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Sample records for model hm polyelectrolytes

  1. Molecular Thermodynamic Model for Polyelectrolyte Solutions with Added Salts

    Institute of Scientific and Technical Information of China (English)

    ZHANGBo; CAIJun; 等

    2002-01-01

    A molecular thermodynamic model of polyelectrolyte developed previously was extended to polyelectrolyte solutions with added salts.Thermodynamic properties,such as activity coefficients of polyelectrolytes or added salts and osmotic coefficients of solvent, of a number of aqueous mixtures of polyelectrolytes and salts are analyzed with the proposed model.Successful correlation is obtained in the range of moderate or higher polyion concentration.For the same sample,thermodynamic properties of polyelectrolytes with and without simple electrolytes can be predicted mutually using parameters from regression data.

  2. Modeling competitive substitution in a polyelectrolyte complex

    Energy Technology Data Exchange (ETDEWEB)

    Peng, B.; Muthukumar, M., E-mail: muthu@polysci.umass.edu [Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003 (United States)

    2015-12-28

    We have simulated the invasion of a polyelectrolyte complex made of a polycation chain and a polyanion chain, by another longer polyanion chain, using the coarse-grained united atom model for the chains and the Langevin dynamics methodology. Our simulations reveal many intricate details of the substitution reaction in terms of conformational changes of the chains and competition between the invading chain and the chain being displaced for the common complementary chain. We show that the invading chain is required to be sufficiently longer than the chain being displaced for effecting the substitution. Yet, having the invading chain to be longer than a certain threshold value does not reduce the substitution time much further. While most of the simulations were carried out in salt-free conditions, we show that presence of salt facilitates the substitution reaction and reduces the substitution time. Analysis of our data shows that the dominant driving force for the substitution process involving polyelectrolytes lies in the release of counterions during the substitution.

  3. Characteristics of model polyelectrolyte multilayer films containing laponite clay nanoparticles.

    Science.gov (United States)

    Elzbieciak, M; Wodka, D; Zapotoczny, S; Nowak, P; Warszynski, P

    2010-01-05

    Polyelectrolyte films structure formed by the "layer-by-layer" (LbL) technique can be enriched by addition of charged nanoparticles like carbon nanotubes and silver or hydroxyapatite nanoparticles, which can improve properties of the polyelectrolyte films or modify their functionality. In our paper we examined the formation and properties of model polyelectrolyte multilayers containing a synthetic layered silicate, Laponite. The Laponite nanoparticles were incorporated into multilayer films, which were formed from weak, branched polycation PEI and strong polyanion PSS. Since charge of PEI is pH-dependent, we build up multilayer films in two deposition conditions: pH = 6 when PEI was strongly charged and pH = 10.5 when charge density of PEI was low. Thicknesses of the films constructed with various numbers of Laponite layers were measured by single wavelength ellipsometry. We also determined the differences in permeability for selected electroactive molecules using cyclic voltamperometry. Properties of the films containing clay nanoparticles were compared with model polyelectrolyte multilayer films PEI/PSS formed at the same conditions. We found that Laponite nanoparticles strongly influenced PEI/PSS multilayer film properties. Replacement of PSS by Laponite eliminated the oscillations of the film thickness in the case when PEI was weakly charged. PSS layer adsorbed on top of PEI/Laponite bilayers increased the thickness of multilayer films and improved their barrier properties so synergistic effects between these properties for polyelectrolytes and Laponite nanoparticles could be observed.

  4. An open-source distributed mesoscale hydrologic model (mHM)

    Science.gov (United States)

    Samaniego, Luis; Kumar, Rohini; Zink, Matthias; Thober, Stephan; Mai, Juliane; Cuntz, Matthias; Schäfer, David; Schrön, Martin; Musuuza, Jude; Prykhodko, Vladyslav; Dalmasso, Giovanni; Attinger, Sabine; Spieler, Diana; Rakovec, Oldrich; Craven, John; Langenberg, Ben

    2014-05-01

    The mesoscale hydrological model (mHM) is based on numerical approximations of dominant hydrological processes that have been tested in various hydrological models such as: HBV and VIC. In general, mHM simulates the following processes: canopy interception, snow accumulation and melting, soil moisture dynamics (n-horizons), infiltration and surface runoff, evapotranspiration, subsurface storage and discharge generation, deep percolation and baseflow, and discharge attenuation and flood routing. The main characteristic of mHM is the treatment of the sub-grid variability of input variables and model parameters which clearly distinguishes this model from existing precipitation-runoff models or land surface models. It uses a Multiscale Parameter Regionalization (MPR) to account for the sub-grid variability and to avoid continuous re-calibration. Effective model parameters are location and time dependent (e.g., soil porosity). They are estimated through upscaling operators that link sub-grid morphologic information (e.g., soil texture) with global transfer-function parameters, which, in turn, are found through multi-basin optimization. Global parameters estimated with the MPR technique are quasi-scale invariant and guarantee flux-matching across scales. mHM is an open source code, written in Fortran 2003 (standard), fully modular, with high computational efficiency, and parallelized. It is portable to multiple platforms (Linux, OS X, Windows) and includes a number of algorithms for sensitivity analysis, analysis of parameter uncertainty (MCMC), and optimization (DDS, SA, SCE). All simulated state variables and outputs can be stored as netCDF files for further analysis and visualization. mHM has been evaluated in all major river basins in Germany and over 80 US and 250 European river basins. The model efficiency (NSE) during validation at proxy locations is on average greater than 0.6. During last years, mHM had been used for number of hydrologic applications such as

  5. Modelling Nitrate uptake in river networks using the new mHM water quality model

    Science.gov (United States)

    Yang, Xiaoqiang; Sinha, Sumit; Samaniego, Luis; Kumar, Rohini; Jomaa, Seifeddine; Rode, Michael

    2016-04-01

    To understand the spatial distribution and temporal dynamics of nitrate uptake in river networks under different land use are critical for the protection of river ecosystem and drinking water supply. To this end, distributed grid-based hydrological water quality models are required. The multi-scale Hydrological Model (mHM) was integrated with the nitrate transport and reaction (NTR) routines. The main equations of NTR routines were introduced from the HYPE (Hydrological Predictions for the Environment) model, which has been fully verified in the literature. The new coupled mHM model with the NTR routines is able to calculate the hydrographs at any point and also the distribution of state variables, which makes it possible to present the distribution of inorganic nitrogen uptake in the whole river network. First, the model is successfully calibrated and validated in the Selke catchment (463 km2) using three gauging stations during the period of 1994-2004 in terms of hydrographs and inorganic nitrogen concentrations. Then, the model performance for in-stream Nitrate uptake predictions are presented and analyzed temporally and spatially, considering the Selke river network characteristics. Particularly, how much the land use affects the amount and the intra-annual dynamics of in-stream uptake are discussed using one forest-dominant sub-catchment (Meisdorf, where forest share is about 72%) with another agriculture-dominant sub-catchment (Hausneindorf, where agriculture share is about 76%). In addition, the seasonal variation of model in-stream nitrate uptake predictions are compared with calculated values using the nitrate assimilatory uptake approach generated from high frequency sensor measurements.

  6. Adsorbed polyelectrolyte coatings decrease Fe(0) nanoparticle reactivity with TCE in water: conceptual model and mechanisms.

    Science.gov (United States)

    Phenrat, Tanapon; Liu, Yueqiang; Tilton, Robert D; Lowry, Gregory V

    2009-03-01

    The surfaces of reactive nanoscale zerovalent iron (NZVI) particles used for in situ groundwater remediation are modified with polymers or polyelectrolytes to enhance colloidal stability and mobility in the subsurface. However, surface modification decreases NZVI reactivity. Here, the TCE dechlorination rate and reaction products are measured as a function of adsorbed polyelectrolyte mass for three commercially available polyelectrolytes used for NZVI surface modification including poly(styrene sulfonate) (PSS), carboxymethyl cellulose (CMC), and polyaspartate (PAP). The adsorbed mass, extended layer thickness, and TCE-polyelectrolyte partition coefficient are measured and used to explain the effect of adsorbed polyelectrolyte on NZVI reactivity. For all modifiers, the dechlorination rate constant decreased nonlinearly with increasing surface excess, with a maximum of a 24-fold decrease in reactivity. The TCE dechlorination pathways were not affected. Consistent with Scheutjens-Fleer theory for homopolymer adsorption, the nonlinear relationship between the dechlorination rate and the surface excess of adsorbed polyelectrolyte suggests that adsorbed polyelectrolyte decreases reactivity primarily by blocking reactive surface sites at low surface excess where they adsorb relatively flat onto the NZVI surface, and by a combination of site blocking and decreasing the aqueous TCE concentration at the NZVI surface due to partitioning of TCE to adsorbed polyelectrolytes. This explanation is also consistent with the effect of adsorbed polyelectrolyte on acetylene formation. This conceptual model should apply to other medium and high molecular weight polymeric surface modifiers on nanoparticles, and potentially to adsorbed natural organic matter.

  7. Cylindrical cell model for the electrostatic free energy of polyelectrolyte complexes

    NARCIS (Netherlands)

    Biesheuvel, P.M.; Cohen Stuart, M.A.

    2004-01-01

    Associative phase separation (complex coacervation) in a mixture of oppositely charged polyelectrolytes can lead to different types of (inter-)polyelectrolyte complexes (soluble micelles, macroscopic precipitation). In a previous report [Langmuir 2004, 20, 2785-2791], we presented a model for the

  8. Polyelectrolytes thermodynamics and rheology

    CERN Document Server

    P M, Visakh; Picó, Guillermo Alfredo

    2014-01-01

    This book discusses current development of theoretical models and experimental findings on the thermodynamics of polyelectrolytes. Particular emphasis is placed on the rheological description of polyelectrolyte solutions and hydrogels.

  9. FLOW STRESS MODEL FOR COLD-FORMED 40HM CONSTRUCTIONAL STEEL

    Directory of Open Access Journals (Sweden)

    Anna Dziubińska

    2014-03-01

    Full Text Available The paper presents the results of research undertaken to investigate cold forming process for 40HM constructional steel suitable for heat treatment. In the first part of the paper, mechanical properties of this steel and its industrial applications are described. The second part of the paper presents the results of the analysis of flow curves for two kinds of steel specimens: those that were subjected to annealing and those that did not undergo any heat treatment. It was found that the application of heat treatment had a significant effect on improving the forming conditions for this steel at room temperature. The experimental flow curves obtained in a compression test were described by constitutive equations illustrating the dependence between flow stresses and strain value. In order to determine the equation coefficients, the Generalized Reduced Gradient method implemented in Microsoft Excel was used. Based on the obtained equations, a material model will be developed to perform numerical simulations of cold forming for 40HM steel, using FEM-based software that aids the design of metal forming technologies.

  10. Molecular Thermodynamic Model for Polyelectrolyte Solutions with Added Salts%含盐聚电解质溶液的分子热力学模型

    Institute of Scientific and Technical Information of China (English)

    张波; 蔡钧; 刘洪来; 胡英

    2002-01-01

    A molecular thermodynamic model of polyelectrolyte developed previously was extended to polyelectrolyte solutions with added salts. Thermodynamic properties, such as activity coefficients of polyelectrolytes or added salts and osmotic coefficients of solvent, of a number of aqueous mixtures of polyelectrolytes and salts are analyzed with the proposed model. Successful correlation is obtained in the range of moderate or higher polyion concentration. For the same sample, thermodynamic properties of polyelectrolytes with and without simple electrolytes can be predicted mutually using parameters from regression data.

  11. Employing satellite retrieved soil moisture for parameter estimation of the hydrologic model mHM

    Science.gov (United States)

    Zink, Matthias; Mai, Juliane; Rakovec, Oldrich; Schrön, Martin; Kumar, Rohini; Schäfer, David; Samaniego, Luis

    2016-04-01

    Hydrological models are usually calibrated against observed streamflow at the catchment outlet and thus they are conditioned by an integral catchment signal. Rakovec et al. 2016 (JHM) recently demonstrated that constraining model parameters against river discharge is a necessary, but not a sufficient condition. Such a procedure ensures the fulfillment of the catchment's water balance but can lead to high predictive uncertainties of model internal states, like soil moisture, or a lack in spatial representativeness of the model. However, some hydrologic applications, as e.g. soil drought monitoring and prediction, rely on this information. Within this study we propose a framework in which the mesoscale Hydrologic Model (mHM) is calibrated with soil moisture retrievals from various sources. The aim is to condition the model on soil moisture (SM), while preserving good performance in streamflow estimation. We identify the most appropriate objective functions by conducting synthetic experiments. The best objective function is determined based on: 1) deviation between synthetic and simulated soil moisture, 2) nonparametric comparison of SM fields (e.g. copulas), and 3) by euclidian distance of model parameters, which is zero if the parameters of the synthetic data are recovered. Those objective functions performing best are used to calibrate mHM against different satellite soil moisture products, e.g. ESA-CCI, H-SAF, and in situ observations. This procedure is tested in three distinct European basins (upper Sava, Neckar, and upper Guadalquivir basin) ranging from snow domination to semi arid climatic conditions. Results obtained with the synthetic experiment indicate that objective functions focusing on the temporal dynamics of SM are preferable to objective functions aiming at spatial patterns or catchment averages. Since the deviation of soil moisture fields (1) and their copulas (2) don't lead to conclusive results, the decision of the best performing objective

  12. H&M – a role model for organic cotton use in textile processing?

    OpenAIRE

    2013-01-01

    Sweden’s Hennes & Mauritz (operating as H&M) is one of the biggest multinational retail-clothing companies in the world. As a result of massive criticism from campaigning non-profit organizations and news media reports that blamed H&M for unfair and substandard working conditions in their ancillary industries, in 1997 the company began to develop a corporate social responsibility (CSR) program and a code of conduct. Today H&M has a wide-ranging, broadly integrated CSR pro-gram. As a part of i...

  13. Calibration of the Distributed Hydrological Model mHM using Satellite derived Land Surface Temperature

    Science.gov (United States)

    Zink, M.; Samaniego, L. E.; Cuntz, M.

    2012-12-01

    A combined investigation of the water and energy balance in hydrologic models can lead to a more accurate estimation of hydrological fluxes and state variables, such as evapotranspiration and soil moisture. Hydrologic models are usually calibrated against discharge measurements, and thus are only trained on information of few points within a catchment. This procedure does not take into account any spatio-temporal variability of fluxes or state variables. Satellite data are a useful source of information to account for this spatial distributions. The objective of this study is to calibrate the distributed hydrological model mHM with satellite derived Land Surface Temperature (LST) fields provided by the Land Surface Analysis - Satellite Application Facility (LSA-SAF). LST is preferred to other satellite products such as soil moisture or evapotranspiration due to its higher precision. LST is obtained by solving the energy balance by assuming that the soil heat flux and the storage term are negligible on a daily time step. The evapotranspiration is determined by closing the water balance in mHM. The net radiation is calculated by using the incoming short- and longwave radiation, albedo and emissivity data provided by LSA-SAF. The Multiscale Parameter Regionalization technique (MPR, Samaniego et al. 2010) is used to determine the aerodynamic resistance among other parameters. The optimization is performed within the time period 2008-2010 using three objective functions that consider 1) only discharge, 2) only LST, and 3) a combination of both. The proposed method is applied to seven major German river basins: Danube, Ems, Main, Mulde, Neckar, Saale, and Weser. The annual coefficient of correlation between LSA-SAF incoming shortwave radiation and 28 meteorological stations operated by the German Weather Service (DWD) is 0.94 (RMSE = 29 W m-2) in 2009. LSA-SAF incoming longwave radiation could be further evaluated at two eddy covariance stations with a very similar

  14. Mutable polyelectrolyte tube arrays: mesoscale modeling and lateral force microscopy.

    Science.gov (United States)

    Cranford, Steven W; Han, Lin; Ortiz, Christine; Buehler, Markus J

    2017-08-23

    In this study, the pH-dependent friction of layer-by-layer assemblies of poly(allylamine hydrochloride) and poly(acrylic acid) (PAH/PAA) are quantified for microtube array structures via experimental and simulated lateral force microscopy (LFM). A novel coarse-grain tube model is developed, utilizing a molecular dynamics (MD) framework with a Hertzian soft contact potential (such that F ∼ δ(3/2)) to allow the efficient dynamic simulation of 3D arrays consisting of hundreds of tubes at micrometer length scales. By quantitatively comparing experimental LFM and computational results, the coupling between geometry (tube spacing and swelling) and material properties (intrinsic stiffness) results in a transition from bending dominated deformation to bending combined with inter-tube contact, independent of material adhesion assumptions. Variation of tube spacing (and thus control of contact) can be used to exploit the normal and lateral resistance of the tube arrays as a function of pH (2.0/5.5), beyond the effect of areal tube density, with increased resistances (potential mutability) up to a factor of ∼60. This study provides a novel modeling platform to assess and design dynamic polyelectrolyte-based substrates/coatings with tailorable stimulus-responsive surface friction. Our results show that micro-geometry can be used alongside stimulus-responsive material changes to amplify and systematically tune mutability.

  15. Polyelectrolyte Microcapsules: Ion Distributions from a Poisson-Boltzmann Model

    Science.gov (United States)

    Tang, Qiyun; Denton, Alan R.; Rozairo, Damith; Croll, Andrew B.

    2014-03-01

    Recent experiments have shown that polystyrene-polyacrylic-acid-polystyrene (PS-PAA-PS) triblock copolymers in a solvent mixture of water and toluene can self-assemble into spherical microcapsules. Suspended in water, the microcapsules have a toluene core surrounded by an elastomer triblock shell. The longer, hydrophilic PAA blocks remain near the outer surface of the shell, becoming charged through dissociation of OH functional groups in water, while the shorter, hydrophobic PS blocks form a networked (glass or gel) structure. Within a mean-field Poisson-Boltzmann theory, we model these polyelectrolyte microcapsules as spherical charged shells, assuming different dielectric constants inside and outside the capsule. By numerically solving the nonlinear Poisson-Boltzmann equation, we calculate the radial distribution of anions and cations and the osmotic pressure within the shell as a function of salt concentration. Our predictions, which can be tested by comparison with experiments, may guide the design of microcapsules for practical applications, such as drug delivery. This work was supported by the National Science Foundation under Grant No. DMR-1106331.

  16. Scrutiny of Appropriate Model Error Specification in Multivariate Assimilation Framework using mHM

    Science.gov (United States)

    Rakovec, O.; Noh, S. J.; Kumar, R.; Samaniego, L. E.

    2015-12-01

    Reliable and accurate predictions of regional scale water fluxes and states is of great challenge to the scientific community. Several sectors of society (municipalities, agriculture, energy, etc.) may benefit from successful solutions to appropriately quantify uncertainties in hydro-meteorological prediction systems, with particular attention to extreme weather conditions.Increased availability and quality of near real-time data enables better understanding of predictive skill of forecasting frameworks. To address this issue, automatic model-observation integrations are required for appropriate model initializations. In this study, the effects of noise specification on the quality of hydrological forecasts is scrutinized via a data assimilation system. This framework has been developed by incorporating the mesoscale hydrologic model (mHM, {http://www.ufz.de/mhm) with particle filtering (PF) approach used for model state updating. In comparison with previous works, lag PF is considered to better account for the response times of internal hydrologic processes.The objective of this study is to assess the benefits of model state updating for prediction of water fluxes and states up to 3-month ahead forecast using particle filtering. The efficiency of this system is demonstrated in 10 large European basins. We evaluate the model skill for five assimilation scenarios using observed (1) discharge (Q); (2) MODIS evapotranspiration (ET); (3) GRACE terrestrial total water storage (TWS) anomaly; (4) ESA-CCI soil moisture; and (5) the combination of Q, ET, TWS, and SM in a hindcast experiment (2004-2010). The effects of error perturbations for both, the analysis and the forecasts are presented, and optimal trade-offs are discussed. While large perturbations are preferred for the analysis time step, steep deterioration is observed for longer lead times, for which more conservative error measures should be considered. From all the datasets, complementary GRACE TWS data together

  17. HM71224, a novel Bruton's tyrosine kinase inhibitor, suppresses B cell and monocyte activation and ameliorates arthritis in a mouse model: a potential drug for rheumatoid arthritis.

    Science.gov (United States)

    Park, Jin Kyun; Byun, Joo-Yun; Park, Ji Ah; Kim, Yu-Yon; Lee, Ye Ji; Oh, Jeong In; Jang, Sun Young; Kim, Young Hoon; Song, Yeong Wook; Son, Jeewoong; Suh, Kwee Hyun; Lee, Young-Mi; Lee, Eun Bong

    2016-04-18

    Bruton's tyrosine kinase (Btk) is critical for activation of B cells and myeloid cells. This study aimed to characterize the effects of HM71224, a novel Btk inhibitor, both in vitro and in a mouse model of experimental arthritis. The kinase inhibition profile of HM71224 was analyzed. The in vitro effects of HM71224 on B cells and monocytes were analyzed by examining phosphorylation of Btk and its downstream signaling molecules, along with cytokine production and osteoclast formation. The in vivo effects of HM71224 were investigated in a mouse model of collagen-induced arthritis (CIA). HM71224 irreversibly bound to and inhibited Btk (IC50 = 1.95 nM). The compound also inhibited the phosphorylation of Btk and its downstream molecules such as PLCγ2, in activated Ramos B lymphoma cells and primary human B cells in a dose-dependent manner. Furthermore, HM71224 effectively inhibited the production of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1β by human monocytes, and osteoclast formation by human monocytes. Finally, HM71224 improved experimental arthritis and prevented joint destruction in a murine model of CIA. HM71224 inhibits Btk in B cells and monocytes and ameliorates experimental arthritis in a mouse model. Thus, HM71224 is a potential novel therapeutic agent for rheumatoid arthritis in humans.

  18. [Mechanical characteristics of synthetic polyelectrolyte gel as a physical model of the cytoskeleton].

    Science.gov (United States)

    Shkliar, T F; Toropova, O A; Safronov, A P; Pollack, G H; Bliakhman, F A

    2011-01-01

    A physical model of the cytoskeleton based on synthetic polyelectrolyte hydrogel of polymethacrylic acid has been proposed. From the physicochemical point of view, the structures of polyelectrolyte gel and the cytoskeleton show a high degree of similarity. It was shown that polyelectrolyte gel can shorten and produce mechanical stress in response to changes in the composition of the surrounding solution. The mechanical properties of the model gel were evaluated: Young modulus (2-6 kPa), stress relaxation time (0.1-1 s), and apparent viscosity (0.3-3 kPa x s). The viscoelastic properties of the gel depend on the degree of its swelling. It has been demonstrated that the mechanical properties of gels of polymethacrylic acid are close to those of biological objects.

  19. Electrostatics of Rigid Polyelectrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Wong, G.C.L.

    2009-06-04

    The organization of rigid biological polyelectrolytes by multivalent ions and macroions are important for many fundamental problems in biology and biomedicine, such as cytoskeletal regulation and antimicrobial sequestration in cystic fibrosis. These polyelectrolytes have been used as model systems for understanding electrostatics in complex fluids. Here, we review some recent results in theory, simulations, and experiments.

  20. A comparison of f{sub 0}E and hmE model calculations with El Arenosillo digisonde observations. Seasonal variations

    Energy Technology Data Exchange (ETDEWEB)

    Mikhailov, A. [Institute of Terrestial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, Troitsk, Moscow Region (Russian Federation); La Morena de, B.A.; Miro, G.; Marin, D. [National Institute of Aerospace Technology, Mazagon, Huelva (Spain)

    1999-08-01

    Seasonal variation of hmE and f{sub 0}F{sub 2} are analyzed using El Arenosillo digisonde observations during solar minimum (1995-1996). Unlike some widely used empirical models daytime hmE show seasonal variations with winter hmE being higher than summer ones and seasonal differences increase with solar zenith angle. Model calculations enable to reproduce the observed hmE seasonal variations but the calculate daytime f{sub 0}F{sub 2} values are too low if conventional EUV fluxes and dissociative recombination rate constants are used. A reduction of {alpha}(NO{sup +}) by taking into T{sub e}>T{sub n} in the E-region as it follows from probe measurements seems to be a plausible solution. The E-region ion composition corresponding to rocket observations may be obtained in model calculations using an appropriate (NO) height distribution. Calculate summer concentrations of (NO) are by a factor of 3-4 larger than winter ones at the hmE-heights.

  1. In Silico Modeling and Functional Interpretations of Cry1Ab15 Toxin from Bacillus thuringiensis BtB-Hm-16

    Directory of Open Access Journals (Sweden)

    Sudhanshu Kashyap

    2013-01-01

    Full Text Available The theoretical homology based structural model of Cry1Ab15 δ-endotoxin produced by Bacillus thuringiensis BtB-Hm-16 was predicted using the Cry1Aa template (resolution 2.25 Å. The Cry1Ab15 resembles the template structure by sharing a common three-domain extending conformation structure responsible for pore-forming and specificity determination. The novel structural differences found are the presence of β0 and α3, and the absence of α7b, β1a, α10a, α10b, β12, and α11a while α9 is located spatially downstream. Validation by SUPERPOSE and with the use of PROCHECK program showed folding of 98% of modeled residues in a favourable and stable orientation with a total energy Z-score of −6.56; the constructed model has an RMSD of only 1.15 Å. These increments of 3D structure information will be helpful in the design of domain swapping experiments aimed at improving toxicity and will help in elucidating the common mechanism of toxin action.

  2. Streamflow hindcasting in European river basins via multi-parametric ensemble of the mesoscale hydrologic model (mHM)

    Science.gov (United States)

    Noh, Seong Jin; Rakovec, Oldrich; Kumar, Rohini; Samaniego, Luis

    2016-04-01

    There have been tremendous improvements in distributed hydrologic modeling (DHM) which made a process-based simulation with a high spatiotemporal resolution applicable on a large spatial scale. Despite of increasing information on heterogeneous property of a catchment, DHM is still subject to uncertainties inherently coming from model structure, parameters and input forcing. Sequential data assimilation (DA) may facilitate improved streamflow prediction via DHM using real-time observations to correct internal model states. In conventional DA methods such as state updating, parametric uncertainty is, however, often ignored mainly due to practical limitations of methodology to specify modeling uncertainty with limited ensemble members. If parametric uncertainty related with routing and runoff components is not incorporated properly, predictive uncertainty by DHM may be insufficient to capture dynamics of observations, which may deteriorate predictability. Recently, a multi-scale parameter regionalization (MPR) method was proposed to make hydrologic predictions at different scales using a same set of model parameters without losing much of the model performance. The MPR method incorporated within the mesoscale hydrologic model (mHM, http://www.ufz.de/mhm) could effectively represent and control uncertainty of high-dimensional parameters in a distributed model using global parameters. In this study, we present a global multi-parametric ensemble approach to incorporate parametric uncertainty of DHM in DA to improve streamflow predictions. To effectively represent and control uncertainty of high-dimensional parameters with limited number of ensemble, MPR method is incorporated with DA. Lagged particle filtering is utilized to consider the response times and non-Gaussian characteristics of internal hydrologic processes. The hindcasting experiments are implemented to evaluate impacts of the proposed DA method on streamflow predictions in multiple European river basins

  3. Multiscale Modeling of Dendrimers and Their Interactions with Bilayers and Polyelectrolytes

    Directory of Open Access Journals (Sweden)

    Ronald G. Larson

    2009-01-01

    Full Text Available Recent advances in molecular dynamics simulation methodologies and computational power have allowed accurate predictions of dendrimer size, shape, and interactions with bilayers and polyelectrolytes with modest computational effort. Atomistic and coarse-grained (CG models show strong interactions of cationic dendrimers with lipid bilayers. The CG simulations with explicit lipid and water capture bilayer penetration and pore formation, showing that pore formation is enhanced at high dendrimer concentration, but suppressed at low temperature and high salt concentration, in agreement with experiments. Cationic linear polymers have also been simulated, but do not perforate membranes, evidently because by deforming into a pancake, the charges on a linear polymer achieve intimate contact with a single bilayer leaflet. The relatively rigid dendrimers, on the other hand, penetrate the bilayer, because only by interacting with both leaflets can they achieve a similar degree of contact between charged groups. Also, a “dendrimer-filled vesicle” structure for the dendrimer-membrane interaction is predicted by mesoscale thermodynamic simulations, in agreement with a picture derived from experimental observations. In simulations of complexes of dendrimer and polyelectrolyte, anionic linear chains wrap around the cationic dendrimer and penetrate inside it. Overall, these new results indicate that simulations can now provide predictions in excellent agreement with experimental observations, and provide atomic-scale insights into dendrimer structure and dynamics.

  4. Dielectric analysis based on spherical-shell model for cationic and anionic spherical polyelectrolyte brushes

    Science.gov (United States)

    Guo, Xiaoxia; Zhao, Kongshuang

    2017-07-01

    We report here a dielectric study on cationic and anionic spherical polyelectrolyte brush (SPB) (consisting of a polystyrene (PS) core and poly (2-aminoethylmethacrylate hydrochloride (PAEMH) chains or poly (acrylic acid) (PAA) chains grafted onto the core) suspensions over a frequency range of 40 Hz-110 MHz. The relaxation behavior of the suspensions shows significant changes in the brush layer properties when changing the particle mass fraction or pH of the system. After eliminating the electrode polarization effect at a low frequency, two definite relaxations related to interfacial polarization, around 100 kHz and 10 MHz respectively, are observed. Based on a single layer spherical-shell model, we developed a curve-fitting procedure to analyze such dielectric spectra for soft particles, and then calculated the dielectric properties of the components of the SPBs (such as the permittivities and conductivities of the layer and solution phase), especially the layer thickness d s of the polyelectrolyte chain (PE) layer. We also found a larger confinement degree of counterions in the PAEMH brush due to the protonation of the amino group. Moreover, the repulsive force between the SPB particles is evaluated by using the d s combined with the relative theoretical formulas. We conclude that by raising (reducing) the acidity of the system, the stability of the PAEMH-SPB (PAA-SPB) suspension was improved. An increase in particle concentration can also improve the stability of these two dispersions.

  5. A simple model for electrical charge in globular macromolecules and linear polyelectrolytes in solution

    Science.gov (United States)

    Krishnan, M.

    2017-05-01

    We present a model for calculating the net and effective electrical charge of globular macromolecules and linear polyelectrolytes such as proteins and DNA, given the concentration of monovalent salt and pH in solution. The calculation is based on a numerical solution of the non-linear Poisson-Boltzmann equation using a finite element discretized continuum approach. The model simultaneously addresses the phenomena of charge regulation and renormalization, both of which underpin the electrostatics of biomolecules in solution. We show that while charge regulation addresses the true electrical charge of a molecule arising from the acid-base equilibria of its ionizable groups, charge renormalization finds relevance in the context of a molecule's interaction with another charged entity. Writing this electrostatic interaction free energy in terms of a local electrical potential, we obtain an "interaction charge" for the molecule which we demonstrate agrees closely with the "effective charge" discussed in charge renormalization and counterion-condensation theories. The predictions of this model agree well with direct high-precision measurements of effective electrical charge of polyelectrolytes such as nucleic acids and disordered proteins in solution, without tunable parameters. Including the effective interior dielectric constant for compactly folded molecules as a tunable parameter, the model captures measurements of effective charge as well as published trends of pKa shifts in globular proteins. Our results suggest a straightforward general framework to model electrostatics in biomolecules in solution. In offering a platform that directly links theory and experiment, these calculations could foster a systematic understanding of the interrelationship between molecular 3D structure and conformation, electrical charge and electrostatic interactions in solution. The model could find particular relevance in situations where molecular crystal structures are not available or

  6. Diffusion of Oligonucleotides from within Iron-Crosslinked Polyelectrolyte-Modified Alginate Beads: A Model System for Drug Release

    CERN Document Server

    Privman, Vladimir; Luz, Roberto A S; Guz, Nataliia; Glasser, M Lawrence; Katz, Evgeny

    2016-01-01

    We developed and experimentally verified an analytical model to describe diffusion of oligonucleotides from stable hydrogel beads. The synthesized alginate beads are Fe3+-cross-linked as well as polyelectrolyte-doped for uniformity and stability at physiological pH. Data on diffusion of oligonucleotides from inside the beads provide physical insights into the volume nature of the immobilization of a fraction of oligonucleotides due to polyelectrolyte cross-linking, i.e., the absence of the surface-layer barrier in this case. Furthermore, our results suggest a new simple approach to measuring the diffusion coefficient of the mobile oligonucleotide molecules inside hydrogel. The considered alginate beads provide a model for a well-defined component in drug release systems and for the oligonucleotide-release transduction steps in drug-delivering and biocomputing applications. This is illustrated by destabilizing the beads with citrate that induces full oligonucleotide release with non-diffusional kinetics.

  7. Single-molecule elasticity of single-stranded DNA, a model flexible polyelectrolyte

    Science.gov (United States)

    McIntosh, Dustin B.

    Understanding the structure of unfolded, flexible polyelectrolytes is important for our comprehension of basic processes in molecular biology (e.g., RNA and protein folding) and our ability to exploit the polymers in technology (e.g., in self-assembled nanostructures). Here, we investigate the structure of single single-stranded DNA molecules and their interactions with ions using magnetic tweezers. Our data reveal that single-stranded DNA is not well-described by ideal polymer models such as the Worm-Like Chain. At low force, we report the first experimental observation of a nonlinear elastic regime revealing the relevance of long-range excluded volume effects. At high force, the extension scales as a logarithm in monovalent salt. Molecular dynamics simulations indicate that this logarithmic regime is the result of ion-stabilized wrinkles at short-length scales along the polymer backbone. Addition of divalent salt to the buffer results in enhanced elasticity indicating increased wrinkling or polymer ''wrapping" around the divalent ions. Using a thermodynamic identity, we are able to count ions as they are released into the bulk upon polymer elongation. We find that ssDNA releases significantly more ions than dsDNA. We posit that the recently termed ''Snake-Like Chain" model (Ullner, J. Phys. Chem B (2003)) for flexible polyelectrolytes may explain these observations. As a first step towards characterizing biologically relevant nucleic acid structures, we measure the effects of base-stacking on ssDNA elasticity. We find that base-stacking in poly(dA) significantly enhances the rigidity of the polymer as evidenced by the low-force elasticity. The unstacking transition of poly(dA) at high force reveals that the intrinsic electrostatic tension on the molecule varies significantly more weakly on salt concentration than predictions from mean-field models. Further, we provide a model-independent estimate of the free energy difference between stacked and unstacked nucleic

  8. Modeling the effects of pH and ionic strength on swelling of anionic polyelectrolyte gels

    Science.gov (United States)

    Drozdov, A. D.; deClaville Christiansen, J.

    2015-07-01

    A constitutive model is developed for the elastic response of an anionic polyelectrolyte gel under swelling in water with an arbitrary pH and an arbitrary molar fraction of dissolved monovalent salt. A gel is treated as a three-phase medium consisting of a solid phase (polymer network), solvent (water), and solute (mobile ions). Transport of solvent and solute is thought of as their diffusion through the polymer network accelerated by an electric field formed by mobile and fixed ions and accompanied by chemical reactions (dissociation of functional groups attached to polymer chains and formation of ion pairs between bound charges and mobile counter-ions). Constitutive equations are derived by means of the free energy imbalance inequality for an arbitrary three-dimensional deformation with finite strains. These relations are applied to analyze equilibrium swelling diagrams on poly(acrylic acid) gel, poly(methacrylic acid) gel, and three composite hydrogels under water uptake in a bath (i) with a fixed molar fraction of salt and varied pH, and (ii) with a fixed pH and varied molar fraction of salt. To validate the ability of the model to predict observations quantitatively, material constants are found by matching swelling curves under one type of experimental conditions and results of simulation are compared with experimental data in the other type of tests.

  9. Hydrophobically modified polyelectrolytes: Characterization, aggregation and adsorption

    Science.gov (United States)

    Islam, Mohammad Ferdous

    The focus of our work was to experimentally study the aggregation and adsorption behavior of model HM polyelectrolytes. Hydrophobically modified alkali soluble emulsions (HASE), the model HM polyelectrolytes, were chosen because they had complex architecture yet possessed key variables for systematic study. The HASE polymers have methacrylic acid (MAA) and ethyl acrylate (EA) in the backbone with pendent hydrophobic groups. Characterization of a single molecule is an important first step in understanding the aggregation and adsorption of these polymers. However, characterizations of the HASE polymers using conventional techniques such as gel permeation chromatography or static light scattering were difficult because of the hydrophobic association. In this study, two different approaches have been taken to prevent the hydrophobic association in aqueous solution: (1) hydrolyze the polymer to cleave the hydrophobic constituents, and (2) use methyl beta-cyclodextrin that has a hydrophobic cavity and a hydrophilic outer shell, to shield the hydrophobes from associating. By taking these two approaches and using gel permeation chromatography (GPC), dynamic (DLS) and static (SLS) light scattering techniques, the molecular weight, hydrodynamic radius and radius of gyration of a single molecule were determined. Except for one chemical site, we were able to determine that branching or grafting did not occur in the polymer chain during synthesis. Our aggregation studies showed that, in aqueous solutions, the HASE polymers formed small aggregates (presumably single micelles of single or a few chains) and large aggregates (presumably formed by bridging between micelles). The radii and masses of the larger aggregates, measured using DLS and SLS, were found to increase with an increase in the polymer concentration, indicating an open association process for the HASE polymers. Our SLS results also showed that, at high salt concentration, the aggregates of the HASE polymer with

  10. A modified box model including charge regulation for protein adsorption in a spherical polyelectrolyte brush

    NARCIS (Netherlands)

    Biesheuvel, P.M.; Wittemann, A.

    2005-01-01

    Recent experiments showed significant adsorption of bovine serum albumin (BSA) in spherical polyelectrolyte brushes (SPB) consisting of polyacrylic acid, even for pH values above the isoelectric point of the protein, when both protein and polyion are negatively charged. To describe these experimenta

  11. The biocompatibility of a polyelectrolyte vitreous body substitute on a high resistance in vitro model of the blood-retinal barrier.

    Science.gov (United States)

    Strotmann, Falko; Wolf, Isabel; Galla, Hans-Joachim

    2013-09-01

    The vitreous body can be regarded as a fascinating simple but important tissue, since it represents the main compartment of the eye and plays a crucial role for proper vision. Several diseases require its removal with following substitution using a liquid artificial vitreous body replacement. We explore the biocompatibility of a poly(AMPS-Na(+))-graft-poly(NIPAAm) polyelectrolyte following the innovative concept of thermo-responsive behaviour, exhibiting enhanced shear viscosity at physiological temperatures. As a powerful model for the blood-retinal barrier, we use the well-established in vitro cell culture model based on highly differentiated porcine brain capillary endothelial cells. Via the quantification of the transendothelial electrical resistance and immunocytochemical staining of tight junction proteins, we are able to show that a barrier integrity affecting impact of the polyelectrolyte was only transient and nearly reversible. Furthermore, the polyelectrolyte hydrogel is characterized by the absence of any acute cell morphology, cell vitality or proliferation affecting impacts. It does not trigger acute apoptotic processes, as can be substantiated via caspase-3 activity and DNA fragmentation assays. In view of the results of this study, it is shown that the polyelectrolyte does not affect the vitality parameters of our porcine brain capillary endothelial cells. It can be suggested that the tested thermo-responsive polyelectrolyte does not affect the sensitive retinal barrier integrity. Thus from the cellular tolerance it might serve as a potential liquid artificial vitreous body replacement to overcome the most prominent difficulties of common vitreal endotamponades.

  12. The model of a polyelectrolyte solution with explicit account of counterions within a self-consistent field theory

    Science.gov (United States)

    Budkov, Yu. A.; Nogovitsyn, E. A.; Kiselev, M. G.

    2013-04-01

    A theoretical approach to calculating the thermodynamic and structural functions of solutions of polyelectrolytes based on Gaussian equivalent representation for the calculation of functional integrals is proposed. It is noted that a new analytical result of this work is the direct assumption of counterions, along with an equation for the gyration radius of a polymer chain as a function of the concentrations of monomers and added low-molecular salt. An equation of state is obtained within the proposed model. Our theoretical results are used to describe the thermodynamic and structural properties of an aqueous solution of sodium polystyrene sulfonate with additions of NaCl.

  13. H&m i Bangladesh

    OpenAIRE

    Refsøe, Anna; Sørensen, Johan; Skytte, Josephine; Skovgaard, Louise

    2014-01-01

    Outsourcing remains an increasingly attractive strategy for many large companies. The enormous distance between the companies and its suppliers, has resulted in a hazy labor policy in the companies suppliers' production factories. Companies find it difficult to maintain ideal working conditions in developing countries due to the geographical distance. This project, focus on H&M's outsourcing to Bangladesh. Bangladesh is interesting because H&M gets 25% of their products produced in the cou...

  14. Structure and dynamics of humic substances and model poly-electrolytes in solution; Structure et dynamique de substances humiques et polyelectrolytes modeles en solution

    Energy Technology Data Exchange (ETDEWEB)

    Roger, G.

    2010-09-15

    In the frame of a study about the feasibility of an underground storage of radioactive wastes, we focused on the role of degraded natural organic matter in the eventual transport of radionuclides in the environment. We are more interested by the determination of electro kinetic properties of these humic substances rather than the description of speciation reaction already widely discussed in the literature. We chose to determine the size and the charge of these humic substances thanks to an original method: high precision conductometry. This technique, associated to a suited transport theory, allows to describe the mobility of charged species in solution when taking into account the pairs interactions. We have participated in the development of this transport theory and we use it in order to determine the size and the charge of humic substances and a reference polyelectrolyte in different conditions of pH and ionic strength. All these experimental results obtained by conductometry were correlated with other experimental and theoretical methods: Atomic Force Microscopy, dynamic light scattering, laser zeta-metry and Monte-Carlo simulations. The obtained results confirm the generally admitted idea that humic substances are nano-metric entities having complexing properties towards cations and that can aggregate to form supra molecular structures. The effect of the ions present in the environment (sodium, calcium, magnesium) has been investigated. Finally the complexation of europium (which is considered as a good analogue of americium 241) has also been analysed by square wave voltammetry. (author)

  15. A modified Poisson-Boltmann model including charge regulation for the adsorption of ionizable polyelectrolytes to charged interfaces, applied to lysozyme adsorption on silica

    NARCIS (Netherlands)

    Biesheuvel, P.M.; Veen, van der M.; Norde, W.

    2005-01-01

    The equilibrium adsorption of polyelectrolytes with multiple types of ionizable groups is described using a modified Poisson-Boltzmann equation including charge regulation of both the polymer and the interface. A one-dimensional mean-field model is used in which the electrostatic potential is

  16. A modified Poisson-Boltzmann model including charge regulation for the adsorption of ionizable polyelectrolytes to charged interfaces, applied to lysozyme adsorption on silica

    NARCIS (Netherlands)

    Biesheuvel, PM; van der Veen, M; Norde, W

    2005-01-01

    The equilibrium adsorption of polyelectrolytes with multiple types of ionizable groups is described using a modified Poisson-Boltzrnann equation including charge regulation of both the polymer and the interface. A one-dimensional mean-field model is used in which the electrostatic potential is

  17. Release retardation of model protein on polyelectrolyte-coated PLGA nano- and microparticles.

    Directory of Open Access Journals (Sweden)

    Chandra Nugraha

    Full Text Available PEM capsules have been proposed for vehicles of drug microencapsulation, with the release triggered by pH, salt, magnetic field, or light. When built on another carrier encapsulating drugs, such as nanoparticles, it could provide additional release barrier to the releasing drug, providing further control to drug release. Although liposomes have received considerable attention with PEM coating for sustained drug release, similar results employing PEM built on poly(lactic-co-lycolic acid (PLGA particles is scant. In this work, we demonstrate that the build-up pH and polyelectrolyte pairs of PEM affect the release retardation of BSA from PLGA particles. PAH/PSS pair, the most commonly used polyelectrolyte pair, was used in comparison with PLL/DES. In addition, we also demonstrate that the release retardation effect of PEM-coated PLGA particles diminishes as the particle size increases. We attribute this to the diminishing relative thickness of the PEM coating with respect to the size of the particle as the particle size increases, reducing the diffusional resistance of the PEM.

  18. Release retardation of model protein on polyelectrolyte-coated PLGA nano- and microparticles.

    Science.gov (United States)

    Nugraha, Chandra; Bora, Meghali; Venkatraman, Subbu S

    2014-01-01

    PEM capsules have been proposed for vehicles of drug microencapsulation, with the release triggered by pH, salt, magnetic field, or light. When built on another carrier encapsulating drugs, such as nanoparticles, it could provide additional release barrier to the releasing drug, providing further control to drug release. Although liposomes have received considerable attention with PEM coating for sustained drug release, similar results employing PEM built on poly(lactic-co-lycolic acid) (PLGA) particles is scant. In this work, we demonstrate that the build-up pH and polyelectrolyte pairs of PEM affect the release retardation of BSA from PLGA particles. PAH/PSS pair, the most commonly used polyelectrolyte pair, was used in comparison with PLL/DES. In addition, we also demonstrate that the release retardation effect of PEM-coated PLGA particles diminishes as the particle size increases. We attribute this to the diminishing relative thickness of the PEM coating with respect to the size of the particle as the particle size increases, reducing the diffusional resistance of the PEM.

  19. Raman Scattered O VI $\\lambda$ 6825 and the Accretion Disk Emission Model in the Symbiotic Stars V1016 Cygni and HM Sagittae

    CERN Document Server

    Lee, Hee-Won

    2007-01-01

    We present the high resolution spectra of the D type symbiotic stars V1016 Cygni and HM Sagittae obtained with the Bohyunsan Optical Echelle Spectrograph (BOES), and investigate the double-peaked asymmetric profiles of the Raman scattered O VI 6825. By adopting a wind accretion disk model, we assume that the O VI emission region is described by a Keplerian thin disk. The Raman scattering occurs in a neutral region near the giant, taking in the form of a slow stellar wind, part of which is ionized by the strong UV radiation from the hot white dwarf. Using a Monte Carlo technique, we compute the line profiles that are modulated by the slow spherical stellar wind from the giant component with the ionization front approximated by a hyperboloid. In order to account for the asymmetry and the existence of a central dip in the profiles, we add an O VI resonance scattering region between the hot white dwarf and the giant star which hinders the incidence of slightly blue O VI photons upon the H I region. Overall good f...

  20. Distributed nitrate transport and reaction routines (NTR) inside the mesoscale Hydrological Model (mHM) framework: Development and Application in the Selke catchment

    Science.gov (United States)

    Sinha, Sumit; Rode, Michael; Kumar, Rohini; Yang, Xiaoqiang; Samaniego, Luis; Borchardt, Dietrich

    2016-04-01

    Precise measurements of where, when and how much denitrification occurs on the basis of measurements alone persist to be vexing and intractable research problem at all spatial and temporal scales. As a result, models have become essential and vital tools for furthering our current understanding of the processes that control denitrification on catchment scale. Emplacement of Water Framework Directive (WFD) and continued efforts in improving water treatment facilities has resulted in alleviating the problems associated with point sources of pollution. However, the problem of eutrophication still persists and is primarily associated with the diffused sources of pollution originating from agricultural area. In this study, the nitrate transport and reaction (NTR) routines are developed inside the distributed mesoscale Hydrological Model (mHM www.ufz.de/mhm) which is a fully distributed hydrological model with a novel parameter regionalization scheme (Samaniego et al. 2010; Kumar et al. 2013) and has been applied to whole Europe (Rakovec et al. 2016) and numerous catchments worldwide. The aforementioned NTR model is applied to a mesoscale river basin, Selke (463 km2) located in central Germany. The NTR model takes in account the critical and pertinent processes like transformation in vadose zone, atmospheric deposition, plant uptake, instream denitrification and also simulates the process of manure and fertilizer application. Both streamflow routines and the NTR model are run on daily time steps. The split-sample approach was used for model calibration (1994-1999) and validation (2000-2004). Flow dynamics at three gauging stations located inside this catchment are successfully captured by the model with consistently high Nash-Sutcliffe Efficiency (NSE) of at least 0.8. Regarding nitrate estimates, the NSE values are greater than 0.7 for both validation and calibration periods. Finally, the NTR model is used for identifying the critical source areas (CSAs) that contribute

  1. Modeling and simulation of the chemically induced swelling behavior of anionic polyelectrolyte gels by applying the theory of porous media

    Science.gov (United States)

    Leichsenring, Peter; Wallmersperger, Thomas

    2017-03-01

    Ionic hydrogels belong to the class of polyelectrolyte gels, also known as ionic gels. Their ability to swell or shrink under different environmental conditions such as change of pH, ion concentration or temperature make them promising materials for new sensoric or actuatoric devices. Numerical simulations play a crucial role for further developing hydrogel based devices. In the present contribution, a thermodynamically consistent continuum model based on the theory of porous media is derived. The governing field equations are solved on a one-dimensional domain by applying the finite element method. For the time discretization an Euler backward algorithm is implemented. The hydrogel swelling behavior is triggered by a chemical stimulus and is analyzed in space and time. Two mechanical configurations are considered: the hydrogel free swelling behavior and a mechanically clamped configuration, where the hydrogel swelling is hindered, are evaluated in detail. The presented results lead to a precise understanding of the chemo-electro-mechanical behavior and the driving pressure contributions.

  2. Charged colloids, polyelectrolytes and biomolecules viewed as strongly coupled Coulomb systems

    CERN Document Server

    Löwen, H; Likos, C N; Blaak, R; Dzubiella, J; Jusufi, A; Hoffmann, N; Harreis, H M

    2003-01-01

    A brief review is given on recent studies of charged soft matter solutions, as modelled by the 'primitive' approach of strongly coupled Coulomb systems, where the solvent just enters as a dielectric background. These include charged colloids, biological macromolecules such as proteins and DNA, polyelectrolytes and polyelectrolyte stars. Also some original results are presented on colloid-polyelectrolyte complex formation near walls and on the anomalous fluid structure of polyelectrolyte stars as a function of increasing concentration.

  3. Molecular Dynamics Simulations of Polyelectrolyte Solutions

    Science.gov (United States)

    Dobrynin, Andrey

    2014-03-01

    confirm predictions of the scaling model of polyelectrolyte solutions. NSF DMR-1004576.

  4. Characterization of a Model Polyelectrolyte Membrane Using a Semi-crystalline Block Copolymer

    Science.gov (United States)

    Beers, Keith; Wang, Xin; Balsara, Nitash

    2011-03-01

    The microstructured block copolymer sulfonated polystyrene-block-polyethylene is studied as model system for use as a proton exchange membrane in a fuel cell. Self-assembly of this system creates proton conducting hydrophilic channels in the form of sulfonated polystyrene domains, while the polyethylene domains create a hydrophobic matrix to provide mechanical stability. This system serves as a powerful model system since the effects of domain size, morphology and crystallinity on water uptake and proton conductivity can be investigated. Similar systems have shown the ability of small hydrophilic channels to prevent drying at high temperatures in humid air, but have focused on amorphous hydrophobic blocks. The morphology, water uptake, and proton conductivity of this semi-crystalline model system will be discussed.

  5. Coarse-grained model of water diffusion and proton conductivity in hydrated polyelectrolyte membrane

    Science.gov (United States)

    Lee, Ming-Tsung; Vishnyakov, Aleksey; Neimark, Alexander V.

    2016-01-01

    Using dissipative particle dynamics (DPD), we simulate nanoscale segregation, water diffusion, and proton conductivity in hydrated sulfonated polystyrene (sPS). We employ a novel model [Lee et al. J. Chem. Theory Comput. 11(9), 4395-4403 (2015)] that incorporates protonation/deprotonation equilibria into DPD simulations. The polymer and water are modeled by coarse-grained beads interacting via short-range soft repulsion and smeared charge electrostatic potentials. The proton is introduced as a separate charged bead that forms dissociable Morse bonds with the base beads representing water and sulfonate anions. Morse bond formation and breakup artificially mimics the Grotthuss mechanism of proton hopping between the bases. The DPD model is parameterized by matching the proton mobility in bulk water, dissociation constant of benzenesulfonic acid, and liquid-liquid equilibrium of water-ethylbenzene solutions. The DPD simulations semi-quantitatively predict nanoscale segregation in the hydrated sPS into hydrophobic and hydrophilic subphases, water self-diffusion, and proton mobility. As the hydration level increases, the hydrophilic subphase exhibits a percolation transition from isolated water clusters to a 3D network. The analysis of hydrophilic subphase connectivity and water diffusion demonstrates the importance of the dynamic percolation effect of formation and breakup of temporary junctions between water clusters. The proposed DPD model qualitatively predicts the ratio of proton to water self-diffusion and its dependence on the hydration level that is in reasonable agreement with experiments.

  6. Coarse-grained model of water diffusion and proton conductivity in hydrated polyelectrolyte membrane

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ming-Tsung; Vishnyakov, Aleksey; Neimark, Alexander V., E-mail: aneimark@rutgers.edu [Department of Chemical and Biochemical Engineering, Rutgers, The State University of New Jersey, 98 Brett Road, Piscataway, New Jersey 08854-8058 (United States)

    2016-01-07

    Using dissipative particle dynamics (DPD), we simulate nanoscale segregation, water diffusion, and proton conductivity in hydrated sulfonated polystyrene (sPS). We employ a novel model [Lee et al. J. Chem. Theory Comput. 11(9), 4395-4403 (2015)] that incorporates protonation/deprotonation equilibria into DPD simulations. The polymer and water are modeled by coarse-grained beads interacting via short-range soft repulsion and smeared charge electrostatic potentials. The proton is introduced as a separate charged bead that forms dissociable Morse bonds with the base beads representing water and sulfonate anions. Morse bond formation and breakup artificially mimics the Grotthuss mechanism of proton hopping between the bases. The DPD model is parameterized by matching the proton mobility in bulk water, dissociation constant of benzenesulfonic acid, and liquid-liquid equilibrium of water-ethylbenzene solutions. The DPD simulations semi-quantitatively predict nanoscale segregation in the hydrated sPS into hydrophobic and hydrophilic subphases, water self-diffusion, and proton mobility. As the hydration level increases, the hydrophilic subphase exhibits a percolation transition from isolated water clusters to a 3D network. The analysis of hydrophilic subphase connectivity and water diffusion demonstrates the importance of the dynamic percolation effect of formation and breakup of temporary junctions between water clusters. The proposed DPD model qualitatively predicts the ratio of proton to water self-diffusion and its dependence on the hydration level that is in reasonable agreement with experiments.

  7. Phase behavior of electrostatically complexed polyelectrolyte gels using an embedded fluctuation model.

    Science.gov (United States)

    Audus, Debra J; Gopez, Jeffrey D; Krogstad, Daniel V; Lynd, Nathaniel A; Kramer, Edward J; Hawker, Craig J; Fredrickson, Glenn H

    2015-02-14

    Nanostructured, responsive hydrogels formed due to electrostatic interactions have promise for applications such as drug delivery and tissue mimics. These physically cross-linked hydrogels are composed of an aqueous solution of oppositely charged triblocks with charged end-blocks and neutral, hydrophilic mid-blocks. Due to their electrostatic interactions, the end-blocks microphase separate and form physical cross-links that are bridged by the mid-blocks. The structure of this system was determined using a new, efficient embedded fluctuation (EF) model in conjunction with self-consistent field theory. The calculations using the EF model were validated against unapproximated field-theoretic simulations with complex Langevin sampling and were found consistent with small angle X-ray scattering (SAXS) measurements on an experimental system. Using both the EF model and SAXS, phase diagrams were generated as a function of end-block fraction and polymer concentration. Several structures were observed including a body-centered cubic sphere phase, a hexagonally packed cylinder phase, and a lamellar phase. Finally, the EF model was used to explore how parameters that directly relate to polymer chemistry can be tuned to modify the resulting phase diagram, which is of practical interest for the development of new hydrogels.

  8. Partial Order Infinitary Term Rewriting and Böhm Trees

    DEFF Research Database (Denmark)

    Bahr, Patrick

    2010-01-01

    We investigate an alternative model of infinitary term rewriting. Instead of a metric, a partial order on terms is employed to formalise (strong) convergence. We compare this partial order convergence of orthogonal term rewriting systems to the usual metric convergence of the corresponding Böhm e...

  9. Actuation and ion transportation of polyelectrolyte gels

    Science.gov (United States)

    Hong, Wei; Wang, Xiao

    2010-04-01

    Consisting of charged network swollen with ionic solution, polyelectrolyte gels are known for their salient characters including ion exchange and stimuli responsiveness. The active properties of polyelectrolyte gels are mostly due to the migration of solvent molecules and solute ions, and their interactions with the fixed charges on the network. In this paper, we extend the recently developed nonlinear field theory of polyelectrolyte gels by assuming that the kinetic process is limited by the rate of the transportation of mobile species. To study the coupled mechanical deformation, ion migration, and electric field, we further specialize the model to the case of a laterally constrained gel sheet. By solving the field equations in two limiting cases: the equilibrium state and the steady state, we calculate the mechanical responses of the gel to the applied electric field, and study the dependency on various parameters. The results recover the behavior observed in experiments in which polyelectrolyte gels are used as actuators, such as the ionic polymer metal composite. In addition, the model reveals the mechanism of the selectivity in ion transportation. Although by assuming specific material laws, the reduced system resembles those in most existing models in the literature, the theory can be easily generalized by using more realistic free-energy functions and kinetic laws. The adaptability of the theory makes it suitable for studying many similar material systems and phenomena.

  10. Intrinsic viscosities of polyelectrolytes: determination and modeling of the effects of extra salt.

    Science.gov (United States)

    Eich, Andreas; Wolf, Bernhard A

    2011-10-24

    Based on early measurements of J. J. Hermans and co-workers (D. T. F. Pals, J. J. Hermans, Recl. Trav. Chim. Pays-Bas 1952, 71, 513-520; D. T. F. Pals, J. J. Hermans, J. Polym. Sci. 1950, 5, 733-734; D. T. F. Pals, J. J. Hermans, J. Polym. Sci. 1948, 3, 897-898), the present contribution demonstrates how primary data should be evaluated in order to obtain reliable intrinsic viscosities. This procedure yields detailed information on the changes of the intrinsic viscosities and of the corresponding viscometric interaction parameters caused by an increasing salinity of water. Both quantities decline from a maximum value in the pure solvent to a minimum value, which is approached in the limit of sufficiently high salt concentrations, and can be modeled quantitatively by means of a Boltzmann sigmoid. Particular attention is paid to the significance of results obtained by means of the method of isoionic dilution, proposed by J. J. Hermans and co-workers. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Precipitation polymerization of hydrophobically modified polyelectrolyte poly(AA-co-ODA) in supercritical carbon dioxide and solution rheology properties

    Science.gov (United States)

    Zhang, Huaiping; Li, Wei; Cao, Qing; Chen, Mingcai

    2014-05-01

    Hydrophobically modified (HM) polyelectrolytes were prepared by using precipitation polymerization of acrylic acid (AA) and octadecyl acrylate (ODA) in various molar ratios in supercritical carbon dioxide. The product was obtained in the form of a white powder and the micrographs show aggregates of primary particles properties.

  12. Conjugated polyelectrolytes fundamentals and applications

    CERN Document Server

    Liu, Bin

    2013-01-01

    This is the first monograph to specifically focus on fundamentals and applications of polyelectrolytes, a class of molecules that gained substantial interest due to their unique combination of properties. Combining both features of organic semiconductors and polyelectrolytes, they offer a broad field for fundamental research as well as applications to analytical chemistry, optical imaging, and opto-electronic devices. The initial chapters introduce readers to the synthesis, optical and electrical properties of various conjugated polyelectrolytes. This is followed by chapters on the applica

  13. Development of Highly-Conductive Polyelectrolytes for Lithium Batteries

    Science.gov (United States)

    Shriver, D. F.; Ratner, M. A.; Vaynman, S.; Annan, K. O.; Snyder, J. F.

    2003-01-01

    Future NASA and Air Force missions require reliable and safe sources of energy with high specific energy and energy density that can provide thousands of charge-discharge cycles at more than 40% depth- of-discharge and that can operate at low temperatures. All solid-state batteries have substantial advantages with respect to stability, energy density, storage fife and cyclability. Among all solid-state batteries, those with flexible polymer electrolytes offer substantial advantages in cell dimensionality and commensurability, low temperature operation and thin film design. The above considerations suggest that lithium-polymer electrolyte systems are promising for high energy density batteries and should be the systems of choice for NASA and US Air Force applications. Polyelectrolytes (single ion conductors) are among most promising avenues for achieving a major breakthrough 'in the applicability of polymer- based electrolyte systems. Their major advantages include unit transference number for the cation, reduced cell polarization, minimal salt precipitation, and favorable electrolyte stability at interfaces. Our research is focused on synthesis, modeling and cell testing of single ion carriers, polyelectrolytes. During the first year of this project we attempted the synthesis of two polyelectrolytes. The synthesis of the first one, the poly(ethyleneoxide methoxy acrylateco-lithium 1,1,2-trifluorobutanesulfonate acrylate, was attempted few times and it was unsuccessful. We followed the synthetic route described by Cowie and Spence. The yield was extremely low and the final product could not be separated from the impurities. The synthesis of this polyelectrolyte is not described in this report. The second polyelectrolyte, comb polysiloxane polyelectrolyte containing oligoether and perfluoroether sidechains, was synthesized in sufficient quantity to study the range of properties such as thermal stability, Li- ion- conductivity and stability toward lithium metal. Also

  14. Entropy and enthalpy of polyelectrolyte complexation: Langevin dynamics simulations.

    Science.gov (United States)

    Ou, Zhaoyang; Muthukumar, M

    2006-04-21

    We report a systematic study by Langevin dynamics simulation on the energetics of complexation between two oppositely charged polyelectrolytes of same charge density in dilute solutions of a good solvent with counterions and salt ions explicitly included. The enthalpy of polyelectrolyte complexation is quantified by comparisons of the Coulomb energy before and after complexation. The entropy of polyelectrolyte complexation is determined directly from simulations and compared with that from a mean-field lattice model explicitly accounting for counterion adsorption. At weak Coulomb interaction strengths, e.g., in solvents of high dielectric constant or with weakly charged polyelectrolytes, complexation is driven by a negative enthalpy due to electrostatic attraction between two oppositely charged chains, with counterion release entropy playing only a subsidiary role. In the strong interaction regime, complexation is driven by a large counterion release entropy and opposed by a positive enthalpy change. The addition of salt reduces the enthalpy of polyelectrolyte complexation by screening electrostatic interaction at all Coulomb interaction strengths. The counterion release entropy also decreases in the presence of salt, but the reduction only becomes significant at higher Coulomb interaction strengths. More significantly, in the range of Coulomb interaction strengths appropriate for highly charged polymers in aqueous solutions, complexation enthalpy depends weakly on salt concentration and counterion release entropy exhibits a large variation as a function of salt concentration. Our study quantitatively establishes that polyelectrolyte complexation in highly charged Coulomb systems is of entropic origin.

  15. HM+ and HM+-He (M = Group 2 metal): Chemical or physical interactions?

    Science.gov (United States)

    Harris, Joe P.; Dodson, Hannah; Breckenridge, W. H.; Wright, Timothy G.

    2014-09-01

    We investigate the HM+-He complexes (M = Group 2 metal) using quantum chemistry. Equilibrium geometries are linear for M = Be and Mg, and bent for M = Ca-Ra; the explanation for this lies in the differing nature of the highest occupied molecular orbitals in the two sets of complexes. The difference primarily occurs as a result of the formation of the H-M+ bond, and so the HM+ diatomics are also studied as part of the present work. The position of the He atom in the complexes is largely determined by the form of the electron density. HM+…He binding energies are obtained and are surprisingly high for a helium complex. The HBe+…He value is almost 3000 cm-1, which is high enough to suspect contributions from chemical bonding. This is explored by examining the natural orbital density and by population analyses.

  16. Structural study of coacervation in protein-polyelectrolyte complexes

    Science.gov (United States)

    Chodankar, S.; Aswal, V. K.; Kohlbrecher, J.; Vavrin, R.; Wagh, A. G.

    2008-09-01

    Coacervation is a dense liquid-liquid phase separation and herein we report coacervation of protein bovine serum albumin (BSA) in the presence of polyelectrolyte sodium polystyrene sulfonate (NaPSS) under varying solution conditions. Small-angle neutron scattering (SANS) measurements have been performed on above protein-polyelectrolyte complexes to study the structural evolution of the process that leads to coacervation and the phase separated coacervate as a function of solution pH , protein-polyelectrolyte ratio and ionic strength. SANS study prior to phase separation on the BSA-NaPSS complex shows a fractal structure representing a necklace model of protein macromolecules randomly distributed along the polystyrene sulfonate chain. The fractal dimension of the complex decreases as pH is shifted away from the isoelectric point (˜4.7) of BSA protein, which indicates the decrease in the compactness of the complex structure due to increase in the charge repulsion between the protein macromolecules bound to the polyelectrolyte. Concentration-dependence studies of the polyelectrolyte in the complex suggest coexistence of two populations of polyelectrolytes, first one fully saturated with proteins and another one free from proteins. Coacervation phase has been obtained through the turbidity measurement by varying pH of the aqueous solution containing protein and polyelectrolyte from neutral to acidic regime to get them to where the two components are oppositely charged. The spontaneous formation of coacervates is observed for pH values less than 4. SANS study on coacervates shows two length scales related to complex aggregations (mesh size and overall extent of the complex) hierarchically branched to form a larger network. The mesh size represents the distance between cross-linked points in the primary complex, which decreases with increase in ionic strength and remains the same on varying the protein-polyelectrolyte ratio. On the other hand, the overall extent of the

  17. On the difference in ionization properties between planar interfaces and linear polyelectrolytes

    Science.gov (United States)

    Borkovec, Michal; Daicic, John; Koper, Ger J. M.

    1997-01-01

    Ionizable planar interfaces and linear polyelectrolytes show markedly different proton-binding behavior. Planar interfaces protonate in a single broad step, whereas polyelectrolytes mostly undergo a two-step protonation. Such contrasting behavior is explained using a discrete-charge Ising model. This model is based on an approximation of the ionizable groups by point charges that are treated within a linearized Poisson–Boltzmann approximation. The underlying reason as to why planar interfaces exhibit mean-field-like behavior, whereas linear polyelectrolytes usually do not, is related to the range of the site–site interaction potential. For a planar interface, this interaction potential is much more long ranged if compared with that of the cylindrical geometry as appropriate to a linear polyelectrolyte. The model results are in semi-quantitative agreement with experimental data for fatty-acid monolayers, water-oxide interfaces, and various linear polyelectrolytes. PMID:9108004

  18. The retention of [99mTc]-d,l-HM-PAO in the human brain after intracarotid bolus injection

    DEFF Research Database (Denmark)

    Lassen, N A; Andersen, A R; Friberg, L

    1988-01-01

    . Cerebral blood flow (F) was measured using the xenon-133 intracarotid injection method. The first-pass extraction E of HM-PAO was calculated from F using an empiric regression equation. The residue curves for the whole brain after intracarotid HM-PAO injection were analyzed to yield a retention fraction (R...... lambda = K1/k2 = 0.67 +/- 0.23 ml/g. Using the kinetic model and assuming constancy of alpha, an algorithm was developed that corrects for the blood flow dependent backflux of HM-PAO and results in a more linear relation between regional cerebral blood flow (rCBF) and HM-PAO distribution....

  19. Sequestration of rhBMP-2 into self-assembled polyelectrolyte complexes promotes anatomic localization of new bone in a porcine model of spinal reconstructive surgery.

    Science.gov (United States)

    Abbah, Sunny-Akogwu; Lam, Wing Moon Raymond; Hu, Tao; Goh, James; Wong, Hee-Kit

    2014-06-01

    Efficient and therapeutically safe delivery of recombinant human bone morphogenetic protein 2 (rhBMP-2) continues to be a central issue in bone tissue engineering. Recent evidence indicates that layer-by-layer self-assembly of polyelectrolyte complexes (PECs) can be used to recreate synthetic matrix environments that would act as tuneable reservoirs for delicate biomolecules and cells. Although preliminary in vitro as well as small-animal in vivo studies support this premise, translation into clinically relevant bone defect volumes in larger animal models remains unreported. Here we explored the use of native heparin-based PEC, deposited on a hydrated alginate gel template, to load bioactive rhBMP-2 and to facilitate lumbar interbody spinal fusion in pigs. We observed that triple PEC deposits with the highest protein sequestration efficiency and immobilization capacity promoted higher volume of new bone formation when compared with single PEC with low sequestration efficiency and immobilization capacity. This also resulted in a significantly enhanced biomechanical stability of the fused spinal segment when compared with PEC carriers with relatively low protein sequestration and immobilization capacities (pcollagen sponge carriers. We conclude that this growth factor sequestration platform is effective in the healing of clinically relevant bone defect volume and could overcome some of the safety concerns and limitations currently associated with rhBMP-2 therapy such as excessive heterotopic ossification.

  20. Protein adsorption in polyelectrolyte brush type cation-exchangers.

    Science.gov (United States)

    Khalaf, Rushd; Coquebert de Neuville, Bertrand; Morbidelli, Massimo

    2016-11-04

    Ion exchange chromatography materials functionalized with polyelectrolyte brushes (PEB) are becoming an integral part of many protein purification steps. Adsorption onto these materials is different than that onto traditional materials, due to the 3D partitioning of proteins into the polyelectrolyte brushes. Despite this mechanistic difference, many works have described the chromatographic behavior of proteins on polyelectrolyte brush type ion exchangers with much of the same methods as used for traditional materials. In this work, unconventional chromatographic behavior on polyelectrolyte brush type materials is observed for several proteins: the peaks shapes reveal first anti-Langmuirian and then Langmuirian types of interactions, with increasing injection volumes. An experimental and model based description of these materials is carried out in order to explain this behavior. The reason for this behavior is shown to be the 3D partitioning of proteins into the polyelectrolyte brushes: proteins that fully and readily utilize the 3D structure of the PEB phase during adsorption show this behavior, whereas those that do not show traditional ion exchange behavior.

  1. Salt Effect on Osmotic Pressure of Polyelectrolyte Solutions: Simulation Study

    Directory of Open Access Journals (Sweden)

    Jan-Michael Y. Carrillo

    2014-07-01

    Full Text Available Abstract: We present results of the hybrid Monte Carlo/molecular dynamics simulations of the osmotic pressure of salt solutions of polyelectrolytes. In our simulations, we used a coarse-grained representation of polyelectrolyte chains, counterions and salt ions. During simulation runs, we alternate Monte Carlo and molecular dynamics simulation steps. Monte Carlo steps were used to perform small ion exchange between simulation box containing salt ions (salt reservoir and simulation box with polyelectrolyte chains, counterions and salt ions (polyelectrolyte solution. This allowed us to model Donnan equilibrium and partitioning of salt and counterions across membrane impermeable to polyelectrolyte chains. Our simulations have shown that the main contribution to the system osmotic pressure is due to salt ions and osmotically active counterions. The fraction of the condensed (osmotically inactive counterions first increases with decreases in the solution ionic strength then it saturates. The reduced value of the system osmotic coefficient is a universal function of the ratio of the concentration of osmotically active counterions and salt concentration in salt reservoir. Simulation results are in a very good agreement with osmotic pressure measurements in sodium polystyrene sulfonate, DNA, polyacrylic acid, sodium polyanetholesulfonic acid, polyvinylbenzoic acid, and polydiallyldimethylammonium chloride solutions.

  2. Biological and Biomimetic Comb Polyelectrolytes

    Directory of Open Access Journals (Sweden)

    Aristeidis Papagiannopoulos

    2010-05-01

    Full Text Available Some new phenomena involved in the physical properties of comb polyelectrolyte solutions are reviewed. Special emphasis is given to synthetic biomimetic materials, and the structures formed by these molecules are compared with those of naturally occurring glycoprotein and proteoglycan solutions. Developments in the determination of the structure and dynamics (viscoelasticity of comb polymers in solution are also covered. Specifically the appearance of multi-globular structures, helical instabilities, liquid crystalline phases, and the self-assembly of the materials to produce hierarchical comb morphologies is examined. Comb polyelectrolytes are surface active and a short review is made of some recent experiments in this area that relate to their morphology when suspended in solution. We hope to emphasize the wide variety of phenomena demonstrated by the vast range of naturally occurring comb polyelectrolytes and the challenges presented to synthetic chemists designing biomimetic materials.

  3. Building Highly Flexible Polyelectrolyte Nanotubes

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    @@ Flexibility of polyelectrolyte nanotubes is necessary if they are to be exploited in applications such as developing photoelectric devices with strong mechanical properties. In a recent attempt, high flexibility has been observed from such nanotubes prepared by a research team headed by Prof. Li Junbai of the CAS Institute of Chemistry (ICCAS).

  4. Ionizable polyelectrolyte brushes: brush height and electrosteric interaction

    NARCIS (Netherlands)

    Biesheuvel, P.M.

    2004-01-01

    Semi-analytical scaling theory is used to describe quenched and annealed (weakly charged, ionizable, charge-regulating) polyelectrolyte brushes in electrolyte solutions of arbitrary salt concentration. An Alexander-De Gennes box model with homogeneous distribution of polymer segments and the free en

  5. Solution properties of star polyelectrolytes having a moderate number of arms

    Science.gov (United States)

    Chremos, Alexandros; Douglas, Jack F.

    2017-07-01

    We investigate polyelectrolyte stars having a moderate number of arms by molecular dynamics simulations of a coarse-grained model over a range of polyelectrolyte concentrations, where both the counter-ions and solvent are treated explicitly. This class of polymeric materials is found to exhibit rather distinct static and dynamic properties from linear and highly branched star polyelectrolyte solutions emphasized in past studies. Moderately branched polymers are particle-like in many of their properties, while at the same time they exhibit large fluctuations in size and shape as in the case of linear chain polymers. Correspondingly, these fluctuations suppress crystallization at high polymer concentrations, leading apparently to an amorphous rather than crystalline solid state at high polyelectrolyte concentrations. We quantify the onset of this transition by measuring the polymer size and shape fluctuations of our model star polyelectrolytes and the static and dynamic structure factor of these solutions over a wide range of polyelectrolyte concentration. Our findings for star polyelectrolytes are similar to those of polymer-grafted nanoparticles having a moderate grafting density, which is natural given the soft and highly deformable nature of both of these "particles."

