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Sample records for stabilized enzyme solution

  1. 21 CFR 864.9400 - Stabilized enzyme solution.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Stabilized enzyme solution. 864.9400 Section 864... and Blood Products § 864.9400 Stabilized enzyme solution. (a) Identification. A stabilized enzyme... enzyme solutions include papain, bromelin, ficin, and trypsin. (b) Classification. Class II (performance...

  2. Enzyme stabilization by glass-derived silicates in glass-exposed aqueous solutions

    Science.gov (United States)

    Ives, J.A.; Moffett, J.R.; Arun, P.; Lam, D.; Todorov, T.I.; Brothers, A.B.; Anick, D.J.; Centeno, J.; Namboodiri, M.A.A.; Jonas, W.B.

    2010-01-01

    Objectives: To analyze the solutes leaching from glass containers into aqueous solutions, and to show that these solutes have enzyme activity stabilizing effects in very dilute solutions. Methods: Enzyme assays with acetylcholine esterase were used to analyze serially succussed and diluted (SSD) solutions prepared in glass and plastic containers. Aqueous SSD preparations starting with various solutes, or water alone, were prepared under several conditions, and tested for their solute content and their ability to affect enzyme stability in dilute solution. Results: We confirm that water acts to dissolve constituents from glass vials, and show that the solutes derived from the glass have effects on enzymes in the resultant solutions. Enzyme assays demonstrated that enzyme stability in purified and deionized water was enhanced in SSD solutions that were prepared in glass containers, but not those prepared in plastic. The increased enzyme stability could be mimicked in a dose-dependent manner by the addition of silicates to the purified, deionized water that enzymes were dissolved in. Elemental analyses of SSD water preparations made in glass vials showed that boron, silicon, and sodium were present at micromolar concentrations. Conclusions: These results show that silicates and other solutes are present at micromolar levels in all glass-exposed solutions, whether pharmaceutical or homeopathic in nature. Even though silicates are known to have biological activity at higher concentrations, the silicate concentrations we measured in homeopathic preparations were too low to account for any purported in vivo efficacy, but could potentially influence in vitro biological assays reporting homeopathic effects. ?? 2009 The Faculty of Homeopathy.

  3. PFP solution stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Aftanas, B.L.

    1996-04-30

    This Functional Design Criteria (FDC) addresses remediation of the plutonium-bearing solutions currently in inventory at the Plutonium Finishing Plant (PFP). The recommendation from the Environmental Impact Statement (EIS) is that the solutions be treated thermally and stabilized as a solid for long term storage. For solutions which are not discardable, the baseline plan is to utilize a denitration process to stabilize the solutions prior to packaging for storage.

  4. Bacteriophage enzymes for the prevention and treatment of bacterial infections: Stability and stabilization of the enzyme lysing Streptococcus pyogenes cells

    Energy Technology Data Exchange (ETDEWEB)

    Klyachko, N. L.; Dmitrieva, N. F.; Eshchina, A. S.; Ignatenko, O. V.; Filatova, L. Y.; Rainina, Evguenia I.; Kazarov, A. K.; Levashov, A. V.

    2008-06-01

    Recombinant, phage associated lytic enzyme Ply C capable to lyse streptococci of groups A and C was stabilized in the variety of the micelles containing compositions to improve the stability of the enzyme for further application in medicine. It was shown that, in the micellar polyelectrolyte composition M16, the enzyme retained its activity for 2 months; while in a buffer solution under the same conditions ((pH 6.3, room temperature), it completely lost its activity in 2 days

  5. Project Management Plan Solution Stabilization

    Energy Technology Data Exchange (ETDEWEB)

    SATO, P.K.

    1999-08-31

    This plan presents the overall objectives, description, justification and planning for the Plutonium Finishing Plant (PFP) Solutions Stabilization subproject. The intent of this plan is to describe how this project will be managed and integrated with other facility stabilization and deactivation activities. This plan supplements the overall integrated plan presented in the Integrated Project Management Plan (IPMP) for the Plutonium Finishing Plant Stabilization and Deactivation Project, HNF-3617. This project plan is the top-level definitive project management document for the PFP Solution Stabilization subproject. It specifies the technical, schedule, requirements and the cost baselines to manage the execution of the Solution Stabilization subproject. Any deviations to the document must be authorized through the appropriate change control process.

  6. Project Management Plan Solution Stabilization

    International Nuclear Information System (INIS)

    SATO, P.K.

    1999-01-01

    This plan presents the overall objectives, description, justification and planning for the Plutonium Finishing Plant (PFP) Solutions Stabilization subproject. The intent of this plan is to describe how this project will be managed and integrated with other facility stabilization and deactivation activities. This plan supplements the overall integrated plan presented in the Integrated Project Management Plan (IPMP) for the Plutonium Finishing Plant Stabilization and Deactivation Project, HNF-3617. This project plan is the top-level definitive project management document for the PFP Solution Stabilization subproject. It specifies the technical, schedule, requirements and the cost baselines to manage the execution of the Solution Stabilization subproject. Any deviations to the document must be authorized through the appropriate change control process

  7. Electro-ultrafiltration of industrial enzyme solutions

    DEFF Research Database (Denmark)

    Enevoldsen, Ann Dorrit; Hansen, Erik Børresen; Jonsson, Gunnar Eigil

    2007-01-01

    To reduce the problems with fouling and concentration polarization during crossflow ultrafiltration of industrial enzyme solutions an electric field is applied across the membrane. The filtration performance during electro-ultrafiltration (EUF) has been tested with several enzymes. Results show...... that EUF is an effective method to filter high concentrated solutions at low crossfiow. The flux improved 3-7 times for enzymes with a significant surface charge at an electric field strength of 1600V/m compared to conventional UF. The greatest improvement is observed at high concentration. Not all enzymes...... can be filtered with EUF, mainly due to a low surface charge and impurities in the feed solution. Using a pulsed electric field did not improve the flux compared to a constant field. Gel electrophoresis experiments of the enzymes appear to be a useful method for estimating the influence...

  8. Stability of Enzymes in Granular Enzyme Products for Laundry Detergents

    DEFF Research Database (Denmark)

    Biran, Suzan; Bach, Poul; Simonsen, Ole

    Enzymes have long been of interest to the detergent industry due to their ability to improve the cleaning efficiency of synthetic detergents, contribute to shortening washing times, and reduce energy and water consumption, provision of environmentally friendlier wash water effluents and fabric care....... However, incorporating enzymes in detergent formulations gives rise to numerous practical problems due to their incompatibility with and stability against various detergent components. In powdered detergent formulations, these issues can be partly overcome by physically isolating the enzymes in separate...... of enzymes, high local pH in granule, oxygen, defects in granulate structure and the effect of other detergent components. However, the actual mechanism of inactivation is not known yet. It is believed that a combination of the factors mentioned above plays a role in the activity loss, and is the focus...

  9. Stability of aflatoxins in solution.

    Science.gov (United States)

    Diaz, Gonzalo J; Cepeda, Sandra M; Martos, Perry A

    2012-01-01

    The stability of aflatoxins B1, B2, G1, and G2 was studied in solutions containing different concentrations of water, acetonitrile, and/or methanol, and in autosampler vials treated with nitric acid or silanized. When stored at room temperature (20 degrees C) for 24 h, aflatoxins G1 and G2 were stable only in solutions containing 100% organic solvent, whereas aflatoxins B1 and B2 were stable in solutions of methanol-water and acetonitrile-water at greater than 60 and 40% organic content, respectively. At 5 degrees C, aflatoxins G1 and G2 showed a significant decrease in concentration only when kept in less than 20% aqueous organic solvent. Significant loss of aflatoxins was realized in standard, commercially available amber type I borosilicate autosampler vials, but chemical etching of the vials with nitric acid or with silanization prevented aflatoxin degradation. These results indicate that aflatoxins are unstable in aqueous solutions and that this instability can be counteracted by the presence of at least 20% organic solvent and keeping the solutions at 5 degrees C or by the use of treated vials.

  10. Effect of irradiation on immobilized enzymes compared with that on enzymes in solution

    International Nuclear Information System (INIS)

    Schachinger, L.; Schippel, C.; Altmann, E.; Diepold, B.; Yang, C.; Jaenike, M.; Hochhaeuser, E.

    1985-01-01

    Glucose oxidase and catalase were immobilized by attaching them to nylon fibers that had been treated with triethyloxonium-tetrafluoroborate, diaminohexane and glutaraldialdehyde according to Morris, Campell and Hornby (1975). This method assures that the enzymes are bound to a side chain of the polyamide structure. Enzyme activity (as measured by the O 2 -uptake and by microcalorimetry) was found to be unchanged after 2 years. The apparent Ksub(m)-constants of the immobilized enzymes with glucose were the same as those for enzymes in solution. GOD and catalase immobilized in poly(acrylamide) gel had the same Ksub(m)-value. Despite the high stability during storage, the radiation induced inactivation of enzymes immobilized on gel or chromosorb, an inorganic carrier, was of the same order of magnitude as that of the dissolved enzymes. The enzymes bound to nylon fibers showed a higher radiation sensitivity. This might have been caused by an additional attack on the binding site of the carrier. (orig.)

  11. Engineering report (conceptual design) PFP solution stabilization

    International Nuclear Information System (INIS)

    Witt, J.B.

    1997-01-01

    This Engineering Report (Conceptual Design) addresses remediation of the plutonium-bearing solutions currently in inventory at the Plutonium Finishing Plant (PFP). The recommendation from the Environmental Impact Statement (EIS) is that the solutions be treated thermally and stabilized as a solid for long term storage. For solutions which are not discardable, the baseline plan is to utilize a denitration process to stabilize the solutions prior to packaging for storage

  12. Engineering report (conceptual design) PFP solution stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Witt, J.B.

    1997-07-17

    This Engineering Report (Conceptual Design) addresses remediation of the plutonium-bearing solutions currently in inventory at the Plutonium Finishing Plant (PFP). The recommendation from the Environmental Impact Statement (EIS) is that the solutions be treated thermally and stabilized as a solid for long term storage. For solutions which are not discardable, the baseline plan is to utilize a denitration process to stabilize the solutions prior to packaging for storage.

  13. Enzyme based soil stabilization for unpaved road construction

    Directory of Open Access Journals (Sweden)

    Renjith Rintu

    2017-01-01

    Full Text Available Enzymes as soil stabilizers have been successfully used in road construction in several countries for the past 30 years. However, research has shown that the successful application of these enzymes is case specific, emphasizing that enzyme performance is dependent on subgrade soil type, condition and the type of enzyme used as the stabilizer. A universal standard or a tool for road engineers to assess the performance of stabilized unbound pavements using well-established enzymes is not available to date. The research aims to produce a validated assessment tool which can be used to predict strength enhancement within a generalized statistical framework. The objective of the present study is to identify new materials for developing the assessment tool which supports enzyme based stabilization, as well as to identify the correct construction sequence for such new materials. A series of characterization tests were conducted on several soil types obtained from proposed construction sites. Having identified the suitable soil type to mix with the enzyme, a trial road construction has been performed to investigate the efficiency of the enzyme stabilization along with the correct construction sequence. The enzyme stabilization has showed significant improvement of the road performance as was evidenced from the test results which were based on site soil obtained before and after stabilization. The research will substantially benefit the road construction industry by not only replacing traditional construction methods with economical/reliable approaches, but also eliminating site specific tests required in current practice of enzyme based road construction.

  14. Stabilization of enzymes against thermal stress and freeze-drying by mannosylglycerate

    NARCIS (Netherlands)

    Ramos, A.; Raven, N.; Sharp, R.J.; Bartolucci, S.; Rossi, M.; Cannio, R.; Lebbink, J.; Oost, van der J.; Vos, de W.M.; Santos, H.

    1997-01-01

    2-O-(beta)-Mannosylglycerate, a solute that accumulates in some (hyper)thermophilic organisms, was purified from Pyrococcus furiosus cells, and its effect on enzyme stabilization in vitro was assessed. Enzymes from hyperthermophilic, thermophilic, and mesophilic sources were examined. The

  15. Iterative Approximate Solutions of Kinetic Equations for Reversible Enzyme Reactions

    OpenAIRE

    Khoshnaw, S.

    2012-01-01

    We study kinetic models of reversible enzyme reactions and compare two techniques for analytic approximate solutions of the model. Analytic approximate solutions of non-linear reaction equations for reversible enzyme reactions are calculated using the Homotopy Perturbation Method (HPM) and the Simple Iteration Method (SIM). The results of the approximations are similar. The Matlab programs are included in appendices.

  16. Stabilization of aqueous alkali metal aluminate solutions

    Energy Technology Data Exchange (ETDEWEB)

    Allenson, S.J.

    1988-03-29

    A method of stabilizing an aqueous solution of alkali metal aluminate is described comprising: admixing an aqueous solution of alkali metal aluminate having a pH of at least 10 with a sufficient amount of vinyl polymer having pendant carboxylate groups to form a solution containing from 0.1 to 2.0 weight percent of an anionic vinyl polymer based on alkali metal aluminate solids. The anionic vinyl polymer has an average molecular weight of at least 500,000.

  17. Stabilization of enzymes in ionic liquids via modification of enzyme charge.

    Science.gov (United States)

    Nordwald, Erik M; Kaar, Joel L

    2013-09-01

    Due to the propensity of ionic liquids (ILs) to inactivate enzymes, the development of strategies to improve enzyme utility in these solvents is critical to fully exploit ILs for biocatalysis. We have developed a strategy to broadly improve enzyme utility in ILs based on elucidating the effect of charge modifications on the function of enzymes in IL environments. Results of stability studies in aqueous-IL mixtures indicated a clear connection between the ratio of enzyme-containing positive-to-negative sites and enzyme stability in ILs. Stability studies of the effect of [BMIM][Cl] and [EMIM][EtSO4 ] on chymotrypsin specifically found an optimum ratio of positively-charged amine-to-negatively-charged acid groups (0.39). At this ratio, the half-life of chymotrypsin was increased 1.6- and 4.3-fold relative to wild-type chymotrypsin in [BMIM][Cl] and [EMIM][EtSO4 ], respectively. The half-lives of lipase and papain were similarly increased as much as 4.0 and 2.4-fold, respectively, in [BMIM][Cl] by modifying the ratio of positive-to-negative sites of each enzyme. More generally, the results of stability studies found that modifications that reduce the ratio of enzyme-containing positive-to-negative sites improve enzyme stability in ILs. Understanding the impact of charge modification on enzyme stability in ILs may ultimately be exploited to rationally engineer enzymes for improved function in IL environments. Copyright © 2013 Wiley Periodicals, Inc.

  18. Structural Bases of Stability-Function Tradeoffs in Enzymes

    Energy Technology Data Exchange (ETDEWEB)

    Beadle, Beth M; Shoichet, Brian K [NWU, MED

    2010-03-05

    The structures of enzymes reflect two tendencies that appear opposed. On one hand, they fold into compact, stable structures; on the other hand, they bind a ligand and catalyze a reaction. To be stable, enzymes fold to maximize favorable interactions, forming a tightly packed hydrophobic core, exposing hydrophilic groups, and optimizing intramolecular hydrogen-bonding. To be functional, enzymes carve out an active site for ligand binding, exposing hydrophobic surface area, clustering like charges, and providing unfulfilled hydrogen bond donors and acceptors. Using AmpC {beta}-lactamase, an enzyme that is well-characterized structurally and mechanistically, the relationship between enzyme stability and function was investigated by substituting key active-site residues and measuring the changes in stability and activity. Substitutions of catalytic residues Ser64, Lys67, Tyr150, Asn152, and Lys315 decrease the activity of the enzyme by 10{sup 3}-10{sup 5}-fold compared to wild-type. Concomitantly, many of these substitutions increase the stability of the enzyme significantly, by up to 4.7 kcal/mol. To determine the structural origins of stabilization, the crystal structures of four mutant enzymes were determined to between 1.90 {angstrom} and 1.50 {angstrom} resolution. These structures revealed several mechanisms by which stability was increased, including mimicry of the substrate by the substituted residue (S64D), relief of steric strain (S64G), relief of electrostatic strain (K67Q), and improved polar complementarity (N152H). These results suggest that the preorganization of functionality characteristic of active sites has come at a considerable cost to enzyme stability. In proteins of unknown function, the presence of such destabilized regions may indicate the presence of a binding site.

  19. Stabilization of enzyme by using hydrophobic ligands

    Energy Technology Data Exchange (ETDEWEB)

    Ota, H.; Yamahara, K.; Kuboi, R. [Osaka University, Osaka (Japan)

    1998-02-01

    The protection (stabilization) effect of various hydrophobic ligands on the denaturation and aggregation of carbonic anhydrase from bovine (CAB) has been quantitatively investigated under various heat stress conditions. In a limited temperature range (40-60degC), where the protein was only partially denatured and the local hydrophobicities (LH) of CAB were positive effective stabilization of the protein is achieved by the addition of various ligands. The importance of balance between hydrophobic head and hydrophilic tail of the ligands is hypothesized. 18 refs., 5 figs.

  20. Modification of polymer surfaces to enhance enzyme activity and stability

    DEFF Research Database (Denmark)

    Hoffmann, Christian

    Enzyme immobilization is an important concept for the development of improved biocatalytic processes, primarily through facilitated separation procedures. However, enzyme immobilization usually comes at a price of reduced biocatalytic activity. For this reason, different immobilization methods have...... already been developed, combining the same goal to improve enzyme activity, stability and selectivity. Polymer materials have shown, due to their easy processibility and versatile properties, high potential as enzyme support. However, in order to achieve improved enzyme performance, the combination...... of different factors, such as the nature of the enzyme, the properties of the support, the type of immobilization and the interaction between enzyme and support, has to be taken into consideration. In this thesis, these factors are pursued and addressed by exploiting various types of polymers with focus...

  1. Stability of tacrolimus solutions in polyolefin containers.

    Science.gov (United States)

    Lee, Jun H; Goldspiel, Barry R; Ryu, Sujung; Potti, Gopal K

    2016-02-01

    Results of a study to determine the stability of tacrolimus solutions stored in polyolefin containers under various temperature conditions are reported. Triplicate solutions of tacrolimus (0.001, 0.01, and 0.1 mg/mL) in 0.9% sodium chloride injection or 5% dextrose injection were prepared in polyolefin containers. Some samples were stored at room temperature (20-25 °C); others were refrigerated (2-8 °C) for 20 hours and then stored at room temperature for up to 28 hours. The solutions were analyzed by stability-indicating high-performance liquid chromatography (HPLC) assay at specified time points over 48 hours. Solution pH was measured and containers were visually inspected at each time point. Stability was defined as retention of at least 90% of the initial tacrolimus concentration. All tested solutions retained over 90% of the initial tacrolimus concentration at all time points, with the exception of the 0.001-mg/mL solution prepared in 0.9% sodium chloride injection, which was deemed unstable beyond 24 hours. At all evaluated concentrations, mean solution pH values did not change significantly over 48 hours; no particle formation was detected. During storage in polyolefin bags at room temperature, a 0.001-mg/mL solution of tacrolimus was stable for 24 hours when prepared in 0.9% sodium chloride injection and for at least 48 hours when prepared in 5% dextrose injection. Solutions of 0.01 and 0.1 mg/mL prepared in either diluent were stable for at least 48 hours, and the 0.01-mg/mL tacrolimus solution was also found to be stable throughout a sequential temperature protocol. Copyright © 2016 by the American Society of Health-System Pharmacists, Inc. All rights reserved.

  2. Thermodynamic stability of radioactivity standard solutions

    Energy Technology Data Exchange (ETDEWEB)

    Iroulard, M.G

    2007-04-15

    The basic requirement when preparing radioactivity standard solutions is to guarantee the concentration of a radionuclide or a radioelement, expressed in the form of activity concentration (Ac = A/m (Bq/g), with A: activity and m: mass of solution). Knowledge of the law of radioactive decay and the half-life of a radionuclide or radioelement makes it possible to determine the activity concentration at any time, and this must be confirmed subsequently by measurement. Furthermore, when radioactivity standard solutions are prepared, it is necessary to establish optimal conditions of thermodynamic stability of the standard solutions. Radioactivity standard solutions are prepared by metrology laboratories from original solutions obtained from a range of suppliers. These radioactivity standard solutions must enable preparation of liquid and/or solid radioactivity standard sources of which measurement by different methods can determine, at a given instant, the activity concentration of the radionuclide or radioelement present in the solution. There are a number of constraints associated with the preparation of such sources. Here only those that relate to the physical and chemical properties of the standard solution are considered, and therefore need to be taken into account when preparing a radioactivity standard solution. These issues are considered in this document in accordance with the following plan: - A first part devoted to the chemical properties of the solutions: - the solubilization media: ultra-pure water and acid media, - the carriers: concentration, oxidation state of the radioactive element and the carrier element. - A second part describing the methodology of the preparation, packaging and storage of standard solutions: - glass ampoules: the structure of glasses, the mechanisms of their dissolution, the sorption phenomenon at the solid-solution interface, - quartz ampoules, - cleaning and packaging: cleaning solutions, internal surface coatings and

  3. Thermodynamic stability of radioactivity standard solutions

    International Nuclear Information System (INIS)

    Iroulard, M.G.

    2007-04-01

    The basic requirement when preparing radioactivity standard solutions is to guarantee the concentration of a radionuclide or a radioelement, expressed in the form of activity concentration (Ac = A/m (Bq/g), with A: activity and m: mass of solution). Knowledge of the law of radioactive decay and the half-life of a radionuclide or radioelement makes it possible to determine the activity concentration at any time, and this must be confirmed subsequently by measurement. Furthermore, when radioactivity standard solutions are prepared, it is necessary to establish optimal conditions of thermodynamic stability of the standard solutions. Radioactivity standard solutions are prepared by metrology laboratories from original solutions obtained from a range of suppliers. These radioactivity standard solutions must enable preparation of liquid and/or solid radioactivity standard sources of which measurement by different methods can determine, at a given instant, the activity concentration of the radionuclide or radioelement present in the solution. There are a number of constraints associated with the preparation of such sources. Here only those that relate to the physical and chemical properties of the standard solution are considered, and therefore need to be taken into account when preparing a radioactivity standard solution. These issues are considered in this document in accordance with the following plan: - A first part devoted to the chemical properties of the solutions: - the solubilization media: ultra-pure water and acid media, - the carriers: concentration, oxidation state of the radioactive element and the carrier element. - A second part describing the methodology of the preparation, packaging and storage of standard solutions: - glass ampoules: the structure of glasses, the mechanisms of their dissolution, the sorption phenomenon at the solid-solution interface, - quartz ampoules, - cleaning and packaging: cleaning solutions, internal surface coatings and

  4. Study of TATP: stability of TATP solutions.

    Science.gov (United States)

    Pachman, Jiri; Matyáš, Robert

    2011-04-15

    Stability of raw TATP (3,3,6,6,9,9-hexamethyl-1,2,4,5,7,8-hexoxonane) samples in solutions of common solvents was studied to highlight problems faced by forensic labs in identification and analysis of organic peroxide samples. The TATP samples were prepared by reaction of acetone and hydrogen peroxide (30%) with the aid of following catalysts: hydrochloric, sulfuric, nitric, perchloric and methanesulfonic acid. Acetone, acetonitrile, methanol and acetonitrile/water solutions of TATP samples were prepared and stored at 50°C. Various degrees of stability were observed for particular combination of catalyst and solvent ranging from totally unstable (catalyst-H(2)SO(4)/any solvent) to very stable (catalyst-HCl/solvent acetonitrile). Purification of crude TATP by re-crystallization results in product stable in all investigated solvents. Stability of solution prepared from re-crystallized DADP (3,3,6,6-tetramethyl-1,2,4,5-tetroxane) was found to be on the same level as the stability of solution of re-crystallized TATP. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

  5. [Stability of some medicinal solutions with captopril].

    Science.gov (United States)

    Imre, Silvia; Vancea, Szende; Muntean, Daniela Lucia; Sipos, Emese; Cociş, Adela; Avrigeanu, Veronica; Mircia, Eleonora

    2008-01-01

    The aim of the study was to investigate the stability of some oral liquid formulations containing 1 mg/ml captopril. The oral solutions were prepared using captopril substance, keeping the formulation as simple as possible to avoid potentially undesirable excipients. Samples were stored for 39 days below 8 degrees C and at 22 +/- 3 degrees C and analysed for physical, chemical and microbiological stability. The formulations with ascorbic acid are stable for seven days either at 8 and 22 degrees C and could be prepared in hospital pharmacy as a more safely alternative to children terapy with tablets powders.

  6. Robust enzyme design: bioinformatic tools for improved protein stability.

    Science.gov (United States)

    Suplatov, Dmitry; Voevodin, Vladimir; Švedas, Vytas

    2015-03-01

    The ability of proteins and enzymes to maintain a functionally active conformation under adverse environmental conditions is an important feature of biocatalysts, vaccines, and biopharmaceutical proteins. From an evolutionary perspective, robust stability of proteins improves their biological fitness and allows for further optimization. Viewed from an industrial perspective, enzyme stability is crucial for the practical application of enzymes under the required reaction conditions. In this review, we analyze bioinformatic-driven strategies that are used to predict structural changes that can be applied to wild type proteins in order to produce more stable variants. The most commonly employed techniques can be classified into stochastic approaches, empirical or systematic rational design strategies, and design of chimeric proteins. We conclude that bioinformatic analysis can be efficiently used to study large protein superfamilies systematically as well as to predict particular structural changes which increase enzyme stability. Evolution has created a diversity of protein properties that are encoded in genomic sequences and structural data. Bioinformatics has the power to uncover this evolutionary code and provide a reproducible selection of hotspots - key residues to be mutated in order to produce more stable and functionally diverse proteins and enzymes. Further development of systematic bioinformatic procedures is needed to organize and analyze sequences and structures of proteins within large superfamilies and to link them to function, as well as to provide knowledge-based predictions for experimental evaluation. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Immobilization, stabilization and patterning techniques for enzyme based sensor systems.

    Energy Technology Data Exchange (ETDEWEB)

    Flounders, A.W.; Carichner, S.C.; Singh, A.K.; Volponi, J.V.; Schoeniger, J.S.; Wally, K.

    1997-01-01

    Sandia National Laboratories has recently opened the Chemical and Radiation Detection Laboratory (CRDL) in Livermore CA to address the detection needs of a variety of government agencies (e.g., Department of Energy, Environmental Protection Agency, Department of Agriculture) as well as provide a fertile environment for the cooperative development of new industrial technologies. This laboratory consolidates a variety of existing chemical and radiation detection efforts and enables Sandia to expand into the novel area of biochemically based sensors. One aspect of this biosensor effort is further development and optimization of enzyme modified field effect transistors (EnFETs). Recent work has focused upon covalent attachment of enzymes to silicon dioxide and silicon nitride surfaces for EnFET fabrication. They are also investigating methods to pattern immobilized proteins; a critical component for development of array-based sensor systems. Novel enzyme stabilization procedures are key to patterning immobilized enzyme layers while maintaining enzyme activity. Results related to maximized enzyme loading, optimized enzyme activity and fluorescent imaging of patterned surfaces will be presented.

  8. Thermal Stabilization of Enzymes Immobilized within Carbon Paste Electrodes.

    Science.gov (United States)

    Wang, J; Liu, J; Cepra, G

    1997-08-01

    In this note we report on the remarkable thermal stabilization of enzymes immobilized in carbon paste electrodes. Amperometric biosensors are shown for the first time to withstand a prolonged high-temperature (>50 °C) stress. Nearly full activity of glucose oxidase is retained over periods of up to 4 months of thermal stress at 60-80 °C. Dramatic improvements in the thermostability are observed for polyphenol oxidase, lactate oxidase, alcohol oxidase, horseradish peroxidase, and amino acid oxidase. Such resistance to heat-induced denaturation is attributed to the conformational rigidity of these biocatalysts within the highly hydrophobic (mineral oil or silicone grease) pasting liquid. While no chemical stabilizer is needed for attaining such protective action, it appears that low humidity (i.e., low water content) is essential for minimizing the protein mobility. Besides their implications for electrochemical biosensors, such observations should lead to a new generation of thermoresistant enzyme reactors based on nonpolar semisolid supports.

  9. Enzyme-polymer composites with high biocatalytic activity and stability

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jungbae; Kosto, Timothy J.; Manimala, Joseph C.; Nauman, E B.; Dordick, Jonathan S.

    2004-08-22

    We have applied vacuum-spraying and electrospinning to incorporate an enzyme into a polymer matrix, creating a novel and highly active biocatalytic composite. As a unique technical approach, enzymes were co-dissolved in toluene with polymers, and the solvent was then rapidly removed by injecting the mixture into a vacuum chamber or by electrospinning. Subsequent crosslinking of the enzyme with glutaraldehyde resulted in stable entrapped enzyme within the polymeric matrices. For example, an amorphous composite of alpha-chymotrypsin and polyethylene showed no significant loss of enzymatic activity in aqueous buffer for one month. Nanofibers of alpha-chymotrypsin and polystyrene also showed no decrease in activity for more than two weeks. The normalized activity of amorphous composite in organic solvents was 3-13 times higher than that of native alpha-chymotrypsin. The activity of nanofibers was 5-7 times higher than that of amorphous composite in aqueous buffer solution. The composites of alpha-chymotrypsin and polymers demonstrate the feasibility of obtaining a wide variety of active and stable biocatalytic materials with many combinations of enzymes and polymers.

  10. Evaluation of pancreatin stability through enzyme activity determination

    Directory of Open Access Journals (Sweden)

    Terra Gleysson De Paula

    2016-09-01

    Full Text Available Pancreatin is a biotechnological product containing an enzyme complex, obtained from porcine pancreas, that is employed in treating pancreatic diseases. Experiments regarding the stability of the pharmaceutical formulation containing pancreatin were performed using standard binary mixtures with 6 excipients in a 1:1 ratio (m/m and a commercial formulation. To accomplish these goals, samples were stored for 1, 3 and 6 months at 40 ± 1 °C and 75 ± 5 % relative humidity (RH and 40 ± 1 °C and 0 % RH. Stress testing was also performed. All samples were analyzed to evaluate the α-amylase, lipase and protease activities through UV/Vis spectrophotometry. The results revealed that the excipient proprieties and the storage conditions affected enzyme stability. Humidity was a strong influencing factor in the reduction of α-amylase and protease activities. Stress testing indicated that pH 9.0 and UV light did not induce substantial alterations in enzyme activity.

  11. Apoferritin Nanoparticle: A Novel and Biocompatible Carrier for Enzyme Immobilization with Enhanced Activity and Stability

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Youyu; Tang, Zhiwen; Wang, Jun; Wu, Hong J.; Lin, Chiann Tso; Lin, Yuehe

    2011-11-01

    Apoferritin is a nanostructured material with a uniform size and spherical structure, and it has excellent bio-compatibility. In this work, we report the use of apoferritin as a novel and biocompatible carrier for stabilizing enzymes and their activities. We used glucose oxidase (GOx) as a model enzyme. GOx was immobilized on the surface of the apoferritin through a green synthetic approach taking advantage of bioaffinity binding between streptavidin and biotin. As a result, a glucose oxidase-biotin/streptavidin/biotin-apoferritin conjugate (Apo-GOx) was prepared using streptavidin as a bridge. The synthesized Apo-GOx was characterized with transmission electron microscopy, ultraviolet, and fluorescence spectroscopy. The activity and stability of GOx on the surface of the apoferritin were studied in different environments, such as temperature, chemicals, and pH, in comparison with the biotinylated GOx (B-GOx). The results showed that the activity of GOx on the apoferritin surface was significantly enhanced. The thermal and chemical stability of the GOx on the apoferritin was also greatly improved compared to free B-GOx in a solution. It was found that the activity of the GOx on the apoferritin only lost 30% in comparison to a 70% loss of free B-GOx after a 2 h incubation at 50oC. There was almost no decrease in activity for the GOx on the apoferritin as compared to an 80% activity decrease for free B-GOx after 30 min incubation in a 5 M urea solution. Glucose detection was used as a model application for the enzyme immobilization method developed in this work. The GOx immobilized apoferritin nanoparticles exhibited high sensitivity for glucose detection with a detection limit of 3 nM glucose. This work offers a novel approach for immobilizing enzymes with enhanced stability and activity, and this method may find a number of applications, such as in enzyme catalysis, DNA assays and immunoassays.

  12. Stability and instability of stationary solutions for sublinear parabolic equations

    Science.gov (United States)

    Kajikiya, Ryuji

    2018-01-01

    In the present paper, we study the initial boundary value problem of the sublinear parabolic equation. We prove the existence of solutions and investigate the stability and instability of stationary solutions. We show that a unique positive and a unique negative stationary solutions are exponentially stable and give the exact exponent. We prove that small stationary solutions are unstable. For one space dimensional autonomous equations, we elucidate the structure of stationary solutions and study the stability of all stationary solutions.

  13. Crosslinked Enzyme Aggregates in Hierarchically-Ordered Mesoporous Silica: A Simple and Effective Method for Enzyme Stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Moon Il; Kim, Jungbae; Lee, Jinwoo; Jia, Hongfei; Na, Hyon Bin; Youn, Jongkyu; Kwak, Ja Hun; Dohnalkova, Alice; Grate, Jay W.; Wang, Ping; Hyeon, Taeghwan; Park, Hyun-Gyu; Chang, Ho Nam

    2007-02-01

    alpha-chymotrypsin (CT) and lipase (LP) were immobilized in hierarchically-ordered mesocellular mesoporous silica (HMMS) in a simple but effective way for the enzyme stabilization, which was achieved by the enzyme adsorption followed by glutaraldehyde (GA) crosslinking. This resulted in the formation of nanometer scale crosslinked enzyme aggregates (CLEAs) entrapped in the mesocellular pores of HMMS (37 nm), which did not leach out of HMMS through narrow mesoporous channels (13 nm). CLEA of alpha-chymotrypsin (CLEA-CT) in HMMS showed a high enzyme loading capacity and significantly increased enzyme stability. No activity decrease of CLEA-CT was observed for two weeks under even rigorously shaking condition, while adsorbed CT in HMMS and free CT showed a rapid inactivation due to the enzyme leaching and presumably autolysis, respectively. With the CLEA-CT in HMMS, however, there was no tryptic digestion observed suggesting that the CLEA-CT is not susceptible to autolysis. Moreover, CLEA of lipase (CLEA-LP) in HMMS retained 30% specific activity of free lipase with greatly enhanced stability. This work demonstrates that HMMS can be efficiently employed as host materials for enzyme immobilization leading to highly enhanced stability of the immobilized enzymes with high enzyme loading and activity.

  14. Evolution of an Antibiotic Resistance Enzyme Constrained by Stability and Activity Trade-offs

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiaojun; Minasov, George; Shoichet, Brian K. (NWU)

    2010-03-08

    Pressured by antibiotic use, resistance enzymes have been evolving new activities. Does such evolution have a cost? To investigate this question at the molecular level, clinically isolated mutants of the {beta}-lactamase TEM-1 were studied. When purified, mutant enzymes had increased activity against cephalosporin antibiotics but lost both thermodynamic stability and kinetic activity against their ancestral targets, penicillins. The X-ray crystallographic structures of three mutant enzymes were determined. These structures suggest that activity gain and stability loss is related to an enlarged active site cavity in the mutant enzymes. In several clinically isolated mutant enzymes, a secondary substitution is observed far from the active site (Met182 {yields} Thr). This substitution had little effect on enzyme activity but restored stability lost by substitutions near the active site. This regained stability conferred an advantage in vivo. This pattern of stability loss and restoration may be common in the evolution of new enzyme activity.

  15. Robust Stability Analysis of Nonlinear Switched Systems with Filippov Solutions

    DEFF Research Database (Denmark)

    Ahmadi, Mohamadreza; Mojallali, Hamed; Wisniewski, Rafal

    2012-01-01

    This paper addresses the stability problem of a class of nonlinear switched systems with partitioned state-space and state-dependent switching. In lieu of the Caratheodory solutions, the general Filippov solutions are considered. This encapsulates solutions with infinite switching in finite time....... which provides sufficient means to construct the corresponding Lyapunov functions via available semi-definite programming techniques....

  16. Stability and Concentration Verification of Ammonium Perchlorate Dosing Solutions

    National Research Council Canada - National Science Library

    Tsui, David

    1998-01-01

    Stability and concentration verification was performed for the ammonium perchlorate dosing solutions used in the on-going 90-Day Oral Toxicity Study conducted by Springborn Laboratories, Inc. (SLI Study No. 3433.1...

  17. Stability of stationary and periodic solutions equations in Banach space

    Directory of Open Access Journals (Sweden)

    A. Ya. Dorogovtsev

    1997-01-01

    Full Text Available Linear difference and differential equations with operator coefficients and random stationary (periodic input are considered. Conditions are presented for the mean stability of stationary (periodic solutions under small perturbation of the coefficients.

  18. Stability of core–shell nanowires in selected model solutions

    Energy Technology Data Exchange (ETDEWEB)

    Kalska-Szostko, B., E-mail: kalska@uwb.edu.pl; Wykowska, U.; Basa, A.; Zambrzycka, E.

    2015-03-30

    Highlights: • Stability of the core–shell nanowires in environmental solutions were tested. • The most and the least aggressive solutions were determined. • The influence of different solutions on magnetic nanowires core was found out. - Abstract: This paper presents the studies of stability of magnetic core–shell nanowires prepared by electrochemical deposition from an acidic solution containing iron in the core and modified surface layer. The obtained nanowires were tested according to their durability in distilled water, 0.01 M citric acid, 0.9% NaCl, and commercial white wine (12% alcohol). The proposed solutions were chosen in such a way as to mimic food related environment due to a possible application of nanowires as additives to, for example, packages. After 1, 2 and 3 weeks wetting in the solutions, nanoparticles were tested by Infrared Spectroscopy, Atomic Absorption Spectroscopy, Transmission Electron Microscopy and X-ray diffraction methods.

  19. Stability of core–shell nanowires in selected model solutions

    International Nuclear Information System (INIS)

    Kalska-Szostko, B.; Wykowska, U.; Basa, A.; Zambrzycka, E.

    2015-01-01

    Highlights: • Stability of the core–shell nanowires in environmental solutions were tested. • The most and the least aggressive solutions were determined. • The influence of different solutions on magnetic nanowires core was found out. - Abstract: This paper presents the studies of stability of magnetic core–shell nanowires prepared by electrochemical deposition from an acidic solution containing iron in the core and modified surface layer. The obtained nanowires were tested according to their durability in distilled water, 0.01 M citric acid, 0.9% NaCl, and commercial white wine (12% alcohol). The proposed solutions were chosen in such a way as to mimic food related environment due to a possible application of nanowires as additives to, for example, packages. After 1, 2 and 3 weeks wetting in the solutions, nanoparticles were tested by Infrared Spectroscopy, Atomic Absorption Spectroscopy, Transmission Electron Microscopy and X-ray diffraction methods

  20. Wind energy systems solutions for power quality and stabilization

    CERN Document Server

    Ali, Mohd Hasan

    2012-01-01

    Unlike conventional power plants, wind plants emit no air pollutants or greenhouse gases--and wind energy is a free, renewable resource. However, the induction machines commonly used as wind generators have stability problems similar to the transient stability of synchronous machines. To minimize power, frequency, and voltage fluctuations caused by network faults or random wind speed variations, control mechanisms are necessary. Wind Energy Systems: Solutions for Power Quality and Stabilization clearly explains how to solve stability and power quality issues of wind generator systems. Covering

  1. Effect of external conditions on the stability of enzymically synthesized carthamin

    Directory of Open Access Journals (Sweden)

    Koshi Saito

    2014-01-01

    Full Text Available Enzymically synthesized carthamin was subjected to testing of its stability under various conditions. It easily turned to unknown reddish-yellow or orange-yellow substances in water. This instability was further accelerated by the presence of a sulfhydryl reagent and or at higher temperature. In a typical result, the rate of the discolouration was calculated to be 21 nmol carthamin h-1 at 20 °C in water and rose to 44.0 nmol carthamin h-1 at 60 °C in water containing 1.0 mM 2-mercaptoethanol. Organic solvents such as methanol, ethanol and acetone showed little effect on carthamin discolouration, while the stability of carthamin in these solvents was gradually decreased by rising temperature. In various buffers, in the acidic range. carthamin was relatively stable, whereas, it turned unstable on the basic side. All of the thiol reagents tested were unfavourable for retaining stability of carthamin in solutions. 2-Mercaptoethanol, reduced glutathione and thioglycollic acid exhibited the strongest degrading effect on the pigment. At the 1.0 mM level, 2-mercaptoethanol reduced the absorption peak at 517 nm by 0.02 min-1, which corresponded to 0.12 nmol carthamin cm-3 min-1 L-Methionine, L-ascorbic and D-araboascorbic acids were found to be strong bathochromic effectors For example, L-methionine rised AA 517 nm up to 0.01 min-1, whose value equaled to 0-1 nmol carthamin cm-3 min-1 at 30 °C Carthamin was absorbed and adsorbed and stabilized by many macro-molecular Substances. Among the compounds tested, cellulose was found to be the most effective stabilizer. The stabilization effect of cellulose was specific for carthamin and the term "SAITO EFFECT" is proposed for it. This effect was reduced by hydrolysis of the carthamin-adsorbed cellulose with Asperqillus cellulase in an incubation system

  2. Nanocaged enzymes with enhanced catalytic activity and increased stability against protease digestion

    Science.gov (United States)

    Zhao, Zhao; Fu, Jinglin; Dhakal, Soma; Johnson-Buck, Alexander; Liu, Minghui; Zhang, Ting; Woodbury, Neal W.; Liu, Yan; Walter, Nils G.; Yan, Hao

    2016-01-01

    Cells routinely compartmentalize enzymes for enhanced efficiency of their metabolic pathways. Here we report a general approach to construct DNA nanocaged enzymes for enhancing catalytic activity and stability. Nanocaged enzymes are realized by self-assembly into DNA nanocages with well-controlled stoichiometry and architecture that enabled a systematic study of the impact of both encapsulation and proximal polyanionic surfaces on a set of common metabolic enzymes. Activity assays at both bulk and single-molecule levels demonstrate increased substrate turnover numbers for DNA nanocage-encapsulated enzymes. Unexpectedly, we observe a significant inverse correlation between the size of a protein and its activity enhancement. This effect is consistent with a model wherein distal polyanionic surfaces of the nanocage enhance the stability of active enzyme conformations through the action of a strongly bound hydration layer. We further show that DNA nanocages protect encapsulated enzymes against proteases, demonstrating their practical utility in functional biomaterials and biotechnology. PMID:26861509

  3. An appraisal of the enzyme stability-activity trade-off.

    Science.gov (United States)

    Miller, Scott R

    2017-07-01

    A longstanding idea in evolutionary physiology is that an enzyme cannot jointly optimize performance at both high and low temperatures due to a trade-off between stability and activity. Although a stability-activity trade-off has been observed for well-characterized examples, such a trade-off is not imposed by any physical chemical constraint. To better understand the pervasiveness of this trade-off, I investigated the stability-activity relationship for comparative biochemical studies of purified orthologous enzymes identified by a literature search. The nature of this relationship varied greatly among studies. Notably, studies of enzymes with low mean synonymous nucleotide sequence divergence were less likely to exhibit the predicted negative correlation between stability and activity. Similarly, a survey of directed evolution investigations of the stability-activity relationship indicated that these traits are often uncoupled among nearly identical yet phenotypically divergent enzymes. This suggests that the presumptive trade-off often reported for investigations of enzymes with high mean sequence divergence may in some cases instead be a consequence of the degeneration over time of enzyme function in unselected environments, rather than a direct effect of thermal adaptation. The results caution against the general assertion of a stability-activity trade-off during enzyme adaptation. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

  4. Stability of Adrenaline in Irrigating Solution for Intraocular Surgery.

    Science.gov (United States)

    Shibata, Yuuka; Kimura, Yasuhiro; Taogoshi, Takanori; Matsuo, Hiroaki; Kihira, Kenji

    2016-01-01

    Intraocular irrigating solution containing 1 µg/mL adrenaline is widely used during cataract surgery to maintain pupil dilation. Prepared intraocular irrigating solutions are recommended for use within 6 h. After the irrigating solution is admistered for dilution, the adrenaline may become oxidized, and this may result in a decrease in its biological activity. However, the stability of adrenaline in intraocular irrigating solution is not fully understood. The aim of this study was to evaluate the stability of adrenaline in clinically used irrigating solutions of varying pH. Six hours after mixing, the adrenaline percentages remaining were 90.6%±3.7 (pH 7.2), 91.1%±2.2 (pH 7.5), and 65.2%±2.8 (pH 8.0) of the initial concentration. One hour after mixing, the percentages remaining were 97.6%±2.0 (pH 7.2), 97.4%±2.7 (pH 7.5), and 95.6%±3.3 (pH 8.0). The degradation was especially remarkable and time dependent in the solution at pH 8.0. These results indicate that the concentration of adrenaline is decreased after preparation. Moreover, we investigated the influence of sodium bisulfite on adrenaline stability in irrigating solution. The percentage adrenaline remaining at 6 h after mixing in irrigating solution (pH 8.0) containing sodium bisulfite at 0.5 µg/mL (concentration in irrigating solution) or at 500 µg/mL (concentration in the undiluted adrenaline preparation) were 57.5 and 97.3%, respectively. Therefore, the low concentration of sodium bisulfite in the irrigating solution may be a cause of the adrenaline loss. In conclusion, intraocular irrigation solution with adrenaline should be prepared just prior to its use in surgery.

  5. On exponential stability and periodic solutions of CNNs with delays

    Science.gov (United States)

    Cao, Jinde

    2000-03-01

    In this Letter, the author analyses further problems of global exponential stability and the existence of periodic solutions of cellular neural networks with delays (DCNNs). Some simple and new sufficient conditions are given ensuring global exponential stability and the existence of periodic solutions of DCNNs by applying some new analysis techniques and constructing suitable Lyapunov functionals. These conditions have important leading significance in the design and applications of globally stable DCNNs and periodic oscillatory DCNNs and are weaker than those in the earlier works [Phys. Rev. E 60 (1999) 3244], [J. Comput. Syst. Sci. 59 (1999)].

  6. Sodium tetraphenylborate solution stability: A long term study

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, M.J.

    1992-06-11

    Sodium tetraphenylborata (NaTPB) is a specialty chemical required for the In Tank Precipitation Process (ITP). It precipitates cesium, aiding in the decontamination of high level radioactive waste solutions. Long term stability of aqueous alkaline solutions of NATPB has been investigated. The focus of the investigation is on the relative stabilities of NATPB solutions exposed to varying temperatures and copper concentrations over an extended period of time. Additionally, vendor-supplied samples, incubated at 40{degree}C, were stored for more than a year without decomposing. Collected data demonstrates that in the absence of elevated copper concentrations, NATPB solutions will remain stable for periods of 1 to 2 years (at a minimum) at maximum expected operating conditions (<40{degree}C). Additionally, biuret, (H{sub 2}NCO){sub 2}NH, was tested as an additive to prevent copper-induced decomposition without success.

  7. Sodium tetraphenylborate solution stability: A long term study

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, M.J.

    1992-06-11

    Sodium tetraphenylborata (NaTPB) is a specialty chemical required for the In Tank Precipitation Process (ITP). It precipitates cesium, aiding in the decontamination of high level radioactive waste solutions. Long term stability of aqueous alkaline solutions of NATPB has been investigated. The focus of the investigation is on the relative stabilities of NATPB solutions exposed to varying temperatures and copper concentrations over an extended period of time. Additionally, vendor-supplied samples, incubated at 40[degree]C, were stored for more than a year without decomposing. Collected data demonstrates that in the absence of elevated copper concentrations, NATPB solutions will remain stable for periods of 1 to 2 years (at a minimum) at maximum expected operating conditions (<40[degree]C). Additionally, biuret, (H[sub 2]NCO)[sub 2]NH, was tested as an additive to prevent copper-induced decomposition without success.

  8. Stabilization of enzymes by multipoint covalent immobilization on supports activated with glyoxyl groups.

    Science.gov (United States)

    López-Gallego, Fernando; Fernandez-Lorente, Gloria; Rocha-Martin, Javier; Bolivar, Juan M; Mateo, Cesar; Guisan, Jose M

    2013-01-01

    Stabilization of enzymes via immobilization techniques is a valuable approach in order to convert a necessary protocol (immobilization) into a very interesting tool to improve key enzyme properties (stabilization). Multipoint covalent attachment of each immobilized enzyme molecule may promote a very interesting stabilizing effect. The relative distances among all enzyme residues involved in immobilization has to remain unaltered during any conformational change induced by any distorting agent. Amino groups are very interesting nucleophiles placed on protein surfaces. The immobilization of enzyme through the region having the highest amount of amino groups (Lys residues) is key for a successful stabilization. Glyoxyl groups are small aliphatic aldehydes that form very unstable Schiff's bases with amino groups and they do not seem to be useful for enzyme immobilization at neutral pH. However, under alkaline conditions, glyoxyl supports are able to immobilize enzymes via a first multipoint covalent immobilization through the region having the highest amount of Lysine groups. Activation of supports with a high surface density of glyoxyl groups and the performance of very intense enzyme-support multipoint covalent attachments are here described.

  9. Evaluation of the effects of enzyme-based liquid chemical stabilizers on subgrade soils

    CSIR Research Space (South Africa)

    Mgangira, Martin B

    2009-07-01

    Full Text Available The purpose of this study was to asses the strength of enzyme treated soil material. Thus the aim of the paper is to present laboratory results on the effects of two enzyme-based liquid chemicals as soil stabilizers. Soil samples were prepared...

  10. Enzyme Stability and Activity in Non-Aqueous Reaction Systems: A Mini Review

    Directory of Open Access Journals (Sweden)

    Shihui Wang

    2016-02-01

    Full Text Available Enormous interest in biocatalysis in non-aqueous phase has recently been triggered due to the merits of good enantioselectivity, reverse thermodynamic equilibrium, and no water-dependent side reactions. It has been demonstrated that enzyme has high activity and stability in non-aqueous media, and the variation of enzyme activity is attributed to its conformational modifications. This review comprehensively addresses the stability and activity of the intact enzymes in various non-aqueous systems, such as organic solvents, ionic liquids, sub-/super-critical fluids and their combined mixtures. It has been revealed that critical factors such as Log P, functional groups and the molecular structures of the solvents define the microenvironment surrounding the enzyme molecule and affect enzyme tertiary and secondary structure, influencing enzyme catalytic properties. Therefore, it is of high importance for biocatalysis in non-aqueous media to elucidate the links between the microenvironment surrounding enzyme surface and its stability and activity. In fact, a better understanding of the correlation between different non-aqueous environments and enzyme structure, stability and activity can contribute to identifying the most suitable reaction medium for a given biotransformation.

  11. Stability of sodium bicarbonate solutions in polyolefin bags.

    Science.gov (United States)

    Wear, Jennifer; McPherson, Timothy B; Kolling, William M

    2010-06-15

    The stability of sodium bicarbonate solutions in sterile water for injection or 5% dextrose injection stored at 21-24 degrees C or 2-4 degrees C was evaluated. Sodium bicarbonate injection was obtained in 50-mL vials of 8.4% (1 meq/mL). A total of 50, 100, or 150 meq of sodium bicarbonate was added to each 1-L polyolefin bag of either sterile water for injection or 5% dextrose injection. All solutions were prepared in a laminar-airflow hood using aseptic technique. Bags were punctured once to remove headspace air and once for the addition of each 50 meq of sodium bicarbonate. Six replicates of each test solution were prepared. The solutions were stored at 21-24 degrees C and 2-4 degrees C. Control solutions (50 and 150 meq) were similarly prepared in triplicate. Control solutions were sparged with either nitrogen gas or oxygen gas before storage. Sodium bicarbonate stability was assessed by measuring solution pH. Bicarbonate content was measured utilizing titration. Both pH and bicarbonate concentrations were measured immediately upon preparation and on days 3, 5, and 7 for both test and control solutions. All 95% confidence interval values for sample solution pH remained within 7.0-8.5 for seven days at 2-4 degrees C. Sodium bicarbonate solutions of 50, 100, and 150 meq in sterile water for injection or 5% dextrose injection were stable for up to seven days when refrigerated. The 50-meq solution was stable for up to 48 hours when stored at room temperature, and the 100- and 150-meq solutions were stable for up to 30 hours when stored at room temperature.

  12. Detection of microwave radiation of cytochrome CYP102 A1 solution during the enzyme reaction

    Directory of Open Access Journals (Sweden)

    Yu.D. Ivanov

    2016-03-01

    Full Text Available Microwave radiation at 3.4–4.2 GHz frequency of the cytochrome P450 CYP102 A1 (BM3 solution was registered during the lauric acid hydroxylation reaction. The microwave radiation generation was shown to occur following the addition of electron donor NADPH to a system containing an enzyme and a substrate. The radiation occurs for the enzyme solutions with enzyme concentrations of 10−8 and 10−9 М. The microwave radiation effect elicited by the aqueous enzyme solution was observed for the first time. The results obtained can be used to elaborate a new approach to enzyme systems research, including studying of the mechanism of interaction of a functioning enzyme system with microenvironment.

  13. Non-homologous isofunctional enzymes: a systematic analysis of alternative solutions in enzyme evolution.

    Science.gov (United States)

    Omelchenko, Marina V; Galperin, Michael Y; Wolf, Yuri I; Koonin, Eugene V

    2010-04-30

    Evolutionarily unrelated proteins that catalyze the same biochemical reactions are often referred to as analogous - as opposed to homologous - enzymes. The existence of numerous alternative, non-homologous enzyme isoforms presents an interesting evolutionary problem; it also complicates genome-based reconstruction of the metabolic pathways in a variety of organisms. In 1998, a systematic search for analogous enzymes resulted in the identification of 105 Enzyme Commission (EC) numbers that included two or more proteins without detectable sequence similarity to each other, including 34 EC nodes where proteins were known (or predicted) to have distinct structural folds, indicating independent evolutionary origins. In the past 12 years, many putative non-homologous isofunctional enzymes were identified in newly sequenced genomes. In addition, efforts in structural genomics resulted in a vastly improved structural coverage of proteomes, providing for definitive assessment of (non)homologous relationships between proteins. We report the results of a comprehensive search for non-homologous isofunctional enzymes (NISE) that yielded 185 EC nodes with two or more experimentally characterized - or predicted - structurally unrelated proteins. Of these NISE sets, only 74 were from the original 1998 list. Structural assignments of the NISE show over-representation of proteins with the TIM barrel fold and the nucleotide-binding Rossmann fold. From the functional perspective, the set of NISE is enriched in hydrolases, particularly carbohydrate hydrolases, and in enzymes involved in defense against oxidative stress. These results indicate that at least some of the non-homologous isofunctional enzymes were recruited relatively recently from enzyme families that are active against related substrates and are sufficiently flexible to accommodate changes in substrate specificity.

  14. On existence and stability of solutions for higher order semilinear ...

    Indian Academy of Sciences (India)

    Home; Journals; Proceedings – Mathematical Sciences; Volume 118; Issue 4. On Existence and Stability of Solutions for Higher Order Semilinear Dirichlet Problems. Marek Galewski ... Author Affiliations. Marek Galewski1. Faculty of Mathematics and Computer Science, University of Lodz, Banacha 22, 90-238 Lodz, Poland ...

  15. The Local Stability of Solutions for a Nonlinear Equation

    Directory of Open Access Journals (Sweden)

    Haibo Yan

    2014-01-01

    Full Text Available The approach of Kruzkov’s device of doubling the variables is applied to establish the local stability of strong solutions for a nonlinear partial differential equation in the space L1(R by assuming that the initial value only lies in the space L1(R∩L∞(R.

  16. Nanobubbles in confined solution: Generation, contact angle, and stability.

    Science.gov (United States)

    Wei, Jiachen; Zhang, Xianren; Song, Fan; Shao, Yingfeng

    2018-02-14

    The formation of gas bubbles presents a frequent challenge to microfluidic operations, for which fluids are geometrically confined to a microscale space. Here, to understand the mechanism of nucleating gas bubbles in microfluidic devices, we investigate the formation and stability of nanobubbles in confined solutions. Our molecular dynamics simulations show that while pinning of the contact line is a prerequisite for the stability of surface nanobubbles in open systems that can exchange gas with surrounding environment, in confined solutions, stable nanobubbles can exist even without pinning. In supersaturated condition, stable bubbles can be found in confined solutions with acute or obtuse contact angle, depending on the substrate hydrophobicity. We also demonstrate that when open to the bulk solution, the stable nanobubbles in closed systems would become unstable unless both supersaturation and pinning of the contact line are satisfied. Our results not only shed light on the design of novel heterogeneous surfaces for generating nanobubbles in confined space with controllable shape and stability but also address the crucial effect of gas exchange with the surroundings in determining the stability of nanobubbles.

  17. Stabilizing the border steady-state solution of two interacting ...

    African Journals Online (AJOL)

    In this paper, we have successfully developed a feedback control which has been used to stabilize an unstable steady-state solution (0, 3.3534). This convergence has occurred when the values of the final time are 190, 200, 210 and 220 which corresponds to the scenario when the value of the step length of our simulation ...

  18. Stabilizing effect of biochar on soil extracellular enzymes after a denaturing stress.

    Science.gov (United States)

    Elzobair, Khalid A; Stromberger, Mary E; Ippolito, James A

    2016-01-01

    Stabilizing extracellular enzymes may maintain enzymatic activity while protecting enzymes from proteolysis and denaturation. A study determined whether a fast pyrolysis hardwood biochar (CQuest™) would reduce evaporative losses, subsequently stabilizing soil extracellular enzymes and prohibiting potential enzymatic activity loss following a denaturing stress (microwaving). Soil was incubated in the presence of biochar (0%, 1%, 2%, 5%, or 10% by wt.) for 36 days and then exposed to microwave energies (0, 400, 800, 1600, or 3200 J g(-1) soil). Soil enzymes (β-glucosidase, β-d-cellobiosidase, N-acetyl-β-glucosaminidase, phosphatase, leucine aminopeptidase, β-xylosidase) were analyzed by fluorescence-based assays. Biochar amendment reduced leucine aminopeptidase and β-xylosidase potential activity after the incubation period and prior to stress exposure. The 10% biochar rate reduced soil water loss at the lowest stress level (400 J microwave energy g(-1) soil). Enzyme stabilization was demonstrated for β-xylosidase; intermediate biochar application rates prevented a complete loss of this enzyme's potential activity after soil was exposed to 400 (1% biochar treatment) or 1600 (5% biochar treatment) J microwave energy g(-1) soil. Remaining enzyme potential activities were not affected by biochar, and activities decreased with increasing stress levels. We concluded that biochar has the potential to reduce evaporative soil water losses and stabilize certain extracellular enzymes where activity is maintained after a denaturing stress; this effect was biochar rate and enzyme dependent. While biochar may reduce the potential activity of certain soil extracellular enzymes, this phenomenon was not universal as the majority of enzymes assayed in this study were unaffected by exposure to biochar. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Enzyme stability, thermodynamics and secondary structures of α-amylase as probed by the CD spectroscopy.

    Science.gov (United States)

    Kikani, B A; Singh, S P

    2015-11-01

    An amylase of a thermophilic bacterium, Bacillus sp. TSSC-3 (GenBank Number, EU710557) isolated from the Tulsi Shyam hot spring reservoir (Gujarat, India) was purified to the homogeneity in a single step on phenyl sepharose 6FF. The molecular weight of the enzyme was 25kD, while the temperature and pH optima for the enzyme catalysis were 80°C and 7, respectively. The purified enzyme was highly thermostable with broad pH stability and displayed remarkable resistance against surfactants, chelators, urea, guanidine HCl and various solvents as well. The stability and changes in the secondary structure of the enzyme under various extreme conditions were determined by the circular dichroism (CD) spectroscopy. The stability trends and the changes in the α-helices and β-sheets were analyzed by Mean Residual Ellipticity (MRE) and K2D3. The CD data confirmed the structural stability of the enzyme under various harsh conditions, yet it indicated reduced α-helix content and increased β-sheets upon denaturation. The thermodynamic parameters; deactivation rate constant, half-life, changes in entropy, enthalpy, activation energy and Gibb's free energy indicated that the enzyme-substrate reactions were highly stable. The overall profile of the enzyme: high thermostability, alkalitolerance, calcium independent nature, dextrose equivalent values and resistance against chemical denaturants, solvents and surfactants suggest its commercial applications. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. The improved stability of enzyme encapsulated in biomimetic titania particles

    International Nuclear Information System (INIS)

    Jiang Yanjun; Sun Qianyun; Jiang Zhongyi; Zhang Lei; Li Jian; Li Lin; Sun Xiaohui

    2009-01-01

    This study demonstrates a novel biomimetic approach for the entrapment of yeast alcohol dehydrogenase (YADH) within titania nanoparticles to improve its stability. Protamine was as the template and catalyst for the condensation of titanium (IV) bis(ammonium lactato) dihydroxide (Ti-BALDH) into titania nanoparticles in which YADH was trapped. The as-prepared titania/protamine/YADH composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The mechanism of YADH encapsulation was tentatively proposed from a series of experimental results. The preliminary investigation showed that encapsulated YADH could retain most of its initial activity. Compared to free YADH, encapsulated YADH exhibited significantly improved thermal, pH and recycling stability. After 5 weeks storage, no substantial loss of catalytic activity for encapsulated YADH was observed

  1. Models for enzyme superactivity in aqueous solutions of surfactants.

    OpenAIRE

    Viparelli, P; Alfani, F; Cantarella, M

    1999-01-01

    Theoretical models are developed here for enzymic activity in the presence of direct micellar aggregates. An approach similar to that of Bru et al. [Bru, Sánchez-Ferrer and Garcia-Carmona (1989) Biochem. J. 259, 355-361] for reverse micelles has been adopted. The system is considered to consist of three pseudo-phases: free water, bound water and surfactant tails. The substrate concentration in each pseudo-phase is related to the total substrate concentration in the reaction medium. In the abs...

  2. Solution stability of Captisol-stabilized melphalan (Evomela) versus Propylene glycol-based melphalan hydrochloride injection.

    Science.gov (United States)

    Singh, Ramsharan; Chen, Jin; Miller, Teresa; Bergren, Michael; Mallik, Rangan

    2016-12-14

    The objective of this study was to compare the stability of recently approved Captisol-stabilized propylene glycol-free melphalan injection (Evomela™) against currently marketed propylene glycol-based melphalan injection. The products were compared as reconstituted solutions in vials as well as admixture solutions prepared from normal saline in infusion bags. Evomela and propylene glycol-based melphalan injection were reconstituted in normal saline and organic custom diluent, respectively, according to their package insert instructions. The reconstituted solutions were diluted in normal saline to obtain drug admixture solutions at specific drug concentrations. Stability of the solutions was studied at room temperature by assay of melphalan and determination of melphalan-related impurities. Results show that based on the increase in total impurities in propylene glycol-based melphalan injection at 0.45 mg/mL, Evomela admixture solutions are about 5, 9, 15 and 29 times more stable at concentrations of 0.45, 1.0, 2.0 and 5.0 mg/mL, respectively. Results confirmed that reconstituted Evomela solution can be stored in the vial for up to 1 h at RT or for up to 24 h at refrigerated temperature (2-8 °C) with no significant degradation. After storage in the vial, it remains stable for an additional 3-29 h after preparation of admixture solution in infusion bags at concentrations of 0.25-5.0 mg/mL, respectively. In addition, Evomela solution in saline, at concentration of 5.0 mg/mL melphalan was bacteriostatic through 72 h storage at 2-8 °C. Formulation of melphalan with Captisol technology significantly improved stability compared to melphalan hydrochloride reconstituted with propylene-glycol based diluents.

  3. [Alanine solution as enzyme reaction buffer used in A to O blood group conversion].

    Science.gov (United States)

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

    2014-06-01

    The aim of this study was to investigate the effect of alanine solution as α-N-acetylgalactosaminidase enzyme reaction buffer on the enzymatic activity of A antigen. The binding ability of α-N-acetylgalactosaminidase with RBC in different reaction buffer such as alanine solution, glycine solution, normal saline (0.9% NaCl), PBS, PCS was detected by Western blot. The results showed that the efficiency of A to O conversion in alanine solution was similar to that in glycine solution, and Western blot confirmed that most of enzymes blinded with RBC in glycine or alanine solution, but few enzymes blinded with RBC in PBS, PCS or normal saline. The evidences indicated that binding of enzyme with RBC was a key element for A to O blood group conversion, while the binding ability of α-N-acetylgalactosaminidase with RBC in alanine or glycine solution was similar. It is concluded that alanine solution can be used as enzyme reaction buffer in A to O blood group conversion. In this buffer, the α-N-acetylgalactosaminidase is closely blinded with RBC and α-N-acetylgalactosaminidase plays efficient enzymatic activity of A antigen.

  4. Stability of core-shell nanowires in selected model solutions

    Science.gov (United States)

    Kalska-Szostko, B.; Wykowska, U.; Basa, A.; Zambrzycka, E.

    2015-03-01

    This paper presents the studies of stability of magnetic core-shell nanowires prepared by electrochemical deposition from an acidic solution containing iron in the core and modified surface layer. The obtained nanowires were tested according to their durability in distilled water, 0.01 M citric acid, 0.9% NaCl, and commercial white wine (12% alcohol). The proposed solutions were chosen in such a way as to mimic food related environment due to a possible application of nanowires as additives to, for example, packages. After 1, 2 and 3 weeks wetting in the solutions, nanoparticles were tested by Infrared Spectroscopy, Atomic Absorption Spectroscopy, Transmission Electron Microscopy and X-ray diffraction methods.

  5. Color stability of ceramic brackets immersed in potentially staining solutions

    Directory of Open Access Journals (Sweden)

    Bruna Coser Guignone

    2015-08-01

    Full Text Available OBJECTIVE: To assess the color stability of five types of ceramic brackets after immersion in potentially staining solutions.METHODS: Ninety brackets were divided into 5 groups (n = 18 according to brackets commercial brands and the solutions in which they were immersed (coffee, red wine, coke and artificial saliva. The brackets assessed were Transcend (3M/Unitek, Monrovia, CA, USA, Radiance (American Orthodontics, Sheboygan, WI, USA, Mystique (GAC International Inc., Bohemia, NY, USA and Luxi II (Rocky Mountain Orthodontics, Denver, CO, USA. Chromatic changes were analyzed with the aid of a reflectance spectrophotometer and by visual inspection at five specific time intervals. Assessment periods were as received from the manufacturer (T0, 24 hours (T1, 72 hours (T2, as well as 7 days (T3 and 14 days (T4 of immersion in the aforementioned solutions. Results were submitted to statistical analysis with ANOVA and Bonferroni correction, as well as to a multivariate profile analysis for independent and paired samples with significance level set at 5%.RESULTS: The duration of the immersion period influenced color alteration of all tested brackets, even though these changes could not always be visually observed. Different behaviors were observed for each immersion solution; however, brackets immersed in one solution progressed similarly despite minor variations.CONCLUSIONS: Staining became more intense over time and all brackets underwent color alterations when immersed in the aforementioned solutions.

  6. Enzyme

    Science.gov (United States)

    Enzymes are complex proteins that cause a specific chemical change in all parts of the body. For ... use them. Blood clotting is another example of enzymes at work. Enzymes are needed for all body ...

  7. Physicochemical stability of a metformin solution from three commercial brands

    Directory of Open Access Journals (Sweden)

    Alemón Medina Radamés

    2014-07-01

    Full Text Available Pharmacological management of insulin resistance and dyslipidaemias in children and adolescents is required to prevent the development of metabolic syndrome (MS and type II diabetes mellitus (DM2. Material and method: we developed extemporaneous formulations from 500 mg-tablets from three generic brands, commercially available in Mexican drugstores: MedimartTM, Farmacias del AhorroTM and Primer NivelTM, dissolved in water sweetened with Splenda, which made them palatable and allowed customised dose adjustment. Solutions were stored at four environmental conditions: 25oC exposed to light, 25oC protected from light, 4oC and 40oC, and their physicochemical stability was assayed. The stability of the drug was determined by ultra performance liquid chromatography and ultraviolet detection (UPLC-UV and by measuring the pH of the stock solution. The mobile phase consisted of (KH2PO4 0.1 M, pH = 6.5, 4.6 mM sodium dodecyl sulphate (SDS and acetonitrile (63:7:30 at 0.8 mL/min, column VARIAN Pursuit C8 150 × 3.9 mm tempered at 40oC, with detection at 236 nm. Results: Metformin from all trademarks was stable at all storage conditions for up to 30 days, retaining more than 90% of the initial amount of active drug, with a pH of 7.4 ± 0.3. Conclusion: Metformin extemporaneous formulations may be developed from either the innovator or generic brands, having the advantage of saving money and conserving the stability of its physicochemical properties. Keywords: Generic metformin, Innovator metformin, Extemporaneous formulation, Physicochemical stability, UPLC-UV.

  8. Structural aspects of magnetic fluid stabilization in aqueous agarose solutions

    Science.gov (United States)

    Nagornyi, A. V.; Petrenko, V. I.; Avdeev, M. V.; Yelenich, O. V.; Solopan, S. O.; Belous, A. G.; Gruzinov, A. Yu.; Ivankov, O. I.; Bulavin, L. A.

    2017-06-01

    Structure characterization of magnetic fluids (MFs) synthesized by three different methods in aqueous solutions of agarose was done by means of small-angle neutron (SANS) and synchrotron X-ray scattering (SAXS). The differences in the complex aggregation observed in the studied magnetic fluids were related to different stabilizing procedures of the three kinds of MFs. The results of the analysis of the scattering (mean size of single polydisperse magnetic particles, fractal dimensions of the aggregates) are consistent with the data of transmission electron microscopy (TEM).

