PDF. Typically, the first phase of biocompatibility testing of new PD solutions involves in vitro testing, employing isolated cells such as peritoneal macrophages or cell culture systems using human peritoneal mesothelial cells. The results of such evaluations are useful in providing insights into the biocompatibility performance of any given formulation, but suffer from several disadvantages, which can be better addressed using animal models. In vivo studies using animals permit the analysis of biocompatibility under conditions that allow for cell-to-cell interactions and dynamic changes in solution composition that more closely mimic the clinical situation. In this paper, we will review the use of animal models for the study of PDF biocompatibility and their application to the assessment of bicarbonate-buffered PDF.

Effect of ozonation on minocycline degradation and N-Nitrosodimethylamine formation.

PubMed

Lv, Juan; Li, Yong M

2018-06-07

The objective of this study was to assess reactivity of Minocycline (MNC) towards ozone and determine the effects of ozone dose, pH value, and water matrix on MNC degradation as well as to characterize N-Nitrosodimethylamine (NDMA) formation from MNC ozonation. The MNC initial concentration of the solution was set in the range of 2-20 mg/L to investigate NDMA formation during MNC ozonation. Four ozone doses (22.5, 37.2, 58.0, and 74.4 mg/min) were tested to study the effect of ozone dose. For the evaluation of effects of pH value, pH was adjusted from 5 to 9 in the presence of phosphate buffer. MNC ozonation experiments were also conducted in natural water to assess the influence of water matirx. The influence of the typical component of natural water was also investigated with the addition of HA and NaHCO 3 solution. Results indicated that ozone was effective in MNC removal. Consequently, NDMA and dimethylamine (DMA) were generated from MNC oxidation. Increasing pH value enhanced MNC removal but led to greater NDMA generation. Water matrices, such as HCO 3 - and humic acid, affected MNC degradation. Conversely, more NDMA accumulated due to the inhibition of NDMA oxidation by oxidant consumption. Though ⋅OH can enhance MNC degradation, ozone molecules were heavily involved in NDMA production. Seven transformation products were identified. However, only DMA and the unidentified tertiary amine containing DMA group contributed to NDMA formation.

Preparation and Properties of Hybrid Nanostructures of Zinc Tetraphenylporphyrinate and an Amphiphilic Copolymer of N-Vinylpyrrolidone in a Neutral Aqueous Buffer Solution

NASA Astrophysics Data System (ADS)

Kurmaz, S. V.; Gak, V. Yu.; Kurmaz, V. A.; Konev, D. V.

2018-02-01

Water-soluble forms of a hydrophobic dye, zinc tetraphenylporphyrinate, are obtained via its solubilization by polymer particles of the micellar type formed by a copolymer of N-vinylpyrrolidone with triethylene glycol dimethacrylate. Hydrodynamic radii R h and the size distribution of such particles in neutral aqueous buffer solutions are determined via dynamic light scattering. The electrochemical activity of the encapsulated dye is found, and its photochemical properties (absorption and fluorescence) are studied.

Ultrastructural investigations for reducing endothelial cell damage of vein grafts during CABG-operation and practical consequences.

PubMed

Hickethier, T; Dämmrich, J; Silber, R E; Finster, S; Elert, O

1999-02-01

In the present study the influence of different storage solutions on endothelial integrity or damage was investigated with direct methods particularly with transmission electron microscopy (TEM), scanning electron microscopy (SEM) and immunohistochemistry. Saphenous vein segments of 10 cm in length were taken surgically from 6 male CABG-patients (aged 60-70) under standardized conditions. Each vein segment was cut into rings, which were incubated at room temperature for 45 minutes in different storage solutions, particularly in 0.9% sodium chloride solution and in buffered solution (M 199) with 5% human serum albumin respectively. Then, the vein segments were fixed in 3.5% glutaraldehyde and prepared for scanning and transmission electron microscopy to evaluate the endothelial damage. In addition, immunohistochemical staining (CD34, PECAM and Factor VIII) was performed. When using 0.9% sodium chloride solution, the SEM-examination revealed that 55% of the cell population was destroyed. In comparison to these findings only 26% of the endothelial cell population was damaged when the venous segment was stored in buffered solution with 5% albumin (p<0.01). In immunohistochemistry (CD34, PECAM, Factor VIII) these findings were supported. This study demonstrates the importance of storage solutions in regard to endothelial integrity. For best preservation of endothelium it is necessary to modify conventional storage methods. So, storage in buffered solution with albumin has shown much better endothelial cell preservation compared with physiological saline which might reduce the obliteration rate of CABG in future.

Shape-Controlled Synthesis of Hybrid Nanomaterials via Three-Dimensional Hydrodynamic Focusing

PubMed Central

2015-01-01

Shape-controlled synthesis of nanomaterials through a simple, continuous, and low-cost method is essential to nanomaterials research toward practical applications. Hydrodynamic focusing, with its advantages of simplicity, low-cost, and precise control over reaction conditions, has been used for nanomaterial synthesis. While most studies have focused on improving the uniformity and size control, few have addressed the potential of tuning the shape of the synthesized nanomaterials. Here we demonstrate a facile method to synthesize hybrid materials by three-dimensional hydrodynamic focusing (3D-HF). While keeping the flow rates of the reagents constant and changing only the flow rate of the buffer solution, the molar ratio of two reactants (i.e., tetrathiafulvalene (TTF) and HAuCl4) within the reaction zone varies. The synthesized TTF–Au hybrid materials possess very different and predictable morphologies. The reaction conditions at different buffer flow rates are studied through computational simulation, and the formation mechanisms of different structures are discussed. This simple one-step method to achieve continuous shape-tunable synthesis highlights the potential of 3D-HF in nanomaterials research. PMID:25268035

Shape-controlled synthesis of hybrid nanomaterials via three-dimensional hydrodynamic focusing.

PubMed

Lu, Mengqian; Yang, Shikuan; Ho, Yi-Ping; Grigsby, Christopher L; Leong, Kam W; Huang, Tony Jun

2014-10-28

Shape-controlled synthesis of nanomaterials through a simple, continuous, and low-cost method is essential to nanomaterials research toward practical applications. Hydrodynamic focusing, with its advantages of simplicity, low-cost, and precise control over reaction conditions, has been used for nanomaterial synthesis. While most studies have focused on improving the uniformity and size control, few have addressed the potential of tuning the shape of the synthesized nanomaterials. Here we demonstrate a facile method to synthesize hybrid materials by three-dimensional hydrodynamic focusing (3D-HF). While keeping the flow rates of the reagents constant and changing only the flow rate of the buffer solution, the molar ratio of two reactants (i.e., tetrathiafulvalene (TTF) and HAuCl4) within the reaction zone varies. The synthesized TTF-Au hybrid materials possess very different and predictable morphologies. The reaction conditions at different buffer flow rates are studied through computational simulation, and the formation mechanisms of different structures are discussed. This simple one-step method to achieve continuous shape-tunable synthesis highlights the potential of 3D-HF in nanomaterials research.

Experimental determination of the hydrothermal solubility of ReS2 and the Re–ReO2 buffer assemblage and transport of rhenium under supercritical conditions

PubMed Central

Xiong, Yongliang; Wood, Scott A

2002-01-01

To understand the aqueous species important for transport of rhenium under supercritical conditions, we conducted a series of solubility experiments on the Re–ReO2 buffer assemblage and ReS2. In these experiments, pH was buffered by the K–feldspar–muscovite–quartz assemblage; in sulfur-free systems was buffered by the Re–ReO2 assemblage; and and in sulfur-containing systems were buffered by the magnetite–pyrite–pyrrhotite assemblage. Our experimental studies indicate that the species ReCl40 is dominant at 400°C in slightly acidic to near-neutral, and chloride-rich (total chloride concentrations ranging from 0.5 to 1.0 M) environments, and ReCl3+ may predominate at 500°C in a solution with total chloride concentrations ranging from 0.5 to 1.5 M. The results also demonstrate that the solubility of ReS2 is about two orders of magnitude less than that of ReO2. This finding not only suggests that ReS2 (or a ReS2 component in molybdenite) is the solubility-controlling phase in sulfur-containing, reducing environments but also implies that a mixing process involving an oxidized, rhenium-containing solution and a solution with reduced sulfur is one of the most effective mechanisms for deposition of rhenium. In analogy with Re, TcS2 may be the stable Tc-bearing phase in deep geological repositories of radioactive wastes.

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.

Environmentally persistent free radicals (EPFRs)-2. Are free hydroxyl radicals generated in aqueous solutions?

PubMed

Khachatryan, Lavrent; Dellinger, Barry

2011-11-01

A chemical spin trap, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), in conjunction with electron paramagnetic resonance (EPR) spectroscopy was employed to measure the production of hydroxyl radical (·OH) in aqueous suspensions of 5% Cu(II)O/silica (3.9% Cu) particles containing environmentally persistent free radicals (EPFRs) of 2-monochlorophenol (2-MCP). The results indicate: (1) a significant differences in accumulated DMPO-OH adducts between EPFR containing particles and non-EPFR control samples, (2) a strong correlation between the concentration of DMPO-OH adducts and EPFRs per gram of particles, and (3) a slow, constant growth of DMPO-OH concentration over a period of days in solution containing 50 μg/mL EPFRs particles + DMPO (150 mM) + reagent balanced by 200 μL phosphate buffered (pH = 7.4) saline. However, failure to form secondary radicals using standard scavengers, such as ethanol, dimethylsulfoxide, sodium formate, and sodium azide, suggests free hydroxyl radicals may not have been generated in solution. This suggests surface-bound, rather than free, hydroxyl radicals were generated by a surface catalyzed-redox cycle involving both the EPFRs and Cu(II)O. Toxicological studies clearly indicate these bound free radicals promote various types of cardiovascular and pulmonary disease normally attributed to unbound free radicals; however, the exact chemical mechanism deserves further study in light of the implication of formation of bound, rather than free, hydroxyl radicals.

Studies on the production of alkaline α-amylase from Bacillus subtilis CB-18.

PubMed

Nwokoro, Ogbonnaya; Anthonia, Odiase

2015-01-01

Amylases are among the main enzymes used in food and other industries. They hydrolyse starch molecules into polymers composing glucose units. Amylases have potential applications in a number of industrial processes including foods and pharmaceutical industries. Alkaline α-amylase has the potential of hydrolysing starch under alkaline pH and is useful in the starch and textile industries and as an ingredient of detergents. Amylases are produced from plants, however, microbial production processes have dominated applications in the industries. Optimization of microbial production processes can result in improved enzyme yields. Amylase activity was assayed by incubating the enzyme solution (0.5 ml) with 1% soluble starch (0.5 ml) in 0.1 M Tris/HCl buffer (pH 8.5). After 30 minutes, the reaction was stopped by the addition of 4 mL of 3,5-dinitrosalicylic acid (DNS) reagent then heated for 10 min in boiling water bath and cooled in a refrigerator. Absorbance readings were used to estimate the units of enzyme activity from glucose standard curve. Hydrolysed native starches from cassava, rice, corn, coco yam, maize and potato and soluble starch were adjusted to pH 8.5 prior to incubation with crude enzyme solution. Reducing sugars produced were therefore determined. The effect of pH on enzyme activity of the alkaline α-amylase was determined by using buffer solutions of different pH (potassium phosphate buffer, 6.0-7.0; Tris-HCl buffer 7.5 to 9.0 and carbonate/bicarbonate buffer, pH 9.5-11) for enzyme assay. The pH stability profile of the enzyme was determined by incubating 0.5 ml of α-amylase enzyme in 0.1 M Tris/HCl buffer (pH 8.5) and 0.5 ml of 1% (w/v) soluble starch (Merck) in 0.1 M Tris/HCl buffer (pH 8.5) for 3 h in various buffers. The effect of temperature on enzyme activity was studied by incubating 0.5 mL of the enzyme solution contained in the test tube and 0.5 mL of 1% soluble starch (Merck) solution prepared in 0.1 M Tris/HCl buffer (pH 8.5) for 3 h at various temperatures (25, 30, 35, 40, 45, 50, 55 and 60°C) in a thermo static water bath. The reactions were stopped by adding DNS reagent. The enzyme activity was therefore determined. Thermal stability was studied by incubating 0.5 ml of enzyme solution in 0.1 M Tris/HCl buffer (pH 8.5) and 0.5 ml of 1% (w/v) soluble starch (Merck) in 0.1 M Tris/HCl buffer (pH 8.5) for 3 h at various temperatures (20, 30, 40, 50, 60 and 70°C) for 60 min. The enzyme displayed optimal activity at pH 8.0 at which it produced maximum specific activity of 34.3 units/mg protein. Maximum stability was at pH 8.0 to 9.0. Maximum activity was observed at temperature of 50°C while thermo stability of the enzyme was observed at 40-50°C. The enzyme displayed a wide range of activities on starch and caused the release of 5.86, 4.75, 5.98, 3.44, 3.96, 8.84 mg/mL reducing sugar from cassava, potato, cocoyam, corn, rice and soluble starch respectively. This investigation reports some biochemical characterization of alkaline α-amylase from Bacillus subtilis CB-18. The substrate specificities of this enzyme on various starches suggested that the alkaline α-amylase enzyme had combined activities on raw and soluble starch.

Nucleation and growth of hydroxyapatite on arc-deposited TiO2 surfaces studied by quartz crystal microbalance with dissipation

NASA Astrophysics Data System (ADS)

Lilja, Mirjam; Butt, Umer; Shen, Zhijian; Bjöörn, Dorota

2013-11-01

Understanding of nucleation and growth kinetics of biomimetically deposited hydroxyapatite (HA) on crystalline TiO2 surfaces is important with respect to the application and performance of HA as functional implant coatings. Arc-evaporation was used to deposit TiO2 coatings dominated by anatase phase, rutile phase or their mixtures. Subsequent formation of HA from phosphate buffered saline solution (PBS) was investigated in real-time using in situ quartz crystal microbalance with dissipation technique (QCM-D). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to characterize the presence, morphology and crystal structure of TiO2 coatings and the formed HA. Increasing temperature of the PBS, increasing flow rate and applying a higher ion concentration in solution were found to accelerate HA nucleation process and hence affect growth kinetics. Lower PBS temperature resulted in the formation of HA coatings with flake-like morphology and increasing HA porosity. All TiO2 coatings under study enabled HA formation at body temperature, while in contrast Ti reference surfaces only supported HA nucleation and growth at elevated temperatures. QCM-D technique is a powerful tool for studying the impact of process parameters during biomimetic coating deposition on coating structure evolution in real time and provides valuable information for understanding, optimizing as well as tailoring the biomimetic HA growth processes.

Plasma Jet (V)UV-Radiation Impact on Biologically Relevant Liquids and Cell Suspension

NASA Astrophysics Data System (ADS)

Tresp, H.; Bussiahn, R.; Bundscherer, L.; Monden, A.; Hammer, M. U.; Masur, K.; Weltmann, K.-D.; Woedtke, Th. V.; Reuter, S.

2014-10-01

In this study the generation of radicals in plasma treated liquids has been investigated. To quantify the contribution of plasma vacuum ultraviolet (VUV) and ultraviolet (UV) radiation on the species investigated, three cases have been studied: UV of plasma jet only, UV and VUV of plasma jet combined, and the plasma effluent including all reactive components. The emitted VUV has been observed by optical emission spectroscopy and its effect on radical formation in liquids has been analyzed by electron spin resonance spectroscopy. Radicals have been determined in ultrapure water (dH2O), as well as in more complex, biorelevant solutions like phosphate buffered saline (PBS) solution, and two different cell culture media. Various compositions lead to different reactive species formation, e.g. in PBS superoxide anion and hydroxyl radicals have been detected, in cell suspension also glutathione thiyl radicals have been found. This study highlights that UV has no impact on radical generation, whereas VUV is relevant for producing radicals. VUV treatment of dH2O generates one third of the radical concentration produced by plasma-effluent treatment. It is relevant for plasma medicine because although plasma sources are operated in open air atmosphere, still VUV can lead to formation of biorelevant radicals. This work is funded by German Federal Ministry of Education a Research (BMBF) (Grant # 03Z2DN12+11).

Glutathione-Triggered Formation of a Fmoc-Protected Short Peptide-Based Supramolecular Hydrogel

PubMed Central

Shi, Yang; Wang, Jingyu; Wang, Huaimin; Hu, Yanhui; Chen, Xuemei; Yang, Zhimou

2014-01-01

A biocompatible method of glutathione (GSH) catalyzed disulfide bond reduction was used to form Fmoc-short peptide-based supramolecular hydrogels. The hydrogels could form in both buffer solution and cell culture medium containing 10% of Fetal Bovine Serum (FBS) within minutes. The hydrogel was characterized by rheology, transmission electron microscopy, and fluorescence emission spectra. Their potential in three dimensional (3D) cell culture was evaluated and the results indicated that the gel with a low concentration of the peptide (0.1 wt%) was suitable for 3D cell culture of 3T3 cells. This study provides an alternative candidate of supramolecular hydrogel for 3D cell culture and cell delivery. PMID:25222132

Fabrication of a magnetic helical mesostructured silica rod

NASA Astrophysics Data System (ADS)

Zhang, Lei; Zhang Qiao, Shi; Cheng, Lina; Yan, Zifeng; Qing Lu, Gao Max

2008-10-01

We report a one-step synthesis of magnetic helical mesostructured silica (MHMS) by self-assembly of an achiral surfactant, magnetic nanocrystals with stearic acid ligands and silicate. This core-shell structured material consists of an Fe3O4 superparamagnetic nanocrystal core and a highly ordered periodic helical mesoporous silica shell. We propose that the formation of the helical structure is induced by the interaction between the surfactant and dissociated stearic acid ligands. The MHMS obtained possesses superparamagnetism, uniform mesostructure, narrow pore size distribution, high surface area, and large pore volume. Furthermore, the drug release process is demonstrated using aspirin as a drug model and MHMS as a drug carrier in a sodium phosphate buffer solution.

A pH/enzyme-responsive polymer film consisting of Eudragit FS 30 D and arabinoxylane as a potential material formulation for colon-specific drug delivery system.

PubMed

Rabito, Mirela Fulgencio; Reis, Adriano Valim; Freitas, Adonilson dos Reis; Tambourgi, Elias Basile; Cavalcanti, Osvaldo Albuquerque

2012-01-01

Polymer film based on pH-dependent Eudragit FS 30 D acrylic polymer in association with arabinoxylane, a polysaccharide issued from gum psyllium, was produced by way of solvent casting. Physical-chemical characterization of the polymer film samples was performed by means of thermogravimetry (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Furthermore, water-equilibrium swelling index (I(s)) and weight loss of the films in KCl buffer solution of pH 1.2, in KH(2)PO(4) buffer solution of pH 5.0, or in KH(2)PO(4) buffer solution of pH 5.0 consisting of 4% enzyme Pectinex 3X-L (w/v) were also carried out for the film characterization. No chemical interactions between the Eudragit FS 30 D and the arabinoxylane polymer chains were evidenced, thus suggesting that the film-forming polymer structure was obtained from a physical mixture of both polymers. The arabinoxylane-loader films showed a more pronounced weight loss after their immersion in buffer solution containing enzyme Pectinex 3X-L. The introduction of the arabinoxylane makes the film more susceptible to undergo an enzymatic degradation. This meant that the enzyme-dependent propriety issued from the arabinoxylane has been imprinted into the film formulation. This type of polymer film is an interesting system for applications in colon-specific drug delivery system.

Fe-SAPONITE and Chlorite Growth on Stainless Steel in Hydrothermal Engineered Barrier Experiments

NASA Astrophysics Data System (ADS)

Cheshire, M. C.; Caporuscio, F. A.; McCarney, M.

2012-12-01

The United States recently has initiated the Used Fuel Disposition campaign to evaluate various generic geological repositories for the disposal of high-level, spent nuclear fuel within environments ranging from hard-rock, salt/clay, to deep borehole settings. Previous work describing Engineered Barrier Systems (EBS) for repositories focused on low temperature and pressure conditions. The focus of this experimental work is to characterize the stability and alteration of a bentonite-based EBS with different waste container materials in brine at higher heat loads and pressures. All experiments were run at ~150 bar and 125 to 300 C for ~1 month. Unprocessed bentonite from Colony, Wyoming was used in the experiments as the clay buffer material. The redox conditions for each system were buffered along the magnetite-iron oxygen fugacity univariant curve using Fe3O4 and Feo filings. A K-Na-Ca-Cl-based salt solution was chosen to replicate deep groundwater compositions. The experimental mixtures were 1) salt solution-clay; 2) salt solution -clay-304 stainless steel; and 3) salt solution -clay-316 stainless steel with a water/bentonite ratio of ~9. Mineralogy and aqueous geochemistry of each experiment was evaluated to monitor the reactions that took place. No smectite illitization was observed in these reactions. However, it appears that K-smectite was produced, possibly providing a precursor to illitization. It is unclear whether reaction times were sufficient for bentonite illitization at 212 and 300 C or whether conditions conducive to illite formation were obtained. The more notable clay mineral reactions occurred at the stainless steel surfaces. Authigenic chlorite and Fe-saponite grew with their basal planes near perpendicular to the steel plate, forming a 10 - 40 μm thick 'corrosion' layer. Partial dissolution of the steel plates was the likely iron source for chlorite/saponite formation; however, dissolution of the Feo/Fe3O4 may also have acted as an iron source, with the steel plates acting as a substrate for chlorite/saponite growth. Trace amounts of pyrite in the bentonite appeared to have reacted to form H2S gas and pentlandite ((Ni,Fe)8S9). Mineral growth on the waste containers was influenced by the container, buffer, and fluid compositions, in addition to pressure and temperature conditions. No significant mineralogical changes were apparent away from the steel-smectite interface. Results of this research show that the waste container may act as a substrate for mineral growth in response to corrosion. However, it is presently unknown whether chlorite and Fe-saponite will act as passivating agents or whether their presence will facilitate further corrosion of the waste containers. The role of these Fe-rich minerals on the stability of steel canisters at elevated heat loads is currently under investigation. LA-UR-12-23845

Acetic Acid Can Catalyze Succinimide Formation from Aspartic Acid Residues by a Concerted Bond Reorganization Mechanism: A Computational Study

PubMed Central

Takahashi, Ohgi; Kirikoshi, Ryota; Manabe, Noriyoshi

2015-01-01

Succinimide formation from aspartic acid (Asp) residues is a concern in the formulation of protein drugs. Based on density functional theory calculations using Ace-Asp-Nme (Ace = acetyl, Nme = NHMe) as a model compound, we propose the possibility that acetic acid (AA), which is often used in protein drug formulation for mildly acidic buffer solutions, catalyzes the succinimide formation from Asp residues by acting as a proton-transfer mediator. The proposed mechanism comprises two steps: cyclization (intramolecular addition) to form a gem-diol tetrahedral intermediate and dehydration of the intermediate. Both steps are catalyzed by an AA molecule, and the first step was predicted to be rate-determining. The cyclization results from a bond formation between the amide nitrogen on the C-terminal side and the side-chain carboxyl carbon, which is part of an extensive bond reorganization (formation and breaking of single bonds and the interchange of single and double bonds) occurring concertedly in a cyclic structure formed by the amide NH bond, the AA molecule and the side-chain C=O group and involving a double proton transfer. The second step also involves an AA-mediated bond reorganization. Carboxylic acids other than AA are also expected to catalyze the succinimide formation by a similar mechanism. PMID:25588215

Acetic acid can catalyze succinimide formation from aspartic acid residues by a concerted bond reorganization mechanism: a computational study.

PubMed

Takahashi, Ohgi; Kirikoshi, Ryota; Manabe, Noriyoshi

2015-01-12

Succinimide formation from aspartic acid (Asp) residues is a concern in the formulation of protein drugs. Based on density functional theory calculations using Ace-Asp-Nme (Ace = acetyl, Nme = NHMe) as a model compound, we propose the possibility that acetic acid (AA), which is often used in protein drug formulation for mildly acidic buffer solutions, catalyzes the succinimide formation from Asp residues by acting as a proton-transfer mediator. The proposed mechanism comprises two steps: cyclization (intramolecular addition) to form a gem-diol tetrahedral intermediate and dehydration of the intermediate. Both steps are catalyzed by an AA molecule, and the first step was predicted to be rate-determining. The cyclization results from a bond formation between the amide nitrogen on the C-terminal side and the side-chain carboxyl carbon, which is part of an extensive bond reorganization (formation and breaking of single bonds and the interchange of single and double bonds) occurring concertedly in a cyclic structure formed by the amide NH bond, the AA molecule and the side-chain C=O group and involving a double proton transfer. The second step also involves an AA-mediated bond reorganization. Carboxylic acids other than AA are also expected to catalyze the succinimide formation by a similar mechanism.

Methods for improved growth of group III nitride buffer layers

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

Melnik, Yurity; Chen, Lu; Kojiri, Hidehiro

Methods are disclosed for growing high crystal quality group III-nitride epitaxial layers with advanced multiple buffer layer techniques. In an embodiment, a method includes forming group III-nitride buffer layers that contain aluminum on suitable substrate in a processing chamber of a hydride vapor phase epitaxy processing system. A hydrogen halide or halogen gas is flowing into the growth zone during deposition of buffer layers to suppress homogeneous particle formation. Some combinations of low temperature buffers that contain aluminum (e.g., AlN, AlGaN) and high temperature buffers that contain aluminum (e.g., AlN, AlGaN) may be used to improve crystal quality and morphologymore » of subsequently grown group III-nitride epitaxial layers. The buffer may be deposited on the substrate, or on the surface of another buffer. The additional buffer layers may be added as interlayers in group III-nitride layers (e.g., GaN, AlGaN, AlN).« less

Dissolution and solubility behavior of fenofibrate in sodium lauryl sulfate solutions.

PubMed

Granero, Gladys E; Ramachandran, Chandrasekharan; Amidon, Gordon L

2005-10-01

The solubility of fenofibrate in pH 6.8 McIlvaine buffers containing varying concentrations of sodium lauryl sulfate was determined. The dissolution behavior of fenofibrate was also examined in the same solutions with rotating disk experiments. It was observed that the enhancement in intrinsic dissolution rate was approximately 500-fold and the enhancement in solubility was approximately 2000-fold in a pH 6.8 buffer containing 2% (w/v) sodium lauryl sulfate compared to that in buffer alone. The micellar solubilization equilibrium coefficient (k*) was estimated from the solubility data and found to be 30884+/-213 L/mol. The diffusivity for the free solute, 7.15x10(-6) cm2/s, was calculated using Schroeder's additive molal volume estimates and Hayduk-Laurie correlation. The diffusivity of the drug-loaded micelle, estimated from the experimental solubility and dissolution data and the calculated value for free solute diffusivity, was 0.86x10(-6) cm2/s. Thus, the much lower enhancement in dissolution of fenofibrate compared to its enhancement in solubility in surfactant solutions appears to be consistent with the contribution to the total transport due to enhanced micellar solubilization as well as a large decrease (approximately 8-fold) in the diffusivity of the drug-loaded micelle.

Double-Blind Crossover Study to Compare Pain Experience During Inferior Alveolar Nerve Block Administration Using Buffered Two Percent Lidocaine in Children.

PubMed

Chopra, Radhika; Jindal, Garima; Sachdev, Vinod; Sandhu, Meera

2016-01-01

Buffering of anesthetic solutions has been suggested to reduce pain on injection and onset of anesthesia. The purpose of this study was to assess the reduction in pain on injection during inferior alveolar nerve block administration in children. A double blind crossover study was designed where 30 six- to 12-year-old patients received two sessions of inferior alveolar nerve block scheduled one week apart. Two percent lidocaine with 1:200,000 epinephrine was given during one appointment, and a buffered solution was given during the other. Pain on injection was assessed using the sound, eye, and motor (SEM) scale, and the time to onset was assessed after gingival probing. The Heft-Parker visual analogue scale (HP-VAS) was self recorded by the patient after administration of local anesthesia. When tested using Mann-Whitney analysis, no significant differences were found between the SEM scores (P=0.71) and HP-VAS scores (P=0.93) for the two solutions used. Student's t test was used to assess the difference in the onset of anesthesia, which was also found to be statistically insignificant (P=0.824). Buffered lidocaine did not reduce the pain on injection or time to onset of anesthesia for inferior alveolar nerve block in children.

Rapid Nanoprobe Signal Enhancement by In Situ Gold Nanoparticle Synthesis.

PubMed

Dias, Jorge T; Svedberg, Gustav; Nystrand, Mats; Andersson-Svahn, Helene; Gantelius, Jesper

2018-03-07

The use of nanoprobes such as gold, silver, silica or iron-oxide nanoparticles as detection reagents in bioanalytical assays can enable high sensitivity and convenient colorimetric readout. However, high densities of nanoparticles are typically needed for detection. The available synthesis-based enhancement protocols are either limited to gold and silver nanoparticles or rely on precise enzymatic control and optimization. Here, we present a protocol to enhance the colorimetric readout of gold, silver, silica, and iron oxide nanoprobes. It was observed that the colorimetric signal can be improved by up to a 10000-fold factor. The basis for such signal enhancement strategies is the chemical reduction of Au 3+ to Au 0 . There are several chemical reactions that enable the reduction of Au 3+ to Au 0 . In the protocol, Good's buffers and H2O2 are used and it is possible to favor the deposition of Au 0 onto the surface of existing nanoprobes, in detriment of the formation of new gold nanoparticles. The protocol consists of the incubation of the microarray with a solution consisting of chloroauric acid and H2O2 in 2-(N-morpholino)ethanesulfonic acid pH 6 buffer following the nanoprobe-based detection assay. The enhancement solution can be applied to paper and glass-based sensors. Moreover, it can be used in commercially available immunoassays as demonstrated by the application of the method to a commercial allergen microarray. The signal development requires less than 5 min of incubation with the enhancement solution and the readout can be assessed by naked eye or low-end image acquisition devices such as a table-top scanner or a digital camera.

Physical Compatibility of Magnesium Sulfate and Sodium Bicarbonate in a Pharmacy-compounded Bicarbonate-buffered Hemofiltration Solution

PubMed Central

Moriyama, Brad; Henning, Stacey A.; Jin, Haksong; Kolf, Mike; Rehak, Nadja N.; Danner, Robert L.; Walsh, Thomas J.; Grimes, George J.

2011-01-01

PURPOSE To assess the physical compatibility of magnesium sulfate and sodium bicarbonate in a pharmacy-compounded bicarbonate-buffered hemofiltration solution used at the National Institutes of Health Clinical Center (http://www.cc.nih.gov). METHODS Two hemofiltration fluid formulations with a bicarbonate of 50 mEq/L and a magnesium of 1.5 mEq/L or 15 mEq/L were prepared in triplicate with an automated compounding device. The hemofiltration solution with a bicarbonate of 50 mEq/L and a magnesium of 1.5 mEq/L contains the maximum concentration of additives that we use in clinical practice. The hemofiltration solution of 15 mEq/L of magnesium and 50 mEq/L of bicarbonate was used to study the physicochemical properties of this interaction. The solutions were stored without light protection at 22 to 25 °C for 48 hours. Physical compatibility was assessed by visual inspection and microscopy. The pH of the solutions was assayed at 3 to 4 hours and 52 to 53 hours after compounding. In addition, electrolyte and glucose concentrations in the solutions were assayed at two time points after preparation: 3 to 4 hours and 50 to 51 hours. RESULTS No particulate matter was observed by visual and microscopic inspection in the compounded hemofiltration solutions at 48 hours. Electrolyte and glucose concentrations and pH were similar at both time points after solution preparation. CONCLUSION Magnesium sulfate (1.5 mEq/L) and sodium bicarbonate (50 mEq/L) were physically compatible in a pharmacy-compounded bicarbonate-buffered hemofiltration solution at room temperature without light protection at 48 hours. PMID:20237384

Synthesis of Gold Nanoparticles with Buffer-Dependent Variations of Size and Morphology in Biological Buffers.

PubMed

Ahmed, Syed Rahin; Oh, Sangjin; Baba, Rina; Zhou, Hongjian; Hwang, Sungu; Lee, Jaebeom; Park, Enoch Y

2016-12-01

The demand for biologically compatible and stable noble metal nanoparticles (NPs) has increased in recent years due to their inert nature and unique optical properties. In this article, we present 11 different synthetic methods for obtaining gold nanoparticles (Au NPs) through the use of common biological buffers. The results demonstrate that the sizes, shapes, and monodispersity of the NPs could be varied depending on the type of buffer used, as these buffers acted as both a reducing agent and a stabilizer in each synthesis. Theoretical simulations and electrochemical experiments were performed to understand the buffer-dependent variations of size and morphology exhibited by these Au NPs, which revealed that surface interactions and the electrostatic energy on the (111) surface of Au were the determining factors. The long-term stability of the synthesized NPs in buffer solution was also investigated. Most NPs synthesized using buffers showed a uniquely wide range of pH stability and excellent cell viability without the need for further modifications.

Bicarbonate absorption stimulates active calcium absorption in the rat proximal tubule.

PubMed Central

Bomsztyk, K; Calalb, M B

1988-01-01

To evaluate the effect of luminal bicarbonate on calcium reabsorption, rat proximal tubules were perfused in vivo. Perfusion solution contained mannitol to reduce water flux to zero. Total Ca concentration was measured by atomic absorption spectrometry, Ca ion concentration in the tubule lumen (CaL2+) and the peritubular capillary (CaP2+), and luminal pH (pHL) with ion-selective microelectrodes and transepithelial voltage (VTE) with conventional microelectrodes. When tubules were perfused with buffer-free Cl-containing solution, net Ca absorption (JCa) averaged 3.33 pmol/min. Even though VTE was 1.64 mV lumen-positive, CaL2+, 1.05 mM, did not fall below the concentration in the capillary blood, 1.07 mM. When 27 mM of Cl was replaced with HCO3, there was luminal fluid acidification. Despite a decrease in VTE and CaL2+, JCa increased to 7.13 pmol/min, indicating that the enhanced JCa could not be accounted for by the reduced electrochemical gradient, delta CCa. When acetazolamide or an analogue of amiloride was added to the HCO3 solution, JCa was not different from the buffer-free solution, suggesting that HCO3-stimulated JCa may be linked to acidification. To further test this hypothesis, we used 27 mM Hepes as the luminal buffer. With Hepes there was luminal fluid acidification and JCa was not different from the buffer-free solution but delta CCa was significantly reduced, indicating enhanced active calcium transport. We conclude from the results of the present study that HCO3 stimulates active Ca absorption, a process that may be linked to acidification-mediated HCO3 absorption. PMID:3366902

Effect of various halide salts on the incompatibility of cyanocobalamin and ascorbic acid in aqueous solution.

PubMed

Ichikawa, Makoto; Ide, Nagatoshi; Shiraishi, Sumihiro; Ono, Kazuhisa

2005-06-01

Combination of cyanocobalamin (VB12) and ascorbic acid (VC) has been widely seen in pharmaceutical products and dietary supplements. However, VB12 has been reported that its behavior in stability in aqueous solution is quite different when VC is mixed. In the present study, we examined the stabilities of these vitamins in acetate buffer (pH 4.8) using high performance liquid chromatography. Degradation of VB12 was not observed in the absence of VC in the buffer. However, when VC was mixed in the VB12 solution, VB12 concentrations decreased in accordance with VC degradation. VB12 and VC degradations were inhibited by adding sodium halides to acetate buffer at pH 4.8. These stabilization effects were also observed in the range from pH 3.5 to 5.3 and by adding potassium, magnesium, and calcium halides. Furthermore, our data demonstrated that increases in the halide anion concentrations and atomic number (Cl-

A Comparison of Blood Factor XII Autoactivation in Buffer, Protein Cocktail, Serum, and Plasma Solutions

PubMed Central

Golas, Avantika; Yeh, Chyi-Huey Josh; Pitakjakpipop, Harit; Siedlecki, Christopher A.; Vogler, Erwin A.

2012-01-01

Activation of blood plasma coagulation in vitro by contact with material surfaces is demonstrably dependent on plasma-volume-to-activator-surface-area ratio. The only plausible explanation consistent with current understanding of coagulation-cascade biochemistry is that procoagulant stimulus arising from the activation complex of the intrinsic pathway is dependent on activator surface area. And yet, it is herein shown that activation of the blood zymogen factor XII (Hageman factor, FXII) dissolved in buffer, protein cocktail, heat-denatured serum, and FXI deficient plasma does not exhibit activator surface-area dependence. Instead, a highly-variable burst of procoagulant-enzyme yield is measured that exhibits no measurable kinetics, sensitivity to mixing, or solution-temperature dependence. Thus, FXII activation in both buffer and protein-containing solutions does not exhibit characteristics of a biochemical reaction but rather appears to be a “mechanochemical” reaction induced by FXII molecule interactions with hydrophilic activator particles that do not formally adsorb blood proteins from solution. Results of this study strongly suggest that activator surface-area dependence observed in contact activation of plasma coagulation does not solely arise at the FXII activation step of the intrinsic pathway. PMID:23117212

Traveling waves in the discrete fast buffered bistable system.

PubMed

Tsai, Je-Chiang; Sneyd, James

2007-11-01

We study the existence and uniqueness of traveling wave solutions of the discrete buffered bistable equation. Buffered excitable systems are used to model, among other things, the propagation of waves of increased calcium concentration, and discrete models are often used to describe the propagation of such waves across multiple cells. We derive necessary conditions for the existence of waves, and, under some restrictive technical assumptions, we derive sufficient conditions. When the wave exists it is unique and stable.

Non-enzymatic browning reaction of glucosamine at mild conditions: Relationship between colour formation, radical scavenging activity and α-dicarbonyl compounds production.

PubMed

Hong, Pui Khoon; Betti, Mirko

2016-12-01

Glucosamine (GlcN, 5% w/v) was incubated in either phosphate buffer or ammonium hydroxide solutions at 40 and 60°C for up to 48h in order to yield caramel solutions. Non-enzymatic browning was monitored via changes in absorption at 280, 320 and 420nm and the physico-chemical properties as well as the generation of short chain α-dicarbonyl compounds were evaluated. Accumulation of GlcN autocondensation products (280nm) proceeded in parallel with the development of pre-melanoidins (320nm) and melanoidins (420nm). The reactive α-dicarbonyls were detected at temperature as low as 40°C within 3h with a maximum level of diacetyl recorded at 6h. The caramel solutions showed a high efficacy in scavenging DPPH and ABTS radicals in accordance with the increasing browning intensity. The results suggest that GlcN browning can be modulated according to the specific desired properties to produce a multi-functional food ingredient that has health-promoting effects. Copyright © 2016 Elsevier Ltd. 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.

Effect of glycine on pH changes and protein stability during freeze-thawing in phosphate buffer systems.

PubMed

Pikal-Cleland, Katherine A; Cleland, Jeffrey L; Anchordoquy, Thomas J; Carpenter, John F

2002-09-01

Previous studies have established that the selective precipitation of a less soluble buffer component during freezing can induce a significant pH shift in the freeze concentrate. During freezing of sodium phosphate solutions, crystallization of the disodium salt can produce a pH decrease as great as 3 pH units which can dramatically affect protein stability. The objective of our study was to determine how the presence of glycine (0-500 mM), a commonly used bulking agent in pharmaceutical protein formulations, affects the pH changes normally observed during freezing in sodium phosphate buffer solutions and to determine whether these pH changes contribute to instability of model proteins in glycine/phosphate formulations. During freezing in sodium phosphate buffers, the presence of glycine significantly influenced the pH. Glycine at the lower concentrations (< or = 50 mM) suppressed the pH decrease normally observed during freezing in 10 and 100 mM sodium phosphate buffer, possibly by reducing the nucleation rate of salt and thereby decreasing the extent of buffer salt crystallization. The presence of glycine at higher concentration (> 100 mM) in the sodium phosphate buffer resulted in a more complete crystallization of the disodium salt as indicated by the frozen pH values closer to the equilibrium value (pH 3.6). Although high concentrations of glycine can facilitate more buffer salt crystallization and these pH shifts may prove to be potentially damaging to the protein, glycine, in its amorphous state, can also act to stabilize a protein via the preferential exclusion mechanism. Copyright 2002 Wiley-Liss Inc.

