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Polyelectrolyte sorbents based on aliphatic ionenes for ion chromatography.

2-4, 3-4, 2-8, 3-8, 3-6, 4-6, 6-8, 6-10-ionenes (polymers with quaternary nitrogen atoms in the main chain) served as modifiers in synthesizing polyelectrolyte sorbents for ion chromatography. The approaches to the synthesis and their stability are discussed. Cluster analysis was applied to separate aliphatic ionenes to three groups as chromatographic modifiers, namely hydrophilic, hydrophobic, and intermediate. Each group is characterized by a certain selectivity to sulfate, perchlorate, iodide and thiocyanate. The sorbents show high selectivity and efficiency up to 15,000 theoretical plates per meter.

Anions↗

Polarizability and complex conductivity of dilute suspensions of spherical colloidal particles with charged (polyelectrolyte) coatings.

The dielectric relaxation of polyelectrolyte-coated colloidal particles is examined via "exact" numerical solutions of the governing electrokinetic equations. The charged polymer coatings are characterized by a nominal charge density, thickness, and permeability. Brush-like segment density profiles are considered here, but more sophisticated segment and charge density profiles are accommodated by the model. The role of added counterions and nonspecific adsorption is considered briefly before examining how the experimentally measured conductivity and dielectric constant increments reflect the frequency of the applied electric field, the strength of the electrolyte, and characteristics of the polymer coatings, namely the charge, charge density, and permeability. Finally, a strategy is suggested by which dielectric spectroscopy and electrophoresis can be used to characterize polymer-coated particles. This approach complements experiments where electroviscous effects such as dynamic light scattering and sedimentation are weak.

Journal Article↗

Adsorption of hydrophobically modified polyelectrolytes at the n-octane/water interface.

The interfacial activity of polyelectrolytes carrying alkyl side chains of different length has been studied. Potassium salts of poly(maleic acid-co-1-olefins), PA-n K2 with n=12 , 14, 16, 18, were synthesized, and the interfacial tension at the aqueous solution/n -octane interface was measured as a function of the length of the alkyl side chain. The results show that the interfacial tension lowering, the limiting excess concentration Gamma (m), and the efficiency of adsorption pC (20) depend on the number of methylene groups in the alkyl side chain. According to Rosen the last two parameters define two different contributions to the standard free energy of adsorption: one arises from the distribution of the polymer between the bulk of the solution and the interface Delta G (dist )(0), and another comes from the configuration adopted at the interface Delta G (int )(0). These free energies were plotted as a function of the number of carbon atoms in the alkyl side chain and a linear relation was found for both of them. From these plots contributions of 0.83 and -0.58 per methylene group were determined for Delta G (0)(dist ) and Delta G (0)(int ), respectively. The positive value for the incremental free energy of distribution is attributed to the formation of a polymer micelle which is stabilized by longer alkyl side chains. On the other hand, the negative value for Delta G (0)(int ) indicates that at the interface the polymer adopts a configuration where the hydrocarbon tail is interacting with the octane molecules.

Journal Article↗

A fluorescence emission study of the formation of induced premicelles in solutions of polyelectrolytes and ionic surfactants.

The interactions between PSS-co-BVE copolymers and ionic surfactants (anionic and cationic) in aqueous solution have been investigated using pyrene as a photophysical probe. Static and dynamic fluorescence determinations have been used to obtain information about the microenvironments formed between both species. Micropolarity studies using the I1/I3 ratio of the vibronic bands of pyrene and the behavior of the I(E)/I(M) ratio between the monomer and excimer emissions show the formation of hydrophobic domains. The interactions between the polyelectrolytes and the oppositely charged surfactants lead to the formation of induced premicelles at surfactant concentrations lower than the cmc of the surfactants. This aggregation process is assumed to be due to electrostatic attraction. At the same concentration, the excimer-to-monomer emission ratio shows its first peak. At higher surfactant concentrations, near the cmc, micelles with the same properties as those found in pure aqueous solution are formed. On the other side, systems containing an anionic surfactant do not show this behavior at low concentrations. There is no apparent dependence of the cac on the composition of the polymer, reinforcing the assumption that the electrostatic interactions induce the formation of the premicelles. The values of the cac's follow the same trend as for the cmc's, DTAC>DTAB>CTAC. The polarity of the induced premicelles, as measured by the I1/I3 ratio, also indicates that the microdomains formed by the longer chain surfactants are more hydrophobic than those of the shorter chain surfactants, as also happens with real micelles.

