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PubMedDate not supplied

[Analytical ion-exchange and gel chromatography of radioisotope-labeled protein (polypeptide) hormones].

On the example of prolactin-I125 the author presents his experience in the use of gel filtration and ion-exchange chromatography for complete characterization of homogeneity and immunological properties of labeled hormones preparations. These methods can be used in studying various aspects of protein and polypeptide hormones metabolism, including various stages of their action mechanism, and also to characterize the hormones manufactured. It was shown that the formation of prolactin complex with gamma-globulins was accompanied by additional polarization of the hormone molecules, this leading to an increased energy of interaction with the ion exchange surface. The effect of polarization of the hormone molecules on the biological properties of the hormones themselves, their complexes with serum proteins and membrane receptors is discussed.

Animals↗
PubMed2002

Two-step K(+)-Na+ and Ag(+)-Na+ ion-exchanged glass waveguides for C-band applications.

A two-step K(+)-Na+ and Ag(+)-Na+ ion-exchange technique is introduced to fabricate single-mode channel waveguides in BK7 glass for the telecom-wavelength region. The dependencies of insertion loss, polarization-dependent loss (PDL), end bending loss of curved waveguides on channel width, diffusion time, and annealing time are investigated. Results show that postannealing is a required process for improving waveguide properties and an optimal annealing time exists. Although relatively narrow mask openings are used in most one-step ion-exchange processes, a wider channel width, to as wide as 10 microm, is preferred for this two-step method. The minimum coupling loss to/from single-mode fiber and the propagation loss is found to be 0.4 dB and 0.3 dB/cm, respectively. For 5-cm-long waveguides the PDL is less than 0.1 dB. For the S-bend structure the cosine curve exhibit apparently a lower bending loss than the double-arc curve.

Journal Article↗
PubMed2001

Treatment of chromium plating process effluents with ion exchange resins.

The surface treatment industry deals with various heavy metals, including the elements Cr, Zn, Ni, Cd, and Cu. Conventional treatments of effluents generate class I solid residue. The aim of this investigation was to study the viability of ion exchange as an alternative process for treatment of rinse water and to determine the efficacy of two ion exchange systems, System 1: "strong" cationic resin-"strong" anionic resin and System 2: "strong" cationic resin-"weak" anionic resin. Commercial resins and solutions taken from rinse tanks of chromium plating companies were used in this investigation. A two-column system, one for the cationic resin and another for the anionic resin, both with 150 ml capacity was mounted. The solution was percolated at a rate of 10 ml/min. The following solutions were used for regeneration of the resins: 2% H2SO4 for the cationic and 4% NaOH for the anionic. The percolated solutions revealed chromium contents of less than 0.25 mg/l, independent of the system used. The "strong" cationic resin-"weak" anionic resin gave excellent regeneration results. The "strong" cationic-"strong" anionic resin presented problems during regeneration, and did not release the retained ions after percolation of 2000 ml of 4% NaOH solution. It is concluded that for this type of treatment, the system composed of "strong" cationic resin and "weak" anionic resin is more appropriate.

Cations↗
PubMed2006

Ion exchange phase transitions in water-filled channels with charged walls.

Ion transport through narrow water-filled channels is impeded by a high electrostatic barrier. The latter originates from the large ratio of the dielectric constants of the water and the surrounding media. We show that "doping," i.e., immobile charges attached to the walls of the channel, substantially reduces the barrier. This explains why most of the biological ion channels are "doped." We show that at rather generic conditions the channels may undergo ion exchange phase transitions (typically of the first order). Upon such a transition a finite latent concentration of ions may either enter or leave the channel, or be exchanged between the ions of different valences. We discuss possible implications of these transitions for the Ca-vs-Na selectivity of biological Ca channels. We also show that transport of divalent Ca ions is assisted by their fractionalization into two separate excitations.

Journal Article↗
PubMed2004

Effect of chromatographic conditions on resolution in high-performance ion-exchange chromatography of proteins on macroporous anion-exchange resin.