Quantitative theory of electroosmotic flow in fused-silica capillaries using an extended site-dissociation--site-binding model.

PubMed

Zhou, Marilyn X; Foley, Joe P

2006-03-15

To optimize separations in capillary electrophoresis, it is important to control the electroosmotic mobility of the running buffer and the factors that affect it. Through the application of a site-dissociation-site-binding model, we demonstrated that the electroosmotic mobility could be controlled qualitatively and quantitatively by the parameters related to the physical and chemical properties of the running buffer: pH, cation valence, ionic strength, viscosity, activity, and dissociation constant. Our study illustrated that the logarithm of the number of apparent silanol sites on a fused-silica surface has a linear relationship with the pH of a buffer solution. The extension of the chemical kinetics approach allowed us to obtain the thickness of the electrical double layer when multivalent inorganic cations are present with monovalent cations in a buffer solution, and we found that the thickness of the electrical double layer does not depend on the charge of anions. The general equation to predict the electroosmotic mobility suggested here also indicates the increase of electroosmotic mobility with temperature. The general equation was experimentally verified by three buffer scenarios: (i) buffers containing only monovalent cations; (ii) buffers containing multivalent inorganic cations; and (iii) buffers containing cations and neutral additives. The general equation can explain the experimental observations of (i) a maximum electroosmotic mobility for the first scenario as the pH was varied at constant ionic strength and (ii) the inversion and maximum value of the electroosmotic mobility for the second scenario when the concentration of divalent cations was varied at constant pH. A good agreement between theory and experiment was obtained for each scenario.

Plasma assisted molecular beam epitaxy growth and effect of varying buffer thickness on the formation of ultra-thin In{sub 0.17}Al{sub 0.83}N/GaN heterostructure on Si(111)

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

Chowdhury, Subhra, E-mail: subhra1109@gmail.com; Biswas, Dhrubes; Department of E and E C E, Indian Institute of Technology Kharagpur, Kharagpur 721302

2015-02-23

This work reports on the detailed plasma-assisted molecular beam epitaxy (PAMBE) growth of ultra-thin In{sub 0.17}Al{sub 0.83}N/GaN heterostructures on Si(111) substrate with three different buffer thickness (600 nm, 400 nm, and 200 nm). Growth through critical optimization of growth conditions is followed by the investigation of impact of varying buffer thickness on the formation of ultra-thin 1.5 nm, In{sub 0.17}Al{sub 0.83}N–1.25 nm, GaN–1.5 nm, In{sub 0.17}Al{sub 0.83}N heterostructure, in terms of threading dislocation (TD) density. Analysis reveals a drastic reduction of TD density from the order 10{sup 10 }cm{sup −2} to 10{sup 8 }cm{sup −2} with increasing buffer thickness resulting smooth ultra-thin active region for thick buffer structure.more » Increasing strain with decreasing buffer thickness is studied through reciprocal space mapping analysis. Surface morphology through atomic force microscopy analysis also supports our study by observing an increase of pits and root mean square value (0.89 nm, 1.2 nm, and 1.45 nm) with decreasing buffer thickness which are resulted due to the internal strain and TDs.« less

Sensing of biologically relevant d-metal ions using a Eu(III)-cyclen based luminescent displacement assay in aqueous pH 7.4 buffered solution.

PubMed

Kotova, Oxana; Comby, Steve; Gunnlaugsson, Thorfinnur

2011-06-28

1·Eu·BPS was developed as a luminescent lanthanide sensor for use in displacement assays for detection of d-metal ions by monitoring the changes in the europium emission, which was quenched for iron(II), with a detection limit of ∼10 pM (0.002 μg L(-1)) for Fe(II) in buffered pH 7.4 solution. This journal is © The Royal Society of Chemistry 2011

Effect of protein solution components in the adsorption of Herbaspirillum seropedicae GlnB protein on mica.

PubMed

Ferreira, Cecília F G; Benelli, Elaine M; Klein, Jorge J; Schreiner, Wido; Camargo, Paulo C

2009-10-15

The adsorption of proteins and its buffer solution on mica surfaces was investigated by atomic force microscopy (AFM). Different salt concentration of the Herbaspirillum seropedicae GlnB protein (GlnB-Hs) solution deposited on mica was investigated. This protein is a globular, soluble homotrimer (36kDa), member of PII-like proteins family involved in signal transducing in prokaryote. Supramolecular structures were formed when this protein was deposited onto bare mica surface. The topographic AFM images of the GlnB-Hs films showed that at high salt concentration the supramolecular structures are spherical-like, instead of the typical doughnut-like shape for low salt concentration. AFM images of NaCl and Tris from the buffer solution showed structures with the same pattern as those observed for high salt protein solution, misleading the image interpretation. XPS experiments showed that GlnB protein film covers the mica surface without chemical reaction.

Buffered lidocaine and bupivacaine mixture - the ideal local anesthetic solution?

PubMed

Best, Corliss A; Best, Alyssa A; Best, Timothy J; Hamilton, Danielle A

2015-01-01

The use of injectable local anesthetic solutions to facilitate pain-free surgery is an integral component of many procedures performed by the plastic surgeon. In many instances, a solution that has both rapid onset and prolonged duration of analgesia is optimal. A combination of lidocaine and bupivacaine, plain or with epinephrine, is readily available in most Canadian health care settings where such procedures are performed, and fulfills these criteria. However, commercially available solutions of both medications are acidic and cause a burning sensation on injection. Buffering to neutral pH with sodium bicarbonate is a practical method to mitigate the burning sensation, and has the added benefit of increasing the fraction of nonionized lipid soluble drug available. The authors report on the proportions of the three drugs to yield a neutral pH, and the results of an initial survey regarding the use of the combined solution with epinephrine in hand surgery.

Formation of hydroxyl radicals and Co3+ in the reaction of Co(2+)-EDTA with hydrogen peroxide. Catalytic effect of Fe3+.

PubMed

Eberhardt, M K; Santos, C; Soto, M A

1993-05-07

Co2+ ions (Co(NO3)2.6H2O) react with H2O2 only in presence of EDTA to yield OH radicals and Co3+. This reaction was carried out in unbuffered aqueous solutions (pH = 2.6). The formation of Co3+ was confirmed by spectroscopy. The Co(3+)-EDTA complex shows two typical absorptions at 382 nm and 532 nm. The Co(3+)-EDTA complex can be prepared by a number of oxidizing agents, like Fe3+, Fe(3+)-EDTA, Ag+, Ag2+, Ce4+, and hydroxyl radicals. Since Fe3+ oxidizes Co(2+)-EDTA to Co(3+)-EDTA and Fe2+ we initiate a chain reaction for .OH formation. Our results show that there are two modes for H2O2 decomposition: (1) One electron transfer to give OH radicals and (2) Decomposition of H2O2 to H2O and O2 without intermediate .OH formation. This reaction depends strongly on the pH of the buffer. The H2O2 decomposition increases with increasing pH and increasing Co2+ concentration.

Inhibition of the aggregation of lactoferrin and (-)-epigallocatechin gallate in the presence of polyphenols, oligosaccharides, and collagen peptide.

PubMed

Yang, Wei; Liu, Fuguo; Xu, Chenqi; Sun, Cuixia; Yuan, Fang; Gao, Yanxiang

2015-05-27

The aggregation of lactoferrin and (-)-epigallocatechin gallate (EGCG) was inhibited by polyphenols, oligosaccharides, and collagen peptide in this study. Polyphenols, oligosaccharides, or collagen peptide can effectively prevent the formation of lactoferrin-EGCG aggregates, respectively. The addition sequence of lactoferrin, polyphenols (oligosaccharides or collagen peptide) and EGCG can affect the turbidity and particle size of the ternary complexes in the buffer solution; however, it hardly affected the ζ-potential and fluorescence characteristics. With either positive or negative charge, polyphenols and collagen peptide disrupted the formation of lactoferrin-EGCG aggregate mainly through the mechanism of its competition with EGCG molecules which surrounded the lactoferrin molecule surface with weaker binding affinities, forming polyphenols or a collagen peptide-lactoferrin-EGCG ternary complex; for neutral oligosaccharides, the ternary complex was generated mainly through steric effects, accompanied by a change in the lactoferrin secondary structure induced by gallic acid, chlorogenic acid, and xylo-oligosaccharide. Polyphenols, oligosaccharides, or collagen peptide restraining the formation of lactoferrin-EGCG aggregate could be applied in the design of clear products in the food, pharmaceutical, and cosmetic industries.

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

Protein-protein interactions during high-moisture extrusion for fibrous meat analogues and comparison of protein solubility methods using different solvent systems.

PubMed

Liu, KeShun; Hsieh, Fu-Hung

2008-04-23

Soy protein, mixed with gluten and starch, was extruded into fibrous meat analogues under high-moisture and high-temperature conditions. The protein solubility of samples collected at different extruder zones and extrudates made with different moistures was determined by 11 extraction solutions consisting of 6 selective reagents and their combinations: phosphate salts, urea, DTT, thiourea, Triton X-100, and CHAPS. Protein solubility by most extractants showed decreasing patterns as the material passed through the extruder, but the solution containing all 6 reagents, known as isoelectric focus (IEF) buffer, solubilized the highest levels and equal amounts of proteins in all samples, indicating that there are no other covalent bonds involved besides disulfide bonds. With regard to relative importance between disulfide bonds and non-covalent interactions, different conclusions could be made from protein solubility patterns, depending on the type of extracting systems and a baseline used for comparison. The observation points out pitfalls and limitation of current protein solubility methodology and explains why controversy exists in the literature. Using the IEF buffer system with omission of one or more selective reagents is considered to be the right methodology to conduct protein solubility study and thus recommended. Results obtained with this system indicate that disulfide bonding plays a more important role than non-covalent bonds in not only holding the rigid structure of extrudates but also forming fibrous texture. The sharpest decrease in protein solubility occurred when the mix passed through the intermediate section of the extruder barrel, indicating formation of new disulfide bonds during the stage of dramatic increase in both temperature and moisture. After this stage, although the physical form of the product might undergo change and fiber formation might occur as it passed through the cooling die, the chemical nature of the product did not change significantly.

Sensitivity improvement in hydrophilic interaction chromatography negative mode electrospray ionization mass spectrometry using 2-(2-methoxyethoxy)ethanol as a post-column modifier for non-targeted metabolomics.

PubMed

Koch, Wendelin; Forcisi, Sara; Lehmann, Rainer; Schmitt-Kopplin, Philippe

2014-09-26

The application of ammonia acetate buffered liquid chromatography (LC) eluents is known to concomitantly lead to ion suppression when electrospray ionization mass spectrometry (ESI-MS) detection is used. In negative ESI mode, post column infusion of 2-(2-methoxyethoxy)ethanol (2-MEE) was shown in the literature to help to compensate this adverse effect occurring in reversed phase liquid chromatography mass spectrometry (RP-LC-MS) analyses. Here a setup of direct infusion and hydrophilic interaction chromatography (HILIC) post-column infusion experiments was established in order to investigate systematically the beneficial effects of 2-MEE. We demonstrate that, 2-MEE can help to improve ESI-MS sensitivity in HILIC too and reveal analyte structure specific behaviors. Our study indicates that 2-MEE especially improves ESI response for small and polar molecules. The ESI response of stable isotope labeled amino acids spiked into biological matrices increases up to 50-fold (i.e. D5-l-glutamic acid) when post column infusion of 2-MEE is applied. A non-targeted analysis of a pooled urine sample via HILIC-ESI-QTOF-MS supports this hypothesis. In direct infusion, the combined application of an ammonia acetate buffered solution together with 2-MEE results in an improved ESI response compared to a non-buffered solution. We observed up to 60-fold increased ESI response of l-lysine. We propose this effect is putatively caused by the formation of smaller ESI droplets and stripping of positive charge from ESI droplets due to evaporation of acetic acid anions. In summary, post-column infusion of 2-MEE especially enhances ESI response of small and polar molecules. Therefore it can be regarded as a valuable add-on in targeted or non-targeted metabolomic HILIC-MS studies since this method sets a focus on this molecule category. Copyright © 2014 Elsevier B.V. All rights reserved.

Tensiometry and dilational rheology of mixed β-lactoglobulin/ionic surfactant adsorption layers at water/air and water/hexane interfaces.

PubMed

Dan, Abhijit; Gochev, Georgi; Miller, Reinhard

2015-07-01

Oscillating drop tensiometry was applied to study adsorbed interfacial layers at water/air and water/hexane interfaces formed from mixed solutions of β-lactoglobulin (BLG, 1 μM in 10 mM buffer, pH 7 - negative net charge) and the anionic surfactant SDS or the cationic DoTAB. The interfacial pressure Π and the dilational viscoelasticity modulus |E| of the mixed layers were measured for mixtures of varying surfactant concentrations. The double capillary technique was employed which enables exchange of the protein solution in the drop bulk by surfactant solution (sequential adsorption) or by pure buffer (washing out). The first protocol allows probing the influence of the surfactant on a pre-adsorbed protein layer thus studying the protein/surfactant interactions at the interface. The second protocol gives access to the residual values of Π and |E| measured after the washing out procedure thus bringing information about the process of protein desorption. The DoTAB/BLG complexes exhibit higher surface activity and higher resistance to desorption in comparison with those for the SDS/BLG complexes due to hydrophobization via electrostatic binding of surfactant molecules. The neutral DoTAB/BLG complexes achieve maximum elastic response of the mixed layer. Mixed BLG/surfactant layers at the water/oil interface are found to reach higher surface pressure and lower maximum dilational elasticity than those at the water/air surface. The sequential adsorption mode experiments and the desorption study reveal that binding of DoTAB to pre-adsorbed BLG globules is somehow restricted at the water/air surface in comparison with the case of complex formation in the solution bulk and subsequently adsorbed at the water/air surface. Maximum elasticity is achieved with washed out layers obtained after simultaneous adsorption, i.e. isolation of the most surface active DoTAB/BLG complex. These specific effects are much less pronounced at the W/H interface. Copyright © 2015 Elsevier Inc. All rights reserved.

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.

Acid-base metabolism: implications for kidney stones formation.

PubMed

Hess, Bernhard

2006-04-01

The physiology and pathophysiology of renal H+ ion excretion and urinary buffer systems are reviewed. The main focus is on the two major conditions related to acid-base metabolism that cause kidney stone formation, i.e., distal renal tubular acidosis (dRTA) and abnormally low urine pH with subsequent uric acid stone formation. Both the entities can be seen on the background of disturbances of the major urinary buffer system, NH3+ <--> NH4+. On the one hand, reduced distal tubular secretion of H+ ions results in an abnormally high urinary pH and either incomplete or complete dRTA. On the other hand, reduced production/availability of NH4+ is the cause of an abnormally low urinary pH, which predisposes to uric acid stone formation. Most recent research indicates that the latter abnormality may be a renal manifestation of the increasingly prevalent metabolic syndrome. Despite opposite deviations from normal urinary pH values, both the dRTA and uric acid stone formation due to low urinary pH require the same treatment, i.e., alkali. In the dRTA, alkali is needed for improving the body's buffer capacity, whereas the goal of alkali treatment in uric acid stone formers is to increase the urinary pH to 6.2-6.8 in order to minimize uric acid crystallization.

LC-MS/MS analysis of uncommon paracetamol metabolites derived through in vitro polymerization and nitration reactions in liquid nitrogen.

PubMed

Trettin, Arne; Jordan, Jens; Tsikas, Dimitrios

2014-09-01

Paracetamol (acetaminophen, APAP) is a commonly used analgesic drug. Known paracetamol metabolites include the glucuronide, sulfate and mercapturate. N-Acetyl-benzoquinonimine (NAPQI) is considered the toxic intermediate metabolite of paracetamol. In vitro and in vivo studies indicate that paracetamol is also metabolized to additional poorly characterized metabolites. For example, metabolomic studies in urine samples of APAP-treated mice revealed metabolites such as APAP-sulfate-APAP and APAP-S-S-APAP in addition to the classical phase II metabolites. Here, we report on the development and application of LC-MS and LC-MS/MS approaches to study reactions of unlabelled and (2)H-labelled APAP with unlabelled and (15)N-labelled nitrite in aqueous phosphate buffers (pH 7.4) upon their immersion into liquid nitrogen (-196°C). In mechanistic studies, these reactions were also studied in aqueous buffer prepared in (18)O-labelled water. LC-MS and LC-MS/MS analyses were performed on a reverse-phase material (C18) using gradient elution (2mM ammonium acetate/acetonitrile), in positive and negative electrospray mode. We identified a series of APAP metabolites including di-, tri- and tetra-APAP, mono- and di-nitro-APAP and nitric ester of di-APAP. Our study indicates that nitrite induces oxidation, i.e., polymerization and nitration of APAP, when buffered APAP/nitrite solutions are immersed into liquid nitrogen. These reactions are specific for nitrite with respect to nitrate and do not proceed via intermediate formation of NAPQI. Potassium ions and physiological saline but not thiols inhibit nitrite- and shock-freeze-induced reactions of paracetamol. The underlying mechanism likely involves in situ formation of NO2 radicals from nitrite secondary to profound pH reduction (down to pH 1) and disproportionation. Polymeric paracetamol species can be analyzed as pentafluorobenzyl derivatives by LC-MS but not by GC-MS. Copyright © 2013 Elsevier B.V. All rights reserved.

Formation of Fe/Mg Smectite under acidic conditions from synthetic Adirondack Basaltic Glass: An Analog to Fe/Mg Smectite Formation on Mars.

NASA Astrophysics Data System (ADS)

Sutter, B.; Peretyazhko, T.; Morris, R. V.; Ming, D. W.

2014-12-01

Smectite has been detected as layered material hundreds of meters thick, in intracrater depositional fans, in plains sediments, and deposits at depth on Mars. If early Mars hosted a dense CO2 atmosphere, then extensive carbonate should have formed in the neutral/alkaline conditions expected for smectite formation. However, large carbonate deposits on Mars have not been discovered. Instead of neutral to moderately alkaline conditions, early Mars may have experienced mildly acidic conditions that allowed for Fe/Mg smectite formation but prevented widespread carbonate formation. The objective of this work is to demonstrate that Fe(II)/Mg-saponite and nontronite can form in mildly acidic solutions (e.g., pH 4). Synthetic basaltic glass (< 53 μm) of Adirondack rock class composition was exposed to pH 4 (acetic acid buffer) and N2 purged (anoxic) solutions amended with 0 and 10 mM Mg or Fe(II). Basaltic glass in these solutions was heated to 200ºC in batch reactors for 1, 7, and 14 days. X-ray diffraction analysis of reacted materials detected the presence of phyllosilicates as indicated by a ~15.03-15.23Ǻ (001) peak. Smectite was confirmed as the phyllosilicate after treatments with glycerol and KCl and heating to 550°C. Trioctahedral saponite was confirmed by the presence of a 4.58 to 4.63 Ǻ (02l) and 1.54Ǻ (060) peaks. Saponite concentration was highest, as indicated by XRD peak intensity, in the 10 mM Mg treatment followed by the 0 mM and then 10 mM Fe(II) treatments. This order of sapontite concentration suggests that Fe(II) additions may have a role in slowing the kinetics of saponite formation relative to the other treatments. Nontronite synthesis was attempted by exposing Adirondack basaltic glass to pH 4 oxic solutions (without N2 purge) at 200ºC for 14 days. X-ray diffraction analysis indicated that mixtures of trioctahedral (saponite) and dioctahedral (nontronite) may have formed in these experiments based on the 02l and 060 peaks. Mössbauer analysis coupled with future experiments are planned to verify if nontronite can be formed under mildly acidic and oxic conditions. Results of this work demonstrate that acidic conditions could have occurred on an early Mars, which allowed for smectite formation but inhibited carbonate formation.

Accumulation of organic compounds leached from plastic materials used in biopharmaceutical process containers.

PubMed

Jenke, Dennis R; Zietlow, David; Garber, Mary Jo; Sadain, Salma; Reiber, Duane; Terbush, William

2007-01-01

Plastic materials are widely used in medical items, such as solution containers, transfusion sets, transfer tubing, and devices. An emerging trend in the biotechnology industry is the utilization of plastic containers to prepare, transport, and store an assortment of solutions including buffers, media, and in-process and finished product. The direct contact of such containers with the product at one or more points in its lifetime raises the possibility that container leachables may accumulate in the finished product. The interaction between several commercially available container materials and numerous model test solutions (representative of buffers and media used in biopharmaceutical applications) was investigated. This paper summarizes the identification of leachables associated with the container materials and documents the levels to which targeted leachables accumulate in the test solutions under defined storage conditions.

Impact of varying buffer thickness generated strain and threading dislocations on the formation of plasma assisted MBE grown ultra-thin AlGaN/GaN heterostructure on silicon

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

Chowdhury, Subhra, E-mail: subhra1109@gmail.com; Biswas, Dhrubes; Department of E and E C E, Indian Institute of Technology Kharagpur, Kharagpur 721302

2015-05-15

Plasma-assisted molecular beam epitaxy (PAMBE) growth of ultra-thin Al{sub 0.2}Ga{sub 0.8}N/GaN heterostructures on Si(111) substrate with three buffer thickness (600 nm/400 nm/200 nm) have been reported. An unique growth process has been developed that supports lower temperature epitaxy of GaN buffer which minimizes thermally generated tensile strain through appropriate nitridation and AlN initiated epitaxy for achieving high quality GaN buffer which supports such ultra-thin heterostructures in the range of 10-15Å. It is followed by investigations of role of buffer thickness on formation of ultra-thin Al{sub 0.2}Ga{sub 0.8}N/GaN heterostructure, in terms of stress-strain and threading dislocation (TD). Structural characterization were performedmore » by High-Resolution X-Ray Diffraction (HRXRD), room-temperature Photoluminescence (RT-PL), High Resolution Transmission Electron Microscopy (HRTEM) and Atomic Force Microscopy (AFM). Analysis revealed increasing biaxial tensile stress of 0.6918 ± 0.04, 1.1084, 1.1814 GPa in heterostructures with decreasing buffer thickness of 600, 400, 200 nm respectively which are summed up with residual tensile strain causing red-shift in RT-PL peak. Also, increasing buffer thickness drastically reduced TD density from the order 10{sup 10} cm{sup −2} to 10{sup 8} cm{sup −2}. Surface morphology through AFM leads to decrease of pits and root mean square value with increasing buffer thickness which are resulted due to reduction of combined effect of strain and TDs.« less

The Effect of Map Boundary on Estimates of Landscape Resistance to Animal Movement

PubMed Central

Koen, Erin L.; Garroway, Colin J.; Wilson, Paul J.; Bowman, Jeff

2010-01-01

Background Artificial boundaries on a map occur when the map extent does not cover the entire area of study; edges on the map do not exist on the ground. These artificial boundaries might bias the results of animal dispersal models by creating artificial barriers to movement for model organisms where there are no barriers for real organisms. Here, we characterize the effects of artificial boundaries on calculations of landscape resistance to movement using circuit theory. We then propose and test a solution to artificially inflated resistance values whereby we place a buffer around the artificial boundary as a substitute for the true, but unknown, habitat. Methodology/Principal Findings We randomly assigned landscape resistance values to map cells in the buffer in proportion to their occurrence in the known map area. We used circuit theory to estimate landscape resistance to organism movement and gene flow, and compared the output across several scenarios: a habitat-quality map with artificial boundaries and no buffer, a map with a buffer composed of randomized habitat quality data, and a map with a buffer composed of the true habitat quality data. We tested the sensitivity of the randomized buffer to the possibility that the composition of the real but unknown buffer is biased toward high or low quality. We found that artificial boundaries result in an overestimate of landscape resistance. Conclusions/Significance Artificial map boundaries overestimate resistance values. We recommend the use of a buffer composed of randomized habitat data as a solution to this problem. We found that resistance estimated using the randomized buffer did not differ from estimates using the real data, even when the composition of the real data was varied. Our results may be relevant to those interested in employing Circuitscape software in landscape connectivity and landscape genetics studies. PMID:20668690

H+, Water and Urea Transport in the Inner Medullary Collecting Duct and Their Role in the Prevention and Pathogenesis of Renal Stone Disease

NASA Astrophysics Data System (ADS)

Wall, Susan M.; Klein, Janet D.

2008-09-01

The inner medullary collecting duct (IMCD) is the final site within the kidney for the reabsorption of urea, water and electrolytes and for the secretion of H+ before the luminal fluid becomes the final urine. Transporters expressed in the IMCD contribute to the generation of the large ion gradients that exist between the interstitium and the collecting duct lumen. Thus, the luminal fluid within the human IMCD can reach an osmolality of 1200 mOsm/kg H2O and a pH of 4. This ability of the human nephron to concentrate and acidify the urine might predispose to stone formation. However, under treatment conditions that predispose to stone formation, such as during hypercalciuria, the kidney mitigates stone formation by reducing solute concentration by reducing H2O reabsorption. Moreover, the kidney attenuates stone formation by tightly controlling acid-base balance, which prevents the bone loss, hypocitraturia and hypercalciuria observed during metabolic acidosis by augmenting net H+ excretion by tightly regulating H+ transporter function and through luminal buffering, particularly with NH3. This article will review the ion transporters present in the mammalian IMCD and their role in the prevention and in the pathogenesis of renal stone formation.

Retention of ionisable compounds on high-performance liquid chromatography XVII. Estimation of the pH variation of aqueous buffers with the change of the methanol fraction of the mobile phase.

PubMed

Subirats, Xavier; Bosch, Elisabeth; Rosés, Martí

2007-01-05

The use of methanol-aqueous buffer mobile phases in HPLC is a common election when performing chromatographic separations of ionisable analytes. The addition of methanol to the aqueous buffer to prepare such a mobile phase changes the buffer capacity and the pH of the solution. In the present work, the variation of these buffer properties is studied for acetic acid-acetate, phosphoric acid-dihydrogenphosphate-hydrogenphosphate, citric acid-dihydrogencitrate-hydrogencitrate-citrate, and ammonium-ammonia buffers. It is well established that the pH change of the buffers depends on the initial concentration and aqueous pH of the buffer, on the percentage of methanol added, and on the particular buffer used. The proposed equations allow the pH estimation of methanol-water buffered mobile phases up to 80% in volume of organic modifier from initial aqueous buffer pH and buffer concentration (before adding methanol) between 0.001 and 0.01 mol L(-1). From both the estimated pH values of the mobile phase and the estimated pKa of the ionisable analytes, it is possible to predict the degree of ionisation of the analytes and therefore, the interpretation of acid-base analytes behaviour in a particular methanol-water buffered mobile phase.

Detection of Legume Protease Inhibitors by the Gel-X-ray Film Contact Print Technique

ERIC Educational Resources Information Center

Mulimani, Veerappa H.; Sudheendra, Kulkarni; Giri, Ashok P.

2002-01-01

Redgram (Cajanus cajan L.) extracts have been analyzed for the protease inhibitors using a new, sensitive, simple, and rapid method for detection of electrophoretically separated protease inhibitors. The detection involves equilibrating the gel successively in the protease assay buffer and protease solution, rinsing the gel in assay buffer, and…

Driving forces and the influence of the buffer composition on the complexation reaction between ibuprofen and HPCD.

PubMed

Perlovich, German L; Skar, Merete; Bauer-Brandl, Annette

2003-10-01

Cyclodextrins are often used in order to increase the aqueous solubility of drug substances by complexation. In order to investigate the complexation reaction of ibuprofen and hydroxypropyl-beta-cyclodextrin, titration calorimetry was used as a direct method. The thermodynamic parameters of the complexation process (stability constant, K(11); complexation enthalpy, deltaH(c) degrees ) were obtained in two different buffer systems (citric acid/sodium-phosphate and phosphoric acid) at various pH values. Based on these data the relative contributions of the enthalpic and entropic terms of the Gibbs energy to the complexation process have been analyzed. In both buffers the enthalpic and entropic terms are of different sign and this case corresponds to a 'nonclassical' model of hydrophobic interaction. In citric buffer, the main driving force of complexation is the entropy, which increases from 60 to 67% while the pH of the solution increases from 3.2 to 8.0. However, for the phosphoric buffer the entropic term decreases from 60 to 45%, while the pH-value of the solution increases from 5.0 to 8.2, and the driving force of the complexation process changes from entropy to enthalpy. The experimental data of the present study are compared to results of other authors and discrepancies discussed in detail.

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

High performance polymer solar cells with as-prepared zirconium acetylacetonate film as cathode buffer layer

PubMed Central

Tan, Zhan'ao; Li, Shusheng; Wang, Fuzhi; Qian, Deping; Lin, Jun; Hou, Jianhui; Li, Yongfang

2014-01-01

Low-work-function active metals are commonly used as cathode in polymer solar cells (PSCs), but sensitivity of the active metals towards moisture and oxygen results in poor stability of the devices. Therefore, solution-proceessable and stable cathode buffer layer is of great importance for the application of PSCs. Here we demonstrate high performance PSCs by employing as-prepared zirconium acetylacetonate (a-ZrAcac) film spin-cast from its ethanol solution as cathode buffer layer. The PSCs based on a low bandgap polymer PBDTBDD as donor and PC60BM as acceptor with a-ZrAcac/Al cathode demonstrated an average power conversion efficiency (PCE) of 8.75% which is significantly improved than that of the devices with traditional Ca/Al cathode. The improved photovoltaic performance is benefitted from the decreased series resistance and enhanced light harvest of the PSCs with the a-ZrAcac/Al cathode. The results indicate that a-ZrAcac is a promising high performance cathode buffer layer for fabricating large area flexible PSCs. PMID:24732976

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.

Evidence for Chemical and Electronic Nonuniformities in the Formation of the Interface of RbF-Treated Cu(In,Ga)Se2 with CdS.

PubMed

Nicoara, Nicoleta; Kunze, Thomas; Jackson, Philip; Hariskos, Dimitrios; Duarte, Roberto Félix; Wilks, Regan G; Witte, Wolfram; Bär, Marcus; Sadewasser, Sascha

2017-12-20

We report on the initial stages of CdS buffer layer formation on Cu(In,Ga)Se 2 (CIGSe) thin-film solar cell absorbers subjected to rubidium fluoride (RbF) postdeposition treatment (PDT). A detailed characterization of the CIGSe/CdS interface for different chemical bath deposition (CBD) times of the CdS layer is obtained from spatially resolved atomic and Kelvin probe force microscopy and laterally integrating X-ray spectroscopies. The observed spatial inhomogeneity in the interface's structural, chemical, and electronic properties of samples undergoing up to 3 min of CBD treatments is indicative of a complex interface formation including an incomplete coverage and/or nonuniform composition of the buffer layer. It is expected that this result impacts solar cell performance, in particular when reducing the CdS layer thickness (e.g., in an attempt to increase the collection in the ultraviolet wavelength region). Our work provides important findings on the absorber/buffer interface formation and reveals the underlying mechanism for limitations in the reduction of the CdS thickness, even when an alkali PDT is applied to the CIGSe absorber.

Organization and ELISA-Based Results of the First Proficiency Testing to Evaluate the Ability of European Union Laboratories to Detect Staphylococcal Enterotoxin Type B (SEB) in Buffer and Milk

PubMed Central

Nia, Yacine; Rodriguez, Mélanie; Zeleny, Reinhard; Herbin, Sabine; Auvray, Frédéric; Fiebig, Uwe; Avondet, Marc-André; Munoz, Amalia; Hennekinne, Jacques-Antoine

2016-01-01

The aim of this work was to organize the first proficiency test (PT) dedicated to staphylococcal enterotoxin B (SEB) detection in milk and buffer solutions. This paper describes the organization of the PT trial according to EN ISO 17043 requirements. Characterization of the SEB stock solution was performed using SDS-PAGE and SE-specific ELISA, and amino acid analysis was used to assign its protein concentration. The solution was then used to prepare six PT materials (four milk and two buffer batches) at a ng/g toxin level, which included one blank and one SEA-containing milk as specificity control. Suitable material homogeneity and stability were assessed using screening and quantitative ELISAs. Among the methods used by the participants, ELISA-based methods demonstrated their efficiency for the detection of SEB in both simple and complex matrices. The results serve as a basis for further improving the detection capabilities in expert laboratories and can therefore be considered as a contribution to biopreparedness. PMID:27649244

Fluoride-containing nanoporous calcium-silicate MTA cements for endodontics and oral surgery: early fluorapatite formation in a phosphate-containing solution.

PubMed

Gandolfi, M G; Taddei, P; Siboni, F; Modena, E; Ginebra, M P; Prati, C

2011-10-01

To test the chemical-physical properties and apatite-forming ability of experimental fluoride-doped calcium silicate cements designed to create novel bioactive materials for use in endodontics and oral surgery. A thermally treated calcium silicate cement (wTC) containing CaCl(2) 5%wt was modified by adding NaF 1%wt (FTC) or 10%wt (F10TC). Cements were analysed by environmental scanning electron microscopy with energy-dispersive X-ray analysis, IR and micro-Raman spectroscopy in wet conditions immediately after preparation or after ageing in a phosphate-containing solution (Dulbecco's phosphate-buffered saline). Calcium and fluoride release and pH of the storage solution were measured. The results obtained were analysed statistically (Tukey's HSD test and two-way anova). The formation of calcium phosphate precipitates (spherulites) was observed on the surface of 24 h-aged cements and the formation of a thick bone-like B-type carbonated apatite layer (biocoating) on 28 day-aged cements. The rate of apatite formation was FTC>F10TC>wTC. Fluorapatite was detected on FTC and F10TC after 1 day of ageing, with a higher fluoride content on F10TC. All the cements released calcium ions. At 5 and 24 h, the wTC had the significantly highest calcium release (P<0.001) that decreased significantly over the storage time. At 3-28 days, FTC and F10TC had significantly higher calcium release than wTC (P<0.05). The F10TC had the significantly highest fluoride release at all times (P<0.01) that decreased significantly over storage time. No significant differences were observed between FTC and wTC. All the cements had a strong alkalinizing activity (OH(-) release) that remained after 28 days of storage. The addition of sodium fluoride accelerated apatite formation on calcium silicate cements. Fluoride-doped calcium silicate cements had higher bioactivity and earlier formation of fluorapatite. Sodium fluoride may be introduced in the formulation of mineral trioxide aggregate cements to enhance their biological behaviour. F-doped calcium silicate cements are promising bone cements for clinical endodontic use. © 2011 International Endodontic Journal.

Stability and tribological performances of fluid phospholipid bilayers: effect of buffer and ions.

PubMed

Dekkiche, F; Corneci, M C; Trunfio-Sfarghiu, A-M; Munteanu, B; Berthier, Y; Kaabar, W; Rieu, J-P

2010-10-15

We have investigated the mechanical and tribological properties of supported Dioleoyl phosphatidylcholine (DOPC) bilayers in different solutions: ultrapure water (pH 5.5), saline solution (150 mM NaCl, pH 5.8), Tris buffer (pH 7.2) and Tris saline buffer (150 mM NaCl, pH 7.2). Friction forces are measured using a homemade biotribometer. Lipid bilayer degradation is controlled in situ during friction tests using fluorescence microscopy. Mechanical resistance to indentation is measured by force spectroscopy with an atomic force microscope. This study confirms that mechanical stability under shear or normal load is essential to obtain low and constant friction coefficients. In ultrapure water, bilayers are not resistant and have poor lubricant properties. On the other hand, in Tris saline buffer, they fully resist to indentation and exhibit low (micro=0.035) and stable friction coefficient with no visible wear during the 50 min of the friction test. The unbuffered saline solution improves the mechanical resistance to indentation but not the lubrication. These results suggest that the adsorption of ions to the zwiterrionic bilayers has different effects on the mechanical and tribological properties of bilayers: higher resistance to normal indentation due to an increase in bilayer cohesion, higher lubrication due to an increase in bilayer-bilayer repulsion. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Effect of light and heat on the stability of montelukast in solution and in its solid state.

PubMed

Al Omari, Mahmoud M; Zoubi, Rufaida M; Hasan, Enas I; Khader, Tariq Z; Badwan, Adnan A

2007-11-05

The chemical stability of montelukast (Monte) in solution and in its solid state was studied. A simultaneous measurement of Monte and its degradation products was determined using a selective HPLC method. The HPLC system comprised a reversed phase column (C18) as the stationary phase and a mixture of ammonium acetate buffer of pH 3.5 and methanol (15:85 v/v) as the mobile phase. The UV detection was conducted at 254 nm. Monte in solution showed instability when exposed to light leading to the formation of its cis-isomer as the major photoproduct. The rate of photodegradation of Monte in solution exposed to various light sources increases in the order of; sodium

A magnetic trap for living cells suspended in a paramagnetic buffer

NASA Astrophysics Data System (ADS)

Winkleman, Adam; Gudiksen, Katherine L.; Ryan, Declan; Whitesides, George M.; Greenfield, Derek; Prentiss, Mara

2004-09-01

This manuscript describes the fabrication and use of a three-dimensional magnetic trap for diamagnetic objects in an aqueous solution of paramagnetic ions; this trap uses permanent magnets. It demonstrates trapping of polystyrene spheres, and of various types of living cells: mouse fibroblast (NIH-3T3), yeast (Saccharomyces cerevisiae), and algae (Chlamydomonas reinhardtii). For a 40mM solution of gadolinium (III) diethylenetriaminepentaacetic acid (Gd .DTPA) in aqueous buffer, the smallest cell (particle) that could be trapped had a radius of ˜2.5μm. The trapped particle and location of the magnetic trap can be translated in three dimensions by independent manipulation of the permanent magnets. This letter a1so characterizes the biocompatibility of the trapping solution.

Slow equilibration of reversed-phase columns for the separation of ionized solutes.

PubMed

Marchand, D H; Williams, L A; Dolan, J W; Snyder, L R

2003-10-10

Reversed-phase columns that have been stored in buffer-free solvents can exhibit pronounced retention-time drift when buffered, low-pH mobile phases are used with ionized solutes. Whereas non-ionized compounds exhibit constant retention times within 20 min of the beginning of mobile phase flow, the retention of ionized compounds can continue to change (by 20% or more) for several hours. If mobile phase pH is changed from low to high and back again, an even longer time may be required before the column reaches equilibration at low pH. The speed of column equilibration for ionized solutes can vary significantly among different reversed-phase columns and is not affected by flow rate.

Reaction of 2-acetylaminofluorene-N-sulfate with RNA and glutathione: evidence for the generation of two reactive intermediates with different reactivities towards RNA and glutathione.

