Ion-exchange Phase Research Articles

Purification of an iron-binding nona-peptide from hydrolysates of porcine blood plasma protein

To isolate a novel iron-binding peptide, porcine plasma protein (PPP) was hydrolyzed using a commercial protease. The degree of hydrolysis and iron-binding capacity was determined using the trinitrobenzenesulfonic acid and orthophenanthroline method, respectively. The hydrolysates of blood plasma protein were then filtered using YM-3 membrane, and an iron-binding peptide was isolated using gel permeation, ion exchange, and normal phase high-performance liquid chromatography. The purified iron-binding peptide was identified to be a nona-peptide, Asp–Leu–Gly–Glu–Gln–Tyr–Phe–Lys–Gly (1055 Da) based on liquid chromatography/electrospray ionization (LC/ESI) tandem mass spectrum and a sequence of porcine plasma protein.

Mobility of Cr(VI) anions in the phase of the amphoteric inorganic ion exchanger

The method of impedance spectroscopy has been used to investigate hydrogel and xerogel of hydrated zirconium dioxide containing Cr(VI) obtained from cation-and anion-substituted forms of an ion exchanger. It is shown that a complex composition of the amphoteric inorganic ion exchanger as well as protonization of its functional groups producing a substantial impact on the value of its electrical conductivity do not make it possible to assess mobility of sorbed ions. Nonetheless, the effective values of internal diffusion mobility of Cr(VI) may be obtained by the kinetic method: diffusion coefficients corresponding to the Cr(VI) → OH constitute 8.57 × 10−12−6.85 × 10−11 m2/s or hydrogel and 3.33 × 10−13−5.45 × 10−12 m2/s for xerogel depending on the sorbate concentration.

Stability of surfactant coated columns for ion chromatography

Ionic surfactant coatings are a popular means to convert reversed-phase columns into ion-exchange phases with adjustable ion-exchange capacity and selectivity. However, the perceived lack of stability of surfactant coatings has hindered their use for routine separations. Coating conditions (acetonitrile content, ionic strength, surfactant concentration and temperature) were varied to determine their effect on coating stability. Under all coating conditions, cetyltrimethylammonium (CTAB) coated columns exhibited an initial decrease in ion retention. However, after the initial 1 L flush, both retention times and efficiency remained stable for >or=3000 column volumes. Greatest column stability and control of column capacity are achieved if the surfactant in the coating solution is below its critical micelle concentration.

Pyridine based thorium(IV) phosphate hybrid fibrous ion exchanger

A new phase of the hybrid fibrous ion exchanger, pyridine based cerium(IV) phosphate (PyCeP), has been synthesized in the form of a sheet like paper by mixing ceric sulphate, phosphoric acid and pyridine in a particular ratio to get the material of the optimum ion exchange characteristics. This material has been characterized with the help of ion exchange capacity, elution and concentration and pH titrations behaviour in addition to some physicochemical studies like X-ray diffraction, IR, TG, DTG and SEM studies. The SEM study confirms the fibrous nature of the material while amorphous nature is revealed by its X- ray spectrum.

Triton X-100 based cerium(IV) phosphate as a new Hg(II) selective, surfactant based fibrous ion exchanger: Synthesis, characterization and adsorption behaviour

Triton X-100 based cerium(IV) phosphate (TX-100CeP) has been synthesized as a new phase of fibrous ion exchanger. It has been characterized using IR, X-ray, SEM, TGA/DTA and elemental analysis in addition to its ion exchange studies such as ion exchange capacity, elution, concentration and thermal behaviour. Its adsorption behaviour has also been studied for some alkaline earths and heavy metal ions in different acidic media. On this basis, the material has been found to be selective for Hg(II), a toxic heavy metal ion. Hence, some binary separations of Hg(II) from other metal ions have been performed on its column, exploring its potential in environmental studies.

New Layered Uranium Phosphate Fluorides: Syntheses, Structures, Characterizations, and Ion‐Exchange Properties of A(UO2)F(HPO4)×xH2O (A: Cs+, Rb+, K+; x = 0—1).

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Kinetics of Reaction of Oximate α‐Nucleophiles with p‐nitrophenyl Acetate in Alkyltriphenyl Phosphonium Bromide Micelles

Rate constants for the nucleophilic hydrolysis of p‐nitrophenyl acetate by the butane 2,3‐dione monoximate ion at pH 7.9 and 27°C have been measured kinetically in alkyltriphenylphosphonium (C12–, C14–, C16–) bromide micellar media. Addition of surfactants led to a significant increase in the pseudo‐first order rate constants. The rate‐surfactant profiles are fitted quantitatively in terms of pseudo phase ion exchange model. There is a decrease in the observed rate with decreasing hydrophobic chain length for the same surfactant head group. Cetyltriphenylphosphonium bromide is more reactive than cetyltrimethylammonium bromide.