We explored chromatographic conditions to obtain high resolution in protein separations by ion-exchange chromatography (IEC) on a macroporous anion-exchange resin of 10 microm in particle diameter. We studied effects of flow-rate, gradient time (steepness of salt concentration gradient) and column length on resolution in wide ranges. It was found that very high resolutions are attainable at long gradient times with long columns. The resolution continuously became higher as the gradient time and the column length became longer except in some special cases. The dependence of resolution on gradient time was particularly great when the column was long and the gradient time for the change of 0-0.5 M NaCl was longer than 2 h. On the other hand, the effect of flow-rate on resolution was very small. Although the separations at long gradient times with long columns have not been popular in high-performance IEC and it takes several hours for one separation, such separations should be advantageous when very high resolutions are required like in proteomics research.

Anion Exchange Resins↗
PubMed1983

[Ion-exchange sorption of calcium and strontium from blood and its plasma].

The authors explored the statics of Ca2+ and Sr2+ sorption from a saline, imitating the salt (mineral) composition of the blood plasma, and from blood plasma. As the plasma concentration was raised, there was a consistent decrease in ion sorption of KU = 2 X 8 cationite characteristic for M2+ complex formation in solution. Conventional constants for formation of complex compounds and mole proportions (%) of free (M2+) and complex forms (MLx-) metals were calculated. The time course of calcium and strontium sorption on KU = 2 X 8 ion-exchange resin from saline and blood plasma was studied. It was discovered that sorption from saline proceeded according to the externally diffusion kinetics type, whereas sorption from plasma according to the mixed type of the ion-exchange kinetics. The kinetic ratios were calculated for the indicated versions of sorption experiments. The mechanisms of sorption found in model experiments were extrapolated to dog experiments with blood decalcination, which supported the adequacy of experimental hemosorption under consideration.

Animals↗
PubMed1995

Intragastric distribution of ion-exchange resins: a drug delivery system for the topical treatment of the gastric mucosa.

Previous studies by this group on freeze-dried oral dosage forms containing finely-divided ion-exchange resins revealed prolonged gastric residence and uniform distribution within the stomach. The present study was carried out to ascertain whether this was due to freeze-drying, properties of the radiolabelled ionic exchange resin, or the small dosing volume used. 99mTc-labelled cholestyramine resin was administered in two dosage forms, a freeze-dried tablet which dissolved in the oral cavity (orally dissolving tablet; ODT) and a 1.5 mL aqueous suspension. Two resin particle sizes (20-40 and 90-125 microns) were studied. Oesophageal transit and intragastric distribution and residence were followed by gamma scintigraphy. In a second study, in six subjects, gastric emptying of the water-soluble fraction of the ODT and 1.5 mL of water, was measured using 99mTc diethylenetriaminepentaacetic acid. Oesophageal transit of a water-soluble marker and resin in suspension was rapid, but the transit of the resin in the ODTs was significantly prolonged. Regardless of particle size or dosage form, the resin was evenly distributed throughout the stomach with 20-25% remaining for 5.5 h. In contrast, the water-soluble marker cleared from the stomach rapidly from both dosage forms. We suggest that oral dose forms containing finely-divided ion-exchange resins may form a useful system for topical treatment of the gastric mucosa, for example in targeting to Helicobacter pylori infection.

Adult↗
PubMed2005

Long-term stable electroosmotic pump with ion exchange membranes.

We present the design, fabrication and test of a novel inline frit-based electroosmotic (EO) pump with ion exchange membranes. The pump is more stable than previous types due to a new flow component that ensures a controlled width of the diffusion layer close to the ion exchange membranes. The pump casing is constructed in polymers while the EO active part, the frit, is made in a nanoporous silica. The pressure capability of the pump is Deltapm/DeltaV = 0.15 bar V(-1). The flow rate to current ratio is Qm/I = 6 microL min(-1) mA(-1). This translates to Deltapm = 4.5 bar and Qm = 6 microL min(-1) at DeltaV = 30 V. The pump has been tested with four different buffer concentrations. In order to investigate day-to-day reproducibility each Q-p pump characteristic has been recorded several times during hour-long operation runs under realistic operating conditions.