PubMed

van den Goorbergh, J A; Meerman, J H; de Wit, H; Mulder, G J

1985-11-01

The sulfate ester of N-hydroxy-2-acetylaminofluorene (AAF-N-sulfate) is one of the reactive intermediates of this carcinogen. This ester breaks down spontaneously to a very reactive nitrenium ion, which reacts with nucleophilic groups in protein, DNA, RNA and glutathione (GSH). Reactions involving the nitrenium ion with several nucleophiles under various conditions were studied. The adduct formation to RNA was much higher in Tris-HCI buffer than in phosphate buffer (at pH 7.4), while adduct formation to deoxy-guanosine monomers was the same in both buffers. The presence of 150 mM KCI had the same decreasing effect in both cases. Ionic strength effects may be involved in these phenomena. GSH decreased RNA adduct formation by 20-45%, while other thiols were much more effective. On the other hand, RNA did not decrease the formation of GSH conjugates from AAF-N-sulfate. The decrease in RNA adduct formation by thiols corresponded with an increase in the formation of 2-acetylaminofluorene (AAF) from AAF-N-sulfate, while no N-hydroxy-AAF was formed. These results suggest that two independent reactive intermediates are formed from AAF-N-sulfate, with different reactivities towards RNA and glutathione. Possibly these intermediates are the 'hard' triplet state nitrenium ion and the 'soft' singlet state nitrenium ion. Cysteine, cysteamine and penicillamine were most effective in the inhibition of RNA adduct formation; the extent of inhibition correlated with the extent of AAF formation. The mechanisms involved are discussed.

Investigation of interaction of an alkaloid harmaline with cucurbit[7]uril: A spectroscopic and calorimetric study

NASA Astrophysics Data System (ADS)

Ahmed, Sayeed Ashique; Seth, Debabrata

2018-01-01

The photophysics of an alkaloid harmaline in aqueous buffer solution and in the presence of cucurbit[7]uril have been studied. The photophysical properties of harmaline were modulated several folds due to addition of cucurbit[7]uril in the aqueous buffer solution. We have observed quenching of fluorescence intensity of harmaline with gradual addition of CB7. Isothermal titration calorimetry technique (ITC) was performed to get an idea about the thermodynamic parameters involved in the complexation process. From ITC, we observed that the complexation process was exothermic in nature and enthalpy driven process.

Reactive solute transport in an acidic stream: Experimental pH increase and simulation of controls on pH, aluminum, and iron

USGS Publications Warehouse

Broshears, R.E.; Runkel, R.L.; Kimball, B.A.; McKnight, Diane M.; Bencala, K.E.

1996-01-01

Solute transport simulations quantitatively constrained hydrologic and geochemical hypotheses about field observations of a pH modification in an acid mine drainage stream. Carbonate chemistry, the formation of solid phases, and buffering interactions with the stream bed were important factors in explaining the behavior of pH, aluminum, and iron. The precipitation of microcrystalline gibbsite accounted for the behavior of aluminum; precipitation of Fe(OH)3 explained the general pattern of iron solubility. The dynamic experiment revealed limitations on assumptions that reactions were controlled only by equilibrium chemistry. Temporal variation in relative rates of photoreduction and oxidation influenced iron behavior. Kinetic limitations on ferrous iron oxidation and hydrous oxide precipitation and the effects of these limitations on field filtration were evident. Kinetic restraints also characterized interaction between the water column and the stream bed, including sorption and desorption of protons from iron oxides at the sediment-water interface and post-injection dissolution of the precipitated aluminum solid phase.

Friability Testing as a New Stress-Stability Assay for Biopharmaceuticals.

PubMed

Torisu, Tetsuo; Maruno, Takahiro; Yoneda, Saki; Hamaji, Yoshinori; Honda, Shinya; Ohkubo, Tadayasu; Uchiyama, Susumu

2017-10-01

A cycle of dropping and shaking a vial containing antibody solution was reported to induce aggregation. In this study, antibody solutions in glass prefillable syringes with or without silicone oil lubrication were subjected to the combined stresses of dropping and shaking, using a friability testing apparatus. Larger numbers of subvisible particles were generated, regardless of silicone oil lubrication, upon combination stress exposure than that with shaking stress alone. Nucleation of antibody molecules upon perturbation by an impact of dropping and adsorption of antibody molecules to the syringe surface followed by film formation and antibody film desorption were considered key steps in the particle formation promoted by combination stress. A larger number of silicone oil droplets was released when silicone oil-lubricated glass syringes containing phosphate buffer saline were exposed to combination stress than that observed with shaking stress alone. Polysorbate 20, a non-ionic surfactant, effectively reduced the number of protein particles, but failed to prevent silicone oil release upon combination stress exposure. This study indicates that stress-stability assays using the friability testing apparatus are effective for assessing the stability of biopharmaceuticals under the combined stresses of dropping and shaking, which have not been tested in conventional stress-stability assays. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Boswellia gum resin/chitosan polymer composites: Controlled delivery vehicles for aceclofenac.

PubMed

Jana, Sougata; Laha, Bibek; Maiti, Sabyasachi

2015-01-01

This study was undertaken to evaluate the effect of Boswellia gum resin on the properties of glutaraldehyde (GA) crosslinked chitosan polymer composites and their potential as oral delivery vehicles for a non-steroidal anti-inflammatory drug, aceclofenac. The incorporation of resinous material caused a significant improvement in drug entrapment efficiency (∼40%) of the polymer composites. Fourier transform infrared (FTIR) spectroscopic analysis confirmed the formation of chitosan-gum resin composites and did not show any evidence of drug-polymer chemical interaction. Field emission scanning electron microscopy (FE-SEM) suggested the formation of particulate polymer composites up to chitosan:gum resin mass ratio of 1:3. Only 8-17% drug was released into HCl solution (pH 1.2) in 2h. The drug release rate of polymer composites was faster in phosphate buffer solution (pH 6.8). The composites released ∼60-68% drug load in 7h. In same duration, the drug release rate suddenly boosted up to 92% as the concentration of gum resin in the composites was raised to 80%. The drug release mechanism deviated from non-Fickian to case-II type with increasing resin concentration in the composites. Hence, GA-treated Boswellia resin-chitosan composites could be considered as alternative vehicles for oral delivery of aceclofenac. Copyright © 2015 Elsevier B.V. All rights reserved.

Turbidity as a probe of tubulin polymerization kinetics: a theoretical and experimental re-examination.

PubMed

Hall, Damien; Minton, Allen P

2005-10-15

We report here an examination of the validity of the experimental practice of using solution turbidity to study the polymerization kinetics of microtubule formation. The investigative approach proceeds via numerical solution of model rate equations to yield the time dependence of each microtubule species, followed by the calculation of the time- and wavelength-dependent turbidity generated by the calculated distribution of rod lengths. The wavelength dependence of the turbidity along the time course is analyzed to search for generalized kinetic regimes that satisfy a constant proportionality relationship between the observed turbidity and the weight concentration of polymerized tubulin. An empirical analysis, which permits valid interpretation of turbidity data for distributions of microtubules that are not long relative to the wavelength of incident light, is proposed. The basic correctness of the simulation work is shown by the analysis of the experimental time dependence of the turbidity wavelength exponent for microtubule formation in taxol-supplemented 0.1 M Pipes buffer (1 mM GTP, 1 mM EGTA, 1 mM MgSO4, pH 6.4). We believe that the general findings and principles outlined here are applicable to studies of other fibril-forming systems that use turbidity as a marker of polymerization progress.

In vitro hemolysis and buffer capacity studies with the novel marine anticancer agent kahalalide F and its reconstitution vehicle cremophor EL/ethanol.

PubMed

Nuijen, B; Bouma, M; Manada, C; Jimeno, J M; Bult, A; Beijnen, J H

2001-01-01

An in vitro biocompatibility study was performed with the pharmaceutical formulation of the investigational, marine-derived anticancer agent kahalalide F developed for early clinical studies. The pharmaceutical formulation consists of a lyophilized product containing 150 micrograms kahalalide F, 3 mg citric acid, 3 mg polysorbate 80, and 150 mg of sucrose per dosage unit, to be reconstituted with 3 mL of a mixture composed of Cremophor EL, ethanol, and water (5/5/90% v/v/v), resulting in a solution of pH 3 and to be further diluted in normal saline for infusion. The reconstituted product, infusion solutions, and Cremophor/ethanol (CE) vehicle were tested for hemolytic potential and buffer capacity. No significant hemolysis due to the kahalalide F formulation as well as the CE vehicle was found using both a static and dynamic test model. FB-ratio's (ratio of formulation solution (F) and volume of blood simulant (B) necessary to maintain physiological pH) as a measure of the buffer capacity of the kahalalide F infusion solutions examined indicated that no vascular irritation due to pH effects is expected in the intended administration schedule in the forthcoming Phase I study.

Hemoglobin bioconjugates with surface-protected gold nanoparticles in aqueous media: The stability depends on solution pH and protein properties.

PubMed

Del Caño, Rafael; Mateus, Lucia; Sánchez-Obrero, Guadalupe; Sevilla, José Manuel; Madueño, Rafael; Blázquez, Manuel; Pineda, Teresa

2017-11-01

The identification of the factors that dictate the formation and physicochemical properties of protein-nanomaterial bioconjugates are important to understand their behavior in biological systems. The present work deals with the formation and characterization of bioconjugates made of the protein hemoglobin (Hb) and gold nanoparticles (AuNP) capped with three different molecular layers (citrate anions (c), 6-mercaptopurine (MP) and ω-mercaptoundecanoic acid (MUA)). The main focus is on the behavior of the bioconjugates in aqueous buffered solutions in a wide pH range. The stability of the bioconjugates have been studied by UV-visible spectroscopy by following the changes in the localized surface resonance plasmon band (LSRP), Dynamic light scattering (DLS) and zeta-potential pH titrations. It has been found that they are stable in neutral and alkaline solutions and, at pH lower than the protein isoelectric point, aggregation takes place. Although the surface chemical properties of the AuNPs confer different properties in respect to colloidal stability, once the bioconjugates are formed their properties are dictated by the Hb protein corona. The protein secondary structure, as analyzed by Attenuated total reflectance infrared (ATR-IR) spectroscopy, seems to be maintained under the conditions of colloidal stability but some small changes in protein conformation take place when the bioconjugates aggregate. These findings highlight the importance to keep the protein structure upon interaction with nanomaterials to drive the stability of the bioconjugates. Copyright © 2017 Elsevier Inc. All rights reserved.

Effect of peritoneal dialysis fluids on activity of echinocandins against Candida spp. biofilm.

PubMed

Tobudic, Selma; Harrison, Nicole; Forstner, Christina; Kussman, Manuel; Burgmann, Heinz

2017-10-01

Peritoneal dialysis fluids (PDFs) impair microorganisms' growth, which may compromise effectivity of some antimicrobials. The purpose of this study was to investigate the effect of three different PDFs (lactate/bicarbonate-buffered Physioneal 40® with 2.2% glucose, lactate-buffered Nutrineal PD4® with 1.1% amino acid, and lactate-buffered Extraneal® with 7.5% icodextrin) on biofilm formation of four different Candida spp and antibiofilm effectiveness of anidulafungin, caspofungin and micafungin against Candida spp. biofilm in PDFs. All tested PDFs attained inhibitory effect on the biofilm formation but also reduced biofilm effectiveness of echinocandins against biofilm in PDFs was detected. © The Author 2017. Published by Oxford University Press on behalf of The International Society for Human and Animal Mycology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Solution dynamics of synthetic and natural polyelectrolytes

NASA Astrophysics Data System (ADS)

Krause, Wendy E.

Polyelectrolytes are abundant in nature and essential to life, and used extensively in industry. This work discussed two polyelectrolytes: sodium poly(2-acrylamido-2-methylpropanesulfonate) (NaPAMS), synthetic polyelectrolyte, and sodium hyaluronate (NaHA), a glycosaminoglycan. Rheological data of NaPAMS solutions of variable chain length and concentration were reported. A strong dependence of viscosity eta on chain length: eta ˜ M2.4 was found. The comparison of the rheological data with two proposed scaling theories (Dobrynin 1995, Witten 1987) forces the conclusion that neither theory is correct. A possible interpretation of the viscosity data falling between the predictions of the two scaling theories is that some chain rigidity may persist beyond the correlation length. A sample model for the conductivity of semidilute polyelectrolytes with no added salt was presented. The model correctly describes the logarithmic decrease of specific conductance observed for many polyelectrolytes at low concentration (below ca. 10-2M), and is in good agreement with data from NaPAMS solutions. NaHA in phosphate buffered saline behaves as a typical polyelectrolyte in the high-salt limit, as Newtonian viscosities are observed over a wide range of shear rates. There is no evidence of intermolecular hydrogen bonding causing gel formation in NaHA solutions without protein present. The viscosity of 3 mg/mL NaHA was measured in the presence of the selected anti-inflammatory agents. Of the seven additives investigated only (D)-penicillamine significantly altered the rheology of HA. (D)-Penicillamine dramatically reduced the viscosity of HA, probably by disrupting intramolecular hydrogen bonding. The plasma proteins albumin and gamma-globulins bind to HA in solution to form a weak reversible gel. The rheology and osmotic pressure of the simple model for synovial fluid, consisting of 3mg/mL NaHA, 11 mg/mL albumin, and 7 mg/mL gamma-globulins in phosphate buffered saline, were studied in the presence and absence of the seven selected anti-inflammatory agents. Only hydroxychloroquine (HCQ) and (D)-penicillamine strongly influence the theology of the synovial fluid model. HCQ reduces the viscosity of the model solution as well as the model's viscoelasticity. (D)-Penicillamine also reduces the viscosity of the synovial fluid model, but has little effect on the viscoelasticity of the solution. None of the additives effected the osmotic pressure of the synovial fluid model.

Detection of fumonisin b1 and ochratoxin a in grain products using microsphere-based fluid array immunoassays.

PubMed

Anderson, George P; Kowtha, Vasudha A; Taitt, Chris R

2010-02-01

Grain products are a staple of diets worldwide and therefore, the ability to accurately and efficiently detect foodborne contaminants such as mycotoxins is of importance to everyone. Here we describe an indirect competitive fluid array fluoroimmunoassay to quantify the mycotoxins, fumonisin B1 and ochratoxin A. Both toxins were immobilized to the surface of microspheres using a variety of intermediate molecules and binding of biotinylated "tracer" antibody tracers determined through flow cytometry using streptavidin-phycoerythrin conjugates and the Luminex100 flow cytometer. Competitive assays were developed where the binding of biotinylated monoclonal antibodies to fumonisin B and ochratoxin A was competitively inhibited by different concentrations of those toxins in solution. Concentrations of fumonisin giving 50% inhibition were 300 pg/mL in buffer, 100 ng/g in spiked oats, and 1 μg/g in spiked cornmeal; analogous concentrations for ochratoxin A were 30 ng/mL in buffer, 30 ng/g in spiked oats, and 10 ng/g in spiked corn. The future challenge will be to expand the number of mycotoxins tested both individually and in multiplexed format using this platform.

Fracture and crack growth in orthotropic laminates. Part 1: Analysis of a hybrid, unidirectional laminate with damage

NASA Technical Reports Server (NTRS)

Goree, J. G.

1982-01-01

The fracture behavior of unifirectional hybrid (buffer strip) composite laminates is studied. Three particular solutions are discussed: (1) broken fibers in a unidirectional half plane; (2) adjoined half planes of different fiber and matrix properties and (3) the solution of two half planes bounding a third distinct region of finite width. This finite width region represents a buffer strip and the potential of this strip to arrest a crack that originates in one of the half planes is investigated. The analysis is based on a materials modeling approach using the classical shear lag assumption to described the stress transfer between fibers. Explicit fiber and matrix properties of the three regions are retained and changes in the laminate behavior as a function of the relative material properties, buffer strip width and initial crack length are discussed.

Solvent-modified ultrafast decay dynamics in conjugated polymer/dye labeled single stranded DNA

NASA Astrophysics Data System (ADS)

Kim, Inhong; Kang, Mijeong; Woo, Han Young; Oh, Jin-Woo; Kyhm, Kwangseuk

2015-07-01

We have investigated that organic solvent (DMSO, dimethyl sulfoxide) modifies energy transfer efficiency between conjugated polymers (donors) and fluorescein-labeled single stranded DNAs (acceptors). In a mixture of buffer and organic solvent, fluorescence of the acceptors is significantly enhanced compared to that of pure water solution. This result can be attributed to change of the donor-acceptor environment such as decreased hydrophobicity of polymers, screening effect of organic solvent molecules, resulting in an enhanced energy transfer efficiency. Time-resolved fluorescence decay of the donors and the acceptors was modelled by considering the competition between the energy harvesting Foerster resonance energy transfer and the energy-wasting quenching. This enables to quantity that the Foerster distance (R0 = 43.3 Å) and resonance energy transfer efficiency (EFRET = 58.7 %) of pure buffer solution become R0 = 38.6 Å and EFRET = 48.0 % when 80% DMSO/buffer mixture is added.

Analysis of pilocarpine and its trans epimer, isopilocarpine, by capillary electrophoresis.

PubMed

Baeyens, W; Weiss, G; Van Der Weken, G; Van Den Bossche, W

1993-05-28

Capillary zone electrophoresis was used for the separation of pilocarpine from its epimer, isopilocarpine, using coated fused-silica capillaries of 20 cm x 25 microm I.D., 8 kV running voltage, migration buffer of 0.1 M sodium dihydrogenphosphate pH 8, detection at 217 nm and injection by electromigration. Injections of aqueous, acid and basic solutions were compared. Linearity of the signal for pilocarpine hydrochloride up to 200 microg ml(-1) in 0.05 M hydrochloric acid was obtained, using naphazoline nitrate as internal standard. Optimization of migration buffer pH using coated silica capillaries of 50 cm x 50 microm I.D. showed that at pH 6.9 pilocarpine can be separated from ++isopilocarpine. Inclusion of beta-cyclodextrin in the buffer allows full baseline separation of both epimers. The method was applied to the analysis of a commercial ophthalmic pilocarpine solution.

Role of osmotic and hydrostatic pressures in bacteriophage genome ejection

NASA Astrophysics Data System (ADS)

Lemay, Serge G.; Panja, Debabrata; Molineux, Ian J.

2013-02-01

A critical step in the bacteriophage life cycle is genome ejection into host bacteria. The ejection process for double-stranded DNA phages has been studied thoroughly in vitro, where after triggering with the cellular receptor the genome ejects into a buffer. The experimental data have been interpreted in terms of the decrease in free energy of the densely packed DNA associated with genome ejection. Here we detail a simple model of genome ejection in terms of the hydrostatic and osmotic pressures inside the phage, a bacterium, and a buffer solution or culture medium. We argue that the hydrodynamic flow associated with the water movement from the buffer solution into the phage capsid and further drainage into the bacterial cytoplasm, driven by the osmotic gradient between the bacterial cytoplasm and culture medium, provides an alternative mechanism for phage genome ejection in vivo; the mechanism is perfectly consistent with phage genome ejection in vitro.

Characterization of pH-fractionated humic acids with respect to their dissociation behaviour.

PubMed

Klučáková, Martina

2016-04-01

Humic acids were divided into several fractions using buffer solutions as extraction agents with different pH values. Two methods of fractionation were used. The first one was subsequent dissolution of bulk humic acids in buffers adjusted to different pH. The second one was sequential dissolution in buffers with increasing pH values. Experimental data were compared with hypothesis of partial solubility of humic acids in aqueous solutions. Behaviour of humic fractions obtained by sequential dissolution, original bulk sample and residual fractions obtained by subsequent dissolution at pH 10 and 12 agrees with the hypothesis. Results demonstrated that regardless the common mechanism, solubility and dissociation degree of various humic fractions may be very different and can be estimated using parameters of the model based on the proposed mechanism. Presented results suggest that dissolving of solid humic acids in water environment is more complex than conventional solubility behaviour of sparingly soluble solids.

Purification and Characterization of [NiFe]-Hydrogenase of Shewanella oneidensis MR-1

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

Shi, Liang; Belchik, Sara M.; Plymale, Andrew E.

2011-08-02

The γ-proteobacterium Shewanella oneidensis MR-1 possesses a periplasmic [NiFe]-hydrogenase (MR-1 [NiFe]-H2ase) that was implicated in both H2 production and oxidation as well as technetium [Tc(VII)] reduction. To characterize the roles of MR-1 [NiFe]-H2ase in these proposed reactions, the genes encoding both subunits of MR-1 [NiFe]-H2ase were cloned into a protein expression vector. The resulting plasmid was transformed into a MR-1 mutant deficient in H2 formation. Expression of MR-1 [NiFe]-H2ase in trans restored the mutant’s ability to produce H2 at 37% of that for wild type. Following expression, MR-1 [NiFe]-H2ase was purified to near homogeneity. The purified MR-1 [NiFe]-H2ase could couplemore » H2 oxidation to reduction of Tc(VII) and methyl viologen directly. Change of the buffers used affected MR-1 [NiFe]-H2ase-mediated Tc(VII) but not methyl viologen reductions. Under the conditions tested, Tc(VII) reduction was complete in Tris buffer but not in HEPES buffer. The reduced Tc(IV) was soluble in Tris buffer but insoluble in HEPES buffer. Transmission electron microscopy analysis revealed that Tc(IV) precipitates formed in HEPES buffer were packed with crystallites. Although X-ray absorption near-edge spectroscopy measurements confirmed that the reduction products found in both buffers were Tc(IV), extended X-ray adsorption fine-structure measurements revealed that these products were very different. While the product in Tris buffer could not be determined, the Tc(IV) product in HEPES buffer was very similar to Tc(IV)O2•nH2O. These results shows for the first time that MR-1 [NiFe]-H2ase is a bidirectional enzyme that catalyzes both H2 formation and oxidation as well as Tc(VII) reduction directly by coupling H2 oxidation.« less

Reductive dehalogenation of 5-bromouracil by aliphatic organic radicals in aqueous solutions; electron transfer and proton-coupled electron transfer mechanisms

NASA Astrophysics Data System (ADS)

Matasović, Brunislav; Bonifačić, Marija

2011-06-01

Reductive dehalogenation of 5-bromouracil by aliphatic organic radicals CO2-rad , rad CH 2OH, rad CH(CH 3)OH, and rad CH(CH 3)O - have been studied in oxygen free aqueous solutions in the presence of organic additives: formate, methanol or ethanol. For radicals production 60Co γ-radiolysis was employed and the yield of bromide was measured by means of ion chromatography. Both radical anions have reducing potential negative enough to transfer an electron to BrU producing bromide ion and U rad radical. High yields of bromide have been measured increasing proportional to the concentration of the corresponding organic additives at a constant dose rate. This is characteristic for a chain process where regeneration of radical ions occurs by H-atom abstraction by U rad radical from formate or ethanol. Results with the neutral radicals conformed earlier proposition that the reduction reaction of α-hydroxyalkyl radicals proceeds by the proton-coupled electron transfer mechanism ( Matasović and Bonifačić, 2007). Thus, while both rad CH 2OH and rad CH(CH 3)OH did not react with BrU in water/alcohol solutions, addition of bicarbonate and acetate in mmol dm -3 concentrations, pH 7, brought about chain debromination to occur in the case of rad CH(CH 3)OH radical as reactant. Under the same conditions phosphate buffer, a base with higher bulk proton affinity, failed to have any influence. The results are taken as additional proofs for the specific complex formation of α-hydroxyalkyl radicals with suitable bases which enhances radicals' reduction potential in comparison with only water molecules as proton acceptors. Rate constants for the H-atom abstraction from ethanol and formate by U rad radicals have been estimated to amount to about ≥85 and 1200 dm 3 mol -1 s -1, respectively.

Formation of hydroxyl radical from San Joaquin Valley particles extracted in a cell-free surrogate lung fluid

NASA Astrophysics Data System (ADS)

Shen, H.; Anastasio, C.

2011-09-01

Previous studies have suggested that the adverse health effects from ambient particulate matter (PM) are linked to the formation of reactive oxygen species (ROS) by PM in cardiopulmonary tissues. While hydroxyl radical (•OH) is the most reactive of the ROS species, there are few quantitative studies of •OH generation from PM. Here we report on •OH formation from PM collected at an urban (Fresno) and rural (Westside) site in the San Joaquin Valley (SJV) of California. We quantified •OH in PM extracts using a cell-free, phosphate-buffered saline (PBS) solution with or without 50 μM ascorbate (Asc). The results show that generally the urban Fresno PM generates much more •OH than the rural Westside PM. The presence of Asc at a physiologically relevant concentration in the extraction solution greatly enhances •OH formation from all the samples. Fine PM (PM2.5) generally makes more •OH than the corresponding coarse PM (PMcf, i.e. with diameters of 2.5 to 10 μm) normalized by air volume collected, while the coarse PM typically generates more •OH normalized by PM mass. •OH production by SJV PM is reduced on average by (97 ± 6) % when the transition metal chelator desferoxamine (DSF) is added to the extraction solution, indicating a dominant role of transition metals. By measuring calibration curves of •OH generation from copper and iron, and quantifying copper and iron concentrations in our particle extracts, we find that PBS-soluble copper is primarily responsible for •OH production by the SJV PM, while iron often makes a significant contribution. Extrapolating our results to expected burdens of PM-derived •OH in human lung lining fluid suggests that typical daily PM exposures in the San Joaquin Valley are unlikely to result in a high amount of pulmonary •OH, although high PM events could produce much higher levels of •OH, which might lead to cytotoxicity.

On the Preparation of Buffer Solutions.

ERIC Educational Resources Information Center

Thomson, Bruce M.; Kessick, Michael A.

1981-01-01

Presents a method, suitable for use on programmable calculators, which allows calculation of the pH and ionic strength (I) of a mixed solution of salts of an acid or amounts necessary to produce a solution of a particular pH and I. Includes limitations when using the calculations described. (SK)

ELECTRODEPOSITION OF PLUTONIUM

DOEpatents

Wolter, F.J.

1957-09-10

A process of electrolytically recovering plutonium from dilute aqueous solutions containing plutonium ions comprises electrolyzing the solution at a current density of about 0.44 ampere per square centimeter in the presence of an acetate-sulfate buffer while maintaining the pH of the solution at substantially 5 and using a stirred mercury cathode.

Propagation of misfit dislocations from buffer/Si interface into Si

DOEpatents

Liliental-Weber, Zuzanna [El Sobrante, CA; Maltez, Rogerio Luis [Porto Alegre, BR; Morkoc, Hadis [Richmond, VA; Xie, Jinqiao [Raleigh, VA

2011-08-30

Misfit dislocations are redirected from the buffer/Si interface and propagated to the Si substrate due to the formation of bubbles in the substrate. The buffer layer growth process is generally a thermal process that also accomplishes annealing of the Si substrate so that bubbles of the implanted ion species are formed in the Si at an appropriate distance from the buffer/Si interface so that the bubbles will not migrate to the Si surface during annealing, but are close enough to the interface so that a strain field around the bubbles will be sensed by dislocations at the buffer/Si interface and dislocations are attracted by the strain field caused by the bubbles and move into the Si substrate instead of into the buffer epi-layer. Fabrication of improved integrated devices based on GaN and Si, such as continuous wave (CW) lasers and light emitting diodes, at reduced cost is thereby enabled.

Bacoside-A, an Indian Traditional-Medicine Substance, Inhibits β-Amyloid Cytotoxicity, Fibrillation, and Membrane Interactions.

PubMed

Malishev, Ravit; Shaham-Niv, Shira; Nandi, Sukhendu; Kolusheva, Sofiya; Gazit, Ehud; Jelinek, Raz

2017-04-19

Bacoside-A, a family of compounds extracted from the Bacopa monniera plant, is a folk-medicinal substance believed to exhibit therapeutic properties, particularly enhancing cognitive functions and improving memory. We show that bacoside-A exerted significant inhibitory effects upon cytotoxicity, fibrillation, and particularly membrane interactions of amyloid-beta (1-42) (Aβ42), the peptide playing a prominent role in Alzeheimer's disease progression and toxicity. Specifically, preincubation of bacoside-A with Aβ42 significantly reduced cell toxicity and inhibited fibril formation both in buffer solution and, more significantly, in the presence of membrane vesicles. In parallel, spectroscopic and microscopic analyses reveal that bacoside-A blocked membrane interactions of Aβ42, while formation of Aβ42 oligomers was not disrupted. These interesting phenomena suggest that inhibition of Aβ42 oligomer assembly into mature fibrils, and blocking membrane interactions of the oligomers are likely the underlying factors for ameliorating amyloid toxicity by bacoside-A and its putative physiological benefits.

Modelling anaerobic digestion acclimatisation to a biodegradable toxicant: application to cyanide.

PubMed

Zaher, U; Moussa, M S; Widyatmika, I N; van Der Steen, P; Gijzen, H J; Vanrolleghem, P A

2006-01-01

The observed acclimatisation to biodegradable toxicants in anaerobic cassava wastewater treatment is explained by modelling anaerobic cyanide degradation. A complete degradation pathway is proposed for cyanide. Cyanide degradation is modelled as enzymatic hydrolysis to formate and ammonia. Ammonia is added to the inorganic nitrogen content of the digester while formate is degraded by the hydrogenotrophic methanogens. Cyanide irreversible enzyme inhibition is modelled as an inhibition factor to acetate uptake processes. Cyanide irreversible toxicity is modelled as a decay factor to the acetate degraders. Cyanide as well as added phosphorus buffer solution were considered in the chemical equilibrium calculations of pH. The observed reversible effect after acclimatisation of sludge is modelled by a population shift between two aceticlastic methanogens that have different tolerance to cyanide toxicity. The proposed pathway is added to the IWA Anaerobic Digestion Model no.1 (ADM1). The ADM1 model with the designed extension is validated by an experiment using three lab-scale upflow anaerobic sludge bed reactors which were exposed to different cyanide loadings.

True and apparent inhibition of amyloid fibril formation.

PubMed

Martins, Pedro M

2013-01-01

A possible therapeutic strategy for amyloid diseases involves the use of small molecule compounds to inhibit protein assembly into insoluble aggregates. According to the recently proposed Crystallization-Like Model, the kinetics of amyloid fibrillization can be retarded by decreasing the frequency of new fibril formation or by decreasing the elongation rate of existing fibrils. To the compounds that affect the nucleation and/or the growth steps we call true inhibitors. An apparent inhibition mechanism may however result from the alteration of thermodynamic properties such as the solubility of the amyloidogenic protein. Apparent inhibitors markedly influence protein aggregation kinetics measured in vitro, yet they are likely to lead to disappointing results when tested in vivo. This is because cells and tissues media are in general much more buffered against small variations in composition than the solutions prepared in lab. Here we show how to discriminate between true and apparent inhibition mechanisms from experimental data on protein aggregation kinetics. The goal is to be able to identify false positives much earlier during the drug development process.

Characterization of Cu buffer layers for growth of L10-FeNi thin films

NASA Astrophysics Data System (ADS)

Mizuguchi, M.; Sekiya, S.; Takanashi, K.

2010-05-01

A Cu(001) layer was fabricated on a Au(001) layer to investigate the use of Cu as a buffer layer for growing L10-FeNi thin films. The epitaxial growth of a Cu buffer layer was observed using reflection high-energy electron diffraction. The flatness of the layer improved drastically with an increase in the substrate temperature although the layer was an alloy (AuCu3). An FeNi thin film was epitaxially grown on the AuCu3 buffer layer by alternate monatomic layer deposition and the formation of an L10-FeNi ordered alloy was expected. The AuCu3 buffer layer is thus a promising candidate material for the growth of L10-FeNi thin films.

Volume of reaction by the Archibald ultracentrifuge method (lobster hemocyanin).

PubMed

Saxena, V P; Kegeles, G; Kikas, R

1976-07-01

Samples of lobster hemocyanin (Homarus americanus) under conditions of reversible reaction between whole (25 S) and half (17 S) molecules have been subjected to accurately known nitrogen pressures in analytical ultracentrifuge cells. A modified pressurization chamber of the type developed by Schumaker and colleagues has been constructed for this purpose. The molecular weight was then determined at the top (liquid-gas) meniscus, by means of the Archibald method. The logarithmic dependence upon pressure of the derived equilibrium constant then gave directly the volume of reaction. Experiments were performed in veronal-citrate buffers at pH 8, where the molar volume of formation of whole (dodecameric) molecules from half molecules appears to be negative, and at pH 8.46 in veronal-citrate buffer in the presence of 0.003 molar free calcium ion, where the molar volume of formation was estimated to be + 390 cm3/mole. In glycine-sodium hydroxide buffer at pH 9.6 containing 0.0047 molar free calcium, the molar volume of formation of whole molecules was estimated to be +120 +/- 70 cm3, corresponding to an estimated difference in partial specific volume between whole molecules and half molecules of only 1.3 (10)-4cm3/gram. The correctness of the sign of this value in glycine buffer has been verified by pressure-jump light-scattering experiments.

Reduction of Mn-oxides by ferrous iron in a flow system: column experiment and reactive transport modeling

NASA Astrophysics Data System (ADS)

Postma, D.; Appelo, C. A. J.

2000-04-01

The reduction of Mn-oxide by Fe2+ was studied in column experiments, using a column filled with natural Mn-oxide coated sand. Analysis of the Mn-oxide indicated the presence of both Mn(III) and Mn(IV) in the Mn-oxide. The initial exchange capacity of the column was determined by displacement of adsorbed Ca2+ with Mg2+. Subsequently a FeCl2 solution was injected into the column causing the reduction of the Mn-oxide and the precipitation of Fe(OH)3. Finally the exchange capacity of the column containing newly formed Fe(OH)3 was determined by injection of a KBr solution. During injection of the FeCl2 solution into the column, an ion distribution pattern was observed in the effluent that suggests the formation of separate reaction fronts for Mn(III)-oxide and Mn(IV)-oxide travelling at different velocities through the column. At the proximal reaction front, Fe2+ reacts with MnO2 producing Fe(OH)3, Mn2+ and H+. The protons are transported downstream and cause the disproportionation of MnOOH at a separate reaction front. Between the two Mn reaction fronts, the dissolution and precipitation of Fe(OH)3 and Al(OH)3 act as proton buffers. Reactive transport modeling, using the code PHREEQC 2.0, was done to quantify and analyze the reaction controls and the coupling between transport and chemical processes. A model containing only mineral equilibria constraints for birnessite, manganite, gibbsite, and ferrihydrite, was able to explain the overall reaction pattern with the sequential appearance of Mn2+, Al3+, Fe3+, and Fe2+ in the column outlet solution. However, the initial breakthrough of a peak of Ca2+ and the observed pH buffering indicated that exchange processes were of importance as well. The amount of potential exchangers, such as birnessite and ferrihydrite, did vary in the course of the experiment. A model containing surface complexation coupled to varying concentrations of birnessite and ferrihydrite and a constant charge exchanger in addition to mineral equilibria provided a satisfactory description of the distribution of all solutes in time and space. However, the observed concentration profiles are more gradual than indicated by the equilibrium model. Reaction kinetics for the dissolution of MnO2 and MnOOH and dissolution of Al(OH)3 were incorporated in the model, which explained the shape of the breakthrough curves satisfactorily. The results of this study emphasize the importance of understanding the interplay between chemical reactions and transport in addition to interactions between redox, proton buffering, and adsorption processes when dealing with natural sediments. Reactive transport modeling is a powerful tool to analyze and quantify such interactions.

[Determination of total mass and morphology analysis of heavy metal in soil with potassium biphthalate-sodium hydroxide by ICP-AES].

PubMed

Qu, Jiao; Yuan, Xing; Cong, Qiao; Wang, Shuang

2008-11-01

Blank soil was used as quality controlling samples, soil sample dealt by potassium biphthalate-sodium hydroxide buffer solution was used as check sample, mixed acid HNO3-HF-HClO4 was chosen to nitrify soil samples, and plasma emission spectrometer (ICP-AES) was used as detecting method. The authors determined the total metal mass of Mo, Pb, As, Hg, Cr, Cd, Zn, Cu and Ni in the extracted and dealt soil samples, and determined the mass of Mo, Pb, As, Hg, Cr, Cd, Zn, Cu and Ni in the three chemical morphologies, including acid extractable morphology, oxide associated morphology, and organics associated modality. The experimental results indicated that the different pH of potassium biphthalate-sodium hydroxide buffer solution had obvious influence on the total mass of heavy metal and morphology transformation. Except for metal element Pb and Zn, the addition of different pH potassium dihydrogen phosphate-sodium hydroxide buffer solution could accelerate the soil samples nitrification and the total mass determination of heavy metal in the soil samples. The potassium biphthalate-sodium hydroxide buffer solution could facilitate the acid extractable morphology of Cr, Cu, Hg and Pb, oxidation associated morphology of As, Hg, Pb and Zn and the organic associated morphology transforming of As and Hg. At pH 5.8, the maximum acid extractable morphology contents of Cu and Hg were 2.180 and 0.632 mg x kg(-1), respectively; at pH 6.2, the maximal oxidation associated morphology content of Pb could achieve 27.792 mg x kg(-1); at pH 6.0, the maximum organic associated morphology content of heavy metal Hg was 4.715 mg x kg(-1).

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.

Efficiency enhancement of polymer solar cells by applying poly(vinylpyrrolidone) as a cathode buffer layer via spin coating or self-assembly.

PubMed

Wang, Haitao; Zhang, Wenfeng; Xu, Chenhui; Bi, Xianghong; Chen, Boxue; Yang, Shangfeng

2013-01-01

A non-conjugated polymer poly(vinylpyrrolidone) (PVP) was applied as a new cathode buffer layer in P3HT:PCBM bulk heterojunction polymer solar cells (BHJ-PSCs), by means of either spin coating or self-assembly, resulting in significant efficiency enhancement. For the case of incorporation of PVP by spin coating, power conversion efficiency (PCE) of the ITO/PEDOT:PSS/P3HT:PCBM/PVP/Al BHJ-PSC device (3.90%) is enhanced by 29% under the optimum PVP spin-coating speed of 3000 rpm, which leads to the optimum thickness of PVP layer of ~3 nm. Such an efficiency enhancement is found to be primarily due to the increase of the short-circuit current (J(sc)) (31% enhancement), suggesting that the charge collection increases upon the incorporation of a PVP cathode buffer layer, which originates from the conjunct effects of the formation of a dipole layer between P3HT:PCBM active layer and Al electrodes, the chemical reactions of PVP molecules with Al atoms, and the increase of the roughness of the top Al film. Incorporation of PVP layer by doping PVP directly into the P3HT:PCBM active layer leads to an enhancement of PCE by 13% under the optimum PVP doping ratio of 3%, and this is interpreted by the migration of PVP molecules to the surface of the active layer via self-assembly, resulting in the formation of the PVP cathode buffer layer. While the formation of the PVP cathode buffer layer is fulfilled by both fabrication methods (spin coating and self-assembly), the dependence of the enhancement of the device performance on the thickness of the PVP cathode buffer layer formed by self-assembly or spin coating is different, because of the different aggregation microstructures of the PVP interlayer.

