Cation-exchange Procedure Research Articles

Immunogenicity and antigenic reactivity of a carrier-free synthetic peptide complex derived from a 70-kDaPlasmodium falciparum exoantigen

A 70-kDa Plasmodium falciparum exoantigen was purified from supernatant fluids of continuous in vitro P. falciparum cultures using sequential cation-exchange and high performance liquid chromatographic procedures. The purified protein was then digested with chymotrypsin and amino-acid sequences were determined for the resulting fragments. Four peptides (termed C2, C3, C5, and C10) were subsequently selected for synthesis based on their predictability for antigenic sites. The peptides were effectively used as a synthetic immunogen (SPf70) when they had been copolymerized with glutaraldehyde in the absence of a carrier. When given with Freund's adjuvant, the synthetic peptide complex was found to be highly immunogenic in rabbits. Serologic reactivity to the peptide complex and peptides C2 and C5 was uniformly high, followed by the responses to peptides C3 and C10. Peptide antigenicity was also assessed with human anti-P. falciparum sera from malaria-endemic regions of Uganda and Venezuela. Enzyme-linked immunosorbent assay (ELISA) data showed that anti-P. falciparum antibodies were specific for and reactive to the peptides. The specificity of the rabbit anti-SPf70 antibodies for P. falciparum antigen was shown by immunoprecipitation of metabolically labeled proteins and by immunoblotting. Herein we describe the peptide sequences of a 70-kDa P. falciparum exoantigen (Pf70) that, when synthesized and constructed as a copolymer (SPf70), are capable of inducing the formation of antibodies that are reactive with the native malarial protein. The high immunogenicity and antigenic reactivity of SPf70 indicate the potential use of this synthetic peptide polymer as an immunogen and a diagnostic reagent.

Speciation and mobilization of aluminium and cadmium in podzols and cambisols of S. Sweden

Processes governing the mobilization of Al and Cd in podzols and cambisols of S. Sweden having different tree layer vegetation (Picea abies, Fagus sylvatica, or Betula pendula) were investigated. Speciation of Al and Cd in soil solutions were performed by a column cation exchange procedure (cf. Driscoll, 1984) in combination with thermodynamic calculations. Podzols in spruce and beech stands were characterized by a high release of organic compounds from the O/Ah horizons, resulting in a high organic complexation of Al (c. 93%) in the soil solution from the E horizon (15 cm lysimeters). Organic complexes were mainly adsorbed/precipitated in the upper Bh horizon and the overall transport of Al at 50 cm depth was governed by a pH dependent dissolution of a solid-phase Al pool. In the cambisols, inorganic Al forms were predominant at both 15 and 50 cm depth, and Al solubility was closely related to solution pH. Secondary minerals like synthetic gibbsite, jurbanite, kaolinite or imogolite could generally not explain measured solution Al3+ activities. Results instead indicated that the relatively large organically bound solid-phase Al pools present in both soil types could do so. The column fractionation procedure could be used only qualitatively for Cd, but results strongly indicated that Cd-organo complexes contributed significantly to the overall mobilization of Cd in the podzol E horizons. In all other soil solutions, Cd2+ was the predominant species. Both solid-phase and solution chemistry suggests that ion exchange processes controlled the Cd2+ activities in these solutions. All reactive solidphase Cd was extractable by NH4Cl and Cd2+ activities could in most cases effectively be modeled by the use of ion exchange equations. Solubilized Al3+ efficiently competed for exchange sites and played an important role for the Cd mobilization in these soils.