Improved Validation of Peptide MS/MS Assignments Using Spectral Intensity Prediction

A major limitation in identifying peptides from complex mixtures by shotgun proteomics is the ability of search programs to accurately assign peptide sequences using mass spectrometric fragmentation spectra (MS/MS spectra). Manual analysis is used to assess borderline identifications; however, it is error-prone and time-consuming, and criteria for acceptance or rejection are not well defined. Here we report a Manual Analysis Emulator (MAE) program that evaluates results from search programs by implementing two commonly used criteria: 1) consistency of fragment ion intensities with predicted gas phase chemistry and 2) whether a high proportion of the ion intensity (proportion of ion current (PIC)) in the MS/MS spectra can be derived from the peptide sequence. To evaluate chemical plausibility, MAE utilizes similarity (Sim) scoring against theoretical spectra simulated by MassAnalyzer software (Zhang, Z. (2004) Prediction of low-energy collision-induced dissociation spectra of peptides. Anal. Chem. 76, 3908-3922) using known gas phase chemical mechanisms. The results show that Sim scores provide significantly greater discrimination between correct and incorrect search results than achieved by Sequest XCorr scoring or Mascot Mowse scoring, allowing reliable automated validation of borderline cases. To evaluate PIC, MAE simplifies the DTA text files summarizing the MS/MS spectra and applies heuristic rules to classify the fragment ions. MAE output also provides data mining functions, which are illustrated by using PIC to identify spectral chimeras, where two or more peptide ions were sequenced together, as well as cases where fragmentation chemistry is not well predicted.

Correlation analysis on partition of rare earth in ion-exchangeable phase from weathered crust ores

The rare earth(RE) in weathered crust ores mainly exists as ion-exchangeable phase, approximately 80%. The correlation analysis on partition of 376 samples in ion-exchangeable phase from weathered crust ores was conducted. The results show that partition both among heavy RE elements and light RE elements with high partition appears positive correlation, but partition sums between the heavy RE elements and the light RE elements appear close negative correlation obviously. Clear negative correlations exist between the light RE elements (except Ce) and yttrium(Y). Matrix of correlation analysis on this partition can be divided into three zones. The correlated coefficient variation from negative to positive in zones B and C occurs at Gd, so does that in zones B and A (except Ce, Eu, and Sm), suggesting that RE elements can be divided into two groups with Gd as border. This phenomenon is called Gadolinium-broken effect.

Sorption of Thiocyanate Silver Complexes and Determination of Silver by Diffuse Reflectance Spectroscopy

The present paper is focused on sorption concentration of silver (I) on some complex-forming ion exchangers in the initial thiocyanate form and subsequent determination of Ag(I) in the phase of anion exchanger AN-25 by diffuse reflectance spectroscopy. The sorption and kinetic characteristics of the sorbents were investigated. The apparent stability constants of thiocyanate silver complexes in the ion exchanger phase were calculated. The sorption-spectroscopic method is proposed for Ag(I) determination in aqueous solutions. The calibration curve is linear in the concentration range of 10-200 mg/L (sample volume is 10.0 mL) and the detection limit is 2 g/mL. The presence of (macrocomponents) as well as of Ni (II), Co (II), Cu (II) do not hinder the determination of silver (I).

New Layered Uranium Phosphate Fluorides: Syntheses, Structures, Characterizations, and Ion-Exchange Properties of A(UO2)F(HPO4)·xH2O (A = Cs+, Rb+, K+; x = 0−1)

Single crystals of three new layered uranium phosphate fluorides, A(UO2)F(HPO4).xH2O (A = Cs+, Rb+, and K+; x = 0-1) have been synthesized by hydrothermal reactions using UO3, H3PO4, HF, and corresponding alkali metal halides as reagents. Although all three new materials have layered structures, each of them contains different structural motifs within the layer. While Cs(UO2)F(HPO4).0.5H2O and Rb(UO2)F(HPO4) reveal noncentrosymmetric crystal structures, K(UO2)F(HPO4).H2O crystallizes in a centrosymmetric space group. In addition, the ion-exchanged phases for all three materials are highly crystalline. Crystal data: Cs(UO2)F(HPO4).0.5H2O, orthorhombic, space group Pca21 (No. 29), with a = 25.656(5) A, b = 6.0394(12) A, c = 9.2072(18) A, and Z = 4; Rb(UO2)F(HPO4), orthorhombic, space group Cmc21 (No. 36), with a = 17.719(4) A, b = 6.8771(14) A, c = 12.139(2) A, and Z = 8; K(UO2)F(HPO4).H2O, monoclinic, P21/n (No. 14), with a = 6.7885(14) A, b = 8.7024(17) A, c = 12.020(2) A, beta = 94.09(3), and Z = 4.