ACCURATE CHEMICAL MASTER EQUATION SOLUTION USING MULTI-FINITE BUFFERS

PubMed Central

Cao, Youfang; Terebus, Anna; Liang, Jie

2016-01-01

The discrete chemical master equation (dCME) provides a fundamental framework for studying stochasticity in mesoscopic networks. Because of the multi-scale nature of many networks where reaction rates have large disparity, directly solving dCMEs is intractable due to the exploding size of the state space. It is important to truncate the state space effectively with quantified errors, so accurate solutions can be computed. It is also important to know if all major probabilistic peaks have been computed. Here we introduce the Accurate CME (ACME) algorithm for obtaining direct solutions to dCMEs. With multi-finite buffers for reducing the state space by O(n!), exact steady-state and time-evolving network probability landscapes can be computed. We further describe a theoretical framework of aggregating microstates into a smaller number of macrostates by decomposing a network into independent aggregated birth and death processes, and give an a priori method for rapidly determining steady-state truncation errors. The maximal sizes of the finite buffers for a given error tolerance can also be pre-computed without costly trial solutions of dCMEs. We show exactly computed probability landscapes of three multi-scale networks, namely, a 6-node toggle switch, 11-node phage-lambda epigenetic circuit, and 16-node MAPK cascade network, the latter two with no known solutions. We also show how probabilities of rare events can be computed from first-passage times, another class of unsolved problems challenging for simulation-based techniques due to large separations in time scales. Overall, the ACME method enables accurate and efficient solutions of the dCME for a large class of networks. PMID:27761104

Effects of air polishing and an amino acid buffered hypochlorite solution to dentin surfaces and periodontal ligament cell survival, attachment, and spreading.

PubMed

Schmidlin, Patrick R; Fujioka-Kobayashi, Masako; Mueller, Heinz-Dieter; Sculean, Anton; Lussi, Adrian; Miron, Richard J

2017-06-01

The aim of this study is to examine morphological changes of dentin surfaces following air polishing or amino acid buffered hypochlorite solution application and to assess their influence on periodontal ligament (PDL) cell survival, attachment, and spreading to dentin discs in vitro. Bovine dentin discs were treated with either (i) Classic, (ii) Plus, or (iii) Perio powder (EMS). Furthermore, Perisolv® a hypochlorite solution buffered with various amino acids was investigated. Untreated dentin discs served as controls. Morphological changes to dentin discs were assessed using scanning electron microscopy (SEM). Human PDL cells were seeded onto the respectively treated discs, and samples were then investigated for PDL cell survival, attachment, and spreading using a live/dead assay, adhesion assay, and SEM imaging, respectively. Both control and Perisolv®-rinsed dentin discs demonstrated smooth surfaces at low and high magnifications. The Classic powders demonstrated the thickest coating followed by the Powder Plus. The Perio powder demonstrated marked alterations of dentin discs by revealing the potential to open dentinal tubules even before rinsing. Seeding of PDL cells demonstrated an almost 100 % survival rate on all samples demonstrating very high biocompatibility for all materials. Significantly higher PDL cell numbers were observed on samples treated with the Perio powder and the Perisolv® solution (approximately 40 % more cells; p < 0.05). SEM imaging revealed the potential for PDL cells to attach and spread on all surfaces. The results from the present study demonstrate that cell survival and spreading of PDL cells on root surfaces is possible following either air polishing or application with Perisolv®. Future in vitro and animal testing is necessary to further characterize the beneficial effects of either system in a clinical setting. The use of air polishing or application with Perisolv amino acid buffered hypochlorite solution was effective in treating root surfaces and allowed for near 100 % PDL cell survival, attachment, and spreading onto all root surfaces.

Role of Self-Association and Supersaturation in Oral Absorption of a Poorly Soluble Weakly Basic Drug.

PubMed

Narang, Ajit S; Badawy, Sherif; Ye, Qingmei; Patel, Dhaval; Vincent, Maria; Raghavan, Krishnaswamy; Huang, Yande; Yamniuk, Aaron; Vig, Balvinder; Crison, John; Derbin, George; Xu, Yan; Ramirez, Antonio; Galella, Michael; Rinaldi, Frank A

2015-08-01

Precipitation of weakly basic drugs in intestinal fluids can affect oral drug absorption. In this study, the implications of self-association of brivanib alaninate in acidic aqueous solution, leading to supersaturation at basic pH condition, on its solubility and oral absorption were investigated. Self-association of brivanib alaninate was investigated by proton NMR spectroscopy, surface tension measurement, dynamic light scattering, isothermal titration calorimetry, and molecular modeling. Drug solubility was determined in various pH media, and its tendency to supersaturate upon pH shift was investigated in buffered and biorelevant aqueous solutions. Pharmacokinetic modeling of human oral drug absorption was utilized for parameter sensitivity analyses of input variables. Brivanib alaninate exhibited continuous, and pH- and concentration-dependent self-association. This phenomenon resulted in positive deviation of drug solubility at acidic pH and the formation of a stable supersaturated drug solution in pH-shift assays. Consistent with the supersaturation phenomenon observed in vitro, oral absorption simulations necessitated invoking long precipitation time in the intestine to successfully predict in vivo data. Self-association of a weakly basic drug in acidic aqueous solution can increase its oral absorption by supersaturation and precipitation resistance at the intestinal pH. This consideration is important to the selection of parameters for oral absorption simulation.

Effect of buffer on the immune response to trivalent oral poliovirus vaccine in Bangladesh: a community based randomized controlled trial.

PubMed

Chandir, Subhash; Ahamed, Kabir U; Baqui, Abdullah H; Sutter, Roland W; Okayasu, Hiromasa; Pallansch, Mark A; Oberste, Mark S; Moulton, Lawrence H; Halsey, Neal A

2014-11-01

Polio eradication efforts have been hampered by low responses to trivalent oral poliovirus vaccine (tOPV) in some developing countries. Since stomach acidity may neutralize vaccine viruses, we assessed whether administration of a buffer solution could improve the immunogenicity of tOPV. Healthy infants 4-6 weeks old in Sylhet, Bangladesh, were randomized to receive tOPV with or without a sodium bicarbonate and sodium citrate buffer at age 6, 10, and 14 weeks. Levels of serum neutralizing antibodies for poliovirus types 1, 2, and 3 were measured before and after vaccination, at 6 and 18 weeks of age, respectively. Serologic response rates following 3 doses of tOPV for buffer recipients and control infants were 95% and 88% (P=.065), respectively, for type 1 poliovirus; 95% and 97% (P=.543), respectively, for type 2 poliovirus; and 90% and 89% (P=.79), respectively, for type 3 poliovirus. Administration of a buffer solution prior to vaccination was not associated with statistically significant increases in the immune response to tOPV; however, a marginal 7% increase (P=.065) in serologic response to poliovirus type 1 was observed. NCT01579825. © The Author 2014. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Protein brownian rotation at the glass transition temperature of a freeze-concentrated buffer probed by superparamagnetic nanoparticles.

PubMed

Eloi, J-C; Okuda, M; Jones, S E Ward; Schwarzacher, W

2013-06-18

For applications from food science to the freeze-thawing of proteins it is important to understand the often complex freezing behavior of solutions of biomolecules. Here we use a magnetic method to monitor the Brownian rotation of a quasi-spherical cage-shaped protein, apoferritin, approaching the glass transition Tg in a freeze-concentrated buffer (Tris-HCl). The protein incorporates a synthetic magnetic nanoparticle (Co-doped Fe3O4 (magnetite)). We use the magnetic signal from the nanoparticles to monitor the protein orientation. As T decreases toward Tg of the buffer solution the protein's rotational relaxation time increases exponentially, taking values in the range from a few seconds up to thousands of seconds, i.e., orders of magnitude greater than usually accessed, e.g., by NMR. The longest relaxation times measured correspond to estimated viscosities >2 MPa s. As well as being a means to study low-temperature, high-viscosity environments, our method provides evidence that, for the cooling protocol used, the following applies: 1), the concentration of the freeze-concentrated buffer at Tg is independent of its initial concentration; 2), little protein adsorption takes place at the interface between ice and buffer; and 3), the protein is free to rotate even at temperatures as low as 207 K. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Polyelectrolyte multilayer assembly as a function of pH and ionic strength using the polysaccharides chitosan and heparin.

PubMed

Boddohi, Soheil; Killingsworth, Christopher E; Kipper, Matt J

2008-07-01

The goal of this work is to explore the effects of solution ionic strength and pH on polyelectrolyte multilayer (PEM) assembly, using biologically derived polysaccharides as the polyelectrolytes. We used the layer-by-layer (LBL) technique to assemble PEM of the polysaccharides heparin (a strong polyanion) and chitosan (a weak polycation) and characterized the sensitivity of the PEM composition and layer thickness to changes in processing parameters. Fourier-transform surface plasmon resonance (FT-SPR) and spectroscopic ellipsometry provided in situ and ex situ measurements of the PEM thickness, respectively. Vibrational spectroscopy and X-ray photoelectron spectroscopy (XPS) provided details of the chemistry (i.e., composition, electrostatic interactions) of the PEM. We found that when PEM were assembled from 0.2 M buffer, the PEM thickness could be increased from less than 2 nm per bilayer to greater than 4 nm per bilayer by changing the solution pH; higher and lower ionic strength buffer solutions resulted in narrower ranges of accessible thickness. Molar composition of the PEM was not very sensitive to solution pH or ionic strength, but pH did affect the interactions between the sulfonates in heparin and amines in chitosan when PEM were assembled from 0.2 M buffer. Changes in the PEM thickness with pH and ionic strength can be interpreted through descriptions of the charge density and conformation of the polyelectrolyte chains in solution.

Reducing interface recombination for Cu(In,Ga)Se{sub 2} by atomic layer deposited buffer layers

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

Hultqvist, Adam; Bent, Stacey F.; Li, Jian V.

2015-07-20

Partial CuInGaSe{sub 2} (CIGS) solar cell stacks with different atomic layer deposited buffer layers and pretreatments were analyzed by photoluminescence (PL) and capacitance voltage (CV) measurements to investigate the buffer layer/CIGS interface. Atomic layer deposited ZnS, ZnO, and SnO{sub x} buffer layers were compared with chemical bath deposited CdS buffer layers. Band bending, charge density, and interface state density were extracted from the CV measurement using an analysis technique new to CIGS. The surface recombination velocity calculated from the density of interface traps for a ZnS/CIGS stack shows a remarkably low value of 810 cm/s, approaching the range of single crystallinemore » II–VI systems. Both the PL spectra and its lifetime depend on the buffer layer; thus, these measurements are not only sensitive to the absorber but also to the absorber/buffer layer system. Pretreatment of the CIGS prior to the buffer layer deposition plays a significant role on the electrical properties for the same buffer layer/CIGS stack, further illuminating the importance of good interface formation. Finally, ZnS is found to be the best performing buffer layer in this study, especially if the CIGS surface is pretreated with potassium cyanide.« less

Reducing interface recombination for Cu(In,Ga)Se 2 by atomic layer deposited buffer layers

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

Hultqvist, Adam; Li, Jian V.; Kuciauskas, Darius

2015-07-20

Partial CuInGaSe2 (CIGS) solar cell stacks with different atomic layer deposited buffer layers and pretreatments were analyzed by photoluminescence (PL) and capacitance voltage (CV) measurements to investigate the buffer layer/CIGS interface. Atomic layer deposited ZnS, ZnO, and SnOx buffer layers were compared with chemical bath deposited CdS buffer layers. Band bending, charge density, and interface state density were extracted from the CV measurement using an analysis technique new to CIGS. The surface recombination velocity calculated from the density of interface traps for a ZnS/CIGS stack shows a remarkably low value of 810 cm/s, approaching the range of single crystalline II-VImore » systems. Both the PL spectra and its lifetime depend on the buffer layer; thus, these measurements are not only sensitive to the absorber but also to the absorber/buffer layer system. Pretreatment of the CIGS prior to the buffer layer deposition plays a significant role on the electrical properties for the same buffer layer/CIGS stack, further illuminating the importance of good interface formation. Finally, ZnS is found to be the best performing buffer layer in this study, especially if the CIGS surface is pretreated with potassium cyanide.« less

Reducing interface recombination for Cu(In,Ga)Se 2 by atomic layer deposited buffer layers

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

Hultqvist, Adam; Li, Jian V.; Kuciauskas, Darius

2015-07-20

Partial CuInGaSe2 (CIGS) solar cell stacks with different atomic layer deposited buffer layers and pretreatments were analyzed by photoluminescence (PL) and capacitance voltage (CV) measurements to investigate the buffer layer/CIGS interface. Atomic layer deposited ZnS, ZnO, and SnOx buffer layers were compared with chemical bath deposited CdS buffer layers. Band bending, charge density, and interface state density were extracted from the CV measurement using an analysis technique new to CIGS. The surface recombination velocity calculated from the density of interface traps for a ZnS/CIGS stack shows a remarkably low value of 810 cm/s, approaching the range of single crystalline II–VImore » systems. Both the PL spectra and its lifetime depend on the buffer layer; thus, these measurements are not only sensitive to the absorber but also to the absorber/buffer layer system. Pretreatment of the CIGS prior to the buffer layer deposition plays a significant role on the electrical properties for the same buffer layer/CIGS stack, further illuminating the importance of good interface formation. Finally, ZnS is found to be the best performing buffer layer in this study, especially if the CIGS surface is pretreated with potassium cyanide.« less

40 CFR Appendix B to Part 425 - Modified Monier-Williams Method

Code of Federal Regulations, 2014 CFR

2014-07-01

... is removed by scrubbing the nitrogen gas stream in a pH 7 buffer solution. The sulfide gas is collected by passage through an alkaline hydrogen peroxide scrubbing solution in which it is oxidized to sulfate. Sulfate concentration in the scrubbing solution is determined by either EPA gravimetric test...

40 CFR Appendix B to Part 425 - Modified Monier-Williams Method

Code of Federal Regulations, 2013 CFR

2013-07-01

... is removed by scrubbing the nitrogen gas stream in a pH 7 buffer solution. The sulfide gas is collected by passage through an alkaline hydrogen peroxide scrubbing solution in which it is oxidized to sulfate. Sulfate concentration in the scrubbing solution is determined by either EPA gravimetric test...

Improvements in multimedia data buffering using master/slave architecture

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

Sheikh, S.; Ganesan, R.

1996-12-31

Advances in the networking technology and multimedia technology has necessitated a need for multimedia servers to be robust and reliable. Existing solutions have direct limitations such as I/O bottleneck and reliability of data retrieval. The system can store the stream of incoming data if enough buffer space is available or the mass storage is clearing the buffer data faster than queue input. A single buffer queue is not sufficient to handle the large frames. Queue sizes are normally several megabytes in length and thus in turn will introduce a state of overflow. The system should also keep track of themore » rewind, fast forwarding, and pause requests, otherwise queue management will become intricate. In this paper, we present a master/slave (server that is designated to monitor the workflow of the complete system. This server holds every other information of slaves by maintaining a dynamic table. It also controls the workload on each of the systems by redistributing request to others or handles the request by itself) approach which will overcome the limitations of today`s storage and also satisfy tomorrow`s storage needs. This approach will maintain the system reliability and yield faster response by using more storage units in parallel. A network of master/slave can handle many requests and synchronize them at all times. Using dedicated CPU and a common pool of queues we explain how queues can be controlled and buffer overflow can be avoided. We propose a layered approach to the buffering problem and provide a read-ahead solution to ensure continuous storage and retrieval of multimedia data.« less

Influence of polysaccharides on wine protein aggregation.

PubMed

Jaeckels, Nadine; Meier, Miriam; Dietrich, Helmut; Will, Frank; Decker, Heinz; Fronk, Petra

2016-06-01

Polysaccharides are the major high-molecular weight components of wines. In contrast, proteins occur only in small amounts in wine, but contribute to haze formation. The detailed mechanism of aggregation of these proteins, especially in combination with other wine components, remains unclear. This study demonstrates the different aggregation behavior between a buffer and a model wine system by dynamic light scattering. Arabinogalactan-protein, for example, shows an increased aggregation in the model wine system, while in the buffer system a reducing effect is observed. Thus, we could show the importance to examine the behavior of wine additives under conditions close to reality, instead of simpler buffer systems. Additional experiments on melting points of wine proteins reveal that only some isoforms of thaumatin-like proteins and chitinases are involved in haze formation. We can confirm interactions between polysaccharides and proteins, but none of these polysaccharides is able to prevent haze in wine. Copyright © 2016. Published by Elsevier Ltd.

[Role of the blood bicarbonate buffer system in the mechanism of fish adaptation to different levels of carbonic acid in an aqueous medium].

PubMed

Romanenko, V D; Kotsar', N I

1976-01-01

The role of a bicarbonate buffer system of fish (Cyprinidae family) blood was studied in their organism addaptive reactions to different levels of CO2 in the aqueous medium. The fish is established to prossess rather effective for maintaining blood acid-base balance. It permits the fish to endure for a long time essential fluctuations of carbonic acid concentration in water. In prevention of possible development of carbonic acid acidosis an essential role belongs to formation of bicarbonates as a blood buffer system stablizing pH is shown to be significant for preventing possible development of acidosis. The adaptation potentialities of Cyprinidae family permit them to endure an increase of CO2 in water and are determined by the ability of their organism to formations of bicarbonate and their retaining in blood.

Optimization of the Energy Level Alignment between the Photoactive Layer and the Cathode Contact Utilizing Solution-Processed Hafnium Acetylacetonate as Buffer Layer for Efficient Polymer Solar Cells.

PubMed

Yu, Lu; Li, Qiuxiang; Shi, Zhenzhen; Liu, Hao; Wang, Yaping; Wang, Fuzhi; Zhang, Bing; Dai, Songyuan; Lin, Jun; Tan, Zhan'ao

2016-01-13

The insertion of an appropriate interfacial buffer layer between the photoactive layer and the contact electrodes makes a great impact on the performance of polymer solar cells (PSCs). Ideal interfacial buffer layers could minimize the interfacial traps and the interfacial barriers caused by the incompatibility between the photoactive layer and the electrodes. In this work, we utilized solution-processed hafnium(IV) acetylacetonate (Hf(acac)4) as an effective cathode buffer layer (CBL) in PSCs to optimize the energy level alignment between the photoactive layer and the cathode contact, with the short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) all simultaneously improved with Hf(acac)4 CBL, leading to enhanced power conversion efficiencies (PCEs). Ultraviolet photoemission spectroscopy (UPS) and scanning Kelvin probe microscopy (SKPM) were performed to confirm that the interfacial dipoles were formed with the same orientation direction as the built-in potential between the photoactive layer and Hf(acac)4 CBL, benefiting the exciton separation and electron transport/extraction. In addition, the optical characteristics and surface morphology of the Hf(acac)4 CBL were also investigated.

[Verification of a decrease in the rigidity of the phage lambda DNA polymeric chain in low ionic strength aqueous solutions by testing the polymer-polymer interlink interactions].

PubMed

Arutiunian, A V; Ivanova, M A; Kurliand, D I; Kapshin, Iu S; Landa, S B; Poshekhonov, S T; Drobchenko, E A; Shevelev, I V

2011-01-01

Changes in the rigidity of the polymetric chain of phage lambda double-strand DNA have been studied by laser correlation spectroscopy. It was shown that, as the ionic strength increases, the effect of the screening of the hydrodynamic interaction of the links of the polymeric chain specific for polymeric coils arises in a DNA solution. It is assumed that the screening occurs when the threshold of the overlapping of DNA coils is achieved. The overlapping of coils is the result of a previously observed significant rise of DNA coil size from abnormally small DNA coils in low ionic strength buffers (about 10(-2) M Na+ or less) to maximum possible large coils in the 5SSC and 5SSC-like buffers. Further analysis of the far interlink interactions in linear lambda phage DNA coils in similar buffers at pH 7 and 4 confirms the earlier proposal about the role of H+ ions in the appearance of abnormally small DNA coils. The abnormal decrease in the DNA coil size in low ionic strength buffers is not a specific feature of lambda phage DNA only.

Cathode buffer composed of fullerene-ethylenediamine adduct for an organic solar cell

NASA Astrophysics Data System (ADS)

Kimoto, Yoshinori; Akiyama, Tsuyoshi; Fujita, Katsuhiko

2017-02-01

We developed a fullerene-ethylenediamine adduct (C60P-DC) for a cathode buffer material in organic bulk heterojunction solar cells, which enhance the open-circuit voltage (V oc). The evaporative spray deposition using ultra dilute solution (ESDUS) technique was employed to deposit the buffer layer onto the organic active layer to avoid damage during the deposition. By the insertion of a C60P-DC buffer layer, V oc and power conversion efficiency (PCE) were increased from 0.41 to 0.57 V and from 1.65 to 2.10%, respectively. The electron-only device with the C60P-DC buffer showed a much lower current level than that without the buffer, indicating that the V oc increase is caused not by vacuum level shift but by hole blocking. The curve fitting of current density-voltage (J-V) characteristics to the equivalent circuit with a single diode indicated that the decrease in reversed saturation current by hole blocking increased caused the V oc.

Self-Functionalization Behind a Solution-Processed NiOx Film Used As Hole Transporting Layer for Efficient Perovskite Solar Cells.

PubMed

Ciro, John; Ramírez, Daniel; Mejía Escobar, Mario Alejandro; Montoya, Juan Felipe; Mesa, Santiago; Betancur, Rafael; Jaramillo, Franklin

2017-04-12

Fabrication of solution-processed perovskite solar cells (PSCs) requires the deposition of high quality films from precursor inks. Frequently, buffer layers of PSCs are formed from dispersions of metal oxide nanoparticles (NPs). Therefore, the development of trustable methods for the preparation of stable colloidal NPs dispersions is crucial. In this work, a novel approach to form very compact semiconducting buffer layers with suitable optoelectronic properties is presented through a self-functionalization process of the nanocrystalline particles by their own amorphous phase and without adding any other inorganic or organic functionalization component or surfactant. Such interconnecting amorphous phase composed by residual nitrate, hydroxide, and sodium ions, proved to be fundamental to reach stable colloidal dispersions and contribute to assemble the separate crystalline nickel oxide NPs in the final film, resulting in a very homogeneous and compact layer. A proposed mechanism behind the great stabilization of the nanoparticles is exposed. At the end, the self-functionalized nickel oxide layer exhibited high optoelectronic properties enabling perovskite p-i-n solar cells as efficient as 16.6% demonstrating the pertinence of the presented strategy to obtain high quality buffer layers processed in solution at room temperature.

Development anmd testing of electrophoresis solutions. Task I.1: Development of optimal buffer system

NASA Technical Reports Server (NTRS)

1985-01-01

Two buffers were explored for testing: low ionic strength electrophoresis buffer with and without density gradient material. It was found that the electrophoresis routine was better tolerated when Ficoll was present. The results of a viability study of primary human fetal kidney (HFK-1) cells at the first passage are shown. Cell strain HFK-1 was used in several experiments at the first and second passage. The HFK consisted mainly of fibroblasts, and HFK-1 has a high epithelioid cell content. The chromosomes of HFK were examined and found to be euploid. The stock medium for cell electrophoresis is described. In this solution density gradient solutes such as sucrose and Ficoll are dissolved to bring the osmolarity to 0.30. Its ionic strength is less than 0.01M, and its conductivity is usually 0.0011 mho/cm. Methods for viability determination included direct microscopic counting of the percent cells attached and spread within 24 hr of plating test cultures or electrophoretically separated fractions. The Cytograf viability assay concept was tested, and shown that blue stained cells scatter less light into the 0.8 to 3.3 deg angular interval than do unstained cells.

Solution Preserves Nucleic Acids in Body-Fluid Specimens

NASA Technical Reports Server (NTRS)

Pierson, Duane L.; Stowe, Raymond P.

2004-01-01

A solution has been formulated to preserve deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) in specimens of blood, saliva, and other bodily fluids. Specimens of this type are collected for diagnostic molecular pathology, which is becoming the method of choice for diagnosis of many diseases. The solution makes it possible to store such specimens at room temperature, without risk of decomposition, for subsequent analysis in a laboratory that could be remote from the sampling location. Thus, the solution could be a means to bring the benefits of diagnostic molecular pathology to geographic regions where refrigeration equipment and diagnostic laboratories are not available. The table lists the ingredients of the solution. The functions of the ingredients are the following: EDTA chelates divalent cations that are necessary cofactors for nuclease activity. In so doing, it functionally removes these cations and thereby retards the action of nucleases. EDTA also stabilizes the DNA helix. Tris serves as a buffering agent, which is needed because minor contaminants in an unbuffered solution can exert pronounced effects on pH and thereby cause spontaneous degradation of DNA. SDS is an ionic detergent that inhibits ribonuclease activity. SDS has been used in some lysis buffers and as a storage buffer for RNA after purification. The use of the solution is straightforward. For example, a sample of saliva is collected by placing a cotton roll around in the subject's mouth until it becomes saturated, then the cotton is placed in a collection tube. Next, 1.5 mL of the solution are injected directly into the cotton and the tube is capped for storage at room temperature. The effectiveness of the solution has been demonstrated in tests on specimens of saliva containing herpes simplex virus. In the tests, the viral DNA, as amplified by polymerase chain reaction, was detected even after storage for 120 days.

Absorption and fluorescence spectroscopic characterisation of the circadian blue-light photoreceptor cryptochrome from Drosophila melanogaster (dCry)

NASA Astrophysics Data System (ADS)

Shirdel, J.; Zirak, P.; Penzkofer, A.; Breitkreuz, H.; Wolf, E.

2008-09-01

The absorption and fluorescence behaviour of the circadian blue-light photoreceptor cryptochrome from Drosophila melanogaster (dCry) in a pH 8 aqueous buffer solution is studied. The flavin adenine dinucleotide (FAD) cofactor of dCry is identified to be present in its oxidized form (FAD ox), and the 5,10-methenyltetrahydrofolate (MTHF) cofactor is found to be hydrolyzed and oxidized to 10-formyldihydrofolate (10-FDHF). The absorption and the fluorescence behaviour of dCry is investigated in the dark-adapted (receptor) state, the light-adapted (signalling) state, and under long-time violet light exposure. Photo-excitation of FAD ox in dCry causes a reductive electron transfer to the formation of anionic FAD semiquinone (FAD rad - ), and photo-excitation of the generated FAD rad - causes an oxidative electron transfer to the back formation of FAD ox. In light adapted dCry a photo-induced equilibrium between FAD ox and FAD rad - exists. The photo-cycle dynamics of signalling state formation and recovery is discussed. Quantum yields of photo-induced signalling state formation of about 0.2 and of photo-induced back-conversion of about 0.2 are determined. A recovery of FAD rad - to FAD ox in the dark with a time constant of 1.6 min at room temperature is found.

Studies on vaginal malodor. I. Study in humans.

PubMed

Chvapil, M; Eskelson, C; Jacobs, S; Chvapil, T; Russell, D H

1978-07-01

Forty-two percent of collagen sponges tested as an intravaginal barrier contraceptive method developed malodor when retained for 5 days. Only 4% developed odor when the sponge was removed within 24 hours after intercourse, rinsed, and reinserted. While sexually active volunteers found odor in 37% of the sponges, odor formed only in 4% of the sponges worn by sexually inactive users. No difference in the rate of odor formation was found when neutral pH (7.0) and acid pH (3.4) collagen sponges were tested, although we believe that a pH 3.4 is too acid and promotes odor formation. The optimal pH of the sponge should be 4.5 to 5.5. Malodor was efficiently extracted from sponges by washing in acid milieu of tap water and vinegar or 0.1 M acetate buffer, pH 4.0. Alkali extraction procedures were ineffective, and lukewarm water was slightly less effective than acid extraction of odor. At the time of malodor development, the high content of polyamines (putrescine, spermine, spermidine) in the ejaculate decreased to undetectable values. We conclude that the ejaculate is the major source of malodor formation in intravaginally worn collagen sponges. Removal, rinsing optimally in vinegar solution, and reinsertion within 24 hours after intercourse reduces the chance of malodor formation.

Solubility enhancement of a bisnaphthalimide tumoricidal agent, DMP 840, through complexation.

PubMed

Raghavan, K S; Nemeth, G A; Gray, D B; Hussain, M A

1996-10-01

The purpose of this research was to enhance the aqueous solubility of DMP 840 by complexation with water-soluble and nontoxic agents, and to understand the nature of the interactions involved in complex formation using nuclear magnetic resonance (1H-NMR). The solubility of DMP 840 in water, saline, acetate buffers, and cosolvent mixtures was determined by high-performance liquid chromatography, and the effect of nicotinamide and pyridoxine concentrations on the solubility of DMP 840 was examined by the phase solubility method. 1H-NMR spectra were acquired in deuterated acetate buffer at 400 MHz on a Varian Unity-400 spectrometer. The aqueous solubility of DMP 840 was sensitive to the presence of chloride and acetate anions in solution, and did not improve in the presence of cosolvents. The use of the nontoxic and water-soluble complex-forming agents nicotinamide and pyridoxine, however, resulted in a linear increase in the aqueous solubility of DMP 840 with both ligands. The solubilization appears to be due to formation of 1:1 complexes between DMP 840 and the bioorganic ligands. The complexation constants were 15.57 M-1 for the DMP 840:nicotinamide complex and 13.36 M-1 for the DMP 840:pyridoxine complex. The NMR results indicate that the interaction is a result of vertical or plane-to-plane stacking and the complexation constants were in agreement with that obtained by phase solubility. The results suggest that the aqueous solubility of a poorly water soluble drug substance such as DMP 840 can be significantly enhanced by its complexation with water-soluble and nontoxic agents.

Dynamics of gold nanoparticles in synthetic and biopolymer solutions

NASA Astrophysics Data System (ADS)

Kohli, Indermeet

Soft matter systems of colloidal particles, polymers, amphiphiles and liquid crystals are ubiquitous in our everyday life. Food, plastics, soap and even human body is comprised of soft materials. Research conducted to understand the behavior of these soft matter systems at molecular level is essential for many interdisciplinary fields of study as well as important for many technological applications. We used gold nanoparticles (Au NPs) to investigate the length-scale dependent dynamics in semidilute poly(ethylene glycol) (PEG)-water, bovine serum albumin (BSA)-phosphate buffer, dextran and particulate solutions. In case of PEG-water solutions, fluctuation correlation spectroscopy was used to measure the diffusion coefficients (D) of the NPs as a function of their radius, Ro (2.5-10 nm), PEG volume fraction, φ (0-0.37) and molecular weight, Mw (5 kg/mol and 35 kg/mol). Our results indicate that the radius of gyration, Rg of the polymer chain is the crossover length scale for the NPs experiencing nanoviscosity or macroviscosity. In BSA-phosphate buffer solutions, we observed a monolayer formation at the NP surface with a thickness of 3.8 nm. The thickness of the adsorbed layer was independent of NP size. Best fit was obtained by the anticooperative binding model with the Hill coefficient of n = 0.63. Dissociation constant (KD) increased with particle size indicating stronger interaction of BSA with smaller sized NPs. We also contrasted the diffusion of gold nanoparticles (AuNPs) in crowded solutions of randomly branched polymer (dextran) and rigid, spherical particles (silica) to understand the roles played by the probe size and structure of the crowding agent in determining the probe diffusion. AuNPs of two different sizes (2.5 nm & 10 nm), dextran of molecular weight 70 kDa and silica particles of radius 10 nm were used. Our results indicated that the AuNP diffusion can be described using the bulk viscosity of the matrix and hydrodynamically dextran behaved similar to soft colloid. In all situations, we observed normal diffusion except for 2.5 nm sized AuNP particles in dextran solution at higher volume fraction. This was caused by transient trapping of particles within the random branches. The results showed the importance of macromolecular architecture in determining the transport properties in intracellular matrix and in cells with spiny dendrites.

Study on the reduction and hysteresis effect of soil nitrogen pollution by Alfalfa in channel buffer bank

NASA Astrophysics Data System (ADS)

Chi, Yixia; Xue, Lianqing; Zhang, Zhanyu; Li, Dongying

2018-01-01

Based on the simulation experiments of solute transport in channel buffer bank and pot experiments, this study analyzed the transport of nitrogen pollution from farmland drains along the South-North Water Transfer east route project; and compared the nitrogen transport rule and purification effect of alfalfa in channel buffer bank soil under situations of bare land and alfalfa mulching. The results showed that: (1) soil nitrogen content decreased gradually with the width increase of channel buffer bank by the soil adsorption and decomposition; (2) the migration rates of nitrogen were 0.06 g·kg-1 by the alfalfa mulching; (3) the removed rates of nitrogen from the soil were 0.088 g·kg-1 by cutting alfalfa; (4) the residual nitrogen of soil with alfalfa was 10% of the bare land. Alfalfa in channel buffer bank had obvious reduction and hysteresis effect to soil nitrogen pollution.

Concept cartoons for diagnosing student’s misconceptions in the topic of buffers

NASA Astrophysics Data System (ADS)

Kusumaningrum, I. A.; Ashadi; Indriyanti, N. Y.

2018-05-01

Student’s misconceptions have been concerned over twenty years in the chemistry education research. It influences students to learn new knowledge and gain a correct concept. The buffer solution is found as a difficult topic due to student’s misconception. However, the research related this subject are still rare. Concept cartoon has been used as one of the effective tools to diagnose misconceptions. This study aims to identify the effectiveness of concept cartoon to diagnose them. The concept cartoon consists of three concept questions. 98 students of grade 11 as respondents of this research and followed by interview for selected students. The data obtain of the study are analyzed by using a scoring key. The detected misconceptions are about what buffers do, what buffers are, and how buffers are able to do what they do. Concept cartoon is potential as a basic tool for remedial teaching.

Expanding the range of free calcium regulation in biological solutions.

PubMed

Dweck, David; Reyes-Alfonso, Avelino; Potter, James D

2005-12-15

Many biological systems use ethylene glycol bis (beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) to regulate the free calcium concentration ([Ca(2+)](free)) in the presence of physiological levels of free Mg(2+) ([Mg(2+)](free)). Frequently, it is necessary to work at [Ca(2+)](free) beyond EGTA's buffering capabilities. Therefore, we have developed methods to extend the buffering range by adding nitrilotriacetic acid (NTA) to solutions containing EGTA. This extension results from NTA having a lower K'(dCa) than EGTA. Such equilibria are solved by pCa Calculator, a computer program designed to aid in the study of Ca(2+)-dependent physiological processes while accounting for the effects of pH, temperature, and ionic strength. With multiple chelators and pH buffers from which to choose, pCa Calculator calculates the total concentration of each species required to achieve specified free concentrations of Ca(2+), ATP, and Mg(2+). The program is intuitive, user-friendly, and flexible enough to fix or vary the [Mg-ATP(2-)] and ionic strength. Moreover, it can account for increases in experimental volume from calcium addition. A comparative analysis is reported for testing solutions in the presence and absence of NTA by measuring the calcium binding affinity of fluorescent cardiac troponin C. These findings demonstrate that EGTA, when used in conjunction with NTA, improves and expands the regulation of free calcium in solution.

Geochemical modeling of reactions and partitioning of trace metals and radionuclides during titration of contaminated acidic sediments.

PubMed

Zhang, Fan; Luo, Wensui; Parker, Jack C; Spalding, Brian P; Brooks, Scott C; Watson, David B; Jardine, Philip M; Gu, Baohua

2008-11-01

Many geochemical reactions that control aqueous metal concentrations are directly affected by solution pH. However, changes in solution pH are strongly buffered by various aqueous phase and solid phase precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior of the soil-solution system is thus critical to predict metal transport under variable pH conditions. This studywas undertaken to develop a practical generic geochemical modeling approach to predict aqueous and solid phase concentrations of metals and anions during conditions of acid or base additions. The method of Spalding and Spalding was utilized to model soil buffer capacity and pH-dependent cation exchange capacity by treating aquifer solids as a polyprotic acid. To simulate the dynamic and pH-dependent anion exchange capacity, the aquifer solids were simultaneously treated as a polyprotic base controlled by mineral precipitation/ dissolution reactions. An equilibrium reaction model that describes aqueous complexation, precipitation, sorption and soil buffering with pH-dependent ion exchange was developed using HydroGeoChem v5.0 (HGC5). Comparison of model results with experimental titration data of pH, Al, Ca, Mg, Sr, Mn, Ni, Co, and SO4(2-) for contaminated sediments indicated close agreement suggesting that the model could potentially be used to predictthe acid-base behavior of the sediment-solution system under variable pH conditions.

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

Element mobilization from Bakken shales as a function of water chemistry.

PubMed

Wang, Lin; Burns, Scott; Giammar, Daniel E; Fortner, John D

2016-04-01

Waters that return to the surface after injection of a hydraulic fracturing fluid for gas and oil production contain elements, including regulated metals and metalloids, which are mobilized through interactions between the fracturing fluid and the shale formation. The rate and extent of mobilization depends on the geochemistry of the formation and the chemical characteristics of the fracturing fluid. In this work, laboratory scale experiments investigated the influence of water chemistry on element mobilization from core samples taken from the Bakken formation, one of the most productive shale oil plays in the US. Fluid properties were systematically varied and evaluated with regard to pH, oxidant level, solid:water ratio, temperature, and chemical additives. Element mobilization strongly depended on solution pH and redox conditions and to a lesser extent on the temperature and solid:water ratio. The presence of oxygen and addition of hydrogen peroxide or ammonium persulfate led to pyrite oxidation, resulting in elevated sulfate concentrations. Further, depending on the mineral carbonates available to buffer the system pH, pyrite oxidation could lower the system pH and enhance the mobility of several metals and metalloids. Copyright © 2016 Elsevier Ltd. All rights reserved.

Contact activation of blood-plasma coagulation

NASA Astrophysics Data System (ADS)

Golas, Avantika

Surface engineering of biomaterials with improved hemocompatibility is an imperative, given the widespread global need for cardiovascular devices. Research summarized in this dissertation focuses on contact activation of FXII in buffer and blood plasma frequently referred to as autoactivation. The extant theory of contact activation imparts FXII autoactivation ability to negatively charged, hydrophilic surfaces. According to this theory, contact activation of plasma involves assembly of proteins comprising an "activation complex" on activating surfaces mediated by specific chemical interactions between complex proteins and the surface. This work has made key discoveries that significantly improve our core understanding of contact activation and unravel the existing paradigm of plasma coagulation. It is shown herein that contact activation of blood factor XII (FXII, Hageman factor) in neat-buffer solution exhibits a parabolic profile when scaled as a function of silanized-glass-particle activator surface energy (measured as advancing water adhesion tension t°a=g° Iv costheta in dyne/cm, where g°Iv is water interfacial tension in dyne/cm and theta is the advancing contact angle). Nearly equal activation is observed at the extremes of activator water-wetting properties --36 < t°a < 72 dyne/cm (O° ≤ theta < 120°), falling sharply through a broad minimum within the 20 < t°a < 40 dyne/cm (55° < theta < 75°). Furthermore, contact activation of FXII in buffer solution produces an ensemble of protein fragments exhibiting either procoagulant properties in plasma (proteolysis of blood factor XI or prekallikrein), amidolytic properties (cleavage of s-2302 chromogen), or the ability to suppress autoactivation through currently unknown biochemistry. The relative proportions of these fragments depend on activator surface chemistry/energy. We have also discovered that contact activation is moderated by adsorption of plasma proteins unrelated to coagulation through an "adsorption-dilution" effect that blocks FXII contact with hydrophobic activator surfaces. The adsorption-dilution effect explains the apparent specificity for hydrophilic activators pursued by earlier investigators. Finally a comparison of FXII autoactivation in buffer, serum, protein cocktail, and plasma solutions is shown herein. Activation of blood plasma coagulation in vitro by contact with material surfaces is demonstrably dependent on plasma-volume-to-activator-surface-area ratio. However, activation of factor XII dissolved in buffer, protein cocktail, heat-denatured serum, and FXI deficient plasma does not exhibit activator surface-area dependence. Instead, a highly-variable burst of procoagulant-enzyme yield is measured that exhibits no measurable kinetics, sensitivity to mixing, or solution-temperature dependence. Thus, FXII activation in both buffer and protein-containing solutions does not exhibit characteristics of a biochemical reaction but rather appears to be a "mechanochemical" reaction induced by FXII molecule interactions with hydrophilic activator particles that do not formally adsorb blood proteins from solution. Results strongly suggest that activator surface-area dependence observed in contact activation of plasma coagulation does not solely arise at the FXII activation step of the intrinsic pathway.

