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Ion Exchangers (ion + exchanger)
Selected AbstractsNa+/H+ exchangers and the regulation of volumeACTA PHYSIOLOGICA, Issue 1-2 2006R. T. Alexander Abstract The regulation of volume is fundamental to life. There exist numerous conditions that can produce perturbations of cell volume. The cell has developed mechanisms to directly counteract these perturbations so as to maintain its physiological volume. Directed influx of the major extracellular cation, sodium, serves to counteract a decreased cell volume through the subsequent osmotically coupled movement of water to the intracellular space. This process, termed regulatory volume increase is often mediated by the ubiquitous sodium/hydrogen ion exchanger, NHE1. Similarly, the maintenance of intravascular volume is essential for the maintenance of blood pressure and consequently the proper perfusion of vital organs. Numerous mechanisms exist to counterbalance alterations in intravascular volume, not the least of which is the renal absorption of sodium filtered at the glomerulus. Two-thirds of filtered sodium and water are absorbed in the renal proximal tubule, a mechanism that intimately involves the apical sodium/hydrogen ion exchanger, NHE3. This isoform is fundamental to the maintenance and regulation of intravascular volume and blood pressure. In this article, the effects of cell volume on the activity of these different isoforms, NHE1 and NHE3, will be described and the consequences of their activity on intracellular and intravascular volume will be explored. [source] Surface-enhanced Raman scattering from analytes adsorbed on gold nanoparticles inside polymer beadsJOURNAL OF RAMAN SPECTROSCOPY, Issue 10 2004Mina Larsson Abstract Porous polymer beads with a large inner area were used as a stabilizing matrix for SERS-active gold particles. A commercially available ion exchanger (SOURCETM) was used together with HAuCl4. Absorbance measurements and an x-ray diffraction study confirmed that nanocrystalline gold was obtained in the polymer beads. Transmission electron microscope measurements were performed and showed that larger nanoparticles, 20,100 nm, were obtained on the surface, whereas in the interior smaller particles, approximately 2,10 nm, could be found. Three analytes, mercaptoethanesulfonate, mercaptopropionic acid and thiocyanate, were adsorbed on the gold particles inside the polymer beads. From all analytes enhanced Raman spectra could be obtained. The distribution of analytes adsorbed on gold nanoparticles was investigated by confocal Raman spectroscopy. SERS spectra from the analytes could be observed throughout the polymer bead, indicating a fairly uniform distribution of analytes adsorbed on gold nanoparticles. Copyright © 2004 John Wiley & Sons, Ltd. [source] Photooxidations of phenol, cyclopentadiene and citronellol with photosensitizers ionically bound at a polymeric ion exchanger,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3-4 2001Robert Gerdes Abstract Different metal tetrasulfophthalocyanines and rose bengal were employed as photosensitizers in the photooxidation of phenol, cyclopentadiene and (S)-(,)-citronellol. Ionically polymer bound photosensitizers were easily obtained by the reaction of negatively charged low-molecular-weight phthalocyanines with the strong basic anion exchanger Amberlite® IRA 400. The activities of the low-molecular-weight and the polymer systems are compared. Especially immobilized phthalocyanines which exhibit the advantages of good activity, as well as stability against photobleaching, and can be used repeatedly. Copyright © 2001 John Wiley & Sons, Ltd. [source] Na+/Ca2+ exchanger modulates the flagellar wave pattern for the regulation of motility activation and chemotaxis in the ascidian spermatozoaCYTOSKELETON, Issue 10 2006Kogiku Shiba Abstract Ion channels and ion exchangers are known to be important participants in various aspects of sperm physiology, e.g. motility activation, chemotaxis, the maintenance of motility and the acrosome reaction in the sperm. We report here on a role of the K+ -independent Na+/Ca2+ exchanger (NCX) on ascidian sperm. Reverse-transcriptase PCR reveals that the NCX is expressed in the testis while immunoblotting and immunolocalization demonstrate that the NCX exists on the sperm in the ascidian Ciona savignyi and C. intestinalis. A potent blocker of the NCX, KB-R7943 was found to block sperm-activating and -attracting factor (SAAF)-induced motility activation, sperm motility