  6. Born energy, acid-base equilibrium, structure and interactions of end-grafted weak polyelectrolyte layers

    Energy Technology Data Exchange (ETDEWEB)

    Nap, R. J.; Tagliazucchi, M.; Szleifer, I., E-mail: igalsz@northwestern.edu [Department of Biomedical Engineering, Department of Chemistry, and Chemistry of Life Processes Institute, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3100 (United States)

    2014-01-14

    This work addresses the effect of the Born self-energy contribution in the modeling of the structural and thermodynamical properties of weak polyelectrolytes confined to planar and curved surfaces. The theoretical framework is based on a theory that explicitly includes the conformations, size, shape, and charge distribution of all molecular species and considers the acid-base equilibrium of the weak polyelectrolyte. Namely, the degree of charge in the polymers is not imposed but it is a local varying property that results from the minimization of the total free energy. Inclusion of the dielectric properties of the polyelectrolyte is important as the environment of a polymer layer is very different from that in the adjacent aqueous solution. The main effect of the Born energy contribution on the molecular organization of an end-grafted weak polyacid layer is uncharging the weak acid (or basic) groups and consequently decreasing the concentration of mobile ions within the layer. The magnitude of the effect increases with polymer density and, in the case of the average degree of charge, it is qualitatively equivalent to a small shift in the equilibrium constant for the acid-base equilibrium of the weak polyelectrolyte monomers. The degree of charge is established by the competition between electrostatic interactions, the polymer conformational entropy, the excluded volume interactions, the translational entropy of the counterions and the acid-base chemical equilibrium. Consideration of the Born energy introduces an additional energetic penalty to the presence of charged groups in the polyelectrolyte layer, whose effect is mitigated by down-regulating the amount of charge, i.e., by shifting the local-acid base equilibrium towards its uncharged state. Shifting of the local acid-base equilibrium and its effect on the properties of the polyelectrolyte layer, without considering the Born energy, have been theoretically predicted previously. Account of the Born energy leads

  7. Born energy, acid-base equilibrium, structure and interactions of end-grafted weak polyelectrolyte layers

    Science.gov (United States)

    Nap, R. J.; Tagliazucchi, M.; Szleifer, I.

    2014-01-01

    This work addresses the effect of the Born self-energy contribution in the modeling of the structural and thermodynamical properties of weak polyelectrolytes confined to planar and curved surfaces. The theoretical framework is based on a theory that explicitly includes the conformations, size, shape, and charge distribution of all molecular species and considers the acid-base equilibrium of the weak polyelectrolyte. Namely, the degree of charge in the polymers is not imposed but it is a local varying property that results from the minimization of the total free energy. Inclusion of the dielectric properties of the polyelectrolyte is important as the environment of a polymer layer is very different from that in the adjacent aqueous solution. The main effect of the Born energy contribution on the molecular organization of an end-grafted weak polyacid layer is uncharging the weak acid (or basic) groups and consequently decreasing the concentration of mobile ions within the layer. The magnitude of the effect increases with polymer density and, in the case of the average degree of charge, it is qualitatively equivalent to a small shift in the equilibrium constant for the acid-base equilibrium of the weak polyelectrolyte monomers. The degree of charge is established by the competition between electrostatic interactions, the polymer conformational entropy, the excluded volume interactions, the translational entropy of the counterions and the acid-base chemical equilibrium. Consideration of the Born energy introduces an additional energetic penalty to the presence of charged groups in the polyelectrolyte layer, whose effect is mitigated by down-regulating the amount of charge, i.e., by shifting the local-acid base equilibrium towards its uncharged state. Shifting of the local acid-base equilibrium and its effect on the properties of the polyelectrolyte layer, without considering the Born energy, have been theoretically predicted previously. Account of the Born energy leads

  8. ST-HM not only cranes

    CERN Document Server

    Bertone, C

    2002-01-01

    This period of LEP dismantling and LHC installation is a real challenge for the ST-HM group. The group is now following several projects to cope with the diversity of requests. Although crane design and procurement still constitutes the majority of the workload, more and more of our time is nowadays dedicated to providing alternative handling solutions. In 2001/2002, our main studies concern cranes for LHC, industrial and shielded motorised doors, the upgrade/replacement of 32 lifts and mobile cranes. The years 2002/2003 will concern mainly the study of LHC handling systems such as trailers and heavy-duty tractors, specifically tailored containers and tools. In parallel, the monorail will be extended in the injection tunnel and CNGS tunnels and a new monorail system for TOF will be installed. Since the tunnel monorail infrastructure will be used for power feed and guidance purposes only, this requires that other transport systems be studied, such as forklift trucks, industrial and telescopic hoists.

  9. Electrostatics and charge regulation in polyelectrolyte multilayered assembly.

    Science.gov (United States)

    Cherstvy, Andrey G

    2014-05-01

    We examine the implications of electrostatic interactions on formation of polyelectrolyte multilayers, in application to field-effect based biosensors for label-free detection of charged macromolecules. We present a quantitative model to describe the experimental potentiometric observations and discuss its possibilities and limitations for detection of polyelectrolyte adsorption. We examine the influence of the ionic strength and pH on the sensor response upon polyelectrolyte layer-by-layer formation. The magnitude of potential oscillations on the sensor-electrolyte interface predicted upon repetitive adsorption charge-alternating polymers agrees satisfactorily with experimental results. The model accounts for different screening by mobile ions in electrolyte and inside tightly interdigitated multilayered structure. In particular, we show that sensors' potential oscillations are larger and more persistent at lower salt conditions, while they decay faster with the number of layers at higher salt conditions, in agreement with experiments. The effects of polyelectrolyte layer thickness, substrate potential, and charge regulation on the sensor surface triggered by layer-by-layer deposition are also analyzed.

  10. 77 FR 26765 - David H.M. Phelps: Debarment Order

    Science.gov (United States)

    2012-05-07

    ... HUMAN SERVICES Food and Drug Administration David H.M. Phelps: Debarment Order AGENCY: Food and Drug... under the Federal Food, Drug, and Cosmetic Act (FD&C Act) debarring David H.M. Phelps for a period of 20.... FDA bases this order on a finding that Mr. Phelps was convicted, as defined in section 306(l)(1)(B)...

  11. The legacy of patient H.M. for neuroscience.

    Science.gov (United States)

    Squire, Larry R

    2009-01-15

    H.M. is probably the best known single patient in the history of neuroscience. His severe memory impairment, which resulted from experimental neurosurgery to control seizures, was the subject of study for five decades until his death in December 2008. Work with H.M. established fundamental principles about how memory functions are organized in the brain.

  12. Polyelectrolyte microcapsules for sustained delivery of water-soluble drugs

    Energy Technology Data Exchange (ETDEWEB)

    Anandhakumar, S.; Debapriya, M. [Department of Materials Engineering, Indian Institute of Science, Bangalore, 560012 (India); Nagaraja, V. [Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, 560012 (India); Raichur, Ashok M., E-mail: amr@materials.iisc.ernet.in [Department of Materials Engineering, Indian Institute of Science, Bangalore, 560012 (India)

    2011-03-12

    Polyelectrolyte capsules composed of weak polyelectrolytes are introduced as a simple and efficient system for spontaneous encapsulation of low molecular weight water-soluble drugs. Polyelectrolyte capsules were prepared by layer-by-layer (LbL) assembling of weak polyelectrolytes, poly(allylamine hydrochloride) (PAH) and poly(methacrylic acid) (PMA) on polystyrene sulfonate (PSS) doped CaCO{sub 3} particles followed by core removal with ethylene-diaminetetraacetic acid (EDTA). The loading process was observed by confocal laser scanning microscopy (CLSM) using tetramethylrhodamineisothiocyanate labeled dextran (TRITC-dextran) as a fluorescent probe. The intensity of fluorescent probe inside the capsule decreased with increase in cross-linking time. Ciprofloxacin hydrochloride (a model water-soluble drug) was spontaneously deposited into PAH/PMA capsules and their morphological changes were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The quantitative study of drug loading was also elucidated which showed that drug loading increased with initial drug concentration, but decreased with increase in pH. The loaded drug was released in a sustained manner for 6 h, which could be further extended by cross-linking the capsule wall. The released drug showed significant antibacterial activity against E. coli. These findings indicate that such capsules can be potential carriers for water-soluble drugs in sustained/controlled drug delivery applications.

  13. Saloplastics: processing compact polyelectrolyte complexes.

    Science.gov (United States)

    Schaaf, Pierre; Schlenoff, Joseph B

    2015-04-17

    Polyelectrolyte complexes (PECs) are prepared by mixing solutions of oppositely charged polyelectrolytes. These diffuse, amorphous precipitates may be compacted into dense materials, CoPECs, by ultracentrifugation (ucPECs) or extrusion (exPECs). The presence of salt water is essential in plasticizing PECs to allow them to be reformed and fused. When hydrated, CoPECs are versatile, rugged, biocompatible, elastic materials with applications including bioinspired materials, supports for enzymes and (nano)composites. In this review, various methods for making CoPECs are described, as well as fundamental responses of CoPEC mechanical properties to salt concentration. Possible applications as synthetic cartilage, enzymatically active biocomposites, self-healing materials, and magnetic nanocomposites are presented.

  14. Interactions of phosphororganic agents with water and components of polyelectrolyte membranes.

    Science.gov (United States)

    Lee, Ming-Tsung; Vishnyakov, Aleksey; Gor, Gennady Yu; Neimark, Alexander V

    2011-11-24

    Interactions of nerve G-agents (sarin and soman) and their simulants DMMP (dimethyl methylphosphonate) and DIFP (diisopropyl fluorophosphate) with water and components of polyelectrolyte membranes are studied using ab initio calculations in conjunction with thermodynamic modeling using the conductor-like screening model for real solvents (COSMO-RS). To test reliability of COSMO-RS calculations, we measured the vapor-liquid equilibrium in DMMP-water mixtures and found quantitative agreement between computed and experimental results. Using COSMO-RS, we studied the interactions of phosphororganic agents with the characteristic fragments of perfluorinated and sulfonated polystyrene (sPS) polyelectrolytes, which are explored for protective clothing membranes. We found that both simulants, DIFP and DMMP, mimic the thermodynamic properties of G-agents reasonably well; however, there are certain specific differences that are discussed. We also suggested that sPS-based polyelectrolytes have less affinity for phosphorganic agents compared to prefluorinated polyelectrolytes similar to Nafion.

  15. Polyelectrolyte properties of proteoglycan monomers

    Science.gov (United States)

    Li, Xiao; Reed, Wayne F.

    1991-03-01

    Light scattering measurements were made on proteoglycan monomers (PGM) over a wide range of ionic strengths Cs, and proteoglycan concentrations [PG]. At low Cs there were clear peaks in the angular scattering intensity curve I(q), which moved towards higher scattering wave numbers q, as [PG]1/3. This differs from the square root dependence of scattering peaks found by neutron scattering from more concentrated polyelectrolyte solutions. The peaks remained roughly fixed as Cs increased, but diminished in height, and superposed I(q) curves yielded a sort of isosbestic point. Under certain assumptions the static structure factor S(q) could be extracted from the measured I(q), and was found to retain a peak. A simple hypothesis concerning coexisting disordered and liquidlike correlated states is presented, which qualitatively accounts for the most salient features of the peaks. There was evidence of a double component scattering autocorrelation decay at low Cs, which, when resolved into two apparent diffusion coefficients, gave the appearance of simultaneous ``ordinary'' and ``extraordinary'' phases. The extraordinary phase was ``removable,'' however, by filtering. At higher Cs the proteoglycans appear to behave as random nonfree draining polyelectrolyte coils, with a near constant ratio of 0.67 between hydrodynamic radius and radius of gyration. The apparent persistence length varied as roughly the -0.50 power of ionic strength, similar to various linear synthetic and biological polyelectrolytes. Electrostatic excluded volume theory accounted well for the dependence of A2 on Cs.

  16. Dissipative particle dynamics simulations of weak polyelectrolyte adsorption on charged and neutral surfaces as a function of the degree of ionization

    CERN Document Server

    Alarcón, F; Goicochea, A Gama

    2012-01-01

    The influence of the chain degree of ionization on the adsorption of weak polyelectrolytes on neutral and on oppositely and likely charged surfaces is investigated for the first time, by means of Monte Carlo simulations with the mesoscopic interaction model known as dissipative particle dynamics. The electrostatic interactions are calculated using the three-dimensional Ewald sum method, with an appropriate modification for confined systems. Effective wall forces confine the linear polyelectrolytes, and electric charges on the surfaces are included. The solvent is included explicitly also and it is modeled as an athermal solvent for the polyelectrolytes. The number of solvent particles is allowed to fluctuate. The results show that the polyelectrolytes adsorb both onto neutral and charged surfaces, with the adsorption regulated by the chain degree of ionization, being larger at lower ionization degrees, where polyelectrolytes are less charged. Furthermore, polyelectrolyte adsorption is strongly modulated by th...

  17. Infrared spectra of HM Sagittae and V1016 Cygni

    Science.gov (United States)

    Puetter, R. C.; Russell, R. W.; Soifer, B. T.; Willner, S. P.

    1978-01-01

    Spectrophotometry of HM Sge from 2 to 13 microns is presented along with 2 to 4-micron spectrophotometry of V1016 Cyg. From 2.5 to 8 microns, the spectrum of HM Sge can be represented by a 950-K blackbody, and a strong silicate emission feature is seen from 8 to 13 microns. Both HM Sge and V1016 Cyg show evidence of CO absorption at 2.3 microns. It is suggested that the infrared radiation from these objects arises from a combination of emission by optically thin dust and by the reddened photosphere of a cool star.

  18. Guided wave sensing of polyelectrolyte multilayers

    DEFF Research Database (Denmark)

    Horvath, R.; Pedersen, H.C.; Cuisinier, F.J.G.

    2006-01-01

    A planar optical waveguide configuration is proposed to monitor the buildup of thick polyelectrolyte multilayers on the surface of the waveguide in aqueous solutions. Instead of detecting the layer by the electromagnetic evanescent field the polyelectrolyte layer acts as an additional waveguiding...... film that is sensed by guided waves instead of evanescent waves. This leads to a considerably improved sensitivity and dynamic range....

  19. The Relation Between the Associate Almost Complex Structure to HM' and (HM',S,T-Cartan Connections

    Directory of Open Access Journals (Sweden)

    Ebrahim Esrafilian

    2006-09-01

    Full Text Available In the present paper, the (HM',S,T-Cartan connections on pseudo-Finsler manifolds, introduced by A. Bejancu and H.R. Farran, are obtained by the natural almost complex structure arising from the nonlinear connection HM'. We prove that the natural almost complex linear connection associated to a (HM',S,T-Cartan connection is a metric linear connection with respect to the Sasaki metric G. Finally we give some conditions for (M',J,G to be a Kähler manifold.

  20. Levi Strauss and H&M Announce Ban on Sandblasting

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    As a commitment to the health and safety of workers across the apparel industry, Levi Strauss & Co. and Hennes & Mauritz AB (H&M) announced plans to implement a global ban on sandblasting in all of their future product

  1. Polyelectrolyte Multilayers: Towards Single Cell Studies

    Directory of Open Access Journals (Sweden)

    Dmitry Volodkin

    2014-05-01

    Full Text Available Single cell analysis (SCA is nowadays recognized as one of the key tools for diagnostics and fundamental cell biology studies. The Layer-by-layer (LbL polyelectrolyte assembly is a rather new but powerful technique to produce multilayers. It allows to model the extracellular matrix in terms of its chemical and physical properties. Utilization of the multilayers for SCA may open new avenues in SCA because of the triple role of the multilayer film: (i high capacity for various biomolecules; (ii natural mimics of signal molecule diffusion to a cell and (iii cell patterning opportunities. Besides, light-triggered release from multilayer films offers a way to deliver biomolecules with high spatio-temporal resolution. Here we review recent works showing strong potential to use multilayers for SCA and address accordingly the following issues: biomolecule loading, cell patterning, and light-triggered release.

  2. Macroion Interaction at Polyelectrolyte Brush Interfaces

    Science.gov (United States)

    Qu, Chen

    2015-03-01

    The effect of macroions, including synthetic polyelectrolytes, DNA and proteins, on the structure and surface properties of charged polymer thin films remains inadequately understood partially due to the complexity involving the hydrophobic effect and the conformational change of polymeric macroions. In this work, we explore a group of inorganic nanocluster based macroions, hydrophilic polyoxometalates (POMs) of robust nanocluster structure and carrying high surface charges (~ 2-42 negative charges) to investigate their interaction with surface tethered poly-2-vinylpyridine (P2VP) brush-like thin films immersed in aqueous solution. We observe the collapse of swollen P2VP chains by adding POM macroions of increased concentration by AFM, QCM and contact goniometer measurements, in sharp contrast to the increased chain stretching by adding monovalent salts. A careful comparison is made between distinct POMs based on their charge, size and chemical nature. These findings serve as a good reference for theoretical model modification and design of new mesoporous composite membranes.

  3. Field-Theoretic Studies of Nanostructured Triblock Polyelectrolyte Gels

    Science.gov (United States)

    Audus, Debra; Fredrickson, Glenn

    2012-02-01

    Recently, experimentalists have developed nanostructured, reversible gels formed from triblock polyelectrolytes (Hunt et al. 2011, Lemmers et al. 2010, 2011). These gels have fascinating and tunable properties that reflect a heterogeneous morphology with domains on the order of tens of nanometers. The complex coacervate domains, aggregated oppositely charged end-blocks, are embedded in a continuous aqueous matrix and are bridged by uncharged, hydrophilic polymer mid-blocks. We report on simulation studies that employ statistical field theory models of triblock polyelectrolytes, and we explore the equilibrium self-assembly of these remarkable systems. As the charge complexation responsible for the formation of coacervate domains is driven by electrostatic correlations, we have found it necessary to pursue full ``field-theoretic simulations'' of the models, as opposed to the familiar self-consistent field theory approach. Our investigations have focused on morphological trends with mid- and end-block lengths, polymer concentration, salt concentration and charge density.

  4. A compact dust shell in the symbiotic system HM Sge

    CERN Document Server

    Sacuto, S; Vannier, M; Cruzal`ebes, P; Sacuto, St\\'{e}phane; Chesneau, Olivier; Vannier, Martin; Cruzal\\`{e}bes, Pierre

    2007-01-01

    We present high spatial resolution observations of the mid-infrared core of the dusty symbiotic system HM Sge. The MIDI interferometer was used with the VLT UTs and ATs providing baselines oriented from PA=42° to 105°. The MIDI visibilities are compared with the ones predicted in the frame of various spherical dust shells published in the literature involving single or double dusty shells. The mid-IR environment is unresolved by a 8m telescope and the MIDI spectrum exhibits a level similar to the ISO spectra recorded 10 yr ago. The estimated Gaussian HWHM of the shell of 12AU in the 8-9$\\mu$m range, and 18AU in the 11-12$\\mu$m range, are much smaller than the angular separation between the Mira and the White Dwarf of 60AU. The discrepancies between the HWHM at different angle orientations suggest an increasing level of asymmetry from 13 to 8$\\mu$m. The observations are well fitted by the densest and smallest model published in the literature based on the ISO data, although such a model does no...

  5. Ionizing radiation in the polyelectrolytes technology

    Science.gov (United States)

    Martin, D.; Dragusin, M.; Radoiu, M.; Moraru, R.; Oproiu, C.; Toma, M.; Ferdes, O.; Jianu, A.; Bestea, V.; Manea, A.

    1999-01-01

    Gamma ray and accelerated electron beam application in the chemistry of polyelectrolytes is presented. The polyelectrolytes preparation is based on radiation induced polymerization of aqueous solutions containing an appropriate mixture of monomers such as acrylamide, acrylic acid, vinyl acetate, diallyldimethylammonium-chloride and certain initiators, complexing agents and chain transfer agents. The effects of absorbed dose, rate of absorbed dose and chemical composition of aqueous solution on the polymerization process are discussed. The results obtained by testing these polyelectrolytes with waste water from food industry are also given.

  6. Functionalized conjugated polyelectrolytes design and biomedical applications

    CERN Document Server

    Wang, Shu

    2014-01-01

    Functionalized Conjugated Polyelectrolytes presents a comprehensive review of these polyelectrolytes and their biomedical applications. Basic aspects like molecular design and optoelectronic properties are covered in the first chapter. Emphasis is placed on the various applications including sensing (chemical and biological), disease diagnosis, cell imaging, drug/gene delivery and disease treatment. This book explores a multi-disciplinary topic of interest to researchers working in the fields of chemistry, materials, biology and medicine. It also offers an integrated perspective on both basic research and application issues. Functionalized conjugated polyelectrolyte materials, which have already drawn considerable interest, will become a major new direction for biomedicine development.

  7. The retention mechanism of technetium-99m-HM-PAO

    DEFF Research Database (Denmark)

    Neirinckx, R D; Burke, J F; Harrison, R C

    1988-01-01

    Preparations of d,l- and meso-hexamethylpropyleneamine oxime (HM-PAO) labeled with technetium-99m were added to rat brain homogenates diluted with phosphate buffer (1:10). The conversion of d,l-HM-PAO to hydrophilic forms took place with an initial rate constant of 0.12 min-1. Incubation...... of the brain homogenate with 2% diethyl maleate for 5 h decreased the homogenate's measured glutathione (GSH) concentration from 160 to 16 microM and decreased the conversion rate to 0.012 min-1. Buffered aqueous solutions of glutathione rapidly converted the HM-PAO tracers to hydrophilic forms having the same...... chromatographic characteristics as found in the brain homogenates. The rate constant for the conversion reaction of d,l-HM-PAO in GSH aqueous solution was 208 and 317 L/mol/min in two different assay systems and for meso-HM-PAO the values were 14.7 and 23.2 L/mol/min, respectively. Rat brain has a GSH...

  8. Responsive polyelectrolyte hydrogels and soft matter micromanipulation

    NARCIS (Netherlands)

    Glazer, P.J.

    2013-01-01

    This dissertation describes experimental studies on the mechanisms underlying the dynamic response of polyelectrolyte hydrogels when submitted to an external electric potential. In addition, we explore the possibilities of miniaturization and manipulation of responsive gels and other soft matter sys

  9. Adsorption of dispersing polyelectrolytes: stabilization of drilling fluids; Adsorption de polyelectrolytes dispersants: stabilisation des fluides de forage

    Energy Technology Data Exchange (ETDEWEB)

    Balastre, M.

    1999-11-10

    Instabilities of concentrated colloidal suspensions are a source of many industrial problems, as in drilling fluid formulations where aggregation and severe settling phenomena can occur. Low molecular weight polyelectrolyte dispersants are used to solve these problems, but their optimal use requires a better understanding of the phenomena that are involved. After materials characterization, adsorption mechanisms of two anionic polyelectrolytes (PANa, PSSNa) on a soluble substrate model, barium sulfate powder are studied. Barium sulfate is the principal additive used to adapt the density of drilling fluids. A simple model allows us to propose a distribution of the microscopic species at the interface. Presence of divalent ions induces the formation of a strong complex with the polyelectrolyte. Adsorption and electro-kinetic data are presented and exchange equilibrium are examined in relation with the surface uptake. The binding mechanism and the surface speciation of the polymer groups are deduced from the ion exchange analysis. The macroscopic behavior of suspensions on different conditions (volume fraction, ionic strength, dispersant concentration) is studied by settling and rheological measurements. The macroscopic properties are connected to structural aspects, and we show that dispersing effects are mostly related to electro-steric repulsion. The dispersion state depends on two principal factors adsorbed amounts and adsorbed layer properties, especially the excess charge, and the molecules conformation. (author)

  10. HM Sagittae - Symbiotic cousin of the RS CVn stars

    Science.gov (United States)

    Blair, W. P.; Stencel, R. E.; Feibelman, W. A.; Shaviv, G.

    1981-01-01

    In the brief time since its brightening in 1975, the optical spectrum of HM Sagittae has shown considerable variation in both its general characteristics and relative line intensity ratios. The observations place HM Sagittae in a small class of objects which are thought to be proto-planetary nebulae, of which V 1016 Cygni is the prototype. Attention is given to derived density and temperature, helium abundance and nebular mass, and an evolutionary scenario. The considered observations show a decrease in the intensity of the continuum and a continuation of the trend toward higher excitation in the spectrum of HM Sagittae. Parallels are seen in the development of this object and V 1016 Cygni, with the implication that the trend toward higher excitation is expected to continue.

  11. Complex Formation Between Polyelectrolytes and Ionic Surfactants

    OpenAIRE

    1998-01-01

    The interaction between polyelectrolyte and ionic surfactant is of great importance in different areas of chemistry and biology. In this paper we present a theory of polyelectrolyte ionic-surfactant solutions. The new theory successfully explains the cooperative transition observed experimentally, in which the condensed counterions are replaced by ionic-surfactants. The transition is found to occur at surfactant densities much lower than those for a similar transition in non-ionic polymer-sur...

  12. Adsorption of anionic polyelectrolytes to dioctadecyldimethylammonium bromide monolayers

    Science.gov (United States)

    Engelking, J.; Menzel, H.

    Monolayers of dioctadecyldimethylammonium bromide (DODA) at the air/water interface were used as model for charged surfaces to study the adsorption of anionic polyelectrolytes. After spreading on a pure water surface the monolayers were compressed and subsequently transferred onto a polyelectrolyte solution employing the Fromherz technique. The polyelectrolyte adsorption was monitored by recording the changes in surface pressure at constant area. For poly(styrene sulfonate) and carboxymethylcellulose the plot of the surface pressure as function of time gave curves which indicate a direct correlation between the adsorbed amount and surface pressure as well as a solely diffusion controlled process. In the case of rigid rod-like poly(p-phenylene sulfonate)s the situation is more complicated. Plotting the surface pressure as function of time results in a curve with sigmoidal shape, characterized by an induction period. The induction period can be explained by a domain formation, which can be treated like a crystallization process. Employing the Avrami expression developed for polymer crystallization, the change in the surface pressure upon adsorption of rigid rod-like poly(p-phenylene sulfonate)s can be described.

  13. Hollow polyelectrolyte multilayer tubes: mechanical properties and shape changes.

    Science.gov (United States)

    Mueller, Renate; Daehne, Lars; Fery, Andreas

    2007-07-26

    In this paper, novel hollow polyelectrolyte multilayer tubes from poly(diallyldimethylammonium chloride) (PDADMAC), poly(styrene sulfonate) (PSS), and poly(allylamine hydrochloride) (PAH) were prepared: Readily available glass fiber templates are coated with polyelectrolytes using the layer-by-layer technique, followed by subsequent fiber dissolution. Depending on the composition of the polymeric multilayer, stable hollow tubes or tubes showing a pearling instability are observed. This instability corresponds to the Rayleigh instability and is a consequence of an increased mobility of the polyelectrolyte chains within the multilayer. The well-defined stable tubes were characterized with fluorescence microscopy, confocal laser scanning microscopy, and atomic force microscopy (AFM). The tubes were found to be remarkably free of defects, which results in an impermeable tube wall for even low molecular weight molecules. The mechanical properties of the tubes were determined with AFM force spectroscopy in water, and because continuum mechanical models apply, the Young's modulus of the wall material was determined. Additionally, scaling relations for the dependency of tube stiffness on diameter and wall thickness were validated. Because both parameters can be experimentally controlled by our approach, the deformability of the tubes can be varied over a broad range and adjusted for the particular needs.

  14. Tunable protein-resistance of polycation-terminated polyelectrolyte multilayers.

    Science.gov (United States)

    Tristán, Ferdinando; Palestino, Gabriela; Menchaca, J-Luis; Pérez, Elías; Atmani, Hassan; Cuisinier, Frédéric; Ladam, Guy

    2009-08-10

    The prevention of nonspecific protein adsorption is a crucial prerequisite for many biomedical and biotechnological applications. Therefore, the design of robust and versatile methods conferring optimal protein-resistance properties to surfaces has become a challenging issue. Here we report the unexpected case of polycation-ending polyelectrolyte multilayers (PEM) that efficiently prevented the adsorption of a negatively charged model protein, glucose oxidase (GOX). PEM films were based on two typical weak poyelectrolytes: poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA). No chemical modification of the polyelectrolytes was required and tunable GOX adsorption was possible by simply changing the buildup pH conditions. Protein-resistance properties are attributed to high film hydration becoming the predominant factor over electrostatic interactions. We explain this effect by oscillations of the internal PAA ionization state throughout the buildup, which results in an excess of carboxylic acid groups within the film. This excess acts as a reservoir of potential carboxylate groups compensating the outer PAH positive charges. Partial results indicated that the system was also resistant to the adsorption of a positively charged protein, lysozyme. Control of the internal ionization of weak polyelectrolyte multilayers might open a route toward simple tuning of protein adsorption. These results should help to rationalize the design of biomaterials, biosensors, or protein separation devices.

  15. Charge-regularization effects on polyelectrolytes

    Science.gov (United States)

    Muthukumar, Murugappan

    2012-02-01

    When electrically charged macromolecules are dispersed in polar solvents, their effective net charge is generally different from their chemical charges, due to competition between counterion adsorption and the translational entropy of dissociated counterions. The effective charge changes significantly as the experimental conditions change such as variations in solvent quality, temperature, and the concentration of added small electrolytes. This charge-regularization effect leads to major difficulties in interpreting experimental data on polyelectrolyte solutions and challenges in understanding the various polyelectrolyte phenomena. Even the most fundamental issue of experimental determination of molar mass of charged macromolecules by light scattering method has been difficult so far due to this feature. We will present a theory of charge-regularization of flexible polyelectrolytes in solutions and discuss the consequences of charge-regularization on (a) experimental determination of molar mass of polyelectrolytes using scattering techniques, (b) coil-globule transition, (c) macrophase separation in polyelectrolyte solutions, (c) phase behavior in coacervate formation, and (d) volume phase transitions in polyelectrolyte gels.

  16. Logistique ST-HM pour le projet LHC

    CERN Document Server

    Prodon, S

    2002-01-01

    Ce papier a pour objectif de présenter la structure mise en place au sein du groupe ST-HM pour assurer la logistique d'installation du projet LHC. L'aspect traèabilité sera tout d'abord évoqué avec notamment la mise en place d'outils informatiques tels que le formulaire EDH de demande d'intervention transport-manutention et le système SIRIAC de suivi et de validation des transports réalisés. Ces développements informatiques s'intègrent dans le cadre plus général des modalités de traèabilité des équipements établies en collaboration avec le groupe SL/MR, chargé de la gestion des espaces pour le projet LHC. Les procédures proprement dites de transport des équipements feront l'objet d'un développement particulier. Leur processus d'élaboration sera détaillé : des premières réunions d'information jusqu'à la validation finale par les trois parties (demandeur, groupe ST-HM et contractant ST-HM). L'intégration de ces documents dans la logistique générale ST-HM de planification des ressou...

  17. The ghrelin receptor agonist HM01 mimics the neuronal effects of ghrelin in the arcuate nucleus and attenuates anorexia-cachexia syndrome in tumor-bearing rats.

    Science.gov (United States)

    Borner, Tito; Loi, Laura; Pietra, Claudio; Giuliano, Claudio; Lutz, Thomas A; Riediger, Thomas

    2016-07-01

    The gastric hormone ghrelin positively affects energy balance by increasing food intake and reducing energy expenditure. Ghrelin mimetics are a possible treatment against cancer anorexia-cachexia syndrome (CACS). This study aimed to characterize the action of the nonpeptidergic ghrelin receptor agonist HM01 on neuronal function, energy homeostasis and muscle mass in healthy rats and to evaluate its possible usefulness for the treatment of CACS in a rat tumor model. Using extracellular single-unit recordings, we tested whether HM01 mimics the effects of ghrelin on neuronal activity in the arcuate nucleus (Arc). Furthermore, we assessed the effect of chronic HM01 treatment on food intake (FI), body weight (BW), lean and fat volumes, and muscle mass in healthy rats. Using a hepatoma model, we investigated the possible beneficial effects of HM01 on tumor-induced anorexia, BW loss, muscle wasting, and metabolic rate. HM01 (10(-7)-10(-6) M) mimicked the effect of ghrelin (10(-8) M) by increasing the firing rate in 76% of Arc neurons. HM01 delivered chronically for 12 days via osmotic minipumps (50 μg/h) increased FI in healthy rats by 24%, paralleled by increased BW, higher fat and lean volumes, and higher muscle mass. Tumor-bearing rats treated with HM01 had 30% higher FI than tumor-bearing controls and were protected against BW loss. HM01 treatment resulted in higher muscle mass and fat mass. Moreover, tumor-bearing rats reduced their metabolic rate following HM01 treatment. Our studies substantiate the possible therapeutic usefulness of ghrelin receptor agonists like HM01 for the treatment of CACS and possibly other forms of disease-related anorexia and cachexia.

  18. Flexible polyelectrolyte conformation in the presence of cationic and anionic surfactants

    Science.gov (United States)

    Passos, C. B.; Kuhn, P. S.; Diehl, A.

    2015-11-01

    In this work we have studied the conformation of flexible polyelectrolyte chains in the presence of cationic and anionic surfactant molecules. We developed a simple theoretical model for the formation of the polyelectrolyte-cationic surfactant complexes and mixed micelles formed by cationic and anionic surfactant molecules, in the framework of the Debye-Hückel-Bjerrum-Manning and Flory theories, with the hydrophobic interaction included explicitly as an effective short-ranged attraction between the surfactant hydrocarbon tails. This simple model allows us to calculate the extension of the polyelectrolyte-cationic surfactant complexes as a function of the anionic surfactant concentration, for different types of cationic and anionic surfactant molecules. A discrete conformational transition from a collapsed state to an elongated coil was found, for all surfactant chain lengths we have considered, in agreement with the experimental observations for the unfolding of ​DNA-cationic surfactant complexes.

  19. Polyelectrolyte coatings prevent interferences from charged nanoparticles in SPME speciation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Zielińska, Katarzyna, E-mail: kzielinska@gmail.com; Leeuwen, Herman P. van

    2014-09-24

    Highlights: • For the first time SPME fiber is coated with polyelectrolyte layer. • Sorption of nanoparticles on the solid phase surface is prevented. • Polyelectrolyte-modified fiber enables extraction of free analyte in presence of sorbing nanoparticles. - Abstract: In this work we present a new approach for protection of the fiber in solid phase microextraction (SPME) from interfering charged particles present in the sample medium. It involves coating of commercial poly(dimethylsiloxane) extraction phase with polyelectrolyte layer composed of poly(diallyldimethylammonium chloride), and poly(sodium 4-styrenesulfonate). The modified fiber provides reproducible, convenient and fast extraction capabilities toward the model analyte, triclosan (TCS). A negatively charged polyelectrolyte coating prevents sorbing oxidic nanoparticles from both partitioning into the PDMS phase and aggregation at its surface. The results for the TCS/nanoparticle sample show that the polyelectrolyte layer-modified solid phase extracts just the free form of the organic compound and enables dynamic speciation analysis of the nanoparticulate target analyte complex.

  20. The experimental study of polyelectrolyte coatings suitability for encapsulation of cells.

    Science.gov (United States)

    Granicka, L H; Antosiak-Iwańska, M; Godlewska, E; Hoser, G; Strawski, M; Szklarczyk, M; Dudziński, K

    2009-01-01

    Living cells encapsulated in polymeric shells are receiving increasing attention because of their possible biotechnological and biomedical applications. The aim of this work is to evaluate how different polyelectrolyte coatings, characterized by different numbers of polyelectrolyte layers and by different polyelectrolyte conformations, affect the viability of encapsulated biological material. We demonstrate the ability to individually encapsulate HL-60 cells as well as rat pancreatic islets within polymeric shells consisting of different PE layers using the layer-by-layer process. Coating of HL-60 cells allows for surviving and functioning of cells for all applied PE as well as for different numbers of layers. The islets encapsulated in applied polyelectrolytes exhibited the lower level of mitochondrial activity as compared to non-encapsulated islets. Nevertheless, encapsulated islets exhibited comparable absorbance values during the whole period of culture. Polyelectrolyte coating seems to be a promising way of allowing capsule void volume minimization in a model of encapsulated biological material for local production of biologically active substances.

  1. Alternate drop coating for forming dual biointerfaces composed of polyelectrolyte multilayers.

    Science.gov (United States)

    Watanabe, Junji; Shen, Heyun; Akashi, Mitsuru

    2009-03-01

    Two types of polyelectrolyte multilayers were formed on both sides of a quartz crystal microbalance (QCM) substrate by a novel alternate drop coating process. In this study, poly(diallyldimethylammonium chloride) (PDDA) and poly(sodium 4-styrene sulfonate) (PSS) were used as strong-strong polyelectrolytes. On the other hand, PDDA and poly(acrylic acid) (PAA) were used as strong-weak polyelectrolytes. The novel alternate drop coating process can separately fabricate each polyelectrolyte multilayer on both sides of the substrate. The substrate provides dual biointerfaces, both sides of which comprise different multilayers, by employing a combination of polymers. The formation of the multilayer by alternate drop coating was evaluated in terms of changes in the frequency of the QCM and model protein adsorption for proteins such as bovine serum albumin, and their characteristics were investigated with those of the conventional alternate adsorption process by performing dip coating. There was no significant difference between the surface properties resulting from the two formation conditions. This result strongly supported the fact that the multilayers fabricated by alternate drop coating were similar in quality to those fabricated by conventional dip coating. The resulting dual biointerfaces with polyelectrolyte multilayers provide alternative biofunctions in terms of individual protein loading. In summary, the novel alternate drop coating process for substrates is a good candidate for the preparation of dual biointerfaces in the biomedical field.

  2. Energy conversion in polyelectrolyte hydrogels

    Science.gov (United States)

    Olvera de La Cruz, Monica; Erbas, Aykut; Olvera de la Cruz Team

    Energy conversion and storage have been an active field of research in nanotechnology parallel to recent interests towards renewable energy. Polyelectrolyte (PE) hydrogels have attracted considerable attention in this field due to their mechanical flexibility and stimuli-responsive properties. Ideally, when a hydrogel is deformed, applied mechanical work can be converted into electrostatic, elastic and steric-interaction energies. In this talk, we discuss the results of our extensive molecular dynamics simulations of PE hydrogels. We demonstrate that, on deformation, hydrogels adjust their deformed state predominantly by altering electrostatic interactions between their charged groups rather than excluded-volume and bond energies. This is due to the hydrogel's inherent tendency to preserve electro-neutrality in its interior, in combination with correlations imposed by backbone charges. Our findings are valid for a wide range of compression ratios and ionic strengths. The electrostatic-energy alterations that we observe in our MD simulations may induce pH or redox-potential changes inside the hydrogels. The resulting energetic difference can be harvested, for instance, analogously to a Carnot engine, or facilitated for sensor applications. Center for Bio-inspired Energy Science (CBES).

  3. MOLECULAR DYNAMIC SIMULATION OF PEPTIDE POLYELECTROLYTES

    Directory of Open Access Journals (Sweden)

    I. M. Neelov

    2014-07-01

    Full Text Available The paper deals with investigation of the conformational properties of some charged homopolypeptides in dilute aqueous solutions by computer simulation. A method of molecular dynamics for the full-atomic models of polyaspartic acid and polylysine with explicit account of water and counter-ions is used for this purpose. For systems containing these polypeptides we calculated time trajectories and the size, shape, distribution functions and time correlation functions of inertia radius and the distances between the ends of peptide chains. We have also calculated the solvatation characteristics of considered polyelectrolytes. We have found out that polyaspartic acid in dilute aqueous solution has more compact structure and more spherical shape than polylysine. We have shown that these differences are due to different interaction between the polypeptides and water molecules (in particular, the quality and quantity of hydrogen bonds formed by these peptides with water, and the difference in an amount of ion pairs formed by the charged groups of the peptides and counter-ions. The obtained results should be taken into account for elaboration of new products based on the investigated peptides and their usage in various industrial and biomedical applications.

  4. Macroion induced dehydration of weak polyelectrolyte brushes

    Science.gov (United States)

    Zheng, Zhongli; Zhu, Y. Elaine

    2014-03-01

    The interaction of macroions, including polyelectrolytes, DNAs, and proteins, with polymer and cellular surfaces is critically related to many biomolecular activities, such as protein adsorption and DNA hybridization at probe surfaces. In an experimental approach to examine the macroion electrostatic interaction with a polymer surface while minimizing the long-debated hydrophobic interaction, we study the interaction of molybdenum-based inorganic polyoxometalate (POM) nanoclusters carrying 42 negative charges as model hydrophilic macroions with surface-tethered poly-2-vinylpyridine (P2VP) brushes immersed in aqueous solutions. By AFM, QCM, and contact goniometer, we have observed the collapse of P2VP chains by adding POM macroions at a constant pH. Surprisingly, added POM macroions can cause the shift of swollen-to-collapse transition pH to a lower value, in contrast to the shift to high pH value by adding simple monovalent salts. At sufficiently high POM concentration, a stable POM-P2VP composite layer, showing little dependence on solution pH and additional salts, can be formed, suggesting a simple route to construct meso-porous polymer membranes.

  5. MELCOR simulation of steam condensation effect on hydrogen behavior in THAI HM-2 experiment

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seongnyeon; Lee, Jung-Jae; Cho, Yong-Jin [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of); Kim, Sung Joong [Hanyang University, Seoul (Korea, Republic of)

    2015-10-15

    In this study, MELCOR simulation was carried out for THAI HM-2 experiment of OECD. As a results, stratification of hydrogen cloud was reasonably captured in MELCOR simulation. Furthermore, the pressure from simulation results in cases where mass transfer coefficient of MELCOR condensation model was modified was good agreement with the experimental results. Containment Filtered Ventilation System (CFVS) has been introduced as facility to prevent containment failure during severe accident. However, possibility of hydrogen risk has been issued due to inflow of hydrogen, condensation and removal of steam and complicated inner structure in CFVS. Preferentially benchmark work for THAI HM-2 experiment of OECD was decided to validate the methodology before detailed assessment of hydrogen risk in CFVS. The objectives of THAI HM-2 experiment were evaluation of hydrogen behavior, verification of numerical analysis tools and so on. In this paper, therefore, MELCOR simulation was carried out in comparison with the experiment results. Additionally, steam condensation effect was considered for detailed simulation. Hydrogen concentration from MELCOR results was underestimated in comparison to the experimental results.

  6. Reversible Self-Assembly of Hydrophilic Inorganic Polyelectrolytes into Highly Conservative, Vesicle-like Structures

    Science.gov (United States)

    Kistler, Melissa; Bhatt, Anish; Liu, Guang; Liu, Tianbo

    2007-03-01

    The hydrophilic polyoxometalate (POM) macroanions are inorganic polyelectrolytes which offer a direct connection between simple ions and organic polyelectrolytes. POM solutions are perfect model systems for studying polyelectrolyte solutions because they are identical in size, shape, mass and charges, with easily tunable charge density. Many types of POM macroanions are highly soluble but undergo reversible self-assembly to form uniform, stable, soft, single-layer vesicle-like ``blackberry'' structures containing >1000 individual POMs in dilute solutions. The driving force of the blackberry formation is likely counterion-mediated attraction (like-charge attraction). The blackberry size can be accurately controlled by solvent quality, or the charge density on macroions. Many unexpected phenomena have been observed in these novel systems. Blackberry structures may be analogous to virus shell structures formed by capsid proteins. References: Nature, 2003, 426, 59; JACS, 2002, 124, 10942; 2003, 125, 312; 2004, 126, 16690; 2005, 127, 6942; 2006, 128, 10103.

  7. Spin-Coated Polyelectrolyte Coacervate Films.

    Science.gov (United States)

    Kelly, Kristopher D; Schlenoff, Joseph B

    2015-07-01

    Thin films of complexes made from oppositely charged polyelectrolytes have applications as supported membranes for separations, cell growth substrates, anticorrosion coatings, biocompatible coatings, and drug release media, among others. The relatively recent technique of layer-by-layer assembly reliably yields conformal coatings on substrates but is impractically slow for films with thickness greater than about 1 μm, even when accelerated many fold by spraying and/or spin assembly. In the present work, thin, uniform, smooth films of a polyelectrolyte complex (PEC) are rapidly made by spin-coating a polyelectrolyte coacervate, a strongly hydrated viscoelastic liquidlike form of PEC, on a substrate. While the apparatus used to deposit the PEC film is conventional, the behavior of the coacervate, especially the response to salt concentration, is highly nontraditional. After glassification by immersion in water, spun-on films may be released from their substrates to yield free-standing membranes of thickness in the micrometer range.

  8. Waste-moulding dusts modified with polyelectrolytes

    Directory of Open Access Journals (Sweden)

    A. Baliński

    2010-04-01

    Full Text Available In the article described problems of the influence of advanced oxidizing process, the supersonic tooling of waste - moulding dusts and their modification with polyelectrolytes, on the technological proprieties of the moulding sands prepared with their participation.Physicochemical characterization of the used polyelectrolytes PSS (poli 4-styreno sodium sulfonate and PEI (poli etyleno imine, in theaspect of their modificatory influences on the waste - moulding dust, was described. Defined the influence of adsorption proprieties ofthe polyelectrolyte PEI on the surface of small parts of the waste - dust, on technological proprieties of the sandmix. Ascertained theprofitable influence of this electrolyte on mechanical proprieties of the moulding sands, that is to say the increase in value of thecompression strength (about 10% and tensile strenght (about 13%, comparatively to analogous proprieties of the moulding sandsprepared with the participation of the not modified waste- dust.

  9. Poly-electrolytes for fuel cells: tools and methods for characterization; Polyelectrolytes pour piles a combustible: outils et methodes de caracterisation

    Energy Technology Data Exchange (ETDEWEB)

    Marechal, M.

    2004-12-15

    The research works reported in the manuscript are a contribution to the study of poly-electrolytes for Proton Exchange Membrane Fuel Cells (PEMFC). They are supported by two investigation tools, i.e. the study of model molecules and accurate conductivity measurements. With regard to the material science domain, the optimization of poly-sulfone sulfonation procedure allows chain breaking to be reduced and even eliminated while obtaining reproducible sulfonation degrees. It is thus possible to improve the mechanical properties of the dense membrane elaborated with these poly-electrolytes before performing the tests on the MEA (Membrane Electrode Assembly). In parallel, the functionalization of microporous silicon made it possible to prepare poly-electrolytes reinforced by the mechanical strength of the silicon separator. With regard to the physicochemical and electrochemical characterizations, the model molecules, with the same functions and groups than for associated polymers, make it possible to amplify the electrochemical or thermal phenomena vs. the corresponding polymers. Thus, they simulate an accelerated ageing of the poly-electrolytes. The development of a new conductivity measurement set allows conductivity to be obtained with a great accuracy, in a wide range of temperature and relative humidity. (author)

  10. Characterization for Soil Fixation by Polyelectrolyte Complex

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Yong Suk; Kwon, Sang Woon; Yang, Heeman; Lee, Kune Woo; Seo, Bumkyoung; Moon, Jei Kwon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    According to report, the radioactivity bulk (approx. 95%) is localized within topsoil. Therefore soil surface on topsoil should be fixed to prevent the spreading of the contaminated soils with Cs-137 by wind and water erosion. Many methods have been developing for soil fixation to remove radioactive contaminants in soil and prevent to diffuse radioactive materials. Various materials have been also used as fixatives such as clays, molecular sieves, polymer, and petroleum based products. One of the methods is a soil fixation or solidification using polyelectrolyte. Polyelectrolytes have many ionic groups and make into the polyelectrolyte complex (PEC) due to electrostatic interaction of polyanion and polycation in an aqueous solution. It can be avoids using the chemical cross-linking agents, and reducing the possible toxicity and other undesirable effects of the reagents. PEC can fix soil particles by flocculation and formation of crust between soil. The method can also prevent a spread of radioactive material by floating on a soil surface. Recently, PEC used for the solidification of soil near the Fukushima nuclear power plant in Japan. The decontamination efficiency of the surface soils reached 90%, and dust release was effectively suppressed during the removal of surface soils. In this study, it was investigated the fixation of the soil by PEC to avoid the spread of the contamination in addition to the separation of soil and PEC. The physicochemical properties of polyelectrolyte complex solution and the stability of fixed soil by PEC were investigated. The mode of the addition is important to prepare the polyelectrolytes complex without PAA agglomerate. The concentration of salt in the polyelectrolyte complex solution is a very important parameter for the soil fixation.

  11. New nanocomposites based on layered aluminosilicate and guanidine containing polyelectrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Khashirov, Azamat A.; Zhansitov, Azamat A.; Khashirova, Svetlana Yu. [Kabardino-Balkarian State University a. Kh.M. Berbekov, 173 Chernyshevskogo st., 360004, Nalchik (Russian Federation); Zaikov, Genadiy E. [N. M. Emanuel Institute of Biochemical Physics of Russian Academy of Sciences, 4, Kosygin St., 119991, Moscow (Russian Federation)

    2014-05-15

    The new functional nanomaterials based on layered aluminosilicate and guanidine containing polyelectrolytes combining high bactericidal activity with an increased ability to bind to heavy metals and organic pollutants were received. To prove the chemical structure of the model compounds (zwitterionic delocalized resonance structures AG/MAG and PAG/PMAG), as well as the presence of such structures in nanocomposites received on their basis and the MMT, IR, {sup 1}H NMR spectroscopy, X-ray diffraction studies and nanoindentation/sclerometry followed by scanning the surface in the area of the indentation were used.

  12. Complexation behavior of oppositely charged polyelectrolytes: Effect of charge distribution

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Mingtian; Li, Baohui, E-mail: dliang@pku.edu.cn, E-mail: baohui@nankai.edu.cn [School of Physics and Key Laboratory of Functional Polymer Materials of Ministry of Education, Nankai University, Tianjin 300071 (China); Zhou, Jihan; Su, Cuicui; Niu, Lin; Liang, Dehai, E-mail: dliang@pku.edu.cn, E-mail: baohui@nankai.edu.cn [Beijing National Laboratory for Molecular Sciences and the Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China)

    2015-05-28

    Complexation behavior of oppositely charged polyelectrolytes in a solution is investigated using a combination of computer simulations and experiments, focusing on the influence of polyelectrolyte charge distributions along the chains on the structure of the polyelectrolyte complexes. The simulations are performed using Monte Carlo with the replica-exchange algorithm for three model systems where each system is composed of a mixture of two types of oppositely charged model polyelectrolyte chains (EGEG){sub 5}/(KGKG){sub 5}, (EEGG){sub 5}/(KKGG){sub 5}, and (EEGG){sub 5}/(KGKG){sub 5}, in a solution including explicit solvent molecules. Among the three model systems, only the charge distributions along the chains are not identical. Thermodynamic quantities are calculated as a function of temperature (or ionic strength), and the microscopic structures of complexes are examined. It is found that the three systems have different transition temperatures, and form complexes with different sizes, structures, and densities at a given temperature. Complex microscopic structures with an alternating arrangement of one monolayer of E/K monomers and one monolayer of G monomers, with one bilayer of E and K monomers and one bilayer of G monomers, and with a mixture of monolayer and bilayer of E/K monomers in a box shape and a trilayer of G monomers inside the box are obtained for the three mixture systems, respectively. The experiments are carried out for three systems where each is composed of a mixture of two types of oppositely charged peptide chains. Each peptide chain is composed of Lysine (K) and glycine (G) or glutamate (E) and G, in solution, and the chain length and amino acid sequences, and hence the charge distribution, are precisely controlled, and all of them are identical with those for the corresponding model chain. The complexation behavior and complex structures are characterized through laser light scattering and atomic force microscopy measurements. The order

  13. Complex coacervation of supercharged proteins with polyelectrolytes.

    Science.gov (United States)

    Obermeyer, Allie C; Mills, Carolyn E; Dong, Xue-Hui; Flores, Romeo J; Olsen, Bradley D

    2016-04-21

    Complexation of proteins with polyelectrolytes or block copolymers can lead to phase separation to generate a coacervate phase or self-assembly of coacervate core micelles. However, many proteins do not coacervate at conditions near neutral pH and physiological ionic strength. Here, protein supercharging is used to systematically explore the effect of protein charge on the complex coacervation with polycations. Four model proteins were anionically supercharged to varying degrees as quantified by mass spectrometry. Proteins phase separated with strong polycations when the ratio of negatively charged residues to positively charged residues on the protein (α) was greater than 1.1-1.2. Efficient partitioning of the protein into the coacervate phase required larger α (1.5-2.0). The preferred charge ratio for coacervation was shifted away from charge symmetry for three of the four model proteins and indicated an excess of positive charge in the coacervate phase. The composition of protein and polymer in the coacervate phase was determined using fluorescently labeled components, revealing that several of the coacervates likely have both induced charging and a macromolecular charge imbalance. The model proteins were also encapsulated in complex coacervate core micelles and micelles formed when the protein charge ratio α was greater than 1.3-1.4. Small angle neutron scattering and transmission electron microscopy showed that the micelles were spherical. The stability of the coacervate phase in both the bulk and micelles improved to increased ionic strength as the net charge on the protein increased. The micelles were also stable to dehydration and elevated temperatures.

  14. INTERACTIONS BETWEEN CATIONIC POLYELECTROLYTE AND PULP FINES

    Directory of Open Access Journals (Sweden)

    Elina Orblin

    2011-05-01

    Full Text Available Papermaking pulps are a mixture of fibres, fibre fragments, and small cells (parenchyma or ray cells, usually called pulp fines. The interactions between pulp fines and a cationic copolymer of acrylamide and acryloxyethyltrimethyl ammonium chloride were investigated based on solid-liquid isotherms prepared under different turbulence, and subsequent advanced surface characterization using X-ray photoelectron spectroscopy (XPS and time-of-flight secondary ion mass spectrometry (ToF-SIMS. The surface charge and surface area of pulp fine substrates were measured by methylene blue sorption-XPS analysis and nitrogen adsorption combined with mercury porosimetry, respectively. The driving force behind polyelectrolyte adsorption was the amount of the surface anionic charge, whereas surface area appeared to be of less importance. Based on a comparison of solid-liquid and XPS sorption isotherms, different polyelectrolyte conformations were suggested, depending on the types of fines: A flatter conformation and partial cell-wall penetration of polyelectrolytes on kraft fines from freshly prepared pulp, and a more free conformation with extended loops and tails on lignocellulosic fines from recycled pulp. Additionally, ToF-SIMS imaging proved that recycled pulp fines contained residual de-inking chemicals (primarily palmitic acid salts that possibly hinder the electrostatic interactions with polyelectrolytes.

  15. Complexation Behavior of Polyelectrolytes and Polyampholytes

    KAUST Repository

    Narayanan Nair, Arun Kumar

    2017-07-25

    We perform grand canonical Monte Carlo simulations to study the pH titrations of isolated polyampholytes and polyelectrolyte-polyampholyte complexes in dilute solutions. Our simulations indicate that the electrostatic interactions promote the coexistence of opposite charges along the polyampholyte chain during titration. The repulsion between excess charges typically dominates the electrostatic interaction and leads to polymer stretching. Salt ions can screen the repulsion between excess charges as well as the fluctuation-induced attraction between opposite charges, and therefore make the variation between titration curves of polyampholytes and the ideal (no electrostatic interactions) curves less significant. We observe that this screening of charge repulsion decreases the chain size. The presence of pearl-necklace configuration of polyampholytes is diminished by the addition of salt. Similar simulations for the polyelectrolyte-polyampholyte system show that the resulting complexes are generally stable in the low pH region. In comparison to ideal case, electrostatic interactions strongly influence the acid-base properties of polyampholyte chains in the adsorbed state by reducing the presence of the coexistence domain of both positive and negative charges in the titration curves. We attribute the complex formation between polyelectrolyte and polyampholyte chains in the high pH region to, e.g., the high salt content. The pH variation leads to abrupt transition between adsorbed and desorbed states. Independent of charge sequence, a polyampholyte chain in a complex is usually located at one of the ends of the polyelectrolyte chain.

  16. Self-consistent-field calculations of proteinlike incorporations in polyelectrolyte complex micelles

    NARCIS (Netherlands)

    Lindhoud, S.; Cohen Stuart, M.A.; Norde, W.; Leermakers, F.A.M.

    2009-01-01

    Self-consistent field theory is applied to model the structure and stability of polyelectrolyte complex micelles with incorporated protein (molten globule) molecules in the core. The electrostatic interactions that drive the micelle formation are mimicked by nearest-neighbor interactions using

  17. Effect of Protein Supercharging on Interaction with Polyelectrolytes

    Science.gov (United States)

    Olsen, Bradley; Obermeyer, Allie; Mills, Carolyn; Dong, Xuehui

    Complexation of proteins with polyelectrolytes can lead to a liquid-liquid phase separation to generate a viscous complex coacervate phase rich in protein and polyelectrolyte. However, many proteins do not readily coacervate at conditions near neutral pH and physiological ionic strength. Here, protein supercharging is used to systematically explore the effect of protein charge on the complex coacervation with polycations. Four model proteins were chemically modified to generate a panel of proteins with varying surface charge, with both the average charge and charge distribution quantified by mass spectrometry. Proteins phase separated with the qP4VP and qPDMAEMA polycations when the ratio of negatively charged residues to positively charged residues was greater than 1.1-1.2. Efficient partitioning of the protein into the coacervate phase required larger charge ratio (1.5-2.0). The model proteins were also encapsulated in complex coacervate core micelles. Dynamic light scattering was used to assess the formation of micelles with POEGMA- b-qP4VP and revealed micellar hydrodynamic radii of approximately 25-30 nm. Small angle neutron scattering and transmission electron microscopy were used to confirm the formation of spherical micelles.

  18. Sustainable Fashion Supply Chain: Lessons from H&M

    Directory of Open Access Journals (Sweden)

    Bin Shen

    2014-09-01

    Full Text Available Sustainability is significantly important for fashion business due to consumers’ increasing awareness of environment. When a fashion company aims to promote sustainability, the main linkage is to develop a sustainable supply chain. This paper contributes to current knowledge of sustainable supply chain in the textile and clothing industry. We first depict the structure of sustainable fashion supply chain including eco-material preparation, sustainable manufacturing, green distribution, green retailing, and ethical consumers based on the extant literature. We study the case of the Swedish fast fashion company, H&M, which has constructed its sustainable supply chain in developing eco-materials, providing safety training, monitoring sustainable manufacturing, reducing carbon emission in distribution, and promoting eco-fashion. Moreover, based on the secondary data and analysis, we learn the lessons of H&M’s sustainable fashion supply chain from the country perspective: (1 the H&M’s sourcing managers may be more likely to select suppliers in the countries with lower degrees of human wellbeing; (2 the H&M’s supply chain manager may set a higher level of inventory in a country with a higher human wellbeing; and (3 the H&M CEO may consider the degrees of human wellbeing and economic wellbeing, instead of environmental wellbeing when launching the online shopping channel in a specific country.

  19. Polyelectrolyte surfactant aggregates and their deposition on macroscopic surfaces

    CERN Document Server

    Voisin, D

    2002-01-01

    Oppositely charged surfactant and polyelectrolyte are present in hair shampoos and conditioners, together with particles (e.g. anti-dandruff agents for scalp) and droplets (e.g. silicone oil for the hair). These are normally formulated at high surfactant concentrations, beyond the flocculation region for the polyelectrolyte concentration used. However, on dilution with water, during application, flocs are formed which carry the particles and droplets to the scalp and hair. The addition of an anionic surfactant to an aqueous solution of cationic polyelectrolyte, at a given concentration, can lead to the formation of polyelectrolyte-surfactant 'particles', in which the surfactant 'binds' to the polyelectrolyte. This occurs from the critical association concentration (CAC), up to the surfactant concentration corresponding to maximum binding. Within this range of surfactant concentrations, the surfactant bound to the polyelectrolyte is thought to associate to form what might be termed 'internal micelles'. Each po...

  20. HM{sup +}–RG complexes (M = group 2 metal; RG = rare gas): Physical vs. chemical interactions

    Energy Technology Data Exchange (ETDEWEB)

    Harris, Joe P.; Dodson, Hannah; Wright, Timothy G., E-mail: Tim.Wright@nottingham.ac.uk [School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom); Breckenridge, W. H. [Department of Chemistry, University of Utah, Salt Lake City, Utah 84112 (United States)

    2015-04-21

    Previous work on the HM{sup +}–He complexes (M = Be–Ra) has been extended to the cases of the heavier rare gas atoms, HM{sup +}–RG (RG = Ne–Rn). Optimized geometries and harmonic vibrational frequencies have been calculated using MP2 theory and quadruple-ζ quality basis sets. Dissociation energies for the loss of the rare gas atom have been calculated at these optimized geometries using coupled cluster with single and double excitations and perturbative triples, CCSD(T)theory, extrapolating interaction energies to the basis set limit. Comparisons are made between the present data and the previously obtained helium results, as well as to those of the bare HM{sup +} molecules; furthermore, comparisons are made to the related M{sup +}–RG and M{sup 2+}–RG complexes. Partial atomic charge analyses have also been undertaken, and these used to test a simple charge-induced dipole model. Molecular orbital diagrams are presented together with contour plots of the natural orbitals from the quadratic configuration with single and double excitations (QCISD) density. The conclusion is that the majority of these complexes are physically bound, with very little sharing of electron density; however, for M = Be, and to a lesser extent M = Mg, some evidence for chemical effects is seen in HM{sup +}–RG complexes involving RG atoms with the higher atomic numbers.

  1. Interaction of HmC1q with leech microglial cells: involvement of C1qBP-related molecule in the induction of cell chemotaxis.

    Science.gov (United States)

    Tahtouh, Muriel; Garçon-Bocquet, Annelise; Croq, Françoise; Vizioli, Jacopo; Sautière, Pierre-Eric; Van Camp, Christelle; Salzet, Michel; Nagnan-le Meillour, Patricia; Pestel, Joël; Lefebvre, Christophe

    2012-02-22

    In invertebrates, the medicinal leech is considered to be an interesting and appropriate model to study neuroimmune mechanisms. Indeed, this non-vertebrate animal can restore normal function of its central nervous system (CNS) after injury. Microglia accumulation at the damage site has been shown to be required for axon sprouting and for efficient regeneration. We characterized HmC1q as a novel chemotactic factor for leech microglial cell recruitment. In mammals, a C1q-binding protein (C1qBP alias gC1qR), which interacts with the globular head of C1q, has been reported to participate in C1q-mediated chemotaxis of blood immune cells. In this study, we evaluated the chemotactic activities of a recombinant form of HmC1q and its interaction with a newly characterized leech C1qBP that acts as its potential ligand. Recombinant HmC1q (rHmC1q) was produced in the yeast Pichia pastoris. Chemotaxis assays were performed to investigate rHmC1q-dependent microglia migration. The involvement of a C1qBP-related molecule in this chemotaxis mechanism was assessed by flow cytometry and with affinity purification experiments. The cellular localization of C1qBP mRNA and protein in leech was investigated using immunohistochemistry and in situ hybridization techniques. rHmC1q-stimulated microglia migrate in a dose-dependent manner. This rHmC1q-induced chemotaxis was reduced when cells were preincubated with either anti-HmC1q or anti-human C1qBP antibodies. A C1qBP-related molecule was characterized in leech microglia. A previous study showed that recruitment of microglia is observed after HmC1q release at the cut end of axons. Here, we demonstrate that rHmC1q-dependent chemotaxis might be driven via a HmC1q-binding protein located on the microglial cell surface. Taken together, these results highlight the importance of the interaction between C1q and C1qBP in microglial activation leading to nerve repair in the medicinal leech.

  2. Interaction of HmC1q with leech microglial cells: involvement of C1qBP-related molecule in the induction of cell chemotaxis

    Directory of Open Access Journals (Sweden)

    Tahtouh Muriel

    2012-02-01

    Full Text Available Abstract Background In invertebrates, the medicinal leech is considered to be an interesting and appropriate model to study neuroimmune mechanisms. Indeed, this non-vertebrate animal can restore normal function of its central nervous system (CNS after injury. Microglia accumulation at the damage site has been shown to be required for axon sprouting and for efficient regeneration. We characterized HmC1q as a novel chemotactic factor for leech microglial cell recruitment. In mammals, a C1q-binding protein (C1qBP alias gC1qR, which interacts with the globular head of C1q, has been reported to participate in C1q-mediated chemotaxis of blood immune cells. In this study, we evaluated the chemotactic activities of a recombinant form of HmC1q and its interaction with a newly characterized leech C1qBP that acts as its potential ligand. Methods Recombinant HmC1q (rHmC1q was produced in the yeast Pichia pastoris. Chemotaxis assays were performed to investigate rHmC1q-dependent microglia migration. The involvement of a C1qBP-related molecule in this chemotaxis mechanism was assessed by flow cytometry and with affinity purification experiments. The cellular localization of C1qBP mRNA and protein in leech was investigated using immunohistochemistry and in situ hybridization techniques. Results rHmC1q-stimulated microglia migrate in a dose-dependent manner. This rHmC1q-induced chemotaxis was reduced when cells were preincubated with either anti-HmC1q or anti-human C1qBP antibodies. A C1qBP-related molecule was characterized in leech microglia. Conclusions A previous study showed that recruitment of microglia is observed after HmC1q release at the cut end of axons. Here, we demonstrate that rHmC1q-dependent chemotaxis might be driven via a HmC1q-binding protein located on the microglial cell surface. Taken together, these results highlight the importance of the interaction between C1q and C1qBP in microglial activation leading to nerve repair in the medicinal

  3. Structures of some surfactant–polyelectrolyte complexes

    Indian Academy of Sciences (India)

    Rema Krishnaswamy; V A Raghunathan; A K Sood

    2003-08-01

    Structures of complexes formed in aqueous solutions by some anionic polyelectrolytes (double and single stranded (ds and ss) DNA, poly(vinyl sulfonate) (PVS), and poly(styrene sulfonate) (PSS)) with a cationic surfactant system consisting of cetyltrimethylammonium bromide (CTAB) and sodium 3-hydroxy-2-naphthoate (SHN) have been determined using small angle X-ray diffraction. All complexes are found to have a two-dimensional (2-D) hexagonal structure at low SHN concentrations. Analysis of the diffraction data shows that the ds DNA–CTAB complex has an intercalated structure, with each DNA strand surrounded by three cylindrical micelles. On increasing SHN concentration, DNA–CTAB–SHN complexes exhibit a hexagonal-to-lamellar transition, whereas PVS complexes show a hexagonal → centered rectangular → lamellar transition. PSS complexes show yet another sequence of structures. These results indicate the significant influence of the chemical nature of the polyelectrolyte on the structure of the complexes.

  4. Polyelectrolytes from NS-novolak production waste

    Energy Technology Data Exchange (ETDEWEB)

    Bajdur, W.M.; Sulkowski, W.W. [Czestochowa Technical University, Dept. of Ergonomics and Work Protection, Czestochowa (Poland)

    2003-09-12

    The chemical modification of polymer plastic wastes into useful products, such as polyelectrolytes, could be a step toward their management. For these products to be obtained, the synthesis of amino derivatives of phenol-formaldehyde resin (NS-novolak) production waste by means of known methods was performed. Products that contained different contents of amino groups in the polymer chains and that were soluble in dilute KOH and NaOH solutions were obtained. The flocculation properties of these products were tested. Studies were conducted of mine water from the Kleofas coal mine and for water from the Czestochowa metallurgical plant blast-furnace circulation system. The amino derivatives of the phenol-formaldehyde resin waste were found to have good flocculation properties. The application of these products caused a decrease in the turbidity and concentration of the dissolved contamination and improved the quality parameters of the purified sewage. These polyelectrolytes could also be used in industrial water treatment.

  5. HM-PAO-SPECT in complicated migraine. Case report

    Energy Technology Data Exchange (ETDEWEB)

    Gruenwald, F.; Ruhlmann, J.; Biersack, H.J.; Durwen, H.; Penin, H.

    1988-10-01

    Three HM-PAO-SPECT investigations have been performed in a female patient with a complicated migraine. 2.5 hours after an attack with right-sided numbness and atonic hemiparesis, at the left side a reduced blood flow was seen parietotemporally and in the subcortical structures. The cerebellum showed crossed diaschisis. During a symptom-free interval the SPECT showed a slightly increased parietotemporal blood blow and a reduced right temporooccipital blood flow. During a seizure with left-sided facial spasm, unsystematic clonic movements in all extremities and a following left-sided hemiparesis, the uptake in the visual cortex was increased by 60%. In the right frontotemporal and left temporal region a slightly increased accumulation was found.

  6. Static and ultrafast optical properties of nanolayered composites. Gold nanoparticles embedded in polyelectrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Kiel, Mareike

    2012-08-16

    In the course of this thesis gold nanoparticle/polyelectrolyte multilayer structures were prepared, characterized, and investigated according to their static and ultrafast optical properties. Using the dip-coating or spin-coating layer-by-layer deposition method, gold-nanoparticle layers were embedded in a polyelectrolyte environment with high structural perfection. Typical structures exhibit four repetition units, each consisting of one gold-particle layer and ten double layers of polyelectrolyte (cationic+anionic polyelectrolyte). The structures were characterized by X-ray reflectivity measurements, which reveal Bragg peaks up to the seventh order, evidencing the high stratification of the particle layers. In the same measurements pronounced Kiessig fringes were observed, which indicate a low global roughness of the samples. Atomic force microscopy (AFM) images verified this low roughness, which results from the high smoothing capabilities of polyelectrolyte layers. This smoothing effect facilitates the fabrication of stratified nanoparticle/polyelectrolyte multilayer structures, which were nicely illustrated in a transmission electron microscopy image. The samples' optical properties were investigated by static spectroscopic measurements in the visible and UV range. The measurements revealed a frequency shift of the reflectance and of the plasmon absorption band, depending on the thickness of the polyelectrolyte layers that cover a nanoparticle layer. When the covering layer becomes thicker than the particle interaction range, the absorption spectrum becomes independent of the polymer thickness. However, the reflectance spectrum continues shifting to lower frequencies (even for large thicknesses). The range of plasmon interaction was determined to be in the order of the particle diameter for 10 nm, 20 nm, and 150 nm particles. The transient broadband complex dielectric function of a multilayer structure was determined experimentally by ultrafast pump

  7. Transport rectification in nanopores with outer membranes modified with surface charges and polyelectrolytes.

    Science.gov (United States)

    Tagliazucchi, Mario; Rabin, Yitzhak; Szleifer, Igal

    2013-10-22

    This work reports a comprehensive theoretical study of the transport-rectification properties of cylindrical nanopores with neutral inner walls and chemically modified outer membrane. The chemical species on the two outer sides of the membrane have charges of opposite sign and can be either surface-confined species (i.e., surface charges) or polyelectrolyte brushes. The advantage of this design over other types of rectifying nanopores is that it requires controlling the composition of the outer walls of the pore (which are easy to access) rather than the inner walls, thus simplifying the fabrication process. Ion-current rectification in nanopores with charged outer walls is ascribed to applied-potential-induced changes in the ionic concentration within the pore. The rectification efficiency is studied as a function of pore length, radius, surface charge and bulk electrolyte concentration. An analytical model is derived for the case of surface-confined charges that predicts the current-potential curves in very good agreement with the numerical calculations. Neutral nanopores with polyelectrolyte-modified outer walls have two distinct advantages compared to surface-charged systems: (i) they exhibit higher rectification factors due to the large charge density immobilized by the polyelectrolyte brushes, and (ii) the applied potential deforms the polyelectrolyte chains toward the oppositely charged electrode. This deformation brings the polyelectrolyte brushes into the pore in the low conductivity state and expels them from the pore in the high conductivity regime. Calculations of the potentials of mean-force suggest that the applied-field-induced conformational changes can be used to control the translocation of cargoes larger than ions, such as proteins and nanoparticles.

  8. FORMULATION AND EVALUATION OF MATRIX TABLETS BASED ON POLYELECTROLYTE COMPLEX BETWEEN OKRA MUCILAGE AND CHITOSAN

    Directory of Open Access Journals (Sweden)

    Ashwini Rajendra

    2012-02-01

    Full Text Available Recent years there has been greater utilization of natural polymers in the development of delivery systems. The present work is an effort towards development of matrix tablets using polyelectrolyte complex formed between the oppositely charged natural polymers like okra mucilage obtained from pods of Abelmoschus esculentus and chitosan. The effect of pH and polymer volume ratio on yield of polyelectrolyte complex was studied. It was observed that the yield was maximum (96.45% at pH 5 and at polymer volume ratio of 9:1 between okra mucilage and chitosan. The prepared polyelectrolyte complex was also characterised by conductimetry, FTIR, DSC. The results confirmed the formation of polyelectrolyte complex between the natural polymers. The matrix tablets were formulated for model drug diclofenac sodium using the best polyelectrolyte complex at different drug to polymer ratios and compared with formulations containing individual polymers as well as marketed formulation. The prepared formulations showed satisfactory physical parameters. Formulations F2 and F3 extended the drug release for more than 8 h with (83.87± 0.8321% and (77.125± 0.125% drug release respectively in 8 h. The formulations F2 and F3 followed zero order kinetics with anomalous diffusion mechanism. The mean dissolution times were 3.6042 and 3.5935 hrs and the % dissolution efficiency were 54.9467 and 55.7203 % for formulations F2 and F3 respectively. The similarity factor f2 for formulation F2 was 61.6751 and for formulation F3, it was found to be 60.5025.The formulations were found to be stable.

  9. Water sorption properties of HM-pectin and liposomes intended to alleviate dry mouth.

    Science.gov (United States)

    Adamczak, Małgorzata I; Martinsen, Ørjan G; Smistad, Gro; Hiorth, Marianne

    2016-06-15

    Pharmaceutical formulations intended for treatment of xerostomia (dry mouth) should be able to keep the oral mucosa hydrated for a prolonged period of time. The products already existing on the market contain water-soluble polymers, however their ability to moisturize the oral mucosa for a longer period of time seems limited. In this paper the sorption properties of water vapor of high-methoxylated pectin (HM-pectin, a hydrophilic biopolymer) and phosphatidylcholine-based (Soya-PC) liposomes have been studied and compared using a gravimetric method. The kinetics of water desorption and sorption have been recorded over the relative humidity range RH=95-0-95%, at 35°C. The obtained isotherms were found to be well described by the n-layer Brunauer-Emmet-Teller (BET) adsorption model. The water isotherms on HM-pectin were Type II (IUPAC), while water isotherms on liposomes were Type III. The maximum water sorption capacity of liposomes (1.2mg water per mg of adsorbent at 95% RH) was found to be twice as high as for pectin. Due to the slower water release from the liposomes, as well as their high water sorption capacity, they seem to have great potential in relieving the symptoms of dry mouth syndrome.