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.

Polydopamine and Polydopamine-Silane Hybrid Surface Treatments in Structural Adhesive Applications.

PubMed

Tran, Ngon T; Flanagan, David P; Orlicki, Joshua A; Lenhart, Joseph L; Proctor, Kenneth L; Knorr, Daniel B

2018-01-30

Numerous studies have focused on the remarkable adhesive properties of polydopamine, which can bind to substrates with a wide range of surface energies, even under aqueous conditions. This behavior suggests that polydopamine may be an attractive option as a surface treatment in structural bonding applications, where good bond durability is required. Here, we assessed polydopamine as a surface treatment for bonding aluminum plates with an epoxy resin. A model epoxy adhesive consisting of diglycidyl ether of bisphenol A (DGEBA) and Jeffamine D230 polyetheramine was employed, and lap shear measurements (ASTM D1002 10) were made (i) under dry conditions to examine initial bond strength and (ii) after exposure to hot/wet (63 °C in water for 14 days) conditions to assess bond durability. Surprisingly, our results showed that polydopamine alone as a surface treatment provided no benefit beyond that obtained by exposing the substrates to an alkaline solution of tris buffer used for the deposition of polydopamine. This implies that polydopamine has a potential Achilles' heel, namely, the formation of a weak boundary layer that was identified using X-ray photoelectron spectroscopy (XPS) of the fractured surfaces. In fact, for longer deposition times (2.5 and 18 h), the tris buffer-treated surface outperformed the polydopamine surface treatments, suggesting that tris buffer plays a unique role in improving adhesive performance even in the absence of polydopamine. We further showed that the use of polydopamine-3-aminopropyltriethoxysilane (APTES) hybrid surface treatments provided significant improvements in bond durability at extended deposition times relative to both polydopamine and an untreated control.

Impact of different environmental conditions on the aggregation of biogenic U(IV) nanoparticles synthesized by Desulfovibrio alaskensis G20

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

Şengör, S. Sevinç; Singh, Gursharan; Dohnalkova, Alice

This study investigates the impact of specific environmental conditions on the formation of colloidal U(IV) nanoparticles by the sulfate reducing bacteria (SRB, Desulfovibrio alaskensis G20). The reduction of soluble U(VI) to less soluble U(IV) was quantitatively investigated under growth and non-growth conditions in bicarbonate or 1,4-piperazinediethanesulfonic acid (PIPES) buffered environments. The results showed that under non-growth conditions, the majority of the reduced U nanoparticles aggregated and precipitated out of solution. High resolution transmission electron microscopy revealed that only a very small fraction of cells had reduced U precipitates in the periplasmic spaces in the presence of PIPES buffer, whereas inmore » the presence of bicarbonate buffer, reduced U was also observed in the cytoplasm with greater aggregation of biogenic U(IV) particles at higher initial U(VI) concentrations. The same experiments were repeated under growth conditions using two different electron donors (lactate and pyruvate) and three electron acceptors (sulfate, fumarate, and thiosulfate). In contrast to the results of the non-growth experiments, even after 0.2 m filtration, the majority of biogenic U(IV) remained in the aqueous phase resulting in potentially mobile biogenic U(IV) nanoparticles. Size fractionation results showed that U(IV) aggregates were between 18 and 200 nm in diameter, and thus could be very mobile. The findings of this study are helpful to assess the size and potential mobility of reduced U nanoparticles under different environmental conditions, and would provide insights on their potential impact affecting U(VI) bioremediation efforts at subsurface contaminated sites.« less

Solution immersed silicon (SIS)-based biosensors: a new approach in biosensing.

PubMed

Diware, M S; Cho, H M; Chegal, W; Cho, Y J; Jo, J H; O, S W; Paek, S H; Yoon, Y H; Kim, D

2015-02-07

A novel, solution immersed silicon (SIS)-based sensor has been developed which employs the non-reflecting condition (NRC) for a p-polarized wave. The SIS sensor's response is almost independent of change in the refractive index (RI) of a buffer solution (BS) which makes it capable of measuring low-concentration and/or low-molecular-weight compounds.

A capillary electrophoresis chip for the analysis of print and film photographic developing agents in commercial processing solutions using indirect fluorescence detection.

PubMed

Sirichai, S; de Mello, A J

2001-01-01

The separation and detection of both print and film developing agents (CD-3 and CD-4) in photographic processing solutions using chip-based capillary electrophoresis is presented. For simultaneous detection of both analytes under identical experimental conditions a buffer pH of 11.9 is used to partially ionise the analytes. Detection is made possible by indirect fluorescence, where the ions of the analytes displace the anionic fluorescing buffer ion to create negative peaks. Under optimal conditions, both analytes can be analyzed within 30 s. The limits of detection for CD-3 and CD-4 are 0.17 mM and 0.39 mM, respectively. The applicability of the method for the analysis of seasoned photographic processing developer solutions is also examined.

Application of solution-processed V2O5 in inverted polymer solar cells based on fluorine-doped tin oxide substrate.

PubMed

Wu, Jian; Zhang, Yupeng; He, Yeyuan; Liu, Chunyu; Guolt, Wenbin; Ruan, Shengping

2014-06-01

We used a hydrothermal method to synthesis the solution-processed V2O5 as anode buffer layer, which applied on inverted polymer solar cells based on FTO substrate. The structure of the device is glass/FTO/TiO2/P3HT:PCBM/V2O5/Ag. We discussed the dependence of device performance on the concentrations of V2O5 solution. It is found that when the concentration of V2O5 is 300 microg/ml, the power conversion efficiency (PCE of 2.38%) is the highest, which is much higher than that of the device without anode buffer layer (PCE of only 0.87%). Moreover, it can significantly reduce the energy consumption and make it more cost-effective.

Viability of Listeria monocytogenes on uncured turkey breast commercially-prepared with and without buffered vinegar during extended storage at 4 degrees and 10 degrees C

USDA-ARS?s Scientific Manuscript database

We determined the viability of Listeria monocytogenes on uncured turkey breast containing buffered vinegar (BV) and surface treated with a stabilized solution of sodium chlorite in vinegar (VSC). Commercially-produced, uncured, deli-style turkey breast was formulated with BV (0.0, 2.0, 2.5, or 3.0%)...

Mapping tradeoffs in values at risk at the interface between wilderness and non-wilderness lands

Treesearch

Alan Watson; Roian Matt; Tim Waters; Kari Gunderson; Steve Carver; Brett Davis

2009-01-01

On the Flathead Indian Reservation in Montana, U.S., the Mission Mountains Tribal Wilderness is bordered by a buffer zone. To successfully improve forest health within that buffer zone and restore fire in the wilderness, the managing agency and the public need to work together to find solutions to increasingly threatening fuel buildups. A combination of qualitative,...

Mechanisms of buffer therapy resistance.

PubMed

Bailey, Kate M; Wojtkowiak, Jonathan W; Cornnell, Heather H; Ribeiro, Maria C; Balagurunathan, Yoganand; Hashim, Arig Ibrahim; Gillies, Robert J

2014-04-01

Many studies have shown that the acidity of solid tumors contributes to local invasion and metastasis. Oral pH buffers can specifically neutralize the acidic pH of tumors and reduce the incidence of local invasion and metastatic formation in multiple murine models. However, this effect is not universal as we have previously observed that metastasis is not inhibited by buffers in some tumor models, regardless of buffer used. B16-F10 (murine melanoma), LL/2 (murine lung) and HCT116 (human colon) tumors are resistant to treatment with lysine buffer therapy, whereas metastasis is potently inhibited by lysine buffers in MDA-MB-231 (human breast) and PC3M (human prostate) tumors. In the current work, we confirmed that sensitive cells utilized a pH-dependent mechanism for successful metastasis supported by a highly glycolytic phenotype that acidifies the local tumor microenvironment resulting in morphological changes. In contrast, buffer-resistant cell lines exhibited a pH-independent metastatic mechanism involving constitutive secretion of matrix degrading proteases without elevated glycolysis. These results have identified two distinct mechanisms of experimental metastasis, one of which is pH-dependent (buffer therapy sensitive cells) and one which is pH-independent (buffer therapy resistant cells). Further characterization of these models has potential for therapeutic benefit. Copyright © 2014 Neoplasia Press, Inc. Published by Elsevier Inc. All rights reserved.

Mechanisms of buffer therapy resistance

PubMed Central

Bailey, Kate M.; Wojtkowiak, Jonathan W.; Cornnell, Heather H.; Ribeiro, Maria C.; Balagurunathan, Yoganand; Hashim, Arig Ibrahim; Gillies, Robert J.

2014-01-01

Many studies have shown that the acidity of solid tumors contributes to local invasion and metastasis. Oral pH buffers can specifically neutralize the acidic pH of tumors and reduce the incidence of local invasion and metastatic formation in multiple murine models. However, this effect is not universal as we have previously observed that metastasis is not inhibited by buffers in some tumor models, regardless of buffer used. B16-F10 (murine melanoma), LL/2 (murine lung) and HCT116 (human colon) tumors are resistant to treatment with lysine buffer therapy, whereas metastasis is potently inhibited by lysine buffers in MDA-MB-231 (human breast) and PC3M (human prostate) tumors. In the current work, we confirmed that sensitive cells utilized a pH-dependent mechanism for successful metastasis supported by a highly glycolytic phenotype that acidifies the local tumor microenvironment resulting in morphological changes. In contrast, buffer-resistant cell lines exhibited a pH-independent metastatic mechanism involving constitutive secretion of matrix degrading proteases without elevated glycolysis. These results have identified two distinct mechanisms of experimental metastasis, one of which is pH-dependent (buffer therapy sensitive cells) and one which is pH-independent (buffer therapy resistant cells). Further characterization of these models has potential for therapeutic benefit. PMID:24862761

Formation of monofunctional cisplatin-DNA adducts in carbonate buffer.

PubMed

Binter, Alexandra; Goodisman, Jerry; Dabrowiak, James C

2006-07-01

Carbonate in its various forms is an important component in blood and the cytosol. Since, under conditions that simulate therapy, carbonate reacts with cisplatin to form carbonato complexes, one of which is taken up and/or modified by the cell [C.R. Centerwall, J. Goodisman, D.J. Kerwood, J. Am. Chem. Soc., 127 (2005) 12768-12769], cisplatin-carbonato complexes may be important in the mechanism of action of cisplatin. In this report we study the binding of cisplatin to pBR322 DNA in two different buffers, using gel electrophoresis. In 23.8mM HEPES, N-(2-hydroxyethyl)-piperazine-N'-2-ethanesulfonic acid, 5mM NaCl, pH 7.4 buffer, cisplatin produces aquated species, which react with DNA to unwind supercoiled Form I DNA, increasing its mobility, and reducing the binding of ethidium to DNA. This behavior is consistent with the formation of the well-known intrastrand crosslink on DNA. In 23.8mM carbonate buffer, 5mM NaCl, pH 7.4, cisplatin forms carbonato species that produce DNA-adducts which do not significantly change supercoiling but enhance binding of ethidium to DNA. This behavior is consistent with the formation of a monofunctional cisplatin adduct on DNA. These results show that aquated cisplatin and carbonato complexes of cisplatin produce different types of lesions on DNA and they underscore the importance of carrying out binding studies with cisplatin and DNA using conditions that approximate those found in the cell.

Accurate chemical master equation solution using multi-finite buffers

DOE PAGES

Cao, Youfang; Terebus, Anna; Liang, Jie

2016-06-29

Here, the discrete chemical master equation (dCME) provides a fundamental framework for studying stochasticity in mesoscopic networks. Because of the multiscale nature of many networks where reaction rates have a large disparity, directly solving dCMEs is intractable due to the exploding size of the state space. It is important to truncate the state space effectively with quantified errors, so accurate solutions can be computed. It is also important to know if all major probabilistic peaks have been computed. Here we introduce the accurate CME (ACME) algorithm for obtaining direct solutions to dCMEs. With multifinite buffers for reducing the state spacemore » by $O(n!)$, exact steady-state and time-evolving network probability landscapes can be computed. We further describe a theoretical framework of aggregating microstates into a smaller number of macrostates by decomposing a network into independent aggregated birth and death processes and give an a priori method for rapidly determining steady-state truncation errors. The maximal sizes of the finite buffers for a given error tolerance can also be precomputed without costly trial solutions of dCMEs. We show exactly computed probability landscapes of three multiscale networks, namely, a 6-node toggle switch, 11-node phage-lambda epigenetic circuit, and 16-node MAPK cascade network, the latter two with no known solutions. We also show how probabilities of rare events can be computed from first-passage times, another class of unsolved problems challenging for simulation-based techniques due to large separations in time scales. Overall, the ACME method enables accurate and efficient solutions of the dCME for a large class of networks.« less

Pre-formulation and chemical stability studies of penethamate, a benzylpenicillin ester prodrug, in aqueous vehicles.

PubMed

Jain, Rohit; Wu, Zimei; Bork, Olaf; Tucker, Ian G

2012-01-01

Penethamate (PNT) is a diethylaminoethyl ester prodrug of benzylpenicillin used to treat bovine mastitis via the intramuscular route. Because of its instability, PNT products must be reconstituted before administration and the reconstituted injection has a short shelf life (7 days at 2-8°C). The purpose of this paper was to investigate whether the stability of PNT can be improved in order to achieve a chemically stable ready-to-use aqueous-based PNT formulation or at least to extend the shelf life of the reconstituted suspension. A chemical stability study of PNT in aqueous-based solutions as a function of pH, buffer strength, solvent mixtures and temperature, supported by studies of its solubility in mixed solvents, allowed predictions of the shelf life of PNT solution and suspension formulations. PNT degraded in aqueous solutions by several pathways over the pH range 2.0-9.3 with a V-shaped pH-rate profile and a minimum pH of around 4.5. The stability of PNT solutions in mixed solvents was greater than in aqueous solutions. For example, in propylene glycol:citrate buffer (60:40, v/v, pH 4.5), the half-life of PNT was 4.3 days compared with 1.8 days in aqueous buffer. However, solubility of PNT in the mixed solvent was higher than that in aqueous solution and this had an adverse effect on the stability of suspensions. By judicious choosing of pH and mixed solvent, it is possible to achieve a storage life of a PNT suspension of 5.5 months at 5°C, not sufficient for a ready-to-use product but a dramatic improvement in the storage life of the reconstituted product.

Accurate chemical master equation solution using multi-finite buffers

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

Cao, Youfang; Terebus, Anna; Liang, Jie

Here, the discrete chemical master equation (dCME) provides a fundamental framework for studying stochasticity in mesoscopic networks. Because of the multiscale nature of many networks where reaction rates have a large disparity, directly solving dCMEs is intractable due to the exploding size of the state space. It is important to truncate the state space effectively with quantified errors, so accurate solutions can be computed. It is also important to know if all major probabilistic peaks have been computed. Here we introduce the accurate CME (ACME) algorithm for obtaining direct solutions to dCMEs. With multifinite buffers for reducing the state spacemore » by $O(n!)$, exact steady-state and time-evolving network probability landscapes can be computed. We further describe a theoretical framework of aggregating microstates into a smaller number of macrostates by decomposing a network into independent aggregated birth and death processes and give an a priori method for rapidly determining steady-state truncation errors. The maximal sizes of the finite buffers for a given error tolerance can also be precomputed without costly trial solutions of dCMEs. We show exactly computed probability landscapes of three multiscale networks, namely, a 6-node toggle switch, 11-node phage-lambda epigenetic circuit, and 16-node MAPK cascade network, the latter two with no known solutions. We also show how probabilities of rare events can be computed from first-passage times, another class of unsolved problems challenging for simulation-based techniques due to large separations in time scales. Overall, the ACME method enables accurate and efficient solutions of the dCME for a large class of networks.« less

Kinetics of apatite formation on a calcium-silicate cement for root-end filling during ageing in physiological-like phosphate solutions.

PubMed

Gandolfi, Maria Giovanna; Taddei, Paola; Tinti, Anna; De Stefano Dorigo, Elettra; Rossi, Piermaria Luigi; Prati, Carlo

2010-12-01

The bioactivity of calcium silicate mineral trioxide aggregate (MTA) cements has been attributed to their ability to produce apatite in presence of phosphate-containing fluids. This study evaluated surface morphology and chemical transformations of an experimental accelerated calcium-silicate cement as a function of soaking time in different phosphate-containing solutions. Cement discs were immersed in Dulbecco's phosphate-buffered saline (DPBS) or Hank's balanced salt solution (HBSS) for different times (1-180 days) and analysed by scanning electron microscopy connected with an energy dispersive X-ray analysis (SEM-EDX) and micro-Raman spectroscopy. SEM-EDX revealed Ca and P peaks after 14 days in DPBS. A thin Ca- and P-rich crystalline coating layer was detected after 60 days. A thicker multilayered coating was observed after 180 days. Micro-Raman disclosed the 965-cm(-1) phosphate band at 7 days only on samples stored in DPBS and later the 590- and 435-cm(-1) phosphate bands. After 60-180 days, a layer approximately 200-900 μm thick formed displaying the bands of carbonated apatite (at 1,077, 965, 590, 435 cm(-1)) and calcite (at 1,088, 713, 280 cm(-1)). On HBSS-soaked, only calcite bands were observed until 90 days, and just after 180 days, a thin apatite-calcite layer appeared. Micro-Raman and SEM-EDX demonstrated the mineralization induction capacity of calcium-silicate cements (MTAs and Portland cements) with the formation of apatite after 7 days in DPBS. Longer time is necessary to observe bioactivity when cements are immersed in HBSS.

AVIRIS onboard data handling and control

NASA Technical Reports Server (NTRS)

Steinkraus, Ronald E.; Hickok, Roger W.

1987-01-01

The timing and flow of detector and ancillary data for the Airborne Visible/Infrared imaging spectrometer (AVIRIS) are controlled within the instrument by its digital electronics assembly. In addition to providing detector and signal chain timing, the digital electronics receives, formats, and rate-buffers digitized science data; collects and formats ancillary (calibration and engineering) data; and merges both into a single tape record. Overall AVIRIS data handling is effected by a combination of dedicated digital electronics to control instrument timing, image data flow, and data rate buffering and a microcomputer programmed to handle real-time control of instrument mechanisms and the coordinated preparation of ancillary data.

A pilot study of the validation of percutaneous testing in cats.

PubMed

Rossi, Michael A; Messinger, Linda; Olivry, Thierry; Hoontrakoon, Raweewan

2013-10-01

Intradermal testing is useful for the identification of environmental allergens to which cats could be hypersensitive; intradermal test reactions are often subtle and difficult to interpret in cats. Percutaneous testing is the standard technique for the detection of significant environmental allergens in people, but it has not yet been evaluated in cats with hypersensitivity dermatitis. The purpose of this study was to evaluate and compare the skin test responses of healthy cats to percutaneous application and intradermal injections of control solutions. Ten clinically healthy cats were studied. Percutaneous applications of 0.0275 and 0.1 mg/mL aqueous histamine, 6 mg/mL glycerinated histamine, 0.9% buffered saline and 50% glycerosaline solution were performed using Greer Pick (Greer Laboratories, Lenoir, NC, USA) and Duotip-Test II (Lincoln Diagnostics, Decatur, IL, USA) percutaneous applicators. Reactions were compared with intradermal injections of 0.0275 mg/mL aqueous histamine and 0.9% buffered saline as controls. Positive responses to histamine solutions were significantly greater with the Greer Pick than with the Duotip-Test II. There were no significant differences between the histamine reactions using the Greer Pick applicator and the intradermal injections. Percutaneous reactions to histamine were more well demarcated and easier to read than intradermal injection reactions. Reactions to the saline controls were not noted. Percutaneous application of 6 mg/mL glycerinated histamine solution, 50% glycerosaline solution and 0.9% buffered saline produced similar positive and negative control wheals. These observations warrant further studies of percutaneous allergen testing in cats with hypersensitivity dermatitis. © 2013 ESVD and ACVD.

Dual-Analyte Fluorescent Sensor Based on [5]Helicene Derivative with Super Large Stokes Shift for the Selective Determinations of Cu2+ or Zn2+ in Buffer Solutions and Its Application in a Living Cell.

PubMed

Sakunkaewkasem, Siwakorn; Petdum, Anuwut; Panchan, Waraporn; Sirirak, Jitnapa; Charoenpanich, Adisri; Sooksimuang, Thanasat; Wanichacheva, Nantanit

2018-05-10

A new fluorescent sensor, M201-DPA, based on [5]helicene derivative was utilized as dual-analyte sensor for determination of Cu 2+ or Zn 2+ in different media and different emission wavelengths. The sensor could provide selective and bifunctional determination of Cu 2+ in HEPES buffer containing Triton-X100 and Zn 2+ in Tris buffer/methanol without interference from each other and other ions. In HEPES buffer, M201-DPA demonstrated the selective ON-OFF fluorescence quenching at 524 nm toward Cu 2+ . On the other hand, in Tris buffer/methanol, M201-DPA showed the selective OFF-ON fluorescence enhancement upon the addition of Zn 2+ , which was specified by the hypsochromic shift at 448 nm. Additionally, M201-DPA showed extremely large Stokes shifts up to ∼150 nm. By controlling the concentration of Zn 2+ and Cu 2+ in a living cell, the imaging of a HepG2 cellular system was performed, in which the fluorescence of M201-DPA in the blue channel was decreased upon addition of Cu 2+ and was enhanced in UV channel upon addition of Zn 2+ . The detection limits of M201-DPA for Cu 2+ and Zn 2+ in buffer solutions were 5.6 and 3.8 ppb, respectively. Importantly, the Cu 2+ and Zn 2+ detection limits of the developed sensors were significantly lower than permitted Cu 2+ and Zn 2+ concentrations in drinking water as established by the U.S. EPA and WHO.

Interaction of HEPES buffer with glass-ceramic scaffold: Can HEPES replace TRIS in SBF?

PubMed

Rohanová, Dana; Horkavcová, Diana; Paidere, Laine; Boccaccini, Aldo Roberto; Bozděchová, Pavlína; Bezdička, Petr

2018-01-01

An international standard (ISO: 23317:2014) exists for the in vitro testing of inorganic biomaterials in simulated body fluid (SBF). This standard uses TRIS buffer to maintain neutral pH in SBF, but in our previous paper, we showed that the interaction of a tested glass-ceramic material with TRIS can produce false-positive results. In this study, we evaluated whether the HEPES buffer, which also belongs to the group of Good´s buffers, would be more suitable for SBF. We compared its suitability in two media: SBF with HEPES and demineralized water with HEPES. The tested scaffold (45S5 bioactive glass-based) was exposed to the media under a static-dynamic arrangement (solutions were replaced on a daily basis) for 15 days. Leachate samples were collected daily for the analysis of Ca 2+ ions and Si (AAS), (PO 4 ) 3- ions (UV-VIS), and to measure pH. The glass-ceramic scaffold was analyzed by SEM/EDS, XRD, and WD-XRF before and after 0.3, 1, 3, 7, 11, and 15 days of exposure. Our results confirmed the rapid selective dissolution of the glass-ceramic crystalline phase (Combeite) containing Ca 2+ ions due to the presence of HEPES, hydroxyapatite supersaturation being reached within 24 h in both solutions. These new results suggest that, like TRIS, HEPES buffer is not suitable for the in vitro testing of highly reactive inorganic biomaterials (glass, glass-ceramics). The ISO standard for such tests requires revision, but HEPES is not a viable alternative to TRIS buffer. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 143-152, 2018. © 2016 Wiley Periodicals, Inc.

Changes in composition and enamel demineralization inhibition activities of gallic acid at different pH values.

PubMed

Zhang, Jingyang; Huang, Xuelian; Huang, Shengbin; Deng, Meng; Xie, Xincheng; Liu, Mingdong; Liu, Hongling; Zhou, Xuedong; Li, Jiyao; Ten Cate, Jacob Martien

2015-01-01

Gallic acid (GA) has been shown to inhibit demineralization and enhance remineralization of enamel; however, GA solution is highly acidic. This study was to investigate the stability of GA solutions at various pH and to examine the resultant effects on enamel demineralization. The stability of GA in H2O or in phosphate buffer at pH 5.5, pH 7.0 and pH 10.0 was evaluated qualitatively by ultraviolet absorption spectra and quantified by high performance liquid chromatography with diode array detection (HPLC-DAD). Then, bovine enamel blocks were subjected to a pH-cycling regime of 12 cycles. Each cycle included 5 min applications with one of the following treatments: 1 g/L NaF (positive control), 4 g/L GA in H2O or buffered at pH 5.5, pH 7.0 and pH 10.0 and buffers without GA at the same pH (negative control), followed by a 60 min application with pH 5.0 acidic buffers and a 5 min application with neutral buffers. The acidic buffers were analysed for dissolved calcium. GA was stable in pure water and acidic condition, but was unstable in neutral and alkaline conditions, in which ultraviolet spectra changed and HPLC-DAD analysis revealed that most of the GA was degraded. All the GA groups significantly inhibited demineralization (p < 0.05) and there was no significant difference of the inhibition efficacy among different GA groups (p > 0.05). GA could inhibit enamel demineralization and the inhibition effect is not influenced by pH. GA could be a useful source as an anti-cariogenic agent for broad practical application.

Efficacy of a Buffered 4% Lidocaine Formulation for Incision and Drainage: A Prospective, Randomized, Double-blind Study.

PubMed

Harreld, Taryn Kratz; Fowler, Sara; Drum, Melissa; Reader, Al; Nusstein, John; Beck, Mike

2015-10-01

Incision and drainage of symptomatic emergency patients with facial swelling is painful even after local anesthetics are administered. The purpose of this prospective, randomized, double-blind study was to compare the pain of infiltration and the pain of an incision and drainage procedure of a buffered versus a nonbuffered 4% lidocaine formulation in symptomatic emergency patients presenting with a diagnosis of pulpal necrosis, associated periapical area, and an acute clinical swelling. Eighty-eight emergency patients were randomly divided into 2 groups to receive 2 intraoral infiltration injections (mesial and distal to the swelling) of either 4% lidocaine with 1:100,000 epinephrine buffered with 0.18 mL 8.4% sodium bicarbonate using the Onpharma (Los Gatos, CA) buffering system or 4% lidocaine with 1:100,000 epinephrine. Subjects rated the pain of needle insertion, needle placement, and solution deposition for each injection using a 170-mm visual analog scale. An incision and drainage procedure was performed, and subjects rated the pain of incision, drainage, and dissection on a 170-mm visual analog scale. No significant differences between the buffered and nonbuffered 4% lidocaine formulations were found for needle insertion, placement, and solution deposition of the infiltration injections or for the treatment phases of incision, drainage, and dissection. Buffering a 4% lidocaine formulation did not significantly decrease the pain of infiltrations or significantly decrease the pain of the incision and drainage procedure when compared with a nonbuffered 4% lidocaine formulation in symptomatic patients with a diagnosis of pulpal necrosis and associated acute swelling. Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

TES buffer-induced phase separation of aqueous solutions of several water-miscible organic solvents at 298.15 K: phase diagrams and molecular dynamic simulations.

PubMed

Taha, Mohamed; Lee, Ming-Jer

2013-06-28

Water and the organic solvents tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, 1-propanol, 2-propanol, tert-butanol, acetonitrile, or acetone are completely miscible in all proportions at room temperature. Here, we present new buffering-out phase separation systems that the above mentioned organic aqueous solutions can be induced to form two liquid phases in the presence of a biological buffer 2-[[1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl]amino]ethanesulfonic acid (TES). The lower liquid phase is rich in water and buffer, and the upper phase is organic rich. This observation has both practical and mechanistic interests. The phase diagrams of these systems were constructed by experimental measurements at ambient conditions. Molecular dynamic (MD) simulations were performed for TES + water + THF system to understand the interactions between TES, water, and organic solvent at molecular level. Several composition-sets for this system, beyond and inside the liquid-liquid phase-splitting region, have been simulated. Interestingly, the MD simulation for compositions inside the phase separation region showed that THF molecules are forced out from the water network to start forming a new liquid phase. The hydrogen-bonds, hydrogen-bonds lifetimes, hydrogen-bond energies, radial distribution functions, coordination numbers, the electrostatic interactions, and the van der Waals interactions between the different pairs have been calculated. Additionally, MD simulations for TES + water + tert-butanol∕acetonitrile∕acetone phase separation systems were simulated. The results from MD simulations provide an explanation for the buffering-out phenomena observed in [TES + water + organic solvent] systems by a mechanism controlled by the competitive interactions of the buffer and the organic solvent with water. The molecular mechanism reported here is helpful for designing new benign separation materials.

Buffer-dependent regulation of aquaporin-1 expression and function in human peritoneal mesothelial cells.

PubMed

Zhai, Yihui; Bloch, Jacek; Hömme, Meike; Schaefer, Julia; Hackert, Thilo; Philippin, Bärbel; Schwenger, Vedat; Schaefer, Franz; Schmitt, Claus P

2012-07-01

Biocompatible peritoneal dialysis fluids (PDF) are buffered with lactate and/or bicarbonate. We hypothesized that the reduced toxicity of the biocompatible solutions might unmask specific effects of the buffer type on mesothelial cell functions. Human peritoneal mesothelial cells (HPMC) were incubated with bicarbonate (B-)PDF or lactate-buffered (L-)PDF followed by messenger RNA (mRNA) and protein analysis. Gene silencing was achieved using small interfering RNA (siRNA), functional studies using Transwell culture systems, and monolayer wound-healing assays. Incubation with B-PDF increased HPMC migration in the Transwell and monolayer wound-healing assay to 245 ± 99 and 137 ± 11% compared with L-PDF. Gene silencing showed this effect to be entirely dependent on the expression of aquaporin-1 (AQP-1) and independent of AQP-3. Exposure of HPMC to B-PDF increased AQP-1 mRNA and protein abundance to 209  ± 80 and 197  ±  60% of medium control; the effect was pH dependent. L-PDF reduced AQP-1 mRNA. Addition of bicarbonate to L-PDF increased AQP-1 abundance by threefold; mRNA half-life remained unchanged. Immunocytochemistry confirmed opposite changes of AQP-1 cell-membrane abundance with B-PDF and L-PDF. Peritoneal mesothelial AQP-1 abundance and migration capacity is regulated by pH and buffer agents used in PD solutions. In vivo studies are required to delineate the impact with respect to long-term peritoneal membrane integrity and function.

Fully packed capillary electrochromatographic microchip with self-assembly colloidal silica beads.

PubMed

Park, Jongman; Lee, Dami; Kim, Won; Horiike, Shigeyoshi; Nishimoto, Takahiro; Lee, Se Hwan; Ahn, Chong H

2007-04-15

A fully packed capillary electrochromatographic (CEC) microchip showing improved solution and chip handling was developed. Microchannels for the CEC microchip were patterned on a cyclic olefin copolymer substrate by injection molding and packed fully with 0.8-microm monodisperse colloidal silica beads utilizing a self-assembly packing technique. The silica packed chip substrate was covered and thermally press-bonded. After fabrication, the chip was filled with buffer solution by self-priming capillary action. The self-assembly packing at each channel served as a built-in nanofilter allowing quick loading of samples and running buffer solution without filtration. Because of a large surface area-to-volume ratio of the silica packing, reproducible control of electroosmotic flow was possible without leveling of the solutions in the reservoirs resulting 1.3% rsd in migration rate. The capillary electrophoretic separation characteristics of the chip were studied using fluorescein isothiocyanate (FITC)-derivatized amino acids as probe molecules. A mixture of FITC and four FITC-derivatized amino acids was successfully separated with 2-mm separation channel length.

Ocular toxicity of beta-blockers and benzalkonium chloride in pigmented rabbits: electrophysiological and morphological studies.

PubMed

Chou, A; Hori, S; Takase, M

1985-01-01

Subconjunctival injection of 0.2 ml of the following solutions was carried out once a day for two weeks in the albino and pigmented rabbit: commercial 0.5% timolol or 1% befunolol ophthalmic solutions, both containing benzalkonium chloride, and also these drug solutions containing no preservative, ophthalmic base solutions containing benzalkonium chloride, physiological saline solution or phosphate buffer solution. One week after daily injections of the commercial drug solutions or base solutions with benzalkonium chloride, the electroretinogram (ERG) showed a marked reduction in the a- and b-wave amplitudes in the pigmented rabbit, but the ERG changes were slight in the albino rabbit. After two weeks of injections, histological studies of the pigmented rabbit eyes revealed retinal detachment, visual cell loss and atrophy of the retinal pigment epithelium and choroid; the changes in the albino rabbit eyes were minimal. Injections of the beta-blockers containing no benzalkonium resulted in no significant changes in the ERG or in the tissue structures of all rabbits. Injections of only physiological saline or phosphate buffer had no deleterious effects. Therefore, the ocular toxicity of the beta-blockers was thought to be minor and the toxic effects seen in this study were thought to be due to benzalkonium chloride, which possibly accumulates in the ocular pigments.

Chemical solution deposition method of fabricating highly aligned MgO templates

DOEpatents

Paranthaman, Mariappan Parans [Knoxville, TN; Sathyamurthy, Srivatsan [Knoxville, TN; Aytug, Tolga [Knoxville, TN; Arendt, Paul N [Los Alamos, NM; Stan, Liliana [Los Alamos, NM; Foltyn, Stephen R [Los Alamos, NM

2012-01-03

A superconducting article includes a substrate having an untextured metal surface; an untextured barrier layer of La.sub.2Zr.sub.2O.sub.7 or Gd.sub.2Zr.sub.2O.sub.7 supported by and in contact with the surface of the substrate; a biaxially textured buffer layer supported by the untextured barrier layer; and a biaxially textured superconducting layer supported by the biaxially textured buffer layer. Moreover, a method of forming a buffer layer on a metal substrate includes the steps of: providing a substrate having an untextured metal surface; coating the surface of the substrate with a barrier layer precursor; converting the precursor to an untextured barrier layer; and depositing a biaxially textured buffer layer above and supported by the untextured barrier layer.

Effects of solutions treated with oxygen radicals in neutral pH region on inactivation of microorganism

NASA Astrophysics Data System (ADS)

Kobayashi, Tsuyoshi; Hashizume, Hiroshi; Ohta, Takayuki; Ishikawa, Kenji; Hori, Masaru; Ito, Masafumi

2015-09-01

The inactivation of microorganisms using nonequilbrium atmospheric pressure plasmas has been attracted much attention due to the low temperature processing and high speed treatment. In this study, we have inactivated E. coli suspended in solutions with neutral pH using an atmospheric-pressure oxygen radical source which can selectively supply electrically neutral oxygen radicals. E. coli cells were suspended with deionized distilled water (DDW) (pH = 6.8) or phosphate buffered saline (PBS) (pH = 7.4) or Citrate-Na buffer (pH = 6.5). The treated samples were diluted and spread on nutrient agar (Nutrient Broth). They were cultured at 37° C. The inactivation effects of oxygen radicals on those cells in solutions were evaluated by colony-counting method. O2 diluted by Ar gas were employed as a working gas for the radical source. The total gas flow rate and the gas mixture ratio of O2/(Ar + O2) were set at 5 slm and 0.6%, respectively. The distance between the radical exit and the suspension surface were set at 10 mm. As a result, the D values for DDW(pH = 6.8), PBS(pH = 7.4) and Citrate-Na buffer(pH = 6.5) were estimated to be 1.4 min, 0.9 min and 16.8 min respectively. The inactivation rates in DDW, PBS were significantly different from that in Citrate-Na buffer. This work was partly supported by JSPS KAKENHI Grant Number 26286072 and project for promoting Research Center in Meijo University.

Growth And Characterization Of LPE CdHgTe/CdZnTe/CdZnTe Structure

NASA Astrophysics Data System (ADS)

Pelliciari, B.; Chamonal, J. P.; Destefanis, G. L.; Dicioccio, L.

1988-05-01

The liquid phase epitaxial technique is used to grow Hgl_x Cdx Te (x = .23) from a Te - rich solution onto a Cdl_y ZnyTe (y = .04) buffer layer grown from a Te-rich solution onto a Cdi_yZnyTe bulk substrate in an open tube multibin horizontal slider apparatus.Growth conditions and physical characterizations of both the buffer layer and the CdHgTe layer are given ; electrical properties of the CdHgTe layer are also presen-ted. PV detectors were successfully obtained on such a structure using an ion-implanted technology and their characteristics at 77 K for a 10.1 ,um cut-off wavelength are given.

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.

Photocurrent enhancement of n-type Cu2O electrodes achieved by controlling dendritic branching growth.

PubMed

McShane, Colleen M; Choi, Kyoung-Shin

2009-02-25

Cu(2)O electrodes composed of dendritic crystals were produced electrochemically using a slightly acidic medium (pH 4.9) containing acetate buffer. The buffer played a key role for stabilizing dendritic branching growth as a pH drop during the synthesis prevents formation of morphologically unstable branches and promotes faceted growth. Dendritic branching growth enabled facile coverage of the substrate with Cu(2)O while avoiding growth of a thicker Cu(2)O layer and increasing surface areas. The resulting electrodes showed n-type behavior by generating anodic photocurrent without applying an external bias (zero-bias photocurrent under short-circuit condition) in an Ar-purged 0.02 M K(2)SO(4) solution. The zero-bias photocurrent of crystalline dendritic electrodes was significantly higher than that of the electrodes containing micrometer-size faceted crystals deposited without buffer. In order to enhance photocurrent further a strategy of improving charge-transport properties by increasing dendritic crystal domain size was investigated. Systematic changes in nucleation density and size of the dendritic Cu(2)O crystals were achieved by altering the deposition potential, Cu(2+) concentration, and acetate concentration. Increasing dendritic crystal size consistently resulted in the improvement of photocurrent regardless of the method used to regulate crystal size. The electrode composed of dendritic crystals with the lateral dimension of ca. 12000 microm(2) showed more than 20 times higher zero-bias photocurrent than that composed of dendritic crystals with the lateral dimension of ca. 100 microm(2). The n-type nature of the Cu(2)O electrodes prepared by this study were confirmed by linear sweep voltammetry with chopped light and capacitance measurements (i.e., Mott-Schottky plots). The flatband potential in a 0.2 M K(2)SO(4) solution (pH 6) was estimated to be -0.78 vs Ag/AgCl reference electrode. The IPCE measured without applying an external bias was approximately 1% for the visible region. With appropriate doping studies and surface treatment to improve charge transport and interfacial kinetics more efficient n-type Cu(2)O electrodes will be prepared for use in various photoelectrochemical and photovoltaic devices.

Matching phosphate and maleate buffer systems for dissolution of weak acids: Equivalence in terms of buffer capacity of bulk solution or surface pH?

