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At least 19 recordsLinked to original sources
PubMed2004

Ion-exchange selectivity of anion exchange resin modified with polystyrenesulfonic acid.

In order to change the ion-exchange selectivity of anion-exchange resin, the surface of a gel-type anion exchange resin was modified with anionic polyelectrolyte, polystyrenesulfonic acid. Using this modified resin, the ion-exchange rate of nitrate was little decreased, but that of sulfate was evidently decreased. It is considered that the ion-exchange reaction of the multivalent anion is suppressed by the greater electrostatic repulsive force against the modification layer than that against the monovalent anion. Thus, this modified resin may be suitable for the selective separation of monovalent anions. The influence of the modified condition on the ion-exchange rate was examined. Furthermore, this modified resin was used to separate nitrate ions from sulfate ions in the aqueous solution.

Anion Exchange Resins↗
PubMed1977

The relationship between anion exchange and net anion flow across the human red blood cell membrane.

The conductive (net) anion permeability of human red blood cells was determined from net KCl or K2SO4 effluxes into low K+ media at high valinomycin concentrations, conditions under which the salt efflux is limited primarily by the net anion permeability. Disulfonic stilbenes, inhibitors of anion exchange, also inhibited KCl or K2SO4 efflux under these conditions, but were less effective at lower valinomycin concentrations where K+ permeability is the primary limiting factor. Various concentrations of 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS) had similar inhibitory effects on net and exchange sulfate fluxes, both of which were almost completely DIDS sensitive. In the case of Cl-, a high correlation was also found between inhibition of net and exchange fluxes, but in this case about 35% of the net flux was insensitive to DIDS. The net and exchange transport processes differed strikingly in their anion selectivity. Net chloride permeability was only four times as high as net sulfate permeability, whereas chloride exchange is over 10,000 times faster than sulfate exchange. Net OH-permeability, determined by an analogous method, was over four orders of magnitude larger than that of Cl-, but was also sensitive to DIDS. These data and others are discussed in terms of the possibility that a common element may be involved in both net and exchange anion transport.

Bicarbonates↗
PubMed1990

Effects of diethyl ether on membrane lipid ordering and on rotational dynamics of the anion exchange protein in intact human erythrocytes: correlations with anion exchange function.

The roles of lipid ordering and protein dynamics on the function of the anion exchange protein (band 3) in intact human erythrocytes have been investigated. The effects of diethyl ether on the ordering of membrane lipids and on the rotational dynamics of band 3 were measured by EPR and saturation-transfer EPR spectroscopies, respectively, and correlated with the anion exchange function of band 3. With increasing concentration, diethyl ether monotonically decreased the ordering of membrane lipids near the polar head-group region, as reported by the lipid-soluble spin probe 5-doxylstearic acid, but produced comparatively little change in the ordering of lipids in the hydrophobic midzone, as reported by 16-doxylstearic acid. The rotational mobility of band 3, as reported by the affinity spin-label bis(sulfo-N-succinimidyl) doxyl-2-spiro-5'-azelate [Anjaneyulu et al. (1989) Biochemistry 28, 6583-6590], also increased monotonically with increasing ether concentration. This increase in rotational mobility was not due to a demonstrable change in its state of oligomerization, since band 3 was readily cross-linked by bis(sulfo-N-succinimidyl) suberate to covalent dimers in the presence or absence of ether. At concentrations up to 2 vol % ether, hemolysis of erythrocytes was negligible, and the spectroscopic changes observed were completely reversed following its removal. Km, Vmax, and Eact. for sulfate uptake into chloride-loaded erythrocytes were not significantly affected by addition of ether.(ABSTRACT TRUNCATED AT 250 WORDS)

Anion Exchange Protein 1, Erythrocyte↗
PubMed1982

The anion transport protein of the red cell membrane. A zipper mechanism of anion exchange.

The anion exchange system of the red cell membrane resides in an integral membrane protein with a molecular mass of approximately 10(5) daltons. We report on the identification of the transport system by means of covalently binding stilbene-disulfonates. We further describe the gross molecular arrangement of the polypeptide in the membrane, as well as recent attempts to identify functionally essential amino acid side chains in the transport system. The presence of a large number of charged amino acid residues in the intramembrane segments of the protein forms the basis of a zipper model of anion exchange. The zipper is closed by salt bridges between oppositely charged residues, which mediate the anion exchange diffusion through minor conformational changes. Salt bridge gates, which are arranged in series through the permeation pathway, function in the exchange mode, because a permeating anion switches the orientation of the charges of the salt bridge between alternative positions. The energy barriers to permeation are thus altered by the passage of a mobile anion. The shift in the relative positions of the charges in the salt bridges implies that anions are admitted alternatingly from the two ends of the salt bridge array.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1998

Expression of cation exchanger NHE and anion exchanger AE isoforms in primary human bone-derived osteoblasts.

