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PubMedDate not supplied

Ion-exchange liquid chromatographic determination of nitrate and nitrite in biological fluids.

A rapid, ion-exchange liquid chromatographic method for the determination of nitrate and nitrite in biological fluids is presented. Samples are deproteinated by ultrafiltration followed by removal of chloride using a silver form cation-exchange resin. Nitrate and nitrite are measured by ion-exchange liquid chromatography with conductivity detection. Recoveries from serum, ocular fluid, and water were determined for fortifications from 10 to 150 mg/L. Average recoveries ranged from 96 to 104% for nitrate and from 89 to 105% for nitrite. Pooled RSD values ranged between 1.5 and 1.9% for these analytes in all matrixes examined. The method of joint confidence hexagons was applied to the data to determine constant and relative bias of the method for each of the 3 matrixes in the study.

Animals↗
PubMed1985

Ion-exchange high-performance liquid chromatographic purification of bovine cardiac and rabbit skeletal muscle troponin subunits.

Bovine cardiac and rabbit skeletal troponin complexes were separated into their respective subunits employing high-performance liquid chromatographic (HPLC) techniques on CM-300 and Q-300 ion-exchangers. Bovine cardiac and rabbit skeletal subunits were separated on the strong anion-exchanger, Q-300, in 8 M urea, 50 mM Tris, 2 mM EGTA, 0.5 mM dithiothreitol, pH 7.5, employing a linear salt gradient and on the weak cation-exchanger, CM-300, in 8 M urea, 50 mM potassium dihydrogen phosphate, 2 mM EGTA, 0.5 mM dithiothreitol, pH 6.5, using a linear salt gradient. To obtain complete purification of all components of troponin both ion-exchangers were required. The initial separation of troponin was carried out on the strong anion-exchanger followed by weak cation-exchange chromatography of the troponin I collected from the strong anion-exchange column. The troponin T subunits obtained from Q-300 chromatography demonstrated heterogeneity (three components: T1, T2 and T3) while the troponin I collected from both sources on the Q-300 column were both resolved into major doublets (I1 and I2) when rechromatographed on the CM-300 column. The three troponin T fractions and two troponin I fractions isolated from ion-exchange HPLC were examined by sodium dodecyl sulfate-urea polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis to confirm that the heterogeneity was due to differences in charge and not molecular weight. These results were in agreement with the charge differences observed from retention times on ion-exchange HPLC. When comparing the same troponin subunit from different muscle sources, considerable differences in the content of charged amino acid residues were also observed.

Animals↗
PubMed2000

Controlled transdermal iontophoresis by ion-exchange fiber.

The objective of this study was to assess the transdermal delivery of drugs using iontophoresis with cation- and anion-exchange fibers as controlled drug delivery vehicles. Complexation of charged model drugs with the ion-exchange fibers was studied as a method to achieve controlled transdermal drug delivery. Drug release from the cation-exchange fiber into a physiological saline was dependent on the lipophilicity of the drug. The release rates of lipophilic tacrine and propranolol were significantly slower than that of hydrophilic nadolol. Permeation of tacrine across the skin was directly related to the iontophoretic current density and drug concentration used. Anion-exchange fiber was tested with anionic sodium salicylate. The iontophoretic flux enhancement of sodium salicylate from the fiber was substantial. As the drug has to be released from the ion-exchange fiber before permeating across the skin, a clear reduction in the drug fluxes from the cationic and anionic fibers were observed compared to the respective fluxes of the drugs in solution. Overall, the ion-exchange fibers act as a drug reservoir, controlling the release and iontophoretic transdermal delivery of the drug.

Administration, Cutaneous↗
PubMed2006

Environmentally benign hardness removal using ion-exchange fibers and snowmelt.