  9. Enzyme-nanoporous gold biocomposite: excellent biocatalyst with improved biocatalytic performance and stability.

    Directory of Open Access Journals (Sweden)

    Xia Wang

    Full Text Available BACKGROUND: Applications involving biomolecules, such as enzymes, antibodies, and other proteins as well as whole cells, are often hampered by their unstable nature at extremely high temperature and in organic solvents. METHODOLOGY/PRINCIPAL FINDINGS: We constructed enzyme-NPG biocomposites by assembling various enzymes onto the surface of nanoporous gold (NPG, which showed much enhanced biocatalytic performance and stability. Various enzymes with different molecular sizes were successfully tethered onto NPG, and the loadings were 3.6, 3.1 and 0.8 mg g(-1 for lipase, catalase and horseradish peroxidase, respectively. The enzyme-NPG biocomposites exhibited remarkable catalytic activities which were fully comparable to those of free enzymes. They also presented enhanced stability, with 74, 78 and 53% of enzymatic activity retained after 20 successive batch reactions. Moreover, these novel biocomposites possessed significantly enhanced reaction durability under various thermal and in organic solvent systems. In a sample transesterification reaction, a high conversion rate was readily achieved by using the lipase-NPG biocomposite. CONCLUSION/SIGNIFICANCE: These nano-biocomposite materials hold great potential in applications such as biosensing, molecular electronics, catalysis, and controlled delivery.

  10. Functionalized Graphene Sheets As Immobilization Matrix for Fenugreek β-Amylase: Enzyme Kinetics and Stability Studies

    Science.gov (United States)

    Srivastava, Garima; Singh, Kritika; Talat, Mahe; Srivastava, Onkar Nath; Kayastha, Arvind M.

    2014-01-01

    β-Amylase finds application in food and pharmaceutical industries. Functionalized graphene sheets were customised as a matrix for covalent immobilization of Fenugreek β-amylase using glutaraldehyde as a cross-linker. The factors affecting the process were optimized using Response Surface Methodology based Box-Behnken design of experiment which resulted in 84% immobilization efficiency. Scanning and Transmission Electron Microscopy (SEM, TEM) and Fourier Tansform Infrared (FTIR) spectroscopy were employed for the purpose of characterization of attachment of enzyme on the graphene. The enzyme kinetic studies were carried out for obtaining best catalytic performance and enhanced reusability. Optimum temperature remained unchanged, whereas optimum pH showed shift towards acidic range for immobilized enzyme. Increase in thermal stability of immobilized enzyme and non-toxic nature of functionalized graphene can be exploited for production of maltose in food and pharmaceutical industries. PMID:25412079

  11. E2 enzyme inhibition by stabilization of a low-affinity interface with ubiquitin.

    Science.gov (United States)

    Huang, Hao; Ceccarelli, Derek F; Orlicky, Stephen; St-Cyr, Daniel J; Ziemba, Amy; Garg, Pankaj; Plamondon, Serge; Auer, Manfred; Sidhu, Sachdev; Marinier, Anne; Kleiger, Gary; Tyers, Mike; Sicheri, Frank

    2014-02-01

    Weak protein interactions between ubiquitin and the ubiquitin-proteasome system (UPS) enzymes that mediate its covalent attachment to substrates serve to position ubiquitin for optimal catalytic transfer. We show that a small-molecule inhibitor of the E2 ubiquitin-conjugating enzyme Cdc34A, called CC0651, acts by trapping a weak interaction between ubiquitin and the E2 donor ubiquitin-binding site. A structure of the ternary CC0651-Cdc34A-ubiquitin complex reveals that the inhibitor engages a composite binding pocket formed from Cdc34A and ubiquitin. CC0651 also suppresses the spontaneous hydrolysis rate of the Cdc34A-ubiquitin thioester without decreasing the interaction between Cdc34A and the RING domain subunit of the E3 enzyme. Stabilization of the numerous other weak interactions between ubiquitin and UPS enzymes by small molecules may be a feasible strategy to selectively inhibit different UPS activities.

  12. Functionalized graphene sheets as immobilization matrix for Fenugreek β-amylase: enzyme kinetics and stability studies.

    Directory of Open Access Journals (Sweden)

    Garima Srivastava

    Full Text Available β-Amylase finds application in food and pharmaceutical industries. Functionalized graphene sheets were customised as a matrix for covalent immobilization of Fenugreek β-amylase using glutaraldehyde as a cross-linker. The factors affecting the process were optimized using Response Surface Methodology based Box-Behnken design of experiment which resulted in 84% immobilization efficiency. Scanning and Transmission Electron Microscopy (SEM, TEM and Fourier Tansform Infrared (FTIR spectroscopy were employed for the purpose of characterization of attachment of enzyme on the graphene. The enzyme kinetic studies were carried out for obtaining best catalytic performance and enhanced reusability. Optimum temperature remained unchanged, whereas optimum pH showed shift towards acidic range for immobilized enzyme. Increase in thermal stability of immobilized enzyme and non-toxic nature of functionalized graphene can be exploited for production of maltose in food and pharmaceutical industries.

  13. Cell culture media impact on drug product solution stability.

    Science.gov (United States)

    Purdie, Jennifer L; Kowle, Ronald L; Langland, Amie L; Patel, Chetan N; Ouyang, Anli; Olson, Donald J

    2016-07-08

    To enable subcutaneous administration of monoclonal antibodies, drug product solutions are often needed at high concentrations. A significant risk associated with high drug product concentrations is an increase in aggregate level over the shelf-life dating period. While much work has been done to understand the impact of drug product formulation on aggregation, there is limited understanding of the link between cell culture process conditions and soluble aggregate growth in drug product. During cell culture process development, soluble aggregates are often measured at harvest using cell-free material purified by Protein A chromatography. In the work reported here, cell culture media components were evaluated with respect to their impact on aggregate levels in high concentration solution drug product during accelerated stability studies. Two components, cysteine and ferric ammonium citrate, were found to impact aggregate growth rates in our current media (version 1) leading to the development of new chemically defined media and concentrated feed formulations. The new version of media and associated concentrated feeds (version 2) were evaluated across four cell lines producing recombinant IgG4 monoclonal antibodies and a bispecific antibody. In all four cell lines, the version 2 media reduced aggregate growth over the course of a 12 week accelerated stability study compared with the version 1 media, although the degree to which aggregate growth decreased was cell line dependent. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:998-1008, 2016. © 2016 American Institute of Chemical Engineers.

  14. Stability of subsystem solutions in agent-based models

    Science.gov (United States)

    Perc, Matjaž

    2018-01-01

    The fact that relatively simple entities, such as particles or neurons, or even ants or bees or humans, give rise to fascinatingly complex behaviour when interacting in large numbers is the hallmark of complex systems science. Agent-based models are frequently employed for modelling and obtaining a predictive understanding of complex systems. Since the sheer number of equations that describe the behaviour of an entire agent-based model often makes it impossible to solve such models exactly, Monte Carlo simulation methods must be used for the analysis. However, unlike pairwise interactions among particles that typically govern solid-state physics systems, interactions among agents that describe systems in biology, sociology or the humanities often involve group interactions, and they also involve a larger number of possible states even for the most simplified description of reality. This begets the question: when can we be certain that an observed simulation outcome of an agent-based model is actually stable and valid in the large system-size limit? The latter is key for the correct determination of phase transitions between different stable solutions, and for the understanding of the underlying microscopic processes that led to these phase transitions. We show that a satisfactory answer can only be obtained by means of a complete stability analysis of subsystem solutions. A subsystem solution can be formed by any subset of all possible agent states. The winner between two subsystem solutions can be determined by the average moving direction of the invasion front that separates them, yet it is crucial that the competing subsystem solutions are characterised by a proper composition and spatiotemporal structure before the competition starts. We use the spatial public goods game with diverse tolerance as an example, but the approach has relevance for a wide variety of agent-based models.

  15. The effect of leachate recirculation with enzyme cellulase addition on waste stability in landfill bioreactor

    Science.gov (United States)

    Saffira, N.; Kristanto, G. A.

    2018-01-01

    Landfill bioreactor with leachate recirculation is known to enhance waste stabilization. However, the composition of waste in Indonesia is comprised by organic waste which is lignocellulosic materials that considered take a long time to degrade under anaerobic condition. To accelerate the degradation process, enzyme addition is ought to do. Cellulase is an enzyme that can catalyse cellulose and other polysaccharide decomposition processes. Therefore, operation of waste degradation using leachate recirculation with a cellulase addition to enhance waste stabilization was investigated using anaerobic bioreactor landfill. The experiment was performed on 2 conditions; leachate recirculation with cellulase addition and recirculation only as a control. The addition of cellulase is reported to be significant in decreasing organic content, represented by volatile solid parameter. The volatile solid reduction in the cellulase augmented reactor and control reactor was 17.86% and 7.90%, respectively. Cellulase addition also resulted in the highest cellulose reduction. Settlement of the landfill in a bioreactor with enzyme addition (32.67%) was reported to be higher than the control (19.33%). Stabilization of landfill review by the decreasing rate constant of the cellulose and lignin ratio parameter was more rapidly achieved by the enzyme addition (0.014 day-1) compared to control (0.002 day-1).

  16. Stability of biodegradable waterborne polyurethane films in buffered saline solutions.

    Science.gov (United States)

    Lin, Ying Yi; Hung, Kun-Che; Hsu, Shan-Hui

    2015-09-21

    The stability of polyurethane (PU) is of critical importance for applications such as in coating industry or as biomaterials. To eliminate the environmental concerns on the synthesis of PU which involves the use of organic solvents, the aqueous-based or waterborne PU (WBPU) has been developed. WBPU, however, may be unstable in an electrolyte-rich environment. In this study, the authors reported the stability of biodegradable WBPU in the buffered saline solutions evaluated by atomic force microscopy (AFM). Various biodegradable WBPU films were prepared by spin coating on coverslip glass, with a thickness of ∼300 nm. The surface AFM images of poly(ε-caprolactone) (PCL) diol-based WBPU revealed nanoglobular structure. The same feature was observed when 20% molar of the PCL diol soft segment was replaced by polyethylene butylenes adipate diol. After hydration in buffered saline solutions for 24 h, the surface domains generally increased in sizes and became irregular in shape. On the other hand, when the soft segment was replaced by 20% poly(l-lactide) diol, a meshlike surface structure was demonstrated by AFM. When the latter WBPU was hydrated, the surface domains appeared to be disconnected. Results from the attenuated total reflectance infrared spectroscopy and x-ray photoelectron spectroscopy indicated that the surface chemistry of WBPU films was altered after hydration. These changes were probably associated with the neutralization of carboxylate by ions in the saline solutions, resulting in the rearrangements of soft and hard segments and causing instability of the WBPU.

  17. Rational Design of Thermally Stable Novel Biocatalytic Nanomaterials: Enzyme Stability in Restricted Spatial Dimensions

    Science.gov (United States)

    Mudhivarthi, Vamsi K.

    Enzyme stability is of intense interest in bio-materials science as biocatalysts, and as sensing platforms. This is essentially because the unique properties of DNA, RNA, PAA can be coupled with the interesting and novel properties of proteins to produce systems with unprecedented control over their properties. In this article, the very first examples of enzyme/NA/inorganic hybrid nanomaterials and enzyme-Polyacrylic acid conjugates will be presented. The basic principles of design, synthesis and control of properties of these hybrid materials will be presented first, and this will be followed by a discussion of selected examples from our recent research findings. Data show that key properties of biological catalysts are improved by the inorganic framework especially when the catalyst is co-embedded with DNA. Several examples of such studies with various enzymes and proteins, including horseradish peroxidase (HRP), glucose oxidase (GO), cytochrome c (Cyt c), met-hemoglobin (Hb) and met-myoglobin (Mb) will be discussed. Additionally, key insights obtained by the standard methods of materials science including XRD, SEM and TEM as well as biochemical, calorimetric and spectroscopic methods will be discussed. Furthermore, improved structure and enhanced activities of the biocatalysts in specific cases will be demonstrated along with the potential stabilization mechanisms. Our hypothesis is that nucleic acids provide an excellent control over the enzyme-solid interactions as well as rational assembly of nanomaterials. These novel nanobiohybrid materials may aid in engineering more effective synthetic materials for gene-delivery, RNA-delivery and drug delivery applications.

  18. Stabilization of oil-in-water emulsions by enzyme catalyzed oxidative gelation of sugar beet pectin

    DEFF Research Database (Denmark)

    Abang Zaidel, Dayang Norulfairuz; Chronakis, Ioannis S.; Meyer, Anne S.

    2013-01-01

    Enzyme catalyzed oxidative cross-linking of feruloyl groups can promote gelation of sugar beet pectin (SBP). It is uncertain how the enzyme kinetics of this cross-linking reaction are affected in emulsion systems and whether the gelation affects emulsion stability. In this study, SBP (2.5% w...... catalyzed oxidative gelation of SBP was evaluated by small angle oscillatory measurements for horseradish peroxidase (HRP) (EC 1.11.1.7) and laccase (EC 1.10.3.2) catalysis, respectively. HRP catalyzed gelation rates, determined from the slopes of the increase of elastic modulus (G0) with time, were higher...

  19. Stability and enzyme inhibition activities of au nanoparticles using an aqueous extract of clove as a reducing and stabilizing agent

    International Nuclear Information System (INIS)

    Hameed, A.; Khan, I.; Naz, S.S.; Islam, N.U.

    2014-01-01

    Gold nanoparticles (AuNPs) were synthesized in one pot using aqueous extract of clove buds (CB) to reduce HAuCl/sub 4/ and stabilize gold in its atomic form at room temperature. To determine the potential of gold nanoparticles with clove buds (AuCB) for in vivo applications, the stability of the nanoparticles was explored as a function of temperature, pH and salt concentration. The suspensions were found to be stable for salt concentrations up to 1 mol/L, temperatures of up to 100 degree C and a pH range of 2-13. Our results indicate that CB exhibited comparable activities to standards of urease and carbonic anhydrase, but its conjugation to Au knocks out the enzyme inhibition activity by about two times. In case of xanthine oxidase activity, CB and its gold Au bio-conjugates (AuCB) are found to be absolutely inactive. (author)

  20. Stability estimates for solution of IBVP to fractional parabolic differential and difference equations

    Science.gov (United States)

    Ashyralyev, Allaberen; Cakir, Zafer

    2016-08-01

    In this work, we investigate initial-boundary value problems for fractional parabolic equations with the Neumann boundary condition. Stability estimates for the solution of this problem are established. Difference schemes for approximate solution of initial-boundary value problem are constructed. Furthermore, we give theorem on coercive stability estimates for the solution of the difference schemes.

  1. Prolonged stability of antimicrobial activity in peritoneal dialysis solutions.

    Science.gov (United States)

    Dooley, David P; Tyler, J Robert; Wortham, William G; Harrison, Linda S; Starnes, William F; Collins, George R; Ozuna, Irene S; Violet, Patty L; Ward, John A

    2003-01-01

    To evaluate the stability of the antimicrobial chemical and bioactivity of gentamicin, vancomycin, and gentamicin and vancomycin in combination, and the stability of the bioactivity of ceftazidime, admixed in standard peritoneal dialysis solutions and then maintained over a 14-day period at room temperature or under refrigeration. Peritoneal dialysis center and microbiology laboratory at a military, teaching medical center. Standard peritoneal dialysate bags admixed with gentamicin, vancomycin, gentamicin and vancomycin in combination, or ceftazidime were stored at either 4 degrees C or 20 degrees C for 14 days. Sequential aliquots were withdrawn and assayed for antibiotic activity by bioassay and, except for ceftazidime, immunoassay for chemical activity. The bioassay was performed using a standardized Kirby-Bauer disc method. Significance was determined by ANOVA and, where the effect size was significant at the p < 0.05 level, the application of the paired t-test or the Wilcoxon signed rank test to the difference in activity between the first and last samples. Antibiotic concentration by immunoassay did not significantly deteriorate over 14 days for vancomycin or gentamicin when either room temperature or refrigerated samples were studied. By bioassay, gentamicin and ceftazidime, but not vancomycin, lost moderate but significant activity over 14 days when refrigerated bags were assayed (except for an insignificant decrement in gentamicin in the combined vancomycin and gentamicin bags). Bags stored at room temperature, in general, lost significant bioactivity over 14 days, but to levels where clinical efficacy would still be expected. The vancomycin bioassay performed on the combination bags demonstrated a remarkably enhanced bioactivity, presumably reflecting synergy with gentamicin. These data indicate that the study antibiotics admixed with peritoneal dialysis fluids retain stable chemical activity, whether refrigerated or kept at room temperature, for at least

  2. Effect of fibrolytic enzymes on the fermentation characteristics, aerobic stability, and digestibility of bermudagrass silage.

    Science.gov (United States)

    Dean, D B; Adesogan, A T; Krueger, N; Littell, R C

    2005-03-01

    The aim of this study was to determine if the nutritive value and aerobic stability of bermudagrass (Cynodon dactylon) silage could be improved by addition of proprietary, exogenous cellulase/hemicellulase enzyme preparations at ensiling. A 5-wk regrowth of Tifton 85 bermudagrass was conserved without treatment (control) or after treatment with exogenous fibrolytic enzymes including Promote NET (Pr), Biocellulase X-20 (X20), Biocellulase A-20 (A20), and Enzyme CT. The respective enzymes were applied at half the recommended rate, the recommended rate, or twice the recommended rate corresponding to 0.65, 1.3, and 2.6 g/kg of DM, 7.3, 14.5, and 29 mg/kg of DM, at 7.3, 14.4, and 29 mg/kg of DM, and 89, 178, and 356 mg/kg of DM, for Pr, X20, A20, and CT, respectively. The enzymes were sprayed on the bermudagrass at ensiling (not added at feeding as suggested by the manufacturers) to test the objectives of the study. Six 1-kg replicates of chopped (5 cm) forage were ensiled for 145 d in 2.8-L mini silos. Three silos per treatment were used for chemical analysis and 3 for aerobic stability monitoring. The silage juice was analyzed for organic acids, pH, water-soluble carbohydrates (WSC), ammonia-N, and soluble N. Freeze-dried samples were analyzed for crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF). In vitro digestibility of DM (IVDMD), NDF (IVNDFD), and ADF (IVADFD) were determined after digesting the silages in buffered rumen fluid for 6 or 48 h in 2 ANKOM(II) Daisy Incubators. Compared with the other silages, those treated with Pr had lower DM losses, and lower pH and ammonia-N concentration than control silages. Residual WSC concentration was greater in Pr- and CT-treated silages than in control silages and greater in Pr-treated silages than CT-treated silages. Compared with control silages, NDF concentration was lower in silages treated with Pr, X20, and CT, and ADF concentration was lower in silages treated with Pr, X20, and A20

  3. Stability of Rosmarinic Acid in Aqueous Extracts from Different Lamiaceae Species after in vitro Digestion with Human Gastrointestinal Enzymes

    OpenAIRE

    Zorić, Zoran; Markić, Joško; Pedisić, Sandra; Bučević-Popović, Viljemka; Generalić-Mekinić, Ivana; Grebenar, Katarina; Kulišić-Bilušić, Tea

    2016-01-01

    The present study compares the gastrointestinal stability of rosmarinic acid in aqueous extracts of thyme, winter savory and lemon balm with the stability of pure rosmarinic acid. The stability of rosmarinic acid was detected after two-phase in vitro digestion process (gastric and duodenal) with human gastrointestinal enzymes. The concentration of rosmarinic acid in undigested and digested samples was detected using HPLC-DAD. Results showed that gastrointestinal stability of pure rosmarinic a...

  4. Stability of furosemide and aminophylline in parenteral solutions

    Directory of Open Access Journals (Sweden)

    Carolina Alves dos Santos

    2011-03-01

    Full Text Available Parenteral solutions (PS are one of the most commonly used drug delivery vehicles. Interactions among the drug, components in the drug's formulation, and the PS can result in the formation of inactive complexes that limit efficacy or increase side effects. The aim of this work was to evaluate possible interactions between the drugs and PS, assess drug stability and to identify degradation products after 20 h at room temperature. Furosemide (FSM and Aminophylline (APN were added to PS containing either 20% mannitol or 0.9% NaCl at pH 6.5-7.5 and 10-11. Their behavior was studied individually and as an admixture, after 1 h oxidation with H2O2, using a spectrophotometer and HPLC. Individually, FSM and APN added to 20% mannitol and 0.9% NaCl solutions had the highest stability at pH 10-11. When FSM and APN were combined, the behavior of FSM was similar to the behavior observed for the drug individually in the same solutions. With the drugs combined in 20% mannitol pH 10-11, HPLC showed that both drugs were stable after a 20 h period yielding two distinct peaks; in oxidized samples, the elution profile showed four peaks with retention times unrelated to the untreated samples.Soluções parenterais de grande volume são frequentemente utilizadas no ambiente hospitalar para a veiculação de fármacos. No entanto, possíveis incompatibilidades entre as estruturas dos fármacos, em diferentes veículos de administração, podem gerar possíveis associações antagônicas ou sinérgicas, resultando em alterações das propriedades físico-químicas, consequentemente, dos efeitos farmacológicos e das respostas clínicas esperadas. Este artigo avaliou a estabilidade e a possível formação de produtos de degradação entre os fármacos furosemida e aminofilina quando estes foram veiculados em soluções parenterais, após o preparo e após o período de 20 h. Furosemida e aminofilina foram adicionadas às soluções de 20% manitol e 0,9% NaCl nos valores

  5. Deubiquitinating enzyme PSMD14 promotes tumor metastasis through stabilizing SNAIL in human esophageal squamous cell carcinoma.

    Science.gov (United States)

    Zhu, Rui; Liu, Yongshuo; Zhou, Honghong; Li, Lei; Li, Yi; Ding, Fang; Cao, Xiufeng; Liu, Zhihua

    2018-04-01

    The epithelial-mesenchymal transition (EMT) transcription factor SNAIL is associated with distant metastasis and poor prognosis of esophageal squamous cell carcinoma (ESCC) patients. The proteolysis of SNAIL is mediated by the ubiquitin-proteasome system. Several E3 ligases have been characterized to promote SNAIL ubiquitination and degradation. However, the reverse process - deubiquitination of SNAIL remains largely unknown. In this study, we performed a mass spectrometry to examine the interaction between SNAIL and deubiquitinating enzyme(s). Subsequently, the deubiquitinating enzyme PSMD14 was identified to target SNAIL for deubiquitination and stabilization. Furthermore, knockdown of PSMD14 significantly blocks SNAIL-induced EMT and then suppresses tumor cell migration and invasion in vitro and tumor metastasis in vivo. In addition, the high expression level of PSMD14 predicts poor prognosis for esophageal cancer patients. These findings suggest PSMD14 as a bona fide deubiquitinating enzyme to regulate SNAIL at the post-translational level and provide a promising therapeutic strategy against tumor metastasis of esophageal cancer. Copyright © 2018 Elsevier B.V. All rights reserved.

  6. Optimization of ultrasound-assisted extraction of pectinase enzyme from guava (Psidium guajava) peel: Enzyme recovery, specific activity, temperature, and storage stability.

    Science.gov (United States)

    Amid, Mehrnoush; Murshid, Fara Syazana; Manap, Mohd Yazid; Islam Sarker, Zaidul

    2016-01-01

    This study aimed to investigate the effects of the ultrasound-assisted extraction conditions on the yield, specific activity, temperature, and storage stability of the pectinase enzyme from guava peel. The ultrasound variables studied were sonication time (10-30 min), ultrasound temperature (30-50 °C), pH (2.0-8.0), and solvent-to-sample ratio (2:1 mL/g to 6:1 mL/g). The main goal was to optimize the ultrasound-assisted extraction conditions to maximize the recovery of pectinase from guava peel with the most desirable enzyme-specific activity and stability. Under the optimum conditions, a high yield (96.2%), good specific activity (18.2 U/mg), temperature stability (88.3%), and storage stability (90.3%) of the extracted enzyme were achieved. The optimal conditions were 20 min sonication time, 40 °C temperature, at pH 5.0, using a 4:1 mL/g solvent-to-sample ratio. The study demonstrated that optimization of ultrasound-assisted process conditions for the enzyme extraction could improve the enzymatic characteristics and yield of the enzyme.

  7. Stability and square integrability of solutions of nonlinear fourth order differential equations

    Directory of Open Access Journals (Sweden)

    Moussadek Remili

    2016-05-01

    Full Text Available The aim of the present paper is to establish a new result, which guarantees the asymptotic stability of zero solution and square integrability of solutions and their derivatives to nonlinear differential equations of fourth order.

  8. Stability of the Simplest Periodic Solutions in the Stuart–Landau Equation with Large Delay

    Directory of Open Access Journals (Sweden)

    A. A. Kashchenko

    2012-01-01

    Full Text Available We study the local dynamics of the Stuart–Landau equation with large delay in the neibourhood of periodic solutions. We find sufficient conditions of instability of periodic solutions and sufficient conditions of their stability.

  9. High-Throughput Feasible Screening Tool for Determining Enzyme Stabilities against Organic Solvents Directly from Crude Extracts.

    Science.gov (United States)

    Wedde, Severin; Kleusch, Christian; Bakonyi, Daniel; Gröger, Harald

    2017-12-14

    Biotransformations in organic chemistry frequently suffer from limitations caused by low water-solubility of substrates and product inhibition. Both, usually are addressed by the addition of organic cosolvents, which often accompanies at the expense of enzyme stability. A common method for measuring enzyme stability is to determine the melting temperature (T m ) of the enzyme. However, current methods are limited to the application of purified enzymes. Herein, for the first time, an easy and fast (organic compounds, the T m values in the crude extract differed by up to 2.4 °C from that of the purified enzymes due to the presence of the host-cell proteins. Thus, the measurement of enzyme stabilities in crude extracts appears to represent conditions in whole-cell catalysts even better. The applied nano differential scanning fluorimetry technology is further proven to be suitable for whole-cell catalysts with two overexpressed enzymes; thus representing a tool for the rapid screening of natural and mutant enzyme libraries in terms of process stability for challenging biotransformations. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Engineering Enzyme Stability and Resistance to an Organic Cosolvent by Modification of Residues in the Access Tunnel

    Czech Academy of Sciences Publication Activity Database

    Koudeláková, T.; Chaloupková, R.; Březovský, J.; Prokop, Z.; Šebestová, E.; Hesseler, M.; Khabiri, Morteza; Plevaka, M.; Kulik, D.; Kutá-Smatanová, Ivana; Řezáčová, Pavlína; Ettrich, Rüdiger; Bornscheuer, U.T.; Damborský, J.

    2013-01-01

    Roč. 52, č. 7 (2013), s. 1959-1963 ISSN 1433-7851 R&D Projects: GA MŠk(CZ) LC06010 Institutional support: RVO:67179843 ; RVO:68378050 Keywords : directed evolution * enzyme catalysis * enzymes * protein engineering * protein stability Subject RIV: CE - Biochemistry; EB - Genetics ; Molecular Biology (UMG-J) Impact factor: 11.336, year: 2013

  11. Stable preparations of tyrosine hydroxylase provide the solution structure of the full-length enzyme

    Science.gov (United States)

    Bezem, Maria T.; Baumann, Anne; Skjærven, Lars; Meyer, Romain; Kursula, Petri; Martinez, Aurora; Flydal, Marte I.

    2016-01-01

    Tyrosine hydroxylase (TH) catalyzes the rate-limiting step in the biosynthesis of catecholamine neurotransmitters. TH is a highly complex enzyme at mechanistic, structural, and regulatory levels, and the preparation of kinetically and conformationally stable enzyme for structural characterization has been challenging. Here, we report on improved protocols for purification of recombinant human TH isoform 1 (TH1), which provide large amounts of pure, stable, active TH1 with an intact N-terminus. TH1 purified through fusion with a His-tagged maltose-binding protein on amylose resin was representative of the iron-bound functional enzyme, showing high activity and stabilization by the natural feedback inhibitor dopamine. TH1 purified through fusion with a His-tagged ZZ domain on TALON is remarkably stable, as it was partially inhibited by resin-derived cobalt. This more stable enzyme preparation provided high-quality small-angle X-ray scattering (SAXS) data and reliable structural models of full-length tetrameric TH1. The SAXS-derived model reveals an elongated conformation (Dmax = 20 nm) for TH1, different arrangement of the catalytic domains compared with the crystal structure of truncated forms, and an N-terminal region with an unstructured tail that hosts the phosphorylation sites and a separated Ala-rich helical motif that may have a role in regulation of TH by interacting with binding partners. PMID:27462005

  12. Schwertmannite stability in anoxic Fe(II)-rich aqueous solution

    Science.gov (United States)

    Paikaray, Susanta; Schröder, Christian; Peiffer, Stefan

    2017-11-01

    Schwertmannite (SHM) is a powerful scavenger for As(III) leading to As(III)-enriched precipitates around acid mine drainage environments that may become exposed to aqueous Fe(II). In this study we have investigated the stability of pure SHM and SHM containing 0.92 wt% As(III) under Fe(II)aq-rich (0.4-1.0 mM) anoxic conditions using XRD, SEM, Mössbauer and FTIR spectroscopic techniques. Schwertmannite transformation proceeded through an alkalinity-driven pathway releasing sulfate and a Fe(II)-catalyzed pathway that generated lepidocrocite and goethite at pH 6 and 6.9 in the presence of 1 mM Fe(II)aq. Lepidocrocite was found to be needle shaped if the SHM contained As(III) and platy for pure SHM. Goethite had a poor degree of crystallinity in As(III) containing SHM. Pre-adsorption of As(III) inhibited the extent of SHM transformation. Fe(II) sorption onto SHM was pH dependent and reflected a sorption edge with complete consumption at pH 6.9, while only ∼20% were adsorbed at pH 5. Surface coverage with Fe(II) appears to be the key parameter controlling extent and products of the transformation process. As(III) concentrations in solution are controlled by two mechanisms: (1) exchange of As(III) for sulfate upon alkalinity-driven transformation of schwertmannite and (2) re-adsorption to new phases formed upon Fe(II)-catalyzed transformation. The adsorbed As(III) has inhibited the extent of transformation and was partly released with the maximum release at pH 5 (0.5%) in the absence of Fe(II)aq.

  13. Squalene mono-oxygenase, a key enzyme in cholesterol synthesis, is stabilized by unsaturated fatty acids.

    Science.gov (United States)

    Stevenson, Julian; Luu, Winnie; Kristiana, Ika; Brown, Andrew J

    2014-08-01

    SM (squalene mono-oxygenase) catalyses the first oxygenation step in cholesterol synthesis, immediately before the formation of the steroid backbone at lanosterol. SM is an important control point in the pathway, and is regulated at the post-translational level by accelerated cholesterol-dependent ubiquitination and proteasomal degradation, which is associated with the accumulation of squalene. Using model cell systems, we report that SM is stabilized by unsaturated fatty acids. Treatment with unsaturated fatty acids such as oleate, but not saturated fatty acids, increased protein levels of SM or SM-N100-GFP (the first 100 amino acids of SM fused to GFP) at the post-translational level and partially overcame cholesterol-dependent degradation, as well as reversing cholesterol-dependent squalene accumulation. Maximum stabilization required activation of fatty acids, but not triacylglycerol or phosphatidylcholine synthesis. The mechanism of oleate-mediated stabilization appeared to occur through reduced ubiquitination by the E3 ubiquitin ligase MARCH6. Stabilization of a cholesterol biosynthetic enzyme by unsaturated fatty acids may help maintain a constant cholesterol/phospholipid ratio.

  14. A new generation approach in enzyme immobilization: Organic-inorganic hybrid nanoflowers with enhanced catalytic activity and stability.

    Science.gov (United States)

    Altinkaynak, Cevahir; Tavlasoglu, Sureyya; Özdemir, Nalan; Ocsoy, Ismail

    2016-11-01

    Many different micro and nano sized materials have been used for enzymes immobilization in order to increase their catalytic activity and stability. Generally, immobilized enzymes with conventional immobilization techniques exhibit improved stability while their activity is lowered compared to free enzymes. Recently, an elegant immobilization approach was discovered in synthesis of flower-like organic-inorganic hybrid nanostructures with extraordinary catalytic activity and stability. In this novel immobilization strategy, proteins (enzymes) and metal ions acted as organic and inorganic components, respectively to form hybrid nanoflowers (hNFs). It is demonstrated that the hNFs highly enhanced catalytic activities and stability in a wide range of experimental conditions (pHs, temperatures and salt concentration, etc.) compared to free and conventionally immobilized enzymes. This review mainly discussed the synthesis, characterization, development and applications of organic-inorganic hybrid nanoflowers formed of various enzymes and metal ions and explained potential mechanism underlying enhanced catalytic activity and stability. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Identifying sequential substrate binding at the single-molecule level by enzyme mechanical stabilization.

    Science.gov (United States)

    Rivas-Pardo, Jaime Andrés; Alegre-Cebollada, Jorge; Ramírez-Sarmiento, César A; Fernandez, Julio M; Guixé, Victoria

    2015-01-01

    Enzyme-substrate binding is a dynamic process intimately coupled to protein structural changes, which in turn changes the unfolding energy landscape. By the use of single-molecule force spectroscopy (SMFS), we characterize the open-to-closed conformational transition experienced by the hyperthermophilic adenine diphosphate (ADP)-dependent glucokinase from Thermococcus litoralis triggered by the sequential binding of substrates. In the absence of substrates, the mechanical unfolding of TlGK shows an intermediate 1, which is stabilized in the presence of Mg·ADP(-), the first substrate to bind to the enzyme. However, in the presence of this substrate, an additional unfolding event is observed, intermediate 1*. Finally, in the presence of both substrates, the unfolding force of intermediates 1 and 1* increases as a consequence of the domain closure. These results show that SMFS can be used as a powerful experimental tool to investigate binding mechanisms of different enzymes with more than one ligand, expanding the repertoire of protocols traditionally used in enzymology.

  16. Caenorhabditis elegans NDX-4 is a MutT-type enzyme that contributes to genomic stability.

    Science.gov (United States)

    Arczewska, Katarzyna D; Baumeier, Christian; Kassahun, Henok; Sengupta, Tanima; Bjørås, Magnar; Kuśmierek, Jarosław T; Nilsen, Hilde

    2011-02-07

    MutT enzymes prevent DNA damage by hydrolysis of 8-oxodGTP, an oxidized substrate for DNA synthesis and antimutagenic, anticarcinogenic, and antineurodegenerative functions of MutT enzymes are well established. MutT has been found in almost all kingdoms of life, including many bacterial species, yeasts, plants and mammals. However, a Caenorhabditis elegans MutT homologue was not previously identified. Here, we demonstrate that NDX-4 exhibits both hallmarks of a MutT-type enzyme with an ability to hydrolyze 8-oxodGTP and suppress the Escherichia coli mutT mutator phenotype. Moreover, we show that NDX-4 contributes to genomic stability in vivo in C. elegans. Phenotypic analyses of an ndx-4 mutant reveal that loss of NDX-4 leads to upregulation of key stress responsive genes that likely compensate for the in vivo role of NDX-4 in protection against deleterious consequences of oxidative stress. This discovery will enable us to use this extremely robust genetic model for further research into the contribution of oxidative DNA damage to phenotypes associated with oxidative stress. Copyright © 2010 Elsevier B.V. All rights reserved.

  17. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed in...

  18. Orbital stability of Gausson solutions to logarithmic Schrodinger equations

    Directory of Open Access Journals (Sweden)

    Alex H. Ardila

    2016-12-01

    Full Text Available In this article we prove of the orbital stability of the ground state for logarithmic Schrodinger equation in any dimension and under nonradial perturbations. This general stability result was announced by Cazenave and Lions [9, Remark II.3], but no details were given there.

  19. Effects of Straw Incorporation on Soil Nutrients, Enzymes, and Aggregate Stability in Tobacco Fields of China

    Directory of Open Access Journals (Sweden)

    Jiguang Zhang

    2016-07-01

    Full Text Available To determine the effects of straw incorporation on soil nutrients, enzyme activity, and aggregates in tobacco fields, we conducted experiments with different amounts of wheat and maize straw in Zhucheng area of southeast Shandong province for three years (2010–2012. In the final year of experiment (2012, straw incorporation increased soil organic carbon (SOC and related parameters, and improved soil enzyme activity proportionally with the amount of straw added, except for catalase when maize straw was used. And maize straw incorporation was more effective than wheat straw in the tobacco field. The percentage of aggregates >2 mm increased with straw incorporation when measured by either dry or wet sieving. The mean weight diameter (MWD and geometric mean diameter (GMD in straw incorporation treatments were higher than those in the no-straw control (CK. Maize straw increased soil aggregate stability more than wheat straw with the same incorporation amount. Alkaline phosphatase was significantly and negatively correlated with soil pH. Sucrase and urease were both significantly and positively correlated with soil alkali-hydrolysable N. Catalase was significantly but negatively correlated with soil extractable K (EK. The MWD and GMD by dry sieving had significantly positive correlations with SOC, total N, total K, and EK, but only significantly correlated with EK by wet sieving. Therefore, soil nutrients, metabolic enzyme activity, and aggregate stability might be increased by increasing the SOC content through the maize or wheat straw incorporation. Moreover, incorporation of maize straw at 7500 kg·hm−2 was the best choice to enhance soil fertility in the tobacco area of Eastern China.

  20. Synthesis of (3S,4S,5S)-trihydroxylpiperidine derivatives as enzyme stabilizers to improve therapeutic enzyme activity in Fabry patient cell lines.

    Science.gov (United States)

    Li, Huang-Yi; Lee, Jay-Der; Chen, Chiao-Wen; Sun, Ying-Chieh; Cheng, Wei-Chieh

    2018-01-20

    A series of 3S,4S,5S-trihydroxylated piperidines bearing structural diversity at C-2 or C-6 positions has been synthesized and tested to determine their ability to stabilize the activity of recombinant human α-Galactosidase A (rh-α-Gal A). Hit molecules were identified by rapid inhibitory activity screening, and then further investigated for their ability to protect this enzyme from thermo-induced denaturation and enhance its activity in Fabry patient cell lines. Our study resulted in the identification of a new class of small molecules as enzyme stabilizers for the potential treatment of Fabry disease. Of these, stabilizer 21 was the most effective, showing a 12-fold increase in rh-α-Gal A activity in Fabry disease cell lines. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  1. Relationship between sol-gel conditions and enzyme stability: a case study with β-galactosidase/silica biocatalyst for whey hydrolysis.

    Science.gov (United States)

    Escobar, Sindy; Bernal, Claudia; Mesa, Monica

    2015-01-01

    The sol-gel process has been very useful for preparing active and stable biocatalysts, with the possibility of being reused. Especially those based on silica are well known. However, the study of the enzyme behavior during this process is not well understood until now and more, if the surfactant is involved in the synthesis mixture. This work is devoted to the encapsulation of β-galactosidase from Bacillus circulans in silica by sol-gel process, assisted by non-ionic Triton X-100 surfactant. The correlation between enzyme activity results for the β-galactosidase in three different environments (soluble in buffered aqueous reference solution, in the silica sol, and entrapment on the silica matrix) explains the enzyme behavior under stress conditions offered by the silica sol composition and gelation conditions. A stable β-galactosidase/silica biocatalyst is obtained using sodium silicate, which is a cheap source of silica, in the presence of non-ionic Triton X-100, which avoids the enzyme deactivation, even at 40 °C. The obtained biocatalyst is used in the whey hydrolysis for obtaining high value products from this waste. The preservation of the enzyme stability, which is one of the most important challenges on the enzyme immobilization through the silica sol-gel, is achieved in this study.

  2. Sensitizing effect of Z,Z-bilirubin IXα and its photoproducts on enzymes in model solutions

    Science.gov (United States)

    Plavskii, V. Yu.; Mostovnikov, V. A.; Tret'yakova, A. I.; Mostovnikova, G. R.

    2008-05-01

    In model systems, we have studied side effects which may be induced by light during phototherapy of hyperbilirubinemia (jaundice) in newborn infants, with the aim of reducing the Z,Z-bilirubin IXα (Z,Z-BR IXα) level. We have shown that the sensitizing effect of Z,Z-BR IXα, localized at strong binding sites of the human serum albumin (HSA) macromolecule, is primarily directed at the amino acid residues of the carrier protein and does not involve the molecules of the enzyme (lactate dehydrogenase (LDH)) present in the buffer solution. The detected photodynamic damage to LDH is due to sensitization by bilirubin photoisomers, characterized by lower HSA association constants and located (in contrast to native Z,Z-BR IXα) on the surface of the HSA protein globule. Based on study of the spectral characteristics of the photoproducts of Z,Z-BR IXα and comparison of their accumulation kinetics in solution and the enzyme photo-inactivation kinetics, we concluded that the determining role in sensitized damage to LDH is played by lumirubin. The photosensitization effect depends on the wavelength of the radiation used for photoconversion of bilirubin. When (at the beginning of exposure) we make sure that identical numbers of photons are absorbed by the pigment in the different spectral ranges, the side effect is minimal for radiation corresponding to the long-wavelength edge of the bilirubin absorption band. We have shown that for a bilirubin/HSA concentration ratio >2 (when some of the pigment molecules are sorbed on the surface of the protein globule), the bilirubin can act as a photosensitizing agent for the enzyme present in solution. We discuss methods for reducing unfavorable side effects of light on the body of newborn infants during phototherapy of hyperbilirubinemia.

  3. Existence and stability of periodic solutions for a delayed prey-predator model with diffusion effects

    Directory of Open Access Journals (Sweden)

    Hongwei Liang

    2016-01-01

    Full Text Available Existence and stability of spatially periodic solutions for a delay prey-predator diffusion system are concerned in this work. We obtain that the system can generate the spatially nonhomogeneous periodic solutions when the diffusive rates are suitably small. This result demonstrates that the diffusion plays an important role on deriving the complex spatiotemporal dynamics. Meanwhile, the stability of the spatially periodic solutions is also studied. Finally, in order to verify our theoretical results, some numerical simulations are also included.

  4. Influence of temperature on the kinetics absorption of carbon dioxide in aqueous of enzyme catalysed MDEA solutions

    NARCIS (Netherlands)

    Penders-van Elk, Nathalie J. M. C.; van Aken, Coen; Versteeg, Geert F.

    In the present work the absorption of carbon dioxide in 1000 mol m(-3) N-methyldiethanolamine (MDEA) solutions with and without enzyme has been studied in a stirred cell reactor in the temperature range 278-343 K and enzyme concentrations ranging from 0 to 1600 gm(-3). During this study a new type

  5. Stabilization of solutions of feather keratins by sodium dodecyl sulphate

    NARCIS (Netherlands)

    Schrooyen, P.M.M.; Dijkstra, Pieter J.; Oberthür, Radulf C.; Bantjes, A.; Bantjes, Adriaan; Feijen, Jan

    2001-01-01

    Feather keratins were extracted from chicken feathers with aqueous solutions of urea and 2-mercaptoethanol. After filtration of the insoluble residue, a feather keratin solution was obtained. Removal of 2-mercaptoethanol and urea by dialysis resulted in aggregation of the keratin polypeptide chains

  6. Solution conformation of the thermolysin inhibitors carbobenzoxy-L-phenylalanine and beta-phenylpropionyl-L-phenylalanine and comparison of the solution conformation to the enzyme-bound conformation.

    Science.gov (United States)

    Shieh, T L; Byrn, S R

    1982-04-01

    The conformations of enzyme inhibitors in solution and bound to the enzyme thermolysin are investigated as a convenient model for understanding the relationship between the conformation of drugs in solution and at the receptor. The solution conformations of carbobenzoxy-L-phenylalanine (I) and beta-phenylpropionyl-L-phenylalanine (II) are determined using nuclear magnetic resonance spectroscopy. These studies show that I and II have essentially the same conformation about both the alpha-beta bond and the C alpha-N bond in Me2SO-d6, acetone-d6, methanol-d4, chloroform-d, and D2O. In addition, the conformations of I and II are similar to phenylalanine and other phenylalanine derivatives. Comparison of the lowest energy solution conformer to that bound by the enzyme thermolysin shows that the lowest energy conformer (in solution) of carbobenzoxy-L-phenylalanine is bound by thermolysin; on the other hand, it is the highest energy conformer (in solution) of beta-phenylpropionyl-L-phenylalanine which is bound to the enzyme. This, to our knowledge, is one of the first experimental conformations of the hypothesis that an enzyme does not always bind the lowest energy conformer of an inhibitor.

  7. Stabilization of periodic solutions in a tethered satellite system by damping injection

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Blanke, Mogens

    2009-01-01

    presents a control design for stabilizing these periodic solutions. The design consists of a control law for stabilizing the open-loop equilibrium and a bias term which forces the system trajectory away from the equilibrium. The tether needs to be positioned away from open-loop equilibrium for the tether...... to affect the orbit parameters. An approximation of the periodic solutions of the closed loop system is found as a series expansion in the parameter plane spanned by the controller gain and the bias term. The stability of the solutions is investigated using linear Floquet analysis of the variational...

  8. Weak stability of Lagrangian solutions to the semigeostrophic equations

    International Nuclear Information System (INIS)

    Faria, Josiane C O; Lopes Filho, Milton C; Nussenzveig Lopes, Helena J

    2009-01-01

    In (Cullen and Feldman 2006 SIAM J. Math. Anal. 37 137–95), Cullen and Feldman proved the existence of Lagrangian solutions for the semigeostrophic system in physical variables with initial potential vorticity in L p , p > 1. Here, we show that a subsequence of the Lagrangian solutions corresponding to a strongly convergent sequence of initial potential vorticities in L 1 converges strongly in L q , q < ∞, to a Lagrangian solution, in particular extending the existence result of Cullen and Feldman to the case p = 1. We also present a counterexample for Lagrangian solutions corresponding to a sequence of initial potential vorticities converging in BM. The analytical tools used include techniques from optimal transportation, Ambrosio's results on transport by BV vector fields and Orlicz spaces

  9. The storage stability of polyvinylbutyral solutions from an electrospinnability standpoint

    Czech Academy of Sciences Publication Activity Database

    Peer, Petra; Stěnička, M.; Pavlinek, V.; Filip, Petr

    2014-01-01

    Roč. 105, July (2014), s. 134-139 ISSN 0141-3910 R&D Projects: GA ČR(CZ) GAP105/11/2342 Institutional support: RVO:67985874 Keywords : electrospinning * nanofibres * polyvinylbutyral * ageing * stability Subject RIV: BK - Fluid Dynamics Impact factor: 3.163, year: 2014

  10. Stability of Solutions to Semilinear Stochastic Evolution Equations

    Czech Academy of Sciences Publication Activity Database

    Leha, G.; Maslowski, Bohdan; Ritter, G.

    1999-01-01

    Roč. 17, č. 6 (1999), s. 1009-1051 ISSN 0736-2994 R&D Projects: GA ČR GA201/95/0629 Institutional research plan: CEZ:AV0Z1019905; CEZ:AV0Z1019905 Keywords : stochastic evolution equations * Lyapunov stability * forward inequality Subject RIV: BA - General Mathematics Impact factor: 0.263, year: 1999

  11. Copper stressed anaerobic fermentation: biogas properties, process stability, biodegradation and enzyme responses.

    Science.gov (United States)

    Hao, He; Tian, Yonglan; Zhang, Huayong; Chai, Yang

    2017-12-01

    The effect of copper (added as CuCl 2 ) on the anaerobic co-digestion of Phragmites straw and cow dung was studied in pilot experiments by investigating the biogas properties, process stability, substrate degradation and enzyme activities at different stages of mesophilic fermentation. The results showed that 30 and 100 mg/L Cu 2+ addition increased the cumulative biogas yields by up to 43.62 and 20.77% respectively, and brought forward the daily biogas yield peak, while 500 mg/L Cu 2+ addition inhibited biogas production. Meanwhile, the CH 4 content in the 30 and 100 mg/L Cu 2+ -added groups was higher than that in the control group. Higher pH values (close to pH 7) and lower oxidation-reduction potential (ORP) values in the Cu 2+ -added groups after the 8th day indicated better process stability compared to the control group. In the presence of Cu 2+ , the degradation of volatile fatty acids (VFAs) and other organic molecules (represented by chemical oxygen demand, COD) generated from hydrolysis was enhanced, and the ammonia nitrogen (NH 4 + -N) concentrations were more stable than in the control group. The contents of lignin and hemicellulose in the substrate declined in the Cu 2+ -added groups while the cellulose contents did not. Neither the cellulase nor the coenzyme F 420 activities could determine the biogas producing efficiency. Taking the whole fermentation process into account, the promoting effect of Cu 2+ addition on biogas yields was mainly attributable to better process stability, the enhanced degradation of lignin and hemicellulose, the transformation of intermediates into VFA, and the generation of CH 4 from VFA.

  12. Boundary value problem for the nonlinear analogues of the Boussinesq equation: Numerical solution and its stability

    Directory of Open Access Journals (Sweden)

    Sherif Amirov

    2017-08-01

    Full Text Available The recent work on the solvability of the boundary value problem for the nonlinear analogue of the Boussinesq equation has been further extended to focus on the characteristics of the solution. Since this type of equation does not have a known analytical solution for arbitrary boundary conditions, the problem has been solved numerically. The stability of the solution and the effect of the input function on the stability have been investigated from the physics point of view. For the special case of a discontinuous function at the right hand side of the equation, the solution has been analyzed around the discontinuity points.

  13. On the stability of soliton solution in NLS-type general field model

    International Nuclear Information System (INIS)

    Chakrabarti, S.; Nayyar, A.H.

    1982-08-01

    A model incorporating the nonlinear Schroedinger equation and its generalizations is considered and the stability of its periodic-in-time solutions under the restriction of a fixed charge Q is analysed. It is shown that the necessary condition for the stability is given by the inequality deltaQ/deltaν<0, where ν is the parameter of periodicity of the solution in time. In particular, one specific class of Lagrangians is considered and, in addition, the sufficient conditions for the stability of the soliton solutions are also determined. This study thus examines both the necessary and the sufficient conditions for the stability of the solutions of nonlinear Schroedinger equation and some of its generalizations. (author)

  14. Design of Surface-Active Artificial Enzyme Particles to Stabilize Pickering Emulsions for High-Performance Biphasic Biocatalysis.

    Science.gov (United States)

    Chen, Zhaowei; Zhao, Chuanqi; Ju, Enguo; Ji, Haiwei; Ren, Jinsong; Binks, Bernard P; Qu, Xiaogang

    2016-02-24

    Surface-active artificial enzymes (SAEs) are designed and constructed by a general and novel strategy. These SAEs can simultaneously stabilize Pickering emulsions and catalyze biphasic biotransformation with superior enzymatic stability and good re-usability; for example, for the interfacial conversion of hydrophobic p-nitrophenyl butyrate into yellow water-soluble p-nitrophenolate catalyzed by esterase-mimic SAE. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Spectroscopic study on the stability of morin in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Bark, Ki Min [Dept. of Chemical Education and Research Institute of Life Science, Gyeongsang National University, Chinju (Korea, Republic of); Im, Seo Eun; Seo, Jung Ja; Park, Ok Hyun; Park, Hyoung Ryun [Dept. of Chemistry, Chonnam National University, Gwangju (Korea, Republic of); Park, Chul Ho [Dept. of Cosmetic Science, Nambu University, Gwangju (Korea, Republic of)

    2015-02-15

    Morin (3,2,4,5,7-pentahydroxyflavone) is a flavonol conjugated to a resorcinol moiety at the C-2 position, different from many other flavonoids. The UV–vis spectrum of morin in neat water reveals two major absorption bands with maxima at 265 and 387 nm. The substance is stable in acidic solution and neat water. However, its absorption maximum at 387 nm continuously shifts to longer wavelengths and new peaks appeared at wavelengths of 312 nm with increasing pH of the solution. The shape of the absorption spectrum of morin depends on the storage time at a given pH, indicating the occurrence of other successive chemical reactions. The fluorescence spectroscopic results also prove that new conjugated double bonds are formed in the deaerated basic solution at the initial state and decompose with time. This behavior indicates that morin is very unstable, and therefore its decomposition occurs by a sequence of multistep reactions in basic solution. Probable reaction pathways for the reaction are suggested based on the spectroscopic results.

  16. Globally exponential stability and periodic solutions of CNNS with variable coefficients and variable delays

    International Nuclear Information System (INIS)

    Liu Haifei; Wang Li

    2006-01-01

    In this Letter, by using the inequality method and the Lyapunov functional method, we analyze the globally exponential stability and the existence of periodic solutions of a class of cellular neutral networks with delays and variable coefficients. Some simple and new sufficient conditions ensuring the existence and uniqueness of globally exponential stability of periodic solutions for cellular neutral networks with variable coefficients and delays are obtained. In addition, one example is also worked out to illustrate our theory

  17. Globally exponential stability and periodic solutions of CNNS with variable coefficients and variable delays

    Energy Technology Data Exchange (ETDEWEB)

    Liu Haifei [School of Management and Engineering, Nanjing University, Nanjing 210093 (China)]. E-mail: hfliu80@126.com; Wang Li [School of Management and Engineering, Nanjing University, Nanjing 210093 (China)

    2006-09-15

    In this Letter, by using the inequality method and the Lyapunov functional method, we analyze the globally exponential stability and the existence of periodic solutions of a class of cellular neutral networks with delays and variable coefficients. Some simple and new sufficient conditions ensuring the existence and uniqueness of globally exponential stability of periodic solutions for cellular neutral networks with variable coefficients and delays are obtained. In addition, one example is also worked out to illustrate our theory.

  18. Hyers-Ulam Stability and Existence of Solutions for Nigmatullin’s Fractional Diffusion Equation

    Directory of Open Access Journals (Sweden)

    Zhuoyan Gao

    2017-01-01

    Full Text Available We discuss stability of time-fractional order heat conduction equations and prove the Hyers-Ulam and generalized Hyers-Ulam-Rassias stability of time-fractional order heat conduction equations via fractional Green function involving Wright function. In addition, an interesting existence result for solution is given.

  19. Stability of lysozyme in aqueous extremolyte solutions during heat shock and accelerated thermal conditions

    NARCIS (Netherlands)

    Avanti, Christina; Saluja, Vinay; Van Streun, Erwin L. P.; Frijlink, Henderik W.; Hinrichs, Wouter L. J.

    2014-01-01

    The purpose of this study was to investigate the stability of lysozyme in aqueous solutions in the presence of various extremolytes (betaine, hydroxyectoine, trehalose, ectoine, and firoin) under different stress conditions. The stability of lysozyme was determined by Nile red Fluorescence

  20. Almost Surely Asymptotic Stability of Exact and Numerical Solutions for Neutral Stochastic Pantograph Equations

    Directory of Open Access Journals (Sweden)

    Zhanhua Yu

    2011-01-01

    Full Text Available We study the almost surely asymptotic stability of exact solutions to neutral stochastic pantograph equations (NSPEs, and sufficient conditions are obtained. Based on these sufficient conditions, we show that the backward Euler method (BEM with variable stepsize can preserve the almost surely asymptotic stability. Numerical examples are demonstrated for illustration.

  1. Robust Stability and H∞ Control of Uncertain Piecewise Linear Switched Systems with Filippov Solutions

    DEFF Research Database (Denmark)

    Ahmadi, Mohamadreza; Mojallali, Hamed; Wisniewski, Rafal

    2012-01-01

    This paper addresses the robust stability and control problem of uncertain piecewise linear switched systems where, instead of the conventional Carathe ́odory solutions, we allow for Filippov solutions. In other words, in contrast to the previous studies, solutions with infinite switching in fini...... algorithm is proposed to surmount the aforementioned matrix inequality conditions....... time along the facets and on faces of arbitrary dimensions are also taken into account. Firstly, based on earlier results, the stability problem of piecewise linear systems with Filippov solutions is translated into a number of linear matrix inequality feasibility tests. Subsequently, a set of matrix...... inequalities are brought forward, which determines the asymptotic stability of the Filippov solutions of a given uncertain piecewise linear system. Afterwards, bilinear matrix inequality conditions for synthesizing a robust controller with a guaranteed H∞ per- formance are formulated. Finally, a V-K iteration...

  2. Comparative studies of the stability of free and immobilized inulinase from Kluyveromyces marxianus NRRL Y-7571 in aqueous-organic solutions

    Directory of Open Access Journals (Sweden)

    F. V. A. Risso

    2010-12-01

    Full Text Available Enzymes have been extensively used in organic solvents to catalyze a variety of reactions of biological and industrial significance. In this work, the characteristics of free and immobilized inulinase were investigated in buffered solutions of butyl acetate. The influences of the organic solvent content on the optimal temperature and pH, the stabilities to temperature and pH and the kinetic parameters were systematically evaluated. The results showed that the organic solvent content had no effect on the optimal pH, either in the free or immobilized inulinase. For the immobilized enzyme, the optimal temperatures ranged from 55ºC to 60ºC, depending on the content of butyl acetate. At higher butyl acetate content, the stability of the immobilized enzyme increased for both pH and temperature. The organic solvent showed the tendency to increase the values of the kinetic parameters Km and v max for both free and immobilized inulinase.

  3. The stability of bubbles formed from supersaturated solutions, and homogeneous nucleation of gas bubbles from solution, both revisited.

    Science.gov (United States)

    Goldman, Saul

    2008-12-25

    The solution of the problem of the relative stability of all possible equilibrium bubble states that can form from a closed, finite, supersaturated gas-liquid solution, maintained at a fixed temperature and a fixed external pressure is given. The supersaturated solution may contain any number of dissolved volatile solutes. The full solution to this problem has remained elusive for decades, because of the complication of pressure inequalities between the bubbles and the constant external (or reservoir) pressure. The method of solution is one that had been used previously to solve the related problem of the stability of a liquid droplet in a supersaturated vapor, where the same complication occurred. The derived equations were found to reduce correctly when simplified; they were consistent with experiment, and the system Gibbs free energy appropriately obeyed the Law of Corresponding States. The expressions were used in the context of transition state theory to provide semiempirical predictions of the rate of homogeneous bubble formation from a supersaturated solution, and the "critical pressure for homogeneous nucleation (P(crit))". The nucleation Gibbs free energy expression derived here had a lower barrier height and resulted in a reduction of P(crit) values, relative to what was obtained from the basis of a pre-existing approximate expression taken from the literature. Applications to chemical engineering and human decompression modeling are briefly described.

  4. Stability of a novel corticosteroid nasal irrigation solution: betamethasone 17-valerate added to extemporaneously prepared nasal irrigation solutions.

    Science.gov (United States)

    Ong, Kheng Yong; Lim, Wei Ching; Ooi, Shing Ming; Loh, Zhi Hui; Kong, Ming Chai; Chan, Lai Wah; Heng, Paul Wan Sia

    2017-05-01

    There are no commercially available nasal irrigation solutions containing corticosteroids. Instead, such preparations are extemporaneously prepared by adding existing corticosteroid formulations to nasal irrigation solutions. The stability of the corticosteroid betamethasone 17-valerate (B17V), in nasal irrigation solutions of different compositions and pH and stored under different temperatures, was studied to determine the optimal choice of solution and storage conditions. Triplicate extemporaneous preparations made with B17V were prepared by adding a predetermined volume of B17V lotion to each nasal irrigation solution: normal saline (NS), sodium bicarbonate (NaHCO 3 ) powder dissolved in tap water, and a commercially available powder mixture (FLO Sinus Care Powder), dissolved in tap water or pre-boiled tap water. Preparations were stored at 30°C and 4°C. Sampling was carried out at 0, 1, 2, 6, and 24 hours. The concentrations of B17V and its degradation compound, betamethasone 21-valerate (B21V), were determined by high-performance liquid chromatography. Preparations stored at 30°C contained a lower amount of B17V and higher amount of B21V than those stored at 4°C. B17V stability in nasal irrigation solutions decreased in the following order: NS, FLO in fresh tap water, FLO in pre-boiled tap water, and NaHCO 3 . The degradation rate of B17V increased with higher storage temperature and higher pH. B17V is most stable when added to NS and least stable in NaHCO 3 solution. FLO solution prepared with either cooled boiled water or tap water is an alternative if administered immediately. Storage at 4°C can better preserve stability of B17V, over a period of 24 hours. © 2017 ARS-AAOA, LLC.

  5. Stability studies of lincomycin hydrochloride in aqueous solution and intravenous infusion fluids.

    Science.gov (United States)

    Czarniak, Petra; Boddy, Michael; Sunderland, Bruce; Hughes, Jeff D

    2016-01-01

    The purpose of this study was to evaluate the chemical stability of Lincocin(®) (lincomycin hydrochloride) in commonly used intravenous fluids at room temperature (25°C), at accelerated-degradation temperatures and in selected buffer solutions. The stability of Lincocin(®) injection (containing lincomycin 600 mg/2 mL as the hydrochloride) stored at 25°C±0.1°C in sodium lactate (Hartmann's), 0.9% sodium chloride, 5% glucose, and 10% glucose solutions was investigated over 31 days. Forced degradation of Lincocin(®) in hydrochloric acid, sodium hydroxide, and hydrogen peroxide was performed at 60°C. The effect of pH on the degradation rate of lincomycin hydrochloride stored at 80°C was determined. Lincomycin hydrochloride w as found to maintain its shelf life at 25°C in sodium lactate (Hartmann's) solution, 0.9% sodium chloride solution, 5% glucose solution, and 10% glucose solution, with less than 5% lincomycin degradation occurring in all intravenous solutions over a 31-day period. Lincomycin hydrochloride showed less rapid degradation at 60°C in acid than in basic solution, but degraded rapidly in hydrogen peroxide. At all pH values tested, lincomycin followed first-order kinetics. It had the greatest stability near pH 4 when stored at 80°C (calculated shelf life of 4.59 days), and was least stable at pH 2 (calculated shelf life of 0.38 days). Lincocin(®) injection was chemically found to have a shelf life of at least 31 days at 25°C when added to sodium lactate (Hartmann's) solution, 0.9% sodium chloride solution, 5% glucose solution, and 10% glucose solution. Solutions prepared at approximately pH 4 are likely to have optimum stability.

  6. Almost Surely Exponential Stability of Numerical Solutions for Stochastic Pantograph Equations

    Directory of Open Access Journals (Sweden)

    Shaobo Zhou

    2014-01-01

    Full Text Available Our effort is to develop a criterion on almost surely exponential stability of numerical solution to stochastic pantograph differential equations, with the help of the discrete semimartingale convergence theorem and the technique used in stable analysis of the exact solution. We will prove that the Euler-Maruyama (EM method can preserve almost surely exponential stability of stochastic pantograph differential equations under the linear growth conditions. And the backward EM method can reproduce almost surely exponential stability for highly nonlinear stochastic pantograph differential equations. A highly nonlinear example is provided to illustrate the main theory.

  7. Stabilization of solutions to higher-order nonlinear Schrodinger equation with localized damping

    Directory of Open Access Journals (Sweden)

    Eleni Bisognin

    2007-01-01

    Full Text Available We study the stabilization of solutions to higher-order nonlinear Schrodinger equations in a bounded interval under the effect of a localized damping mechanism. We use multiplier techniques to obtain exponential decay in time of the solutions of the linear and nonlinear equations.

  8. Existence and stability of almost periodic solutions to differential equations with piecewise constant arguments

    Directory of Open Access Journals (Sweden)

    Samuel Castillo

    2015-03-01

    Full Text Available This work concerns the existence of almost periodic solutions for certain differential equations with piecewise constant arguments. The coefficients of these equations are almost periodic and the equation can be seen as perturbations of a linear equation satisfying an exponential dichotomy on a difference equation. The stability of that solution on a semi-axis is also studied.

  9. Hydrodynamics of exploding foils: Progress on similarity solution and a stability analysis for early time

    International Nuclear Information System (INIS)

    Hunter, J.H.

    1986-01-01

    This report addresses two broad aspects of the behaviors of hydrodynamic flows, resulting from laser heated, exploding foils. In Part I, various aspects of the similarity solutions are considered, whereas in Part II the stability of the flows at early times are examined, before the similarity solutions are established. 5 refs., 3 figs

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

    Directory of Open Access Journals (Sweden)

    Shu-Chiao Lin

    2015-12-01

    Conclusion: 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.

  11. A heuristic solution for the stability problem in conventional submarines

    Directory of Open Access Journals (Sweden)

    M. Sinclair

    2003-12-01

    Full Text Available Seafaring vessels must meet a few very obvious conditions in order to be of any use. The one condition is that they should stay afloat when loaded. The other condition is that they should float upright and with a level keel. The technical terms for these conditions are gravitational stability and trim. In practice some very precise numerical values are calculated for certain parameters in order to describe these conditions. After each refit of a submarine, the numerical values for the parameters referred to above must be recalculated. In the conventional submarines used by the South African Navy these new values must then be translated into the physical redistribution of weights housed in bays in the keel of the submarine. This paper discusses the problem of how this redistribution must be done in order to minimise the amount of work necessary. A heuristic algorithm is proposed by means of which a satisfactory redistribution may economically be computed.

  12. [Stability of oral rehydration solutions in various packing materials].

    Science.gov (United States)

    Santoro, M I; Hackmann, E R; Moudatsos, K M

    1993-10-01

    The aim of this research was to provide data to select an ideal packing material to preserve the integrity of oral rehydration salts (ORS), a therapeutic formulation that is essential in developing countries. Previous research had verified that water is the factor that most affects ORS stability. For this research, a pharmaceutical industry prepared an ORS batch that was packed in six different types of packing materials. The humidity determination was made after storage of samples during 36 weeks at room temperature, at room temperature with 76% relative humidity, and at 40 degrees C with 80% relative humidity. The moisture in the samples was measured at pre-determined intervals using methods like loss on drying at 50 degrees C and the Karl Fischer method. The results indicated that the most efficient packing material was composed of 18g polyester, 35 g aluminum, and 50 g polyethylene (packing material no. 6).

  13. Co-Immobilization of Enzymes and Magnetic Nanoparticles by Metal-Nucleotide Hydrogelnanofibers for Improving Stability and Recycling

    Directory of Open Access Journals (Sweden)

    Chunfang Li

    2017-01-01

    Full Text Available In this paper we report a facile method for preparing co-immobilized enzyme and magnetic nanoparticles (MNPs using metal coordinated hydrogel nanofibers. Candida rugosa lipase (CRL was selected as guest protein. For good aqueous dispersity, low price and other unique properties, citric acid-modified magnetic iron oxide nanoparticles (CA-Fe3O4 NPs have been widely used for immobilizing enzymes. As a result, the relative activity of CA-Fe3O4@Zn/AMP nanofiber-immobilized CRL increased by 8-fold at pH 10.0 and nearly 1-fold in a 50 °C water bath after 30 min, compared to free CRL. Moreover, the immobilized CRL had excellent long-term storage stability (nearly 80% releative activity after storage for 13 days. This work indicated that metal-nucleotide nanofibers could efficiently co-immobilize enzymes and MNPs simultaneously, and improve the stability of biocatalysts.

  14. Rippled shock front solutions for testing hydrodynamic stability simulations

    International Nuclear Information System (INIS)

    Munro, D.H.

    1989-01-01

    The response of a shock front to arbitrary small perturbations can be calculated analytically. Such rippled shock front solutions are useful for determining the accuracy of hydrodynamic simulation codes such as LASNEX [Comments Plasma Phys. Controlled Fusion 2, 51 (1977)], which are used to compute perturbation growth in inertial fusion targets. The LASNEX fractional errors are of order κ 2 L 2 , where κ is the transverse wavenumber of the perturbation, and L is the largest zone dimension. Numerical errors are about 25% for a calculation using 26 zones per transverse wavelength

  15. Linear stability of stationary solutions of the Vlasov-Poisson system in three dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Batt, J.; Rein, G. [Muenchen Univ. (Germany). Mathematisches Inst.; Morrison, P.J. [Texas Univ., Austin, TX (United States)

    1993-03-01

    Rigorous results on the stability of stationary solutions of the Vlasov-Poisson system are obtained in both the plasma physics and stellar dynamics contexts. It is proven that stationary solutions in the plasma physics (stellar dynamics) case are linearly stable if they are decreasing (increasing) functions of the local, i.e. particle, energy. The main tool in the analysis is the free energy of the system, a conserved quantity. In addition, an appropriate global existence result is proven for the linearized Vlasov-Poisson system and the existence of stationary solutions that satisfy the above stability condition is established.

  16. Stability and periodicity of solutions for delay dynamic systems on time scales

    Directory of Open Access Journals (Sweden)

    Zhi-Qiang Zhu

    2014-04-01

    Full Text Available This article concerns the stability and periodicity of solutions to the delay dynamic system $$ x^{\\triangle}(t=A(t x(t + F(t, x(t, x(g(t+C(t $$ on a time scale. By the inequality technique for vectors, we obtain some stability criteria for the above system. Then, by using the Horn fixed point theorem, we present some conditions under which our system is asymptotically periodic and its periodic solution is unique. In particular, the periodic solution is positive under proper assumptions.

  17. Existence and Stability of the Solution of a Nonlinear Boundary Value Problem

    Directory of Open Access Journals (Sweden)

    Agneta M. Balint

    2012-01-01

    Full Text Available The purpose is to find conditions assuring the existence of solutions for a nonlinear, boundary value problem in case of the axis-symmetric Young-Laplace differential equation. The equation describes the capillary surface between two static fluids. Necessary or sufficient conditions are found for the existence of a solution. The static stability of the obtained solution is also analyzed and stability or instability results are revealed. For the NdYAG microfiber growth, by the pulling-down method, numerical illustrations are given.

  18. Effects of metal ions on stability and activity of hyperthermophilic pyrolysin and further stabilization of this enzyme by modification of a Ca2+-binding site.