The ion exchange phase in corrosion of nuclear waste glasses

The diffusion-controlled ion exchange phase in the corrosion of nuclear waste borosilicate glasses has been examined using the Doremus’ model accounting for interdiffusion and exchange of the cations in the glass with protons from the water. Ion exchange is the principal radionuclide release mechanism for conditions when glass network hydrolysis is suppressed, such as in silica-saturated solutions when ion exchange may persist over geological time scales. In dilute aqueous solutions ion exchange controls the initial cation release and can dominate for tens and many hundreds of years if temperatures are low at low and neutral pH. Ion exchange rates are shown to have inverse square root time dependences, an Arrhenius-controlled temperature relationship and a 10 −0.5pH dependence with the pH of the contacting water. Due to radioactive decay the radionuclide releases from nuclear waste glasses are limited to certain upper values, which can be calculated based on available experimental data.

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.

Effect of complexants on the adsorption and color reactions of lanthanum(III), uranium(VI), thorium(IV), and zirconium(IV) with Arsenazo M in the solid phase of an ANKB-50 fibrous ion-exchanger

The effect of complexants—acetic, aminoacetic, tartaric, malonic, and oxalic acids; EDTA; and Na2CO3—on the adsorption and subsequent determination of thorium(IV), lanthanum(III), uranium(VI), and zirconium(IV) with Arsenazo M in the solid phase of polyacrylonitrile fiber filled with an ANKB-50 anion exchanger was studied. Complexing agents were introduced into the solution at the step of metal ion adsorption. It was shown that zirconium and uranium interacted with the iminodiacetate groups of the adsorbent in the course of adsorption; the adsorption of elements from 10−3 to 10−2 M complexant solutions (except for tartaric and oxalic acids and EDTA) under the optimum conditions was enhanced as compared to their adsorption from pure solutions; complexation with Arsenazo M in the solid phase proceeded at a higher acidity than in the solution. When the elements were present simultaneously, their total concentration and individual thorium could be determined from malonic acid solutions with Arsenazo M by varying the concentration of acid and the adsorption pH.

Role of ion exchange in the corrosion of nuclear waste glasses

ABSTRACTThe ion exchange phase of corrosion of nuclear waste glasses was modelled using Doremus' theory of interdiffusion and numerically analysed for British Magnox waste and Russian K-26 glasses. It is shown that even in non-silica -saturated conditions the ion exchange phase plays a significant role in the overall radionuclide release inventory particularly for short-lived radionuclides.

A Kunitz proteinase inhibitor from Archidendron ellipticum seeds: Purification, characterization, and kinetic properties

Leguminous plants in the tropical rainforests are a rich source of proteinase inhibitors and this work illustrates isolation of a serine proteinase inhibitor from the seeds of Archidendron ellipticum (AeTI), inhabiting Great Nicobar Island, India. AeTI was purified to homogeneity by acetone and ammonium sulfate fractionation, and ion exchange, size exclusion and reverse phase chromatography (HPLC). SDS–PAGE of AeTI revealed that it is constituted by two polypeptide chains (α-chain, M r 15,000 and β-chain, M r 5000), the molecular weight being ∼20 kDa. N-terminal sequence showed high homology with other serine proteinase inhibitors belonging to the Mimosoideae subfamily. Both Native-PAGE as well as isoelectric focussing showed four isoinhibitors (p I values of 4.1, 4.55, 5.27 and 5.65). Inhibitory activity of AeTI remained unchanged over a wide range of temperatures (0–60 °C) and pH (1–10). The protein inhibited trypsin in the stoichiometric ratio of 1:1, but lacked similar stoichiometry against chymotrypsin. Also, AeTI-trypsin complex was stable to SDS unlike the SDS unstable AeTI-chymotrypsin complex. AeTI, which possessed inhibition constants ( K i) of 2.46 × 10 −10 and 0.5 × 10 −10 M against trypsin and chymotrypsin activity, respectively, retained over 70% of inhibitory activity after being stored at −20 °C for more than a year. Initial studies on the insecticidal properties of AeTI indicate it to be a very potent insect antifeedant.

