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Low Solubility (low + solubility)
Selected AbstractsSolubilities and surface activities of phthalates investigated by surface tension measurementsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2001Marianne Thomsen Abstract Aueous solutions of DEP (di-ethyl), DnBP (di- n -butyl), DnH(6)P (di- n -hexyl), and DEHP (di-[2-ethyl-hexyl])phthalates have been investigated by use of surface tension measurements at temperatures between 10 and 35°C. A tensiometric approach allows for the determination of unimeric solubilities and ,G°, which is the standard Gibbs free energy change, for the dissolution of phthalates in water. The unimeric solubility of the phthalates increase with decreasing temperature. The ,G° shows a linear increase with increasing phthalate alkyl chain length. The contribution of enthalpy (,H°) and entropy (,S°) to ,G° were calculated from the temperature-dependent solubilities. The contributions of both ,H° and ,S° are negative and increase in magnitude with increasing alkyl chain length, suggesting hydrophobic interactions between phthalates and water. The ability of different phthalates to lower the surface tension decreases with increasing alkyl chain length, whereas the relative affinity for adsorption in the air-water interface increases drastically for long-chain phthalates. Despite the low surface activity of phthalates compared with that of common surfactants, they show significant affinity for adsorption in air-water interfaces of natural surface waters. This property, combined with their low solubilities, may affect the fate of these compounds within the natural environment, because they form emulsions above unimeric saturation in aqueous media. [source] Evidence for an amphipathicity independent cellular uptake of amphipathic cell-penetrating peptidesFEBS JOURNAL, Issue 19 2000Anne Scheller The cellular uptake of a peptide set derived from membrane-permeable ,-helical amphipathic peptides by stepwise alterations of structure forming propensity and charge was studied by confocal laser scanning microscopy (CLSM) combined with HPLC. For CLSM monitoring, an online protocol was employed that avoided bias of the uptake results by washout. Using this protocol, extensive fluorescence, approaching the intensity of the external peptide, was observed in the cytosol and nucleus within minutes in all cases, irrespective of the degree of amphipathicity. HPLC analyses of the cell lysates revealed the unmetabolized peptides to be the predominant source of the intracellular fluorescence. Significant amphipathicity-dependent differences became apparent only after washing the peptide-loaded cells, reflecting the effects of amphipathicity on resistance to wash out. Exposure of the cells to the peptides at 37 and 0 °C led to similar results, indicating the nonendocytic character of the uptake. With a view to practical applications , the results of the present study open the possibility of exploiting nonamphipathic peptides as vectors for translocating polar compounds into the cell interior, which would circumvent substantial obstacles currently connected with the use of amphipathic vector peptides, such as membrane toxicity and low solubility. Moreover, differences in the uptake of several members of the investigated peptide series into different cell types present a promising basis for the design of cell-type specific vector peptides. [source] Organoselenium-substituted poly(p -phenylenevinylene)HETEROATOM CHEMISTRY, Issue 7 2005Nicolai Stuhr-Hansen A new type of conjugated polymer, organoselenium substituted poly(p -phenyleneviny- lene) (PPV), was synthesized from the corresponding alkylselenenyl p -xylylene dibromide via a Gilch route using potassium tert -butoxide in THF. The p -xylylene dibromide precursors were synthesized by reacting lithiated bis(methoxymethyl)benzenes with elemental selenium, followed by alkylation of the generated selenolates. As a final demasking step, the bromomethyl functions were liberated by ether cleavage using boron tribromide. Bis-alkylselenenyl PPV was obtained with an average molecular weight Mw of approximately 300,000 g/mol and with polydispersity Mw/Mn = 2. Due to low solubility, monoalkylselenenyl PPV was obtained with a considerably lower average molecular weight in the proximity of 16,000 g/mol and with a polydispersity slightly larger than 3. Absorption and fluorescence spectroscopy revealed that the bis-alkylselenenyl PPV is extensively conjugated. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:656,662, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20167 [source] Solubility of root-canal sealers in water and artificial salivaINTERNATIONAL ENDODONTIC JOURNAL, Issue 10 2003E. Schäfer Abstract Aim, To compare the weight loss of eight different root-canal sealers in water and in artificial saliva with different pH values. Methodology, For standardized samples (n = 12 per group), ring moulds were filled with epoxy resin (AH 26, AH Plus)-, silicone (RSA RoekoSeal)-, calcium hydroxide (Apexit, Sealapex)-, zinc oxide,eugenol (Aptal-Harz)-, glass-ionomer (Ketac Endo)- and polyketone (Diaket)-based sealers. These samples were immersed in double-distilled water or artificial saliva with different pH values (7.0, 5.7 and 4.5) for 30 s, 1 min, 2 min, 5 min, 10 min, 20 min, 1 h, 2 h, 10 h, 24 h, 48 h, 72 h, 14 days and 28 days. Mean loss of weight was determined and analysed statistically using a one-way anova and Student,Newman,Keuls test for all pairwise comparisons. Results, Most sealers were of low solubility, although Sealapex, Aptal-Harz and Ketac Endo showed a marked weight loss in all liquids. Even after 28 days of storage in water, AH 26, AH Plus, RSA RoekoSeal, and Diaket showed less than 3% weight loss. At exposure times greater than 14 days, Sealapex showed the significantly greatest weight loss of all sealers tested (P < 0.05). Aptal-Harz and Ketac Endo were significantly more soluble in saliva (pH 4.5) than in water (P < 0.05). Conclusions, Under the conditions of the present study, AH Plus showed the least weight loss of all sealers tested, independent of the solubility medium used. Sealapex, Aptal-Harz and Ketac Endo had a marked weight loss in all liquids. [source] Dissolution of root canal sealer cements in volatile solventsINTERNATIONAL ENDODONTIC JOURNAL, Issue 1 2000J. M. Whitworth Whitworth JM, Boursin EM. Dissolution of root canal sealer cements in volatile solvents. International Endodontic Journal, 33, 19,24, 2000. Aim There are few published data on the solubility profiles of endodontic sealers in solvents commonly employed in root canal retreatment. This study tested the hypothesis that root canal sealer cements are insoluble in the volatile solvents chloroform and halothane. Methodology Standardized samples (n=5) of glass ionomer (Ketac Endo), zinc oxide-eugenol (Tubli-Seal EWT), calcium hydroxide (Apexit) and epoxy resin (AH Plus) based sealers were immersed in chloroform or halothane for 30 s, 1 min, 5 min and 10 min. Mean loss of weight was plotted against time of exposure, and differences in behaviour assessed by multiple paired t-tests (P <0.01). Results Clear differences were shown in the solubility profiles of major classes of root canal sealer cements in two common volatile solvents. In comparison with other classes of material, Ketac Endo was the least soluble in chloroform and halothane (P <0.01), with less than 1% weight loss after 10 min exposure to either solvent. Apexit had low solubility with 11.6% and 14.19% weight loss after 10 min exposure to chloroform and halothane, respectively. The difference between solvents was not significant (P >0.01). Tubli-Seal EWT was significantly less soluble in halothane than chloroform (5.19% and 62.5% weight loss after 10 min exposure, respectively (P <0.01)). Its solubility in halothane was not significantly different from that of Apexit. AH Plus was significantly more soluble than all other materials in both chloroform and halothane (96% and 68% weight loss after 10 min exposure, respectively (P <0.01)). Conclusions There are significant differences in the solubility profiles of major classes of root canal sealer in common organic solvents. Efforts should continue to find a more universally effective solvent for use in root canal retreatment. [source] Catalytic Hydroxylation in Biphasic Systems using CYP102A1 MutantsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2005Steffen Abstract Cytochrome P450 monooxygenases are biocatalysts that hydroxylate or epoxidise a wide range of hydrophobic organic substrates. Their technical application is, however, limited to a small number of whole-cell processes. The use of the isolated P450 enzymes is believed to be impractical due to their low stability, stoichiometric need of the expensive cofactor NAD(P)H and low solubility of most substrates in aqueous media. We investigated the