    Science.gov (United States)

    Zeng, Jing; Gao, Xiaowei; Dai, Zheng; Tang, Bing; Tang, Xiao-Feng

    2014-05-01

    Pyrolysin is an extracellular subtilase produced by the marine hyperthermophilic archaeon Pyrococcus furiosus. This enzyme functions at high temperatures in seawater, but little is known about the effects of metal ions on the properties of pyrolysin. Here, we report that the supplementation of Na(+), Ca(2+), or Mg(2+) salts at concentrations similar to those in seawater destabilizes recombinant pyrolysin but leads to an increase in enzyme activity. The destabilizing effect of metal ions on pyrolysin appears to be related to the disturbance of surface electrostatic interactions of the enzyme. In addition, mutational analysis of two predicted high-affinity Ca(2+)-binding sites (Ca1 and Ca2) revealed that the binding of Ca(2+) is important for the stabilization of this enzyme. Interestingly, Asn substitutions at residues Asp818 and Asp820 of the Ca2 site, which is located in the C-terminal extension of pyrolysin, resulted in improvements in both enzyme thermostability and activity without affecting Ca(2+)-binding affinity. These effects were most likely due to the elimination of unfavorable electrostatic repulsion at the Ca2 site. Together, these results suggest that metal ions play important roles in modulating the stability and activity of pyrolysin.

  19. Effects of Metal Ions on Stability and Activity of Hyperthermophilic Pyrolysin and Further Stabilization of This Enzyme by Modification of a Ca2+-Binding Site

    Science.gov (United States)

    Zeng, Jing; Gao, Xiaowei; Dai, Zheng; Tang, Bing

    2014-01-01

    Pyrolysin is an extracellular subtilase produced by the marine hyperthermophilic archaeon Pyrococcus furiosus. This enzyme functions at high temperatures in seawater, but little is known about the effects of metal ions on the properties of pyrolysin. Here, we report that the supplementation of Na+, Ca2+, or Mg2+ salts at concentrations similar to those in seawater destabilizes recombinant pyrolysin but leads to an increase in enzyme activity. The destabilizing effect of metal ions on pyrolysin appears to be related to the disturbance of surface electrostatic interactions of the enzyme. In addition, mutational analysis of two predicted high-affinity Ca2+-binding sites (Ca1 and Ca2) revealed that the binding of Ca2+ is important for the stabilization of this enzyme. Interestingly, Asn substitutions at residues Asp818 and Asp820 of the Ca2 site, which is located in the C-terminal extension of pyrolysin, resulted in improvements in both enzyme thermostability and activity without affecting Ca2+-binding affinity. These effects were most likely due to the elimination of unfavorable electrostatic repulsion at the Ca2 site. Together, these results suggest that metal ions play important roles in modulating the stability and activity of pyrolysin. PMID:24561589

  20. Optical spectroscopic methods for probing the conformational stability of immobilised enzymes.

    Science.gov (United States)

    Ganesan, Ashok; Moore, Barry D; Kelly, Sharon M; Price, Nicholas C; Rolinski, Olaf J; Birch, David J S; Dunkin, Ian R; Halling, Peter J

    2009-07-13

    We report the development of biophysical techniques based on circular dichroism (CD), diffuse reflectance infrared Fourier transform (DRIFT) and tryptophan (Trp) fluorescence to investigate in situ the structure of enzymes immobilised on solid particles. Their applicability is demonstrated using subtilisin Carlsberg (SC) immobilised on silica gel and Candida antartica lipase B immobilised on Lewatit VP.OC 1600 (Novozyme 435). SC shows nearly identical secondary structure in solution and in the immobilised state as evident from far UV CD spectra and amide I vibration bands. Increased near UV CD intensity and reduced Trp fluorescence suggest a more rigid tertiary structure on the silica surface. After immobilised SC is inactivated, these techniques reveal: a) almost complete loss of near UV CD signal, suggesting loss of tertiary structure; b) a shift in the amide I vibrational band from 1658 cm(-1) to 1632 cm(-1), indicating a shift from alpha-helical structure to beta-sheet; c) a substantial blue shift and reduced dichroism in the far UV CD, supporting a shift to beta-sheet structure; d) strong increase in Trp fluorescence intensity, which reflects reduced intramolecular quenching with loss of tertiary structure; and e) major change in fluorescence lifetime distribution, confirming a substantial change in Trp environment. DRIFT measurements suggest that pressing KBr discs may perturb protein structure. With the enzyme on organic polymer it was possible to obtain near UV CD spectra free of interference by the carrier material. However, far UV CD, DRIFT and fluorescence measurements showed strong signals from the organic support. In conclusion, the spectroscopic methods described here provide structural information hitherto inaccessible, with their applicability limited by interference from, rather than the particulate nature of, the support material.

  1. Estimation of stability constants of metal monoacidocomplexes in aqueous solutions (1:2) of electrolytes

    International Nuclear Information System (INIS)

    Ryazanov, M.A.

    1992-01-01

    On the basis of the concept of the model of isoactive solutions it is shown that osmosis pressure of aqueous solutions (1:2) of electrolytes is well described by the Van-der-Vaals model for ideal associated gas. Stabilisty constants were calculated using osmosis mole parts of interacting particles as a concentrational scale. Stability constants in the scale of osmosis mole parts are equal to thermodynamic contstants, rated for an infinitely diluted solution

  2. The linear stability of the Schwarzschild solution to gravitational perturbations in the generalised wave gauge

    OpenAIRE

    Johnson, Thomas

    2018-01-01

    In a recent seminal paper \\cite{D--H--R} of Dafermos, Holzegel and Rodnianski the linear stability of the Schwarzschild family of black hole solutions to the Einstein vacuum equations was established by imposing a double null gauge. In this paper we shall prove that the Schwarzschild family is linearly stable as solutions to the Einstein vacuum equations by imposing instead a generalised wave gauge: all sufficiently regular solutions to the system of equations that result from linearising the...

  3. Valency stabilization of Polyvalent Iron Ions in Solution By some Organic additives during Gamma Irradiation

    International Nuclear Information System (INIS)

    Barakat, M.F.; Abdel Hamid, M.M.

    2012-01-01

    Valency stabilization of polyvalent ions in gamma irradiated aqueous solutions is sometimes necessary for the success of some chemical operations. In some previous publications valency stabilization of some polyvalent ions in solution upon gamma irradiation was achieved by using additives capable of interacting with the oxidizing or reducing species formed by water radiolysis in the medium. The results showed that the duration of valency stabilization depends on the concentration of the additives used.In the present work, a series of some organic additives has been used to investigate their capability in inducing valency stabilization of polyvalent iron ions when subjected to extended gamma irradiation periods. The results showed that the efficiency of valency stabilization depends on the amount and chemical structure of the organic additive used

  4. Aquifex aeolicus membrane hydrogenase for hydrogen biooxidation: Role of lipids and physiological partners in enzyme stability and activity

    Energy Technology Data Exchange (ETDEWEB)

    Infossi, Pascale; Lojou, Elisabeth; Giudici-Orticoni, Marie-Therese [Unite de Bioenergetique et Ingenierie des Proteines, UPR 9036, Institut de Microbiologie de la Mediterranee - CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20 (France); Chauvin, Jean-Paul [Institut de Biologie du developpement de Marseille Luminy, UMR 6216, Parc Scientifique de Luminy, 163 Avenue de Luminy, BP 907, 13009 Marseille (France); Herbette, Gaetan [Spectropole FI 1739, Aix-Marseille Universite case 511, Faculte de St Jerome Avenue Escadrille Normandie Niemen, 13397 Marseille Cedex 20 (France); Brugna, Myriam [Unite de Bioenergetique et Ingenierie des Proteines, UPR 9036, Institut de Microbiologie de la Mediterranee - CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20 (France); Universite de Provence, 3 Place Victor Hugo, 13331 Marseille Cedex 03 (France)

    2010-10-15

    Hydrogenase I from the hyperthermophilic bacterium Aquifex aeolicus is a good candidate for biotechnological devices thanks to its ability to oxidize hydrogen at high temperature, even in the presence of oxygen and CO. In order to enhance the enzyme stability and the catalytic efficiency, we investigated the hydrogen oxidation process with hydrogenase I embedded in a physiological-like environment. Hydrogenase I partners in the metabolic chain, namely membrane quinone and cytochrome b, were purified and fully characterized. The complex hydrogenase I-cytochrome b was inserted into liposomes. Surface Plasmon Resonance revealed that quinone took part in the stabilization of the complex. By use of molecular modelization and electrochemistry analysis, enzyme stability has been demonstrated to be stronger and enzymatic efficiency to be five times higher when hydrogenase is embedded into the liposomes. This result raises the possibility of using hydrogenases as biocatalysts in fuel cells. (author)

  5. Stability-indicating HPLC method for the determination of the stability of oxytocin parenteral solutions prepared in polyolefin bags.

    Science.gov (United States)

    Kaushal, G; Sayre, B E; Prettyman, T

    2012-02-01

    Oxytocin is very commonly used in clinical settings and is a nonapeptide hormone that stimulates the contraction of uterine smooth muscles. In this study the stability of extemporaneously compounded oxytocin solutions was investigated in polyolefin bags. The sterile preparations of oxytocin were compounded to the strength of 0.02 U/mL in accordance with United States Pharmacopeia (USP) standards. In order to carry out the stability testing of these parenteral products, the solutions were stored under three different temperature conditions of -20°C (frozen), 2-6°C (refrigerated), and 22-25°C (room temperature). Three solutions from each temperature were withdrawn and were assessed for stability on days 0, 7, 15, 21, and 30 as per the USP guidelines. The assay of oxytocin was examined by an HPLC method at each time point. No precipitation, cloudiness or color change was observed during this study at all temperatures. The assay content by HPLC revealed that oxytocin retains greater than at least 90% of the initial concentrations for 21 days. There was no significant change in pH and absorbance values for 21 days under all the conditions of storage. Oxytocin parenteral solutions in the final concentration of 0.02 U/mL and diluted in normal saline are stable for at least 30 days under frozen and refrigerated conditions for 30 days. At the room temperature, the oxytocin solutions were stable for at least 21 days. The stability analysis results show that the shelf-life of 21 days observed in this study was far better than their recommended expiration dates.

  6. The stability of oxymetazoline hydrochloride in aqueous solution.

    Science.gov (United States)

    Stanisz, Beata

    2002-01-01

    The kinetics of the hydrolysis reaction of oxymetazoline hydrochloride in aqueous solution at three temperatures (343 K, 353 K, 363 K), over the pH-range 0.5-12.5 and ionic strength 0.5 has been investigated. The changes of concentration of oxymetazoline hydrochloride were followed by the HPLC method with UV detection. In the pH range from 0.45 to 12.50, the hydrolysis of oxymetazoline consists of hydrolysis of oxymetazoline molecules catalyzed by hydrogen ions, spontaneous hydrolysis of the dissociated and undissociated oxymetazoline molecules. A minimal rate of the hydrolysis oxymetazoline was observed to occur in the pH range from 2.0 to 5.0. Thermodynamic parameters of the reaction: energy, entropy and enthalpy of activation and the frequency factor for the specific rate constants were determined.

  7. Thermal stability and kinetic constants for 129 variants of a family 1 glycoside hydrolase reveal that enzyme activity and stability can be separately designed.

    Directory of Open Access Journals (Sweden)

    Dylan Alexander Carlin

    Full Text Available Accurate modeling of enzyme activity and stability is an important goal of the protein engineering community. However, studies seeking to evaluate current progress are limited by small data sets of quantitative kinetic constants and thermal stability measurements. Here, we report quantitative measurements of soluble protein expression in E. coli, thermal stability, and Michaelis-Menten constants (kcat, KM, and kcat/KM for 129 designed mutants of a glycoside hydrolase. Statistical analyses reveal that functional Tm is independent of kcat, KM, and kcat/KM in this system, illustrating that an individual mutation can modulate these functional parameters independently. In addition, this data set is used to evaluate computational predictions of protein stability using the established Rosetta and FoldX algorithms. Predictions for both are found to correlate only weakly with experimental measurements, suggesting improvements are needed in the underlying algorithms.

  8. Efficient downstream processing of maltodextrin phosphorylase from Escherichia coli and stabilization of the enzyme by immobilization onto hydroxyapatite.

    Science.gov (United States)

    Eis, C; Griessler, R; Maier, M; Weinhäusel, A; Bock, B; Kulbe, K D; Haltrich, D; Schinzel, R; Nidetzky, B

    1997-12-03

    Downstream processing by biospecific chromatography of maltodextrin phosphorylase from Escherichia coli, overexpressed in E. coli, was substantially improved by a novel approach using ceramic hydroxyapatite. Wild-type and a less active mutant enzyme were purified from crude bacterial cell extracts in one efficient separation step that yielded phosphorylase in purity > 95% in at least 90% recoveries. At pH 6.9 and 25 degrees C, wild-type and mutant phosphorylases eluted from the hydroxyapatite column at a phosphate concentration of 0.4 M whereas calcium ions failed to displace the enzymes. The dynamic capacity for phosphorylase binding in the presence of bulk proteins was approximately 3 mg enzyme ml-1 matrix. The interaction of E. coli phosphorylase with hydroxyapatite seems to be mediated by surface amino groups, so that the bound enzyme retained almost full catalytic activity. Compared to the soluble enzyme, immobilization onto hydroxyapatite resulted in a more than 30-fold stabilization of wild-type phosphorylase against thermal and proteolytic inactivation and thus could improve the operational stability of phosphorylase during conversion of polysaccharide to glucose 1-phosphate.

  9. Biological denitrification of brine: the effect of compatible solutes on enzyme activities and fatty acid degradation.

    Science.gov (United States)

    Cyplik, Paweł; Piotrowska-Cyplik, Agnieszka; Marecik, Roman; Czarny, Jakub; Drozdzyńska, Agnieszka; Chrzanowski, Łukasz

    2012-09-01

    The effect of the addition of compatible solutes (ectoine and trehalose) on the denitrification process of saline wastewater was studied. In saline wastewater, it was observed that the initial concentration of nitrates was 500 mg N l⁻¹. A fatty substance isolated from oiled bleaching earth (waste of vegetable oil refining process) was used as a source of carbon.The consortium, which was responsible for the denitrification process originated from the wastewater of the vegetable oil industry. The consortium of microorganisms was identified by the use of restriction fragment length polymorphism of 16S rRNA gene amplicons and sequencing techniques. It was noted that ectoine affects significantly the activity of lipase and nitrate reductase, and resulted in faster denitrification compared to saline wastewater with the addition of trehalose or control saline wastewater (without compatible solutes). It was observed that relative enzyme activities of lipase and nitrate reductase increased by 32 and 35%, respectively, in the presence of 1 mM ectoine. This resulted in an increase in specific nitrate reduction rate in the presence of 1 mM ectoine to 5.7 mg N g⁻¹ VSS h⁻¹, which was higher than in the absence of ectoine (3.2 mg N g⁻¹ VSS h⁻¹). The addition of trehalose did not have an effect on nitrate removals. Moreover, it was found that trehalose was used up completely by bacteria as a source of carbon in the denitrification process. The fatty acids were biodegraded by 74% in the presence of 1 mM ectoine.

  10. DUB3 Deubiquitylating Enzymes Regulate Hippo Pathway Activity by Regulating the Stability of ITCH, LATS and AMOT Proteins

    DEFF Research Database (Denmark)

    Nguyen, Thanh Hung; Kugler, Jan-Michael; Cohen, Stephen Michael

    2017-01-01

    /TAZ, is regulated by ubiquitin mediated protein turnover and several ubiquitin ligase complexes have been implicated in human cancer. However, little is known about the deubiquitylating enzymes that counteract these ubiquitin ligases in regulation of the Hippo pathway. Here we identify the DUB3 family...... deubiquitylating enzymes as regulators of Hippo pathway activity. We provide evidence that DUB3 proteins regulate YAP/TAZ activity by controlling the stability of the E3 ligase ITCH, the LATS kinases and the AMOT family proteins. As a novel Hippo pathway regulator, DUB3 has the potential to act a tumor suppressor...

  11. Metal sulfide nanoparticles synthesized via enzyme treatment of biopolymer stabilized nanosuspensions

    Science.gov (United States)

    Kim, Yi-Yeoun; Walsh, Dominic

    2010-02-01

    Nanoparticles of CuS, CuxS, Ag2S and CdS were successfully prepared using a novel general and green synthetic process to give dextran biopolymer stabilised metal sulfifde nanosuspensions. Following preparation, dextranase enzyme was used to remove the bulk of the bound dextran to give pure stable metal sulfide nanocrystals for application in for example aspects of medicine, photonics and solar cells. Particles of good homogeneity were obtained and the CuS nanoparticle size was controlled to 9-27 nm by adjusting the reaction conditions. Cu2S nanoparticles were 14 nm, Ag2S nanoparticles were 20-50 nm and CdS nanoparticles were 9 nm is size. The complexing mechanism of nanoparticle sulfides to dextrans was further studied using carboxylmethyl dextran as a complexing agent and crosslinked Sephadex (dextran) `beads as substrate. Particles were characterized by TEM, XRD, TGA, FT-IR and zeta-potential measurement, and their UV-vis spectroscopic absorption properties were determined. Stabilization of the sulfide nanoparticles with soluble hydroxylated biopolymers such as dextran is previously unreported and is here interpreted in terms of viscosity, pH of the system and weak polar S-H or S(metal)OH2+ interactions with dextran depending on the material. Notably, the complexing mechanism appears to differ significantly from that taking place in known dextran-metal oxide systems. The process shown here has good potential for scale-up as a biosynthetic route for a range of functional sulfide nanoparticles.Nanoparticles of CuS, CuxS, Ag2S and CdS were successfully prepared using a novel general and green synthetic process to give dextran biopolymer stabilised metal sulfifde nanosuspensions. Following preparation, dextranase enzyme was used to remove the bulk of the bound dextran to give pure stable metal sulfide nanocrystals for application in for example aspects of medicine, photonics and solar cells. Particles of good homogeneity were obtained and the CuS nanoparticle size

  12. Global stability and existence of periodic solutions of discrete delayed cellular neural networks

    International Nuclear Information System (INIS)

    Li Yongkun

    2004-01-01

    We use the continuation theorem of coincidence degree theory and Lyapunov functions to study the existence and stability of periodic solutions for the discrete cellular neural networks (CNNs) with delays xi(n+1)=xi(n)e-bi(n)h+θi(h)-bar j=1maij(n)fj(xj(n))+θi(h)-bar j=1mbij(n)fj(xj(n- τij(n)))+θi(h)Ii(n),i=1,2,...,m. We obtain some sufficient conditions to ensure that for the networks there exists a unique periodic solution, and all its solutions converge to such a periodic solution

  13. Sulfonation of polyvinylidene difluoride resin and its application in extraction of restriction enzymes from DNA digestion solutions.

    Science.gov (United States)

    Yang, Jing; Dong, Chunxia; Huang, Xu; Zhao, Jindong

    2003-11-01

    Sulfonation of polyvinylidene difluoride (PVDF) resin was achieved by incubation of the resin with sulfuric acid at a moderately high temperature. The sulfonated PVDF (SPVDF) resin was studied for its ability to extract restriction enzymes from DNA digestion solutions. The SPVDF resin was effective in adsorbing restriction enzymes such as EcoRI and BamHI and the extraction procedure was easy and simple to perform. The adsorption depended upon the amount of the resin added. We found that 1 mg of the SPVDF resin could completely remove all restriction enzyme activity routinely used in DNA digestion within 2 min after its addition. Treatment of a digestion solution with the SPVDF resin did not change the reaction solution and the same digestion buffer could be used for another digestion of the same DNA with other enzymes. We also found that, in comparison with normal PVDF, the SPVDF resin adsorbed less DNA, resulting in less loss of DNA in the extraction step. The potential application of the SPVDF resin in other procedures of molecular cloning and enzyme purification is discussed.

  14. Proteolysis of Sardine (Sardina pilchardus and Anchovy (Stolephorus commersonii by Commercial Enzymes in Saline Solutions

    Directory of Open Access Journals (Sweden)

    Chau Minh Le

    2015-01-01

    Full Text Available Fish sauce production is a very long process and there is a great interest in shortening it. Among the different strategies to speed up this process, the addition of external proteases could be a solution. This study focuses on the eff ect of two commercial enzymes (Protamex and Protex 51FP on the proteolysis of two fish species traditionally converted into fish sauce: sardine and anchovy, by comparison with classical autolysis. Hydrolysis reactions were conducted with fresh fish at a temperature of 30 °C and under different saline conditions (from 0 to 30 % NaCl. Hydrolysis degree and liquefaction of the raw material were used to follow the process. As expected, the proteolysis decreased with increasing amount of salt. Regarding the fi sh species, higher rate of liquefaction and higher hydrolysis degree were obtained with anchovy. Between the two proteases, Protex 51FP gave better results with both fi sh types. This study demonstrates that the addition of commercial proteases could be helpful for the liquefaction of fi sh and cleavage of peptide bonds that occur during fi sh sauce production and thus speed up the production process.

  15. Proteolysis of Sardine (Sardina pilchardus) and Anchovy (Stolephorus commersonii) by Commercial Enzymes in
Saline Solutions.

    Science.gov (United States)

    Le, Chau Minh; Donnay-Moreno, Claire; Bruzac, Sandrine; Baron, Régis; Nguyen, Huong Thi My; Bergé, Jean Pascal

    2015-03-01

    Fish sauce production is a very long process and there is a great interest in shortening it. Among the different strategies to speed up this process, the addition of external proteases could be a solution. This study focuses on the effect of two commercial enzymes (Protamex and Protex 51FP) on the proteolysis of two fish species traditionally converted into fish sauce: sardine and anchovy, by comparison with classical autolysis. Hydrolysis reactions were conducted with fresh fish at a temperature of 30 °C and under different saline conditions (from 0 to 30% NaCl). Hydrolysis degree and liquefaction of the raw material were used to follow the process. As expected, the proteolysis decreased with increasing amount of salt. Regarding the fish species, higher rate of liquefaction and higher hydrolysis degree were obtained with anchovy. Between the two proteases, Protex 51FP gave better results with both fish types. This study demonstrates that the addition of commercial proteases could be helpful for the liquefaction of fish and cleavage of peptide bonds that occur during fish sauce production and thus speed up the production process.

  16. The Effects of Electroless Nickel Plating Bath Conditions on Stability of Solution and Properties of Deposit

    International Nuclear Information System (INIS)

    Huh, Jin; Lee, Jae Ho

    2000-01-01

    Electroless depositions of nickel were conducted in different bath conditions to find optimum conditions of electroless nickel plating at low operating temperature and pH. The effect of complexing reagent on stability of plating solution was investigated. Sodium citrate complexed plating solution is more stable than sodium pyrophosphate complexed solution. The effects of nickel salt concentration, reducing agent, complexing agent and inhibitor on deposition rate was investigated. The effects of pH on deposition rate and content of phosphorous in deposited nickel were also analyzed. Electroless deposited nickel become crystallized with increasing pH due to lower phosphorous content. In optimum operating bath condition, deposition rate was 7 μm/hr at 60 .deg. C and pH 10.0 without stabilizer. The rate was decreased with stabilizer concentration

  17. Effect of repeated immersion solution cycles on the color stability of denture tooth acrylic resins

    OpenAIRE

    Paulo Maurício Batista da Silva; Emílio José Tabaré Rodríguez Acosta; Matheus Jacobina; Luciana de Rezende Pinto; Vinícius Carvalho Porto

    2011-01-01

    OBJECTIVE: Chemical solutions have been widely used for disinfection of dentures, but their effect on color stability of denture tooth acrylic resins after repeated procedures is still unclear. The aim of this in vitro study was to evaluate whether repeated cycles of chemical disinfectants affected the color stability of two denture tooth acrylic resins. MATERIAL AND METHODS: Sixty disc-shaped specimens (40 mm x 3 mm) were fabricated from two different brands (Artiplus and Trilux) of denture ...

  18. Time-dependent physicochemical characteristics of Malaysian residual soil stabilized with magnesium chloride solution

    OpenAIRE

    Latifi, Nima; Rashid, Ahmad Safuan A.; Ecemiş, Nurhan; Tahir, Mahmood Md; Marto, Aminaton

    2016-01-01

    The effects of non-traditional additives on the geotechnical properties of tropical soils have been the subject of investigation in recent years. This study investigates the strength development and micro-structural characteristics of tropical residual soil stabilized with magnesium chloride (MgCl2) solution. Unconfined compression strength (UCS) and standard direct shear tests were used to assess the strength and shear properties of the stabilized soil. In addition, the micro-structural char...

  19. Stability studies of lincomycin hydrochloride in aqueous solution and intravenous infusion fluids

    Directory of Open Access Journals (Sweden)

    Czarniak P

    2016-03-01

    Full Text Available Petra Czarniak, Michael Boddy, Bruce Sunderland, Jeff D Hughes School of Pharmacy, Curtin University, Perth, WA, Australia Purpose: The purpose of this study was to evaluate the chemical stability of Lincocin® (lincomycin hydrochloride in commonly used intravenous fluids at room temperature (25°C, at accelerated-degradation temperatures and in selected buffer solutions.Materials and methods: The stability of Lincocin® injection (containing lincomycin 600 mg/2 mL as the hydrochloride stored at 25°C±0.1°C in sodium lactate (Hartmann’s, 0.9% sodium chloride, 5% glucose, and 10% glucose solutions was investigated over 31 days. Forced degradation of Lincocin® in hydrochloric acid, sodium hydroxide, and hydrogen peroxide was performed at 60°C. The effect of pH on the degradation rate of lincomycin hydrochloride stored at 80°C was determined.Results: Lincomycin hydrochloride was found to maintain its shelf life at 25°C in sodium lactate (Hartmann’s solution, 0.9% sodium chloride solution, 5% glucose solution, and 10% glucose solution, with less than 5% lincomycin degradation occurring in all intravenous solutions over a 31-day period. Lincomycin hydrochloride showed less rapid degradation at 60°C in acid than in basic solution, but degraded rapidly in hydrogen peroxide. At all pH values tested, lincomycin followed first-order kinetics. It had the greatest stability near pH 4 when stored at 80°C (calculated shelf life of 4.59 days, and was least stable at pH 2 (calculated shelf life of 0.38 days.Conclusion: Lincocin® injection was chemically found to have a shelf life of at least 31 days at 25°C when added to sodium lactate (Hartmann’s solution, 0.9% sodium chloride solution, 5% glucose solution, and 10% glucose solution. Solutions prepared at approximately pH 4 are likely to have optimum stability. Keywords: lincomycin, stability, pH, intravenous fluids, IV additives

  20. Radiation stability of colloidal metals in aqueous solutions: silver and other metals

    International Nuclear Information System (INIS)

    Ershov, B.G.

    1998-01-01

    The effect of accelerated electrons and γ-rays of 60N i on the stability of aqueous solutions of colloidal silver was studied. The threshold of absorbed dose, at which the stability dramatically decreases and coagulation of the metal occurs, was found. This critical dose corresponds to the reduction of silver ions determining the electrical potential of the sols. Radiation neutralization was also found for cadmium was not observed in the case of thallium, copper and platinum. A mechanism of the effect of radiation, taking into account the electrostatic factor in the stability of metal sols, was considered. (author)

  1. Stabilization of Periodic Solutions in a Thedered Satellite System by Damping Injection

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Blanke, Mogens

    2009-01-01

    to affect the orbit parameters. An approximation of the periodic solutions of the closed loop system is found as a series expansion in the parameter plane spanned by the controller gain and the bias term. The stability of the solutions is investigated using linear Floquet analysis of the variational...... presents a control design for stabilizing these periodic solutions. The design consists of a control law for stabilising the open-loo equibrilibrium and a bias term which forces the system trajectory away from the equilibrium. The tether needs to be positioned away from open-loop equilibrium for the tether...... equation and the region of stable periodic solutions in the parameter plane is found....

  2. Existence and Stability of Solutions for Implicit Multivalued Vector Equilibrium Problems

    Directory of Open Access Journals (Sweden)

    Li Qiuying

    2011-01-01

    Full Text Available A class of implicit multivalued vector equilibrium problems is studied. By using the generalized Fan-Browder fixed point theorem, some existence results of solutions for the implicit multivalued vector equilibrium problems are obtained under some suitable assumptions. Moreover, a stability result of solutions for the implicit multivalued vector equilibrium problems is derived. These results extend and unify some recent results for implicit vector equilibrium problems, multivalued vector variational inequality problems, and vector variational inequality problems.

  3. Stability of Rosmarinic Acid in Aqueous Extracts from Different Lamiaceae Species after in vitro Digestion with Human Gastrointestinal Enzymes

    Directory of Open Access Journals (Sweden)

    Zoran Zorić

    2016-01-01

    Full Text Available The present study compares the gastrointestinal stability of rosmarinic acid in aqueous extracts of thyme, winter savory and lemon balm with the stability of pure rosmarinic acid. The stability of rosmarinic acid was detected after two-phase in vitro digestion process (gastric and duodenal with human gastrointestinal enzymes. The concentration of rosmarinic acid in undigested and digested samples was detected using HPLC-DAD. Results showed that gastrointestinal stability of pure rosmarinic acid was significantly higher than that of rosmarinic acid from plant extracts after both gastric and intestinal phases of digestion. Among plant extracts, rosmarinic acid was the most stable in lemon balm after gastric (14.10 % and intestinal digestion phases (6.5 %. The temperature (37 °C and slightly alkaline medium (pH=7.5 did not aff ect the stability of rosmarinic acid, while acid medium (pH=2.5 significantly decreased its stability (≥50 %. In addition, the stability rate of rosmarinic acid is influenced by the concentration of human gastrointestinal juices.

  4. C-terminal lysine repeats in Streptomyces topoisomerase I stabilize the enzyme–DNA complex and confer high enzyme processivity

    Science.gov (United States)

    Strzałka, Agnieszka; Szafran, Marcin J.; Strick, Terence

    2017-01-01

    Abstract Streptomyces topoisomerase I (TopA) exhibits exceptionally high processivity. The enzyme, as other actinobacterial topoisomerases I, differs from its bacterial homologs in its C-terminal domain (CTD). Here, bioinformatics analyses established that the presence of lysine repeats is a characteristic feature of actinobacterial TopA CTDs. Streptomyces TopA contains the longest stretch of lysine repeats, which terminate with acidic amino acids. DNA-binding studies revealed that the lysine repeats stabilized the TopA–DNA complex, while single-molecule experiments showed that their elimination impaired enzyme processivity. Streptomyces coelicolor TopA processivity could not be restored by fusion of its N-terminal domain (NTD) with the Escherichia coli TopA CTD. The hybrid protein could not re-establish the distribution of multiple chromosomal copies in Streptomyces hyphae impaired by TopA depletion. We expected that the highest TopA processivity would be required during the growth of multigenomic sporogenic hyphae, and indeed, the elimination of lysine repeats from TopA disturbed sporulation. We speculate that the interaction of the lysine repeats with DNA allows the stabilization of the enzyme–DNA complex, which is additionally enhanced by acidic C-terminal amino acids. The complex stabilization, which may be particularly important for GC-rich chromosomes, enables high enzyme processivity. The high processivity of TopA allows rapid topological changes in multiple chromosomal copies during Streptomyces sporulation. PMID:28981718

  5. Molecular hydrogel-stabilized enzyme with facilitated electron transfer for determination of H2O2 released from live cells.

    Science.gov (United States)

    Zhou, Jie; Liao, Chuanan; Zhang, Limin; Wang, Qigang; Tian, Yang

    2014-05-06

    In this work, small molecular hydrogel was first employed as a surrounding matrix to stabilize an enzyme model, Cytochrome c (Cyt c), and more importantly to facilitate electron transfer between redox enzyme and electrode. Direct electron transfer of Cyt c was successfully achieved in the molecular hydrogel with redox formal potential (E(0')) of 100.7 ± 3.2 mV versus Ag|AgCl and heterogeneous electron transfer rate constant (ks) up to 18.6 ± 2.3 s(-1). Experimental data demonstrated that Cyt c was stably immobilized into the molecular hydrogel and retained its inherent bioactive activity toward H2O2. The direct redox reaction of Cyt c, followed by the biochemical reaction between Cyt c and H2O2, established a reliable approach to determine H2O2 at an optimized potential with high selectivity over other reactive oxygen species (ROS), oxygen, metal ions, ascobic acid (AA), and so on. In addition, the present biosensor for H2O2 also exhibited wide linear range and low detection limit, which fulfills the requirements for detection of H2O2 in a biological system. The remarkable analytical performance of the present biosensor, as well as the long-term stability and good reproducibility ascribed to the molecular hydrogel-stabilized enzyme, provided a durable platform for real-time determination of H2O2 from live cells.

  6. Dispensing an enzyme-conjugated solution into an ELISA plate by adapting ink-jet printers.

    Science.gov (United States)

    Lonini, Luca; Accoto, Dino; Petroni, Silvia; Guglielmelli, Eugenio

    2008-04-24

    The rapid and precise delivery of small volumes of bio-fluids (from picoliters to nanoliters) is a key feature of modern bioanalytical assays. Commercial ink-jet printers are low-cost systems which enable the dispensing of tiny droplets at a rate which may exceed 10(4) Hz per nozzle. Currently, the main ejection technologies are piezoelectric and bubble-jet. We adapted two commercial printers, respectively a piezoelectric and a bubble-jet one, for the deposition of immunoglobulins into an ELISA plate. The objective was to perform a comparative evaluation of the two classes of ink-jet technologies in terms of required hardware modifications and possible damage on the dispensed molecules. The hardware of the two printers was modified to dispense an enzyme conjugate solution, containing polyclonal rabbit anti-human IgG labelled with HRP in 7 wells of an ELISA plate. Moreover, the ELISA assay was used to assess the functional activity of the biomolecules after ejection. ELISA is a common and well-assessed technique to detect the presence of particular antigens or antibodies in a sample. We employed an ELISA diagnostic kit for the qualitative screening of anti-ENA antibodies to verify the ability of the dispensed immunoglobulins to bind the primary antibodies in the wells. Experimental tests showed that the dispensing of immunoglobulins using the piezoelectric printer does not cause any detectable difference on the outcome of the ELISA test if compared to manual dispensing using micropipettes. On the contrary, the thermal printhead was not able to reliably dispense the bio-fluid, which may mean that a surfactant is required to modify the wetting properties of the liquid.

  7. Direct NMR Monitoring of Phase Separation Behavior of Highly Supersaturated Nifedipine Solution Stabilized with Hypromellose Derivatives.

    Science.gov (United States)

    Ueda, Keisuke; Higashi, Kenjirou; Moribe, Kunikazu

    2017-07-03

    We investigated the phase separation behavior and maintenance mechanism of the supersaturated state of poorly water-soluble nifedipine (NIF) in hypromellose (HPMC) derivative solutions. Highly supersaturated NIF formed NIF-rich nanodroplets through phase separation from aqueous solution containing HPMC derivative. Dissolvable NIF concentration in the bulk water phase was limited by the phase separation of NIF from the aqueous solution. HPMC derivatives stabilized the NIF-rich nanodroplets and maintained the NIF supersaturation with phase-separated NIF for several hours. The size of the NIF-rich phase was different depending on the HPMC derivatives dissolved in aqueous solution, although the droplet size had no correlation with the time for which NIF supersaturation was maintained without NIF crystallization. HPMC acetate and HPMC acetate succinate (HPMC-AS) effectively maintained the NIF supersaturation containing phase-separated NIF compared with HPMC. Furthermore, HPMC-AS stabilized NIF supersaturation more effectively in acidic conditions. Solution 1 H NMR measurements of NIF-supersaturated solution revealed that HPMC derivatives distributed into the NIF-rich phase during the phase separation of NIF from the aqueous solution. The hydrophobicity of HPMC derivative strongly affected its distribution into the NIF-rich phase. Moreover, the distribution of HPMC-AS into the NIF-rich phase was promoted at lower pH due to the lower aqueous solubility of HPMC-AS. The distribution of a large amount of HPMC derivatives into NIF-rich phase induced the strong inhibition of NIF crystallization from the NIF-rich phase. Polymer distribution into the drug-rich phase directly monitored by solution NMR technique can be a useful index for the stabilization efficiency of drug-supersaturated solution containing a drug-rich phase.

  8. A note on existence and stability of solutions for semilinear Dirichlet ...

    Indian Academy of Sciences (India)

    (Math. Sci.) Vol. 121, No. 2, May 2011, pp. 201–215. c Indian Academy of Sciences. A note on existence and stability of solutions for semilinear. Dirichlet problems. MAREK GALEWSKI. Institute of Mathematics, Technical University of Lodz, Wolczanska 215,. 90-924 Lodz, Poland. E-mail: marek.galewski@p.lodz.pl.

  9. Solutions Stability of Initial Boundary Problem, Modeling of Dynamics of Some Discrete Continuum Mechanical System

    Directory of Open Access Journals (Sweden)

    D. A. Eliseev

    2015-01-01

    Full Text Available The solution stability of an initial boundary problem for a linear hybrid system of differential equations, which models the rotation of a rigid body with two elastic rods located in the same plane is studied in the paper. To an axis passing through the mass center of the rigid body perpendicularly to the rods location plane is applied the stabilizing moment proportional to the angle of the system rotation, derivative of the angle, integral of the angle. The external moment provides a feedback. A method of studying the behavior of solutions of the initial boundary problem is proposed. This method allows to exclude from the hybrid system of differential equations partial differential equations, which describe the dynamics of distributed elements of a mechanical system. It allows us to build one equation for an angle of the system rotation. Its characteristic equation defines the stability of solutions of all the system. In the space of feedback-coefficients the areas that provide the asymptotic stability of solutions of the initial boundary problem are built up.

  10. Analytical Approximation Methods for the Stabilizing Solution of the Hamilton-Jacobi Equation

    NARCIS (Netherlands)

    Sakamoto, Noboru; van der Schaft, Arjan J.

    2008-01-01

    In this paper, two methods for approximating the stabilizing solution of the Hamilton-Jacobi equation are proposed using symplectic geometry and a Hamiltonian perturbation technique as well as stable manifold theory. The first method uses the fact that the Hamiltonian lifted system of an integrable

  11. Analytical Approximation Methods for the Stabilizing Solution of the Hamilton–Jacobi Equation

    NARCIS (Netherlands)

    Sakamoto, Noboru; Schaft, Arjan J. van der

    2008-01-01

    In this paper, two methods for approximating the stabilizing solution of the Hamilton–Jacobi equation are proposed using symplectic geometry and a Hamiltonian perturbation technique as well as stable manifold theory. The first method uses the fact that the Hamiltonian lifted system of an integrable

  12. Almost Surely Asymptotic Stability of Numerical Solutions for Neutral Stochastic Delay Differential Equations

    Directory of Open Access Journals (Sweden)

    Zhanhua Yu

    2011-01-01

    convergence theorem. It is shown that the Euler method and the backward Euler method can reproduce the almost surely asymptotic stability of exact solutions to NSDDEs under additional conditions. Numerical examples are demonstrated to illustrate the effectiveness of our theoretical results.

  13. Stability and square integrability of derivatives of solutions of nonlinear fourth order differential equations with delay

    Directory of Open Access Journals (Sweden)

    Erdal Korkmaz

    2017-06-01

    Full Text Available Abstract In this paper, we give sufficient conditions for the boundedness, uniform asymptotic stability and square integrability of the solutions to a certain fourth order non-autonomous differential equations with delay by using Lyapunov’s second method. The results obtained essentially improve, include and complement the results in the literature.

  14. Stability and square integrability of derivatives of solutions of nonlinear fourth order differential equations with delay.

    Science.gov (United States)

    Korkmaz, Erdal

    2017-01-01

    In this paper, we give sufficient conditions for the boundedness, uniform asymptotic stability and square integrability of the solutions to a certain fourth order non-autonomous differential equations with delay by using Lyapunov's second method. The results obtained essentially improve, include and complement the results in the literature.

  15. Existence and global exponential stability of periodic solution of CNNs with impulses

    Energy Technology Data Exchange (ETDEWEB)

    Li Yongkun [Department of Mathematics, Yunnan University, Kunming, Yunnan 650091 (China); Xing Zhiwei [Department of Mathematics, Yunnan University, Kunming, Yunnan 650091 (China)

    2007-08-15

    Sufficient conditions are obtained for the existence and global exponential stability of a unique periodic solution of cellular neural networks with variable time delays and impulses by using Mawhin's continuation theorem of coincidence degree and by means of a method based on delay differential inequality.

  16. Existence and global exponential stability of periodic solution of CNNs with impulses

    International Nuclear Information System (INIS)

    Li Yongkun; Xing Zhiwei

    2007-01-01

    Sufficient conditions are obtained for the existence and global exponential stability of a unique periodic solution of cellular neural networks with variable time delays and impulses by using Mawhin's continuation theorem of coincidence degree and by means of a method based on delay differential inequality

  17. Stabilization of periodic solutions in a tethered satellite system by damping injection

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Blanke, Mogens

    2009-01-01

    A spacecraft with electrodynamic tether orbiting the Earth will be subject to a periodic forcing term induced by the variation of the magnetic field along the orbit. The periodic forcing term leads to a family of unstable periodic solutions for a tether carrying a constant current. This paper...... to affect the orbit parameters. An approximation of the periodic solutions of the closed loop system is found as a series expansion in the parameter plane spanned by the controller gain and the bias term. The stability of the solutions is investigated using linear Floquet analysis of the variational...

  18. Stability of a1 mg/mL oral solution zidovudine

    International Nuclear Information System (INIS)

    Garcia Penna, Caridad Margarita; Morales Lacarrere, Ivan; Martinez Espinosa, Vivian

    2011-01-01

    The carrying out of a high-performance liquid chromatography analytical method was assessed; applicable to stability study of oral solution zidovudine (1 mg/mL) was made. The analytical method was linear, precise, specific and exact in the study concentrations. The stability study of oral solution zidovudine (1 mg/mL) was conducted determining expiring date. The shelf life study was conducted over 24 months at room temperature; whereas that of accelerated stability was conducted with the product under wet and temperature conditions; analysis was carried out over three months. Formula met quality specifications described in Pharmacopeia. Results from the shelf life study demonstrated that product keeps the parameters determining its quality during that time and in accelerated studies there was not significant product degradation. Under above mentioned conditions two years were established as expiring date

  19. Effects of solute-solute interactions on protein stability studied using various counterions and dendrimers.

    Directory of Open Access Journals (Sweden)

    Curtiss P Schneider

    Full Text Available Much work has been performed on understanding the effects of additives on protein thermodynamics and degradation kinetics, in particular addressing the Hofmeister series and other broad empirical phenomena. Little attention, however, has been paid to the effect of additive-additive interactions on proteins. Our group and others have recently shown that such interactions can actually govern protein events, such as aggregation. Here we use dendrimers, which have the advantage that both size and surface chemical groups can be changed and therein studied independently. Dendrimers are a relatively new and broad class of materials which have been demonstrated useful in biological and therapeutic applications, such as drug delivery, perturbing amyloid formation, etc. Guanidinium modified dendrimers pose an interesting case given that guanidinium can form multiple attractive hydrogen bonds with either a protein surface or other components in solution, such as hydrogen bond accepting counterions. Here we present a study which shows that the behavior of such macromolecule species (modified PAMAM dendrimers is governed by intra-solvent interactions. Attractive guanidinium-anion interactions seem to cause clustering in solution, which inhibits cooperative binding to the protein surface but at the same time, significantly suppresses nonnative aggregation.

  20. Stabilization of red fruit-based smoothies by high-pressure processing. Part A. Effects on microbial growth, enzyme activity, antioxidant capacity and physical stability.

    Science.gov (United States)

    Hurtado, Adriana; Guàrdia, Maria Dolors; Picouet, Pierre; Jofré, Anna; Ros, José María; Bañón, Sancho

    2017-02-01

    Non-thermal pasteurization by high-pressure processing (HPP) is increasingly replacing thermal processing (TP) to maintain the properties of fresh fruit products. However, most of the research on HPP-fruit products only partially addresses fruit-pressure interaction, which limits its practical interest. The objective of this study was to assess the use of a mild HPP treatment to stabilize red fruit-based smoothies (microbial, enzymatic, oxidative and physical stability). HPP (350 MPa/10 °C/5 min) was slightly less effective than TP (85 °C/7 min) in inactivating microbes (mesophilic and psychrophilic bacteria, coliforms, yeasts and moulds) in smoothies kept at 4 °C for up to 28 days. The main limitation of using HPP was its low efficacy in inactivating oxidative (polyphenol oxidase and peroxidase) and hydrolytic (pectin methyl esterase) enzymes. Data on antioxidant status, colour parameters, browning index, transmittance, turbidity and viscosity confirmed that the HPP-smoothies have a greater tendency towards oxidation and clarification, which might lead to undesirable sensory and nutritional changes (see Part B). The microbial quality of smoothies was adequately controlled by mild HPP treatment without affecting their physical-chemical characteristics; however, oxidative and hydrolytic enzymes are highly pressure-resistant, which suggests that additional strategies should be used to stabilize smoothies. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  1. Magnetically responsive enzyme powders

    Science.gov (United States)

    Pospiskova, Kristyna; Safarik, Ivo

    2015-04-01

    Powdered enzymes were transformed into their insoluble magnetic derivatives retaining their catalytic activity. Enzyme powders (e.g., trypsin and lipase) were suspended in various liquid media not allowing their solubilization (e.g., saturated ammonium sulfate and highly concentrated polyethylene glycol solutions, ethanol, methanol, 2-propanol) and subsequently cross-linked with glutaraldehyde. Magnetic modification was successfully performed at low temperature in a freezer (-20 °C) using magnetic iron oxides nano- and microparticles prepared by microwave-assisted synthesis from ferrous sulfate. Magnetized cross-linked enzyme powders were stable at least for two months in water suspension without leakage of fixed magnetic particles. Operational stability of magnetically responsive enzymes during eight repeated reaction cycles was generally without loss of enzyme activity. Separation of magnetically modified cross-linked powdered enzymes from reaction mixtures was significantly simplified due to their magnetic properties.

  2. Treatment of invasive fungal infections: stability of voriconazole infusion solutions in PVC bags

    Directory of Open Access Journals (Sweden)

    Andréa I.H. Adams

    Full Text Available Voriconazole is a novel broad-spectrum antifungal drug, employed in the treatment of invasive fungal infections, and represents an alternative to amphotericin B treatment. The manufacturer recommends that any unused reconstituted product should be stored at 2ºC to 8ºC, for no more than 24 h, but no recommendations about i.v. infusion solutions are given. Previous works have reported on the stability of voriconazole in polyolefin bags and just one in 5% dextrose polyvinyl chloride (PVC bags, at a 4 mg.mL-1 concentration. In this work, the stability of voriconazole as an i.v. infusion solution in 0.9% sodium chloride and in 5% dextrose, in PVC bags, at 0.5 mg.mL-1, stored at 4 ºC and at room temperature, protected from light, was evaluated. These infusion solutions were analyzed for a 21-day period. Chemical stability was evaluated by HPLC assay. Visual inspection was performed and pH of the solutions was measured. No color change or precipitation in the solutions was observed. The drug content remained above 90% for 11 days in 0.9% sodium chloride and for 9 days in 5% dextrose solutions. The i.v. infusion solutions stored at room temperature were not stable. At room temperature, the voriconazole content dropped down to 88.3 and 86.6%, in 0.9% sodium chloride or 5% dextrose solutions, respectively, two days after admixture. Assays performed at the end of the study suggest the sorption of voriconazole by the PVC bags. The results of this study allow cost-effective batch production in the hospital pharmacy.

  3. Uranium (VI) complexing by macrocyclic or chelating ligands in aqueous solutions stability, formation kinetics, polarographic properties

    International Nuclear Information System (INIS)

    Brighli, M.

    1984-07-01

    Stability of chelates (with EDTA,N,N ethylenediamine diacetic acid EDDA nitrilotriacetic acid NTA and iminodiacetic acid) of UO 2 2+ and UO 4 species of uranium VI is studied in aqueous solution (NaClO 4 3M at 25 deg celcius). Structure in solution are proposed and discussed for mononuclear species. Only complexing kinetics (formation and acid hydrolysis) of UO 4 with EDDA and NTA are studied by spectrophotometry (other reactions are too fast). Besides UO 2 2+ complexes are formed with crown ethers I5C5 and I8C6 in aqueous solution (TEA ClO 4 M/10 at 25 deg celcius. Complexes are probably stabilized by solvation. Results are confirmed by voltametry and reduction mechanisms of UO 2 2+ and its complexes on mercury drop are proposed. 143 refs [fr

  4. Stability and color changes of thermally treated betanin, phyllocactin, and hylocerenin solutions.

    Science.gov (United States)

    Herbach, Kirsten M; Stintzing, Florian C; Carle, Reinhold

    2006-01-25

    Thermal degradation of betanin, phyllocactin (malonyl-betanin), and hylocerenin (3' '-hydroxy-3' '-methyl-glutaryl-betanin) solutions isolated from purple pitaya (Hylocereus polyrhizus [Weber] Britton and Rose) was monitored by spectrophotometric and high-performance liquid chromatography-diode array detection (HPLC-DAD) analyses. For betanin and phyllocactin solutions, the color shift upon thermal treatment was found to be nearly identical, while hylocerenin samples exhibited an intelligibly higher chromatic steadiness. Betanin proved to be the most stable individual pigment structure, while the enhanced tinctorial stability of the integral phyllocactin and especially hylocerenin solutions was due to the formation of red degradation products exhibiting improved color retention as opposed to their respective genuine pigments. Individual structure-related stability characteristics can exclusively be assessed by HPLC-DAD analyses and may not be noticed by mere spectrophotometric assessment of color and tinctorial strength.

  5. Stability of Non-constant Equilibrium Solutions for Bipolar Full Compressible Navier-Stokes-Maxwell Systems

    Science.gov (United States)

    Li, Xin; Wang, Shu; Feng, Yue-Hong

    2018-01-01

    We study the stability of smooth solutions near non-constant equilibrium states for a bipolar full compressible Navier-Stokes-Maxwell system in a three-dimensional torus T= (R/Z)^3 . This system is quasilinear hyperbolic-parabolic. In the first part, by using the maximum principle, we find a non-constant steady state solution with small amplitude for this system. In the second part, with the help of suitable choices of symmetrizers and classic energy estimates, we prove that global smooth solutions exist and converge to the non-constant steady states as the time goes to infinity. As a byproduct, we obtain the global stability for the bipolar full compressible Navier-Stokes-Poisson system.

  6. Evaluation of the stability of linezolid in aqueous solution and commonly used intravenous fluids

    Directory of Open Access Journals (Sweden)

    Taylor R

    2017-07-01

    Full Text Available Rachel Taylor, Bruce Sunderland, Giuseppe Luna, Petra Czarniak School of Pharmacy, Faculty of Health Sciences, Curtin University, Bentley, WA, Australia Purpose: The aim was to evaluate the stability of linezolid in commonly used intravenous fluids and in aqueous solution to determine the kinetics of degradation and shelf-life values at alkaline pH values. Methods: Forced degradation studies were performed on linezolid in solution to develop a validated high-performance liquid chromatography analysis. Sodium chloride 0.9%, sodium lactate, and glucose 5% and glucose 10% solution containing 2.0 mg/mL linezolid were stored at 25.0°C (±0.1°C for 34 days. The effect of temperature on the stability of linezolid in 0.1 M sodium hydroxide solution was investigated to determine the activation energy. The degradation rates of linezolid at selected pH values at 70.0°C and the influence of ionic strength were also examined. Activation energy data were applied to determine the shelf-life values at selected pH values, and a pH rate profile was constructed over the pH range of 8.7–11.4. The stability of intravenous linezolid (Zyvox® solution was evaluated by storing at 70.0°C for 72 hours. Results: Linezolid was found to maintain >95.0% of its initial concentration after storage at 25.0°C for 34 days in sodium lactate, 0.9% in sodium chloride, and 5% and 10% in glucose solutions. Linezolid was degraded at alkaline pH values by first-order kinetics. Activation energy data showed that temperature, but not ionic strength, influenced the degradation rate significantly. An activation energy of 58.22 kJ/mol was determined for linezolid in 0.1 M sodium hydroxide solution. Linezolid was least stable at high pH values and at elevated temperatures. It was determined that linezolid has adequate stability for the preparation of intravenous fluids for clinical administration. Conclusion: Linezolid was found to have a shelf life of 34 days at 25°C when added to

  7. STABILITY OF A CYLINDRICAL SOLUTE-SOLVENT INTERFACE: EFFECT OF GEOMETRY, ELECTROSTATICS, AND HYDRODYNAMICS.

    Science.gov (United States)

    Li, B O; Sun, Hui; Zhou, Shenggao

    The solute-solvent interface that separates biological molecules from their surrounding aqueous solvent characterizes the conformation and dynamics of such molecules. In this work, we construct a solvent fluid dielectric boundary model for the solvation of charged molecules and apply it to study the stability of a model cylindrical solute-solvent interface. The motion of the solute-solvent interface is defined to be the same as that of solvent fluid at the interface. The solvent fluid is assumed to be incompressible and is described by the Stokes equation. The solute is modeled simply by the ideal-gas law. All the viscous force, hydrostatic pressure, solute-solvent van der Waals interaction, surface tension, and electrostatic force are balanced at the solute-solvent interface. We model the electrostatics by Poisson's equation in which the solute-solvent interface is treated as a dielectric boundary that separates the low-dielectric solute from the high-dielectric solvent. For a cylindrical geometry, we find multiple cylindrically shaped equilibrium interfaces that describe polymodal (e.g., dry and wet) states of hydration of an underlying molecular system. These steady-state solutions exhibit bifurcation behavior with respect to the charge density. For their linearized systems, we use the projection method to solve the fluid equation and find the dispersion relation. Our asymptotic analysis shows that, for large wavenumbers, the decay rate is proportional to wavenumber with the proportionality half of the ratio of surface tension to solvent viscosity, indicating that the solvent viscosity does affect the stability of a solute-solvent interface. Consequences of our analysis in the context of biomolecular interactions are discussed.

  8. Carbapenems and SHV-1 β-Lactamase Form Different Acyl-Enzyme Populations in Crystals and Solution

    Science.gov (United States)

    Kalp, Matthew; Carey, Paul R.

    2009-01-01

    The reactions between single crystals of the SHV-1 β-lactamase enzyme and the carbapenems, meropenem, imipenem and ertapenem, have been studied by Raman microscopy. Aided by quantum mechanical calculations, major populations of two acyl-enzyme species, a labile Δ2-pyrroline and a more tightly bound Δ1-pyrroline, have been identified for all three compounds. These isomers differ only in the position of the double bond about the carbapenem nucleus. This discovery is consonant with X-ray crystallographic findings that also identified two populations for meropenem bound in SHV-1: one with the acyl C=O group in the oxyanion hole and the second with the acyl group rotated 180 degrees compared to its expected position [Nukaga, M., Bethel, C. R., Thomson, J. M., Hujer, A. M., Distler, A. M., Anderson, V. E., Knox, J. R., and Bonomo, R. A. (2008) Journal of the American Chemical Society]. When crystals of the Δ1 and Δ2 containing acyl-enzymes were exposed to solutions with no carbapenem, rapid deacylation of the Δ2 species was observed by kinetic Raman experiments. However, no change in the Δ1 population was observed over 1 hour, the effective lifetime of the crystal. These observations lead to the hypothesis that the stable Δ1 species is due to the form seen by X-ray with the acyl carbonyl outside the oxyanion hole, while the Δ2 species corresponds to the form with the carbonyl inside the oxyanion hole. Soak-in and soak-out Raman experiments also demonstrated that tautomeric exchange between the Δ1 and Δ2 forms does not occur on the crystalline enzyme. When meropenem or ertapenem were reacted with SHV-1 in solution, the Raman difference spectra demonstrated that only a major population corresponding to the Δ1 acyl-enzyme could be detected. The 1003 cm-1 mode of the phenyl ring positioned on the C3 side chain of ertapenem acts as an effective internal Raman intensity standard and the ratio of its intensity to that of the 1600 cm-1 feature of Δ1 provides an

  9. Functional Inference of Methylenetetrahydrofolate Reductase Gene Polymorphisms on Enzyme Stability as a Potential Risk Factor for Down Syndrome in Croatia

    Directory of Open Access Journals (Sweden)

    Jadranka Vraneković

    2010-01-01

    Full Text Available Understanding the biochemical structure and function of the methylenetetrahydrofolate reductase gene (MTHFR provides new evidence in elucidating the risk of having a child with Down syndrome (DS in association with two common MTHFR polymorphisms, C677T and A1298C. The aim of this study was to evaluate the risk for DS according to the presence of MTHFR C677T and A1298C polymorphisms as well as the stability of the enzyme configuration. This study included mothers from Croatia with a liveborn DS child (n = 102 or DS pregnancy (n = 9 and mothers with a healthy child (n = 141. MTHFR C677T and A1298C polymorphisms were assessed by PCR-RFLP. Allele/genotype frequencies differences were determined using χ2 test. Odds ratio and the 95% confidence intervals were calculated to evaluate the effects of different alleles/genotypes. No statistically significant differences were found between the frequencies of allele/genotype or genotype combinations of the MTHFR C677T and A1298C polymorphisms in the case and the control groups. Additionally, the observed frequencies of the stable (677CC/1298AA, 677CC/1298AC, 677CC/1298CC and unstable (677CT/1298AA, 677CT/1298AC, 677TT/1298AA enzyme configurations were not significantly different. We found no evidence to support the possibility that MTHFR polymorphisms and the stability of the enzyme configurations were associated with risk of having a child with DS in Croatian population.

  10. Antioxidants as stabilizers for His6-OPH: is this an unusual or regular role for them with enzymes?

    Science.gov (United States)

    Efremenko, Elena N; Lyagin, Ilya V; Cuong, Le H; Huong, Le M

    2017-11-01

    The effect of 14 different antioxidants on the activity of a hexahistidine-tagged organophosphorus hydrolase (His6-OPH) has been studied in vitro. It has been found that antioxidants can have a positive, neutral or negative effect on the activity of His6-OPH in a native form or in the form of an enzyme-polyelectrolyte complex, while the enzyme itself does not affect their antioxidant activity. A significant stabilizing effect of a number of antioxidants on His6-OPH has been shown against its inhibiting with organic solvents (DMSO and isopropyl alcohol). The kinetics of the process has been studied. Based on molecular docking of all tested antioxidants to the surface of His6-OPH dimer, options of their localization have been identified. These data were used to explain the revealed stabilizing effect of the antioxidants on the enzyme as well as their negative influence on His6-OPH activity. © The Authors 2017. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.

  11. VMCast: A VM-Assisted Stability Enhancing Solution for Tree-Based Overlay Multicast.

    Directory of Open Access Journals (Sweden)

    Weidong Gu

    Full Text Available Tree-based overlay multicast is an effective group communication method for media streaming applications. However, a group member's departure causes all of its descendants to be disconnected from the multicast tree for some time, which results in poor performance. The above problem is difficult to be addressed because overlay multicast tree is intrinsically instable. In this paper, we proposed a novel stability enhancing solution, VMCast, for tree-based overlay multicast. This solution uses two types of on-demand cloud virtual machines (VMs, i.e., multicast VMs (MVMs and compensation VMs (CVMs. MVMs are used to disseminate the multicast data, whereas CVMs are used to offer streaming compensation. The used VMs in the same cloud datacenter constitute a VM cluster. Each VM cluster is responsible for a service domain (VMSD, and each group member belongs to a specific VMSD. The data source delivers the multicast data to MVMs through a reliable path, and MVMs further disseminate the data to group members along domain overlay multicast trees. The above approach structurally improves the stability of the overlay multicast tree. We further utilized CVM-based streaming compensation to enhance the stability of the data distribution in the VMSDs. VMCast can be used as an extension to existing tree-based overlay multicast solutions, to provide better services for media streaming applications. We applied VMCast to two application instances (i.e., HMTP and HCcast. The results show that it can obviously enhance the stability of the data distribution.

  12. Formulation development and stability testing of oral morphine solution utilizing preformulation approach.

    Science.gov (United States)

    Preechagoon, Detpon; Sumyai, Viroj; Tontisirin, Khanittha; Aumpon, Sirikul; Pongjanyakul, Thaned

    2005-08-18

    Prefomulation approach utilizing the fractional-ordered randomized blocked design was employed for the formulation development and stability testing of morphine solution. Factors expecting to affect the stability of morphine were evaluated, i.e., vehicle, antioxidant, chelating agent, and pH of the solution. Eight formulations of a possible 16 were prepared according to the block design. The stability of the preparations was tested after 35 days of storage. The data of preformulation study were used for formulation development. The presence of glycerin and ethylenediamine-tetraacetic acid in the formulation, and the pH of the solution adjusted to 4, stabilized morphine. The concentration of morphine decreased drastically in the formulations containing sodium metabisulfite, and those pH adjusted to 6. After 35 days, only 65% of morphine was found in the formulation containing sodium metabisulfite and pH adjusted to 6. The results of preformulation study were used for preparing oral morphine preparations. Samples were kept in amber glass bottles and stored at 4 degrees C and 25 degrees C/75% RH for 13 months. No precipitation of the four formulations was detected. Only a decrease of odor and a small increase of pH value of the preparations (preformulation approach. They were stable more than 13 months when stored at 4 degrees C and 25 degrees C/75% RH.

  13. VMCast: A VM-Assisted Stability Enhancing Solution for Tree-Based Overlay Multicast.

    Science.gov (United States)

    Gu, Weidong; Zhang, Xinchang; Gong, Bin; Zhang, Wei; Wang, Lu

    2015-01-01

    Tree-based overlay multicast is an effective group communication method for media streaming applications. However, a group member's departure causes all of its descendants to be disconnected from the multicast tree for some time, which results in poor performance. The above problem is difficult to be addressed because overlay multicast tree is intrinsically instable. In this paper, we proposed a novel stability enhancing solution, VMCast, for tree-based overlay multicast. This solution uses two types of on-demand cloud virtual machines (VMs), i.e., multicast VMs (MVMs) and compensation VMs (CVMs). MVMs are used to disseminate the multicast data, whereas CVMs are used to offer streaming compensation. The used VMs in the same cloud datacenter constitute a VM cluster. Each VM cluster is responsible for a service domain (VMSD), and each group member belongs to a specific VMSD. The data source delivers the multicast data to MVMs through a reliable path, and MVMs further disseminate the data to group members along domain overlay multicast trees. The above approach structurally improves the stability of the overlay multicast tree. We further utilized CVM-based streaming compensation to enhance the stability of the data distribution in the VMSDs. VMCast can be used as an extension to existing tree-based overlay multicast solutions, to provide better services for media streaming applications. We applied VMCast to two application instances (i.e., HMTP and HCcast). The results show that it can obviously enhance the stability of the data distribution.

  14. Stability of twisted rods, helices and buckling solutions in three dimensions

    International Nuclear Information System (INIS)

    Majumdar, Apala; Raisch, Alexander

    2014-01-01

    We study stability problems for equilibria of a naturally straight, inextensible, unshearable Kirchhoff rod allowed to deform in three dimensions (3D), subject to terminal loads. We investigate the stability of the twisted, straight state in 3D for three different boundary-value problems, cast in terms of Dirichlet and Neumann boundary conditions for the Euler angles, with and without isoperimetric constraints. In all cases, we obtain explicit stability estimates in terms of the twist, external load and elastic constants and in the Dirichlet case, we compute bifurcation diagrams for the Euler angles as a function of the external load. In the same vein, we obtain explicit stability estimates for a family of prototypical helical equilibria in 3D and demonstrate that they are stable for a range of tensile and compressive forces. We propose a numerical L 2 -gradient flow model to study the stability and dynamical evolution (in viscous model situations) of Kirchhoff rod equilibria. In Nizette and Goriely 1999 J. Math. Phys. 40 2830–66, the authors construct a family of localized buckling solutions. We apply our L 2 -gradient flow model to these localized buckling solutions, demonstrate that they are unstable, study their evolution and the simulations demonstrate rich spatio-temporal patterns that strongly depend on the boundary conditions and imposed isoperimetric constraints. (paper)

  15. Stability of twisted rods, helices and buckling solutions in three dimensions

    KAUST Repository

    Majumdar, Apala

    2014-11-03

    © 2014 IOP Publishing Ltd & London Mathematical Society. We study stability problems for equilibria of a naturally straight, inextensible, unshearable Kirchhoff rod allowed to deform in three dimensions (3D), subject to terminal loads. We investigate the stability of the twisted, straight state in 3D for three different boundary-value problems, cast in terms of Dirichlet and Neumann boundary conditions for the Euler angles, with and without isoperimetric constraints. In all cases, we obtain explicit stability estimates in terms of the twist, external load and elastic constants and in the Dirichlet case, we compute bifurcation diagrams for the Euler angles as a function of the external load. In the same vein, we obtain explicit stability estimates for a family of prototypical helical equilibria in 3D and demonstrate that they are stable for a range of tensile and compressive forces. We propose a numerical L2-gradient flow model to study the stability and dynamical evolution (in viscous model situations) of Kirchhoff rod equilibria. In Nizette and Goriely 1999 J. Math. Phys. 40 2830-66, the authors construct a family of localized buckling solutions. We apply our L2-gradient flow model to these localized buckling solutions, demonstrate that they are unstable, study their evolution and the simulations demonstrate rich spatio oral patterns that strongly depend on the boundary conditions and imposed isoperimetric constraints.

  16. Color stability of siloranes versus methacrylate-based composites after immersion in staining solutions.

    Science.gov (United States)

    Arocha, Mariana A; Mayoral, Juan R; Lefever, Dorien; Mercade, Montserrat; Basilio, Juan; Roig, Miguel

    2013-07-01

    The purpose of this study was to determine, by using a spectrophotometer device, the color stability of silorane in comparison with four methacrylate-based composites after being immersed in different staining solutions such as coffee, black tea, red wine, orange juice, and coke, and distilled water as control group. Four restorative methacrylate-based composites (Filtek Z250, TetricEvoCeram, Venus Diamond, and Grandio) and one silorane (FiltekSilorane) of shade A2 were selected to measure their color stability (180 disk samples) after 4 weeks of immersion in six staining solutions: black tea, coffee, red wine, orange juice, coke, and distilled water. The specimen's color was measured each week by means of a spectrophotometer (CIE L*a*b* system). Statistical analysis was carried out performing an ANOVA and LSD Test in order to statistically analyze differences in L*a*b*and ∆E values. All materials showed significant discoloration (p < 0.05) when compared to the control group (immersed in distilled water). The Highest ∆E observed was with red wine, whereas coke led to the lowest one. Silorane showed the highest color stability compared with methacrylate-based composites. Methacrylate-based materials immersed in staining solutions showed lower color stability when compared with silorane. Great differences in ∆E were found among the methacrylate-based materials tested. Although color stability of methacrylate-based composites immersed in staining solutions has been widely investigated, this has not been done for long immersion periods with silorane-based composites.

  17. Stability of cyclosporine solutions stored in polypropylene-polyolefin bags and polypropylene syringes.

    Science.gov (United States)

    Li, Mengqing; Forest, Jean-Marc; Coursol, Christian; Leclair, Grégoire

    2011-09-01

    The stability of cyclosporine diluted to 0.2 or 2.5 mg/mL with 0.9% sodium chloride injection or 5% dextrose injection and stored in polypropylene-polyolefin containers or polypropylene syringes was evaluated. Intravenous cyclosporine solutions (0.2 and 2.5 mg/mL) were aseptically prepared and transferred to 250-mL polypropylene-polyolefin bags or 60-mL polypropylene syringes. Chemical stability was measured using a stability-indicating high-performance liquid chromatography (HPLC) assay. Physical stability was assessed by visual inspection and a dynamic light scattering (DLS) method. After 14 days, HPLC assay showed that the samples of i.v. cyclosporine stored in polypropylene-polyolefin bags remained chemically stable (>98% of initial amount remaining); the physical stability of the samples was confirmed by DLS and visual inspection. The samples stored in polypropylene syringes were found to contain an impurity (attributed to leaching of a syringe component by the solution) that could be detected by HPLC after 1 day; on further investigation, no leaching was detected when the syringes were exposed to undiluted i.v. cyclosporine 50 mg/mL for 10 minutes. Samples of i.v. cyclosporine solutions of 0.2 and 2.5 mg/mL diluted in 0.9% sodium chloride injection or 5% dextrose injection and stored at 25 °C in polypropylene-polyolefin bags were physically and chemically stable for at least 14 days. When stored in polypropylene syringes, the samples were contaminated by an impurity within 1 day; however, the short-term (i.e., ≤10 minutes) use of the syringes for the preparation and transfer of i.v. cyclosporine solution is considered safe.

  18. Overall conformation of covalently stabilized domain-swapped dimer of human cystatin C in solution

    Science.gov (United States)

    Murawska, Magdalena; Szymańska, Aneta; Grubb, Anders; Kozak, Maciej

    2017-11-01

    Human cystatin C (HCC), a small protein, plays a crucial role in inhibition of cysteine proteases. The most common structural form of human cystatin C in crystals is a dimer, which has been evidenced both for the native protein and its mutants. In these structures, HCC dimers were formed through the mechanism of domain swapping. The structure of the monomeric form of human cystatin C was determined for V57N mutant and the mutant with the engineered disulfide bond (L47C)-(G69C) (known as stab1-HCC). On the basis of stab1-HCC, a number of covalently stabilized oligomers, including also dimers have been obtained. The aim of this study was to analyze the structure of the covalently stabilized dimer HCC in solution by the small angle X-ray scattering (SAXS) technique and synchrotron radiation. Experimental data confirmed that in solution this protein forms a dimer, which is characterized by the radius of gyration RG = 3.1 nm and maximum intramolecular distance Dmax = 10.3 nm. Using the ab initio method and program DAMMIN, we propose a low resolution structure of stabilized covalently cystatin C in solution. Stab-HCC dimer adopts in solution an elongated conformation, which is well reconstructed by the ab initio model.