  10. CFD Analysis of the Hydrogen/Steam Behavior in the OECD-NEA THAI Test HM-2 experiment

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Se-Hong; Choi, Choengryul [ELSOLTEC, Yongin (Korea, Republic of); Cho, Yong-Jin; Lee, Seongnyeon; Lee, Jung-Jae [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2015-10-15

    In this study, a three-dimensional CFD analysis has been carried out and compared with the OECD-NEA THAI Test HM-2 experiment in order to verify adopted numerical models including condensation and evaporation models. This CFD simulation has predicted flows, temperature, pressure, species concentrations and so on inside the THAI vessel. Hydrogen could be generated by active reactions of fuel-cladding and steam in the reactor vessel during a severe accident of a nuclear power plant, and released into the atmosphere inside the containment. A local concentration of hydrogen which is higher than a flammability limit could lead to hydrogen combustion inside the containment. Therefore, it is important to predict local hydrogen concentration distribution for assessment of hydrogen combustion, deflagration and detonation risks. When mixture of hydrogen, steam and noncondensable gases is released at a high energy level, very complex behaviors and phenomena occur, which include steam condensation and evaporation. In CFD (computational fluid dynamics) analysis, numerical modeling for condensation and evaporation phenomena is important to predict flows and local hydrogen concentration accurately. In this study, a three-dimensional CFD analysis is carried out and compared with the results of the OECD-NEA THAI Test HM-2 experiment in order to verify adopted numerical models including condensation and evaporation models. The comparison between the CFD results and HM-2 experiment data has shown a good reasonable agreement physically.

  11. Hydrophobically modified polyelectrolytes : synthesis, properties and interactions with surfactants

    NARCIS (Netherlands)

    Nieuwkerk, A.C.

    1998-01-01

    Hydrophobically modified polyelectrolytes can form micelle-like aggregates, so-called microdomains, in aqueous solution. The hydrophobic side chains constitute the apolar inner part of these microdomains and the hydrophilic groups on the polyelectrolyte backbone are at the surface of the

  12. Stabilization of protein-loaded starch microgel by polyelectrolytes

    NARCIS (Netherlands)

    Li, Y.; Norde, W.; Kleijn, J.M.

    2012-01-01

    The interaction of biocompatible polyelectrolytes (chargeable poly(amino acids)) with oxidized starch microgel particles has been studied. The aim was to form a polyelectrolyte complex layer around the outer shell of microgel particles filled with functional ingredients to slow down the release of

  13. Stabilization of Protein-Loaded Starch Microgel by Polyelectrolytes

    NARCIS (Netherlands)

    Li, Yuan; Norde, Willem; Kleijn, J. Mieke

    2012-01-01

    The interaction of biocompatible polyelectrolytes (chargeable poly(amino acids)) with oxidized starch microgel particles has been studied. The aim was to form a polyelectrolyte complex layer around the outer shell of microgel particles filled with functional ingredients to slow down the release of

  14. Weak polyelectrolyte multilayers as tunable membranes for solvent resistant nanofiltration

    NARCIS (Netherlands)

    Ilyas, Shazia; Joseph, Nithya; Szymczyk, Anthony; Volodin, Alexander; Nijmeijer, Kitty; Vos, de Wiebe M.; Vankelecom, Ivo F.J.

    2016-01-01

    This manuscript encompasses the investigation into the solvent resistant nanofiltration (SRNF) performance of multilayer membranes prepared from weak polyelectrolytes. These weak polyelectrolytes are unique in that the charge density is not fixed and depends on the coating pH, adding an extra variab

  15. Influence of the Hydrophobicity of Polyelectrolytes on Polyelectrolyte Complex Formation and Complex Particle Structure and Shape

    Directory of Open Access Journals (Sweden)

    Gudrun Petzold

    2011-08-01

    Full Text Available Polyelectrolyte complexes (PECs were prepared by structural uniform and strongly charged cationic and anionic modified alternating maleic anhydride copolymers. The hydrophobicity of the polyelectrolytes was changed by the comonomers (ethylene, isobutylene and styrene. Additionally, the n−/n+ ratio of the molar charges of the polyelectrolytes and the procedure of formation were varied. The colloidal stability of the systems and the size, shape, and structure of the PEC particles were investigated by turbidimetry, dynamic light scattering (DLS and atomic force microscopy (AFM. Dynamic light scattering indicates that beside large PEC particle aggregates distinct smaller particles were formed by the copolymers which have the highest hydrophobicity (styrene. These findings could be proved by AFM. Fractal dimension (D, root mean square (RMS roughness and the surface profiles of the PEC particles adsorbed on mica allow the following conclusions: the higher the hydrophobicity of the polyelectrolytes, the broader is the particle size distribution and the minor is the swelling of the PEC particles. Hence, the most compact particles are formed with the very hydrophobic copolymer.

  16. New polyelectrolyte complex particles as colloidal dispersions based on weak synthetic and/or natural polyelectrolytes

    Directory of Open Access Journals (Sweden)

    2011-06-01

    Full Text Available This study aims to evidence the formation of stable polyelectrolyte complex particles as colloidal dispersions using some weak polyelectrolytes: chitosan and poly(allylamine hydrochloride as polycations and poly(acrylic acid (PAA and poly(2-acrylamido-2-methylpropanesulfonic acid – co – acrylic acid (PAMPSAA as polyanions. Polyelectrolyte complex particles as colloidal dispersion were prepared by controlled mixing of the oppositely charged polymers, with a constant addition rate. The influences of the polyelectrolytes structure and the molar ratio between ionic charges on the morphology, size, and colloidal stability of the complex particles have been deeply investigated by turbidimetry, dynamic light scattering and atomic force microscopy. A strong influence of polyanion structure on the values of molar ratio n–/n+ when neutral complex particles were obtained has been noticed, which shifts from the theoretical value of 1.0, observed when PAA was used, to 0.7 for PAMPSAA based complexes. The polyions chain characteristics influenced the size and shape of the complexes, larger particles being obtained when chitosan was used, for the same polyanion, and when PAMPSAA was used, for the same polycation.

  17. Huge Differences in the Kinetics of Swelling Enhancement and De-enhancement of Permanently Charged Polyelectrolyte Brushes.

    Science.gov (United States)

    Chu, Xiao; Yang, Jingfa; Zhao, Jiang

    2016-10-06

    As demonstrated previously (X. Chu et al., Soft Matter 2014, 10, 5568), permanently charged polyelectrolyte brushes can experience an enhancement of swelling by exposure to an external monovalent salt solution in moderate concentrations. Beyond the previous static measurements, the kinetics of the swelling enhancement and de-enhancement were investigated in the current study by using a quartz crystal microbalance with dissipation (QCM-D). By developing an effective approach to quantify the response in QCM-D, a vast difference in swelling enhancement and de-enhancement of a model permanently charged polyelectrolyte brush (sodium polystyrene sulfonate, NaPSS) was discovered. The results indicate new physics of the charged brushes: the difference in the attachment and detachment of counterions to the polyelectrolyte chains.

  18. Polyelectrolyte coating of ferumoxytol nanoparticles for labeling of dendritic cells

    Science.gov (United States)

    Celikkin, Nehar; Jakubcová, Lucie; Zenke, Martin; Hoss, Mareike; Wong, John Erik; Hieronymus, Thomas

    2015-04-01

    Engineered magnetic nanoparticles (MNPs) are emerging to be used as cell tracers, drug delivery vehicles, and contrast agents for magnetic resonance imaging (MRI) for enhanced theragnostic applications in biomedicine. In vitro labeling of target cell populations with MNPs and their implantation into animal models and patients shows promising outcomes in monitoring successful cell engraftment, differentiation and migration by using MRI. Dendritic cells (DCs) are professional antigen-presenting cells that initiate adaptive immune responses. Thus, DCs have been the focus of cellular immunotherapy and are increasingly applied in clinical trials. Here, we addressed the coating of different polyelectrolytes (PE) around ferumoxytol particles using the layer-by-layer technique. The impact of PE-coated ferumoxytol particles for labeling of DCs and Flt3+ DC progenitors was then investigated. The results from our studies revealed that PE-coated ferumoxytol particles can be readily employed for labeling of DC and DC progenitors and thus are potentially suitable as contrast agents for MRI tracking.

  19. Fabrication of ultrathin polyelectrolyte fibers and their controlled release properties.

    Science.gov (United States)

    Chunder, Anindarupa; Sarkar, Sourangsu; Yu, Yingbo; Zhai, Lei

    2007-08-01

    Ultrathin fibers comprising 2-weak polyelectrolytes, poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) were fabricated using the electrospinning technique. Methylene blue (MB) was used as a model drug to evaluate the potential application of the fibers for drug delivery. The release of MB was controlled in a nonbuffered medium by changing the pH of the solution. The sustained release of MB in a phosphate buffered saline (PBS) solution was achieved by constructing perfluorosilane networks on the fiber surfaces as capping layers. Temperature controlled release of MB was obtained by depositing temperature sensitive PAA/poly(N-isopropylacrylamide) (PNIPAAM) multilayers onto the fiber surfaces. The controlled release of drugs from electrospun fibers have potential applications as drug carriers in biomedical science.

  20. ST-HM design section Strategy and working methods

    CERN Document Server

    Bertone, C

    2003-01-01

    The design section of the ST-HM group is devoted to realise all studies for new transport and handling equipment to be procured and installed according to the needs of CERN. In year 2002, the design section has gradually passed from strong engagement in few huge projects to a multitude of ‘less expensive’ projects that require a fast solution and procurement for the LHC installation. The future tasks of our section will be feasibility studies of transport and handling manoeuvres as required for the installation of LHC components and the calculation of lifting tools. In addition the procurement of not yet defined items to solve problems that will occur during the LHC installation. This document gives an overview of the organisation of the design section, the projects and will also underline some problems, such as the incompatibility between the urgency of the users and long CERN purchasing procedures, the work overload, the increasing design requirements for handling tools and operations that were original...

  1. Polyelectrolytes-promoted Forward Osmosis Processes

    KAUST Repository

    Ge, Q.C.

    2012-11-07

    The development of the forward osmosis (FO) process has been constrained by the slow development of appropriate draw solutions. Two significant concerns related to draw solutions are the draw solute leakage and intensive-energy requirement in recycling draw solutes after the FO process. FO would be much attractive if there is no draw solute leakage and the recycle of draw solutes is easy and economic.In this study, polyelectrolytes of a series of polyacrylic acid sodium salts (PAA-Na), were explored as draw solutes in the FO process. The characteristics of high solubility in water and flexibility in structural configuration ensure the suitability of PAA-Na as draw solutes and their relative ease in recycle through pressure-driven ultrafiltration (UF) membrane processes. The high water flux with insignificant salt leakage in the FO process and the high salt rejection in UF recycle processes reveal the superiority of PAA-Na to conventional ionic salts, such as NaCl, when comparing their FO performance via the same membranes. The repeatable performance of PAA-Na after recycle indicates the absence of any aggregation problems. The overall performance demonstrates that polyelectrolytes of PAA-Na series are promising as draw solutes, and the new concept of using polyelectrolytes as draw solutes in FO processes is applicable. The magnetic nanoparticle draw solutes can generate reasonably high osmotic pressure in FO system due to the functional groups on the nanoparticles surface and they can be regenerated through magnetic field and reused as draw solutes. Thermo-responsive magnetic nanoparticles are able to be regenerated with high efficiency as the thermo-responsive property can assist the regeneration in a low-strength magnetic field.

  2. Rheological Behavior of the Guanidio Polyelectrolytes

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yu-mei; JIANG Jian-ming; CHEN Yan-mo

    2002-01-01

    The rheological behavior of polyhexamethylene guanidine hydrochloride (PHGC) and polyethylene guanidine stearate (PHGS) has been investigated using the capillary rheometer. It is shown that the polyelectrolyte melts are non-Newtonian of shear. thinning fluid. The melt viscosity, the flow activation energy and the flow temperature are high even if the molecular weight is not high. The melting viscosity of PHGC is higher than that of PHGS at the same experimental conditions. By comparison with the case of PHGS the non-Newtonian index of PHGC is smaller, the flow activation energy and the flow temperature of PHGC are higher, which was caused by the difference in their molecular structure.

  3. Precipitate-Coacervate Transformation in Polyelectrolyte-Mixed Micelle Systems.

    Science.gov (United States)

    Comert, Fatih; Nguyen, Duy; Rushanan, Marguerite; Milas, Peker; Xu, Amy Y; Dubin, Paul L

    2017-05-04

    The polycation/anionic-nonionic mixed micelle, poly(diallyldimethylammonium chloride)-sodium dodecyl sulfate/Triton X-100 (PDADMAC-SDS/TX100), is a model polyelectrolyte-colloid system in that the micellar mole fraction of SDS (Y) controls the micelle surface charge density, thus modulating the polyelectrolyte-colloid interaction. The exquisite temperature dependence of this system provides an important additional variable, controlling both liquid-liquid (L-L) and liquid-solid (L-S) phase separation, both of which are driven by the entropy of small ion release. In order to elucidate these transitions, we applied high-precision turbidimetry (±0.1 %), isothermal titration calorimetry, and epifluorescence microscopy which demonstrates preservation of micelle structure under all conditions. The L-S region at large Y including precipitation displays a remarkable linear, inverse Y-dependence of the L-S transition temperature Ts. In sharp contrast, the critical temperature for L-L coacervation Tφ, shows nearly symmetrical effects of positive and negative deviations in Y from the point of soluble complex neutrality, which is controlled in solution by the micelle charge and the number of micelles bound per polymer chain n (Zcomplex = Zpolymer + nZmicelle). In solid-like states, n no longer signifies the number of micelles bound per polymer chain, since the proximity of micelles inverts the host-guest relationship with each micelle binding multiple PE chains. This intimate binding goes hand-in-hand with the entropy of release of micelle-localized charge-compensating ions whose concentration depends on Y. These ions need not be released in L-L coacervation, but during L-S transition their displacement by PE accounts for the inverse dependence of Ts on micelle charge, Y.

  4. H&M "Finally" Lands in Beijing Fashion and quality at the best price

    Institute of Scientific and Technical Information of China (English)

    Wang Ting

    2009-01-01

    @@ On April 23rd, H&M, Hennes & Mauritz AB, opened its much anticipated first store in Beijing. This full-concept store is the only H&M store in Beijing carrying Matthew Williamson's exclusive spring collection, also launched in the same day.

  5. In vitro evaluation of the antimicrobial activity of HM-242, a novel antiseptic compound.

    Science.gov (United States)

    Okunishi, Junji; Nishihara, Yutaka; Maeda, Shirou; Ikeda, Masahiro

    2009-09-01

    The antimicrobial activities of N(4)-octyl-6,6-dimethyl-N(2)-(4-methylbenzyl)-1,6-dihydro-1,3,5-triazine-2,4-diamine (HM-242), a novel synthetic compound, were compared with those of chlorhexidine gluconate (CHG). HM-242 was a more potent microbicide than CHG in vitro; however, its minimal inhibitory concentrations were similar. In particular, HM-242 killed various Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis, both efficiently and rapidly. HM-242 also showed potent virucidal activity against enveloped viruses such as influenza virus and herpes simplex virus. These characteristics suggest that HM-242 may well be useful as an antiseptic.

  6. Fluorescent Polystyrene Sulfonate for Polyelectrolyte Studies

    Science.gov (United States)

    Huberty, Wayne; Tong, Xiaowei; Balamurugan, Sreelatha; Zhang, Donghui; Russo, Paul

    2012-02-01

    The slow-mode decay found by dynamic light scattering for polyelectrolytes in low-salt conditions has perplexed investigators since its first observation. Many characterization methods have suggested temporary or transient aggregation, although there is still no consensus on the cause. Many different polyelectrolytes demonstrate the slow-mode decay, but the sodium salt of polystyrene sulfonate (NaPSS) is the most popular choice for study. Commercially available NaPSS may have hydrophobic patches due to incomplete sulfonation leading to associations apart from any putative ionic mechanisms. Therefore, essentially full sulfonation, or ``patchless'', NaPSS should be synthesized. To facilitate fluorescence measurements, which can provide new insights to the slow-mode phenomenon, the material must be rendered fluorescent (F-NaPSS). Several approaches to F-NaPSS have appeared; some labeled a previously synthesized NaPSS without concern for its hydrophobic patches. Other strategies include a free radical copolymerization of styrene sulfonate and a vinyl amine to provide side chains viable for labeling. This method is successful, but yields only small amounts of nearly monodisperse polymer after fractionation. In this presentation, a high-yield synthesis of fully sulfonated, low-polydispersity, fluorescently tagged polymer will be discussed.

  7. On the scattering properties of polyelectrolyte gels

    Science.gov (United States)

    Barrat, Jean-Louis; Joanny, Jean-François; Pincus, Phil

    1992-08-01

    We present a simple model for scattering properties of polyelectrolyte gels at swelling equilibrium. In the weak screening limit where the Debye-Hückel screening length is larger than the mesh size of the gel, the direct electrostatic interactions are negligible and the swelling is driven by the osmotic pressure of the counterions. The tension created by this pressure is transmitted through the crosslinks to the elastic chains which behave as isolated chains with an applied force at their end points. The structure factor of the gel can be split into a frozen component due to the average concentration heterogeneities and a thermodynamic component due to concentration fluctuations. The frozen component has a peak at a wavevector of the order of the mesh size of the gel, the thermodynamic component has a peak at a higher wavevector of the order of the inverse transverse radius of the chains. At infinite times the dynamic structure factor relaxes towards the frozen component of the static structure factor. In the limit of small wavevectors the relaxation is diffusive with a diffusion constant equal to the Stokes diffusion constant of the Pincus blobs of the stretched chains. The diffusion constant shows a minimum at a wavevector of the order of the inverse transverse radius of the chains. Nous présentons un modèle simple pour étudier la diffusion de rayonnement par des gels polylectrolytes à l'équilibre de gonflement. Dans la limite d'écrantage faible où la longueur d'écran de Debye-Hückel est plus grande que la maille du gel, les interactions électrostatiques directes sont négligeables et le gonflement est dû à la pression osmotique des contreions. La tension créée par cette pression est transmise par les noeuds du gel aux chaines élastiques qui se comportent comme des chaines isolées avec une force extérieure appliquée aux extrémités. Le facteur de structure du gel est la somme d'une composante gelée due aux hétérogénéités de concentration

  8. Langmuir and langmuir-blodgett films of metallosupramolecular polyelectrolyte-amphiphile complexes.

    Science.gov (United States)

    Lehmann, Pit; Symietz, Christian; Brezesinski, Gerald; Krass, Henning; Kurth, Dirk G

    2005-06-21

    A detailed analysis of a metallosupramolecular polyelectrolyte-amphiphile complex (PAC) at the air-water interface is presented. Langmuir isotherms, Brewster angle microscopy, and X-ray reflectance and diffraction methods are employed to investigate the structure of the Langmuir monolayers. The PAC is self-assembled from 1,3-bis[4'-oxa-(2,2':6',2' '-terpyridinyl)]propane, iron acetate, and dihexadecyl phosphate (DHP). Spreading the PAC at the air-water interface results in a monolayer that consists of two strata. DHP forms a monolayer at the top of the interface, while the metallosupramolecular polyelectrolyte is immersed in the aqueous subphase. Both strata are coupled to each other through electrostatic interactions. The monolayers can be transferred onto solid substrates, resulting in well-ordered multilayers. Such multilayers are model systems for well-ordered metal ions in two dimensions.

  9. Model Polyelectrolytes in Turbulent Couette Flow

    Science.gov (United States)

    Price, Brian; Hoagland, David A.

    1997-03-01

    Isolated polymer chains in strong flow are deformed significantly from their equilibrium conformations, imparting a pronounced change in the local velocity field. Turbulent drag reduction by dilute polymer solutions is an important example. The onset of drag reduction appears dependent on a characteristic shear stress at the wall τw for a given polymer. (Virk, P.S. AIChE Journal 21 1975) Length and time scales formed from τw and solvent kinematic viscosity provide different scalings of the onset with chain length. It is likely that length polydispersity could be responsible for the disparity among the previously reported results concerning the correct onset condition. We have employed preparative gel electrophoresis to produce samples of very low polydispersity to determine the onset scaling of drag reduction in turbulent couette flow. The same technique provides information about chain scission in turburlence, yielding an indirect indication of chain conformation.

  10. Theory of polyelectrolyte complexation—Complex coacervates are self-coacervates

    Science.gov (United States)

    Delaney, Kris T.; Fredrickson, Glenn H.

    2017-06-01

    The complexation of mixtures of cationic and anionic polymers to produce complex-coacervate phases is a subject of fundamental importance to colloid and polymer science as well as to applications including drug delivery, sensing technologies, and bio-inspired adhesives. Unfortunately the theoretical underpinnings of complex coacervation are widely misunderstood and conceptual mistakes have propagated in the literature. Here, a simple symmetric polyelectrolyte mixture model in the absence of salt is used to discuss the salient features of the phase diagram, including the location of the critical point, binodals, and spinodals. It is argued that charge compensation by dimerization in the dilute region renders the phase diagram of an oppositely charged polyelectrolyte mixture qualitatively and quantitatively similar to that of a single-component symmetric diblock polyampholyte solution, a system capable of "self-coacervation." The theoretical predictions are verified using fully fluctuating field-theoretic simulations for corresponding polyelectrolyte and diblock polyampholyte models. These represent the first comprehensive, approximation-free phase diagrams for coacervate and self-coacervate systems to appear in the literature.

  11. Polyelectrolyte multilayers: An odyssey through interdisciplinary science

    Science.gov (United States)

    Jaber, Jad A.

    This dissertation provides an overview of a self assembled multilayer technique based on the alternating deposition of oppositely charged polyelectrolytes onto charged solid supports. The basic principles and methodologies governing this technique are laid down, and new strategies are built upon the latter, in an effort to develop innovative technologies that would be beneficial for making new products or improving the quality of existing ones. Fundamental studies to characterize the water content, efficiency of ion-pairing, differential strength of electrostatic interactions, topology, and viscoelastic properties of polyelectrolyte multilayers, PEMUs, are illustrated and conducted. In addition, polyelectrolyte multilayers that are stimulus responsive, or support active and controlled bio-motor protein interactions are described. Attenuated total reflectance Fourier transform infrared, (ATR), spectroscopy was used to compare the extent of swelling and doping within PAH/PSS and PDADMA/PSS polyelectrolyte multilayers. Unlike PDADMA/PSS, whose water content depended on the solution ionic strength, PAH/PSS was resistant to swelling by salt. It was stable up to 4.0 M sodium chloride, with 6 water molecules per ion-pair. Using the infrared active perchlorate sodium salt, the amount of residual persistent extrinsic sites in both PDADMA/PSS and PAH/PSS was determined to be 3% and 6%, respectively. The free energy of association between the polymer segments, in the presence of sodium perchlorate, was in the order of 4.5 kJ mol-1 and -9.5 kJ mol-1 for PDADMA/PSS and PAH/PSS correspondingly. Thus, indicating the relatively strong electrostatic association between the polymer segments in a PAH/PSS relative to PDADMA/PSS multilayer. Adjusting the pH of the solution in contact with the PAH/PSS multilayer to 11.5 resulted in a first order discontinuous dissociation of the Pol+Pol- bonds. Techniques used to study the mechanical properties of single muscle fiber were adapted to

  12. IONIC SELF-ASSEMBLY AND HUMIDITY SENSITIVITY OF POLYELECTROLYTE MULTILAYERS

    Institute of Scientific and Technical Information of China (English)

    Hai-hu Yu; De-sheng Jiang

    2002-01-01

    Multilayer thin films of alternately adsorbed layers of polyelectrolytes PDDA and PS-119 were formed on both planar silica substrates and optical fibers through the ionic self-assembly technique. Intrinsic Fabry-Perot cavities were fabricated by stepwise assembling the polyelectrolytes onto the ends of optical fibers for the purposes of fiber optical device and sensor development. Ionically assembled polyelectrolyte multilayer thin films, in whichthere are hydrophilic side groups with strong affinity towards water molecules, are a category of humidity-sensitive functional materials. The polyelectrolyte multilayer thin film Fabry-Perot cavity-type fiber optical humidity sensor can work over a wide range from about 0% RH to about 100% RH with a response time less than 1 s.

  13. Electrokinetics of pH-regulated zwitterionic polyelectrolyte nanoparticles

    Science.gov (United States)

    Yeh, Li-Hsien; Tai, Yi-Hsuan; Wang, Nan; Hsu, Jyh-Ping; Qian, Shizhi

    2012-11-01

    The electrokinetic behavior of pH-regulated, zwitterionic polyelectrolyte (PE) nanoparticles (NPs) in a general electrolyte solution containing multiple ionic species is investigated for the first time. The NPs considered are capable of simulating entities such as proteins, biomolecules, and synthetic polymers. The applicability of the model proposed is verified by the experimental data of succinoglycan nanoparticles available in the literature. We show that, in addition to their effective charge density, counterion condensation, double-layer polarization, and electro-osmotic flow of unbalanced counterions inside the double layer all significantly affect the electrophoretic behaviors of NPs. Our model successfully predicts many interesting electrophoretic behaviors, which qualitatively agree with experimental observations available in the literature. In contrast, because the effects of double-layer polarization and charge regulation are neglected, the existing theoretical models fail to explain the experimental results. The results gathered provide necessary information for the interpretation of relevant electrophoresis data in practice, and for nanofluidic applications such as biomimetic ion channels and nanopore-based sensing of single biomolecules.The electrokinetic behavior of pH-regulated, zwitterionic polyelectrolyte (PE) nanoparticles (NPs) in a general electrolyte solution containing multiple ionic species is investigated for the first time. The NPs considered are capable of simulating entities such as proteins, biomolecules, and synthetic polymers. The applicability of the model proposed is verified by the experimental data of succinoglycan nanoparticles available in the literature. We show that, in addition to their effective charge density, counterion condensation, double-layer polarization, and electro-osmotic flow of unbalanced counterions inside the double layer all significantly affect the electrophoretic behaviors of NPs. Our model successfully

  14. Anisotropic Diffusion of Polyelectrolyte Chains within Multi-layer Films

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Li [Stevens Institute of Technology, Hoboken, New Jersey; Kozlovskaya, Veronika [University of Alabama, Birmingham; Kharlampieva, Eugenia [University of Alabama, Birmingham; Ankner, John Francis [ORNL; Sukhishvili, Prof. Svetlana A. [Stevens Institute of Technology, Hoboken, New Jersey

    2012-01-01

    We found diffusion of polyelectrolyte chains within multilayer films to be highly anisotropic, with the preferential chain motion parallel to the substrate. The degree of anisotropy was quantified by a combination of fluorescence recovery after photobleaching and neutron reflectometry, probing chain diffusion in directions parallel and perpendicular to the substrate, respectively. Chain mobility was controlled by ionic strength of annealing solutions and steric hindrance to ionic pairing of interacting polyelectrolytes.

  15. Identification of a new antagonistic bacteria HM-7 against the cucumber Fusarium wilt%黄瓜枯萎病拮抗菌HM-7的鉴定

    Institute of Scientific and Technical Information of China (English)

    唐蕊; 张雪辉; 殷世群; 万慧洁

    2016-01-01

    It was studied that the initially identification of the selected antagonistic bacteria HM-7 of cucumber fusarium wilt in order to lay the foundation to the development of biological pesticide. HM-7 was identified according to the cultural characteristics in different medium and its individual form under a microscope,with 16S rDNA complete sequence analysis by comparing the consequences with standard strains and then construct a phylogenetic tree. The results showed that HM-7 was initially identified as Bacillus amyloquefaciens. Bacillus genus is one of microbial groups which were researched exten⁃sively and deeply,and it was one of the main sources of bio-control bacteria which applied in biological control of plant dis⁃ease. So HM-7 is expected to be developed for biological pesticide.%为开发防治黄瓜枯萎病的生物制剂奠定基础,通过对已筛选的黄瓜枯萎病拮抗菌HM-7进行培养特征观察、显微观察、革兰氏染色、16S rDNA全序列分析、系统发育分析等研究,初步鉴定拮抗菌HM-7为解淀粉芽孢杆菌。芽孢杆菌属是研究较为广泛和深入的微生物类群之一,也是植物病害生物防治生防菌的主要来源之一,因此拮抗菌HM-7有望开发为生物制剂应用于农业生产。

  16. POLYMER COLLOIDS FORMED BY POLYELECTROLYTE COMPLEXATION OF VINYL POLYMERS AND POLYSACCHARIDES IN AQUEOUS SOLUTION

    Institute of Scientific and Technical Information of China (English)

    Hui-dan Liu; Takahiro Sato

    2013-01-01

    The polyelectrolyte complex formed from the polyanion and polycation was studied by turbidimetry,static and electrophoretic light scattering,and elementary analysis.Sodium salts of polyacrylate (PA) and heparin (Hep) were chosen as the polyanion,and hydrochloric salts of poly(vinyl amine) (PVA) and chitosan (Chts) as the polycation.Although these vinyl polymers and polysaccharides have remarkably different backbone chemical structures and linear charge densities,all the four combinations PA-PVA,PA-Chts,Hep-PVA,and Hep-Chts provide almost stoichiometric polyelectrolyte complexes which are slightly charged owing to the adsorption of the excess polyelectrolyte component onto the neutral complex.The charges stabilize the complex colloids in aqueous solution of a non-stoichiometric mixture,and the aggregation number of the complex colloids increases with approaching to the stoichiometric mixing ratio.The mixing ratio dependence of the aggregation number for the four complexes is explained by the model proposed in the previous study.

  17. Improving Photocatalytic Activity through Electrostatic Self-Assembly: Polyelectrolytes as Tool for Solar Energy Conversion?

    Science.gov (United States)

    Groehn, Franziska

    2015-03-01

    With regard to the world's decreasing energy resources, developing strategies to exploit solar energy become more and more important. One approach is to take advantage of photocatalysis. Inspired by natural systems such as assemblies performing photosynthesis, it is highly promising to self-assemble synthetic functional species to form more effective or tailored supramolecular units. In this contribution, a new type of photocatalytically active self-assembled nanostructures in aqueous solution will be presented: supramolecular nano-objects obtained through self-assembly of macroions and multivalent organic or inorganic counterions. Polyelectrolyte-porphyrin nanoscale assemblies exhibit up to 10-fold higher photocatalytic activity than the corresponding porphyrins without polymeric template. Other self-assembled catalysts based on polyelectrolytes can exhibit expressed selectivity in a photocatalytic model reaction or even allow catalytic reactions in solution that are not possible with the building blocks only. Further, current results on combining different functional units at the polyelectrolyte template represent a next step towards more complex supramolecular structures for solar energy conversion.

  18. Stereoregularity Drives Precipitation in Polyelectrolyte Complex Formation

    Science.gov (United States)

    Tirrell, Matthew; Perry, Sarah; Leon, Lorraine; Kade, Matthew; Priftis, Dimitris; Black, Katie; Hoffman, Kyle; Whitmer, Jonathan; Qin, Jian; de Pablo, Juan

    2014-03-01

    This study investigates the effect of stereoregularity on the formation of polypeptide-based complex formation and assembly into micelles, hydrogels and ordered phases. We demonstrate that fluid complex coacervate formation (rather than solid complex precipitation) between oppositely charged polypeptides requires at least one racemic partner in order to disrupt backbone hydrogen bonding networks and prevent the hydrophobic collapse of the polymers into compact, fibrillar secondary structures. Computer simulations bear this out and enable visualization of the molecular structure of the complexes. The ability to choose between conditions of fluid phase formation and solid phase formation is a useful tool in developing new self-assembled materials based on polyelectrolyte complex formation. Support from the Argonne National Laboratory Laboratory Research and Development Program (2011-217) is gratefully acknowledged.

  19. Novel cationic polyelectrolyte coatings for capillary electrophoresis.

    Science.gov (United States)

    Duša, Filip; Witos, Joanna; Karjalainen, Erno; Viitala, Tapani; Tenhu, Heikki; Wiedmer, Susanne K

    2016-01-01

    The use of bare fused silica capillary in CE can sometimes be inconvenient due to undesirable effects including adsorption of sample or instability of the EOF. This can often be avoided by coating the inner surface of the capillary. In this work, we present and characterize two novel polyelectrolyte coatings (PECs) poly(2-(methacryloyloxy)ethyl trimethylammonium iodide) (PMOTAI) and poly(3-methyl-1-(4-vinylbenzyl)-imidazolium chloride) (PIL-1) for CE. The coated capillaries were studied using a series of aqueous buffers of varying pH, ionic strength, and composition. Our results show that the investigated polyelectrolytes are usable as semi-permanent (physically adsorbed) coatings with at least five runs stability before a short coating regeneration is necessary. Both PECs showed a considerably decreased stability at pH 11.0. The EOF was higher using Good's buffers than with sodium phosphate buffer at the same pH and ionic strength. The thickness of the PEC layers studied by quartz crystal microbalance was 0.83 and 0.52 nm for PMOTAI and PIL-1, respectively. The hydrophobicity of the PEC layers was determined by analysis of a homologous series of alkyl benzoates and expressed as the distribution constants. Our result demonstrates that both PECs had comparable hydrophobicity, which enabled separation of compounds with log Po/w > 2. The ability to separate cationic drugs was shown with β-blockers, compounds often misused in doping. Both coatings were also able to separate hydrolysis products of the ionic liquid 1,5-diazabicyclo[4.3.0]non-5-ene acetate at highly acidic conditions, where bare fused silica capillaries failed to accomplish the separation.

  20. Nanoparticle gel electrophoresis: bare charged spheres in polyelectrolyte hydrogels.

    Science.gov (United States)

    Li, Fei; Hill, Reghan J

    2013-03-15

    Nanoparticle gel electrophoresis has recently emerged as an attractive means of separating and characterizing nanoparticles. Consequently, a theory that accounts for electroosmotic flow in the gel, and coupling of the nanoparticle and hydrogel electrostatics and hydrodynamics, is required, particularly for gels in which the mesh size is comparable to or smaller than the particle radii. Here, we present an electrokinetic model for charged, spherical colloidal particles undergoing electrophoresis in charged (polyelectrolyte) hydrogels: the gel-electrophoresis analogue of Henry's theory for electrophoresis in Newtonian electrolytes. We compare numerically exact solutions of the model with several independent asymptotic approximations, identifying regions in the parameter space where these approximations are accurate or break down. As previously assumed in the literature, Henry's formula, modified by the addition of a constant electroosmotic flow mobility, is accurate only for nanoparticles that are small compared to the hydrogel mesh size. We derived an exact analytical solution of the full model by judiciously modifying the theory of Allison et al. for uncharged gels, drawing on the superposition methodology of Doane et al. to account for hydrogel charge. This furnishes accurate and economical mobility predictions for the entire parameter space. The present model suggests that nanoparticle size separations (with diameters ≲40 nm) are optimal at low ionic strength, with a gel mesh size that is selected according to the particle charging mechanism. For weakly charged particles, optimal size separation is achieved when the Brinkman screening length is matched to the mean particle size. Copyright © 2012 Elsevier Inc. All rights reserved.

  1. Practical guidelines and consideration of using RRHP for 5hmC detection.

    Science.gov (United States)

    Sun, Xueguang; Chung, Tzu Hung; Tan, Darany; Kim, Angela

    2016-02-01

    5-hydroxymethylcytosine (5hmC) is an epigenetic modification, which has been associated with gene expression in many biological contexts. Reduced representation hydroxymethylation profiling was developed as an enzymatic-based method for genome-wide 5hmC detection. It exploits β-glucosyltransferase to inhibit enzymatic cleavage of adapters ligated to a genomic library, allowing only fragments with glucosylated 5hmC residues at adapter junctions to be amplified and sequenced. The simple workflow and high sensitivity make it an efficient assay for 5hmC mapping. In this review, we discuss some technical consideration in applying reduced representation hydroxymethylation profiling, such as the use of alternative restriction enzymes for increased genomic coverage in different species, application of control libraries and specifications for multiplexing, data processing and normalization.

  2. Hm-MyD88 and Hm-SARM: two key regulators of the neuroimmune system and neural repair in the medicinal leech.

    Science.gov (United States)

    Rodet, F; Tasiemski, A; Boidin-Wichlacz, C; Van Camp, C; Vuillaume, C; Slomianny, C; Salzet, M

    2015-04-16

    Unlike mammals, the CNS of the medicinal leech can regenerate damaged neurites, thus restoring neural functions after lesion. We previously demonstrated that the injured leech nerve cord is able to mount an immune response promoting the regenerative processes. Indeed neurons and microglia express sensing receptors like Hm-TLR1, a leech TLR ortholog, associated with chemokine release in response to a septic challenge or lesion. To gain insights into the TLR signaling pathways involved during these neuroimmune responses, members of the MyD88 family were investigated. In the present study, we report the characterization of Hm-MyD88 and Hm-SARM. The expression of their encoding gene was strongly regulated in leech CNS not only upon immune challenge but also during CNS repair, suggesting their involvement in both processes. This work also showed for the first time that differentiated neurons of the CNS could respond to LPS through a MyD88-dependent signalling pathway, while in mammals, studies describing the direct effect of LPS on neurons and the outcomes of such treatment are scarce and controversial. In the present study, we established that this PAMP induced the relocalization of Hm-MyD88 in isolated neurons.

  3. Effect of ethanol (EtOH) and dietary histidine (His) on fetal brain histamine (Hm)

    Energy Technology Data Exchange (ETDEWEB)

    Lin, G.W.J.; Liying Jin (Rutgers-the State Univ., Piscataway, NJ (United States))

    1991-03-15

    The authors have previously shown that gestational EtOH consumption decreased free His in fetal tissues, including the brain. His is the precursor of Hm, a neurotransmitter, and since central nervous system (CNS) dysfunction is frequently observed in the offspring of alcoholic women, experiments were conducted to examine the effects of gestational EtOH consumption on fetal brain Hm. Pregnant Sprague-Dawley rats were fed 35% EtOH-calorie liquid diets with three levels of His from gestation day (GD) 7 to 21. Control rats (LHC, MHC and HHC) were pair-fed with isocaloric sucrose substituted for EtOH. ON GD-21, fetal and maternal tissue were analyzed for His and H. In all tissues examined (fetal brain, plasma and liver, and maternal plasma and liver), His was increased with the increase of dietary His. Hm was also increased in fetal brain and liver in 0.8% dietary His groups. EtOH feeding decreased His in all fetal tissues but increased Hm in fetal brain and liver. The values of fetal brain Hm were: 805 {plus minus} 89 vs 574 {plus minus}47 (LHE vs LHC), 690 {plus minus} 29 vs 446 {plus minus} 32 (MHE vs MHC) and 1,335 {plus minus} 165 vs 938 {plus minus} 72 (HHE vs HHC), an increase of 40-50% by EtOH. Alteration in fetal brain Hm may contribute to the CNS dysfunction.

  4. Adsorption of a synthetic heparinoid polyelectrolyte on an ion-exchanging surface

    NARCIS (Netherlands)

    Froehling, Peter E.; Bantjes, Adriaan; Kolar, Z.

    1977-01-01

    The adsorption of a synthetic heparinoid polyelectrolyte on poly(vinylchloride) previously treated with tridodecylmethylammonium chloride (TDMAC) was studied using radiotracer techniques to provide a more quantitative picture of antithrombogenic surface coatings. 125I-labeled polyelectrolyte was use

  5. Multilayered Polyelectrolyte Films:A Tool for Biomaterial Coatings and Tissue Engineering?

    Institute of Scientific and Technical Information of China (English)

    Jean-Claude; VOEGEL; Joёlle; OGIER; Catherine; PICART; Nadia; JESSEL; Philippe; LAVALLE; Vincent; BALL; Bernard; SENGER; Pierre; SCHAAF

    2005-01-01

    1 Physicochemical aspects of multilayered polyelectrolyte films Multilayered polyelectrolyte films are obtained by alternated depositions on a solid surface of polyanions and polycations~([1]). The driving force for the build-up results from the charge excess which appears on the top of the film after each new polyelectrolyte adsorption. The film top becomes thus positively (respectively negatively) charged when the film is ending by a polycation (respectively polyanion). Various polyelectrolyte systems hav...

  6. Complex formation between polyelectrolytes and oppositely charged oligoelectrolytes

    Science.gov (United States)

    Zhou, Jiajia; Barz, Matthias; Schmid, Friederike

    2016-04-01

    We study the complex formation between one long polyanion chain and many short oligocation chains by computer simulations. We employ a coarse-grained bead-spring model for the polyelectrolyte chains and model explicitly the small salt ions. We systematically vary the concentration and the length of the oligocation and examine how the oligocations affects the chain conformation, the static structure factor, the radial and axial distribution of various charged species, and the number of bound ions in the complex. At low oligocation concentration, the polyanion has an extended structure. Upon increasing the oligocation concentration, the polyanion chain collapses and forms a compact globule, but the complex still carries a net negative charge. Once the total charge of the oligocations is equal to that of the polyanion, the collapse stops and is replaced by a slow expansion. In this regime, the net charge on the complexes is positive or neutral, depending on the microion concentration in solution. The expansion can be explained by the reduction of the oligocation bridging. We find that the behavior and the structure of the complex are largely independent of the length of oligocations, and very similar to that observed when replacing the oligocations by multivalent salt cations, and conclude that the main driving force keeping the complex together is the release of monovalent counterions and coions. We speculate on the implications of this finding for the problem of controlled oligolyte release and oligolyte substitution.

  7. Lipid monolayers and adsorbed polyelectrolytes with different degrees of polymerization.

    Science.gov (United States)

    Ortmann, Thomas; Ahrens, Heiko; Lawrenz, Frank; Gröning, Andreas; Nestler, Peter; Günther, Jens-Uwe; Helm, Christiane A

    2014-06-17

    Polystyrene sulfonate (PSS) of different molecular weight M(w) is adsorbed to oppositely charged DODAB monolayers from dilute solutions (0.01 mmol/L). PSS adsorbs flatly in a lamellar manner, as is shown by X-ray reflectivity and grazing incidence diffraction (exception: PSS with M(w) below 7 kDa adsorbs flatly disordered to the liquid expanded phase). The surface coverage and the separation of the PSS chains are independent of PSS M(w). On monolayer compression, the surface charge density increases by a factor of 2, and the separation of the PSS chains decreases by the same factor. Isotherms show that on increase of PSS M(w) the transition pressure of the LE/LC (liquid expanded/liquid condensed) phase transition decreases. When the contour length exceeds the persistence length (21 nm), the transition pressure is low and constant. For low-M(w) PSS (<7 kDa) the LE/LC transition of the lipids and the disordered/ordered transition of adsorbed PSS occur simultaneously, leading to a maximum in the contour length dependence of the transition enthalpy. These findings show that lipid monolayers at the air/water interface are a suitable model substrate with adjustable surface charge density to study the equilibrium conformation of adsorbed polyelectrolytes as well as their interactions with a model membrane.

  8. Coacervation in Symmetric Mixtures of Oppositely Charged Rodlike Polyelectrolytes

    Science.gov (United States)

    Kumar, Rajeev; Fredrickson, Glenn

    2010-03-01

    Phase separation in the salt-free symmetric mixtures of oppositely charged rodlike polyelectrolytes is studied using quasi-analytical calculations. Stability analyses for the isotropic-isotropic and the isotropic-nematic phase transitions in the symmetric mixtures are carried out. It is shown that electrostatics favor nematic ordering. Also, the coexistence curves for the symmetric mixtures are computed, and the effects of the linear charge density and the electrostatic interaction strength on the phase boundaries are studied. It is found that the counterions are uniformly distributed in the coexisting phases for low electrostatic interaction strengths characterized by the linear charge density of the polyelectrolytes and the Bjerrum's length. However, the counterions also phase separate along with the rodlike polyelectrolytes with an increase in the electrostatic interaction strength. It is shown that the number density of the counterions is higher in the concentrated (or coacervate) phase than in the dilute (or supernatant) phase. In contrast to the rodlike mixtures, flexible polyelectrolyte mixtures can undergo only isotropic-isotropic phase separation. A comparison of the coexistence curves for the weakly charged rodlike with the flexible polyelectrolyte mixtures reveals that the electrostatic driving force for the isotropic-isotropic phase separation is stronger in the flexible mixtures.

  9. Polyelectrolyte (PE) induced interactions between Charged and zwitterionic Colloids

    Science.gov (United States)

    Pryamitsyn, Victor; Ganesan, Venkat

    2014-03-01

    A numerical self-consistent field (SCF) theory approach was developed for studying mixture of polyelectrolytes with charged and uncharged nanoparticles. Such an approach was used to analyze within the mean-field limit the polyelectrolyte-mediated effective interactions between the particles. The system considered allows for the local PE and particle charges to be defined by the local concentration of ionizable on groups on the particles and polyelectrolytes, ambient conditions like pH and the local electrostatic potential. Calculation of the free energy of a system of one, two and three particles in the polyelectrolyte solution allowdd us to calculate the particle insertion free energy, two and three body particle-particle interactions as a function of the properties of solution, polymer-particle interactions and the particle size. For the situation involving acidic PE and a base type positively charged particles, the PE mediated particle-particle interaction is purely repulsive for the larger particle-particle distances at low polymer concentrations. At short-particle particle distances and/or higher polyelectrolyte concentrations the particle-particle interaction becomes a depletion-type attraction. For Zwitterionic positively chaged paticles particles we have found a a range

  10. Electrostatic Self-Assembled Multilayers from Side Chain Azo Polyelectrolytes

    Institute of Scientific and Technical Information of China (English)

    庹新林; 陈峥; 邓永红; 王晓工; 刘德山

    2002-01-01

    Photoresponsive behavior and self-assembly properties of three side chain azo polyelectrolytes, poly (2-(4-phenylazophenoxy) ethanol-co-acrylic acid) (PPAPE), poly (2-(4-(4′-nitrophenylazo) phenoxy) ethanol-co-acrylic acid) (PNAPE), and poly (2-(4-(4′-ethoxyphenylazo) phenoxy) ethanol-co-acrylic acid) (PEAPE), were studied. These polyelectrolytes with different degrees of functionalization of azo chromophores were fabricated into nano-composite multilayers using two types of dipping solutions through a layer-by-layer electrostatic self-assembling process. Results show that the ratio between tetrahydrofuran (THF) and H2O significantly influences the photoresponsive behavior of PNAPE in THF-H2O mixture. The THF-H2O dipping solution, used in this work for self-assembly of hydrophobic polyelectrolytes, is proved to be as applicable as aqueous dipping solution for normal self-assembly of hydrophobic polyelectrolytes. However, significant differences in the multilayer growth between the two systems were also observed, which resulted from the remarkable difference of the existing forms of the polyelectrolytes in these two dipping solutions.

  11. Generation of mechanical force by grafted polyelectrolytes in an electric field: application to polyelectrolyte-based nano-devices

    Science.gov (United States)

    Brilliantov, N. V.; Budkov, Yu. A.; Seidel, C.

    2016-11-01

    We analyse theoretically and by means of molecular dynamics (MD) simulations the generation of mechanical force by a polyelectrolyte (PE) chain grafted to a plane. The PE is exposed to an external electric field that favours its adsorption on the plane. The free end of the chain is linked to a deformable target body. By varying the field, one can alter the length of the non-adsorbed part of the chain. This entails variation of the deformation of the target body and hence variation of the force arising in the body. Our theoretical predictions for the generated force are in very good agreement with the MD data. Using the theory developed for the generated force, we study the effectiveness of possible PE-based nano-vices, composed of two clenching planes connected by PEs and exposed to an external electric field. We exploit the Cundall-Strack solid friction model to describe the friction between a particle and the clenching planes. We compute the diffusion coefficient of a clenched particle and show that it drastically decreases even in weak applied fields. This demonstrates the efficacy of the PE-based nano-vices, which may be a possible alternative to the existing nanotube nano-tweezers and optical tweezers. This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'.

  12. Polyelectrolyte Layer-by-Layer Assembly on Organic Electrochemical Transistors.

    Science.gov (United States)

    Pappa, Anna-Maria; Inal, Sahika; Roy, Kirsty; Zhang, Yi; Pitsalidis, Charalampos; Hama, Adel; Pas, Jolien; Malliaras, George G; Owens, Roisin M

    2017-03-29

    Oppositely charged polyelectrolyte multilayers (PEMs) were built up in a layer-by-layer (LbL) assembly on top of the conducting polymer channel of an organic electrochemical transistor (OECT), aiming to combine the advantages of well-established PEMs with a high performance electronic transducer. The multilayered film is a model system to investigate the impact of biofunctionalization on the operation of OECTs comprising a poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) film as the electrically active layer. Understanding the mechanism of ion injection into the channel that is in direct contact with charged polymer films provides useful insights for novel biosensing applications such as nucleic acid sensing. Moreover, LbL is demonstrated to be a versatile electrode modification tool enabling tailored surface features in terms of thickness, softness, roughness, and charge. LbL assemblies built up on top of conducting polymers will aid the design of new bioelectronic platforms for drug delivery, tissue engineering, and medical diagnostics.

  13. Polyelectrolyte Layer-by-Layer Assembly on Organic Electrochemical Transistors

    KAUST Repository

    Pappa, Anna-Maria

    2017-03-06

    Oppositely charged polyelectrolyte multilayers (PEMs) were built up in a layer-by-layer (LbL) assembly on top of the conducting polymer channel of an organic electrochemical transistor (OECT), aiming to combine the advantages of well-established PEMs with a high performance electronic transducer. The multilayered film is a model system to investigate the impact of biofunctionalization on the operation of OECTs comprising a poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) film as the electrically active layer. Understanding the mechanism of ion injection into the channel that is in direct contact with charged polymer films provides useful insights for novel biosensing applications such as nucleic acid sensing. Moreover, LbL is demonstrated to be a versatile electrode modification tool enabling tailored surface features in terms of thickness, softness, roughness, and charge. LbL assemblies built up on top of conducting polymers will aid the design of new bioelectronic platforms for drug delivery, tissue engineering, and medical diagnostics.

  14. Polyelectrolyte coating of ferumoxytol nanoparticles for labeling of dendritic cells

    Energy Technology Data Exchange (ETDEWEB)

    Celikkin, Nehar; Jakubcová, Lucie; Zenke, Martin [Institute for Biomedical Engineering, Department of Cell Biology, RWTH Aachen University Hospital, Pauwelsstrasse 30, 52074 Aachen (Germany); Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Pauwelsstrasse 20, 52074 Aachen (Germany); Hoss, Mareike [Institute of Pathology, Electron Microscopy Facility, RWTH Aachen University Hospital, Pauwelsstrasse 30, 52074 Aachen (Germany); Wong, John Erik, E-mail: John.Wong@avt.rwth-aachen.de [Chemical Process Engineering, RWTH Aachen University, Turmstrasse 46, 52056 Aachen (Germany); DWI – Leibniz Institute for Interactive Materials Research, Forckenbeckstrasse 50, Aachen (Germany); Hieronymus, Thomas, E-mail: thomas.hieronymus@rwth-aachen.de [Institute for Biomedical Engineering, Department of Cell Biology, RWTH Aachen University Hospital, Pauwelsstrasse 30, 52074 Aachen (Germany); Helmholtz Institute for Biomedical Engineering, RWTH Aachen University, Pauwelsstrasse 20, 52074 Aachen (Germany)

    2015-04-15

    Engineered magnetic nanoparticles (MNPs) are emerging to be used as cell tracers, drug delivery vehicles, and contrast agents for magnetic resonance imaging (MRI) for enhanced theragnostic applications in biomedicine. In vitro labeling of target cell populations with MNPs and their implantation into animal models and patients shows promising outcomes in monitoring successful cell engraftment, differentiation and migration by using MRI. Dendritic cells (DCs) are professional antigen-presenting cells that initiate adaptive immune responses. Thus, DCs have been the focus of cellular immunotherapy and are increasingly applied in clinical trials. Here, we addressed the coating of different polyelectrolytes (PE) around ferumoxytol particles using the layer-by-layer technique. The impact of PE-coated ferumoxytol particles for labeling of DCs and Flt3{sup +} DC progenitors was then investigated. The results from our studies revealed that PE-coated ferumoxytol particles can be readily employed for labeling of DC and DC progenitors and thus are potentially suitable as contrast agents for MRI tracking.

  15. Sonication-assisted synthesis of polyelectrolyte-coated curcumin nanoparticles.

    Science.gov (United States)

    Zheng, Zhiguo; Zhang, Xingcai; Carbo, Daniel; Clark, Cheryl; Nathan, Cherie-Ann; Lvov, Yuri

    2010-06-01

    A new method of nanoparticle formulation for poorly water-soluble materials was demonstrated for curcumin. The drug was dissolved in organic solvent that is miscible with water (ethanol), and drug nucleation was initiated by gradual worsening of the solution by the addition of an aqueous polyelectrolyte assisted by ultrasonication. Curcumin crystals of 60-100 nm size were obtained depending on the component concentrations, sonication power, and initial solvent. Layer-by-layer shell assembly with biocompatible polyelectrolytes was used to provide a particle coating with a high surface potential and the stabilization of drug nanocolloids. Polyelectrolyte layer-by-layer encapsulation allowed sustained drug release from nanoparticles over the range of 10-20 h.

  16. Superhydrophilic Polyelectrolyte Brush Layers with Imparted Anti-Icing Properties

    DEFF Research Database (Denmark)

    Chernyy, Sergey; Järn, Mikael; Shimizu, Kyoko;

    2014-01-01

    This work demonstrates the feasibility of superhydrophilic polyelectrolyte brush coatings for anti-icing applications. Five different types of ionic and nonionic polymer brush coatings of 25-100 nm thickness were formed on glass substrates using silane chemistry for surface premodification followed......(-), SO4(2-), and C12SO3(-) ions. By consecutive measurements of the strength of ice adhesion toward ion-incorporated polymer brushes on glass it was found that Li(+) ions reduce ice adhesion by 40% at -18 °C and 70% at -10 °C. Ag(+) ions reduce ice adhesion by 80% at -10 °C relative to unmodified glass....... In general, superhydrophilic polyelectrolyte brushes exhibit better anti-icing property at -10 °C compared to partially hydrophobic brushes such as poly(methyl methacrylate) and surfactant exchanged polyelectrolyte brushes. The data are interpreted using the concept of a quasi liquid layer (QLL...

  17. Synthesis of the d,I-HM-PAO and formulation of nucleo-equipment for the obtention of {sup 99m} Tc-(d,I)-HM-PAO; Sintesis del d,I-HM-PAO y formulacion de nucleo-equipos para la obtencion de {sup 99m} Tc-(d,I)-HM-PAO

    Energy Technology Data Exchange (ETDEWEB)

    Lezama C, J.; Ferro F, G.; Alcazar A, P

    1991-09-15

    Most brain imaging radiopharmaceuticals are conventional hydrophilic compounds that are excluded from entering the normal brain by an intact blood-brain barrier (BBB). Under pathologic conditions, the barrier is disrupted and radiotracer concentrates in the leisure for positive identification. {sup 99m} Tc- hexa methyl propylene amine oxime ({sup 99} {sup m} Tc-HM-PAO) is a newer-type lipophilic agent that enter the normal brain through an intact BBB. Studies with this agent offer the promise of measuring cerebral perfusion in the normal and diseased brain. In this paper we present the synthesis and Tc-99m labelling of d,I-HM-PAO. The synthesis of the ligand was carried out by condensation of two molecular equivalents of butanedione monoxime with one molecular equivalent of 1,3 propanediamine provided a bis imine intermediate, which was reduced with sodium borohydride to get the meso and d,I diastereoisomers of HM-PAO. Separation of these was achieved by fractional crystallization. {sup 99m} Tc-(d,I)HM-PAO was obtained by stannous ion reduction of Mo-99/Tc-99m generator eluate in the presence of the ligand. Complex radiochemical purity was determined by instant thin layer chromatography and paper chromatography. Finally, we obtained {sup 99m} Tc-(d,I)HM-PAO with a high radiochemical yield, in excess of 90%. However, for subsequent clinical studies the preparation has to be done a few minutes before application because our product has a low stability. (Author)

  18. Insight into the electrical properties and chain conformation of spherical polyelectrolyte brushes by dielectric spectroscopy

    Science.gov (United States)

    Guo, Xiaoxia; Zhao, Kongshuang

    2017-02-01

    We report here a dielectric study on three kinds of anionic spherical polyelectrolyte brush (SPBs, consisting of a polystyrene (PS) core and three different poly (acrylic acid) chains grafted onto the core) suspensions over a frequency ranging from 40 Hz to 110 MHz. The relaxation behavior of the SPB suspensions shows significant changes in the brush-layer properties when the mass fraction of SPBs and the pH of the suspensions change. Two definite relaxations related to the interfacial polarization are observed around 100 kHz and 10 MHz. A single-layer spherical-shell model is applied to describe the SPB suspensions wherein the suspended SPB is modeled as a spherical-shell composite particle in which an insulated PS sphere is surrounded by a conducting ion-permeable shell (the polyelectrolyte chain layer). We developed the curve-fitting procedure to analyze the dielectric spectrum in order to obtain the dielectric properties of the components of the SPBs, especially the properties of the polyelectrolyte brush. Based on this method and model, the permittivity and conductivity of the brush layer, ζ potential, etc are calculated. The ordered orientation of the water molecules in the layer leads to an additional electrical dipole moment; increasing pH causes the brush layer to swell. In addition, the repulsive force between the SPB particles are evaluated using the brush-layer thickness, which is obtained by fitting dielectric spectra, combined with relative theoretical formulas. Increasing PH values or SPB concentration would improve the stability of the SPBs dispersion.

  19. Multilayered polyelectrolyte microcapsules: interaction with the enzyme cytochrome C oxidase.

    Science.gov (United States)

    Pastorino, Laura; Dellacasa, Elena; Noor, Mohamed R; Soulimane, Tewfik; Bianchini, Paolo; D'Autilia, Francesca; Antipov, Alexei; Diaspro, Alberto; Tofail, Syed A M; Ruggiero, Carmelina

    2014-01-01

    Cell-sized polyelectrolyte capsules functionalized with a redox-driven proton pump protein were assembled for the first time. The interaction of polyelectrolyte microcapsules, fabricated by electrostatic layer-by-layer assembly, with cytochrome c oxidase molecules was investigated. We found that the cytochrome c oxidase retained its functionality, that the functionalized microcapsules interacting with cytochrome c oxidase were permeable and that the permeability characteristics of the microcapsule shell depend on the shell components. This work provides a significant input towards the fabrication of an integrated device made of biological components and based on specific biomolecular functions and properties.

  20. CONJUGATED POLYMERS AND POLYELECTROLYTES IN SOLAR PHOTOCONVERSION, Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Schanze, Kirk S [University of Florida

    2014-08-05

    This DOE-supported program investigated the fundamental properties of conjugated polyelectrolytes, with emphasis placed on studies of excited state energy transport, self-assembly into conjugated polyelectroyte (CPE) based films and colloids, and exciton transport and charge injection in CPE films constructed atop wide bandgap semiconductors. In the most recent grant period we have also extended efforts to examine the properties of low-bandgap donor-acceptor conjugated polyelectrolytes that feature strong visible light absorption and the ability to adsorb to metal-oxide interfaces.

  1. Multilayered polyelectrolyte microcapsules: interaction with the enzyme cytochrome C oxidase.

    Directory of Open Access Journals (Sweden)

    Laura Pastorino

    Full Text Available Cell-sized polyelectrolyte capsules functionalized with a redox-driven proton pump protein were assembled for the first time. The interaction of polyelectrolyte microcapsules, fabricated by electrostatic layer-by-layer assembly, with cytochrome c oxidase molecules was investigated. We found that the cytochrome c oxidase retained its functionality, that the functionalized microcapsules interacting with cytochrome c oxidase were permeable and that the permeability characteristics of the microcapsule shell depend on the shell components. This work provides a significant input towards the fabrication of an integrated device made of biological components and based on specific biomolecular functions and properties.

  2. New Insights into 5hmC DNA Modification: Generation, Distribution and Function

    Directory of Open Access Journals (Sweden)

    Dong-Qiao Shi

    2017-07-01

    Full Text Available Dynamic DNA modifications, such as methylation/demethylation on cytosine, are major epigenetic mechanisms to modulate gene expression in both eukaryotes and prokaryotes. In addition to the common methylation on the 5th position of the pyrimidine ring of cytosine (5mC, other types of modifications at the same position, such as 5-hydroxymethyl (5hmC, 5-formyl (5fC, and 5-carboxyl (5caC, are also important. Recently, 5hmC, a product of 5mC demethylation by the Ten-Eleven Translocation family proteins, was shown to regulate many cellular and developmental processes, including the pluripotency of embryonic stem cells, neuron development, and tumorigenesis in mammals. Here, we review recent advances on the generation, distribution, and function of 5hmC modification in mammals and discuss its potential roles in plants.

  3. H, HM, and THM-C processes in natural barriers

    Energy Technology Data Exchange (ETDEWEB)

    Javeri, V.; Le, T.T.; Cui, Y.J.; Delage, P.; Li, X.J.; Wieczorek, K.; Jockwer, N.; Romero, E.; Lima, A.; Gens, A.; Li, X.L.; Francois, B.; Nuth, M.; Laloui, L.; Chen, W.; Jia, S.; Yu, H.; Wu, G.; Li, X.; Bernier, F.; Tan, X.; Wu, G.; Jia, S.; Giot, R.; Hoxha, D.; Giraud, A.; Homand, F.; Su, K.; Chavant, C.; Duveau, G.; Jia, Y.; Shao, J.F.; Peron, H.; Laloui, L.; Hueckel, T.; Hu, L.B.; Auvray, C.; Lequiller, B.; Cuisinier, O.; Ferber, V.; Cui, Y.J.; Deneele, D.; Uhlig, L.; Jobmann, M.; Polster, M.; Vaunat, J.; Garrite, B.; Wileveau, Y.; Sato, H.; Jacinto, A.; Sanchez, M.; Ledesma, A.; Morel, J.; Balland, C.; Armand, G.; Nguyen Minh, D.; Vales, F.; Pham, Q.T.; Gharbi, H.; Mokni, N.; Olivella, S.; Li, X.; Smets, St.; Valcke, E.; Karnland, O.; Nilsson, U.; Olsson, S.; Sellin, P.; Fernandez, A.M.; Melon, A.M.; Villar, M.V.; Turrero, M.J.; Garitte, B.; Guimaraes, L.D.N.; Gens, A.; Mayor, J.C.; Koliji, A.; Laloui, L.; Vulliet, L.; Hamdi, N.; Marzouki, A.; Srasra, E.; Cuss, R.J.; Harrington, J.F.; Noy, D.J.; Birchall, D.J.; Marschall, P.; Mallet, A.; Ababou, R.; Matray, J.M.; Renaud, V.; Maison, T.; Enachescu, C.; Frieg, B.; Rohs, St.; Paris, B.; Robinet, J.C.; Bui, T.D.; Barnichon, J.D.; Plas, F.; Klubertanz, G.; Folly, M.; Hufschmied, P.; Frank, E

    2007-07-01

    This session gathers 30 articles (posters) dealing with: the three Dimensional analyses of combined gas, heat and nuclide transport in a repository considering coupled thermo-hydro geomechanical processes; the experimental study on the thermo-hydro-mechanical behaviour of boom clay; hydraulic in-situ measurements in the Opalinus clay in the frame of a heater test performed at the Mont Terri URL; the hydro-mechanical behaviour of natural boom clay in controlled-suction tests; a constitutive approach to address the thermal and hydric impacts in the concept of deep radioactive waste repositories; the numerical analysis on stability of boom clay tunnel by shield construction; a thermo-hydro-mechanical model for clay in unsaturated conditions; the 3D modelling of TER experiment accounting for fully anisotropic thermo-poro-elastic behaviour; the hydro-mechanical modeling of shaft excavation in Meuse/Haute-Marne laboratory; the modelling of drying damage in engineered and natural clay barriers for nuclear waste disposal; the elasto-viscoplastic behaviour of Meuse/Haute-Marne argillite: laboratory tests and modelling; the long-term behaviour of a lime treated soil under percolation conditions; the stress redistribution and hydro-mechanical effects due to excavation and drilling operations in TER experiment; a thermodynamic model on swelling of bentonite buffer and backfill materials; the 3D analysis of a heating test in the Opalinus clay; the THM analysis of a 'mock-up' laboratory experiment using a double-structure expansive model; the measurement of the effect of re-confinement on rock properties around a slot; a laboratory Study of desaturation - re-saturation effects on a clay-stone; the deformation induced by dissolution of salts in porous media; the bentonite swelling pressure in pure water and saline solutions; the mineralogy and sealing properties of various bentonites and smectite-rich clay materials; the evaluation of the geochemical processes occurring

  4. Polyelectrolyte surfactant aggregates and their deposition on macroscopic surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Voisin, David

    2002-07-01

    Oppositely charged surfactant and polyelectrolyte are present in hair shampoos and conditioners, together with particles (e.g. anti-dandruff agents for scalp) and droplets (e.g. silicone oil for the hair). These are normally formulated at high surfactant concentrations, beyond the flocculation region for the polyelectrolyte concentration used. However, on dilution with water, during application, flocs are formed which carry the particles and droplets to the scalp and hair. The addition of an anionic surfactant to an aqueous solution of cationic polyelectrolyte, at a given concentration, can lead to the formation of polyelectrolyte-surfactant 'particles', in which the surfactant 'binds' to the polyelectrolyte. This occurs from the critical association concentration (CAC), up to the surfactant concentration corresponding to maximum binding. Within this range of surfactant concentrations, the surfactant bound to the polyelectrolyte is thought to associate to form what might be termed 'internal micelles'. Each polyelectrolyte-surfactant particle in the region of the CAC, and just beyond, contains many polyelectrolyte chains, held together essentially by micelle bridges. These particles, however, remain net positively charged, and therefore stable. At the other end of the binding range of the surfactant, so many internal micelles are present that the polymer-surfactant particles are now net negatively charged. Indeed binding stops since no further micelles can be accommodated. Again, the particles are stable. However, there exists a range of surfactant concentrations, lying within the range referred to above, where the net charge is reduced sufficiently that the polymer-surfactant particles will flocculate to form much larger structures. The onset of this second range might be termed the 'critical flocculation concentration' (CFC), and the end, the 'critical stabilisation concentration' (CSC). In this work, the CFC and

  5. Speech errors of amnesic H.M.: unlike everyday slips-of-the-tongue.

    Science.gov (United States)

    MacKay, Donald G; James, Lori E; Hadley, Christopher B; Fogler, Kethera A

    2011-03-01

    Three language production studies indicate that amnesic H.M. produces speech errors unlike everyday slips-of-the-tongue. Study 1 was a naturalistic task: H.M. and six controls closely matched for age, education, background and IQ described what makes captioned cartoons funny. Nine judges rated the descriptions blind to speaker identity and gave reliably more negative ratings for coherence, vagueness, comprehensibility, grammaticality, and adequacy of humor-description for H.M. than the controls. Study 2 examined "major errors", a novel type of speech error that is uncorrected and reduces the coherence, grammaticality, accuracy and/or comprehensibility of an utterance. The results indicated that H.M. produced seven types of major errors reliably more often than controls: substitutions, omissions, additions, transpositions, reading errors, free associations, and accuracy errors. These results contradict recent claims that H.M. retains unconscious or implicit language abilities and produces spoken discourse that is "sophisticated," "intact" and "without major errors." Study 3 examined whether three classical types of errors (omissions, additions, and substitutions of words and phrases) differed for H.M. versus controls in basic nature and relative frequency by error type. The results indicated that omissions, and especially multi-word omissions, were relatively more common for H.M. than the controls; and substitutions violated the syntactic class regularity (whereby, e.g., nouns substitute with nouns but not verbs) relatively more often for H.M. than the controls. These results suggest that H.M.'s medial temporal lobe damage impaired his ability to rapidly form new connections between units in the cortex, a process necessary to form complete and coherent internal representations for novel sentence-level plans. In short, different brain mechanisms underlie H.M.'s major errors (which reflect incomplete and incoherent sentence-level plans) versus everyday slips

  6. ELECTROPORATION OF CONFLUENT HM-1 ES CELLS LEADS TO HIGHER AMOUNT COLONIES

    Directory of Open Access Journals (Sweden)

    A.ALENA BENCSIK

    2013-12-01

    Full Text Available Electroporation is used to induce homologous recombination in the genome of the murine ES (embryonic stem cells. Routinelly subconfluent ES cells are recommended to be used in such experiments. Electroporation of immunoglobulin specific targeting vectors with different length of homology leads to reduced number of selected colonies. The enrichment of double selected colonies is high and thus the amount of HM-1 ES cell colonies for the analysis is very low. Here we show that the electroporation of confluent HM-1 ES cells leads to an increased amount of simple and double selected colonies.

  7. On the mesoscopic origins of high viscosities in some polyelectrolyte-surfactant mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Ingo, E-mail: ingo.hoffmann@tu-berlin.de [Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 124, Sekr. TC 7, D-10623 Berlin (Germany); Institut Max von Laue-Paul Langevin (ILL), F-38042 Grenoble Cedex 9 (France); Farago, Bela; Schweins, Ralf; Falus, Peter; Sharp, Melissa [Institut Max von Laue-Paul Langevin (ILL), F-38042 Grenoble Cedex 9 (France); Prévost, Sylvain [Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 124, Sekr. TC 7, D-10623 Berlin (Germany); Helmholtz-Zentrum Berlin, D-14109 Berlin (Germany); Gradzielski, Michael, E-mail: michael.gradzielski@tu-berlin.de [Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 124, Sekr. TC 7, D-10623 Berlin (Germany)

    2015-08-21

    Oppositely charged polyelectrolyte (PE) surfactant mixtures allow the control of rheological parameters of a solution even at fairly low concentrations. For example, addition of 0.3 wt. % of anionic surfactant to a 1 wt. % solution of the polycation JR 400 increases the viscosity by 4 orders of magnitude. Recently, we could show that this increase is related to the formation of mixed, rod-like PE/surfactant aggregates which interconnect several polyelectrolyte chains [Hoffmann et al., Europhys. Lett. 104, 28001 (2013)]. In this paper, we refine our structural model of the aggregates to obtain a more consistent picture of their internal structure for different anionic surfactants. Combining small angle neutron scattering (SANS) and neutron spin-echo (NSE) allows us to determine the size of the aggregates. By comparing different contrasts, the internal structure of the aggregates can be elucidated and it is seen that the PE in the aggregates retains a relatively high freedom of movement. We proceeded to investigate the influence of the surfactant concentration and the surfactant type on structure and dynamics of the mixed aggregates. It is seen that the structural parameters of the aggregates depend very little on the surfactant concentration and headgroup. However, it is crucial to incorporate a sufficient amount of PE in the aggregates to increase the viscosity of the aggregates. By comparing viscous samples at 1 wt. % PE concentration with samples at a PE concentration of 0.3 wt. %, where no significant increase in viscosity is observed, we find that similar aggregates are formed already at this lower PE concentrations. However, the amount of PE incorporated in them is insufficient to interconnect several PE chains and therefore, they do not increase viscosity. So, our detailed investigation combining contrast variation SANS and NSE does not only allow to explain the viscosity behavior but also to deduced detailed information regarding the structures and

  8. Electric double layer electrostatics of pH-responsive spherical polyelectrolyte brushes in the decoupled regime.

    Science.gov (United States)

    Li, Hao; Chen, Guang; Das, Siddhartha

    2016-11-01

    Understanding the behavior and properties of spherical polyelectrolyte brushes (SPEBs), which are polyelectrolyte brushes grafted to a spherical core, is fundamental to many applications in biomedical, chemical and petroleum engineering as well as in pharmaceutics. In this paper, we study the pH-responsive electrostatics of such SPEBs in the decoupled regime. In the first part of the paper, we derive the scaling conditions in terms of the grafting density of the PEs on the spherical core that ensure that the analysis can be performed in the decoupled regime. In such a regime the elastic and the excluded volume effects of polyelectrolyte brushes (PEBs) can be decoupled from the electrostatic effects associated with the PE charge and the induced EDL. As a consequence the PE brush height, assumed to be dictated by the balance of the elastic and excluded volume effects, can be independent of the electrostatic effects. In the second part, we quantify the pH-responsive electrostatics of the SPEBs - we pinpoint that the radial monomer distribution for a given brush molecule exhibit a non-unique cubic distribution that decays away from the spherical core. Such a monomer distribution ensures that the hydrogen ion concentration is appropriately accounted for in the description of the SPEB thermodynamics. We anticipate that the present analysis, which provides possibly one of the first models for probing the electrostatics of pH-responsive SPEBs in a thermodynamically-consistent framework, will be vital for understanding the behavior of a large number of entities ranging from PE-coated NPs and stealth liposomes to biomolecules like bacteria and viruses.

  9. Polyelectrolytes Ability in Reducing Atrazine Concentration in Water: Surface Effects

    NARCIS (Netherlands)

    Mohd Amin, M.F.; Heijman, S.G.J.; Lopes, S.I.C.; Rietveld, L.C.

    2014-01-01

    This paper reports on the direct ability of two positively charged organic polyelectrolytes (natural-based and synthetic) to reduce the atrazine concentration in water. The adsorption study was set up using multiple glass vessels with different polymer dosing levels followed by ultrafiltration with

  10. Polyelectrolyte brushes in mixed ionic medium studied via intermolecular forces

    Science.gov (United States)

    Farina, Robert; Laugel, Nicolas; Pincus, Philip; Tirrell, Matthew

    2011-03-01

    The vast uses and applications of polyelectrolyte brushes make them an attractive field of research especially with the growing interest in responsive materials. Polymers which respond via changes in temperature, pH, and ionic strength are increasingly being used for applications in drug delivery, chemical gating, etc. When polyelectrolyte brushes are found in either nature (e.g., surfaces of cartilage and mammalian lung interiors) or commercially (e.g., skin care products, shampoo, and surfaces of medical devices) they are always surrounded by mixed ionic medium. This makes the study of these brushes in varying ionic environments extremely relevant for both current and future potential applications. The polyelectrolyte brushes in this work are diblock co-polymers of poly-styrene sulfonate (N=420) and poly-t-butyl styrene (N=20) which tethers to a hydrophobic surface allowing for a purely thermodynamic study of the polyelectrolyte chains. Intermolecular forces between two brushes are measured using the SFA. As multi-valent concentrations are increased, the brushes collapse internally and form strong adhesion between one another after contact (properties not seen in a purely mono-valent environment).

  11. Polyelectrolyte stabilized multilayered liposomes for oral delivery of paclitaxel

    DEFF Research Database (Denmark)

    Jain, Sanyog; Kumar, Dinesh; Swarnakar, Nitin K

    2012-01-01

    Paclitaxel (PTX) loaded layersome formulations were prepared using layer-by-layer assembly of the polyelectrolytes over liposomes. Stearyl amine was utilized to provide positive charge to the liposomes, which were subsequently coated with anionic polymer polyacrylic acid (PAA) followed by coating...