The authors used isoform-specific antibodies against cation (NHE) and anion (AE) exchange isoforms in order to establish their specific expression and localization in dispersed human bone-derived cells. Immunocytochemical preparations of permeabilized osteoblasts probed with polyclonal antibodies were optically analysed by conventional immunofluorescence and con-focal laser scanning microscopy. These techniques demonstrated the abundant presence of epitopes of the cation exchangers NHE1 and NHE3 and the anion exchanger AE2 in these cells. The NHE1 and NHE3 isoform proteins were predominantly located in subplasmalemmal and nucleoplasmic vesicles. The AE2 isoform was densely localized to a subcellular location characteristic of the Golgi complex. The molecular identity of the AE and NHE isoforms was investigated by RT-PCR that confirmed the presence of NHE1 and NHE3 transcripts in addition to NHE4. RT-PCR and diagnostic restriction analysis of amplified AE cDNA established preferential AE2 expression. Since AE2 has been shown to act as a sulfate transporter at low pH, it is possible that it performs this function in the osteoblast Golgi complex where sulfation reactions occur post-translationally on numerous extracellular matrix macromolecules prior to secretion and mineralization. The Na(+)/H(+)exchanger proteins are regulated by mitogenic and non-mitogenic stimuli in the osseus environment and are involved in the large fluxes of ions and protons that necessarily occur during bone formation and resorption and thus play an important role in intracellular ion homeostasis in osteoblasts.

Alkaline Phosphatase↗
PubMedDate not supplied

The purification of oligodeoxyribonucleotides with a high guanosine content by anion exchange HPLC.

Anion exchange HPLC purification of synthetic oligonucleotides with a high guanosine content is difficult. This study has demonstrated that these sequences can be successfully purified by anion exchange HPLC using standard conditions provided that the base protecting groups (isobutyryl[ib] and benzoyl[bz]) are retained on the otherwise deprotected oligomer.

Chromatography, High Pressure Liquid↗
PubMed1988

The development of colonic transport mechanisms in early life: evidence for reduced anion exchange.

An anion exchange mechanism exists in colonic mucosa whereby chloride is absorbed and bicarbonate secreted. Using an in vivo non-equilibrium dialysis method we investigated rectal electrolyte movement in preterm neonates and older children. Our results show that anion exchange is poorly developed in infancy and appears to be absent in premature neonates, and suggest that complete maturation of this mechanism is not present until the end of the first year of life. This may render the young infant, and more especially the preterm infant, more susceptible to chloride depletion.

Bicarbonates↗
PubMed1982

Anion exchange and anion-cation co-transport systems in mammalian cells.

Electroneutral anion transfer in the Ehrlich ascites tumour cell has been found to occur by two separate mechanisms. One is an exchange diffusion system with many similarities to that found in erythrocytes, e.g. saturation kinetics with 'self-inhibition', a relatively pronounced temperature dependence, competitive interactions of Br-, NO3- and SCN-, and a low conductive PCl- of 4 x 10(-8) cm s-1. The main differences are that the Cl- flux in Ehrlich cells at 38 degrees C is one thousandth of the flux in red cells, and that the specificity of the system is less pronounced. It is suggested that the density of anion exchange sites in Ehrlich cells could be the same as in red blood cells, but with a lower turnover rate. The other system is an anion-cation co-transport system capable of mediating a secondary active Cl- influx. This system has a volume-regulatory function and is activated by a reduction in cell volume and intracellular [Cl-]. The two transport systems can be separated by using DIDS as an inhibitor of anion exchange and bumetanide as an inhibitor of co-transport. Under normal steady-state conditions Cl- flux is dominated by the exchange system. It is suggested that intracellular pH regulation can be achieved by the two systems operating in parallel, because the chloride disequilibrium maintained by the co-transport system can drive an influx of bicarbonate through the exchange mechanism.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMedDate not supplied

Membrane integration and topology of the first transmembrane segment in normal and Southeast Asian ovalocytosis human erythrocyte anion exchanger 1.

Anion exchanger 1 (AE1, or Band 3) is an integral membrane glycoprotein found in erythrocytes, responsible for the electroneutral exchange of chloride and bicarbonate ions across the plasma membrane. Southeast Asian ovalocytosis (SAO) results from a nine-amino acid deletion in the first transmembrane segment (TM) of the AE1 protein that abolishes its transport function. The effects of the SAO deletion on: (1) the efficiency of integration of TM1 into the membrane, and (2) the precise positioning of TM1 relative to the membrane were investigated using scanning N-glycosylation mutagenesis in a cell-free transcription/translation system and in transfected HEK293 cells. AE1 or SAO constructs containing either the endogenous N-glycosylation site at Asn642 in extracellular loop 4 (EC4) or single N-glycosylation sites engineered into an expanded extracellular loop 1 (EC1) were used. N-glycosylation efficiency of EC1 in the SAO construct was significantly lower than that of the AE1 construct, indicating that the SAO deletion impairs membrane integration of TM1 and the translocation of EC1 across the membrane. Scanning N-glycosylation mapping of EC1 in the cell-free system and in transfected cells showed that the C-terminus of both AE1 and SAO TM1 were at the same position relative to the membrane. Thus, the SAO deletion is likely to cause a pulling-in of the polar amino acid sequence immediately N-terminal to the deletion into the lipid bilayer, allowing SAO TM1 that was inserted to assume a transmembrane disposition.