Purification and structural analysis of the novel glycoprotein allergen Cyn d 24, a pathogenesis‐related protein PR‐1, from Bermuda grass pollen

Bermuda grass pollen (BGP) contains a very complex mixture of allergens, but only a few have been characterized. One of the allergens, with an apparent molecular mass of 21 kDa, has been shown to bind serum IgE from 29% of patients with BGP allergy. A combination of chromatographic techniques (ion exchange and reverse phase HPLC) was used to purify the 21 kDa allergen. Immunoblotting was performed to investigate its IgE binding and lectin-binding activities, and the Lysyl-C endopeptidase digested peptides were determined by N-terminal sequencing. The cDNA sequence was analyzed by RACE PCR-based cloning. The protein mass and the putative glycan structure were further elucidated using MALDI-TOF mass spectrometry. The purified 21 kDa allergen was designated Cyn d 24 according to the protocol of International Union of Immunological Societies (IUIS). It has a molecular mass of 18,411 Da by MALDI-TOF analysis and a pI of 5.9. The cDNA encoding Cyn d 24 was predicted to produce a 153 amino acid mature protein containing tow conserved sequences seen in the pathogen-related protein family. Carbohydrate analysis showed that the most abundant N-linked glycan is a alpha(3)-fucosylated pauci-mannose (Man3GlcNAc2) structure, without a Xyl beta-(1,2)-linked to the branching beta-Man. Thus, Cyn d 24 is a glycoprotein and the results of the sequence alignment indicate that this novel allergen is a pathogenesis-related protein 1. To the best of our knowledge, this is the first study to identify any grass pollen allergen as a pathogenesis-related protein 1.

Innovations in the synthesis of Fe-(exchanged)-zeolites

Several aspects on the preparation of Fe-zeolites are discussed. In contrast to the many studies highlighting the characterisation of the active sites, new approaches for incorporation of Fe are presented. Full utilization of exchange capacity of zeolites has been achieved by a controlled alkaline treatment of the parent sample. With this method, iron can be fully exchanged by liquid phase ion-exchange on ZSM5 without the formation of inactive Fe-oxides. The second topic is the use of a mild oxidant (H 2O 2, and peroxides in general) to break down strong complexating equilibria during ion-exchange by controlled redox titration of the ligands. Hydrogen peroxide oxidizes effectively chelating groups releasing Fe species at a controlled rate. The method is demonstrated for the preparation of Fe-FER through Ferric-citrate. The final concept discussed is the detemplating of the zeolite with the simultaneous incorporation of the iron (combined detemplation and ion-exchange). This one-pot preparation minimizes the number of steps considerably. To realize this, a strong oxidant is necessary to remove the organic template, and Fe-cations for exchange. Both requirements are met with the Fenton's-chemistry (Fe 3+/2+/H 2O 2 mixtures) involving radical chemistry.

Ion exchanger as canonical assembly: Calculation of the phase composition in multicomponent systems

Ion exchanger is considered as the phase space being Gibbs canonical assembly. It is shown, that the canonical energy distribution results in a linear dependence of the differential free energy of ion exchange on the molar fraction of counterions in the ion exchanger phase in binary or multicomponent systems. A method for calculating of the phase composition of an ion exchanger at equilibrium with a multicomponent solution of electrolytes was proposed and tested for many experimental model systems.

TRAUMA-HEMORRHAGIC SHOCK MESENTERIC LYMPH FROM RAT CONTAINS A MODIFIED FORM OF ALBUMIN THAT IS IMPLICATED IN ENDOTHELIAL CELL TOXICITY

It has been proposed that factors originating from the gut after severe trauma/shock are introduced into the systemic circulation through the mesenteric lymphatics and are responsible for the cellular injury and inflammation that culminates in acute multiple organ dysfunction syndrome (MODS). Indeed, it has been shown that lymph collected from shocked but not sham-shocked animals causes endothelial cell death, neutrophil activation, and bone marrow (BM) colony growth suppression in vitro. In an attempt to isolate the factor(s) in lymph responsible for endothelial cell toxicity, lymph from shock and sham animals was fractionated by solid phase extraction (SPE) and ion exchange chromatography (IEX). The separation of shock lymph by both methodologies yielded two fractions having major detectable toxicity to endothelial cells, whereas no toxicity was detected from sham lymph separations by either method. Subsequent analysis of each SPE toxic fraction by gel electrophoresis and mass spectrometry suggests the toxicity is associated with a modified form of rat serum albumin (mod-RSA) and multiple lipid-based factors. Therefore, we have been able to demonstrate by two different separation techniques that shock lymph contains two or more factors that may account for the toxicity to endothelial cells. Further investigations are needed to determine the type of RSA modification and the identity of the lipid factors and their role in MODS.