  12. Salt-induced release of lipase from polyelectrolyte complex micelles

    NARCIS (Netherlands)

    Lindhoud, Saskia; de Vries, Renko; Schweins, Ralf; Stuart, Martien A. Cohen; Norde, Willem

    2009-01-01

    With the aim to gain insight into the possible applicability of protein-filled polyelectrolyte complex micelles under physiological salt conditions, we studied the behavior of these micelles as a function of salt concentration. The micelles form by electrostatically driven co-assembly from strong ca

  13. Humidity Sensitive Properties of a Silicone-containing Polyelectrolyte Material

    Institute of Scientific and Technical Information of China (English)

    Mu Jie YANG; Zong Wu YAO; You Si CHEN; Yang LI

    2006-01-01

    Resistive-type film humidity sensors were prepared with a silicone-containing polyelectrolyte (Si-PE) and their humidity sensitive properties have been investigated. The sensors so obtained show high sensitivity to humidity variation over a wide range of RH (20-96%).In addition, they exhibit high reversibility, quick response and well long-term stability.

  14. Polyelectrolytes Ability in Reducing Atrazine Concentration in Water: Surface Effects

    NARCIS (Netherlands)

    Mohd Amin, M.F.; Heijman, S.G.J.; Lopes, S.I.C.; Rietveld, L.C.

    2014-01-01

    This paper reports on the direct ability of two positively charged organic polyelectrolytes (natural-based and synthetic) to reduce the atrazine concentration in water. The adsorption study was set up using multiple glass vessels with different polymer dosing levels followed by ultrafiltration with

  15. Formation of surface-attached microstructured polyelectrolyte brushes

    Institute of Scientific and Technical Information of China (English)

    Hai Ning Zhang

    2008-01-01

    Surface-attached micropatterned polyelectrolyte brushes on planar solid surfaces are generated using free radical polymerization photo-initiated by self-assembled initiator monolayers. It is shown that the formed patterns can be either negative or positive with different patterning processes.

  16. The bulk phase behavior of short polyelectrolyte chains: A Monte Carlo study

    Science.gov (United States)

    Orkoulas, Gerassimos; Kumar, Sanat

    2002-03-01

    While polyelectrolytes form an important class of materials in chemistry and biochemistry, their understanding at the theoretical level is still lacking. The strong Coulombic repulsions and attractions, the resulting Debye screening and the concomitant unlike-charge association (known as counterion condensation) render standard neutral polymer theories difficult to apply. Indeed, most theoretical and numerical investigations have been focused on the dilute-to-semidilute regime at somewhat weak Coulomb couplings. In this work, we consider a lattice model of flexible charged chains with an appropriate number of oppositely charged counterions to ensure electrical neutrality. Electrostatic interactions are explicitly taken into account and handled via Ewald sums in the simulations. The solvent is modeled as a uniform dielectric continuum. By performing grand canonical Monte Carlo simulations, we demonstrate that at strong Coulomb couplings (low reduced temperatures) the system separates into polymer rich and poor phases respectively. The type of phase coexistence occurring in these polyelectrolyte systems bears resemblances to the gas-liquid transition of the restricted primitive model of ionic solutions. The approach to the Flory theta point is studied by increasing the chain length. The critical point dependence on the chain length is found to be rather weak. A plausible explanation lies in the formation of long-lived network structures via a bead-counterion mechanism. Finally, the ability of the system to form gels via bead-counterion junctions is examined and analyzed.

  17. Tc-99m HM-PAO labelling of leukocytes for detection of inflammatory bowel disease

    Energy Technology Data Exchange (ETDEWEB)

    Schuemichen, C.; Schoelmerich, J.

    1986-10-01

    Labelling of purified leukocytes with the brain imaging agent Tc-99m HM-PAO proved to be a reliable method, yielding a 45% labelling efficiency in phosphate buffer and leaving more than 85% of the leukocytes viable. In fifteen patients with M. Crohn, a positive finding was shown in all cases on the six hour image.

  18. Behavior of foF2 and hmF2 after sunset

    Science.gov (United States)

    Danilov, A. D.; Vanina-Dart, L. B.

    2010-12-01

    The time behavior of the foF2 and hmF2 values at the time moment T(ss + 2 h) 2 h after sunset is considered. It is assumed that at this moment, the horizontal winds in the thermosphere in the strongest way influence hmF2 and, therefore, foF2. It is found that a fairly well pronounced and statistically significant change (trend) is observed for the foF2(ss + 2)/ foF2(14) ratio, the sign of the change being different for different stations and even different seasons at the same station. A similar picture is obtained for the value of hmF2(ss + 2). It is shown that a positive correlation between the trends of these two values is observed. This confirms the initial concept of the paper that the foF2 and hmF2 trends are caused by long-term trends in the thermospheric dynamics.

  19. Alcohol--Induced Polyelectrolyte-Surfactant Complex Coacervate Systems: Characterization and Applications in Enzyme and Protein Extraction

    Science.gov (United States)

    Nejati Moshtaghin, Mahboubeh

    of FA, oppositely charged amphiphiles (surfactant-polyelectrolyte), and the charge ratio of the surfactant-polyelectrolyte on the extent of coacervation have been investigated. Furthermore, the chemical composition of each phase formed in the coacervate system was determined as a function of HFIP percentage. Phase diagrams of HFIP-PMA-CTAB and 2-propanol-PMA-CTAB were studied. The phase separation occurs over a wide range of polyelectrolyte, surfactant and alcohol concentration. In addition, a study of the dependence of coacervate volume on phase composition in different system (as defined by concentrations and mole charge ratio of amphihiles and alcohols) provided useful insight about possible underlying interactions and mechanisms. It has been concluded that neutralization favors coacervation in both systems. However, according to the compositional analysis of both HFIP and 2-propanol SPCC system, it seems that coacervation mechanisms are different. In Chapter III the properties of 2-propanol--SPCC, with analogous surfactant (CTAB) and polyelectrolyte (PMA) used in Chapter II, will be investigated. In particular, we are interested in examining the difference between the phase separation characteristics of the coacervates induced by 2-propanol and HFIP as coacervator. For this purpose, the phase behavior and the chemical composition of the phases will be analyzed as a function of 2-propanol and constituents concentrations. Chapter IV contains results of our investigations on the activity of a model enzyme (Trypsin) in 2-propanol- and FA-induced SPCC system. These investigations will facilitate understanding whether the aliphatic alcohol, AA- and FA-induced SPCC system denature the model enzymes. Such investigations also help in evaluation of the applicability of the coacervate systems developed in this work in proteomics where the proteolytic activity of enzymes is used for protein digestion. Finally, in Chapter V, the efficiency of the coacervate system (2-propanol

  20. Calculation of the Specific Heats for the H-M and E-IV Phase Transitions in NH4I

    Institute of Scientific and Technical Information of China (English)

    H. Yurtseven; H. Kaya

    2003-01-01

    This study gives our calculation for the specific heats Cvi due to an Ising model using the observed Cp data for the JT-JZT and JL-TV phase transitions in NH^I. By fitting to the Cp data we determine the values of the critical exponent for the pressure of 0.14GPa (H-M phase transition) and for the pressures of 0.75, 1.35 and 1.97GPa (E-HV phase transition) in NH^I. Our exponent values are close to the predicted values of the specific heat in a three-dimensional Ising model. Our calculated Cyi are in good agreement with the experimental Cp for NH^I in most cases.

  1. Monte Carlo simulation and equation of state for flexible charged hard-sphere chain fluids: polyampholyte and polyelectrolyte solutions.

    Science.gov (United States)

    Jiang, Hao; Adidharma, Hertanto

    2014-11-07

    The thermodynamic modeling of flexible charged hard-sphere chains representing polyampholyte or polyelectrolyte molecules in solution is considered. The excess Helmholtz energy and osmotic coefficients of solutions containing short polyampholyte and the osmotic coefficients of solutions containing short polyelectrolytes are determined by performing canonical and isobaric-isothermal Monte Carlo simulations. A new equation of state based on the thermodynamic perturbation theory is also proposed for flexible charged hard-sphere chains. For the modeling of such chains, the use of solely the structure information of monomer fluid for calculating the chain contribution is found to be insufficient and more detailed structure information must therefore be considered. Two approaches, i.e., the dimer and dimer-monomer approaches, are explored to obtain the contribution of the chain formation to the Helmholtz energy. By comparing with the simulation results, the equation of state with either the dimer or dimer-monomer approach accurately predicts the excess Helmholtz energy and osmotic coefficients of polyampholyte and polyelectrolyte solutions except at very low density. It also well captures the effect of temperature on the thermodynamic properties of these solutions.

  2. Polyelectrolyte multilayer coatings for the separation of proteins by capillary electrophoresis: Influence of polyelectrolyte nature and multilayer crosslinking.

    Science.gov (United States)

    Bekri, Samya; Leclercq, Laurent; Cottet, Hervé

    2015-06-19

    The present work aims at studying the influence of the nature of the polyelectrolytes used in successive multiple ionic polymers on the performances of protein separation in acetic acid volatile background electrolyte. A broad library of polyelectrolyte multilayers was compared on the basis of 9 different weak/strong polyanions and 8 different weak/strong polycations. More than 20 couples of different polyelectrolytes were investigated. The separation efficiencies (expressed as the N/l ratio, where N is the plate number and l is the capillary effective length) were systematically compared for the separation of a protein test mixture. The coating stability was evaluated by the relative standard deviation of the migration times. For weak polyelectrolyte multilayers, the influence of the polymer crosslinking on the coating stability and separation efficiency has been studied. Intra-day repeatability of 100 successive runs, and capillary-to-capillary reproducibility were tested on coatings of each category (crosslinked and non crosslinked). The main (not obvious) result rising from this study is that the nature of the polyanion constituting the multilayers is of primary importance for the performance in terms of separation efficiency and stability, even when the mulilayers finish with a polycation.

  3. Forming Reversible Gels with Triblock Polyelectrolytes: a Field-theoretic Study

    Science.gov (United States)

    Audus, Debra; Fredrickson, Glenn

    2011-03-01

    Recently, two research groups have formed reversible gels using triblock polyelectrolytes (Lemmers et al. 2010; Hunt et al., in preparation). This gel formation is driven by a phenomenon called complex coacervation, in which two oppositely charged homopolymers in solution phase separate into a polymer rich phase, known as a coacervate, and a solution phase. If instead, the polymers are triblocks with a neutral midblock and charged end blocks, under appropriate conditions they will microphase separate into micelles with cores of coacervated charged groups and coronas of neutral midblocks. These neutral midblocks act as bridges between the micelles, thereby creating a gel. One of the advantages of forming gels in this way is that the coacervate domains, and thus the gel, can be easily tuned by varying parameters such as pH, salt concentration and temperature. In order to understand the microstructures and solution sensitivity of these reversible gels, we have numerically simulated field-theoretic models of triblock polyelectrolyte mixtures in an implicit solvent. Because coacervation is driven by charge correlations, the usual mean-field assumption fails, and it is necessary to study the model beyond the level of SCFT.

  4. 小松HM400-2铰卡发动机燃油过滤的改造%Reform of Komatsu HM400-2 Articulated Dump Truck Engine Fuel Filter

    Institute of Scientific and Technical Information of China (English)

    朱志兴

    2015-01-01

    小松HM400-2铰接式卡车发动机燃油系统采用的是高压共轨技术,但因燃油适应能力差,导致高压共轨油槽故障频发.此故障成为制约该设备利用率关键因素之一.通过对高压共轨技术介绍,结合该铰接式卡车发动机燃油系统结构特点进行了分析,对共轨油槽故障现象进行了描述和分析.借鉴同型号发动机燃油过滤结构成功经验基础上,提出了燃油系统中过滤器的改造方案,并组织实施,取得了良好效果.%Engine fuel system of articulated truck of Komatsu HM400-2 model is using the high pressure common rail technology. Its adaptability to poor quality fuel causes frequent faults to high pressure common rail tank. This kind of fault restricts the equipment utilization rate becomes one of the key factors to decrease the equipment failure rate. In this article, the high pressure common rail technology is introduced, the common rail tank failure phenomena is described and analyzed, combining the characteristics of the articulated truck engine fuel system structure. Based on the same model engine fuel filter structure of successful experience, the retrofit scheme of fuel oil filter system is put forward, and implemented, which has obtained the good effect.

  5. Tailor-made release triggering from hot-melt extruded complexes of basic polyelectrolyte and poorly water-soluble drugs.

    Science.gov (United States)

    Kindermann, Christoph; Matthée, Karin; Strohmeyer, Jutta; Sievert, Frank; Breitkreutz, Jörg

    2011-10-01

    The aim of the study was the formulation of polyelectrolyte complexes composed of poorly water-soluble acid drugs and basic polymethacrylates by hot-melt extrusion enabling a tailor-made release pattern by the addition of inorganic salts. The influence of different electrolytes was analyzed at varying conditions in order to control drug delivery from the complexes. Poorly water-soluble model drugs naproxen and furosemide were applied in their non-ionic form. After hot-melt extrusion of the naproxen-polymethacrylate powder blend, XRPD and DSC measurements indicated the formation of a single-phase amorphous system. Milled extrudates were stable under storage at long-term and intermediate conditions. Polyelectrolyte complex formation by an acid-base reaction during hot-melt extrusion could be proven by the lack of vibrations of dimethylamino and carboxylic groups by FT-IR and Raman spectroscopy. The complexes did not dissolve in demineralized water. Drug release could be immediately induced by addition of neutral electrolytes. Tailor-made dissolution profiles were realized by controlled electrolyte triggering. Maximal effects were achieved by concentrations of 0.05-0.15 M NaCl. Different anions of alkali halogenides revealed variant magnitudes of the effect depending on the anion radius. Polyelectrolyte complex formation and dissolution principles were also confirmed for furosemide.

  6. Layer-by-layer coating of textile with two oppositely charged cyclodextrin polyelectrolytes for extended drug delivery.

    Science.gov (United States)

    Junthip, Jatupol; Tabary, Nicolas; Chai, Feng; Leclercq, Laurent; Maton, Mickael; Cazaux, Frederic; Neut, Christel; Paccou, Laurent; Guinet, Yannick; Staelens, Jean-Noel; Bria, Marc; Landy, David; Hédoux, Alain; Blanchemain, Nicolas; Martel, Bernard

    2016-06-01

    The coating of a nonwoven textile by polyelectrolyte multilayer film (PEM) issued from cationic and anionic β-cyclodextrin (βCD) polyelectrolytes according to the layer-by-layer (LbL) technique was successfully attempted. The tert-butyl benzoic acid (TBBA) was used as drug model to evaluate the loading capacity and sustained release properties of this PEM system. The build-up of the multilayer assembly was monitored in situ by optical waveguide lightmode spectroscopy (OWLS) on the one hand, and was assessed by gravimetry on the other hand when applied onto the textile substrate. In parallel, the complexation study of TBBA with both CD polyelectrolytes was also investigated by nuclear magnetic resonance (NMR) and isothermal titration calorimetry (ITC). The influence of thermal crosslinking of the multilayered coating on its stability and on TBBA release kinetics in phosphate buffered saline (PBS) at 37°C was studied. Finally, biological and microbiological tests were performed to investigate the cytocompatibility and the intrisic antibacterial activity of multilayer assemblies. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1408-1424, 2016.

  7. Polyelectrolyte complexes : Preparation, characterization, and use for control of wet and dry adhesion between surfaces

    OpenAIRE

    Ankerfors, Caroline

    2012-01-01

    This thesis examines polyelectrolyte complex (PEC) preparation, adsorption behaviour, and potential use for control of wet and dry adhesion between surfaces. PEC formation was studied using a jet-mixing method not previously used for mixing polyelectrolytes. The PECs were formed using various mixing times, and the results were compared with those for PECs formed using the conventional polyelectrolyte titration method. The results indicated that using the jet mixer allowed the size of the form...

  8. Polyaniline-Doped Spherical Polyelectrolyte Brush Nanocomposites with Enhanced Electrical Conductivity, Thermal Stability, and Solubility Property

    Directory of Open Access Journals (Sweden)

    Na Su

    2015-09-01

    Full Text Available The synthesis procedure and dopant are crucial to the electrical conductivity, thermal stability, and solubility properties of polyaniline (PANI. In this paper, high-performance PANI was synthesized by means of chemical oxidative polymerization using anionic spherical polyelectrolyte brushes (ASPB as dopant. The bonding structure, crystallographic structure, morphology, and thermal stability of the conductive nanocomposite were analyzed by Fourier transform infrared spectroscopy (FTIR, X-ray diffraction (XRD, scanning electron microscopy (SEM, and thermo-gravimetric analysis (TGA respectively. Meanwhile, investigation on the electrical conductivity suggested that the room-temperature electrical conductivity of PANI doped with ASPB (PANI/ASPB was 19.3 S/cm, which was higher than that of PANI (7.0 S/cm, PANI doped with poly(sodium-p-styrenesulfonate (PSS (PANI/PSS (14.6 S/cm, PANI doped with SiO2 (PANI/SiO2 (18.2 S/cm, and PANI doped with canonic spherical polyelectrolyte brushes (CSPB (PANI/CSPB (8.0 S/cm. Meanwhile, the addition of ASPB improved the thermal stability and solubility properties of PANI. ASPB played the role of template. Conductive mechanism of PANI/ASPB nanocomposite can be explained by the theoretical models of three-dimensional variable range-hopping (3D VRH.

  9. Conformal nano-thin modified polyelectrolyte coatings for encapsulation of cells.

    Science.gov (United States)

    Granicka, L H; Antosiak-Iwańska, M; Godlewska, E; Strawski, M; Szklarczyk, M; Maranowski, B; Kowalewski, C; Wiśniewsk, J

    2011-10-01

    Encapsulation of cells in polymeric shells allows for separation of biological material from produced factors, which may find biotechnological and biomedical applications. Human T-lymphocyte cell line Jurkat as well as rat pancreatic islets were encapsulated using LbL technique within shells of polyelectrolyte modified by incorporation of biotin complexed with avidin to improve cell coating and to create the potential ability to elicit specific biochemical responses. The coating with nano-thin modified shells allowed for maintenance of the evaluated cells' integrity and viability during the 8-day culture. The different PE impact may be observed on different biological materials. The islets exhibited lower mitochondrial activity than the Jurkat cells. Nevertheless, coating of cells with polyelectrolyte modified membrane allowed for functioning of both model cell types: 10 μm leukemia cells or 150 μm islets during the culture. Applied membranes maintained the molecular structure during the culture period. The conclusion is that applied modified membrane conformation may be recommended for coating shells for biomedical purposes.

  10. Single chains of strong polyelectrolytes in aqueous solutions at extreme dilution: Conformation and counterion distribution

    Science.gov (United States)

    Xu, Guofeng; Luo, Shuangjiang; Yang, Qingbo; Yang, Jingfa; Zhao, Jiang

    2016-10-01

    The molecular conformation of two typical polyelectrolytes, sodium polystyrene sulfonate (NaPSS) and quarternized poly-4-vinylpyridine (QP4VP), was studied in aqueous solutions without salt addition at the single molecular level. By fluorescence correlation spectroscopy, the hydrodynamic radius (Rh) of NaPSS and QP4VP with the molecular weight ranging more than one order of magnitude was measured. The scaling analysis of Rh exhibits scaling exponent of 0.70 and 0.86 for NaPSS and QP4VP in solutions without added salts, respectively, showing the conformation is much more expanded than random coil. Numerical fittings using the model of diffusion of a rod molecule agree with the data well, indicating that the polyelectrolyte chains take the rod-like conformation under the condition without salt addition. Further investigations by determining the electric potential of single PSS- chains using the photon counting histogram technique demonstrate the enhanced counterion adsorption to the charged chain at higher molecular weight.

  11. Employment of Gibbs-Donnan-based concepts for interpretation of the properties of linear polyelectrolyte solutions

    Science.gov (United States)

    Marinsky, J.A.; Reddy, M.M.

    1991-01-01

    Earlier research has shown that the acid dissociation and metal ion complexation equilibria of linear, weak-acid polyelectrolytes and their cross-linked gel analogues are similarly sensitive to the counterion concentration levels of their solutions. Gibbs-Donnan-based concepts, applicable to the gel, are equally applicable to the linear polyelectrolyte for the accommodation of this sensitivity to ionic strength. This result is presumed to indicate that the linear polyelectrolyte in solution develops counterion-concentrating regions that closely resemble the gel phase of their analogues. Advantage has been taken of this description of linear polyelectrolytes to estimate the solvent uptake by these regions. ?? 1991 American Chemical Society.

  12. Comprehensive and Systematic Analysis of the Immunocompatibility of Polyelectrolyte Capsules.

    Science.gov (United States)

    Zyuzin, Mikhail V; Díez, Paula; Goldsmith, Meir; Carregal-Romero, Susana; Teodosio, Cristina; Rejman, Joanna; Feliu, Neus; Escudero, Alberto; Almendral, María Jesús; Linne, Uwe; Peer, Dan; Fuentes, Manuel; Parak, Wolfgang J

    2017-02-15

    The immunocompability of polyelectrolyte capsules synthesized by layer-by-layer deposition has been investigated. Capsules of different architecture and composed of either non-degradable or biodegradable polymers, with either positively or negatively charged outer surface, and with micrometer size, have been used, and the capsule uptake by different cell lines has been studied and quantified. Immunocompatibility studies were performed with peripheral blood mononuclear cells (PBMCs). Data demonstrate that incubation with capsules, at concentrations relevant for practical applications, did not result in a reduced viability of cells, as it did not show an increased apoptosis. Presence of capsules also did not result in an increased expression of TNF-α, as detected with antibody staining, as well as at mRNA level. It also did not result in increased expression of IL-6, as detected at mRNA level. These results indicate that the polyelectrolyte capsules used in this study are immunocompatible.

  13. Fibrillar films obtained from sodium soap fibers and polyelectrolyte multilayers.

    Science.gov (United States)

    Zawko, Scott A; Schmidt, Christine E

    2011-08-01

    An objective of tissue engineering is to create synthetic polymer scaffolds with a fibrillar microstructure similar to the extracellular matrix. Here, we present a novel method for creating polymer fibers using the layer-by-layer method and sacrificial templates composed of sodium soap fibers. Soap fibers were prepared from neutralized fatty acids using a sodium chloride crystal dissolution method. Polyelectrolyte multilayers (PEMs) of polystyrene sulfonate and polyallylamine hydrochloride were deposited onto the soap fibers, crosslinked with glutaraldehyde, and then the soap fibers were leached with warm water and ethanol. The morphology of the resulting PEM structures was a dense network of fibers surrounded by a nonfibrillar matrix. Microscopy revealed that the PEM fibers were solid structures, presumably composed of polyelectrolytes complexed with residual fatty acids. These fibrillar PEM films were found to support the attachment of human dermal fibroblasts.

  14. Aqueous dispersions of silver nanoparticles in polyelectrolyte solutions

    Indian Academy of Sciences (India)

    Dan Donescu; Raluca Somoghi; Marius Ghiurea; Raluca Ianchis; Cristian Petcu; Stefania Gavriliu; Magdalena Lungu; Claudia Groza; Carmen R Ionescu; Carmen Panzaru

    2013-03-01

    In this report, we present the versatile and effective technique, using environmental friendly reductant glucose, to prepare stable silver nanodispersions by reduction of Ag+ ions. Alternant copolymers of maleic anhydride with vinyl acetate and styrene sulphonate sodium acid salt polyelectrolytes were synthesized in aqueous solution and used as stabilizers. The formation of nano silver particles was confirmed by UV-Vis spectrophotometry and TEM measurements. Dynamic Light Scattering (DLS) measurements were needed to study how the reagents and their concentrations influence particle size. SEM images show the nanostructure of the hybrid films and indicate a strong interaction between the polyelectrolyte and the silver NPs. Moreover, the silver NPs could be stored for one year without observation of aggregates or sedimentation. The final solid products obtained after evaporating to dryness can be used to produce stable dispersions upon mixing with water. Few of the final products were found to exhibit a high antibacterial and antifungal activity.

  15. Interaction of Fluorocarbon Containing Hydrophobically Modified Polyelectrolyte with Nonionic Surfactants

    Institute of Scientific and Technical Information of China (English)

    GUO,Jin-Feng(郭金峰); ZHUANG,Dong-Qing(庄东青); ZHOU,Hui(周晖); ZHANG,Yun-Xiang(章云祥)

    2002-01-01

    The interaction of fluorocarbon containing hydrophobically modified polyelectrolyte (FMPAANa) with two kinds of nonionic surfactants (hydrogenated and fluorinated) in a semidilute (0.5 wt% ) aqueous solution had been studied by rheological measurements. Association behavior was found in both systems. The hydrophobic interaction of FMPAANa with fluorinated surfactant (FC171) is much stronger than that with hydrogenated surfactant (NP7.5) at low surfactant concentrations. The interaction is strengthened by surfactants being added for the density of active junctions increased. Whereas distinct phenomena for FC171 and NP7. 5 start to be found as the surfactants added over their respective certain concentration. The interaction of polyelectrolyte with fluorinated surfactant increases dramatical ly while that with hydrogenated surfactant decreases.

  16. Polyelectrolyte Multilayers in Microfluidic Systems for Biological Applications

    Directory of Open Access Journals (Sweden)

    Saugandhika Minnikanti

    2014-07-01

    Full Text Available The formation of polyelectrolyte multilayers (PEMs for the first time, two decades ago, demonstrating the assembly on charged substrates in a very simple and efficient way, has proven to be a reliable method to obtain structures tunable at the nanometer scale. Much effort has been put into the assembly of these structures for their use in biological applications. A number of these efforts have been in combination with microfluidic systems, which add to the nanoassembly that is already possible with polyelectrolytes, a new dimension in the construction of valuable structures, some of them not possible with conventional systems. This review focuses on the advancements demonstrated by the combination of PEMs and microfluidic systems, and their use in biological applications.

  17. Determination of three characteristic regimes of weakly charged polyelectrolytes monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Farhan [Department of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Shin, Kwanwoo [Department of Chemistry and Interdisciplinary Program of Integrated Biotechnology, Sogang University, Seoul 121-742 (Korea, Republic of)], E-mail: kshin@sogang.ac.kr; Choi, Jae-Hak [Advanced Radiation Technology Institute, KAERI, Jeongeup 580-185 (Korea, Republic of); Satija, Sushil K. [National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Kim, Joon-Seop [Department of Polymer Science and Engineering, Chosun University (Korea, Republic of); Rafailovich, Miriam H.; Sokolov, Jon [Department of Materials Science and Engineering, Stony Brook University, Stony Brook, NY 11794 (United States)

    2008-09-15

    We have demonstrated that monolayer films of randomly charged polystyrene sulfonated acid (PSSA) can be produced by the Langmuir technique, and observed the micro-domain structures, produced by the phase separation of electrostatically charged moieties and the hydrophobic moieties. Using atomic force microscopy and Langmuir isotherm, we found three specific regimes for the polyelectrolytes with various degrees of sulfonation (4-35%); very low charged PSSA (4-5%) in the hydrophobic regime, moderately charged PSSA (6-16%) which possessed a well-balanced nature between electrostatic and the hydrophobic interactions, and strongly amphiphilic nature of PSSA (6-16%) in the ionomer regime. Finally, we could categorize PSSA 35% in the polyelectrolyte regime, due to the dominance of the electrostatic interactions over the hydrophobic interactions.

  18. Porphyrin Diacid-Polyelectrolyte Assemblies: Effective Photocatalysts in Solution

    Directory of Open Access Journals (Sweden)

    Sabine Frühbeißer

    2016-05-01

    Full Text Available Developing effective and versatile photocatalytic systems is of great potential in solar energy conversion. Here we investigate the formation of supramolecular catalysts by electrostatic self-assembly in aqueous solution: Combining positively charged porphyrins with negatively charged polyelectrolytes leads to nanoscale assemblies where, next to electrostatic interactions, π–π interactions also play an important role. Porphyrin diacid-polyelectrolyte assemblies exhibit a substantially enhanced catalytic activity for the light-driven oxidation of iodide. Aggregates with the hexavalent cationic porphyrin diacids show up to 22 times higher catalytic activity than the corresponding aggregates under neutral conditions. The catalytic activity can be increased by increasing the valency of the porphyrin and by choice of the loading ratio. The structural investigation of the supramolecular catalysts took place via atomic force microscopy and small angle neutron scattering. Hence, a new facile concept for the design of efficient and tunable self-assembled photocatalysts is presented.

  19. Polyelectrolyte Coacervates Deposited as High Gas Barrier Thin Films.

    Science.gov (United States)

    Haile, Merid; Sarwar, Owais; Henderson, Robert; Smith, Ryan; Grunlan, Jaime C

    2017-01-01

    Multilayer coatings consisting of oppositely charged polyelectrolytes have proven to be extraordinarily effective oxygen barriers but require many processing steps to fabricate. In an effort to prepare high oxygen barrier thin films more quickly, a polyelectrolyte complex coacervate composed of polyethylenimine and polyacrylic acid is prepared. The coacervate fluid is applied as a thin film using a rod coating process. With humidity and thermal post-treatment, a 2 µm thin film reduces the oxygen transmission rate of 0.127 mm poly(ethylene terephthalate) by two orders of magnitude, rivalling conventional oxygen barrier technologies. These films are fabricated in ambient conditions using low-cost, water-based solutions, providing a tremendous opportunity for single-step deposition of polymeric high barrier thin films.

  20. Ultramicroelectrode studies of oxygen reduction in polyelectrolyte membranes

    Energy Technology Data Exchange (ETDEWEB)

    Holdcroft, S.; Abdou, M.S.; Beattie, P.; Basura, V. [Simon Fraser Univ., Burnaby, BC (Canada). Dept. of Chemistry

    1997-12-31

    A study on the oxygen reduction reaction in a solid state electrochemical cell was presented. The oxygen reduction reaction is a rate limiting reaction in the operation of solid polymer electrolyte fuel cells which use H{sub 2} and O{sub 2}. Interest in the oxygen reduction reaction of platinum electrodes in contact with Nafion electrolytes stems from its role in fuel cell technology. The kinetics of the oxygen reduction reaction in different polyelectrolyte membranes, such as Nafion and non-Nafion membranes, were compared. The electrode kinetics and mass transport parameters of the oxygen reduction reaction in polyelectrolyte membranes were measured by ultramicroelectrode techniques. The major difference found between these two classes of membrane was the percentage of water, which is suggestive of superior electrochemical mass transport properties of the non-Nafion membranes. 2 refs. 1 fig.

  1. 印尼Multistrada公司将开拓1200hm2胶园

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    依计划,印度尼西亚汽车和摩托车轮胎生产商MultistradaArahSarana(MASA)上市公司,将在2012—2013年期间在面积1200hm2的土地上种植橡胶树。该企业准备好了4000亿盾资金。

  2. Complex Coacervation composed of Polyelectrolytes Alginate and Chitosan

    Institute of Scientific and Technical Information of China (English)

    盛楠楠

    2016-01-01

    Alginate sodium (ALG) and chitosan (CHI) can form fiber, films, microspheres, hydrogels and all with a wide range of biomedical applications.Few works have been done as a result of the easily flocculation of chitosan in negatively charged matrix.Complex coacervation composed of polyelectrolytes alginate and chitosan were successfully fabricated.The results showed that the lower molecular weights of the chitosan is better for the fabricated of the complex coacervation.

  3. Formation of polyelectrolyte multilayers: ionic strengths and growth regimes

    NARCIS (Netherlands)

    Tang, K.; Besseling, N.A.M.

    2015-01-01

    This article presents a study of layer-by-layer (LbL) formation of poly-electrolyte multilayers (PEMs). Upon increasing ionic strength LbL growth patterns vary from linear for the lowest salt concentrations ([NaCl] = 0, 0.001, and 0.01 M) to exponential (for [NaCl] = 0.5 and 1 M). The slope of the

  4. Polyelectrolyte Biomaterial Interactions Provide Nanoparticulate Carrier for Oral Insulin Delivery

    OpenAIRE

    Reis, Catarina Pinto; Ribeiro, António J; Veiga, Francisco; Neufeld, Ronald J; Damgé, Christiane

    2008-01-01

    Nanospheres are being developed for the oral delivery of peptide-based drugs such as insulin. Mucoadhesive, biodegradable, biocompatible, and acid-protective biomaterials are described using a combination of natural polyelectrolytes, with particles formulated through nanoemulsion dispersion followed by triggered in situgel complexation. Biomaterials meeting these criteria include alginate, dextran, chitosan, and albumin in which alginate/dextran forms the core matrix complexed with chitosan a...

  5. Kinetics of swelling of polyelectrolyte gels: Fixed degree of ionization

    Science.gov (United States)

    Sen, Swati; Kundagrami, Arindam

    2015-12-01

    The swelling kinetics of uncharged and charged polymer (polyelectrolyte) gels in salt-free conditions is studied in one dimension by solving the constitutive equation of motion (Newton's law for the elementary gel volume) of the displacement variable by two theoretical methods: one in which the classical definition of stress is used with the bulk modulus taken as a parameter, and the other in which a phenomenological expression of the osmotic stress as a function of polymer density and degree of ionization is taken as an input to the dynamics. The time-evolution profiles for spatially varying polymer density and stress, along with the location of the gel-solvent interface, are obtained from the two methods. We show that both the polymer density (volume fraction) and stress inside the gel follow expected behaviours of being maximum for the uniformly shrunken gel, and relaxing slowly to the lowest values as the gel approaches equilibrium. We further show that, by comparing the temporal profiles of the gel-solvent interface and other variables between the two methods, one may attempt to assign an effective bulk modulus to the polyelectrolyte gel as a function of the degree of ionization and other parameters of the gel such as hydrophobicity, cross-link density, and the temperature. The major result we get is that the effective bulk modulus of a polyelectrolyte gel increases monotonically with its degree of ionization. In the process of identifying the parameters for a monotonic swelling, we calculated using a well-known expression of the free energy the equilibrium results of two-phase co-existence and the critical point of a polyelectrolyte gel with a fixed degree of ionization.

  6. Formation of polyelectrolyte multilayers: ionic strengths and growth regimes

    NARCIS (Netherlands)

    Tang, K.; Besseling, N.A.M.

    2015-01-01

    This article presents a study of layer-by-layer (LbL) formation of poly-electrolyte multilayers (PEMs). Upon increasing ionic strength LbL growth patterns vary from linear for the lowest salt concentrations ([NaCl] = 0, 0.001, and 0.01 M) to exponential (for [NaCl] = 0.5 and 1 M). The slope of the l

  7. Kinetics of swelling of polyelectrolyte gels: Fixed degree of ionization

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Swati; Kundagrami, Arindam, E-mail: arindam@iiserkol.ac.in [Department of Physical Sciences, Indian Institute of Science Education and Research, Kolkata, Mohanpur 741246, West Bengal (India)

    2015-12-14

    The swelling kinetics of uncharged and charged polymer (polyelectrolyte) gels in salt-free conditions is studied in one dimension by solving the constitutive equation of motion (Newton’s law for the elementary gel volume) of the displacement variable by two theoretical methods: one in which the classical definition of stress is used with the bulk modulus taken as a parameter, and the other in which a phenomenological expression of the osmotic stress as a function of polymer density and degree of ionization is taken as an input to the dynamics. The time-evolution profiles for spatially varying polymer density and stress, along with the location of the gel-solvent interface, are obtained from the two methods. We show that both the polymer density (volume fraction) and stress inside the gel follow expected behaviours of being maximum for the uniformly shrunken gel, and relaxing slowly to the lowest values as the gel approaches equilibrium. We further show that, by comparing the temporal profiles of the gel-solvent interface and other variables between the two methods, one may attempt to assign an effective bulk modulus to the polyelectrolyte gel as a function of the degree of ionization and other parameters of the gel such as hydrophobicity, cross-link density, and the temperature. The major result we get is that the effective bulk modulus of a polyelectrolyte gel increases monotonically with its degree of ionization. In the process of identifying the parameters for a monotonic swelling, we calculated using a well-known expression of the free energy the equilibrium results of two-phase co-existence and the critical point of a polyelectrolyte gel with a fixed degree of ionization.

  8. X-ray properties of the young open clusters HM1 and IC2944/2948

    CERN Document Server

    Naze, Yael; Sana, Hugues; Corcoran, Michael F

    2013-01-01

    Using XMM data, we study for the first time the X-ray emission of HM1 and IC2944/2948. Low-mass, pre-main-sequence objects with an age of a few Myr are detected, as well as a few background or foreground objects. Most massive stars in both clusters display the usual high-energy properties of that type of objects, though with log(Lx/Lbol) apparently lower in HM1 than in IC2944/2948. Compared with studies of other clusters, it seems that a low signal-to-noise ratio at soft energies, due to the high extinction, may be the main cause of this difference. In HM1, the two Wolf-Rayet stars show contrasting behaviors: WR89 is extremely bright, but much softer than WR87. It remains to be seen whether wind-wind collisions or magnetically confined winds can explain these emissions. In IC2944/2948, the X-ray sources concentrate around HD101205; a group of massive stars to the north of this object is isolated, suggesting that there exist two subclusters in the field-of-view.

  9. VLT Phase Resolved Optical Spectroscopy of the Ultra-Compact Binary HM Cnc

    CERN Document Server

    Mason, Elena; Dall'Osso, S; Stella, L; Munari, U; Marconi, G; O'Brian, K; Covino, S; Fugazza, D

    2010-01-01

    A 321.5 s modulation was discovered in 1999 in the X-ray light curve of HM Cnc. In 2001 and 2002, optical photometric and spectroscopic observations revealed that HM Cnc is a very blue object with no intrinsic absorptions but broad (FWHM 1500 km s^-1) low equivalent width emission lines (EW 1-6A), which were first identified with the HeII Pickering series. The combination of X-ray and optical observations pictures HM Cnc as a double degenerate binary hosting two white dwarfs, and possibly being the shortest orbital period binary discovered so far. The present work is aimed at studying the orbital motion of the two components by following the variations of the shape, centroid and intensity of the emission lines through the orbit. In February 2007, we carried out the first phase resolved optical spectroscopic study with the VLT/FORS2 in the High Time Resolution (HIT) mode, yielding five phase bins in the 321 s modulation. Despite the low SNR, the data show that the intensity of the three most prominent emission...

  10. X-ray Properties of the Young Open Clusters HM1 and IC 2944-2948

    Science.gov (United States)

    Naze, Y.; Rauw, G.; Sana, H.; Corcoran, Michael F.

    2013-01-01

    Using XMM-Newton data, we study for the first time the X-ray emission of HM1 and IC 2944/2948. Low-mass, pre-main-sequence objects with an age of a few Myr are detected, as well as a few background or foreground objects. Most massive stars in both clusters display the usual high-energy properties of that type of objects, though with log [L(sub X)/L(sub BOL)] apparently lower in HM1 than in IC2944/2948. Compared with studies of other clusters, it seems that a low signal-to-noise ratio at soft energies, due to the high extinction, may be the main cause of this difference. In HM1, the two Wolf-Rayet stars show contrasting behaviors:WR89 is extremely bright, but much softer than WR87. It remains to be seen whether wind-wind collisions or magnetically confined winds can explain these emissions. In IC 2944/2948, the X-ray sources concentrate around HD 101205; a group of massive stars to the north of this object is isolated, suggesting that there exist two subclusters in the field-of-view.

  11. Forming lipid bilayer membrane arrays on micropatterned polyelectrolyte film surfaces.

    Science.gov (United States)

    Zhang, Ying; Wang, Lei; Wang, Xuejing; Qi, Guodong; Han, Xiaojun

    2013-07-01

    A novel method of forming lipid bilayer membrane arrays on micropatterned polyelectrolyte film surfaces is introduced. Polyelectrolyte films were fabricated by the layer-by-layer technique on a silicon oxide surface modified with a 3-aminopropyltriethoxysilane (APTES) monolayer. The surface pK(a) value of the APTES monolayer was determined by cyclic voltammetry to be approximately 5.61, on the basis of which a pH value of 2.0 was chosen for layer-by-layer assembly. Micropatterned polyelectrolyte films were obtained by deep-UV (254 nm) photolysis though a mask. Absorbed fluorescent latex beads were used to visualize the patterned surfaces. Lipid bilayer arrays were fabricated on the micropatterned surfaces by immersing the patterned substrates into a solution containing egg phosphatidylcholine vesicles. Fluorescence recovery after photobleaching studies yielded a lateral diffusion coefficient for probe molecules of 1.31±0.17 μm(2) s(-1) in the bilayer region, and migration of the lipid NBD PE in bilayer lipid membrane arrays was observed in an electric field.

  12. Solubilization of trichloroethylene by polyelectrolyte/surfactant complexes

    Energy Technology Data Exchange (ETDEWEB)

    Uchiyama, Hirotaka; Christian, S.D.; Tucker, E.E.; Scamehorn, J.F. (Univ. of Oklahoma, Norman, OK (United States))

    1994-12-01

    An automated vapor pressure method is used to obtain solubilization isotherms for trichloroethylene (TCE) in polyelectrolyte/surfactant complexes throughout a wide range of solute activities at 20 and 25 C. The polyelectrolyte chosen is sodium poly(styrenesulfonate), PSS< and the surfactant is cetylpyridinium chloride or N-hexadecylpyridinium chloride, CPC. Data are fitted to the quadratic equation K = K[sub 0](1[minus][alpha]X + [beta]X[sup 2]), which correlates the solubilization equilibrium constant (K) with the mole fraction of TCE (X) in the micelles or complexes at each temperature. Activity coefficients are also obtained for TCE in the PSS/CPC complexes as a function of X. The general solubilization of TCE in PSS/CPC complexes resembles that of TCE in CPC micelles, as well as that of benzene or toluene in CPC micelles, suggesting that TCE solubilizes in ionic micelles both within the hydrocarbon micellar interior and near the micellar surface. The presence of the polyelectrolyte causes a small decrease in the ability of the cationic surfactant to solubilize TCE, while greatly reducing the concentration of the surfactant present in monomeric form. PSS/CPC complexes may be useful in colloid-enhanced ultrafiltration processes to purify organic-contaminated water.

  13. Linear Viscoelasticity and Swelling of Polyelectrolyte Complex Coacervates

    Science.gov (United States)

    Hamad, Fawzi; Colby, Ralph

    2012-02-01

    The addition of near equimolar amounts of poly(diallyldimethylammonium chloride) to poly(isobutylene-alt-maleate sodium), results in formation of a polyelectrolyte complex coacervate. Zeta-potential titrations conclude that these PE-complexes are nearly charge-neutral. Swelling and rheological properties are studied at different salt concentrations in the surrounding solution. The enhanced swelling observed at high salt concentration suggests the system behaves like a polyampholyte gel, and weaker swelling at very low salt concentrations implies polyelectrolyte gel behavior. Linear viscoelastic oscillatory shear measurements indicate that the coacervates are viscoelastic liquids and that increasing ionic strength of the medium weakens the electrostatic interactions between charged units, lowering the relaxation time and viscosity. We use the time-salt superposition idea recently proposed by Spruijt, et al., allowing us to construct master curves for these soft materials. Similar swelling properties observed when varying molecular weights. Rheological measurements reveal that PE-complexes with increasing molecular weight polyelectrolytes form a network with higher crosslink density, suggesting time-molecular weight superposition idea.

  14. Changes of Resistance During Polyelectrolyte-enhanced Stirred Batch Ultrafiltration

    Institute of Scientific and Technical Information of China (English)

    ZHU Xin-Sheng; Kwang-Ho CHOO

    2007-01-01

    The permeation flux or the resistance in the ultrafiltration process is mainly limited by osmotic pressure,and it may originate from various kinds of polymer interactions. However, the real origin of permeation resistance hasn't been clarified yet in the light of polymer solution nature. The removal of nitrate contamination by polyelectrolytes was carried out with stirred batch ultrafiltration. The polyelectrolyte concentrations both in permeate and retentate were analyzed with total organic carbon analyzer and permeate mass was acquired by electronic balance connected with computer. The total resistance was calculated and interpreted based on the osmotic pressures in three concentration regimes. In the dilute region, the resistance was proportional to polymer concentration; in the semidilute region, the resistance depended on polymer concentration in the parabolic relationship; in the highly concentrated solution regime, the osmotic pressure factor (OPF) would dominate the total resistance; and the deviation from OPF control could come from the electrostatic repulsion between the tightly compacted and charged polyelectrolyte particles at extremely concentrated solution regime. It was first found that dilute and semidilute concentration regions can be easily detected by plotting the log-log curves of the polymer concentration versus the ratio of the total resistance to polymer concentration. The new concept OPF was defined and did work well at highly concentrated regime.

  15. Exploration of polyelectrolytes as draw solutes in forward osmosis processes

    KAUST Repository

    Ge, Qingchun

    2012-03-01

    The development of the forward osmosis (FO) process has been constrained by the slow development of appropriate draw solutions. Two significant concerns related to draw solutions are the draw solute leakage and intensiveenergy requirement in recycling draw solutes after the FO process. FO would be much attractive if there is no draw solute leakage and the recycle of draw solutes is easy and economic. In this study, polyelectrolytes of a series of polyacrylic acid sodium salts (PAA-Na), were explored as draw solutes in the FO process. The characteristics of high solubility in water and flexibility in structural configuration ensure the suitability of PAA-Na as draw solutes and their relative ease in recycle through pressure-driven membrane processes. The high water flux with insignificant salt leakage in the FO process and the high salt rejection in recycle processes reveal the superiority of PAA-Na to conventional ionic salts, such as NaCl, when comparing their FO performance via the same membranes. The repeatable performance of PAA-Na after recycle indicates the absence of any aggregation problems. The overall performance demonstrates that polyelectrolytes of PAA-Na series are promising as draw solutes, and the new concept of using polyelectrolytes as draw solutes in FO processes is applicable. © 2011 Elsevier Ltd.

  16. Antibacterial polyelectrolyte-coated Mg alloys for biomedical applications

    Science.gov (United States)

    Seraz, Md. S.; Asmatulu, R.; Chen, Z.; Ceylan, M.; Mahapatro, A.; Yang, S. Y.

    2014-04-01

    This study deals with two biomedical subjects: corrosion rates of polyelectrolyte-coated magnesium (Mg) alloys, mainly used for biomedical purposes, and antibacterial properties of these alloys. Thin sheets of Mg alloys were coated with cationic polyelectrolyte chitosan (CHI) and anionic polyelectrolyte carboxymethyl cellulose (CMC) using a layer-by-layer coating method and then embedded with antibacterial agents under vacuum. Electrochemical impedance spectroscopy was employed to analyze these samples in order to detect their corrosion properties at different conditions. In the electrochemical analysis section, a corrosion rate of 72 mille inches per year was found in a salt solution for the sample coated with a 12 phosphonic acid self-assembled monolayer and 9 CHI/CMC multilayers. In the antibacterial tests, gentamicin was used to investigate the effects of the drug embedded with the coated surfaces against the Escherichia coli (E. coli) bacteria. Antibacterial studies were tested using the disk diffusion method. Based on the standard diameter of the zone of inhibition chart, the antibacterial diffusion from the surface strongly inhibited bacterial growth in the regions. The largest recorded diameter of the zone of inhibition was 50 mm for the pre-UV treated and gentamicin-loaded sample, which is more than three times the standard diameter.

  17. Deflocculation of Cellulosic Suspensions with Anionic High Molecular Weight Polyelectrolytes

    Directory of Open Access Journals (Sweden)

    Markus Heikki Juhani Korhonen

    2014-04-01

    Full Text Available Pulp fibers have a strong tendency to form flocs in water suspensions, which may cause their undesirable distribution in the paper sheets. This flocculation can be controlled by adding, e.g., an anionic high molecular weight polyelectrolyte in the fiber suspension. The objective of this study was to investigate the effect of anionic polyelectrolytes on deflocculation kinetics, dewatering, and rheology of cellulosic suspensions. The results showed that both microfibrillated cellulose (MFC and macroscopic pulp fibers can be dispersed using anionic polyacrylamides (APAM. The higher the molecular weight of APAM, the higher is its effect. Adsorption experiments illustrate that anionic polyelectrolytes do not strongly attach to cellulose surfaces but they can be partly entrapped or can disperse nanocellulose fibrils (increase the swelling. Based on rheological experiments, the MFC network became weaker with APAM addition. Similar to the flocculation mechanism of cellulosic materials with polymers, deflocculation is also time dependent. Deflocculation occurs very rapidly, and the maximum deflocculation level is achieved within a few seconds. When mixing is continued, the floc size starts to increase again. Also dewatering was found to be strongly dependent on the contact time with the APAMs. These results indicate that the positive effects of anionic deflocculants are quickly diminished due to shear forces, and therefore, the best deflocculating effect is achieved using as short a contact time as possible.

  18. Structure-based computational study of two disease resistance gene homologues (Hm1 and Hm2) in maize (Zea mays L.) with implications in plant-pathogen interactions.

    Science.gov (United States)

    Dehury, Budheswar; Patra, Mahesh Chandra; Maharana, Jitendra; Sahu, Jagajjit; Sen, Priyabrata; Modi, Mahendra Kumar; Choudhury, Manabendra Dutta; Barooah, Madhumita

    2014-01-01

    The NADPH-dependent HC-toxin reductases (HCTR1 and 2) encoded by enzymatic class of disease resistance homologous genes (Hm1 and Hm2) protect maize by detoxifying a cyclic tetrapeptide, HC-toxin, secreted by the fungus Cochliobolus carbonum race 1(CCR1). Unlike the other classes' resistance (R) genes, HCTR-mediated disease resistance is an inimitable mechanism where the avirulence (Avr) component from CCR1 is not involved in toxin degradation. In this study, we attempted to decipher cofactor (NADPH) recognition and mode of HC-toxin binding to HCTRs through molecular docking, molecular dynamics (MD) simulations and binding free energy calculation methods. The rationality and the stability of docked complexes were validated by 30-ns MD simulation. The binding free energy decomposition of enzyme-cofactor complex was calculated to find the driving force behind cofactor recognition. The overall binding free energies of HCTR1-NADPH and HCTR2-NADPH were found to be -616.989 and -16.9749 kJ mol-1 respectively. The binding free energy decomposition revealed that the binding of NADPH to the HCTR1 is mainly governed by van der Waals and nonpolar interactions, whereas electrostatic terms play dominant role in stabilizing the binding mode between HCTR2 and NADPH. Further, docking analysis of HC-toxin with HCTR-NADPH complexes showed a distinct mode of binding and the complexes were stabilized by a strong network of hydrogen bond and hydrophobic interactions. This study is the first in silico attempt to unravel the biophysical and biochemical basis of cofactor recognition in enzymatic class of R genes in cereal crop maize.

  19. HmCRIP, a cysteine-rich intestinal protein, is expressed by an identified regenerating nerve cell.

    Science.gov (United States)

    Emes, R D; Wang, W-Z; Lanary, K; Blackshaw, S E

    2003-01-02

    A Hirudo medicinalis cDNA isolated from regenerating CNS tissue at 24 h post-axotomy was identified as a leech homologue of the mammalian cysteine-rich intestinal proteins (CRIPs) and named HmCRIP. HmCRIP is up-regulated within 6 h of axotomy, peaking at 24 h. This is the first demonstration of a CRIP homologue in regenerating CNS and in a serotonergic neurone. In rodents CRIP is an important factor in the regulation of the inflammatory immune response through control of Th1/Th2 differentiation. The role of HmCRIP in the regeneration competent environment of the annelid central nervous system is discussed.

  20. Adsorption of polyelectrolytes at liquid-liquid interfaces and its effect on

    NARCIS (Netherlands)

    Boehm, J.T.C.

    1974-01-01

    In this study we have investigated the adsorption behaviour of a number of synthetic polyelectrolytes at the paraffin oil-water interface and the properties of paraffin oil-in-water emulsions stabilized by these polyelectrolytes.Polyacrylic acid (PAA), polymethacrylic acid (PMA) and the copolymers o

  1. Adsorption of polyelectrolytes at liquid-liquid interfaces and its effect on emulsification

    NARCIS (Netherlands)

    Böhm, J.T.C.

    1974-01-01

    In this study we have investigated the adsorption behaviour of a number of synthetic polyelectrolytes at the paraffin oil-water interface and the properties of paraffin oil-in-water emulsions stabilized by these polyelectrolytes.

    Polyacrylic acid (PAA), polymethacrylic acid (PMA)

  2. Temperature-induced changes in polyelectrolyte films at the solid-liquid interface

    CERN Document Server

    Steitz, R; Tauer, K; Khrenov, Yu V; Klitzing, K V

    2002-01-01

    Polyelectrolyte multilayers (film thickness 30-60 nm) were built on top of silicon substrates by layer-by-layer deposition of oppositely charged polyelectrolytes from aqueous solutions. Three kinds of films were investigated: (A) films of a homo-polyelectrolyte and a diblock copolymer with a thermosensitive poly(N-isopropyl-acrylamide) block and (B) and (C) two reference systems built solely from homo-polyelectrolytes of opposite charges. Thermal behavior and subsequent structural changes of the functionalized films against D sub 2 O were investigated by neutron reflectometry. All films showed irreversible annealing effects upon heating. In addition, the thermosensitive films showed a decrease in thickness at elevated temperature (>30 C) while the reference samples, composed of thermo-insensitive polyelectrolytes only, did not. (orig.)

  3. X-ray properties of the young open clusters HM1 and IC 2944/2948

    Science.gov (United States)

    Nazé, Y.; Rauw, G.; Sana, H.; Corcoran, M. F.

    2013-07-01

    Using XMM-Newton data, we study for the first time the X-ray emission of HM1 and IC 2944/2948. Low-mass, pre-main-sequence objects with an age of a few Myr are detected, as well as a few background or foreground objects. Most massive stars in both clusters display the usual high-energy properties of that type of objects, though with log [LX/LBOL] apparently lower in HM1 than in IC 2944/2948. Compared with studies of other clusters, it seems that a low signal-to-noise ratio at soft energies, due to the high extinction, may be the main cause of this difference. In HM1, the two Wolf-Rayet stars show contrasting behaviors: WR89 is extremely bright, but much softer than WR87. It remains to be seen whether wind-wind collisions or magnetically confined winds can explain these emissions. In IC 2944/2948, the X-ray sources concentrate around HD 101205; a group of massive stars to the north of this object is isolated, suggesting that there exist two subclusters in the field-of-view. Tables 2, 5, and Figs. 5, 9 are available in electronic form at http://www.aanda.orgBased on observations collected with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).Tables 1, 3 and 4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/555/A83

  4. Precision temperature monitoring (PTM) and Humidity monitoring (HM) sensors of the CMS electromagnetic calorimeter

    CERN Multimedia

    2006-01-01

    A major aspect for the ECAL detector control is the monitoring of the system temperature and the verification that the required temperature stability of the crystal volume and the APDs, expected to be (18 ± 0.05)C, is achieved. The PTM is designed to read out thermistors, placed on both the front and back of the crystals, with a relative precision better than 0.01 C. In total there are ten sensors per supermodule. The humidity level in the electronics compartment is monitored by the HM system and consists of one humidity sensor per module.

  5. Purification and properties of an acid phosphatase from Entamoeba histolytica HM-1:IMSS.

    Science.gov (United States)

    Aguirre-García, M M; Cerbón, J; Talamás-Rohana, P

    2000-04-24

    Entamoeba histolytica contains and secretes acid phosphatase, which has been proposed as a virulence factor in some pathogenic microorganisms. In this work, we purified and characterised a membrane-bound acid phosphatase (MAP) from E. histolytica HM-1:IMSS and studied the effect of different chemical compounds on the secreted acid phosphatase and MAP activities. MAP purification was accomplished by detergent solubilisation, and affinity and ion exchange chromatographies. The enzyme showed a pI of 5.5-6.2, an optimum pH of 5.5, and a Km value of 1.14 mM with p-nitrophenyl phosphate.

  6. Swellable drug-polyelectrolyte matrices of drug-carboxymethylcellulose complexes. Characterization and delivery properties.

    Science.gov (United States)

    Rigo, María V Ramírez; Allemandi, Daniel A; Manzo, Ruben H

    2009-02-01

    This article reports the development and delivery properties of swellable drug-polyelectrolyte matrices prepared with complexes of the acid form of carboxymethylcellulose (HCMC). Drug-polyelelectrolyte complexes (HCMC-D) were obtained by neutralization of HCMC with two model basic drugs (atenolol and metoclopramide). Characterization through FT-infrared spectroscopy, power X-ray diffraction, and DSC indicates the ionic nature of the interaction between the carboxylic groups of HCMC and the basic group of D. Matrices prepared by compacting (HCMC-D) alone or in a mixture with sodium carboxymethylcellulose were subjected to measurements of solvent up-take, dynamics of swelling, and release kinetics. Delivery rate of mixed matrices is a function of its composition and may be widely modulated. They exhibited anomalous delivery kinetics with Korsmeyer exponent n in the range 0.67-0.87. Experimental results indicate that the erosion of the hydrogel layer is the main delivery process.

  7. Ratchet rectification effect on the translocation of a flexible polyelectrolyte chain.

    Science.gov (United States)

    Mondal, Debasish; Muthukumar, M

    2016-08-28

    We report a three dimensional Langevin dynamics simulation of a uniformly charged flexible polyelectrolyte chain, translocating through an asymmetric narrow channel with periodically varying cross sections under the influence of a periodic external electric field. When reflection symmetry of the channel is broken, a rectification effect is observed with a favored direction for the chain translocation. For a given volume of the channel unit and polymer length, the rectification occurs below a threshold frequency of the external periodic driving force. We have also observed that the extent of the rectification varies non-monotonically with increasing molecular weight and the strength of geometric asymmetry of the channel. Observed non-monotonicity of the rectification performance has been interpreted in terms of a competition between two effects arising from the channel asymmetry and change in conformational entropy. An analytical model is presented with predictions consistent with the simulation results.

  8. The Effect of Salt on the Complex Coacervation of Vinyl Polyelectrolytes

    Directory of Open Access Journals (Sweden)

    Sarah L. Perry

    2014-06-01

    Full Text Available Complex coacervation is an electrostatically-driven phase separation phenomenon that is utilized in a wide range of everyday applications and is of great interest for the creation of self-assembled materials. Here, we utilized turbidity to characterize the effect of salt type on coacervate formation using two vinyl polyelectrolytes, poly(acrylic acid sodium salt (pAA and poly(allylamine hydrochloride (pAH, as simple models for industrial and biological coacervates. We confirmed the dominant role of salt valence on the extent of coacervate formation, while demonstrating the presence of significant secondary effects, which can be described by Hofmeister-like behavior. These results revealed the importance of ion-specific interactions, which are crucial for the informed design of coacervate-based materials for use in complex ionic environments, and can enable more detailed theoretical investigations on the role of subtle electrostatic and thermodynamic effects in complex coacervation.

  9. Morphology of cobalt ferrite nanoparticle-polyelectrolyte multilayered nanocomposites

    Science.gov (United States)

    Alcantara, G. B.; Paterno, L. G.; Fonseca, F. J.; Morais, P. C.; Soler, M. A. G.

    2011-05-01

    Novel magnetic nanocomposite films with controlled morphology were produced via the electrostatic layer-by-layer assembly of cationic CoFe 2O 4 nanoparticles and anionic poly(3,4-ethylenedioxy thiophene)/poly(styrene sulfonic acid) (PEDOT:PSS) complex. The electrostatic interaction between nanoparticle and the polyelectrolyte complex ensured a stepwise growth of the nanocomposite film with virtually identical amounts of materials being adsorbed at each deposition cycle as observed by UV-vis spectroscopy. AFM images acquired under the tapping mode revealed a globular morphology with dense and continuous layers of nanoparticles with voids being filled with polymeric material.

  10. Tailor-made polyelectrolyte microcapsules: from multilayers to smart containers.

    Science.gov (United States)

    Peyratout, Claire S; Dähne, Lars

    2004-07-19

    This review addresses the fabrication and properties of novel polyelectrolyte microcapsules, with an emphasis on their mechanical and permeability properties. Ease of preparation through layer-by-layer self assembly, accurate control over wall thickness as well as flexibility in the choice of constituents make these capsules very promising for numerous applications in materials and life science. Moreover, by engineering the inner and outer interfaces, these capsules can be used as microreactors for precipitation, crystallization, and polymerization reactions, as well as enzymatic, and heterogeneous catalysis.

  11. Preparation and Properties of Water-soluble Conjugated Polyelectrolyte

    Institute of Scientific and Technical Information of China (English)

    BAO Xiangjun; HONG Ruibin; HU Jianhua; ZHONG Yiping; LIU Ping; DENG Wenji

    2014-01-01

    The water-soluble conjugated polyelectrolyte, poly[3-(1′-ethyloxy-2′-N- methylimidazole) thiophene] (PEOIMT), was prepared. Its photophysical and electrochemical properties, and response characteristics to the external condition (e g, temperature response, solvent response and pH response), were investigated. The results show the PEOIMT belongs to the organic semiconductor. The interaction between the PEOIMT and the bovine serum albumin (BSA) was investigated using UV-vis spectroscopy. It was found that the PEOIMT could interact with the BSA. The PEOIMT can be used as a biosensor to detect the BSA.

  12. ANALYSIS OF VISCOSITY ABNORMALITIES OF POLYELECTROLYTES IN DILUTE SOLUTIONS

    Institute of Scientific and Technical Information of China (English)

    Jian-qiang Chen; Yu-fang Shao; Zhen Yang; Hu Yang; Rong-shi Cheng

    2011-01-01

    It was found that the interface effects in viscous capillary flow influenced the process of viscosity measurement greatly,and the abnormal viscosity behaviors of polyelectrolytes as well as neutral polymers in dilute solution region were ascribed to interface effect.According to this theory,we have reviewed the previous viscosity data of derivatives of poly-2-vinylpyridine reported by Maclay and Fuoss first.Then,the abnormal viscosity behaviors of a series of sodium polystyrene sulfonate samples with various molecular weights in dilute aqueous solutions were studied further.The solute adsorption behaviors and structural information of polymers have been discussed carefully.

  13. Encapsulation of Bacterial Spores in Nanoorganized Polyelectrolyte Shells (Postprint)

    Science.gov (United States)

    2009-05-27

    Baca, H.; Ashley, C.; Carnes , E.; Lopez, D.; Flemming, J.; Dunphy, D.; Singh, S.; Lopez, G.; Brozik, S.; Werner-Washburne, M.; Brinker, J. Science...concentration of aqueous polyelectrolytes was 2 mg/mL ( pH 6.8). All polymer samples were treated briefly in a sonicating bath and then vortex mixed before...positively charged and PGA is negatively charged at pH 6.5-7 due to amine and acid ionized Scheme 1 Figure 1. ζ-potential of a B. subtilis spore in DI water at

  14. Charge Inversion Effects in Electrophoresis of Polyelectrolytes in the Presence of Multivalent Counterions and Transversal Electric Fields

    Directory of Open Access Journals (Sweden)

    Sorin Nedelcu

    2014-12-01

    Full Text Available By molecular dynamics simulations we investigate the transport of charged polymers in confinement, under externally applied electric fields, in straight cylinders of uniform diameter and in the presence of monovalent or multivalent counterions. The applied electric field has two components; a longitudinal component along the axis of the cylinder and a transversal component perpendicular to the cylinder axis. The direction of electrophoretic velocity depends on the polyelectrolyte length, valency of the counterions present in solution and transversal electric field value. A statistical model is put forward in order to explain these observations.

  15. Computation of Isobaric Vapor-Liquid Equilibrium Data for Binary and Ternary Mixtures of Methanol, Water, and Ethanoic Acid from T, p, x, and HmE Measurements

    Directory of Open Access Journals (Sweden)

    Daming Gao

    2012-01-01

    Full Text Available Vapor-liquid equilibrium (VLE data for the strongly associated ternary system methanol + water + ethanoic acid and the three constituent binary systems have been determined by the total pressure-temperature-liquid-phase composition-molar excess enthalpy of mixing of the liquid phase (p, T, x, HmE for the binary systems using a novel pump ebulliometer at 101.325 kPa. The vapor-phase compositions of these binary systems had been calculated from Tpx and HmE based on the Q function of molar excess Gibbs energy through an indirect method. Moreover, the experimental T, x data are used to estimate nonrandom two-liquid (NRTL, Wilson, Margules, and van Laar model parameters, and these parameters in turn are used to calculate vapor-phase compositions. The activity coefficients of the solution were correlated with NRTL, Wilson, Margules, and van Laar models through fitting by least-squares method. The VLE data of the ternary system were well predicted from these binary interaction parameters of NRTL, Wilson, Margules, and van Laar model parameters without any additional adjustment to build the thermodynamic model of VLE for the ternary system and obtain the vapor-phase compositions and the calculated bubble points.

  16. Entering and exiting the protein-polyelectrolyte coacervate phase via nonmonotonic salt dependence of critical conditions.

    Science.gov (United States)

    Antonov, Margarita; Mazzawi, Malek; Dubin, Paul L

    2010-01-11

    Critical conditions for coacervation of poly(dimethyldiallylammonium chloride) (PDADMAC) with bovine serum albumin were determined as a function of ionic strength, pH, and protein/polyelectrolyte stoichiometry. The resultant phase boundaries, clearly defined with this narrow molecular weight distribution PDADMAC sample, showed nonmonotonic ionic strength dependence, with the pH-induced onset of coacervation (at pH(phi)) occurring most readily at 20 mM NaCl. The corresponding onset of soluble complex formation, pH(c), determined using high-precision turbidimetry sensitive to changes of less than 0.1% transmittance units, mirrored the ionic strength dependence of pH(phi). This nonmonotonic binding behavior is attributable to simultaneous screening of short-range attraction and long-range repulsion. The similarity of pH(c) and pH(phi) was explained by the effect of salt on protein binding, and consequently on the number of bound proteins relative to that required for charge neutralization of the complex, a requirement for phase separation. Expansion of the coacervation regime with chitosan, a polycation with charge spacing similar to that of PDADMAC, could be due to either the charge mobility or chain stiffness of the former. The pH(phi) versus I phase boundary for PDADMAC correctly predicted entrance into and egress from the coacervation region by addition of either salt or water. The ability to induce or suppress coacervation via protein/polyelectrolyte stoichiometry r was found to be consistent with the proposed model. The results indicate that the conjoint effects of I, r, and pH on coacervation could be represented by a three-dimensional phase boundary.

  17. Electrohydrodynamics of soft polyelectrolyte multilayers: point of zero-streaming current.

    Science.gov (United States)

    Duval, Jérôme F L; Küttner, David; Werner, Carsten; Zimmermann, Ralf

    2011-09-06

    We report a comprehensive formalism for the electrokinetics (streaming current, I(str)) at soft multilayered polyelectrolyte films. These assemblies generally consist of a succession of permeable diffuse layers that differ in charge density, thickness, and hydrodynamic softness. The model, which extends one that we recently reported for the electrokinetics of monolayered soft thin films (Langmuir 2010, 26, 18169-18181), is valid without any restriction in the number and thickness of layers, or in the degree of dissociation and density of ionizable groups they carry. It further covers the limiting cases of hard and free draining films and correctly compares to semianalytical expressions derived for I(str) under conditions where the Debye-Hückel approximation applies. The flexibility of the theory is illustrated by simulations of I(str) for a two-layer assembly of cationic and anionic polymers over a large range of pH values and electrolyte concentrations. On this basis, it is shown that the point of zero streaming current (PZSC) of soft multilayered interphases, defined by the pH value where I(str) = 0, generally depends on the concentration of the (indifferent) electrolyte. The magnitude and direction of the shift in PZSC with varying salinity are intrinsically governed by the dissymmetry in protolytic characteristics and density of dissociable groups within each layer constituting the film, together with the respective film thickness and hydrodynamic softness. The fundamental effects covered by the theory are illustrated by streaming current measurements performed on two practically relevant systems, a polyelectrolyte bilayer prepared from poly(ethylene imine) (PEI) and poly(acrylic acid) (PAA) and a polymer-cushioned (PEI) bilayer lipid membrane.

  18. Auricularia auricular polysaccharide-low molecular weight chitosan polyelectrolyte complex nanoparticles: Preparation and characterization

    Directory of Open Access Journals (Sweden)

    Wei Xiong

    2016-06-01

    Full Text Available Novel polyelectrolyte complex nanoparticles (AAP/LCS NPs were prepared in this study and these were produced by mixing negatively charged auricularia auricular polysaccharide (AAP with positively charged low molecular weight chitosan (LCS in an aqueous medium. The AAP was extracted and purified from auricularia auricular, and then characterized by micrOTOF-Q mass spectrometry, UV/Vis spectrophotometry, moisture analyzer and SEM. The yield, moisture, and total sugar content of the AAP were 4.5%, 6.2% and 90.12% (w/w, respectively. The AAP sample was water-soluble and exhibited white flocculence. The characteristics of AAP/LCS NPs, such as the particle size, zeta potential, morphology, FT-IR spectra, DSC were investigated. The results obtained revealed that the AAP/LCS NPs had a spherical shape with a diameter of 223 nm and a smooth surface, and the results of the FT-IR spectra and DSC investigations indicated that there was an electrostatic interaction between the two polyelectrolyte polymers. Bovine serum albumin (BSA, pI = 4.8 and bovine hemoglobin (BHb, pI = 6.8 were used as model drugs to investigate the loading and release features of the AAP/LCS NPs. The results obtained showed that the AAP/LCS NPs had a higher entrapment efficiency (92.6% for BHb than for BSA (81.5%. The cumulative release of BSA and BHb from AAP/LCS NPs after 24 h in vitro was 95.4% and 91.9%, respectively. The in vitro release demonstrated that AAP/LCS NPs provided a sustained release matrix suitable for the delivery of protein drugs. These studies demonstrate that AAP/LCS NPs have a very promising potential as a delivery system for protein drugs.

  19. Self-Assembly of Metallic and Magnetic Nanoparticles into Polyelectrolyte Multilayers

    Science.gov (United States)

    Riffard, Lucie

    Gold nanoparticles were wrapped with polyelectrolytes and were deposited on a substrate coated with polyelectrolyte multilayer films. The adsorption of the colloids on the surface was followed by AFM and UV-VIS spectroscopy. The results suggested that the deposition of particles on a surface was performed successfully just by using a very simple and quick dipping method. Using the same technique, magnetic particles were coated with polyelectrolytes and deposited on polyelectrolyte multilayer films. Once again the adsorption of the particles on polymer films was achieved and more complex assemblies were then built. They consisted of a succession of polyelectrolyte films and magnetic nanoparticles. As the colloids exhibit magnetic properties, the possibility of controlling properties of thin polymer films with a strong magnet is investigated. Magnetic colloids were embedded into a polymer assembly which undergoes the effects of a magnet. Its thickness changes were analyzed by ellipsometry when the sample was immersed in water. It appeared that magnetic nanoparticles were able to squeeze a polyelectrolyte thin film in presence of a magnet, despite the polymer chains resistance. This phenomenon can be used as nano-switches in various applications in medical field for example. In the future, it could be interesting to study the effect of an oscillating magnetic field on composite polyelectrolyte multilayer-magnetic particles. If the thickness fluctuates with the magnetic field, new applications towards the nanodisplacement of a fluid on a surface can be possible: the oscillations at the surface moving the adjacent fluid.

  20. Influence of higher valent ions on flexible polyelectrolyte stiffness and counter-ion distribution.

    Science.gov (United States)

    Chremos, Alexandros; Douglas, Jack F

    2016-04-28

    We investigate the influence of counter-ion valency on the flexibility of highly charged flexible polymer chains using molecular dynamics simulations that include both salt and an explicit solvent. As observed experimentally, we find that divalent counter-ions greatly reduce the chain persistence length, lp, in comparison with monovalent counter-ions. On the other hand, polyelectrolyte chains having trivalent counter-ions adopt a much more compact conformation than polyelectrolytes having monovalent and divalent counter-ions. We demonstrate that the tendency of polyelectrolyte chains to become deformed by proximal high valence counter-ions is due to chain "coiling" around the counter-ions. In particular, we find that the number of contacts that the proximal counter-ions have with the polyelectrolyte dictates the extent of chain coiling. This ion-binding induced coiling mechanism influences not only the conformational properties of the polyelectrolyte, but also the counter-ion distribution around the chain. Specifically, we find that higher valent counter-ions lead both to a counter-ion enrichment in close proximity to the polyelectrolyte and to a significant reduction in the spatial extent of the diffuse counter-ion cloud around the polyelectrolyte.

  1. Key considerations in the determination of polyelectrolyte concentration by the colloidal titration method

    Directory of Open Access Journals (Sweden)

    Miguel A. Zanuttini

    2007-01-01

    Full Text Available Medium or high charge density cationic polyelectrolytes are frequently used for water treatment. In the papermaking wet-end they are used as retention agents or as flocculating aids. Negative polyelectrolytes that enter the papermaking system increase the demand for cationic poly-electrolytes. Polyelectrolyte concentration can be determined by the colloidal titration method, using either of two options for detecting the endpoint: i visual observation or spectrophotometric determination of the colour change of an indicator, or ii streaming current measurement. This work discusses the best conditions for the application of the titration using spectrophotometric measurement for the end point detection. Poly-diallyldimethylammonium chloride was used as the cationic polyelec-trolyte, potassium polyvinyl sulphate as the negative polyelectrolyte, and o-toluidine blue as the positive indicator dye. The polyelectrolyte concen-tration range, interference from the metal ions affecting the indicator color change, the optimal indicator concentration to avoid precipitation problems, and the effect of adding a surfactant to the indicator solution were also considered. Titration curves were analyzed and optimized. Under these conditions the technique provided results with acceptable precision.