PubMed

Cristofoletti, Rodrigo; Dressman, Jennifer B

2016-06-01

The development of in vitro dissolution tests able to anticipate the in vivo fate of drug products has challenged pharmaceutical scientists over time, especially in the case of ionizable compounds. In the seminal model proposed by Mooney et al. thirty-five years ago, the pH at the solid-liquid interface (pH0) was identified as a key parameter in predicting dissolution rate. In the current work it is demonstrated that the in vitro dissolution of the weak acid ibuprofen in maleate and phosphate buffer systems is a function of the pH0, which in turn is affected by properties of the drug and the medium. The reported pH0 for ibuprofen dissolution in bicarbonate buffer, the predominant buffer species in the human small intestine under fasting conditions, can be achieved by reducing the phosphate buffer concentration to 5.0mM or the maleate buffer concentration to 2.2mM. Using this approach to identify the appropriate buffer/buffer capacity combination for in vitro experiments in FaSSIF-type media, it would be possible to increase the physiological relevance of this important biopharmaceutics tool. However, the necessity of monitoring and adjusting the bulk pH during the experiments carried out in 5.0mM phosphate or 2.2mM maleate buffers must also be taken into consideration. Copyright © 2016 Elsevier B.V. All rights reserved.

Analysis of hydroxamate siderophores in soil solution using liquid chromatography with mass spectrometry and tandem mass spectrometry with on-line sample preconcentration.

PubMed

Olofsson, Madelen A; Bylund, Dan

2015-10-01

A liquid chromatography with electrospray ionization mass spectrometry method was developed to quantitatively and qualitatively analyze 13 hydroxamate siderophores (ferrichrome, ferrirubin, ferrirhodin, ferrichrysin, ferricrocin, ferrioxamine B, D1 , E and G, neocoprogen I and II, coprogen and triacetylfusarinine C). Samples were preconcentrated on-line by a switch-valve setup prior to analyte separation on a Kinetex C18 column. Gradient elution was performed using a mixture of an ammonium formate buffer and acetonitrile. Total analysis time including column conditioning was 20.5 min. Analytes were fragmented by applying collision-induced dissociation, enabling structural identification by tandem mass spectrometry. Limit of detection values for the selected ion monitoring method ranged from 71 pM to 1.5 nM with corresponding values of two to nine times higher for the multiple reaction monitoring method. The liquid chromatography with mass spectrometry method resulted in a robust and sensitive quantification of hydroxamate siderophores as indicated by retention time stability, linearity, sensitivity, precision and recovery. The analytical error of the methods, assessed through random-order, duplicate analysis of soil samples extracted with a mixture of 10 mM phosphate buffer and methanol, appears negligible in relation to between-sample variations. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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...

Double-Blind Comparison of Phlebitis Produced by Cephalothin Infusions with Buffered and Unbuffered Diluents

PubMed Central

Carrizosa, Jaime; Levison, Matthew E.; Kaye, Donald

1974-01-01

In a double-blind study with each patient as his own control, a buffered and an unbuffered cephalothin solution was administered to 13 patients in opposite arms for a period of 48 h each. Neither the incidence of phlebitis nor the degree of phlebitis was different with the two diluents, and there was no difference in the time of onset of phlebitis. PMID:4840431

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

Inorganic Substrates and Encapsulation Layers for Transient Electronics

DTIC Science & Technology

2014-07-01

surface oxidation of the nitrides, the measurements were conducted shortly after oxide removal in buffered oxide etchant (BOE) 6:1 (Transene Company Inc...values for the time-dependent dissolution of thermally grown SiO2 (dry oxidation) in buffer solutions (black, pH 7.4; red, pH 8; blue, pH 10...22 5.1.3 Contractor will Identify and Measure Key Performance Characteristics of Candidate Metal Conductive Layers for

Religion as problem, religion as solution: religious buffers of the links between religious/spiritual struggles and well-being/mental health.

PubMed

Abu-Raiya, Hisham; Pargament, Kenneth I; Krause, Neal

2016-05-01

Previous studies have established robust links between religious/spiritual struggles (r/s struggles) and poorer well-being and psychological distress. A critical issue involves identifying the religious factors that buffer this relationship. This is the first study to empirically address this question. Specifically, it examines four religious factors (i.e., religious commitment, life sanctification, religious support, religious hope) as potential buffers of the links between r/s struggle and one indicator of subjective well-being (i.e., happiness) and one indicator of psychological distress (i.e., depressive symptoms). We utilized a cross-sectional design and a nationally representative sample of American adults (N = 2140) dealing with a wide range of major life stressors. We found that the interactions between r/s struggle and all potential moderators were significant in predicting happiness and/or depression. The linkage between r/s struggle and lower levels of happiness was moderated by higher levels of each of the four proposed religious buffers. Religious commitment and life sanctification moderated the ties between r/s struggles and depressive symptoms. The findings underscore the multifaceted character of religion: Paradoxically, religion may be a source of solutions to problems that may be an inherent part of religious life.

Modeling transient heat transfer in nuclear waste repositories.

PubMed

Yang, Shaw-Yang; Yeh, Hund-Der

2009-09-30

The heat of high-level nuclear waste may be generated and released from a canister at final disposal sites. The waste heat may affect the engineering properties of waste canisters, buffers, and backfill material in the emplacement tunnel and the host rock. This study addresses the problem of the heat generated from the waste canister and analyzes the heat distribution between the buffer and the host rock, which is considered as a radial two-layer heat flux problem. A conceptual model is first constructed for the heat conduction in a nuclear waste repository and then mathematical equations are formulated for modeling heat flow distribution at repository sites. The Laplace transforms are employed to develop a solution for the temperature distributions in the buffer and the host rock in the Laplace domain, which is numerically inverted to the time-domain solution using the modified Crump method. The transient temperature distributions for both the single- and multi-borehole cases are simulated in the hypothetical geological repositories of nuclear waste. The results show that the temperature distributions in the thermal field are significantly affected by the decay heat of the waste canister, the thermal properties of the buffer and the host rock, the disposal spacing, and the thickness of the host rock at a nuclear waste repository.

Photovoltaic devices comprising zinc stannate buffer layer and method for making

DOEpatents

Wu, Xuanzhi; Sheldon, Peter; Coutts, Timothy J.

2001-01-01

A photovoltaic device has a buffer layer zinc stannate Zn.sub.2 SnO.sub.4 disposed between the semiconductor junction structure and the transparent conducting oxide (TCO) layer to prevent formation of localized junctions with the TCO through a thin window semiconductor layer, to prevent shunting through etched grain boundaries of semiconductors, and to relieve stresses and improve adhesion between these layers.

The quantitation of buffering action I. A formal & general approach.

PubMed

Schmitt, Bernhard M

2005-03-15

Although "buffering" as a homeostatic mechanism is a universal phenomenon, the quantitation of buffering action remains controversial and problematic. Major shortcomings are: lack of a buffering strength unit for some buffering phenomena, multiple and mutually incommensurable units for others, and lack of a genuine ratio scale for buffering strength. Here, I present a concept of buffering that overcomes these shortcomings. Briefly, when, for instance, some "free" H+ ions are added to a solution (e.g. in the form of strong acid), buffering is said to be present when not all H+ ions remain "free" (i.e., bound to H2O), but some become "bound" (i.e., bound to molecules other than H2O). The greater the number of H+ ions that become "bound" in this process, the greater the buffering action. This number can be expressed in two ways: 1) With respect to the number of total free ions added as "buffering coefficient b", defined in differential form as b = d(bound)/d(total). This measure expresses buffering action from nil to complete by a dimensionless number between 0 and 1, analogous to probabilites. 2) With respect to the complementary number of added ions that remain free as "buffering ratio B", defined as the differential B = d(bound)/d(free). The buffering ratio B provides an absolute ratio scale, where buffering action from nil to perfect corresponds to dimensionless numbers between 0 and infinity, and where equal differences of buffering action result in equal intervals on the scale. Formulated in purely mathematical, axiomatic form, the concept reveals striking overlap with the mathematical concept of probability. However, the concept also allows one to devise simple physical models capable of visualizing buffered systems and their behavior in an exact yet intuitive way. These two measures of buffering action can be generalized easily to any arbitrary quantity that partitions into two compartments or states, and are thus suited to serve as standard units for buffering action. Some exemplary treatments of classical and non-classical buffering phenomena are presented in the accompanying paper.

Analysis of the complex formation of heparin with protamine by light scattering and analytical ultracentrifugation: implications for blood coagulation management.

PubMed

Maurer, Jürgen; Haselbach, Stephanie; Klein, Oliver; Baykut, Doan; Vogel, Vitali; Mäntele, Werner

2011-02-02

Heparin, a linear glycosaminoglycan, is used in different forms in anticoagulation treatment. Protamine, a highly positive charged peptide containing about 32 amino acids, acts as an antagonist for heparin to restore normal blood coagulation. The complex formation of protamine with heparin was analyzed by a combination of analytical ultracentrifugation and light scattering. Titration of heparin with protamine in blood plasma preparations results in a drastic increase of turbidity, indicating the formation of nanoscale particles. A similar increase of turbidity was observed in physiological saline solution with or without human serum albumin (HSA). Particle size analysis by analytical ultracentrifugation revealed a particle radius of approximately 30 nm for unfractionated heparin and of approximately 60 nm for low molecular weight heparin upon complexation with excess protamine, in agreement with atomic force microscopy data. In the absence of HSA, larger and more heterogeneous particles were observed. The particles obtained were found to be stable for hours. The particle formation kinetics was analyzed by light scattering at different scattering angles and was found to be complete within several minutes. The time course of particle formation suggests a condensation reaction, with sigmoidal traces for low heparin concentrations and quasi-first-order reaction for high heparin concentrations. Under all conditions, the final scattering intensity reached after several minutes was found to be proportional to the amount of heparin in the blood plasma or buffer solution, provided that excess protamine was available and no multiple scattering occurred. On the basis of a direct relation between particle concentration and the heparin concentration present before protaminization, a light scattering assay was developed which permits the quantitative analysis of the heparin concentration in blood plasma and which could complement or even replace the activated clotting time test, which is currently the most commonly used method for blood coagulation management.

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.

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.

The stability of water- and fat-soluble vitamin in dentifrices according to pH level and storage type.

PubMed

Park, Jung-Eun; Kim, Ki-Eun; Choi, Yong-Jun; Park, Yong-Duk; Kwon, Ha-Jeong

2016-02-01

The purpose of this study is to evaluate the vitamin stabilities in dentifrices by analyzing various vitamins according to the level and storage temperature. The stabilities of water- and fat-soluble vitamins were investigated in buffer solution at different pH values (4, 7, 8, 10 and 11) for 14 days and in dentifrices at different pH (7 and 10) for 5 months at two temperature conditions (room and refrigeration temperature) by analyzing the remaining amounts using HPLC methods. In the buffer solution, the stability of vitamins B1 , B6 and C was increased as the pH values increased. Vitamins E and K showed poor stability at pH 4, and vitamin B3 showed poor stability at pH 11. In dentifrices, the storage temperature highly influenced vitamin stability, especially vitamins C and E, but the stabilities of vitamins B1 and C according to pH values did not correspond to the buffer solution tests. Vitamin B group was relatively stable in dentifrices, but vitamin C completely disappeared after 5 months. Vitamin K showed the least initial preservation rates. Vitamins were not detected in commercial dentifrices for adults and detected amounts were less than the advertised contents in dentifrices for children. Copyright © 2015 John Wiley & Sons, Ltd.

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.

Caged Naloxone: Synthesis, Characterization, and Stability of 3- O-(4,5-Dimethoxy-2-nitrophenyl)carboxymethyl Naloxone (CNV-NLX).

PubMed

Lewin, Anita H; Fix, Scott E; Zhong, Desong; Mayer, Louise D; Burgess, Jason P; Mascarella, S Wayne; Reddy, P Anantha; Seltzman, Herbert H; Carroll, F Ivy

2018-03-21

The photolabile analogue of the broad-spectrum opioid antagonist naloxone, 3- O-(4,5-dimethoxy-2-nitrophenyl)carboxymethyl naloxone (also referred to as "caged naloxone", 3- O-(α-carboxy-6-nitroveratryl)naloxone, CNV-NLX), has been found to be a valuable biochemical probe. While the synthesis of CNV-NLX is simple, its characterization is complicated by the fact that it is produced as a mixture of α R,5 R,9 R,13 S,14 S and α S,5 R,9 R,13 S,14 S diastereomers. Using long-range and heteronuclear NMR correlations, the 1 H NMR and 13 C NMR resonances of both diastereomers have been fully assigned, confirming the structures. Monitoring of solutions of CNV-NLX in saline buffer, in methanol, and in DMSO has shown CNV-NLX to be stable for over a week under fluorescent laboratory lights at room temperature. Exposure of such solutions to λ 365 nm from a hand-held UV lamp led to the formation of naloxone and CNV-related breakdown products.

Effects of self-aggregation on the hydration of an amphiphilic antidepressant drug in different aqueous media

NASA Astrophysics Data System (ADS)

Taboada, Pablo; Gutiérrez-Pichel, Manuel; Mosquera, Víctor

2004-03-01

Apparent molal volumes and adiabatic compressibilities of aqueous solutions of the amphiphilic antidepressant drug clomipramine hydrochloride have been determined from density and ultrasound velocity measurements in the temperature range 288.15-313.15 K in buffered aqueous solution of pH 3.0 and 5.5. Critical concentrations of aggregation of this drug were obtained from inflections on the plots of the sound velocity against drug concentration. Apparent molal adiabatic compressibilities of the aggregates formed by the drug, calculated by combining the ultrasound velocity and density data, were typical of those for a stacked aggregate. From the temperature dependence of the critical concentration and using the mass action model combined with the Phillips definition of the critical concentration the thermodynamic standard quantities: free Gibbs energy, enthalpy and entropy of aggregate formation were calculated. The critical concentration and energy involved in the aggregation process of this drug have been also evaluated experimentally using isothermal titration calorimetry at 298.15 K. The solvent-drug interactions have been discussed from compressibility and calorimetry data.

Geochemical Modeling of Reactions and Partitioning of Trace Metals and Radionuclides during Titration of Contaminated Acidic Sediments

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

Zhang, Fan; Parker, Jack C.; Luo, Wensui

2008-01-01

Many geochemical reactions that control aqueous metal concentrations are directly affected by solution pH. However, changes in solution pH are strongly buffered by various aqueous phase and solid phase precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior of the soil-solution system is thus critical to predict metal transport under variable pH conditions. This study was undertaken to develop a practical generic geochemical modeling approach to predict aqueous and solid phase concentrations of metals and anions during conditions of acid or base additions. The method of Spalding and Spalding was utilized to model soil buffer capacity and pH-dependent cationmore » exchange capacity by treating aquifer solids as a polyprotic acid. To simulate the dynamic and pH-dependent anion exchange capacity, the aquifer solids were simultaneously treated as a polyprotic base controlled by mineral precipitation/dissolution reactions. An equilibrium reaction model that describes aqueous complexation, precipitation, sorption and soil buffering with pH-dependent ion exchange was developed using HydroGeoChem v5.0 (HGC5). Comparison of model results with experimental titration data of pH, Al, Ca, Mg, Sr, Mn, Ni, Co, and SO{sub 4}{sup 2-} for contaminated sediments indicated close agreement, suggesting that the model could potentially be used to predict the acid-base behavior of the sediment-solution system under variable pH conditions.« less

Thyroglobulin assay in fluids from lymph node fine needle-aspiration washout: influence of pre-analytical conditions.

PubMed

Casson, Florence Boux de; Moal, Valérie; Gauchez, Anne-Sophie; Moineau, Marie-Pierre; Sault, Corinne; Schlageter, Marie-Hélène; Massart, Catherine

2017-04-01

The aim of this study was to evaluate the pre-analytical factors contributing to uncertainty in thyroglobulin measurement in fluids from fine-needle aspiration (FNA) washout of cervical lymph nodes. We studied pre-analytical stability, in different conditions, of 41 samples prepared with concentrated solutions of thyroglobulin (FNA washout or certified standard) diluted in physiological saline solution or buffer containing 6% albumin. In this buffer, over time, no changes in thyroglobulin concentrations were observed in all storage conditions tested. In albumin free saline solution, thyroglobulin recovery rates depended on initial sample concentrations and on modalities of their conservation (in conventional storage tubes, recovery mean was 56% after 3 hours-storage at room temperature and 19% after 24 hours-storage for concentrations ranged from 2 to 183 μg/L; recovery was 95%, after 3 hours or 24 hours-storage at room temperature, for a concentration of 5,656 μg/L). We show here that these results are due to non-specific adsorption of thyroglobulin in storage tubes, which depends on sample protein concentrations. We also show that possible contamination of fluids from FNA washout by plasma proteins do not always adequately prevent this adsorption. In conclusion, non-specific adsorption in storage tubes strongly contributes to uncertainty in thyroglobulin measurement in physiological saline solution. It is therefore recommended, for FNA washout, to use a buffer containing proteins provided by the laboratory.

Capillary electrochromatography and capillary electrochromatography-electrospray mass spectrometry for the separation of non-steroidal anti-inflammatory drugs.

PubMed

Desiderio, C; Fanali, S

2000-10-20

In this study capillary electrochromatography (CEC) was utilized for the separation of ten non-steroidal anti-inflammatory drugs (NSAIDs). Experiments were carried out in a commercially available CE instrument using a packed capillary with RP-18 silica particles where the stationary phase completely filled the capillary. The mobile phase consisted of a mixture of ammonium formate buffer pH 2.5 and acetonitrile. Selectivity and resolution were studied changing the pH and the concentration of the buffer, the acetonitrile content mobile phase and the capillary temperature. The optimum experimental conditions for CEC separation of the studied drug mixture were found using 50 mM ammonium formate pH 2.5-acetonitrile (40:60) at 25 degrees C. The CEC capillary was coupled to an electrospray mass spectrometer for the characterization of the NSAIDs. A mobile phase composed by the same buffer but with a higher concentration of acetonitrile (90%) was used in order to speed up the separation of analytes.

GaAs buffer layer technique for vertical nanowire growth on Si substrate

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

Xu, Xiaoqing, E-mail: steelxu@stanford.edu; Parizi, Kokab B.; Huo, Yijie

2014-02-24

Gold catalyzed vapor-liquid-solid method is widely applied to III–V nanowire (NW) growth on Si substrate. However, the easy oxidation of Si, possible Si contamination in the NWs, high defect density in the NWs, and high sensitivity of the NW morphology to growth conditions largely limit its controllability. In this work, we developed a buffer layer technique by introducing a GaAs thin film with predefined polarity as a template. It is found that samples grown on these buffer layers all have high vertical NW yields in general, due to the single-orientation of the buffer layers. Low temperature buffer with smoother surfacemore » leads to highest yield of vertical NWs, while high temperature (HT) buffer with better crystallinity results in perfect NW quality. The defect-free property we observed here is very promising for optoelectronic device applications based on GaAs NW. Moreover, the buffer layers can eliminate Si contamination by preventing Si-Au alloy formation and by increasing the thickness of the Si diffusion barrier, thus providing more flexibility to vertical NW growth. The buffer layer technique we demonstrated here could be easily extended to other III-V on Si system for electronic and photonic applications.« less

Bicarbonate buffered peritoneal dialysis fluid upregulates angiopoietin-1 and promotes vessel maturation.

PubMed

Eich, Gwendolyn; Bartosova, Maria; Tischer, Christian; Wlodkowski, Tanja Tamara; Schaefer, Betti; Pichl, Sebastian; Kraewer, Nicole; Ranchin, Bruno; Vondrak, Karel; Liebau, Max Christoph; Hackert, Thilo; Schmitt, Claus Peter

2017-01-01

Ultrafiltration decline is a progressive issue for patients on chronic peritoneal dialysis (PD) and can be caused by peritoneal angiogenesis induced by PD fluids. A recent pediatric trial suggests better preservation of ultrafiltration with bicarbonate versus lactate buffered fluid; underlying molecular mechanisms are unknown. Angiogenic cytokine profile, tube formation capacity and Receptor Tyrosine Kinase translocation were assessed in primary human umbilical vein endothelial cells following incubation with bicarbonate (BPDF) and lactate buffered (LPDF), pH neutral PD fluid with low glucose degradation product content and lactate buffered, acidic PD fluid with high glucose degradation product content (CPDF). Peritoneal biopsies from age-, PD-vintage- and dialytic glucose exposure matched, peritonitis-free children on chronic PD underwent automated histomorphometry and immunohistochemistry. In endothelial cells angiopoietin-1 mRNA and protein abundance increased 200% upon incubation with BPDF, but decreased by 70% with LPDF as compared to medium control; angiopoietin-2 remained unchanged. Angiopoietin-1/Angiopoietin-2 protein ratio was 15 and 3-fold increased with BPDF compared to LPDF and medium. Time-lapse microscopy with automated network analysis demonstrated less endothelial cell tube formation with BPDF compared to LPDF and CPDF incubation. Receptor Tyrosine Kinase translocated to the cell membrane in BPDF but not in LPDF or CPDF incubated endothelial cells. In children dialyzed with BPDF peritoneal vessels were larger and angiopoietin-1 abundance in CD31 positive endothelium higher compared to children treated with LPDF. Bicarbonate buffered PD fluid promotes vessel maturation via upregulation of angiopoietin-1 in vitro and in children on dialysis. Our findings suggest a molecular mechanism for the observed superior preservation of ultrafiltration capacity with bicarbonate buffered PD fluid with low glucose degradation product content.

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.

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.

Real-time HD Exchange Kinetics of Proteins from Buffered Aqueous Solution with Electrothermal Supercharging and Top-Down Tandem Mass Spectrometry

NASA Astrophysics Data System (ADS)

Going, Catherine C.; Xia, Zijie; Williams, Evan R.

2016-06-01

Electrothermal supercharging (ETS) with electrospray ionization produces highly charged protein ions from buffered aqueous solutions in which proteins have native folded structures. ETS increases the charge of ribonuclease A by 34%, whereas only a 6% increase in charge occurs for a reduced-alkylated form of this protein, which is unfolded and its structure is ~66% random coil in this solution. These results indicate that protein denaturation that occurs in the ESI droplets is the primary mechanism for ETS. ETS does not affect the extent of solution-phase hydrogen-deuterium exchange (HDX) that occurs for four proteins that have significantly different structures in solution, consistent with a droplet lifetime that is considerably shorter than observable rates of HDX. Rate constants for HDX of ubiquitin are obtained with a spatial resolution of ~1.3 residues with ETS and electron transfer dissociation of the 10+ charge-state using a single capillary containing a few μL of protein solution in which HDX continuously occurs. HDX protection at individual residues with ETS HDX is similar to that with reagent supercharging HDX and with solution-phase NMR, indicating that the high spray potentials required to induce ETS do not lead to HD scrambling.

Retrieval of Au, Ag, Cu precious metals coupled with electric energy production via an unconventional coupled redox fuel cell reactor.

PubMed

Zhang, Hui-Min; Fan, Zheng; Xu, Wei; Feng, Xiao; Wu, Zu-Cheng

2017-09-15

The recovery of heavy metals from aqueous solutions or e-wastes is of upmost importance. Retrieval of Au, Ag, and Cu with electricity generation through building an ethanol-metal coupled redox fuel cells (CRFCs) is demonstrated. The cell was uniquely assembled on PdNi/C anode the electro-oxidation of ethanol takes place to give electrons and then go through the external circuit reducing metal ions to metallic on the cathode, metals are recovered. Taking an example of removal of 100mgL -1 gold in 0.5M HAc-NaAc buffer solution as the catholyte, 2.0M ethanol in 1.0M alkaline solution as the anolyte, an open circuit voltage of 1.4V, more than 96% of gold removal efficiency in 20h, and equivalent energy production of 2.0kWhkg -1 of gold can be readily achieved in this system. When gold and copper ions coexist, it was confirmed that metallic Cu is formed on the cathodic electrode later than metallic Au formation by XPS analysis. Thus, this system can achieve step by step electrodeposition of gold and copper while the two metal ions coexisting. This work develops a new approach to retrieve valuable metals from aqueous solution or e-wastes. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of Exposed Surface Area, Volume and Environmental pH on the Calcium Ion Release of Three Commercially Available Tricalcium Silicate Based Dental Cements.

PubMed

Rajasekharan, Sivaprakash; Vercruysse, Chris; Martens, Luc; Verbeeck, Ronald

2018-01-13

Tricalcium silicate cements (TSC) are used in dental traumatology and endodontics for their bioactivity which is mostly attributed to formation of calcium hydroxide during TSC hydration and its subsequent release of calcium and hydroxide ions. The aim of this study was to determine the effect of volume (Vol), exposed surface area (ESA) and pH of surrounding medium on calcium ion release. Three commercially available hydraulic alkaline dental cements were mixed and condensed into cylindrical tubes of varying length and diameter ( n = 6/group). For the effect of ESA and Vol, tubes were immersed in 10 mL of deionized water. To analyze the effect of environmental pH, the tubes were randomly immersed in 10 mL of buffer solutions with varying pH (10.4, 7.4 or 4.4). The solutions were collected and renewed at various time intervals. pH and/or calcium ion release was measured using a pH glass electrode and atomic absorption spectrophotometer respectively. The change of pH, short-term calcium ion release and rate at which calcium ion release reaches maximum were dependent on ESA ( p < 0.05) while maximum calcium ion release was dependent on Vol of TSC ( p < 0.05). Maximum calcium ion release was significantly higher in acidic solution followed by neutral and alkaline solution ( p < 0.05).

Effect of Exposed Surface Area, Volume and Environmental pH on the Calcium Ion Release of Three Commercially Available Tricalcium Silicate Based Dental Cements

PubMed Central

Rajasekharan, Sivaprakash; Vercruysse, Chris; Martens, Luc; Verbeeck, Ronald

2018-01-01

Tricalcium silicate cements (TSC) are used in dental traumatology and endodontics for their bioactivity which is mostly attributed to formation of calcium hydroxide during TSC hydration and its subsequent release of calcium and hydroxide ions. The aim of this study was to determine the effect of volume (Vol), exposed surface area (ESA) and pH of surrounding medium on calcium ion release. Three commercially available hydraulic alkaline dental cements were mixed and condensed into cylindrical tubes of varying length and diameter (n = 6/group). For the effect of ESA and Vol, tubes were immersed in 10 mL of deionized water. To analyze the effect of environmental pH, the tubes were randomly immersed in 10 mL of buffer solutions with varying pH (10.4, 7.4 or 4.4). The solutions were collected and renewed at various time intervals. pH and/or calcium ion release was measured using a pH glass electrode and atomic absorption spectrophotometer respectively. The change of pH, short-term calcium ion release and rate at which calcium ion release reaches maximum were dependent on ESA (p < 0.05) while maximum calcium ion release was dependent on Vol of TSC (p < 0.05). Maximum calcium ion release was significantly higher in acidic solution followed by neutral and alkaline solution (p < 0.05). PMID:29342837

Polymicrobial Biofilm Inhibition Effects of Acetate-Buffered Chitosan Sponge Delivery Device.

PubMed

Jennings, Jessica Amber; Beenken, Karen E; Parker, Ashley C; Smith, James Keaton; Courtney, Harry S; Smeltzer, Mark S; Haggard, Warren O

2016-04-01

Polymicrobial biofilm-associated implant infections present a challenging clinical problem. Through modifications of lyophilized chitosan sponges, degradable drug delivery devices for antibiotic solution have been fabricated for prevention and treatment of contaminated musculoskeletal wounds. Elution of amikacin, vancomycin, or a combination of both follows a burst release pattern with vancomycin released above minimum inhibitory concentration for Staphylococcus aureus for 72 h and amikacin released above inhibitory concentrations for Pseudomonas aeruginosa for 3 h. Delivery of a vancomycin, amikacin, or a combination of both reduces biofilm formation on polytetrafluoroethylene catheters in an in vivo model of contamination. Release of dual antibiotics from sponges is more effective at preventing biofilm formation than single-loaded chitosan sponges. Treatment of pre-formed biofilm with high-dose antibiotic release from chitosan sponges shows minimal reduction after 48 h. These results demonstrate infection-preventive efficacy for antibiotic-loaded sponges, as well as the need for modifications in the development of advanced materials to enhance treatment efficacy in removing established biofilm. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Size-dependent reactivity of diamond nanoparticles.

PubMed

Williams, Oliver A; Hees, Jakob; Dieker, Christel; Jäger, Wolfgang; Kirste, Lutz; Nebel, Christoph E

2010-08-24

Photonic active diamond nanoparticles attract increasing attention from a wide community for applications in drug delivery and monitoring experiments as they do not bleach or blink over extended periods of time. To be utilized, the size of these diamond nanoparticles needs to be around 4 nm. Cluster formation is therefore the major problem. In this paper we introduce a new technique to modify the surface of particles with hydrogen, which prevents cluster formation in buffer solution and which is a perfect starting condition for chemical surface modifications. By annealing aggregated nanodiamond powder in hydrogen gas, the large (>100 nm) aggregates are broken down into their core ( approximately 4 nm) particles. Dispersion of these particles into water via high power ultrasound and high speed centrifugation, results in a monodisperse nanodiamond colloid, with exceptional long time stability in a wide range of pH, and with high positive zeta potential (>60 mV). The large change in zeta potential resulting from this gas treatment demonstrates that nanodiamond particle surfaces are able to react with molecular hydrogen at relatively low temperatures, a phenomenon not witnessed with larger (20 nm) diamond particles or bulk diamond surfaces.

Development of freeze-dried albumin-free formulation of recombinant factor VIII SQ.

PubMed

Osterberg, T; Fatouros, A; Mikaelsson, M

1997-07-01

To develop a stable freeze-dried formulation of recombinant factor VIII-SQ (r-VIII SQ) without the addition of albumin. Different formulations were evaluated for their protective effect during sterile filtration, freeze-thawing, freeze-drying, reconstitution and long term storage. Factor VIII activity (VIII:C), visual inspection, clarity, solubility, moisture content and soluble aggregates and/ or fragments were assayed. A combination of non-crystallising excipients (L-histidine and sucrose), a non-ionic surfactant (polysorbate 80) and a crystalline bulking agent (sodium chloride) was found to preserve the factor VIII activity during formulation, freeze-drying and storage. Calcium chloride was included to prevent dissociation of the heavy and light chains of r-VIII SQ. Sodium chloride was chosen as the primary bulking agent since the concentration of sodium chloride necessary for dissolution of r-VIII SQ in the buffer will inhibit the crystallization of many potential cake formers. It was found that L-histidine, besides functioning as a buffer, also protected r-VIII SQ during freeze-drying and storage. A pH close to 7 was found to be optimal. Some potential macromolecular stabilisers, PEG 4000, Haes-steril and Haemaccel, were evaluated but they did not improve the recovery of VIII:C. The freeze-dried formulation was stable for at least two years at 7 degrees C and for at least one year at 25 degrees C. The reconstituted solution was stable for at least 100 hours at 25 degrees C. The albumin-free formulation resulted in consistently high recovery of VIII:C, very low aggregate formation and good storage stability. The stability of the reconstituted solution makes the formulation suitable for continuous administration via infusion pump. The formulation strategy described here may also be useful for other proteins which require a high ionic strength.

Buffer capacity of 4% succinylated gelatin does not provide any advantages over acidic 6% hydroxyethyl starch 130/0.4 for acid-base balance during experimental mixed acidaemia in a porcine model.

PubMed

Esche, V; Russ, M; Melzer, S; Grossmann, B; Boemke, W; Unger, J K

2008-11-01

Four percent gelatine is an alkaline compound due to NH2 groups, whereas 6% hydroxyethyl starch 130/0.4 (HES130) has acidic features. We investigated whether these solutions lead to differences in acid-base balance in pigs during acidaemia and correction of pH. Anaesthetized pigs were randomized to HES130 or gelatine infusion (n = 5 per group). Animals received acid infusion (0.4 M solution of lactic acid and HCl diluted in normal saline) and low tidal volume ventilation (6-7 mL kg(-1), PaCO2 of 80-85 mmHg, pH 7.19-7.24). Measurements were made before and after induction of acidaemia, before and after correction of pH with haemofiltration (continuous venovenous haemofiltration) and tris-hydroxymethylaminomethane infusion. We measured parameters describing acid-base balance according to Stewart's approach, ketone body formation, oxygen delivery, haemodynamics, diuresis and urinary pH. Acid-base balance did not differ significantly between the groups. In HES130-treated pigs, the haemodilution-based drop of haemoglobin (1.4 +/- 1.0 g dL(-1), median +/- SD) was paralleled by an increase in the cardiac output (0.5 +/- 0.4 L min(-1). Lacking increases in cardiac output, gelatine-treated pigs demonstrated a reduction in oxygen delivery (149.4 +/- 106.0 mL min(-1)). Tris-hydroxymethylaminomethane volumes required for pH titration to desired values were significantly higher in the gelatine group (0.7 +/- 0.1 mL kg(-1) h(-1) vs. HES130: 0.5 +/- 0.2 mL kg(-1) h(-1)). The buffer capacity of gelatine did not lead to favourable differences in acid-base balance in comparison to HES130.

Design of optimal buffer layers for CuInGaSe2 thin-film solar cells(Conference Presentation)

NASA Astrophysics Data System (ADS)

Lordi, Vincenzo; Varley, Joel B.; He, Xiaoqing; Rockett, Angus A.; Bailey, Jeff; Zapalac, Geordie H.; Mackie, Neil; Poplavskyy, Dmitry; Bayman, Atiye

2016-09-01

Optimizing the buffer layer in manufactured thin-film PV is essential to maximize device efficiency. Here, we describe a combined synthesis, characterization, and theory effort to design optimal buffers based on the (Cd,Zn)(O,S) alloy system for CIGS devices. Optimization of buffer composition and absorber/buffer interface properties in light of several competing requirements for maximum device efficiency were performed, along with process variations to control the film and interface quality. The most relevant buffer properties controlling performance include band gap, conduction band offset with absorber, dopability, interface quality, and film crystallinity. Control of an all-PVD deposition process enabled variation of buffer composition, crystallinity, doping, and quality of the absorber/buffer interface. Analytical electron microscopy was used to characterize the film composition and morphology, while hybrid density functional theory was used to predict optimal compositions and growth parameters based on computed material properties. Process variations were developed to produce layers with controlled crystallinity, varying from amorphous to fully epitaxial, depending primarily on oxygen content. Elemental intermixing between buffer and absorber, particularly involving Cd and Cu, also is controlled and significantly affects device performance. Secondary phase formation at the interface is observed for some conditions and may be detrimental depending on the morphology. Theoretical calculations suggest optimal composition ranges for the buffer based on a suite of computed properties and drive process optimizations connected with observed film properties. Prepared by LLNL under Contract DE-AC52-07NA27344.

40 CFR Appendix A to Part 425 - Potassium Ferricyanide Titration Method

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 30 2014-07-01 2014-07-01 false Potassium Ferricyanide Titration..., App. A Appendix A to Part 425—Potassium Ferricyanide Titration Method Source The potassium... buffered sulfide solution is titrated with standard potassium ferricyanide solution in the presence of a...

40 CFR Appendix A to Part 425 - Potassium Ferricyanide Titration Method

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 31 2013-07-01 2013-07-01 false Potassium Ferricyanide Titration..., App. A Appendix A to Part 425—Potassium Ferricyanide Titration Method Source The potassium... buffered sulfide solution is titrated with standard potassium ferricyanide solution in the presence of a...

An improved robust buffer allocation method for the project scheduling problem

NASA Astrophysics Data System (ADS)

Ghoddousi, Parviz; Ansari, Ramin; Makui, Ahmad

2017-04-01

Unpredictable uncertainties cause delays and additional costs for projects. Often, when using traditional approaches, the optimizing procedure of the baseline project plan fails and leads to delays. In this study, a two-stage multi-objective buffer allocation approach is applied for robust project scheduling. In the first stage, some decisions are made on buffer sizes and allocation to the project activities. A set of Pareto-optimal robust schedules is designed using the meta-heuristic non-dominated sorting genetic algorithm (NSGA-II) based on the decisions made in the buffer allocation step. In the second stage, the Pareto solutions are evaluated in terms of the deviation from the initial start time and due dates. The proposed approach was implemented on a real dam construction project. The outcomes indicated that the obtained buffered schedule reduces the cost of disruptions by 17.7% compared with the baseline plan, with an increase of about 0.3% in the project completion time.

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.

Accurate determination of aldehydes in amine catalysts or amines by 2,4-dinitrophenylhydrazine derivatization.

PubMed

Barman, Bhajendra N

2014-01-31

Carbonyl compounds, specifically aldehydes, present in amine catalysts or amines are determined by reversed-phase liquid chromatography using ultraviolet detection of their corresponding 2,4-dinitrophenylhydrazones. The primary focus has been to establish optimum conditions for determining aldehydes accurately because these add exposure concerns when the amine catalysts are used to manufacture polyurethane products. Concentrations of aldehydes determined by this method are found to vary with the pH of the aqueous amine solution and the derivatization time, the latter being problematic when the derivatization reaction proceeds slowly and not to completion in neutral and basic media. Accurate determination of aldehydes in amines through derivatization can be carried out at an effective solution pH of about 2 and with derivatization time of 20min. Hydrochloric acid has been used for neutralization of an amine. For complete derivatization, it is essential to protonate all nitrogen atoms in the amine. An approach for the determination of an adequate amount of acid needed for complete derivatization has been described. Several 0.2M buffer solutions varying in pH from 4 to 8 have also been used to make amine solutions for carrying out derivatization of aldehydes. These solutions have effective pHs of 10 or higher and provide much lower aldehyde concentrations compared to their true values. Mechanisms for the formation of 2,4-dinitrophenylhydrazones in both acidic and basic media are discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

Role of Ca++ in Shoot Gravitropism. [avena

NASA Technical Reports Server (NTRS)

Rayle, D. L.

1985-01-01

A cornerstone in the argument that Ca(2+) levels may regulate growth is the finding the EGTA promotes straight growth. The usual explanation for these results is that Ca(2+) chelation from cell walls results in wall loosening and thus accelerated straight growth. The ability of frozen-thawed Avena coleoptile tissue (subjected to 15g tension) to extend in response to EGTA and Quin II was examined. The EGTA when applied in weakly buffered (i.e., 0.1mM) neutral solutions initiates rapid extension. When the buffer strength is increased, similar concentrations of EGTA produce no growth response. This implies when EGTA liberated protons are released upon Ca(2+) chelation they can either initiate acid growth (low buffer conditions) or if consumed (high buffer conditions) have no effect. Thus Ca(2+) chelation in itself apparently does not result in straight growth.

NoSQL: collection document and cloud by using a dynamic web query form

NASA Astrophysics Data System (ADS)

Abdalla, Hemn B.; Lin, Jinzhao; Li, Guoquan

2015-07-01

Mongo-DB (from "humongous") is an open-source document database and the leading NoSQL database. A NoSQL (Not Only SQL, next generation databases, being non-relational, deal, open-source and horizontally scalable) presenting a mechanism for storage and retrieval of documents. Previously, we stored and retrieved the data using the SQL queries. Here, we use the MonogoDB that means we are not utilizing the MySQL and SQL queries. Directly importing the documents into our Drives, retrieving the documents on that drive by not applying the SQL queries, using the IO BufferReader and Writer, BufferReader for importing our type of document files to my folder (Drive). For retrieving the document files, the usage is BufferWriter from the particular folder (or) Drive. In this sense, providing the security for those storing files for what purpose means if we store the documents in our local folder means all or views that file and modified that file. So preventing that file, we are furnishing the security. The original document files will be changed to another format like in this paper; Binary format is used. Our documents will be converting to the binary format after that direct storing in one of our folder, that time the storage space will provide the private key for accessing that file. Wherever any user tries to discover the Document files means that file data are in the binary format, the document's file owner simply views that original format using that personal key from receive the secret key from the cloud.

The use of physiological solutions or media in calcium phosphate synthesis and processing.