  19. Evaluation of solution stability for two-component polydisperse systems by small-angle scattering

    Science.gov (United States)

    Kryukova, A. E.; Konarev, P. V.; Volkov, V. V.

    2017-12-01

    The article is devoted to the modelling of small-angle scattering data using the program MIXTURE designed for the study of polydisperse multicomponent mixtures. In this work we present the results of solution stability studies for theoretical small-angle scattering data sets from two-component models. It was demonstrated that the addition of the noise to the data influences the stability range of the restored structural parameters. The recommendations for the optimal minimization schemes that permit to restore the volume size distributions for polydisperse systems are suggested.

  20. Rapid delivery of diazepam from supersaturated solutions prepared using prodrug/enzyme mixtures: toward intranasal treatment of seizure emergencies.

    Science.gov (United States)

    Kapoor, Mamta; Winter, Tate; Lis, Lev; Georg, Gunda I; Siegel, Ronald A

    2014-05-01

    Current treatments for seizure emergencies, such as status epilepticus, include intravenous or rectal administration of benzodiazepines. While intranasal delivery of these drugs is desirable, the small volume of the nasal cavity and low drug solubility pose significant difficulties. Here, we prepared supersaturated diazepam solutions under physiological conditions and without precipitation, using a prodrug/enzyme system. Avizafone, a peptide prodrug of diazepam, was delivered with--Aspergillus oryzae (A.O.) protease, an enzyme identified from a pool of hydrolytic enzymes in assay buffer, pH 7.4 at 32°C. This enzyme converted avizafone to diazepam at supersaturated concentrations. In vitro permeability studies were performed at various prodrug/enzyme ratios using Madin-Darby canine kidney II-wild type (MDCKII-wt) monolayers, a representative model of the nasal epithelium. Monolayer integrity was examined using TEER measurement and the lucifer yellow permeability assay. Prodrug/drug concentrations were measured using HPLC. Enzyme kinetics with avizafone-protease mixtures revealed K(M) = 1,501 ± 232 μM and V(max) = 1,369 ± 94 μM/s. Prodrug-protease mixtures, when co-delivered apically onto MDCKII-wt monolayers, showed 2-17.6-fold greater diazepam flux (S = 1.3-15.3) compared to near-saturated diazepam (S = 0.7). Data for prodrug conversion upstream (apical side) and drug permeability downstream (basolateral side) fitted reasonably well to a previously developed in vitro two compartment pharmacokinetic model. Avizafone-protease mixtures resulted in supersaturated diazepam in less than 5 min, with the rate and extent of supersaturation determined by the prodrug/enzyme ratio. Together, these results suggest that an intranasal avizafone-protease system may provide a rapid and alternative means of diazepam delivery.

  1. Adsorption of Trametes versicolor laccase to soil iron and aluminum minerals: enzyme activity, kinetics and stability studies.

    Science.gov (United States)

    Wu, Yue; Jiang, Ying; Jiao, Jiaguo; Liu, Manqiang; Hu, Feng; Griffiths, Bryan S; Li, Huixin

    2014-02-01

    Laccases play an important role in the degradation of soil phenol or phenol-like substance and can be potentially used in soil remediation through immobilization. Iron and aluminum minerals can adsorb extracellular enzymes in soil environment. In the present study, we investigated the adsorptive interaction of laccase, from the white-rot fungus Trametes versicolor, with soil iron and aluminum minerals and characterized the properties of the enzyme after adsorption to minerals. Results showed that both soil iron and aluminum minerals adsorbed great amount of laccase, independent of the mineral specific surface areas. Adsorbed laccases retained 26-64% of the activity of the free enzyme. Compared to the free laccase, all adsorbed laccases showed higher Km values and lower Vmax values, indicating a reduced enzyme-substrate affinity and a lower rate of substrate conversion in reactions catalyzed by the adsorbed laccase. Adsorbed laccases exhibited increased catalytic activities compared to the free laccase at low pH, implying the suitable application of iron and aluminum mineral-adsorbed T. versicolor laccase in soil bioremediation, especially in acid soils. In terms of the thermal profiles, adsorbed laccases showed decreased thermal stability and higher temperature sensitivity relative to the free laccase. Moreover, adsorption improved the resistance of laccase to proteolysis and extended the lifespan of laccase. Our results implied that adsorbed T. versicolor laccase on soil iron and aluminum minerals had promising potential in soil remediation. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

  2. Artificial-enzyme gel membrane-based biosurveillance sensor with high reproducibility and long-term storage stability.

    Science.gov (United States)

    Ikeno, Shinya; Yoshida, Tetsuya; Haruyama, Tetsuya

    2009-02-01

    We propose that the most sophisticated strategy for primary biosurveillance is to exploit structural commonality through the detection of biologically relevant phosphoric substances. A novel assay, an artificial-enzyme membrane was designed and synthesized for sensor fabrication. This artificial-enzyme catalyzes the hydrolysis of the diphosphoric acid anhydride structure. This structure-selective, albeit not molecule-selective, catalytic hydrolysis was successfully coupled with amperometric detection. Since the catalytic reaction produces a dephosphorylation product (PO(4)(3-)), it can be reduced by an electrode potential of -250 mV vs. Ag/AgCl. Owing to the structural selectivity of the artificial-enzyme membrane, the sensor can detect biological phosphoric substances comprehensively that have the diphosphoric acid anhydride structure. The sensor successfully determined various biological phosphoric substances at concentrations in the micromolar (microM) to millimolar (mM) range, and it showed good functional stability and reproducibility in terms of sensor responses. This sensor was used to detect Escherichia coli lysed by heat treatment, and the response increased with increasing bacterial numbers. This unique technique for analyzing molecular commonality can be applied to the surveillance of biocontaminants, e.g. microorganisms, spores and viruses. Artificial-enzyme-based detection is a novel strategy for practical biosurveillance in the front line.

  3. Researches on the stability of porphyra-334 solution and its influence factors

    Science.gov (United States)

    Zhang, Zhaohui; Gao, Xin; Yuri, Tashiro; Shingo, Matsukawa; Hiroo, Ogawa

    2004-10-01

    The stability of porphyra-334 in solutions of different pH values at different temperatures was studied. In high acidic conditions, below pH3, the absorption maximum, λmax, of porphyra-334 shows hypsochromic shift towards lower wavelength and the absorbance also has a light decrease. In high alkaline conditions of over pH12, the absorbance of porphyra-334 decreases and an unknown compound with a peak maximum at 225 nm appears. The peak height of the unknown compound increases with the decrease of absorbance of porphyra-334. This might be related to the decomposition of porphyra-334. At room temperature, porphyra-334 solutions, except high alkaline solutions, are stable. Increasing the temperature, especially higher than 60°C, promotes the decomposition of porphyra-334 and causes the absorbance decrease both in basic and acidic solutions.

  4. Encapsulation of a Nerve Agent Detoxifying Enzyme by a Mesoporous Zirconium Metal-Organic Framework Engenders Thermal and Long-Term Stability.

    Science.gov (United States)

    Li, Peng; Moon, Su-Young; Guelta, Mark A; Harvey, Steven P; Hupp, Joseph T; Farha, Omar K

    2016-07-06

    Immobilized enzymes typically have greater thermal and operational stability than their soluble form. Here we report that for the first time, a nerve agent detoxifying enzyme, organophosphorus acid anhydrolase (OPAA), has been successfully encapsulated into a water-stable zirconium metal-organic framework (MOF). This MOF features a hierarchical mesoporous channel structure and exhibits a 12 wt % loading capacity of OPAA. The thermal and long-term stabilities of OPAA are both significantly enhanced after immobilization.

  5. Pressure stabilization is not a general property of thermophilic enzymes: the adenylate kinases of Methanococcus voltae, Methanococcus maripaludis, Methanococcus thermolithotrophicus, and Methanococcus jannaschii.

    OpenAIRE

    Konisky, J; Michels, P C; Clark, D S

    1995-01-01

    The application of 50-MPa pressure did not increase the thermostabilities of adenylate kinases purified from four related mesophilic and thermophilic marine methanogens. Thus, while it has been reported that some thermophilic enzymes are stabilized by pressure (D. J. Hei and D. S. Clark, Appl. Environ. Microbiol. 60:932-939, 1994), hyperbaric stabilization is not an intrinsic property of all enzymes from deep-sea thermophiles.

  6. Thermal Stability of RNA Structures with Bulky Cations in Mixed Aqueous Solutions.

    Science.gov (United States)

    Nakano, Shu-Ichi; Tanino, Yuichi; Hirayama, Hidenobu; Sugimoto, Naoki

    2016-10-04

    Bulky cations are used to develop nucleic-acid-based technologies for medical and technological applications in which nucleic acids function under nonaqueous conditions. In this study, the thermal stability of RNA structures was measured in the presence of various bulky cations in aqueous mixtures with organic solvents or polymer additives. The stability of oligonucleotide, transfer RNA, and polynucleotide structures was decreased in the presence of salts of tetrabutylammonium and tetrapentylammonium ions, and the stability and salt concentration dependences were dependent on cation sizes. The degree to which stability was dependent on salt concentration was correlated with reciprocals of the dielectric constants of mixed solutions, regardless of interactions between the cosolutes and RNA. Our results show that organic solvents affect the strength of electrostatic interactions between RNA and cations. Analysis of ion binding to RNA indicated greater enhancement of cation binding to RNA single strands than to duplexes in media with low dielectric constants. Furthermore, background bulky ions changed the dependence of RNA duplex stability on the concentration of metal ion salts. These unique properties of large tetraalkylammonium ions are useful for controlling the stability of RNA structures and its sensitivity to metal ion salts. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  7. Stability of chitosan nanoparticles for L-ascorbic acid during heat treatment in aqueous solution.

    Science.gov (United States)

    Jang, Keum-Il; Lee, Hyeon Gyu

    2008-03-26

    This study investigated the stability and characteristics of L-ascorbic acid (AA)-loaded chitosan (CS) nanoparticles during heat processing in aqueous solutions. AA-loaded CS nanoparticles were prepared by ionic gelation of CS with tripolyphosphate (TPP) anions. The smallest CS nanoparticles (170 nm) were obtained with a CS concentration of 1.5 mg/mL and a TPP concentration of 0.6 mg/mL. As the concentration of AA increased from 0.1 to 0.3 mg/mL, the particle size increased, while the zeta potential decreased, and the encapsulation efficiency of AA remained within a fixed range (10-12%). During heat processing at various temperatures, the size and zeta potential of the particles decreased rapidly in the first 5 min and then slowly fell to the regular range. At the beginning of the release profiles, the burst release-related stability of the surface increased with the temperature. Then, the release of the internal AA was constantly higher with a longer release time. Consequently, it was confirmed that the stability of AA-loaded CS nanoparticles was affected by temperature but that the internal stability was greater than the surface stability. These results demonstrate the stability of CS nanoparticles for AA during heat processing and suggest the possible use of AA-loaded CS nanoparticles to enhance antioxidant effects because of the continuous release of AA from CS nanoparticles in food processing.

  8. Effect of different solutions on color stability of acrylic resin-based dentures.

    Science.gov (United States)

    Goiato, Marcelo Coelho; Nóbrega, Adhara Smith; dos Santos, Daniela Micheline; Andreotti, Agda Marobo; Moreno, Amália

    2014-01-01

    The aim of this study was to evaluate the effect of thermocycling and immersion in mouthwash or beverage solutions on the color stability of four different acrylic resin-based dentures (Onda Cryl, OC; QC20, QC; Classico, CL; and Lucitone, LU). The factors evaluated were type of acrylic resin, immersion time, and solution (mouthwash or beverage). A total of 224 denture samples were fabricated. For each type of resin, eight samples were immersed in mouthwashes (Plax-Colgate, PC; Listerine, LI; and Oral-B, OB), beverages (coffee, CP; cola, C; and wine, W), and artificial saliva (AS; control). The color change (DE) was evaluated before (baseline) and after thermocycling (T1), and after immersion in solution for 1 h (T2), 3 h (T3), 24 h (T4), 48 h (T5), and 96 h (T6). The CIE Lab system was used to determine the color changes. The thermocycling test was performed for 5000 cycles. Data were submitted to three-way repeated-measures analysis of variance and Tukey's test (pacrylic resin. Similarly, when the samples were immersed in each beverage, all studied factors influenced the color change values. In general, regardless of the solution, LU exhibited the greatest DE values in the period from T1 to T5; and QC presented the greatest DE values at T6. Thus, thermocycling and immersion in the various solutions influenced the color stability of acrylic resins and QC showed the greatest color alteration.

  9. A mathematical model of oxidative deamination of amino acid catalyzed by two D-amino acid oxidases and influence of aeration on enzyme stability.

    Science.gov (United States)

    Findrik, Zvjezdana; Valentović, Ivana; Vasić-Rački, Ðurđa

    2014-03-01

    Two D-amino acid oxidases (DAAO) from different sources (Arthrobacter protophormiae and porcine kidney) were used to oxidatively deaminate D-methionine in the batch reactor. A mathematical model of the process was developed and validated by the experiments carried out without and with oxygen supply by aeration. Kinetic parameters of the model were estimated from the initial reaction rate experiments. Aeration increased the reaction rate in the initial part of the reaction and reduced the time necessary to achieve the final substrate conversion. However, it had a negative influence on the operational stability of enzymes. Operational stability decay rate constants estimated from the experimental data increased with the airflow rate, which indicated lower operational stability of enzymes. It was found that oxygen concentration significantly influenced the stability of DAAO from porcine kidney. Enzyme from microbial source had better operational stability and one order of magnitude lower values of decay rate constants.

  10. Method of Lyapunov functions in problems of stability of solutions of systems of differential equations with impulse action

    International Nuclear Information System (INIS)

    Ignat'yev, A O

    2003-01-01

    A system of ordinary differential equations with impulse action at fixed moments of time is considered. The system is assumed to have the zero solution. It is shown that the existence of a corresponding Lyapunov function is a necessary and sufficient condition for the uniform asymptotic stability of the zero solution. Restrictions on perturbations of the right-hand sides of differential equations and impulse actions are obtained under which the uniform asymptotic stability of the zero solution of the 'unperturbed' system implies the uniform asymptotic stability of the zero solution of the 'perturbed' system

  11. Structuring and sedimentation stability of titanium phosphate nanoparticles in polymer solutions.

    Science.gov (United States)

    Uryupina, O Ya; Serebryakova, N V; Roldughin, V I

    2003-07-01

    The influence of dispersed phase nature on the sedimentation stability as well as coagulation structure of titanium phosphate (TP) nanoparticles in polymer suspensions has been investigated. Two systems are considered: (i). TP suspension in toluene/ethyl cellosolve mixed solution of ephoxy resin E-40 and (ii). multicomponent system, ferric oxide, talc and TP suspension in toluene/ethyl cellosolve solution of E-40, as a model of the practical varnish-paint systems. For the case of a polar solvent, a unique phenomenon, extremal dependence of the strength of model systems on the concentration TP, is detected and increase of sedimentation stability of TP organic suspensions with time of contact of TP with a solvent is observed. Data of FTIR-spectroscopy show that phenomena detected result from the formation adsorption shell possessing high structural viscosity on TP nanopaticles.

  12. Evaluation of the Magnesium Hydroxide Treatment Process for Stabilizing PFP Plutonium/Nitric Acid Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Gerber, Mark A.; Schmidt, Andrew J.; Delegard, Calvin H.; Silvers, Kurt L.; Baker, Aaron B.; Gano, Susan R.; Thornton, Brenda M.

    2000-09-28

    This document summarizes an evaluation of the magnesium hydroxide [Mg(OH)2] process to be used at the Hanford Plutonium Finishing Plant (PFP) for stabilizing plutonium/nitric acid solutions to meet the goal of stabilizing the plutonium in an oxide form suitable for storage under DOE-STD-3013-99. During the treatment process, nitric acid solutions bearing plutonium nitrate are neutralized with Mg(OH)2 in an air sparge reactor. The resulting slurry, containing plutonium hydroxide, is filtered and calcined. The process evaluation included a literature review and extensive laboratory- and bench-scale testing. The testing was conducted using cerium as a surrogate for plutonium to identify and quantify the effects of key processing variables on processing time (primarily neutralization and filtration time) and calcined product properties.

  13. Multi-stability and almost periodic solutions of a class of recurrent neural networks

    International Nuclear Information System (INIS)

    Liu Yiguang; You Zhisheng

    2007-01-01

    This paper studies multi-stability, existence of almost periodic solutions of a class of recurrent neural networks with bounded activation functions. After introducing a sufficient condition insuring multi-stability, many criteria guaranteeing existence of almost periodic solutions are derived using Mawhin's coincidence degree theory. All the criteria are constructed without assuming the activation functions are smooth, monotonic or Lipschitz continuous, and that the networks contains periodic variables (such as periodic coefficients, periodic inputs or periodic activation functions), so all criteria can be easily extended to fit many concrete forms of neural networks such as Hopfield neural networks, or cellular neural networks, etc. Finally, all kinds of simulations are employed to illustrate the criteria

  14. Stability of the trivial solution for linear stochastic differential equations with Poisson white noise

    International Nuclear Information System (INIS)

    Grigoriu, Mircea; Samorodnitsky, Gennady

    2004-01-01

    Two methods are considered for assessing the asymptotic stability of the trivial solution of linear stochastic differential equations driven by Poisson white noise, interpreted as the formal derivative of a compound Poisson process. The first method attempts to extend a result for diffusion processes satisfying linear stochastic differential equations to the case of linear equations with Poisson white noise. The developments for the method are based on Ito's formula for semimartingales and Lyapunov exponents. The second method is based on a geometric ergodic theorem for Markov chains providing a criterion for the asymptotic stability of the solution of linear stochastic differential equations with Poisson white noise. Two examples are presented to illustrate the use and evaluate the potential of the two methods. The examples demonstrate limitations of the first method and the generality of the second method

  15. The crystallization of a solid solution in a solvent and the stability of a growth interface

    International Nuclear Information System (INIS)

    Malmejac, Yves

    1971-03-01

    The potential uses of germanium-silicon alloys as thermoelectric generators in hitherto unexploited temperature ranges initiated the present study. Many delicate problems are encountered in the classical methods of preparation. An original technique was sought for crystallization in a metallic solvent. The thermodynamic equilibria between the various phases of the ternary System used were studied in order to justify the method used. The conditions (temperature and composition) were determined in which the cooling of a ternary liquid mixture induces the precipitation of a binary solid solution with the desired composition. If large crystals are to be obtained from the solid solution, metallic solvent precipitation must be replaced by a mono-directional solvent crystallization. The combined effect of a certain number of simple physical phenomena on the stability of a crystal liquid interface was studied: the morphological stability of the crystal growth interface is the first step towards obtaining perfect crystals. (author) [fr

  16. Stability of busulfan solutions in polypropylene syringes and infusion bags as determined with an original assay.

    Science.gov (United States)

    Guichard, Nicolas; Bonnabry, Pascal; Rudaz, Serge; Fleury-Souverain, Sandrine

    2017-11-15

    The stability of busulfan solution in 0.9% sodium chloride and stored in polypropylene syringes or infusion bags was evaluated. Busulfan solutions (0.54 mg/mL) were prepared and transferred to 50-mL polypropylene syringes and 100- and 500-mL polypropylene infusion bags and stored at 2-8 and 23-27 °C. Chemical stability was measured using a stability-indicating, ultrahigh performance liquid chromatography coupled to mass spectrometry method. The stability of busulfan was assessed by measuring the percentage of the initial concentration remaining at the end of each time point of analysis. The initial busulfan concentration was defined as 100%. Stability was defined as retention of at least 90% of the initial busulfan concentration. A visual inspection of the samples for particulate matter, clarity, and color without instrumentation of magnification was conducted at each time point of analysis. The visual inspection demonstrated no influence of the storage container when busulfan infusions diluted in 0.9% sodium chloride injection were stored at 23-27 °C. No color change or precipitate was observed at this temperature; however, a rapid decrease of the busulfan content in all containers stored at room temperature was observed. Busulfan in syringes was chemically stable for 12 hours, while busulfan in infusion bags (100 and 500 mL) was stable only for 3 hours at 23-27 °C. Busulfan 0.54-mg/mL solution in 0.9% sodium chloride injection was physically and chemically stable for 30 hours when stored in 50-mL polypropylene syringes at 2-8 °C and protected from light. Copyright © 2017 by the American Society of Health-System Pharmacists, Inc. All rights reserved.

  17. Stability of periodic steady-state solutions to a non-isentropic Euler-Poisson system

    Science.gov (United States)

    Liu, Cunming; Peng, Yue-Jun

    2017-06-01

    We study the stability of periodic smooth solutions near non-constant steady-states for a non-isentropic Euler-Poisson system without temperature damping term. The system arises in the theory of semiconductors for which the doping profile is a given smooth function. In this stability problem, there are no special restrictions on the size of the doping profile, but only on the size of the perturbation. We prove that small perturbations of periodic steady-states are exponentially stable for large time. For this purpose, we introduce new variables and choose a non-diagonal symmetrizer of the full Euler equations to recover dissipation estimates. This also allows to make the proof of the stability result very simple and concise.

  18. Synthesis, characterization and thermal stability of solid solutions Zr (Y, Fe, MoO2

    Directory of Open Access Journals (Sweden)

    Felipe Legorreta-García

    2015-05-01

    Full Text Available The synthesis of Fe3+, Mo4+ and Y3+ fully stabilized zirconia by the nitrate/urea combustion route and thermal stability in air was investigated. The solid solution obtained was characterized by X ray diffraction (XRD, scanning electron microscopy (SEM and used the BET method for determining specific surface. The ceramic powders obtained were calcined at 1473 K in air atmosphere in order to determine their thermal stability. The scanning electron microscopy (SEM results showed a homogeneous grain surface, measuring several tens of micrometers across. The crystallographic study revealed that by this method it was successfully achieved zirconia doped with Fe3+, Mo4+ and Y3+ ions in the zirconia tetragonal monophase, even after calcinations.

  19. Gravitational waves and stability of cosmological solutions in the theory with anomaly-induced corrections

    International Nuclear Information System (INIS)

    Fabris, Júlio C.; Pelinson, Ana M.; Salles, Filipe de O.; Shapiro, Ilya L.

    2012-01-01

    The dynamics of metric perturbations is explored in the gravity theory with anomaly-induced quantum corrections. Our first purpose is to derive the equation for gravitational waves in this theory on the general homogeneous and isotropic background, and then verify the stability of such background with respect to metric perturbations. The problem under consideration has several interesting applications. Our first purpose is to explore the stability of the classical cosmological solutions in the theory with quantum effects taken into account. There is an interesting literature about stability of Minkowski and de Sitter spaces and here we extend the consideration also to the radiation and matter dominated cosmologies. Furthermore, we analyze the behavior of metric perturbations during inflationary period, in the stable phase of the Modified Starobinsky inflation

  20. Synthesis, characterization and thermal stability of solid solutions Zr (Y, Fe, Mo)O {sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Legorreta-Garcia, F.; Esperanza Hernandez-Cruz, L.; Villanueva-Ibanez, M.; Flores-Gonzalez, M. A.

    2015-10-01

    The synthesis of Fe{sup 3}+, Mo{sup 4+} and Y{sup 3+} fully stabilized zirconia by the nitrate/urea combustion route and thermal stability in air was investigated. The solid solution obtained was characterized by X ray diffraction (XRD), scanning electron microscopy (SEM) and used the BET method for determining specific surface. The ceramic powders obtained were calcined at 1473 K in air atmosphere in order to determine their thermal stability. The scanning electron microscopy (SEM) results showed a homogeneous grain surface, measuring several tens of micrometers across. The crystallographic study revealed that by this method it was successfully achieved zirconia doped with Fe{sup 3+}, Mo{sup 4+} and Y{sup 3+} ions in the zirconia tetragonal monophase, even after calcinations. (Author)

  1. Noether symmetries and stability of ideal gas solutions in Galileon cosmology

    Science.gov (United States)

    Dimakis, N.; Giacomini, Alex; Jamal, Sameerah; Leon, Genly; Paliathanasis, Andronikos

    2017-03-01

    A class of generalized Galileon cosmological models, which can be described by a pointlike Lagrangian, is considered in order to utilize Noether's theorem to determine conservation laws for the field equations. In the Friedmann-Lemaître-Robertson-Walker universe, the existence of a nontrivial conservation law indicates the integrability of the field equations. Because of the complexity of the latter, we apply the differential invariants approach in order to construct special power-law solutions and study their stability.

  2. Existence and stability of periodic solution in impulsive Hopfield neural networks with finite distributed delays

    International Nuclear Information System (INIS)

    Yang Xiaofan; Liao Xiaofeng; Evans, David J.; Tang Yuanyan

    2005-01-01

    In this Letter, we introduce a class of Hopfield neural networks with periodic impulses and finite distributed delays. We then derive a sufficient condition for the existence and global exponential stability of a unique periodic solution of the networks, which assumes neither the differentiability nor the monotonicity of the activation functions. Our condition extends and generalizes a known condition for the global exponential periodicity of continuous Hopfield neural networks with finite distributed delays

  3. Global exponential stability of periodic solution for shunting inhibitory CNNs with delays [rapid communication

    Science.gov (United States)

    Li, Yongkun; Liu, Chunchao; Zhu, Lifei

    2005-03-01

    By using the continuation theorem of coincidence degree theory and constructing suitable Lyapunov functions, we study the existence and stability of periodic solution for shunting inhibitory cellular neural networks (SICNNs) with delays x˙ij(t)=-aij(t)xij(t)-∑Bkl∈Nr(i,j)Bijkl(t)fij(xkl(t))xij(t)-∑Ckl∈Nr(i,j)Cijkl(t)gij(xkl(t-τkl))xij(t)+Lij(t).

  4. An Investigation into the Gastrointestinal Stability of Exenatide in the Presence of Pure Enzymes, Everted Intestinal Rings and Intestinal Homogenates.

    Science.gov (United States)

    Sun, Yanan; Wang, Mengshu; Sun, Bingxue; Li, Feng; Liu, Shubo; Zhang, Yong; Zhou, Yan; Chen, Yan; Kong, Wei

    2016-01-01

    The purpose of this study was to investigate the gastrointestinal stability of exenatide to determine the key factor(s) contributing to peptide degradation during the oral delivery process. The effects of pH and various digestive enzymes on the degradation kinetics of exenatide were determined. Moreover, the degradation clearances of peptide were also examined using rat everted intestinal rings and intestinal homogenates from various intestinal locations. Exenatide was comparatively stable within a pH range of 1.2-8. However, obvious degradation was observed in the presence of digestive enzymes. The order of enzymes, in terms of ability to degradate exenatide, was chymotrypsin>aminopeptidase N>carboxypeptidase A>trypsin>pepsin. Chymotrypsin showed the greatest ability to degrade exenatide (half-life t1/2, 5.784×10(-2) h), whereas aminopeptidase N and carboxylpeptidase A gave t1/2 values of 3.53 and 10.16 h, respectively. The degradation of exenatide was found to be peptide concentration- and intestinal site-dependent, with a lower clearance in the upper part of the duodenum and the lower part of the ileum. When using intestinal homogenates as enzyme sources, the order, in terms of peptide degradation ability, was ileum>jejunum>duodenum. However, no significant difference was observed in the remaining peptide concentrations throughout 2 h of incubation, which may be due to the involvement of cytosolic enzymes. These results revealed key factors contributing to peptide degradation, and suggest that the inhibition of chymotrypsin and site-specific delivery of exenatide might be advantageous in overcoming metabolic obstacles during its oral delivery.

  5. Effect of hydrogen peroxide on improving the heat stability of whey protein isolate solutions.

    Science.gov (United States)

    Sutariya, Suresh; Patel, Hasmukh

    2017-05-15

    Whey protein isolate (WPI) solutions (12.8%w/w protein) were treated with varying concentrations of H 2 O 2 in the range of 0-0.144 H 2 O 2 to protein ratios (HTPR) by the addition of the required quantity of H 2 O 2 and deionized water. The samples were analyzed for heat stability, rheological properties, denaturation level of β-lactoglobulin (β-LG) and α-lactalbumin (α-LA). The samples treated with H 2 O 2 concentration >0.072 (HTPR) showed significant improvement in the heat stability, and decreased whey protein denaturation and aggregation. The WPI solution treated with H 2 O 2 (>0.072 HTPR) remained in the liquid state after heat treatment at 120°C, whereas the control samples formed gel upon heat treatment. Detailed analysis of these samples suggested that the improvement in the heat stability of H 2 O 2 treated WPI solution was attributed to the significant reduction in the sulfhydryl-disulfide interchange reaction during denaturation of β-LG and α-LA. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Enzyme allocation problems in kinetic metabolic networks: Optimal solutions are elementary flux modes

    Czech Academy of Sciences Publication Activity Database

    Müller, Stefan; Regensburger, G.; Steuer, Ralf

    2014-01-01

    Roč. 347, APR 2014 (2014), s. 182-190 ISSN 0022-5193 R&D Projects: GA MŠk(CZ) EE2.3.20.0256 Institutional support: RVO:67179843 Keywords : metabolic optimization * enzyme kinetics * oriented matroid * elementary vector * conformal sum Subject RIV: EI - Biotechnology ; Bionics Impact factor: 2.116, year: 2014

  7. Extensive Lysine Methylation in Hyperthermophilic Crenarchaea: Potential Implications for Protein Stability and Recombinant Enzymes

    Directory of Open Access Journals (Sweden)

    Catherine H. Botting

    2010-01-01

    Full Text Available In eukarya and bacteria, lysine methylation is relatively rare and is catalysed by sequence-specific lysine methyltransferases that typically have only a single-protein target. Using RNA polymerase purified from the thermophilic crenarchaeum Sulfolobus solfataricus, we identified 21 methyllysines distributed across 9 subunits of the enzyme. The modified lysines were predominantly in α-helices and showed no conserved sequence context. A limited survey of the Thermoproteus tenax proteome revealed widespread modification with 52 methyllysines in 30 different proteins. These observations suggest the presence of an unusual lysine methyltransferase with relaxed specificity in the crenarchaea. Since lysine methylation is known to enhance protein thermostability, this may be an adaptation to a thermophilic lifestyle. The implications of this modification for studies and applications of recombinant crenarchaeal enzymes are discussed.

  8. Temperature Affects the Production, Aktivity and Stability of Ligninolytic Enzymes in Pleurotus ostreatus and Trametes versicolor

    Czech Academy of Sciences Publication Activity Database

    Šnajdr, Jaroslav; Baldrian, Petr

    2007-01-01

    Roč. 52, č. 5 (2007), s. 498-502 ISSN 0015-5632 R&D Projects: GA AV ČR KJB600200516; GA MŠk LC06066; GA MŠk OC 155 Institutional research plan: CEZ:AV0Z50200510 Keywords : lïgninolytic enzymes * laccase * pleurotus ostreatus Subject RIV: EE - Microbiology, Virology Impact factor: 0.989, year: 2007

  9. Aqueous solutions that model the cytosol : studies on polarity, chemical reactivity and enzyme kinetics

    NARCIS (Netherlands)

    Asaad, N.; den Otter, M.J.; Engberts, J.B.F.N.

    2004-01-01

    Concentrated solutions of a series of organic compounds have been prepared and the effects of these solutes on the properties of the solvent system assessed as a function of their concentration and nature. Polarity, as measured by Reichardt's E-T(30) probe, exhibits a linear variation with both

  10. Supramolecular stabilization of metastable tautomers in solution and the solid state.

    Science.gov (United States)

    Juribašić, Marina; Bregović, Nikola; Stilinović, Vladimir; Tomišić, Vladislav; Cindrić, Marina; Sket, Primož; Plavec, Janez; Rubčić, Mirta; Užarević, Krunoslav

    2014-12-22

    This work presents a successful application of a recently reported supramolecular strategy for stabilization of metastable tautomers in cocrystals to monocomponent, non-heterocyclic, tautomeric solids. Quantum-chemical computations and solution studies show that the investigated Schiff base molecule, derived from 3-methoxysalicylaldehyde and 2-amino-3-hydroxypyridine (ap), is far more stable as the enol tautomer. In the solid state, however, in all three obtained polymorphic forms it exists solely as the keto tautomer, in each case stabilized by an unexpected hydrogen-bonding pattern. Computations have shown that hydrogen bonding of the investigated Schiff base with suitable molecules shifts the tautomeric equilibrium to the less stable keto form. The extremes to which supramolecular stabilization can lead are demonstrated by the two polymorphs of molecular complexes of the Schiff base with ap. The molecules of both constituents of molecular complexes are present as metastable tautomers (keto anion and protonated pyridine, respectively), which stabilize each other through a very strong hydrogen bond. All the obtained solid forms proved stable in various solid-state and solvent-mediated methods used to establish their relative thermodynamic stabilities and possible interconversion conditions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Competition between kaolinite flocculation and stabilization in divalent cation solutions dosed with anionic polyacrylamides.

    Science.gov (United States)

    Lee, Byung Joon; Schlautman, Mark A; Toorman, Erik; Fettweis, Michael

    2012-11-01

    Divalent cations have been reported to develop bridges between anionic polyelectrolytes and negatively-charged colloidal particles, thereby enhancing particle flocculation. However, results from this study of kaolinite suspensions dosed with various anionic polyacrylamides (PAMs) reveal that Ca(2+) and Mg(2+) can lead to colloid stabilization under some conditions. To explain the opposite but coexisting processes of flocculation and stabilization with divalent cations, a conceptual flocculation model with (1) particle-binding divalent cationic bridges between PAM molecules and kaolinite particles and (2) polymer-binding divalent cationic bridges between PAM molecules is proposed. The particle-binding bridges enhanced flocculation and aggregated kaolinite particles in large, easily-settleable flocs whereas the polymer-binding bridges increased steric stabilization by developing polymer layers covering the kaolinite surface. Both the particle-binding and polymer-binding divalent cationic bridges coexist in anionic PAM- and kaolinite-containing suspensions and thus induce the counteracting processes of particle flocculation and stabilization. Therefore, anionic polyelectrolytes in divalent cation-enriched aqueous solutions can sometimes lead to the stabilization of colloidal particles due to the polymer-binding divalent cationic bridges. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Stability constant determinations for technetium (IV) complexation with selected amino carboxylate ligands in high nitrate solutions

    Energy Technology Data Exchange (ETDEWEB)

    Omoto, Trevor; Wall, Nathalie A. [Washington State Univ., Pullman, WA (United States). Dept. of Chemistry

    2017-10-01

    The stability constants for Tc(IV) complexation with the ligands IDA, NTA, HEDTA, and DTPA were determined in varied nitrate concentrations using liquid-liquid extraction methods. The determined log β{sub 101} stability constants at 0.5 M NaNO{sub 3} were found to be 9.2±0.3, 10.3±0.3, and 15.3±0.3 for IDA, NTA, and HEDTA, respectively. The log β{sub 111} stability constant for DTPA was determined to be 22.0±0.6. These determined stability constants show a slight decrease in magnitude as a function of increasing NaNO{sub 3} concentration. These stability constants were used to model the total dissolution of Tc(IV) in acidic aqueous solutions in the presence of each ligand. The results of these predictive models indicate that amino carboxylic ligands have a high potential for increasing the aqueous dissolution of Tc(IV); at pH 2.3, 0.01 M ligand yield dissolved Tc(IV) concentrations of 1.42.10{sup -5} M, 1.33.10{sup -5} M, 6.07.10{sup -6} M, 9.65.10{sup -7} M, for DTPA, HEDTA, NTA, and IDA, respectively.

  13. Ionic liquids as cosolvents for glycosylation by sucrose phosphorylase: balancing acceptor solubility and enzyme stability

    Czech Academy of Sciences Publication Activity Database

    De Winter, K.; Verlinden, K.; Křen, Vladimír; Weignerová, Lenka; Soetaert, W.; Desmet, T.

    2013-01-01

    Roč. 15, č. 7 (2013), s. 1949-1955 ISSN 1463-9262 R&D Projects: GA MŠk(CZ) 7E11011 Institutional support: RVO:61388971 Keywords : DISACCHARIDE PHOSPHORYLASES * THERMAL-STABILITY * ALPHA-GLUCOSIDASE Subject RIV: CE - Biochemistry Impact factor: 6.852, year: 2013

  14. Improvement of thermal-stability of enzyme immobilized onto mesoporous zirconia

    Directory of Open Access Journals (Sweden)

    Yuichi Masuda

    2014-03-01

    Thereafter, FDH immobilized on MPZ showed higher catalytic activity than that on MPS. Enhancement of catalytic activity was obtained by improving the substrate affinity derived from interparticle voids of MPZ. In addition, the FDH immobilized on MPZ had a very great higher thermal stability. Further investigation using transmittance Infrared spectroscopy indicated that the high-order structure of the FDH immobilized on MPZ did not get altered after the heat-treatment.

  15. COMPLEX ANALYSIS IN THE RIVER BASIN OF TOPLIŢA AND TECHNOLOGICAL SOLUTIONS FOR SLOPES STABILIZATION

    Directory of Open Access Journals (Sweden)

    Dănuţ Tanislav

    2010-01-01

    Full Text Available Landslides distribution is differentiated function of various causal factors or conditions (litology, declivity, land use,precipitations. For each factor, it can be depicted some homogeneous areas, with numerical coefficients, in a incresingsuccession (1 – very high; … 5 – very low, using the GIS. The complex arrangement involves the analysis and diagnosisof watershed planning, establishing its vulnerability to the action of natural and anthropogenic factors. New technologiesfor earth reinforcement with other engineering works to stabilize the slopes, are durable works because the chemicalproperties of high density polyethylene, which does not react with any other environmental component (ex. earth geogridreinforcement. New technologies for earth reinforcement executed in complex with other engineering works to stabilizethe slopes, are durable works because the chemical properties of high density polyethylene, which does not react withany other environmental component. Using special technology to stabilize determined substantial time and cost savingscompared to traditional solutions. The landscape of slopes reinforced with geogrids, due to external quality topsoil isclearly superior to the classical solutions of stabilization.

  16. Preservative solution that stabilizes erythrocyte morphology and leukocyte viability under ambient conditions.

    Science.gov (United States)

    Sandlin, Rebecca D; Wong, Keith H K; Boneschansker, Leo; Carey, Thomas R; Miller, Kathleen L; Rose, Gregory; Haber, Daniel A; Maheswaran, Shyamala; Irimia, Daniel; Stott, Shannon L; Toner, Mehmet

    2017-07-18

    The deterioration of whole blood ex vivo represents a logistical hurdle in clinical and research settings. Here, a cocktail preservative is described that stabilizes leukocyte viability and erythrocyte morphology in whole blood under ambient storage. Neutrophil biostabilization was explored using a sophisticated microfluidic assay to examine the effectiveness of caspase inhibition to stabilize purified neutrophils. Following 72 h ambient storage, neutrophils remained fully functional to migrate towards chemical cues and maintained their ability to undergo NETosis after stimulation. Furthermore, stored neutrophils exhibited improved CD45 biomarker retention and reduced apoptosis and mortality compared to untreated controls. To stabilize erythrocyte morphology, a preservative solution was formulated using Taguchi methods of experimental design, and combined with the caspase inhibitor to form a whole blood cocktail solution, CS WB . CS WB was evaluated in blood from healthy donors and from women with metastatic breast cancer stored under ambient conditions for 72 h. CS WB -treated samples showed a significant improvement in erythrocyte morphology compared to untreated controls. Leukocytes in CS WB -treated blood exhibited significantly higher viability and CD45 biomarker retention compared to untreated controls. This 72 h shelf life under ambient conditions represents an opportunity to transport isolates or simply ease experimental timelines where blood degradation is problematic.

  17. Stability of interbed for salt cavern gas storage in solution mining considering cusp displacement catastrophe theory

    Directory of Open Access Journals (Sweden)

    Le Yu

    2015-03-01

    Full Text Available Cusp displacement catastrophe theory can be introduced to propose a new method about instability failure of the interbed for gas storage cavern in bedded salt in solution mining. We can calculate initial fracture drawing pace of this interbed to obtain 2D and 3D gas storage shapes at this time. Moreover, Stability evaluation of strength reduction finite element method (FEM based on this catastrophe theory can used to evaluate this interbed stability after initial fracture. A specific example is simulated to obtain the influence of the interbed depth, cavern internal pressure, and cavern building time on stability safety factor (SSF. The results indicate: the value of SSF will be lower with the increase of cavern building time in solution mining and the increase of interbed depth and also this value remains a rise with the increase of cavern internal pressure Especially, we can conclude that the second-fracture of the interbed may take place when this pressure is lower than 6 MPa or after 6 days later of the interbed after initial fracture. According to above analysis, some effective measures, namely elevating the tube up to the top of the interbed, or changing the circulation of in-and-out lines, can be introduced to avoid the negative effects when the second-fracture of the interbed may occur.

  18. Hammerhead ribozyme activity and oligonucleotide duplex stability in mixed solutions of water and organic compounds

    Directory of Open Access Journals (Sweden)

    Shu-ichi Nakano

    2014-01-01

    Full Text Available Nucleic acids are useful for biomedical targeting and sensing applications in which the molecular environment is different from that of a dilute aqueous solution. In this study, the influence of various types of mixed solutions of water and water-soluble organic compounds on RNA was investigated by measuring the catalytic activity of the hammerhead ribozyme and the thermodynamic stability of an oligonucleotide duplex. The compounds with a net neutral charge, such as poly(ethylene glycol, small primary alcohols, amide compounds, and aprotic solvent molecules, added at high concentrations changed the ribozyme-catalyzed RNA cleavage rate, with the magnitude of the effect dependent on the NaCl concentration. These compounds also changed the thermodynamic stability of RNA base pairs of an oligonucleotide duplex and its dependence on the NaCl concentration. Specific interactions with RNA molecules and reduced water activity could account for the inhibiting effects on the ribozyme catalysis and destabilizing effects on the duplex stability. The salt concentration dependence data correlated with the dielectric constant, but not with water activity, viscosity, and the size of organic compounds. This observation suggests the significance of the dielectric constant effects on the RNA reactions under molecular crowding conditions created by organic compounds.

  19. Stability of a family of travelling wave solutions in a feedforward chain of phase oscillators

    International Nuclear Information System (INIS)

    Lanford, O E III; Mintchev, S M

    2015-01-01

    Travelling waves are an important class of signal propagation phenomena in extended systems with a preferred direction of information flow. We study the generation of travelling waves in unidirectional chains of coupled oscillators communicating via a phase-dependent pulse-response interaction borrowed from mathematical neuroscience. Within the context of such systems, we develop a widely applicable, jointly numerical and analytical methodology for deducing existence and stability of periodic travelling waves. We provide careful numerical studies that support the existence of a periodic travelling wave solution as well as the asymptotic relaxation of a single oscillator to the wave when it is forced with the wave profile. Using this evidence as an assumption, we analytically prove global stability of waves in the infinite chain, with respect to initial perturbations of downstream sites. This rigorous stability result suggests that asymptotic relaxation to the travelling wave occurs even when the forcing is perturbed from the wave profile, a property of the motivating system that is supported by previous work as well as the convergence of the more sophisticated numerical algorithm that we propose in order to compute a high-precision approximation to the solution. We provide additional numerical studies that show that the wave is part of a one-parameter family, and we illustrate the structural robustness of this family with respect to changes in the coupling strength. (paper)

  20. Storage stability and improved quality of fish products by enzyme suppression and gamma-irradiation

    International Nuclear Information System (INIS)

    Ninjoor, V.; Doke, S.N.; Nadkarni, G.B.

    1981-01-01

    The occurrence and distribution of lysosomal hydrolases in the skeletal muscle and skin of a variety of fish species have been demonstrated. As compared with the skeletal muscle, the skin contained two to ten times more activity of hydrolytic enzymes. In the case of Bombay duck (Harpodon nehereus), the drip represented a rich source of lysosomal enzymes. The involvement of these hydrolases in accentuating fish spoilage was examined by measuring the release of cathepsin D and accumulated hydrolytic end-products during progressive autolysis. The data showed that the shelf-life of fresh-water fish Tilapia mossambica could be extended by removing the skin, while that of Bombay duck by eliminating drip. Sodium tripolyphosphate (NaTPP) dip treatment was shown to inhibit the activity of lysosomal hydrolases of Bombay duck. Combination treatment consisting of NaTPP dip and irradiation (100 krad) resulted in a two-week extension in the shelf-life of Bombay duck fillets when stored at 0-4 0 C. (author)

  1. Effect of repeated immersion solution cycles on the color stability of denture tooth acrylic resins

    Science.gov (United States)

    da SILVA, Paulo Maurício Batista; ACOSTA, Emílio José Tabaré Rodríguez; JACOBINA, Matheus; PINTO, Luciana de Rezende; PORTO, Vinícius Carvalho

    2011-01-01

    Objective Chemical solutions have been widely used for disinfection of dentures, but their effect on color stability of denture tooth acrylic resins after repeated procedures is still unclear. The aim of this in vitro study was to evaluate whether repeated cycles of chemical disinfectants affected the color stability of two denture tooth acrylic resins. Material and Methods Sixty disc-shaped specimens (40 mm x 3 mm) were fabricated from two different brands (Artiplus and Trilux) of denture tooth acrylic resin. The specimens from each brand (n=30) were randomly divided into 6 groups (n=5) and immersed in the following solutions: distilled water (control group) and 5 disinfecting solutions (1% sodium hypochlorite, 2% sodium hypochlorite, 5.25% sodium hypochlorite, 2% glutaraldehyde, and 4% chlorhexidine gluconate). Tooth color measurements were made by spectrophotometry. Before disinfection, the initial color of each tooth was recorded. Further color measurements were determined after subjecting the specimens to 7, 21, 30, 45, 60, and 90 immersion cycles in each tested solution. Color differences (ΔE*) were determined using the CIE L*a*b* color system. Data were analyzed using two-way repeated measures analysis of variance (ANOVA) followed by Tukey tests. The significance level was set at 5%. Results There were statistically significant differences in ΔE* among the 5 disinfectants and water during the 90 cycles of immersion for both denture tooth acrylic resins. Distilled water promoted the greatest color change in both denture tooth acrylic resins, nevertheless none of tested disinfectants promoted ΔE* values higher than 1.0 on these acrylic materials during the 90 cycles of disinfection. Conclusions Repeated immersion cycles in disinfecting solutions alter ∆E* values, however these values do not compromise the color of the tested denture tooth acrylic resins because they are imperceptible to the human eye. PMID:22230997

  2. Effect of repeated immersion solution cycles on the color stability of denture tooth acrylic resins

    Directory of Open Access Journals (Sweden)

    Paulo Maurício Batista da Silva

    2011-12-01

    Full Text Available OBJECTIVE: Chemical solutions have been widely used for disinfection of dentures, but their effect on color stability of denture tooth acrylic resins after repeated procedures is still unclear. The aim of this in vitro study was to evaluate whether repeated cycles of chemical disinfectants affected the color stability of two denture tooth acrylic resins. MATERIAL AND METHODS: Sixty disc-shaped specimens (40 mm x 3 mm were fabricated from two different brands (Artiplus and Trilux of denture tooth acrylic resin. The specimens from each brand (n=30 were randomly divided into 6 groups (n=5 and immersed in the following solutions: distilled water (control group and 5 disinfecting solutions (1% sodium hypochlorite, 2% sodium hypochlorite, 5.25% sodium hypochlorite, 2% glutaraldehyde, and 4% chlorhexidine gluconate. Tooth color measurements were made by spectrophotometry. Before disinfection, the initial color of each tooth was recorded. Further color measurements were determined after subjecting the specimens to 7, 21, 30, 45, 60, and 90 immersion cycles in each tested solution. Color differences (ΔE* were determined using the CIE L*a*b* color system. Data were analyzed using two-way repeated measures analysis of variance (ANOVA followed by Tukey tests. The significance level was set at 5%. RESULTS: There were statistically significant differences in ΔE* among the 5 disinfectants and water during the 90 cycles of immersion for both denture tooth acrylic resins. Distilled water promoted the greatest color change in both denture tooth acrylic resins, nevertheless none of tested disinfectants promoted ΔE* values higher than 1.0 on these acrylic materials during the 90 cycles of disinfection. CONCLUSIONS: Repeated immersion cycles in disinfecting solutions alter ΔE* values, however these values do not compromise the color of the tested denture tooth acrylic resins because they are imperceptible to the human eye.

  3. Effect of different solutions on color stability of acrylic resin-based dentures

    Directory of Open Access Journals (Sweden)

    Marcelo Coelho Goiato

    2014-01-01

    Full Text Available The aim of this study was to evaluate the effect of thermocycling and immersion in mouthwash or beverage solutions on the color stability of four different acrylic resin-based dentures (Onda Cryl, OC; QC20, QC; Classico, CL; and Lucitone, LU. The factors evaluated were type of acrylic resin, immersion time, and solution (mouthwash or beverage. A total of 224 denture samples were fabricated. For each type of resin, eight samples were immersed in mouthwashes (Plax-Colgate, PC; Listerine, LI; and Oral-B, OB, beverages (coffee, CP; cola, C; and wine, W, and artificial saliva (AS; control. The color change (DE was evaluated before (baseline and after thermocycling (T1, and after immersion in solution for 1 h (T2, 3 h (T3, 24 h (T4, 48 h (T5, and 96 h (T6. The CIE Lab system was used to determine the color changes. The thermocycling test was performed for 5000 cycles. Data were submitted to three-way repeated-measures analysis of variance and Tukey's test (p < 0.05. When the samples were immersed in each mouthwash, all assessed factors, associated or not, significantly influenced the color change values, except there was no association between the mouthwash and acrylic resin. Similarly, when the samples were immersed in each beverage, all studied factors influenced the color change values. In general, regardless of the solution, LU exhibited the greatest DE values in the period from T1 to T5; and QC presented the greatest DE values at T6. Thus, thermocycling and immersion in the various solutions influenced the color stability of acrylic resins and QC showed the greatest color alteration.

  4. Effect of repeated immersion solution cycles on the color stability of denture tooth acrylic resins.

    Science.gov (United States)

    Silva, Paulo Maurício Batista da; Acosta, Emílio José Tabaré Rodríguez; Jacobina, Matheus; Pinto, Luciana de Rezende; Porto, Vinícius Carvalho

    2011-01-01

    Chemical solutions have been widely used for disinfection of dentures, but their effect on color stability of denture tooth acrylic resins after repeated procedures is still unclear. The aim of this in vitro study was to evaluate whether repeated cycles of chemical disinfectants affected the color stability of two denture tooth acrylic resins. Sixty disc-shaped specimens (40 mm x 3 mm) were fabricated from two different brands (Artiplus and Trilux) of denture tooth acrylic resin. The specimens from each brand (n=30) were randomly divided into 6 groups (n=5) and immersed in the following solutions: distilled water (control group) and 5 disinfecting solutions (1% sodium hypochlorite, 2% sodium hypochlorite, 5.25% sodium hypochlorite, 2% glutaraldehyde, and 4% chlorhexidine gluconate). Tooth color measurements were made by spectrophotometry. Before disinfection, the initial color of each tooth was recorded. Further color measurements were determined after subjecting the specimens to 7, 21, 30, 45, 60, and 90 immersion cycles in each tested solution. Color differences (ΔE*) were determined using the CIE L*a*b* color system. Data were analyzed using two-way repeated measures analysis of variance (ANOVA) followed by Tukey tests. The significance level was set at 5%. There were statistically significant differences in ΔE* among the 5 disinfectants and water during the 90 cycles of immersion for both denture tooth acrylic resins. Distilled water promoted the greatest color change in both denture tooth acrylic resins, nevertheless none of tested disinfectants promoted ΔE* values higher than 1.0 on these acrylic materials during the 90 cycles of disinfection. Repeated immersion cycles in disinfecting solutions alter ΔE* values, however these values do not compromise the color of the tested denture tooth acrylic resins because they are imperceptible to the human eye.

  5. Stability of antimicrobial activity of peracetic acid solutions used in the final disinfection process

    Directory of Open Access Journals (Sweden)

    Solange Alves da Silva COSTA

    2015-01-01

    Full Text Available The instruments and materials used in health establishments are frequently exposed to microorganism contamination, and chemical products are used before sterilization to reduce occupational infection. We evaluated the antimicrobial effectiveness, physical stability, and corrosiveness of two commercial formulations of peracetic acid on experimentally contaminated specimens. Stainless steel specimens were contaminated with Staphylococcus aureus, Escherichia coli, Candida albicans, blood, and saliva and then immersed in a ready peracetic acid solution: 2% Sekusept Aktiv (SA or 0.25% Proxitane Alpha (PA, for different times. Then, washes of these instruments were plated in culture medium and colony-forming units counted. This procedure was repeated six times per day over 24 non-consecutive days. The corrosion capacity was assessed with the mass loss test, and the concentration of peracetic acid and pH of the solutions were measured with indicator tapes. Both SA and PA significantly eliminated microorganisms; however, the SA solution was stable for only 4 days, whereas PA remained stable throughout the experiment. The concentration of peracetic acid in the SA solutions decreased over time until the chemical was undetectable, although the pH remained at 5. The PA solution had a concentration of 500-400 mg/L and a pH of 2-3. Neither formulation induced corrosion and both reduced the number of microorganisms (p = 0.0001. However, the differences observed in the performance of each product highlight the necessity of establishing a protocol for optimizing the use of each one.

  6. Spectral stability of undercompressive shock profile solutions of a modified KdV-Burgers equation

    Directory of Open Access Journals (Sweden)

    Jeff Dodd

    2007-10-01

    Full Text Available It is shown that certain undercompressive shock profile solutions of the modified Korteweg-de Vries-Burgers equation $$ partial_t u + partial_x(u^3 = partial_x^3 u + alpha partial_x^2 u, quad alpha geq 0 $$ are spectrally stable when $alpha$ is sufficiently small, in the sense that their linearized perturbation equations admit no eigenvalues having positive real part except a simple eigenvalue of zero (due to the translation invariance of the linearized perturbation equations. This spectral stability makes it possible to apply a theory of Howard and Zumbrun to immediately deduce the asymptotic orbital stability of these undercompressive shock profiles when $alpha$ is sufficiently small and positive.

  7. Stability of 2 mg/mL Adenosine Solution in Polyvinyl Chloride and Polyolefin Infusion Bags.

    Science.gov (United States)

    DeAngelis, Michael; Ferrara, Alexander; Gregory, Kaleigh; Zammit, Kimberly; Zhao, Fang

    2018-04-01

    Adenosine is a potent endogenous mediator of vasodilation. Compounded sterile solutions of adenosine are used in cardiac catheterization lab to perform stress tests on the heart. These tests are used to determine the fractional flow reserve (FFR) and are commonly used in the management and diagnosis of cardiovascular conditions. The purpose of this study was to assess the physical and chemical stability of 2 mg/mL adenosine in 0.9% Sodium Chloride Injection, USP in polyvinyl chloride [PVC]) and polyolefin infusion bags stored at room temperature (20°C-25°C) and under refrigeration (2°C-8°C). The compounding and analytical methods used in this study were very similar to those described in the prior publications from the authors' laboratory. To ensure a uniform starting concentration of all stability samples, a batch of 2 mg/mL adenosine solution was prepared and then packaged into empty PVC and polyolefin infusion bags. These stability samples were prepared in triplicate for each bag type and storage temperature (a total of 12 samples). The infusion bag samples were assessed for stability immediately after preparation and after 1 day, 3 days, 7 days, and 14 days. At each time point, the infusion bags were first visually inspected against a light background for color change, clarity, and particulates. Aliquots were drawn from each sample at each time point for pH analysis and high-performance liquid chromatography (HPLC) analysis. Over 14 days of storage at room temperature or refrigeration, no considerable change in visual appearance or pH was observed in any bags. All samples retained 90% to 110% of the initial drug concentration. No significant degradation peaks were observed in the HPLC chromatograms.

  8. Macromolecular Stabilization by Excluded Cosolutes: Mean Field Theory of Crowded Solutions.

    Science.gov (United States)

    Sapir, Liel; Harries, Daniel

    2015-07-14

    We propose a mean field theory to account for the experimentally determined temperature dependence of protein stabilization that emerges in solutions crowded by preferentially excluded cosolutes. Based on regular solution theory and employing the Flory-Huggins approximation, our model describes cosolutes in terms of their size, and two temperature-dependent microscopic parameters that correspond to macromolecule-cosolute and bulk solution interactions. The theory not only predicts a "depletion force" that can account for the experimentally observed stabilization of protein folding or association in the presence of excluded cosolutes but also predicts the full range of associated entropic and enthalpic components. Remarkably, depending on cosolute identity and in accordance with experiments, the theory describes entropically as well as enthalpically dominated depletion forces, even those disfavored by entropy. This emerging depletion attraction cannot be simply linked to molecular volumes. Instead, the relevant parameter is an effective volume that represents an interplay between solvent, cosolute, and macromolecular interactions. We demonstrate that the apparent depletion free energy is often accompanied by significant yet compensating entropy and enthalpy terms that, although having a net zero contribution to stabilization, can obscure the underlying molecular mechanism. This study underscores the importance of including often-neglected free energy terms that correspond to solvent-cosolute and cosolute-macromolecule interactions, which for most typical cosolutes are expected to be temperature dependent. We propose that experiments specifically aimed at resolving the temperature-dependence of cosolute exclusion from macromolecular surfaces should help reveal the full range of the underlying molecular mechanisms of the depletion force.

  9. Hybrid quantum and classical methods for computing kinetic isotope effects of chemical reactions in solutions and in enzymes.

    Science.gov (United States)

    Gao, Jiali; Major, Dan T; Fan, Yao; Lin, Yen-Lin; Ma, Shuhua; Wong, Kin-Yiu

    2008-01-01

    A method for incorporating quantum mechanics into enzyme kinetics modeling is presented. Three aspects are emphasized: 1) combined quantum mechanical and molecular mechanical methods are used to represent the potential energy surface for modeling bond forming and breaking processes, 2) instantaneous normal mode analyses are used to incorporate quantum vibrational free energies to the classical potential of mean force, and 3) multidimensional tunneling methods are used to estimate quantum effects on the reaction coordinate motion. Centroid path integral simulations are described to make quantum corrections to the classical potential of mean force. In this method, the nuclear quantum vibrational and tunneling contributions are not separable. An integrated centroid path integral-free energy perturbation and umbrella sampling (PI-FEP/UM) method along with a bisection sampling procedure was summarized, which provides an accurate, easily convergent method for computing kinetic isotope effects for chemical reactions in solution and in enzymes. In the ensemble-averaged variational transition state theory with multidimensional tunneling (EA-VTST/MT), these three aspects of quantum mechanical effects can be individually treated, providing useful insights into the mechanism of enzymatic reactions. These methods are illustrated by applications to a model process in the gas phase, the decarboxylation reaction of N-methyl picolinate in water, and the proton abstraction and reprotonation process catalyzed by alanine racemase. These examples show that the incorporation of quantum mechanical effects is essential for enzyme kinetics simulations.

  10. Stability of Almost Periodic Solution for a General Class of Discontinuous Neural Networks with Mixed Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    Yingwei Li

    2013-01-01

    Full Text Available The global exponential stability issues are considered for almost periodic solution of the neural networks with mixed time-varying delays and discontinuous neuron activations. Some sufficient conditions for the existence, uniqueness, and global exponential stability of almost periodic solution are achieved in terms of certain linear matrix inequalities (LMIs, by applying differential inclusions theory, matrix inequality analysis technique, and generalized Lyapunov functional approach. In addition, the existence and asymptotically almost periodic behavior of the solution of the neural networks are also investigated under the framework of the solution in the sense of Filippov. Two simulation examples are given to illustrate the validity of the theoretical results.

  11. Ferulic acid stabilizes a solution of vitamins C and E and doubles its photoprotection of skin.

    Science.gov (United States)

    Lin, Fu-Hsiung; Lin, Jing-Yi; Gupta, Ravindra D; Tournas, Joshua A; Burch, James A; Selim, M Angelica; Monteiro-Riviere, Nancy A; Grichnik, James M; Zielinski, Jan; Pinnell, Sheldon R

    2005-10-01

    Ferulic acid is a potent ubiquitous plant antioxidant. Its incorporation into a topical solution of 15%l-ascorbic acid and 1%alpha-tocopherol improved chemical stability of the vitamins (C+E) and doubled photoprotection to solar-simulated irradiation of skin from 4-fold to approximately 8-fold as measured by both erythema and sunburn cell formation. Inhibition of apoptosis was associated with reduced induction of caspase-3 and caspase-7. This antioxidant formulation efficiently reduced thymine dimer formation. This combination of pure natural low molecular weight antioxidants provides meaningful synergistic protection against oxidative stress in skin and should be useful for protection against photoaging and skin cancer.

  12. Phase-locked solutions and their stability in the presence of ...

    Indian Academy of Sciences (India)

    (k = 0) and the rest correspond to travelling waves (k = 0), with wave speed equal to. (k)/k. It turns out that in general only a few of the solutions φ ,k can be stable. The linear stability is determined by the variational equation. ∂. ∂t u(x, t) = −. ∫ 1. −1. G(z) cos(πkz + α)[u(x, t) − u(x − z, t)]dz, where u(x, t) = φ(x, t) − φ ,k(x, t).

  13. Global stability, periodic solutions, and optimal control in a nonlinear differential delay model

    Directory of Open Access Journals (Sweden)

    Anatoli F. Ivanov

    2010-09-01

    Full Text Available A nonlinear differential equation with delay serving as a mathematical model of several applied problems is considered. Sufficient conditions for the global asymptotic stability and for the existence of periodic solutions are given. Two particular applications are treated in detail. The first one is a blood cell production model by Mackey, for which new periodicity criteria are derived. The second application is a modified economic model with delay due to Ramsey. An optimization problem for a maximal consumption is stated and solved for the latter.

  14. Global exponential stability of periodic solution for shunting inhibitory CNNs with delays

    International Nuclear Information System (INIS)

    Li Yongkun; Liu Chunchao; Zhu Lifei

    2005-01-01

    By using the continuation theorem of coincidence degree theory and constructing suitable Lyapunov functions, we study the existence and stability of periodic solution for shunting inhibitory cellular neural networks (SICNNs) with delays x-bar ij (t)=-a ij (t)x ij (t)--bar B kl -bar Nr(i,j)B ij kl (t)f ij (x kl (t))x ij (t)--bar C kl -bar Nr(i,j)C ij kl (t)g ij (x kl (t-τ kl ))x ij (t)+L ij (t)

  15. Global exponential stability and existence of periodic solutions of CNNs with delays

    Science.gov (United States)

    Dong, Meifang

    2002-07-01

    In this Letter, we establish general sufficient conditions for global exponential stability and existence of periodic solutions of a class of cellular neural networks (CNNs) with delays. The key to proving the sufficient conditions is the construction of a new Lyapunov functional. An elementary inequality, which may be of independent interest, has been employed in the proof. Checking the sufficient conditions is often reduced to checking some algebraic relations among certain set of parameter. Our sufficient conditions recover the known results in literature as special cases. Finally, we give two examples to illustrate the usage of our main results.

  16. Structural aspects of magnetic fluid stabilization in aqueous agarose solutions

    Energy Technology Data Exchange (ETDEWEB)

    Nagornyi, A.V. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Taras Shevchenko National University of Kyiv, Kyiv (Ukraine); Petrenko, V.I., E-mail: vip@nf.jinr.ru [Joint Institute for Nuclear Research, Dubna (Russian Federation); Taras Shevchenko National University of Kyiv, Kyiv (Ukraine); Avdeev, M.V. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Yelenich, O.V.; Solopan, S.O.; Belous, A.G. [V.I.Vernadsky Institute of General and Inorganic Chemistry of the Ukrainian NAS, Kyiv (Ukraine); Gruzinov, A.Yu. [National Research Centre “Kurchatov Institute”, Moscow (Russian Federation); Ivankov, O.I. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Institute for Safety Problems of Nuclear Power Plants of the Ukrainian NAS, Kyiv (Ukraine); Bulavin, L.A. [Taras Shevchenko National University of Kyiv, Kyiv (Ukraine); Institute for Safety Problems of Nuclear Power Plants of the Ukrainian NAS, Kyiv (Ukraine)

    2017-06-01

    Structure characterization of magnetic fluids (MFs) synthesized by three different methods in aqueous solutions of agarose was done by means of small-angle neutron (SANS) and synchrotron X-ray scattering (SAXS). The differences in the complex aggregation observed in the studied magnetic fluids were related to different stabilizing procedures of the three kinds of MFs. The results of the analysis of the scattering (mean size of single polydisperse magnetic particles, fractal dimensions of the aggregates) are consistent with the data of transmission electron microscopy (TEM). - Highlights: • MFs synthesized by three different methods in agarose solution were studied. • all MFs are agglomerated colloidal systems whose structures are nevertheless stable in time. • differences in the complex aggregation were observed in the studied magnetic fluids. • results of the SAXS and SANS analysis are consistent with TEM data.

  17. Role of AP-endonuclease (Ape1) active site residues in stabilization of the reactant enzyme-DNA complex.

    Science.gov (United States)

    Batebi, Hossein; Dragelj, Jovan; Imhof, Petra

    2018-04-01

    Apurinic/apyrimidinic endonuclease 1 (Ape1) is an important metal-dependent enzyme in the base excision repair mechanism, responsible for the backbone cleavage of abasic DNA through a phosphate hydrolysis reaction. Molecular dynamics simulations of Ape1 complexed to its substrate DNA performed for models containing 1 or 2 Mg 2+ -ions as cofactor located at different positions show a complex with 1 metal ion bound on the leaving group site of the scissile phosphate to be the most likely reaction-competent conformation. Active-site residue His309 is found to be protonated based on pKa calculations and the higher conformational stability of the Ape1-DNA substrate complex compared to scenarios with neutral His309. Simulations of the D210N mutant further support the prevalence of protonated His309 and strongly suggest Asp210 as the general base for proton acceptance by a nucleophilic water molecule. © 2018 Wiley Periodicals, Inc.

  18. The Colloidal Stabilization of Quantum Dots: Towards Manufacturable, Efficient Solution-Processed Solar Cells

    Science.gov (United States)

    Rollny, Lisa

    Understanding colloidal stabilization can influence the design of optoelectronic devices and enable improvements to their performance and stability. For photovoltaics, important characteristics of the active layer material are high conductivity along with a minimum of recombination centers. In order to capitalize on the benefits of solution-processed materials, it is important to minimize the number of processing steps: ideally, to achieve a low-cost solution, materials would be deposited using a single process step compatible with roll-to-roll manufacturing. Prior to this work, the highest-performing colloidal quantum dots (CQD) solar cells have relied on several deposition steps that are repeated in a layer-by-layer (LBL) fashion. The purpose of these process steps has been to remove the long insulating ligands used in synthesis and replace them with short ligands that allow electrical conduction. The large number of steps combined, typically implemented via spin coating, leads to inefficient materials utilization and fails to show a path to a manufacturable solution. In this work, the first CQD solar cells were designed, built, and characterized combining state-of-art performance with scalable manufacture. Firstly, I report the first automated CQD synthesis to result in CQDs that form high-performance CQD solar cells. I analyze the CQD synthesis and by separating it into two phases---nucleation and growth phase---my insights are used to create higher-quality CQDs exhibiting enhanced monodispersity. I then proceed to develop a CQD ink: a CQD solution ready for direct deposition to form a semiconducting film exhibiting low trap state density. In early trials the CQD ink showed only limited power conversion efficiencies of 2%. I designed a new ink strategy, which I term cleavable hemiketal ligands. This novel two-component ligand strategy enables the combination of colloidal stabilization (via this longer two-component ligand) and cleavability (enabling excellent

  19. Long-Term Stability of Tramadol and Ketamine Solutions for Patient-Controlled Analgesia Delivery.

    Science.gov (United States)

    Gu, Junfeng; Qin, Wengang; Chen, Fuchao; Xia, Zhongyuan

    2015-08-26

    Subanesthetic doses of ketamine as an adjuvant to tramadol in patient-controlled analgesia (PCA) for postoperative pain have been shown to improve the quality of analgesia. However, there are no such commercially available drug mixtures, and the stability of the combination has rarely been assessed. Admixtures were assessed for periods of up to 14 days at 4°C and 25°C. Three different mixtures of tramadol and ketamine (tramadol 5.0 mg/mL + ketamine 0.5 mg/mL, tramadol 5.0 mg/mL + ketamine 1.0 mg/mL, and tramadol 5.0 mg/mL + ketamine 2.0 mg/mL) were prepared in polyolefin bags by combining these 2 drugs with 0.9% sodium chloride (normal saline [NS]). The chemical stability of the admixtures was evaluated by a validated high-performance liquid chromatography (HPLC) method and by measurement of pH values. Solution appearance and color were assessed by observing the samples against black and white backgrounds. Solutions were considered stable if they maintained 90% of the initial concentration of each drug. The percentages of initial concentration of tramadol and ketamine in the various solutions remained above 98% when stored at 4°C or 25°C over the testing period. No changes in color or turbidity were observed in any of the prepared solutions. Throughout this period, pH values remained stable. The results indicate that the drug mixtures of tramadol with ketamine in NS for PCA delivery systems were stable for 14 days when stored in polyolefin bags at 4°C or 25°C.

  20. Co-immobilization of multiple enzymes by metal coordinated nucleotide hydrogel nanofibers: improved stability and an enzyme cascade for glucose detection.