  2. Impact of polyelectrolytes and their corresponding multilayers to human primary endothelial cells.

    Science.gov (United States)

    Nolte, Andrea; Hossfeld, Susanne; Schroeppel, Birgit; Mueller, Anne; Stoll, Dieter; Walker, Tobias; Wendel, Hans Peter; Krastev, Rumen

    2013-07-01

    The layer-by-layer technique, which allows simple preparation of polyelectrolyte multilayers, came into the focus of research for development of functionalized medical devices. Numerous literature exist that concentrate on the film build-up and the behaviour of cells on polyelectrolyte multilayers. However, in case of very soft polyelectrolyte multilayers, studies of the cell behaviour on these films are sometimes misleading with regard to clinical applications because cells do not die due to cytotoxicity but due to apoptosis by missing cell adhesion. It turns out that the adhesion in vitro, and thus, the viability of cells on polyelectrolyte multilayers is mostly influenced by their mechanical properties. In order to decide, which polyelectrolyte multilayers are suitable for implants, we take this problem into account by putting the substrates with soft films on top of pre-cultured human primary endothelial cells ('reverse assay'). Hence, the present work aims giving a more complete and reliable study of typical polyelectrolyte multilayers with regard to clinical applications. In particular, coatings consisting of hyaluronic acid and chitosan as natural polymers and sulfonated polystyrene and polyallylamine hydrochlorite as synthetic polymers were studied. The adsorption of polyelectrolytes was characterized by physico-chemical methods which show regular buildup. Biological examination of the native or modified polyelectrolyte multilayers was based on their effect to cell adhesion and morphology of endothelial cells by viability assays, immunostaining and scanning electron microscopy. Using the standard method, which is typically applied in literature--seeding cells on top of films--shows that the best adhesion and thus, viability can be achieved using sulfonated polystyrene/polyallylamine hydrochlorite. However, putting the films on top of endothelial cells reveals that hyaluronic acid/chitosan may also be suitable for clinical applications: This result is

  3. Catalytic polyelectrolyte multilayers at the bipolar membrane interface.

    Science.gov (United States)

    Abdu, Said; Sricharoen, Kittikun; Wong, John E; Muljadi, Eko S; Melin, Thomas; Wessling, Matthias

    2013-11-13

    Bipolar membranes are laminated anion and cation exchange membranes that split water at their interface very efficiently upon application of an electric field. This paper investigates the layer-by-layer (LbL) deposition of polyelectrolyte multilayers, as a tool to introduce molecularly thin catalyst groups at this interface of bipolar membranes. The bipolar membranes were prepared by first modifying an anion exchange membrane by consecutive dipping LbL assembly, then casting a thin highly charged intermediate layer followed by casting a cation exchange layer. The results reveal that polyelectrolytes of higher charge density coated on the anion exchange layer yield better performance. Several parameters of the LbL interface deposition were varied. Out of the investigated LbL assembly parameters, ionic strength and number of layers have shown the largest influence on catalytic activity as well as ionic selectivity. The membrane with two bilayers of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) and poly(ethyleneimine) (PEI), where the PEI was prepared in 0.5 M NaCl, gave rise to the best performance. Surprisingly, detailed data analysis at low electrical potential suggests that the interface layers of a bipolar membrane play a major role in its permselectivity. Previously, only the bulk thickness of the anion and cation exchange membrane was assumed to influence the bipolar membrane selectivity.

  4. Study of sporadical properties of crosslinked polyelectrolyte multilayers

    Science.gov (United States)

    Balu, Deebika

    Polyelectrolyte multilayers (PEM) have become a highly studied class of materials due to the range of their applicability in many areas of research, including biology, chemistry and materials science. Recent advances in surface coatings have enabled modification of PEM surfaces to provide desirable properties such as controlled release, super-hydrophobicity, biocompatibility, antifouling and antibacterial properties. In the past decade, antimicrobial PEM coatings have been investigated as a safer alternative to the traditional disinfection methods that usually involve application of hazardous chemicals onto the surface to be cleaned. These antimicrobial coatings could be applied to common surfaces prone to colonization of bacteria (such as bench tops, faucet handles, etc) to supplement routine sanitization protocols by providing sustained antimicrobial activity. Vegetative bacteria (such as Escherichia coli) are more susceptible to antimicrobial agents than bacterial species that form spores. Hence, the antimicrobial activity of PEM coatings fabricated using Layer by Layer (LbL) technique were assayed using Bacillus anthracis spores (Sterne strain). In this thesis, the sporicidal effect of various polyelectrolyte multilayer coatings containing cross-linked polymers immersed in bleach have been evaluated as potential augmentation to existing disinfection methods.

  5. Charge regulation and local dielectric function in planar polyelectrolyte brushes.

    Science.gov (United States)

    Kumar, Rajeev; Sumpter, Bobby G; Kilbey, S Michael

    2012-06-21

    Understanding the effect of inhomogeneity on the charge regulation and dielectric properties, and how it depends on the conformational characteristics of the macromolecules is a long-standing problem. In order to address this problem, we have developed a field-theory to study charge regulation and local dielectric function in planar polyelectrolyte brushes. The theory is used to study a polyacid brush, which is comprised of chains end-grafted at the solid-fluid interface, in equilibrium with a bulk solution containing monovalent salt ions, solvent molecules, and pH controlling acid. In particular, we focus on the effects of the concentration of added salt and pH of the bulk in determining the local charge and dielectric function. Our theoretical investigations reveal that the dipole moment of the ion-pairs formed as a result of counterion adsorption on the chain backbones play a key role in affecting the local dielectric function. For polyelectrolytes made of monomers having dipole moments lower than the solvent molecules, dielectric decrement is predicted inside the brush region. However, the formation of ion-pairs (due to adsorption of counterions coming from the dissociation of added salt) more polar than the solvent molecules is shown to increase the magnitude of the dielectric function with respect to its bulk value. Furthermore, an increase in the bulk salt concentration is shown to increase the local charge inside the brush region.

  6. Formation of Soft Nanoparticles via Polyelectrolyte Complexation: A Viscometric Study

    Directory of Open Access Journals (Sweden)

    Rondon Céline

    2014-05-01

    Full Text Available This paper describes the formation of soft nanoparticles resulting from electrostatically driven complexation of oppositely charged polyelectrolytes. The system was composed of a strong polyanion (polystyrene sulfonate, PSS and a weak polycation (poly(allylamine hydrochloride, PAH in large excess. Soft nanoparticles were obtained by pouring a PSS solution into a PAH one under constant stirring. The polyelectrolyte complexes (PEC were characterized through a viscometric study complemented by Dynamic Light Scattering (DLS, electrophoretic mobility and suspension turbidity measurements. PEC suspensions were centrifuged and by measuring the viscosity of the supernatant, we were able to estimate the free polycation concentration and hence the percentage of complexed polycation. We also measured the relative viscosity of the suspensions; from the estimated contribution of the PEC particles and of the polycation in excess, the average particle volume fraction was estimated. From all viscometric data, we could derive the evolution of the binding stoichiometry in PEC and of the effective particle volume fraction as a function of the mixing ratio (ratio of the cationic to anionic groups and of the pH. Our results emphasize the importance of charge accessibility in controlling both the stoichiometry and packing density of the complexes.

  7. Responsive block copolymer photonics triggered by protein-polyelectrolyte coacervation.

    Science.gov (United States)

    Fan, Yin; Tang, Shengchang; Thomas, Edwin L; Olsen, Bradley D

    2014-11-25

    Ionic interactions between proteins and polyelectrolytes are demonstrated as a method to trigger responsive transitions in block copolymer (BCP) photonic gels containing one neutral hydrophobic block and one cationic hydrophilic block. Poly(2-vinylpyridine) (P2VP) blocks in lamellar poly(styrene-b-2-vinylpyridine) block copolymer thin films are quaternized with primary bromides to yield swollen gels that show strong reflectivity peaks in the visible range; exposure to aqueous solutions of various proteins alters the swelling ratios of the quaternized P2VP (QP2VP) gel layers in the PS-QP2VP materials due to the ionic interactions between proteins and the polyelectrolyte. Parameters such as charge density, hydrophobicity, and cross-link density of the QP2VP gel layers as well as the charge and size of the proteins play significant roles on the photonic responses of the BCP gels. Differences in the size and pH-dependent charge of proteins provide a basis for fingerprinting proteins based on their temporal and equilibrium photonic response. The results demonstrate that the BCP gels and their photonic effect provide a robust and visually interpretable method to differentiate different proteins.

  8. Emulsion-core and polyelectrolyte-shell nanocapsules: biocompatibility and neuroprotection against SH-SY5Y cells

    Energy Technology Data Exchange (ETDEWEB)

    Piotrowski, Marek, E-mail: ncpiotro@cyf-kr.edu.pl; Szczepanowicz, Krzysztof [Polish Academy of Sciences, Jerzy Haber Institute of Catalysis and Surface Chemistry (Poland); Jantas, Danuta; Leśkiewicz, Monika; Lasoń, Władysław [Polish Academy of Sciences, Institute of Pharmacology (Poland); Warszyński, Piotr [Polish Academy of Sciences, Jerzy Haber Institute of Catalysis and Surface Chemistry (Poland)

    2013-11-15

    The emulsion-core and polyelectrolyte-coated nanocapsules, designed as water-insoluble neuroprotective drug delivery system, were synthesized using layer-by-layer saturation method. The isopropyl myristate was used as oil phase and docusate sodium salt as emulsifier. For the polyelectrolyte shell preparation, synthetic polyelectrolytes, cationic (PDADMAC, PAH, and PLL) and anionic (PGA) were used. The particle size and zeta potential of nanocapsules were characterized by the dynamic light scattering. The average size of synthesized nanocapsules ranged from ∼80 to ∼100 nm. Zeta potential values ranged from less than approximately −30 mV for the polyanion layers to greater than approximately +30 mV for the polycation layers. Biocompatibilities of the synthesized nanocarriers were evaluated against SH-SY5Y human neuroblastoma cells using various biochemical assays. The results obtained show that synthesized nanocapsules coated with PLL and PGA were nontoxic to SH-SY5Y cells, and they were used as nanocarriers for model neuroprotective drug (a calpain inhibitor MDL 28170). The neuroprotective action of the encapsulated MDL 28170 against hydrogen peroxide-induced oxidative stress cytotoxicity was evaluated in the same cell line. The results showed that nanoencapsulated form of MDL 28170 were biocompatible and protected SH-SY5Y cells against the H{sub 2}O{sub 2} (0.5 mM/24 h)-induced damage in 20–40 times lower concentrations than those of the same drug added directly to the culture medium. These data suggest that the nanoscale carriers of neuroprotective drugs might serve as novel promising therapeutic agents for oxidative stress-related neurodegenerative processes.

  9. Polyelectrolyte Conformation, Interactions and Hydrodynamics as Studied by Light Scattering.

    Science.gov (United States)

    Ghosh, Snehasish

    Polyelectrolyte conformation, interactions and hydrodynamics show a marked dependence on the ionic strength (C_{rm s}) of the medium, the concentration (C_{rm p}) of the polymer itself and their charge density (xi). The apparent electrostatic persistence length obtained from static light scattering varied approximately as the inverse square root of C _{rm s} for highly pure, high molecular weight hyaluronate (HA) as well as for variably ionized acrylamide/sodium acrylate copolymers (NaPAA), and linearly with xi. The experimental values of persistence length and second virial coefficient (A_2) are compared to predictions from theories based on the Debye-Huckel approximation for the Poisson-Boltzmann equation and on excluded-volume. Although the mean square radius of gyration () depended strongly on C _{rm s}. decreasing with increasing C_{rm s} for both HA and NaPAA indicating clear evidence of polyion expansion, dynamic light scattering values of the translational diffusion coefficient (D) remains constant when extrapolated to infinite polymer concentration for both the polymers. The behavior of D is compared to predictions from coupled mode theory in the linear limit. The effects of NaOH on the conformations, interactions, diffusion and hydrolysis rates of HA are characterized in detail using static, dynamic and time-dependent light scattering supplemented by size exclusion chromatography (SEC). For the HA , A_2 and the hydrolysis rates all resemble superposing titration curves, while the D remains independent of both the concentration of NaOH, and the contraction of . The indication is that the interactions, conformations and the hydrolysis rates are all controlled by the titration of the HA hydroxyl groups by the NaOH to yield -O ^-, which (i) destroys single strand hydrogen bonds, leading to de-stiffening and contraction of the HA coil and a large decrease in intermolecular interaction, and (ii) slowly depolymerizes HA. The experimental results of HA

  10. Tribological behavior of HM1 steel fabricated by precision spray forming under high temperature

    Science.gov (United States)

    Cheng, Y. Q.; Zhang, P.; Zhu, M. D.; Sun, Y. S.

    2015-12-01

    In this study, we investigated the tribological behavior of HM1 steel fabricated by precision spay forming (PSF). WE used block ring friction test for our investigation, at various temperature, which was compared with that of the as-cast specimen. The results indicate that the wear rate and the friction coefficient of the PSFed specimen are reduced compared to that of the as-cast specimen. Attribution to these results is the fine grain, the eliminated segregation of elements, and the uniformly distributed matrix material elements for the PSFed specimen. SEM morphology of wear scar shows that the mainly wear mechanism of the as-cast specimen is adhesive wear, while the wear mechanism of the PSFed specimen is mainly abrasive wear.

  11. ähm vs. niinku - Verzögerungssignale in deutschen und finnischen Diskussionen

    Directory of Open Access Journals (Sweden)

    Margarethe Olbertz-Siitonen

    2015-05-01

    Full Text Available Dieser Beitrag beschäftigt sich kontrastiv mit dem Gebrauch von Verzögerungssignalen in deutschen und finnischen Seminardiskussionen. Die voranalytische  Durchsicht der Videomitschnitte zeigte, dass die deutschen Studenten unvergleichlich  häufiger die Verzögerungspartikeln äh und ähm  einsetzten als ihre finnischen Kommilitonen, die in ähnlicher Funktion v.a. die Partikel niinku ('sozusagen' benutzten. Diese  Beobachtung ist insofern von Bedeutung, als es meist die finnischen Gesprächsteilnehmer sind, die in deutsch-finnischen Kontaktsituationen auf eine Fremdsprache (Deutsch  zurückgreifen müssen: Möglicherweise steht finnischen Gesprächspartnern in der Interaktion mit deutschen Muttersprachlern keine deutsche Entsprechung für niinku zur Ver- fügung. Gegebenenfalls resultierende Kommunikationsprobleme sollten dementsprechend nicht vornehmlich interkulturell, sondern interlingual bewertet werden.

  12. Strong Typed Böhm Theorem and Functional Completeness on the Linear Lambda Calculus

    Directory of Open Access Journals (Sweden)

    Satoshi Matsuoka

    2016-04-01

    Full Text Available In this paper, we prove a version of the typed Böhm theorem on the linear lambda calculus, which says, for any given types A and B, when two different closed terms s1 and s2 of A and any closed terms u1 and u2 of B are given, there is a term t such that t s1 is convertible to u1 and t s2 is convertible to u2. Several years ago, a weaker version of this theorem was proved, but the stronger version was open. As a corollary of this theorem, we prove that if A has two different closed terms s1 and s2, then A is functionally complete with regard to s1 and s2. So far, it was only known that a few types are functionally complete.

  13. [Evaluation of crossing calibration of (123)I-MIBG H/M ration, with the IDW scatter correction method, on different gamma camera systems].

    Science.gov (United States)

    Kittaka, Daisuke; Takase, Tadashi; Akiyama, Masayuki; Nakazawa, Yasuo; Shinozuka, Akira; Shirai, Muneaki

    2011-01-01

    (123)I-MIBG Heart-to-Mediastinum activity ratio (H/M) is commonly used as an indicator of relative myocardial (123)I-MIBG uptake. H/M ratios reflect myocardial sympathetic nerve function, therefore it is a useful parameter to assess regional myocardial sympathetic denervation in various cardiac diseases. However, H/M ratio values differ by site, gamma camera system, position and size of region of interest (ROI), and collimator. In addition to these factors, 529 keV scatter component may also affect (123)I-MIBG H/M ratio. In this study, we examined whether the H/M ratio shows correlation between two different gamma camera systems and that sought for H/M ratio calculation formula. Moreover, we assessed the feasibility of (123)I Dual Window (IDW) method, which is a scatter correction method, and compared H/M ratios with and without IDW method. H/M ratio displayed a good correlation between two gamma camera systems. Additionally, we were able to create a new H/M calculation formula. These results indicated that the IDW method is a useful scatter correction method for calculating (123)I-MIBG H/M ratios.

  14. Excimer formation and singlet-singlet energy transfer of organoluminophores in the premicellar and micellar-polyelectrolytes solutions

    Science.gov (United States)

    Bisenbaev, Adel K.; Levshin, L. V.; Saletsky, A. M.

    1991-05-01

    Recently the investigation of photoprocesses in organized synthetical structures (ionic micelles, vesicles, linear polyelectrolytes, polymer gels etc.), intermolecular interactions of which are formed by hydrophobic and electric forces, have been of great interest.12 These systems are of particular interest due to the possibility of using luminescent data, which reflected the peculiarities of photoprocesses in organized assemblies. This can be used to establishing the mechanism of photobiological processes. Due to the very complex nature of biostructures our approximation can be considered phenomenological, however it gives the possibility of revealing the energy dissipation path in biosystems. Such model approach is based on a principal resemblance between a living matter and synthetical polymolecular structures with a certain degree of organization. This resemblance is displayed in theoretical models of synthetic polymers,3 which are the foundation of modern ideas on biomolecule conformation. Organized synthetical structures like ionic micelles, polymer gel, bilayer and strong polyelectrolytes could be made to represent biosystems like cell, protoplasm, membrane and NADH, respectively. In this paper we report some new results on the complex formation of dyes and detergents in premicellar region and singlet-singlet energy transfer from pyrene (Py) excimer to dye monomers in ionic micellar-polyion-water system.

  15. Periodic nanoscale patterning of polyelectrolytes over square centimeter areas using block copolymer templates.

    Science.gov (United States)

    Oded, Meirav; Kelly, Stephen T; Gilles, Mary K; Müller, Axel H E; Shenhar, Roy

    2016-05-18

    Nano-patterned materials are beneficial for applications such as solar cells, opto-electronics, and sensing owing to their periodic structure and high interfacial area. Here, we present a non-lithographic approach for assembling polyelectrolytes into periodic nanoscale patterns over cm(2)-scale areas. Chemically modified block copolymer thin films featuring alternating charged and neutral domains are used as patterned substrates for electrostatic self-assembly. In-depth characterization of the deposition process using spectroscopy and microscopy techniques, including the state-of-the-art scanning transmission X-ray microscopy (STXM), reveals both the selective deposition of the polyelectrolyte on the charged copolymer domains as well as gradual changes in the film topography that arise from further penetration of the solvent molecules and possibly also the polyelectrolyte into these domains. Our results demonstrate the feasibility of creating nano-patterned polyelectrolyte layers, which opens up new opportunities for structured functional coating fabrication.

  16. Electrodeposition of a palladium nanocatalyst by ion confinement in polyelectrolyte multilayers.

    Science.gov (United States)

    Vago, Miguel; Tagliazucchi, Mario; Williams, Federico J; Calvo, Ernesto J

    2008-11-30

    A highly efficient and selective material for electrocatalytic hydrogenation has been prepared by depositing monodisperse palladium nanoparticles of size (6+/-1) nm by electrochemical reduction of PdCl(4)(2-) confined in a polyelectrolyte multilayer film.

  17. STUDY OF THE DIGESTED SLUDGE DEWATERING EFFECTIVENESS USING POLYELECTROLYTE GEL BASED ON ORGANIC POLYMERS

    Directory of Open Access Journals (Sweden)

    Marcin Głodniok

    2016-02-01

    Full Text Available The paper addresses the problems connected with sewage sludge dewatering. The premise of the study was the analysis of whether there are opportunities to increase the efficiency of dewatering sludge, a relatively low-cost involving the use of innovative polymers. The authors analyzed the impact of the new type of polyelectrolyte gel on the effectiveness of dewatering sludge. Laboratory studies were carried out at polyelectrolyte dose selection and laboratory testing on the press chamber designed to simulate the actual operation of sludge dewatering system. Two different doses of polyelectrolyte were tested for dose I – 4 ml/m3 and dose II – 8 ml/m3. The conducted analysis on laboratory press showed an increase of sludge dewatering efficiency by about 2% for dose no. I and by about 13% for dose no. II, in comparison to the test without polyelectrolyte.

  18. Evaluation of Brāhmī ghṛtam in children suffering from Attention Deficit Hyperactivity Disorder

    Directory of Open Access Journals (Sweden)

    Supriya Bhalerao

    2013-01-01

    Full Text Available Introduction: Attention Deficit Hyperactivity Disorder (ADHD is characterized by a persistent pattern of inattention and/or hyperactivity-impulsivity. In view of the adverse effects associated with psycho-stimulants used for the treatment of this disorder, efficacy of Brāhmīghṛtam was evaluated in this condition. Materials and Methods: After following due ethical considerations, children of either sex between the age group of 6 and 12 years diagnosed to be suffering from mixed variety of ADHD as per The Diagnostic and Statistical Manual of Mental Disorders (DSM IV criteria irrespective of other co-morbid psychiatric illnesses were recruited in the study. Initially a pilot study (n = 10 was carried out to confirm the efficacy of the identified dose of Brāhmīghṛtam. Using this dose, further therapeutic confirmatory study (n = 27 was carried out, wherein Brāhmīghṛtam was compared with methylphenidate. Effect on ADHD symptoms was assessed using the Dupaul ADHD rating scale and this was the main efficacy parameter. Results: In the pilot exploratory study, Brāhmīghṛtam showed 66% decrease in total ADHD score. In the therapeutic confirmatory study, only 16% improvement was seen with Brāhmīghṛtam, which was similar to methylphenidate, standard treatment for ADHD that was used as a comparator in the present study. No side-effects were reported in both studies. Conclusion: Our study thus has adequately demonstrated efficacy and safety of Brāhmīghṛtam in ADHD.

  19. Interactions of a family 18 chitinase with the designed inhibitor HM508 and its degradation product, chitobiono-delta-lactone.

    Science.gov (United States)

    Vaaje-Kolstad, Gustav; Vasella, Andrea; Peter, Martin G; Netter, Catharina; Houston, Douglas R; Westereng, Bjørge; Synstad, Bjørnar; Eijsink, Vincent G H; van Aalten, Daan M F

    2004-01-30

    We describe enzymological and structural analyses of the interaction between the family 18 chitinase ChiB from Serratia marcescens and the designed inhibitor N,N'-diacetylchitobionoxime-N-phenylcarbamate (HM508). HM508 acts as a competitive inhibitor of this enzyme with a K(i) in the 50 microM range. Active site mutants of ChiB show K(i) values ranging from 1 to 200 microM, providing insight into some of the interactions that determine inhibitor affinity. Interestingly, the wild type enzyme slowly degrades HM508, but the inhibitor is essentially stable in the presence of the moderately active D142N mutant of ChiB. The crystal structure of the D142N-HM508 complex revealed that the two sugar moieties bind to the -2 and -1 subsites, whereas the phenyl group interacts with aromatic side chains that line the +1 and +2 subsites. Enzymatic degradation of HM508, as well as a Trp --> Ala mutation in the +2 subsite of ChiB, led to reduced affinity for the inhibitor, showing that interactions between the phenyl group and the enzyme contribute to binding. Interestingly, a complex of enzymatically degraded HM508 with the wild type enzyme showed a chitobiono-delta-lactone bound in the -2 and -1 subsites, despite the fact that the equilibrium between the lactone and the hydroxy acid forms in solution lies far toward the latter. This shows that the active site preferentially binds the (4)E conformation of the -1 sugar, which resembles the proposed transition state of the reaction.

  20. Controlled Release of the Indomethacin Microencapsulation Based on Layer-by-layer Assembly by Polyelectrolyte Multilayers

    Institute of Scientific and Technical Information of China (English)

    CHEN You-fang; LIN Xian-fu

    2007-01-01

    Indomethacin has been encapsulated with polyelectrolyte multilayers for controlled release. Gelatin and alginate were alternatively deposited on indomethacin microcrystals. The released amount of indomethacin from coated microcrystals in pH6. 8phosphate buffer solution (PBS) was measured with a UV spectrophometer. The polyelectrolyte multilayer capsule thickness was proved to control the release rate. The effects of osmotic pressure existed during the release process of indomethacin from microcapsules coated by (gelatin/alginate) 4.

  1. BINDING OF IONIC SURFACTANTS ON OPPOSITELY CHARGED POLYELECTROLYTES OBSERVED BY FLUORESCENCE METHODS

    Institute of Scientific and Technical Information of China (English)

    Zhen Tong; Chao-yang Wang; Bi-ye Ren; Xin-xing Liu; Fang Zeng

    2003-01-01

    Our recent studies concerning the binding of ionic surfactants on oppositely charged polyelectrolytes observed with fluorescence techniques are reviewed. The cationic surfactants cetyltrimethylammonium bromide (CTAB),dodecyltrimethylammonium chloride (DTAC), and nonionic surfactant octaethylene glycol monododecyl ether (C12E8) were allowed to bind on anionic poly(2-acrylamido-2-methylpropanesulfonic acid) (PAMPS) and its pyrene and/or naphthalene labeled copolymers. The relative excimer emission intensity IE/IM of a cationic probe 1-pyrenemethylamine hydrochloride were chosen to monitor the binding process and the conformation change of surfactant-bound polyelectrolytes. The 1:1aggregation of polyelectrolyte-CTAB with respect to the charge was found as long as the CTAB concentration was slightly higher than its critical aggregation concentration (CAC). The intermolecular NRET indicated that the CTAB-bound polyelectrolytes aggregated together through the hydrophobic interaction between the CTAB tails. However, neither 1:1polyelectrolyte-DTAC aggregation nor intermolecular aggregation of DTAC-bound polyelectrolyte was observed owing to its weaker hydrophobicity of 12 carbon atoms in the tail, which is shorter than that of CTAB. As known from the fluorescence results, nonionic surfactant C12E8 did not bind on the anionic polyelectrolytes, but the presence of PAMPS promoted the micelle formation for C12E8 at the CAC slightly below its critical micelle concentration (CMC). The solid complex of dansyl labeled AMPS copolymer-surfactant exhibited a decrease in local polarity with increasing charge density of the polyelectrolyte or with alkane tail length of the surfactant. SAXS suggested a lamella structure for the AMPS copolymersurfactant solid complexes with a long period of 3.87 nm for CTAB and 3.04 nm for DTAC, respectively.

  2. Environmentally friendly cellulose-based polyelectrolytes in wastewater treatment.

    Science.gov (United States)

    Grenda, Kinga; Arnold, Julien; Gamelas, José A F; Rasteiro, Maria G

    2017-09-01

    Natural-based polyelectrolytes (PELs), with all the advantages coming from being produced from renewable and biodegradable sources, are a potential solution for the removal of dyes from wastewater. In this work, surplus Eucalyptus bleached cellulose fibres from a paper mill were modified to increase the charge and solubility of cellulose. First, reactive aldehyde groups were introduced in the cellulose backbone by periodate oxidation of cellulose. Further modification with alkylammonium produced positively charged cellulose-based PELs. The final products were characterized by several analytical techniques. The PEL with the highest substitution degree of cationic groups was evaluated for its performance in decolouration processes, bentonite being used as aid. This was found to be effective for colour removal of either anionic or cationic dyes. Bio-PELs can thus be considered as very favourable eco-friendly flocculation agents for decolouration of harsh effluents from several industries, considering their biodegradable nature and thus the ability to produce less sludge.

  3. Morphology of cobalt ferrite nanoparticle-polyelectrolyte multilayered nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Alcantara, G.B.; Paterno, L.G. [Universidade de Brasilia, Instituto de Fisica, Brasilia-DF 70910-900 (Brazil); Fonseca, F.J. [Universidade de Sao Paulo, EPUSP, Depto de Engenharia de Sistemas Eletronicos, Sao Paulo-SP 05508-900 (Brazil); Morais, P.C. [Universidade de Brasilia, Instituto de Fisica, Brasilia-DF 70910-900 (Brazil); Soler, M.A.G., E-mail: soler@unb.b [Universidade de Brasilia, Instituto de Fisica, Brasilia-DF 70910-900 (Brazil)

    2011-05-15

    Novel magnetic nanocomposite films with controlled morphology were produced via the electrostatic layer-by-layer assembly of cationic CoFe{sub 2}O{sub 4} nanoparticles and anionic poly(3,4-ethylenedioxy thiophene)/poly(styrene sulfonic acid) (PEDOT:PSS) complex. The electrostatic interaction between nanoparticle and the polyelectrolyte complex ensured a stepwise growth of the nanocomposite film with virtually identical amounts of materials being adsorbed at each deposition cycle as observed by UV-vis spectroscopy. AFM images acquired under the tapping mode revealed a globular morphology with dense and continuous layers of nanoparticles with voids being filled with polymeric material. - Research Highlights: Novel magnetic nanocomposite films with controlled morphology assembled by layer-by-layer. Electrostatic interaction of cationic CoFe{sub 2}O{sub 4} nanoparticles and anionic (PEDOT:PSS). Globular morphology of dense layers of nanoparticles with voids being filled with polymeric material.

  4. PROPERTIES OF DOUBLE-STRANDED DNA AS A POLYELECTROLYTE.

    Science.gov (United States)

    OHNISHI, T

    1963-11-01

    The stability of the structure of double-stranded DNA in the salt-free solution is discussed on the basis of the polyelectrolyte theory. Assuming that DNA is an infinitely long rod, and the formation of double strands is divided into combining process and folding process, the free energy changes required in these processes are calculated by the use of the exact solutions of two-dimensional Poisson-Boltzmann equation for the one rod and the two rod systems.By strong depression of electrostatic interaction due to counter-ion condensation phenomena, the free energy change is remarkably decreased so that the double-stranded structure of DNA can be stabilized by energy of hydrogen bonds between base pairs. The increase of the activity coefficient of a counterion upon heat denaturation of DNA is also explained.

  5. Polyelectrolyte Complexation: A Field-Theoretic Description of Phase Behavior

    Science.gov (United States)

    Audus, Debra; Fredrickson, Glenn

    2010-03-01

    Our research focuses on a type of polyelectrolyte complexation called complex coacervation where two oppositely charged polymers in solution phase separate to form a dense polymer phase, known as the coacervate, and a supernatant, which typically has very low concentrations of polymer. To understand the effects of various parameters on coacervation, we previously developed a simple analytic theory for flexible polymers and small ions, which reproduces many general experimental trends. However, this theory is only valid for symmetric oppositely charged polymers, which limits its direct applicability to many experimental systems. Consequently, we have extended this theory to describe more complicated experimental systems where salt concentrations are high, pH equilibria shift with the complexation process, polymer concentrations are highly asymmetric, and counterion condensation may play an important role. To validate the modified theory, we compare our predictions with an exhaustive study of the phase behavior of polyacrylic acid and polyallylamine hydrochloride.

  6. New polyaniline(PAni)-polyelectrolyte (PDDMAC) composites: Synthesis and applications

    Energy Technology Data Exchange (ETDEWEB)

    Prakash, S.; Rao, Chepuri R.K.; Vijayan, M. [Functional Materials Division, Central Electrochemical Research Institute, Karaikudi-630 006 (India)

    2008-07-20

    Conducting and electroactive polymer blends of polyaniline (PAni) with polyelectrolyte, poly(diallydimethylammoniumchloride) (PDDMAC) have been synthesized by an in situ polymerization method and the resulting composites have been characterized by FT-IR, UV-Vis, XRD, AFM and electrochemical techniques. The blends are conducting and electroactive with even lower loadings of PAni and can be cast as films. The conductivity of the cast films containing 0.04-1.5 wt% PAni ranged from 4.5 x 10{sup -6} to 42 x 10{sup -6} S/cm. Some of the composites are tested for their corrosion inhibition property for pure iron in 1 M HCl solutions and were found to be active inhibitors. (author)

  7. Rapid polyelectrolyte-based membrane immunoassay for the herbicide butachlor.

    Science.gov (United States)

    Dzantiev, B B; Byzova, N A; Zherdev, A V; Hennion, M C

    2005-01-01

    Oppositely charged water-soluble polyelectrolytes were used in the developed membrane immunoenzyme assay for the herbicide butachlor. High-affinity and rapid binding between polyanion polymethacrylate and polycation poly(N-ethyl-4-vinylpyridinium) was applied to separate reacted and free immunoreactants. Competitive immunoassay format with peroxidase-labeled antigen was realized. The insoluble colored product of the peroxidase reaction was formed by bound labeled immune complexes and was reflectometrically detected. The assay combines short duration (15 min), high sensitivity (0.03 g/mL) and availability for out-of-laboratory testing. Different image processing algorithms were used to determine the herbicide content. Low variation coefficients of the measurements in the proposed quantitative assay, namely 4.8-9.0% for the range of antigen concentrations from 0.1 to 3.0 ng/mL, are evidence of the assay effectiveness. Possibility to control the butachlor content in mineral, artesian, and drinking water was demonstrated.

  8. Polyelectrolyte membranes based on hydrocarbon polymer containing fullerene

    Science.gov (United States)

    Saga, Shota; Matsumoto, Hidetoshi; Saito, Keiichiro; Minagawa, Mie; Tanioka, Akihiko

    In the present study, composite polyelectrolyte membranes were prepared from sulfonated polystyrene and fullerene. The additive effect of the fullerene on the membrane properties - electric resistance, mechanical strength, oxidation resistance, and methanol permeability - were measured. The addition of fullerene improved the oxidation resistance, and reduced the methanol crossover. The mechanical strength of the fullerene-composite membrane, on the other hand, was not improved. The direct methanol fuel cell (DMFC) based on a 1.4 wt% fullerene-composite membrane showed the highest power density of 47 mW cm -2 at the current density of 200 mA cm -2 (this value is 60% of the Nafion-based DMFC). The transmission electron microscopy (TEM) observations suggest that the improved dispersity of the fullerene and the reduced number of micropores in the membranes would improve its performance in the fuel cell.

  9. Voltage-controlled metal binding on polyelectrolyte-functionalized nanopores.

    Science.gov (United States)

    Actis, Paolo; Vilozny, Boaz; Seger, R Adam; Li, Xiang; Jejelowo, Olufisayo; Rinaudo, Marguerite; Pourmand, Nader

    2011-05-17

    Most of the research in the field of nanopore-based platforms is focused on monitoring ion currents and forces as individual molecules translocate through the nanopore. Molecular gating, however, can occur when target analytes interact with receptors appended to the nanopore surface. Here we show that a solid state nanopore functionalized with polyelectrolytes can reversibly bind metal ions, resulting in a reversible, real-time signal that is concentration dependent. Functionalization of the sensor is based on electrostatic interactions, requires no covalent bond formation, and can be monitored in real time. Furthermore, we demonstrate how the applied voltage can be employed to tune the binding properties of the sensor. The sensor has wide-ranging applications and, its simplest incarnation can be used to study binding thermodynamics using purely electrical measurements with no need for labeling.

  10. Self-assembled polyelectrolyte nanorings observed by liquid-cell AFM

    Energy Technology Data Exchange (ETDEWEB)

    Menchaca, J-Luis [Instituto de Fisica, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, San Luis Potosi (Mexico); Flores, Hector [Facultad de Estomatologia, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, San Luis Potosi (Mexico); Cuisinier, Frederic [INSERM U 595, Federation de Recherche Odontologiques, Universite Louis Pasteur, 11 rue Humann, 67085 Strasbourg Cedex (France); Perez, ElIas [Instituto de Fisica, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, San Luis Potosi (Mexico)

    2004-06-09

    Self-assembled polyelectrolyte nanorings formed by polyelectrolytes are presented for the first time in this work. They are formed by poly(ethylenimine) (PEI) and poly(sodium 4-styrenesulfanate) (PSS) during the two first steps of the formation of the self-assembled polyelectrolyte films (SAPFs). These are formed on a negatively charged glass surface and observed by an in situ liquid-cell AFM technique, which has recently been introduced as an alternative technique to follow polyelectrolyte multilayer formation without drying effects (Menchaca et al 2003 Colloids Surf. A 222 185). Nanoring formation strongly depends on the preparation method and parameters such as polyelectrolyte filtration, air and CO{sub 2} presence during SAPFs formation and buffer solution. A necessary condition to obtain nanorings is that polyelectrolyte solutions have to be filtered prior to injection into the liquid-cell AFM. The outer diameter of nanorings can be varied from hundreds of nanometres to microns by changing these parameters. Nanorings are stable in the liquid cell for hours but they disappear on contact with air. Additionally, carbonate ions seem to be mainly responsible for the formation of this novel structure.

  11. Changes in the Activity and Structure of Urease in the Interaction with Polyelectrolytes

    Science.gov (United States)

    Saburova, E. A.; Tikhonenko, S. A.; Dybovskaya, Yu. N.; Sukhorukov, B. I.

    2008-03-01

    The influence of polyelectrolytes on the structural and catalytic characteristics of urease ( Canavalia ensiformis) was studied by the methods of steady-state kinetics, fluorescence spectroscopy, and circular dichroism. It was shown that, of the four polyelectrolytes studied, two of which were negatively charged (polystyrene sulfonate and dextran sulfate) and two were positively charged (polyallylamine (PAA) and polydiallyl dimethylammonium chloride), only PAA was a potent urease inhibitor: 0.5 μg/ml of PAA provided a 50% degree of inhibition for enzyme at neutral pH. It was found that polyelectrolyte did not inhibit urease in the presence of micromolar concentrations of ammonium chloride. Based on the experimental data and the calculated structure of urease from Canavalia ensiformis and on the identity with the amino acid sequence of urease from Bacillus pasteurii, the mechanism of urease inactivation by the PAA polyelectrolyte is discussed. This mechanism does not resemble the inhibiting action of polyelectrolytes on the previously studied oligomeric proteins—lactate dehydrogenase, glutamate dehydrogenase, and hemoglobin. It is proposed that the specific cation-binding sites determining the structural dynamics of the enzyme-polyelectrolyte complex play the regulating role in the urease molecule.

  12. A stable nanoplatform for antitumor activity using PEG-PLL-PLA triblock co-polyelectrolyte.

    Science.gov (United States)

    Lim, Chaemin; Sim, Taehoon; Hoang, Ngoc Ha; Oh, Kyung Taek

    2017-05-01

    Polyelectrolyte has been proposed as an efficient approach for various types of drug formulations. However, one drawback of using the conventional polyelectrolyte for drug delivery is its dissociation in in vivo conditions by counter ions due to the lack of self-assembling aggregation force. In this study, we reported a stable nanoplatform based on triblock co-polyelectrolyte composed of a poly(ethylene glycol), poly(l-lysine), and poly(lactic acid). These co-polyelectrolytes formed stable aggregates through the hydrophobic interaction of PLA and showed consistent particle sizes under a high salt concentration. In addition, the doxorubicin (Dox) loaded triblock co-polyelectrolyte demonstrated enhanced cellular uptake and drug cytotoxicity with a positive charge from the poly(l-lysine) layer. In vivo, the triblock aggregates exhibited intensive accumulation at the targeted tumor site for 24h with good antitumor therapeutic efficacy. Therefore, the prepared stable triblock co-polyelectrolyte may have considerable potential as a nanomedicinal platform for anticancer and multi-drug combination therapy. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Complexation and coacervation of like-charged polyelectrolytes inspired by mussels.

    Science.gov (United States)

    Kim, Sangsik; Huang, Jun; Lee, Yongjin; Dutta, Sandipan; Yoo, Hee Young; Jung, Young Mee; Jho, YongSeok; Zeng, Hongbo; Hwang, Dong Soo

    2016-02-16

    It is well known that polyelectrolyte complexes and coacervates can form on mixing oppositely charged polyelectrolytes in aqueous solutions, due to mainly electrostatic attraction between the oppositely charged polymers. Here, we report the first (to the best of our knowledge) complexation and coacervation of two positively charged polyelectrolytes, which provides a new paradigm for engineering strong, self-healing interactions between polyelectrolytes underwater and a new marine mussel-inspired underwater adhesion mechanism. Unlike the conventional complex coacervate, the like-charged coacervate is aggregated by strong short-range cation-π interactions by overcoming repulsive electrostatic interactions. The resultant phase of the like-charged coacervate comprises a thin and fragile polyelectrolyte framework and round and regular pores, implying a strong electrostatic correlation among the polyelectrolyte frameworks. The like-charged coacervate possesses a very low interfacial tension, which enables this highly positively charged coacervate to be applied to capture, carry, or encapsulate anionic biomolecules and particles with a broad range of applications.

  14. Encapsulation of curcumin in polyelectrolyte nanocapsules and their neuroprotective activity

    Science.gov (United States)

    Szczepanowicz, Krzysztof; Jantas, Danuta; Piotrowski, Marek; Staroń, Jakub; Leśkiewicz, Monika; Regulska, Magdalena; Lasoń, Władysław; Warszyński, Piotr

    2016-09-01

    Poor water solubility and low bioavailability of lipophilic drugs can be potentially improved with the use of delivery systems. In this study, encapsulation of nanoemulsion droplets was utilized to prepare curcumin nanocarriers. Nanosize droplets containing the drug were encapsulated in polyelectrolyte shells formed by the layer-by-layer (LbL) adsorption of biocompatible polyelectrolytes: poly-L-lysine (PLL) and poly-L-glutamic acid (PGA). The size of synthesized nanocapsules was around 100 nm. Their biocompatibility and neuroprotective effects were evaluated on the SH-SY5Y human neuroblastoma cell line using cell viability/toxicity assays (MTT reduction, LDH release). Statistically significant toxic effect was clearly observed for PLL coated nanocapsules (reduction in cell viability about 20%-60%), while nanocapsules with PLL/PGA coating did not evoke any detrimental effects on SH-SY5Y cells. Curcumin encapsulated in PLL/PGA showed similar neuroprotective activity against hydrogen peroxide (H2O2)-induced cell damage, as did 5 μM curcumin pre-dissolved in DMSO (about 16% of protection). Determination of concentration of curcumin in cell lysate confirmed that curcumin in nanocapsules has cell protective effect in lower concentrations (at least 20 times) than when given alone. Intracellular mechanisms of encapsulated curcumin-mediated protection engaged the prevention of the H2O2-induced decrease in mitochondrial membrane potential (MMP) but did not attenuate Reactive Oxygen Species (ROS) formation. The obtained results indicate the utility of PLL/PGA shell nanocapsules as a promising, alternative way of curcumin delivery for neuroprotective purposes with improved efficiency and reduced toxicity.

  15. Regenerable Polyelectrolyte Membrane for Ultimate Fouling Control in Forward Osmosis.

    Science.gov (United States)

    Kang, Yan; Zheng, Sunxiang; Finnerty, Casey; Lee, Michael J; Mi, Baoxia

    2017-03-21

    This study demonstrated the feasibility of using regenerable polyelectrolyte membranes to ultimately control the irreversible membrane fouling in a forward osmosis (FO) process. The regenerable membrane was fabricated by assembling multiple polyethylenimine (PEI) and poly(acrylic acid) (PAA) bilayers on a polydopamine-functionalized polysulfone support. The resulting membrane exhibited higher water flux and lower solute flux in FO mode (with the active layer facing feed solution) than in PRO mode (with the active layer facing draw solution) using trisodium citrate as draw solute, most likely due to the unique swelling behavior of the polyelectrolyte membrane. Membrane regeneration was conducted by first dissembling the existing PEI-PAA bilayers using strong acid and then reassembling fresh PEI-PAA bilayers on the membrane support. It was found that, after the acid treatment, the first covalently bonded PEI layer and some realigned PAA remained on the membrane support, acting as a beneficial barrier that prevented the acid-foulant mixture from penetrating into the porous support during acid treatment. The water and solute flux of the regenerated membrane was very similar to that of the original membrane regardless of alginate fouling, suggesting an ultimate solution to eliminating the irreversible membrane fouling in an FO process. With a procedure similar to the typical membrane cleaning protocol, in situ membrane regeneration is not expected to noticeably increase the membrane operational burden but can satisfactorily avoid the expensive replacement of the entire membrane module after irreversible fouling, thereby hopefully reducing the overall cost of the membrane-based water-treatment system.

  16. Nasal inserts containing ondansetron hydrochloride based on Chitosan–gellan gum polyelectrolyte complex: In vitro–in vivo studies

    Energy Technology Data Exchange (ETDEWEB)

    Sonje, Ashish G.; Mahajan, Hitendra S., E-mail: hsmahajan@rediffmail.com

    2016-07-01

    The aim of this study was the production of ondansetron hydrochloride loaded lyophilized insert for nasal delivery. The nasal insert was prepared by the lyophilisation technique using Chitosan–gellan gum polyelectrolyte complex as the polymer matrix. The ondansetron loaded inserts were evaluated with respect to water uptake, bioadhesion, drug release kinetic study, ex vivo permeation study, and in vivo study. Lyophilised nasal inserts were characterized by differential scanning calorimetry, scanning electron microscopy and X-ray diffraction study. Scanning electron microscopy confirmed the porous sponge like structure of inserts whereas release kinetic model revealed that drug release followed non-fickian case II diffusion. The nasal delivery showed improved bioavailability as compared to oral delivery. In conclusion, the ondansetron containing nasal inserts based on Chitosan–gellan gum complex with potential muco-adhesive potential is suitable for nasal delivery. - Highlights: • Chitosan–gellan gum polyelectrolyte complex based inserts have been prepared. • The synthesized polymer complex demonstrated important insert properties. • No toxicity was observed toward nasal mucosa. • In vivo study demonstrates the enhancement of bioavailability.

  17. Local and systemic delivery of VEGF siRNA using polyelectrolyte complex micelles for effective treatment of cancer.

    Science.gov (United States)

    Kim, Sun Hwa; Jeong, Ji Hoon; Lee, Soo Hyeon; Kim, Sung Wan; Park, Tae Gwan

    2008-07-14

    For efficient cancer therapy, small interfering RNA (siRNA) should be stably and efficiently delivered into the target tissue and readily taken up by cancer cells. To address these needs, a polyelectrolyte complex (PEC) micelle-based siRNA delivery system was developed for anti-angiogenic gene therapy. The interaction between poly(ethylene glycol) (PEG)-conjugated vascular endothelial growth factor siRNA (VEGF siRNA-PEG) and polyethylenimine (PEI) led to the spontaneous formation of nanoscale polyelectrolyte complex micelles (VEGF siRNA-PEG/PEI PEC micelles), having a characteristic siRNA/PEI PEC inner core with a surrounding PEG shell layer. Intravenous as well as intratumoral administration of the PEC micelles significantly inhibited VEGF expression at the tumor tissue and suppressed tumor growth in an animal tumor model without showing any detectable inflammatory responses in mice. Upon examination of the PEC micelle distribution and in vivo optical imaging following intravenously injection, enhanced accumulation of the PEC micelles was also observed in the tumor region. This study demonstrates the feasibility of using PEC micelles as a potential carrier for therapeutic siRNAs in local and systemic treatment of cancer.

  18. Properties of Plant Based Plasticizer HM-828 and Its Effect on PVC%生物基增塑剂HM-828性能及其对PVC性能的影响

    Institute of Scientific and Technical Information of China (English)

    毋亭亭; 潘海泉; 邓健能; 钟增培; 李道斌

    2016-01-01

    研究了新型环保生物基增塑剂二乙酰环氧植物油酸甘油酯(HM-828)的结构及主要性能;选用环氧大豆油(ESO)、邻苯二甲酸二辛酯( DOP)、邻苯二甲酸二异壬酯( DINP)、已二酸二辛酯( DOA)、偏苯三酸三辛酯( TOTM)及HM-828为增塑剂分别制备了增塑聚氯乙烯( PVC),对添加40份增塑剂的PVC制品的动态热稳定性、热老化质量损失、拉伸性能、硬度等进行表征。结果表明:六种增塑PVC混合物料中, DOA扭矩最小,加工能耗最低; HM-828的增塑性能与DOP和DINP相近; DOP/DINP/DOA/TOTM四种物料的耐热性不及HM-828和ESO;六种增塑PVC制品的热老化质量损失为DOA>DOP>DINP>HM-828>TOTM>ESO;其拉伸强度均大于20 MPa,断裂伸长率均大于270%;以DOP/DINP/DOA增塑PVC制品的邵氏硬度比另外三种高出7度左右。%The structure and physicochemical properties of glycery 1,2-diacetate-3-(9,10-) epoxy octadecanate was researched which was called as HM-828, a new environmentally friendly plant based plasticizer. Polyvinyl chloride (PVC) was plasticized by epoxidized soybean oil ( ESO) , dioctyl phthalate ( DOP) , diisononyl phthalate ( DINP) , dioctyl adipate (DOA), trioctyl trimellitate (TOTM) and HM-828 for plasticizer, separately. Dynamic thermal stability, thermal aging quality loss, tensile properties and hardness of PVC with 40 portion plasticizer were characterized. It was found that the PVC plasticized by DOA had the minimum torque and energy consumption in the process. The plasticizing capacity of HM-828 was similar to DOP and DINP. The heat resistance of the PVC plasticized by DOP/DINP/DOA/TOTM were worse than those plasticized by HM-828 and ESO. The thermal aging quality loss of plasticized PVC were DOA>DOP>DINP>HM-828>TOTM>ESO, and their tensile strength and elongation at break were greater than 20 MPa and 270%, respectively. The Shore Hardness of the PVC plasticized by DOP/DINP/DOA were higher of about 7 degrees than others.

  19. 水稻淡绿叶突变体 HM133的遗传分析与基因定位%Genetic Analysis and Gene Mapping of a Pale Green Leaf Mutant HM133 in Rice

    Institute of Scientific and Technical Information of China (English)

    施勇烽; 贺彦; 郭丹; 吕向光; 黄奇娜; 吴建利

    2016-01-01

    The pale green leaf mutant HM133 was identified from an EMS-induced IR64 mutant bank.The contents of photosynthetic pigments including chlorophyll and carotenoid of HM133 were reduced significantly at 6 weeks and 1 5 weeks after sowing when compared with IR64.The net photosynthetic rate of HM133 was considerably lower than that of the wild-type IR64 at heading stage while the stomatal conductance was apparently increased.The agronomic traits including plant height,number of filled grain per panicle and seed-setting rate decreased significantly in the mutant compared with the wild-type.In addition,the mutant exhibited a less number of grana,irregular arrangement of thylakoid layer in the chloroplast at the tillering stage.Genetic and mapping analysis showed that the pale green phenotype was controlled by a single recessive gene located in the long arm of chromosome 3 between SSR markers RM143 and RM3684.The interval contains an ORF OsChlD encoding magnesium-chelatase D subunit.Sequence analysis revealed that the mutant allele carried a nucleotide substitution from G to A in the tenth exon of OsChlD , which led to the substitution of glutamic acid for arginine acid.Therefore,it is deduced that OsChlD is the candidate gene controlling the pale green leaf phenotype of HM133 .%EMS 诱导籼稻品种 IR64获得淡绿叶突变体 HM133.与野生型 IR64相比,HM133播种后的第6周和第15周的光合色素含量以及抽穗期的净光合速率显著降低,气孔导度则明显上升;此外,突变体株高、每穗实粒数和结实率等农艺性状也较野生型显著下降.叶绿体超微结构分析表明,分蘖期 HM133类囊体基粒片层形状不规则,堆叠凌乱、排列疏松.遗传分析表明 HM133淡绿叶性状受单隐性核基因控制.通过分子标记将该基因定位于第3染色体长臂 RM143和 RM3684之间.该区间内包含编码镁螯合酶 D 亚基的基因 OsCHLD .序列分析表明 HM133中该基因第10外显子上有一个从 G

  20. Correlation between flexibility of chain-like polyelectrolyte and thermodynamic properties of its solution

    Directory of Open Access Journals (Sweden)

    T. Sajevic

    2011-09-01

    Full Text Available Structural and thermodynamic properties of the model solution containing charged oligomers and the equivalent number of counterions were studied by means of the canonical Monte Carlo simulation technique. The oligomers are represented as (flexible freely jointed chains or as a linear (rigid array of charged hard spheres. In accordance with the primitive model of electrolyte solutions, the counterions are modeled as charged hard spheres and the solvent as dielectric continuum. Significant differences in the pair distribution functions, obtained for the rigid (rod-like and flexible model are found but the differences in thermodynamic properties, such as, enthalpy of dilution and excess chemical potential, are less significant. The results are discussed in light of the experimental data an aqueous polyelectrolyte solutions. The simulations suggest that deviations from the fully extended (rod-like conformation yield slightly stronger binding of counterions. On the other hand, the flexibility of polyions, even when coupled with the ion-size effects, cannot be blamed for qualitative differences between the theoretical results and experimental data for enthalpy of dilution.

  1. Synthesis, self-assembly and photoinduced surface-relief gratings of a polyacrylate-based Azo polyelectrolyte

    Science.gov (United States)

    He, Yaning; Wang, Haopeng; Tuo, Xinlin; Deng, Wei; Wang, Xiaogong

    2004-06-01

    A polyacrylate-based azo polyelectrolyte was synthesized and characterized by the spectroscopic methods and thermal analysis. Layer-by-layer self-assembly of the azo polyelectrolyte through electrostatic adsorption was explored. By using a dipping solution of the anionic azo polyelectrolyte in anhydrous DMF, together with an aqueous solution of cationic poly(diallyldimethylammonium chloride) (PDAC), high quality multilayer films were obtained through the sequential deposition of the oppositely charged polyelectrolytes. With interfering illumination of Ar + laser beams (488 nm), significant surface-relief gratings formed on the self-assembled multiplayer films were observed.

  2. Polyelectrolytes: Influence on Evaporative Self-Assembly of Particles and Assembly of Multilayers with Polymers, Nanoparticles and Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Tatiana Bukreeva

    2010-12-01

    Full Text Available Assembling polyelectrolyte multilayers in a bottom-up approach is reported for polymers, particles, nanoparticles, and carbon nanotubes. Effects of polyelectrolyte multilayers on evaporative self-assembly of particles, which are of interest to a number of applications including photonic crystals, films and substrates, are investigated. Polyelectrolyte multilayer coatings bring multifunctionality to spherical particles and planar films. Studying the construction of polyelectrolyte assemblies is convenient in the planar layout: it is reported here for incorporation of gold and magnetic nanoparticles as well as of carbon nanotubes. Gold nanoparticles concentration is controlled within the films. Potential applications of both spherical structures and planar films are highlighted.

  3. Geen recht de moed te verliezen. Leven en werken van dr. H.M. de Lange (1919-2001)

    NARCIS (Netherlands)

    Witte-Rang, M.E.

    2008-01-01

    This study deals with the contribution of the Dutch economist Dr. H.M. de Lange to the ecumenical debate on social-ethics. To this end, the first part gives a description of the work of De Lange. Through the individual De Lange the study provides an insight in the worldwide ecumenical movement and t

  4. Positive allosteric modulation of the human metabotropic glutamate receptor 4 (hmGluR4) by SIB-1893 and MPEP

    DEFF Research Database (Denmark)

    Mathiesen, Jesper Mosolff; Svendsen, Nannette; Bräuner-Osborne, Hans

    2003-01-01

    We have identified 2-methyl-6-(2-phenylethenyl)pyridine (SIB-1893) and 2-methyl-6-phenylethynyl pyridine hydrochloride (MPEP) as positive allosteric modulators for the hmGluR4. SIB-1893 and MPEP enhanced the potency and efficacy of L-2-amino-4-phophonobutyrate (L-AP4) in guanosine 5'-O-(3-[(35)S]...

  5. Winds in collision. II - An analysis of the X-ray emission from the eruptive symbiotic HM Sge

    Science.gov (United States)

    Willson, L. A.; Wallerstein, G.; Brugel, E. W.; Stencel, R. E.

    1984-01-01

    X-ray emissions from HM Sge obtained in 1981 from the HEAO-2 satellite are analyzed and compared quantitatively with observations of HM Sge made in 1980 and of HM Sge, V 1016 Cyg, and RR Tel made in 1979. The change in the X-ray emission from HM Sge between 1979 and 1981 is found to be consistent with the X-ray luminosity and/or temperature of the emitting region declining with an e-folding timescale of the order of one to several decades. Comparison with X-ray data from V 1016 Cyg and RR Tel gives a composite X-ray light curve that is also consistent with such a decline. A comparison of the X-ray observation with spectroscopic information makes it possible to constrain the properties of the X-ray emitting region: the result is consistent with emission from an optically thin region between the two stars in the system where their winds collide head on. It is also shown that the observations are inconsistent with a stellar (blackbody) source, with emission from an accretion disk around a white dwarf or a neutron star, and with emission from a single star wind from either a white dwarf or a neutron star.

  6. Effects of calcium pH, and blockiness on kinetic rheological behaviour and microstructure of HM pectin gels

    NARCIS (Netherlands)

    Lofgren, C.; Guillotin, S.E.; Evenbratt, E.; Schols, H.A.; Hermansson, A.M.

    2005-01-01

    The kinetic behavior during gel formation and the microstructure of 0.75% high methoxyl (HM) pectin gels in 60% sucrose have been investigated by oscillatory measurements and transmission electron microscopy for three comparable citrus pectin samples differing in their degree of blockiness (DB). Ca2

  7. A new naphthalenepropanoic acid analog from the marine-derived actinomycetes Micromonospora sp. HS-HM-036.

    Science.gov (United States)

    Gao, Mei-Yue; Qi, Huan; Li, Jian-Song; Zhang, Hui; Zhang, Ji; Wang, Ji-Dong; Xiang, Wen-Sheng

    2017-09-01

    A new naphthalenepropanoic acid analog (1) was isolated from the broth of the actinomycetes Micromonospora sp. HS-HM-036. The structure of compound 1 was determined based on MS and extensive NMR analysis. A preliminary investigation of the biological activity of compound 1 was also described.

  8. Structural and preliminary molecular dynamics studies of the Rhodobacter sphaeroides reaction center and its mutant form L(M196)H + H(M202)L

    Science.gov (United States)

    Klyashtorny, V. G.; Fufina, T. Yu.; Vasilieva, L. G.; Shuvalov, V. A.; Gabdulkhakov, A. G.

    2014-07-01

    Pigment-protein interactions are responsible for the high efficiency of the light-energy transfer and conversion in photosynthesis. The reaction center (RC) from the purple bacterium Rhodobacter sphaeroides is the most convenient model for studying the mechanisms of primary processes of photosynthesis. Site-directed mutagenesis can be used to study the effect of the protein environment of electron-transfer cofactors on the optical properties, stability, pigment composition, and functional activity of RC. The preliminary analysis of RC was performed by computer simulation of the amino acid substitutions L(M196)H + H(M202)L at the pigment-protein interface and by estimating the stability of the threedimensional structure of the mutant RC by the molecular dynamics method. The doubly mutated reaction center was overexpressed, purified, and crystallized. The three-dimensional structure of this mutant was determined by X-ray crystallography and compared with the molecular dynamics model.

  9. Extraction of [99mTc]-d,l-HM-PAO across the blood-brain barrier

    DEFF Research Database (Denmark)

    Andersen, A R; Friberg, H; Knudsen, K B

    1988-01-01

    The initial extraction (E) across the blood-brain barrier (BBB) of [99mTc]-d,l-HM-PAO after intracarotid injection was measured in 14 Wistar rats and 6 patients using the double indicator, single injection method with Na-24 as the cotracer. In both series, cerebral blood flow (CBF) was measured...... using the initial slope of the xenon-133 washout curve after intracarotid bolus injection. In rats, bolus size (20 or 120 microliters), bolus type (saline or 10% albumin), or CBF were changed. First-pass extraction was dependent on CBF (p less than 0.001): With a small bolus of saline and at resting CBF...... the apparent extraction across brain capillaries. In patients using a bolus of 1 ml saline, E decreased linearly with increasing CBF (r = -0.81, p less than 0.001). For a CBF of 0.59 ml/g/min and an average apparent E of 0.72, an apparent PS product of 0.76 ml/g/min was calculated.(ABSTRACT TRUNCATED AT 250...

  10. Identification and Gene Mapping of a Spotted-leaf Mutant hm197 in Rice%水稻斑点叶突变体hm197的鉴定及其基因定位

    Institute of Scientific and Technical Information of China (English)

    李小红; 吴建利; 施勇烽; 张晓波; 奉保华; 宋莉欣; 王惠梅; 徐霞; 黄奇娜; 郭丹

    2015-01-01

    A stable inherited rice spotted-leaf mutant hm197 was isolated from a diepoxybutane-induced IR64 mutant bank.Under natural conditions,brown lesions were first observed on the tips of the mutant leaves 10 weeks after sowing,and spread gradually downward to cover the whole leaf blades.Genetic analysis indicated that the mutant trait was controlled by a novel single recessive nuclear gene,tentatively termed as splhm97 ,located in the long arm of chromosome 4.Agronomic traits including the plant height,seed-setting rate and 1000-grain weight were significantly decreased in hm197 .The initiation of brown lesions in hm197 was induced by natural sun light.In addition,the photosynthetic pigment contents and net photosynthetic rate in the mutant were significantly lower than those in the wild type IR64.Histochemical analysis showed that H2 O2 and O2∸ accumulation were presented in and around the lesions in hm197 .Furthermore,senescence-related parameters including the activities of SOD,APX,total soluble protein and MDA contents were also significantly altered in the mutant while resistance to bacterial blight pathogens was largely enhanced in the mutant in contrast to the wild type IR64.%通过双环氧丁烷(diepoxybutane)诱变籼稻品种 IR64获得遗传稳定的水稻褐色斑点叶突变体hm197.在自然条件下,该突变体褐色斑点自播种后10周开始于叶尖出现,而后慢慢扩散至全叶.遗传分析表明,该褐色斑点性状受一对隐性核基因控制,暂名splhm197,并将其定位在第4染色体长臂上140 kb的区段内.与野生型IR64相比,突变体株高、结实率和千粒重等农艺性状均显著下降.遮光处理表明,hm197褐色斑点的形成受自然光照的诱导.此外,hm197光合色素含量和光合效率也比野生型显著降低.组织化学分析表明,突变体中有过氧化氢和大量超氧阴离子 O2∸的沉积.与 IR64相比, hm197叶片中清除氧自由基酶系统中 SOD和 APX活性极显著上升,其余

  11. Electrochemical metal speciation in natural and model polyelectrolyte systems.

    NARCIS (Netherlands)

    Hoop, van den M.A.G.T.

    1994-01-01

    The purpose of the research described in this thesis was to examine the applicability of electro-analytical techniques in obtaining information on the speciation of metals, i.e. their distribution over different physico-chemical forms, in aquatic systems containing charged macromolecules. In chapter

  12. Electrochemical metal speciation in natural and model polyelectrolyte systems

    NARCIS (Netherlands)

    Hoop, van den M.A.G.T.

    1994-01-01

    The purpose of the research described in this thesis was to examine the applicability of electro-analytical techniques in obtaining information on the speciation of metals, i.e. their distribution over different physico-chemical forms, in aquatic systems containing charged macromolecules.

  13. The 2009-2012 Ionosonde and IRI2012 Variability of foF 2, hmF 2, M3000F2, B 0, B1 Parameters over Warsaw

    Directory of Open Access Journals (Sweden)

    Szwabowski Michał

    2016-08-01

    Full Text Available This paper presents comparisons of variability and accordance of ionospheric parameters foF2, hmF2, M3000F2, B0, B1 over the middle latitude station in Warsaw (52.21°N, 21.06°E. Examination included observational data from Space Research Centre ionosonde in Poland and International Reference Ionosphere (IRI 2012 model, for the time period of increasing solar activity from 2009 to 2012. The analysis concerned: trend, monthly median differences in twenty-four hours variability, local minima and maxima. Results are presented as tables of semi-annual data, and plots of difference in four-year period. The study indicated good agreement of foF2 and hmF2 parameters. Underestimations of B1 and M3000F2, variability of B0 parameter in Bil-2000, Gul-1987, and ABT-2009 option, were taken into consideration.

  14. Estimativa da entalpia reticular de adutos (DM Hm o utilizando-se formas modificadas da equação de Kapustinskii Estimating the value of lattice enthalpy (DM Hm o for adducts by using modified forms of Kapustinskii equation

    Directory of Open Access Journals (Sweden)

    Robson Fernandes de Farias

    1999-04-01

    Full Text Available In this work are presented two modified forms of Kapustinskii equation that could be used to estimate the values of the lattice enthalphies for adducts: DM Hm o=(-n.z+ .z- .10(2/D.(1-d*/D .K and DM Hm o=(-n.z+ .z-.10(2/d.(1-d*/d.K.d. Two new parameters related with steric effects and donor power of the ligands, J anddare introduced. The proposed equations were tested for 49 adducts (mainly from the zinc group halides. The difference between experimental (calorimetric and calculated values (using the proposed equations values are less than 5% for 41 of the tested adducts.

  15. Identification and characterization of microRNAs from Entamoeba histolytica HM1-IMSS.

    Science.gov (United States)

    Mar-Aguilar, Fermín; Trevino, Victor; Salinas-Hernández, Jannet E; Taméz-Guerrero, Marcela M; Barrón-González, María P; Morales-Rubio, Eufemia; Treviño-Neávez, Jaime; Verduzco-Martínez, Jorge A; Morales-Vallarta, Mario R; Reséndez-Pérez, Diana

    2013-01-01

    Entamoeba histolytica is the causative agent of amebiasis, a disease that is a major source of morbidity and mortality in the developing world. MicroRNAs (miRNAs) are a large group of non-coding RNAs that play important roles in regulating gene expression and protein translation in animals. Genome-wide identification of miRNAs is a critical step to facilitating our understanding of genome organization, genome biology, evolution, and post-transcriptional regulation. We sequenced a small RNA library prepared from a culture of trophozoites of Entamoeba histolytica Strain HM1-IMSS using a deep DNA sequencing approach. Deep sequencing yielded 16 million high-quality short sequence reads containing a total of 5 million non-redundant sequence reads. Based on a bioinformatics pipeline, we found that only 0.5% of these non-redundant small RNA reads were a perfect match with the drafted E. histolytica genome. We did not find miRNA homologs in plant or animal miRNAs. We discovered 199 new potential Entamoeba histolytica miRNAs. The expression and sequence of these Ehi-miRNAs were further validated through microarray by µParaflo Microfluidic Biochip Technology. Ten potential miRNAs were additionally confirmed by real time RT-PCR analysis. Prediction of target genes matched 32 known genes and 34 hypothetical genes. These results show that there is a number of regulatory miRNAs in Entamoeba histolytica. The collection of miRNAs in this parasite could be used as a new platform to study genomic structure, gene regulation and networks, development, and host-parasite interactions.

  16. Identification and Characterization of microRNAS from Entamoeba histolytica HM1-IMSS

    Science.gov (United States)

    Salinas-Hernández, Jannet E.; Taméz-Guerrero, Marcela M.; Barrón-González, María P.; Morales-Rubio, Eufemia; Treviño-Neávez, Jaime; Verduzco-Martínez, Jorge A.; Morales-Vallarta, Mario R.; Reséndez-Pérez, Diana

    2013-01-01

    Background Entamoeba histolytica is the causative agent of amebiasis, a disease that is a major source of morbidity and mortality in the developing world. MicroRNAs (miRNAs) are a large group of non-coding RNAs that play important roles in regulating gene expression and protein translation in animals. Genome-wide identification of miRNAs is a critical step to facilitating our understanding of genome organization, genome biology, evolution, and post-transcriptional regulation. Methodology/Principal Findings We sequenced a small RNA library prepared from a culture of trophozoites of Entamoeba histolytica Strain HM1-IMSS using a deep DNA sequencing approach. Deep sequencing yielded 16 million high-quality short sequence reads containing a total of 5 million non-redundant sequence reads. Based on a bioinformatics pipeline, we found that only 0.5% of these non-redundant small RNA reads were a perfect match with the drafted E. histolytica genome. We did not find miRNA homologs in plant or animal miRNAs. We discovered 199 new potential Entamoeba histolytica miRNAs. The expression and sequence of these Ehi-miRNAs were further validated through microarray by µParaflo Microfluidic Biochip Technology. Ten potential miRNAs were additionally confirmed by real time RT-PCR analysis. Prediction of target genes matched 32 known genes and 34 hypothetical genes. Conclusions/Significance These results show that there is a number of regulatory miRNAs in Entamoeba histolytica. The collection of miRNAs in this parasite could be used as a new platform to study genomic structure, gene regulation and networks, development, and host-parasite interactions. PMID:23874540

  17. Identification and characterization of microRNAs from Entamoeba histolytica HM1-IMSS.

    Directory of Open Access Journals (Sweden)

    Fermín Mar-Aguilar

    Full Text Available BACKGROUND: Entamoeba histolytica is the causative agent of amebiasis, a disease that is a major source of morbidity and mortality in the developing world. MicroRNAs (miRNAs are a large group of non-coding RNAs that play important roles in regulating gene expression and protein translation in animals. Genome-wide identification of miRNAs is a critical step to facilitating our understanding of genome organization, genome biology, evolution, and post-transcriptional regulation. METHODOLOGY/PRINCIPAL FINDINGS: We sequenced a small RNA library prepared from a culture of trophozoites of Entamoeba histolytica Strain HM1-IMSS using a deep DNA sequencing approach. Deep sequencing yielded 16 million high-quality short sequence reads containing a total of 5 million non-redundant sequence reads. Based on a bioinformatics pipeline, we found that only 0.5% of these non-redundant small RNA reads were a perfect match with the drafted E. histolytica genome. We did not find miRNA homologs in plant or animal miRNAs. We discovered 199 new potential Entamoeba histolytica miRNAs. The expression and sequence of these Ehi-miRNAs were further validated through microarray by µParaflo Microfluidic Biochip Technology. Ten potential miRNAs were additionally confirmed by real time RT-PCR analysis. Prediction of target genes matched 32 known genes and 34 hypothetical genes. CONCLUSIONS/SIGNIFICANCE: These results show that there is a number of regulatory miRNAs in Entamoeba histolytica. The collection of miRNAs in this parasite could be used as a new platform to study genomic structure, gene regulation and networks, development, and host-parasite interactions.

  18. Systematic modification of the rheological properties of colloidal suspensions with polyelectrolyte multilayers.

    Science.gov (United States)

    Hess, Andreas; Pretzl, Melanie; Heymann, Lutz; Fery, Andreas; Aksel, Nuri

    2011-09-01

    Tailoring rheological properties of colloidal suspensions with the adsorption of polyelectrolyte multilayers (PEMs) is based on the idea of controlling macroscopic mechanical properties by modifying the particle surface in a reproducible and well-understood manner. With layer-by-layer self-assembly, monodisperse polystyrene particles are coated with up to ten layers of the oppositely charged strong polyelectrolytes: poly(diallyl dimethyl ammonium chloride) and poly(styrene sulfonate). The conformation of the adsorbed polyelectrolyte is controlled by the ionic strength of the used aqueous polyelectrolyte solution. For 1M NaCl solution, a brushlike adsorption of the polyelectrolyte is expected. The ability of PEMs to serve on a nanoscale level as surface modifiers and influence macroscopic rheological properties like viscoelasticity, yield stress, and shear banding is discussed. The mechanical behavior of these suspensions is qualitatively described by the theory of Derjaguin-Landau-Verwey-Overbeek with short-range repulsion and long-range attraction. A scaling rule is proposed which distinguishes between the precusor and the multilayer regime.

  19. Stability of polyelectrolyte-coated iron nanoparticles for T2-weighted magnetic resonance imaging

    Science.gov (United States)

    McGrath, Andrew J.; Dolan, Ciaran; Cheong, Soshan; Herman, David A. J.; Naysmith, Briar; Zong, Fangrong; Galvosas, Petrik; Farrand, Kathryn J.; Hermans, Ian F.; Brimble, Margaret; Williams, David E.; Jin, Jianyong; Tilley, Richard D.

    2017-10-01

    Iron nanoparticles are highly-effective magnetic nanoparticles for T2 magnetic resonance imaging (MRI). However, the stability of their magnetic properties is dependent on good protection of the iron core from oxidation in aqueous media. Here we report the synthesis of custom-synthesized phosphonate-grafted polyelectrolytes (PolyM3) of various chain lengths, for efficient coating of iron nanoparticles with a native iron oxide shell. The size of the nanoparticle-polyelectrolyte assemblies was investigated by transmission electron microscopy and dynamic light scattering, while surface attachment was confirmed by Fourier transform infrared spectroscopy. Low cytotoxicity was observed for each of the nanoparticle-polyelectrolyte (;Fe-PolyM3;) assemblies, with good cell viability (>80%) remaining up to 100 μg mL-1 Fe in HeLa cells. When applied in T2-weighted MRI, corresponding T2 relaxivities (r2) of the Fe-PolyM3 assemblies were found to be dependent on the chain length of the polyelectrolyte. A significant increase in contrast was observed when polyelectrolyte chain length was increased from 6 to 65 repeating units, implying a critical chain length required for stabilization of the α-Fe nanoparticle core.

  20. Polyelectrolyte multilayers prepared from water-soluble poly(alkoxythiophene) derivatives.

    Science.gov (United States)

    Lukkari, J; Salomäki, M; Viinikanoja, A; Aäritalo, T; Paukkunen, J; Kocharova, N; Kankare, J

    2001-06-27

    Electronically conducting polyanion and polycation based on poly(alkoxythiophene) derivatives, poly-3-(3'-thienyloxy)propanesulfonate (P3TOPS) and poly-3-(3'-thienyloxy)propyltriethylammonium (P3TOPA) have been synthesized. Both polymers are water-soluble and exhibit high conjugation length in solution and in the solid state. These polyelectrolytes were used to prepare conducting and electroactive polyelectrolyte multilayers by the sequential layer-by-layer adsorption technique. In aqueous solutions multilayers of P3TOPS with inactive polyelectrolytes (e.g., poly(diallyldimethylammonium chloride), PDADMA) displayed electrochemical and optical behavior similar to polythiophene films prepared in organic media. Their in-plane conductivity was low (ca. 1.6 x 10(-)(5) S cm(-)(1)). The conductivity could, however, be increased by a factor of ca. 40 in "all-thiophene" films, in which P3TOPA was substituted for the inactive polycation (PDADMA). The interpenetration of layers is of prime importance in films containing conducting components. The interpenetration of P3TOPS was studied by measuring the charge-transfer rate across an insulating polyelectrolyte multilayer between the substrate and the P3TOPS layer with modulated electroreflectance. The extent of interpenetration was 8-9 polyelectrolyte layers, the length scale (7-15 nm) depending on the nature of the insulating layer and, especially, on the ionic strength of the solution used for the adsorption of P3TOPS.