PubMed

Tas, A Cuneyt

2014-05-01

This review examined the literature to spot uses, if any, of physiological solutions/media for the in situ synthesis of calcium phosphates (CaP) under processing conditions (i.e. temperature, pH, concentration of inorganic ions present in media) mimicking those prevalent in the human hard tissue environments. There happens to be a variety of aqueous solutions or media developed for different purposes; sometimes they have been named as physiological saline, isotonic solution, cell culture solution, metastable CaP solution, supersaturated calcification solution, simulated body fluid or even dialysate solution (for dialysis patients). Most of the time such solutions were not used as the aqueous medium to perform the biomimetic synthesis of calcium phosphates, and their use was usually limited to the in vitro testing of synthetic biomaterials. This review illustrates that only a limited number of research studies used physiological solutions or media such as Earle's balanced salt solution, Bachra et al. solutions or Tris-buffered simulated body fluid solution containing 27mM HCO3(-) for synthesizing CaP, and these studies have consistently reported the formation of X-ray-amorphous CaP nanopowders instead of Ap-CaP or stoichiometric hydroxyapatite (HA, Ca10(PO4)6(OH)2) at 37°C and pH 7.4. By relying on the published articles, this review highlights the significance of the use of aqueous solutions containing 0.8-1.5 mMMg(2+), 22-27mM HCO3(-), 142-145mM Na(+), 5-5.8mM K(+), 103-133mM Cl(-), 1.8-3.75mM Ca(2+), and 0.8-1.67mM HPO4(2-), which essentially mimic the composition and the overall ionic strength of the human extracellular fluid (ECF), in forming the nanospheres of X-ray-amorphous CaP. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Quantifying the sensitivity of G. oxydans ATCC 621H and DSM 3504 to osmotic stress triggered by soluble buffers.

PubMed

Luchterhand, B; Fischöder, T; Grimm, A R; Wewetzer, S; Wunderlich, M; Schlepütz, T; Büchs, J

2015-04-01

In Gluconobacter oxydans cultivations on glucose, CaCO3 is typically used as pH-buffer. This buffer, however, has disadvantages: suspended CaCO3 particles make the medium turbid, thereby, obstructing analysis of microbial growth via optical density and scattered light. Upon searching for alternative soluble pH-buffers, bacterial growth and productivity was inhibited most probably due to osmotic stress. Thus, this study investigates in detail the osmotic sensitivity of G. oxydans ATCC 621H and DSM 3504 using the Respiratory Activity MOnitoring System. The tested soluble pH-buffers and other salts attained osmolalities of 0.32-1.19 osmol kg(-1). This study shows that G. oxydans ATCC 621H and DSM 3504 respond quite sensitively to increased osmolality in comparison to other microbial strains of industrial interest. Osmolality values of >0.5 osmol kg(-1) should not be exceeded to avoid inhibition of growth and product formation. This osmolality threshold needs to be considered when working with soluble pH-buffers.

BACTERIAL BIOFILM FORMATION UNDER MICROGRAVITY CONDITIONS. (R825503)

EPA Science Inventory

Although biofilm formation is widely documented on Earth, it has not been demonstrated in the absence of gravity. To explore this possibility, Pseudomonas aeruginosa, suspended in sterile buffer, was flown in a commercial payload on space shuttle flight STS-95. During earth or...

Novel inclusion complex of ibuprofen tromethamine with cyclodextrins: physico-chemical characterization.

PubMed

Al Omari, Mahmoud M; Daraghmeh, Nidal H; El-Barghouthi, Musa I; Zughul, Mohammad B; Chowdhry, Babur Z; Leharne, Stephen A; Badwan, Adnan A

2009-10-15

Guest-host interactions of ibuprofen tromethamine salt (Ibu.T) with native and modified cyclodextrins (CyDs) have been investigated using several techniques, namely phase solubility diagrams (PSDs), proton nuclear magnetic resonance ((1)H NMR), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffractometry (XRPD), scanning-electron microscopy (SEM) and molecular mechanics (MM). From the analysis of PSD data (A(L)-type) it is concluded that the anionic tromethamine salt of ibuprofen (pK(a)=4.55) forms 1:1 soluble complexes with all CyDs investigated in buffered water at pH 7.0, while the neutral form of Ibu forms an insoluble complex with beta-CyD (B(S)-type) in buffered water at pH 2.0. Ibu.T has a lower tendency to complex with beta-CyD (K(11)=58 M(-1) at pH 7.0) compared with the neutral Ibu (K(11)=4200 M(-1)) in water. Complex formation of Ibu.T with beta-CyD (DeltaG(o)=-20.4 kJ/mol) is enthalpy driven (DeltaH(o)=-22.9 kJ/mol) and is accompanied by a small unfavorable entropy (DeltaS(o)=-8.4 J/mol K) change. (1)H NMR studies and MM computations revealed that, on complexation, the hydrophobic central benzene ring of Ibu.T and part of the isobutyl group reside within the beta-CyD cavity leaving the peripheral groups (carboxylate, tromethamine and methyl groups) located near the hydroxyl group networks at either rim of beta-CyD. PSD, (1)H NMR, DSC, FT-IR, XRPD, SEM and MM studies confirmed the formation of Ibu.T/beta-CyD inclusion complex in solution and the solid state.

40 CFR Appendix B to Subpart Nnn... - Free Formaldehyde Analysis of Insulation Resins by Hydroxylamine Hydrochloride

Code of Federal Regulations, 2013 CFR

2013-07-01

... buffer. 3.350-mL burette for 1.0 N sodium hydroxide. 3.4Magnetic stirrer and stir bars. 3.5250-mL beaker... N sodium hydroxide solution. 4.2Hydroxylamine hydrochloride solution, 100 grams per liter, pH... hydrochloric acid, and 0.1 N sodium hydroxide. 5.5Add 50 mL of the hydroxylamine hydrochloride solution...

40 CFR Appendix B to Subpart Nnn... - Free Formaldehyde Analysis of Insulation Resins by Hydroxylamine Hydrochloride

Code of Federal Regulations, 2014 CFR

2014-07-01

... buffer. 3.350-mL burette for 1.0 N sodium hydroxide. 3.4Magnetic stirrer and stir bars. 3.5250-mL beaker... N sodium hydroxide solution. 4.2Hydroxylamine hydrochloride solution, 100 grams per liter, pH... hydrochloric acid, and 0.1 N sodium hydroxide. 5.5Add 50 mL of the hydroxylamine hydrochloride solution...

Dakin Solution Alters Macrophage Viability and Function

DTIC Science & Technology

2014-07-18

A, Guerrero JM, Calvo JR. Comparative effects of two endodontic irrigants, chlorhexidine digluconate and sodium hypochlorite , on macrophage adhesion...July 2014 Available online 18 July 2014 Keywords: Sodium hypochlorite Dakin solution Macrophages Phagocytosis a b s t r a c t Background: Macrophages are...important in wound defense and healing. Dakin’s solution (DS), buffered sodium hypochlorite , has been used since World War I as a topical antimi

Membrane Pore Formation by Amyloid beta (25-35) Peptide

NASA Astrophysics Data System (ADS)

Kandel, Nabin; Tatulian, Suren

Amyloid (A β) peptide contributes to Alzheimer's disease by a yet unidentified mechanism. One of the possible mechanisms of A β toxicity is formation of pores in cellular membranes. We have characterized the formation of pores in phospholipid membranes by the Aβ25 - 35 peptide (GSNKGAIIGLM) using fluorescence, Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) techniques. CD and FTIR identified formation of β-sheet structure upon incubation of the peptide in aqueous buffer for 2 hours. Unilamellar vesicles composed of a zwitterionic lipid, 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC), and 70 % POPC plus 30 % of an acidic lipid, 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG), are made in 30 mM CaCl2. Quin-2, a fluorophore that displays increased fluorescence upon Ca2+ binding, is added to the vesicles externally. Peptide addition results in increased Quin-2 fluorescence, which is interpreted by binding of the peptide to the vesicles, pore formation, and Ca2+ leakage. The positive and negative control measurements involve addition of a detergent, Triton X-100, which causes vesicle rupture and release of total calcium, and blank buffer, respectively.

Mechanism of Indole-3-acetic Acid Conjugation

PubMed Central

Goren, Raphael; Bukovac, Martin J.; Flore, James A.

1974-01-01

Formation of indole-3-acetic acid-aspartate in detached primary leaves of cowpea (Vigna sinensis Endl.) floating on 14C-indole-3-acetic acid (3 μc; 3.15 μm, phosphate-citrate buffer, pH 4.75), almost doubled when leaves were pretreated with 31.5 μm12C-indole-3-acetic acid for 17 hr and then transferred to 14C-indole-3-acetic acid for 4 hours as compared with leaves preincubated in buffer only. When leaves were preincubated with ethylene (11.0 and 104 μl/l) instead of 12C-indole-3-acetic acid, no induction of indole-3-acetylaspartic acid formation was observed, and the rate of indole-3-acetylaspartic acid formation decreased as compared with control leaves. Rhizobitoxine (1.87 μm) inhibited indole-3-acetic acid-induced ethylene production but did not prevent the formation of indole-3-acetylaspartic acid. In view of the similarity of these results and those previously obtained with α-naphthaleneacetic acid, it is concluded that ethylene has no role in the auxin-induced indole-3-acetylaspartic acid formation in cowpea leaves. PMID:16658669

Effects of cationic species on visual color formation in model Maillard reactions of pentose sugars and amino acids.

PubMed

Rizzi, George P

2008-08-27

Effects of cationic species on Maillard browning were examined after heating (ca. 100 degrees C) aqueous pH 7.2 buffered solutions of amino acids and pentose sugars. Metallic ions of Group I metals (Li, Na, K, Rb and Cs) produced a small increase in browning (A420), but somewhat greater effects were observed with ions of Group II metals Ca and Mg. Browning was suppressed by triethylammonium ion, but unaffected by a salt of the stronger base, guanidine. The quaternary amine salt choline chloride produced enhanced browning and served as a model for phospholipid involvement in Maillard reactions. With alpha,omega-diamino acids increases in browning were observed which related to lowered pK2 values resulting from positively charged omega-substituents in these molecules.

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.

Using single buffers and data reorganization to implement a multi-megasample fast Fourier transform

NASA Technical Reports Server (NTRS)

Brown, R. D.

1992-01-01

Data ordering in large fast Fourier transforms (FFT's) is both conceptually and implementationally difficult. Discribed here is a method of visualizing data orderings as vectors of address bits, which enables the engineer to use more efficient data orderings and reduce double-buffer memory designs. Also detailed are the difficulties and algorithmic solutions involved in FFT lengths up to 4 megasamples (Msamples) and sample rates up to 80 MHz.

Formation of hydroxyl radical from San Joaquin Valley particles extracted in a cell-free surrogate lung fluid

PubMed Central

Shen, H.; Anastasio, C.

2011-01-01

Previous studies have suggested that the adverse health effects from ambient particulate matter (PM) are linked to the formation of reactive oxygen species (ROS) by PM in cardiopulmonary tissues. While hydroxyl radical (•OH) is the most reactive of the ROS species, there are few quantitative studies of •OH generation from PM. Here we report on •OH formation from PM collected at an urban (Fresno) and rural (Westside) site in the San Joaquin Valley (SJV) of California. We quantified •OH in PM extracts using a cell-free, phosphate-buffered saline (PBS) solution with or without 50μM ascorbate (Asc). The results show that generally the urban Fresno PM generates much more •OH than the rural Westside PM. The presence of Asc at a physiologically relevant concentration in the extraction solution greatly enhances •OH formation from all the samples. Fine PM (PM2.5) generally makes more •OH than the corresponding coarse PM (PMcf, i.e. with diameters of 2.5 to 10 μm) normalized by air volume collected, while the coarse PM typically generates more •OH normalized by PM mass. •OH production by SJV PM is reduced on average by (97±6)% when the transition metal chelator desferoxamine (DSF) is added to the extraction solution, indicating a dominant role of transition metals. By measuring calibration curves of •OH generation from copper and iron, and quantifying copper and iron concentrations in our particle extracts, we find that PBS-soluble copper is primarily responsible for •OH production by the SJV PM, while iron often makes a significant contribution. Extrapolating our results to expected burdens of PM-derived •OH in human lung lining fluid suggests that typical daily PM exposures in the San Joaquin Valley are unlikely to result in a high amount of pulmonary •OH, although high PM events could produce much higher levels of •OH, which might lead to cytotoxicity. PMID:22121357

Improved Stability of a Model IgG3 by DoE-Based Evaluation of Buffer Formulations

DOE PAGES

Chavez, Brittany K.; Agarabi, Cyrus D.; Read, Erik K.; ...

2016-01-01

Formulating appropriate storage conditions for biopharmaceutical proteins is essential for ensuring their stability and thereby their purity, potency, and safety over their shelf-life. Using a model murine IgG3 produced in a bioreactor system, multiple formulation compositions were systematically explored in a DoE design to optimize the stability of a challenging antibody formulation worst case. The stability of the antibody in each buffer formulation was assessed by UV/VIS absorbance at 280 nm and 410 nm and size exclusion high performance liquid chromatography (SEC) to determine overall solubility, opalescence, and aggregate formation, respectively. Upon preliminary testing, acetate was eliminated as a potentialmore » storage buffer due to significant visible precipitate formation. An additional 2 4full factorial DoE was performed that combined the stabilizing effect of arginine with the buffering capacity of histidine. From this final DoE, an optimized formulation of 200 mM arginine, 50 mM histidine, and 100 mM NaCl at a pH of 6.5 was identified to substantially improve stability under long-term storage conditions and after multiple freeze/thaw cycles. Therefore, our data highlights the power of DoE based formulation screening approaches even for challenging monoclonal antibody molecules.« less

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.

Measurements of atmospheric nitrous acid and nitric acid

NASA Astrophysics Data System (ADS)

Huang, Gu; Zhou, Xianliang; Deng, Guohong; Qiao, Huancheng; Civerolo, Kevin

A highly sensitive technique for the measurement of atmospheric HONO and HNO 3 is reported. The technique is based on aqueous scrubbing using two coil samplers, followed by conversion of HNO 3 to nitrite, derivatization of nitrite to a highly light-absorbing azo dye with sulfanilamide (SA) and N-(1-naphthyl) ethylenediamine (NED), and high performance liquid chromatography (HPLC) analysis. HNO 3 concentration was obtained by the difference of the two channels. Two scrubbing solutions were used for sampling the two species: a 1-mM phosphate buffer solution (pH 7) for the measurement of HONO and a 180 mM NH 4Cl/NH 3 buffer solution (pH 8.5) for the measurement of HONO+HNO 3. The scrubbing solution flow rate was 0.24 ml min -1 and the gas sampling flow rate was 2 l min -1. HNO 3 in the NH 4Cl/NH 3 buffer solution was quantitatively reduced to nitrite along an on-line 0.8-cm Cd reductor column. Nitrite in both channels was derivatized with 2 mM SA and 0.2 mM NED in 25 mM HCl. Quantitative derivatization was achieved within 5 min at 55°C. The azo dye derivative was then separated from the SA/NED reagent by reversed-phase HPLC and detected with a UV-vis detector at 540 nm. With an on-line SEP-PAK C-18 cartridge for the reagent purification, the method detection limit is estimated to be better than 1 pptv for HONO and about 20 pptv for HNO 3. The sample integration time was about 2 min and the sampling frequency is every 10 min. Data collected in downtown Albany and Whiteface Mountain, NY, are shown as examples of applications of this technique in both urban and remote clean environments.

Correlated fluorescence-atomic force microscopy studies of the clathrin mediated endocytosis in SKMEL cells

NASA Astrophysics Data System (ADS)

Hor, Amy; Luu, Anh; Kang, Lin; Scott, Brandon; Bailey, Elizabeth; Hoppe, Adam; Smith, Steve

2017-02-01

Clathrin-mediated endocytosis (CME) is one of the central pathways for cargo transport into cells, and plays a major role in the maintenance of cellular functions, such as intercellular signaling, nutrient intake, and turnover of plasma membrane in cells. The clathrin-mediated endocytosis process involves invagination and formation of clathrin-coated vesicles. However, the biophysical mechanisms of vesicle formation are still debated. Currently, there are two models describing membrane bending during the formation of clathrin cages: the first involves the deposition of all clathrin molecules to the plasma membrane, forming a flat lattice prior to membrane bending, whereas in the second model, membrane bending happens simultaneously as the clathrin arrives to the site to form a clathrin-coated cage. We investigate clathrin vesicle formation mechanisms through the utilization of tapping-mode atomic force microscopy for high resolution topographical imaging in neutral buffer solution of unroofed cells exposing the inner membrane, combined with fluorescence imaging to definitively label intracellular constituents with specific fluorophores (actin filaments labeled with green phalloidin and clathrin coated vesicles with the fusion protein Tq2) in SKMEL (Human Melanoma) cells. An extensive statistical survey of many hundreds of CME events, at various stages of progression, are observed via this method, allowing inferences about the dominant mechanisms active in CME in SKMEL cells. Results indicate a mixed model incorporating aspects of both the aforementioned mechanisms for CME.

Sample collection system for gel electrophoresis

DOEpatents

Olivares, Jose A.; Stark, Peter C.; Dunbar, John M.; Hill, Karen K.; Kuske, Cheryl R.; Roybal, Gustavo

2004-09-21

An automatic sample collection system for use with an electrophoretic slab gel system is presented. The collection system can be used with a slab gel have one or more lanes. A detector is used to detect particle bands on the slab gel within a detection zone. Such detectors may use a laser to excite fluorescently labeled particles. The fluorescent light emitted from the excited particles is transmitted to low-level light detection electronics. Upon the detection of a particle of interest within the detection zone, a syringe pump is activated, sending a stream of buffer solution across the lane of the slab gel. The buffer solution collects the sample of interest and carries it through a collection port into a sample collection vial.

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.

Effect of coexisting Al(III) ions on Pb(II) sorption on biochars: Role of pH buffer and competition.

PubMed

Yang, Yuxi; Zhang, Weihua; Qiu, Hao; Tsang, Daniel C W; Morel, Jean-Louis; Qiu, Rongliang

2016-10-01

Biochar is being widely considered as a promising amendment agent for immobilizing heavy metals in contaminated acidic soils, where plenty of soluble Al(III) ions exist. In view of uncertain significance of the effects of coexisting Al(III) on Pb(II) sorption by biochars, this study used kenaf core biochar (KB550; high carbon, low ash) and sewage sludge biochar (SB550; low carbon, high ash) pyrolyzed at 550 °C to elucidate the influence of coexisting Al(III) species and biochars' mineral components on Pb(II) immobilization conducted in aqueous solution with initial pHs of 3.0-4.5. Results showed that Al(III) reduced Pb(II) sorption on KB550 primarily via pH buffering against biochar alkalinity, thus inhibiting lead carbonate formation. In contrast, the reduction on SB550 mainly resulted from direct competition for sorption sites, especially on Fe-rich phengite 2M1 and metakaolinite. Because of Pb-P precipitation and Pb-K interlayer exchange, the residual Pb(II) adsorption capacity resistant to coexisting Al(III) was 3-5 times higher on SB550 than on KB550. The Pb-K interlayer exchange was enhanced by lower pH and coexisting Al(III), while Pb-P precipitation was the dominant Pb(II) sorption mechanism on SB550 resistant to Al(III) buffering and competition at higher pH. Application of these two biochars as amendments confirmed that the mineral-rich SB550 was more suitable for Pb(II) immobilization in acidic soils with high levels of extractable Al(III). Copyright © 2016 Elsevier Ltd. All rights reserved.

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.

Drug adsorption to plastic containers and retention of drugs in cultured cells under in vitro conditions.

PubMed

Palmgrén, Joni J; Mönkkönen, Jukka; Korjamo, Timo; Hassinen, Anssi; Auriola, Seppo

2006-11-01

Loss of drug content during cell culture transport experiment can lead to misinterpretations in permeability analysis. This study analyses drug adsorption to various plastic containers and drug retention in cultured cells under in vitro conditions. The loss of various drugs to polystyrene tubes and well plates was compared to polypropylene and glass tubes both in deionised water and buffer solution. In cellular uptake experiments, administered drugs were obtained from cultured cells by liquid extraction. Samples were collected at various time points and drug concentrations were measured by a new HPLC-MS/MS method. Acidic drugs (hydrochlorothiazide, naproxen, probenicid, and indomethacin) showed little if any sorption to all tested materials in either water or buffer. In the case of basic drugs, substantial loss to polystyrene tubes and well plates was observed. After 4.5 h, the relative amount remaining in aqueous test solution stored in polystyrene tubes was 64.7 +/- 6.8%, 38.4 +/- 9.1%, 31.9 +/- 6.7%, and 23.5 +/- 6.1% for metoprolol, medetomidine, propranolol, and midazolam, respectively. Interestingly, there was no significant loss of drugs dissolved in buffer to any of the tested materials indicating that buffer reduced surficial interaction. The effect of drug concentration to sorption was also tested. Results indicated that the higher the concentration in the test solution the lower the proportional drug loss, suggesting that the polystyrene contained a limited amount of binding sites. Cellular uptake studies showed considerable retention of drugs in cultured cells. The amounts of absorbed drugs in cellular structures were 0.45%, 4.88%, 13.15%, 43.80%, 23.57% and 11.22% for atenolol, metoprolol, medetomidine, propranolol, midazolam, and diazepam, respectively. Overall, these findings will benefit development and validation of further in vitro drug permeation experiments.

Effect of two storage solutions on surface topography of two root-end fillings.

PubMed

Asgary, Saeed; Eghbal, Mohammad Jafar; Parirokh, Masoud; Ghoddusi, Jamileh

2009-12-01

The effect of different storage solutions on surface topography of mineral trioxide aggregate (MTA) and new experimental cement (NEC) as root-end fillings was investigated. Twenty-four single-rooted teeth were cleaned, shaped and obturated in a same manner. After root-end resection, 3-mm deep root-end cavities were ultrasonically prepared. Samples were randomly divided into four test groups (A1-A2-B1-B2, n = 6). Root-end cavities in groups A and B were filled with MTA and NEC, respectively, and were then stored in 100% humidity for 24 h. The samples of groups 1 and 2 were, respectively, immersed in normal saline (NS) and phosphate buffer saline solutions for 1 week. The samples were imaged under stereomicroscope before and after immersion and were then investigated and analysed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA). Results showed significant difference among studied groups. Surface topography of all samples was altered by crystal formation and precipitation on root-end fillings except for group A1 (MTA-NS). SEM and EDXA results showed that the composition and structure of precipitated crystals were comparable with that of standard hydroxyapatite. It was concluded that biocompatibility, sealing ability, and cementogenic activity of MTA and probably NEC may be attributed to this fundamental bioactive reaction.

Long-Term In Vitro Degradation of a High-Strength Brushite Cement in Water, PBS, and Serum Solution

PubMed Central

Ajaxon, Ingrid; Öhman, Caroline; Persson, Cecilia

2015-01-01

Bone loss and fractures may call for the use of bone substituting materials, such as calcium phosphate cements (CPCs). CPCs can be degradable, and, to determine their limitations in terms of applications, their mechanical as well as chemical properties need to be evaluated over longer periods of time, under physiological conditions. However, there is lack of data on how the in vitro degradation affects high-strength brushite CPCs over longer periods of time, that is, longer than it takes for a bone fracture to heal. This study aimed at evaluating the long-term in vitro degradation properties of a high-strength brushite CPC in three different solutions: water, phosphate buffered saline, and a serum solution. Microcomputed tomography was used to evaluate the degradation nondestructively, complemented with gravimetric analysis. The compressive strength, chemical composition, and microstructure were also evaluated. Major changes from 10 weeks onwards were seen, in terms of formation of a porous outer layer of octacalcium phosphate on the specimens with a concomitant change in phase composition, increased porosity, decrease in object volume, and mechanical properties. This study illustrates the importance of long-term evaluation of similar cement compositions to be able to predict the material's physical changes over a relevant time frame. PMID:26587540

Structure, stability and behaviour of nucleic acids in ionic liquids

PubMed Central

Tateishi-Karimata, Hisae; Sugimoto, Naoki

2014-01-01

Nucleic acids have become a powerful tool in nanotechnology because of their conformational polymorphism. However, lack of a medium in which nucleic acid structures exhibit long-term stability has been a bottleneck. Ionic liquids (ILs) are potential solvents in the nanotechnology field. Hydrated ILs, such as choline dihydrogen phosphate (choline dhp) and deep eutectic solvent (DES) prepared from choline chloride and urea, are ‘green’ solvents that ensure long-term stability of biomolecules. An understanding of the behaviour of nucleic acids in hydrated ILs is necessary for developing DNA materials. We here review current knowledge about the structures and stabilities of nucleic acids in choline dhp and DES. Interestingly, in choline dhp, A–T base pairs are more stable than G–C base pairs, the reverse of the situation in buffered NaCl solution. Moreover, DNA triplex formation is markedly stabilized in hydrated ILs compared with aqueous solution. In choline dhp, the stability of Hoogsteen base pairs is comparable to that of Watson–Crick base pairs. Moreover, the parallel form of the G-quadruplex is stabilized in DES compared with aqueous solution. The behaviours of various DNA molecules in ILs detailed here should be useful for designing oligonucleotides for the development of nanomaterials and nanodevices. PMID:25013178

Multianalyte detection using a capillary-based flow immunosensor.

PubMed

Narang, U; Gauger, P R; Kusterbeck, A W; Ligler, F S

1998-01-01

A highly sensitive, dual-analyte detection system using capillary-based immunosensors has been designed for explosive detection. This model system consists of two capillaries, one coated with antibodies specific for 2,4,6-trinitrotoluene (TNT) and the other specific for hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) combined into a single device. The fused silica capillaries are prepared by coating anti-TNT and anti-RDX antibodies onto the silanized inner walls using a hetero-bifunctional crosslinker. After immobilization, the antibodies are saturated with a suitable fluorophorelabeled antigen. A "T" connector is used to continuously flow the buffer solution through the individual capillaries. To perform the assay, an aliquot of TNT or RDX or a mixture of the two analytes is injected into the continuous flow stream. In each capillary, the target analyte displaces the fluorophore-labeled antigen from the binding pocket of the antibody. The labeled antigen displaced from either capillary is detected downstream using two portable spectrofluorometers. The limits of detection for TNT and RDX in the multi-analyte formate are 44 fmol (100 microliters of 0.1 ng/ml TNT solution) and 224 fmol (100 microliters of 0.5 ng/ml RDX solution), respectively. The entire assay for both analytes can be performed in less than 3 min.

Protein Buffering in Model Systems and in Whole Human Saliva

PubMed Central

Lamanda, Andreas; Cheaib, Zeinab; Turgut, Melek Dilek; Lussi, Adrian

2007-01-01

The aim of this study was to quantify the buffer attributes (value, power, range and optimum) of two model systems for whole human resting saliva, the purified proteins from whole human resting saliva and single proteins. Two model systems, the first containing amyloglucosidase and lysozyme, and the second containing amyloglucosidase and α-amylase, were shown to provide, in combination with hydrogencarbonate and di-hydrogenphosphate, almost identical buffer attributes as whole human resting saliva. It was further demonstrated that changes in the protein concentration as small as 0.1% may change the buffer value of a buffer solution up to 15 times. Additionally, it was shown that there was a protein concentration change in the same range (0.16%) between saliva samples collected at the time periods of 13:00 and others collected at 9:00 am and 17:00. The mode of the protein expression changed between these samples corresponded to the change in basic buffer power and the change of the buffer value at pH 6.7. Finally, SDS Page and Ruthenium II tris (bathophenantroline disulfonate) staining unveiled a constant protein expression in all samples except for one 50 kDa protein band. As the change in the expression pattern of that 50 kDa protein band corresponded to the change in basic buffer power and the buffer value at pH 6.7, it was reasonable to conclude that this 50 kDa protein band may contain the protein(s) belonging to the protein buffer system of human saliva. PMID:17327922

Controlled release formulation of an anti-depression drug based on a L-phenylalanate-zinc layered hydroxide intercalation compound

NASA Astrophysics Data System (ADS)

Hashim, Norhayati; Sharif, Sharifah Norain Mohd; Isa, Illyas Md; Hamid, Shahidah Abdul; Hussein, Mohd Zobir; Bakar, Suriani Abu; Mamat, Mazidah

2017-06-01

The intercalation of L-phenylalanate (LP) into the interlayer gallery of zinc layered hydroxide (ZLH) has been successfully executed using a simple direct reaction method. The synthesised intercalation compound, zinc layered hydroxide-L-phenylalanate (ZLH-LP), was characterised using PXRD, FTIR, CHNS, ICP-OES, TGA/DTG, FESEM and TEM. The PXRD patterns of the intercalation compound demonstrate an intense and symmetrical peak, indicating a well-ordered crystalline layered structure. The appearance of an intercalation peak at a low angle of 2θ with a basal spacing of 16.3 Å, signifies the successful intercalation of the L-phenylalanate anion into the interlayer gallery of the host. The intercalation is also validated by FTIR spectroscopy and CHNS elemental analysis. Thermogravimetric analysis confirms that the ZLH-LP intercalation compound has higher thermal stability than the pristine L-phenylalanine. The observed percentage of L-phenylalanate accumulated release varies in each release media, with 84.5%, 79.8%, 63.8% and 61.8% release in phosphate buffer saline (PBS) solution at pH 4.8, deionised water, PBS solution at pH 7.4 and NaCl solution, respectively. The release behaviour of LP from its intercalation compounds in deionised water and PBS solution at pH 4.8 follows pseudo second order, whereas in NaCl solution and PBS solution at pH 7.4, it follows the parabolic diffusion model. This study shows that the synthesised ZLH-LP intercalation compound can be used for the formation of a new generation of materials for targeted drug release with controlled release properties.

Dial-A-Decon Solution Chemistry GAP Testing

DTIC Science & Technology

2012-04-01

34 The tubes were serially diluted using Buttcrfield’s buffer solution and plated in triplicate on Tryptic Soy Agar. Plates were enumerated the...of 200 uL HD to 10 mL of the surfactant solution. The energy to create the oil in water (O/W) emulsions was provided by magnetic stirring. Solutions...emulsify a mixture of water and oil such as HD, one or more emulsifiers are required. Each surfactant system can be characterized by an HLB value

High-performance liquid chromatographic determination of pantoprazole and its main impurities in pharmaceuticals.

PubMed

Letica, Jelena; Marković, Slavko; Zirojević, Jelena; Nikolić, Katarina; Agbaba, Danica

2010-01-01

An RP-HPLC method for simultaneous separation and quantification of pantoprazole and its five main impurities in pharmaceutical formulations was developed and validated. The separation was accomplished on a Zorbax Eclipse XDB C18 column (5 microm particle size, 150 x 4.6 mm id) using a gradient with mobile phase A [buffer-acetonitrile (70 + 30, v/v)], and mobile phase B [buffer-acetonitrile (30 + 70, v/v)]. The buffer was 0.01 M ammonium acetate solution with addition of 1 mL triethylamine/L of the solution, adjusted to pH 4.5 with orthophosphoric acid. The eluent flow rate was 1 mL/min, the temperature of the column was 30 degrees C, and the eluate was monitored at 290 nm. Linearity (r = 0.999), recovery (97.6-105.8%), RSD (0.55-1.90%), and LOQ (0.099-1.48 microg/mL) were evaluated and found to be satisfactory. The proposed method can be used for simultaneous identification and quantification of the analyzed compounds in pharmaceutical formulations.

Hybridization parameters revisited: solutions containing SDS.

PubMed

Rose, Ken; Mason, John O; Lathe, Richard

2002-07-01

Salt concentration governs nucleic acid hybridization according to the Schildkraut-Lifson equation. High concentrations of SDS are used in some common protocols, but the effects of SDS on hybridization stringency have not been reported. We investigated hybridization parameters in solutions containing SDS. With targets immobilized on nylon membranes and PCR- or transcription-generated probes, we report that the 50% dissociation temperature (Tm*) in the absence of SDS was 15 degrees C-17degrees C lower than the calculated Tm. SDS had only modest effects on Tm* [1% (w/v) equating to 8 mM NaCl]. RNA/DNA hybrids were approximately 11 degrees C more stable than DNA/DNA hybrids. Incomplete homology (69%) significantly reduced the Tm* for DNA/DNA hybrids (approximately /4degrees C; 0.45 degrees C/% nonhomology) but far less so for RNA/DNA hybrids (approximately 2.3 degrees C; approximately 0.07 degrees C/% non-homology); incomplete homology also markedly reduced the extent of hybridization. On these nylonfilters, SDS had a major effect on nonspecific binding. Buffers lacking SDS, or with low salt concentration, gave high hybridization backgrounds; buffers containing SDS, or high-salt buffers, gave reproducibly low backgrounds.

Buffer Therapy for Cancer

PubMed Central

Ribeiro, Maria de Lourdes C; Silva, Ariosto S.; Bailey, Kate M.; Kumar, Nagi B.; Sellers, Thomas A.; Gatenby, Robert A.; Ibrahim-Hashim, Arig; Gillies, Robert J.

2013-01-01

Oral administration of pH buffers can reduce the development of spontaneous and experimental metastases in mice, and has been proposed in clinical trials. Effectiveness of buffer therapy is likely to be affected by diet, which could contribute or interfere with the therapeutic alkalinizing effect. Little data on food pH buffering capacity was available. This study evaluated the pH and buffering capacity of different foods to guide prospective trials and test the effect of the same buffer (lysine) at two different ionization states. Food groups were derived from the Harvard Food Frequency Questionnaire. Foods were blended and pH titrated with acid from initial pH values until 4.0 to determine “buffering score”, in mmol H+/pH unit. A “buffering score” was derived as the mEq H+ consumed per serving size to lower from initial to a pH 4.0, the postprandial pH of the distal duodenum. To differentiate buffering effect from any metabolic byproduct effects, we compared the effects of oral lysine buffers prepared at either pH 10.0 or 8.4, which contain 2 and 1 free base amines, respectively. The effect of these on experimental metastases formation in mice following tail vein injection of PC-3M prostate cancer cells were monitored with in vivo bioluminescence. Carbohydrates and dairy products’ buffering score varied between 0.5 and 19. Fruits and vegetables showed a low to zero buffering score. The score of meats varied between 6 and 22. Wine and juices had negative scores. Among supplements, sodium bicarbonate and Tums® had the highest buffering capacities, with scores of 11 and 20 per serving size, respectively. The “de-buffered” lysine had a less pronounced effect of prevention of metastases compared to lysine at pH 10. This study has demonstrated the anti-cancer effects of buffer therapy and suggests foods that can contribute to or compete with this approach to manage cancer. PMID:24371544

Long life hydrocarbon conversion catalyst and method of making

DOEpatents

Tonkovich, Anna Lee Y [Pasco, WA; Wang, Yong [Richland, WA; Gao, Yufei [Kennewick, WA

2002-11-12

The present invention includes a catalyst that has at least four layers, (1) porous support, (2) buffer layer, (3) interfacial layer, and optionally (4) catalyst layer. The buffer layer provides a transition of thermal expansion coefficient from the porous support to the interfacial layer thereby reducing thermal expansion stress as the catalyst is heated to high operating temperatures. The method of the present invention for making the at least three layer catalyst has the steps of (1) selecting a porous support, (2) solution depositing an interfacial layer thereon, and optionally (3) depositing a catalyst material onto the interfacial layer; wherein the improvement comprises (4) depositing a buffer layer between the porous support and the interfacial layer.

Impact of added nutrients in sweet sorghum syrup fermentation to produce ethanol

USDA-ARS?s Scientific Manuscript database

This work demonstrated that sweet sorghum syrup was efficiently converted to ethanol by yeast. Fermentation broth with sweet sorghum syrup performed better (at least faster) than with only pure sugars due to the pH-buffering effect of sweet sorghum syrup solutions. Sugar solutions containing up to 2...

Selective and Sensitive Detection of Heavy Metal Ions in 100% Aqueous Solution and Cells with a Fluorescence Chemosensor Based on Peptide Using Aggregation-Induced Emission.

PubMed

Neupane, Lok Nath; Oh, Eun-Taex; Park, Heon Joo; Lee, Keun-Hyeung

2016-03-15

A fluorescent peptidyl chemosensor for the detection of heavy metal ions in aqueous solution as well as in cells was synthesized on the basis of the peptide receptor for the metal ions using an aggregation-induced emission fluorophore. The peptidyl chemosensor (1) bearing tetraphenylethylene fluorophore showed an exclusively selective turn-on response to Hg(2+) among 16 metal ions in aqueous buffered solution containing NaCl. The peptidyl chemosensor complexed Hg(2+) ions and then aggregated in aqueous buffered solution, resulting in the significant enhancement (OFF-On) of emissions at around 470 nm. The fluorescent sensor showed a highly sensitive response to Hg(2+), and about 1.0 equiv of Hg(2+) was enough for the saturation of the emission intensity change. The detection limit (5.3 nM, R(2) = 0.99) of 1 for Hg(2+) ions was lower than the maximum allowable level of Hg(2+) in drinking water by EPA. Moreover, the peptidyl chemosensor penetrated live cells and detected intracellular Hg(2+) ions by the turn-on response.

Integrated Arrival and Departure Schedule Optimization Under Uncertainty

NASA Technical Reports Server (NTRS)

Xue, Min; Zelinski, Shannon

2014-01-01

In terminal airspace, integrating arrivals and departures with shared waypoints provides the potential of improving operational efficiency by allowing direct routes when possible. Incorporating stochastic evaluation as a post-analysis process of deterministic optimization, and imposing a safety buffer in deterministic optimization, are two ways to learn and alleviate the impact of uncertainty and to avoid unexpected outcomes. This work presents a third and direct way to take uncertainty into consideration during the optimization. The impact of uncertainty was incorporated into cost evaluations when searching for the optimal solutions. The controller intervention count was computed using a heuristic model and served as another stochastic cost besides total delay. Costs under uncertainty were evaluated using Monte Carlo simulations. The Pareto fronts that contain a set of solutions were identified and the trade-off between delays and controller intervention count was shown. Solutions that shared similar delays but had different intervention counts were investigated. The results showed that optimization under uncertainty could identify compromise solutions on Pareto fonts, which is better than deterministic optimization with extra safety buffers. It helps decision-makers reduce controller intervention while achieving low delays.

Nucleation of protein crystals under the influence of solution shear flow.

PubMed

Penkova, Anita; Pan, Weichun; Hodjaoglu, Feyzim; Vekilov, Peter G

2006-09-01

Several recent theories and simulations have predicted that shear flow could enhance, or, conversely, suppress the nucleation of crystals from solution. Such modulations would offer a pathway for nucleation control and provide a novel explanation for numerous mysteries in nucleation research. For experimental tests of the effects of shear flow on protein crystal nucleation, we found that if a protein solution droplet of approximately 5 microL (2-3 mm diameter at base) is held on a hydrophobic substrate in an enclosed environment and in a quasi-uniform constant electric field of 2 to 6 kV cm(-1), a rotational flow with a maximum rate at the droplet top of approximately 10 microm s(-1) is induced. The shear rate varies from 10(-3) to 10(-1) s(-1). The likely mechanism of the rotational flow involves adsorption of the protein and amphiphylic buffer molecules on the air-water interface and their redistribution in the electric field, leading to nonuniform surface tension of the droplet and surface tension-driven flow. Observations of the number of nucleated crystals in 24- and 72-h experiments with the proteins ferritin, apoferritin, and lysozyme revealed that the crystals are typically nucleated at a certain radius of the droplet, that is, at a preferred shear rate. Variations of the rotational flow velocity resulted in suppression or enhancement of the total number of nucleated crystals of ferritin and apoferritin, while all solution flow rates were found to enhance lysozyme crystal nucleation. These observations show that shear flow may strongly affect nucleation, and that for some systems, an optimal flow velocity, leading to fastest nucleation, exists. Comparison with the predictions of theories and simulations suggest that the formation of ordered nuclei in a "normal" protein solution cannot be affected by such low shear rates. We conclude that the flow acts by helping or suppressing the formation of ordered nuclei within mesoscopic metastable dense liquid clusters. Such clusters were recently shown to exist in protein solutions and to constitute the first step in the nucleation mechanism of many protein and nonproteinsystems.