and sperm chemotaxis. We further analyzed the effects of this blocker on motility parameters such as the flagellar waveform, curvature, beat frequency, amplitude and wavelength of the sperm flagella. Inhibition of the NCX caused two distinct effects: a low concentration of KB-R7943 induced symmetric bending, whereas a high concentration of KB-R7943 resulted in asymmetric flagellar bending. These findings suggest that the NCX plays important roles in the regulation of SAAF-induced sperm chemotaxis, motility activation and motility maintenance in the ascidian. This study provides new information toward an understanding of Ca2+ transport systems in sperm motility and chemotaxis. Cell Motil. Cytoskeleton 2006. © 2006 Wiley-Liss, Inc. [source] Defective regulation of cholangiocyte Cl,/HCO,3 and Na+/H+ exchanger activities in primary biliary cirrhosisHEPATOLOGY, Issue 6 2002Saida Melero Primary biliary cirrhosis (PBC) is a disorder of unknown origin with autoimmune features. Recently, impaired biliary secretion of bicarbonate has been shown in patients with PBC. Here we have investigated whether bile duct epithelial cells isolated from PBC patients exhibit defects in transepithelial bicarbonate transport by analyzing the activities of 2 ion exchangers, Cl,/HCO,3 anion exchanger 2 (AE2) and Na+/H+ exchanger (NHE) in isolated cholangiocytes. AE2 and NHE activities were studied in basal conditions and after stimulation with cyclic adenosine monophosphate (cAMP) and extracellular adenosine triphosphate (ATP), respectively. Cholangiocytes were grown from needle liver biopsies from 12 PBC patients, 8 normal controls, and 9 patients with other liver diseases. Also, intrahepatic cholangiocytes were cultured after immunomagnetic isolation from normal liver tissue (n = 6), and from recipients undergoing liver transplantation for end-stage PBC (n = 9) and other forms of liver disease (n = 8). In needle-biopsy cholangiocytes, basal AE2 activity was significantly decreased in PBC as compared with normal livers and disease controls. In addition, we observed that though cAMP increased AE2 activity in cholangiocytes from both normal and non-PBC livers, this effect was absent in PBC cholangiocytes. Similarly, though in cholangiocytes from normal and disease control livers extracellular ATP induced a marked enhancement of NHE activity, cholangiocytes from PBC patients failed to respond to purinergic stimulation. In conclusion, our findings provide functional evidence that PBC cholangiocytes exhibit a widespread failure in the regulation of carriers involved in transepithelial H+/HCO,3 transport, thus, providing a molecular basis for the impaired bicarbonate secretion in this cholestatic syndrome. [source] Colloid deposition experiments as a diagnostic tool for biomass attachment onto bioproduct adsorbent surfacesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2008Canan Tari Abstract BACKGROUND: Detrimental processing conditions can be expected in any downstream operation where direct contacting between a crude feedstock and a reactive solid phase is supposed to occur. In this paper we have investigated the factors influencing intact yeast cells deposition onto anion and cation exchangers currently utilized for expanded-bed adsorption of biotechnological products. The aim of this study was twofold: (a) to confirm previous findings relating biomass deposition with surface energetics according to the extended Derjaguin, Landau, Verwey and Overbeek theory (XDLVO) theory; and (b) to provide a simple experimental tool to evaluate biomass deposition onto process surfaces. RESULTS:Biomass deposition experiments were performed on an automated workstation utilizing a packed-bed format. Two commercial ion exchangers intended for the direct capture of bioproducts in the presence of suspended biological particles were employed. Intact yeast cells in the late exponential phase of growth were selected as model bio-colloids. Cell deposition was systematically evaluated as a function of fluid-phase conductivity and quantitatively expressed as a biomass deposition parameter (,). CONCLUSION: , ,0.15 was established as a criterion to reflect negligible biomass adhesion to the process support(s). Biomass deposition experiments further confirmed predictions made on the basis of free interfacial energy calculations as per the extended DLVO approach. Copyright © 2008 Society of Chemical Industry [source] Tailoring orthogonal proteomic routines to understand protein separation during ion exchange chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2008Rosa Cabrera Abstract Surface charge, molecular weight, and folding state are known to influence protein chromatographic behaviour onto ion exchangers. Experimentally, information related to such factors can be gathered via 2-DE methods. The application of 2-D PAGE under denaturing/reducing conditions was already shown to reveal separation trends within a large protein population from cell extracts. However, ion-exchange chromatography normally runs under native conditions. A tailored protocol consisting in a first separation based on IEF on ImmobilineTM strips under native conditions followed by a second dimension SDS-PAGE run was adopted. The chromatographic versus electrophoretic separation behaviours of two model proteins, thaumatin (TAU) and BSA, were compared to better understand which proteomic routine would be better suited to anticipate IEX chromatographic separations. It was observed that the information contained in the pI value obtained with the adapted 2-DE protocol showed better correlation with the IEX chromatographic behaviour. On the other hand, chromatographic separations performed in the presence of urea as a denaturant have demonstrated the potential influence of hydrodynamic radius/conformation on protein separation. Moreover, the information provided by such 2-D system correlated well with the chromatographic behaviour of an additional set of pure proteins. An initial prediction of protein ion-exchange chromatographic behaviour could be possible utilizing an experimental approach based on 2-DE running under milder chemical conditions. This technique provides information that more closely resembles the separation behaviour observed with a complex biotechnological feedstock. [source] Organic ion exchangers as beads.POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 7-8 2006Synthesis, applications, characterization Abstract Two less explored strategies in the preparation of porous organic ion exchangers in bead form are presented in this paper: the preparation of macroporous strong base anion exchangers with N,N -diethyl-2-hydroxyethyl benzylammonium chloride units, a less explored chloromethylation reagent of the styrene-divinylbenzene copolymers being used, and the preparation of anion exchangers with primary amine groups by the aminolysis-hydrolysis reaction with 1,2-diaminoethane of the nitrile groups, contained in some porous copolymers of acrylonitrile-divinylbenzene, followed by the carboxymethylation of the primary amine groups to prepare chelating ion exchangers. The influence of porogen nature, monomers dilution and crosslinking degree on the properties of the ion exchangers was examined. Structural characterization, functionalization-morphology correlations, the ion exchange properties, and potential applications for the ion exchangers thus prepared have been discussed. Copyright © 2006 John Wiley & Sons, Ltd. [source] Purification of homogeneous forms of fungal peroxygenaseBIOTECHNOLOGY JOURNAL, Issue 11 2009René Ullrich Abstract Extracellular peroxygenase from the agaric fungus Agrocybe aegerita is a versatile biocatalyst that oxygenates various substrates by means of hydrogen peroxide. The enzyme is routinely produced in suspensions of soybean meal and has until now been purified by several steps of fast protein liquid chromatography (FPLC) using different ion exchangers. The final protein fraction had a molecular mass of 46 kDa but still consisted of several incompletely separated proteins with slightly differing isoelectric points (pI 5.2, 5.6, 6.1), probably representing differently glycosylated isoforms. This made it difficult to further purify the individual protein forms. Since homogeneous protein fractions are a pre-requisite for X-ray crystallography and specific structure-function studies, an appropriate FPLC procedure was developed starting with pre-purification of crude peroxygenase on SP Sepharose followed by chromatofocusing on a Mono P column and elution with a pH gradient. Three sufficiently separated main protein peaks were eluted from the Mono P column and confirmed to be distinct forms of aromatic peroxygenase with different pIs. All A. aegerita peroxygenase forms oxygenated toluene and naphthalene and no catalytic differences were observed between them. We tested also two devices for preparative isoelectric focusing (Rotofor, IsoPrime systems) for peroxygenase separation but resolution and protein recovery were not sufficient. [source] | |||||||||||||