Many industrial unit operations and unit processes require near-complete removal of hardness to avoid scaling in heat-transfer equipment, fouling in membranes, and high consumption of detergents and sequestering chemicals in cooling and wash water. Lime softening and cation exchange are the most commonly used processes practiced to date for hardness removal. Herein, we report and discuss the results and attributes of a new hardness removal process using ion-exchange fibers (IX-fibers). Most importantly, the process uses harvested snowmelt (or rainwater) as the regenerant chemical along with sparged carbon dioxide. Consequently, the spent regenerant does not contain a high concentration of aggressive chemicals such as sodium chloride or acid like traditional ion-exchange processes nor does the process produce voluminous sludges similar to lime softening. The bulk of carbon dioxide consumed during regeneration remains sequestered in the aqueous phase as alkalinity. IX-fibers form the heart of the process. They are essentially thin cylindrical polymeric strands 10-20 microm in diameter. The weak-acid carboxylate functional groups reside near to the surface of these cylindrical fibers. Low intraparticle diffusional resistance is the underlying reason IX-fibers are amenable to efficient regeneration with snowmelt sparged with carbon dioxide. When the carbon dioxide partial pressure is increased to 6.8 atm, over 90% calcium desorption efficiency is obtained. On the contrary, commercial weak-acid ion-exchange resins in spherical bead forms are ineffective for regeneration with carbon-dioxide-sparged snowmelt due to extremely slow ion-exchange kinetics involving counter-transport of Ca2+ and H+.

Acids, Noncarboxylic↗
PubMedDate not supplied

Development of an spFRET method to measure structure changes in ion exchange proteins.

AIM: Understanding the mechanism of tightly coupled ion exchange proteins, important effectors of cell volume regulation and other physiologically important transport processes requires means to observe dynamic changes in structure during the transport cycle. As a step towards this goal, we have applied single-pair fluorescence resonance energy transfer to a monomeric bacterial oxalate-formate exchanger (OxlT). METHODS: A His-9 tagged OxlT mutant containing two cysteines at positions 17 and 224 was labelled with cyanine dye maleimides (Cy3 donor and Cy5 acceptor) and attached to glass coverslips for measurements of donor and acceptor emission from single molecules, as described (P. Pal et al. Biophys J89, L11, 2005). RESULTS: Time-series data from 20 spots containing donor and acceptor provided evidence for single-pair energy transfer. From the efficiency of energy transfer, the mean donor-acceptor distance was determined to be 44.2 A. Considering the size of the probes, this is in good agreement with the Calpha distance of 39.6 A for the corresponding sites found in the OxlT structural (homology) model (Q. Yang et al. Proc Natl Acad Sci102, 8513, 2005). CONCLUSION: These results demonstrate the feasibility of single-pair fluorescence resonance energy transfer to measure distances between known sites in single OxlT molecules. This technique provides a potential means to test models for transport-related conformational changes, as well as to detect real-time structure alterations during the catalytic transport cycle.

Carbocyanines↗
PubMed2002

[Study on dynamic adsorption of HF gas by ion-exchange fiber].

The dynamic adsorption capacity of HF gas utilizing domestic FA-weak basic ion-exchange fiber as adsorbent is studied. Also, the factors influencing dynamic adsorption are investigated and the re-adsorption effect of HF gas is tested. The results showed that the pierce through adsorption amount of HF by ion-exchange fiber is 75 mg/g, and the saturated adsorption amount of HF by the fiber is 152 mg/g. There is no obvious change in adsorption effect after a repeated 5-run regeneration of the fiber, showing its good chemical stability.

Adsorption↗
PubMed1990

Amino acid analysis of physiological fluids by high-performance liquid chromatography with phenylisothiocyanate derivatization and comparison with ion-exchange chromatography.

The suitability of pre-column derivatization with phenylisothiocyanate followed by high-performance liquid chromatography was investigated as a means of analyzing free amino acids in plasma and other physiological fluids. A comparison was made between this method and a conventional ion-exchange method. The correlation coefficient for all the amino acids tested was greater than 0.9, except for proline and tryptophan. Various forms of sample preparation were tried for plasma and amniotic fluid; it was finally decided that protein precipitation with acetonitrile was most suitable. Ultrafiltration was used for cerebrospinal fluid preparation while urine was treated the same as a standard mixture. The retention times relative to the internal standard (nor-leucine) are given for over 90 compounds. Some of these were chromatographed underivatized because they are known to be present in some physiological fluids and absorb at 254 nm because of their aromaticity. The imprecision for this method compared favourably with the standard ion-exchange method although each had specific amino acids for which the imprecision was poor. The technique is suitable for the same routine clinical analysis purposes as high-resolution ion-exchange chromatography. It also offers the advantages of speed of analysis, sensitivity and equipment versatility over the conventional ion-exchange methods.

Amino Acids↗
PubMed2005

Disease-associated changes in the expression of ion channels, ion receptors, ion exchangers and Ca(2+)-handling proteins in heart hypertrophy.