Journal Article↗

Rapid intravenous rehydration by means of a single polyelectrolyte solution with or without dextrose.

We compared the efficacy and safety of a single polyelectrolyte solution, Dhaka solution (DS), containing 133 mmol/L sodium, 13 mmol/L potassium, 98 mmol/L chloride, and 48 mmol/L acetate with and without 139 mmol/L (25 gm/L) dextrose in the rapid (4 hours) rehydration of 67 patients with diarrhea and moderate or severe dehydration requiring parenteral fluid therapy. Of the 67 patient, 31 were randomly assigned to receive the dextrose-containing solution (DS + D) and 36 DS without dextrose. On admission to the hospital, the two groups of patients were similar with respect to enteric pathogens detected, proportion with hyponatremia, magnitude of dehydration as assessed by clinical criteria, serum protein or creatinine concentration, and plasma glucose levels. At the end of the 4-hour infusion, both groups of patients had similar decreases in serum creatinine and protein levels and similar volume of urine output, but patients receiving DS + D had a significantly higher plasma glucose level than patients receiving DS (7.8 mmol/L (140 mg/dl) vs 5.39 mmol/L (97 mg/dl), P less than 0.01). One patient in the DS group had hypoglycemia (plasma glucose 2.0 mmol/L (36 mg/dl) at 4 hours. No other complications were noted. Serum protein values 24 hours after admission were little changed from 4-hour values, suggesting that rehydration was complete at the end of 4 hours. We conclude that, in our patients, rehydration can be carried out safely and rapidly with the use of a single solution and that adding 139 mmol/L (25 gm/L) of dextrose to the solution can prevent hypoglycemia without producing an osmotic diuresis.

Adolescent↗

Conformation of surface bound polyelectrolytes: I. Implications for cell electrophoresis.

We present a self-consistent calculation for a layer of short-chain polyelectrolytes grafted to a planar interface. Individual self-avoiding chain configurations are generated on a tetrahedral lattice. By evaluating the complete ensemble of configurations in the presence of a self-consistent field we determine averages for the equilibrium layer height, segment and charge density profiles. These describe the response of the layer to changes in the surrounding medium, in particular to electrolyte concentration. This self-consistent model of a biological cell, which is known to have an extended layer of charge exterior to the membrane bilayer surface, is applied to the problem of cell electrophoretic mobility. We compare the electrophoretic mobility deduced from the application of this model with that for a constant profile of charge and segments and with the case of a constant segment profile with a plane of charge, usually assumed in the literature. We find that, within the region of concentrations studied here and with the chain lengths used, there is general agreement between the different descriptions.

Animals↗

Removal of organic polyelectrolytes and their metal complexes by adsorption onto xonotlite.

Natural organic polyelectrolytes (humic and fulvic acids) and their metal complexes were removed by adsorption onto xonotlite. The removal percentages of humic and fulvic acids by xonotlite were approximately 80% and 30%, respectively. Humic acid removal from solution by adsorption onto xonotlite took place more readily than fulvic acid removal. The molecular weight distributions of the humic substances remaining in solution after adsorption with the xonotlite were measured with size exclusion chromatography. A comparison of molecular weight distributions demonstrated conclusively that large molecular weight components were adsorbed preferentially, indicating that adsorption efficiency depends on the number of functional groups of humic substances. Furthermore, the surface topography of the adsorbent was observed before and after adsorption by scanning electron microscopy. The calculated heat of adsorption was of 330 kJ mol(-1) which was evaluated from the Clapeyron-Clausius equation. Therefore, the adsorption type can be considered chemical. Since xonotlite can be easily synthesized and obtained at low cost, the adsorption method of humic and fulvic acids is superior to their precipitation.

Adsorption↗

Anaerobic digestion of polyelectrolyte flocculated waste activated sludge.