    Science.gov (United States)

    Liang, Hao; Jiang, Shuhui; Yuan, Qipeng; Li, Guofeng; Wang, Feng; Zhang, Zijie; Liu, Juewen

    2016-03-21

    Preserving enzyme activity and promoting synergistic activity via co-localization of multiple enzymes are key topics in bionanotechnology, materials science, and analytical chemistry. This study reports a facile method for co-immobilizing multiple enzymes in metal coordinated hydrogel nanofibers. Specifically, four types of protein enzymes, including glucose oxidase, Candida rugosa lipase, α-amylase, and horseradish peroxidase, were respectively encapsulated in a gel nanofiber made of Zn(2+) and adenosine monophosphate (AMP) with a simple mixing step. Most enzymes achieved quantitative loading and retained full activity. At the same time, the entrapped enzymes were more stable against temperature variation (by 7.5 °C), protease attack, extreme pH (by 2-fold), and organic solvents. After storing for 15 days, the entrapped enzyme still retained 70% activity while the free enzyme nearly completely lost its activity. Compared to nanoparticles formed with AMP and lanthanide ions, the nanofiber gels allowed much higher enzyme activity. Finally, a highly sensitive and selective biosensor for glucose was prepared using the gel nanofiber to co-immobilize glucose oxidase and horseradish peroxidase for an enzyme cascade system. A detection limit of 0.3 μM glucose with excellent selectivity was achieved. This work indicates that metal coordinated materials using nucleotides are highly useful for interfacing with biomolecules.

  1. Increased stability of S-nitrosothiol solutions via pH modulations.

    Science.gov (United States)

    Hornyák, István; Marosi, Krisztina; Kiss, Levente; Gróf, Pál; Lacza, Zsombor

    2012-02-01

    S-nitrosothiol (RSNO) solutions represent a valuable source of nitric oxide and could be used as topical vasodilators, but their fast decomposition rate poses a serious obstacle to their potentially widespread therapeutic use. Our aim was to characterize and quantify the effect of pH on S-nitrosothiol formation and decomposition in simple aqueous solutions of S-nitrosoglutathione (GSNO), S-nitroso-N-acetylcysteine (SNAC) and S-nitroso-3-mercaptopropionic acid (SN3MPA). Furthermore, we investigated the effect of storage pH on the stability of GSNO incorporated in poly(ethylene glycol)/ poly(vinyl alcohol) matrices. S-nitrosothiol concentrations were measured spectrophotometrically and laser Doppler scanning method was used to assess dermal blood flow. GSH and NAC solutions reached a complete transformation to nitrosothiols when synthesized using acidic NaNO(2) solution. The initial concentration of all investigated RSNOs decreased more slowly with pH adjusted to mildly basic values (8.4-8.8) for the storage period. Polymer gels of PVA/PEG compositions at mildly basic storage pH further reduced the decomposition rate succeeding to contain 46.8% of the initial GSNO concentration for 25 days. This amount of topically administered GSNO was still capable of increasing the dermal blood flow over 200% in human subjects.

  2. An investigation into the stability and sterility of citric acid solutions used for cough reflex testing.

    Science.gov (United States)

    Falconer, James R; Wu, Zimei; Lau, Hugo; Suen, Joanna; Wang, Lucy; Pottinger, Sarah; Lee, Elaine; Alazawi, Nawar; Kallesen, Molly; Gargiulo, Derryn A; Swift, Simon; Svirskis, Darren

    2014-10-01

    Citric acid is used in cough reflex testing in clinical and research settings to assess reflexive cough in patients at risk of swallowing disorders. To address a lack of knowledge in this area, this study investigated the stability and sterility of citric acid solutions. Triplicate solutions of citric acid (0.8 M) in isotonic saline were stored at 4 ± 2 °C for up to 28 days and analysed by high-performance liquid chromatography. Microbiological sterility of freshly prepared samples and bulk samples previously used for 2 weeks within the hospital was determined using a pour plate technique. Microbial survival in citric acid was determined by inoculating Staphylococcus aureus, Escherichia coli, or Candida albicans into citric acid solution and monitoring the number of colony-forming units/mL over 40 min. Citric acid solutions remained stable at 4 °C for 28 days (98.4 ± 1.8 % remained). The freshly prepared and clinical samples tested were sterile. However, viability studies revealed that citric acid solution allows for the survival of C. albicans but not for S. aureus or E. coli. The microbial survival study showed that citric acid kills S. aureus and E. coli but has no marked effect on C. albicans after 40 min. Citric acid samples at 0.8 M remained stable over the 4-week testing period, with viable microbial cells absent from samples tested. However, C. albicans has the ability to survive in citric acid solution if inadvertently introduced in practice. For this reason, in clinical and research practice it is suggested to use single-use aliquots prepared aseptically which can be stored for up to 28 days at 4 °C.

  3. Domains of macrophage N(O) synthase have divergent roles in forming and stabilizing the active dimeric enzyme.

    Science.gov (United States)

    Ghosh, D K; Abu-Soud, H M; Stuehr, D J

    1996-02-06

    The cytokine-inducible NO synthase (iNOS) is a flavin-containing hemeprotein that must dimerize to generate NO. Trypsin cleaves the dimeric enzyme into an oxygenase domain fragment that remains dimeric, contains heme and H4biopterin, and binds L-arginine and a reductase domain fragment that is monomeric, binds NADPH, FAD, FMN, and catalyzes the reduction of cytochrome c [Ghosh, D. K. & Stuehr, D. J. (1995) Biochemistry 34, 801-807]. The current study investigates the isolated oxygenase and reductase domains of iNOS to understand how they form and stabilize the active dimeric enzyme. The dimeric oxygenase domain dissociated into folded, heme-containing monomers when incubated with 2-5 M urea, whereas the reductase domain unfolded under these conditions and lost its ability to catalyze NADPH-dependent cytochrome c reduction. Spectral analysis of the dissociation reaction showed that it caused structural changes within the oxygenase domain and exposed the distal side of the heme to solvent, enabling it to bind dithiothreitol as a sixth ligand. Importantly, the oxygenase domain monomers could reassociate into a dimeric form even in the absence of the reductase domain. The reaction required L-arginine and H4biopterin and completely reversed the structural changes in heme pocket and protein structure that occurred upon dissociating the original dimer. Together, this confirms that the oxygenase domain contains all of the determinants needed for subunit dimerization and indicates that the dimeric structure greatly affects the heme and protein environment in the oxygenase domain.

  4. Assessment of natural sepiolite on cadmium stabilization, microbial communities, and enzyme activities in acidic soil.

    Science.gov (United States)

    Sun, Yuebing; Sun, Guohong; Xu, Yingming; Wang, Lin; Liang, Xuefeng; Lin, Dasong; Hu, Fazhi

    2013-05-01

    A pot trial was conducted to assess the efficiency of sepiolite-induced cadmium (Cd) immobilization in ultisoils. Under Cd concentrations of 1.25, 2.5, and 5 mg kg(-1), the available Cd in the soil after the application of 1-10 % sepiolite decreased by a maximum of 44.4, 23.0, and 17.0 %, respectively, compared with no sepiolite treatments. The increase in the values of soil enzyme activities and microbial number proved that a certain metabolic recovery occurred after sepiolite treatment. The dry biomass of spinach (Spinacia oleracea) increased with increasing sepiolite concentration in the soil. However, the concentration (dry weight) of Cd in the spinach shoots decreased with the increase in sepiolite dose, with maximum reduction of 92.2, 90.0, and 84.9 %, respectively, compared with that of unamended soils. Under a Cd level of 1.25 mg kg(-1), the Cd concentration in the edible parts of spinach at 1 % sepiolite amendment was lower than 0.2 mg kg(-1) fresh weight, the maximum permissible concentration (MPC) of Cd in vegetable. Even at higher Cd concentrations (2.5 and 5 mg kg(-1)), safe spinach was produced when the sepiolite treatment was up to 5 %. The results showed that sepiolite-assisted remediation could potentially succeed on a field scale by decreasing Cd entry into the food chain.

  5. The restriction enzyme SgrAI: structure solution via combination of poor MIRAS and MR phases

    Energy Technology Data Exchange (ETDEWEB)

    Dunten, Pete W., E-mail: pete@slac.stanford.edu [Stanford Synchrotron Radiation Laboratory, Stanford University, Menlo Park, CA 94025 (United States); Little, Elizabeth J.; Horton, Nancy C. [Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, AZ 85721 (United States); Stanford Synchrotron Radiation Laboratory, Stanford University, Menlo Park, CA 94025 (United States)

    2009-04-01

    Phase information from both MIRAS and MR was used to produce an interpretable electron-density map of the novel type II restriction endonuclease SgrAI bound to DNA. The MR solution corrected an instructive error in the initially chosen averaging transformation. Uninterpretable electron-density maps were obtained using either MIRAS phases or MR phases in attempts to determine the structure of the type II restriction endonuclease SgrAI bound to DNA. While neither solution strategy was particularly promising (map correlation coefficients of 0.29 and 0.22 with the final model, respectively, for the MIRAS and MR phases and Phaser Z scores of 4.0 and 4.3 for the rotation and translation searches), phase combination followed by density modification gave a readily interpretable map. MR with a distantly related model located a dimer in the asymmetric unit and provided the correct transformation to use in averaging electron density between SgrAI subunits. MIRAS data sets with low substitution and MR solutions from only distantly related models should not be ignored, as poor-quality starting phases can be significantly improved. The bootstrapping strategy employed to improve the initial MIRAS phases is described.

  6. Stability theory of critical cases and the bifurcation points of the stationary solutions of the Lorenz model

    International Nuclear Information System (INIS)

    Bakasov, A.A.; Govorkov, B.B. Jr.

    1990-08-01

    The critical case in stability theory is the case when it is impossible to study the stability of solutions over the linear part of ordinary differential equations. This situation is usual at the bifurcation points. There exists a powerful and constructive approach to investigate the stability - the theory of critical cases created by Lyapunov. The famous Lorenz model is used in this article as an illustration of the power of the method (new results). (author). 27 refs

  7. Bilirubin oxidase label for an enzyme-linked affinity assay with O2 as substrate in a neutral pH NACL solution.

    Science.gov (United States)

    Kim, Hyug-Han; Zhang, Yongchao; Heller, Adam

    2004-04-15

    Laccase, a copper enzyme catalyzing the four-electron reduction of O(2) to water, has been shown by others to be a useful label in enzyme-linked immunoassays, in which the substrate is ambient O(2) instead of an added chemical, such as hydrogen peroxide, or a phosphate ester of a phenol. Laccase-catalyzed O(2) reduction is, however, inhibited by halides, which complex the enzyme's copper ions. Replacement of laccase by bilirubin oxidase, a copper enzyme retaining its maximal activity at high chloride concentrations and at pH 7.2, allows enzyme-amplified affinity assays with O(2) as the substrate in neutral-pH chloride solutions, exemplified here by the assay of DNA, the duplexes of which are unstable at low ionic strength but are stable in strong NaCl solutions.

  8. Stability of the ready-to-use solutions of eribulin for intravenous infusion.

    Science.gov (United States)

    Poujol, S; Dell'ova, M; Bekhtari, K; Bressolle, F; Pinguet, F

    2012-09-01

    A simple HPLC-UV method was developed to determine the stability of ready-to-use eribulin solutions under different storage conditions. The developed method was validated with respect to linearity, accuracy, precision and ruggedness. The following admixtures were prepared: 3-mL polypropylene syringes at concentration of 440 μg/mL and multilayer laminate polyolefin containers containing 0.9% sodium chloride (50 mL) at concentrations of 15.4 and 43.3 μg/mL. The open-vial stability of eribulin was also evaluated. The following storage conditions were tested: 4 °C in the refrigerator; 20 °C under room light exposure; and 20 °C with light-protection. The drug was also subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. The retention time of eribulin was 4.9 min. Admixtures of eribulin solutions in vials, syringes or polyolefin bags at clinically relevant concentrations were physically compatible and chemically stable for at least 14 days at 4 °C in the refrigerator and at 20 °C with or without any protection against light. Degradation was only found to occur under oxidation conditions. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  9. Membrane permeation of testosterone from either solutions, particle dispersions, or particle-stabilized emulsions.

    Science.gov (United States)

    Binks, Bernard P; Fletcher, Paul D I; Johnson, Andrew J; Elliott, Russell P

    2012-02-07

    We derive a unified model that accounts for the variation in extent and rate of membrane permeation by a permeating species with the type of donor compartment formulation (aqueous and oil solutions, particle dispersions, and oil-in-water and water-in-oil emulsions stabilized by particles) initially containing the permeant. The model is also applicable to either closed-loop or open-flow configurations of the receiver compartment of the permeation cell. Predictions of the model are compared with measured extents and rates of permeation of testosterone across an 80 μm thick polydimethylsiloxane (PDMS) membrane from donor compartments initially containing testosterone dissolved in either aqueous or isopropylmyristate (IPM) solutions, aqueous or IPM dispersions of silica nanoparticles or IPM-in-water or water-in-IPM emulsions stabilized by silica nanoparticles. Using a single set of input parameters, the model successfully accounts for the wide variations in permeation behavior observed for the different donor formulation types with either closed-loop or open flow configurations of the permeation cell receiver compartment.

  10. In-use stability of enrofloxacin solution for injection in multi-dose containers

    Directory of Open Access Journals (Sweden)

    Šandor Ksenija

    2012-01-01

    Full Text Available The in-use stability study in this paper was designed as far as possible to simulate the practical usage of multi-dose containers products in veterinary practice and to establish the influence of storage conditions on drug's quality. According to literature data, shelf-live of enrofloxacin solutions for injection tested in this study is 28 days after opening. In-use (open container stability testing of enrofloxacin injection solutions was studied during a period of 112 days, and the physical-chemical parameters and microbiological contamination were assessed. A spectrophotometric method was validated for the quantification of enrofloxacin. The validation method yielded good results and included the selectivity, linearity, intra-assay precision (1.26% RSD, inter-assay precision (1.52% RSD, limit of detection (0.18 μg/mL, limit of quantification (0.54 μg/mL and accuracy. The results of spectrophotometric analyses were presented as the mean drug concentration of enrofloxacin vs. time of sampling. The findings of physical, chemical and microbiological parameters were in accordance with the producers' specifications and no extreme changes during prescribed storage occurred. The study was extended from the drug's proposed shelf-life after opening for the next 84 days and in that period no significant changes were recorded.

  11. Stability-indicating liquid Chromatographic assaymethod for Opthalmic solutions containing combination of Dexamethasone and Chloramphenicol

    International Nuclear Information System (INIS)

    Rao, R.M.; Al-Ashban, R.M.; Shah, A.H.

    2004-01-01

    A selective high-performance chromatographic procedure for the stability monitoring of ophthalmic solutions containing a combination of dexamethasone and chloramphenicolis demonstrated. The separation of the active components and the degradation product of chloramphenicol (1-amino-1-(4-nitrophenyl)-propane-1, 3diol) was achieved on a u-Bondapack C-18 column ( 5 um, 300 mm x 3.9 mm) maintained at ambient temperature (15-20C) by utilizing a mobile phase consisting acidified water (5% actified water with glacial acetic acid ) : acetonitrile : triethyl amine 700 : 300 : 2and pH was adjusted to 5.0 by using 10 M Na OH. The flow rate was 1.5 ml min-1; and elutes were followed with UV-detection at 254 nm. Complete resolution of dexamethasone, chloramphenicol and its hydrolytic product could be attained. The sensitivity, accuracy and specificity were tested. The method was successfully applied in post-marketing stability of the commercial batches of ophthalmic solutions. (author)

  12. Thermal Stability Results of a Fischer-Tropsch Fuel With Various Blends of Aromatic Solution

    Science.gov (United States)

    Lindsey, Jennifer; Klettlinger, Suder

    2013-01-01

    Fischer-Tropsch (F-T) jet fuel composition differs from petroleum-based, conventional commercial jet fuel because of differences in feedstock and production methodology. F-T fuel typically has a lower aromatic and sulfur content and consists primarily of iso and normal paraffins. The ASTM D3241 specification for Jet Fuel Thermal Oxidation Test (JFTOT) break point testing method was used to test the breakpoint of a baseline commercial grade F-T jet fuel, and various blends of this F-T fuel with an aromatic solution. The goal of this research is to determine the effect of aromatic content on the thermal stability of F-T fuel. The testing completed in this report was supported by the NASA Fundamental Aeronautics Subsonic Fixed Wing Project. Two different aromatic content fuels from Rentech, as well as these fuels with added aromatic blend were analyzed for thermal stability using the JFTOT method. Preliminary results indicate a reduction in thermal stability occurs upon increasing the aromatic content to 10% by adding an aromatic blend to the neat fuel. These results do not specify a failure based on pressure drop, but only on tube color. It is unclear whether tube color correlates to more deposition on the tube surface or not. Further research is necessary in order to determine if these failures are true failures based on tube color. Research using ellipsometry to determine tube deposit thickness rather than color will be continued in follow-up of this study.

  13. Deubiquitinating enzyme USP22 positively regulates c-Myc stability and tumorigenic activity in mammalian and breast cancer cells.

    Science.gov (United States)

    Kim, Dongyeon; Hong, Ahyoung; Park, Hye In; Shin, Woo Hyun; Yoo, Lang; Jeon, Seo Jeong; Chung, Kwang Chul

    2017-12-01

    The proto-oncogene c-Myc has a pivotal function in growth control, differentiation, and apoptosis and is frequently affected in human cancer, including breast cancer. Ubiquitin-specific protease 22 (USP22), a member of the USP family of deubiquitinating enzymes (DUBs), mediates deubiquitination of target proteins, including histone H2B and H2A, telomeric repeat binding factor 1, and cyclin B1. USP22 is also a component of the mammalian SAGA transcriptional co-activating complex. In this study, we explored the functional role of USP22 in modulating c-Myc stability and its physiological relevance in breast cancer progression. We found that USP22 promotes deubiquitination of c-Myc in several breast cancer cell lines, resulting in increased levels of c-Myc. Consistent with this, USP22 knockdown reduces c-Myc levels. Furthermore, overexpression of USP22 stimulates breast cancer cell growth and colony formation, and increases c-Myc tumorigenic activity. In conclusion, the present study reveals that USP22 in breast cancer cell lines increases c-Myc stability through c-Myc deubiquitination, which is closely correlated with breast cancer progression. © 2017 Wiley Periodicals, Inc.

  14. Integrated cellulosic enzymes hydrolysis and fermentative advanced yeast bioconversion solution ready for biomass biorefineries

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Manoj [DSM Innovation, Inc., San Francisco, CA (United States)

    2011-05-04

    These are slides from this conference. Lignocellulosic biomass is the most abundant, least expensive renewable natural biological resource for the production of biobased products and bioenergy is important for the sustainable development of human civilization in 21st century. For making the fermentable sugars from lignocellulosic biomass, a reduction in cellulase production cost, an improvement in cellulase performance, and an increase in sugar yields are all vital to reduce the processing costs of biorefineries. Improvements in specific cellulase activities for non-complexed cellulase mixtures can be implemented through cellulase engineering based on rational design or directed evolution for each cellulase component enzyme, as well as on the reconstitution of cellulase components. In this paper, we will provide DSM's efforts in cellulase research and developments and focus on limitations. Cellulase improvement strategies based on directed evolution using screening on relevant substrates, screening for higher thermal tolerance based on activity screening approaches such as continuous culture using insoluble cellulosic substrates as a powerful selection tool for enriching beneficial cellulase mutants from the large library. We will illustrate why and how thermostable cellulases are vital for economic delivery of bioproducts from cellulosic biomass using biochemical conversion approach.

  15. Existence and exponential stability for anti-periodic solutions for shunting inhibitory cellular neural networks with continuously distributed delays

    Directory of Open Access Journals (Sweden)

    Yuanheng Wu

    2009-08-01

    Full Text Available This article concerns anti-periodic solutions for shunting inhibitory cellular neural networks (SICNNs, with continuously distributed delays, arising from the description of the neurons state in delayed neural networks. Without assuming global Lipschitz conditions of activation functions, we obtain existence and local exponential stability of anti-periodic solutions.

  16. A Semilinear Wave Equation with a Boundary Condition of Many-Point Type: Global Existence and Stability of Weak Solutions

    Directory of Open Access Journals (Sweden)

    Giai Giang Vo

    2015-01-01

    Full Text Available This paper is devoted to the study of a wave equation with a boundary condition of many-point type. The existence of weak solutions is proved by using the Galerkin method. Also, the uniqueness and the stability of solutions are established.

  17. Magnetically responsive enzyme powders

    International Nuclear Information System (INIS)

    Pospiskova, Kristyna; Safarik, Ivo

    2015-01-01

    Powdered enzymes were transformed into their insoluble magnetic derivatives retaining their catalytic activity. Enzyme powders (e.g., trypsin and lipase) were suspended in various liquid media not allowing their solubilization (e.g., saturated ammonium sulfate and highly concentrated polyethylene glycol solutions, ethanol, methanol, 2-propanol) and subsequently cross-linked with glutaraldehyde. Magnetic modification was successfully performed at low temperature in a freezer (−20 °C) using magnetic iron oxides nano- and microparticles prepared by microwave-assisted synthesis from ferrous sulfate. Magnetized cross-linked enzyme powders were stable at least for two months in water suspension without leakage of fixed magnetic particles. Operational stability of magnetically responsive enzymes during eight repeated reaction cycles was generally without loss of enzyme activity. Separation of magnetically modified cross-linked powdered enzymes from reaction mixtures was significantly simplified due to their magnetic properties. - Highlights: • Cross-linked enzyme powders were prepared in various liquid media. • Insoluble enzymes were magnetized using iron oxides particles. • Magnetic iron oxides particles were prepared by microwave-assisted synthesis. • Magnetic modification was performed under low (freezing) temperature. • Cross-linked powdered trypsin and lipase can be used repeatedly for reaction

  18. Inhalation Properties and Stability of Nebulized Naked siRNA Solution for Pulmonary Therapy.

    Science.gov (United States)

    Tahara, Kohei; Hashimoto, Wakana; Takeuchi, Hirofumi

    2016-01-01

    The use of naked unmodified small interfering RNA (N-siRNA) without vector has previously been investigated as a pulmonary therapy. However, little is known regarding stabilities and aerodynamic particle sizes of N-siRNA-containing droplets; nebulizers have not yet been optimized for N-siRNA solutions. Thus, in this study, we investigated the feasibility of inhaled N-siRNA solutions for pulmonary therapy using nebulization. Various nebulizers and N-siRNA concentrations were assessed in terms of siRNA integrity after nebulization, and inhalation properties including aerodynamic particle size were examined. In comparison with ultrasonic-, air-jet-, and vibrating-mesh nebulizers, N-siRNA integrity was not affected by nebulization. Thus, in further experiments, performances of N-siRNA aerosols with different nebulizers and N-siRNA concentrations were evaluated and screened using an aerodynamic particle sizer (APS) which employed the time-of-flight principle or a cascade impactor. Mean mass aerodynamic diameters of N-siRNA-containing droplets from vibrating-mesh nebulizers tended to decrease with increasing N-siRNA concentrations, reflecting the influence of N-siRNA solutions on surface tension, as indicated by contact angles. These data indicate the utility of APS instruments for investigating the nebulized characteristics of expensive drugs including siRNAs and may facilitate the development of N-siRNA inhalation formulations.

  19. Color stability of white mineral trioxide aggregate in contact with hypochlorite solution.

    Science.gov (United States)

    Camilleri, Josette

    2014-03-01

    One of the uses of white mineral trioxide aggregate (MTA) is as an apical barrier in immature teeth. Although this treatment has been reported to have high success rates, a number of cases of discoloration have been noted. The aim of this research was to investigate the color stability of white MTA in contact with various solutions used in endodontics. The change in color of white MTA after immersion in water, sodium hypochlorite, or hydrogen peroxide was assessed by viewing the color change on digital photographs and also by using a spectrophotometer. White MTA, white Portland cement, and bismuth oxide were assessed. The changes in the material after immersion in the different solutions were assessed by x-ray diffraction analysis and Fourier transform infrared spectroscopy. Immersion of white MTA and bismuth oxide in sodium hypochlorite resulted in the formation of a dark brown discoloration. This change was not observed in Portland cement. X-ray diffraction analysis and Fourier transform infrared analysis displayed the reduction of sodium hypochlorite in contact with bismuth oxide and MTA to sodium chloride. Contact of white MTA and other bismuth-containing materials with sodium hypochlorite solution should be avoided. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  20. Extended stability of intravenous 0.9% sodium chloride solution after prolonged heating or cooling.

    Science.gov (United States)

    Puertos, Enrique

    2014-03-01

    The primary objective of this study was to evaluate the stability and sterility of an intravenous 0.9% sodium chloride solution that had been cooled or heated for an extended period of time. Fifteen sterile 1 L bags of 0.9% sodium chloride solution were randomly selected for this experiment. Five bags were refrigerated at an average temperature of 5.2°C, 5 bags were heated at an average temperature of 39.2°C, and 5 bags were stored at an average room temperature of 21.8°C to serve as controls. All samples were protected from light and stored for a period of 199 days prior to being assayed and analyzed for microbial and fungal growth. There was no clinically significant difference in the mean sodium values between the refrigerated samples, the heated samples, and the control group. There were no signs of microbial or fungal growth for the duration of the study. A sterile intravenous solution of 0.9% sodium chloride that was heated or cooled remained stable and showed no signs of microbial or fungal growth for a period of 199 days. This finding will allow hospitals and emergency medical technicians to significantly extend the expiration date assigned to these fluids and therefore obviate the need to change out these fluids every 28 days as recommended by the manufacturer.

  1. Stability of equilibrium solutions of Hamiltonian systems with n-degrees of freedom and single resonance in the critical case

    Science.gov (United States)

    dos Santos, Fabio; Vidal, Claudio

    2018-04-01

    In this paper we give new results for the stability of one equilibrium solution of an autonomous analytic Hamiltonian system in a neighborhood of the equilibrium point with n-degrees of freedom. Our Main Theorem generalizes several results existing in the literature and mainly we give information in the critical cases (i.e., the condition of stability and instability is not fulfilled). In particular, our Main Theorem provides necessary and sufficient conditions for stability of the equilibrium solutions under the existence of a single resonance. Using analogous tools used in the Main Theorem for the critical case, we study the stability or instability of degenerate equilibrium points in Hamiltonian systems with one degree of freedom. We apply our results to the stability of Hamiltonians of the type of cosmological models as in planar as in the spatial case.

  2. Stability study of Azure B, Eosin Y and commercial Romanowsky Giemsa stock solutions using high performance liquid chromatography.

    Science.gov (United States)

    Van Liedekerke, B M; Nelis, H J; Wittekind, D H; De Leenheer, A P

    1991-04-01

    The stability of Azure B and Eosin Y in stock solutions of the individual compounds as well as in mixtures of the two dyes was studied. The purpose of the study of these two essential constituents of the Romanowsky Giemsa stain, commonly used in cytology and histology, was to select a stable mixture as a definitive stock solution. Two specific high performance liquid chromatographic methods were used to monitor qualitative and quantitative changes in solutions. Several parameters influencing the stability of Azure B were examined e.g. the type of counter ion, the presence of Eosin Y and the type of solvent used. The second part focused on the stability of Eosin Y in mixtures with different cationic dyes submitted to high temperatures. In conclusion, an Azure B SCN-Eosin Y acid mixture in dimethylsulphoxide (concentrations 0.75% and 0.12%, respectively) was selected as being the most appropriate composition of a stock solution for the Romanowsky Giemsa stain.

  3. Formation and thermodynamic stability of (polymer + porphyrin) supramolecular structures in aqueous solutions

    International Nuclear Information System (INIS)

    Costa, Viviana C.P. da; Hwang, Barrington J.; Eggen, Spencer E.; Wallace, Megan J.; Annunziata, Onofrio

    2014-01-01

    Highlights: • Thermodynamic stability of a (polymer + porphyrin) supramolecular structure was characterized. • Isothermal titration calorimetry provided two ways to determine reaction enthalpies. • Exothermic (polymer + porphyrin) binding competes with porphyrin self-association. • (Polymer + porphyrin) binding is entropically favored with respect to porphyrin self-association. • Spectral shifts show importance of porphyrin central hydrogens in polymer binding. - Abstract: Optical properties of porphyrins can be tuned through (polymer + porphyrin) (host + guest) binding in solution. This gives rise to the formation of supramolecular structures. In this paper, the formation, thermodynamic stability and spectroscopic properties of (polymer + porphyrin) supramolecular structures and their competition with porphyrin self-association were investigated by both isothermal titration calorimetry (ITC) and absorption spectroscopy. Specifically, reaction enthalpies and equilibrium constants were measured for meso-tetrakis(4-sulfonatophenyl) porphyrin (TPPS) self-association and TPPS binding to the polymer poly(vinylpyrrolidone) (PVP, 40 kg/mol) in aqueous solutions at pH 7 and three different temperatures (12, 25 and 37 °C). ITC, compared to spectroscopic techniques, provides two independent means to determine reaction enthalpies: direct measurements and Van’t Hoff plot. This was used as a criterion to assess that (1) self-association of TPPS is limited to the formation of dimers and (2) TPPS binds to PVP in its monomeric state only. The formation of TPPS dimers and (PVP + TPPS) supramolecular structures are both enthalpically driven. However, (polymer + porphyrin) binding was found to be entropically favored compared to dimerization. Furthermore, the reaction enthalpies of these two processes significantly depend on temperature. This behavior was attributed to hydrophobic interactions. Finally, the limiting absorption spectra of monomeric, dimeric and polymer

  4. Critical survey of stability constants of EDTA complexes critical evaluation of equilibrium constants in solution stability constants of metal complexes

    CERN Document Server

    Anderegg, G

    2013-01-01

    Critical Survey of Stability Constants of EDTA Complexes focuses on the computations, values, and characteristics of stability constants. The book emphasizes that for a critical discussion of experimentally determined stability constants, it is important to consider the precision of the values that manifests the self-consistency of the constant, taking into consideration the random errors. The publication reviews the stability constants of metal complexes. The numerical calculations affirm the reactions and transformations of metal ions when exposed to varying conditions. The text also present

  5. On the stability of the cosmological solutions in f(R, G) gravity

    International Nuclear Information System (INIS)

    De la Cruz-Dombriz, Álvaro; Sáez-Gómez, Diego

    2012-01-01

    Modified gravity is one of the most promising candidates for explaining the current accelerating expansion of the Universe, and even its unification with the inflationary epoch. Nevertheless, the wide range of models capable of explaining the phenomena of dark energy imposes that current research focuses on a more precise study of the possible effects of modified gravity on both cosmological and local levels. In this paper, we focus on the analysis of a type of modified gravity, the so-called f(R, G) gravity, and we perform a deep analysis on the stability of important cosmological solutions. This not only can help to constrain the form of the gravitational action, but also facilitate a better understanding of the behavior of the perturbations in this class of higher order theories of gravity, which will lead to a more precise analysis of the full spectrum of cosmological perturbations in future. (paper)

  6. Global exponential stability of periodic solution for shunting inhibitory CNNs with delays

    Energy Technology Data Exchange (ETDEWEB)

    Li Yongkun [Department of Mathematics, Yunnan University, Kunming, Yunnan 650091 (China)]. E-mail: yklie@ynu.edu.cn; Liu Chunchao [Department of Mathematics, Yunnan University, Kunming, Yunnan 650091 (China); Zhu Lifei [Department of Mathematics, Yunnan University, Kunming, Yunnan 650091 (China)

    2005-03-28

    By using the continuation theorem of coincidence degree theory and constructing suitable Lyapunov functions, we study the existence and stability of periodic solution for shunting inhibitory cellular neural networks (SICNNs) with delays x-bar {sub ij}(t)=-a{sub ij}(t)x{sub ij}(t)--bar B{sup kl}-bar Nr(i,j)B{sub ij}{sup kl}(t)f{sub ij}(x{sub kl}(t))x{sub ij}(t)--bar C{sup kl}-bar Nr(i,j)C{sub ij}{sup kl}(t)g{sub ij}(x{sub kl}(t-{tau}{sub kl}))x{sub ij}(t)+L{sub ij}(t)

  7. Brassinosteroid-induced CO{sub 2} assimilation is associated with increased stability of redox-sensitive photosynthetic enzymes in the chloroplasts in cucumber plants

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yu Ping; Cheng, Fei; Zhou, Yan Hong; Xia, Xiao Jian; Mao, Wei Hua; Shi, Kai [Department of Horticulture, Zijingang Campus, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058 (China); Chen, Zhi Xiang [Department of Horticulture, Zijingang Campus, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058 (China); Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907-2054 (United States); Yu, Jing Quan, E-mail: jqyu@zju.edu.cn [Department of Horticulture, Zijingang Campus, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058 (China); Key Laboratory of Horticultural Plants Growth, Development and Quality Improvement, Ministry of Agriculture of China, Yuhangtang Road 866, Hangzhou 310058 (China)

    2012-09-28

    Highlights: Black-Right-Pointing-Pointer Activity of certain Calvin cycle enzymes and CO{sub 2} assimilation are induced by BRs. Black-Right-Pointing-Pointer BRs upregulate the activity of the ascorbate-glutathione cycle in the chloroplasts. Black-Right-Pointing-Pointer BRs increase the chloroplast thiol reduction state. Black-Right-Pointing-Pointer A BR-induced reducing environment increases the stability of photosynthetic enzymes. -- Abstract: Brassinosteroids (BRs) play important roles in plant growth, development, photosynthesis and stress tolerance; however, the mechanism underlying BR-enhanced photosynthesis is currently unclear. Here, we provide evidence that an increase in the BR level increased the quantum yield of PSII, activities of Rubisco activase (RCA) and fructose-1,6-bisphosphatase (FBPase), and CO{sub 2} assimilation. BRs upregulated the transcript levels of genes and activity of enzymes involved in the ascorbate-glutathione cycle in the chloroplasts, leading to an increased ratio of reduced (GSH) to oxidized (GSSG) glutathione in the chloroplasts. An increased GSH/GSSG ratio protected RCA from proteolytic digestion and increased the stability of redox-sensitive enzymes in the chloroplasts. These results strongly suggest that BRs are capable of regulating the glutathione redox state in the chloroplasts through the activation of the ascorbate-glutathione cycle. The resulting increase in the chloroplast thiol reduction state promotes CO{sub 2} assimilation, at least in part, by enhancing the stability and activity of redox-sensitive photosynthetic enzymes through post-translational modifications.

  8. Effect of Different Irrigation Solutions on the Colour Stability of Three Calcium Silicate-Based Materials.

    Science.gov (United States)

    F, Sobhnamayan; A, Adl; S, Ghanbaran

    2017-06-01

    Previous studies have shown discoloration of mineral trioxide aggregate (MTA) in contact with root canal irrigation solutions. However, there are limited data on colour stability of other calcium silicate-based materials (CSMs). This in vitro study aimed to evaluate the colour stability of three CSMs in contact with different irrigation solutions. Three CSMs including White MTA (wMTA) Angelus, calcium enriched mixture (CEM), and Biodentine were assessed in this study. Forty five samples of each material were mixed according to the manufactures' instructions and then placed in silicone tubes. After 24 hours, the materials were removed from the moulds and 9 samples of each material left dry or immersed in normal saline, 5% sodium hypochlorite (NaOCL), 2% chlorhexidinegluconate (CHX), or 17%EDTA for 24 hours. Colour changes were measured with a spectrophotometer. Data were evaluated with 2-way analysis of variance, one way analysis of variance and Tukey post hoc tests. The highest discoloration of all materials was observed after contact with CHX. In the MTA Angelus and CEM cement groups, significant differences were observed between CHX and NaOCl and also between these two irrigants with the other three irrigants ( p < 0.05). In the Biodentine group, CHX created statistically significant discoloration compared to other irrigants ( p < 0.05). Only wMTA Angelus showed a significantly higher discoloration in contact with EDTA compared to normal saline and dry condition ( p < 0.05). wMTA Angelus showed a significantly higher colour change compared with CEM cement and Biodentine after contact with NaOCl, CHX, and EDTA ( p < 0.05). The contact of wMTA, CEM cement, and Biodentine with CHX should be avoided because this leads to severe discoloration. Contact with sodium hypochlorite also leads to discoloration of wMTA and CEM cements. Among of the three tested materials, wMTA showed the highest discoloration after contact with NaOCl, CHX, and EDTA.

  9. Effect of Different Irrigation Solutions on the Colour Stability of Three Calcium Silicate-Based Materials

    Science.gov (United States)

    F, Sobhnamayan; A, Adl; S, Ghanbaran

    2017-01-01

    Statement of Problem: Previous studies have shown discoloration of mineral trioxide aggregate (MTA) in contact with root canal irrigation solutions. However, there are limited data on colour stability of other calcium silicate-based materials (CSMs). Objectives: This in vitro study aimed to evaluate the colour stability of three CSMs in contact with different irrigation solutions. Materials and Methods: Three CSMs including White MTA (wMTA) Angelus, calcium enriched mixture (CEM), and Biodentine were assessed in this study. Forty five samples of each material were mixed according to the manufactures’ instructions and then placed in silicone tubes. After 24 hours, the materials were removed from the moulds and 9 samples of each material left dry or immersed in normal saline, 5% sodium hypochlorite (NaOCL), 2% chlorhexidinegluconate (CHX), or 17%EDTA for 24 hours. Colour changes were measured with a spectrophotometer. Data were evaluated with 2-way analysis of variance, one way analysis of variance and Tukey post hoc tests. Results: The highest discoloration of all materials was observed after contact with CHX. In the MTA Angelus and CEM cement groups, significant differences were observed between CHX and NaOCl and also between these two irrigants with the other three irrigants (p Biodentine group, CHX created statistically significant discoloration compared to other irrigants (p Biodentine after contact with NaOCl, CHX, and EDTA (p Biodentine with CHX should be avoided because this leads to severe discoloration. Contact with sodium hypochlorite also leads to discoloration of wMTA and CEM cements. Among of the three tested materials, wMTA showed the highest discoloration after contact with NaOCl, CHX, and EDTA. PMID:28959768

  10. Improved air stability of perovskite solar cells via solution-processed metal oxide transport layers

    Science.gov (United States)

    You, Jingbi; Meng, Lei; Song, Tze-Bin; Guo, Tzung-Fang; Yang, Yang (Michael); Chang, Wei-Hsuan; Hong, Ziruo; Chen, Huajun; Zhou, Huanping; Chen, Qi; Liu, Yongsheng; De Marco, Nicholas; Yang, Yang

    2016-01-01

    Lead halide perovskite solar cells have recently attracted tremendous attention because of their excellent photovoltaic efficiencies. However, the poor stability of both the perovskite material and the charge transport layers has so far prevented the fabrication of devices that can withstand sustained operation under normal conditions. Here, we report a solution-processed lead halide perovskite solar cell that has p-type NiOx and n-type ZnO nanoparticles as hole and electron transport layers, respectively, and shows improved stability against water and oxygen degradation when compared with devices with organic charge transport layers. Our cells have a p-i-n structure (glass/indium tin oxide/NiOx/perovskite/ZnO/Al), in which the ZnO layer isolates the perovskite and Al layers, thus preventing degradation. After 60 days storage in air at room temperature, our all-metal-oxide devices retain about 90% of their original efficiency, unlike control devices made with organic transport layers, which undergo a complete degradation after just 5 days. The initial power conversion efficiency of our devices is 14.6 ± 1.5%, with an uncertified maximum value of 16.1%.

  11. An investigation on the chemical stability and a novel strategy for long-term stabilization of diphenylalanine nanostructures in aqueous solution

    Directory of Open Access Journals (Sweden)

    H. Nezammahalleh

    2015-01-01

    Full Text Available The stability of diphenylalanine (FF microwires and microtubes in phosphate buffer solution was investigated and a novel strategy was developed for their chemical stabilization. This stability investigation was carried out by optical microscopy and by high performance liquid chromatography (HPLC. These microstructures dissolve in the solution depending upon their degree of FF saturation. The dissolution mechanisms of the structures in kinetically limited processes were found by accurately fitting the experimental dissolution data to a theoretical kinetic equation. The dissolution data were well fitted to the particular Avrami-Erofe’ev kinetic expression (R2 > 0.98. These findings suggest that the structures can be stabilized by a decrease in the hydration of the constituent molecules thorough a chemical conformational induced transition upon heat treatment. The stable microtubes were fabricated in a novel three step procedure consisting of the reduction of silver ions in unstable FF microtubes by a citrate reductant, the stabilization by chemical conformational induced transition upon heat treatment, and the consequent oxidation of the reduced silver by a persulfate oxidant. These materials were characterized by electron microscopy and powder X-ray diffraction techniques. The long-term stability of both structures was also confirmed by optical microscopy and HPLC.

  12. Stability study of docetaxel solution (0.9%, saline) using Non-PVC and PVC tubes for intravenous administration.

    Science.gov (United States)

    Park, Kang Hoon; Chung, Dong June

    2015-01-01

    Di-2-ethylhexyl phthalate (DEHP) are added to poly(vinyl chloride)(PVC) infusion tubes as a plasticizer to ensure tube flexibility. In addition to previously reported disadvantages of DEHP, released DEHP molecules from PVC tubes can easily interact with surfactants in anticancer drug solutions (i.e., polysorbate 80 for Taxotere®-Inj) and reduce the solubility of docetaxel in aqueous solution during anticancer drug administration. In this study, we investigated the in vitro stability of docetaxel in a 0.9% saline solution under an intravenous administration condition using a PVC tube (high DEHP content) and non-PVC infused tube. The docetaxel solution circulating through the non-PVC tube had better solution stability than through the PVC tube(high DEHP content).

  13. The thermodynamic stability induced by solute co-segregation in nanocrystalline ternary alloys

    International Nuclear Information System (INIS)

    Liang, Tao; Chen, Zheng; Zhang, Jinyong; Zhang, Ping; Yang, Xiaoqin

    2017-01-01

    The grain growth and thermodynamic stability induced by solute co-segregation in ternary alloys are presented. Grain growth behavior of the single-phase supersaturated grains prepared in Ni-Fe-Pb alloy melt at different undercoolings was investigated by performing isothermal annealings at T = 400 C-800 C. Combining the multicomponent Gibbs adsorption equation and Guttmann's grain boundary segregation model, an empirical relation for isothermal grain growth was derived. By application of the model to grain growth in Ni-Fe-Pb, Fe-Cr-Zr and Fe-Ni-Zr alloys, it was predicted that driving grain boundary energy to zero is possible in alloys due to the co-segregation induced by the interactive effect between the solutes Fe/Pb, Zr/Ni and Zr/Cr. A non-linear relationship rather than a simple linear relation between 1/D* (D* the metastable equilibrium grain size) and ln(T) was predicted due to the interactive effect.

  14. The thermodynamic stability induced by solute co-segregation in nanocrystalline ternary alloys

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Tao; Chen, Zheng; Zhang, Jinyong; Zhang, Ping [China Univ. of Mining and Technology, Xuzhou (China). School of Mateial Science and Engineering; Yang, Xiaoqin [China Univ. of Mining and Technology, Xuzhou (China). School of Chemical Engineering and Technology

    2017-06-15

    The grain growth and thermodynamic stability induced by solute co-segregation in ternary alloys are presented. Grain growth behavior of the single-phase supersaturated grains prepared in Ni-Fe-Pb alloy melt at different undercoolings was investigated by performing isothermal annealings at T = 400 C-800 C. Combining the multicomponent Gibbs adsorption equation and Guttmann's grain boundary segregation model, an empirical relation for isothermal grain growth was derived. By application of the model to grain growth in Ni-Fe-Pb, Fe-Cr-Zr and Fe-Ni-Zr alloys, it was predicted that driving grain boundary energy to zero is possible in alloys due to the co-segregation induced by the interactive effect between the solutes Fe/Pb, Zr/Ni and Zr/Cr. A non-linear relationship rather than a simple linear relation between 1/D* (D* the metastable equilibrium grain size) and ln(T) was predicted due to the interactive effect.

  15. The Steroidogenic Enzyme AKR1C3 Regulates Stability of the Ubiquitin Ligase Siah2 in Prostate Cancer Cells*

    Science.gov (United States)

    Fan, Lingling; Peng, Guihong; Hussain, Arif; Fazli, Ladan; Guns, Emma; Gleave, Martin; Qi, Jianfei

    2015-01-01

    Re-activation of androgen receptor (AR) activity is the main driver for development of castration-resistant prostate cancer. We previously reported that the ubiquitin ligase Siah2 enhanced AR transcriptional activity and prostate cancer cell growth. Among the genes we found to be regulated by Siah2 was AKR1C3, which encodes a key androgen biosynthetic enzyme implicated in castration-resistant prostate cancer development. Here, we found that Siah2 inhibition in CWR22Rv1 prostate cancer cells decreased AKR1C3 expression as well as intracellular androgen levels, concomitant with inhibition of cell growth in vitro and in orthotopic prostate tumors. Re-expression of either wild-type or catalytically inactive forms of AKR1C3 partially rescued AR activity and growth defects in Siah2 knockdown cells, suggesting a nonenzymatic role for AKR1C3 in these outcomes. Unexpectedly, AKR1C3 re-expression in Siah2 knockdown cells elevated Siah2 protein levels, whereas AKR1C3 knockdown had the opposite effect. We further found that AKR1C3 can bind Siah2 and inhibit its self-ubiquitination and degradation, thereby increasing Siah2 protein levels. We observed parallel expression of Siah2 and AKR1C3 in human prostate cancer tissues. Collectively, our findings identify a new role for AKR1C3 in regulating Siah2 stability and thus enhancing Siah2-dependent regulation of AR activity in prostate cancer cells. PMID:26160177

  16. Stability analysis of the soliton solutions for the generalized quintic derivative nonlinear Schrödinger equation

    Science.gov (United States)

    Yue, Chen; Seadawy, Aly; Lu, Dianchen

    The propagation of hydrodynamic wave packets and media with negative refractive index is studied in a quintic derivative nonlinear Schrödinger (DNLS) equation. The quintic DNLS equation describe the wave propagation on a discrete electrical transmission line. We obtain a Lagrangian and the invariant variational principle for quintic DNLS equation. By using a class of ordinary differential equation, we found four types of exact solutions of the quintic DNLS equation, which are kink-type solitary wave solution, antikink-type solitary wave solution, sinusoidal solitary wave solution, bell-type solitary wave solution. By applying the modulation instability to discuss stability analysis of the obtained solutions. Modulation instabilities of continuous waves and localized solutions on a zero background have been investigated.

  17. Stability analysis of the soliton solutions for the generalized quintic derivative nonlinear Schrödinger equation

    Directory of Open Access Journals (Sweden)

    Chen Yue

    2016-01-01

    Full Text Available The propagation of hydrodynamic wave packets and media with negative refractive index is studied in a quintic derivative nonlinear Schrödinger (DNLS equation. The quintic DNLS equation describe the wave propagation on a discrete electrical transmission line. We obtain a Lagrangian and the invariant variational principle for quintic DNLS equation. By using a class of ordinary differential equation, we found four types of exact solutions of the quintic DNLS equation, which are kink-type solitary wave solution, antikink-type solitary wave solution, sinusoidal solitary wave solution, bell-type solitary wave solution. By applying the modulation instability to discuss stability analysis of the obtained solutions. Modulation instabilities of continuous waves and localized solutions on a zero background have been investigated.

  18. Optical studies of the solution phase reduction and stabilization of indigo tetrasulfonate in polyelectrolyte complexes.

    Science.gov (United States)

    Hoene, Becca; Rivera, Dion

    2017-09-01

    Ultraviolet-visible (UV-vis) and fluorescence spectroscopy have been used to characterize the polyelectrolyte complexes (PECs) formed when potassium indigo tetrasulfonate (ITS) interacts with poly diallydimethylammonium chloride (PDADMAC) through columbic attraction in the presence of the reducing agent sodium bisulfite, NaHSO 3 . The PDADMAC facilitates both the reduction of the ITS and the stabilization of the reduced state of the ITS in an atmospheric oxygen environment. Dilutions of the dye solution show that the PEC is stable to dilutions of at least 1 to 1000. UV-vis studies indicate that the reduced ITS (ITS red ) forms what is likely a J-aggregate in the presence of PDADMAC with an absorbance band red shifted from the normal absorbance band of reduced ITS by roughly 130 nm, 390 nm to 520 nm. Excitation of the PEC solution at either 390 nm or 520 nm produces an emission spectrum of the aggregated complex with an emission maximum near 534 nm. Monomer emission at 480 nm of ITS red represents only 3.0 ± 0.5% of the emission signal of the aggregated complex. Kinetic studies using fluorescence spectroscopy over a temperature range of 30 to 70 °C and dilutions of dye solutions ranging from 1:10 to 1:1000 yield data for the oxidation of ITS red that is best fit by a first order rate constant. Kinetic data displays two distinctive regimes, a short time rate and a long time rate. These two distinct kinetic regimes are likely due to the reduced ITS interacting with an outer PEC environment and an inner PEC environment. First order rate constants could be used to estimate Δ ‡ H and Δ ‡ S of the oxidation reaction. Fluorescence data was used to calculate the partitioning of reduced ITS molecules between the outer and inner PEC environments. Partitioning from the inner to outer PEC environment was found to be entropically driven. Addition of NaCl to the diluted dye solutions could alter the kinetics of the oxidation but the significance of the effect depended on

  19. Optical studies of the solution phase reduction and stabilization of indigo tetrasulfonate in polyelectrolyte complexes

    Directory of Open Access Journals (Sweden)

    Becca Hoene

    2017-09-01

    Full Text Available Ultraviolet-visible (UV-vis and fluorescence spectroscopy have been used to characterize the polyelectrolyte complexes (PECs formed when potassium indigo tetrasulfonate (ITS interacts with poly diallydimethylammonium chloride (PDADMAC through columbic attraction in the presence of the reducing agent sodium bisulfite, NaHSO3. The PDADMAC facilitates both the reduction of the ITS and the stabilization of the reduced state of the ITS in an atmospheric oxygen environment. Dilutions of the dye solution show that the PEC is stable to dilutions of at least 1 to 1000. UV–vis studies indicate that the reduced ITS (ITSred forms what is likely a J-aggregate in the presence of PDADMAC with an absorbance band red shifted from the normal absorbance band of reduced ITS by roughly 130 nm, 390 nm to 520 nm. Excitation of the PEC solution at either 390 nm or 520 nm produces an emission spectrum of the aggregated complex with an emission maximum near 534 nm. Monomer emission at 480 nm of ITSred represents only 3.0 ± 0.5% of the emission signal of the aggregated complex. Kinetic studies using fluorescence spectroscopy over a temperature range of 30 to 70 °C and dilutions of dye solutions ranging from 1:10 to 1:1000 yield data for the oxidation of ITSred that is best fit by a first order rate constant. Kinetic data displays two distinctive regimes, a short time rate and a long time rate. These two distinct kinetic regimes are likely due to the reduced ITS interacting with an outer PEC environment and an inner PEC environment. First order rate constants could be used to estimate Δ‡H and Δ‡S of the oxidation reaction. Fluorescence data was used to calculate the partitioning of reduced ITS molecules between the outer and inner PEC environments. Partitioning from the inner to outer PEC environment was found to be entropically driven. Addition of NaCl to the diluted dye solutions could alter the kinetics of the oxidation but the significance of the effect

  20. Static response and stability of coated microbubbles—multiplicity of solutions and parameter estimation

    Energy Technology Data Exchange (ETDEWEB)

    Lytra, Alkmini; Pelekasis, Nikos, E-mail: pel@uth.gr [Department of Mechanical Engineering, University of Thessaly, Pedion Areos, Volos 38334 (Greece)

    2014-08-01

    The static response of a coated microbubble subject to an external pressure distribution is investigated, in order to identify different response patterns with varying viscoelastic properties of the shell. Theoretical and numerical analysis of the axisymmetric response of a microbubble is performed via the static force balance, in order to obtain the radial and tangential (polar) displacements of a shell subject to a uniform or point load. The stretching and bending stiffnesses of the shell, along with the compressibility of the internal gas, comprise the resistance to deformation of the microbubble. The finite element methodology, with B-splines as basis functions, is employed for the solution of the nonlinear static problem while Newton’s iterations provide the converged solution. The Jacobian matrix provides necessary information regarding stability of the emerging static configurations. The buckling instability of a uniformly loaded shell results in a subcritical bifurcation that is characterized by symmetric/asymmetric shapes for the parameter range pertaining to polymeric/phospholipid shells. As the relative importance of bending stiffness with respect to stretching decreases symmetric shapes determine the primary buckling instability. Strain softening shell behavior conforms to this pattern due to the increase of the effective area dilatation modulus during compression. Increasing the resistance to compression forces the asymmetric and symmetric solution families to terminate at larger bubble volumes. When a point load is considered the force deformation curve is characterized by a transition from a linear Reissner-type to a nonlinear Pogorelov-type response, followed by a regime where resistance to compression dominates. Identifying these regimes in atomic force microscopy measurements can be used for estimating the area dilatation and bending modulus of the shell. (paper)

  1. Validation of an analytical method applicable to study of 1 mg/mL oral Risperidone solution stability

    International Nuclear Information System (INIS)

    Abreu Alvarez, Maikel; Garcia Penna, Caridad Margarita; Martinez Miranda, Lissette

    2010-01-01

    A validated analytical method by high-performance liquid chromatography (HPLC) was applicable to study of 1 mg/mL Risperidone oral solution stability. The above method was linear, accurate, specific and exact. A stability study of the 1 mg/mL Risperidone oral solution was developed determining its expiry date. The shelf life study was conducted for 24 months at room temperature; whereas the accelerated stability study was conducted with product under influence of humidity and temperature; analysis was made during 3 months. Formula fulfilled the quality specifications described in Pharmacopeia. The results of stability according to shelf life after 24 months showed that the product maintains the parameters determining its quality during this time and in accelerated studies there was not significant degradation (p> 0.05) in the product. Under mentioned conditions expiry date was of 2 years

  2. Foam capacity and stability of Sodium Dodecyl Sulfate (SDS) on the presence of contaminant coffee and Cd ions in solution

    Science.gov (United States)

    Haryanto, B.; Chang, C. H.; Kuo, A. T.; Siswarni, M. Z.; Sinaga, T. M. A.

    2018-02-01

    In this study, the effect of the coffee colloidal particle and Cd ion contaminant on the foam capacity and stability of sodium dodecyl sulfate (SDS) solution was investigated. The foam was generated by using a foam generator. The foam capacity of SDS was first evaluated at different concentrations. After the foam capacity reaching a constant value, the foam stability was then measured by flowing to a column. The results showed that the presence the coffee colloidal particles or Cd ions in the solution would decrease the foam capacity and stability of SDS. In addition, the decreased foam capacity and stability was more pronounced in the presence of coffee colloidal particles than Cd ions. The colloidal particles may have stronger interaction with SDS and thus reduce the formation of the foam.

  3. Effect of neohesperidin dihydrochalcone on the activity and stability of alpha-amylase: a comparative study on bacterial, fungal, and mammalian enzymes.

    Science.gov (United States)

    Kashani-Amin, Elaheh; Ebrahim-Habibi, Azadeh; Larijani, Bagher; Moosavi-Movahedi, Ali Akbar

    2015-10-01

    Neohesperidin dihydrochalcone (NHDC) was recently introduced as an activator of mammalian alpha-amylase. In the current study, the effect of NHDC has been investigated on bacterial and fungal alpha-amylases. Enzyme assays and kinetic analysis demonstrated the capability of NHDC to significantly activate both tested alpha-amylases. The ligand activation pattern was found to be more similar between the fungal and mammalian enzyme in comparison with the bacterial one. Further, thermostability experiments indicated a stability increase in the presence of NHDC for the bacterial enzyme. In silico (docking) test locates a putative binding site for NHDC on alpha-amylase surface in domain B. This domain shows differences in various alpha-amylase types, and the different behavior of the ligand toward the studied enzymes may be attributed to this fact. Copyright © 2015 John Wiley & Sons, Ltd.

  4. Investigations of foam formation and its stabilization in the extraction systems: TBP in kerosene-nitric acid solutions

    International Nuclear Information System (INIS)

    Zielinski, A.

    1980-01-01

    The paper is devoted to studies of foam formation and its stabilization in TBP - kerosene - nitric acid solutions extracting systems. It was experimentally found, that TBP acts as a stabilizator of thin, liquid foam films as well as an emulgator in forming dispersions. The stabilizing effect of fine emulsions w/o on formed foams column was observed. Relevant references on the subject are also reviewed. (author)

  5. Evolution toward small molecule inhibitor resistance affects native enzyme function and stability, generating acarbose-insensitive cyclodextrin glucanotransferase variants

    NARCIS (Netherlands)

    Kelly, Ronan M.; Leemhuis, Hans; Gatjen, Linda; Dijkhuizen, Lubbert; Gätjen, Linda

    2008-01-01

    Small molecule inhibitors play an essential role in the selective inhibition of enzymes associated with human infection and metabolic disorders. Targeted enzymes may evolve toward inhibitor resistance through selective incorporation of mutations. Acquisition of insensitivity may, however, result in

  6. Beyond-use date determination of buprenorphine buccal solution using a stability-indicating high-performance liquid chromatographic assay.

    Science.gov (United States)

    Kirk, Loren Madden; Brown, Stacy D

    2015-12-01

    The objectives of this study included developing and validating a stability-indicating high-performance liquid chromatographic (HPLC) method with ultraviolet (UV) detection for the determination of buprenorphine in a buccal solution for veterinary use, and applying that method to determine the stability of a 3 mg/ml buprenorphine preparation in room temperature and refrigerated storage conditions. This preparation, intended for buccal administration in feline patients, plays an important role in pain management in cats. A stability-indicating HPLC method was developed and validated for system suitability, accuracy, repeatability, intermediate precision, specificity, linearity and robustness based on US Pharmacopeia (USP) General Chapter . The method was then applied to the study of potency changes over 90 days in a buccal buprenorphine solution stored at two temperatures. All HPLC-UV method data met acceptable criteria for the quantification of buprenorphine in a buccal solution formulation. The buprenorphine concentrations found in each stability sample remained within the 90-110% of label claim throughout the 90 days of study. All stability test bottles of the buprenorphine buccal solution retained their original appearance. For the room temperature bottles, some white particulate matter was noted in the threads of the container bottles starting at day 21. The pH of the preparations during the course of the study was in the range of 3.57-4.06 and 4.01-4.16 for the room temperature and refrigerated samples, respectively. Pharmacists have compounded a concentrated 3 mg/ml buccal solution to use easily in the home care or outpatient setting for treatment of feline pain. Prior to this investigation, pharmacists empirically assigned beyond-use dates to this formulation based on standards in USP General Chapter Pharmaceutical Compounding - Nonsterile Preparations. This study of a 3 mg/ml buprenorphine buccal solution indicates stability through 90 days. © ISFM and

  7. Global exponential stability and existence of periodic solutions in BAM networks with delays and reaction-diffusion terms

    International Nuclear Information System (INIS)

    Song Qiankun; Cao Jinde

    2005-01-01

    Both exponential stability and periodic solutions are considered for a class of bi-directional associative memory (BAM) neural networks with delays and reaction-diffusion terms by constructing suitable Lyapunov functional and some analysis techniques. The general sufficient conditions are given ensuring the global exponential stability and existence of periodic solutions of BAM neural networks with delays and reaction-diffusion terms. These presented conditions are in terms of system parameters and have important leading significance in the design and applications of globally exponentially stable and periodic oscillatory neural circuits for BAM with delays and reaction-diffusion terms

  8. Existence and Asymptotic Stability of Periodic Solutions of the Reaction-Diffusion Equations in the Case of a Rapid Reaction

    Science.gov (United States)

    Nefedov, N. N.; Nikulin, E. I.

    2018-01-01

    A singularly perturbed periodic in time problem for a parabolic reaction-diffusion equation in a two-dimensional domain is studied. The case of existence of an internal transition layer under the conditions of balanced and unbalanced rapid reaction is considered. An asymptotic expansion of a solution is constructed. To justify the asymptotic expansion thus constructed, the asymptotic method of differential inequalities is used. The Lyapunov asymptotic stability of a periodic solution is investigated.

  9. Effect of Different Irrigation Solutions on the Colour Stability of Three Calcium Silicate-Based Materials

    Directory of Open Access Journals (Sweden)

    Sobhnamayan F

    2017-06-01

    Full Text Available Abstract: Statement of Problem: Previous studies have shown discoloration of mineral trioxide aggregate (MTA in contact with root canal irrigation solutions. However, there are limited data on colour stability of other calcium silicate–based materials (CSMs. Objectives: This in vitro study aimed to evaluate the colour stability of three CSMs in contact with different irrigation solutions. Materials and Methods: Three CSMs including White MTA (wMTA Angelus, calcium enriched mixture (CEM, and Biodentine were assessed in this study. Forty five samples of each material were mixed according to the manufactures’ instructions and then placed in silicone tubes. After 24 hours, the materials were removed from the moulds and 9 samples of each material left dry or immersed in normal saline, 5% sodium hypochlorite (NaOCL, 2% chlorhexidinegluconate (CHX, or 17%EDTA for 24 hours. Colour changes were measured with a spectrophotometer. Data were evaluated with 2-way analysis of variance, one way analysis of variance and Tukey post hoc tests. Results: The highest discoloration of all materials was observed after contact with CHX. In the MTA Angelus and CEM cement groups, significant differences were observed between CHX and NaOCl and also between these two irrigants with the other three irrigants (p < 0.05. In the Biodentine group, CHX created statistically significant discoloration compared to other irrigants (p < 0.05. Only wMTA Angelus showed a significantly higher discoloration in contact with EDTA compared to normal saline and dry condition (p < 0.05. wMTA Angelus showed a significantly higher colour change compared with CEM cement and Biodentine after contact with NaOCl, CHX, and EDTA (p < 0.05. Conclusions: The contact of wMTA, CEM cement, and Biodentine with CHX should be avoided because this leads to severe discoloration. Contact with sodium hypochlorite also leads to discoloration of wMTA and CEM cements. Among of the three tested materials, w

  10. Effect of staining solutions and repolishing on color stability of direct composites

    Directory of Open Access Journals (Sweden)

    Fabrício Mariano Mundim

    2010-06-01

    Full Text Available OBJECTIVES: The purpose of this study was to assess the color change of three types of composite resins exposed to coffee and cola drink, and the effect of repolishing on the color stability of these composites after staining. MATERIALS AND METHODS: Fifteen specimens (15 mm diameter and 2 mm thick were fabricated from microhybrid (Esthet-X; Dentsply and Filtek Z-250; 3M ESPE and high-density hybrid (Surefil; Dentsply composites, and were finished and polished with aluminum oxide discs (Sof-Lex; 3M ESPE. Color of the specimens was measured according to the CIE L*a*b* system in a refection spectrophotometer (PCB 6807; BYK Gardner. After baseline color measurements, 5 specimens of each resin were immersed in different staining solutions for 15 days: G1 - distilled water (control, G2 - coffee, G3 - cola soft drink. Afterwards, new color measurement was performed and the specimens were repolished and submitted to new color reading. Color stability was determined by the difference (ΔE between the coordinates L*, a*, and b* obtained from the specimens before and after immersion into the solutions and after repolishing. RESULTS: There was no statistically signifcant difference (ANOVA, Tukey's test; p>0.05 among the ΔE values for the different types of composites after staining or repolishing. For all composite resins, coffee promoted more color change (ΔE>3.3 than distilled water and the cola soft drink. After repolishing, the ΔE values of the specimens immersed in coffee decreased to clinically acceptable values (ΔE<3.3, but remained signifcantly higher than those of the other groups. CONCLUSIONS: No signifcant difference was found among composite resins or between color values before and after repolishing of specimens immersed in distilled water and cola. Immersing specimens in coffee caused greater color change in all types of composite resins tested in this study and repolishing contributed to decrease staining to clinically acceptable

  11. On stability of exponential cosmological solutions with non-static volume factor in the Einstein-Gauss-Bonnet model

    International Nuclear Information System (INIS)

    Ivashchuk, V.D.

    2016-01-01

    A (n + 1)-dimensional gravitational model with Gauss-Bonnet term and a cosmological constant term is considered. When ansatz with diagonal cosmological metrics is adopted, the solutions with an exponential dependence of the scale factors, a i ∝ exp(v i t), i = 1,.., n, are analyzed for n > 3. We study the stability of the solutions with non-static volume factor, i.e. K(v) = sum k=1 n v k ≠ 0. We prove that under a certain restriction R imposed solutions with K(v) > 0 are stable, while solutions with K(v) < 0 are unstable. Certain examples of stable solutions are presented. We show that the solutions with v 1 = v 2 = v 3 = H > 0 and zero variation of the effective gravitational constant are stable if the restriction R is obeyed. (orig.)

  12. On stability of exponential cosmological solutions with non-static volume factor in the Einstein-Gauss-Bonnet model

    Energy Technology Data Exchange (ETDEWEB)

    Ivashchuk, V.D. [VNIIMS, Center for Gravitation and Fundamental Metrology, Moscow (Russian Federation); Peoples' Friendship University of Russia (RUDN University), Institute of Gravitation and Cosmology, Moscow (Russian Federation)

    2016-08-15

    A (n + 1)-dimensional gravitational model with Gauss-Bonnet term and a cosmological constant term is considered. When ansatz with diagonal cosmological metrics is adopted, the solutions with an exponential dependence of the scale factors, a{sub i} ∝ exp(v{sup i}t), i = 1,.., n, are analyzed for n > 3. We study the stability of the solutions with non-static volume factor, i.e. K(v) = sum {sub k=1}{sup n} v{sup k} ≠ 0. We prove that under a certain restriction R imposed solutions with K(v) > 0 are stable, while solutions with K(v) < 0 are unstable. Certain examples of stable solutions are presented. We show that the solutions with v{sup 1} = v{sup 2} = v{sup 3} = H > 0 and zero variation of the effective gravitational constant are stable if the restriction R is obeyed. (orig.)

  13. Color stabilities of calcium silicate-based materials in contact with different irrigation solutions.

    Science.gov (United States)

    Keskin, Cangul; Demiryurek, Ebru Ozsezer; Ozyurek, Taha

    2015-03-01

    Mineral trioxide aggregate (MTA) has been reported to cause tooth discoloration when applied in the esthetic zone. A previous study has shown discoloration of MTA in contact with root canal irrigation solutions. Moreover, there are limited data on color stability of novel calcium silicate-based materials. This study aimed to evaluate color changes of 4 calcium silicate-based materials in contact with different irrigation solutions. ProRoot white MTA (Dentsply Tulsa Dental, Johnson City, TN), white MTA Angelus (Angelus Solucoes Odontologicas, Londrina, Brazil), Biodentine (Septodont, Saint Maur des Fosses, France), and BioAggregate (Innovative Bioceramix, Vancouver, BC, Canada) samples were assessed. Materials were mixed according to the manufacturers' instructions. Cylindric samples (10-mm diameter and 2-mm height) were obtained by curing in molds for each material's setting time at 100% humidity and 37°C. Each specimen was immersed in 5% sodium hypochlorite, 2% chlorhexidine gluconate, or distilled water for 24 hours. Color changes were measured with a spectrophotometer. Data were analyzed by using 2-way analysis of variance and post hoc Bonferroni tests. All materials exhibited clinically perceptible discoloration when immersed in sodium hypochlorite and chlorhexidine gluconate. ProRoot white MTA showed a statistically significant difference from Bioaggregate, Biodentine, and white MTA Angelus. Distilled water did not cause clinically perceptible discoloration of any material. In esthetically critical regions, compounds free of bismuth oxide, Biodentine, and BioAggregate can be considered as alternatives to MTA. However, all calcium silicate-based materials exhibited clinically perceptible color changes. Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  14. Long time enzyme replacement therapy stabilizes obstructive lung disease and alters peripheral immune cell subsets in Fabry patients.

    Science.gov (United States)

    Odler, Balázs; Cseh, Áron; Constantin, Tamás; Fekete, György; Losonczy, György; Tamási, Lilla; Benke, Kálmán; Szilveszter, Bálint; Müller, Veronika

    2017-11-01

    Fabry disease is an X-linked lysosomal storage disorder, causing accumulation of globotriaosylceramid in different organs. Glycolipids are activators of different immune cell subsets the resulting inflammation is responsible for organ damage. Pulmonary involvement leads to airway inflammation; however, data on severity, as well as the effect of enzyme replacement therapy on lung function parameters and changes in peripheral immune cell subsets on lung involvement are sparse. Seven Fabry patients and four carriers underwent detailed clinical examinations screening for pulmonary manifestations. Repetitive measurements were performed on five patients on ERT (average follow-up 5 years). Patients with Fabry disease and control volunteers were included into peripheral blood cell measurements. Lung involvement was present in all patients. Symptoms suggestive for lung disease were mild, however, obstructive ventilatory disorder, dominantly affecting small airways accompanied by hyperinflation was demonstrated in all affected patients. ERT resulted in small improvement of FEV1 in most treated patients. Decreased ratio of myeloid DC, Th17 cells while increase in T helper (Th)1 cells, and no change in Th2 and regulatory T (Treg) cells were detected in Fabry patients. Fabry disease results mainly in mild symptoms related to lung involvement, characterized by moderate non-reversible obstructive ventilatory disorder. Stabilization of airway obstruction during follow-up was observed using ERT in most patients, emphasizing the importance of this treatment in respect of pulmonary manifestations. Changes of immune cell subsets in the peripheral blood might play a role in inflammatory process, including small airways in Fabry patient's lung. © 2016 John Wiley & Sons Ltd.