  1. Characterization of novel lactoferrin loaded capsules prepared with polyelectrolyte complexes.

    Science.gov (United States)

    Wu, Qing-Xi; Zhang, Qi-Lei; Lin, Dong-Qiang; Yao, Shan-Jing

    2013-10-15

    Novel capsules loaded with lactoferrin (LF) were prepared using polyelectrolyte complexes that were formed by water soluble chitosan (WSC), sodium cellulose sulfate (NaCS) and sodium polyphosphate (PPS). Normal chitosan (soluble in acidic conditions) was chosen as a control to prepare similar capsules with NaCS and PPS. (1)H NMR and FTIR spectra analysis showed that WSC was in a form of chitosan hydrochloride which can be directly dissolved and protonated in acid-free water. SEM results showed that the capsules had a typical wall-capsule structure with a regular spherical shape and an average diameter of 1.97 mm. TGA studies revealed that the thermal stability of the capsules were enhanced and the moisture content of the drug-free/loaded capsules were 6.3% and 3.2%. SDS-PAGE results showed that the primary structures of the processed LF in the capsules were unchanged. Drug loading (LE%) and encapsulation efficiency (EE%) analysis showed that the capsules had a higher LE% (45.6%) and EE% (70.7%) than that of the control. In vitro release studies showed that the capsules had a regular and sustainable release profiles in simulated colonic fluid. All of these results indicated that the capsules prepared could be used as a candidate protein drug carrier for colon. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. Characterization of Responsive Hydrogel Nanoparticles upon Polyelectrolyte Complexation

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    Su-Kyoung Lee

    2017-02-01

    Full Text Available Characterization of responsive hydrogels and their interaction with other molecules have significantly expanded our understanding of the functional materials. We here report on the response of poly(N-isopropylacrylamide-co-acrylic acid (pNIPAm-co-AAc nanogels to the addition of the poly(allylamine hydrochloride (PAH in aqueous dispersions. We find that the hydrodynamic radius and stability of nanogels are dependent on the PAH/nanogel stoichiometry. If the nanogel solution is titrated with very small aliquots of PAH, the nanogels decrease in radius until the equivalence point, followed by aggregation at suprastoichiometric PAH additions. Conversely, when titrated with large aliquots, the nanogel charge switches rapidly from anionic to cationic, and no aggregation is observed. This behavior correlates well with electrophoretic mobility measurements, which shows the nanogel charge transitioning from negative to positive upon PAH addition. The volume phase transition temperature (VPTT of the nanogels is also measured to discover the effect of polyelectrolyte complexation on the deswelling thermodynamics. These data show that charge neutralization upon PAH addition decreases the VPTT of the nanogel at pH 6.5. However, if an excess amount of PAH is added to the nanogel solution, the VPTT shifts back to higher temperatures due to the formation of a net positive charge in the nanogel network.

  3. Polyelectrolyte Multilayers: A Versatile Tool for Preparing Antimicrobial Coatings.

    Science.gov (United States)

    Séon, Lydie; Lavalle, Philippe; Schaaf, Pierre; Boulmedais, Fouzia

    2015-12-01

    The prevention of pathogen colonization of medical implants represents a major medical and financial issue. The development of antimicrobial coatings aimed at protecting against such infections has thus become a major field of scientific and technological research. Three main strategies are developed to design such coatings: (i) the prevention of microorganisms adhesion and the killing of microorganisms (ii) by contact and (iii) by the release of active compounds in the vicinity of the implant. Polyelectrolyte multilayer (PEM) technology alone covers the entire widespread spectrum of functionalization possibilities. PEMs are obtained through the alternating deposition of polyanions and polycations on a substrate, and the great advantages of PEMs are that (i) they can be applied to almost any type of substrate whatever its shape and composition; (ii) various chemical, physicochemical, and mechanical properties of the coatings can be obtained; and (iii) active compounds can be embedded and released in a controlled manner. In this article we will give an overview of the field of PEMs applied to the design of antimicrobial coatings, illustrating the large versatility of the PEM technology.

  4. Underwater Reversible Adhesion Between Oppositely Charged Weak Polyelectrolytes

    Science.gov (United States)

    Alfhaid, Latifah; Geoghegan, Mark; Williams, Nicholas; Seddon, William

    2015-03-01

    Force-distance data has shown that the adhesion between two oppositely charged polyelectrolytes: poly(methacrylic acid) (PMAA, a polyacid) and poly[2-(diethylamino)ethyl methacrylate] (PDEAEMA, a polybase), was controllable by varying the pH level of their surrounding. Accordingly, adhesive force at the interface between these two polymers was higher inside basic surroundings at pH 6 and 7, and then it started to decrease at pH level below 3 and above 8. Stimulating adhesion between PMAA gel and PDEAEMA brushes by adding salt to their surrounded water has only a limited effect on the adhesive force between them, contradicting previous results. Increasing the molar concentration of sodium chloride (NaCl) in the surrounded water of these two polymers from 0.1 to 1M did not decrease the adhesion forces between a PMAA gel and a grafted PDEAEMA layer (brush). The JKR equation was used to evaluate the adhesion forces between the polymer gel and the brushes and it was observed that the adhesion increased with the elastic modulus of the gel decreased.

  5. Fibers by interfacial polyelectrolyte complexation – processes, materials and applications

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    Andrew C.A. Wan

    2016-10-01

    Full Text Available Interfacial polyelectrolyte (polyion complexation (IPC is a process whereby fibers and capsules are formed through interactions at the interface of oppositely charged polymers. Since its discovery in the late 1990s, the IPC fiber process, in particular, has been investigated for various applications such as tissue engineering, drug delivery, flexible electronics and biosensing. The advent of the IPC fiber and process has been supported by its unique mechanism of formation that makes it amenable to encapsulation and functionalization. In this first review on IPC fibers, we consolidate the current knowledge of the IPC process, mechanism of fiber formation and fiber physical properties, while documenting the various polycation–polyanion pairs and encapsulants that have been used to date. We review the rapidly accumulating literature on IPC fibers for tissue engineering, describing how they have been used to release protein factors in a sustained manner, made into random or spatially well-defined scaffolds and decorated with appropriate functionalities and extracellular matrices in order to tailor the microenvironment for cell growth and function.

  6. Preparation of photoluminescent carbon dots-embedded polyelectrolyte microcapsules

    Institute of Scientific and Technical Information of China (English)

    Xiaoling Yang; Liming Peng; Jie Zong; Yihua Zhu

    2013-01-01

    Two types of photoluminescent carbon dots (CDs)-embedded polyelectrolyte (PE) microcapsules were successfully prepared via the layer-by-layer (LbL) assembly approach on sacrificial templates.For the first type,the PE microcapsules with CDs embedded in the cavity were produced from assembly of five pairs of poly(sodium 4-styrensulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) on CDs-pre-loaded meso-porous silica.For the second type,the PE microcapsules with CDs embedded in the wall were made of CDs and PAH,which were derived from SiO2 particles as templates.Microscope images confirmed the introduction of CDs into the two CDs-embedded microcapsules.These two microcapsules also retained the optical properties of free CDs.Photoluminescence spectra revealed that the two types of microcapsules had excitation-dependent photoluminescence behavior.When the excitation wavelength changed from 280 to 340 nm,photoluminescence emission peak of the PE microcapsules with CDs embedded in the cavity shifts from 369 to 377 nm,while for microcapsules with CDs embedded in the wall,emission peak shifts from 367 to 390 nm.Due to low toxicity,good hydrophilicity and photoluminescence properties of CDs,these two kinds of photo-luminescent microcapsules have competitive potential for application in carriers for imaging,drug delivery and biosensors.

  7. Effect of Temperature on Polyelectrolyte Expansion of Lignosulfonate

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    Hao Li

    2014-11-01

    Full Text Available The temperature effect on the polyelectrolyte expansion of sodium lignosulfonate (SL was studied in the range of 20 to 38 °C. A narrow molecular-weight distribution fraction of sodium lignosulfonate was first obtained by gel column chromatography, which was suitable for the hydrodynamic radius (Rh measurement by dynamic light scattering (DLS. Dynamic light scattering experiments showed that the hydrodynamic radius of sodium lignosulfonate decreased with increasing temperature. Using a quartz crystal microbalance (QCM and atomic force microscopy (AFM, it was found that the adsorbed sodium lignosulfonate film lost water with increasing temperature and reabsorbed water with decreasing temperature. Surface tension and contact angle experiments showed that there were more hydrophobic groups on the surface of the sodium lignosulfonate molecule as the temperature increased. It can be concluded that the sodium lignosulfonate molecule shrank and became more hydrophobic with increasing temperature. Analysis suggests that the decreasing of the hydrogen-bond interactions between the sodium lignosulfonate molecule and water molecules with increasing temperature is the primary reason for the molecular conformation change of sodium lignosulfonate.

  8. Functional polyelectrolyte multilayer membranes for water purification applications

    Energy Technology Data Exchange (ETDEWEB)

    Tripathi, Bijay P., E-mail: bijayptripathi@yahoo.com [Department of Nanostructured Materials, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 01069 Dresden (Germany); Dubey, Nidhi C. [Department of Nanostructured Materials, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 01069 Dresden (Germany); Technische Universität Dresden, Department of Chemistry, 01069 Dresden (Germany); Stamm, M., E-mail: stamm@ipfdd.de [Department of Nanostructured Materials, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 01069 Dresden (Germany); Technische Universität Dresden, Department of Chemistry, 01069 Dresden (Germany)

    2013-05-15

    Highlights: ► LBL film on the surface and in to the pores was prepared via flow through method. ► The membranes showed high rejection of Congo Red with sufficiently high flux. ► High antifouling ability in terms of both organic and bio fouling was observed. -- Abstract: A diverse set of supported multilayer assemblies with controllable surface charge, hydrophilicity, and permeability to water and solute was fabricated by pressure driven permeation of poly(sodium 4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDDA) solution through poly(ethylene terephthalate) (PET) track-etched membranes. The polyelectrolyte multilayer fabrication was confirmed by means of FTIR, SEM, AFM, ellipsometry, zetapotential, and contact angle characterization. The prepared membranes were characterized in terms of their pure water permeability, flux recovery, and resistance to organic and biofouling properties. The antifouling behavior of the membranes was assessed in terms of protein adsorption and antibacterial behavior. Finally, the membranes were tested for rejection of selected water soluble dyes to establish their usefulness for organic contaminant removal from water. The membranes were highly selective and capable of nearly complete rejection of congo red with sufficiently high fluxes. The feasibility of regenerating the prepared membranes fouled by protein was also demonstrated and good flux recovery was obtained. In summary, the multilayer approach to surface and pore modification was shown to enable the design of membranes with the unique combination of desirable separation characteristics, regenerability of the separation layer, and antifouling behavior.

  9. Polyelectrolyte decomplexation via addition of salt: charge correlation driven zipper.

    Science.gov (United States)

    Antila, Hanne S; Sammalkorpi, Maria

    2014-03-20

    We report the first atomic scale studies of polyelectrolyte decomplexation. The complex between DNA and polylysine is shown to destabilize and spontaneously open in a gradual, reversible zipper-like mechanism driven by an increase in solution salt concentration. Divalent CaCl2 is significantly more effective than monovalent NaCl in destabilizing the complex due to charge correlations and water binding capability. The dissociation occurs accompanied by charge reversal in which charge correlations and ion binding chemistry play a key role. Our results are in agreement with experimental work on complex dissociation but in addition show the underlying microstructural correlations driving the behavior. Comparison of our full atomic level detail and dynamics results with theoretical works describing the PEs as charged, rigid rods reveals that although charge correlation involved theories provide qualitatively similar responses, considering also specific molecular chemistry and molecular level water contributions provides a more complete understanding of PE complex stability and dynamics. The findings may facilitate controlled release in gene delivery and more in general tuning of PE membrane permeability and mechanical characteristics through ionic strength.

  10. Counterion condensation of differently flexible polyelectrolytes in aqueous solutions in the dilute and semidilute regime.

    Science.gov (United States)

    Truzzolillo, D; Bordi, F; Cametti, C; Sennato, S

    2009-01-01

    The low-frequency limit of the electrical conductivity (dc conductivity) of differently flexible polyions in aqueous solutions has been measured over an extended polyion concentration range, covering both the dilute and semidilute (entangled and unentangled) regime, up to the concentrated regime. The data have been analyzed taking into account the different flexibility of the polymer chains according to the scaling theory of polyion solutions, in the case of flexible polyions, and according to the Manning model, in the case of rigid polyions. In both cases, the fraction f of free counterions, released into the aqueous phase from the ionizable polyion groups, has been evaluated and its dependence on the polyion concentration determined. Our results show that the counterion condensation follows at least three different regimes in dependence on the polyion concentration. The fraction f of free counterions remains constant only in the semidilute regime (a region that we have named the Manning regime), while there is a marked dependence on the polyion concentration both in the dilute and in the concentrated regime. These results are briefly discussed in the light of the scaling theory of polyelectrolyte aqueous solutions.

  11. Bombardment induced ion transport - part IV: ionic conductivity of ultra-thin polyelectrolyte multilayer films.

    Science.gov (United States)

    Wesp, Veronika; Hermann, Matthias; Schäfer, Martin; Hühn, Jonas; Parak, Wolfgang J; Weitzel, Karl-Michael

    2016-02-14

    The dependence of the ionic conductance of ultra-thin polyelectrolyte multilayer (PEM) films on the temperature and the number of bilayers has been investigated by the recently developed low energy bombardment induced ion transport (BIIT) method. To this end multilayers of alternating poly(sodium 4-styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) layers were deposited on a metal electrode and subsequently bombarded by a low energy potassium ion beam. Ions are transported through the film according to the laws of electro-diffusion towards a grounded backside electrode. They are neutralized at the interface between the polymer film and the metal electrode. The detected neutralization current scales linearly with the acceleration potential of the ion beam indicating Ohmic behavior for the (PAH/PSS)x multilayer, where x denotes the number of bilayers. The conductance exhibits a non-monotonic dependence on the number of bilayers, x. For 2 ≤ x ≤ 8 the conductance increases non-linearly with the number of bilayers. For x ≥ 8 the conductance decreases with increasing number of bilayers. The variation of the conductance is rationalized by a model accounting for the structure dependence of the conductivity. The thinnest sample for which the conductance has been measured is the single bilayer reflecting properties dominated by the interface. The activation energy for the ion transport is 0.49 eV.

  12. Effect of calcium/sodium ion exchange on the osmotic properties and structure of polyelectrolyte gels.

    Science.gov (United States)

    Horkay, Ferenc; Basser, Peter J; Hecht, Anne-Marie; Geissler, Erik

    2015-12-01

    We discuss the main findings of a long-term research program exploring the consequences of sodium/calcium ion exchange on the macroscopic osmotic and elastic properties, and the microscopic structure of representative synthetic polyelectrolyte (sodium polyacrylate, (polyacrylic acid)) and biopolymer gels (DNA). A common feature of these gels is that above a threshold calcium ion concentration, they exhibit a reversible volume phase transition. At the macroscopic level, the concentration dependence of the osmotic pressure shows that calcium ions influence primarily the third-order interaction term in the Flory-Huggins model of polymer solutions. Mechanical tests reveal that the elastic modulus is practically unaffected by the presence of calcium ions, indicating that ion bridging does not create permanent cross-links. At the microscopic level, small-angle neutron scattering shows that polyacrylic acid and DNA gels exhibit qualitatively similar structural features in spite of important differences (e.g. chain flexibility and chemical composition) between the two polymers. The main effect of calcium ions is that the neutron scattering intensity increases due to the decrease in the osmotic modulus. At the level of the counterion cloud around dissolved macroions, anomalous small-angle X-ray scattering measurements made on DNA indicate that divalent ions form a cylindrical sheath enveloping the chain, but they are not localized. Small-angle neutron scattering and small-angle X-ray scattering provide complementary information on the structure and interactions in polymer solutions and gels.

  13. Ultrathin free-standing polyelectrolyte nanocomposites: a novel method for preparation and characterization of assembly dynamics.

    Science.gov (United States)

    Ferri, James K; Dong, Wen-Fei; Miller, Reinhard

    2005-08-11

    We present a new opportunity for the investigation of the dynamics of electrostatic ultrathin-film assembly and the elucidation of time scales required for layer-by-layer adsorption of polyelectrolytes using a novel pendant drop technique which allows for the synthesis of free-standing nanocomposites. In short, a charged molecular template, i.e., a lipid monolayer, is deposited on a pendant drop and compressed to present a defined surface charge density to the subphase of the drop. The subphase is then cycled alternatively between solutions of polycations, saline, and polyanions by injection and withdrawal of liquid from coaxial capillaries on which the drop was formed, resulting in encapsulation of the drop volume by a polymeric composite membrane. The in situ dynamics of the process are followed by axisymmetric drop shape analysis. As a model, nanocomposites of dimyristoyl phosphatidyl glycerol-(polyallylamine hydrochloride/polystyrene sulfonate)(n=1-3) were prepared. The characteristic time scales for assembly range from 1 to 4 min and increase with film thickness. It is also demonstrated that small-amplitude (>1%) perturbations in the film density during adsorption prolong the assembly. Both these results underscore the nonequilibrium nature of these materials.

  14. A two-step process for controlling the surface smoothness of polyelectrolyte-based microcapsules.

    Science.gov (United States)

    Lacík, I; Anilkumar, A V; Wang, T G

    2001-01-01

    Biocompatibility is one of the crucial requirements to be fulfilled when designing devices for immunoisolation of transplanted cells. The quality of the capsule surface (smoothness/roughness) influences the nature of cell overgrowth on it by immunocytes, which eventually may lead to the transplant failure. A microcapsule has been developed based on the polyelectrolyte complexation of the polyanions sodium alginate and cellulose sulphate with the polycation poly(methylene-co-guanidine), which was successfully tested in rodent animal models. Recently, the principles for controlling the surface smoothness of these capsules has been identified. This paper reports on a two-step process used for production of stable capsules with improved surface properties. The methodology involves separating the process of drop shape recovery and precursor capsule formation from the process of membrane formation by applying a two-reactor design. The multi-loop reactors are connected in series, and the process separation is given by the different composition of cation solutions flowing in each reactor. This process enables one to prepare the microcapsule immunoisolation device, which can differ in the extent of surface roughness and, thus, is suitable for studying the effect of surface morphology of the immunoisolation device on cell overgrowth. The effect of this process on the capsule permeability has also been evaluated.

  15. 2010年地球森林覆盖面积将增加2500万hm2

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    在为期4天的亚太地区有关森林生物(Asia Pacific Regional Forests For Life)会议上.世界野生动植物基金(WWF)亚太地区的森林管理人员透露,WWF确立了新的工作目标,到2010年,地球林地覆盖面积将增加2500万hm2,使地球森林覆盖面积达到3亿hm2。这一目标除了确保对不同品种的森林予以足够的保护外,将主要通过加强森林管理来实现。

  16. Draft Genome Sequence of the D-Xylose-Fermenting Yeast Spathaspora arborariae UFMG-HM19.1AT.

    Science.gov (United States)

    Lobo, Francisco P; Gonçalves, Davi L; Alves, Sergio L; Gerber, Alexandra L; de Vasconcelos, Ana Tereza R; Basso, Luiz C; Franco, Glória R; Soares, Marco A; Cadete, Raquel M; Rosa, Carlos A; Stambuk, Boris U

    2014-01-16

    The draft genome sequence of the yeast Spathaspora arborariae UFMG-HM19.1A(T) (CBS 11463 = NRRL Y-48658) is presented here. The sequenced genome size is 12.7 Mb, consisting of 41 scaffolds containing a total of 5,625 predicted open reading frames, including many genes encoding enzymes and transporters involved in d-xylose fermentation.

  17. Polyelectrolyte properties of filamentous biopolymers and their consequences in biological fluids.

    Science.gov (United States)

    Janmey, Paul A; Slochower, David R; Wang, Yu-Hsiu; Wen, Qi; Cēbers, Andrejs

    2014-03-14

    Anionic polyelectrolyte filaments are common in biological cells. DNA, RNA, the cytoskeletal filaments F-actin, microtubules, and intermediate filaments, and polysaccharides such as hyaluronan that form the pericellular matrix all have large net negative charge densities distributed over their surfaces. Several filamentous viruses with diameters and stiffnesses similar to those of cytoskeletal polymers also have similar negative charge densities. Extracellular protein filaments such collagen, fibrin and elastin, in contrast, have notably smaller charge densities and do not behave as highly charged polyelectrolytes in solution. This review summarizes data that demonstrate generic counterion-mediated effects on four structurally unrelated biopolymers of similar charge density: F-actin, vimentin, Pf1 virus, and DNA, and explores the possible biological and pathophysiological consequences of the polyelectrolyte properties of biological filaments.

  18. Condensation of semiflexible polyelectrolytes in mixed solutions of mono- and multivalent salts

    Science.gov (United States)

    Plunk, Amelia A.; Luijten, Erik

    2013-03-01

    The salt-dependent condensation of highly charged polyelectrolytes in aqueous solution is a topic of great biological and industrial importance that has been widely studied over the past decades. It is well established that interaction with multivalent counterions leads to the formation of bundle-like aggregates for rigid polyelectrolytes and to collapsed structures or disordered aggregates for flexible polyelectrolytes. Here, we investigate the behavior of semiflexible chain molecules, where the electrostatically induced aggregation is impeded by the intrinsic bending stiffness of the polymer. Moreover, we study the competition between monovalent and multivalent counterions in mixed solutions and establish the threshold salt concentration required for condensation. Our findings are relevant for a range of biomedical problems, including the fabrication of nanoparticles for gene delivery and the packaging of DNA by histones. This work is supported by the National Science Foundation.

  19. Recent Progress and Perspectives in the Electrokinetic Characterization of Polyelectrolyte Films

    Directory of Open Access Journals (Sweden)

    Ralf Zimmermann

    2015-12-01

    Full Text Available The analysis of the charge, structure and molecular interactions of/within polymeric substrates defines an important analytical challenge in materials science. Accordingly, advanced electrokinetic methods and theories have been developed to investigate the charging mechanisms and structure of soft material coatings. In particular, there has been significant progress in the quantitative interpretation of streaming current and surface conductivity data of polymeric films from the application of recent theories developed for the electrohydrodynamics of diffuse soft planar interfaces. Here, we review the theory and experimental strategies to analyze the interrelations of the charge and structure of polyelectrolyte layers supported by planar carriers under electrokinetic conditions. To illustrate the options arising from these developments, we discuss experimental and simulation data for plasma-immobilized poly(acrylic acid films and for a polyelectrolyte bilayer consisting of poly(ethylene imine and poly(acrylic acid. Finally, we briefly outline potential future developments in the field of the electrokinetics of polyelectrolyte layers.

  20. Treatment of effluents of poultry slaughterhouse with aluminum salts and natural polyelectrolytes.

    Science.gov (United States)

    Ikeda, E; Rodrigues, D G; Nozaki, J

    2002-08-01

    A mixture of aluminum salts and natural polyelectrolytes, extracted from the cactus Opuntia ficus indica, has been used for cleaning of wastewater from poultry slaughterhouse. The aggregation and settling properties of colloids and complex organics such as oil, grease, fats, proteins, and suspended solids, was increased if compared with conventional methods of wastewater treatment using only aluminum or iron sulfate. A mixture of aluminum salt in a concentration range of 300 to 600 mg l(-1) and natural polyelectrolytes of 0.6 to 0.8 mg l(-1) was used for flocculation and coagulation. The combination of coagulant and natural polyelectrolytes was able to remove chemical oxygen demand (86%), oil and grease (93%), turbidity (89%), and suspended solids (93%). Methanization activity was also investigated for the effluents in natura.

  1. Design of Chitosan and Its Water Soluble Derivatives-Based Drug Carriers with Polyelectrolyte Complexes

    Science.gov (United States)

    Wu, Qing-Xi; Lin, Dong-Qiang; Yao, Shan-Jing

    2014-01-01

    Chitosan, the cationic polysaccharide derived from the natural polysaccharide chitin, has been studied as a biomaterial for more than two decades. As a polycationic polymer with favorable properties, it has been widely used to form polyelectrolyte complexes with polyanions for various applications in drug delivery fields. In recent years, a growing number of studies have been focused on the preparation of polyelectrolyte complexes based on chitosan and its water soluble derivatives. They have been considered well-suited as biomaterials for a number of vital drug carriers with targeted/controlled release profiles, e.g., films, capsules, microcapsules. In this work, an overview highlights not only the favorable properties of chitosan and its water soluble derivatives but also the good performance of the polyelectrolyte complexes produced based on chitosan. Their various types of applications as drug carriers are reviewed in detail. PMID:25532565

  2. Synthesis and characterization of CdS-polyelectrolyte-Bi2S3 thin film by SILAR

    Science.gov (United States)

    Desale, Dipalee J.; Shaikh, Shaheed; Siddiqui, Farha; AnilGhule, Ravikiran Birajadar; Sharma, Ramphal

    2012-06-01

    CdS-Polyelectrolyte-Bi2S3 was grown by cost effective successive ionic layer adsorption and reaction method (SILAR) on glass substrate. The polyelectrolyte used as a protecting layer for excessive ionic loss during the exchange reaction between the cation and anions of the reactants. Thin films was characterized for structural, morphological and an I-V characteristic. The X-ray diffraction pattern (XRD) pattern shows that, CdS-Polyelectrolyte-Bi2S3 thin films have mixed phase of hexagonal and orthorhombic crystal structures corresponding to CdS and Bi2S3 respectively. Scanning electron microscopy (SEM) corresponds deposition of the material along with the presence of bundle like shape is observed in thin film. The I-V measurement under dark and illumination to 100 mW/cm2 shows increase in photoconductivity.

  3. Layer-by-layer self-assembly of polyelectrolyte functionalized MoS2 nanosheets.

    Science.gov (United States)

    Shen, Jianfeng; Pei, Yu; Dong, Pei; Ji, Jin; Cui, Zheng; Yuan, Junhua; Baines, Robert; Ajayan, Pulickel M; Ye, Mingxin

    2016-05-01

    Few-layered polyelectrolyte functionalized MoS2 nanosheets were obtained for the first time through in situ polymerization of MoS2 nanosheets with poly(acrylic acid) and poly(acrylamide), both of which demonstrated excellent dispersibility and stability in water. After designing and optimizing the components of this series of polyelectrolyte functionalized MoS2 nanosheets, by exploiting the electrostatic interactions present in the modified MoS2 nanosheets, we further created a series of layer-by-layer (LBL) self-assembling MoS2-based films. To this end, uniform MoS2 nanosheet-based LBL films were precisely deposited on substrates such as quartz, silicon, and ITO. The polyelectrolyte functionalized MoS2 nanosheet assembled LBL film-modified electrodes demonstrated enhanced electrocatalytic activity for H2O2. As such, they are conducive to efficient sensors and advanced biosensing systems.

  4. Chitosan-Based Zwitterionic Polyelectrolytes and Their N-Phosphobetainates: Facile Synthesis and Aqueous Solution Behaviors

    Institute of Scientific and Technical Information of China (English)

    Hongmei Kang; Yuanli Cai; Haijia Zhang; Junjie Deng; Pengsheng Liu

    2005-01-01

    @@ 1Introduction Chitosan has remarkable potential applications in pharmaceutical and cosmetic formulations[1], e.g. for drug delivery systems, tissue engineering, transplant and cell regeneration due to its excellent biocompatibility, biodegradability, mucoadhesion, etc. Its major drawback as considered for pharmaceutical and cosmetic formulations is its poor solubility due to strong hydrogen bonding and compact structures. Considerable efforts were focused on improving its solubility and enforcing its functionality[1]. As well-known that phosphorylcholine (PC), the structural component of cell membrane, is an amphiphile containing the zwitterionic quaternary ammonium and phosphonic acid moieties (phosphobetaine groups). There has been an intensive effort over the past decades to prepare and explore potential applications of the synthetic PC-polymers[2].In this paper, we describe a facile synthesis of chitosan derivatives containing zwitterionic secondary/tertiary amine and phosphonic acid groups and their further N-phosphobetainates. The polyelectrolyte effect and anti-polyelectrolyte effect of the chitosan-based zwitterionic polyelectrolytes were studied.

  5. The class characteristic mark of the H&M Mul-T-Lock picking tool in toolmarks examination.

    Science.gov (United States)

    Volkov, Nikolai; Finkelstein, Nir; Novoselsky, Yehuda; Tsach, Tsadok

    2014-07-01

    Mul-T-Lock is a high security lock cylinder distinguished by the use of a telescoping "pin-in-pin"-tumbler design. Picking the Mul-T-Lock cylinder with a traditional picking tool is highly complicated because it can get stuck between the inner and outer pins. The H&M Mul-T-Lock picking tool was designed to overcome this problem and facilitate the picking of the "pin-in-pin" cylinder. The purpose of this research is to determine whether H&M Mul-T-Lock picking tool leaves class characteristic mark and whether it can be distinguished from traditional picking tools marks and from regular key marks. It also describes and determines the class characteristic mark left on telescopic pins, its origin, recurrence, and its benefit to the toolmarks examiner. When receiving a Mul-T-Lock from a crime scene, a toolmarks examiner can quickly determine whether or not it was picked by an H&M Mul-T-Lock picking tool by noticing the class characteristic mark which this typical tool leaves.

  6. Technetium-99m d,l-HM-PAO: a new radiopharmaceutical for SPECT imaging of regional cerebral blood perfusion

    Energy Technology Data Exchange (ETDEWEB)

    Neirinckx, R.D.; Canning, L.R.; Piper, I.M.; Nowotnik, D.P.; Pickett, R.D.; Holmes, R.A.; Volkert, W.A.; Forster, A.M.; Weisner, P.S.; Marriott, J.A.

    1987-02-01

    Following investigation of a large number of new ligands based upon propylene amine oxime (PnAO) the d,l-diastereoisomer of hexamethyl propyleneamine oxime (HM-PAO) was selected as the preferred ligand for 99mTc as a tracer for cerebral perfusion imaging. The neutral, lipophilic 99mTc complex of d,l-HM-PAO was formed in high yield by stannous reduction of 99Mo/99mTc generator eluate using a kit formulation of the ligand. Two minutes following i.v. administration of this complex in rats, 2.25% of the injected dose appears in the brain. Little washout of the tracer is observed up to 24 hr postinjection. By qualitative autoradiographic comparison with iodoantipyrine this new radiopharmaceutical displays blood flow dependent brain uptake with little redistribution of the tracer over time. The lipophilic 99mTc complex converts slowly in vitro to a secondary complex. This conversion process may account for the ability of (99mTc)d,l-HM-PAO to be retained within the brain without redistribution.

  7. Assessment of the arterial input curve for [99mTc]-d,l-HM-PAO by rapid octanol extraction

    DEFF Research Database (Denmark)

    Andersen, A R; Friberg, H; Lassen, N A

    1988-01-01

    a rapid method for measuring the radiochemical purity (RCP) of lipophilic [99mTc]-d,l-HM-PAO. In saline, the RCP declined with a half-life of more than 1 h. In human plasma and whole blood, the conversion of [99mTc]-d,l-HM-PAO was biexponential due to the differences in the conversion rates of the d and l...... isomeric forms. The initial half-life representing the conversion rate of the l form was 1.7 min in blood and 1.4 min in plasma, while the conversion half-life of the d form was 7.4 and 24.4 min, respectively. In vivo, the RCP of arterial blood sampled after an i.v. bolus injection showed an initial peak...... value of 75% (68-79%) during the initial, first passage of the bolus. It declined to approximately 35% (29-40%) after 1.5 min and reached very low levels (about 1%) at 6 to 10 min. Quantitative measurements of cerebral blood flow using [99mTc]-d,l-HM-PAO necessitates a rapid method for RCP determination...

  8. Comparison of technetium-99m-HM-PAO leukocytes with indium-111-oxine leukocytes for localizing intraabdominal sepsis

    Energy Technology Data Exchange (ETDEWEB)

    Mountford, P.J.; Kettle, A.G.; O' Doherty, M.J.; Coakley, A.J. (Kent and Canterbury Hospital (England))

    1990-03-01

    Technetium-99m-HM-PAO (({sup 99m}Tc)HM-PAO) leukocyte and indium-111-oxine (111In-oxine) leukocyte scanning were carried out simultaneously in 41 patients at 4 hr and 24 hr after reinjection to determine whether the 4-hr {sup 99m}Tc scan could replace the 24-hr {sup 111}In scan for detecting intraabdominal sepsis. Abdominal infection was confirmed in 12 cases. The 4-hr {sup 99}Tc-leukocyte scan, the 4-hr {sup 111}In-leukocyte scan, and the 24-hr {sup 111}In-leukocyte scan yielded a sensitivity of 100%, 67%, and 100%, respectively, and a specificity of 62%, 90%, and 86%, respectively. The 24-hr {sup 99m}Tc-leukocyte scan also produced a sensitivity of 100%, but it was falsely positive in all 29 cases without infection due to physiologic bowel uptake. False-positive 4-hr {sup 99m}Tc-leukocyte scans were also produced by physiologic bowel uptake in seven cases all of whom had true-negative 4-hr and 24-hr {sup 111}In-leukocyte scans. Because of the high incidence of false-positive 4-hr ({sup 99m}Tc)HM-PAO leukocyte scans, it was concluded that they could not replace 24-hr {sup 111}In-leukocyte scans for detecting intraabdominal sepsis, and that serial {sup 99m}Tc leukocyte scans starting earlier than 4 hr after reinjection must be evaluated.

  9. EFFECT OF MIXING CONDITIONS ON FLOCCULATION KINETICS OF WASTEWATERS CONTAINING PROTEINS AND OTHER BIOLOGICAL COMPOUNDS USING FIBROUS MATERIALS AND POLYELECTROLYTES

    Directory of Open Access Journals (Sweden)

    L.A. CHEN

    1998-12-01

    Full Text Available The application of a combined system of a polyelectrolyte, carboxymethyl cellulose (CMC, and highly fibrillated fibrous materials, cellulose triacetate fibrets (CTF, for the recovery of proteins and other biological compounds from model and actual biological systems has been demonstrated . In the present work, reaction batches were scaled-up to a one-liter agitated vessel, with a standard configuration. The effect of mixing conditions on the adsorption and flocculation process was studied. It was observed that flocculation time was very fast, occurring within the period of polymer addition. Long term shearing did not result in floc breakage and the values of percentage light transmission and protein concentration of the final filtrate remained the same during the incubation period. Increasing the shear rate resulted in improved process efficiency, up to an optimum value, above which performance was poorer. Perikinetic and orthokinetic rate parameters were calculated and results analyzed in view of these parameters.

  10. 精密喷射成形HM1钢摩擦磨损性能研究%Friction and wear properties of HM1 steel processed by precision spray forming

    Institute of Scientific and Technical Information of China (English)

    程永奇; 汪存龙; 张鹏; 孙友松

    2014-01-01

    为了探索提高HM1钢耐磨性能的制备新途径,采用往复式滑动干摩擦实验研究了精密喷射成形HM1钢摩擦磨损性能并对其磨损机制进行了分析,同时还与铸态材料进行了对比。结果表明:不同载荷下,喷射态和喷射回火态HM1钢摩擦系数均低于铸态;当载荷为100 N时,与铸态相比,喷射态磨损量比其低约34%,喷射回火态磨损量比其减少约48%。对磨痕形貌分析表明,当载荷为40 N时,铸态试样以粘着磨损为主,当载荷为100 N时,转换为粘着磨损与磨粒磨损共存,并伴随严重的氧化磨损;对于喷射态和喷射回火态试样,则以磨粒磨损为主,氧化磨损减轻。%To improve the wear resistance of HM1 steel, the friction and wear properties of HM1 steel processed by precision spray forming ( PSF) were studied by dry friction of reciprocating sliding and the wear mechanisms were analyzed, and the results were compared to the as-casted HM1 steel. The results indicated that the friction coefficient of HM1 steel processed by precision spray forming and precision spray forming with tempering ( PSFT) was lower than that of the as-casted material. The wear rate of the PSFTed specimens was lower about 34% than that of the as-casted specimens under the loads of 100 N. While, the wear rate of the PSFTed specimens was lower about 48% than that of the as-casted specimens under the loads of 100 N. SEM morphology of wear scar showed that the mainly wear mechanism of the as-casted specimens under the load of 40 N was adhesive wear and the wear mechanism was converted to the coexistence of adhesive wear and abrasive wear with severely oxidation wear under the load of 100 N. While the wear mechanism of the PSFed and PSFTed specimens was mainly abrasive wear with mildly oxidation wear.

  11. Structure-property relationships in the design, assembly and applications of polyelectrolyte multilayer thin films

    Science.gov (United States)

    Rmaile, Hassan H.

    Ultrathin films consisting of an alternating sequence of positively and negatively charged polyelectrolytes have been prepared by means of the electrostatic layer-by-layer sequential assembly technique. To augment their typical applications in the water treatment, personal care as well as the pulp and paper industry, the structure and the design of these polyelectrolytes were tailored synthetically to satisfy the requirements of different types of applications. Some were used for surface modifications, hydrophobic and hydrophilic coatings, corrosion protection, conducting and biocompatible surfaces. Others were found to be very efficient for membrane and chromatographic applications. The ease with which these multilayer coatings can be constructed, their robustness and stability make them very good candidates for industrial applications. The dissertation focuses mainly on the structure-property relationships of these polyelectrolytes and their corresponding thin films. Various polyelectrolytes were synthesized or modified in a strategic approach and gave novel and promising properties. Some of them exhibited permeabilities that were higher than any membranes reported in the literature. Also, some are potentially very useful for designing drug delivery systems such as tablets or encapsulations since they were shown to control the permeability of sample drugs and vitamins very efficiently based on their sensitivity to pH changes. Other synthesized polyelectrolytes proved to be very effective in preventing protein adsorption or promoting cell growth and differentiation. Some systems were very useful as robust stationary phases for simple chiral separations in capillary electrochromatography. Along with modifications and improvements, the approach might one day be applied commercially for chiral separations using high performance liquid chromatography and replace currently used stationary phases. Last but not least, the potential for these polyelectrolytes and their

  12. Facile preparation of cobaltocenium-containing polyelectrolyte via click chemistry and RAFT polymerization.

    Science.gov (United States)

    Yan, Yi; Zhang, Jiuyang; Qiao, Yali; Tang, Chuanbing

    2014-01-01

    A facile method to prepare cationic cobaltocenium-containing polyelectrolyte is reported. Cobaltocenium monomer with methacrylate is synthesized by copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction between 2-azidoethyl methacrylate and ethynylcobaltocenium hexafluorophosphate. Further controlled polymerization is achieved by reversible addition-fragmentation chain transfer polymerization (RAFT) by using cumyl dithiobenzoate (CDB) as a chain transfer agent. Kinetic study demonstrates the controlled/living process of polymerization. The obtained side-chain cobaltocenium-containing polymer is a metal-containing polyelectrolyte that shows characteristic redox behavior of cobaltocenium. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Polyelectrolyte Properties in Mono and Multi-Valent Ionic Media: Brushes and Complex Coacervates

    Science.gov (United States)

    Farina, Robert M.

    Materials composed of polyelectrolytes have unique and interesting physical properties resulting primarily from their charged monomer segments. Polyelectrolytes, which exist in many different biological and industrial forms, have also been shown to be highly responsive to external environmental changes. Here, two specific polyelectrolyte systems, brushes and complex coacervates, are discussed in regards to how their properties can be tailored by adjusting the surrounding ionic environment with mono and multi-valent ions. End-tethered polyelectrolyte brushes, which constitute an interesting and substantial portion of polyelectrolyte applications, are well known for their ability to provide excellent lubrication and low friction when coated onto surfaces (e.g. articular cartilage and medical devices), as well as for their ability to stabilize colloidal particles in solution (e.g. paint and cosmetic materials). These properties have been extensively studied with brushes in pure mono-valent ionic media. However, polyelectrolyte brush interactions with multi-valent ions in solution are much less understood, although highly relevant considering mono and multi-valent counterions are present in most applications. Even at very low concentrations of multi-valent ions in solution, dramatic polyelectrolyte brush physical property changes can occur, resulting in collapsed chains which also adhere to one another via multi-valent bridging. Here, the strong polyelectrolyte poly(sodium styrene sulfonate) was studied using the Surface Forces Apparatus (SFA) and electrochemistry in order to investigate brush height and intermolecular interactions between two brushes as a function of multi-valent counterion population inside a brush. Complex coacervates are formed when polyanions and polycations are mixed together in proper conditions of an aqueous solution. This mixing results in a phase separation of a polymer-rich, coacervate phase composed of a chain network held together via

  14. Biofunctionalization of polyelectrolyte microcapsules with biotinylated polyethylene glycol-grafted liposomes.

    Science.gov (United States)

    Gao, Jie; Reibetanz, Uta; Venkatraman, Subbu; Neu, Björn

    2011-08-11

    Hollow polyelectrolyte microcapsules (PEMC) are prepared using layer-by-layer self-assembly of polyelectrolytes on melamine formaldehyde templates, followed by template dissolution, and subsequent coating with biotinylated polyethylene glycol-grafted liposomes. These potential site-specific carrier systems show a high specificity for NeutrAvidin binding and a strong resistance against unspecific protein binding. It is concluded that this design with NeutrAvidin as the outermost layer of such capsules provides an ideal platform for the biofunctionalization of PEMC as drug delivery systems or as artificial cell-like structures for biomimetic studies.

  15. The effect of temperature and pressure on the oxygen reduction reactions in polyelectrolyte membranes

    Energy Technology Data Exchange (ETDEWEB)

    Holdcroft, S.; Abdou, M.S.; Beattie, P.; Basura, V. [Simon Fraser Univ., Burnaby, BC (Canada). Dept. of Chemistry

    1997-12-31

    The effect of temperature and pressure on the oxygen reduction reaction in polyelectrolyte membranes was described. Polyelectrolytes chosen for the experiment differed in composition, weight and flexibility of the polymer chains. The study was conducted in a solid state electrochemical cell at temperatures between 30 and 95 degrees C and in the pressure range of 1 to 5 atm. The solubility of oxygen in these membranes was found to follow Henry`s Law, while the diffusion coefficient decreased with pressure. The effect of temperature on the solubility of oxygen and the diffusion coefficient of oxygen in the membranes was similar to that observed in solution electrolytes. 2 refs., 3 figs.

  16. Multiple internalization pathways of polyelectrolyte multilayer capsules into mammalian cells.

    Science.gov (United States)

    Kastl, Lena; Sasse, Daniel; Wulf, Verena; Hartmann, Raimo; Mircheski, Josif; Ranke, Christiane; Carregal-Romero, Susana; Martínez-López, José Antonio; Fernández-Chacón, Rafael; Parak, Wolfgang J; Elsasser, Hans-Peter; Rivera Gil, Pilar

    2013-08-27

    Polyelectrolyte multilayer (PEM) capsules are carrier vehicles with great potential for biomedical applications. With the future aim of designing biocompatible, effective therapeutic delivery systems (e.g., for cancer), the pathway of internalization (uptake and fate) of PEM capsules was investigated. In particular the following experiments were performed: (i) the study of capsule co-localization with established endocytic markers, (ii) switching-off endocytotic pathways with pharmaceutical/chemical inhibitors, and (iii) characterization and quantification of capsule uptake with confocal and electron microscopy. As result, capsules co-localized with lipid rafts and with phagolysosomes, but not with other endocytic vesicles. Chemical interference of endocytosis with chemical blockers indicated that PEM capsules enter the investigated cell lines through a mechanism slightly sensitive to electrostatic interactions, independent of clathrin and caveolae, and strongly dependent on cholesterol-rich domains and organelle acidification. Microscopic characterization of cells during capsule uptake showed the formation of phagocytic cups (vesicles) to engulf the capsules, an increased number of mitochondria, and a final localization in the perinuclear cytoplasma. Combining all these indicators we conclude that PEM capsule internalization in general occurs as a combination of different sequential mechanisms. Initially, an adsorptive mechanism due to strong electrostatic interactions governs the stabilization of the capsules at the cell surface. Membrane ruffling and filopodia extensions are responsible for capsule engulfing through the formation of a phagocytic cup. Co-localization with lipid raft domains activates the cell to initiate a lipid-raft-mediated macropinocytosis. Internalization vesicles are very acidic and co-localize only with phagolysosome markers, excluding caveolin-mediated pathways and indicating that upon phagocytosis the capsules are sorted to

  17. Complexation of oppositely charged polyelectrolytes in gene delivery and biology

    Science.gov (United States)

    Shklovskii, Boris

    2009-03-01

    Charge inversion of a DNA double helix by a positively charged flexible polymer (polyelectrolyte) is widely used to facilitate DNA contact with negative cell membranes for gene delivery. Motivated by this application in the first part of the talk I study the phase diagram a solution of long polyanions (PA) with a shorter polycations (PC) as a function the ratio of total charges of PC and PA in the solution, x, and the concentration of monovalent salt. Each PA attracts many PCs to form a complex. When x= 1, the complexes are neutral and condense in a macroscopic drop. When x is far away from 1, complexes are strongly charged and stable. PA are overcharged by PC at x > 1 and undercharged by PC at x vegetable viruses from long ss-RNA molecule paying role of scaffold and identical capsid proteins with long positive tails. I show that optimization Coulomb energy of the virus leads to the charge of RNA twice larger than the total charge of the capsid, in agreement with the experimental data. Then I discuss kinetics of the Coulomb complexation driven virus self-assembly. Capsid proteins stick to unassembled chain of ss RNA (which we call ``antenna'') and slide on it towards the assembly site. I show that at excess of capsid proteins such one-dimensional diffusion accelerates self-assembly more than ten times. On the other hand at excess of ss-RNA, antenna slows self-assembly down. Several experiments are proposed to verify the role of ss-RNA antenna in self-assembly.

  18. Ionic conductivity studies of gel polyelectrolyte based on ionic liquid

    Energy Technology Data Exchange (ETDEWEB)

    Cha, E.H. [The Faculty of Liberal Arts (Chemistry), Hoseo University, Asan Choongnam 336-795 (Korea); Lim, S.A. [Functional Proteomics Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea); Park, J.H. [Department of Herbal Medicine, Hoseo University, Asan Choongnam 336-795 (Korea); Kim, D.W. [Department of Chemical Technology, Han Bat National University, Daejon 305-719 (Korea); Macfarlane, D.R. [School of Chemistry, Monash University, Clayton, Vic. 3800 (Australia)

    2008-04-01

    Novel lithium polyelectrolyte-ionic liquids have been prepared and characterized of their properties. Poly(lithium 2-acrylamido-2-methyl propanesulfonate) (PAMPSLi) and its copolymer with N-vinyl formamide (VF) also has been prepared as a copolymer. 1-Ethyl-3-methylimidazolium tricyanomethanide (emImTCM) and N,N-dimethyl-N-propyl-N-butyl ammonium tricyanomethanide (N{sub 1134}TCM) which are chosen because of the same with the anion of ionic liquid were prepared. The ionic conductivity of copolymer system (PAMPSLi/PVF/emImTCM: 5.43 x 10{sup -3} S cm{sup -1} at 25 C) exhibits about over four times higher than that of homopolymer system (PAMPSLi/emImTCM: 1.28 x 10{sup -3} S cm{sup -1} at 25 C). Introduction of vinyl formamide into the copolymer type can increase the dissociation of the lithium cations from the polymer backbone. The ionic conductivity of copolymer with emImTCM (PAMPSLi/PVF/emImTCM) exhibits the higher conductivity than that of PAMPSLi/PVF/N{sub 1134}TCM (2.48 x 10{sup -3} S cm{sup -1}). Because of using the polymerizable anion it is seen to maintain high flexibility of imidazolium cation effectively to exhibit the higher conductivity. And also the viscosity of emImTCM (19.56 cP) is lower than that of N{sub 1134}TCM (28.61 cP). Low viscosity leads to a fast rate of diffusion of redox species. (author)

  19. Polyelectrolyte complex/PVA membranes for diffusion dialysis.

    Science.gov (United States)

    Wang, Cong; Wu, Cuiming; Wu, Yonghui; Gu, Jingjing; Xu, Tongwen

    2013-10-15

    Polyelectrolyte complexes (PECs)/polyvinyl alcohol (PVA) membranes are prepared from PVA, anion exchange and cation exchange multisilicon copolymers, which contain plenty of functional groups of OH, N(+)(CH3)3/Si(OCH3)3, and SO3Na/Si(OCH3)3, respectively. The OH and Si(OCH3)3 groups can undertake sol-gel reaction to form crosslinking structure, while the N(+)(CH3)3 and SO3Na groups can be combined through electrostatic interaction. The PECs/PVA membranes exhibit improved thermal stability, swelling resistance and flexibility as compared with single anion or cation exchange hybrid membranes. The PECs/PVA membranes have the water uptakes (WR) of 25.3-70.4%, initial decomposition temperatures (IDTs) of 246-285°C, tensile strength of 23.1-33.8 MPa, and elongation at break of 3.5-13.1%. The membranes can be potentially applied for both acid and alkali recovery through diffusion dialysis (DD) process. The separation factor (S) for HCl/FeCl2 mixture can reach up to 89.9, which is about five times higher than that of commercial DF-120 membrane (18.5 at 25°C). The dialysis coefficients of NaOH (UOH) are in the range of 0.014-0.019 m/h, around 7-9 times higher than the value of commercial SPPO membrane (0.002 m/h at 25°C). The membranes also show potential usefulness for industrial acidic and alkali wastes treatment.

  20. Engineering muscle tissues on microstructured polyelectrolyte multilayer films.

    Science.gov (United States)

    Monge, Claire; Ren, Kefeng; Berton, Kevin; Guillot, Raphael; Peyrade, David; Picart, Catherine

    2012-08-01

    The use of surface coating on biomaterials can render the original substratum with new functionalities that can improve the chemical, physical, and mechanical properties as well as enhance cellular cues such as attachment, proliferation, and differentiation. In this work, we combined biocompatible polydimethylsiloxane (PDMS) with a biomimetic polyelectrolyte multilayer (PEM) film made of poly(L-lysine) and hyaluronic acid (PLL/HA) for skeletal muscle tissue engineering. By microstructuring PDMS in grooves of a different width (5, 10, 30, and 100 μm) and by modulating the stiffness of the (PLL/HA) films, we guided skeletal muscle cell differentiation into myotubes. We found optimal conditions for both the formation of parallel-oriented myotubes and their maturation. Significantly, the myoblasts were collectively prealigned to the grooves before their differentiation. Before fusion, the highest aspect ratio and orientation of nuclei were observed for the 5 and 10 μm wide micropatterns. The formation of myotubes was observed regardless of the size of the micropatterns, and we found that their typical width was 10-12 μm. Their maturation was characterized by the immunolabeling of type II isomyosin. The amount of myosin striation was not affected by the topography, except for the 5 μm wide micropatterns. We highlighted the spatial constraints that led to an important nuclei deformation and further impairment of maturation within the 5 μm grooves. Altogether, our results show that the PEM film combined with PDMS is a powerful tool that is used for skeletal muscle engineering. This work opens perspectives for the development of skeletal muscle tissue in contact with films containing bioactive peptides or growth factors as well as for the study of pathogenic myotubes.

  1. Research on Market Readiness for Fashion Brand Entry into Shijiazhuang : Feasibility Study of H&M Company Entry into Shijiazhuang Market

    OpenAIRE

    Chang, Mengjia

    2011-01-01

    The purpose of this study was to find out whether the Shijiazhuang City in China is a proper market for H&M. This thesis introduces the H&M Company, the situational analysis of the relevant market, and the attitude of Chinese people living in Shijiazhuang City towards H&M. The author chose quantitative method as research methodology. Data was collected by using a questionnaire consisting of fourteen multiple-choice questions and one open-ended question. The respondents were all native Chi...

  2. Polyelectrolyte Complex Based Interfacial Drug Delivery System with Controlled Loading and Improved Release Performance for Bone Therapeutics

    Directory of Open Access Journals (Sweden)

    David Vehlow

    2016-03-01

    Full Text Available An improved interfacial drug delivery system (DDS based on polyelectrolyte complex (PEC coatings with controlled drug loading and improved release performance was elaborated. The cationic homopolypeptide poly(l-lysine (PLL was complexed with a mixture of two cellulose sulfates (CS of low and high degree of substitution, so that the CS and PLL solution have around equal molar charged units. As drugs the antibiotic rifampicin (RIF and the bisphosphonate risedronate (RIS were integrated. As an important advantage over previous PEC systems this one can be centrifuged, the supernatant discarded, the dense pellet phase (coacervate separated, and again redispersed in fresh water phase. This behavior has three benefits: (i Access to the loading capacity of the drug, since the concentration of the free drug can be measured by spectroscopy; (ii lower initial burst and higher residual amount of drug due to removal of unbound drug and (iii complete adhesive stability due to the removal of polyelectrolytes (PEL excess component. It was found that the pH value and ionic strength strongly affected drug content and release of RIS and RIF. At the clinically relevant implant material (Ti40Nb similar PEC adhesive and drug release properties compared to the model substrate were found. Unloaded PEC coatings at Ti40Nb showed a similar number and morphology of above cultivated human mesenchymal stem cells (hMSC compared to uncoated Ti40Nb and resulted in considerable production of bone mineral. RIS loaded PEC coatings showed similar effects after 24 h but resulted in reduced number and unhealthy appearance of hMSC after 48 h due to cell toxicity of RIS.

  3. Estimativa da entalpia de decomposição (deltaD Hmº de adutos por termogravimetria Estimative of deltaD Hmº for adducts by thermogravimetry

    Directory of Open Access Journals (Sweden)

    Robson Fernandes de Farias

    1998-07-01

    Full Text Available An empirical equation: deltaD HmO = t i/2.2(2-n is obtained and tested for 102 adducts (mainly adducts with zinc group halides. In the equation, t i is the Kelvin temperature of the beginning of the thermal decomposition of the adduct, (obtained by thermogravimetry, and n is the number of ligands. For 1/3 of the tested adducts the difference between experimental and calculated values was less than 5%. For about 1/3 of the adducts that difference exceeds 15%.

  4. Isolation of bovine coronavirus (BCoV in monolayers of HmLu-1 cells Isolamento de coronavírus bovino (BCoV em monocamada de cultura de células da linhagem HmLu-1

    Directory of Open Access Journals (Sweden)

    José Antonio Jerez

    2005-09-01

    Full Text Available Isolation of BCoV was performed in monolayers of HmLu-1 cells, using 20 fecal samples from clinical cases of diarrhea in calves. Samples were positive for BCoV by means of hemagglutination / hemagglutination inhibition (HA/HI. Up to the fifth serial passage, 13 of these isolates presented syncytial cytopathic effect, similar to Kakegawa standard strain. When isolates were submitted to seroneutralization with gammaglobulin anti-bovine coronavirus, 8 of them were considered to be positive, once cytopathic effect was neutralized. After titration and seroneutralization in microplates, only three of them were confirmed as positive. The lineage HmLu-1 showed higher permissivity to BCoV isolation, but the low intensity of viral replication demonstrated that new methodologies should be developed for this purpose and then submitted to confirmation of isolation by means of seroneutralization.A partir de 20 amostras fecais de bezerros, com quadro clínico de diarréia, positivas para BCoV por hemaglutinação/inibição da hemaglutinação (HA/HI, procedeu-se o isolamento viral em monocamadas de células da linhagem HmLu-1. Até a quinta passagem seriada, 13 apresentaram efeito citopático do tipo sincicial, semelhante à amostra padrão Kakegawa de BCoV. Ao serem submetidas a uma reação de soroneutralização com gamaglobulina anti-coronavírus bovino, 8 delas foram consideradas positivas, uma vez que o efeito citopático foi neutralizado. Ao serem tituladas e submetidas à reação de soroneutralização em microplacas, apenas 3 delas puderam ser confirmadas como positivas. As células da linhagem HmLu-1 mostraram-se permissivas para o isolamento de BCoV, todavia a baixa intensidade na replicação viral demonstrou ser necessário o desenvolvimento de novas metodologias para se poder alcançar esse intuito e a confirmação do isolamento por soroneutralização.

  5. Introducing a high gravity field to enhance infiltration of small molecules into polyelectrolyte multilayers.

    Science.gov (United States)

    Liu, Xiaolin; Zhao, Kun; Jiang, Chao; Wang, Yue; Shao, Lei; Zhang, Yajun; Shi, Feng

    2015-07-28

    Loading functional small molecules into nano-thin films is fundamental to various research fields such as membrane separation, molecular imprinting, interfacial reaction, drug delivery etc. Currently, a general demand for enhancing the loading rate without affecting the film structures exists in most infiltration phenomena. To handle this issue, we have introduced a process intensification method of a high gravity technique, which is a versatile energy form of mechanical field well-established in industry, into the investigations on diffusion/infiltration at the molecular level. By taking a polyelectrolyte multilayer as a model thin film and a photo-reactive molecule, 4,4'-diazostilbene-2,2'-disulfonic acid disodium salt (DAS), as a model small functional molecule, we have demonstrated remarkably accelerated adsorption/infiltration of DAS into a poly(allylamine hydrochloride) (PAH)/poly(acrylic acid) (PAA) multilayer by as high as 20-fold; meanwhile, both the film property of the multilayer and photoresponsive-crosslinking function of DAS were not disturbed. Furthermore, the infiltration of DAS and the surface morphology of the multilayer could be tuned based on their high dependence on the intensity of the high gravity field regarding different rotating speeds. The mechanism of the accelerated adsorption/infiltration under the high gravity field was interpreted by the increased turbulence of the diffusing layer with the thinned laminar boundary layer and the stepwise delivery of the local concentration gradient from the solution to the interior of the multilayer. The introduction of mechanical field provides a simple and versatile strategy to address the paradox of the contradictory loading amount and loading rate, and thus to promote applications of various membrane processes.

  6. Preparation of conductive PDDA/(PEDOT:PSS) multilayer thin film: influence of polyelectrolyte solution composition.

    Science.gov (United States)

    Jurin, F E; Buron, C C; Martin, N; Filiâtre, C

    2014-10-01

    Self-assembled multilayer films made of PEDOT:PSS poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) and PDDA poly(diallyldimethylammonium chloride) were prepared using layer-by-layer method. In order to modify the growth regime of the multilayer, to fabricate an electrical conductive film and to control its thickness, the effects of pH, type of electrolyte, ionic strength and polyelectrolyte concentration were investigated. Optical reflectometry measurements show that the pH of the solutions has no effect on the film growth while the adsorbed amount increases more rapidly when BaCl2 is used instead of NaCl as electrolyte. An increase in the ionic strength (with NaCl) induces a change in the growth regime from a linear to an exponential one at low polyelectrolyte concentration. As UV-vis measurements indicate, no decomplexation of PEDOT was recorded after film preparation. With polyelectrolyte concentration below 1 g L(-1), no conductive films were obtained even if 50 bilayers were deposited. A conductive film was prepared with a polyelectrolyte concentration of 1 g L(-1) and the measured conductivity was 0.3 S m(-1). A slight increase in conductivity was recorded when BaCl2 was used probably due to a modification of the film structure. Copyright © 2014 Elsevier Inc. All rights reserved.

  7. Investigation on the interaction of Safranin T with anionic polyelectrolytes by spectrophotometric method.

    Science.gov (United States)

    Fradj, Anouar Ben; Lafi, Ridha; Hamouda, Sofiane Ben; Gzara, Lassaad; Hamzaoui, Ahmed Hichem; Hafiane, Amor

    2014-10-15

    Understanding the role played by chemical additives such as NaCl salt, acid and Cetylpyridinium Chloride (CPC) surfactant on the interaction between dye and polyelectrolyte contributes to optimization of processes using polyelectrolytes in the removal of dye from aqueous solution. Herein we focus in the interaction between Safranin T, a cationic dye, with two anionic polyelectrolytes, poly(ammonium acrylate) and poly(acrylic acid) using spectrophotometric method and conductivity measurement. In aqueous solution, each of anionic polyelectrolytes forms a complex with the dye and induces a metachromasy indicated by the blue shift of the absorbance of the dye. The stoichiometry of complexes evaluated by the molar ratio method are 1:1 for Safranin T poly(ammonium acrylate) and 2:1 in the case of Safranin T poly(acrylic acid). The effect of additives on the stability of complexes has been studied by varying concentrations of the salt and the surfactant and pH of the solution. The thermodynamic parameters of interaction ΔG, ΔH and ΔS at different temperatures were evaluated to determine the stability constant of the complexes.

  8. PREPARATION OF POLYELECTROLYTE MULTILAYER COATED MICROBUBBLES FOR USE AS ULTRASOUND CONTRAST AGENT

    Institute of Scientific and Technical Information of China (English)

    Zhan-wen Xing; Heng-te Ke; Shao-qin Liu; Zhi-fei Dai; Jin-rui Wang; Ji-bin Liu

    2008-01-01

    Objective To prepare and characterize polyelectrolyte multilayer film coated microbubbles for use as ultrasound contrast agent (UCA) and evaluate its effects in ultrasonic imaging on normal rabbit's fiver parenchyma.Methoda Pcrfluorocarbon (PFC)-containing microbubbles (ST68-PFC) were prepared by sonication based on surfactant ( Span 60 and Tween 80). Subsequently, the resulting ST68-PFC microbnbbles were coated using oppositely charged polyclectrolytes by microbubble-templated layer-by-layer self-assembly technique via electrostatic interaction.The enhancement effects in ultrasonic imaging on normal rabbit's liver parenchyma were assessed.Results The obtained microbubbles exhibited a narrow size distribution. The polyelectrolytes were successfully assembled onto the surface of ST68-PFC microbubbles. In vivo experiment showed that polyelectrolyte multilayer film coated UCA effectively enhanced the imaging of rabbit's liver parenchyma.Conclnsions The novel microbubbles UCA coated with polyelectrolyte multilayer, when enabled more function,has no obvious difference in enhancement effects compared with the pre-modified microbnbbles. The polymers with chemically active groups ( such as amino group and carboxyl group) can be used as the outermost layer for attachment of targeting ligands onto microbubbles, allowing selective targeting of the microbubbles to combine with desired sites.

  9. Polyelectrolyte coatings prevent interferences from charged nanoparticles in SPME speciation analysis

    NARCIS (Netherlands)

    Zielinska, K.; Leeuwen, van H.P.

    2014-01-01

    In this work we present a new approach for protection of the fiber in solid phase microextraction (SPME) from interfering charged particles present in the sample medium. It involves coating of commercial poly(dimethylsiloxane) extraction phase with polyelectrolyte layer composed of

  10. Interaction of a hydophobic weak polyelectrolyte star with an apolar surface

    NARCIS (Netherlands)

    Rudd, O.V.; Leermakers, F.A.M.; Birshtein, T.M.

    2014-01-01

    We consider star-like polymers with weak, that is, pH-dependent, hydrophobic polyelectrolyte arms. For low ionic strength conditions, a microphase-segregated quasimicellar structure is found, for which the star features a compact apolar core and a charged and swollen corona. This state is jump-like

  11. Adsorption of polyelectrolytes and charged block copolymers on oxides consequences for colloidal stability

    NARCIS (Netherlands)

    Hoogeveen, N.G.

    1996-01-01


    The aim of the study described in this thesis was to examine the adsorption properties of polyelectrolytes and charged block copolymers on oxides, and the effect of these polymers on the colloidal stability of oxidic dispersions. For this purpose the interaction of some well-characterised

  12. Incorporation of a Cationic Conjugated Polyelectrolyte CPE within an Aqueous Poly(vinyl alcohol) Sol

    DEFF Research Database (Denmark)

    Knaapila, Matti; Stewart, Beverly; Costa, Telma

    2016-01-01

    We report on a multiscale polymer-within-polymer structure of the cationic conjugated polyelectrolyte poly{[9,9-bis(6-N,N,N-trimethylammonium)hexyl]fluorene phenylene} (HTMAPFP) in aqueous poly(vinyl alcohol).(PVA) sol. Molecular dynamics simulations and small-angle neutron scattering (SANS) data...

  13. Mechanism of rate enhancement of wood fiber saccharification by cationic polyelectrolytes.

    Science.gov (United States)

    Mora, Sandeep; Lu, Jian; Banerjee, Sujit

    2011-09-01

    Cationic polyelectrolytes can increase the cellulase-induced hydrolysis rates of bleached wood fiber. We show that the polymer associates mainly with the amorphous region of fiber and acts principally on endoglucanase. Fiber/water partitioning of the enzyme follows a Langmuir isotherm for the untreated fiber but a Freundlich isotherm is obeyed for the polymer-treated fiber.

  14. Polyelectrolyte coatings prevent interferences from charged nanoparticles in SPME speciation analysis

    NARCIS (Netherlands)

    Zielinska, K.; Leeuwen, van H.P.

    2014-01-01

    In this work we present a new approach for protection of the fiber in solid phase microextraction (SPME) from interfering charged particles present in the sample medium. It involves coating of commercial poly(dimethylsiloxane) extraction phase with polyelectrolyte layer composed of poly(diallyldimet

  15. Adsorption of polyelectrolytes and charged block copolymers on oxides. Consequences for colloidal stability.

    NARCIS (Netherlands)

    Hoogeveen, N.G.

    1996-01-01

    The aim of the study described in this thesis was to examine the adsorption properties of polyelectrolytes and charged block copolymers on oxides, and the effect of these polymers on the colloidal stability of oxidic dispersions. For this purpose the interaction of some well-characterised polyelectr

  16. Role of pH gradients in the actuation of electro-responsive polyelectrolyte gels

    NARCIS (Netherlands)

    Glazer, P.J.; van Erp, M.; Embrechts, A.; Lemay, Serge Joseph Guy; Mendes, E.

    2012-01-01

    Polyelectrolyte gels are able to mimic artificial muscles, swelling, shrinking or bending in response to environmental stimuli. Mechanical response is also observed in the presence of an electric field, in which case electrical energy is directly converted into mechanical energy. Although several

  17. Regulation of anionic lipids in binary membrane upon the adsorption of polyelectrolyte: A Monte Carlo simulation

    Directory of Open Access Journals (Sweden)

    Xiaozheng Duan

    2013-06-01

    Full Text Available We employ Monte Carlo simulations to investigate the interaction between an adsorbing linear flexible cationic polyelectrolyte and a binary fluid membrane. The membrane contains neutral phosphatidyl–choline, PC and multivalent anionic (phosphatidylinositol, PIP2 lipids. We systematically study the influences of the solution ionic strength, the chain length and the bead charge density of the polyelectrolyte on the lateral rearrangement and the restricted mobility of the multivalent anionic lipids in the membrane. Our findings show that, the cooperativity effect and the electrostatic interaction of the polyelectrolyte beads can significantly affect the segregation extent and the concentration gradients of the PIP2 molecules, and further cooperate to induce the complicated hierarchical mobility behaviors of PIP2 molecules. In addition, when the polyelectrolyte brings a large amount of charges, it can form a robust electrostatic well to trap all PIP2 and results in local overcharge of the membrane. This work presents a mechanism to explain the membrane heterogeneity formation induced by the adsorption of charged macromolecule.

  18. The photoluminescent lifetime of polyelectrolytes in thin films formed via layer by layer self-assembly.

    Science.gov (United States)

    Reilly, Roseanne S; Smyth, Ciarán A; Rakovich, Yury P; McCabe, Eithne M

    2009-03-04

    We present results on luminescence lifetime studies of thin multilayer films of polyelectrolyte molecules produced via layer by layer (LbL) electrostatic assembly. We found that, in contrast to common assumptions, LbL films show measurable photoluminescent lifetimes with an average value of 6 ns. Scanning fluorescence lifetime imaging microscopy studies combined with steady-state photoluminescence measurements imply that this lifetime may be due to aggregation of polyelectrolyte molecules during preparation of LbL films. This conclusion has been further confirmed by atomic force microscopy (AFM). AFM images clearly show the presence of 100-200 nm high aggregates on the surface of these films. This aggregation of polyelectrolyte molecules contributes significantly to the experimentally detected luminescence decays of any light-emitting samples attached to LbL film, especially in a single molecule detection regime. To demonstrate this effect we compare photoluminescence lifetime results for CdTe quantum dots deposited on the surface of LbL polyelectrolyte films.

  19. Charge Density Quantification of Polyelectrolyte Polysaccharides by Conductometric Titration: An Analytical Chemistry Experiment

    Science.gov (United States)

    Farris, Stefano; Mora, Luigi; Capretti, Giorgio; Piergiovanni, Luciano

    2012-01-01

    An easy analytical method for determination of the charge density of polyelectrolytes, including polysaccharides and other biopolymers, is presented. The basic principles of conductometric titration, which is used in the pulp and paper industry as well as in colloid and interface science, were adapted to quantify the charge densities of a…

  20. Cationic β-cyclodextrin polymer applied to a dual cyclodextrin polyelectrolyte multilayer system.

    Science.gov (United States)

    Junthip, Jatupol; Tabary, Nicolas; Leclercq, Laurent; Martel, Bernard

    2015-08-01

    A polyelectrolyte multilayer film (PEM) based on cationic and anionic β-cyclodextrin polyelectrolytes was coated onto a textile substrate for future drug delivery purposes. We firstly synthesized a novel cationic β-cyclodextrin polymer (polyEPG-CD) by crosslinking β-cyclodextrin (βCD) with epichlorohydrin (EP) under basic conditions, in the presence of glycidyltrimetrylammonium chloride (GTMAC) as cationizing group. The influence of preparation conditions has been investigated in order to preferably obtain a water soluble fraction whose charge density and molecular weights were optimal for the layer-by-layer (LbL) deposition process. The different cationic cyclodextrin polymers obtained were characterized by FTIR, NMR, colloidal titration, conductimetry, thermogravimetric analysis and size exclusion chromatography. Besides, the counterpart polyelectrolyte was a β-cyclodextrin polymer crosslinked with citric acid, polyCTR-CD, whose synthesis and characterization have been previously reported. Finally we realized the Layer by Layer (LbL) build-up of the PEM coating onto the textile support, using the dip coating method, by alternatively soaking it in cationic polyEPG-CD and anionic polyCTR-CD solutions. This multilayer self-assembly was monitored by SEM, gravimetry and OWLS in function of both polyelectrolytes concentrations and ratios. Solutions parameters such as pH, ionic strenght were also discussed.

  1. The solvation and ion condensation properties for sulfonated polyelectrolytes in different solvents—a computational study

    Science.gov (United States)

    Smiatek, J.; Wohlfarth, A.; Holm, C.

    2014-02-01

    In contrast to the broad knowledge about aqueous polyelectrolyte solutions, less is known about the properties in aprotic and apolar solvents. We therefore investigate the behavior of sulfonated polyelectrolytes in sodium form in the presence of different solvents via all-atom molecular dynamics simulations. The results clearly reveal strong variations in ion condensation constants and polyelectrolyte conformations for different solvents like water, dimethyl sulfoxide (DMSO) and chloroform. The binding free energies of the solvent contacts with the polyelectrolyte groups validate the influence of different solvent qualities. With regard to the ion condensation behavior, the numerical findings show that the explicit values for the condensation constants depend on the preferential binding coefficient as derived by the evaluation of Kirkwood-Buff integrals. Surprisingly, the smallest ion condensation constant is observed for DMSO compared to water, whereas in the presence of chloroform, virtually no free ions are present, which is in good agreement to the donor number concept. In contrast to the results for the low condensation constants, the sodium conductivity in DMSO is smaller compared to water. We are able to relate this result to the observed smaller diffusion coefficient for the sodium ions in DMSO.

  2. COAGULANT – POLYELECTROLYTE SYSTEM FOR THE CONDITIONING DIGESTED AND SONICATED SEWAGE SLUDGE

    Directory of Open Access Journals (Sweden)

    Beata Bień

    2014-10-01

    Full Text Available The article presents the results of research on the impact of inorganic coagulants and polyelectrolytes and their common action on sonicated digested sludge. Sonication of sludge samples was carried out under static conditions for 60, 120 and 180 seconds. The ultrasonic wave of f = 20 kHz and two different amplitudes of A = 15.25 μm was used in tests. The coagulant PIX123 and the polyelectrolyte Zetag 8160 were used for conditioning. On the basis of CST test the doses of chemical reagents were chosen for conditioning. The results showed the effect of application of the PIX123 and Zetag 8160 and their combination on non-sonicated and sonicated sludge. The lowest CST was achieved for non-sonicated sludge while polyelectrolyte was applied. For sonicated sludge better results were achieved when PIX123 was used. The combination of coagulant and polyelectrolyte allowed to achieve COD reduction, but the best results were achieved for sludge prepared by PIX123. The application of Zetag8160 in this case was not satisfactory.

  3. Clinical application of /sup 99m/Tc-HM-PAO for cerebral blood flow imaging by SPECT. Comparison with cerebral blood flow study by PET

    Energy Technology Data Exchange (ETDEWEB)

    Inugami, Atsushi; Uemura, Kazuo; Shishido, Fumio; Tomura, Noriaki; Higano, Shuichi; Fujita, Hideaki; Kanno, Iwao

    1988-02-01

    Recently, a new tracer for cerebral blood flow (CBF) study; /sup 99m/Tc-labelled-hexamethyl-propyleneamine-oxime (/sup 99m/Tc-HM-PAO) was developed by Amersham international institute. In this paper, we reported the initial experience of tomographic CBF imaging with /sup 99m/Tc-HM-PAO in the comparison of CBF study using positron CT (PET) and 0 approx. 15 labelled CO/sub 2/. Thirty-nine patients with cerebro-vascular disease were examined mainly in the acute phase. All the subjects showed verious disturbances of CBF, which corresponded well to the PET study. However, the image-contrast with /sup 99m/Tc-HM-PAO were inferior to those of the PET study. /sup 99m/Tc-HM-PAO is considered to a good radiopharmaceutical which is readily applicable to eaven an emergency cases.

  4. Evaluation of [sup 99m]Tc-HM-PAO thigh accumulation in patients with cerebro-vascular disease

    Energy Technology Data Exchange (ETDEWEB)

    Nishigaki, Hiroshi; Adachi, Itaru; Komori, Tsuyoshi; Tatsu, Yoshimitsu; Hisada, Youichi; Sueyoshi, Kouzou; Narabayashi, Isamu (Osaka Medical College, Takatsuki (Japan))

    1993-06-01

    Technetium-99m d,l-hexamethyl-propyleneamine oxime ([sup 99m]Tc-HM-PAO) cerebral SPECT and whole body scintigraphy (WBS) were performed in 5 patients without cerebro-vascular disease (CVD) (Group 1), 31 patients with CVD but not hemiparesis (Group 2) and 18 patients with CVD and hemiparesis (Group 3). Four ROIs were drawn manually around the whole body (WB), brain (Br), right and left thigh (Th). We calculated some ratios: the total counts in the brain over the total counts in the whole body (Br/WB), the total counts in the thigh over the total counts in the whole body (Th/WB) and the mean counts in the thigh over the mean counts in the brain (Th/Br).The Br/WB was 6.9[+-]1.8%, rt-Th/WB was 4.9[+-]2.1%, lt-Th/WB was 5.1[+-]1.3% and Th/Br was 0.46[+-]0.17 in group 1. Whole body scintigraphies in group 1 revealed clear and similar images between right and left thigh. The Br/WB was 6.7[+-]1.4%, Th/WB of paretic side was 4.6[+-]1.0%, Th/WB of non-paretic side was 5.8[+-]1.2% and Th/Br was 0.47[+-]0.18 in group 3. The Th/WB in non paretic side was significantly higher than that in paretic side (p<0.01). The thigh images in group 3 revealed clear differences between paretic and non-paretic thighes. In conclusion we could acquire the clear thigh images with [sup 99m]Tc-HM-PAO. It was possible that we evaluated not only cerebral perfusion but also muscle atrophy and/or perfusion in patients with CVD using [sup 99m]Tc-HM-PAO. (author).