This work examined how adding one of three polyelectrolyte flocculants (T3052: cationic, T2000: non-ionic, and T1052: anionic) affected the anaerobic digestion of wastewater sludge. Methane production, floc characteristics (morphology and zeta-potential) and process parameters (soluble chemical oxygen demands (SCODs) and reductive potentials) were monitored along the digestion tests. The digestion rates of T2000- and T1052-conditioned sludge resembled that for original sludge. The T3052-flocculated sludge generated methane at a higher rate during the first 6 days of digestion than did the original one. In the following stage, the digestion rate of sludge flocculated with T3052 at dosage exceeding 15 g/kg dried solids declined. For example, at 40 days of digestion the methane production amounts for original, 15 g/kg DS flocculated, and 40 g/kg flocculated sludge were of 136, 105, and 85 g/kg DS, respectively. The role of flocculants could change in different stages of digestion. The dosed polymers had no apparent toxicity to the inoculum used. The changes in SCOD, adenosintriphosphate concentrations, oxidative and reductive potential, and zeta-potentials did not correlate with the noted hindered digestion for T3052-conditioned sludge. Microphotographic observation revealed that the flocs of T3052-conditioned sludge were not only of a large size, but also were resistant to structural deterioration during digestion. Therefore, mass transfer resistance was proposed to account for the hindered digestion efficiency observed for T3052-conditioned sludge.

Anaerobiosis↗

The effect of temperature on the Donnan potentials in biological polyelectrolyte gels: cornea and striated muscle.

The effect of temperature on the fixed electric charge in biological polyelectrolyte gels was studied between 10 and 35 degrees C using the Donnan microelectrode technique. Two tissues; cornea and striated muscle were used. In cornea, there is a gentle and uniform decrease in fixed charge over the temperature range. In rigor muscle, there is a dramatic step-function decrease in charge at around 28 degrees C. There is a charge decrease in relaxed muscle at around the same temperature, but the step function is less distinct. The significance of these different experimental relationships is discussed in relation to the Saroff model for ion binding to proteins, linked to the possible disordering effects of excess electric charge. The diverse effects in these systems are important for the physiological functions of the different tissues.

Animals↗

Enhanced DNA synthesis accompanied by constitutive phosphorylation of the ERK pathway in human fibroblasts cultured on a polyelectrolyte complex.

In this study, we examined the cellular and molecular responses of fibroblasts cultured on a polyelectrolyte complex (PEC) derived from sulfated chitin as a polyanion and chitosan as a polycation. On PEC-coated dishes, the fibroblasts aggregated and then developed spheroid-like structures. At earlier stages of culture, DNA synthesis of cells cultured on PEC was stimulated approximately 75% higher than control cells. Among various signaling molecules examined, including mitogen-activated protein kinases, Akt/PKB and p53, an extracellular-signal-regulated kinase (ERK) was selectively and constitutively phosphorylated in cells cultured on PEC. The constitutive phosphorylation of ERK was derived from an activation of the ERK kinase MEK, but not from an inactivation of the ERK phosphatase MKP-1. Furthermore, ERK phosphorylation was almost abolished by a membrane receptor tyrosine kinase inhibitor. The enhanced phosphorylation of focal adhesion kinase, a downstream molecule of integrins, was also observed in cells cultured on PEC. These results suggest that fibroblasts recognize PEC as a continuous mitogenic stimulant which results in the constitutive activation of the MEK-ERK pathway toward mitogenesis. Further, PEC interacts with the cell membrane leading to activation of membrane molecules, including integrins and receptor tyrosine kinases. These responses may account, at least in part, for the potential use of PEC as a biomaterial for tissue regeneration.

Cell Aggregation↗

Polyelectrolyte complexes as vehicles for affinity precipitation of proteins.

Polyelectrolyte complexes (PECs) were formed with polyethylene imine (PEI) and polyacrylic acid sodium salt (PA). The aqueous solubility of such PLCs is dependent on the stoichiometry between the polymers, the charge densities of the polymers and salts present in the solution. Cibacron blue 3GA (CB) was coupled to the PEI and the PECs were used for affinity precipitation of lactate dehydrogenase (LDH) in beef heart extracts. The affinity precipitation was induced by a shift in pH, while the desorption and separation of LDH from the PECs was performed by addition of KCl combined with a shift in pH. LDH was obtained with a yield of 85% and a purification factor of approx. 11-fold. The polymers were recovered and reused once and the results became similar. Prior to the affinity precipitation, interfering nucleic acids were removed by precipitation with PEI.

