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Combined application of ion implantation and ion exchange treatment is described for the formation of monomode KTiOP[O.sub.4] waveguide. The results have shown that the lattice damages formed by ion implantation have acted as a diffusion barrier, which has stopped the Rb ion and K ion exchange in the deeper depth.

The structural analysis of cytosolic domain (cdAE1), cytosolic domain kidney anion exchanger 1 (cdkAE1), and novel truncation mutant cd[Delta]54AE1 which lacks the first 54 residues but retains the core [beta]-strand is reported. The absence of the central [beta]-strand in cdkAE1 is found to result in a less stable and more open structure than cdAE1 and might account for the altered protein binding properties of kAE1 in addition to the loss of the acidic amino-terminal region.

The sequestration of [Fe.sup.3+] by the ferric binding protein (FbpA) in the presence of sulfate in order to form FeFbpA-S[O.sub.4] is described. Anion lability and affect on the iron affinity and reduction potential for FeFbpA-X have shown that synergestic anion exchange might be an important regulator in iron delivery to the cytosol.

Mn2P2S6 single-crystal nanorods and nanotubes are successfully prepared based on the 'rolling mechanism' through a facile ion-exchange solvothermal process, which overcame the disadvantages of methods reported. This method is expected to extend to the preparation of other M2P2S6 1D nanostructured materials with higher purity and uniformity.

A study on the direct electropoymerization of benzene dissolved in the ionic liquid 1-hexyl-3-methylimidazoliumtris(pentafluoroethyl)trifluorophosphate is carried out at room temperature by applying the electrochemical quartz crystal microbalance technique. The analysis of the damping changes indicates that the Sauerbrey equation could be applied for data evaluation.

In order to probe the conformations, gas-phase acidities, and sites of deprotonation of isomeric flavonoid aglycons and glycosides the gas-phase hydrogen/deuterium (H/D) exchange is used. Within the flavonoid isomers, H/D exchange is sensitive to structural differences.

Binary cation pairs like Ca(super +2) and K(super +) are studied to interpret and predict the ion exchange equilibrium between heulandite and aqueous solutions. The outcome of this study provides necessary data required to model Sr transport in aquifers in low-grade metabasalts.

In the study conducted the application to determination of ionization constants of functional groups and to the investigation of the hydrolysis and sorption of copper on different types of sorbents are described. It is suggested that the developed method can be useful for the investigation of ion exchangers, and it has the potential to increase the interactions in other porous systems.

The preparation and characteristics of a series of organic derivatives of ZrPO4Cl(CH3)2SO are reported. The thermal behavior of these organic derivatives is discussed.

Heterogeneous cation-exchange membranes differing in their binder poly(vinyl chloride) and ion-exchange resin ratios as well as the mesh size of the resin particles are prepared by solution casting technique. The volume fractions of the respective phases are evaluated by considering the membrane as a combination of joint-gel phase and integral phase,

Copper-alkali ion exchange is used for doping superficial layers of different silicate glasses with copper ions. The luminescence decay-time signal is stimulated by a biexponential behavior, interpreted on the basis of a four-level scheme.

An algorithm for simulating ion exchange batch mode experiments utilizing a known binary or ternary linear or nonlinear selectivity matrix and disequilibrium concentrations in exchange and solution phases was developed, and can be used to calculate initial equilibrium conditions for the initiation of numerical transport simulations, to generate binary isotherms (by repeated applications), and to separate ion-exchange from other solute reactions in soils. The algorithm is an iterative process utilizing a binary search to determine the sorbed phase concentrations defined by the selectivity values and dissolved phase concentrations while maintaining the correct total mass of all ions. It was developed to aid in the separation of ion-exchange from other retention processes when empirical determination of exchange isotherms are difficult or impossible.

Mice lacking the [Na.sup.+]/[H.sup.+] exchanger isoform 1 (NHE1) manifest neurological diseases that include ataxia, motor deficits, and a seizure disorder. The molecular basis for the phenotype has not been clear, and it has not been determined how the lack of NHE1 leads, in particular, to the seizure disorder. We have shown in this work that hippocampal CA1 neurons in mutant mice have a much higher excitability than in wild-type mice. This higher excitability is partly based on an upregulation of the [Na.sup.+] current density (608.2 [+ or -] 123.2 pA/pF in NHE1 mutant vs. 334.7 [+ or -] 63.7 pA/pF in wild type in [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]. Alterations in [Na.sup.+] channel characteristics, including steady-state inactivation (shift of 18 mV in the depolarization direction in the mutant), recovery from inactivation ([[Tau].sub.h] = 5.22 [+ or -] 0.49 ms in wild-type neurons and 2.20 [+ or -] 0.20 ms in mutant neurons), and deactivation (at -100 mV, [[Tau].sub.d] = 1.75 [+ or -] 0.53 ms in mutant and 0.21 [+ or -] 0.05 ms in wild-type neurons) further enhance the differences in excitability between mutant and wild-type mice. Our investigation demonstrates the existence of an important functional interaction between the NHE1 protein and the voltage-sensitive [Na.sup.+] channel. We hypothesize that the increased neuronal excitability and possibly the seizure disorder in mice lacking the NHE1 is due, at least in part, to changes in [Na.sup.+] channel expression and/or regulation. sodium channels; sodium-hydrogen exchanger mutant mice