  5. Positive allosteric modulation of the human metabotropic glutamate receptor 4 (hmGluR4) by SIB-1893 and MPEP

    OpenAIRE

    Mathiesen, Jesper Mosolff; Svendsen, Nannette; Bräuner-Osborne, Hans; Thomsen, Christian; Ramirez, M Teresa

    2003-01-01

    We have identified 2-methyl-6-(2-phenylethenyl)pyridine (SIB-1893) and 2-methyl-6-phenylethynyl pyridine hydrochloride (MPEP) as positive allosteric modulators for the hmGluR4. SIB-1893 and MPEP enhanced the potency and efficacy of L-2-amino-4-phophonobutyrate (L-AP4) in guanosine 5′-O-(3-[35S]thiotriphosphate ([35S]GTPγS) binding and efficacy in cAMP studies. These effects were fully blocked by the mGluR4 competitive antagonist (RS)-α-cyclopropyl-4-phosphonophenylglycine (CPPG), indicating a...

  6. Estimativa da entalpia de decomposição (deltaD Hmº) de adutos por termogravimetria

    OpenAIRE

    Robson Fernandes de Farias

    1998-01-01

    An empirical equation: deltaD HmO = t i/2.2(2-n) is obtained and tested for 102 adducts (mainly adducts with zinc group halides). In the equation, t i is the Kelvin temperature of the beginning of the thermal decomposition of the adduct, (obtained by thermogravimetry), and n is the number of ligands. For 1/3 of the tested adducts the difference between experimental and calculated values was less than 5%. For about 1/3 of the adducts that difference exceeds 15%.

  7. Cytotoxicity and antibacterial property of titanium alloy coated with silver nanoparticle-containing polyelectrolyte multilayer

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xinming [School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 (China); Li, Zhaoyang [School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin, 300072 (China); Yuan, Xubo [School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 (China); Cui, Zhenduo [School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin, 300072 (China); Bao, Huijing; Li, Xue; Liu, Yunde [School of Laboratory Medicine, Tianjin Medical University, Tianjin, 300203 (China); Yang, Xianjin, E-mail: xjyang@tju.edu.cn [School of Materials Science and Engineering, Tianjin University, Tianjin, 300072 (China); Tianjin Key Laboratory of Composite and Functional Materials, Tianjin, 300072 (China)

    2013-07-01

    Silver nanoparticle (AgNP) was incorporated into dopamine-modified alginate/chitosan (DAL/CHI) polyelectrolyte multilayer to modify the surface of titanium alloy and improve its antibacterial property. Scanning electron microscopy showed that AgNP with the size of 50 nm embedded in DAL/CHI multilayers homogeneously. X-ray photoelectron spectroscopy analysis indicated that the nanoparticles were silver (0) with peaks at 368.4 and 374.4 eV, respectively. The formation of silver (0) without the addition of reductants was due to the self-polymerization of dopamine, which can reduce the silver cation into neutral metal. The polyelectrolyte multilayer coating enhanced the wettability of titanium alloy and promoted the fibroblast proliferation significantly, which could be attributed to the excellent biocompatibility of DAL/CHI. Despite the slight fall of L929 cell activity after AgNP incorporation, AgNP-DAL/CHI multilayer inhibited the growth of both Escherichia coli and Staphylococcus aureus. The above results demonstrate that dopamine decoration is a simple and effective way to induce the in-situ formation of AgNP within polyelectrolyte multilayer. Furthermore, the AgNP-containing multilayer considerably enhances the antibacterial activity of titanium alloy. The fabrication of AgNP-DAL/CHI multilayer on the surface of titanium implant might have great potential in orthopedic use. - Highlights: • Polyelectrolyte multilayer was fabricated through layer-by-layer assembly. • AgNP was formed in-situ and embedded within polyelectrolyte multilayer. • Surface of titanium was modified by AgNP-DAL/CHI multilayer with a facile method. • AgNP-DAL/CHI multilayer enhanced antibacterial activity of titanium alloy.

  8. Composite scaffold of poly(vinyl alcohol) and interfacial polyelectrolyte complexation fibers for controlled biomolecule delivery.

    Science.gov (United States)

    Cutiongco, Marie Francene A; Choo, Royden K T; Shen, Nathaniel J X; Chua, Bryan M X; Sju, Ervi; Choo, Amanda W L; Le Visage, Catherine; Yim, Evelyn K F

    2015-01-01

    Controlled delivery of hydrophilic proteins is an important therapeutic strategy. However, widely used methods for protein delivery suffer from low incorporation efficiency and loss of bioactivity. The versatile interfacial polyelectrolyte complexation (IPC) fibers have the capacity for precise spatiotemporal release and protection of protein, growth factor, and cell bioactivity. Yet its weak mechanical properties limit its application and translation into a viable clinical solution. To overcome this limitation, IPC fibers can be incorporated into polymeric scaffolds such as the biocompatible poly(vinyl alcohol) hydrogel (PVA). Therefore, we explored the use of a composite scaffold of PVA and IPC fibers for controlled biomolecule release. We first observed that the permeability of biomolecules through PVA films were dependent on molecular weight. Next, IPC fibers were incorporated in between layers of PVA to produce PVA-IPC composite scaffolds with different IPC fiber orientation. The composite scaffold demonstrated excellent mechanical properties and efficient biomolecule incorporation. The rate of biomolecule release from PVA-IPC composite grafts exhibited dependence on molecular weight, with lysozyme showing near-linear release for 1 month. Angiogenic factors were also incorporated into the PVA-IPC grafts, as a potential biomedical application of the composite graft. While vascular endothelial growth factor only showed a maximum cumulative release of 3%, the smaller PEGylated-QK peptide showed maximum release of 33%. Notably, the released angiogenic biomolecules induced endothelial cell activity thus indicating retention of bioactivity. We also observed lack of significant macrophage response against PVA-IPC grafts in a rabbit model. Showing permeability, mechanical strength, precise temporal growth factor release, and bioinertness, PVA-IPC fibers composite scaffolds are excellent scaffolds for controlled biomolecule delivery in soft tissue engineering.

  9. Composite scaffold of poly(vinyl alcohol and interfacial polyelectrolyte complexation fibers for controlled biomolecule delivery

    Directory of Open Access Journals (Sweden)

    Marie Francene Arnobit Cutiongco

    2015-02-01

    Full Text Available Controlled delivery of hydrophilic proteins is an important therapeutic strategy. However, widely used methods for protein delivery suffer from low incorporation efficiency and loss of bioactivity. The versatile interfacial polyelectrolyte complexation (IPC fibers have the capacity for precise spatiotemporal release and protection of protein, growth factor and cell bioactivity. Yet its weak mechanical properties limit its application and translation into a viable clinical solution. To overcome this limitation, IPC fibers can be incorporated into polymeric scaffolds such as the biocompatible poly(vinyl alcohol hydrogel (PVA. Therefore, we explored the use of a composite scaffold of PVA and IPC fibers for controlled biomolecule release. We first observed that the permeability of biomolecules through PVA films were dependent on molecular weight, with lysozyme showing near-linear release for 1 month. Next, IPC fibers were incorporated in between layers of PVA to produce PVA-IPC composite scaffolds with different IPC fiber orientation. The composite scaffold demonstrated excellent mechanical properties and efficient biomolecule incorporation. The rate of biomolecule release from PVA-IPC composite grafts exhibited dependence on molecular weight. Angiogenic factors were also incorporated into the PVA-IPC grafts, as a potential biomedical application of the composite graft. While vascular endothelial growth factor only showed a maximum cumulative release of 3%, the smaller PEGylated-QK peptide showed maximum release of 33%. Notably, the released angiogenic biomolecules induced endothelial cell metabolic activity thus indicating retention of bioactivity. We also observed lack of significant macrophage response against PVA-IPC grafts in a rabbit model. Showing permeability, mechanical strength, precise temporal growth factor release and bioinertness, PVA-IPC fibers composite scaffolds are excellent scaffolds for controlled biomolecule delivery in soft

  10. Adaptive growth factor delivery from a polyelectrolyte coating promotes synergistic bone tissue repair and reconstruction.

    Science.gov (United States)

    Shah, Nisarg J; Hyder, Md Nasim; Quadir, Mohiuddin A; Dorval Courchesne, Noémie-Manuelle; Seeherman, Howard J; Nevins, Myron; Spector, Myron; Hammond, Paula T

    2014-09-01

    Traumatic wounds and congenital defects that require large-scale bone tissue repair have few successful clinical therapies, particularly for craniomaxillofacial defects. Although bioactive materials have demonstrated alternative approaches to tissue repair, an optimized materials system for reproducible, safe, and targeted repair remains elusive. We hypothesized that controlled, rapid bone formation in large, critical-size defects could be induced by simultaneously delivering multiple biological growth factors to the site of the wound. Here, we report an approach for bone repair using a polyelectrolye multilayer coating carrying as little as 200 ng of bone morphogenetic protein-2 and platelet-derived growth factor-BB that were eluted over readily adapted time scales to induce rapid bone repair. Based on electrostatic interactions between the polymer multilayers and growth factors alone, we sustained mitogenic and osteogenic signals with these growth factors in an easily tunable and controlled manner to direct endogenous cell function. To prove the role of this adaptive release system, we applied the polyelectrolyte coating on a well-studied biodegradable poly(lactic-co-glycolic acid) support membrane. The released growth factors directed cellular processes to induce bone repair in a critical-size rat calvaria model. The released growth factors promoted local bone formation that bridged a critical-size defect in the calvaria as early as 2 wk after implantation. Mature, mechanically competent bone regenerated the native calvaria form. Such an approach could be clinically useful and has significant benefits as a synthetic, off-the-shelf, cell-free option for bone tissue repair and restoration.

  11. Adsorption of tannic acid on polyelectrolyte monolayers determined in situ by streaming potential measurements.

    Science.gov (United States)

    Oćwieja, M; Adamczyk, Z; Morga, M

    2015-01-15

    Physicochemical characteristics of tannic acid (tannin) suspensions comprising its stability for a wide range of ionic strength and pH were thoroughly investigated using UV-vis spectrophotometry, dynamic light scattering and microelectrophoretic measurements. These studies allowed to determine the hydrodynamic diameter of the tannic acid that was 1.63 nm for the pH range 3.5-5.5. For pH above 6.0 the hydrodynamic diameter significantly decreased as a result of the tannin hydrolysis. The electrophoretic mobility measurements confirmed that tannic acid is negatively charged for these values of pH and ionic strength 10(-4)-10(-2) M. Therefore, in order to promote adsorption of tannin molecules on negatively charged mica, the poly(allylamine hydrochloride) (PAH) supporting monolayers were first adsorbed under diffusion transport conditions. The coverage of polyelectrolyte monolayers was regulated by changing bulk concentration of PAH and the adsorption time. The electrokinetic characteristics of bare and PAH-covered mica were determined using the streaming potential measurements. The zeta potential of these PAH monolayers was highly positive, equal to 46 mV for ionic strength of 10(-2) M. The kinetics of tannin adsorption on these PAH supporting monolayers was evaluated by the in situ the streaming potential measurements. The zeta potential of PAH monolayers abruptly decreases with the adsorption of tannin molecules that was quantitatively interpreted in terms of the three-dimensional electrokinetic model. The acid-base characteristics of tannin monolayers were acquired via the streaming potential measurements for a broad range of pH. The obtained results indicate that it is possible to control adsorption of tannin on positively charged surfaces in order to designed new multilayer structures of desirable electrokinetic properties and stability.

  12. {sup 99m}Tc-ECD and {sup 99m}Tc-HM-PAO SPECT in five patients with MELAS

    Energy Technology Data Exchange (ETDEWEB)

    Katagiri, Shinako; Nishimaki, Hiroshi; Kitano, Masashi; Horiike, Shigeharu; Kan, Shinichi; Ishii, Katsumi; Matsubayashi, Takashi; Sakai, Fumihiko [Kitasato Univ., Sagamihara, Kanagawa (Japan). School of Medicine

    1998-03-01

    Cerebral perfusion was studied in five patients with mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes syndrome (MELAS), using single photon emission computed tomography (SPECT) with {sup 99m}Tc-ethyl cysteinate dimer ({sup 99m}Tc-ECD) or {sup 99m}Tc-hexamethyl propyleneamine oxime ({sup 99m}Tc-HM-PAO). In four cases, regional cerebral blood flow (rCBF) was evaluated by the method reported by Mastuda et al. Immediately after the stroke-like episodes, accumulation of the tracer was relatively increased in the temporooccipital lobe, and also increased rCBF was shown in the same area. However, the region showed decreased radioactivity at the chronic stage, and rCBF decreased also. These findings are consistent with positron emission tomography (PET) at the acute stage and autopsy. {sup 99m}Tc-ECD SPECT and {sup 99m}Tc-HM-PAO SPECT may be useful in the diagnosis and assessment of the progress of the MELAS. (author)

  13. Layer-by-layer self-assembly of composite polyelectrolyte-Nafion membranes for direct methanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, S.P.; Liu, Z.; Tian, Z.Q. [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

    2006-04-18

    A novel composite polyelectrolyte/Nafion membrane is demonstrated that is fabricated using the layer-by-layer self-assembly of oppositely charged polyelectrolytes. A direct methanol fuel cell based on such a membrane is shown to achieve a significant reduction in methanol crossover and an increase in power density of 42 %, in comparison to that which uses a pristine Nafion membrane. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  14. Influence of Layer-by-Layer Polyelectrolyte Deposition and EDC/NHS Activated Heparin Immobilization onto Silk Fibroin Fabric

    OpenAIRE

    M. Fazley Elahi; Guoping Guan; Lu Wang; Martin W. King

    2014-01-01

    To enhance the hemocompatibility of silk fibroin fabric as biomedical material, polyelectrolytes architectures have been assembled through the layer-by-layer (LbL) technique on silk fibroin fabric (SFF). In particular, 1.5 and 2.5 bilayer of oppositely charged polyelectrolytes were assembled onto SFF using poly(allylamine hydrochloride) (PAH) as polycationic polymer and poly(acrylic acid) (PAA) as polyanionic polymer with PAH topmost. Low molecular weight heparin (LMWH) activated with 1-ethyl...

  15. Biocompatible long-sustained release oil-core polyelectrolyte nanocarriers: From controlling physical state and stability to biological impact.

    Science.gov (United States)

    Szczepanowicz, Krzysztof; Bazylińska, Urszula; Pietkiewicz, Jadwiga; Szyk-Warszyńska, Lilianna; Wilk, Kazimiera A; Warszyński, Piotr

    2015-08-01

    It has been generally expected that the most applicable drug delivery system (DDS) should be biodegradable, biocompatible and with incidental adverse effects. Among many micellar aggregates and their mediated polymeric systems, polyelectrolyte oil-core nanocarriers have been found to successfully encapsulate hydrophobic drugs in order to target cells and avoid drug degradation and toxicity as well as to improve drug efficacy, its stability, and better intracellular penetration. This paper reviews recent developments in the formation of polyelectrolyte oil-core nanocarriers by subsequent multilayer adsorption at micellar structures, their imaging, physical state and stability, drug encapsulation and applications, in vitro release profiles and in vitro biological evaluation (cellular uptake and internalization, biocompatibility). We summarize the recent results concerning polyelectrolyte/surfactant interactions at interfaces, fundamental to understand the mechanisms of formation of stable polyelectrolyte layered structures on liquid cores. The fabrication of emulsion droplets stabilized by synergetic surfactant/polyelectrolyte complexes, properties, and potential applications of each type of polyelectrolyte oil-core nanocarriers, including stealth nanocapsules with pegylated shell, are discussed and evaluated. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Layer-by-layer self-assembly of polyelectrolyte functionalized MoS2 nanosheets

    Science.gov (United States)

    Shen, Jianfeng; Pei, Yu; Dong, Pei; Ji, Jin; Cui, Zheng; Yuan, Junhua; Baines, Robert; Ajayan, Pulickel M.; Ye, Mingxin

    2016-05-01

    Few-layered polyelectrolyte functionalized MoS2 nanosheets were obtained for the first time through in situ polymerization of MoS2 nanosheets with poly(acrylic acid) and poly(acrylamide), both of which demonstrated excellent dispersibility and stability in water. After designing and optimizing the components of this series of polyelectrolyte functionalized MoS2 nanosheets, by exploiting the electrostatic interactions present in the modified MoS2 nanosheets, we further created a series of layer-by-layer (LBL) self-assembling MoS2-based films. To this end, uniform MoS2 nanosheet-based LBL films were precisely deposited on substrates such as quartz, silicon, and ITO. The polyelectrolyte functionalized MoS2 nanosheet assembled LBL film-modified electrodes demonstrated enhanced electrocatalytic activity for H2O2. As such, they are conducive to efficient sensors and advanced biosensing systems.Few-layered polyelectrolyte functionalized MoS2 nanosheets were obtained for the first time through in situ polymerization of MoS2 nanosheets with poly(acrylic acid) and poly(acrylamide), both of which demonstrated excellent dispersibility and stability in water. After designing and optimizing the components of this series of polyelectrolyte functionalized MoS2 nanosheets, by exploiting the electrostatic interactions present in the modified MoS2 nanosheets, we further created a series of layer-by-layer (LBL) self-assembling MoS2-based films. To this end, uniform MoS2 nanosheet-based LBL films were precisely deposited on substrates such as quartz, silicon, and ITO. The polyelectrolyte functionalized MoS2 nanosheet assembled LBL film-modified electrodes demonstrated enhanced electrocatalytic activity for H2O2. As such, they are conducive to efficient sensors and advanced biosensing systems. Electronic supplementary information (ESI) available: SEM, AFM and TEM characterization of PAA-MoS2 and PAM-MoS2 nanocomposites. More characterization and electrochemical properties of LBL films

  17. Phase behavior and molecular thermodynamics of coacervation in oppositely charged polyelectrolyte/surfactant systems: a cationic polymer JR 400 and anionic surfactant SDS mixture.

    Science.gov (United States)

    Li, Dongcui; Kelkar, Manish S; Wagner, Norman J

    2012-07-17

    Coacervation in mixtures of polyelectrolytes and surfactants with opposite charge is common in nature and is also technologically important to consumer health care products. To understand the complexation behavior of these systems better, we combine multiple experimental techniques to systematically study the polymer/surfactant binding interactions and the phase behavior of anionic sodium dodecyl sulfate (SDS) surfactant in cationic JR 400 polymer aqueous solutions. The phase-behavior study resolves a discrepancy in the literature by identifying a metastable phase between the differing redissolution phase boundaries reported in the literature for the surfactant-rich regime. Isothermal titration calorimetry analyzed within the framework of the simple Satake-Yang model identifies binding parameters for the surfactant-lean phase, whereas a calculation for polymer-bound micelles coexisting with free micelles is analyzed in the surfactant-rich redissolution regime. This analysis provides a preliminary understanding of the interactions governing the observed phase behavior. The resulting thermodynamic properties, including binding constants and the molar Gibbs free energies, enthalpies, and entropies, identify the relative importance of both hydrophobic and electrostatic interactions and provide a first approximation for the corresponding microstructures in the different phases. Our study also addresses the stability and metastability of oppositely charged polyelectrolytes and surfactant mixtures.

  18. Entamoeba histolytica: expression and localization of Gal/GalNAc lectin in virulent and non-virulent variants from HM1:IMSS strain.

    Science.gov (United States)

    López-Vancell, R; Arreguín Espinosa, R; González-Canto, A; Néquiz Avendaño, M; García de León, M C; Olivos-García, A; López-Vancell, D; Pérez-Tamayo, R

    2010-07-01

    We have purified Gal/GalNAc lectin from Entamoeba histolytica by electroelution. The purified protein was used to immunize rabbits and obtain polyclonal IgG's anti-lectin. These antibodies were used as tools to analyze the expression and localization of the amoebic lectin in both virulent (vEh) and non-virulent (nvEh) variants of axenically cultured HM1:IMSS strain. vEh is able to induce liver abscesses in hamsters, whereas nvEh has lost this ability. In vitro, amoebic trophozoites from both variants equally express this protein as shown by densitometric analysis of the corresponding band in Western blots from lysates. In both types of trophozoites, the pattern of distribution of the lectin was mainly on the surface. We have also compared by immunohistochemistry the presence and distribution of lectin in the in vivo liver lesions produced in hamsters. In order to prolong the survival of nvEh to analyze both variants in an in vivo model, hamsters inoculated with nvEh were treated with methyl prednisolone. Our results suggest that the Gal/GalNAc lectin is equally expressed in both nvEh and vEh.

  19. Interferometry study of aqueous lubrication on the surface of polyelectrolyte brush.

    Science.gov (United States)

    Kobayashi, Motoyasu; Tanaka, Hiroyoshi; Minn, Myo; Sugimura, Joichi; Takahara, Atsushi

    2014-11-26

    The water lubrication behavior of a polyelectrolyte brush was investigated by using double-spacer-layer ultra-thin-film interferometry to determine the thickness of the aqueous lubrication layer present at the interface between the brush and a spherical glass lens. A hydrophilic poly{[2-(methacryloyloxy)ethyl]trimethylammonium chloride} brush was prepared on an optical glass disk coated with layers of semireflective chromium and silica. The thickness of the hydrodynamic lubrication layer was estimated interferometrically. On increasing the sliding velocity from 10(-5) to 10(-1) m·s(-1), the gap between the rotating disk and loading sphere glass lens showed a marked increase to 130 nm at 2×10(-2) m·s(-1), and the friction coefficient simultaneously decreased to 0.01-0.02, indicating that the polyelectrolyte brush promoted the formation of a fluid lubrication layer that separates the rubbing surfaces, preventing direct contact and providing a low friction coefficient.

  20. Low Molecular Weight Chitosan–Insulin Polyelectrolyte Complex: Characterization and Stability Studies

    Directory of Open Access Journals (Sweden)

    Zakieh I. Al-Kurdi

    2015-03-01

    Full Text Available The aim of the work reported herein was to investigate the effect of various low molecular weight chitosans (LMWCs on the stability of insulin using USP HPLC methods. Insulin was found to be stable in a polyelectrolyte complex (PEC consisting of insulin and LMWC in the presence of a Tris-buffer at pH 6.5. In the presence of LMWC, the stability of insulin increased with decreasing molecular weight of LMWC; 13 kDa LMWC was the most efficient molecular weight for enhancing the physical and chemical stability of insulin. Solubilization of insulin-LMWC polyelectrolyte complex (I-LMWC PEC in a reverse micelle (RM system, administered to diabetic rats, results in an oral delivery system for insulin with acceptable bioactivity.

  1. Persistence length of a polyelectrolyte in salty water: Monte Carlo study.

    Science.gov (United States)

    Nguyen, T T; Shklovskii, B I

    2002-08-01

    We address the long standing problem of the dependence of the electrostatic persistence length l(e) of a flexible polyelectrolyte (PE) on the screening length r(s) of the solution within the linear Debye-Hückel theory. The standard Odijk, Skolnick, and Fixman (OSF) theory suggests l(e) proportional, variant r(2)s, while some variational theories and some computer simulations suggest l(e) proportional, variant r(s). In this paper, we use Monte Carlo simulations to study the conformation of a simple polyelectrolyte. Using four times longer PEs than in previous simulations and refined methods for the treatment of the simulation data, we show that the results are consistent with the OSF dependence l(e) proportional, variant r(2)s. The linear charge density of the PE, which enters in the coefficient of this dependence is properly renormalized to take into account local fluctuations.

  2. Stable Aqueous Suspension and Self-Assembly of Graphite Nanoplatelets Coated with Various Polyelectrolytes

    Directory of Open Access Journals (Sweden)

    Jue Lu

    2010-01-01

    Full Text Available Exfoliated graphite nanoplatelets (xGnPs with an average thickness of 1–10 nm present an inexpensive alternative to carbon nanotubes in many applications. In this paper, stable aqueous suspension of xGnP was achieved by noncovalent functionalization of xGnP with polyelectrolytes. The surfactants and polyelectrolytes were compared with respect to their ability to suspend graphite nanoplatelets. The surface charge of the nanoplatelets was characterized with zeta potential measurements, and the bonding strength of the polymer chains to the surface of xGnP was characterized with Raman spectroscopy. This robust method opens up the possibility of using this inexpensive nanomaterial in many applications, including electrochemical devices, and leads to simple processing techniques such as layer-by-layer deposition. Therefore, the formation of xGnP conductive coatings using layer-by-layer deposition was also demonstrated.

  3. Characterization of polyelectrolyte behavior of the polysaccharides chitosan, heparin, and hyaluronan, by light scattering and viscometry.

    Science.gov (United States)

    Boddohi, Soheil; Yonemura, Susan; Kipper, Matt

    2008-03-01

    This study on the polyelectrolyte behavior of polysaccharides in solution is motivated by our recent work in development of nanostructured polysaccharide-based surface coatings. Chitosan behaves as a weak polycation, and hyaluronan behaves as a weak polyanion, while heparin behaves as a strong polyanion. The ability to control the conformation of these polysaccharides in solution, by changing the solution ionic strength and pH may offer the opportunity to further tune the nanoscale features of polysaccharide-based surface coatings assembled from solution. In the work reported here, the solution conformation of these polymers is determined from gel permeation chromatography coupled to differential refractive index, light scattering, and viscometry detection. These results are related to the nanostructure of chitosan-heparin and chitosan-hyaluronan surface coatings based on polyelectrolyte multilayers.

  4. Interest of Polyelectrolyte Multilayer thin Films in Tissue Engineering:Application to Vascular Allograft

    Institute of Scientific and Technical Information of China (English)

    Halima KERDJOUDJ; Cedric BOURA; Vanessa MOBY; Dominique DUMAS; Luc MARCHAL; Jean-Claude VOEGEL; Jean-Fran(c)ois STOLTZ; Patrick MENU

    2005-01-01

    @@ 1 Introduction Obstructive atherosclerosis vascular disease remains one of the greatest public health threats in the world. Surgical treatment to replace diseased blood vessels is usually done using major human allografts (veins or arteries) or synthetic prosthesis ( PTFE, Dacron). However, these substitutes have not a good pateney, because of the lack of endothelial cells (ECs) layer, which prevents thrombus formation. The challenge of tissue engineering vessels is to build-up blood/substitute interface near native vessels.In order to improve ECs adhesion, it is necessary to precoat the intra-luminal vessel. Recently, a new surface modification technique arose, based on the alternate adsorption of oppositely charged polyelectrolytes. Our objective was to favour the endothelialization of the cryo-preserved allografts, treated with a thin polyelectrolyte multilayered film, made of PSS (poly (sodium-4-styrenesulfonate) ) or PAH (poly (allylamine hydrochloride) ).

  5. Design of polyelectrolyte multilayer membranes for ion rejection and wastewater effluent treatment

    Science.gov (United States)

    Sanyal, Oishi

    Polyelectrolyte multilayer (PEM) membranes present a special class of nanostructured membranes which have potential applications in a variety of water treatment operations. These membranes are fabricated by the layer-by-layer (LbL) assembly of alternately charged polyelectrolytes on commercial membrane surfaces. A large variety of polyelectrolytes and their varied deposition conditions (pH, number of bilayers etc.) allow very fine tuning of the membrane performance in terms of permeability and rejection. The first part of this thesis is about the application of PEM membranes to the removal of perchlorate ion from water. Being a monovalent ion, it is most effectively removed by a reverse osmosis (RO) membrane. However, these membranes inherently have very low fluxes which lead to high pressure requirements. In our work, we modified the surface of a nanofiltration (NF) membrane by the LbL assembly of oppositely charged polyelectrolytes. The appropriate tuning of the LbL conditions led to the development of a membrane with significantly higher flux than RO membranes but with equivalent perchlorate rejection. This was one of the best trade-offs offered by PEM membranes for monovalent ion rejection as has been reported in literature so far. While PEM membranes have mostly shown great potential in ion-rejection studies, they have seldom been tested for real wastewater effluents. The second part of this thesis, therefore, deals with evaluating the applicability of PEM membranes to treating an electrocoagulation (EC)-treated high strength wastewater. Two types of very commonly used polyelectrolyte combinations were tried out -- one of which was an ionically crosslinked system and the other one was covalently crosslinked. Both the types of PEM membranes showed a high level of COD reduction from the feed stream with higher fluxes than commercial RO membranes. One major challenge in using membranes for wastewater treatment is their fouling propensity. Like many other

  6. Lipophilic polyelectrolyte gels as super-absorbent polymers for nonpolar organic solvents.

    Science.gov (United States)

    Ono, Toshikazu; Sugimoto, Takahiro; Shinkai, Seiji; Sada, Kazuki

    2007-06-01

    Polyelectrolyte gels that are known as super-absorbent polymers swell and absorb water up to several hundred times their dried weights and have become ubiquitous and indispensable materials in many applications. Their superior swelling abilities originate from the electrostatic repulsion between the charges on the polymer chains and the osmotic imbalance between the interior and exterior of the gels. However, no super-absorbent polymers for volatile organic compounds (VOCs), and especially for nonpolar organic solvents (epsilonpolymer networks. This expands the potential of polyelectrolytes that have been used only in aqueous solutions or highly polar solvents, and provides soft materials that swell in a variety of media. These materials could find applications as protective barriers for VOCs spilled in the environment and as absorbents for waste oil.

  7. Cell adhesive behavior on thin polyelectrolyte multilayers: cells attempt to achieve homeostasis of its adhesion energy.

    Science.gov (United States)

    Mehrotra, Sumit; Hunley, S Christopher; Pawelec, Kendell M; Zhang, Linxia; Lee, Ilsoon; Baek, Seungik; Chan, Christina

    2010-08-03

    Linearly growing ultrathin polyelectrolyte multilayer (PEM) films of strong polyelectrolytes, poly(diallyldimethylammonium chloride) (PDAC), and sulfonated polystyrene, sodium salt (SPS) exhibit a gradual shift from cytophilic to cytophobic behavior, with increasing thickness for films of less than 100 nm. Previous explanations based on film hydration, swelling, and changes in the elastic modulus cannot account for the cytophobicity observed with these thin films as the number of bilayers increases. We implemented a finite element analysis to help elucidate the observed trends in cell spreading. The simulation results suggest that cells maintain a constant level of energy consumption (energy homeostasis) during active probing and thus respond to changes in the film stiffness as the film thickness increases by adjusting their morphology and the number of focal adhesions recruited and thereby their attachment to a substrate.

  8. Counterions release from electrostatic complexes of polyelectrolytes and proteins of opposite charge : a direct measurement

    CERN Document Server

    Gummel, Jérémie; Boué, François

    2009-01-01

    Though often considered as one of the main driving process of the complexation of species of opposite charges, the release of counterions has never been experimentally directly measured on polyelectrolyte/proteins complexes. We present here the first structural determination of such a release by Small Angle Neutron Scattering in complexes made of lysozyme, a positively charged protein and of PSS, a negatively charged polyelectrolyte. Both components have the same neutron density length, so their scattering can be switched off simultaneously in an appropriate "matching" solvent; this enables determination of the spatial distribution of the single counterions within the complexes. The counterions (including the one subjected to Manning condensation) are expelled from the cores where the species are at electrostatic stoichiometry.

  9. Local pH and effective pKA of weak polyelectrolytes - insights from computer simulations.

    Science.gov (United States)

    Nová, Lucie; Uhlík, Filip; Košovan, Peter

    2017-03-09

    In this work we study the titration behavior of weak polyelectrolytes by computer simulations. We analyze the local pH near the chains at various conditions and provide molecular-level insight which complements the recent experimental determination of this quantity. Next, we analyze the non-ideal titration behaviour of weak polyelectrolytes in solution, calculate the effective ionization constant and compare the simulation results with theoretical predictions. In contrast with the universal behaviour with respect to chain length, we find non-universality and deviations from theory with respect to polymer concentration and permittivity of the solvent. The latter we explain in terms of counterion condensation and ion correlation effects, which lead to reversal of the non-ideal titration behaviour at very low permittivities. We discuss the impact of these findings on the interpretation of experimental results.

  10. Suitability of polyelectrolyte shells modified with fullerene derivate for immunoisolation of cells. Experimental study.

    Science.gov (United States)

    Borkowska, M; Godlewska, E; Antosiak-Iwańska, M; Kinasiewicz, J; Strawski, M; Szklarczyk, M; Granicka, L H

    2012-12-01

    The polymeric permiselective membranes application for immunoisolation of cells separating the transplanted cells from the host immunological system may eliminate immunosuppressive therapy during transplantation. The suitability of polyelectrolyte modified nanocoatings for immunoisolation of cells was assessed. The polymeric shells modified with incorporated fullerene derivate were applied for encapsulation of human T-lymphocyte cell line Jurkat or rat pancreatic islets of Langerhans using layer-by-layer technique. Hydroxylated fullerene was incorporated to the polyelectrolyte shell for hydrophility increase as well as for layer stability improvement. Evaluation with AFM, FTIR, fluorescence microscopy confirmed the nanocoating presence on the encapsulated cells. It was observed that polylysine-polyethyleneimine membrane with incorporated fullerenol allowed for encapsulated cells functioning in vitro. Membrane conformation applied for encapsulation of pancreatic rat islets allowed for glucose level decline during xenotransplantation into mice. The elaborated nanocoating may be recommended as the possible alternative to the space consuming microencapsulation for biomedical purposes.

  11. Spherical polyelectrolyte brushes as a nanoreactor for synthesis of ultrafine magnetic nanoparticles

    Science.gov (United States)

    Zhu, Yan; Chen, Kaimin; Wang, Xiang; Guo, Xuhong

    2012-07-01

    Ultrafine magnetic nanoparticles (MNP, 1.4-5.8 nm) were generated within a nanoreactor of spherical polyelectrolyte brushes (SPB). SPB consist of a solid polystyrene (PS) core and densely grafted poly(acrylic acid) (PAA) chains. Due to strong chemical coordination between carboxyl groups in PAA and MNP surfaces, the obtained magnetic spherical polyelectrolyte brushes (MSPB) kept excellent stability and maintained pH sensitivity. The magnetic properties of MSPB were confirmed by a vibrating sample magnetometer (VSM). The size and the size dispersion of MNP can be modulated by varying adding sequences (conventional coprecipitation or reverse coprecipitation), or nanoreactor structure (with or without crosslinking). MNP content in MSPB could be adjusted by multicycle reactions. This new strategy makes it possible to synthesize ultrafine inorganic nanoparticles with tunable size in SPB.

  12. hm extrapolation chamber: Study of its behavior in beta radiation fields at the Calibration Laboratory of IPEN

    Science.gov (United States)

    Antonio, Patrícia L.; Xavier, Marcos; Caldas, Linda V. E.

    2014-11-01

    The Calibration Laboratory (LCI) at the Instituto de Pesquisas Energéticas e Nucleares (IPEN) is going to establish a Böhm extrapolation chamber as a primary standard system for the dosimetry and calibration of beta radiation sources and detectors. This chamber was already tested in beta radiation beams with an aluminized Mylar entrance window, and now, it was characterized with an original Hostaphan entrance window. A comparison between the results of the extrapolation chamber with the two entrance windows was performed. The results showed that this extrapolation chamber presents the same effectiveness in beta radiation fields as a primary standard system with both entrance windows, showing that any one of them may be utilized.

  13. Die etiek van HM Kuitert na aanleiding van sy boek Suicide - wat is er tegen? Selfdoding in moreel perspectief

    Directory of Open Access Journals (Sweden)

    R. M. Naudé

    1988-01-01

    Full Text Available The ethics of HM Kuitert according to his book entitled. Suicide - wat is er tegen? Selfdoding in moreel perspektief According to several publications Kuitert is criticised as a humanist. This paper tests his view on suicide to this accusation. It is found that Kuitert accepts teleology and solidarity as norms for his ethics and uses it as a method for his arguments against suicide. His goal is to offer an ethic which is acceptable for the Christian and the non-Christian. This results in outonomy with less emphasis on the theological argument against suicide. The result of this study is that the ethics of Kuitert cannot be described as mere humanism. Outonomy is judged as a form of theonomy.

  14. Winds in collision. I - Geometric implications of the emission lines for V 1016 Cyg and HM Sge

    Science.gov (United States)

    Willson, L. A.; Salzer, J.; Wallerstein, G.; Brugel, E.

    1984-01-01

    Emission line profiles and radial velocity data obtained from spectra in the visual region are presented for V1016 Cyg and HM Sge. The profiles of the forbidden emission lines are found to be inconsistent with spherical symmetry for the hot nebular material. It is argued that part of the nebular material in a detached binary system where both stars have spontaneous winds will naturally assume the shape of a curved, roughly conical, shell. The data can be satisfactorily interpreted in terms of the interaction of a low-velocity wind from a red giant with a high-velocity wind from a white dwarf in a detached binary system. This scheme provides a natural assignment of emission line forming regions to different portions of the interaction shell and the two winds, explaining both the profiles and the velocities of the features.

  15. Technetium-99m HM-PAO-SPECT study of regional cerebral perfusion in early Alzheimer's disease

    Energy Technology Data Exchange (ETDEWEB)

    Perani, D.; Di Piero, V.; Vallar, G.; Cappa, S.; Messa, C.; Bottini, G.; Berti, A.; Passafiume, D.; Scarlato, G.; Gerundini, P.

    1988-09-01

    Regional cerebral perfusion was evaluated by single photon emission computed tomography (SPECT) using technetium-99m hexamethylpropyleneamine oxime ((/sup 99m/Tc)HM-PAO) in sixteen patients with Alzheimer's disease (AD) in early clinical phase and in 16 healthy elderly controls. In all patients transmission computed tomography (TCT) and/or magnetic resonance imaging (MRI) did not show focal brain abnormalities. Relative to normal subjects, AD patients showed significant reductions in cortical/cerebellar activity ratio: cortical perfusion was globally depressed with the largest reductions in frontal and posterior temporo-parietal cortices. Asymmetries of relative perfusion between cerebral hemispheres were also demonstrated when language was affected or visuospatial functions were unevenly impaired. In patients with early AD, SPECT provides functional information to be compared with clinical and psychometric data.

  16. Ultrasonic compatibilization of polyelectrolyte complex based on polysaccharides for biomedical applications

    OpenAIRE

    Belluzo, M. Soledad; Medina, Lara F.; Cortizo, Ana María; Cortizo, María Susana

    2016-01-01

    In recent years, there has been an increasing interest in the design of biomaterials for cartilage tissue engineering. This type of materials must meet several requirements. In this study, we apply ultrasound to prepare a compatibilized blend of polyelectrolyte complexes (PEC) based on carboxymethyl cellulose (CMC) and chitosan (CHI), in order to improve stability and mechanical properties through the interpolymer macroradicals coupling produced by sonochemical reaction. We study the kinetic ...

  17. Triclosan loaded electrospun nanofibers based on a cyclodextrin polymer and chitosan polyelectrolyte complex.

    Science.gov (United States)

    Ouerghemmi, Safa; Degoutin, Stéphanie; Tabary, Nicolas; Cazaux, Frédéric; Maton, Mickaël; Gaucher, Valérie; Janus, Ludovic; Neut, Christel; Chai, Feng; Blanchemain, Nicolas; Martel, Bernard

    2016-11-20

    This work focuses on the relevance of antibacterial nanofibers based on a polyelectrolyte complex formed between positively charged chitosan (CHT) and an anionic hydroxypropyl betacyclodextrin (CD)-citric acid polymer (PCD) complexing triclosan (TCL). The study of PCD/TCL inclusion complex and its release in dynamic conditions, a cytocompatibility study, and finally the antibacterial activity assessment were studied. The fibers were obtained by electrospinning a solution containing chitosan mixed with PCD/TCL inclusion complex. CHT/TCL and CHT-CD/TCL were also prepared as control samples. The TCL loaded nanofibers were analyzed by Scanning Electron Microscopy (SEM), Fourier Transformed Infrared spectroscopy (FTIR) and X-Ray Diffraction (XRD). Nanofibers stability and swelling behavior in aqueous medium were pH and CHT:PCD weight ratio dependent. Such results confirmed that CHT and PCD interacted through ionic interactions, forming a polyelectrolyte complex. A high PCD content in addition to a thermal post treatment at 90°C were necessary to reach a nanofibers stability during 15days in soft acidic conditions, at pH=5.5. In dynamic conditions (USP IV system), a prolonged release of TCL with a reduced burst effect was observed on CHT-PCD polyelectrolyte complex based fibers compared to CHT-CD nanofibers. These results were confirmed by a microbiology study showing prolonged antibacterial activity of the nanofibers against Escherichia coli and Staphylococcus aureus. Such results could be explained by the fact that the stability of the polyelectrolyte CHT-PCD complex in the nanofibers matrix prevented the diffusion of the PCD/triclosan inclusion complex in the supernatant, on the contrary of the similar system including cyclodextrin in its monomeric form.

  18. Charge regulation of weak polyelectrolytes at low- and high-dielectric-constant substrates

    CERN Document Server

    Netz, R R

    2003-01-01

    As is well known, the effective charge of weak polyelectrolytes (PEs) decreases with decreasing salt concentration due to the electrostatic repulsion between dissociated charges. Close to dielectric boundaries, image-charge effects influence the dissociation equilibrium. At low-dielectric-constant substrates, one finds a further charge decrease and repulsion from the interface, while at high-dielectric-constant (e.g. metallic) substrates, the effective charge increases and the PE is attracted to the interface.

  19. Development of a robust pH-sensitive polyelectrolyte ionomer complex for anticancer nanocarriers

    Directory of Open Access Journals (Sweden)

    Lim CM

    2016-02-01

    Full Text Available Chaemin Lim,1,* Yu Seok Youn,2,* Kyung Soo Lee,1 Ngoc Ha Hoang,1 Taehoon Sim,1 Eun Seong Lee,3 Kyung Taek Oh1 1Department of Pharmaceutical Sciences, College of Pharmacy, Chung-Ang University, Seoul, 2Department of Pharmaceutical Sciences, School of Pharmacy, Sungkyunkwan University, Suwon, 3Division of Biotechnology, The Catholic University of Korea, Gyeonggi-do, South Korea *These authors contributed equally to this work Abstract: A polyelectrolyte ionomer complex (PIC composed of cationic and anionic polymers was developed for nanomedical applications. Here, a poly(ethylene glycol–poly(lactic acid–poly(ethylene imine triblock copolymer (PEG–PLA–PEI and a poly(aspartic acid (P[Asp] homopolymer were synthesized. These polyelectrolytes formed stable aggregates through electrostatic interactions between the cationic PEI and the anionic P(Asp blocks. In particular, the addition of a hydrophobic PLA and a hydrophilic PEG to triblock copolyelectrolytes provided colloidal aggregation stability by forming a tight hydrophobic core and steric hindrance on the surface of PIC, respectively. The PIC showed different particle sizes and zeta potentials depending on the ratio of cationic PEI and anionic P(Asp blocks (C/A ratio. The doxorubicin (dox-loaded PIC, prepared with a C/A ratio of 8, demonstrated pH-dependent behavior by the deprotonation/protonation of polyelectrolyte blocks. The drug release and the cytotoxicity of the dox-loaded PIC (C/A ratio: 8 increased under acidic conditions compared with physiological pH, due to the destabilization of the formation of the electrostatic core. In vivo animal imaging revealed that the prepared PIC accumulated at the targeted tumor site for 24 hours. Therefore, the prepared pH-sensitive PIC could have considerable potential as a nanomedicinal platform for anticancer therapy. Keywords: polyelectrolyte ionomer complex, PEG–PLA–PEI, nanomedicine, pH-sensitive, animal imaging

  20. Application of the Böhm chamber for reference beta dose measurements and the calibration of personal dosimeters

    Directory of Open Access Journals (Sweden)

    Skubacz Krystian

    2016-03-01

    Full Text Available Thermoluminescent dosimeters (TLDs currently used in personal and area dosimetry are often utilized to measure doses of ionizing radiation in fields with a more complex structure and therefore they should be calibrated in relation to different radiation types. The results of such calibration presented for UD-813 TLDs allowed for evaluation of their capability in relation to different radiation types like the beta and photon radiation of different energies and neutron radiation generated by the 241Am-Be source. The detector response for 60 keV photons was 10% higher than for the 662 keV gamma radiation of 137Cs. There were also response differences in relation to photon and beta radiation between detectors with an enhanced concentration of lithium 6Li and boron 10B and detectors containing a natural level of these isotopes. Measurements of the reference beta doses were performed with the help of the Böhm chamber. This method is relatively more complicated compared to determining the reference photon and neutron doses and is described thoroughly in this paper. The corrected current measured by the Böhm chamber for the chosen parameters was a linear function for an entire available range of the chamber depths. The percentage of errors related to the evaluated reference beta doses were below 2% despite a rather large number of corrections that should be taken into account. The calibration distances varied from 11 cm to 50 cm. For this range and beta particle energy, the absorption of radiation in the air was negligible and their attenuation had a predominantly geometric character.

  1. Biomimetic hydration lubrication with various polyelectrolyte layers on cross-linked polyethylene orthopedic bearing materials.

    Science.gov (United States)

    Kyomoto, Masayuki; Moro, Toru; Saiga, Kenichi; Hashimoto, Masami; Ito, Hideya; Kawaguchi, Hiroshi; Takatori, Yoshio; Ishihara, Kazuhiko

    2012-06-01

    Natural joints rely on fluid thin-film lubrication by the hydrated polyelectrolyte layer of cartilage. However, current artificial joints with polyethylene (PE) surfaces have considerably less efficient lubrication and thus much greater wear, leading to osteolysis and aseptic loosening. This is considered a common factor limiting prosthetic longevity in total hip arthroplasty (THA). However, such wear could be mitigated by surface modification to mimic the role of cartilage. Here we report the development of nanometer-scale hydrophilic layers with varying charge (nonionic, cationic, anionic, or zwitterionic) on cross-linked PE (CLPE) surfaces, which could fully mimic the hydrophilicity and lubricity of the natural joint surface. We present evidence to support two lubrication mechanisms: the primary mechanism is due to the high level of hydration in the grafted layer, where water molecules act as very efficient lubricants; and the secondary mechanism is repulsion of protein molecules and positively charged inorganic ions by the grafted polyelectrolyte layer. Thus, such nanometer-scaled hydrophilic polymers or polyelectrolyte layers on the CLPE surface of acetabular cup bearings could confer high durability to THA prosthetics.

  2. Densely charged polyelectrolyte-stuffed nanochannel arrays for power generation from salinity gradient

    Science.gov (United States)

    Kwak, Su Hong; Kwon, Seung-Ryong; Baek, Seol; Lim, Seung-Min; Joo, Young-Chang; Chung, Taek Dong

    2016-05-01

    We devised anodized aluminium oxide (AAO) frame-supported polyelectrolytic ion-exchange membranes for the application of electrical power generation systems where salinity differences are present. A series of polyelectrolytic AAO membranes (PAMs) were fabricated as a function of concentration of monomers and cross-linkers. Of the ion-selective PAMs as made, the membranes from the most concentrated monomers and cross-linkers, C-PAM100 and A-PAM100, showed the highest area resistances and permselectivities (the resistances were 4.9 and 2.9 Ω · cm2, the permseletivities for C-PAM100 and A-PAM100 were 99 and 89%, respectively). The measured resistances and permselectivities allowed the power density to be estimated for C-PAM100 and A-PAM100, 3.5 W/m2, and experimentally obtained power density using a reverse electrodialysis (RED) stack was 17.3 mW/m2. In addition, we investigated the influence of an AAO framework on a membrane resistance by comparing the PAMs with polyelectrolyte-stuffed capillaries, revealing that the resistance of the PAM has plenty of potential to be further reduced by optimizing the AAO pore spaces.

  3. Liquid-liquid and liquid-solid phase separation in protein-polyelectrolyte systems.

    Science.gov (United States)

    Comert, Fatih; Dubin, Paul L

    2017-01-01

    The coacervation of systems containing colloids (e.g. proteins or micelles) and polyelectrolytes (notably ionic polysaccharides) is often accompanied by precipitation. This can introduce inhomogeneity, irreversibility and irreproducible kinetics in applications in food science and bioengineering, with negative impact on texture and stability of food products, and unpredictable delivery of active "payloads." The relationship between coacervation and precipitation is obscure in that coacervates might be intermediates in the formation of precipitates, or else the two phenomena might proceed by different but possibly simultaneous mechanisms. This review will summarize the recent literature on coacervation/precipitation in protein-polyelectrolyte systems for which reports are most abundant, particularly in the context of food science. We present current findings and opinions about the relationship between the two types of phase separation. Results vary considerably depending not only on the protein-polyelectrolyte pairs chosen, but also on conditions including macromolecular concentrations and ionic strength. Nevertheless, we offer some general approaches that could explain a variety of observations. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Polyelectrolyte-Functionalized Nanofiber Mats Control the Collection and Inactivation of Escherichia coli

    Science.gov (United States)

    Rieger, Katrina A.; Porter, Michael; Schiffman, Jessica D.

    2016-01-01

    Quantifying the effect that nanofiber mat chemistry and hydrophilicity have on microorganism collection and inactivation is critical in biomedical applications. In this study, the collection and inactivation of Escherichia coli K12 was examined using cellulose nanofiber mats that were surface-functionalized using three polyelectrolytes: poly (acrylic acid) (PAA), chitosan (CS), and polydiallyldimethylammonium chloride (pDADMAC). The polyelectrolyte functionalized nanofiber mats retained the cylindrical morphology and average fiber diameter (~0.84 µm) of the underlying cellulose nanofibers. X-ray photoelectron spectroscopy (XPS) and contact angle measurements confirmed the presence of polycations or polyanions on the surface of the nanofiber mats. Both the control cellulose and pDADMAC-functionalized nanofiber mats exhibited a high collection of E. coli K12, which suggests that mat hydrophilicity may play a larger role than surface charge on cell collection. While the minimum concentration of polycations needed to inhibit E. coli K12 was 800 µg/mL for both CS and pDADMAC, once immobilized, pDADMAC-functionalized nanofiber mats exhibited a higher inactivation of E. coli K12, (~97%). Here, we demonstrate that the collection and inactivation of microorganisms by electrospun cellulose nanofiber mats can be tailored through a facile polyelectrolyte functionalization process. PMID:28773422

  5. Molecular-dynamics simulations and x-ray analysis of dye precipitates in the polyelectrolyte microcapsules

    Science.gov (United States)

    Saphiannikova, Marina; Radtchenko, Igor; Sukhorukov, Gleb; Shchukin, Dmitri; Yakimansky, Alexander; Ilnytskyi, Jaroslav

    2003-05-01

    The precipitate of the Disperse Red-1 dye in bulk and in confined microsized volumes was investigated by x-ray powder diffraction and molecular-dynamics simulations. The diffraction patterns exhibited two different precipitation regimes: In bulk when dye molecules form a distinct crystallite structure and inside polyelectrolyte capsules with a diameter up to 8 μm when the precipitate presumably represents a very fine polycrystalline powder. The latter result was further supported by molecular-dynamics simulations carried out for up to 640 dye molecules in the NVT ensemble. Calculations have also shown that effects of confined geometry and steric restrictions arising due to encapsulated polyelectrolyte molecules can not prohibit dye nucleation and subsequent crystallization. However, nonspecific interactions between Disperse Red-1 and encapsulated polyelectrolyte could cause the onset of heterogeneous nucleation resulting in formation of a fine polycrystalline powder. The formation process was directly observed building configuration snapshots and calculating the Gay-Berne orientational order parameter and radial distribution function resolved parallel and perpendicular to the director. Comparison of powder diagrams derived from simulation data indicates that it is nearly impossible to distinguish a fine polycrystalline powder from the isotropic system.

  6. Filterability of membrane bioreactor (MBR) sludge: impacts of polyelectrolytes and mixing with conventional activated sludge.

    Science.gov (United States)

    Yigit, Nevzat O; Civelekoglu, Gokhan; Cinar, Ozer; Kitis, Mehmet

    2010-01-01

    The main objective of this work was to investigate the filterability of MBR sludge and its mixture with conventional activated sludge (CAS). In addition, the impacts of type and dose of various polyelectrolytes, filter type and sludge properties on the filterability of both MBR and Mixed sludges were determined. Specific cake resistance (SCR) measured by the Buchner funnel filtration test apparatus and the solids content of the resulting sludge cake were used to assess the dewaterability of tested sludges. The type of filter paper used in Buchner tests affected the results of filterability for MBR, CAS and Mixed sludges. SCR values and optimum polyelectrolyte doses increased with increasing MLSS concentrations in the MBR, which suggested that increase in MLSS concentrations accompanied by increases in EPS and SMP concentrations and a shift toward smaller particles caused poorer dewaterability of the MBR sludge. The significant differences observed among the filterability of CAS and MBR sludges suggested that MLSS alone is not a good predictor of sludge dewaterability. Combining CAS and MBR sludges at different proportions generally improved their dewaterability. Combining MBR sludges having typically high MLSS and EPS concentrations with CAS having much lower MLSS concentrations may be an option for full-scale treatment plants experiencing sludge dewaterability problems. Better filterability and higher cake dry solids were achieved with cationic polyelectrolytes compared to anionic and non-ionic ones for all sludge types tested.

  7. Polyelectrolyte-Functionalized Nanofiber Mats Control the Collection and Inactivation of Escherichia coli

    Directory of Open Access Journals (Sweden)

    Katrina A. Rieger

    2016-04-01

    Full Text Available Quantifying the effect that nanofiber mat chemistry and hydrophilicity have on microorganism collection and inactivation is critical in biomedical applications. In this study, the collection and inactivation of Escherichia coli K12 was examined using cellulose nanofiber mats that were surface-functionalized using three polyelectrolytes: poly (acrylic acid (PAA, chitosan (CS, and polydiallyldimethylammonium chloride (pDADMAC. The polyelectrolyte functionalized nanofiber mats retained the cylindrical morphology and average fiber diameter (~0.84 µm of the underlying cellulose nanofibers. X-ray photoelectron spectroscopy (XPS and contact angle measurements confirmed the presence of polycations or polyanions on the surface of the nanofiber mats. Both the control cellulose and pDADMAC-functionalized nanofiber mats exhibited a high collection of E. coli K12, which suggests that mat hydrophilicity may play a larger role than surface charge on cell collection. While the minimum concentration of polycations needed to inhibit E. coli K12 was 800 µg/mL for both CS and pDADMAC, once immobilized, pDADMAC-functionalized nanofiber mats exhibited a higher inactivation of E. coli K12, (~97%. Here, we demonstrate that the collection and inactivation of microorganisms by electrospun cellulose nanofiber mats can be tailored through a facile polyelectrolyte functionalization process.

  8. Solid polyelectrolyte fuel cell power supply system; Kotai kobunshigata nenryo denchi dengen system

    Energy Technology Data Exchange (ETDEWEB)

    Aoki, T. [Kanagawa (Japan); Kadoma, H. [Yokohama (Japan); Hashizaki, K.; Tani, T. [Mitsubishi Heavy Industries Ltd., Tokyo (Japan)

    1996-06-11

    When a previous solid polyelectrolyte fuel cell power supply system is used underwater, the water generated by the cell reaction is stored in a water storage tank and it is necessary that the system is suspended in case the generated water is full in the water storage tank to take the system out of water and the water in the tank is discharged in the atmosphere. The solid polyelectrolyte fuel cell power supply system of this invention is equipped with a discharge pump to exhaust the generated water out of the closed vessel accommodating the system or equipped with a device to exhaust the generated water into the outside water accompanied with gushing of high-pressure gas into the outside water. As a result, the water generated by the cell reaction can be exhausted from the system into the outside water at any required time so that the fuel cell power supply system can be operated continuously as far as the supply of the fuel or the oxidizer last. By the installment of this function, a solid polyelectrolyte fuel cell power supply system can be used as an independent underwater power source or as a power source for an underwater moving body. 4 figs.

  9. Densely charged polyelectrolyte-stuffed nanochannel arrays for power generation from salinity gradient

    Science.gov (United States)

    Kwak, Su Hong; Kwon, Seung-Ryong; Baek, Seol; Lim, Seung-Min; Joo, Young-Chang; Chung, Taek Dong

    2016-01-01

    We devised anodized aluminium oxide (AAO) frame-supported polyelectrolytic ion-exchange membranes for the application of electrical power generation systems where salinity differences are present. A series of polyelectrolytic AAO membranes (PAMs) were fabricated as a function of concentration of monomers and cross-linkers. Of the ion-selective PAMs as made, the membranes from the most concentrated monomers and cross-linkers, C-PAM100 and A-PAM100, showed the highest area resistances and permselectivities (the resistances were 4.9 and 2.9 Ω · cm2, the permseletivities for C-PAM100 and A-PAM100 were 99 and 89%, respectively). The measured resistances and permselectivities allowed the power density to be estimated for C-PAM100 and A-PAM100, 3.5 W/m2, and experimentally obtained power density using a reverse electrodialysis (RED) stack was 17.3 mW/m2. In addition, we investigated the influence of an AAO framework on a membrane resistance by comparing the PAMs with polyelectrolyte-stuffed capillaries, revealing that the resistance of the PAM has plenty of potential to be further reduced by optimizing the AAO pore spaces. PMID:27194475

  10. CaSO4 and cationic polyelectrolyte as possible pectin precipitants in sugar beet juice clarification

    Directory of Open Access Journals (Sweden)

    Kuljanin Tatjana

    2015-01-01

    Full Text Available Three pectin preparations were isolated from fresh sugar beet pulp during the 150 minutes of extraction, at pH values of 1, 3.5 and 8.5. CaSO4 precipitant was added to 100 cm3 of 0.1% (wt solution of pectin. Studies were performed with 9 different concentrations of CaSO4 solution (50-450 mg dm-3 with the addition of a cationic polyelectrolyte (cationic PAM in concentrations of 3 and 5 mg dm-3. The efficiency of pectin precipitation was monitored by measuring the zeta potential of pectin preparations. Optimal amounts of precipitant CaSO4, without the use of a cationic polyelectrolyte, were as follows: 490-678 mg CaSO4/g pectin. After the use of a cationic polyelectrolyte, the optimal amounts of CaSO4 were smaller (353-512 mg/g pectin. These quantities are significantly lower than the average amount of CaO used in the conventional clarification process of sugar beet juice (about 9 g/g pectin of sugar beet juice. [Projekat Ministarstva nauke Republike Srbije, br. TR -31055

  11. Comparative study of cytotoxicity of ferromagnetic nanoparticles and magnetitecontaining polyelectrolyte microcapsules

    Science.gov (United States)

    Minaeva, O. V.; Brodovskaya, E. P.; Pyataev, M. A.; Gerasimov, M. V.; Zharkov, M. N.; Yurlov, I. A.; Kulikov, O. A.; Kotlyarov, A. A.; Balykova, L. A.; Kokorev, A. V.; Zaborovskiy, A. V.; Pyataev, N. A.; Sukhorukov, G. B.

    2017-01-01

    The cytotoxicity of magnetite nanoparticles (MNP) stabilized with citrate acidand polyelectrolyte multilayer microcapsules containing these particles in the shell is analyzed. Microcapsules were prepared by co-precipitation of iron (II) and (III) chlorides. Polyelectrolyte microcapsules synthesized by the layer-by-layer method from biodegradable polymers polyarginine and dextran sulfate. Cytotoxicity of the synthesized objects was studied on the L929 cells culture and human leucocytes. It was also investigated the phagocytic activity of leukocytes for the MNP and magnetite containing polyelectrolyte microcapsules (MCPM). A set of tests (MTT assay, neutral red uptake assay, lactate dehydrogenase release assay) was used to study the cytotoxicity in vitro. All the tests have shown that the magnetic nanoparticles have a greater cytotoxicity in comparison with microcapsules containing an equivalent amount of magnetite. In contrast to the mouse fibroblast culture, human leukocytes were more resistant to the toxic effects of magnetite. At the concentrations used in our studies no significant reduction in the viability of leukocytes has been registered. Both MNP and MCPM undergo phagocytosis, however, the phagocytic activity of leukocytes for these particles was lower than for the standard objects (latex microparticles).

  12. Metallosupramolecular coordination polyelectrolytes: potential building blocks for molecular-based devices.

    Science.gov (United States)

    Kurth, Dirk G

    2002-04-01

    Metal-ion-induced self-assembly of ditopic ligands, based on bisterpyridines, and transition metal ions result in formation of metallosupramolecular coordination polyelectrolytes (MEPE). The positive charge of MEPE can be utilized in several ways to process highly ordered architectures. Alternating adsorption of MEPE and oppositely charged polyelectrolytes on solid substrates results in multilayers. The sequential nature of this process allows combining MEPEs with other functional components. This process permits nanometer thickness control, is readily adapted for automated processing, and is applicable to two-dimensional substrates as well as to colloidal templates. The surface chemical properties of MEPE are readily controlled by complexing MEPE with negatively charged amphiphiles. The resulting polyelectrolyte-amphiphile complexes (PAC) are soluble in organic solvents and form liquid crystalline phases. The PAC also spreads at the air-water interface as Langmuir monolayer, which can be transferred onto solid substrates. The resulting Langmuir-Blodgett multilayers are highly ordered and anisotropic. Materials with transition metal ions possess many interesting properties, including spin transitions, magnetism, as well as photochemical assets that are relevant for the construction of functional devices and materials. The presented approach combines principles of supramolecular and colloidal chemistry as well as surface science, is highly modular in nature, and provides extensive control of structure and function from molecular to macroscopic levels.

  13. Pair interactions in polyelectrolyte-nanoparticle systems: Influence of dielectric inhomogeneities and the partial dissociation of polymers and nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Pryamitsyn, Victor [Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712 (United States); Ganesan, Venkat, E-mail: venkat@che.utexas.edu [Department of Chemical Engineering and Institute for Computational and Engineering Sciences, University of Texas at Austin, Austin, Texas 78712 (United States)

    2015-10-28

    We study the effective pair interactions between two charged spherical particles in polyelectrolyte solutions using polymer self-consistent field theory. In a recent study [V. Pryamitsyn and V. Ganesan, Macromolecules 47, 6095 (2015)], we considered a model in which the particles possess fixed charge density, the polymers contain a prespecified amount of dissociated charges and, the dielectric constant of the solution was assumed to be homogeneous in space and independent of the polymer concentration. In this article, we present results extending our earlier model to study situations in which either or both the particle and the polymers possess partially dissociable groups. Additionally, we also consider the case when the dielectric constant of the solution depends on the local concentration of the polymers and when the particle’s dielectric constant is lower than that of the solvent. For each case, we quantify the polymer-mediated interactions between the particles as a function of the polymer concentrations and the degree of dissociation of the polymer and particles. Consistent with the results of our previous study, we observe that the polymer-mediated interparticle interactions consist of a short-range attraction and a long-range repulsion. The partial dissociablity of the polymer and particles was seen to have a strong influence on the strength of the repulsive portion of the interactions. Rendering the dielectric permittivity to be inhomogeneous has an even stronger effect on the repulsive interactions and results in changes to the qualitative nature of interactions in some parametric ranges.

  14. HM-EH-RT: hybrid multimodal energy harvesting from rotational and translational motions

    Directory of Open Access Journals (Sweden)

    Miles Larkin

    2013-12-01

    Full Text Available This paper presents a novel hybrid multimodal energy harvesting device consisting of an unbalanced rotary disk that supports two transduction methods, piezoelectric and electromagnetic. The device generates electrical energy from oscillatory motion either orthogonal or parallel to the rotary axis to power electronic devices. Analytical models for the electromagnetic and piezoelectric systems were developed to describe the mechanical and electrical behavior of the device. From these models, numerical simulations were performed to predict power generation capabilities. The device was fabricated, and several components were optimized experimentally. The energy harvester was then experimentally characterized using a modal shaker in several different orientations. The device generates a maximum RMS power output of 120 mW from the electromagnetic system at 5 Hz and 0.8 g, and 4.23 mW from the piezoelectric system at 20.2 Hz and 0.4 g excitation acceleration. The device is 180 mm in diameter and 45 mm thick including the rotor height. Further size optimization will produce an energy harvester capable of being used as a wearable device to power mobile electronics for multiple applications.

  15. Dynamics of polyelectrolyte adsorption on surfaces: Applications in the detection of iron in water

    Science.gov (United States)

    Gammana, Madhira N.

    Layer by layer (LbL) self assembly is a simple multilayer thin (nanometer scale) film fabricating technique. The mechanism of film growth remains a topic of much controversy. For example, several models have been proposed to explain the origin of linear and exponential film growth that are attributed to differences in the dynamic processes that occur at the molecular level during film formation. The problem is that there are no methods that directly measure the dynamics of polymer formation during LbL film formation. In this thesis, I describe the essential elements of an ATR-IR spectroscopic method that was developed to enable measurement of the dynamics of the mass adsorbed and polyelectrolyte conformation during the formation of PEM's. In particular, I followed the sequential adsorption of Sodium polyacrylate (NaPA) and Poly (diallyldimethylammonium) chloride (PDADMAC) from deionized (DI) water and as a function of ionic strength to show that polymer diffusion occurs between layers when adsorbed from DI water. In contrast, a denser layer occurs with no polymer interdiffusion for deposition from 0.02M ionic strength solutions of NaPA and PDADMAC. While the mass deposited increased with ionic strength, linear multilayer growth in films were observed in all cases. This finding disputes a common viewpoint that interdiffusion of polymer layers is a key feature of exponential film growth. The theme of polymer layer adsorption was used in the detection of Fe 3+ in seawater. A new approach, developed previously in Tripp's group, utilized "vertical amplification" in which a block copolymer assembled on membranes provided multiple anchoring points extending from the surface for attaching a siderophore, desferrioxamine B (DFB). The Fe3+ chelates with the siderophore producing a red color that can be quantified by visible spectroscopy. However, the rate of Fe3+ uptake was found to be dependent on flow rate. The origin of this flow rate dependence was identified by the work

  16. Cellular uptake and cell-to-cell transfer of polyelectrolyte microcapsules within a triple co-culture system representing parts of the respiratory tract

    Science.gov (United States)

    Kuhn, Dagmar A.; Hartmann, Raimo; Fytianos, Kleanthis; Petri-Fink, Alke; Rothen-Rutishauser, Barbara; Parak, Wolfgang J.

    2015-06-01

    Polyelectrolyte multilayer microcapsules around 3.4 micrometers in diameter were added to epithelial cells, monocyte-derived macrophages, and dendritic cells in vitro and their uptake kinetics were quantified. All three cell types were combined in a triple co-culture model, mimicking the human epithelial alveolar barrier. Hereby, macrophages were separated in a three-dimensional model from dendritic cells by a monolayer of epithelial cells. While passing of small nanoparticles has been demonstrated from macrophages to dendritic cells across the epithelial barrier in previous studies, for the micrometer-sized capsules, this process could not be observed in a significant amount. Thus, this barrier is a limiting factor for cell-to-cell transfer of micrometer-sized particles.

  17. Study of the effects of the reaction conditions on the modification of clays with polyelectrolytes and silanes.

    Science.gov (United States)

    de la Orden, M U; Arranz, J; Lorenzo, V; Pérez, E; Martínez Urreaga, J

    2010-02-01

    New organically modified clays have been obtained from sodium montmorillonite, using either a cationic polyelectrolyte (polyethylenimine) or a novel homemade bisphenol-A silane as modifiers. The modification processes have been carried out in different reaction media, in order to study the effects on the properties of the modified clays of several reaction parameters, such as the pH of the polyethylenimine solution or the nature of the solvent used in the silanization. The obtained clays were characterized using X-ray diffraction, thermogravimetric analysis, and FTIR spectroscopy. Clays modified with polyelectrolyte or silane show significant increases in the basal spacing. The properties of polyelectrolyte-modified clays depend on the pH of the treating solution. The increase in the basal spacing of polyelectrolyte-modified clays varies only slightly with the pH; however, this reaction parameter clearly determines the total amount of polyelectrolyte introduced in the clay. The properties and applications of silane-modified clays are strongly dependent on the presence of water in the reaction media used for the silanization. These results have been explained by considering that the reaction conditions determine the nature and the amount of material intercalated into the clay.

  18. Fine tuning of the pH-sensitivity of laponite-doxorubicin nanohybrids by polyelectrolyte multilayer coating.

    Science.gov (United States)

    Xiao, Shili; Castro, Rita; Maciel, Dina; Gonçalves, Mara; Shi, Xiangyang; Rodrigues, João; Tomás, Helena

    2016-03-01

    Despite the wide research done in the field, the development of advanced drug delivery systems with improved drug delivery properties and effective anticancer capability still remains a great challenge. Based on previous work that showed the potentialities of the nanoclay Laponite as a pH-sensitive doxorubicin (Dox) delivery vehicle, herein we report a simple method to modulate its extent of drug release at different pH values. This was achieved by alternate deposition of cationic poly(allylamine) hydrochloride and anionic poly(sodium styrene sulfonate) (PAH/PSS) polyelectrolytes over the surface of Dox-loaded Laponite nanoparticles using the electrostatic layer-by-layer (LbL) self-assembly approach. The successful formation of polyelectrolyte multilayer-coated Dox/Laponite systems was confirmed by Dynamic Light Scattering and zeta potential measurements. Systematic studies were performed to evaluate their drug release profiles and anticancer efficiency. Our results showed that the presence of the polyelectrolyte multilayers improved the sustained release properties of Laponite and allowed a fine tuning of the extension of drug release at neutral and acidic pH values. The cytotoxicity presented by polyelectrolyte multilayer-coated Dox/Laponite systems towards MCF-7 cells was in accordance with the drug delivery profiles. Furthermore, cellular uptake studies revealed that polyelectrolyte multilayer-coated Dox/Laponite nanoparticles can be effectively internalized by cells conducting to Dox accumulation in cell nucleus.

  19. Continuous testing system for Baeyer-Villiger biooxidation using recombinant Escherichia coli expressing cyclohexanone monooxygenase encapsulated in polyelectrolyte complex capsules.

    Science.gov (United States)

    Bučko, Marek; Schenkmayerová, Andrea; Gemeiner, Peter; Vikartovská, Alica; Mihovilovič, Marko D; Lacík, Igor

    2011-08-10

    An original strategy for universal laboratory testing of Baeyer-Villiger monooxygenases based on continuous packed-bed minireactor connected with flow calorimeter and integrated with bubble-free oxygenation is reported. Model enantioselective Baeyer-Villiger biooxidations of rac-bicyclo[3.2.0]hept-2-en-6-one to corresponding lactones (1R,5S)-3-oxabicyclo-[3.3.0]oct-6-en-3-one and (1S,5R)-2-oxabicyclo-[3.3.0]oct-6-en-3-one as important chiral synthons for the synthesis of bioactive compounds were performed in the minireactor equipped with a column packed with encapsulated recombinant cells Escherichia coli overexpressing cyclohexanone monooxygenase. The cells were encapsulated in polyelectrolyte complex capsules formed by reaction of oppositely charged polymers utilizing highly reproducible and controlled encapsulation process. Encapsulated cells tested in minireactor exhibited high operational stability with 4 complete substrate conversions to products and 6 conversions above 80% within 14 repeated consecutive biooxidation tests. Moreover, encapsulated cells showed high enzyme stability during 91 days of storage with substrate conversions above 80% up to 60 days of storage. Furthermore, usable thermometric signal of Baeyer-Villiger biooxidation obtained by flow calorimetry using encapsulated cells was utilized for preparatory kinetic study in order to guarantee sub-inhibitory initial substrate concentration for biooxidation tests.

  20. Stabilization of aqueous nanoscale zerovalent iron dispersions by anionic polyelectrolytes: adsorbed anionic polyelectrolyte layer properties and their effect on aggregation and sedimentation

    Energy Technology Data Exchange (ETDEWEB)

    Phenrat, Tanapon; Saleh, Navid [Carnegie Mellon University, Department of Civil and Environmental Engineering (United States); Sirk, Kevin [Carnegie Mellon University, Department of Chemical Engineering (United States); Kim, Hye-Jin [Carnegie Mellon University, Department of Civil and Environmental Engineering (United States); Tilton, Robert D. [Carnegie Mellon University, Department of Chemical Engineering (United States); Lowry, Gregory V. [Carnegie Mellon University, Department of Civil and Environmental Engineering (United States)], E-mail: glowry@cmu.edu

    2008-05-15

    Nanoscale zerovalent iron (NZVI) particles are 5-40 nm sized Fe{sup 0}/Fe-oxide particles that rapidly transform many environmental contaminants to benign products and are a promising in situ remediation agent. Rapid aggregation and limited mobility in water-saturated porous media limits the ability to deliver NZVI dispersions in the subsurface. This study prepares stable NZVI dispersions through physisorption of commercially available anionic polyelectrolytes, characterizes the adsorbed polymer layer, and correlates the polymer coating properties with the ability to prevent rapid aggregation and sedimentation of NZVI dispersions. Poly(styrene sulfonate) with molecular weights of 70 k and 1,000 k g/mol (PSS70K and PSS1M), carboxymethyl cellulose with molecular weights of 90 k and 700 k g/mol (CMC90K and CMC700K), and polyaspartate with molecular weights of 2.5 k and 10 k g/mol (PAP2.5K and 10K) were compared. Particle size distributions were determined by dynamic light scattering during aggregation. The order of effectiveness to prevent rapid aggregation and stabilize the dispersions was PSS70K(83%) > {approx}PAP10K(82%) > PAP2.5K(72%) > CMC700K(52%), where stability is defined operationally as the volume percent of particles that do not aggregate after 1 h. CMC90K and PSS1M could not stabilize RNIP relative to bare RNIP. A similar trend was observed for their ability to prevent sedimentation, with 40, 34, 32, 20, and 5 wt%, of the PSS70K, PAP10K, PAP2.5K, CMC700K, and CMC90K modified NZVI remaining suspended after 7 h of quiescent settling, respectively. The stable fractions with respect to both aggregation and sedimentation correlate well with the adsorbed polyelectrolyte mass and thickness of the adsorbed polyelectrolyte layers as determined by Oshima's soft particle theory. A fraction of the particles cannot be stabilized by any modifier and rapidly agglomerates to micron sized aggregates, as is also observed for unmodified NZVI. This non

  1. SPECT with [99mTc]-d,l-hexamethyl-propylene amine oxime (HM-PAO) compared with regional cerebral blood flow measured by PET

    DEFF Research Database (Denmark)

    Yonekura, Y; Nishizawa, S; Mukai, Thomas Søgaard;

    1988-01-01

    In order to validate the use of technetium-99m-d,l-hexamethylpropyleneamine oxime (HM-PAO) as a flow tracer, a total of 21 cases were studied with single photon emission computerized tomography (SPECT), and compared to regional cerebral blood flow (rCBF) measured by position emission tomography (...