  15. The ubiquitin-conjugating enzyme UBE2O modulates c-Maf stability and induces myeloma cell apoptosis

    Directory of Open Access Journals (Sweden)

    Yujia Xu

    2017-07-01

    Full Text Available Abstract Background UBE2O is proposed as a ubiquitin-conjugating enzyme, but its function was largely unknown. Methods Mass spectrometry was applied to identify c-Maf ubiquitination-associated proteins. Immunoprecipitation was applied for c-Maf and UBE2O interaction. Immunoblotting was used for Maf protein stability. Luciferase assay was used for c-Maf transcriptional activity. Lentiviral infections were applied for UBE2O function in multiple myeloma (MM cells. Flow cytometry and nude mice xenografts were applied for MM cell apoptosis and tumor growth assay, respectively. Results UBE2O was found to interact with c-Maf, a critical transcription factor in MM, by the affinity purification/tandem mass spectrometry assay and co-immunoprecipitation assays. Subsequent studies showed that UBE2O mediated c-Maf polyubiquitination and degradation. Moreover, UBE2O downregulated the transcriptional activity of c-Maf and the expression of cyclin D2, a typical gene modulated by c-Maf. DNA microarray revealed that UBE2O was expressed in normal bone marrow cells but downregulated in MGUS, smoldering MM and MM cells, which was confirmed by RT-PCR in primary MM cells, suggesting its potential role in myeloma pathophysiology. When UBE2O was restored, c-Maf protein in MM cells was significantly decreased and MM cells underwent apoptosis. Furthermore, the human MM xenograft in nude mice showed that re-expression of UBE2O delayed the growth of myeloma xenografts in nude mice in association with c-Maf downregulation and activation of the apoptotic pathway. Conclusions UBE2O mediates c-Maf polyubiquitination and degradation, induces MM cell apoptosis, and suppresses myeloma tumor growth, which provides a novel insight in understanding myelomagenesis and UBE2O biology.

  16. The Steroidogenic Enzyme AKR1C3 Regulates Stability of the Ubiquitin Ligase Siah2 in Prostate Cancer Cells.

    Science.gov (United States)

    Fan, Lingling; Peng, Guihong; Hussain, Arif; Fazli, Ladan; Guns, Emma; Gleave, Martin; Qi, Jianfei

    2015-08-21

    Re-activation of androgen receptor (AR) activity is the main driver for development of castration-resistant prostate cancer. We previously reported that the ubiquitin ligase Siah2 enhanced AR transcriptional activity and prostate cancer cell growth. Among the genes we found to be regulated by Siah2 was AKR1C3, which encodes a key androgen biosynthetic enzyme implicated in castration-resistant prostate cancer development. Here, we found that Siah2 inhibition in CWR22Rv1 prostate cancer cells decreased AKR1C3 expression as well as intracellular androgen levels, concomitant with inhibition of cell growth in vitro and in orthotopic prostate tumors. Re-expression of either wild-type or catalytically inactive forms of AKR1C3 partially rescued AR activity and growth defects in Siah2 knockdown cells, suggesting a nonenzymatic role for AKR1C3 in these outcomes. Unexpectedly, AKR1C3 re-expression in Siah2 knockdown cells elevated Siah2 protein levels, whereas AKR1C3 knockdown had the opposite effect. We further found that AKR1C3 can bind Siah2 and inhibit its self-ubiquitination and degradation, thereby increasing Siah2 protein levels. We observed parallel expression of Siah2 and AKR1C3 in human prostate cancer tissues. Collectively, our findings identify a new role for AKR1C3 in regulating Siah2 stability and thus enhancing Siah2-dependent regulation of AR activity in prostate cancer cells. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  17. First-principles thermodynamics study of phase stability in inorganic halide perovskite solid solutions

    Science.gov (United States)

    Bechtel, Jonathon S.; Van der Ven, Anton

    2018-04-01

    Halide substitution gives rise to a tunable band gap as a function of composition in halide perovskite materials. However, photoinduced phase segregation, observed at room temperature in mixed halide A Pb (IxBr1-x) 3 systems, limits open circuit voltages and decreases photovoltaic device efficiencies. We investigate equilibrium phase stability of orthorhombic P n m a γ -phase CsM (XxY1-x) 3 perovskites where M is Pb or Sn, and X and Y are Br, Cl, or I. Finite-temperature phase diagrams are constructed using a cluster expansion effective Hamiltonian parameterized from first-principles density-functional-theory calculations. Solid solution phases for CsM (IxBr1-x) 3 and CsM (BrxCl1-x) 3 are predicted to be stable well below room temperature while CsM (IxCl1-x) 3 systems have miscibility gaps that extend above 400 K. The height of the miscibility gap correlates with the difference in volume between end members. Also layered ground states are found on the convex hull at x =2 /3 for CsSnBr2Cl ,CsPbI2Br , and CsPbBrCl2. The impact of these ground states on the finite temperature phase diagram is discussed in the context of the experimentally observed photoinduced phase segregation.

  18. STABILITY OF DOW CORNING Q2-3183A ANTIFOAM IN IRRADIATED HYDROXIDE SOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    White, T; Crawford, C; Burket, P; Calloway, B

    2009-10-19

    Researchers at the Savannah River National Laboratory (SRNL) examined the stability of Dow Corning Q2-3183A antifoam to radiation and aqueous hydroxide solutions. Initial foam control studies with Hanford tank waste showed the antifoam reduced foaming. The antifoam was further tested using simulated Hanford tank waste spiked with antifoam that was heated and irradiated (2.1 x 10{sup 4} rad/h) at conditions (90 C, 3 M NaOH, 8 h) expected in the processing of radioactive waste through the Waste Treatment and Immobilization Plant (WTP) at Hanford. After irradiation, the concentration of the major polymer components polydimethylsiloxane (PDMS) and polypropylene glycol (PPG) in the antifoam was determined by gel permeation chromatography (GPC). No loss of the major polymer components was observed after 24 h and only 15 wt% loss of PDMS was reported after 48 h. The presence of degradation products were not observed by gas chromatography (GC), gas chromatography mass spectrometry (GCMS) or high performance liquid chromatography mass spectrometry (HPLC-MS). G values were calculated from the GPC analysis and tabulated. The findings indicate the antifoam is stable for 24 h after exposure to gamma radiation, heat, and alkaline simulated waste.

  19. Stability of midazolam hydrochloride injection 1-mg/mL solutions in polyvinyl chloride and polyolefin bags.

    Science.gov (United States)

    Karlage, Kelly; Earhart, Zachary; Green-Boesen, Kelly; Myrdal, Paul B

    2011-08-15

    The stability of midazolam hydrochloride injection 1-mg/mL solutions in polyvinyl chloride (PVC) and polyolefin bags under varying conditions was evaluated. Triplicate solutions of midazolam hydrochloride 1-mg/mL were prepared in polyolefin and PVC i.v. bags by diluting midazolam hydrochloride injection 5 mg/mL with 5% dextrose injection. Bags were then stored under refrigeration (3-4 °C), exposed to light at room temperature (20-25 °C), or protected from light in amber bags at room temperature. Samples were taken immediately after preparation (day 0) and on days 1, 2, 3, 6, 13, 20, and 27 for analysis with a stability-indicating high-performance liquid chromatography assay in order to determine solution concentration. Stability was defined as retention of at least 90% of the initial drug concentration. The pH of each solution was also measured weekly. Sterility of the i.v. bags was determined at the end of the study by microbiological testing with culture in growth media. Differences in concentrations under the various storage conditions and bags used were analyzed using analysis of variance. All solutions retained over 98% of the initial midazolam hydrochloride concentration, with no statistically significant (p ≥ 0.05) change in concentration over the four-week period. Stability was not affected by temperature, exposure to light, or bag type. The pH of all solutions remained between 3.2 and 3.4 throughout the study. Sterility after 28 days was retained. Midazolam hydrochloride 1-mg/mL solutions diluted in 5% dextrose injection remained stable over 27 days in both polyolefin and PVC i.v. bags, regardless of storage condition.

  20. Suzuki coupling reactions catalyzed by poly(N-ethyl-4-vinylpyridinium bromide stabilized palladium nanoparticles in aqueous solution

    Directory of Open Access Journals (Sweden)

    2008-04-01

    Full Text Available InIn this work, it was investigated to use of poly(N-ethyl-4-vinylpyridinium bromide stabilized palladium nanoparticles in the Suzuki reaction between phenylboronic acid and aryl halides in aqueous solution. The nanoparticles were isolated and re-used several times with low loss of activity.

  1. Existence and Asymptotic Stability of Solutions of a Functional Integral Equation via a Consequence of Sadovskii’s Theorem

    Directory of Open Access Journals (Sweden)

    Agnieszka Chlebowicz

    2014-01-01

    Full Text Available Using the technique of measures of noncompactness and, in particular, a consequence of Sadovskii’s fixed point theorem, we prove a theorem about the existence and asymptotic stability of solutions of a functional integral equation. Moreover, in order to illustrate our results, we include one example and compare our results with those obtained in other papers appearing in the literature.

  2. On the numerical stability of spline function approximations to solutions of Volterra integral equations of the second kind

    CERN Document Server

    El-Tom, M E A

    1974-01-01

    A procedure, using spine functions of degree m, deficiency k-1, for obtaining approximate solutions to nonlinear Volterra integral equations of the second kind is presented. The paper is an investigation of the numerical stability of the procedure for various values of m and k. (5 refs).

  3. A new strategy to stabilize oxytocin in aqueous solutions : I. The effects of divalent metal ions and citrate buffer

    NARCIS (Netherlands)

    Avanti, Christina; Amorij, Jean-Pierre; Setyaningsih, Dewi; Hawe, Andrea; Jiskoot, Wim; Visser, Jan; Kedrov, Alexej; Driessen, Arnold J. M.; Hinrichs, Wouter L. J.; Frijlink, Henderik W.

    In the current study, the effect of metal ions in combination with buffers (citrate, acetate, pH 4.5) on the stability of aqueous solutions of oxytocin was investigated. Both monovalent metal ions (Na+and K+) and divalent metal ions (Ca2+, Mg2+, and Zn2+) were tested all as chloride salts. The

  4. Global Exponential Stability of Positive Almost Periodic Solutions for a Fishing Model with a Time-Varying Delay

    Directory of Open Access Journals (Sweden)

    Hong Zhang

    2014-01-01

    Full Text Available This paper is concerned with a nonautonomous fishing model with a time-varying delay. Under proper conditions, we employ a novel argument to establish a criterion on the global exponential stability of positive almost periodic solutions of the model with almost periodic coefficients and delays. Moreover, an example and its numerical simulation are given to illustrate the main results.

  5. Effects of Metal Ions on Stability and Activity of Hyperthermophilic Pyrolysin and Further Stabilization of This Enzyme by Modification of a Ca2+-Binding Site

    OpenAIRE

    Zeng, Jing; Gao, Xiaowei; Dai, Zheng; Tang, Bing; Tang, Xiao-Feng

    2014-01-01

    Pyrolysin is an extracellular subtilase produced by the marine hyperthermophilic archaeon Pyrococcus furiosus. This enzyme functions at high temperatures in seawater, but little is known about the effects of metal ions on the properties of pyrolysin. Here, we report that the supplementation of Na+, Ca2+, or Mg2+ salts at concentrations similar to those in seawater destabilizes recombinant pyrolysin but leads to an increase in enzyme activity. The destabilizing effect of metal ions on pyrolysi...

  6. Stabilization of the ADP/metaphosphate intermediate during ATP hydrolysis in pre-power stroke myosin: quantitative anatomy of an enzyme.

    Science.gov (United States)

    Kiani, Farooq Ahmad; Fischer, Stefan

    2013-12-06

    It has been proposed recently that ATP hydrolysis in ATPase enzymes proceeds via an initial intermediate in which the dissociated γ-phosphate of ATP is bound in the protein as a metaphosphate (PγO3(-)). A combined quantum/classical analysis of this dissociated nucleotide state inside myosin provides a quantitative understanding of how the enzyme stabilizes this unusual metaphosphate. Indeed, in vacuum, the energy of the ADP(3-) · PγO3(-) · Mg(2+) complex is much higher than that of the undissociated ATP(4-). The protein brings it to a surprisingly low value. Energy decomposition reveals how much each interaction in the protein stabilizes the metaphosphate state; backbone peptides of the P-loop contribute 50% of the stabilization energy, and the side chain of Lys-185(+) contributes 25%. This can be explained by the fact that these groups make strong favorable interactions with the α- and β-phosphates, thus favoring the charge distribution of the metaphosphate state over that of the ATP state. Further stabilization (16%) is achieved by a hydrogen bond between the backbone C=O of Ser-237 (on loop Switch-1) and a water molecule perfectly positioned to attack the PγO3(-) in the subsequent hydrolysis step. The planar and singly negative PγO3(-) is a much better target for the subsequent nucleophilic attack by a negatively charged OH(-) than the tetrahedral and doubly negative PγO4(2-) group of ATP. Therefore, we argue that the present mechanism of metaphosphate stabilization is common to the large family of nucleotide-hydrolyzing enzymes. Methodologically, this work presents a computational approach that allows us to obtain a truly quantitative conception of enzymatic strategy.

  7. The stability of DLC film on nitrided CoCrMo alloy in phosphate buffer solution

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, T.F.; Liu, B.; Wu, B.J.; Liu, J.; Sun, H.; Leng, Y.X., E-mail: yxleng@263.net; Huang, N.

    2014-07-01

    CoCrMo alloy is often used as the material for metal artificial joint, but metal debris and metal ions are the main concern on tissue inflammation or tissue proliferation for metal prosthesis. In this paper, nitrogen ion implantation and diamond like carbon (DLC) film composite treatment was used to reduce the wear and ion release of biomedical CoCrMo substrate. The mechanical properties and stability of N-implanted/DLC composite layer in phosphate buffer solution (PBS) was evaluated to explore the full potential of N-implanted/DLC composite layer as an artificial joint surface modification material. The results showed that the DLC film on N implanted CoCrMo (N-implanted/DLC composite layer) had the higher surface hardness and wear resistance than the DLC film on virgin CoCrMo alloy, which was resulted from the strengthen effect of the N implanted layer on CoCrMo alloy. After 30 days immersion in PBS, the structure of DLC film on virgin CoCrMo or on N implanted CoCrMo had no visible change. But the adhesion and corrosion resistance of DLC on N implanted CoCrMo (N-implanted/DLC composite layer) was weakened due to the dissolution of the N implanted layer after 30 days immersion in PBS. The adhesion reduction of N-implanted/DLC composite layer was adverse for in vivo application in long term. So researcher should be cautious to use N implanted layer as an inter-layer for increasing CoCrMo alloy load carrying capacity in vivo environment.

  8. Stability of the neurotensin receptor NTS1 free in detergent solution and immobilized to affinity resin.

    Directory of Open Access Journals (Sweden)

    Jim F White

    2010-09-01

    Full Text Available Purification of recombinant membrane receptors is commonly achieved by use of an affinity tag followed by an additional chromatography step if required. This second step may exploit specific receptor properties such as ligand binding. However, the effects of multiple purification steps on protein yield and integrity are often poorly documented. We have previously reported a robust two-step purification procedure for the recombinant rat neurotensin receptor NTS1 to give milligram quantities of functional receptor protein. First, histidine-tagged receptors are enriched by immobilized metal affinity chromatography using Ni-NTA resin. Second, remaining contaminants in the Ni-NTA column eluate are removed by use of a subsequent neurotensin column yielding pure NTS1. Whilst the neurotensin column eluate contained functional receptor protein, we observed in the neurotensin column flow-through misfolded NTS1.To investigate the origin of the misfolded receptors, we estimated the amount of functional and misfolded NTS1 at each purification step by radio-ligand binding, densitometry of Coomassie stained SDS-gels, and protein content determination. First, we observed that correctly folded NTS1 suffers damage by exposure to detergent and various buffer compositions as seen by the loss of [(3H]neurotensin binding over time. Second, exposure to the neurotensin affinity resin generated additional misfolded receptor protein.Our data point towards two ways by which misfolded NTS1 may be generated: Damage by exposure to buffer components and by close contact of the receptor to the neurotensin affinity resin. Because NTS1 in detergent solution is stabilized by neurotensin, we speculate that the occurrence of aggregated receptor after contact with the neurotensin resin is the consequence of perturbations in the detergent belt surrounding the NTS1 transmembrane core. Both effects reduce the yield of functional receptor protein.

  9. Effects of intermolecular interactions on the stability of carbon nanotube–gold nanoparticle conjugates in solution

    Directory of Open Access Journals (Sweden)

    Konczak L

    2016-11-01

    Full Text Available Lukasz Konczak,1 Jolanta Narkiewicz-Michalek,2 Giorgia Pastorin,3 Tomasz Panczyk1 1Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Cracow, 2Department of Chemistry, Maria Curie-Sklodowska University, Lublin, Poland; 3Department of Pharmacy, National University of Singapore, Singapore Abstract: This work deals with the role of intermolecular interactions in the stability of a carbon nanotube (CNT capped by functionalized gold nanoparticles (AuNPs. The importance of such a system is due to its potential application as a pH-controlled drug carrier. Our preliminary experimental studies showed that fabrication of such a nanobottle/nanocontainer is feasible and it is possible to encapsulate the anticancer drug cisplatin inside the inner space of a CNT and seal its ends by functionalized AuNPs. The expected behavior, that is, detachment of AuNPs at acidic pH and the release of cisplatin, was, however, not observed. On the other hand, our theoretical studies of chemically identical system led to the conclusion that the release of cisplatin at acidic pH should be observed. Therefore, in this work, a deeper theoretical analysis of various factors that could be responsible for the disagreement between experimental and theoretical results were performed. The study found that the major factor is a large dispersion interaction component acting between CNT and AuNP in solution in the case of the experimental system. This factor can be controlled to some extent by tuning the system size or the ratio between AuNP diameter and CNT diameter. Thus, such kind of a pH-sensitive drug carrier is still of great interest, but its structural parameters need to be properly adjusted. Keywords: hydrazone bond, drug delivery, dispersion interactions, cisplatin, acidic pH

  10. Solution-processed, nanostructured hybrid solar cells with broad spectral sensitivity and stability.

    Science.gov (United States)

    Zhou, Renjia; Zheng, Ying; Qian, Lei; Yang, Yixing; Holloway, Paul H; Xue, Jiangeng

    2012-06-07

    Hybrid organic-inorganic solar cells, as an alternative to all-organic solar cells, have received significant attention for their potential advantages in combining the solution-processability and versatility of organic materials with high charge mobility and environmental stability of inorganic semiconductors. Here we report efficient and air-stable hybrid organic-inorganic solar cells with broad spectral sensitivity based on a low-gap polymer poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) and spherical CdSe nanoparticles. The solvents used for depositing the hybrid PCPDTBT:CdSe active layer were shown to strongly influence the film morphology, and subsequently the photovoltaic performance of the resulted solar cells. Appropriate post-deposition annealing of the hybrid film was also shown to improve the solar cell efficiency. The inclusion of a thin ZnO nanoparticle layer between the active layer and the metal cathode leads to a significant increase in device efficiency especially at long wavelengths, due to a combination of optical and electronic effects including more optimal light absorption in the active layer and elimination of unwanted hole leakage into the cathode. Overall, maximum power conversion efficiencies up to 3.7 ± 0.2% and spectral sensitivity extending above 800 nm were achieved in such PCPDTBT:CdSe nanosphere hybrid solar cells. Furthermore, the devices with a ZnO nanoparticle layer retained ∼70% of the original efficiency after storage under ambient laboratory conditions for over 60 days without any encapsulation.

  11. Changes in the color, chemical stability and antioxidant capacity of thermally treated anthocyanin aqueous solution over storage.

    Science.gov (United States)

    Sui, Xiaonan; Bary, Solène; Zhou, Weibiao

    2016-02-01

    Many anthocyanin-containing foods are thermally processed to ensure their safety, and stored for some time before being consumed. However, the combination of thermal processing and subsequent storage has a significant impact on anthocyanins. This study aimed to investigate the color, chemical stability, and antioxidant capacity of thermally treated anthocyanin aqueous solutions during storage at 4, 25, 45, and 65 °C, respectively. Anthocyanin aqueous solutions were thermally treated before storage. Results showed that the degradation rate of anthocyanins in aqueous solutions was much faster than those in real food. The color of the anthocyanin aqueous solutions changed dramatically during storage. The anthocyanin aqueous solutions stored at 4 °C showed the best chemical stability. Interestingly, the antioxidant capacity of the anthocyanin aqueous solutions stored at lower temperatures remained the same; however, the antioxidant capacity of those thermally treated at 120 or 140 °C and stored at 45 or 65 °C significantly decreased. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. High Pressure Homogenization of Porcine Pepsin Protease: Effects on Enzyme Activity, Stability, Milk Coagulation Profile and Gel Development.

    Directory of Open Access Journals (Sweden)

    Bruno Ricardo de Castro Leite Júnior

    Full Text Available This study investigated the effect of high pressure homogenization (HPH (up to 190 MPa on porcine pepsin (proteolytic and milk-clotting activities, and the consequences of using the processed enzyme in milk coagulation and gel formation (rheological profile, proteolysis, syneresis, and microstructure. Although the proteolytic activity (PA was not altered immediately after the HPH process, it reduced during enzyme storage, with a 5% decrease after 60 days of storage for samples obtained with the enzyme processed at 50, 100 and 150 MPa. HPH increased the milk-clotting activity (MCA of the enzyme processed at 150 MPa, being 15% higher than the MCA of non-processed samples after 60 days of storage. The enzyme processed at 150 MPa produced faster aggregation and a more consistent milk gel (G' value 92% higher after 90 minutes when compared with the non-processed enzyme. In addition, the gels produced with the enzyme processed at 150 MPa showed greater syneresis after 40 minutes of coagulation (forming a more compact protein network and lower porosity (evidenced by confocal microscopy. These effects on the milk gel can be associated with the increment in MCA and reduction in PA caused by the effects of HPH on pepsin during storage. According to the results, HPH stands out as a process capable of changing the proteolytic characteristics of porcine pepsin, with improvements on the milk coagulation step and gel characteristics. Therefore, the porcine pepsin submitted to HPH process can be a suitable alternative for the production of cheese.

  13. High Pressure Homogenization of Porcine Pepsin Protease: Effects on Enzyme Activity, Stability, Milk Coagulation Profile and Gel Development.

    Science.gov (United States)

    Leite Júnior, Bruno Ricardo de Castro; Tribst, Alline Artigiani Lima; Cristianini, Marcelo

    2015-01-01

    This study investigated the effect of high pressure homogenization (HPH) (up to 190 MPa) on porcine pepsin (proteolytic and milk-clotting activities), and the consequences of using the processed enzyme in milk coagulation and gel formation (rheological profile, proteolysis, syneresis, and microstructure). Although the proteolytic activity (PA) was not altered immediately after the HPH process, it reduced during enzyme storage, with a 5% decrease after 60 days of storage for samples obtained with the enzyme processed at 50, 100 and 150 MPa. HPH increased the milk-clotting activity (MCA) of the enzyme processed at 150 MPa, being 15% higher than the MCA of non-processed samples after 60 days of storage. The enzyme processed at 150 MPa produced faster aggregation and a more consistent milk gel (G' value 92% higher after 90 minutes) when compared with the non-processed enzyme. In addition, the gels produced with the enzyme processed at 150 MPa showed greater syneresis after 40 minutes of coagulation (forming a more compact protein network) and lower porosity (evidenced by confocal microscopy). These effects on the milk gel can be associated with the increment in MCA and reduction in PA caused by the effects of HPH on pepsin during storage. According to the results, HPH stands out as a process capable of changing the proteolytic characteristics of porcine pepsin, with improvements on the milk coagulation step and gel characteristics. Therefore, the porcine pepsin submitted to HPH process can be a suitable alternative for the production of cheese.

  14. Controlling Microstructure of Yttria-Stabilized Zirconia Prepared from Suspensions and Solutions by Plasma Spraying with High Feed Rates.

    Czech Academy of Sciences Publication Activity Database

    Mušálek, Radek; Medřický, Jan; Tesař, Tomáš; Kotlan, Jiří; Pala, Zdeněk; Lukáč, František; Illková, Ksenia; Hlína, Michal; Chráska, Tomáš; Sokołowski, P.; Curry, N.

    2017-01-01

    Roč. 26, č. 8 (2017), s. 1787-1803 ISSN 1059-9630 R&D Projects: GA ČR GA15-12145S Institutional support: RVO:61389021 Keywords : hybrid plasma torch * microstructure * solution * precursor spraying * suspension spraying * thermal barrier * coatings (TBCs) * water-stabilized plasma * yttria-stabilized zirconia (YSZ) Subject RIV: JK - Corrosion ; Surface Treatment of Materials OBOR OECD: Coating and films Impact factor: 1.488, year: 2016 https://link.springer.com/article/10.1007/s11666-017-0622-x

  15. Biocatalytic Single Enzyme Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Grate, Jay W.; Kim, Jungbae

    2004-03-31

    As an innovative way of enzyme stabilization, we recently developed a new enzyme composite of nano-meter scale that we call "single-enzyme nanoparticles (SENs)" (9). Each enzyme molecule is surrounded with a porous composite organic/inorganic network of less than a few nanometers think. This approach represents a new type of enzyme-containing nanostructure. In experiments with perotease (chymotrypsin, CT), the activity of single enzyme nanoparticle form of the enzyme was greatly stabilized compared to the free form, without imposing a serious mass transfer limitation of substrates. In this chapter we will describe the synthesis, characterization and catalytic activity of the new SENs.

  16. Existence and global exponential stability of periodic solution of memristor-based BAM neural networks with time-varying delays.

    Science.gov (United States)

    Li, Hongfei; Jiang, Haijun; Hu, Cheng

    2016-03-01

    In this paper, we investigate a class of memristor-based BAM neural networks with time-varying delays. Under the framework of Filippov solutions, boundedness and ultimate boundedness of solutions of memristor-based BAM neural networks are guaranteed by Chain rule and inequalities technique. Moreover, a new method involving Yoshizawa-like theorem is favorably employed to acquire the existence of periodic solution. By applying the theory of set-valued maps and functional differential inclusions, an available Lyapunov functional and some new testable algebraic criteria are derived for ensuring the uniqueness and global exponential stability of periodic solution of memristor-based BAM neural networks. The obtained results expand and complement some previous work on memristor-based BAM neural networks. Finally, a numerical example is provided to show the applicability and effectiveness of our theoretical results. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Zirconium-cerin solid solutions: thermodynamic model and thermal stability at high temperature; Solutions solides de zirconium dans la cerine: modele thermodynamique et stabilite thermique a haute temperature

    Energy Technology Data Exchange (ETDEWEB)

    Janvier, C.

    1998-04-02

    The oxides-gaseous dioxygen equilibria and the textural thermal stability of six zirconium-cerin solutions Ce{sub 1-x}Zr{sub x}O{sub 2} (0solutions and the gaseous oxygen by thermal gravimetric analysis at 600 degrees Celsius has shown that these solutions have not a ideal behaviour. A thermodynamic model where the point defects of solutions are included describe them the best. It becomes then possible to know the variations of the concentrations of the point defects in terms of temperature, oxygen pressure and zirconium concentration. A kinetic study (by calcination at 950 degrees Celsius of the solid solutions) of the specific surface area decrease has revealed a minima (0

  18. A DFT study of the stability of SIAs and small SIA clusters in the vicinity of solute atoms in Fe

    Science.gov (United States)

    Becquart, C. S.; Ngayam Happy, R.; Olsson, P.; Domain, C.

    2018-03-01

    The energetics, defect volume and magnetic properties of single SIAs and small SIA clusters up to size 6 have been calculated by DFT for different configurations like the parallel 〈110〉 dumbbell, the non parallel 〈110〉 dumbbell and the C15 structure. The most stable configurations of each type have been further analyzed to determine the influence on their stability of various solute atoms (Ti, V, Cr, Mn, Co, Ni, Cu, Mo, W, Pd, Al, Si, P), relevant for steels used under irradiation. The results show that the presence of solute atoms does not change the relative stability order among SIA clusters. The small SIA clusters investigated can bind to both undersized and oversized solutes. Several descriptors have been considered to derive interesting trends from results. It appears that the local atomic volume available for the solute is the main physical quantity governing the binding energy evolution, whatever the solute type (undersized or oversized) and the cluster configuration (size and type).

  19. Existence and Stability of Solutions for Hadamard-Stieltjes Fractional Integral Equations

    Directory of Open Access Journals (Sweden)

    Saïd Abbas

    2015-01-01

    Full Text Available We give some existence results and Ulam stability results for a class of Hadamard-Stieltjes integral equations. We present two results: the first one is an existence result based on Schauder’s fixed point theorem and the second one is about the generalized Ulam-Hyers-Rassias stability.

  20. Effect of five staining solutions on the colour stability of two acrylics and three composite resins based provisional restorations.

    Science.gov (United States)

    Türker, Sebnem Begüm; Koçak, Ayşe; Aktepe, Esra

    2006-09-01

    The effect of coffee, tea, coca-cola, orange-juice and red wine on the colour stability of acrylic and composite based provisional materials were evaluated. Two acrylic resins and three composite resins were studied. 48 standardized specimens for each provisional material were prepared. Each group was divided into 6 subgroups. Specimens from each group were immersed in staining solutions at room temperature for 30 days. Red wine and tea caused the most significant colour changes and orange juice showed the least significant colour changes. deltaE of all of the provisional restorations materials was changed after the immersion in all of the staining solutions during the experimental process.

  1. Engineering solutions to the long-term stabilization and isolation of uranium mill tailings in the United States

    International Nuclear Information System (INIS)

    Sanders, D.R.; Lommler, J.C.

    1995-01-01

    Engineering solutions to the safe and environmentally protective disposal and isolation of uranium mill tailings in the US include many factors. Cover design, materials selection, civil engineering, erosive forces, and cost effectiveness are only a few of those factors described in this paper. The systems approach to the engineering solutions employed in the US is described, with emphasis on the standards prescribed for the Uranium Mill Tailings Remedial Action Project. Stabilization and isolation of the tailings from humans and the environment are the primary goals of the US uranium mill tailings control standards. The performance of cover designs with respect to water infiltration, radon exhalation, geotechnical stability, erosion protection, human and animal intrusion prevention, and longevity are addressed. The need for and frequency of surveillance efforts to ensure continued disposal system performance are also assessed

  2. Stability of small-amplitude periodic solutions near Hopf bifurcations in time-delayed fully-connected PLL networks

    Science.gov (United States)

    Ferruzzo Correa, Diego P.; Bueno, Átila M.; Castilho Piqueira, José R.

    2017-04-01

    In this paper we investigate stability conditions for small-amplitude periodic solutions emerging near symmetry-preserving Hopf bifurcations in a time-delayed fully-connected N-node PLL network. The study of this type of systems which includes the time delay between connections has attracted much attention among researchers mainly because the delayed coupling between nodes emerges almost naturally in mathematical modeling in many areas of science such as neurobiology, population dynamics, physiology and engineering. In a previous work it has been shown that symmetry breaking and symmetry preserving Hopf bifurcations can emerge in the parameter space. We analyze the stability along branches of periodic solutions near fully-synchronized Hopf bifurcations in the fixed-point space, based on the reduction of the infinite-dimensional space onto a two-dimensional center manifold in normal form. Numerical results are also presented in order to confirm our analytical results.

  3. Enhanced Stability of All Solution-Processed Organic Thin-Film Transistors Using Highly Conductive Modified Polymer Electrodes

    Science.gov (United States)

    Han, Jeong In; Kim, Yong-Hoon; Park, Sung Kyu

    2012-09-01

    Enhanced stability of all solution-processed organic thin-film transistors (OTFTs) has been achieved by replacing metallic electrodes with glycerol-modified poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) polymer electrodes. The modified PEDOT:PSS showed a substantially low electrical resistivity of 6.4×10-3 Ω cm with improved environmental stability and water-resistant characteristics, which are crucial for highly reliable applications. Additionally, the modified PEDOT:PSS electrodes were highly stable under intense mechanical stress, allowing their application to flexible electronics. Particularly, all solution-processed flexible and transparent OTFTs with the modified PEDOT:PSS electrodes showed a field-effect mobility decrease of only 2.7% after a tensile mode mechanical fatigue test, while OTFTs with metallic electrodes showed a mobility decrease of 56.6% under identical test conditions.

  4. Chapter 1. Bending the Curve: Ten Scalable Solutions for Carbon Neutrality and Climate Stability

    Directory of Open Access Journals (Sweden)

    V. Ramanathan

    2016-12-01

    Full Text Available We are living in a world of over seven billion people, with annual greenhouse gas emissions of approximately 50 billion tons a year and rising steadily. If continued unabated, the world is on target to warm by about 2 °C in less than 40 years, pushing the climate to a regime unlike any that has been witnessed in the last million years. Nonetheless, we still have time to avert such a catastrophic scenario, or delay its occurrence by several decades to provide human societies and the ecosystem with the time to adjust. In order to mitigate the possibility of climate disruption, we need to recognize that fossil fuel based technologies have become outdated and transform the energy system to that of low-carbon, sustainable and secure energy systems. In addition, we have to mitigate emissions of the four short-lived climate pollutants to bring immediate relief from climate change and protect vulnerable societies. Stability of the climate system involves not only the centrality of scientific and technological advancements and investments, but also necessary shifts in social structure and behavior by individuals, communities and societies worldwide as well as market based instruments, sub-national collaborations and governance structure. Fortunately, living laboratories—such as the State of California and the University of California system, which has pledged to become carbon neutral by 2025—provide demonstrable solutions which hold promise in alleviating the climate warming in the next generation. These jurisdictions are tiny emitters in the global picture, but they offer the potential for leverage through demonstrating (Figure 1 new technologies as well as workable institutions that cut emissions. We outline 10 pragmatic solutions—a “kit of parts” rooted in California but scalable to the world—that taken together, can “bend the curve” of the upward trajectory of human-caused warming trends. Wholesale transformation of our current

  5. SOLUTION OF THE STABILITY PROBLEM FOR 360 DEGREE SELF-ACTING, GAS-LUBRICATED BEARINGS OF INFINITE LENGTH

    Science.gov (United States)

    The stability of self-acting, gas-lubricated bearings was investigated. Two approaches to the solution are presented and their results are compared. Also, the relation between the present work and other, more simplified, methods available in the literature is discussed. The particular case of a 360 degree journal bearing of infinite length is treated, and the changes necessary to use the same theories with other geometries are pointed out. Available experimental results are collected and compared with theory.

  6. Radiation inactivation of angiotensin-converting enzyme in solutions. Communication 3. The effect of NaCl

    International Nuclear Information System (INIS)

    Orlova, M.A.; Kost, O.A.; Nikol'skaya, I.I.; Troshina, N.N.; Binevskij, P.V.

    1999-01-01

    The effect of 0-0.15 M NaCl on the dose response of angiotensin-converting enzyme is described. The data represented at three-dimensional surfaces demonstrate the existence of special areas where definite mechanisms of dose response are predominant. In acidic and alkaline media, the regions of high values of enzyme activation can be emphasized; moreover, the oscillations of enzyme activity can also be detected. At pH 7.5, when angiotensin-converting enzyme conformation is less rigid, activation peaks on the three-dimensional surface are less pronounced indicating the decreasing effect of NaCl on dose response at this pH value [ru

  7. Simultaneous and continuous stabilization of As and Pb in contaminated solution and soil by a ferrihydrite-gypsum sorbent.

    Science.gov (United States)

    Kameda, Kentaro; Hashimoto, Yohey; Wang, Shan-Li; Hirai, Yasumasa; Miyahara, Hidetaka

    2017-04-05

    For the increasing need of stabilization both cationic and anionic metal(loid)s simultaneously, we newly developed a metal sorbent (FIXALL), consisting mainly of ferrihydrite and gypsum. The objectives of this study were to determine the molecular mechanisms of Pb and As stabilization in an aqueous system and to examine a simultaneous and long-term (up to 754days) effect on Pb and As stabilization in an anthropogenically contaminated soil using the FIXALL sorbent. When the solution contained a low concentration of Pb (5mgL -1 ), the mechanisms of Pb removal by FIXALL were based chiefly on the formation of inner-sphere surface complex with ferrihydrite. In the highly concentrated Pb solution (1200mgL -1 ), contrarily, the removal of Pb by FIXALL was the direct consequence of the dissolution of gypsum and subsequent precipitation of PbSO 4 , which strengthens the drawback of low capability of ferrihydrite for Pb removal. Regardless of initial concentrations, the primary mechanism of FIXALL for As stabilization is attributed to the formation of inner-sphere surface complex with ferrihydrite. A contaminated soil study demonstrated that FIXALL could decrease the concentration of water soluble As and Pb simultaneously and continuously for 754days without notable changes in their chemical species and soil pH. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Colloidal stability of gold nanorod solution upon exposure to excised human skin: Effect of surface chemistry and protein adsorption.

    Science.gov (United States)

    Mahmoud, Nouf N; Al-Qaoud, Khaled M; Al-Bakri, Amal G; Alkilany, Alaaldin M; Khalil, Enam A

    2016-06-01

    In this study, we evaluated the colloidal stability of gold nanorods (with positive, negative and neutral surface charge) in solution upon contact with excised human skin. UV-vis absorption, plasmon peak broadening index (PPBI%) and transmission electron microscope analysis were used to follow nanoparticles aggregation in solution. Our results show that positively charged gold nanorods aggregate extensively upon exposure to excised human skin compared to negatively and neutrally charged gold nanorods. Skin-induced aggregation of cationic gold nanorods was linked to the adsorption of proteins released from the dermis layer to the surface of gold nanorods. Protein adsorption significantly screen nanorod's effective surface charge and induce their aggregation. Moreover, we demonstrate that the presence of polyethylene glycol polymer on the surface of cationic gold nanorods minimize this aggregation significantly by providing steric repulsion (non-electrostatic stabilization mechanism). This work highlights the importance of evaluating the colloidal stability of nanoparticles in solution upon contact with skin, which is a "usually overlooked" parameter when studying the nanoparticle-skin interaction. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Impact of microbial growth inhibition and proteolytic activity on the stability of a new formulation containing a phytate-degrading enzyme obtained from mushroom.

    Science.gov (United States)

    Spier, Michele R; Siepmann, Francieli B; Staack, Larissa; Souza, Priscila Z; Kumar, Vikas; Medeiros, Adriane B P; Soccol, Carlos R

    2016-10-02

    The development of stable enzymes is a key issue in both the food and feed industries. Consequently, the aim of the current study is to evaluate the impact of various additives (sodium chloride, sodium citrate, mannitol, methylparaben, polyethylene glycol 3350, ethylenediaminetetraacetic acid disodium salt, and a serine protease inhibitor) on the stability of a mushroom phytase produced by solid-state cultivation and recovery. Also observed was the effect of the additives on microbial growth inhibition by monitoring both the change in optical density over 30 days of storage and proteolytic activity. Initially, eight experimental formulations were prepared along with a control. After screening, a 3(2) factorial design was applied to define suitable concentrations of the selected additives. Among the eight formulations tested, the formulation containing NaCl, PEG 3350, and methylparaben retained all of the initial phytase activity after 50 days of storage, with no detected interference from protease activity. Sodium citrate, a metal chelation agent, presented the unusual effect of reducing protease activity in the formulations. Although all formulations presented better phytase stability when compared to the control, NaCl and PEG were both able to prolong the stability of the enzyme activity and also to inhibit microbial growth during storage, making them favorable for application as food and feed additives.

  10. The influences of inoculants from municipal sludge and solid waste on compost stability, maturity and enzyme activities during chicken manure composting.

    Science.gov (United States)

    Li, Shuyan; Li, Jijin; Yuan, Jing; Li, Guoxue; Zang, Bing; Li, Yangyang

    2017-07-01

    The aim of this study was to investigate the influence of inoculants on compost stability, maturity and enzyme activities during composting of chicken manure and cornstalk. Two microbial inoculants (originated from aerobic municipal sludge and municipal solid waste, respectively) were used in composting at the rate of 0.3% of initial raw materials (wet weight). No microbial inoculums were added to the control. The experiment was conducted under aerobic conditions for 53 days. The results show that enzyme activity is an important index to comprehensively evaluate the composting stability and maturity. Microbes originated from sludge works best in terms of composting stability and maturity (C:N ratio decreased from 15.5 to 10, and germination index increased to 109%). Microbial inoculums originated from sludge and municipal solid waste extended the time of thermophilic phase for 11 and 7 days, respectively. Microbial inoculums originated from sludge and MSW significantly increased the average of catalase activity (by 15.0% and 12.1%, respectively), urease activity (by 21.5% and 12.2%, respectively) and cellulase activity (by 32.1% and 26.1%, respectively) during composting.

  11. Policing in Peacekeeping and Related Stability Operations: Problems and Proposed Solutions

    National Research Council Canada - National Science Library

    Serafino, Nina M

    2004-01-01

    One of the most crucial and difficult tasks in peacekeeping and related stability operations is creating a secure and stable environment, both for the foreign peacekeepers and for the indigenous population...

  12. Stabilization of the solution of a doubly nonlinear parabolic equation

    International Nuclear Information System (INIS)

    Andriyanova, È R; Mukminov, F Kh

    2013-01-01

    The method of Galerkin approximations is employed to prove the existence of a strong global (in time) solution of a doubly nonlinear parabolic equation in an unbounded domain. The second integral identity is established for Galerkin approximations, and passing to the limit in it an estimate for the decay rate of the norm of the solution from below is obtained. The estimates characterizing the decay rate of the solution as x→∞ obtained here are used to derive an upper bound for the decay rate of the solution with respect to time; the resulting estimate is pretty close to the lower one. Bibliography: 17 titles

  13. Existence and exponential stability of almost periodic solution for stochastic cellular neural networks with delay

    International Nuclear Information System (INIS)

    Huang Zaitang; Yang Qigui

    2009-01-01

    The paper considers the problems of existence of quadratic mean almost periodic and global exponential stability for stochastic cellular neural networks with delays. By employing the Holder's inequality and fixed points principle, we present some new criteria ensuring existence and uniqueness of a quadratic mean almost periodic and global exponential stability. These criteria are important in signal processing and the design of networks. Moreover, these criteria are also applied in others stochastic biological neural systems.

  14. Stability of transition waves and positive entire solutions of Fisher-KPP equations with time and space dependence

    Science.gov (United States)

    Shen, Wenxian

    2017-09-01

    This paper is concerned with the stability of transition waves and strictly positive entire solutions of random and nonlocal dispersal evolution equations of Fisher-KPP type with general time and space dependence, including time and space periodic or almost periodic dependence as special cases. We first show the existence, uniqueness, and stability of strictly positive entire solutions of such equations. Next, we show the stability of uniformly continuous transition waves connecting the unique strictly positive entire solution and the trivial solution zero and satisfying certain decay property at the end close to the trivial solution zero (if it exists). The existence of transition waves has been studied in Liang and Zhao (2010 J. Funct. Anal. 259 857-903), Nadin (2009 J. Math. Pures Appl. 92 232-62), Nolen et al (2005 Dyn. PDE 2 1-24), Nolen and Xin (2005 Discrete Contin. Dyn. Syst. 13 1217-34) and Weinberger (2002 J. Math. Biol. 45 511-48) for random dispersal Fisher-KPP equations with time and space periodic dependence, in Nadin and Rossi (2012 J. Math. Pures Appl. 98 633-53), Nadin and Rossi (2015 Anal. PDE 8 1351-77), Nadin and Rossi (2017 Arch. Ration. Mech. Anal. 223 1239-67), Shen (2010 Trans. Am. Math. Soc. 362 5125-68), Shen (2011 J. Dynam. Differ. Equ. 23 1-44), Shen (2011 J. Appl. Anal. Comput. 1 69-93), Tao et al (2014 Nonlinearity 27 2409-16) and Zlatoš (2012 J. Math. Pures Appl. 98 89-102) for random dispersal Fisher-KPP equations with quite general time and/or space dependence, and in Coville et al (2013 Ann. Inst. Henri Poincare 30 179-223), Rawal et al (2015 Discrete Contin. Dyn. Syst. 35 1609-40) and Shen and Zhang (2012 Comm. Appl. Nonlinear Anal. 19 73-101) for nonlocal dispersal Fisher-KPP equations with time and/or space periodic dependence. The stability result established in this paper implies that the transition waves obtained in many of the above mentioned papers are asymptotically stable for well-fitted perturbation. Up to the author

  15. Stability and Compatibility of Antibiotics in Peritoneal Dialysis Solutions Applied to Automated Peritoneal Dialysis in The Pediatric Population.

    Science.gov (United States)

    Deslandes, Guillaume; Grégoire, Matthieu; Bouquié, Régis; Le Marec, Aude; Allard, Sophie; Dailly, Eric; Pineau, Alain; Allain-Launay, Emma; Jolliet, Pascale; Roussey, Gwenaëlle; Navas, Dominique

    ♦ OBJECTIVES: Assess the stability of several antibiotics in peritoneal dialysis (PD) solutions under common conditions of use in pediatrics, particularly in automated PD. ♦ METHODS: Amoxicillin, cefazolin, cefepime, ceftazidime, imipenem, cotrimoxazole, tobramycin, vancomycin, and the association of ceftazidime + vancomycin and ceftazidime + tobramycin, were tested in 3 different PD solutions: bicarbonate/lactate solution with 2 glucose concentrations (Physioneal 1.36 and 3.86%; Baxter Healthcare Corporation, Deerfield, IL, USA) and an icodextrin-containing solution (Extraneal; Baxter Healthcare Corporation, Deerfield, IL, USA). Concentrations were those recommended in guidelines for the treatment of peritonitis in pediatrics. Physioneal bags were incubated at 37°C for 24 hours, whereas Extraneal bags were stored 12 hours at room temperature (22 ± 2°C) and then 12 hours at 37°C. Drug concentrations were determined using high performance liquid chromatography (HPLC). Each measure was taken in triplicate. Stability of antibiotics was defined as less than 10% degradation of the drug over time. ♦ RESULTS: Cefazolin, cotrimoxazole, tobramycin, and vancomycin were stable under studied conditions. Ceftazidime was stable 24 hours in icodextrin, 12 hours in Physioneal 1.36% and 6 hours in Physioneal 3.86%. The association of tobramycin or vancomycin did not influence the stability of ceftazidime. Cefepime and amoxicillin were stable 6 h, 4 h, and 8 h in Physioneal 1.36%, 3.86% and Extraneal, respectively. The stability of imipenem was very low: 2 h in Physioneal and 6 h in Extraneal. Moreover, an increasingly yellow coloration was observed with the use of imipenem, whereas no color change or precipitation occurred in other bags. ♦ CONCLUSION: Cefazolin, tobramycin, cotrimoxazole, and vancomycin are stable in PD solutions up to 24 hours and can be administered in the PD bag for the treatment of peritonitis, even in automated PD under studied conditions. However

  16. Effects of solution crowding on actin polymerization reveal the energetic basis for nucleotide-dependent filament stability.

    Science.gov (United States)

    Frederick, Kendra B; Sept, David; De La Cruz, Enrique M

    2008-05-02

    Actin polymerization is a fundamental cellular process involved in cell structure maintenance, force generation, and motility. Phosphate release from filament subunits following ATP hydrolysis destabilizes the filament lattice and increases the critical concentration (C(c)) for assembly. The structural differences between ATP- and ADP-actin are still debated, as well as the energetic factors that underlie nucleotide-dependent filament stability, particularly under crowded intracellular conditions. Here, we investigate the effect of crowding agents on ATP- and ADP-actin polymerization and find that ATP-actin polymerization is largely unaffected by solution crowding, while crowding agents lower the C(c) of ADP-actin in a concentration-dependent manner. The stabilities of ATP- and ADP-actin filaments are comparable in the presence of physiological amounts (approximately 30% w/v) and types (sorbitol) of low molecular weight crowding agents. Crowding agents act to stabilize ADP-F-actin by slowing subunit dissociation. These observations suggest that nucleotide hydrolysis and phosphate release per se do not introduce intrinsic differences in the in vivo filament stability. Rather, the preferential disassembly of ADP-actin filaments in cells is driven through interactions with regulatory proteins. Interpretation of the experimental data according to osmotic stress theory implicates water as an allosteric regulator of actin activity and hydration as the molecular basis for nucleotide-dependent filament stability.

  17. Application of membrane LaF3 electrode in the determination of stability constants of Uranyl Fluoride complex in solution

    International Nuclear Information System (INIS)

    Muzakky; Iswani GS; Mintolo

    1996-01-01

    A membrane electrode LaF 3 has been applied in the determination of uranyl fluoride complex stability constant in solution. The determination is based on the detection of free F ion in solution as a result of hydrolysis reaction (process) of uranyl ions into the uranyl hydroxide form at low pH. The experiment results showed that there was no effect of ammonium carbonate 2 M titran, flow rate on the electrode response. The F release is optimum at pH 1. The free F ion in solution is calculated from the standard curve at pH 1, after the fluoride concentration at the same pH has been corrected. Using the plot of average number of ligand binding (n) versus minus log of free ligand (-log F) the value of β1 = 4.4, β2 = 7.48, β3=9.73, and β4 = 11.67

  18. Stabilization of the autoproteolysis of TNF-alpha converting enzyme (TACE) results in a novel crystal form suitable for structure-based drug design studies.

    Science.gov (United States)

    Ingram, Richard N; Orth, Peter; Strickland, Corey L; Le, Hung V; Madison, Vincent; Beyer, Brian M

    2006-04-01

    The crystallization of TNF-alpha converting enzyme (TACE) has been useful in understanding the structure-activity relationships of new chemical entities. However, the propensity of TACE to undergo autoproteolysis has made enzyme handling difficult and impeded the identification of inhibitor soakable crystal forms. The autoproteolysis of TACE was found to be specific (Y352-V353) and occurred within a flexible loop that is in close proximity to the P-side of the active site. The rate of autoproteolysis was found to be proportional to the concentration of TACE, suggesting a bimolecular reaction mechanism. A limited specificity study of the S(1)' subsite was conducted using surrogate peptides and suggested substitutions that would stabilize the proteolysis of the loop at positions Y352-V353. Two mutant proteases (V353G and V353S) were generated and proved to be highly resistant to autoproteolysis. The kinetics of the more resistant mutant (V353G) and wild-type TACE were compared and demonstrated virtually identical IC(50) values for a panel of competitive inhibitors. However, the k(cat)/K(m) of the mutant for a larger substrate (P6 - P(6)') was approximately 5-fold lower than that for the wild-type enzyme. Comparison of the complexed wild-type and mutant structures indicated a subtle shift in a peripheral P-side loop (comprising the mutation site) that may be involved in substrate binding/turnover and might explain the mild kinetic difference. The characterization of this stabilized form of TACE has yielded an enzyme with similar native kinetic properties and identified a novel crystal form that is suitable for inhibitor soaking and structure determination.

  19. Properties and stabilization of an extracellular alpha-glucosidase from the extremely thermophilic archaebacteria Thermococcus strain AN1: enzyme activity at 130 degrees C.

    Science.gov (United States)

    Piller, K; Daniel, R M; Petach, H H

    1996-01-04

    An extracellular alpha-glucosidase from the thermophilic archaebacterium Thermococcus strain AN1 was purified 875-fold in five steps (Hiload Q-Sepharose, phenyl Sepharose, HPHT-hydroxyapatite, gel filtration and Mono Q chromatography) with a yield of 4%. It is a monomer with a molecular mass of about 60 kDa and a pI around 5. At 98 degrees C, the purified enzyme in buffer has a half-life around 35 min, which is increased to around 215 min in presence of 1% (w/v) dithiothreitol and 1% (w/v) BSA. Dithiothreitol (1%, w/v) and BSA (0.4%, w/v) also substantially increase the enzyme activity. The Km at 75 degrees C is 0.41 mM with pNP-alpha-D-glucopyranoside as substrate. The substrate preference of the enzyme is: pNP-alpha-D-glucoside > nigerose > panose > palatinose > isomaltose > maltose and turanose. No activity was found against starch, pullulan, amylose, maltotriose, maltotetraose, isomaltotriose, cellobiose and beta-gentiobiose. A variety of techniques including immobolization (e.g., on epoxy and glass beads), chemical modification (cross- and cocross-linking) and the use of additives (including polyhydroxylic molecules, BSA, salts, etc.) were applied to enhance stability at temperatures above 100 degrees C. The half-life could be increased from about 4 min at 100 degrees C to 30-60 min at 130 degrees C in presence of 90% (w/v) sorbitol, 1% (w/v) dithiothreitol and 1% (w/v) BSA, and by cross-linking with BSA in the presence of 90% (w/v) sorbitol. The stabilized enzyme showed good activity at 130 degrees C.

  20. Stationary solution of the compressible magnetohydrodynamic equation and its stability with respect to initial disturbance

    Directory of Open Access Journals (Sweden)

    WU Renchao

    2016-06-01

    Full Text Available In this paper, we consider three dimensional compressible viscous magnetohydro dynamic equations(MHD with external potentialforce. We first derive the corresponding non-constantstationary solutions. Then we show global well-posedness of the initial value problem for the three dimensional compressible viscous magnetohydrodynamic equations, provided that rescribed initial data is close to the stationary solution.

  1. The stability of high-Tc BSCCO/Ag superconducting microcomposites in water, some inorganic solutions and organic solvents

    International Nuclear Information System (INIS)

    Gao, W.; Chen, J.; Yang, C.O.; McNabb, D.; Sande, J. vander

    1992-01-01

    Bi(Pb)-Sr-Ca-Cu-O/Ag (BSCCO/Ag) superconducting microcomposites with zero-resistance temperatures from 102 to 108 K and critical current densities of ∝600 A/cm 2 at 77 K were produced by oxidation and annealling of metallic precursor alloys. The stabilities and degradation behavior of BSCCO/Ag specimens in various environments were studied by a combination of mass loss measurement, electrical transport measurement and microstructural observation. The environmental conditions used in the present work were moist air, distilled water, aqueous solutions of NaCl, NaOH and acetic acid, and organic solvents methanol and acetone. Although there is a general tendency toward a decrease in critical current density after a long exposure to most of the testing conditions, the specimens containing a high percent of Ag (≥70 wt.%) showed very little decrease in Tc and J c up to 200 days of exposure in moist air and distilled water, and up to 20 days in NaCl solution, methanol and acetone. It was found that the superconducting ''2223'' phase is stable in water, neutral solutions and the organic solvents, reacts very slowly with basic solutions, and dissolves rapidly in acidic solutions. Some non-superconducting Ca-rich oxides dissolve in water and neutral and basic solutions and therefore damage the connection of the superconducting grains in low-Ag containing specimens. The excellent stability of the BSCCO/Ag superconducting microcomposites containing high Ag provides an important advantage for their potential industrial application. (orig.)

  2. Stability of Solutions of Parabolic PDEs with Random Drift and Viscosity Limit

    International Nuclear Information System (INIS)

    Deck, T.; Potthoff, J.; Vage, G.; Watanabe, H.

    1999-01-01

    Let u α be the solution of the Ito stochastic parabolic Cauchy problem ∂u/∂t - L =ξ.∇u,u , where ξ is a space-time noise. We prove that u α depends continuously on α , when the coefficients in L α converge to those in L 0 . This result is used to study the diffusion limit for the Cauchy problem in the Stratonovich sense: when the coefficients of L α tend to 0 the corresponding solutions u α converge to the solution u 0 of the degenerate Cauchy problem ∂u 0 /∂t=ξ o ∇u 0 , u o . These results are based on a criterion for the existence of strong limits in the space of Hida distributions (S) * . As a by-product it is proved that weak solutions of the above Cauchy problem are in fact strong solutions

  3. Effects of sorbitol and glycerol on the structure, dynamics, and stability of Mycobacterium tuberculosis pyrazinamidase

    Directory of Open Access Journals (Sweden)

    Mehrnoosh Khajehzadeh

    2016-01-01

    Conclusion: It can be concluded that the native conformation of the enzyme was stabilized in the sorbitol and glycerol and tend to exclude from the PZase surface, forcing the enzyme to keep it in the compactly folded conformation. The glycerol molecules stabilized PZase by decreasing the loops flexibility and then compacting the enzyme structure. It appears that more stability of PZase in glycerol solution correlates with its amphiphilic orientation, which decreases the unfavorable interactions of hydrophobic regions.

  4. Benchmark reaction rates, the stability of biological molecules in water, and the evolution of catalytic power in enzymes.

    Science.gov (United States)

    Wolfenden, Richard

    2011-01-01

    The rates of enzyme reactions fall within a relatively narrow range. To estimate the rate enhancements produced by enzymes, and their expected affinities for transition state analog inhibitors, it is necessary to measure the rates of the corresponding reactions in water in the absence of a catalyst. This review describes the spontaneous cleavages of C-C, C-H, C-N, C-O, P-O, and S-O bonds in biological molecules, as well as the uncatalyzed reactions that correspond to phosphoryl transfer reactions catalyzed by kinases and to peptidyl transfer in the ribosome. The rates of these reactions, some with half-lives in excess of one million years, span an overall range of 10¹⁹-fold. Moreover, the slowest reactions tend to be most sensitive to temperature, with rates that increase as much as 10⁷-fold when the temperature is raised from 25° to 100°C. That tendency collapses, by many orders of magnitude, the time that would have been required for chemical evolution on a warm earth. If the catalytic effect of primitive enzymes, like that of modern enzymes and many nonenzymatic catalysts, were mainly to reduce a reaction's enthalpy of activation, then the resulting rate enhancement would have increased automatically as the surroundings cooled. By reducing the time required for early chemical evolution in a warm environment, these findings counter the view that not enough time has passed for terrestrial life to have evolved to its present level of complexity.

  5. [Human thrombin: drug stability and stabilization].

    Science.gov (United States)

    Kolodzeĭskaia, M V; Sokolovskiĭ, V A; Volkov, G L

    2006-01-01

    Stabilization of enzymes is a key factor when using biocatalysis in practice. Each enzyme stability depends both on the structure of its molecule and on the effect of various environmental factors, thus, one of the methods of the enzyme stability preservation is the formation of optimal macromedium. Thus, water structure and enzyme hydration change in the presence of solvable additives that affects its stability and catalytic properties. The paper deals with a new method of stabilization of human thrombin developed by the authors. It is proposed to use some known organic-ligands which have ion group and different nonpolar hydrophobic groups instead of traditional additives (salts, aminoacids, polyols, polyethylene glycols etc.). Thrombin stabilization proceeds in the conditions something changed compared with traditional ones. Processes of thrombin stabilization by the above compound have been investigated, enzyme stability at different temperatures and long-term storage of diluted solutions of the preparation in different conditions have been studied. It has been established that rosselin and orange II are the most efficient ligands. Optimal finite concentrations of stabilizing agents make approximately 0.0012-0.0014 M which are rather low in the system thrombin-ligand. It has been found that diluted solutions of thrombin are more stable, than concentrated ones. In the latter case the process of autolysis is included that affects negatively the catalytic effect of the enzyme, as far as there occurs the change of thrombin molecule structure, especially of thrombin beta-chain sections, evoking conformational changes of some sites of its active centre. The experiments directed to increasing thrombin intensity in the presence of organic ligands rosselin and orange II are discussed in details. Special attention is given to autolytic method of thrombin inactivation. It is admitted on the basis of already obtained data that thrombin binding with organic ligands proceeds

  6. Understanding the role of histidine in the GHSxG acyltransferase active site motif: evidence for histidine stabilization of the malonyl-enzyme intermediate.

    Directory of Open Access Journals (Sweden)

    Sean Poust

    Full Text Available Acyltransferases determine which extender units are incorporated into polyketide and fatty acid products. The ping-pong acyltransferase mechanism utilizes a serine in a conserved GHSxG motif. However, the role of the conserved histidine in this motif is poorly understood. We observed that a histidine to alanine mutation (H640A in the GHSxG motif of the malonyl-CoA specific yersiniabactin acyltransferase results in an approximately seven-fold higher hydrolysis rate over the wildtype enzyme, while retaining transacylation activity. We propose two possibilities for the reduction in hydrolysis rate: either H640 structurally stabilizes the protein by hydrogen bonding with a conserved asparagine in the ferredoxin-like subdomain of the protein, or a water-mediated hydrogen bond between H640 and the malonyl moiety stabilizes the malonyl-O-AT ester intermediate.

  7. NUMERICAL SOLUTION OF THE PROBLEM ON STABILITY OF A LIQUID BRIDGE BETWEEN TWO COAXIAL CYLINDERS

    Directory of Open Access Journals (Sweden)

    Yu. N. Gorbacheva

    2013-01-01

    Full Text Available The problem on equilibrium shapes and stability of axially symmetric liquid bridge between the end faces of two coaxial vertical cylinders of equal radius in gravitational field is considered. A scheme of spline type for numerical solving of the problem is developed. Construction of the scheme is based on an approximation of the free surface by parametric cubic splines which exactly satisfy equations of the differential problem at grid nodes. Equilibrium free-surface shapes in a wide range of problem parameters are obtained. Critical values of the bridge height corresponding to the loss of equilibrium stability depending on the Bond number are determined.

  8. On the stabilization of niobium(V) solutions by zirconium(IV) and hafnium(IV)

    DEFF Research Database (Denmark)

    Sørensen, E.; Bjerre, A.B.

    1992-01-01

    Niobium cannot be separated from zirconium or hafnium when these elements occur together in solution with common anions such as chloride and sulphate. This is ascribed to the co-polymerization of niobium(V) and the hydrolysed ionic species of zirconium(IV) and hafnium(IV) to form colloidal partic...... particles. In hydrochloric acid the particles are positively charged, whereas in sulphate solution the Zr- and Hf-sulphate complexes confer a negative charge. The two cases are considered separately....

  9. Soliton solutions and their stability for the flow of relativistic fluids through channels

    Science.gov (United States)

    Lerche, I.; Wiita, P. J.

    1980-01-01

    The flow of a perfect relativistic fluid through channels of various cross-sections is considered with reference to models of radio galaxies. Soliton-like solutions are found and their topologies are discussed. The calculations show that these solutions are unstable. It is suggested that under realistic astrophysical conditions the growth rate of the instabilities is so slow that soliton-type blobs may persist for a significant time.

  10. Stability of plane wave solutions in complex Ginzburg-Landau equation with delayed feedback

    OpenAIRE

    Puzyrev, D.; Yanchuk, S.; Vladimirov, A. G.; Gurevich, S. V.

    2013-01-01

    We perform bifurcation analysis of plane wave solutions in one-dimensional cubic-quintic Ginzburg-Landau equation with delayed feedback. Our study reveals how multistability and snaking behavior of plane waves emerge as time delay is introduced. For intermediate values of the delay, bifurcation diagrams are obtained by a combination of analytical and numerical methods. For large delays, using an asymptotic approach we classify plane wave solutions into strongly unstable, weakly unstable, and ...

  11. A note on existence and stability of solutions for semilinear Dirichlet ...

    Indian Academy of Sciences (India)

    R → R are Caratheodory functions; Fk and Gk are continuously differentiable in x for. a.e. t ∈ [0,π]; ... x are locally Lipschitz in x uniformly in t ∈ [0,π] and k = 0, 1, 2. .... 204. Marek Galewski. Now we describe what we mean by the weak solution. Let βk > 0. Function u ∈. H2. 0 (0,π) is a weak solution to (3.1) if for any h ∈ H2.

  12. A scanner-based colorimetric mercuric ion detection using Tween-20-stabilized AuNPs solution in 96-well plates.

    Science.gov (United States)

    Poorahong, Sujittra; Niammusik, Anusorn; Chaykleang, Pawinee; Kanatharana, Pproespichaya; Thavarungkul, Panote; Thammakhet-Buranachai, Chongdee

    2017-09-19

    This paper reports the development of a sensitive, high-throughput colorimetric method for the detection of trace mercuric ions (Hg 2+ ). The method is based on the binding of the analyte to gold nanoparticles (AuNPs) modified with Tween-20. Tween-20 was used as a nonionic stabilizer to allow a good dispersion of AuNPs in solution. When mercuric ions were added to the solution, they replaced the Tween-20 stabilizer on the surface of the AuNPs due to their stronger binding affinity. This caused the NPs to aggregate and the color of the solution to change from red to blue. The quantitative analysis of Hg 2+ was achieved by plotting the Red Green Blue (RGB) values of the scanned images of the analyte samples in the AuNP solution against concentrations of Hg 2+ . Since the reaction was carried out in 96-well plates, ninety-six samples were analyzed simultaneously, reducing the cost and time of analysis. The experimental parameters optimized were the concentrations of Tween-20 and NaCl, the reactants ratio, and the incubation time. Under the optimum conditions, the calibration plot of the assay was linear over an Hg 2+ concentration range of 0.10-2.00 mg L -1 , and the detection limit was 0.050 mg L -1 (S/N  =  3). The selectivity of the technique was high with no significant colorimetric responses to the presence of 100-fold excesses of other metal ions. Quantification was validated with Hg 2+ standard solutions and spiked tap and waste water samples, and the accuracy of the technique was confirmed. The developed technique is simple and cost effective because it requires no complicated instruments, yet the results demonstrate it to be a very powerful technique with the potential to be developed for on-site mercury detection.

  13. Stabilization of enzymes activities of lipoxygenase pathway by irradiation to improve the production of olive oil aroma

    International Nuclear Information System (INIS)

    Musrati, Imen

    2009-01-01

    The main purpose of this work was to improve the synthesis of volatile compounds leading to green note in olives and olive tree leaves by improving enzymes activities of lipoxygenase pathway. Lipoxygenase (LOX), hydroperoxyde lyase (HPL) and alcohol dehydrogenase (ADH) activities were tested in olives and olive tree leaves during maturation. The gamma irradiation effects on these samples were studied. LOX, HPL and ADH showed maximum activities at black stage for olives and in December for olive leaves. Those activities, from olives and Chemlali olive leaves, were improved after irradiation with 0,5KGy. For the case of Chetoui olive leaves, the irradiation treatment was unfavorable because it causes a loss in enzymes activities. (Author)

  14. Phase stability of a reversible supramolecular polymer solution mixed with nanospheres

    NARCIS (Netherlands)

    Tuinier, R.

    2011-01-01

    Theory is presented for the phase stability of mixtures containing nanospheres and non-adsorbing reversible supramolecular polymers. This was made possible by incorporating the depletion thickness and osmotic pressure of reversible supramolecular polymer chains into generalized free-volume theory,

  15. Effect of finishing and polishing on the color stability of a composite resin immersed in staining solutions

    Directory of Open Access Journals (Sweden)

    Maiara Justo Polli

    2015-01-01

    Full Text Available Objective: To evaluate the influence of finishing/polishing methods and staining solutions using different immersion periods on the color stability of a microhybrid composite resin. Materials and Methods: Ninety specimens were fabricated using a stainless steel mold and polyester strips. The samples were randomly divided into five groups according to the finishing and polishing performed: Control group (no surface treatment was performed, Diamond Pro group, Diamond burs group, Enhance group, and SiC paper group. After finishing and polishing, six samples from each group were immersed in coffee, red wine, or water for 30 days. The color measurements were obtained using digital photography before immersion and after 7, 15, and 30 days of immersion. The red, green, and blue values provided by the Adobe Photoshop software were converted into CIELab values. A three-way analysis of variance and Tukey's test were used for statistical analysis (P ≤ 0.05. Results: The finishing and polishing methods, staining solutions, immersion times, and their interaction had statistically significant effects on the color change (P = 0.00. Coffee and red wine caused intense staining. Among the polishing methods, the highest color change value was observed in the control group (P < 0.05 and the Diamond Pro disks provided the most stain-resistant surfaces (P ≤ 0.05. Conclusion: The finishing and polishing method, staining solution, and immersion time influences the color stability. Finishing and polishing should be applied to obtain a more stain-resistant surface.

  16. The influence of small additions of diethylenetriamine on the detonation waves stability for nitromethane/acetone solution

    Science.gov (United States)

    Mochalova, V.; Utkin, A.

    2014-05-01

    Instability of detonation front in the nitromethane/acetone (NM/A) solution was observed in our previous work: at 10% of acetone the amplitude of heterogeneities was about 20 microns and at 20% of acetone this size was 50 microns. It is known that small additions of diethylenetriamine (DETA) considerably increase the initial rate of chemical reaction in detonation waves for NM. It was expected that DETA would influence the stability of detonation waves in the NM/A solution too. To investigate this phenomenon the laser interferometer VISAR was used for the recording of particle velocity profiles in detonation waves for NM/A. It was found that at the addition of 0.5% DETA to NM/A 90/10 the oscillations in the velocity profile decreased several times over. At the addition of 1% DETA the profile is smooth, i.e. the heterogeneities disappear and detonation wave becomes steady-state. In NM/A 80/20 at the addition of 5% DETA the heterogeneities size is reduced by the order. The increase of detonation wave velocity of NM/A grater than 1% was observed at small concentrations of DETA. Thus it was found that small additions of DETA to the NM/A solution with an unstable detonation front resulted not only in the decrease of heterogeneities size but in their disappearance and stabilization of detonation waves.

  17. Stabilization

    Directory of Open Access Journals (Sweden)

    Muhammad H. Al-Malack

    2016-07-01

    Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.

  18. Chemical Stability of Cd(II and Cu(II Ionic Imprinted Amino-Silica Hybrid Material in Solution Media

    Directory of Open Access Journals (Sweden)

    Buhani Buhani

    2012-02-01

    Full Text Available Chemical stability of Cd(II and Cu(II ionic imprinted amino-silica (HAS material of (i-Cd-HAS and i-Cu-HAS derived from silica modification with active compound (3-aminopropyl-trimethoxysilane (3-APTMS has been studied in solution media.  Stability test was performed with HNO3 0.1 M (pH 1.35 to investigate material stability at low pH condition, acetat buffer at pH 5.22 for adsorption process optimum pH condition, and in the water (pH 9.34 for base condition.  Material characteristics were carried out with infrared spectrophotometer (IR and atomic absorption spectrophotometer (AAS.  At interaction time of 4 days in acid and neutral condition, i-Cd-HAS is more stable than i-Cu-HAS with % Si left in material 95.89 % (acid media, 43.82 % (close to neutral, and 9.39 % (base media.Keywords: chemical stability, amino-silica hybrid, ionic imprinting technique.

  19. Serial deletion reveals structural basis and stability for the core enzyme activity of human glutaminase 1 isoforms: relevance to excitotoxic neurodegeneration.