Speciation of copper in soil solutions from podzols and cambisols of S. Sweden

Factors affecting the mobilization of Cu in spruce, beech, and birch forest soil profiles (podzols and cambisols) at two background sites in S. Sweden were evaluated. Inorganic forms and organically bound forms of Cu in soil solutions form 15 and 50 cm depths were estimated using a column cation exchange procedure. At 15 cm depth (approximately corresponding to lower E horizon in the podzols or to lower Ah horizon in the cambisols), almost all Cu in the soil solution was organically bound (non-exchangeable Cu=90 to 98% of total Cu) in both podzols and cambisols. Organically complexed Cu also constituted the predominant Cu form (non-exchangeable Cu=62 to 83% of total Cu) in soil solutions from the 50 cm depth, despite a relatively low [DOC] (3 to 14 mg L−1) and highly Al saturated organic compounds. Copper followed the same mobilization pattern as DOC, being highest at 15 cm depth in the podzol spruce and beech stands, and decreased with depth in all six stands. Results indicated that solution pH affected Cu mobilization in cases where the soluble DOC concentration was relatively low, as an increased pH seemed to increase the amount of Cu bound per g DOC.

Synthesis and luminescence properties of europium(3+)-intercalated cadmium thiophosphate (Cd2P2S6)

Eu 3+ cations have been intercalated by a cation-exchange procedure into the layered lattice of Cd 2 P 2 S 6 . Highly hydrated intercalate cations initially insert into the interlamellar interstices. The water of hydration may be completely removed by heating to ∼80 o C. Upon long standing at room temperature or upon heating at about 40 o C, some of the Eu 3+ cations shift to Cd 2+ vacancy sites in the host lattice. The coordination of the Eu 3+ was examined by photoluminescence and photoexcitation spectroscopy

Analysis of rare-earth elements in geological samples by gradient ion chromatography: An alternative to ICP and INAA

An application of high-performance ion chromatography (HPIC) for the analysis of rare-earth elements (REE) in geological samples is described. The technique (developed by Heberling and coworkers on synthetic solutions) is shown to be capable of determining 12 of the REE in a wide variety of rock types with an accuracy and precision comparable to that of inductively coupled plasma (ICP) atomic emission spectroscopy. By this HPIC method it is not possible to obtain data for Ho, due to interference by Y, or Lu which is not sufficiently well resolved from Yb. The HPIC instrument used in this study is a Dionex® 4000i Gradient ion chromatograph in which eluant composition and flow rate are microprocessor controlled. Separation of the REE was effected using a Dionex® CS 5 solumn with conditions similar to those outlined by Heberling and coworkers. The eluted REE were reacted with a colour complexing agent and detected photometrically using a UV/visible light detector at a wavelength of 520 nm. Analysis by HPIC requires that the sample be taken into solution and the matrix removed. Sample dissolution and removal of matrix elements, that would otherwise interfere with the chromatogram, were achieved using standard cationexchange procedures routinely applied in the preparation of samples for ICP analysis. Providing that a transition metal-free solution remains after matrix removal, the full range of REE can be determined in ∼20 min. However, if ppb levels of the transition metals are present in the analyte solution, these must be removed during the early part of the HPIC analysis so increasing the run time to ∼42 min. REE data obtained by this HPIC technique for a number of international rock standards compare favourably with the published data on these well-characterised samples.

Agkistrodon piscivorus piscivorus platelet aggregation inhibitor: a potent inhibitor of platelet activation.

Applaggin (Agkistrodon piscivorus piscivorus platelet aggregation inhibitor) is a potent inhibitor of platelet activation. The protein is isolated from the venom of the North American water moccasin snake in three steps, including gel filtration, cation exchange, and reverse-phase HPLC procedures. The purified protein migrates as a 17,700-Da polypeptide by SDS/PAGE under nonreducing conditions and as a 9800-Da peptide in the presence of thiol. The behavior of applaggin on SDS/PAGE would indicate that the protein is a disulfide-linked dimer. Applaggin has been completely sequenced by Edman degradation and consists of 71 amino acids. The sequence is rich in cysteine and contains Arg-Gly-Asp at residues 50-52. Applaggin blocks platelet aggregation induced by ADP, collagen, thrombin, or arachidonic acid with IC50 values ranging from 12 to 128 nM (0.2-2.3 micrograms/ml) depending on the agonist and its concentration. This inhibition is found to correlate with inhibition of thromboxane A2 generation and of dense granule release of serotonin. Inhibition by applaggin of serotonin release induced by ADP, gamma-thrombin, and collagen was monitored in plasma under stirred conditions with [3H]serotonin-loaded platelets, and IC50 values for inhibition are found to range from less than 10 to 145 nM. At saturating concentrations, 125I-labeled applaggin (125I-applaggin) binds to 28,500 sites per unstimulated, washed platelet with a Kd of 1.22 x 10(-7) M. Binding of 125I-applaggin to platelets is inhibited by the synthetic undecapeptide Arg8-Gly-Asp-Val at 200 microM.