Journal Article↗
PubMed2001

Kinetic studies of clavulanic acid recovery by ion exchange chromatography.

Clavulanic acid (CA) is a beta-lactamase inhibitor produced by strains of Streptomyces clavuligerus. Nowadays, the combination of CA with amoxycillin is the most successful example of the use of a beta-lactam antibiotic sensitive to beta-lactamases together with an inhibitor of these enzymes. Clavulanic acid is purified from fermentation broth by a series of steps consisting mainly of two-phase separation processes such as liquid-liquid extraction, adsorption or ion-exchange chromatography, among others. Amberlite IRA 400, a strong anion-exchange resin, has a very high adsorption capacity for CA (Mayer et al. 1997). This resin can be pre-treated with NaCl (chloride cycle), to remove selectively only those anions, which are able to displace chloride from the resin or with NaOH (hydroxyl cycle), to remove all species of anions. In order to decide the best operating conditions for CA recovery by ion-exchange resins and then to construct a model of this separation process, batch experiments were conducted using Amberlite IRA 400 in the chloride cycle. These runs were carried out in a 200 ml stirred tank, at two different initial solution pH, 6.2 and 4.0; the temperature was maintained at 10 degrees C and 20 degrees C during adsorption and 30 degrees C during the desorption step. It was possible, on the basis of these batch results, to model the separation process, including the adsorption kinetics, equilibrium data and mass transfer limitations.

Adsorption↗
PubMed1986

Ion-exchange resin bezoar in a neonate.

A case of impacted ion-exchange resin causing intestinal obstruction associated with intraluminal calcification is described. This cause of bowel obstruction with intraluminal opacification has not previously been reported.

Bezoars↗
PubMed1991

Rapid measurement of leucine-specific activity in biological fluids by ion-exchange chromatography and post-column ninhydrin detection.

Commonly used methods for the measurement of leucine-specific activity use either high-performance liquid chromatography (HPLC) and pre-column derivatization or conventional ion-exchange chromatography. These are time-consuming, labor-intensive, relatively costly procedures, requiring high concentrations of radioactivity for accuracy. The present paper describes a method for the measurement of plasma leucine-specific activity using HPLC equipment, a large-bore ion-exchange column and post-column ninhydrin detection. With this method, determination of leucine concentration and leucine radioactivity was found to be linear (r2 greater than 0.999) over physiological ranges for both standards and deproteinized plasma. The intra- and inter-assay coefficients of variation for leucine concentrations were 1.4 and 2.7%, respectively. The intra- and inter-assay coefficients of variation for leucine-specific activities were 1.5 and 1.9%, respectively. The automated method is relatively fast (injection to injection time approximately 45 min), economical and capable of accurately assessing relatively small amounts of radioactivity.

Chromatography, High Pressure Liquid↗
PubMed1989

Reversible conversion of octadecyl-bonded silica to ion-exchange surfaces for protein separations.

Octadecyl-bonded silica, commonly used for reverse-phase high-pressure liquid chromatography, was modified using surfactants bearing ionizable groups and the modified packing used in ion-exchange chromatography of proteins. The surfactants 2-(n-hexadecylheptaethoxy)acetic acid, 1-(n-hexadecyloctaethoxy)ethylene-diamine, and N-(n-hexadecyloctaethoxy)pyridinium were adsorbed onto test columns packed with octadecyl-bonded silica particles. The proteins lysozyme, bovine serum albumin, trypsin, horse serum cholinesterase, and bovine liver carboxylesterase were used to study the ion-exchange characteristics of the modified packings. The retention order of the proteins on the surfactant-modified stationary phases were as predicted by the isoelectric point of each protein. In addition, the interaction of enzymes with the packings did not result in significant loss of enzymatic activity. Surfactant removal was possible with the use of organic solvents and this allowed the octadecyl-bonded surface to be used again in the reverse-phase mode. During the course of the experiments, no degradation in the packing's performance was observed due to loss of adsorbed surfactant, even after over 85,000 column volumes of sodium chloride and Tris-HCl buffers were circulated through the column.

Animals↗