High effective cytosolic H+ buffering in mouse cortical astrocytes attributable to fast bicarbonate transport.

PubMed

Theparambil, Shefeeq M; Deitmer, Joachim W

2015-09-01

Cytosolic H(+) buffering plays a major role for shaping intracellular H(+) shifts and hence for the availability of H(+) for biochemical reactions and acid/base-coupled transport processes. H(+) buffering is one of the prime means to protect the cell from large acid/base shifts. We have used the H(+) indicator dye BCECF and confocal microscopy to monitor the cytosolic H(+) concentration, [H(+)]i, in cultured cortical astrocytes of wild-type mice and of mice deficient in sodium/bicarbonate cotransporter NBCe1 (NBCe1-KO) or in carbonic anhydrase isoform II (CAII-KO). The steady-state buffer strength was calculated from the amplitude of [H(+)]i transients as evoked by CO2/HCO3(-) and by butyric acid in the presence and absence of CO2/HCO3(-). We tested the hypotheses if, in addition to instantaneous physicochemical H(+) buffering, rapid acid/base transport across the cell membrane contributes to the total, "effective" cytosolic H(+) buffering. In the presence of 5% CO2/26 mM HCO3(-), H(+) buffer strength in astrocytes was increased 4-6 fold, as compared with that in non-bicarbonate, HEPES-buffered solution, which was largely attributable to fast HCO3 (-) transport into the cells via NBCe1, supported by CAII activity. Our results show that within the time frame of determining physiological H(+) buffering in cells, fast transport and equilibration of CO2/H(+)/HCO3(-) can make a major contribution to the total "effective" H(+) buffer strength. Thus, "effective" cellular H(+) buffering is, to a large extent, attributable to membrane transport of base equivalents rather than a purely passive physicochemical process, and can be much larger than reported so far. Not only physicochemical H(+) buffering, but also rapid import of HCO3(-) via the electrogenic sodium-bicarbonate cotransporter NBCe1, supported by carbonic anhydrase II (CA II), was identified to enhance cytosolic H(+) buffer strength substantially. © 2015 Wiley Periodicals, Inc.

Red blood cell (RBC) suspensions in confined microflows: Pressure-flow relationship.

PubMed

Stauber, Hagit; Waisman, Dan; Korin, Netanel; Sznitman, Josué

2017-10-01

Microfluidic-based assays have become increasingly popular to explore microcirculation in vitro. In these experiments, blood is resuspended to a desired haematocrit level in a buffer solution, where frequent choices for preparing RBC suspensions comprise notably Dextran and physiological buffer. Yet, the rational for selecting one buffer versus another is often ill-defined and lacks detailed quantification, including ensuing changes in RBC flow characteristics. Here, we revisit RBC suspensions in microflows and attempt to quantify systematically some of the differences emanating between buffers. We measure bulk flow rate (Q) of RBC suspensions, using PBS- and Dextran-40, as a function of the applied pressure drop (ΔP) for two hematocrits (∼0% and 23%). Two distinct microfluidic designs of varying dimensions are employed: a straight channel larger than and a network array similar to the size of individual RBCs. Using the resulting pressure-flow curves, we extract the equivalent hydrodynamic resistances and estimate the relative viscosities. These efforts are a first step in rigorously quantifying the influence of the 'background' buffer on RBC flows within microfluidic devices and thereby underline the importance of purposefully selecting buffer suspensions for microfluidic in vitro assays. Copyright © 2017. Published by Elsevier Ltd.

Inositol bisphosphate and inositol trisphosphate inhibit cell-to-cell passage of carboxyfluorescein in staminal hairs ofSetcreasea purpurea.

PubMed

Tucker, E B

1988-06-01

pH-buffered carboxyfluorescein (Buffered-CF) alone (control), or Buffered-CF solutions containing one of the following: (1)D-myo-inositol (I); (2)D-myo-inositol 2-monophosphate (IP1); (3)D-myo-inositol 1,4-bisphosphate (IP2); (4)D-myo-inositol 1,4,5-trisphosphate (IP3); (5)D-fructose 2,6-diphosphate (F-2,6P2) were microinjected into the terminal cells of staminal hairs ofSetcreasea purpurea Boom. Passage of the CF from this terminal cell along the chain of cells towards the filament was monitored for 5 min using fluorescence microscopy and quantified using computer-assisted fluorescence-intensity video analysis. Cell-to-cell transport of CF in hairs microinjected with Buffered-CF containing either I, IP1 or F-2,6P2 was similar to that in hairs microinjected with Buffered-CF only. On the other hand, cell-to-cell transport of CF in hairs microinjected with Buffered-CF containing either IP2 or IP3 was inhibited. These results indicate that polyphosphoinositols may be involved in the regulation of intercellular transport of low-molecular-weight, hydrophilic molecules in plants.

A mathematical model of tumour and blood pHe regulation: The HCO3-/CO2 buffering system.

PubMed

Martin, Natasha K; Gaffney, Eamonn A; Gatenby, Robert A; Gillies, Robert J; Robey, Ian F; Maini, Philip K

2011-03-01

Malignant tumours are characterised by a low, acidic extracellular pH (pHe) which facilitates invasion and metastasis. Previous research has proposed the potential benefits of manipulating systemic pHe, and recent experiments have highlighted the potential for buffer therapy to raise tumour pHe, prevent metastases, and prolong survival in laboratory mice. To examine the physiological regulation of tumour buffering and investigate how perturbations of the buffering system (via metabolic/respiratory disorders or changes in parameters) can alter tumour and blood pHe, we develop a simple compartmentalised ordinary differential equation model of pHe regulation by the HCO3-/CO2 buffering system. An approximate analytical solution is constructed and used to carry out a sensitivity analysis, where we identify key parameters that regulate tumour pHe in both humans and mice. From this analysis, we suggest promising alternative and combination therapies, and identify specific patient groups which may show an enhanced response to buffer therapy. In addition, numerical simulations are performed, validating the model against well-known metabolic/respiratory disorders and predicting how these disorders could change tumour pHe. Copyright © 2010 Elsevier Inc. All rights reserved.

ZnS/Zn(O,OH)S-based buffer layer deposition for solar cells

DOEpatents

Bhattacharya, Raghu N [Littleton, CO

2009-11-03

The invention provides CBD ZnS/Zn(O,OH)S and spray deposited ZnS/Zn(O,OH)S buffer layers prepared from a solution of zinc salt, thiourea and ammonium hydroxide dissolved in a non-aqueous/aqueous solvent mixture or in 100% non-aqueous solvent. Non-aqueous solvents useful in the invention include methanol, isopropanol and triethyl-amine. One-step deposition procedures are described for CIS, CIGS and other solar cell devices.

40 CFR Appendix B to Subpart Nnn... - Free Formaldehyde Analysis of Insulation Resins by Hydroxylamine Hydrochloride

Code of Federal Regulations, 2012 CFR

2012-07-01

... 4.0 with pH 4.0 buffer and pH 7 with pH 7.0 buffer. 3.350-mL burette for 1.0 N sodium hydroxide. 3.... 3.8Timer. 4. Reagents 4.1Standardized 1.0 N sodium hydroxide solution. 4.2Hydroxylamine.... Start the timer. 5.6Stir for 5 minutes. Titrate to pH 4.0 with standardized 1.0 N sodium hydroxide...

Oral bioavailability of ketoprofen in suspension and solution formulations in rats: the influence of poloxamer 188.

PubMed

Fischer, Sarah Maud; Parmentier, Johannes; Buckley, Stephen Timothy; Reimold, Isolde; Brandl, Martin; Fricker, Gert

2012-11-01

The aim of the current study was to investigate the effect of poloxamer 188 (P-188) on the bioavailability of the BCS class 2 drug ketoprofen in vivo. Aqueous suspension and solution formulations of ketoprofen with and without P-188 were orally administered to fasted male Wistar rats. The intrinsic dissolution rate and solubility of ketoprofen in simulated intestinal fluid, in both the presence and absence of P-188, was measured. The AUC and C(max) were found to be significantly enhanced when ketoprofen was administered as suspension and P-188 was present in the formulation (Susp P-188) as compared to the surfactant-free formulation (∼4-fold higher AUC, 7-fold higher C(max) ). While drug solubility appeared to be almost unaffected by P-188, a significantly faster dissolution was observed. In addition, the influence of P-188 on the drug absorption process was investigated by comparison of solution formulations with and without P-188. The in-vivo performance of these solutions, a pure buffer solution and a P-188-containing buffer solution showed no significant difference, suggesting that the increase in bioavailability for Susp P-188 was primarily a consequence of the dissolution rate-enhancing effect. © 2012 The Authors. JPP © 2012 Royal Pharmaceutical Society.

The roles of buffer layer thickness on the properties of the ZnO epitaxial films

NASA Astrophysics Data System (ADS)

Tang, Kun; Huang, Shimin; Gu, Shulin; Zhu, Shunming; Ye, Jiandong; Xu, Zhonghua; Zheng, Youdou

2016-12-01

In this article, the authors have investigated the optimization of the buffer thickness for obtaining high-quality ZnO epi-films on sapphire substrates. The growth mechanism of the buffers with different thickness has been clearly revealed, including the initial nucleation and vertical growth, the subsequent lateral growth with small grain coalescence, and the final vertical growth along the existing larger grains. Overall, the quality of the buffer improves with increasing thickness except the deformed surface morphology. However, by a full-scale evaluation of the properties for the epi-layers, the quality of the epi-film is briefly determined by the surface morphology of the buffer, rather than the structural, optical, or electrical properties of it. The best quality epi-layer has been grown on the buffer with a smooth surface and well-coalescent grains. Meanwhile, due to the huge lattice mismatch between sapphire and ZnO, dislocations are inevitably formed during the growth of buffers. More importantly, as the film grows thicker, the dislocations may attracting other smaller dislocations and defects to reduce the total line energy and thus result in the formation of V-shape defects, which are connected with the bottom of the threading dislocations in the buffers. The V-defects appear as deep and large hexagonal pits from top view and they may act as electron traps which would affect the free carrier concentration of the epi-layers.

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

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.

Chemical evolution of RNA under hydrothermal conditions and the role of thermal copolymers of amino acids for the prebiotic degradation and formation of RNA

NASA Technical Reports Server (NTRS)

Kawamura, K.; Nagahama, M.; Kuranoue, K.

2005-01-01

The roles of thermal copolymers of amino acids (TCAA) were studied for the prebiotic degradation of RNA. A weak catalytic ability of TCAA consisted of Glu, L-Ala, L-Val, L-Glu, L-Asp, and optionally L-His was detected for the cleavage of the ribose phosphodiester bond of a tetranucleotide (5'-dCrCdGdG) in aqueous solution at 80 degees C. The rate constants of the disappearance of 5'-dCrCdGdG were determined in aqueous solutions using different pH buffer and TCAA. The degradation rates were enhanced 1.3-3.0 times in the presence of TCAA at pH 7.5 and 8.0 at 80 degrees C, while the hydrolysis of oligoguanylate (oligo(G)) was accelerated about 1.6 times at pH 8.0. A weak inhibitory activity for the cleavage of oligo(G) was detected in the presence of 0.055 M TCAA-Std. On the other hand, our recent study on the influences of TCAA for the template-directed reaction of oligo(G) on a polycytidylic acid template showed that TCAA has an acceleration activity for the degradation of the activated nucleotide monomer and an acceleration activity for the formation of G5' ppG capped oligo(G). This series of studies suggest that efficient and selective catalytic or inhibitory activities for either the degradation or formation of RNA under hydrothermal conditions could have hardly emerged from the simple thermal condensation products of amino acids. A scenario is going to be deduced on the chemical evolution of enzymatic activities and RNA molecules concerning hydrothermal earth conditions. c2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

The kinetics of lanthanide complexation by EDTA and DTPA in lactate media.

PubMed

Nash, K L; Brigham, D; Shehee, T C; Martin, A

2012-12-28

The interaction of trivalent lanthanide and actinide cations with polyaminopolycarboxylic acid complexing agents in lactic acid buffer systems is an important feature of the chemistry of the TALSPEAK process for the separation of trivalent actinides from lanthanides. To improve understanding of metal ion coordination chemistry in this process, the results of an investigation of the kinetics of lanthanide complexation by ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) and diethylenetriamine-N,N,N',N'',N''-pentaacetic acid (DTPA) in 0.3 M lactic acid/0.3 M ionic strength solution are reported. Progress of the reaction was monitored using the distinctive visible spectral changes attendant to lanthanide complexation by the colorimetric indicator ligand Arsenazo III, which enables the experiment but plays no mechanistic role. Under the conditions of these experiments, the reactions occur in a time regime suitable for study by stopped-flow spectrophotometric techniques. Experiments have been conducted as a function of EDTA/DTPA ligand concentration, total lactic acid concentration, and pH. The equilibrium perturbation reaction proceeds as a first order approach to equilibrium over a wide range of conditions, allowing the simultaneous determination of complex formation and dissociation rate constants. The rate of the complexation reaction has been determined for the entire lanthanide series (except Pm(3+)). The predominant pathway for lanthanide-EDTA and lanthanide-DTPA dissociation is inversely dependent on the total lactate concentration; the complex formation reaction demonstrates a direct dependence on [H(+)]. Unexpectedly, the rate of the complex formation reaction is seen in both ligand systems to be fastest for Gd(3+). Correlation of these results indicates that in 0.3 M lactate solutions the exchange of lanthanide ions between lactate complexes and the polyaminopolycarboxylate govern the process.

Solution formulation development of a VEGF inhibitor for intravitreal injection.

PubMed

Marra, Michelle T; Khamphavong, Penney; Wisniecki, Peter; Gukasyan, Hovhannes J; Sueda, Katsuhiko

2011-03-01

PF-00337210 is a potent, selective small molecule inhibitor of VEGFRs and has been under consideration for the treatment of age-related macular degeneration. An ophthalmic solution formulation intended for intravitreal injection was developed. This formulation was designed to maximize drug properties such that the formulation would precipitate upon injection into the vitreous for sustained delivery. As a parenteral formulation with additional constraints dictated by this specialized delivery route, multiple features were balanced in order to develop a successful formulation. Some of these considerations included low dosing volumes (≤0.1 mL), a limited repertoire of safe excipients for intravitreal injection, and the unique physical chemical properties of the drug. The aqueous solubility as a function of pH was characterized, buffer stressing studies to select the minimal amount of buffer were conducted, and both chemical and physical stability studies were executed. The selected formulation consisted of an isotonic solution comprised of PF-00337210 free base in a citrate-buffered vehicle containing NaCl for tonicity. The highest strength for regulatory toxicology studies was 60 mg/mL. The selected formulation exhibited sufficient chemical stability upon storage with no precipitation, and acceptable potency and recovery through an intravitreal dosing syringe. Formulation performance was simulated by precipitation experiments using extracted vitreous humor. In simulated injection experiments, PF-00337210 solutions reproducibly precipitated upon introduction to the vitreous so that a depot was formed. To our knowledge, this is the first time that a nonpolymeric in situ-forming depot formulation has been developed for intravitreal delivery, with the active ingredient as the precipitating agent. © 2011 American Association of Pharmaceutical Scientists

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.

Electrophoretic extraction of proteins from two-dimensional electrophoresis gel spots

DOEpatents

Zhang, Jian-Shi; Giometti, C.S.; Tollaksen, S.L.

1987-09-04

After two-dimensional electrophoresis of proteins or the like, resulting in a polyacrylamide gel slab having a pattern of protein gel spots thereon, an individual protein gel spot is cored out from the slab, to form a gel spot core which is placed in an extraction tube, with a dialysis membrane across the lower end of the tube. Replicate gel spots can be cored out from replicate gel slabs and placed in the extraction tube. Molten agarose gel is poured into the extraction tube where the agarose gel hardens to form an immobilizing gel, covering the gel spot cores. The upper end portion of the extraction tube is filled with a volume of buffer solution, and the upper end is closed by another dialysis membrane. Upper and lower bodies of a buffer solution are brought into contact with the upper and lower membranes and are provided with electrodes connected to the positive and negative terminals of a dc power supply, thereby producing an electrical current which flows through the upper membrane, the volume of buffer solution, the agarose, the gel spot cores and the lower membrane. The current causes the proteins to be extracted electrophoretically from the gel spot cores, so that the extracted proteins accumulate and are contained in the space between the agarose gel and the upper membrane. 8 figs.

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.

Characterization of a protein conjugate using an asymmetrical-flow field-flow fractionation and a size-exclusion chromatography with multi-detection system.

PubMed

Rebolj, Katja; Pahovnik, David; Zagar, Ema

2012-09-04

In this study we present detailed characterization of a protein-PEG conjugate using two separation techniques, that is, asymmetrical-flow field-flow fractionation (AF4) and size-exclusion chromatography (SEC), which were online coupled to a series of successively connected detectors: an ultraviolet, a multiangle light-scattering, a quasi-elastic light-scattering, and a refractive-index detector (UV-MALS(QELS)-RI). Matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used as a complementary characterization technique. The results of AF4 as well as SEC on two columns connected in series, with both separation techniques coupled to a multidetection system, indicate the uniform molar mass and chemical composition of the conjugate, that is, the molar ratio of protein to PEG is 1/1, the presence of minute amounts of residual unreacted protein and the aggregates with the same chemical composition as that of the conjugate. Since the portion of aggregated species is smaller in the acetate buffer solution containing 5% sorbitol than in the acetate buffer solution with 200-mM sodium chloride, the former buffer solution is more suitable for conjugate storage. The separation using only one SEC column results in poorly resolved peaks of the PEGylated protein conjugate and the aggregates, whereas MALDI-TOF MS analysis reveal the presence of the residual protein, but not the aggregates.

Modified DALI LDL-apheresis using trisodium citrate anticoagulation plus bicarbonate or lactate-buffered hemofiltration substitution fluids as primers.

PubMed

Bosch, T; Wendler, T; Maschke, H

2003-06-01

DALI (direct adsorption of lipids) is the first LDL-apheresis technique able to adsorb low-density lipoprotein (LDL) and lipoproteina) directly from whole blood. In the standard procedure, acid citrate dextrose (ACD-A) is used as anticoagulation and the adsorber is rinsed with a specially manufactured priming solution (PS). Using neutral trisodium citrate (TSC) instead of ACD-A might improve the acid-base homeostasis during DALI apheresis; moreover, applying wholesale hemofiltration solutions instead of the special PS might avoid the use of two separate solutions for both priming before and reinfusion after the treatment, thus simplifiying the procedure. The present study was performed to test the effect of neutral (TSC) anticoagulation and of two different commercially available hemofiltration (HF) priming solutions on the efficacy and biocompatibility of DALI apheresis. Five hypercholesterolemic chronic DALI patients were treated prospectively, on a weekly or biweekly basis, 3 times each by standard DALI-apheresis (A). by DALI using 4% TSC and bicarbonate-buffered HF BIC35-210 priming (B). as well as by DALI using 4% TSC and lactate-buffered HF 23 priming (C). After the sessions, the extracorporeal circuit (ECC) was rinsed with saline in study arm A and with the corresponding HF solutions in study arms B and C, respectively. Acute LDL-cholesterol reductions in the study arms A/B/C averaged 64/64/63%, for Lp(a) 62/64/62%, respectively (n=15). Clinically, all sessions were essentially uneventful and no clots were observed in the ECC. No major differences were found between the 3 study arms with respect to biocompatibility (elastase, C3a, thrombin-antithrombin, beta-thromboglobulin, bradykinin). DALI apheresis using TSC anticoagulation and HF solutions for both priming and reinfusion proved to be as safe and effective as the standard DALI apheresis. These modifications, however, further simplify the procedure.

Improved biocompatibility of bicarbonate/lactate-buffered PDF is not related to pH.

PubMed

Zareie, Mohammad; Keuning, Eelco D; ter Wee, Piet M; Schalkwijk, Casper G; Beelen, Robert H J; van den Born, Jacob

2006-01-01

Chronic exposure to conventional peritoneal dialysis fluid (PDF) is associated with functional and structural alterations of the peritoneal membrane. The bioincompatibility of conventional PDF can be due to hypertonicity, high glucose concentration, lactate buffering system, presence of glucose degradation products (GDPs) and/or acidic pH. Although various investigators have studied the sole effects of hyperosmolarity, high glucose, GDPs and lactate buffer in experimental PD, less attention has been paid to the chronic impact of low pH in vivo. Rats received daily 10 ml of either conventional lactate-buffered PDF (pH 5.2; n=7), a standard bicarbonate/lactate-buffered PDF with physiological pH (n=8), bicarbonate/lactate-buffered PDF with acidic pH (adjusted to pH 5.2 with 1 N hydrochloride, n=5), or bicarbonate/lactate buffer, without glucose, pH 7.4 (n=7). Fluids were instilled via peritoneal catheters connected to implanted subcutaneous mini vascular access ports for 8 weeks. Control animals with or without peritoneal catheters served as control groups (n=8/group). Various functional (2 h PET) and morphological/cellular parameters were analyzed. Compared with control groups and the buffer group, conventional lactate-buffered PDF induced a number of morphological/cellular changes, including angiogenesis and fibrosis in various peritoneal tissues (all parameters P<0.05), accompanied by increased glucose absorption and reduced ultrafiltration capacity. Daily exposure to standard or acidified bicarbonate/lactate-buffered PDF improved the performance of the peritoneal membrane, evidenced by reduced new vessel formation in omentum (P<0.02) and parietal peritoneum (P<0.008), reduced fibrosis (P<0.02) and improved ultrafiltration capacity. No significant differences were found between standard and acidified bicarbonate/lactate-buffered PDF. During PET, acidic PDF was neutralized within 15 to 20 min. The bicarbonate/lactate-buffered PDF, acidity per se did not contribute substantially to peritoneal worsening in our in vivo model for PD, which might be explained by the buffering capacity of the peritoneum.

[Study on the interaction of hemoglobin and Cu(II)-ARS complex].

PubMed

Wu, Xiao-Hua; Miao, Ji-Gen; Miao, Yu-Qing; Chen, Jian-Rong

2007-06-01

The reaction of hemoglobin (Hb) with copper(II)-Alizarin red S (ARS) complex was studied in H3PO4-KH2PO4 buffer solution (pH 4. 2) by ultraviolet-visible spectrophotometry. The results show that the interaction of Hb and Cu(II)-ARS complex produces red ionic association complex with its maximum absorption peak at 537 nm. At the maximum absorption, the composition of the complex was determined to be n(Hb) : n(Cu(II)) : n(ARS) =1 : 4 : 8, and the apparent molar absorptivity was 1.52 x 10(5) L x mol(-1) x cm(-1). The concentration of Hb is linear with the absorbency in the range of 1.0 x 10(-7)-2.0 x 10(-6) mol x L(-1) and the regression equation was established as A = 0.026 9 + 151 675c (mol x L(-1)) with the coefficient r = 0.997 2. The effects of solution acidity, reagent amount, reaction time, temperature, ionic strength and the added surfactant were examined on the formation of the Hb-Cu(II)-ARS complex. A preliminary investigation was carried out to elucidate the reaction mechanism, and it could be concluded that the Hb and Cu(II)-ARS complex are combined mainly by electrostatic attraction. Further investigation was also undertaken to find out the effects of common amino acids and metallic ions on the formation of Hb-Cu(II)-ARS complex.

Study on the interaction of graphene oxide‑silver nanocomposites with bovine serum albumin and the formation of nanoparticle-protein corona.

PubMed

Xu, Xiangyu; Mao, Xuyan; Wang, Yunfei; Li, Dandan; Du, Zhongyu; Wu, Weihua; Jiang, Liang; Yang, Jie; Li, Jianjun

2018-05-09

The interaction between graphene oxide-sliver nanocomposites (GO-AgNCPs) and bovine serum albumin (BSA) in aqueous buffer solution was investigated by using several spectroscopic and imaging techniques. The visible absorbance intensity of GO-AgNCPs increased with increasing concentrations of BSA, and a slight redshift of the surface plasmon resonance band (SPR) occurred due to the absorption of BSA on the surface of GO-AgNCPs. Fluorescence data revealed a static quenching process of BSA caused by GO-AgNCPs. Thermodynamic parameters of the absorption process, including adsorption equilibrium constants, changes in Gibbs free energy (ΔG), enthalpy (ΔH) and entropy (ΔS), were evaluated at different temperatures. Negative values of ΔG showed that this process was spontaneous and the BSA-GO-AgNCPs complex might form in aqueous solution. Negative values of ΔH and ΔS suggested that the binding was mainly an enthalpy-driven process, and van der Waals forces and hydrogen bonding were the major force in the formation of the nanoparticle-protein corona. Analysis of synchronous, three dimensional (3D) fluorescence and circular dichroism (CD) spectra demonstrated that the conformation of BSA was slightly altered in the presence of GO-AgNCPs. The protein corona formed on the surface of GO-AgNCPs was directly observed by scanning probe microscopy (SPM). Copyright © 2018 Elsevier B.V. All rights reserved.

Evaluation of sonication treatment and buffer composition on rumen bacteria protein extraction and carboxymethylcellulase activity.

PubMed

Prauchner, Carlos A; Kozloski, Gilberto V; Farenzena, Roberta

2013-05-01

The methodological procedures for studying the fibrolytic activity of rumen bacteria are not clearly established. In this study the efficiency of sonication treatment and buffer composition (i.e. buffer varying in tonicity or pH) on the level of protein extraction from the residue of forage samples incubated in the rumen of a grazing steer and the effect of buffer composition or CaCl₂ concentration on the carboxymethylcellulase (CMCase) activity of the released protein were evaluated. The amount of protein released from the residue of incubation was higher (P < 0.05) for the sonicated material and increased linearly with increasing buffer pH (P < 0.05). The CMCase activity of the released protein was not improved by sonication treatment, whereas it was higher (P < 0.05) for hypotonic than for hypertonic buffer. Both linear and quadratic effects (P < 0.05) of buffer pH on CMCase activity were significant, with CMCase activity being maximal at pH 5.4-6.1. CMCase activity was higher (P < 0.05) at a CaCl₂ concentration of 1 mmol L(-1) compared with lower values. Although sonication treatment increases the amount of protein extracted from rumen bacteria adhered to the residue of incubation, the CMCase activity of the released protein might be measured without sonication treatment and should be carried out with a hypotonic buffer solution that includes a calcium source. When pH is not a treatment factor, the buffer pH should be between 5.5 and 6. © 2012 Society of Chemical Industry.

SnS2 films deposited from molecular ink as Cd-free alternative buffer layer for solar cells

NASA Astrophysics Data System (ADS)

Jariwala, Akshay; Chaudhuri, Tapas K.; Toshniwal, Aditi; Patel, Sanjay; Kheraj, Vipul; Ray, Abhijit

2018-05-01

This work investigates the potential of SnS2 as a Cd-free alternative buffer layer for CIGS solar cells. The suitability of SnS2 film as a buffer layer has been evaluated by numerical analysis using SCAPS software. A new simple method for preparation of SnS2 films by dip-coating from molecular ink is reported. The formation of SnS2 is confirmed by Raman spectroscopy. The films are smooth and shiny with roughness of 2-3 nm. The films are n-type with band gap of 2.6 eV and electrical conductivity of 10-3 S/cm.

Ca2+ transients in cardiac myocytes measured with high and low affinity Ca2+ indicators.

PubMed Central

Berlin, J R; Konishi, M

1993-01-01

Intracellular calcium ion ([Ca2+]i) transients were measured in voltage-clamped rat cardiac myocytes with fura-2 or furaptra to quantitate rapid changes in [Ca2+]i. Patch electrode solutions contained the K+ salt of fura-2 (50 microM) or furaptra (300 microM). With identical experimental conditions, peak amplitude of stimulated [Ca2+]i transients in furaptra-loaded myocytes was 4- to 6-fold greater than that in fura-2-loaded cells. To determine the reason for this discrepancy, intracellular fura-2 Ca2+ buffering, kinetics of Ca2+ binding, and optical properties were examined. Decreasing cellular fura-2 concentration by lowering electrode fura-2 concentration 5-fold, decreased the difference between the amplitudes of [Ca2+]i transients in fura-2 and furaptra-loaded myocytes by twofold. Thus, fura-2 buffers [Ca2+]i under these conditions; however, Ca2+ buffering is not the only factor that explains the different amplitudes of the [Ca2+]i transients measured with these indicators. From the temporal comparison of the [Ca2+]i transients measured with fura-2 and furaptra, the apparent reverse rate constant for Ca2+ binding of fura-2 was at least 65s-1, much faster than previously reported in skeletal muscle fibers. These binding kinetics do not explain the difference in the size of the [Ca2+]i transients reported by fura-2 and furaptra. Parameters for fura-2 calibration, Rmin, Rmax, and beta, were obtained in salt solutions (in vitro) and in myocytes exposed to the Ca2+ ionophore, 4-Br A23187, in EGTA-buffered solutions (in situ). Calibration of fura-2 fluorescence signals with these in situ parameters yielded [Ca2+]i transients whose peak amplitude was 50-100% larger than those calculated with in vitro parameters. Thus, in vitro calibration of fura-2 fluorescence significantly underestimates the amplitude of the [Ca2+]i transient. These data suggest that the difference in amplitude of [Ca2+]i transients in fura-2 and furaptra-loaded myocytes is due, in part, to Ca2+ buffering by fura-2 and use of in vitro calibration parameters. PMID:8274651

Functional and molecular characterization of transmembrane intracellular pH regulators in human dental pulp stem cells.

PubMed

Chen, Gunng-Shinng; Lee, Shiao-Pieng; Huang, Shu-Fu; Chao, Shih-Chi; Chang, Chung-Yi; Wu, Gwo-Jang; Li, Chung-Hsing; Loh, Shih-Hurng

2018-06-01

Homeostasis of intracellular pH (pH i ) plays vital roles in many cell functions, such as proliferation, apoptosis, differentiation and metastasis. Thus far, Na + -H + exchanger (NHE), Na + -HCO 3 - co-transporter (NBC), Cl - /HCO 3 - exchanger (AE) and Cl - /OH - exchanger (CHE) have been identified to co-regulate pH i homeostasis. However, functional and biological pH i -regulators in human dental pulp stem cells (hDPSCs) have yet to be identified. Microspectrofluorimetry technique with pH-sensitive fluorescent dye, BCECF, was used to detect pH i changes. NH 4 Cl and Na + -acetate pre-pulse were used to induce intracellular acidosis and alkalosis, respectively. Isoforms of pH i -regulators were detected by Western blot technique. The resting pH i was no significant difference between that in HEPES-buffered (nominal HCO 3 - -free) solution or CO 2 /HCO 3 -buffered system (7.42 and 7.46, respectively). The pH i recovery following the induced-intracellular acidosis was blocked completely by removing [Na + ] o , while only slowed (-63%) by adding HOE694 (a NHE1 specific inhibitor) in HEPES-buffered solution. The pH i recovery was inhibited entirely by removing [Na + ] o , while adding HOE 694 pulse DIDS (an anion-transporter inhibitor) only slowed (-55%) the acid extrusion. Both in HEPES-buffered and CO 2 /HCO 3 -buffered system solution, the pH i recovery after induced-intracellular alkalosis was entirely blocked by removing [Cl - ] o . Western blot analysis showed the isoforms of pH i regulators, including NHE1/2, NBCe1/n1, AE1/2/3/4 and CHE in the hDPSCs. We demonstrate for the first time that resting pH i is significantly higher than 7.2 and meditates functionally by two Na + -dependent acid extruders (NHE and NBC), two Cl - -dependent acid loaders (CHE and AE) and one Na + -independent acid extruder(s) in hDPSCs. These findings provide novel insight for basic and clinical treatment of dentistry. Copyright © 2018 Elsevier Ltd. All rights reserved.

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.

The early growth and interface of YBa 2Cu 3O y thin films deposited on YSZ substrates

NASA Astrophysics Data System (ADS)

Gao, J.; Tang, W. H.; Yau, C. Y.

2001-11-01

Epitaxial thin films of YBa 2Cu 3O y (YBCO) have been prepared on yttrium-stabilized zirconia substrates with and without a buffer layer. The early growth, crystallinity and surface morphology of these thin films have been characterized by X-ray diffraction, rocking curves, scanning electron microscope, in situ conductance measurements, and surface step profiler. The full width at half maximum of the ( 0 0 5 ) peak of rocking curve was found to be less than 0.1°. Over a wide scanning range of 2000 μm the average surface roughness is just 5 nm, indicating very smooth films. Grazing incident X-ray reflection and positron annihilation spectroscopy shows well-defined interfaces between layers and substrate. By applying a new Eu 2CuO 4 (ECO) buffer layer the initial formation of YBCO appears to grow layer-by-layer rather than the typical island growth mode. The obtained results reveal significant improvements at the early formation and crystallinity of YBCO by using the 214-T ‧ ECO as a buffer layer.

Radiation chemistry of physiological saline reinvestigated: evidence that chloride-derived intermediates play a key role in cytotoxicity.

PubMed

Saran, M; Bors, W

1997-01-01

Contrary to common belief, hydrogen peroxide (H2O2) and hypochlorite (HOCl) are not produced continuously and independently during the irradiation of buffer solution containing chloride. Different buildup and decay reactions are involved in a complex interaction of these substances during irradiation. Which of the species predominates is determined by the parameters of the solution. The amount of either compound detectable after irradiation depends on the dissolved gas (O2, N2O or N2), on the pH value and to some extent on the presence of catalytic metals: Under slightly acidic conditions, low oxygen content and high generation rates of OH radicals, the only detectable species is hypochlorite; at high oxygen content and at pH values in the physiological range, hydrogen peroxide is the main detectable product. However, H2O2 and HOCl react with each other in a pH-dependent way, yielding the stable products O2 and Cl-. This reaction limits the expected lifetime of both species in aqueous solution to some tens of seconds. Therefore, analysis of the sample solution after irradiation determines only the substance that was present in greater relative concentration at the termination of irradiation. Such analysis, however, does not allow conclusions about the processes that occurred during irradiation. We have investigated the decay and formation reactions of H2O2 and HOCl under all relevant irradiation conditions and found evidence that the formation and further reaction of HOCl-, the precursor of HOCl, is of central importance even in cases where no significant amounts of H2O2 or HOCl are detectable after irradiation. We discuss the consequences of these results for the cytotoxicity observed after irradiation of cells suspended in physiological saline and conclude that analogous processes must also be relevant for irradiations under in vivo conditions.

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.

Effect of Carboxymethylation on the Rheological Properties of Hyaluronan

PubMed Central

Wendling, Rian J.; Christensen, Amanda M.; Quast, Arthur D.; Atzet, Sarah K.; Mann, Brenda K.

2016-01-01

Chemical modifications made to hyaluronan to enable covalent crosslinking to form a hydrogel or to attach other molecules may alter the physical properties as well, which have physiological importance. Here we created carboxymethyl hyaluronan (CMHA) with varied degree of modification and investigated the effect on the viscosity of CMHA solutions. Viscosity decreased initially as modification increased, with a minimum viscosity for about 30–40% modification. This was followed by an increase in viscosity around 45–50% modification. The pH of the solution had a variable effect on viscosity, depending on the degree of carboxymethyl modification and buffer. The presence of phosphates in the buffer led to decreased viscosity. We also compared large-scale production lots of CMHA to lab-scale and found that large-scale required extended reaction times to achieve the same degree of modification. Finally, thiolated CMHA was disulfide crosslinked to create hydrogels with increased viscosity and shear-thinning aspects compared to CMHA solutions. PMID:27611817

Direct Assembly of Modified Proteins on Carbon Nanotubes in an Aqueous Solution

NASA Technical Reports Server (NTRS)

Kim, Jae-Woo; Lillehei, Peter T.; Park, Cheol; Harrison, Joycelyn S.

2007-01-01

Carbon nanotubes (CNTs) have superior mechanical and electrical properties that have opened up many potential applications. However, poor dispersibility and solubility, due to the substantial van der Waals attraction between tubes, have prevented the use of CNTs in practical applications, especially biotechnology applications. Effective dispersion of CNTs into small bundles or individual tubes in solvents is crucial to ensure homogeneous properties and enable practical applications. In addition to dispersion of CNTs into a solvent, the selection of appropriate solvent, which is compatible with a desired matrix, is an important factor to improve the mechanical, thermal, optical, and electrical properties of CNT-based fibers and composites. In particular, dispersion of CNTs into an aqueous system has been a challenge due to the hydrophobic nature of CNTs. Here we show an effective method for dispersion of both single wall CNTs (SWCNTs) and few wall CNTs (FWCNTs) in an aqueous buffer solution. We also show an assembly of cationized Pt-cored ferritins on the well dispersed CNTs in an aqueous buffer solution.

Corrosion in low dielectric constant Si-O based thin films: Buffer concentration effects

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

Zeng, F. W.; Lane, M. W., E-mail: mlane@ehc.edu; Gates, S. M.

2014-05-15

Organosilicate glass (OSG) is often used as an interlayer dielectric (ILD) in high performance integrated circuits. OSG is a brittle material and prone to stress-corrosion cracking reminiscent of that observed in bulk glasses. Of particular concern are chemical-mechanical planarization techniques and wet cleans involving solvents commonly encountered in microelectronics fabrication where the organosilicate film is exposed to aqueous environments. Previous work has focused on the effect of pH, surfactant, and peroxide concentration on the subcritical crack growth of these films. However, little or no attention has focused on the effect of the conjugate acid/base concentration in a buffer. Accordingly, thismore » work examines the “strength” of the buffer solution in both acidic and basic environments. The concentration of the buffer components is varied keeping the ratio of acid/base and therefore pH constant. In addition, the pH was varied by altering the acid/base ratio to ascertain any additional effect of pH. Corrosion tests were conducted with double-cantilever beam fracture mechanics specimens and fracture paths were verified with ATR-FTIR. Shifts in the threshold fracture energy, the lowest energy required for bond rupture in the given environment, G{sub TH}, were found to shift to lower values as the concentration of the base in the buffer increased. This effect was found to be much larger than the effect of the hydroxide ion concentration in unbuffered solutions. The results are rationalized in terms of the salient chemical bond breaking process occurring at the crack tip and modeled in terms of the chemical potential of the reactive species.« less

Branch target buffer design and optimization

NASA Technical Reports Server (NTRS)

Perleberg, Chris H.; Smith, Alan J.

1993-01-01

Consideration is given to two major issues in the design of branch target buffers (BTBs), with the goal of achieving maximum performance for a given number of bits allocated to the BTB design. The first issue is BTB management; the second is what information to keep in the BTB. A number of solutions to these problems are reviewed, and various optimizations in the design of BTBs are discussed. Design target miss ratios for BTBs are developed, making it possible to estimate the performance of BTBs for real workloads.