  2. Analysis of the machinery and intermediates of the 5hmC-mediated DNA demethylation pathway in aging on samples from the MARK-AGE Study

    Science.gov (United States)

    Valentini, Elisabetta; Zampieri, Michele; Malavolta, Marco; Bacalini, Maria Giulia; Calabrese, Roberta; Guastafierro, Tiziana; Reale, Anna; Franceschi, Claudio; Hervonen, Antti; Koller, Bernhard; Bernhardt, Jürgen; Slagboom, P. Eline; Toussaint, Olivier; Sikora, Ewa; Gonos, Efstathios S.; Breusing, Nicolle; Grune, Tilman; Jansen, Eugène; Dollé, Martijn E.T.; Moreno-Villanueva, María; Sindlinger, Thilo; Bürkle, Alexander; Ciccarone, Fabio; Caiafa, Paola

    2016-01-01

    Gradual changes in the DNA methylation landscape occur throughout aging virtually in all human tissues. A widespread reduction of 5-methylcytosine (5mC), associated with highly reproducible site-specific hypermethylation, characterizes the genome in aging. Therefore, an equilibrium seems to exist between general and directional deregulating events concerning DNA methylation controllers, which may underpin the age-related epigenetic changes. In this context, 5mC-hydroxylases (TET enzymes) are new potential players. In fact, TETs catalyze the stepwise oxidation of 5mC to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC), driving the DNA demethylation process based on thymine DNA glycosylase (TDG)-mediated DNA repair pathway. The present paper reports the expression of DNA hydroxymethylation components, the levels of 5hmC and of its derivatives in peripheral blood mononuclear cells of age-stratified donors recruited in several European countries in the context of the EU Project ‘MARK-AGE’. The results provide evidence for an age-related decline of TET1, TET3 and TDG gene expression along with a decrease of 5hmC and an accumulation of 5caC. These associations were independent of confounding variables, including recruitment center, gender and leukocyte composition. The observed impairment of 5hmC-mediated DNA demethylation pathway in blood cells may lead to aberrant transcriptional programs in the elderly. PMID:27587280

  3. Performing Arts: A Subject-Based Aspect Report on Provision in Scotland's Colleges by HM Inspectors on Behalf of the Scottish Funding Council

    Science.gov (United States)

    Education Scotland, 2011

    2011-01-01

    The Her Majesty's Inspectorate of Education (HMIE) publication, "External quality arrangements for Scotland's colleges," September 2008, specifies that HM Inspectors (HMIs) will produce a number of subject aspect reports over the four years 2008-12. These reports complement in a subject-specific context the generic evaluations of learning and…

  4. A Subject-Based Aspect Report on Provision in Scotland's Colleges by HM Inspectors on Behalf of the Scottish Funding Council: Hospitality and Tourism

    Science.gov (United States)

    Her Majesty's Inspectorate of Education, 2010

    2010-01-01

    The HM Inspectorate of Education publication, "External quality arrangements for Scotland's colleges, September 2008," specifies that HMIE will produce a number of subject aspect reports over the four years 2008-12. These reports complement in a subject specific context the generic evaluations of learning and teaching in HMIE's reports…

  5. Sewage sludge dehydration with biodegradable polyelectrolytes as flocculants. Final report. Pt. 1. Development of synthetic polyelectrolytes; Klaerschlammentwaesserung unter Einsatz biologisch abbaubarer Polyelektrolyte als Flockungshilfsmittel. Abschlussbericht. T. 1. Entwicklung der synthetischen Polyelektrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Matuschewski, H.; Gohlke, U.; Jaeger, W.

    1997-09-01

    Polyelectrolytes with improved degradability were to be developed for dehydration of uncontaminated sewage sludge. Part-project I investigated the synthesis of polymers. For this purpose, polyvinyl alcohol was functionalized into polyelectrolytes by etheration, Mannich reaction, acetalisation and graft copolymerisation. Some of the new polymers have very good flocculation and dehydration characteristics. (SR) [Deutsch] Ziel des Vorhabens war es, Ergebnisse zur Entwaesserung nicht kontaminierter Klaerschlaemme mit Polyelektrolyten mit verbesserter Abbaubarkeit zu erarbeiten. Ziel des Teilvorhabens I war die Synthese entsprechender Polymerer. Dazu wurde Polyvinylalkohol durch Veretherung, Mannichreaktion, Acetalisierung und Propfcopolymerisation zu Polyelektrolyten funktionalisiert. Die neuen Polymere weisen zum Teil sehr gute Flockungs- und Entwaesserungseigenschaften auf. (SR)

  6. THE EFFECTS OF RETAIL SERVICESCAPE ON BRAND IMAGE AND PURCHASE INTENTION: P&B AND H&M EXAMPLE

    Directory of Open Access Journals (Sweden)

    Meltem KARAKAŞOĞLU

    2016-08-01

    Full Text Available Competion in the retail sector is increasing rapidly and retail brands compete not only with competitors that have physical retail shops but also with online shopping platforms. Consumers shop not only to buy products but at the same time they may desire some benefits such as being happy, or socializing. In other words, consumers want to have favorable experiences as they are shopping. Individuals tend to linger longer in environments that they like and they tend to escape from environments that they do not like. By creating and managing retail servicescapes properly it is possible to attract consumers to a retail shop and at the same time make them spend more time and money in the shop. The aim of this study is to understand the effects of retail servicescape factors on brand image and purchase intention. For the purpose of the study two retail brands were chosen (Pull and Bear and H&M and data were collected from university students using face to face surveys. Research results show that retail servicescape has a statistically significant effect on brand image and purchase intention. Additionally, brand image has a statistically significant effect on purchase intention.

  7. Block Entanglement in the Single-Hole Hubbard Model

    Institute of Scientific and Technical Information of China (English)

    YAO Kai-Lun; SUN Xiao-Zhong; LIU Zu-Li; LI Yan-Chao; YU Li; GAO Guo-Ying

    2006-01-01

    @@ We investigate the distribution of the entanglement of the one-dimensional single-hole Hubbard model (HM)and study the relationship between the entanglement and quantum phase transition in the model. The von Neumann entropy of a block with neighbouring spins L for a single-hole HM is calculated using the densitymatrix renormalization group.

  8. An electrochemical aptasensor for chiral peptide detection using layer-by-layer assembly of polyelectrolyte-methylene blue/polyelectrolyte-graphene multilayer

    Energy Technology Data Exchange (ETDEWEB)

    Qin Haixia; Liu Jiyang; Chen Chaogui [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Wang Jiahi, E-mail: jhwang@ciac.jl.cn [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Wang Erkang, E-mail: ekwang@ciac.jl.cn [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)

    2012-01-27

    Highlights: Black-Right-Pointing-Pointer An electrochemical aptasensor for selective detection of peptide is constructed. Black-Right-Pointing-Pointer This aptasensor is based on grapheme multilayer via layer-by-layer assembly. Black-Right-Pointing-Pointer Such multilayer facilitates electron transfer and provides more adsorption sites. - Abstract: Here we demonstrate for the first time that by physically adsorbing aptamer onto conductive film assembled via alternate adsorption of graphene/polyelectrolyte and methylene blue/polyelectrolyte, a label-free electrochemical aptasensor with high sensitivity and selectivity for peptide detection is constructed. Graphene multilayer derived from layer-by-layer assembly has played significant roles in this sensing strategy: allowing accumulation of methylene blue, facilitating electron transfer and providing much more adsorption site. As compared to previous electrochemical aptasensors, the current sensor based on graphene multilayer alternated with electroactive molecule layer offers extremely high capability for sensitive detection of target without interference of environmental surrounding. This electroactive probe-confined graphene multilayer confers great flexibility to combine with differential pulse voltammetry (DPV) together. In the presence of target D entiomer of arginine vasopressin (D-VP), the binding of peptide to aptamer block the electron transfer process of MB, leading to decreased current peak of DPV. By this way, this electrochemical aptasensor based on electroactive molecule-intercalated graphene multilayer provide highly sensitive and specific detection of D-VP with the lowest detectable concentration of 1 ng mL{sup -1} and a wide detection range from 1 to 265 ng mL{sup -1}.

  9. Mediating gel formation from structurally controlled poly(electrolytes) through multiple "head-to-body" electrostatic interactions.

    Science.gov (United States)

    Srour, Hassan; Ratel, Olivier; Leocmach, Mathieu; Adams, Emma A; Denis-Quanquin, Sandrine; Appukuttan, Vinukrishnan; Taberlet, Nicolas; Manneville, Sébastien; Majesté, Jean-Charles; Carrot, Christian; Andraud, Chantal; Monnereau, Cyrille

    2015-01-01

    Tuning the chain-end functionality of a short-chain cationic homopolymer, owing to the nature of the initiator used in the atom transfer radical polymerization (ATRP) polymerization step, can be used to mediate the formation of a gel of this poly(electrolyte) in water. While a neutral end group gives a solution of low viscosity, a highly homogeneous gel is obtained with a phosphonate anionic moiety, as characterized by rheometry and diffusion nuclear magnetic resonance (NMR). This novel type of supramolecular control over poly(electrolytic) gel formation could find potential use in a variety of applications in the field of electro-active materials.

  10. Size, flexibility, and scattering functions of semiflexible polyelectrolytes with excluded volume effects: Monte Carlo simulations and neutron scattering experiments

    DEFF Research Database (Denmark)

    Cannavacciuolo, L.; Sommer, C.; Pedersen, J.S.;

    2000-01-01

    We present a systematic Monte Carlo study of the scattering function S(q) of semiflexible polyelectrolytes at infinite dilution, in solutions with different concentrations of added salt. In the spirit of a theoretical description of polyelectrolytes in terms of the equivalent parameters, namely...... outlined in the Odijk-Skolnick-Fixman theory, in which the behavior of charged polymers is described only in terms of increasing local rigidity and excluded volume effects. Moreover, the Monte Carlo data are found to be in very good agreement with experimental scattering measurements with equilibrium...

  11. Catalytic membranes prepared using layer-by-layer adsorption of polyelectrolyte/metal nanoparticle films in porous supports.

    Science.gov (United States)

    Dotzauer, David M; Dai, Jinhua; Sun, Lei; Bruening, Merlin L

    2006-10-01

    Layer-by-layer adsorption of polyelectrolytes and gold nanoparticles within porous supports provides a convenient method for forming catalytic membranes. The polyelectrolyte film effectively immobilizes the gold nanoparticles without inhibiting access to catalytic sites, as shown by the similar rate constants for nanoparticle-catalyzed 4-nitrophenol reduction in solution and in membranes. Modified alumina membranes reduce >99% of 0.4 mM 4-nitrophenol at linear flow rates of 0.98 cm/s, and the modification process is also applicable to track-etched polycarbonate supports.

  12. In situ monitoring of the formation of nanoscale polyelectrolyte coatings on optical fibers using Surface Plasmon Resonances.

    Science.gov (United States)

    Shevchenko, Yanina; Ahamad, Nur Uddin; Ianoul, Anatoli; Albert, Jacques

    2010-09-13

    Deposition of a conformal nanoscale polymer coating was characterized using a fiber SPR sensor. The sensor platform consisted of an unmodified gold-coated single mode fiber where SPR was excited through the coupling of the core mode into the cladding modes using a Tilted Fiber Bragg Grating. The results from this study show how the sensor can monitor in real time the formation of polyelectrolyte coatings during a process consisting of several stages of immersion. The experimental data was further calibrated by simulations and Atomic Force Microscope imaging allowing us to determine the thickness and refractive index of the adsorbed polyelectrolyte.

  13. pH and Salt Effects on the Associative Phase Separation of Oppositely Charged Polyelectrolytes

    Directory of Open Access Journals (Sweden)

    Prateek K. Jha

    2014-05-01

    Full Text Available The classical Voorn-Overbeek thermodynamic theory of complexation and phase separation of oppositely charged polyelectrolytes is generalized to account for the charge accessibility and hydrophobicity of polyions, size of salt ions, and pH variations. Theoretical predictions of the effects of pH and salt concentration are compared with published experimental data and experiments we performed, on systems containing poly(acrylic acid (PAA as the polyacid and poly(N,N-dimethylaminoethyl methacrylate (PDMAEMA or poly(diallyldimethyl ammonium chloride (PDADMAC as the polybase. In general, the critical salt concentration below which the mixture phase separates, increases with degree of ionization and with the hydrophobicity of polyelectrolytes. We find experimentally that as the pH is decreased below 7, and PAA monomers are neutralized, the critical salt concentration increases, while the reverse occurs when pH is raised above 7. We predict this asymmetry theoretically by introducing a large positive Flory parameter (= 0.75 for the interaction of neutral PAA monomers with water. This large positive Flory parameter is supported by molecular dynamics simulations, which show much weaker hydrogen bonding between neutral PAA and water than between charged PAA and water, while neutral and charged PDMAEMA show similar numbers of hydrogen bonds. This increased hydrophobicity of neutral PAA at reduced pH increases the tendency towards phase separation despite the reduction in charge interactions between the polyelectrolytes. Water content and volume of coacervate are found to be a strong function of the pH and salt concentration.

  14. Brownian dynamics simulations of polyelectrolyte adsorption in shear flow with hydrodynamic interaction.

    Science.gov (United States)

    Hoda, Nazish; Kumar, Satish

    2007-12-21

    The adsorption of single polyelectrolyte molecules in shear flow is studied using Brownian dynamics simulations with hydrodynamic interaction (HI). Simulations are performed with bead-rod and bead-spring chains, and electrostatic interactions are incorporated through a screened Coulombic potential with excluded volume accounted for by the repulsive part of a Lennard-Jones potential. A correction to the Rotne-Prager-Yamakawa tensor is derived that accounts for the presence of a planar wall. The simulations show that migration away from an uncharged wall, which is due to bead-wall HI, is enhanced by increases in the strength of flow and intrachain electrostatic repulsion, consistent with kinetic theory predictions. When the wall and polyelectrolyte are oppositely charged, chain behavior depends on the strength of electrostatic screening. For strong screening, chains get depleted from a region close to the wall and the thickness of this depletion layer scales as N(1/3)Wi(2/3) at high Wi, where N is the chain length and Wi is the Weissenberg number. At intermediate screening, bead-wall electrostatic attraction competes with bead-wall HI, and it is found that there is a critical Weissenberg number for desorption which scales as N(-1/2)kappa(-3)(l(B)|sigmaq|)(3/2), where kappa is the inverse screening length, l(B) is the Bjerrum length, sigma is the surface charge density, and q is the bead charge. When the screening is weak, adsorbed chains are observed to align in the vorticity direction at low shear rates due to the effects of repulsive intramolecular interactions. At higher shear rates, the chains align in the flow direction. The simulation method and results of this work are expected to be useful for a number of applications in biophysics and materials science in which polyelectrolyte adsorption plays a key role.

  15. Single-chain-in-mean-field simulations of weak polyelectrolyte brushes

    Science.gov (United States)

    Léonforte, F.; Welling, U.; Müller, M.

    2016-12-01

    Structural properties of brushes which are composed of weak acidic and basic polyelectrolytes are studied in the framework of a particle-based approach that implicitly accounts for the solvent quality. Using a semi-grandcanonical partition function in the framework of the Single-Chain-in-Mean-Field (SCMF) algorithm, the weak polyelectrolyte is conceived as a supramolecular mixture of polymers in different dissociation states, which are explicitly treated in the partition function and sampled by the SCMF procedure. One obtains a local expression for the equilibrium acid-base reaction responsible for the regulation of the charged groups that is also incorporated to the SCMF sampling. Coupled to a simultaneous treatment of the electrostatics, the approach is shown to capture the main features of weak polyelectrolyte brushes as a function of the bulk pH in the solution, the salt concentration, and the grafting density. Results are compared to experimental and theoretical works from the literature using coarse-grained representations of poly(acrylic acid) (PAA) and poly(2-vinyl pyridine) (P2VP) polymer-based brushes. As the Born self-energy of ions can be straightforwardly included in the numerical approach, we also study its effect on the local charge regulation mechanism of the brush. We find that its effect becomes significant when the brush is dense and exposed to high salt concentrations. The numerical methodology is then applied (1) to the study of the kinetics of collapse/swelling of a P2VP brush and (2) to the ability of an applied voltage to induce collapse/swelling of a PAA brush in a pH range close to the pKa value of the polymer.

  16. Mechanical Reinforcement of Wool Fiber through Polyelectrolyte Complexation with Chitosan and Gellan Gum

    Directory of Open Access Journals (Sweden)

    Khairul Anuar Mat Amin

    2013-10-01

    Full Text Available The formation of polyelectrolyte complex (PEC wool fibers formed by dipping chitosan or gellan gum-treated wool fibers into biopolymer solutions of opposite charge is reported. Treating wool fibers with chitosan (CH and gellan gum (GG solutions containing food dyes resulted in improved mechanical characteristics compared to wool fibers. In contrast, pH modification of the solutions resulted in the opposite effect. The mechanical characteristics of PEC-treated fibers were affected by the order of addition, i.e., dipping GG-treated fibers into chitosan resulted in mechanical reinforcement, whereas the reverse-order process did not.

  17. A fiber-optic pH sensor based on polyelectrolyte multilayers embedded with gold nanoparticles

    Science.gov (United States)

    Tou, Z. Q.; Chan, C. C.; Leong, Stephanie

    2014-07-01

    We report the fabrication and characterization of an optical fiber pH sensor based on localized surface plasmon resonance. Gold nanoparticles (AuNPs) are embedded in a polyelectrolyte multilayer (PEM) consisting of chitosan and poly(sodium 4-styrenesulfonate). The absorbance and scattering properties of the AuNPs are affected by the pH-dependent swell state of the PEM. Both transmission- and reflection-based sensors are investigated and the measured transmittance/reflectance pH response can be closely fitted with the extended Henderson-Hasselbach equation. The reflection-based sensor can potentially be used for in vivo applications.

  18. Reduction of Intimal Hyperplasia in Injured Rat Arteries Promoted by Catheter Balloons Coated with Polyelectrolyte Multilayers that Contain Plasmid DNA Encoding PKCδ

    Science.gov (United States)

    Bechler, Shane L.; Si, Yi; Yu, Yan; Ren, Jun; Liu, Bo; Lynn, David M.

    2012-01-01

    New therapeutic approaches that eliminate or reduce the occurrence of intimal hyperplasia following balloon angioplasty could improve the efficacy of vascular interventions and improve the quality of life of patients suffering from vascular diseases. Here, we report that treatment of arteries using catheter balloons coated with thin polyelectrolyte-based films (‘polyelectrolyte multilayers’, PEMs) can substantially reduce intimal hyperplasia in an in vivo rat model of vascular injury. We used a layer-by-layer (LbL) process to coat the surfaces of inflatable catheter balloons with PEMs composed of nanolayers of a cationic poly(β-amino ester) (polymer 1) and plasmid DNA (pPKCδ) encoding the δ isoform of protein kinase C (PKCδ), a regulator of apoptosis and other cell processes that has been demonstrated to reduce intimal hyperplasia in injured arterial tissue when administered via perfusion using viral vectors. Insertion of balloons coated with polymer 1/pPKCδ multilayers into injured arteries for 20 min resulted in local transfer of DNA and elevated levels of PKCδ expression in the media of treated tissue 3 days after delivery. IFC and IHC analysis revealed these levels of expression to promote downstream cellular processes associated with up-regulation of apoptosis. Analysis of arterial tissue 14 days after treatment revealed polymer 1/pPKCδ-coated balloons to reduce the occurrence of intimal hyperplasia by ~60% compared to balloons coated with films containing empty plasmid vectors. Our results demonstrate the potential therapeutic value of this nanotechnology-based approach to local gene delivery in the clinically important context of balloon-mediated vascular interventions. These PEM-based methods could also prove useful for other in vivo applications that require short-term, surface-mediated transfer of plasmid DNA. PMID:23069712

  19. Adsorption of weak polyelectrolytes on charged nanoparticles. Impact of salt valency, pH, and nanoparticle charge density. Monte Carlo simulations.

    Science.gov (United States)

    Carnal, Fabrice; Stoll, Serge

    2011-10-27

    Complex formation between a weak flexible polyelectrolyte chain and one positively charged nanoparticle in presence of explicit counterions and salt particles is investigated using Monte Carlo simulations. The influence of parameters such as the nanoparticle surface charge density, salt valency, and solution property such as the pH on the chain protonation/deprotonation process and monomer adsorption at the nanoparticle surface are systematically investigated. It is shown that the nanoparticle presence significantly modifies chain acid/base and polyelectrolyte conformational properties. The importance of the attractive electrostatic interactions between the chain and the nanoparticle clearly promotes the chain deprotonation leading, at high pH and nanoparticle charge density, to fully wrapped polyelectrolyte at the nanoparticle surface. When the nanoparticle bare charge is overcompensated by the polyelectrolyte charges, counterions and salt particles condense at the surface of the polyelectrolyte-nanoparticle complex to compensate for the excess of charges providing from the adsorbed polyelectrolyte chain. It is also shown that the complex formation is significantly affected by the salt valency. Indeed, with the presence of trivalent salt cations, competition is observed between the nanoparticle and the trivalent cations. As a result, the amount of adsorbed monomers is less important than in the monovalent and divalent case and chain conformations are different due to the collapse of polyelectrolyte segments around trivalent cations out of the nanoparticle adsorption layer.

  20. Influence of anionic and cationic polyelectrolytes on the conductivity and morphology of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) films

    Energy Technology Data Exchange (ETDEWEB)

    Valtakari, Dimitar, E-mail: dimitar.valtakari@abo.fi [Abo Akademi University, Laboratory of Paper Coating and Converting, Center for Functional Materials at Biological Interfaces (FUNMAT), Porthansgatan 3, FI-20500 Åbo/Turku (Finland); Bollström, Roger [Omya International AG, CH 4665 Oftringen (Switzerland); Toivakka, Martti; Saarinen, Jarkko J. [Abo Akademi University, Laboratory of Paper Coating and Converting, Center for Functional Materials at Biological Interfaces (FUNMAT), Porthansgatan 3, FI-20500 Åbo/Turku (Finland)

    2015-09-01

    Conductivity of the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) strongly depends on the film morphology, which can be altered by the presence of polyelectrolytes. Aqueous dispersion of PEDOT:PSS was studied with anionic sodium polyacrylate (PA) and cationic poly(dimethyldiallylammonium chloride) (pDADMAC) polyelectrolytes that are typically used in papermaking as retention aids and dispersing agents in the paper pigment coating formulations. Spin-coated PEDOT:PSS films on a PA coated glass formed non-uniform layers with lowered conductivity compared to the reference PEDOT:PSS films on a clean glass substrate. On contrary, spin-coated PEDOT:PSS on a pDADMAC coated glass formed uniform layers with good conductivity. These results point out the importance of surface chemistry when using renewable and recyclable paper-based substrates with the PEDOT:PSS films. - Highlights: • PEDOT:PSS polymer was studied in the presence of polyelectrolytes. • Uniform layers of PEDOT:PSS and polyelectrolytes were spin-coated on glass. • Cationic polyelectrolyte was found to be more susceptible to humidity. • Cationic polyelectrolyte improves the conductivity of PEDOT:PSS. • PEDOT:PSS forms non-uniform layers on anionic polyelectrolyte coated glass.

  1. Encapsulation of the herbicide picloram by using polyelectrolyte biopolymers as layer-by-layer materials.

    Science.gov (United States)

    Wang, Xiaojing; Zhao, Jing

    2013-04-24

    Microcapsules of the herbicide picloram (PLR) were formulated by a layer-by-layer (LbL) self-assembly method using the polyelectrolyte biopolymers of biocompatible chitosan (CS) and the UV-absorbent sodium lignosulfonate (SL) as shell materials. The herbicide PLR was recrystallized and characterized using XRD analysis. The obtained PLR-loaded microcapsules were characterized by using SEM, FTIR, CLSM, and ζ-potential measurements. The herbicide loading and encapsulation efficiency were also analyzed for the PLR-loaded microcapsules. The influence of LbL layer numbers on herbicide release and photodegradation rates was investigated in vitro. The results showed that the release rates and photodegradation rates of PLR in microcapsules decreased with increasing number of CS/SL self-assembly layers. The results demonstrated that polyelectrolyte biopolymer-based LbL multilayer microcapsules can be a promising approach for the controlled release of PLR as well as other pesticides with poor photostability or short half-release time.

  2. Magnetic switch of permeability for polyelectrolyte microcapsules embedded with Co@Au nanoparticles.

    Science.gov (United States)

    Lu, Zonghuan; Prouty, Malcolm D; Guo, Zhanhu; Golub, Vladimir O; Kumar, Challa S S R; Lvov, Yuri M

    2005-03-01

    We explored using a magnetic field to modulate the permeability of polyelectrolyte microcapsules prepared by layer-by-layer self-assembly. Ferromagnetic gold-coated cobalt (Co@Au) nanoparticles (3 nm diameter) were embedded inside the capsule walls. The final 5 mum diameter microcapsules had wall structures consisting of 4 bilayers of poly(sodium styrene sulfonate)/poly(allylamine hydrochloride) (PSS/PAH), 1 layer of Co@Au, and 5 bilayers of PSS/PAH. External alternating magnetic fields of 100-300 Hz and 1200 Oe were applied to rotate the embedded Co@Au nanoparticles, which subsequently disturbed and distorted the capsule wall and drastically increased its permeability to macromolecules like FITC-labeled dextran. The capsule permeability change was estimated by taking the capsule interior and exterior fluorescent intensity ratio using confocal laser scanning microscopy. Capsules with 1 layer of Co@Au nanoparticles and 10 polyelectrolyte bilayers are optimal for magnetically controlling permeability. A theoretical explanation was proposed for the permeability control mechanisms. "Switching on" of these microcapsules using a magnetic field makes this method a good candidate for controlled drug delivery in biomedical applications.

  3. Microstructure and Phase Behavior of Cationic Gemini/Anionic Polyelectrolyte/Water Ternary System

    Institute of Scientific and Technical Information of China (English)

    皮瑛瑛; 尚亚卓; 彭昌军; 刘洪来

    2006-01-01

    The microstructure of cationic gemini surfactant 1,6-bis(dodecyldimethylammonium) hexane dibromide [C12H25(CH3)2N-(CH2)6-N(CH3)2C12H25·2Br] (12-6-12·2Br-) and oppositely charged polyelectrolyte poly(acrylic acid,sodium salt) (NaPA) in aqueous solution has been studied by using fluorescence, conductivity measurement, freeze-etching and TEM. The data obtained from fluorescence and conductivity measurement show that micelle-like or complex can form between the gemini surfactant (12-6-12.2Br-) and polyelectrolyte NaPA due to the static electric interaction and hydrophobic forces. Through freeze-etching and TEM, the microstructure of the mixture solution has been studied, which is consistent with the result from micropolarity. Comparing the fluorescence spectrum of system of dodecyltrimethylammonium bromide (DTAB) and NaPA with that of system of gemini surfactant (12-6-12.2Br-) and NaPA, it can be found that the interaction of (12-6-12.2Br-) and NaPA in aqueous solution has also been detected. It can be shown that the precipitate will transform into gel in higher NaPA concentration.

  4. Dynamic XPS measurements of ultrathin polyelectrolyte films containing antibacterial Ag–Cu nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Taner-Camcı, Merve; Suzer, Sefik, E-mail: suzer@fen.bilkent.edu.tr [Department of Chemistry, Bilkent University, 06800 Ankara (Turkey)

    2014-03-15

    Ultrathin films consisting of polyelectrolyte layers prepared by layer-by-layer deposition technique and containing also Ag and Cu nanoparticles exhibit superior antibacterial activity toward Escherichia coli. These films have been investigated with XPS measurements under square wave excitation at two different frequencies, in order to further our understanding about the chemical/physical nature of the nanoparticles. Dubbed as dynamical XPS, such measurements bring out similarities and differences among the surface structures by correlating the binding energy shifts of the corresponding XPS peaks. Accordingly, it is observed that the Cu2p, Ag3d of the metal nanoparticles, and S2p of cysteine, the stabilizer and the capping agent, exhibit similar shifts. On the other hand, the C1s, N1s, and S2p peaks of the polyelectrolyte layers shift differently. This finding leads us the claim that the Ag and Cu atoms are in a nanoalloy structure, capped with cystein, as opposed to phase separated entities.

  5. Self-Assembled Polyelectrolyte Nanoparticles as Fluorophore-Free Contrast Agents for Multicolor Optical Imaging

    Directory of Open Access Journals (Sweden)

    Da Hye Shin

    2015-03-01

    Full Text Available In this work, we describe the fabrication of self-assembled polyelectrolyte nanoparticles that provide a multicolor optical imaging modality. Poly(γ-glutamic acid(γ-PGA formed self-assembled nanoparticles through electrostatic interactions with two different cationic polymers: poly(L-lysine(PLL and chitosan. The self-assembled γ-PGA/PLL and γ-PGA/chitosan nanoparticles were crosslinked by glutaraldehyde. Crosslinking of the ionic self-assembled nanoparticles with glutaraldehyde not only stabilized the nanoparticles but also generated a strong autofluorescence signal. Fluorescent Schiff base bonds (C=N and double bonds (C=C were generated simultaneously by crosslinking of the amine moiety of the cationic polyelectrolytes with monomeric glutaraldehyde or with polymeric glutaraldehyde. The unique optical properties of the nanoparticles that resulted from the crosslinking by glutaraldehyde were analyzed using UV/Vis and fluorescence spectroscopy. We observed that the fluorescence intensity of the nanoparticles could be regulated by adjusting the crosslinker concentration and the reaction time. The nanoparticles also exhibited high performance in the labeling and monitoring of therapeutic immune cells (macrophages and dendritic cells. These self-assembled nanoparticles are expected to be a promising multicolor optical imaging contrast agent for the labeling, detection, and monitoring of cells.

  6. A novel, biodegradable and reversible polyelectrolyte platform for topical-colonic delivery of pentosan polysulphate.

    Science.gov (United States)

    Shah, Hardik K; Conkie, Jim A; Tait, Robert C; Johnson, James R; Wilson, Clive G

    2011-02-14

    The goal of the present work was to develop a swellable hydrogel colonic delivery system, which would maximise the availability of the therapeutic agent at a site of inflammation, especially where the water is scarce. A novel method was developed to manufacture a biodegradable and reversible polyelectrolyte complex (PEC) containing chitosan and poly acrylic-acid (PAA). The PEC was analysed using FTIR and DSC, which confirmed the formation of non-permanent swollen gel-network at an alkaline pH. Pentosan polysulphate (PPS) was incorporated in a PEC and an activated partial thromboplastin time assay was developed to measure the release of PPS from PEC. In vitro studies suggested that the release of PPS was dependent on the initial drug loading and the composition of the PEC. The gel strength of the swollen network, determined using a texture analyser, was dependent on polymer composition and the amount of PPS incorporated. Bacterial enzymes were collected from the rat caecum and colon for the digestion studies and characterised for glucosidase activity, glucuronidase activity and protein content. The digestion of the reversible polyelectrolyte complexes was measured using a dinitro salicylic acid assay and an increased release of drug was also confirmed in the presence of bacterial enzymes.

  7. Polymer Physics Prize Lecture: Polyelectrolyte complexes: New routes to useful soft materials

    Science.gov (United States)

    Tirrell, Matthew

    2012-02-01

    Mixtures of oppositely charged polyelectrolytes may form precipitates (phase-separated solids) or coacervates (phase-separated fluids). Coacervates have been known for a long time to have interesting properties such as very low interfacial tension with water and a resultant ability to coat surfaces, engulf particles and invade porous media. Most prior work on coacervate complexes has been done with structurally complex (e.g., gum Arabic), biologically derived macromolecules (e.g., gelation). Our work is focusing on phase behavior and self-assembly in classes of structurally simpler polymers. Polypeptides are one such class, where we can produce anionic, cationic and neutral, water-soluble polymers all with the some backbone and varying in small side-group structures. We are able to demonstrate very general patterns in phase behavior over different members of this class of polymers. Coacervate formation is the rule rather than the exception in these materials, with such formation quite strongly peaked at balanced stoichiometry of the polyelectrolyte components. One molar salt is usually sufficient to dissolve the coacervate phases that form. Block copolymer mixtures containing oppositely charged blocks can form self-assembled structures: micelles with diblocks and hydrogels with triblocks. The structure and properties of these assemblies can be tuned based on knowledge of the bulk phase behavior response to molecular weight, stoichiometry and salt concentration. Examples of phase behavior and structure-property relationship will be discussed.

  8. Phosphonic acid functionalized poly(pentafluorostyrene) as polyelectrolyte membrane for fuel cell application

    Science.gov (United States)

    Atanasov, Vladimir; Oleynikov, Andrey; Xia, Jiabing; Lyonnard, Sandrine; Kerres, Jochen

    2017-03-01

    In this paper we introduce polyelectrolyte membranes based on phosphonated poly(pentafluorostyrene) (PPFS) and their performances in a fuel cell. The polyelectrolytes were obtained via partial phosphonation of PPFS varying the phosphonation degree from 17 to 66%. These membranes showed a high resistance to temperature (Tdecomp. = 355-381 °C) and radical attack (96-288 h in Fenton's test). A blend membrane consisting of 82 wt% fully phosphonated PPFS and 18 wt% poly(benzimidazole) is compared to the 66% phosphonated membrane having similar ion-conductivity (σ = 57 mS cm-1 at 120 °C, 90% RH). In the fuel cell the blend showed the best performance reaching 0.40 W cm-2 against 0.34 W cm-2 for the 42 wt% phosphonated membrane and 0.35 W cm-2 for Nafion 212. Furthermore, the blend maintained its operation at potentiostatic regime (0.5 V) for 620 h without declining in its performance. The highest power density of 0.78 W cm-2 was reached for the blend with a thickness of 15 μm using humidified oxygen (RH > 90%) at the cathode side. The switch from humidified to dry gasses during operation reduced the current density down to 0.6 A cm-2, but the cell maintained under operation for 66 h.

  9. Human mesenchymal stem cell osteoblast differentiation, ECM deposition, and biomineralization on PAH/PAA polyelectrolyte multilayers.

    Science.gov (United States)

    Pattabhi, Sudhakara Rao; Lehaf, Ali M; Schlenoff, Joseph B; Keller, Thomas C S

    2015-05-01

    Polyelectrolyte multilayer (PEMU) coatings built layer by layer with alternating pairs of polyelectrolytes can be tuned to improve cell interactions with surfaces and may be useful as biocompatible coatings to improve fixation between implants and tissues. Here, we show that human mesenchymal stromal cells (hMSCs) induced with bone differentiation medium (BDM) to become osteoblasts biomineralize crosslinked PEMUs built with the polycation poly(allylamine hydrochloride) (PAH) and the polyanion poly(acrylic acid) (PAA). Degrees of hMSC osteoblast differentiation and surface biomineralization on the smooth PAH-terminated PEMUs (PAH-PEMUs) and microstructured PAA-terminated PEMUs (PAA-PEMUs) reflect differences in cell-deposited extracellular matrix (ECM). BDM-induced hMSCs expressed higher levels of the early osteoblast differentiation marker alkaline phosphatase and collagen 1 (COL1) sooner on PAA-PEMUs than on PAH-PEMUs. Cells on both types of PEMUs proceeded to express the later stage osteoblast differentiation marker bone sialoprotein (BSP), but the BDM-induced cells organized a more amorphous Collagen I and denser BSP localization on PAA-PEMUs than on PAH-PEMUs. These ECM properties correlated with greater biomineralization on the PAA-PEMUs than on PAH-PEMUs. Together, these results confirm the suitability of PAH/PAA PEMUs as a substrate for hMSC osteogenesis and highlight the importance of substrate effects on ECM organization and BSP presentation on biomineralization. © 2014 Wiley Periodicals, Inc.

  10. Effects of conformational ordering on protein/polyelectrolyte electrostatic complexation: ionic binding and chain stiffening.

    Science.gov (United States)

    Cao, Yiping; Fang, Yapeng; Nishinari, Katsuyoshi; Phillips, Glyn O

    2016-03-31

    Coupling of electrostatic complexation with conformational transition is rather general in protein/polyelectrolyte interaction and has important implications in many biological processes and practical applications. This work studied the electrostatic complexation between κ-carrageenan (κ-car) and type B gelatin, and analyzed the effects of the conformational ordering of κ-car induced upon cooling in the presence of potassium chloride (KCl) or tetramethylammonium iodide (Me4NI). Experimental results showed that the effects of conformational ordering on protein/polyelectrolyte electrostatic complexation can be decomposed into ionic binding and chain stiffening. At the initial stage of conformational ordering, electrostatic complexation can be either suppressed or enhanced due to the ionic bindings of K(+) and I(-) ions, which significantly alter the charge density of κ-car or occupy the binding sites of gelatin. Beyond a certain stage of conformational ordering, i.e., helix content θ > 0.30, the effect of chain stiffening, accompanied with a rapid increase in helix length ζ, becomes dominant and tends to dissociate the electrostatic complexation. The effect of chain stiffening can be theoretically interpreted in terms of double helix association.

  11. Cellular uptake and distribution of graphene oxide coated with layer-by-layer assembled polyelectrolytes

    Science.gov (United States)

    Li, Yiye; Lu, Zhenzhen; Li, Zhongjun; Nie, Guangjun; Fang, Ying

    2014-05-01

    We report a facile approach for the fabrication of a new class of graphene oxide (GO)-based nanoassemblies by layer-by-layer (LbL) technique. The single-layer thickness and intrinsic negatively charged carboxyl groups of GO nanosheets provide a natural platform for LbL assembly of polyelectrolyte nanofilms by electrostatic forces at mild and aqueous conditions. The general applicability of our approach is demonstrated by the preparation of GO nanoassemblies with sizes of 100-200 nm using various charged polyelectrolytes, including synthetic polymers, polypeptides, and DNA oligonucleotides. Systemic assessment of cytotoxicity and acute stress response show that no discernable signs of cytotoxicity are associated with exposure of GO and its nanoassemblies [GO/PLL (poly ( l-lysine)), GO/PLL/PSS (poly(sodium-4-styrenesulfonate)), GO/PLL-PEG (PEGlayted PLL), GO/PLL/PLGA-PEG (PEGlayted poly ( l-glutamic acid))] up to 1 μg/mL. Studies on cellular uptake and subcellular localization show that a representative nanoassembly, GO/PLL-PEG, can effectively cross cell membranes and localize mainly in lysosomal compartments, without induction of noticeable harmful effects as confirmed by detection of mitochondrial depolarization and lysosomal pH.

  12. Polyelectrolyte carbon quantum-dots: new player as a noninvasive imaging probe in Drosophila.

    Science.gov (United States)

    Parvin, Nragish; Mandal, Tapas K; Roy, Partha

    2013-10-01

    It is since long that X-ray or magnetic resonance imaging is being used for biomedical diagnosis. But till date noninvasive soft tissue imaging is not very well established. Towards this end the dietary uptake of polyelectrolyte carbon quantum dots (PECQDs) and their uses as a fluorescent probe is a new approach for imaging live specimens. In the present study we demonstrate that polyelectrolyte carbon quantum dots, which are nontoxic and have fluorescence properties can be used for in vivo imaging of internal organs. Carbon quantum dots surface were abound in polymer of free carboxyl groups making it water soluble. Our used PECQDs are less than equal to 50 nm sized and are capable to emit multi colour fluorescence. It is synthesized from waste plant materials like shaded leaves, unused shrubs, herbs etc. An exposure of 1 ppm level of soluble carbon quantum dots for 12 hours in drosophila permitted the fluorescence microscopy imaging of the different stages of their development and their non invasive internal organs without any remarkable toxic effects. Finally the fluorescent material was found to be excreted out of the animals. The current data suggests that visualization of internal organs with a fluorescent probe in live cells could help in determining the efficacy of therapeutic treatments directly without the need of any invasive procedures.

  13. Enhanced optical and nonlinear optical responses in a polyelectrolyte templated Langmuir-Blodgett film.

    Science.gov (United States)

    Rajesh, K; Balaswamy, B; Yamamoto, K; Yamaki, H; Kawamata, J; Radhakrishnan, T P

    2011-02-01

    Optical and nonlinear optical properties like fluorescence and second harmonic generation (SHG) of molecular materials can be strongly influenced by the mode of assembly of the molecules. The Langmuir-Blodgett (LB) technique is an elegant route to the controlled assembly of molecules in ultrathin films, and complexation of ionic amphiphiles in the Langmuir film by polyions introduced in the aqueous subphase provides a simple and efficient access to further control, stabilization, and optimization. The monolayer LB film of the hemicyanine-based amphiphile, N-n-octadecyl-4-[2-(4-(N,N-ethyloctadecylamino)phenyl)ethenyl]pyridinium possessing a "tail-head-tail" structure, shows fluorescence as well as SHG response. The concomitant enhancement of both of these linear and nonlinear optical attributes is achieved through templating with the polyanion of carboxymethylcellulose. Brewster angle and atomic force microscopy reveal the influence of polyelectrolyte templating on the morphology of the Langmuir and LB films. Polarized absorption and fluorescence spectroscopy provide insight into the impact of complexation with the polyelectrolyte on the orientation and deaggregation of the hemicyanine headgroup leading to fluorescence and SHG enhancement in the LB film.

  14. Surface Tension and Lamellar Spacing in Polyelectrolyte Blends and Block Copolymers

    Science.gov (United States)

    Sing, Charles; Olvera de La Cruz, Monica

    2015-03-01

    Heterogeneous polymer systems such as block copolymers (BCPs) are governed primarily by a competition between the surface tension between different chemical species and the entropic stretching of the polymer chains. Charged BCPs represent a class of materials that is currently of great interest to the polymer community due to the promise of charged BCPs as nanostructured membranes for batteries and fuel cells. The inclusion of charge presents a powerful way to tune the structure of BCPs, and we develop our understanding of how to do so by investigating the interfacial properties (surface tension and microstructure size) of polyelectrolyte blends and block copolymers. We use a new method that combines the features of liquid state (LS) theory and self consistent field theory (SCFT) into a multiscale LS-SCFT theory that provides beyond-mean-field predictions of polyelectrolyte systems. We find that charge size, charge correlations, and the fraction of charged monomers plays a crucial role in determining surface tension, and we therefore demonstrate how BCP structure changes upon inclusion of charges. Finally, we will show that these predictions provide the ideal basis for comparison to experiment and subsequent refinement of LS-SCFT theory.

  15. Release behavior of active material from poly(vinyl amine)/polyelectrolyte composite hollow particles

    Energy Technology Data Exchange (ETDEWEB)

    Han, Joo-Hyun; Lee, Han-Saem; Suh, Kyung-Do, E-mail: kdsuh@hanyang.ac.kr

    2011-10-10

    Polyvinyl amine (PVAm) hydrogel hollow particles treated by layer-by-layer (LbL) assembly methods were fabricated. The structures of the prepared particles were confirmed through zeta-potential measurements and scanning electron microscopy (SEM). In addition, the loading amount and release rate of Chromotrope 2R (CR) from the prepared particles in each deposition step was investigated. The loading amount had an alternating tendency according to an increase in the layer number. When the outermost layer consisted of poly(sodium 4-styrenesulfonate) (PSS), CR permeation was prevented by ionic repulsion between the PSS and CR. On the other hand, CR easily permeated into the particles when the outermost layer was poly(diallyldimethyl ammonium chloride) (PDDA). The release rate was then changed by ionic interaction between the CR and the cationic polyelectrolyte and by the ionic repulsive force between the CR and the anionic polyelectrolyte. These results indicate that PVAm hydrogel hollow particles treated by the LbL method could potentially be used in the controlled release of water-soluble materials. - Research Highlights: {yields} The effect of ionic interactions on the loading and release behaviors of drug was demonstrated. {yields} Ionic interaction between drug and particles leads to increment of loading efficiency and decreasing the release rate. {yields} Ionic repulsive force leads to opposite tendency compared with ionic interaction.

  16. Solubilization and separation of p-tert-butylphenol using polyelectrolyte/surfactant complexes in colloid-enhanced ultrafiltration

    Energy Technology Data Exchange (ETDEWEB)

    Uchiyama, Hirotaka; Christian, S.D.; Tucker, E.E.; Scamehorn, J.F. (Univ. of Oklahoma, Norman, OK (United States))

    1994-03-15

    Water-soluble polyelectrolyte/surfactant complexes, involving oppositely charged species, can form at quite low thermodynamic activities of the surfactant. This fact can be exploited in colloid-enhanced ultrafiltration separations, where both molecular organic pollutants and toxic ions are to be removed from contaminated aqueous streams. Investigations have been made of (a) the solubilization and ultrafiltration of solutions of organic solutes in polymer/surfactant solutions, for comparison with studies of micellar surfactant solutions in the absence of added polymers; (b) the penetration of surfactant through the membrane (leakage of monomer) in dialysis and ultrafiltration experiments; and (c) the utility of polyelectrolytes as scavengers'' for surfactant species that-enter the permeate or filtrate in colloid-enhanced ultrafiltration separations. The polyelectrolyte chosen for the studies is sodium poly(styrenesulfonate) and the surfactant is cetylpyridinium chloride (hexadecylpyridinium chloride). A detailed study has been made of the solubilization and separation of p-tert-butylphenol in aqueous mixtures of sodium poly(styrenesulfonate) and cetylpyridinium chloride, at polyelectrolyte to surfactant mole ratios of two to one and three to one.

  17. Dynamics of polyelectrolyte adsorption and colloidal flocculation upon mixing studied using mono-dispersed polystyrene latex particles

    NARCIS (Netherlands)

    Feng, Lili; Cohen Stuart, Martien; Adachi, Yasuhisa

    2015-01-01

    The dynamic behavior of polyelectrolytes just after their encounter with the surface of bare colloidal particles is analyzed, using the flocculation properties of mono-dispersed polystyrene latex (PSL) particles. Applying a Standardized Colloid Mixing (SCM) approach, effects of ionic strength and

  18. Weak polyelectrolyte multilayers as tunable separation layers for micro-pollutant removal by hollow fiber nanofiltration membranes

    NARCIS (Netherlands)

    Ilyas, Shazia; Mehran Abtahi, S.; Akkilic, Namik; Roesink, Hendrik Dirk Willem; de Vos, Wiebe Matthijs

    2017-01-01

    The presence of micro-pollutants in wastewater and in drinking water and its sources, is posing both environmental and health concerns. This work describes the development of weak polyelectrolyte multilayer (PEM) based hollow fiber nanofiltration (NF) membranes to remove micro-pollutants from

  19. Adsorption of flexible polyelectrolytes : a theoretical and experimental study of polystyrene sulfonate adsorption on polyoxymethylene single crystals

    NARCIS (Netherlands)

    Papenhuijzen, J.

    1985-01-01

    The objective of the present work was to collect systematic adsorption data for a well-defined polyelectrolyte on an uncharged, homogeneous surface, and to compare these with the new theory that was recently developed by Van der Schee.

    In chapter 1 we shortly describe which factor

  20. Adsorption of polyelectrolyte on the surface of ZnO nanoparticles and the stability of colloidal dispersions

    Institute of Scientific and Technical Information of China (English)

    LIUFU Shengcong; XIAO Hanning; LI Yuping

    2005-01-01

    The present study focuses on the adsorption of a polyelectrolyte, the component of which is a polymer of maleic anhydride sodium salt, on the surface of nanometric zinc oxide particles and the colloidal stability of aqueous dispersions. FTIR spectroscopic data provided evidence in support of hydrogen bonding and chemical interaction in the case of the polyelectrolyte-ZnO system. The adsorption isotherms showed the influences of polyelectrolyte concentration, pH and ionic strength on the adsorption. With the increase of pH the saturated adsorbed amount decreased, while the thickness of adsorption layer increased. The saturated adsorbed amount increased with increasing salt concentration, and decreased with further increasing salt concentration. It should be noted that in the presence of a CaCl2 solution the adsorbed amount and the adsorption layer thickness were greater than those in the NaCl solution of the same concentration. The change of the absorbance of zinc oxide dispersions showed that the absorbance decreased slowly at high pH. There was a maximum point for the absorbance of the zinc oxide dispersions in the presence of various polyelectrolyte concentrations. The change of dispersion stability resulted from the change of macromolecular chains conformation at the interface.

  1. 基于PIC16单片机和HM1500的湿度测量%Humidity Measurement Based on PIC16 Chip Series

    Institute of Scientific and Technical Information of China (English)

    高美珍

    2004-01-01

    HM1500湿度变送器是一种精密湿度传感器,采用HUMIREL公司的湿敏电容HS1101设计制造,可用于加热、通风和空气调节(HAVC)系统、环境监控、洁净空间、蔬菜大棚、粮食仓贮等的湿度检测与控制.介绍了HM1500湿度变送器的主要性能指标,给出了其与PIC系列单片机的接口及温度误差的补偿方法.

  2. Fission gas release behaviour of a 103 GWd/tHM fuel disc during a 1200 °C annealing test

    Science.gov (United States)

    Noirot, J.; Pontillon, Y.; Yagnik, S.; Turnbull, J. A.; Tverberg, T.

    2014-03-01

    Within the Nuclear Fuel Industry Research (NFIR) program, several fuel variants, in the form of thin circular discs, were irradiated in the Halden Boiling Water Reactor (HBWR) to a range of burn-ups ˜100 GWd/tHM. The design of the assembly was similar to that used in other HBWR programs: the assembly contained several rods with fuel discs sandwiched between Mo discs, which limited temperature gradients within the fuel discs. One such rod contained standard grain UO2 discs (3D grain size = 18 μm) reaching a burn-up of 103 GWd/tHM. After the irradiation, the gas release upon rod puncturing was measured to be 2.9%.

  3. Molecular Weight and Charge Density Asymmetry in Polyelectrolyte Complexation

    Science.gov (United States)

    Audus, Debra; Fredrickson, Glenn; Duechs, Dominik

    2009-03-01

    We investigate the phase diagram of oppositely charged polymers in a good solvent using a field-theoretic model. Mean-field solutions fail to predict the experimentally observed macroscopic phase separation into a solvent-rich phase and a dense liquid aggregate of polymers - a ``complex coacervate.'' We therefore study the model within a one-loop approximation, which accounts for Gaussian fluctuations in electrostatic and chemical potentials. Our particular focus is the effect of molecular weight, ionic strength, and charge asymmetry on the phase envelope. A set of dimensionless parameters is identified that dictate the size and shape of the two-phase region. Our results should be helpful in guiding experimental studies of coacervation.

  4. A systematic review of health manpower forecasting models.

    NARCIS (Netherlands)

    Martins-Coelho, G.; Greuningen, M. van; Barros, H.; Batenburg, R.

    2011-01-01

    Context: Health manpower planning (HMP) aims at matching health manpower (HM) supply to the population’s health requirements. To achieve this, HMP needs information on future HM supply and requirement (S&R). This is estimated by several different forecasting models (FMs). In this paper, we review

  5. 2011 HM{sub 102}: DISCOVERY OF A HIGH-INCLINATION L5 NEPTUNE TROJAN IN THE SEARCH FOR A POST-PLUTO NEW HORIZONS TARGET

    Energy Technology Data Exchange (ETDEWEB)

    Parker, Alex H.; Holman, Matthew J.; McLeod, Brian A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Buie, Marc W.; Borncamp, David M.; Spencer, John R.; Stern, S. Alan [Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238 (United States); Osip, David J. [Carnegie Observatories, Las Campanas Observatory, Casilla 601, La Serena (Chile); Gwyn, Stephen D. J.; Fabbro, Sebastian; Kavelaars, J. J. [Canadian Astronomy Data Centre, National Research Council of Canada, 5071 W. Saanich Road, Victoria, BC V9E 2E7 (Canada); Benecchi, Susan D.; Sheppard, Scott S. [Department of Terrestrial Magnetism, Carnegie Institute of Washington, 5251 Broad Branch Road NW, Washington, DC 20015 (United States); Binzel, Richard P.; DeMeo, Francesca E. [Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Fuentes, Cesar I.; Trilling, David E. [Department of Physics and Astronomy, Northern Arizona University, S San Francisco St, Flagstaff, AZ 86011 (United States); Gay, Pamela L. [Center for Science, Technology, Engineering and Mathematics (STEM) Research, Education, and Outreach, Southern Illinois University, 1220 Lincoln Dr, Carbondale, IL 62901 (United States); Petit, Jean-Marc [CNRS, UTINAM, Universite de Franche Comte, Route de Gray, F-25030 Besancon Cedex, (France); Tholen, David J., E-mail: aparker@cfa.harvard.edu [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Dr, Honolulu, HI 96822 (United States); and others

    2013-04-15

    We present the discovery of a long-term stable L5 (trailing) Neptune Trojan in data acquired to search for candidate trans-Neptunian objects for the New Horizons spacecraft to fly by during an extended post-Pluto mission. This Neptune Trojan, 2011 HM{sub 102}, has the highest inclination (29. Degree-Sign 4) of any known member of this population. It is intrinsically brighter than any single L5 Jupiter Trojan at H{sub V} {approx} 8.18. We have determined its gri colors (a first for any L5 Neptune Trojan), which we find to be similar to the moderately red colors of the L4 Neptune Trojans, suggesting similar surface properties for members of both Trojan clouds. We also present colors derived from archival data for two L4 Neptune Trojans (2006 RJ{sub 103} and 2007 VL{sub 305}), better refining the overall color distribution of the population. In this document we describe the discovery circumstances, our physical characterization of 2011 HM{sub 102}, and this object's implications for the Neptune Trojan population overall. Finally, we discuss the prospects for detecting 2011 HM{sub 102} from the New Horizons spacecraft during its close approach in mid- to late-2013.

  6. Performance-oriented packaging: A guide to identifying and designing. Identifying and designing hazardous materials packaging for compliance with post HM-181 DOT Regulations

    Energy Technology Data Exchange (ETDEWEB)

    1994-08-01

    With the initial publication of Docket HM-181 (hereafter referred to as HM-181), the U.S. Department of Energy (DOE), Headquarters, Transportation Management Division decided to produce guidance to help the DOE community transition to performance-oriented packagings (POP). As only a few individuals were familiar with the new requirements, elementary guidance was desirable. The decision was to prepare the guidance at a level easily understood by a novice to regulatory requirements. This document identifies design development strategies for use in obtaining performance-oriented packagings that are not readily available commercially. These design development strategies will be part of the methodologies for compliance with post HM-181 U.S. Department of Transportation (DOT) packaging regulations. This information was prepared for use by the DOE and its contractors. The document provides guidance for making decisions associated with designing performance-oriented packaging, and not for identifying specific material or fabrication design details. It does provide some specific design considerations. Having a copy of the regulations handy when reading this document is recommended to permit a fuller understanding of the requirements impacting the design effort. While this document is not written for the packaging specialist, it does contain guidance important to those not familiar with the new POP requirements.

  7. Characterization and Genetic Analysis of a Novel Rice Spotted-leaf Mutant HM47 with Broad-spectrum Resistance to Xanthomonas oryzae pv.oryzae(F)

    Institute of Scientific and Technical Information of China (English)

    Bao-Hua Feng; Yang Yang; Yong-Feng Shi; Hai-Chao Shen; Hui-Mei Wang; Qi-Na Huang; Xia Xu

    2013-01-01

    A stable inherited rice spotted-leaf mutant HM47 derived from an EMS-induced IR64 mutant bank was identified.The mutant expressed hypersensitive response (HR)-like symptoms throughout its whole life from the first leaf to the flag leaf,without pathogen invasion.Initiation of the lesions was induced by light under natural summer field conditions.Expression of pathogenesis-related genes including PAL,PO-C1,POX22.3 and PBZ1 was enhanced significantly in association with cell death and accumulation of H2O2 at and around the site of lesions in the mutant in contrast to that in the wild-type (WT).Disease reaction to Xanthomonas oryzae pv.oryzae from the Philippines and China showed that HM47 is a broad-spectrum disease-resistant mutant with enhanced resistance to multiple races of bacterial blight pathogens tested.An F2 progeny test showed that bacterial blight resistance to race HB-17 was cosegregated with the expression of lesions.Genetic analysis indicated that the spotted-leaf trait was controlled by a single recessive gene,tentatively named splHM47,flanked by two insertion/deletion markers in a region of approximately 74 kb on the long arm of chromosome 4.Ten open reading frames are predicted,and all of them are expressed proteins.Isolation and validation of the putative genes are currently underway.

  8. Combination with a defucosylated anti-HM1.24 monoclonal antibody plus lenalidomide induces marked ADCC against myeloma cells and their progenitors.

    Directory of Open Access Journals (Sweden)

    Takeshi Harada

    Full Text Available The immunomodulatory drug lenalidomide (Len has drawn attention to potentiate antibody-dependent cellular cytotoxicity (ADCC-mediated immunotherapies. We developed the defucosylated version (YB-AHM of humanized monoclonal antibody against HM1.24 (CD317 overexpressed in multiple myeloma (MM cells. In this study, we evaluated ADCC by YB-AHM and Len in combination against MM cells and their progenitors. YB-AHM was able to selectively kill via ADCC MM cells in bone marrow samples from patients with MM with low effector/target ratios, which was further enhanced by treatment with Len. Interestingly, Len also up-regulated HM1.24 expression on MM cells in an effector-dependent manner. HM1.24 was found to be highly expressed in a drug-resistant clonogenic "side population" in MM cells; and this combinatory treatment successfully reduced SP fractions in RPMI 8226 and KMS-11 cells in the presence of effector cells, and suppressed a clonogenic potential of MM cells in colony-forming assays. Collectively, the present study suggests that YB-AHM and Len in combination may become an effective therapeutic strategy in MM, warranting further study to target drug-resistant MM clonogenic cells.

  9. Assessment of industrial operation at low coke rate and coal injection in excess of 220 kg/tHM. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Sert, D.; Godijn, R. [IRSID, Maizieres-les-Metz (France)

    2002-07-01

    High coal injection rates have been achieved on several blast furnaces, but only for limited periods. The aim of this project was to establish the required conditions for achieving very low coke rates (greater than 300 kg/tHM) and coal rate in excess of 220 kg/tHM, under long-term industrial conditions. But despite some improvement in the coke and coal ratio ratios, the search for safe operation, on the one hand, and some technological problems, on the other, did not enable the initial objectives to be reached. Despite this result, various studies undertaken during the course of the project produced some interesting conclusions related to the search for high coal rate operation. These studies dealt with: the comparison of the burden at both plants; the way to promote coal combustion; evaluation of the thermo-chemical conditions of the shaft at coal rates around 18 kg/tHM; monitoring the evolution in time of the hearth ocnditions at high coal injection practice; the blast furnace process at high coal injection rate.

  10. 密度对玉米产量(>15000kg·hm-2)及其产量构成因子的影响%Effects of Density on Maize Yield and Yield Components

    Institute of Scientific and Technical Information of China (English)

    王楷; 王克如; 王永宏; 赵健; 赵如浪; 王喜梅; 李健; 梁明晰; 李少昆

    2012-01-01

    [目的]研究密度对高产玉米(>15000kg·hm-2)产量及其构成因子的影响,揭示高产玉米产量形成机制,为玉米持续稳定高产提供依据.[方法]连续两年在新疆和宁夏高产玉米区,以郑单958为试材,以1.5万株/hm2为一个密度梯度,设置从1.5万株/hm2至18万株/hm2不同密度处理,充分满足水肥需求,进行高产栽培实践,在实现高产基础之上分析其产量及产量构成因子特征.[结果]两年多点共68个处理,最低和最高单产分别为7675.5和20503.5kg·hm-2,其中有47个处理达到15000kg·hm-2以上的产量;对产量构成特征的分析表明,要达到15000kg·hm-2以上的高产,最低、最高密度分别为5.25万株/hm2和16.28万株/hm2;最低、最高收获穗数分别为6.66万穗/hm2和13.84万穗/hm2;最低、最高穗粒数分别为365和657粒;最低、最高千粒重分别为237和404g.[结论]密度与单产呈抛物线关系,以10.5万株/hm2密度处理单产最高;随着产量的提高,种植密度、单位面积穗数、穗粒数和千粒重表现出最适值范围变窄的趋势.随种植密度增加,单位面积穗数呈增加趋势,穗粒数和千粒重呈下降趋势,而单位面积粒数呈增加并趋于不变趋势.%[Objective] Field experiments were conducted to study the influence of density on maize yield (> 15 000 kg·hm-2) and yield components in order to exploring the formation mechanism of high-yield so as to provide a basis for stable high-yield maize. [Method] The experiments were carried out in high-yield maize areas of Xinjiang and Ningxia regions. Zhengdan 958 (ZD958) was planted at different densities from 15 000 plants/hm2 to 180 000 plants/hm2 by making 15 000 plants/hm2 as a density gradient with fully satisfy fertilizer and water demand. High-yield cultivation was practiced, and then the yield and yield component, characteristics were analyzed based on the high-yield (> 15 000 kg·hm-2). [Result] The 68 different density level plots were

  11. Conformation transitions of a single polyelectrolyte chain in a poor solvent: a replica-exchange lattice Monte-Carlo study.

    Science.gov (United States)

    Wang, Lang; Wang, Zheng; Jiang, Run; Yin, Yuhua; Li, Baohui

    2017-03-15

    The thermodynamic behaviors of a strongly charged polyelectrolyte chain in a poor solvent are studied using replica-exchange Monte-Carlo simulations on a lattice model, focusing on the effects of finite chain length and the solvent quality on the chain conformation and conformation transitions. The neutralizing counterions and solvent molecules are considered explicitly. The thermodynamic quantities that vary continuously with temperature over a wide range are computed using the multiple histogram reweighting method. Our results suggest that the strength of the short-range hydrophobic interaction, the chain length, and the temperature of the system, characterized by ε, N, and T, respectively, are important parameters that control the conformations of a charged chain. When ε is moderate, the competition between the electrostatic energy and the short-range hydrophobic interaction leads to rich conformations and conformation transitions for a longer chain with a fixed length. Our results have unambiguously demonstrated the stability of the n-pearl-necklace structures, where n has a maximum value and decreases with decreasing temperature. The maximum n value increases with increasing chain length. Our results have also demonstrated the first-order nature of the conformation transitions between the m-pearl and the (m-1)-pearl necklaces. With the increase of ε, the transition temperature increases and the first-order feature becomes more pronounced. It is deduced that at the thermodynamic limit of infinitely long chain length, the conformational transitions between the m-pearl and the (m-1)-pearl necklaces may remain first order when ε > 0 and m = 2 or 3. Pearl-necklace conformations cannot be observed when either ε is too large or N is too small. To observe a pearl-necklace conformation, the T value needs to be carefully chosen for simulations performed at only a single temperature.

  12. Mesophase Separation and Probe Dynamics in Protein-Polyelectrolyte Coacervates

    Science.gov (United States)

    Kayitmazer, A. Basak; Bohidar, H. B.; Mattison, K. W.; Bose, A.; Russo, P. S.; Dubin, P. L.

    2007-03-01

    Protein-PE coacervates (PPC's) are self-assembling monophasic biomacromolecular fluids whose unique properties arise from transient heterogeneities. Among these properties are: high viscosity coupled with anomalously high protein diffusivity; rheological behavior intermediate between viscous solutions and gels; and little perturbation of protein native state. Despite their discovery 50 years ago, structure of coacervates is still poorly understood. Among the two models suggested for coacervate structure so far, we have verified the validity of one that proposes two states for protein in the coacervate. Cryo-TEM and static light scattering experiments on bovine serum albumin-poly(diallydimethylammonium chloride) coacervates have revealed heterogeneous scattering centers of several hundred nm, consistent with the presence of partially inter-connected dense domains surrounded by a large proportion of dilute domains, inferred from rheology. Fluorescence photobleaching recovery measurements of protein self-diffusion in coacervates have revealed temporal and spatial mesophasic heterogeneities over broad time and length scales; i.e. 50-700 nm and 0.5-30 sec.

  13. Electrically driven ion separations and nanofiltration through membranes coated with polyelectrolyte multilayers

    Science.gov (United States)

    White, Nicholas

    Polyelectrolyte multilayer (PEM) films deposited using the layer-by-layer (LBL) method are attractive for their simple deposition, tailorable nature, scalability, and charge or size-based selectivity for solutes. This dissertation explores ion separations in electrodialysis (ED) and solute removal through nanofiltration with PEMs deposited on polymer membranes. ED membranes typically exhibit modest selectivities between monovalent and divalent ions. In contrast, this work shows that K+/Mg 2+ ED selectivities reach values >1000 when using Nafion 115 cation-exchange membranes coated with multilayer poly(4-styrenesulfonate) (PSS)/protonated poly(allylamine) (PAH) films. For comparison, the corresponding K+ /Mg2+ selectivity of bare Nafion 115 is 20,000, presumably because the applied current is below the limiting value for K+ and H+ transport is negligible at this high K+ concentration. The high selectivities of these membranes may enable electrodialysis applications such as purification of salts that contain divalent or trivalent ions. The high ED selectivities of (PAH/PSS)5PAH-coated Nafion membranes translate to separations with Li+/Co2+ and K +/La3+. Even with adsorption of only 3 polyelectrolyte layers, Nafion membranes exhibit a Li+/Co2+ selectivity >23. However, the resistance to monovalent-ion passage does not decrease significantly with fewer polyelectrolyte layers. At overlimiting currents, hydroxides from water splitting form insoluble metal hydroxides to foul the membrane. With 0.1 M source-phase salt concentrations, transference numbers for monovalent cations approach unity and selectivities are >5000 because the diffusion-limited K+ or Li+ currents exceed the applied current. However, ED selectivities gradually decline with time. Thus, future research should aim to increase membrane stability and limiting currents to fully exploit the remarkable selectivity of these membranes. PEMs deposited on commercial ultrafiltration (UF) membranes also show high

  14. Interaction between immobilized polyelectrolyte complex nanoparticles and human mesenchymal stromal cells

    Directory of Open Access Journals (Sweden)

    Woltmann B

    2014-05-01

    Full Text Available Beatrice Woltmann,1 Bernhard Torger,2,3 Martin Müller,2,3,* Ute Hempel1,*1Dresden University of Technology, Faculty of Medicine Carl Gustav Carus, Institute of Physiological Chemistry, Dresden, Germany; 2Leibniz Institute of Polymer Research Dresden, Department of Polyelectrolytes and Dispersions, Dresden, Germany; 3Dresden University of Technology, Department of Chemistry and Food Chemistry, Dresden, Germany*These authors contributed equally to this workBackground: Implant loosening or deficient osseointegration is a major problem in patients with systemic bone diseases (eg, osteoporosis. For this reason, the stimulation of the regional cell population by local and sustained drug delivery at the bone/implant interface to induce the formation of a mechanical stable bone is promising. The purpose of this study was to investigate the interaction of polymer-based nanoparticles with human bone marrow-derived cells, considering nanoparticles’ composition and surface net charge.Materials and methods: Polyelectrolyte complex nanoparticles (PECNPs composed of the polycations poly(ethyleneimine (PEI, poly(L-lysine (PLL, or (N,N-diethylaminoethyldextran (DEAE in combination with the polyanions dextran sulfate (DS or cellulose sulfate (CS were prepared. PECNPs’ physicochemical properties (size, net charge were characterized by dynamic light scattering and particle charge detector measurements. Biocompatibility was investigated using human mesenchymal stromal cells (hMSCs cultured on immobilized PECNP films (5–50 nmol·cm-2 by analysis for metabolic activity of hMSCs in dependence of PECNP surface concentration by MTS (3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H-tetrazolium, inner salt assay, as well as cell morphology (phase contrast microscopy.Results: PECNPs ranging between ~50 nm and 150 nm were prepared. By varying the ratio of polycations and polyanions, PECNPs with a slightly positive (PEC+NP or negative (PEC

  15. 3D solid supported inter-polyelectrolyte complexes obtained by the alternate deposition of poly(diallyldimethylammonium chloride and poly(sodium 4-styrenesulfonate

    Directory of Open Access Journals (Sweden)

    Eduardo Guzmán

    2016-02-01

    Full Text Available This work addresses the formation and the internal morphology of polyelectrolyte layers obtained by the layer-by-layer method. A multimodal characterization showed the absence of stratification of the films formed by the alternate deposition of poly(diallyldimethylammonium chloride and poly(sodium 4-styrenesulfonate. Indeed the final organization might be regarded as three-dimensional solid-supported inter-polyelectrolyte films. The growth mechanism of the multilayers, followed using a quartz crystal microbalance, evidences two different growth trends, which show a dependency on the ionic strength due to its influence onto the polymer conformation. The hydration state does not modify the multilayer growth, but it contributes to the total adsorbed mass of the film. The water associated with the polyelectrolyte films leads to their swelling and plastification. The use of X-ray photoelectron spectroscopy has allowed for deeper insights on the internal structure and composition of the polyelectrolyte multilayers.

  16. Approach Based on Polyelectrolyte-Induced Nanoassemblies for Enhancing Sensitivity of Pyrenyl Probes.

    Science.gov (United States)

    Yao, Zhiyi; Qiao, Yadong; Liang, Haiqin; Ge, Wenqi; Zhang, Li; Cao, Zhong; Wu, Hai-Chen

    2016-11-01

    We have developed a unique approach for enhancing the sensitivity of pyrenyl probes based on polyelectrolyte-induced nanoassemblies and explored its sensing application toward 2,4,6-trinitrophenol (TNP). The key issue of the method is the formation of the nanoassemblies which possess high-density charges, specific surface area, and inner hydrophobic regions. These properties would help increase the loading of analytes and promote probe-analyte interactions, thereby leading to the prominent enhancement of the sensitivity. In the course of TNP detection, pyrene nanoassemblies can bind TNP efficiently through cooperative noncovalent interactions including electrostatic, π-π stacking, and charge-transfer interactions, resulting in the distinct fluorescent responses of pyrene moieties. This system has excellent selectivity and sensitivity for TNP detection. The detection limit is as low as 5 nM. It may be used for monitoring the TNP concentrations in real-world samples.

  17. Microencapsulation of Ginger Volatile Oil Based on Gelatin/Sodium Alginate Polyelectrolyte Complex.

    Science.gov (United States)

    Wang, Lixia; Yang, Shiwei; Cao, Jinli; Zhao, Shaohua; Wang, Wuwei

    2016-01-01

    The coacervation between gelatin and sodium alginate for ginger volatile oil (GVO) microencapsulation as functions of mass ratio, pH and concentration of wall material and core material load was evaluated. The microencapsulation was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), and thermal gravimetric analysis (TGA). SEM and FT-IR studies indicated the formation of polyelectrolyte complexation between gelatin and sodium alginate and successful encapsulation of GVO into the microcapsules. Thermal property study showed that the crosslinked microparticles exhibited higher thermal stability than the neat GVO, gelatin, and sodium alginate. The stability of microencapsulation of GVO in a simulated gastric and an intestinal situation in vitro was also studied. The stability results indicated that the release of GVO from microcapsules was much higher in simulated intestinal fluid, compared with that in simulated-gastric fluid.

  18. pH-regulated ionic current rectification in conical nanopores functionalized with polyelectrolyte brushes.

    Science.gov (United States)

    Zeng, Zhenping; Ai, Ye; Qian, Shizhi

    2014-02-14

    Mimicking biological ion channels capable of pH-regulated ionic transport, synthetic nanopores functionalized with pH-tunable polyelectrolyte (PE) brushes have been considered as versatile tools for active transport control of ions, fluids, and bioparticles on the nanoscale. The ionic current rectification (ICR) phenomenon through a conical nanopore functionalized with PE brushes whose charge highly depends upon the local solution properties (i.e., pH and background salt concentration) is studied theoretically for the first time. The results show that the rectification magnitude, as well as the preferential rectification direction, is sensitive to the pH stimulus. The bulk concentration of the background salt can also significantly influence the charge of the PE brushes and accordingly affect the ICR phenomenon. The obtained results provide an insightful understanding of the pH-regulated ICR and guidelines for designing nanopores functionalized with PE brushes for pH-tunable applications.

  19. Conjugated polyelectrolyte hole transport layer for inverted-type perovskite solar cells

    Science.gov (United States)

    Choi, Hyosung; Mai, Cheng-Kang; Kim, Hak-Beom; Jeong, Jaeki; Song, Seyeong; Bazan, Guillermo C.; Kim, Jin Young; Heeger, Alan J.

    2015-06-01

    Organic-inorganic hybrid perovskite materials offer the potential for realization of low-cost and flexible next-generation solar cells fabricated by low-temperature solution processing. Although efficiencies of perovskite solar cells have dramatically improved up to 19% within the past 5 years, there is still considerable room for further improvement in device efficiency and stability through development of novel materials and device architectures. Here we demonstrate that inverted-type perovskite solar cells with pH-neutral and low-temperature solution-processable conjugated polyelectrolyte as the hole transport layer (instead of acidic PEDOT:PSS) exhibit a device efficiency of over 12% and improved device stability in air. As an alternative to PEDOT:PSS, this work is the first report on the use of an organic hole transport material that enables the formation of uniform perovskite films with complete surface coverage and the demonstration of efficient, stable perovskite/fullerene planar heterojunction solar cells.

  20. Highly Conductive Graphene and Polyelectrolyte Multilayer Thin Films Produced From Aqueous Suspension.

    Science.gov (United States)

    Stevens, Bart; Guin, Tyler; Sarwar, Owais; John, Alyssa; Paton, Keith R; Coleman, Jonathan N; Grunlan, Jaime C

    2016-09-27

    Rapid, large-scale exfoliation of graphene in water has expanded its potential for use outside niche applications. This work focuses on utilizing aqueous graphene dispersions to form thin films using layer-by-layer processing, which is an effective method to produce large-area coatings from water-based solutions of polyelectrolytes. When layered with polyethyleneimine, graphene flakes stabilized with cholate are shown to be capable of producing films thinner than 100 nm. High surface coverage of graphene flakes results in electrical conductivity up to 5500 S m(-1) . With the relative ease of processing, the safe, cost effective nature of the ingredients, and the scalability of the deposition method, this system should be industrially attractive for producing thin conductive films for a variety of electronic and antistatic applications.