    Science.gov (United States)

    Li, Yuju; Peer, Justin; Zhao, Runze; Xu, Yinghua; Wu, Beiqing; Wang, Yi; Tian, Changhai; Huang, Yunlong; Zheng, Jialin

    2017-01-01

    sequence in cells increased extracellular glutamate concentrations to levels comparable to those of full-length KGA and GAC expressions, suggesting that the core enzyme activity of the protein lies within the central 219 AA - 550 AA. Full-length KGA and GAC retained enzyme activities when kept at 4 °C. In contrast, 219 AA - 550 AA truncated protein lost glutaminase activities more readily compared with full-length KGA and GAC, suggesting that the N-terminal and C-terminal coding regions are required for the stability KGA and GAC. Glutaminase isoforms KGA and GAC have similar efficacy to catalyze the conversion of glutamine to glutamate. The core enzyme activity of glutaminase 1 protein is within the central 219 AA - 550 AA. The N-terminal and C-terminal coding regions of KGA and GAC help maintain the long-term activities of the enzymes.

  20. Preparation of polyurethane/montmorillonite nanocomposites by solution: characterization using low-field NMR and study of thermal stability

    International Nuclear Information System (INIS)

    Silva, Marcos Anacleto da; Tavares, Maria Ines B.

    2009-01-01

    Polyurethanes (PU) are important and versatile class of polymer materials, especially because of their desirable properties, such as high abrasion resistance, tear strength, excellent shock absorption, flexibility and elasticity. However, there also exist some disadvantages, for example, low thermal stability and barrier properties. To overcome the disadvantages, research on novel polyurethane/clay nanocomposites has been carried out. The investigation of the structure of polyurethane/clay nanocomposites has been mostly done by X-ray diffraction (XRD) and transmission electron microscopy (TEM). In this work, PU/clay films were prepared by solution, and the obtained nanocomposites were characterized by XRD and low-field nuclear magnetic resonance (NMR). Low field NMR measurements were able to provide important information on molecular dynamics of the polymeric nanocomposites PU/OMMT. In addition, they also confirmed the results obtained by XRD. The thermal stability was determined by thermogravimetric analysis (TGA). (author)

  1. Stabilizing a solution of the 2D Navier-Stokes system in the exterior of a bounded domain by means of a control on the boundary

    International Nuclear Information System (INIS)

    Gorshkov, Aleksei V

    2012-01-01

    The problem of stabilizing a solution of the 2D Navier-Stokes system defined in the exterior of a bounded domain with smooth boundary is investigated. For a given initial velocity field a control on the boundary of the domain must be constructed such that the solution stabilizes to a prescribed vortex solution or trivial solution at the rate of 1/t k . On the way, related questions are investigated, concerning the behaviour of the spectrum of an operator under a relatively compact perturbation and the existence of attracting invariant manifolds. Bibliography: 21 titles.

  2. Existence and global exponential stability of periodic solutions for n-dimensional neutral dynamic equations on time scales.

    Science.gov (United States)

    Li, Bing; Li, Yongkun; Zhang, Xuemei

    2016-01-01

    In this paper, by using the existence of the exponential dichotomy of linear dynamic equations on time scales and the theory of calculus on time scales, we study the existence and global exponential stability of periodic solutions for a class of n-dimensional neutral dynamic equations on time scales. We also present an example to illustrate the feasibility of our results. The results of this paper are completely new and complementary to the previously known results even in both the case of differential equations (time scale [Formula: see text]) and the case of difference equations (time scale [Formula: see text]).

  3. The existence and global exponential stability of a periodic solution of a class of delay differential equations

    International Nuclear Information System (INIS)

    Tang, X H; Zou, Xingfu

    2009-01-01

    By employing Schauder's fixed point theorem and a non-Liapunov method (matrix theory, inequality analysis), we obtain some new criteria that ensure existence and global exponential stability of a periodic solution to a class of functional differential equations. Applying these criteria to a cellular neural network with time delays (delayed cellular neural network, DCNN) under a periodic environment leads to some new results that improve and generalize many existing ones we know on this topic. These results are of great significance in designs and applications of globally stable periodic DCNNs

  4. Theoretical and experimental study of metastable solid solutions and phase stability within the immiscible Ag-Mo binary system

    Science.gov (United States)

    Sarakinos, K.; Greczynski, G.; Elofsson, V.; Magnfält, D.; Högberg, H.; Alling, B.

    2016-03-01

    Metastable solid solutions are phases that are synthesized far from thermodynamic equilibrium and offer a versatile route to design materials with tailor-made functionalities. One of the most investigated classes of metastable solid solutions with widespread technological implications is vapor deposited ternary transition metal ceramic thin films (i.e., nitrides, carbides, and borides). The vapor-based synthesis of these ceramic phases involves complex and difficult to control chemical interactions of the vapor species with the growing film surface, which often makes the fundamental understanding of the composition-properties relations a challenging task. Hence, in the present study, we investigate the phase stability within an immiscible binary thin film system that offers a simpler synthesis chemistry, i.e., the Ag-Mo system. We employ magnetron co-sputtering to grow Ag1-xMox thin films over the entire composition range along with x-ray probes to investigate the films structure and bonding properties. Concurrently, we use density functional theory calculations to predict phase stability and determine the effect of chemical composition on the lattice volume and the electronic properties of Ag-Mo solid solutions. Our combined theoretical and experimental data show that Mo-rich films (x ≥ ˜0.54) form bcc Mo-Ag metastable solid solutions. Furthermore, for Ag-rich compositions (x ≤ ˜0.21), our data can be interpreted as Mo not being dissolved in the Ag fcc lattice. All in all, our data show an asymmetry with regards to the mutual solubility of Ag and Mo in the two crystal structures, i.e., Ag has a larger propensity for dissolving in the bcc-Mo lattice as compared to Mo in the fcc-Ag lattice. We explain these findings in light of isostructural short-range clustering that induces energy difference between the two (fcc and bcc) metastable phases. We also suggest that the phase stability can be explained by the larger atomic mobility of Ag atoms as compared to that

  5. Effects of mannose, fructose, and fucose on the structure, stability, and hydration of lysozyme in aqueous solution

    DEFF Research Database (Denmark)

    Rahim, Abdoul; Peters, Günther H.J.; Jalkanen, Karl J.

    2013-01-01

    The bio-protective properties of monosaccharaides, namely mannose, fructose and fucose, on the stability and dynamical properties of the NMR determined hen egg-white lysozyme structure have been investigated by means of molecular dynamics simulations at room temperature in aqueous solution and in 7...... and 13 wt % concentrations of the three sugars. Results are discussed in the framework of the bio-protective phenomena. The three sugars show similar bio-protective behaviours at room temperature (300 K) in the concentration range studied as shown by the small RMSDs of the resulting MD structures from...

  6. Solid/solution Cu fractionations/speciation of a Cu contaminated soil after pilot-scale electrokinetic remediation and their relationships with soil microbial and enzyme activities

    International Nuclear Information System (INIS)

    Wang Quanying; Zhou Dongmei; Cang Long; Li Lianzhen; Wang Peng

    2009-01-01

    The aim of this study was to investigate the detailed metal speciation/fractionations of a Cu contaminated soil before and after electrokinetic remediation as well as their relationships with the soil microbial and enzyme activities. Significant changes in the exchangeable and adsorbed-Cu fractionations occurred after electrokinetic treatment, while labile soil Cu in the solution had a tendency to decrease from the anode to the cathode, and the soil free Cu 2+ ions were mainly accumulated in the sections close to the cathode. The results of regression analyses revealed that both the soil Cu speciation in solution phase and the Cu fractionations in solid phase could play important roles in the changes of the soil microbial and enzyme activities. Our findings suggest that the bioavailability of soil heavy metals and their ecotoxicological effects on the soil biota before and after electroremediation can be better understood in terms of their chemical speciation and fractionations. - The assessment of the roles of soil solution speciation and solid-phase fractionations in metal bioavailability after electrokinetic remediation deserves close attention.

  7. Heavy emulsifying solution on a petrolium base stabilized by calcium soaps of organic acids

    Energy Technology Data Exchange (ETDEWEB)

    Anikeenko, G.I.; Kasperskii, B.V.; Penkov, A.I.; Vakhrushev, L.P.

    1980-01-01

    These studies make possible the solution to the problem at hand through a special selection of organic acids contained in the emulsifier. It was found that the addition of an organic acid mixture obtained from sebacious acid production to the oil-based emulsifying solution (OBES) results in clearly defined thixotropic properties in the emulsifying system. Additional studies have shown that the electrostability of OBES increases 1.5 to 1.8X following the addition of 225g of bentonite to 1 1 of emulsion (tested on bentonite) with a 20% increase in the calcium chloride content.

  8. On the stabilization of NbV-solutions by ZrIV and HfIV

    International Nuclear Information System (INIS)

    Soerensen, E.; Bjerre, A.B.

    1987-11-01

    Niobium cannot be separated from zirconium or hafnium when these elements occur together in solution with common anions such as Cl- and SO 4 --. This is ascribed to the copolymerisation of Nb v and the hydrolyzed ionic species of Zr IV v and Hf IV by which the colloidal particles are masked as Zr- and Hf-compounds. In HCl the particles are positively charged as opposed to when they are in sulphate solution where the Zr- and Hf- sulphate complexes confer a negative charge. The two cases are considered separately. (author)

  9. On global asymptotic stability of solutions of a system of ordinary differential equations

    Science.gov (United States)

    Filimonov, M. Yu.

    2017-12-01

    To investigate global asymptotic stability in general of an equilibrium position of an autonomous system of ordinary differential equations, considered by V.A. Pliss, a function different from the Lyapunov functions is applied. V.A. Pliss proved that for this system it is impossible to construct the Lyapunov function as a sum of a quadratic form and an integral of some nonlinear function defined by the right-hand side of the system.

  10. CONCERNS OF CONTEMPORARY DISINFECTION: CHLORINE OR STABILIZED LIQUID SOLUTION OF CHLORINE DIOXIDE

    OpenAIRE

    Abdulah Gagić; Selma Selimović; Suad Jukić; Ajla Ališah; Aida Kustura

    2014-01-01

    It is common that experts use routine procedures for disinfection. Every part of the disinfection procedure is routinely done: preparation of the disinfection media, selection of the type of disinfection, protective measures, effect control and environmental issues. This article offers a new insight into the use of stabilized liquid chlorine dioxide as a qualitative alternative disinfectant for wider application by comparing it to the most frequently used chlorine and its compounds. When used...

  11. Solution and stability of a set of P TH order linear differential equations with periodic coefficients via Chebyshev polynomials

    Directory of Open Access Journals (Sweden)

    Sinha S. C.

    1996-01-01

    Full Text Available Chebyshev polynomials are utilized to obtain solutions of a set of p th order linear differential equations with periodic coefficients. For this purpose, the operational matrix of differentiation associated with the shifted Chebyshev polynomials of the first kind is derived. Utilizing the properties of this matrix, the solution of a system of differential equations can be found by solving a set of linear algebraic equations without constructing the equivalent integral equations. The Floquet Transition Matrix (FTM can then be computed and its eigenvalues (Floquet multipliers subsequently analyzed for stability. Two straightforward methods, the ‘differential state space formulation’ and the ‘differential direct formulation’, are presented and the results are compared with those obtained from other available techniques. The well-known Mathieu equation and a higher order system are used as illustrative examples.

  12. Solution and stability of a set of PTH order linear differential equations with periodic coefficients via Chebyshev polynomials

    Directory of Open Access Journals (Sweden)

    S. C. Sinha

    1996-01-01

    Full Text Available Chebyshev polynomials are utilized to obtain solutions of a set of pth order linear differential equations with periodic coefficients. For this purpose, the operational matrix of differentiation associated with the shifted Chebyshev polynomials of the first kind is derived. Utilizing the properties of this matrix, the solution of a system of differential equations can be found by solving a set of linear algebraic equations without constructing the equivalent integral equations. The Floquet Transition Matrix (FTM can then be computed and its eigenvalues (Floquet multipliers subsequently analyzed for stability. Two straightforward methods, the ‘differential state space formulation’ and the ‘differential direct formulation’, are presented and the results are compared with those obtained from other available techniques. The well-known Mathieu equation and a higher order system are used as illustrative examples.

  13. Existence and Stability of the Periodic Solution with an Interior Transitional Layer in the Problem with a Weak Linear Advection

    Directory of Open Access Journals (Sweden)

    Nikolay N. Nefedov

    2018-01-01

    Full Text Available In the paper, we study a singularly perturbed periodic in time problem for the parabolic reaction-advection-diffusion equation with a weak linear advection. The case of the reactive term in the form of a cubic nonlinearity is considered. On the basis of already known results, a more general formulation of the problem is investigated, with weaker sufficient conditions for the existence of a solution with an internal transition layer to be provided than in previous studies. For convenience, the known results are given, which ensure the fulfillment of the existence theorem of the contrast structure. The justification for the existence of a solution with an internal transition layer is based on the use of an asymptotic method of differential inequalities based on the modification of the terms of the constructed asymptotic expansion. Further, sufficient conditions are established to fulfill these requirements, and they have simple and concise formulations in the form of the algebraic equation w(x0,t = 0 and the condition wx(x0,t < 0, which is essentially a condition of simplicity of the root x0(t and ensuring the stability of the solution found. The function w is a function of the known functions appearing in the reactive and advective terms of the original problem. The equation w(x0,t = 0 is a problem for finding the zero approximation x0(t to determine the localization region of the inner transition layer. In addition, the asymptotic Lyapunov stability of the found periodic solution is investigated, based on the application of the so-called compressible barrier method. The main result of the paper is formulated as a theorem. 

  14. Post-reconstitution Stability of Telavancin with Commonly Used Diluents and Intravenous Infusion Solutions

    Directory of Open Access Journals (Sweden)

    Zhengtian Gu, PhD

    2015-12-01

    Conclusions: These results are supportive of a total hold time for reconstituted telavancin in vials plus the time in IV infusion solutions in polyvinyl chloride bags to not exceed 12 hours under ambient conditions and 7 days under refrigeration.

  15. A calorimetric study of solute effects on the kinetic stability of a-amylase

    DEFF Research Database (Denmark)

    Olsen, Søren Nymand; Andersen, Kim Bruno; Øgendal, Lars Holm

    2009-01-01

    In this study we evaluated the applications of isothermal titration calorimetry (ITC) to Study solute effects on the kinetics of irreversible protein denaturation. More specifically, denaturation of Bacillus Halmapalus alpha-amylase (BHA) was initiated by addition of EDTA to the calorimetric cell...

  16. Long-term stability of earthen materials in contact with acidic tailings solutions

    International Nuclear Information System (INIS)

    Peterson, S.R.; Erikson, R.L.; Gee, G.W.

    1982-11-01

    The objectives of the studies documented in this report were to use experimental and geochemical computer modeling tools to assess the long-term environmental impact of leachate movement from acidic uranium mill tailings. Liner failure (i.e., an increase in the permeability of the liner material) was not found to be a problem when various acidic tailings solutions leached through liner materials for periods up to 3 years. On the contrary, materials that contained over 30% clay showed a decrease in permeability with time in the laboratory columns. The high clay materials tested appear suitable for lining tailings impoundment ponds. The decreases in permeability are attributed to pore plugging resulting from the precipitation of minerals and solids. This precipitation takes place due to the increase in pH of the tailings solution brought about by the buffering capacity of the soil. Geochemical modeling predicts, and x-ray characterization confirms, that precipitation of solids from solution is occurring in the acidic tailings solution/liner interactions studied. In conclusion the same mineralogical changes and contaminant reactions predicted by geochemical modeling and observed in laboratory studies were found at a drained evaporation pond (Lucky Mc in Wyoming) with a 4 year history of acid attack

  17. THE EXISTENCE OF THE STABILIZING SOLUTION OF THE RICCATI EQUATION ARISING IN DISCRETE-TIME STOCHASTIC ZERO SUM LQ DYNAMIC GAMES WITH PERIODIC COEFFICIENTS

    Directory of Open Access Journals (Sweden)

    Vasile Dr ̆agan

    2017-06-01

    Full Text Available We investigate the problem for solving a discrete-time periodic gen- eralized Riccati equation with an indefinite sign of the quadratic term. A necessary condition for the existence of bounded and stabilizing solution of the discrete-time Riccati equation with an indefinite quadratic term is derived. The stabilizing solution is positive semidefinite and satisfies the introduced sign conditions. The proposed condition is illustrated via a numerical example.

  18. NMR spectroscopic characterization of a beta-(1,4)-glycosidase along its reaction pathway: stabilization upon formation of the glycosyl-enzyme intermediate.

    Science.gov (United States)

    Poon, David K Y; Ludwiczek, Martin L; Schubert, Mario; Kwan, Emily M; Withers, Stephen G; McIntosh, Lawrence P

    2007-02-20

    NMR spectroscopy was used to search for mechanistically significant differences between the thermodynamic and dynamic properties of the 34 kDa (alpha/beta)8-barrel catalytic domain of beta-(1,4)-glycosidase Cex (or CfXyn10A) in its free (apo-CexCD) and trapped glycosyl-enzyme intermediate (2FCb-CexCD) states. The main chain chemical shift perturbations due to the covalent modification of CexCD with the mechanism-based inhibitor 2,4-dinitrophenyl 2-deoxy-2-fluoro-beta-cellobioside are limited to residues within its active site. Thus, consistent with previous crystallographic studies, formation of the glycosyl-enzyme intermediate leads to only localized structural changes. Furthermore, 15N relaxation methods demonstrated that the backbone amide and tryptophan side chains of apo-CexCD are very well ordered on both the nanosecond to picosecond and millisecond to microsecond time scales and that these dynamic features also do not change significantly upon formation of the trapped intermediate. However, covalent modification of CexCD led to the increased protection of many amides and indoles, clustered around the active site of the enzyme, against fluctuations leading to hydrogen exchange. Similarly, thermal denaturation studies demonstrated that 2FCb-CexCD has a significantly higher midpoint unfolding temperature than apo-CexCD. The covalently modified protein also exhibited markedly increased resistance to proteolytic degradation by thermolysin relative to apo-CexCD. Thus, the local and global stability of CexCD increase along its reaction pathway upon formation of the glycosyl-enzyme intermediate, while its structure and fast time scale dynamics remain relatively unperturbed. This may reflect thermodynamically favorable interactions with the relatively rigid active site of Cex necessary to bind, distort, and subsequently hydrolyze glycoside substrates.

  19. Real cause of detrimental carbonation in chemically stabilized layers and possible solutions

    CSIR Research Space (South Africa)

    Botha, PB

    2005-10-01

    Full Text Available Raubenheimer Raubex, Republic of South Africa raubex@roadworks.co.za ABSTRACT Up till very recently detrimental “carbonation” of cement and lime stabilized layers in Southern Africa, which normally manifests itself in the form of a thin loose powdery... for at least 7 days. Furthermore, this water driven reaction may in some cases continue long past the original construction period (up 60 days), showing that the Initial Consumption of Lime (ICL) as measured in the laboratory, is often not enough...

  20. Supersaturating drug delivery systems: effect of hydrophilic cyclodextrins and other excipients on the formation and stabilization of supersaturated drug solutions.

    Science.gov (United States)

    Brewster, M E; Vandecruys, R; Verreck, G; Peeters, J

    2008-03-01

    Supersaturating drug delivery systems (SDDS) utilize two important design elements in their preparation including converting the drug of interest into a high energy state or other rapidly dissolving form to facilitate the formation of supersaturated drug solutions and providing a means for stabilizing the formed supersaturated solution such that significant drug absorption is possible from the gastrointestinal tract. This has been referred to as a "spring" and "parachute" approach. The current effort is designed to assess materials which may affect properties in SDDS. To this end, a series of excipients was tested in a co-solvent/solvent quench method to assess their ability to attain and maintain supersaturation for a group of 14 drug development candidates. The approach focussed on hydrophilic cyclodextrins including hydroxypropyl-beta-cyclodextrin (HPbetaCD) and sulfobutyl-beta-cyclodextrin (SBEbetaCD). Various rheological polymers and surfactants were also included in the study. Consistent with previous investigations, the pharmaceutical polymers, as a class, had minimal effects on the extent of supersaturation but tended to be good stabilizers while the surfactants tended to provide for the greatest degree of supersaturation but the formed systems were poorly stable. This study found that hydrophilic cyclodextrins, especially SBEbetaCD, gave superior results in terms of attaining and maintaining supersaturation. A knowledge of the behavior and performance of excipients in this context can be useful in designing solid oral dosage forms for difficult-to-formulate drugs and drug candidates.

  1. Effects of pH on the stability of cyanidin and cyanidin 3-O-β-glucopyranoside in aqueous solution

    Directory of Open Access Journals (Sweden)

    Rakić Violeta P.

    2015-01-01

    Full Text Available The colour variation, colour intensity and stability at various pH values (2.0, 4.0, 7.0 and 9.0 of cyanidin 3-O-β-glucopyranoside (Cy3Glc and its aglycone cyanidin was investigated during a period of 8 hours storage at 25ºC. Our data showed that pH of aqueous solution had impact on spectroscopic profile of cyanidin and Cy3Glc. Beginning with the most acidic solutions, increasing the pH induce bathochromic shifts of absorbance maximum in the visible range for all examined pH values (with the exception pH 4.0 for cyanidin, while the presence of the 3-glucosidic substitution induce hypsochromic shift. Compared to cyanidin, Cy3Glc has higher colour intensity and higher stability in the whole pH range, except at pH 7.0. The 3-glucosidic substitution influences on the colour intensity of Cy3Glc in the alkaline region. After 8-hour incubation of Cy3Glc and cyanidin at pH 2.0 and 25 ºC, 99% of Cy3Glc and only 27% of cyanidin remained unchanged.

  2. The effect of disinfecting solutions on the dimensional stability of dental alginate impression materials.

    Science.gov (United States)

    Muzaffar, Danish; Braden, Michael; Parker, Sandra; Patel, Mangala P

    2012-07-01

    Dimensional changes occur in set dental alginate impression materials when immersed in disinfecting solutions. In this contribution the dimensional changes of two alginates in two disinfecting solutions, and for two specimen thicknesses, have been studied. The results were analyzed theoretically. The dimensional changes of two commercial alginates (Blueprint Cremix and Hydrogum), have been measured, in distilled water and two disinfecting solutions (Perform ID/sodium hypochlorite), using a traveling microscope, at 5 min intervals over a period of 1h. Samples of simple geometry have been studied, namely rectangular strips with thicknesses of 1.5 and 3mm, respectively. In all cases, both alginates continuously shrank with time, in the three immersion liquids, over the hour of measurement, indicating transfer of water from the alginate into the external water or disinfecting solution. The t(1/2) shrinkage plots were generally linear, but with an intercept on the t(1/2) axis, indicating the possibility of an initial expansion at very short times. In most cases, the ratios of slopes for both thicknesses were 1.33-1.54, in contrast to the theoretical value of 2. Perform ID however gave anomalous results for the 1.5mm thick samples. At 10 min their shrinkage was 1.34-1.72%, compared with -0.42% to 0.67% in the other two media. The effects of thickness observed were not in accord with simple Fickian theory because of the various ions diffusing into and out of the alginate. Moreover, the water content of the alginate decreased consequent on the cross-linking process. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  3. Stability of the isentropic Riemann solutions of the full multidimensional Euler system

    Czech Academy of Sciences Publication Activity Database

    Feireisl, Eduard; Kreml, Ondřej; Vasseur, A.

    2015-01-01

    Roč. 47, č. 3 (2015), s. 2416-2425 ISSN 0036-1410 R&D Projects: GA ČR GA13-00522S EU Projects: European Commission(XE) 320078 - MATHEF Institutional support: RVO:67985840 Keywords : Euler system * isentropic solutions * Riemann problem * rarefaction wave Subject RIV: BA - General Mathematics Impact factor: 1.486, year: 2015 http://epubs.siam.org/doi/abs/10.1137/140999827

  4. Stabilization of solutions of quasilinear second order parabolic equations in domains with non-compact boundaries

    International Nuclear Information System (INIS)

    Karimov, Ruslan Kh; Kozhevnikova, Larisa M

    2010-01-01

    The first mixed problem with homogeneous Dirichlet boundary condition and initial function with compact support is considered for quasilinear second order parabolic equations in a cylindrical domain D=(0,∞)xΩ. Upper bounds are obtained, which give the rate of decay of the solutions as t→∞ as a function of the geometry of the unbounded domain Ω subset of R n , n≥2. Bibliography: 18 titles.

  5. Bitumen stabilized ballast: a potential solution for railway track-bed

    OpenAIRE

    D'Angelo, Giacomo; Thom, Nicholas; Lo Presti, Davide

    2016-01-01

    Railway ballast degradation under dynamic loads progressively leads to loss of mechanical performance and geometry of the track, so that maintenance interventions are frequently needed. In order to systematically avoid this issue, recently solutions have been proposed to reinforce track-bed by using polyurethane and/or resins as well as asphalt layers among others. Nonetheless, their main limitations are related to the high initial cost and low productivity.\\ud To cope with these limitations,...

  6. Hydration interactions and stability of soluble microbial products in aqueous solutions.

    Science.gov (United States)

    Wang, Ling-Ling; Wang, Long-Fei; Ye, Xiao-Dong; Yu, Han-Qing

    2013-10-01

    Soluble microbial products (SMP) are organic compounds excreted by microorganisms in their metabolism and decay and the main constituents in effluent from biological wastewater treatment systems. They also have an important contribution to the dissolved organic matters in natural aqueous systems. So far the interactions between SMP colloids have not been well explored. In this work, the interactions between SMP colloids in water and salt solutions were studied by using a combination of static and dynamic light scattering, Fourier transform infrared spectra, Zeta potential and acid-base titration techniques. The second osmotic virial coefficient had a larger value in a 750-mM salt solution than that in a 50-mM solution, indicating that repulsion between SMP colloids increased with an increase in salt concentration, which is contrary with the classic Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory. Such a repulsion was attributed to water structuring and enhanced by the accumulation of hydrophilic counter ions around SMP colloids and the formed hydration force. The repulsion and hydration effect led to the dispersing and deeper draining structure, accompanied by a decreased hydrodynamic radius and increased diffusion coefficient. This hydration force was related to so-called ion specific effect, and electrolyte sodium chloride had a more substantial effect on hydration force than KCl, CsCl, NaBr and NaI. Our results provide an experimental approach to explore the SMP structures, inter-colloid interactions and confirm the non-DLVO forces. Copyright © 2013 Elsevier Ltd. All rights reserved.

  7. Stability of perchlorate hydrates and their liquid solutions at the Phoenix landing site, Mars

    Science.gov (United States)

    Chevrier, Vincent F.; Hanley, Jennifer; Altheide, Travis S.

    2009-05-01

    We studied the low-temperature properties of sodium and magnesium perchlorate solutions as potential liquid brines at the Phoenix landing site. We determined their theoretical eutectic values to be 236 ± 1 K for 52 wt% sodium perchlorate and 206 ± 1 K for 44.0 wt% magnesium perchlorate. Evaporation rates of solutions at various concentrations were measured under martian conditions, and range from 0.07 to 0.49 mm h-1 for NaClO4 and from 0.06 to 0.29 mm h-1 for Mg(ClO4)2. The extrapolation to Phoenix landing site conditions using our theoretical treatment shows that perchlorates are liquid during the summer for at least part of the day, and exhibit very low evaporation rates. Moreover, magnesium perchlorate eutectic solutions are thermodynamically stable over vapour and ice during a few hours a day. We conclude that liquid brines may be present and even stable for short periods of time at the Phoenix landing site.

  8. Pupil size stability of the cubic phase mask solution for presbyopia

    Science.gov (United States)

    Almaguer, Citlalli; Acosta, Eva; Arines, Justo

    2018-01-01

    Presbyopia correction involves different types of studies such as lens design, clinical study, and the development of objective metrics, such as the visual Strehl ratio. Different contact lens designs have been proposed for presbyopia correction, but performance depends on pupil diameter. We will analyze the potential use of a nonsymmetrical element, a cubic phase mask (CPM) solution, to develop a contact or intraocular lens whose performance is nearly insensitive to changes in pupil diameter. We will show the through focus optical transfer function of the proposed element for different pupil diameters ranging from 3 to 7 mm. Additionally, we will show the images obtained through computation and experiment for a group of eye charts with different visual acuities. Our results show that a CPM shaped as 7.07 μm*(Z33-Z3-3)-0.9 μm Z20 is a good solution for a range of clear vision with a visual acuity of at least 0.1 logMar from 0.4 to 6 m for pupil diameters in the 3- to 7-mm range. Our results appear to be a good starting point for further development and study of this kind of CPM solution for presbyopia.

  9. Stability-Indicating HPLC Method for Simultaneous Determination of Chloramphenicol, Dexamethasone Sodium Phosphate and Tetrahydrozoline Hydrochloride in Ophthalmic Solution.

    Science.gov (United States)

    AlAani, Hashem; Alnukkary, Yasmin

    2016-03-01

    A simple stability-indicating RP-HPLC assay method was developed and validated for quantitative determination of Chloramphenicol, Dexamethasone Sodium Phosphate and Tetrahydrozoline Hydrochloride in ophthalmic solution in the presence of 2-amino-1-(4-nitrophenyl)propane-1,3-diol, a degradation product of Chloramphenicol, and Dexamethasone, a degradation product of Dexamethasone Sodium Phosphate. Effective chromatographic separation was achieved using C18 column (250 mm, 4.6 mm i.d., 5 μm) with isocratic mobile phase consisting of acetonitrile - phosphate buffer (pH 4.0; 0.05 M) (30:70, v/v) at a flow rate of 1 mL/minute. The column temperature was maintained at 40°C and the detection wavelength was 230 nm. The proposed HPLC procedure was statistically validated according to the ICH guideline, and was proved to be stability-indicating by resolution of the APIs from their forced degradation products. The developed method is suitable for the routine analysis as well as stability studies.

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

    Science.gov (United States)

    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®.

  11. Stability and activity of hydroxyethyl starch-coated polyplexes in frozen solutions or lyophilizates.

    Science.gov (United States)

    Noga, Matthäus; Edinger, Daniel; Wagner, Ernst; Winter, Gerhard; Besheer, Ahmed

    2014-07-20

    Despite their great potential, gene delivery polyplexes have a number of limitations, including their tendency for aggregation in vivo or upon storage. In previous studies, we could show that hydroxyethyl starch (HES)-decoration of polyplexes reduces aggregation in vitro and in vivo. The current study investigates the ability of HES-decoration to improve the stability of polyplexes upon storage as frozen-liquid or lyophilizate, and uses naked polyplexes or PEGylated ones as controls. For this purpose, freeze-thaw (FT) experiments of the polyplexes were conducted in the presence of standard excipients (glucose, sucrose or trehalose). Dynamic light scattering (DLS) measurements showed that HES-decoration imparted better stability when glucose was used, while both HES and PEG were effective in inhibiting aggregation in the presence of trehalose or sucrose. In contrast, the lyophilized HES-coated polyplexes were more stable than the PEGylated ones as shown by DLS, even after storage for 10 weeks at an elevated temperature. Evaluation of the gene transfer efficiency of the stored samples showed no negative effect of storage, except for the lyophilized naked polyplexes. In general, this study shows that, while both HES- or PEG-coats could prevent aggregation under frozen-liquid storage, the HES-coat resulted in superior protective effect upon lyophilization, with possible advantages for in vivo application. In summary, our developed HES-coats provided effective cryo- and lyoprotection to the DNA polyplexes. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Full Stability of Locally Optimal Solutions in Second-Order Cone Programs

    Czech Academy of Sciences Publication Activity Database

    Mordukhovich, B. S.; Outrata, Jiří; Sarabi, E.

    2014-01-01

    Roč. 24, č. 4 (2014), s. 1581-1613 ISSN 1052-6234 R&D Projects: GA ČR GAP402/12/1309 Grant - others:Australian Research Council(AU) DP-12092508; Australian Research Council(AU) DP-110102011; Portuguese Foundation of Science and Technologies(PT) MAT/11109; USA National Science Foundation(US) DMS -1007132 Institutional support: RVO:67985556 Keywords : variational analysis * second-order cone programming * full stability of local minimizers * nondegeneracy * strong regularity * quadratic growth * second-order subdifferentials * coderivatives Subject RIV: BA - General Mathematics Impact factor: 1.829, year: 2014 http://library.utia.cas.cz/separaty/2014/MTR/outrata-0434303.pdf

  13. The effect of β-cyclodextrin in the photochemical stability of propranolol hydrochloride in aqueous solution

    Directory of Open Access Journals (Sweden)

    Tathiane Lilian Ansolin

    2014-04-01

    Full Text Available The degradation of propranolol hydrochloride (1-isopropylamino-3-(naphthoxy-2-propranolol in an aqueous solution was analyzed when irradiated by light UV, with and without β-cyclodextrin. There was an increase in the compound´s photostability in nanocavity when compared with the drug without the cyclodextrins’ cavity. First order kinetic model was employed for the degradation of propranolol in aqueous media and in cyclodextrins’ cavity. The kinetic parameter was obtained by the drug´s absorption and electronic fluorescence. As a rule, encapsulation of propranolol in β-cyclodextrin decreases photodegradation speed by 53%.

  14. A combined approach for enhancing the stability of recombinant cis-dihydrodiol naphthalene dehydrogenase from Pseudomonas putida G7 allowed for the structural and kinetic characterization of the enzyme.

    Science.gov (United States)

    Costa, Débora Maria Abrantes; Costa, Mariana Amalia Figueiredo; Guimarães, Samuel Leite; Coitinho, Juliana Barbosa; Gómez, Stefanya Velásquez; Brandão, Tiago Antônio da Silva; Nagem, Ronaldo Alves Pinto

    2017-04-01

    The second enzyme of the naphthalene degradation pathway in Pseudomonas putida G7 is NahB, a dehydrogenase that converts cis-1,2-dihydroxy-1,2-dihydronaphthalene to 1,2-dihydroxynaphthalene. We report the cloning, optimization of expression, purification, kinetic studies and preliminary structural characterization of the recombinant NahB. The nahB gene was cloned into a T7 expression vector and the enzyme was overexpressed in Escherichia coli Rosetta (DE3) as an N-terminal hexa-histidine-tagged protein (6xHis-NahB). Using methods of enhancing protein stability in solution, we tested different expression, cell lysis, and purification protocols with and without ligand supplementation. The protein stability was evaluated by dynamic light scattering and circular dichroism spectroscopy assays. Best-derived protocols (expression at 18 °C, cell lysis with homogenizer, and three purification steps) were used to produce 20 mg of homogeneous 6xHis-NahB per liter of culture. The secondary and quaternary structures of 6xHis-NahB were assessed by circular dichroism and size-exclusion chromatography experiments, respectively. The enzyme was NAD + -dependent and active at pH 7.0 and 9.4 for the oxidation of the substrate. The Michaelis-Menten parameters determined at pH 7.0 and 25 °C for the substrate and cofactor, presented respective K m values of 6 and 350 μM, and a k cat value of 8.3 s -1 . Furthermore, we identified conditions for the crystallization of 6xHis-NahB. X-ray diffraction data were collected from a single 6xHis-NahB crystal which diffracted to 2.21 Å. The crystal belongs to space group I222, with unit-cell parameters a = 63.62, b = 69.50, and c = 117.47 Å. The tertiary structure of 6xHis-NahB was determined using the molecular replacement method. Further structural refinement is currently underway. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Effect of temperature on chlorproguanil and proguanil hydrochloride solutions: a chemical stability study.

    Science.gov (United States)

    Kolawole, J A; Mustapha, A; Abdul-Aguye, I; Ochekpe, N

    1996-04-01

    Chlorproguanil and proguanil hydrochloride solutions in 0.5 M hydrochloric acid, water and 1 M ammonium hydroxide were subjected to different temperatures (22-80 degrees C) for 68 h. The decomposition rate constants for chlorproguanil ranged from 1.60 to 47.6 x 10(3) h-1 in acid, 3.5 to 18 x 10(3) h-1 in water and 3.87 to 32.5 x 10(3) h-1 in base, between 50 degrees C and 80 degrees C. The activation energy Ea was 96.5, 52.12 and 62.1 kJ mol-1 in acid, water and base respectively. The proguanil decomposition rate constant ranged from 1.72 to 18.5 x 10(3) h-1 in acid, 1.58 to 9.67 x 10(3) h-1 in water and 2.34 to 15.77 x 10(3) h-1 in base, between 50 degrees C and 80 degrees C, with Ea values of 54.7, 73.3 and 62.5 kJ mol-1. Three unidentified degradation products were separated in the acid solution for each of the compounds. Chlorproguanil and proguanil are stable (t1/2 values over 30 days and up to 287 days respectively) in acid, water and base at temperatures below 22 degrees C.

  16. Thermodynamic Stability of Actinide-Dioxide Solid Solutions and Surface Interactions with Water

    Science.gov (United States)

    Asta, Mark

    2012-02-01

    Fluorite-structured actinide dioxides are the most common forms of fuel used in nuclear energy production worldwide. This talk will provide an overview of insights into the energetics of these compounds derived through the combination of density-functional-theory-based computational studies (including Hubbard-U corrections) and calorimetric measurements. The talk will focus on two main topics: the mixing energetics of cation solid solutions, and the energetics of water adsorption on the surfaces of these compounds. For the first topic, we present results for ThO2 and UO2 based solid solutions, highlighting the roles of elastic energy arising from cation size mismatch, electrostatic interactions, and charge-transfer reactions, in governing the sign and magnitude of the mixing energetics. For water adsorption, we contrast results for surface and adsorption energies on two fluorite-structured compounds, ThO2 and CeO2, that are relevant for understanding the behavior of water on actinide oxide surfaces more generally. Through a comparison between calorimetric measurements and computational results we assess the level of accuracy achieved in the computational modeling, and suggest areas where further experimental studies would be particularly useful.

  17. Effect of morin on pharmacokinetics of piracetam in rats, in vitro enzyme kinetics and metabolic stability assay using rapid UPLC method.

    Science.gov (United States)

    Sahu, Kapendra; Shaharyar, Mohammad; Siddiqui, Anees A

    2013-07-01

    The aim of this study was to investigate the effect of Morin on the pharmacokinetics of Piracetam in rats, in vitro enzyme kinetics and metabolic stability (high throughput) studies using human liver microsomes in UPLC. For pharmacokinetics studies, male Wistar rats were pretreated with Morin (10 mg/kg) for one week and on the last day, a single dose of Piracetam (50 mg/kg) was given orally. In another group, both Morin and Piracetam were co-administered to evaluate the acute effect of Morin on Piracetam. The control group received oral distilled water for one week and administered with Piracetam on the last day. As Morin is an inhibitor of P- Glycoprotein (P-gp) and CYP 3A, it was anticipated to improve the bioavailability of Piracetam. Amazingly, relative to control, the areas under the concentration time curve and peak plasma concentration of Piracetam were 1.50- and 1.45-fold, respectively, greater in the Morin-pretreated group. However, co-administration of Morin had no significant effect on these parameters. Apart from the aforementioned merits, the results of this study are further confirmed by clinical trials; Piracetam dosages should be adjusted to avoid potential drug interaction when Piracetam is used clinically in combination with Morin and Morin-containing dietary supplements. The in vitro enzyme kinetics were performed to determined km, Vmax & CLins . The in vitro metabolic stability executed for the estimation of metabolic rate constant and half-life of Piracetam. These studies also extrapolate to in vivo intrinsic hepatic clearance (Clint, in vivo ) from in vitro intrinsic hepatic clearance (CLint, in vitro ). Copyright © 2012 John Wiley & Sons, Ltd.

  18. Stability and uniqueness of slowly oscillating periodic solutions to Wright's equation

    Science.gov (United States)

    Jaquette, Jonathan; Lessard, Jean-Philippe; Mischaikow, Konstantin

    2017-12-01

    In this paper, we prove that Wright's equation y‧ (t) = - αy (t - 1) { 1 + y (t) } has a unique slowly oscillating periodic solution (SOPS) for all parameter values α ∈ [ 1.9 , 6.0 ], up to time translation. Our proof is based on the same strategy employed earlier by Xie [27]; show that every SOPS is asymptotically stable. We first introduce a branch and bound algorithm to control all SOPS using bounding functions at all parameter values α ∈ [ 1.9 , 6.0 ]. Once the bounding functions are constructed, we then control the Floquet multipliers of all possible SOPS by solving rigorously an eigenvalue problem, again using a formulation introduced by Xie. Using these two main steps, we prove that all SOPS of Wright's equation are asymptotically stable for α ∈ [ 1.9 , 6.0 ], and the proof follows. This result is a step toward the proof of the Jones' Conjecture formulated in 1962.

  19. Investigation of factors affecting the stability of lysozyme spray dried from ethanol-water solutions

    DEFF Research Database (Denmark)

    Ji, Shuying; Thulstrup, Peter Waaben; Mu, Huiling

    2017-01-01

    Formulation composition and processing conditions can be adjusted to enhance the structural integrity as well as the bioactivity of proteins in the spray drying process. In this study, lysozyme was chosen as a model pharmaceutical protein to study these aspects when spray drying from water......-ethanol mixtures. The effect of formulation additives (trehalose, Tween 20 and phosphate-buffered saline) and processing conditions (inlet temperature and storage time of lysozyme in the feed solution before the spray drying process) on the protein bioactivity was investigated. The results showed...... that the bioactivities of spray dried lysozyme with these additives were about 5-10% higher than that without additives. The bioactivity of the spray dried lysozyme was found to increase with a decrease in the inlet temperature from 130°C to 80°C, with similar findings when shortening the storage time of the feed...

  20. Stability and sedimentation of silver nanoparticles in the presence of monovalent, divalent and trivalent electrolyte solutions.

    Science.gov (United States)

    Chen, Shao-Feng; Zhang, Hongyin

    2014-01-01

    The present study seeks to elucidate the effect of different electrolytes on the stability of citrate-coated silver nanoparticles synthesized by the reduction of the Ag(NH3)(2)(+) complex via Tollens' method. Time-resolved dynamic light scattering technique was used to measure the aggregation behavior of the nanoparticles over a range of electrolyte (NaCl, CaCl₂, and AlCl₃) concentrations. From the aggregation kinetic data, the critical coagulation concentration values were calculated as 0.11, 1.7 × 10⁻³, and 5.06 × 10⁻⁶ M for NaCl, CaCl₂, and AlCl₃, respectively. Supernatant of the nanoparticle suspension in presence of the three electrolytes was collected and measured using inductively coupled plasma mass spectrometry to quantify the sedimentation. It was found that the silver nanoparticle aggregates settled rapidly in the slow aggregation and fast aggregation regimes. Their sedimentation followed a nanoparticle size-dependent manner.

  1. The combined effect of food-simulating solutions, brushing and staining on color stability of composite resins.

    Science.gov (United States)

    Silva, Tânia Mara Da; Sales, Ana Luísa Leme Simões; Pucci, Cesar Rogerio; Borges, Alessandra Bühler; Torres, Carlos Rocha Gomes

    2017-01-01

    Objective: This study evaluated the effect of food-simulating media associated with brushing and coffee staining on color stability of different composite resins. Materials and methods: Eighty specimens were prepared for each composite: Grandio SO (Voco), Amaris (Voco), Filtek Z350XT (3M/ESPE), Filtek P90 (3M/ESPE). They were divided into four groups according to food-simulating media for 7 days: artificial saliva (control), heptane, citric acid and ethanol. The composite surface was submitted to 10,950 brushing cycles (200 g load) in an automatic toothbrushing machine. The specimens were darkened with coffee solution at 37 °C for 24 h. After each treatment, color measurements were assessed by spectrophotometry, using CIE L*a*b* system. The overall color change (Δ E ) was determined for each specimen at baseline ( C 1) and after the treatments (food-simulating media immersion/ C 2, brushing/ C 3 and dye solution/ C 4). Data were analyzed by two-way repeated measures ANOVA and Tukey's tests ( p Grandio (3.75) bc , P90 (3.36) c . According to food-simulating media: heptane (4.41) a , citric acid (4.24) a , ethanol (4.02) ab , artificial saliva (3.76) b . For the treatments: dye solution (4.53) a , brushing (4.26) a , after food-simulating media (3.52) b . Conclusions: The composite resin Filtek Z350XT showed significantly higher staining than all other composite resin tested. The immersion in heptane and citric acid produced the highest color alteration than other food-simulating media. The exposure of samples to brushing protocols and darkening in coffee solution resulted in significant color alteration of the composite resins.

  2. Growth kinetics and long-term stability of CdS nanoparticles in aqueous solution under ambient conditions

    International Nuclear Information System (INIS)

    Mullaugh, Katherine M.; Luther, George W.

    2011-01-01

    The ubiquity of naturally occurring nanoparticles in the aquatic environment is now widely accepted, but a better understanding of the conditions that promote their formation and persistence is needed. Using cadmium sulfide (CdS) as a model metal sulfide species, thiolate-capped CdS nanoparticles were prepared in the laboratory to evaluate how aquatic conditions influence metal sulfide nanoparticle growth and stability. This work examines CdS nanoparticle growth directly in aqueous solution at room temperature by utilizing the size-dependent spectroscopic properties of semiconductors detectable by UV/vis. CdS nanoparticle growth was governed by oriented attachment, a non-classical mechanism of crystallization in which small precursor nanoparticles coalesce to form larger nanoparticle products. Nanoparticle growth was slowed with increasing capping agent and decreasing ionic strength. In addition to examining the short-term (hours) growth of the nanoparticles, a long-term study was conducted in which cysteine-capped CdS nanoparticles were monitored over 3 weeks in solutions of various ionic strengths. The long-term study revealed an apparent shift from small nanoparticles to nanoparticles twice their original size, suggesting nanoparticle growth may continue through oriented attachment over longer time scales. High-ionic strength solutions resulted in salt-induced aggregation and eventual settling of nanoparticles within days, whereas low-ionic strength solutions were stable against settling over the course of the experiment. Sulfide recovery from cysteine-capped CdS nanoparticles as acid volatile sulfide was nearly quantitative after 2 weeks in fully oxygenated water, demonstrating significantly slowed oxidation of sulfide when complexed to Cd(II) within CdS nanoparticles. The nanoparticles were also shown to be resistant to oxidation by Fe(III) (hydr)oxide. This study illustrates that aggregation, rather than chemical oxidation, is likely more important to the

  3. A strategic approach for direct recovery and stabilization of Fusarium sp. ICT SAC1 cutinase from solid state fermented broth by carrier free cross-linked enzyme aggregates.

    Science.gov (United States)

    Chaudhari, Sandeep A; Singhal, Rekha S

    2017-05-01

    The major hurdles in commercial exploitation of cutinase (having both esterolytic and lipolytic activities) with potent industrial applications are its high production cost, operational instability and reusability. Although commercially available in immobilized form, its immobilization process (synthesis of support/carrier) makes it expensive. Herein we tried to address multiple issues of production cost, stability, and reusability, associated with cutinase. Waste watermelon rinds, an agroindustrial waste was considered as a cheap support for solid state fermentation (SSF) for cutinase production by newly isolated Fusarium sp. ICT SAC1. Subsequently, carrier free cross-linked enzyme aggregates of cutinase (cut-CLEA) directly from the SSF crude broth were developed. All the process variables affecting CLEA formation along with the different additives were evaluated. It was found that 50% (w/v) of ammonium sulphate, 125μmol of glutaraldehyde, cross-linking for 1h at 30°C and broth pH of 7.0, yielded 58.12% activity recovery. All other additives (hexane, butyric acid, sodium dodecyl sulphate, Trition-X 100, Tween-20, BSA) evaluated presented negative results to our hypothesis. Kinetics and morphology studies confirmed the diffusive nature of cut-CLEA and BSA cut-CLEA. Developed CLEA showed better thermal, solvent, detergent and storage stability, making it more elegant and efficient for industrial biocatalytic process. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Reduced Dental Plaque Formation in Dogs Drinking a Solution Containing Natural Antimicrobial Herbal Enzymes and Organic Matcha Green Tea

    Directory of Open Access Journals (Sweden)

    Michael I. Lindinger

    2016-01-01

    Full Text Available The results of an exploratory, multicenter clinical study confirmed the hypothesis that a novel, natural, and safe oral care product (OCP reduced the rate of plaque formation on teeth of dogs consuming the OCP (antimicrobial plant-derived enzymes, organic matcha green tea, cultured dextrose, sodium bicarbonate, and ascorbic acid compared to controls. Healthy dogs without periodontitis, of varying breeds, sex, and age, were recruited and enrolled, using nonrandomized stratification methods, into a control and treatment groups. Treatment group dogs drank only water into which OCP was suspended, for 28 days. Control group dogs drank their normal household water. On day 0 all teeth were cleaned by a veterinarian and gingivitis was assessed. On days 14, 21, and 28 plaque index, plaque thickness, gingivitis, freshness of breath, and general health were assessed. Over the 28 days of study, dogs on the OCP had significant reduction in plaque index and plaque thickness compared to controls. By day 14 OCP reduced plaque formation by 37%; the 28-day reduction in plaque index and coverage averaged 22% with no measurable gingivitis or calculus. Conclusion. Using the OCP attenuated dental plaque formation when consumed as normal drinking water and in the absence of other modes of oral care.

  5. Tank Waste Transport Stability: Summaries of Hanford Slurry and Salt-Solution Studies in FY 2000

    Energy Technology Data Exchange (ETDEWEB)

    Welch, T.D.

    2002-07-08

    This report is a collection of summary articles on FY 2000 studies of slurry transport and salt-well pumping related to Hanford tank waste transfers. These studies are concerned with the stability (steady, uninterrupted flow) of tank waste transfers, a subset of the Department of Energy (DOE) Tanks Focus Area Tank (TFA) Waste Chemistry effort. This work is a collaborative effort of AEA Technology plc, the Diagnostic Instrumentation and Analysis Laboratory at Mississippi State University (DIAL-MSU), the Hemispheric Center for Environmental Technology at Florida International University (HCET-FIU), Numatec Hanford Corporation (NHC), and the Oak Ridge National Laboratory (ORNL). The purpose of this report is to provide, in a single document, an overview of these studies to help the reader identify contacts and resources for obtaining more detailed information and to help promote useful interchanges between researchers and users. Despite over 50 years of experience in transporting radioactive tank wastes to and from equipment and tanks at the Department of Energy's Hanford, Savannah River, and Oak Ridge sites, waste slurry transfer pipelines and process piping become plugged on occasion. At Hanford, several tank farm pipelines are no longer in service because of plugs. At Savannah River, solid deposits in the outlet line of the 2H evaporator have resulted in an unplanned extended downtime. Although waste transfer criteria and guidelines intended to prevent pipeline plugging are in place, they are not always adequate. To avoid pipeline plugging in the future, other factors that are not currently embodied in the transfer criteria may need to be considered. The work summarized here is being conducted to develop a better understanding of the chemical and waste flow dynamics during waste transfer. The goal is to eliminate pipeline plugs by improving analysis and engineering tools in the field that incorporate this understanding.

  6. Solution stabilities of some mixed ligand complexes of UO22+ and Th4+ with complexones and salicylic acids

    International Nuclear Information System (INIS)

    Singh, R.K.; Saxena, M.C.

    1991-01-01

    Formation constants (log Ksub(MAL)sup(MA)) of mixed ligands complexes (MAL), where M = UO 2 2+ or Th 4+ , A = IMDA, NTA, HEDTA, EDTA, CDTA or DTPA, L = salicylic acid (SA) or 5-sulphosalicylic acid (SSA), have been determined by pH titrations using Irving-Rossotti approach at 25 o C and at I =0.2 (mol dm -3 , KNO 3 ). The solution stabilities exhibit the sequence (i) Th 4+ >UO 2 2+ , (ii) IMDA>NTA>HEDTA>EDTA>CDTA>DTPA, and (iii) SA>SSA with respect to metal ions, primary ligands and secondary ligands, respectively. The formation constants log Ksub(ML)sup(M) and log Ksub(ML 2 )sup(ML) have also been determined. The Δlog K values have been found to be negative-increasing numerically with the negative charge on the deprotonated primary ligand (A n- ). (author). 17 refs., 1 tab

  7. A stabilized finite element formulation for the solution of the Navier-Stokes equations in axisymmetric geometry

    International Nuclear Information System (INIS)

    Souza, Altivo Monteiro de

    2008-12-01

    The world energy consumption has been increasing strongly in recent years. Nuclear energy has been regarded as a suitable option to supply this growing energy demand in industrial scale. In view of the need of improving the understanding and capacity of analysis of nuclear power plants, modern simulation techniques for flow and heat transfer problems are gaining greater importance. A large number of problems found in nuclear reactor engineering can be dealt assuming axial symmetry. Thus, in this work a stabilized finite element formulation for the solution of the Navier-Stokes and energy equations for axisymmetric problems have been developed and tested. The formulation has been implemented in the NS S OLVER M PI 2 D A program developed at the Parallel Computation Laboratory of the Instituto de Engenharia Nuclear (LCP/IEN) and is now available either for safety analysis or design of nuclear systems. (author)

  8. Instability of Wind Turbine Converters during Current Injection to Low Voltage Grid Faults and PLL Frequency Based Stability Solution

    DEFF Research Database (Denmark)

    Göksu, Ömer; Teodorescu, Remus; Bak, Claus Leth

    2014-01-01

    In recent grid codes for wind power integration, wind turbines are required to stay connected during grid faults even when the grid voltage drops down to zero; and also to inject reactive current in proportion to the voltage drop. However, a physical fact, instability of grid-connected converters...... during current injection to very low (close to zero) voltage faults, has been omitted, i.e., failed to be noticed in the previous wind power studies and grid code revisions. In this paper, the instability of grid side converters of wind turbines defined as loss of synchronism (LOS), where the wind...... turbines lose synchronism with the grid fundamental frequency (e.g., 50 Hz) during very deep voltage sags, is explored with its theory, analyzed and a novel stability solution based on PLL frequency is proposed; and both are verified with power system simulations and by experiments on a grid...

  9. Atomic scale determination of enzyme flexibility and active site stability through static modes: case of dihydrofolate reductase.

    Science.gov (United States)

    Brut, Marie; Estève, Alain; Landa, Georges; Renvez, Guillaume; Djafari Rouhani, Mehdi; Vaisset, Marc

    2011-02-24

    A Static Mode approach is used to screen the biomechanical properties of DHFR. In this approach, a specific external stimulus may be designed at the atomic scale granularity to arrive at a proper molecular mechanism. In this frame, we address the issues related to the overall molecular flexibility versus loop motions and versus enzymatic activity. We show that backbone motions are particularly important to ensure DHFR domain communication and notably highlight the role of a α-helix in Met20 loop motion. We also investigate the active site flexibility in different bound states. Whereas in the occluded conformation the Met20 loop is highly flexible, in the closed conformation backbone motions are no longer significant, the Met20 loop is rigidified by new intra- and intermolecular weak bonds, which stabilizes the complex and promotes the hydride transfer. Finally, while various simulations, including I14 V and I14A mutations, confirm that Ile14 is a key residue in catalytic activity, we isolate and characterize at the atomic scale how a specific intraresidue chemical group makes it possible to assist ligand positioning, to direct the nicotinamide ring toward the folate ring.

  10. Selective pressure causes an RNA virus to trade reproductive fitness for increased structural and thermal stability of a viral enzyme.

    Directory of Open Access Journals (Sweden)

    Moshe Dessau

    Full Text Available The modulation of fitness by single mutational substitutions during environmental change is the most fundamental consequence of natural selection. The antagonistic tradeoffs of pleiotropic mutations that can be selected under changing environments therefore lie at the foundation of evolutionary biology. However, the molecular basis of fitness tradeoffs is rarely determined in terms of how these pleiotropic mutations affect protein structure. Here we use an interdisciplinary approach to study how antagonistic pleiotropy and protein function dictate a fitness tradeoff. We challenged populations of an RNA virus, bacteriophage Φ6, to evolve in a novel temperature environment where heat shock imposed extreme virus mortality. A single amino acid substitution in the viral lysin protein P5 (V207F favored improved stability, and hence survival of challenged viruses, despite a concomitant tradeoff that decreased viral reproduction. This mutation increased the thermostability of P5. Crystal structures of wild-type, mutant, and ligand-bound P5 reveal the molecular basis of this thermostabilization--the Phe207 side chain fills a hydrophobic cavity that is unoccupied in the wild-type--and identify P5 as a lytic transglycosylase. The mutation did not reduce the enzymatic activity of P5, suggesting that the reproduction tradeoff stems from other factors such as inefficient capsid assembly or disassembly. Our study demonstrates how combining experimental evolution, biochemistry, and structural biology can identify the mechanisms that drive the antagonistic pleiotropic phenotypes of an individual point mutation in the classic evolutionary tug-of-war between survival and reproduction.

  11. Clozapine-carboxylic acid plasticized co-amorphous dispersions: Preparation, characterization and solution stability evaluation

    Directory of Open Access Journals (Sweden)

    Ali Ahmed Mahmoud Abdelhaleem

    2015-06-01

    Full Text Available This study addressed the possibility of forming of co-amorphous systems between clozapine (CZ and various carboxylic acid plasticizers (CAPs. The aim was to improve the solubility and oral bioavailability of clozapine. Co-amorphous dispersions were prepared using modified solvent evaporation methodology at drug/plasticizer stoichiometric ratios of 1:1, 1:1.5 and 1:2. Solid state characterization was performed using differential scanning calorimetry, X-ray diffraction and infra red spectroscopy. Highly soluble homogeneous co-amorphous dispersions were formed between clozapine and CAPs via hydrogen bonding. The co-amorphous dispersions formed with tartaric acid (1:2 showed the highest dissolution percentage (> 95 % in 20 minutes compared to pure crystalline CZ (56 %. Highly stable solutions were obtained from co-amorphous CZ-citric and CZ-tartaric acid at 1:1.5 molar ratio. The prepared dispersions suggest the possibility of peroral or sublingual administration of highly soluble clozapine at a reduced dose with the great chance to bypass the first pass metabolism.

  12. Stabilized Discretization in Spline Element Method for Solution of Two-Dimensional Navier-Stokes Problems

    Directory of Open Access Journals (Sweden)

    Neng Wan

    2014-01-01

    Full Text Available In terms of the poor geometric adaptability of spline element method, a geometric precision spline method, which uses the rational Bezier patches to indicate the solution domain, is proposed for two-dimensional viscous uncompressed Navier-Stokes equation. Besides fewer pending unknowns, higher accuracy, and computation efficiency, it possesses such advantages as accurate representation of isogeometric analysis for object boundary and the unity of geometry and analysis modeling. Meanwhile, the selection of B-spline basis functions and the grid definition is studied and a stable discretization format satisfying inf-sup conditions is proposed. The degree of spline functions approaching the velocity field is one order higher than that approaching pressure field, and these functions are defined on one-time refined grid. The Dirichlet boundary conditions are imposed through the Nitsche variational principle in weak form due to the lack of interpolation properties of the B-splines functions. Finally, the validity of the proposed method is verified with some examples.

  13. One-step synthesis and applications of fluorescent Cu nanoclusters stabilized by L-cysteine in aqueous solution

    International Nuclear Information System (INIS)

    Yang, Xiaoming; Feng, Yuanjiao; Zhu, Shanshan; Luo, Yawen; Zhuo, Yan; Dou, Yao

    2014-01-01

    Graphical abstract: An innovative and simple strategy for synthesizing high-fluorescent Cu nanoclusters stabilized with L-cysteine has been successfully established in aqueous solution. Significantly, the Cu nanoclusters were employed for sensitive and selective detections of Hg 2+ , coding and fluorescent staining, suggesting their potential toward various applications. - Highlights: • A novel, one-step strategy for synthesizing water-soluble CuNCs was established. • A simple, selective, and cost-effective assay for Hg 2+ was developed. • CuNCs may broaden ways for fluorescent staining and coding. - Abstract: Herein, an innovative and simple strategy for synthesizing high fluorescent Cu nanoclusters was successfully established while L-cysteine played a role as the stabilizer. Meaningfully, the current Cu nanoclusters together with a quantum yield of 14.3% were prepared in aqueous solution, indicating their extensive applications. Subsequently, the possible fluorescence mechanism was elucidated by fluorescence, UV–vis, HR-TEM, FTIR, XPS, and MS. Additionally, the CuNCs were employed for assaying Hg 2+ on the basis of the interactions between Hg 2+ and L-cysteine; thus facilitating the quenching of their fluorescence. The proposed analytical strategy permitted detections of Hg 2+ in a linear range of 1.0 × 10 −7 mol L −1 × 10 −3 mol L −1 , with a detection limit of 2.4 × 10 −8 mol L −1 at a signal-to-noise ratio of 3. Significantly, this CuNCs described here were further applied for coding and fluorescent staining, suggesting may broaden avenues toward diverse applications

  14. Numerical solutions of magnetohydrodynamic stability of axisymmetric toroidal plasmas using cubic B-spline finite element method

    International Nuclear Information System (INIS)

    Cheng, C.Z.

    1988-12-01

    A nonvariational ideal MHD stability code (NOVA) has been developed. In a general flux coordinate (/psi/, θ, /zeta/) system with an arbitrary Jacobian, the NOVA code employs Fourier expansions in the generalized poloidal angle θ and generalized toroidal angle /zeta/ directions, and cubic-B spline finite elements in the radial /psi/ direction. Extensive comparisons with these variational ideal MHD codes show that the NOVA code converges faster and gives more accurate results. An extended version of NOVA is developed to integrate non-Hermitian eigenmode equations due to energetic particles. The set of non-Hermitian integro-differential eigenmode equations is numerically solved by the NOVA-K code. We have studied the problems of the stabilization of ideal MHD internal kink modes by hot particle pressure and the excitation of ''fishbone'' internal kink modes by resonating with the energetic particle magnetic drift frequency. Comparisons with analytical solutions show that the values of the critical β/sub h/ from the analytical theory can be an order of magnitude different from those computed by the NOVA-K code. 24 refs., 11 figs., 1 tab

  15. Solution processed transition metal oxide anode buffer layers for efficiency and stability enhancement of polymer solar cells

    Science.gov (United States)

    Ameen, M. Yoosuf; Shamjid, P.; Abhijith, T.; Reddy, V. S.

    2018-01-01

    Polymer solar cells were fabricated with solution-processed transition metal oxides, MoO3 and V2O5 as anode buffer layers (ABLs). The optimized device with V2O5 ABL exhibited considerably higher power conversion efficiency (PCE) compared to the devices based on MoO3 and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) ABLs. The space charge limited current measurements and impedance spectroscopy results of hole-only devices revealed that V2O5 provided a very low charge transfer resistance and high hole mobility, facilitating efficient hole transfer from the active layer to the ITO anode. More importantly, incorporation of V2O5 as ABL resulted in substantial improvement in device stability compared to MoO3 and PEDOT:PSS based devices. Unencapsulated PEDOT:PSS-based devices stored at a relative humidity of 45% have shown complete failure within 96 h. Whereas, MoO3 and V2O5 based devices stored in similar conditions retained 22% and 80% of their initial PCEs after 96 h. Significantly higher stability of the V2O5-based device is ascribed to the reduction in degradation of the anode/active layer interface, as evident from the electrical measurements.

  16. Effect of chitosan on the heat stability of whey protein solution as a function of pH.

    Science.gov (United States)

    Zhao, Zhengtao; Xiao, Qian

    2017-03-01

    Chitosan was reported to interact with proteins through electrostatic interactions. Their interaction was influenced by pH, which was not fully characterized. Further research on the interactions between protein and chitosan at different pH and their influence on the thermal denaturation of proteins is necessary. In this research, the effect of chitosan on the heat stability of whey protein solution at pH 4.0-6.0 was studied. At pH 4.0, a small amount chitosan was able to prevent the heat-induced denaturation and aggregation of whey protein molecules. At higher pH values (5.5 and 6.0), whey proteins complexed with chitosan through electrostatic attraction. The formation of chitosan-whey protein complexes at pH 5.5 improved the heat stability of dispersions and no precipitation could be detected up to 20 days. The dispersion with a medium amount of chitosan (chitosan:whey protein 1:5) produced the most stable particles, which had an average radius of 135 ± 14 nm and a zeta potential value of 36 ± 1 mV. In contrast, at pH 6.0 only the dispersion with a high amount of chitosan (chitosan:whey protein 1:2) showed good shelf stability up to 20 days. It was possible to produce heat-stable whey protein beverages by regulating the interaction between chitosan and whey protein molecules. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  17. Investigation of influence of NaOH and NaCl activating solutions on bentonite stabilization in suspension fertilizers

    Science.gov (United States)

    Hoffmann, Krystyna; Hoffmann, Józef; Mikła, Daniel; Huculak-Mä Czka, Marta; Skut, Jakub

    2010-05-01

    purposes. In this paper research aimed at activating Jaroszów bentonite were presented. 2. MATERIALS AND METHODS The studies on activating clay minerals were carried out using the exchange of Ca2+, K+, Mg2+ ions to Na+ ions. For activation process the NaOH and NaCl solutions of concentrations 0,1M and 2,0M respectively were applied. For the purposes mentioned above 5g of weighed portion of mineral were introduced into four 250 ml conical flasks, two of them were filled with 100 ml of 0,1M and 2.0 M NaOH solution. Two remaining flasks were filled with 100 ml of 0,1M and 2.0 M NaCl solution. The samples preparred acoording to this instructions were shaken for 1 and 8 hours, and subsequently subjected to a vacuum filtration in order to separete solid fraction from filtrate. Mineral which remaied on the filter was dried in temperature of 110oC for 2 hours. 1g of dried mineral was collected for further examinations, mixed with 100 ml of distilled water and poured into the 25 ml measuring cylinder. Then every day for 14 days a change of the volume of deposit, suspension and pure solution above the suspension have been measured. 3. RESULTS DISCUSSION "Jaroszów" bentonite, activated with Na+ ions using 0,1M NaOH solution constitutes the most beneficial agent stabilizing the solid phase in the aqueous environment. The time factor didn't have considerable influence on bentonite activation. Results were similar for 1h as well as 8h. The addition of NaOH sustained suspension on respectively high level, about 80% vol., after 14 measurement days.

  18. Color stability of resin used for caries infiltration after exposure to different staining solutions.

    Science.gov (United States)

    Borges, Ab; Caneppele, Tmf; Luz, M; Pucci, Cr; Torres, Crg

    2014-01-01

    PURPOSE : The aim of this study was to investigate the staining behavior of demineralized enamel infiltrated by low-viscosity resin. METHODS AND MATERIALS : Bovine enamel/dentin cylindrical samples (3 × 2 mm) were assigned into four groups (n=45) according to the enamel treatment: sound enamel (control), demineralization + artificial saliva, demineralization + daily application of 0.05% NaF, demineralization + resin infiltration (Icon, DMG). Artificial white spot lesions were produced in groups with demineralization. After the treatments, color was assessed by spectrophotometry, using the CIE L*a*b* system. The specimens (n=15) were then immersed in deionized water, red wine, or coffee for 10 minutes daily for eight days. Color was measured again, and the specimens were repolished with sandpaper discs. The final color was assessed. Data were analyzed by two-way analysis of variance and Tukey tests (α=0.05). A paired t-test was used for comparison between staining and repolishing conditions. RESULTS : There were significant differences for surface treatment and dye after staining and repolishing. Immersion in wine and coffee resulted in significantly increased color alteration (ΔE) compared with water (p=0.001). The resin-infiltrated group exhibited the highest staining values (p=0.001). The repolishing procedures resulted in significantly decreased color change. The exposure of specimens to colored solutions resulted in significant color alteration. The demineralized enamel treated with resin infiltration showed significantly higher staining than all other tested groups; however, the repolishing of the specimens minimized the staining effect.

  19. Enzymes from extremophiles.

    Science.gov (United States)

    Demirjian, D C; Morís-Varas, F; Cassidy, C S

    2001-04-01

    The industrial application of enzymes that can withstand harsh conditions has greatly increased over the past decade. This is mainly a result of the discovery of novel enzymes from extremophilic microorganisms. Recent advances in the study of extremozymes point to the acceleration of this trend. In particular, enzymes from thermophilic organisms have found the most practical commercial use to date because of their overall inherent stability. This has also led to a greater understanding of stability factors involved in adaptation of these enzymes to their unusual environments.

  20. Hydrogen storage and stability properties of Pd-Pt solid-solution nanoparticles revealed via atomic and electronic structure.

    Science.gov (United States)

    Kumara, Loku Singgappulige Rosantha; Sakata, Osami; Kobayashi, Hirokazu; Song, Chulho; Kohara, Shinji; Ina, Toshiaki; Yoshimoto, Toshiki; Yoshioka, Satoru; Matsumura, Syo; Kitagawa, Hiroshi

    2017-11-06

    Bimetallic Pd 1-x Pt x solid-solution nanoparticles (NPs) display charging/discharging of hydrogen gas, which has relevance for fuel cell technologies; however, the constituent elements are immiscible in the bulk phase. We examined these material systems using high-energy synchrotron X-ray diffraction, X-ray absorption fine structure and hard X-ray photoelectron spectroscopy techniques. Recent studies have demonstrated the hydrogen storage properties and catalytic activities of Pd-Pt alloys; however, comprehensive details of their structural and electronic functionality at the atomic scale have yet to be reported. Three-dimensional atomic-scale structure results obtained from the pair distribution function (PDF) and reverse Monte Carlo (RMC) methods suggest the formation of a highly disordered structure with a high cavity-volume-fraction for low-Pt content NPs. The NP conduction band features, as extracted from X-ray absorption near-edge spectra at the Pd and Pt L III -edge, suggest that the Pd conduction band is filled by Pt valence electrons. This behaviour is consistent with observations of the hydrogen storage capacity of these NPs. The broadening of the valence band width and the down-shift of the d-band centre away from the Fermi level upon Pt substitution also provided evidence for enhanced stability of the hydride (ΔH) features of the Pd 1-x Pt x solid-solution NPs with a Pt content of 8-21 atomic percent.