The molecular pathology of cardiac hypertrophy is multifactorial with transcript regulation of ion channels, ion exchangers and Ca(2+)-handling proteins being speculative. We therefore investigated disease-associated changes in gene expression of various ion channels and their receptors as well as ion exchangers, cytoskeletal proteins and Ca(2+)-handling proteins in normotensive and spontaneously hypertensive (SHR) rats. We also compared experimental findings with results from hypertrophic human hearts, previously published (Borlak, J., and Thum, T., 2003. Hallmarks of ion channel gene expression in end-stage heart failure. FASEB J. 17, 1592-1608). We observed significant (P < 0.05) induction in transcript level of ATP-driven ion exchangers (Atp1A1, NCX-1, SERCA2a), ion channels (L-type Ca(2+)-channel, K(ir)3.4, Na(v)1.5) and RyR-2 in hypertrophic hearts, while gene expression was repressed in diseased human hearts. Further, the genes coding for calreticulin and calmodulin, PMCA 1 and 4 as well as alpha-skeletal actin were significantly (P < 0.05) changed in hypertrophic human heart, but were unchanged in hypertrophic left ventricles of the rat heart. Notably, transcript level of alpha- and beta-MHC, calsequestrin, K(ir)6.1 (in the right ventricle only), phospholamban as well as troponin T were repressed in both diseased human and rat hearts. Our study enabled an identification of disease-associated candidate genes. Their regulation is likely to be the result of an imbalance between pressure load/stretch force and vascular tonus and the observed changes may provide a rational for the rhythm disturbances observed in patients with cardiac hypertrophy.

Animals↗
PubMed2001

Ion-exchange chromatography by dicarboxyl cellulose gel.

A new column packing material for ion-exchange chromatography was prepared from cellulose gel by periodate oxidation followed by chlorite oxidation to form spatially paired carboxyl groups (dicarboxyl cellulose, DCC). The carboxyl group was quantitatively introduced to spherical cellulose gel by controlling the extent of oxidation. The DCC gels were examined for their ion-exchange activity for various amines at pH of 2.5-5.5. In this pH range, aromatic amines with acid dissociation constant (pKa) below 2.7 showed no interaction with DCC gels as expected from their lack of protonation. The amines with pKa greater than 3.3, both aromatic and aliphatic, showed strong interaction corresponding to the amount of carboxyl introduced to the gel. However, these amines showed anomalous dependence on pH of the mobile phase, showing a maximum in retention factor at around pH 4. This is in contrast with the nearly constant retention factor of these amines on conventional carboxylated cellulose packing at pH greater than 4.0. The maximum retention factor at pH 4 of DCC gel was 4-5-times greater than that of conventional gel having a similar amount of carboxyls. Since pKa of dicarboxyl groups ranges 3-5 as determined by acid-base titration, the pH giving maximum retention corresponds to the pH at which one of paired carboxyls is dissociated. Possible cause of this anomaly is presented in terms of dissociation state of dicarboxyl groups and its interaction with amines.

Calibration↗
PubMed1991

Protein separations on tentacle ion exchangers.

This study was undertaken to introduce new tentacle ion exchange materials to the biochromatographer. The differences in the bioseparation media have been shown with a four-component protein mixture. By controlling the sample loading and the flow rate, each material can be made to perform satisfactorily, according to the demands of the biochromatographer, whether for high resolution or high sample capacity. The controlled manufacturing techniques of the Fractogel and LiChrospher DEAE materials make any analytical or process separations equivalent and reproducible. When even higher capacities are required, the biochromatographer need only use the wider diameter Superformance glass columns packed with the equivalent Fractogel.

Chromatography, Ion Exchange↗
PubMed1989

Histamine selective microelectrode based on a synthetic organic liquid ion exchanger.

A two-barrel organic ion-sensitive microelectrode has been developed to electrochemically detect histamine activity. The synthesis of the histamine-sensitive liquid ion exchanger, composed of tetrafluorophenylboron histamine plus 3-nitro-o-xylol, and the construction of the two-barrel microelectrode (0.1-0.5 micron tip diameter) sensitive to histamine based on such an exchanger is reported. The calibration curves, their slope, selectivity, stability and detection limits for different solutions are described. High selectivity for Na+, K+, Ca2+ was observed.

Biosensing Techniques↗