Quantitative Determination of Vermiculite by a Rubidium Fixation Method

AbstractA rubidium‐fixation method for the quantitative determination of vermiculite is described. The results obtained by this procedure were similar to, but more precise than, the results obtained by the conventional cation exchange procedures. The exchangeable Rb of a Rb‐saturated and heated sample is replaced by NH4 and the remaining fixed Rb is determined directly by dissolving the sample. The vermiculite content is calculated from the fixed Rb content. The Rb‐fixation method is well suited for determining small changes of vermiculite content in soils.

Determination of rare earth elements in geological samples by inductively coupled plasma mass spectrometry

The determination of rare earth elements (REE) in geological samples has become increasingly important in recent years as their physical and chemical characteristics have been widely studied. Inductively coupled plasma mass spectrometry (ICP-MS) is an ideal analytical technique for the determination of this elemental group, with good sensitivity and determination limits while offering a range of modes for sample introduction. If REE are separated from their matrix and pre-concentrated, using for example cation-exchange procedures, determination limits of better than 1 ng g–1 can be achieved.

Column chromatographic speciation of chromium for Cr(VI) and several species of Cr(III)

Chromium can be present in aqueous solution as Cr(VI) or in monomeric, dimeric, trimeric and higher polymeric forms of Cr(III). Many monomeric forms of Cr(III) are possible, with the water molecules of Cr(H2O) 6 3+ substituted by anionic or neutral species. This proliferation of Cr(III) species makes the complete speciation of chromium a continuing challenge to the analyst. A simple and effective cation exchange procedure for the separation of various of these species uses a small glass column containing 1 mL of pre-treated cation exchange resin (Na+ form). Stepwise elution with solutions of perchloric acid, Ca2+ (pH=2) and La3+ (pH=2) separates Cr(VI) and seven Cr(III) species from CrX3 to tetramer. Radiometric (Cr-51), spectrophotometric and other detection methods can be employed; the use of radiochromium gives the lowest detection limit.

Isolation of high‐purity zirconia from Australian zircon sands using an ion‐exchange process

AbstractZirconia produced by acid‐leaching zircon sand can be significantly contaminated by other elements leached from the sand. A simple cationexchange procedure has been developed that allows separation of the impurity elements from the zirconium to give zirconia with up to 99.99% purity. The addition of formic acid to the acid‐leach solution prior to ion exchange provides the removal of about three‐quarters of the hafnium present in the product zirconia.

Zur Methodik der Elementspezies-Analytik in Lebensmitteln

Potentiometry with an ion-selective electrode as well as a cation-chelate-exchange procedure (combined with AAS) are presented as useful methods for the determination of stabilities of element species, for example of calcium in milk. The cation-exchange procedure is also applicable to other metals (e.g., magnesium) and other foodstuffs (e.g., meat extracts). New results of Ca- and Mg-extractabilities by the use of different aqueous extraction solutions (including enzymic solutions) are reported. Ultrafiltration, dialysis and gel-chromatography are further methods especially for the separation and analysis of protein-containing element species. Unoccupied binding fields can be detected after addition of Cu(II) ions by combination of gel chromatography and UV/VIS spectroscopy, as shown by example of rape-flour. The experiences gained in the analysis of element species in foodstuffs are combined to a strategy of analysis.