behaviour of an isolated bacterial monooxygenase (mutants of CYP102A1) in a biphasic reaction system supported by cofactor recycling with the NADP+ -dependent formate dehydrogenase from Pseudomonas sp 101. Using this experimental set-up cyclohexane, octane and myristic acid were hydroxylated. To reduce the process costs a novel NADH-dependent mutant of CYP102A1 was designed. For recycling of NADH an NAD+ -dependent FDH was used. The stability of the monooxygenase mutants under the reaction conditions in the biphasic system was quite high as revealed by total turnover numbers of up to 12,850 in the NADPH-dependent cyclohexane hydroxylation and up to 30,000 in the NADH-dependent myristic acid oxidation. [source] Efficiency of naphthalene biodegradation by Pseudomonas putida G7 in soilJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2004Andrei E Filonov Abstract The efficiency of naphthalene degradation by Pseudomonas putida G7 in soil was assessed using a mathematical model. The number of microorganisms and the concentration of naphthalene in soil samples were monitored. The feasibility of a spectrofluorometric method for naphthalene assay in soil samples was compared with high pressure liquid chromatography. A proposed mathematical model described the growth of the naphthalene-degrading strains and the consumption of substrates (naphthalene, naphthalene degradation intermediates and soil organic substances) in soil. To describe the growth kinetics of microorganisms having high affinity to substrates with low solubility, two differential equations with substrate exponent 2/3 were proposed. These equations were used to describe utilization of soil organic matter. The model parameters characterize the growth rates for different substrates and respective yield coefficients, specific bacterial death and adaptation rates, and also the rates of PAHs degradation and evaporation. These characteristics can be used in choosing the bacterial strains for biopreparations and efficient clean-up biotechnology of polluted soils. Copyright © 2004 Society of Chemical Industry [source] POTASSIUM HYDROXIDE REPLACEMENT FOR LYE (SODIUM HYDROXIDE) IN TOMATO PEELINGJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 1 2006D.J. DAS ABSTRACT Lye (sodium hydroxide [NaOH]) peeling is the most common method for peeling tomatoes in the Midwest U.S. With the rise in the cost of NaOH and the associated disposal problems, alternative methods for peeling need to be examined. Solutions of NaOH, potassium hydoxide (KOH) and calcium hydroxide (Ca[OH]2) at different concentrations were compared to determine their efficacy as peeling agents. Ca(OH)2 was ineffective as a peeling agent because of its low solubility. KOH produced peeling equivalent to NaOH, but at half the normality. A lower normality is needed because of the increased reactivity of KOH compared to NaOH. This is further demonstrated by the addition of salts to the solution. The use of KOH instead of NaOH may result in cost savings and decreased waste disposal problems. [source] Solubility and degradation of polyhydroxyalkanoate biopolymers in propylene carbonateAICHE JOURNAL, Issue 6 2010Christopher W. J. McChalicher Abstract New biobased materials and chemicals require different processing strategies than petroleum-derived commodities. The extraction and recovery of polyhydroxyalkanoate (PHA) biopolymers from the residual cellular biomass is particularly difficult because the polymer is accumulated within the cell. PHAs have low solubility in many classical polymer solvents and are most often dissolved using undesirable chlorinated solvents. The solubility kinetics is greatly diminished when these polymers are highly crystalline. Here, 1,2-propylene carbonate is used to dissolve highly crystalline polyhydroxybutyrate at ambient pressures and moderate temperatures. We have used kinetic studies of the dissolution of the crystalline material to determine the energy barrier for dissolution of the system. Further, the degradation of polyhydroxybutyrate and similarly prepared PHA block copolymers were studied during this extraction process using molecular weight characterization by gel permeation chromatography. Finally, we have used these findings to extract PHA block copolymers from dried biomass at the bench scale. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Aqueous versus non-aqueous salt delivery strategies to enhance oral bioavailability of a mitogen-activated protein kinase-activated protein kinase (MK-2) inhibitor in ratsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2009Po-Chang Chiang Abstract A potent pyridine-containing MK2 inhibitor has recently been internally discovered. In pre-clinical dosing, the low solubility of the neutral form limited oral bioavailability and dose escalation in toxicity studies. A mesylate salt was developed as part of a formulation strategy to enhance both oral bioavailability and dose escalation orally in pre-clinical rat studies. Several non-aqueous systems were used to deliver the mesylate salt, which resulted in varied oral bioavailability. It was found that administration of an aqueous chaser immediately after dosing drastically increased the oral bioavailability of the salt. This finding implies that the quantity of water present in vivo is an important consideration when evaluating salts of free bases with low aqueous solubility in pre-clinical in vivo rat models where limited aqueous vehicle may be presented. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:248,256, 2009 [source] Measurement of dissociation constants (pKa values) of organic compounds by multiplexed capillary electrophoresis using aqueous and cosolvent buffers,JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2008Marina Shalaeva Abstract Evaluation of a multiplexed capillary electrophoresis (CE) method for pKa measurements of organic compounds, including low solubility compounds, is presented. The method is validated on a set of 105 diverse compounds, mostly drugs, and results are compared to literature values obtained from multiple references. Two versions of the instrument in two different labs were used to collect data over a period of 3 years and inter-laboratory and inter-instrument variations are discussed. Twenty-four point aqueous and mixed cosolvent buffer systems were employed to improve the accuracy of pKa measurements. It has been demonstrated that the method allows direct pKa measurements in aqueous buffers for many compounds of low solubility, often unattainable by other methods. The pKa measurements of compounds with extremely low solubility using multiplexed CE with methanol/water cosolvent buffers are presented. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:2581,2606, 2008 [source] Biological, pharmaceutical, and analytical considerations with respect to the transport media used in the absorption screening system, Caco-2JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2003Françoise M. Ingels Abstract During the evaluation and selection of drug candidates, the Caco-2 cell culture system is commonly used for the determination of intestinal transport characteristics and to anticipate permeability limited drug absorption. Although classic HBSS-like buffered salt solutions are commonly used to perform Caco-2 transport experiments, different shortcomings (e.g., adsorption and low solubility) have been associated with the use of plain aqueous buffers. As transport experiments performed with unoptimized conditions may compromize the value of the Caco-2 model as a permeation screening tool, many efforts have been made to optimize the experimental conditions of Caco-2 transport assays. In this minireview, the hurdles associated with the use of saline aqueous buffers in Caco-2 transport experiments are summarized and the different options, which have been proposed to overcome these issues, are reviewed and discussed. Biologically, pharmaceutically, as well as analytically relevant media affecting the outcome of the transport experiments are described. Unfortunately, up to now, no systematic studies comparing the different experimental conditions have been performed, jeopardizing the possibility to define a (single) optimal solution to overcome the different issues associated with the use of saline aqueous buffers. Based on the reported options it can be proposed to use DMSO (,1%) in standard screening procedures for the ranking of compounds based on their apical to basolateral transport. If compounds are not soluble in DMSO 1%, dimethylacetamide (3%) or N -1-methyl-pyrrolidone (2.5%) are good alternatives. However, these options do not imitate the in vivo situation. If one wants to take into account the physiological relevance of the media, the use of a biologically relevant apical medium (e.g., FASSIF) in combination with an analytically friendly, sink condition creating basolateral solvent (e.g., containing a micelle forming agent) can be suggested. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:1545,1558, 2003 [source] Evaluation of sulfobetaine-type polymer resin as an SPE adsorbent in the analysis of trace tetracycline antibiotics in honeyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 21 2009Tomoyasu Tsukamoto Abstract A new sulfobetaine polymer resin SPE method combined with HPLC-MS/MS for the determination of tetracycline (TC) antibiotics residues from honey samples is presented. The sulfobetaine resin was synthesized and was packed into a syringe-type tube, which served as the SPE cartridge for selective adsorption of TCs. TCs were quantitatively adsorbed on the sulfobetaine cartridge, when the loading solvent was 95%,v/v acetonitrile solution, and TCs adsorbed were not eluted by aqueous acetonitrile washing solution. TFA aqueous solution was used for eluting the adsorbed TCs. The proposed SPE method has been applied to the determination of TCs in honey samples. The recoveries of TCs spiked in honey samples ranged from 70 to 80%. Reduction of the recoveries might be derived from low solubility of TCs in acetonitrile. Compared with other SPE resins, this resin was superior in terms of selectivity with simple pretreatment. [source] Characterization of two series of nitrogen-containing dendrimers by natural abundance 15N NMRMAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2008Rodolphe Deloncle Abstract Two series of small generation dendrimers built with phosphorus atoms at each branching point and various types of nitrogen atoms at natural abundance of 15N within the branches are characterized by a gradient enhanced GHNMQC (gradient hydrogen,nitrogen multiple quantum coherence) 1H15N NMR technique. The first series contains two types of nitrogen atoms, included in phosphorhydrazone linkages (CHNNMeP(S)), whereas the second series contains four types of nitrogen atoms included in azobenzene linkages (ArNNAr,) in addition to the phosphorhydrazone. The influence of the trans/cis isomerization of the azo bond on the 15N NMR has also been studied. Despite the low solubility of the azobenzene-containing dendrimers, which renders the detection of some signals difficult, 15N NMR appears as a very sensitive tool to detect chemical changes in the dendritic structure. Copyright © 2008 John Wiley & Sons, Ltd. [source] Sevoflurane: an ideal agent for adult day-case anesthesia?ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 8 2003S. Ghatge Sevoflurane has several properties which make it potentially useful as a day case anaesthetic. Following induction of anaesthesia with propofol, awakening from sevoflurane is faster compared to isoflurane, faster or similar compared to propofol and comparable (in the majority of studies) to desflurane. Subsequent recovery and discharge is generally similar following all agents. Sevoflurane may also be used to induce anaesthesia, which is generally well-received and causes less hypotension and apnoea compared to propofol. When used as a maintenance anaesthetic, the incidence of postoperative nausea and vomiting after sevoflurane is comparable to other inhaled anaesthetics, but this complication appears more common after inhaled inductions. The tolerability and low solubility of sevoflurane facilitate titration of anaesthesia and may reduce the need for opioid analgesia, which in turn may limit the occurrence of nausea and vomiting. [source] Chemoprotective effect of plant phenolics against anthracycline-induced toxicity on rat cardiomyocytes.PHYTOTHERAPY RESEARCH, Issue 2 2004Part I. Silymarin, its flavonolignans Abstract Silymarin, an extract of ,avonolignans from the dried fruits of milk thistle (Silybum marianum L. Gaertneri) and its constituents silibinin, dehydrosilibinin, silychristin and silydianin were tested for protective effects on rat cardiomyocytes exposed to doxorubicin. Silymarin and individual ,avonolignans did not exert cytotoxicity in the range 25,100 µm (incubation 9 h). Dehydrosilibinin was tested only at 25 µm concentration due to its low solubility. All substances increased the cell ATP level. Silymarin and ,avonolignans displayed a dose-dependent cytoprotection against doxorubicin (100 µm, incubation 8 h). The protective effects of silymarin, silibinin, dehydrosilibinin and silychristin were comparable to that of dexrasoxane, while silydianin exerted the best protective effect. The ability of silymarin complex and its components to protect cardiomyocytes