Acrylic Resins↗

Polyelectrolyte theory of charged-ligand binding to nucleic acids.

The Poisson-Boltzmann framework provides simple and sound formulae for evaluation of the interactions of polynucleotides with charged ligands. The theory is based on the observation that shape-dependent effects are small. Hence the results for the charged plane may be used as a first approximation for polyelectrolytes. The counterion distribution and the extent of counterion or ligand binding is derived on the basis of a sum-rule for counterion concentrations, combined with the mass-action law. Calculations require no more than a pocket calculator even in the case of mixed-salt solutions. Significant qualitative results are given, and applied to the problems of site-binding and of repressor-DNA interaction.

Binding Sites↗

Equilibrium behavior of an isotropic polyelectrolyte gel model of the tectorial membrane: effect of pH.

An isotropic polyelectrolyte gel model (Weiss and Freeman, 1996a) of the tectorial membrane (TM) was extended to incorporate the effect of pH. The effect of pH is analyzed in order to interpret measurements of the effect of pH on the dimensions of the TM (Freeman et al., 1996a). The pH dependence of the model results from the binding of hydrogen ions to TM macromolecules--to both neutral sites with basic pK and negatively charged sites with acidic pK. Parameters of the model can be based on estimates of the concentration in the TM of collagen and glycosaminoglycans (GAGs), two identified constituents of the TM that account for approximately 40% of its dry weight. The resulting model shows swelling responses at both high and low pH that are qualitatively similar to the measurement on the TM but that differ quantitatively. Alternatively, parameters of the model can be chosen in an ad hoc fashion to closely fit the measurements of TM swelling as a function of pH. Taken together these results suggest that either estimates of the collagen and GAG content of the TM are in error or constituents of the TM, which have not yet been identified, contain appreciable pH-dependent fixed charge and contribute to the swelling behavior of the TM.

Binding Sites↗

Determination of cefaclor by selective sample enrichment/clean-up on silica gel bonded polyelectrolyte in ion-exchange column chromatography.

A silica gel-bound cationic polyelectrolyte, poly[N-chloranil N,N,N',N'- tetramethylethylene diammonium dichloride], modified as ion-exchanger capable of molecular recognition of beta-lactam antibiotic, was used in solid phase extraction through column chromatography for a sample clean-up and enrichment of analyte from a dilute solution. The optimum and selective sorption conditions for a model antibiotic, cefaclor, were established. The high selectivity of polymer at pH 9.5 and flow rate as high as 5 ml/min were observed for the quantitative sorption of cefaclor. The desorption by 0.1 N HCl at flow rate of 0.1 ml/min and subsequent heating at 80 degrees C for 2 h allowed the antibiotic to be detected as corresponding oxazolone form in UV-spectrophotometric and differential pulse adsorptive stripping voltammetric measurements. The potential of the suggested approach was illustrated by estimating cefaclor in urine and blood plasma samples.

Cefaclor↗

Reagentless biosensors based on self-deposited redox polyelectrolyte-oxidoreductases architectures.

Reagentless fructose and alcohol biosensors have been produced with a versatile enzyme immobilisation technique which mimics natural interactions and flexibility of living systems. The electrode architecture is built up on electrostatic interactions by the sequential adsorption of redox polyelectrolytes and redox enzymes giving rise to the efficient transformation of substrate fluxes into electrocatalytic currents. All investigated multilayer structures were self-deposited on 3-mercapto-1-propanesulfonic acid monolayers self-assembled on gold electrodes. Fructose dehydrogenase, horseradish peroxidase (HRP) and the couple HRP-alcohol oxidase were electrochemically connected with a cationic poly[(vinylpyridine)Os(bpy)2Cl] redox polymer (RP) interface in a layer-by-layer self-deposited architecture. The dependence of the distance on the electrochemical response of this interface was also studied showing a clear decrease in the Faradaic current when the distance to the electrode surface was increased. The sensitivities obtained for each biosensor were 19.3, 58.1 and 10.6 mA M(-1) cm(-1) for fructose, H2O2 and methanol, respectively. The sensitivity values can be easily controlled by a rational deposition and manipulation of the charge in the catalytic layers. The electrostatic assembly of the electrochemical interface and the catalytic layers resulted in integrated biochemical systems in which mass transfer diffusion and heterogeneous catalytic and electron transfer steps are efficiently coupled and can be easily manipulated.