  1. Head to head comparison of the formulation and stability of concentrated solutions of HESylated versus PEGylated anakinra.

    Science.gov (United States)

    Liebner, Robert; Meyer, Martin; Hey, Thomas; Winter, Gerhard; Besheer, Ahmed

    2015-02-01

    Although PEGylation of biologics is currently the gold standard for half-life extension, the technology has a number of limitations, most importantly the non-biodegradability of PEG and the extremely high viscosity at high concentrations. HESylation is a promising alternative based on coupling to the biodegradable polymer hydroxyethyl starch (HES). In this study, we are comparing HESylation with PEGylation regarding the effect on the protein's physicochemical properties, as well as on formulation at high concentrations, where protein stability and viscosity can be compromised. For this purpose, the model protein anakinra is coupled to HES or PEG by reductive amination. Results show that coupling of HES or PEG had practically no effect on the protein's secondary structure, and that it reduced protein affinity by one order of magnitude, with HESylated anakinra more affine than the PEGylated protein. The viscosity of HESylated anakinra at protein concentrations up to 75 mg/mL was approximately 40% lower than that of PEG-anakinra. Both conjugates increased the apparent melting temperature of anakinra in concentrated solutions. Finally, HESylated anakinra was superior to PEG-anakinra regarding monomer recovery after 8 weeks of storage at 40°C. These results show that HESylating anakinra offers formulation advantages compared with PEGylation, especially for concentrated protein solutions. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  2. Photo-stability study of a solution-processed small molecule solar cell system: correlation between molecular conformation and degradation.

    Science.gov (United States)

    Newman, Michael J; Speller, Emily M; Barbé, Jérémy; Luke, Joel; Li, Meng; Li, Zhe; Wang, Zhao-Kui; Jain, Sagar M; Kim, Ji-Seon; Lee, Harrison Ka Hin; Tsoi, Wing Chung

    2018-01-01

    Solution-processed organic small molecule solar cells (SMSCs) have achieved efficiency over 11%. However, very few studies have focused on their stability under illumination and the origin of the degradation during the so-called burn-in period. Here, we studied the burn-in period of a solution-processed SMSC using benzodithiophene terthiophene rhodamine:[6,6]-phenyl C 71 butyric acid methyl ester (BTR:PC 71 BM) with increasing solvent vapour annealing time applied to the active layer, controlling the crystallisation of the BTR phase. We find that the burn-in behaviour is strongly correlated to the crystallinity of BTR. To look at the possible degradation mechanisms, we studied the fresh and photo-aged blend films with grazing incidence X-ray diffraction, UV-vis absorbance, Raman spectroscopy and photoluminescence (PL) spectroscopy. Although the crystallinity of BTR affects the performance drop during the burn-in period, the degradation is found not to originate from the crystallinity changes of the BTR phase, but correlates with changes in molecular conformation - rotation of the thiophene side chains, as resolved by Raman spectroscopy which could be correlated to slight photobleaching and changes in PL spectra.

  3. SOLUTIONING

    Directory of Open Access Journals (Sweden)

    Maria de Hoyos Guajardo, Ph.D. Candidate, M.Sc., B.Eng.

    2004-11-01

    Full Text Available The theory that is presented below aims to conceptualise how a group of undergraduate students tackle non-routine mathematical problems during a problem-solving course. The aim of the course is to allow students to experience mathematics as a creative process and to reflect on their own experience. During the course, students are required to produce a written ‘rubric’ of their work, i.e., to document their thoughts as they occur as well as their emotionsduring the process. These ‘rubrics’ were used as the main source of data.Students’ problem-solving processes can be explained as a three-stage process that has been called ‘solutioning’. This process is presented in the six sections below. The first three refer to a common area of concern that can be called‘generating knowledge’. In this way, generating knowledge also includes issues related to ‘key ideas’ and ‘gaining understanding’. The third and the fourth sections refer to ‘generating’ and ‘validating a solution’, respectively. Finally, once solutions are generated and validated, students usually try to improve them further before presenting them as final results. Thus, the last section deals with‘improving a solution’. Although not all students go through all of the stages, it may be said that ‘solutioning’ considers students’ main concerns as they tackle non-routine mathematical problems.

  4. Enhanced electrical stability of nitrate ligand-based hexaaqua complexes solution-processed ultrathin a-IGZO transistors

    Science.gov (United States)

    Choi, C.; Baek, Y.; Lee, B. M.; Kim, K. H.; Rim, Y. S.

    2017-12-01

    We report solution-processed, amorphous indium–gallium–zinc-oxide-based (a-IGZO-based) thin-film transistors (TFTs). Our proposed solution-processed a-IGZO films, using a simple spin-coating method, were formed through nitrate ligand-based metal complexes, and they were annealed at low temperature (250 °C) to achieve high-quality oxide films and devices. We investigated solution-processed a-IGZO TFTs with various thicknesses, ranging from 4 to 16 nm. The 4 nm-thick TFT films had smooth morphology and high-density, and they exhibited excellent performance, i.e. a high saturation mobility of 7.73  ±  0.44 cm2 V‑1 s‑1, a sub-threshold swing of 0.27 V dec‑1, an on/off ratio of ~108, and a low threshold voltage of 3.10  ±  0.30 V. However, the performance of the TFTs degraded as the film thickness was increased. We further performed positive and negative bias stress tests to examine their electrical stability, and it was noted that the operating behavior of the devices was highly stable. Despite a small number of free charges, the high performance of the ultrathin a-IGZO TFTs was attributed to the small effect of the thickness of the channel, low bulk resistance, the quality of the a-IGZO/SiO2 interface, and high film density.

  5. Defect and phase stability of solid solutions of Mg2X with an antifluorite structure: An ab initio study

    International Nuclear Information System (INIS)

    Viennois, Romain; Jund, Philippe; Colinet, Catherine; Tédenac, Jean-Claude

    2012-01-01

    First principles calculations are done for Mg 2 X (X=Si, Ge or Sn) antifluorite compounds and their solid solutions in order to investigate their pseudo-binary phase diagram. The formation energies of the end-member compounds agree qualitatively with the experiments. For X=Si and Ge, there is a complete solubility, but we observe a miscibility gap in the pseudo-binary phase diagram Mg 2 Si–Mg 2 Sn. This agrees with the most recent experiments and phase diagram assessments. Calculated electronic properties of Mg 2 Si 1−x Sn x alloys qualitatively agree with experiments and in particular the energy bandgap decreases when Si is substituted by Sn. Supercell calculations are also done in order to determine the most stable defects and the doping induced by these defects in the three end-member compounds. We find that the intrinsic n-doping in pure Mg 2 Si can be attributed to the presence of magnesium atoms in interstitial positions. In Mg 2 Ge and Mg 2 Sn, since other defects are stable, they can be also of p-type. - Graphical abstract: Evidence of a miscibility gap from the plot of the formation energy vs x Si (silicon content) for the solid solutions Mg 2 Si–Mg 2 Sn. Highlights: ► First-principles study of the stability of Mg 2 Si–Mg 2 X alloys (X=Ge or Sn) and their defects. ► Mg 2 Si–Mg 2 Ge alloys form a complete series of solid solutions. ► Miscibility gap is found in Mg 2 Si–Mg 2 Sn alloys. ► Interstitial defects are more stable in Mg 2 Si and induce n-doping.

  6. Thermal stability of α-amylase in aqueous cosolvent systems

    Indian Academy of Sciences (India)

    Prakash

    Enhancement of the structural stability of enzymes is of great importance for their application in several industrial processes. The mechanism of thermal denaturation depends on various physicochemical parameters of the solution in which the reaction is catalysed. Any process that enhances the structural stability and rate ...

  7. The combined effect of food-simulating solutions, brushing and staining on color stability of composite resins

    Science.gov (United States)

    Silva, Tânia Mara Da; Sales, Ana Luísa Leme Simões; Pucci, Cesar Rogerio; Borges, Alessandra Bühler; Torres, Carlos Rocha Gomes

    2017-01-01

    Abstract Objective: This study evaluated the effect of food-simulating media associated with brushing and coffee staining on color stability of different composite resins. Materials and methods: Eighty specimens were prepared for each composite: Grandio SO (Voco), Amaris (Voco), Filtek Z350XT (3M/ESPE), Filtek P90 (3M/ESPE). They were divided into four groups according to food-simulating media for 7 days: artificial saliva (control), heptane, citric acid and ethanol. The composite surface was submitted to 10,950 brushing cycles (200 g load) in an automatic toothbrushing machine. The specimens were darkened with coffee solution at 37 °C for 24 h. After each treatment, color measurements were assessed by spectrophotometry, using CIE L*a*b* system. The overall color change (ΔE) was determined for each specimen at baseline (C1) and after the treatments (food-simulating media immersion/C2, brushing/C3 and dye solution/C4). Data were analyzed by two-way repeated measures ANOVA and Tukey’s tests (p composites (p = .001), time (p = .001) and chemical degradation (p = .002). The mean of ΔE for composites were: Z350XT (5.39)a, Amaris (3.89)b, Grandio (3.75)bc, P90 (3.36)c. According to food-simulating media: heptane (4.41)a, citric acid (4.24)a, ethanol (4.02)ab, artificial saliva (3.76)b. For the treatments: dye solution (4.53)a, brushing (4.26)a, after food-simulating media (3.52)b. Conclusions: The composite resin Filtek Z350XT showed significantly higher staining than all other composite resin tested. The immersion in heptane and citric acid produced the highest color alteration than other food-simulating media. The exposure of samples to brushing protocols and darkening in coffee solution resulted in significant color alteration of the composite resins. PMID:28642926

  8. Investigation on the influence of the TBP diluents on the primary emulsion stability in model extraction systems: TBP-diluents-water solutions of HNO3

    International Nuclear Information System (INIS)

    Rogoz, F.

    1983-01-01

    In the extraction systems containing little quantities of TBP in carbon tetrachloride (CCl 4 ) and kerosene the stable emulsions are created; for higher concentrations of TBP the emulsion stability decreases and increases again for the highest concentrations of TBP. In the TBP solutions in N-octane and benzene the great influence on the primary emulsion stability is observed only for the high concentrations of TBP. The addition of MBP has considerably less influence on the primary emulsion stability than the addition of DBP has, for all used diluents. (author)

  9. Flexible ITO-free organic solar cells applying aqueous solution-processed V2O5 hole transport layer: An outdoor stability study

    Directory of Open Access Journals (Sweden)

    F. Anderson S. Lima

    2016-02-01

    Full Text Available Solution processable semiconductor oxides have opened a new paradigm for the enhancement of the lifetime of thin film solar cells. Their fabrication by low-cost and environmentally friendly solution-processable methods makes them ideal barrier (hole and electron transport layers. In this work, we fabricate flexible ITO-free organic solar cells (OPV by printing methods applying an aqueous solution-processed V2O5 as the hole transport layer (HTL and compared them to devices applying PEDOT:PSS. The transparent conducting electrode was PET/Ag/PEDOT/ZnO, and the OPV configuration was PET/Ag/PEDOT/ZnO/P3HT:PC60BM/HTL/Ag. Outdoor stability analyses carried out for more than 900 h revealed higher stability for devices fabricated with the aqueous solution-processed V2O5.

  10. Stability of Hyperthermophilic Proteins

    DEFF Research Database (Denmark)

    Stiefler-Jensen, Daniel

    to life at high temperatures so are their enzymes, as a result the high stability is accompanied by low activity at moderate temperatures. Thus, much effort had been put into decoding the mechanisms behind the high stability of the thermophilic enzymes. The hope is to enable scientist to design enzymes...... in the high stability of hyperthermophilic enzymes. The thesis starts with an introduction to the field of protein and enzyme stability with special focus on the thermophilic and hyperthermophilic enzymes and proteins. After the introduction three original research manuscripts present the experimental data...

  11. Stabilization of the norm of the solution of a mixed problem in an unbounded domain for parabolic equations of orders 4 and 6

    International Nuclear Information System (INIS)

    Mukminov, F Kh; Bikkulov, I M

    2004-01-01

    The behaviour as t→∞ of the solution of a mixed problem for parabolic equations in an unbounded domain with two exits to infinity is studied. A certain class of domains is distinguished, in which an estimate characterizing the stabilization of solutions and determined by the geometry of the domain is established. This estimate is proved to be sharp in a certain sense for a broad class of domains with two exits to infinity.

  12. Stability analysis of new exact traveling-wave solutions of new coupled KdV and new coupled Zakharov-Kuznetsov systems

    Science.gov (United States)

    Seadawy, Aly R.; Arshad, M.; Lu, Dianchen

    2017-04-01

    In this article, our aim is to further extend the applications of modified extended direct algebraic method on new coupled systems, which have many important applications in mathematical physics. many exact solutions out of which some are new in different forms such as soliton, solitary wave, periodic, elliptic function solutions of new coupled KdV and new coupled Zakharov-Kuznetsov (ZK) systems are constructed by employing this method. The constructed exact solutions are also presented graphically. The modulation instability is utilized to discuss the stability of obtained solutions. All solutions are stable and exact solutions. The obtained results show that the modified extended method is general and effective. Furthermore, many other new coupled systems arising in mathematical physics can also be solved by this powerful and effective method.

  13. Stability of Naturally Relevant Ternary Phases in the Cu–Sn–S system in Contact with an Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Andrea Giaccherini

    2016-07-01

    Full Text Available A relevant research effort is devoted to the synthesis and characterization of phases belonging to the ternary system Cu–Sn–S, mainly for their possible applications in semiconductor technology. Among all ternary phases, kuramite, Cu3SnS4, mohite, Cu2SnS3, and Cu4Sn7S16 have attracted the highest interest. Numerous studies were carried out claiming for the description of new phases in the ternary compositional field. In this study, we revise the existing literature on this ternary system, with a special focus on the phases stable in a temperature range at 25 °C. The only two ternary phases observed in nature are mohite and kuramite. Their occurrence is described as very rare. A numerical modelling of the stable solid phases in contact with a water solution was underwent to define stability relationships of the relevant phases of the system. The numerical modelling of the Eh-pH diagrams was carried out through the phreeqc software with the lnll.dat thermodynamic database. Owing to the complexity of this task, the subsystems Cu–O–H, Sn–O–H, Cu–S–O–H and Sn–S–O–H were firstly considered. The first Pourbaix diagram for the two naturally relevant ternary phases is then proposed.

  14. Metal-Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations.

    Science.gov (United States)

    Zhang, Teng; Manna, Kuntal; Lin, Wenbin

    2016-03-09

    New and active earth-abundant metal catalysts are critically needed to replace precious metal-based catalysts for sustainable production of commodity and fine chemicals. We report here the design of highly robust, active, and reusable cobalt-bipyridine- and cobalt-phenanthroline-based metal-organic framework (MOF) catalysts for alkene hydrogenation and hydroboration, aldehyde/ketone hydroboration, and arene C-H borylation. In alkene hydrogenation, the MOF catalysts tolerated a variety of functional groups and displayed unprecedentedly high turnover numbers of ∼2.5 × 10(6) and turnover frequencies of ∼1.1 × 10(5) h(-1). Structural, computational, and spectroscopic studies show that site isolation of the highly reactive (bpy)Co(THF)2 species in the MOFs prevents intermolecular deactivation and stabilizes solution-inaccessible catalysts for broad-scope organic transformations. Computational, spectroscopic, and kinetic evidence further support a hitherto unknown (bpy(•-))Co(I)(THF)2 ground state that coordinates to alkene and dihydrogen and then undergoing σ-complex-assisted metathesis to form (bpy)Co(alkyl)(H). Reductive elimination of alkane followed by alkene binding completes the catalytic cycle. MOFs thus provide a novel platform for discovering new base-metal molecular catalysts and exhibit enormous potential in sustainable chemical catalysis.

  15. A salt water battery with high stability and charging rates made from solution processed conjugated polymers with polar side chains

    KAUST Repository

    Moia, Davide

    2017-11-28

    We report a neutral salt water based battery which uses p-type and n-type solution processed polymer films as the cathode and the anode of the cell. The specific capacity of the electrodes (approximately 30 mAh cm-3) is achieved via formation of bipolarons in both the p-type and n-type polymers. By engineering ethylene glycol and zwitterion based side chains attached to the polymer backbone we facilitate rapid ion transport through the non-porous polymer films. This, combined with efficient transport of electronic charge via the conjugated polymer backbones, allowed the films to maintain constant capacity at high charge and discharge rates (>1000 C-rate). The electrodes also show good stability during electrochemical cycling (less than 30% decrease in capacity over >1000 cycles) and an output voltage up to 1.4 V. The performance of these semiconducting polymers with polar side-chains demonstrates the potential of this material class for fast-charging, water based electrochemical energy storage devices.

  16. On stability of the solutions of inverse problem for determining the right-hand side of a degenerate parabolic equation with two independent variables

    Science.gov (United States)

    Kamynin, V. L.; Bukharova, T. I.

    2017-01-01

    We prove the estimates of stability with respect to perturbations of input data for the solutions of inverse problems for degenerate parabolic equations with unbounded coefficients. An important feature of these estimates is that the constants in these estimates are written out explicitly by the input data of the problem.

  17. Ternary system of dihydroartemisinin with hydroxypropyl-β-cyclodextrin and lecithin: simultaneous enhancement of drug solubility and stability in aqueous solutions.

    Science.gov (United States)

    Wang, Dan; Li, Haiyan; Gu, Jingkai; Guo, Tao; Yang, Shuo; Guo, Zhen; Zhang, Xueju; Zhu, Weifeng; Zhang, Jiwen

    2013-09-01

    The purpose of this study was to simultaneously improve the solubility and stability of dihydroartemisinin (DHA) in aqueous solutions by a ternary cyclodextrin system comprised of DHA, hydroxypropyl-β-cyclodextrin (HP-β-CD) and a third auxiliary substance. Solubility and phase solubility studies were carried out to evaluate the solubilizing efficiency of HP-β-CD in association with various auxiliary substances. Then, the solid binary (DHA-HP-β-CD or DHA-lecithin) and ternary systems were prepared and characterized by Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC) and power X-ray diffraction (PXRD). The effect of the ternary system on the solubility, dissolution and stability of DHA in aqueous solutions was also investigated. As a result, the soybean lecithin was found to be the most promising third component in terms of solubility enhancement. For the solid characterization, the disappearance of the drug crystallinity indicated the formation of new solid phases, implicating the formation of the ternary system. The dissolution rate of the solid ternary system was much faster than that of the drug alone and binary systems. Importantly, compared with binary systems, the ternary system showed a significant improvement in the stability of DHA in Hank's balanced salt solutions (pH 7.4). The solubility and stability of DHA in aqueous solutions were simultaneously enhanced by the ternary system, which might be attributed to the possible formation of a ternary complex. For the ternary interactions, results of molecular docking studies further indicated that the lecithin covered the top of the wide rim of HP-β-CD and surrounded around the peroxide bridging of DHA, providing the possibility for the ternary complex formation. In summary, the ternary system prepared in our study, with simultaneous enhancement of DHA solubility and stability in aqueous solutions, might have an important pharmaceutical potential in the development of a better

  18. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Molecular Dynamics Study of Stability of Solid Solutions and Amorphous Phase in the Cu-Al System

    Science.gov (United States)

    Yang, Bin; Lai, Wen-Sheng

    2009-06-01

    The relative stability of fcc and bcc solid solutions and amorphous phase with different compositions in the Cu-Al system is studied by molecular dynamics simulations with n-body potentials. For Cu1-xAlx alloys, the calculations show that the fcc solid solution has the lowest energies in the composition region with x 0.72, while the bee solid solution has the lowest energies in the central composition range, in agreement with the ball-milling experiments that a single bcc solid solution with 0.30 < x < 0.70 is obtained. The evolution of structures in solid solutions and amorphous phase is studied by the coordination number (CN) and bond-length analysis so as to unveil the underlying physics. It is found that the energy sequence among three phases is determined by the competition in energy change originating from the bond length and CNs (or the number of bonds).

  19. The Influence of pH and Temperature on the Stability of N-[(Piperidinemethylene]daunorubicin Hydrochloride and a Comparison of the Stability of Daunorubicin and Its Four New Amidine Derivatives in Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Mikołaj Piekarski

    2014-01-01

    Full Text Available The influence of pH and temperature on the stability of N-[(piperidinemethylene]daunorubicin hydrochloride (PPD was investigated. Degradation was studied using an HPLC method. Specific acid-base catalysis of PPD involves hydrolysis of protonated molecules of PPD catalyzed by hydrogen ions and spontaneous hydrolysis under the influence of water zwitterions, unprotonated molecules, and monoanions of PPD. The thermodynamic parameters of these reactions, energy, enthalpy, and entropy, were calculated. Also, the stability of daunorubicin and its new amidine derivatives (piperidine, morpholine, pyrrolidine, and hexahydroazepin-1-yl in aqueous solutions was compared and discussed.

  20. Enzyme recycling in lignocellulosic biorefineries

    DEFF Research Database (Denmark)

    Jørgensen, Henning; Pinelo, Manuel

    2017-01-01

    platform. Cellulases are the most important enzymes required in this process, but the complex nature of lignocellulose requires several other enzymes (hemicellulases and auxiliary enzymes) for efficient hydrolysis. Enzyme recycling increases the catalytic productivity of the enzymes by reusing them...... upscaled and tested in industrial settings, mainly because of many difficulties with recycling of enzymes from the complex lignocellulose hydrolyzate at industrially relevant conditions, i.e., high solids loadings. The challenges are associated with the large number of different enzymes required...... for efficient hydrolysis, enzyme stability, and the detrimental interaction between enzyme and lignin. This review provides a comprehensive overview of the various methods for enzyme recovery and recycling, for example recycling of free enzymes, readsorption to fresh material, recycling of solids, membrane...

  1. Optimization of Parameters that Affect the Activity of the Alkaline Protease from Halotolerant Bacterium, Bacillus acquimaris VITP4, by the Application of Response Surface Methodology and Evaluation of the Storage Stability of the Enzyme.

    Science.gov (United States)

    Chittoor, Jabeena Thaz; Balaji, Lavanya; Jayaraman, Gurunathan

    2016-03-01

    It was previously shown that the activity of a serine protease from a moderately halotolerant Bacillus aquimaris VITP4 strain is active in a wide range of pH and temperatures and could be modulated by the presence of the divalent metal ions. In the present study, a quantitative analysis was done in order to explore the parameters that are contributing to the protease activity. Changes in the secondary structure of the enzyme was determined by circular dichroism analysis. The conditions for the optimal activity was investigated by Response Surface Methodology. Stability of the enzyme was determined by thermal inactivation experiments. The initial one-factor-at-a-time experiments have indicated that the activity of the enzyme could be enhanced not only by the presence of low concentrations of NaCl but also by divalent metal ions, such as Ca 2+ , Mn 2+ and Cu 2+ . A clear dependence of the activity to the secondary structure of the enzyme could be established using circular dichroism spectroscopy. In the next level of optimization, four factors; viz. pH, temperature, concentration of Ca2+, and Mn 2+ were used to optimize the conditions required for the maximal activity of the enzyme by Response Surface Methodology, and the data could be explained using quadratic model. Under optimal condition of 43°C, pH 8.0, 8.2 mM Ca 2+ , and 4.3 mM Mn 2+ a 1.5 times enhancement in the enzyme activity could be achieved. The storage stability of the enzyme under these selected conditions has indicated a non-linear relation between the conditions for the enzymatic activity as well as stability. However, the condition for the maximal stability (267±18 min) has corresponded to that of the optimal conditions for the maximal activity. This study, for the first time, has explored the possibility of using statistical methods for identifying the optimal conditions for alkaline protease activity isolated from the halotolerant Bacillus aquimaris VITP4.

  2. Modulation stability and optical soliton solutions of nonlinear Schrödinger equation with higher order dispersion and nonlinear terms and its applications

    Science.gov (United States)

    Arshad, Muhammad; Seadawy, Aly R.; Lu, Dianchen

    2017-12-01

    In optical fibers, the higher order non-linear Schrödinger equation (NLSE) with cubic quintic nonlinearity describes the propagation of extremely short pulses. We constructed bright and dark solitons, solitary wave and periodic solitary wave solutions of generalized higher order NLSE in cubic quintic non Kerr medium by applying proposed modified extended mapping method. These obtained solutions have key applications in physics and mathematics. Moreover, we have also presented the formation conditions on solitary wave parameters in which dark and bright solitons can exist for this media. We also gave graphically the movement of constructed solitary wave and soliton solutions, that helps to realize the physical phenomena's of this model. The stability of the model in normal dispersion and anomalous regime is discussed by using the modulation instability analysis, which confirms that all constructed solutions are exact and stable. Many other such types of models arising in applied sciences can also be solved by this reliable, powerful and effective method.

  3. Influence of calcium chelators on concentrated micellar casein solutions : from micellar structure to viscosity and heat stability

    NARCIS (Netherlands)

    Kort, de E.J.P.

    2012-01-01

    In practice it is challenging to prepare a concentrated medical product with high heat stability
    and low viscosity. Calcium chelators are often added to dairy products to improve heat stability,
    but this may increase viscosity through interactions with the casein proteins. The aim of

  4. Problems experiences with the construction of cement and lime stabilized layers and working solutions for these problems

    CSIR Research Space (South Africa)

    Botha, PB

    2005-10-01

    Full Text Available Stabilized layers are used extensively in South-Africa in the construction of roads. The layers are usually stabilized with hydrated road lime, cement, slag, fly-ash, bitumen emulsion, foamed asphalt or a combination of several of these agents...

  5. Determination of the stability of antibiotics in matrix and reference solutions using a straightforward procedure applying mass spectrometric detection

    NARCIS (Netherlands)

    Berendsen, B.J.A.; Elbers, I.J.W.; Stolker, A.A.M.

    2011-01-01

    The stability of an antibiotic is a very important characteristic, especially in the field of antibiotic residue analysis. During method development or validation, the stability of the antibiotic has to be demonstrated no matter if the method is used for screening, confirmation, qualitative or

  6. Pectic enzymes

    NARCIS (Netherlands)

    Benen, J.A.E.; Voragen, A.G.J.; Visser, J.

    2003-01-01

    The pectic enzymes comprise a diverse group of enzymes. They consist of main-chain depolymerases and esterases active on methyl- and acetylesters of galacturonosyl uronic acid residues. The depolymerizing enzymes comprise hydrolases as wel as lyases

  7. Stability of 10 mg/mL cefuroxime solution for intracameral injection in commonly used polypropylene syringes and new ready-to-use cyclic olefin copolymer sterile vials using the LC-UV stability-indicating method.

    Science.gov (United States)

    Feutry, Frédéric; Simon, Nicolas; Genay, Stéphanie; Lannoy, Damien; Barthélémy, Christine; Décaudin, Bertrand; Labalette, Pierre; Odou, Pascal

    2016-01-01

    Injecting intracameral cefuroxime has been found beneficial in reducing the risk of postoperative endophthalmitis but its use has been limited through a lack of approved marketing and of ready-to-use single-units as well as the problem of aseptic compounding. Our aim was to assess a new automated primary packaging system which should ensure a higher level of sterility, thanks to its closed, sterile, ready-to-use polymer vial called "Crystal® vial". The chemical stability of a 10 mg/mL cefuroxime solution was compared in 1 mL Crystal® vials and 1 mL Luer-lock polypropylene syringes (actual reference) to eliminate any potential and specific interactions with its cyclic olefin copolymer (COC) body and elastomer stopper. Cefuroxime solution was introduced into vials and syringes and stored at -20 °C, +5 °C and +25°C/60% Relative Humidity. Cefuroxime concentration and the relative amount of the main degradation product (descarbamoyl-cefuroxime) were both determined by an HPLC/UV method indicating stability. Solutions were considered steady if the concentration remained at over 90% of the initial value. In the adapted storage conditions, the evolution of osmolality, pH and sterility was assessed. Stability profiles were identical between vials and syringes in all storage and temperature conditions. The solution was stable (cefuroxime concentration, pH and osmolality) and still sterile for 365 days at -20°C. The concentration fell below 90% after 21 days at +5 °C and after 16 h at +25°C/60%s relative humidity. The COC and thermoplastic elastomer of the vials had no impact on the degradation process confirming its possible use for a ready-to-use cefuroxime solution single-unit dose.

  8. Similar influence of stabilized alkaline and neutral sodium hypochlorite solutions on the fracture resistance of root canal-treated bovine teeth.

    Science.gov (United States)

    Souza, Erick Miranda; Calixto, Amanda Martins; Lima, Camila Nara E; Pappen, Fernanda Geraldo; De-Deus, Gustavo

    2014-10-01

    Stabilizing sodium hypochlorite (NaOCl) at an alkaline pH is proposed to increase solution stability and tissue dissolution ability; however, a reduction on the flexural strength of dentin discs has been found to be a side effect. This study sought to determine whether a stabilized alkaline NaOCl reduces the fracture resistance of root canal-treated bovine teeth after root canal preparation compared with a neutral solution counterpart. The 4 anterior incisors were removed from 20 mandibular bovine jaws, and each 1 was randomly assigned to 1 of 4 groups (20 teeth each). Teeth were prepared with a sequence of 6 K-type files. The following experimental groups received a different irrigation regimen: G1: distilled water (negative control), G2: 5% NaOCl at a pH of 7.2, and G3: 5% NaOCl at a pH of 12.8; in the positive control group (G4), teeth remained untreated. The time of contact and volume of solution were carefully standardized. After bone and periodontal ligament simulation, teeth were subjected to a fracture resistance test. A significant difference was observed among the 4 groups tested (analysis of variance, P .05). No differences were observed between positive and negative control groups (Tukey test, P > .05). Stabilized alkaline and neutral NaOCl solutions similarly reduced the fracture resistance of root canal-treated bovine teeth by about 30%. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  9. Temperature stability of Poly-[hemoglobin-superoxide dismutase-catalase-carbonic anhydrase] in the form of a solution or in the lyophilized form during storage at -80 °C, 4 °C, 25 °C and 37 °C or pasteurization at 70 °C.

    Science.gov (United States)

    Bian, Y Z; Guo, C; Chang, T M S

    2016-01-01

    Polyhemoglobin-superoxide dismutase-catalase-carbonic anhydrase (Poly-[Hb-SOD-CAT-CA]) contains all three major functions of red blood cells (RBCs) at an enhanced level. It transports oxygen, removes oxygen radicals and transports carbon dioxide. Our previous studies in a 90-min 30 mm Hg Mean Arterial Pressure (MAP) sustained hemorrhagic shock rat model shows that it is more effective than blood in the lowering of elevated intracellular pCO2, recovery of ST-elevation and histology of the heart and intestine. This paper is to analyze the storage and temperature stability. Allowable storage time for RBC is about 1 d at room temperature and 42 d at 4 °C. Also, RBC cannot be pasteurized to remove infective agents like HIV and Ebola. PolyHb can be heat sterilized and can be stored for 1 year even at room temperature. However, Poly-[Hb-SOD-CAT-CA] contains both Hb and enzymes and enzymes are particularly sensitive to storage and heat. We thus carried out studies to analyze its storage stability at different temperatures and heat pasteurization stability. Results of storage stability show that lyophilization extends the storage time to 1 year at 4 °C and 40 d at room temperature (compared to respectively, 42 d and 1 d for RBC). After the freeze-dry process, the enzyme activities of Poly-[SFHb-SOD-CAT-CA] was 100 ± 2% for CA, 100 ± 2% for SOD and 93 ± 3.5% for CAT. After heat pasteurization at 70 °C for 2 h, lyophilized Poly-[Hb-SOD-CAT-CA] retained good enzyme activities of CA 97 ± 4%, SOD 100 ± 2.5% and CAT 63.8 ± 4%. More CAT can be added during the crosslinking process to maintain the same enzyme ratio after heat pasteurization. Heat pasteurization is possible only for the lyophilized form of Poly-[Hb-SOD-CAT-CA] and not for the solution. It can be easily reconstituted by dissolving in suitable solutions that continues to have good storage stability though less than that for the lyophilized form. According to the P50 value, Poly-[SFHb-SOD-CAT-CA] retains its

  10. Use of a screening method to determine excipients which optimize the extent and stability of supersaturated drug solutions and application of this system to solid formulation design.

    Science.gov (United States)

    Vandecruys, Roger; Peeters, Jef; Verreck, Geert; Brewster, Marcus E

    2007-09-05

    Assessing the effect of excipients on the ability to attain and maintain supersaturation of drug-based solution may provide useful information for the design of solid formulations. Judicious selection of materials that affect either the extent or stability of supersaturating drug delivery systems may be enabling for poorly soluble drug candidates or other difficult-to-formulate compounds. The technique suggested herein is aimed at providing a screening protocol to allow preliminary assessment of these factors based on small to moderate amounts of drug substance. A series of excipients were selected that may, by various mechanisms, affect supersaturation including pharmaceutical polymers such as HMPC and PVP, surfactants such as Polysorbate 20, Cremophor RH40 and TPGS and hydrophilic cyclodextrins such as HPbetaCD. Using a co-solvent based method and 25 drug candidates, the data suggested, on the whole, that the surfactants and the selected cyclodextrin seemed to best augment the extent of supersaturation but had variable benefits as stabilizers, while the pharmaceutical polymers had useful effect on supersaturation stability but were less helpful in increasing the extent of supersaturation. Using these data, a group of simple solid dosage forms were prepared and tested in the dog for one of the drug candidates. Excipients that gave the best extent and stability for the formed supersaturated solution in the screening assay also gave the highest oral bioavailability in the dog.

  11. Diluting ferric carboxymaltose in sodium chloride infusion solution (0.9% w/v) in polypropylene bottles and bags: effects on chemical stability.

    Science.gov (United States)

    Philipp, Erik; Braitsch, Michaela; Bichsel, Tobias; Mühlebach, Stefan

    2016-01-01

    This study was designed to assess the physicochemical stability of colloidal ferric carboxymaltose solution (Ferinject) when diluted and stored in polypropylene (PP) bottles and bags for infusion. Two batches of ferric carboxymaltose solution (Ferinject) were diluted (500 mg, 200 mg and 100 mg iron in 100 mL saline) in PP bottles or bags under aseptic conditions. The diluted solutions were stored at 30°C and 75%±5% relative humidity (rH) for 72 h, and samples were withdrawn aseptically at preparation and after 24 h, 48 h and 72 h. Multiple parameters were used to test stability-related measures (pH, total iron and iron (II) content, molecular weight range determination, microbial contamination and particles count ≥10 μm). Overall, Ferinject diluted in 0.9% (w/v) NaCl solution and stored in PP bottles and bags was stable within the specifications for the complex and the acceptability limits set for all assays. In both containers, total iron content remained stable, within 10% of the theoretical iron content, and levels of iron (II) remained far below the threshold of acceptability. All preparations were free from sediments, particle numbers were acceptable and there was no microbial contamination. The molecular weight distribution and polydispersity index were also acceptable. Under the tested experimental conditions, colloidal ferric carboxymaltose solution (Ferinject) diluted in saline in PP infusion bottles or bags demonstrated physical and chemical stability for up to 72 h at 30°C and 75% rH. Because of the lack of additional clinical data, when using ferric carboxymaltose, physicians/pharmacists should refer to the dilution and storing recommendations given in the product's summary of product characteristics.

  12. Asymptotic behaviour and stability of solutions of a singularly perturbed elliptic problem with a triple root of the degenerate equation

    Science.gov (United States)

    Butuzov, V. F.

    2017-06-01

    We construct and justify asymptotic expansions of solutions of a singularly perturbed elliptic problem with Dirichlet boundary conditions in the case when the corresponding degenerate equation has a triple root. In contrast to the case of a simple root, the expansion is with respect to fractional (non-integral) powers of the small parameter, the boundary-layer variables have another scaling, and the boundary layer has three zones. This gives rise to essential modifications in the algorithm for constructing the boundary functions. Solutions of the elliptic problem are stationary solutions of the corresponding parabolic problem. We prove that such a stationary solution is asymptotically stable and find its global domain of attraction.

  13. The stability and degradation kinetics of acetylsalicylic acid in different organic solutions revisited – an UHPLC–ESI-QTOF spectrometry study

    Directory of Open Access Journals (Sweden)

    Skibinski Robert

    2016-04-01

    Full Text Available Ultra high performance liquid chromatography (UHPLC, coupled with accurate quadrupole-time-of-flight (Q-TOF mass spectrometry, was used for the stability study of acetylsalicylic acid within a variety of different organic solutions: methanol, ethanol, propan-2-ol, acetonitrile, tetrahydrofuran and 1,4-dioxane. With the use of gradient elution chromatography and mass spectrometry detection in negative ionization, MS and MS/MS spectra were recorded simultaneously. In addition, quantitative, as well as qualitative analysis was performed during one assay. The stability of acetylsalicylic acid in such solutions was tested at room temperature, in a 12h period. In the work, in all cases, only one main degradation product, salicylic acid, was found. What is more, the work revealed that the degradation of aspirin in the tested organic solutions yields apparent second-order kinetics. The study also demonstrated that acetonitrile and 1,4-dioxane turned out to be the most stable solvents, and an above 80% of initial concentration of acetylsalicylic acid was found in this case. Furthermore, the most popular analytical solvents, methanol and ethanol, were found to be very unstable media. Herein, below 40% of initial concentration of acetylsalicylic acid was seen after 12h. The obtained results were also compared with the degradation of acetylsalicylic acid in a water solution. In this situation, only about 25% of the analyzed compound was resolved to salicylic acid in the same time frame.

  14. Preparation and stability of ethanol-free solution of [18F]florbetapir ([18F]AV-45) for positron emission tomography amyloid imaging.

    Science.gov (United States)

    Hayashi, Kazutaka; Tachibana, Akiko; Tazawa, Shusaku; Mizukawa, Yosuke; Osaki, Katsuhiko; Morimoto, Yoko; Zochi, Riyo; Kurahashi, Masahiro; Aki, Hatsumi; Takahashi, Kazuhiro

    2013-05-15

    We have developed an ethanol-free formulation method of [(18) F]florbetapir ([(1) (8) F]AV-45) using a commercially available automated JFE multi-purpose synthesizer. We have also evaluated the radiochemical stability in an ethanol-free solution of [(18) F]AV-45 under visible light irradiation and dark conditions by comparison with a conventional 10% ethanol solution of [(18) F]AV-45. [(18) F]AV-45 was obtained with a radiochemical yield of 55.1 ± 2.2% (decay-corrected to end of bombardment), specific activity of 591.6 ± 90.3 GBq/µmol and radiochemical purity of >99% within a total synthesis time of about 73 min. The radiochemical purity of [(18) F]AV-45 formulated by dissolving the ethanol-free solution was found to decrease as a function of the period of exposure to visible light. In contrast, the visible light photolysis could be suppressed by adding 10% ethanol to the formulation or by avoiding exposure to visible light. In the radiosynthesis of [(18) F]AV-45 formulated by dissolving the ethanol-free solution, [(18) F]AV-45 could be obtained with high radiochemical purity and high stability by avoiding exposure to visible light. Copyright © 2013 John Wiley & Sons, Ltd.

  15. Modulation stability and dispersive optical soliton solutions of higher order nonlinear Schrödinger equation and its applications in mono-mode optical fibers

    Science.gov (United States)

    Arshad, Muhammad; Seadawy, Aly R.; Lu, Dianchen

    2018-01-01

    In mono-mode optical fibers, the higher order non-linear Schrödinger equation (NLSE) describes the propagation of enormously short light pulses. We constructed optical solitons and, solitary wave solutions of higher order NLSE mono-mode optical fibers via employing modified extended mapping method which has important applications in Mathematics and physics. Furthermore, the formation conditions are also given on parameters in which optical bright and dark solitons can exist for this media. The moment of the obtained solutions are also given graphically, that helps to realize the physical phenomena's of this model. The modulation instability analysis is utilized to discuss the model stability, which verifies that all obtained solutions are exact and stable. Many other such types of models arising in applied sciences can also be solved by this reliable, powerful and effective method. The method can also be functional to other sorts of higher order nonlinear problems in contemporary areas of research.

  16. Stability of antibiotics and amino acids in two synthetic L-amino acid solutions commonly used for total parenteral nutrition in children

    DEFF Research Database (Denmark)

    Colding, H; Andersen, G E

    1978-01-01

    The stability and interaction at 29 degrees C of ampicillin, carbenicillin, gentamicin, and polymyxin B were examined in a common electrolyte solution, invertose darrow, and in two synthetic l-amino acid solutions, one commercial (vamin with fructose; Vitrum) and the other a neonatal preparation...... modified for use in newborn infants. The concentration of amino acids was measured before and after the addition of these antibiotics. The concentration of antibiotics was measured over a 24-h period with a microbiological method. The concentration of ampicillin in invertose darrow fell 52%, and in vamin...... of the penicillins. The concentration of gentamicin and polymyxin B was unchanged in all solutions over a 24-h period. With the exception of cystine, the concentration of all amino acids remained constant after 24 h in the neonatal preparation with and without the different combinations of antibiotics. For cystine...

  17. Technology of Synergy Manifestation in the Research of Solution's Stability of Differential Equations System

    Science.gov (United States)

    Dvoryatkina, Svetlana N.; Melnikov, Roman A. M.; Smirnov, Eugeny I.

    2017-01-01

    Effectiveness of mathematical education as non-linear, composite and open system, formation and development of cognitive abilities of the trainee are wholly defined in the solution of complex tasks by means of modern achievements in science to high school practice adaptation. The possibility of complex tasks solution arises at identification of…

  18. Enzymatic decolorization of anthraquinone and diazo dyes using horseradish peroxidase enzyme immobilized onto various polysulfone supports.

    Science.gov (United States)

    Celebi, Mithat; Kaya, Mehmet Arif; Altikatoglu, Melda; Yildirim, Huseyin

    2013-10-01

    In this study, covalent immobilization of the horseradish peroxidase (HRP) onto various polysulfone supports was investigated. For this purpose, different polysulfones were methacrylated with methacryloyl chloride, and then, nonwoven fabric samples were coated by using solutions of these methacrylated polysulfones. Finally, support materials were immersed into aquatic solution of HRP enzyme for covalent immobilization. Structural analysis of enzyme immobilization onto various polysulfones was confirmed with Fourier transform infrared spectroscopy, atomic force microscopy, and proton nuclear magnetic resonance spectroscopy. Decolorization of textile diazo (Acid Black 1) and anthraquinone (Reactive Blue 19) dyes was investigated by UV-visible spectrophotometer. Covalently immobilized enzyme has been used seven times in freshly prepared dye solutions through 63 days. Dye decolorization performance of the immobilized systems was observed that still remained high (70%) after reusing three times. Enzyme activities of immobilized systems were determined and compared to free enzyme activity at different conditions (pH, temperature, thermal stability, storage stability). Enzyme activities of immobilized systems and free enzyme were also investigated at the different temperatures and effects of temperature and thermal resistance for different incubation time at 50 °C. In addition, storage activity of free and immobilized enzymes was determined at 4 °C at different incubation days.

  19. Enhanced removal of humic acid from aqueous solution by novel stabilized nano-amorphous calcium phosphate: Behaviors and mechanisms

    Science.gov (United States)

    Jiang, Ling; Li, Yiming; Shao, Yi; Zhang, Yong; Han, Ruiming; Li, Shiyin; Wei, Wei

    2018-01-01

    Stabilized nano-amorphous calcium phosphate (nACP) was prepared using polyethylene glycol as stabilizer to obtain a nanosized amorphous adsorbent. The produced nACP was evaluated by using XRD, FTIR, SEM and X-ray photoelectron spectroscopy (XPS). The sedimentation test demonstrated that nACP exhibited better stability than crystallized hydroxyapatite. The adsorption efficiency of the nACP material for aqueous humic acid (HA) was evaluated from the point of view of medium pH, adsorption time, temperature, and ionic strength, as well as the presences of metal ions. The results of the study showed very good adsorption performance towards aqueous HA. The Sips modeling results revealed that the stabilized nACP adsorbent had a considerably high adsorption capacity (248.3 mg/g) for HA at 298 K. The adsorption data fitted well into pseudo-second order and Elovich kinetic models. XPS analyses indicated that HA retention on nACP material might be due to the surface complexation reaction between oxygen-containing group and calcium of HA and nACP, respectively. Moreover, the HA adsorption capacity of nACP could still keep more than 86% after four adsorption-desorption cycles. By taking into account all results it was concluded that the nACP adsorbent leveraged its stability in combination with its high uptake capacity to offer a great promise for HA adsorption from water.

  20. Stability constants of the fluoride complexes of actinides in aqueous solution and their correlation with fundamental properties

    International Nuclear Information System (INIS)

    Chaudhuri, N.K.; Sawant, R.M.

    1997-09-01

    Stability constants of the fluoride complexes of the actinides in different oxidation states measured by potentiometric method using fluoride ion selective electrode have been presented. Procedure and precautions required to overcome certain difficulties particular to actinide ions have been discussed. Literature data from various sources have been compiled. In order to have a reasonable comparison the stability constant (β 1 ) values obtained in diverse ionic strength media are converted to thermodynamic stability constant, β 1 0 , using Davies equation (a modification of Debye-Huckel equation). A correlation of the β 1 0 values with the fundamental properties of the actinide ions using various models available in the literature has been attempted. A semiempirical relation recently developed by Brown, Sylva and Ellis (BSE equation) appears to be most suitable. Using the values of ionic radii and best available values of the stability constants of a large number of metal ions from recent compilations a comparative study of the various models or relations available in the literature has been tried. For metal ions in general, the best correlation is obtained with the BSE equation. In an attempt to accommodate the unusual trend in the stability constants of the tetravalent actinides a modification in a parameter of the BSE equation has been proposed. Good agreement between the theoretically calculated and experimentally determined values for actinides in different oxidation states is then obtained in most of the cases. (author)

  1. NMR investigation of acrolein stability in hydroalcoholic solution as a foundation for the valid HS-SPME/GC–MS quantification of the unsaturated aldehyde in beverages

    Energy Technology Data Exchange (ETDEWEB)

    Kächele, Martin [Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weissenburger Strasse 3, D-76187 Karlsruhe (Germany); Hochschule Mannheim, Paul-Wittsack-Strasse 10, D-68163 Mannheim (Germany); Monakhova, Yulia B. [Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weissenburger Strasse 3, D-76187 Karlsruhe (Germany); Bruker Biospin GmbH, Silbersteifen, 76287 Rheinstetten (Germany); Department of Chemistry, Saratov State University, Astrakhanskaya Street 83, 410012 Saratov (Russian Federation); Kuballa, Thomas [Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weissenburger Strasse 3, D-76187 Karlsruhe (Germany); Lachenmeier, Dirk W., E-mail: lachenmeier@web.de [Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weissenburger Strasse 3, D-76187 Karlsruhe (Germany); Ministry of Rural Affairs and Consumer Protection, Kernerplatz 10, 70182 Stuttgart (Germany)

    2014-04-01

    Highlights: • Acrolein in hydroalcoholic solution degrades to 1,3,3-propanetriol and 3-hydroxypropionaldehyde. • Hydroquinone (0.2%) at pH 3.0 stabilizes acrolein solutions. • Quantitative HS-SPME/GC–MS determination of acrolein in alcoholic beverages was developed (LOD 14 μg L⁻¹. • 6 of 117 samples had acrolein levels above the WHO threshold (1500 μg L⁻¹). Abstract: Acrolein (propenal) is found in many foods and beverages and may pose a health hazard due to its cytotoxicity. Considerable knowledge gaps regarding human exposure to acrolein exist, and there is a lack of reliable analytical methods. Hydroalcoholic dilutions prepared for calibration purposes from pure acrolein show considerable degradation of the compound and nuclear magnetic resonance (NMR) spectroscopy showed that 1,3,3-propanetriol and 3-hydroxypropionaldehyde are formed. The degradation can be prevented by addition of hydroquinone as stabilizer to the calibration solutions, which then show linear concentration-response behaviour required for quantitative analysis. The stabilized calibration solutions were used for quantitative headspace solid-phase microextraction/gas chromatography–mass spectrometry (HS-SPME/GC–MS) determination of acrolein in alcoholic beverages with a detection limit of 14 μg L⁻¹. Of 117 tested alcoholic beverages, 64 were tested positive with the highest incidence in grape marc spirits and whiskey (100%, mean 252 μg L⁻¹), followed by fruit spirits (86%, mean 591 μg/L⁻¹), tequila (86%, mean 404 μg L⁻¹), Asian spirits (43%, mean 54 μg L⁻¹) and wine (9%, mean 0.7 μg L⁻¹). Acrolein could not be detected in beer, vodka, absinthe and bottled water. Six of the fruit and grape marc spirits had acrolein levels above the World Health Organization (WHO) provisional tolerable concentration of 1.5 mg L⁻¹.

  2. NMR investigation of acrolein stability in hydroalcoholic solution as a foundation for the valid HS-SPME/GC–MS quantification of the unsaturated aldehyde in beverages

    International Nuclear Information System (INIS)

    Kächele, Martin; Monakhova, Yulia B.; Kuballa, Thomas; Lachenmeier, Dirk W.

    2014-01-01

    Highlights: • Acrolein in hydroalcoholic solution degrades to 1,3,3-propanetriol and 3-hydroxypropionaldehyde. • Hydroquinone (0.2%) at pH 3.0 stabilizes acrolein solutions. • Quantitative HS-SPME/GC–MS determination of acrolein in alcoholic beverages was developed (LOD 14 μg L −1 ). • 6 of 117 samples had acrolein levels above the WHO threshold (1500 μg L −1 ). - Abstract: Acrolein (propenal) is found in many foods and beverages and may pose a health hazard due to its cytotoxicity. Considerable knowledge gaps regarding human exposure to acrolein exist, and there is a lack of reliable analytical methods. Hydroalcoholic dilutions prepared for calibration purposes from pure acrolein show considerable degradation of the compound and nuclear magnetic resonance (NMR) spectroscopy showed that 1,3,3-propanetriol and 3-hydroxypropionaldehyde are formed. The degradation can be prevented by addition of hydroquinone as stabilizer to the calibration solutions, which then show linear concentration-response behaviour required for quantitative analysis. The stabilized calibration solutions were used for quantitative headspace solid-phase microextraction/gas chromatography–mass spectrometry (HS-SPME/GC–MS) determination of acrolein in alcoholic beverages with a detection limit of 14 μg L −1 . Of 117 tested alcoholic beverages, 64 were tested positive with the highest incidence in grape marc spirits and whiskey (100%, mean 252 μg L −1 ), followed by fruit spirits (86%, mean 591 μg/L −1 ), tequila (86%, mean 404 μg L −1 ), Asian spirits (43%, mean 54 μg L −1 ) and wine (9%, mean 0.7 μg L −1 ). Acrolein could not be detected in beer, vodka, absinthe and bottled water. Six of the fruit and grape marc spirits had acrolein levels above the World Health Organization (WHO) provisional tolerable concentration of 1.5 mg L −1

  3. Explaining Operational Instability of Amine Transaminases : Substrate-Induced Inactivation Mechanism and Influence of Quaternary Structure on Enzyme-Cofactor Intermediate Stability

    NARCIS (Netherlands)

    Borner, Tim; Ramisch, Sebastian; Reddem, Eswar R.; Bartsch, Sebastian; Vogel, Andreas; Thunnissen, Andy-Mark W. H.; Adlercreutz, Patrick; Grey, Carl

    The insufficient operational stability of amine transaminases (ATA) constitutes a limiting factor for high productivity in chiral amine synthesis. In this work, we investigated the operational stability of a tetrameric ATA with 92% sequence identity to a Pseudomonas sp. transaminase and compared it

  4. Effect of a surface sealant on the color stability of composite resins after immersion in staining solution.

    Science.gov (United States)

    Pedroso, Lauana Borges; Barreto, Luma Franciélle Cabreira; Miotti, Leonardo Lamberti; Nicoloso, Gabriel Ferreira; Durand, Leticia Brandão

    2016-01-01

    This study evaluated the influence of surface sealants on the color stability of 2 different composite resins after immersion in coffee. Four groups were created (n = 10): microhybrid composite, microhybrid with surface sealant, nanofilled composite, and nanofilled composite with surface sealant. Half of the specimens of each group were immersed in distilled water and half were immersed in coffee for 48 hours. Color was measured before and after immersion. Groups with surface sealants presented less color variation when compared with the groups without surface sealants. The nanofilled resin specimens presented the greatest color variation within the groups without sealant. The surface sealant positively influenced the color stability of composite resin specimens immersed in coffee. When surface sealant was not applied, the microhybrid specimens had better color stability than the nanofilled.

  5. Efficient Immobilization of Porcine Pancreatic α-Amylase on Amino-Functionalized Magnetite Nanoparticles: Characterization and Stability Evaluation of the Immobilized Enzyme.

    Science.gov (United States)

    Akhond, M; Pashangeh, Kh; Karbalaei-Heidari, H R; Absalan, G

    2016-11-01

    The potential of the modified magnetic nanoparticles for covalent immobilization of porcine pancreatic α-amylase has been investigated. The synthesis and immobilization processes were simple and fast. The co-precipitation method was used for synthesis of magnetic iron oxide (Fe 3 O 4 ) nanoparticles (NPs) which were subsequently coated with silica through sol-gel reaction. The amino-functionalized NPs were prepared by treating silica-coated NPs with 3-aminopropyltriethoxysilane followed by covalent immobilization of α-amylase by glutaraldehyde. The optimum enzyme concentration and incubation time for immobilization reaction were 150 mg and 4 h, respectively. Upon this immobilization, the α-amylase retained more than 50 % of its initial specific activity. The optimum pH for maximal catalytic activity of the immobilized enzyme was 6.5 at 45 °C. The kinetic studies on the immobilized enzyme and its free counterpart revealed an acceptable change of K m and V max . The Km values were found as 4 and 2.5 mM for free and immobilized enzymes, respectively. The V max values for the free and immobilized enzymes were calculated as 1.75 and 1.03 μmol mg -1  min -1 , in order, when starch was used as the substrate. A quick separation of immobilized amylase from reaction mixture was achieved when a magnetically active support was applied. In comparison to the free enzyme, the immobilized enzyme was thermally stable and was reusable for 9 cycles while retaining 68 % of its initial activity.

  6. Room temperature synthesis of PbSe quantum dots in aqueous solution: Stabilization by interactions with ligands

    Science.gov (United States)

    Primera-Pedrozo, Oliva M.; Arslan, Zikri; Rasulev, Bakhtiyor; Leszczynski, Jerzy

    2011-01-01

    An aqueous route of synthesis is described for rapid synthesis of lead selenide quantum dots (PbSe QDs) at room temperature in an attempt to produce water-soluble and stable nanocrystals. Several thiol-ligands, including thioglycolic acid (TGA), thioglycerol (TGC), 3-mercaptopropionic acid (MPA), 2-mercaptoethyleamine hydrochloride (MEA), 6-mercaptohexanoic acid (MHA), and L-cysteine (L-cys), were used for capping/stabilization of PbSe QDs. The effects of the ligands on the stability of PbSe QDs were evaluated for a period of two months at room temperature under normal light conditions and at 4 °C in dark. The TGA- and MEA-capped QDs exhibited the highest stability prior to purification, almost two months when kept in dark at 4 °C. However, the stability of TGA-capped QDs was reduced substantially after purification to about 5 days under same conditions, while MEA-capped QDs did not show any significant instability. The stabilization energies of Pb-thiolate complexes determined by theoretical DFT simulations supported the experimental results. The PbSe QDs capped with TGA, MPA and MEA were successfully purified and re-dispersed in water, while those stabilized with TGC, MHA and L-cys aggregated during purification attempts. The purified PbSe QDs possess very susceptible surface resulting in poor stability for about 30 – 45 min after re-dispersion in water. In the presence of an excess of free ligand, the stability increased up to 5 days for TGA-capped QDs at pH 7.19, 9 –12 days for MPA-capped QDs at pH 7.3–7.5 and 45–47 days for MEA-capped QDs at pH 7.35. X-Ray Diffraction (XRD) results showed that the QDs possess a cubic rock salt structure with the most intense peaks located at 2θ = 25.3° (200) and 2θ = 29.2° (100). TEM images showed that the size of the QDs ranges between 5 and 10 nm. ICP-MS results revealed that Pb:Se ratio was 1.26, 1.28, 3.85, 1.18, and 1.31 for the QDs capped with TGA, MPA, MEA, L-Cys, and TGC, respectively. The proposed method

  7. Continuous-Flow Applications of Silica-Encapsulated Enzymes

    National Research Council Canada - National Science Library

    Luckarift, Heather R; Johnson, Glenn R; Tomczak, Melanie M; Naik, Rajesh R; Spain, Jim C

    2006-01-01

    .... The enzyme/inorganic nanocomposites exhibit excellent mechanical stability and provide an effective method for developing immobilized enzyme reactors, applicable to biocatalysis, biosensors and drug discovery...

  8. Evaluation of Thermostabilities of Enzymes, Mediators and Immobilizing Membranes for Enzyme Sensors

    Science.gov (United States)

    Yamada, Yohei; Ohnishi, Yuki; Hayashi, Tetsuya; Isobe, Yoshifumi; Yabutani, Tomoki

    The stability of the constituents of electrochemical measurement, electron mediators, enzymes and enzyme-immobilizing membranes was evaluated under high temperature (maximum 75°C) by electrochemical analysis, UV-Vis spectrometry (UV-Vis) and UV circular dichroism (CD). As a result of stability evaluation of mediators at 75°C, electrochemical activity of 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid ammonium salt (ABTS), potassium ferricyanide (K3[Fe(CN)6]) and ferrocenemethanol (FcOH) were not changed, but 2,6-dichloroindophenol (DCIP), p-benzoquinone (p-BQ), vitaminK3 (VK3) were greatly decreased. The stability of diaphorase from Bacillus stearothermophilus (DI) were compared between in-solution and in several types of membranes, Agarose H, Poly-L-lysine (PLL) and poly-ion-complex (PIC) by electrochemical analysis. In solution, activity and secondary structure of DI were changed at 65°C or higher. This tendency of activity was not much different in Agarose H but in PLL, the activity was almost kept until 70°C. It was suggested that DI was fixed on the electrodes in high concentration and the elimination of DI seldom arise in PLL from the magnitude of the current response and the results of prolonged stability evaluation.

  9. Stability of silver nanoparticles (nAg) in aqueous solution: the role of particle size and water ionic strength

    CSIR Research Space (South Africa)

    Radebe, N

    2014-01-01

    Full Text Available , South Africa Silver nanoparticles Nanosilver (nAg) • Amongst the most widely used ENP’s ≈30% registered commercial nano-products • Antimicrobial properties • Antiseptic activity • High electrical and thermal conductivity • Chemical stability...

  10. Study of Water-Oil Emulsion Breaking by Stabilized Solution Consisting of Anionic Surface Acting Agent - Soda Ash - Polymer (ASP)

    Science.gov (United States)

    Kulichkov, S. V.; Avtomonov, E. G.; Andreeva, L. V.; Solomennik, S. F.; Nikitina, A. V.

    2018-01-01

    The paper provides a laboratory research of breaking natural water-oil emulsions: - by non-stabilized ASP; by stabilized ASP; by mixture of stabilized and non-stabilized ASP in different proportions and production of refinery water of the required quality with the use of IronGuard 2495 as flocculant. Oil-in-water emulsion is stable. Classic methods are not suitable for residual water treatment: sediment gravity flow; filtration; centrifuge test. Microemulsion formed after ASP application has low boundary tension and high pH. It contributes to transfer of oil phase into a water one, forming oil-in-water emulsion. Alkaline condition has adverse effect on demulsifying ability of agents, flocculation and boundary tension. For breaking of water-oil emulsion at EBU before the interchanger water or water-oil emulsion from the wells that were not APS-treated in ratio of 1:9 shall be delivered. Residual water after EBU must be prepared in water tanks by dilution in great volume.

  11. Dimensionless Analytical Solution and New Design Formula for Lateral-Torsional Buckling of I-Beams under Linear Distributed Moment via Linear Stability Theory

    Directory of Open Access Journals (Sweden)

    Wen-Fu Zhang

    2017-01-01

    Full Text Available Even for the doubly symmetric I-beams under linear distributed moment, the design formulas given by codes of different countries are quite different. This paper will derive a dimensionless analytical solution via linear stability theory and propose a new design formula of the critical moment of the lateral-torsional buckling (LTB of the simply supported I-beams under linear distributed moment. Firstly, the assumptions of linear stability theory are reviewed, the dispute concerning the LTB energy equation is introduced, and then the thinking of Plate-Beam Theory, which can be used to fully resolve the challenge presented by Ojalvo, is presented briefly; secondly, by introducing the new dimensionless coefficient of lateral deflection, the new dimensionless critical moment and Wagner’s coefficient are derived naturally from the total potential energy. With these independent parameters, the new dimensionless analytical buckling equation is obtained; thirdly, the convergence performance of the dimensionless analytical solution is discussed by numerical solutions and its correctness is verified by the numerical results given by ANSYS; finally, a new trilinear mathematical model is proposed as the benchmark of formulating the design formula and, with the help of 1stOpt software, the four coefficients used in the proposed dimensionless design formula are determined.

  12. Shelf life stability comparison in air for solution processed pristine PDPP3T polymer and doped spiro-OMeTAD as hole transport layer for perovskite solar cell

    Directory of Open Access Journals (Sweden)

    Ashish Dubey

    2016-06-01

    Full Text Available This data in brief includes forward and reverse scanned current density–voltage (J–V characteristics of perovskite solar cells with PDPP3T and spiro-OMeTAD as HTL, stability testing conditions of perovskite solar cell shelf life in air for both PDPP3T and spiro-OMeTAD as HTL as per the description in Ref. [1], and individual J–V performance parameters acquired with increasing time exposed in ambient air are shown for both type of devices using PDPP3T and spiro-OMeTAD as HTL. The data collected in this study compares the device stability with time for both PDPP3T and spiro-OMeTAD based perovskite solar cells and is directly related to our research article “solution processed pristine PDPP3T polymer as hole transport layer for efficient perovskite solar cells with slower degradation” [2].

  13. Membrane Assisted Enzyme Fractionation

    DEFF Research Database (Denmark)

    Yuan, Linfeng

    . In this thesis, separations using crossflow elecro-membrane filtration (EMF) of amino acids, bovine serum albumin (BSA) and industrial enzymes from Novozymes were performed. The main objective of this study was to investigate the technological feasibility of EMF in the application of industrial enzyme...... fractionation, such as removal of a side activity from the main enzyme activity. As a proof-of-concept, amino acids were used as model solution to test the feasibility of EMF in the application of amphoteric molecule separation. A single amino acid was used to illustrate the effect of an electric field...... on the separation performance were very small in the investigated range. The mass transport of each enzyme can be well explained by the Extended-Nernst-Planck equation. Better separation was observed at lower feed concentration, higher solution pH in the investigated range and with a polysulfone (PS) MF membrane...

  14. Solution NMR characterization of Sgf73(1-104) indicates that Zn ion is required to stabilize zinc finger motif

    International Nuclear Information System (INIS)

    Lai, Chaohua; Wu, Minhao; Li, Pan; Shi, Chaowei; Tian, Changlin; Zang, Jianye

    2010-01-01

    Zinc finger motif contains a zinc ion coordinated by several conserved amino acid residues. Yeast Sgf73 protein was identified as a component of SAGA (Spt/Ada/Gcn5 acetyltransferase) multi-subunit complex and Sgf73 protein was known to contain two zinc finger motifs. Sgf73(1-104), containing the first zinc finger motif, was necessary to modulate the deubiquitinase activity of SAGA complex. Here, Sgf73(1-104) was over-expressed using bacterial expression system and purified for solution NMR (nuclear magnetic resonance) structural studies. Secondary structure and site-specific relaxation analysis of Sgf73(1-104) were achieved after solution NMR backbone assignment. Solution NMR and circular dichroism analysis of Sgf73(1-104) after zinc ion removal using chelation reagent EDTA (ethylene-diamine-tetraacetic acid) demonstrated that zinc ion was required to maintain stable conformation of the zinc finger motif.

  15. Stability analysis solutions and optical solitons in extended nonlinear Schrödinger equation with higher-order odd and even terms

    Science.gov (United States)

    Peng, Wei-Qi; Tian, Shou-Fu; Zou, Li; Zhang, Tian-Tian

    2018-01-01

    In this paper, the extended nonlinear Schrödinger equation with higher-order odd (third order) and even (fourth order) terms is investigated, whose particular cases are the Hirota equation, the Sasa-Satsuma equation and Lakshmanan-Porsezian-Daniel equation by selecting some specific values on the parameters of higher-order terms. We first study the stability analysis of the equation. Then, using the ansatz method, we derive its bright, dark solitons and some constraint conditions which can guarantee the existence of solitons. Moreover, the Ricatti equation extension method is employed to derive some exact singular solutions. The outstanding characteristics of these solitons are analyzed via several diverting graphics.

  16. On a delay differential equation arising from a car-following model: Wavefront solutions with constant-speed and their stability

    OpenAIRE

    Stumpf, Eugen

    2016-01-01

    This work is concerned with the study of a scalar delay differential equation \\begin{equation*} z^{\\prime\\prime}(t)=h^2\\,V(z(t-1)-z(t))+h\\,z^\\prime(t) \\end{equation*} motivated by a simple car-following model on an unbounded straight line. Here, the positive real $h$ denotes some parameter, and $V$ is a so-called \\textit{optimal velocity function} of the traffic model involved. We analyze the existence and local stability properties of solutions $z(t)=c\\,t+d$, $t\\in\\mathbb{R}$, with $c,d\\in\\m...

  17. Immobilized enzymes: understanding enzyme - surface interactions at the molecular level.

    Science.gov (United States)

    Hoarau, Marie; Badieyan, Somayesadat; Marsh, E Neil G

    2017-11-22

    Enzymes immobilized on solid supports have important and industrial and medical applications. However, their uses are limited by the significant reductions in activity and stability that often accompany the immobilization process. Here we review recent advances in our understanding of the molecular level interactions between proteins and supporting surfaces that contribute to changes in stability and activity. This understanding has been facilitated by the application of various surface-sensitive spectroscopic techniques that allow the structure and orientation of enzymes at the solid/liquid interface to be probed, often with monolayer sensitivity. An appreciation of the molecular interactions between enzyme and surface support has allowed the surface chemistry and method of enzyme attachement to be fine-tuned such that activity and stability can be greatly enhanced. These advances suggest that a much wider variety of enzymes may eventually be amenable to immobilization as green catalysts.

  18. Effects of solution crowding on actin polymerization reveal the energetic basis for nucleotide-dependent filament stability

    OpenAIRE

    Frederick, Kendra B.; Sept, David; De La Cruz, Enrique M.

    2008-01-01

    Actin polymerization is a fundamental cellular process involved in cell structure maintenance, force generation, and motility. Phosphate release from filament subunits following ATP hydrolysis destabilizes the filament lattice and increases the critical concentration (Cc) for assembly. The structural differences between ATP- and ADP-actin are still debated, as well as the energetic factors that underlie nucleotide-dependent filament stability, particularly under crowded intracellular conditio...

  19. Graphene-oxide-supported Pt nanoparticles with high activity and stability for hydrazine electro-oxidation in a strong acidic solution

    Science.gov (United States)

    Kim, Ji Dang; Choi, Myong Yong; Choi, Hyun Chul

    2017-10-01

    Graphene-oxide-supported Pt (GO-Pt) nanoparticles were prepared by performing diimide-activated amidation and used in an electrocatalyst for hydrazine electro-oxidation in 0.5 M H2SO4 solution. The physico-chemical properties of the GO-Pt nanoparticles were characterized with various techniques, which revealed that highly dispersed Pt nanoparticles with an average size of 2.6 nm were densely deposited on the amidated GO due to their strong adhesion. Cyclic voltammograms were obtained and demonstrate that the GO-Pt catalyst exhibits significantly improved catalytic activity and long-term stability in hydrazine electro-oxidation in a strong acidic solution when compared to commercial Pt/C and Pt metal electrodes. These enhanced electrochemical properties are attributed to the large electrochemically active surface area that results from the smaller size and excellent dispersion of the Pt nanoparticles on amidated GO.

  20. Effect of electrolyte valency, alginate concentration and pH on engineered TiO₂ nanoparticle stability in aqueous solution.

    Science.gov (United States)

    Loosli, Frédéric; Le Coustumer, Philippe; Stoll, Serge

    2015-12-01

    Agglomeration and disagglomeration processes are expected to play a key role on the fate of engineered nanoparticles in natural aquatic systems. These processes are investigated here in detail by studying first the stability of TiO2 nanoparticles in the presence of monovalent and divalent electrolytes at different pHs (below and above the point of zero charge of TiO2) and discussing the importance of specific divalent cation adsorption with the help of the DLVO theory as well as the importance of the nature of the counterions. Then the impact of one polysaccharide (alginate) on the stability of agglomerates formed under pH and water hardness representative of Lake Geneva environmental conditions is investigated. In these conditions the large TiO2 agglomerates (diameter>1μm) are positively charged due to Ca(2+) and Mg(2+) specific adsorption and alginate, which is negatively charged, adsorbs onto the agglomerate surface. Our results indicate that the presence of alginate at typical natural organic matter concentration (1-10 mg L(-1)) strongly modifies the TiO2 agglomerate (50 mg L(-1)) stability by inducing their partial and rapid disagglomeration. The importance of disagglomeration is found dependent on the alginate concentration with maximum of disagglomeration obtained for alginate concentration ≥8 mg L(-1) and leading to 400 nm fragments. From an environmental point of view partial restabilization of TiO2 agglomerates in the presence of alginate constitutes an important outcome. Disagglomeration will enhance their transport and residence time in aquatic systems which is an important step in the current knowledge on risk assessment associated to engineered nanoparticles. Copyright © 2015 Elsevier B.V. All rights reserved.