against doxorubicin-induced oxidative stress is due mainly to their cell membrane stabilization effect, radical scavenging and iron chelating potency. Copyright © 2004 John Wiley & Sons, Ltd. [source] Contributions of common sources of polycyclic aromatic hydrocarbons to soil contaminationREMEDIATION, Issue 3 2006John A. Simon Asphalt products, particularly sealants, are prepared using petroleum products that contain a com-plex mixture of aliphatic and aromatic hydrocarbons, including polycyclic aromatic hydrocarbons (PAHs). Clearly, these products are ubiquitous in urban environments, which raises an issue regard-ing the potential for PAHs to be transported from parking lots to underlying or adjacent soil, surface-water bodies, or groundwater. Based on a literature review, there are limited studies focus-ing on this issue; however, the studies that have been published have fascinating conclusions. The literature shows, as expected, that asphalt-based products contain PAHs. The highest PAH concen-trations are present in asphalt sealants, particularly those manufactured using coal tar. Furthermore, due to the low solubility and high partition coefficients of PAHs, the potential for PAHs to leach from asphalt surfaces is negligible, which has been confirmed by leachability studies. Thus, there is little risk that PAHs will be present in stormwater runoff or leach into groundwater from asphalt-paved areas in a dissolved form. However, asphalt pavement and sealants produce particulate matter that can contain concentrations of PAHs in the sub-percent range (100s to 1,000s mg/kg total PAHs) that is transported in stormwater runoff. Some studies show that this can cause soil and sediment con-tamination with total PAH concentrations in the range of 1 to 10 mg/kg. From a remediation per-spective, many site cleanups are conducted to remediate the presence of PAHs to cleanup goals below 1 mg/kg or, in some cases, 0.1 mg/kg or lower. From a total risk perspective, remediating sites to low PAH cleanup goals may be unwarranted in light of the risk of transportable PAHs produced from paved parking surfaces. In other words, is it reasonable to conduct a cleanup to remediate low PAH concentrations and then redevelop the area with asphalt pavement and sealant, which may pose a greater PAH-related risk? © 2006 Wiley Periodicals, Inc. [source] Expression, crystallization and preliminary X-ray crystallographic study of ethanolamine ammonia-lyase from Escherichia coliACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2010Naoki Shibata Ethanolamine ammonia-lyase (EAL) catalyzes the adenosylcobalamin-dependent conversion of ethanolamine to acetaldehyde and ammonia. The wild-type enzyme shows a very low solubility. N-terminal truncation of the Escherichia coli EAL ,-subunit dramatically increases the solubility of the enzyme without altering its catalytic properties. Two deletion mutants of the enzyme [EAL(,,4,30) and EAL(,,4,43)] have been overexpressed, purified and crystallized using the sitting-drop vapour-diffusion method. Crystals of EAL(,,4,30) and EAL(,,4,43) diffracted to approximately 8.0 and 2.1,Å resolution, respectively. [source] Crystallization and preliminary X-ray diffraction of the DEAD-box protein Mss116p complexed with an RNA oligonucleotide and AMP-PNPACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 8 2009Mark Del Campo The Saccharomyces cerevisiae DEAD-box protein Mss116p is a general RNA chaperone which functions in mitochondrial group I and group II intron splicing, translation and RNA-end processing. For crystallization trials, full-length Mss116p and a C-terminally truncated protein (Mss116p/,598,664) were overproduced in Escherichia coli and purified to homogeneity. Mss116p exhibited low solubility in standard solutions (,1,mg,ml,1), but its solubility could be increased by adding 50,mMl -arginine plus 50,mMl -glutamate and 50% glycerol to achieve concentrations of ,10,mg,ml,1. Initial crystals were obtained by the microbatch method in the presence of a U10 RNA oligonucleotide and the ATP analog AMP-PNP and were then improved by using seeding and sitting-drop vapor diffusion. A cryocooled crystal of Mss116p/,598,664 in complex with AMP-PNP and U10 belonged to space group P21212, with unit-cell parameters a = 88.54, b = 126.52, c = 55.52,Å, and diffracted X-rays to beyond 1.9,Å resolution using synchrotron radiation from sector 21 at the Advanced Photon Source. [source] | |||||||||||||||||||||||||