Alcohol Oxidoreductases↗

Molecular organization and dynamics of micellar phase of polyelectrolyte-surfactant complexes: ESR spin probe study.

Molecular dynamics and organization of the micellar phase of complexes of linear polyelectrolytes with ionogenic and non-ionogenic surfactants was studied by the ESR spin probe method. Complexes of polyacrylic acid (PAA) and sodium polystyrenesulfonate (PSS) with alkyltrimethylammonium bromides (ATAB), as well as complexes of poly-N,N'-dimethyldiallylammonium chloride (PDACL) with sodium dodecylsulfate (SDS) were studied. The micellar phase of such complexes is highly organized molecular system, molecular ordering of which near the polymeric chain is much higher than in the 'center' of the micelle, it depends on the polymer-detergent interaction, flexibility of polymeric chain and length of carbonic part of the detergent molecule. Complexes of polymethacrylic acid (PMAA) with non-ionic detergent (dodecyl-substituted polyethyleneglycol), show that the local mobility of surfactant in such complexes is significantly lower than in 'free' micelles and depends on the number of micellar particles participating in formation of complexes.

Acrylic Resins↗

Plastic microfluidic devices modified with polyelectrolyte multilayers

Control of the polymer surface chemistry is a crucial aspect of development of plastic microfluidic devices. When commercially available plastic substrates are used to fabricate microchannels, differences in the EOF mobility from plastic to plastic can be very high. Therefore, we have used polyelectrolyte multilayers (PEMs) to alter the surface of microchannels fabricated in plastics. Optimal modification of the microchannel surfaces was obtained by coating the channels with alternating layers of poly(allylamine hydrochloride) and poly(styrene sulfonate). Polystyrene (PS) and poly(ethylene terephthalate) glycol (PETG) were chosen as substrate materials because of the significant differences in the polymer chemistries and in the EOF of channels fabricated in these two plastic materials. The efficacy of the surface modification has been evaluated using XPS and by measuring the EOF mobility. When microchannels prepared in both PS and PETG are modified with PEMs, they demonstrate very similar electroosmotic mobilities. The PEMs are easily fabricated and provide a means for controlling the flow direction and the electroosmotic mobility in the channels. The PEM-coated microchannels have excellent wettability, allowing facile filling of the channels. In addition, the PEMs produce reproducible results and are robust enough to withstand long-term storage.

Journal Article↗

Covalently bound ionene polyelectrolyte-silica gel stationary phases for HPLC.

Micelle-mimetic ionene-based stationary phases for high-performance liquid chromatography (HPLC) are prepared by attaching [3,16]- and [3,22]-ionenes to aminopropyl silica through a carbon-nitrogen bond. These [x,y]-ionenes are polyelectrolytic molecules consisting of dimethylammonium charge centers interconnected by alternating alkyl chain segments containing x and y methylene groups, some of which can form aggregate species whose properties mimic those of conventional surfactant micelles. These ionene-bonded stationary phases were characterized using different recommended HPLC test mixtures. Test solute chromatographic behavior on the ionene phases was found to be similar to that of intermediate oligomeric or polymeric C-18 and/or phenyl phases, depending upon the specific test mixture employed. In addition, the phases exhibit significant solute shape recognition ability. The ionene stationary phases were successfully employed for the separation of the components of the recommended ASTM reversed-phase test mixture, as well as for ortho-, meta- and para-disubstituted benzenes and other positional or geometric isomeric compounds. The ionene materials allow for chromatographic separations under either reversed-phase or ion-exchange conditions. The retention mechanism on these multimodal phases can occur by hydrophobic partitioning or electrostatic interactions, depending upon the characteristics of the components of the analyte mixture (neutral or anionic). The effects of alteration of the percent organic modifier, flow rate and temperature of the mobile phase on chromatographic retention and efficiency on these phases were briefly examined.

Journal Article↗