Preservation of Biological LH and FSH Activity after Application on HPLC. Comparison between Cation-Exchange and Reverse-Phase High Performance Liquid Chromatography

Abstract A cation-exchange high-performance liquid chromatography procedure is described for the separation of bioactive lutropin from follitropin in a human urinary gonadotropin standard preparation (1st IRP 70/45). The results clearly demonstrate that recovered protein retained most of its biological activity following the chromatography. Due to a lack of efficient and quick methods for purifying pituitary or urinary gonadotropins, this method could prove to be valuable for this purpose. This method has also been shown to be quick (less than 20 min) and efficient for separation of impurities or degradation products from bovine follitropin with 92% preservation of its biological activity. Our results suggest that ion exchange HPLC procedure will play a powerful role in the isolation of gonadotropins and other biologically active compounds.

Propylene hydroformylation on rhodium zeolites X and Y: I. Catalytic activity

Propylene hydroformylation activity at atmospheric pressure over RhNaX and RhNaY is a function of the cation-exchange procedure. The best method for the preparation of catalysts with reproducible activity is NaY exchange at pH 6 and 90 °C by dropwise addition of aqueous RhCl 3 with subsequent stirring for 5 h. These catalysts show activity for hydrogenation, hydroformylation, and synthesis of C 7-ketones. Reaction selectivity is a function of the exchange conditions and activation procedure. The rate dependence upon the partial pressures of carbon monoxide, hydrogen, and propylene is similar to that reported for homogeneous hydroformylation. The selective poisoning of an active RhNaY catalyst is consistent with hydroformylation active sites located on the surface of the zeolite particles.

ChemInform Abstract: IMPROVED RICHMAN‐ATKINS SYNTHESES OF CYCLIC POLYAMINES PARTICULARLY 1,4,7‐TRIAZACYCLONONANE (TACN) AND 1,4,7‐TRIAZACYCLODECANE (TACD), WITH THE AID OF CATION EXCHANGE IN PURIFICATION AND ISOLATION

AbstractDie Tri‐N‐tosyl‐Derivate (VIa) und (VIb) der Titelverbindungen werden jeweils nach zwei Methoden dargestellt: Kondensation des Tri‐N‐tosyl‐diethylentriamins (I) mit den Ditosylaten (IIa) bzw. (IIb) und Kondensation des Bis‐(tosyloxyeth′yl)‐tosylamids (IV) mit den Di‐N‐tosyl‐alkylendi‐ aminen (Va) bzw. (Vb) [im Falle der Kondensation von (IV) mit (Va) entstehen neben (VIa) höhere Kondensationsprodukte in wechselnden Mengen].

The group separation of the rare-earth elements and yttrium from geologic materials by cation-exchange chromatography

Demand is increasing for the determination of the rare-earth elements (REE) and yttrium in geologic materials. Due to their low natural abundance in many materials and the interferences that occur in many methods of determination, a separation procedure utilizing gradient strong-acid cation-exchange chromatography is often used to preconcentrate and isolate these elements from the host-rock matrix. Two separate gradient strong-acid cation-exchange procedures were characterized and the major elements as well as those elements thought to provide the greatest interference for the determination of the REE in geologic materials were tested for separation from the REE. Simultaneous inductively coupled argon plasma—atomic emission spectroscopy (ICAP—AES) measurements were used to construct the chromatograms for the elution studies, allowing the elution patterns of all the elements of interest to be determined in a single fraction of eluent. As a rock matrix, U.S. Geological Survey standard reference BCR— 1 basalt was digested using both an acid decomposition procedure and a lithium metaborate fusion. Hydrochloric and nitric acids were tested as eluents and chromatograms were plotted using the ICAP—AES data; and we observed substantial differences in the elution patterns of the REE and as well as in the solution patterns of Ba, Ca, Fe and Sr. The nitric acid elution required substantially less eluent to elute the REE and Y as a group when compared to the hydrochloric acid elution, and provided a clearer separation of the REE from interfering and matrix elements.