Amino Acid Sequence↗
PubMed2004

Demonstration of simultaneous anion-exchange and reversed-phase behavior on a strong anion-exchange column.

We demonstrate in this report that a conventional silica-based strong anion-exchange column can exhibit reversed-phase chromatographic behavior simultaneously with ion-exchange in a methanol-aqueous phthalate mobile phase. Reversed-phase behavior is shown for PAHs in relatively high methanol-content mobile phases, while polar organics exhibit reversed-phase behavior in 0-10% (v/v) methanol-water eluents. At low concentrations (0-10% v/v) methanol has little or no effect on anion retention, while the anions exhibit only slight increases in retention in 60-80% (v/v) methanol at near-neutral pH values. Likewise, pH changes used to manipulate anion retention have essentially no effect on PAH retention, and cause only small decreases in retention for most of the polar organics studied. Little or no pH-effect was seen on a phenyl column (no exchange group) or with acetate mobile phase. It is shown that manipulation of pH and methanol content allows the grouping of neutral organic analytes early in a chromatogram, followed by the anions, with no class overlap. Several example chromatograms are given, including that of a red wine sample. Column efficiency was good for anions but only modest for organics.

Chromatography, Ion Exchange↗
PubMed1992

Selective protein separations using Formed-In-Place anion exchange membranes.

Anion exchange membranes prepared by adsorption of polymers on Formed-In-Place microfiltration substrates were formed and ion-exchange separations of solutions containing two proteins were determined by ion exchange membrane sequential separation procedures, similar to affinity membrane separation procedures. Representative ion exchange separation processes utilizing adsorbed poly(ethylene imine) (PEI) as the ion exchange membrane for the separation of the components of solutions containing two proteins, bovine serum albumin (BSA) and lysozyme and ovalbumin and lysozyme, are described. The stability of the PEI adsorbed layer, binding characteristics of the BSA to the membrane and purification properties of the procedure were determined.

Adsorption↗
PubMed2005

Gestational profile of Na+/H+ exchanger and Cl-/HCO3- anion exchanger mRNA expression in placenta using real-time QPCR.

The onset of maternal blood flow (10-12 weeks gestation) results in increased oxygenation of the placenta. We investigated whether the expressions of Na+/H+ exchanger (NHE) and Cl-/HCO3- anion exchanger (AE), thought to have an important role in maintaining intracellular pH of the syncytiotrophoblast and fetal pH homeostasis, are altered at the same time as this increase in blood flow. Real-time quantitative PCR was used to examine steady state levels of NHE (NHE1, 2, 3) and AE (AE1, 2) mRNA expression in early (6-9 weeks) and late (10-13 weeks) first trimester and full-term (38-40 weeks) placentas. beta-Actin, IF2B and GAPDH mRNA was also measured. None of the genes showed a significant difference in expression between the early and late first trimester groups. However, NHE2 (p < 0.001) and GAPDH (p < 0.05) mRNA expression significantly increased 18- and 3.7-fold between early first trimester and term. In conclusion, this study provides additional evidence that GAPDH is an unsuitable housekeeping gene for normalization of transcript levels in placenta. The expression of NHE and AE in the villous placenta is not altered concomitant with the onset of maternal blood flow. However, NHE2 transcripts appear to be gestationally regulated, which may contribute to changes in NHE activity.

Adult↗
PubMed2000

Comparison of chromatographic ion-exchange resins. I. Strong anion-exchange resins.