Improved Richman-Atkins syntheses of cyclic polyamines particularly 1,4,7-Triazacyclononane (tacn) and 1,4,7-Triazacyclodecane (tacd), with the aid of cation-exchange in purification and isolation

Richman-Atkins cyclization syntheses for the cyclic triamines 1,4,7-triazacyclononane (tacn) and 1,4,7-triazacyclodecane (tacd) with the alternative possible sets of reagents as tosyl derivatives have been examined in detail and compared. The cyclizations from the tritosyl derivative of diethylenetriamine (dientt) and the appropriate diols as ditosylates proceeded relatively cleanly, although there were small amounts of higher products and some carry through of dientt for tacn. The alternative cyclizations, from 2,2'-(tosy1imino)bisethyl ditosylate and a ditosyl diamine, gave little reaction to form tacn as the tritosyl derivative. The reaction to form tritosyl tacd proceeded further, but was accompanied by significant formation of higher condensation products, particularly the hexamines 1,4,7,11,14,17-hexaazacycloeicosane (2 : 2 cyclic dimer) and 3,7,10,13-tetraazahexade- cane-1,16-diamine. A cation-exchange procedure, applied after the detosylation stage, is described for obtaining the required pure 1 : 1 cyclic polyamines as their hydrochloride salts with high recovery. This is an effective method for removing higher co-products. These may be recovered, and by this means the above hexamines were isolated in admixture.

A versatile cation-exchange procedure for measuring the seven major forms of vitamin B 6 in biological samples

A cation-exchange procedure for detecting nanogram quantities of all seven common vitamin B6 metabolites in a variety of biological samples is presented. The procedure uses gradient elution with a single column to effect separation of the seven compounds within 40 to 60 min, depending on the complexity of the sample. Postcolumn addition of buffer and bisulfite ion permits sensitive fluorometric detection of all B6 compounds at the same wavelengths (330 nm activation, 400 nm emission).

Comparison of High Performance Liquid Chromatographic, Radiometric, and Lactobacillus casei Methods for the Determination of Folacin in Selected Foods

ABSTRACTThe results of reverse phase high performance liquid chromatographic (HPLC), competitive binding radiometric, and Lactobacillus casei methods were compared for the determination of total folacin in raw cabbage, a fortified cereal, and a fortified infant formula. A cation exchange procedure was developed which permitted the analysis of cabbage folacin by reverse phase HPLC after hydrolysis of folacin polyglutamates with endogenous conjugase. Although general agreement was observed between assays for the cereal product, marked variation was found for cabbage and the infant formula. These results suggest that the accuracy of the radiometric and L. casei assays may be influenced by the distribution of folacin derivatives present and other sample components. Reverse phase HPLC provides a direct analysis which is not subject to such variability.

Ion exchange separation of carrier-free 140Ba and 140La from their equilibrium mixture using nitrilotriacetic acid and ascorbic acid as eluents

A simple cation exchange procedure for separation of 140Ba- 140La using Dowex 50W-X8 and nitrilotriacetic acid or ascorbic acid as the eluent has been described. The optimal separation of the daughter from the parent has been achieved using a 4% Na-nitrilotriacetate or Na-ascorbate solution at pH 7. The parent, 140Ba, left in the column can be eluted with dilute hydrochloric acid or it can be retained in the column for milking off the daughter, 140La, when needed. The radiochemical purity of the separated isotopes, 140Ba and 140La, were verified by γ-ray spectrometry.

Selective cation-exchange procedure for the detection of hydroxamic acids

Selective cation-exchange procedure for the detection of hydroxamic acids