A comparative study has been undertaken on various strong anion-exchangers to investigate the pH dependence, titration curves, efficiency, binding strength, and dynamic capacity of the chromatographic resins. The resins tested included: Macro-Prep 25Q, TSK-Gel Q-5PW-HR, Poros QE/M, Q Sepharose FF, Q HyperD 20, Q Zirconia, Source 30Q, Fractogel EMD TMAE 650s, and Express-Ion Q. Testing was performed with five different proteins: Anti-FVII Mab (IgG), aprotinin, BSA, lipolase, and myoglobin. The dependence of pH on retention varies from generally low to very high for proteins with low pI. No direct link between pH dependence on retention and titration curves of the different resins was observed. Efficiency results show the expected trend of lower dependence of the plate height with increasing flow-rate of resins for medium and high pressure operation compared to the soft resins. Binding to the anion-exchange resins as a function of ionic strength may vary depending on the specific protein. Generally, binding and elution at a high salt concentration may be performed with Poros QE/M or Macro-Prep 25Q, while binding and elution at low salt concentration may be done with TSK-Gel Q-5PW. Dynamic capacities are strongly dependent on the specific protein employed and for some resins dependent on the flow-rate. A general good agreement was obtained between this study and data obtained by suppliers for the dynamic capacity. The results of this study may be used for selection of resins for testing in process development, however, the data does not tell anything about specific selectivity differences or resolution between a target protein and a given impurity. None of the resins studied here should be regarded as good or bad, but more or less suitable for a specific purpose, and only testing for the specific application will determine which one is the optimal resin.

Anion Exchange Resins↗
PubMed2005

Control of oligonucleotide retention on a pH-stabilized strong anion exchange column.

Strong anion exchange columns are preferred for oligonucleotide analyses due to their ability to effectively control secondary structure and poly(G) interactions. Methacrylate-based anion exchange phases minimize hydrophobic interactions with oligonucleotides, but they also tend to hydrolyze under alkaline conditions. In this article, we report the use of an anion exchange column prepared from a new class of methacrylate monomers designed to improve hydrolytic stability. This column is used to show predictable adjustment of oligonucleotide retention by eluent pH and composition. Features of the new column include (i) large, predictable, pH-dependent retention shifts (varying with specific changes in 5' or 3' terminal bases with NaCl-based eluents); (ii) reduced retention when solvent is added to NaCl-based eluents; and (iii) suppression of much of the column's hydrophobic interactions when CH3CN is used with NaClO4-based eluents at a neutral pH (i.e., this eluent system separates oligonucleotides primarily in order of their length). These observations will aid the development of elution conditions for both size-dependent and base sequence-dependent (or base composition-dependent) separations.

Chromatography, Ion Exchange↗
PubMed2000

Molecular characterization of anion exchangers in the cochlea.

Anion exchange proteins (AE) in the inner ear have been the focus of attention for some time. They have been suggested to play a role as anion exchangers for the regulation of endolymphatic pH or as anion exchangers and anchor proteins for the maintenance of the shape and turgor of outer hair cells, and they also have been discussed as a candidate protein for motile hair cell responses that follow high-frequency stimulation. The existence of anion exchangers in hair cells and the specific isoforms which are expressed in hair cells and the organ of Corti is controversial. Using a polyclonal antibody to AE1 (AB 1992, Chemicon), we immunoprecipitated a 100 kDa AE polypeptide in isolated outer hair cells which, due to its glycosylation, is comprised of AE2 than AE1 isoforms. We confirmed AE2 expression in outer hair cells with the help of subtype-specific monoclonal and polyclonal antibodies to AE, AE subtype-specific primers and AE subtype-specific cDNA and found glycosylated truncated as well as full-length AE2 isoforms. No AE1 or AE3 subtypes were noted in outer hair cells. In contrast, AE2 and AE3 but not AE1 subtypes were seen in supporting cells of the organ of Corti. Their expression preceded the development of cochlear function, coincident with the establishment of the endocochlear potential and the differentiation of supporting cells. While most developmental processes in the inner ear usually begin in the basal cochlear turn, the AE2 expression in outer hair cells (but not that of AE2 and AE3 in supporting cells) progressed from the apical to the basal cochlear turn, reminiscent of the maturation of frequency-dependency. Irrespective of their presumed individual role as either anion exchanger, anchor protein or motility protein, the differential expression and developmental profile of these proteins suggest a most important role of anion exchange proteins in the development of normal hearing. These findings may also provide novel insights into AE function in general.

Animals↗
PubMed1994

High-performance anion exchange of small anions with polyethyleneimine-coated porous zirconia.

The preparation and chromatographic characterization of an ion-exchange high-performance liquid chromatographic support by deposition and crosslinking of polyethyleneimine (PEI) on the surface of porous zirconia is described. Adsorption and evaporation methods were used for coating PEI onto the zirconia particles. These two stationary phases were compared by elemental analysis, ion-exchange capacity and by chromatography. High efficiency and good selectivity were observed for inorganic and organic anions. The addition of a strong, hard Lewis base to the mobile phase dramatically improved the peak shape and efficiency of para benzoic acid derivatives. PEI-coated zirconia showed a distinct elution sequence for organic anions when compared to bare zirconia or silica-based phases. The polyamine coated zirconia was stable over a pH range from 2.75 to 9. Flow studies, using nitrite as a probe solute, showed that both coating procedures produced packed columns with good mass-transfer properties.

Anions↗