The mutual diffusion coefficient of methanol in a series of polyphosphazene-based cation exchange membrane is measured using tracer-desorption (super 1)H nuclear magnetic resonance (NMR). The (super 1)H NMR technique helps in measuring the growth of a solute NMR signal in the bulk solution as it diffuses out of a thin film membrane.

Macroporous poly(styrene--divinylbenzene) (PSDVB), PRP-1, a reversed-phase adsorbent, and PSDVB-based strong acid cation exchangers and strong base and weak base anion exchangers were evaluated as stationary phases for capillary electrochromatography (CEC). Electroosmotic flow (EOF) for adsorbent and exchanger packed fusedsilica capillaries for acetone as the marker increases with increasing ion exchange capacity, buffer organic solvent concentration, and applied voltage, is nearly independent of pH, and decreases with increased buffer ionic strength. For anion exchangers, EOF is reversed. Thiourea, acetone, acrylamide, nitromethane, propanal, and acetic acid were evaluated as EOF markers and undergo weak interaction with the PSDVB-based stationary phases. EOF in a basic buffer is greater than or equal to silica-based C-18 and cation exchanger packed capillaries. For an acidic buffer, EOF for a PRP-1 capillary is almost twice the C-18 packed capillary. As analyte hydrophobicity increases, retention and migration time increases for the PSDVB-based stationary phases. As exchange capacity increases, availability of the polymeric matrix for analyte partitioning decreases, causing analyte migration time to decrease. Increasing buffer organic solvent concentration decreases analyte retention. The PSDVB-based stationary phases provide good resolving power and reproducibility and are applicable to the CEC separation of neutral, weakly acidic, and basic analytes. Efficiency, however, is less than obtained with silica-based stationary phases. Because of stability in a strong acid buffer, the CEC separation of weak acids, where dissociation is suppressed, and weak bases as cations is possible. Separations of short-chain alkyl aldehydes, methyl ketones, aromatic hydrocarbons, substituted benzene derivatives, and short-chain carboxylic acids are described.

Within pharmaceutical drug discovery, significant needs currently exist for the analysis and purification of structurally diverse samples prior to or immediately following high-throughput screening. These processes are required to facilitate rapid and accurate biological profiling, structural determination, and resupply of new drug candidates. Reversed-phase high-performance liquid chromatography (RP-HPLC) coupled with electrospray ionization mass spectrometry (ESI-MS) for both analytical and preparative applications has become the small molecule separation/ detection tool of choice for meeting many of these needs. However, the separation selectivity provided by RP-HPLC has been limited to the hydrophobicity-based resolution of relatively nonpolar sample components, and for high-throughput drug discovery applications, no sufficient alternative procedures have been identified. In this investigation, a mixed-mode anion--cation exchange/hydrophilic interaction chromatography (ACE-HILIC) method has been developed to provide both direct compatibility with ESI-MS and evaporative light-scattering detection (ELSD) and separation selectivity highly orthogonal to RP-HPLC. The technique employed silica-based small-pore weak ion exchange resins eluted with a combined aqueous and pH gradient. A diverse set of dipeptide probes was employed for the elucidation of the relative contributions of three retention mechanisms. ACE-HILIC-ESI-MS-ELSD should prove useful for the analysis and purification of compounds from both biological (e.g., natural products) and synthetic (e.g., combinatorial chemistry) sources of molecular diversity.

X-ray diffraction data were collected from frozen crystals (100 [degrees] K) of the KcsA [K.sup.+] channel equilibrated with solutions containing barium chloride. Difference electron density maps ([F.sub.barium] -- [F.sub.native], 5.0 [Angstrom] resolution) show that [Ba.sup.2+] resides at a single location within the selectivity filter. The [Ba.sup.2+] blocking site corresponds to the internal aspect (adjacent to the central cavity) of the 'inner ion' position where an alkali metal cation is found in the absence of the blocking [Ba.sup.2+] ion. The location of [Ba.sup.2+] with respect to [Rb.sup.+] ions in the pore is in good agreement with the findings on the functional interaction of [Ba.sup.2+] with [K.sup.+] (and [Rb.sup.+]) in [Ca.sup.2+]-activated [K.sup.+] channels (Neyton, J., and C. Miller. 1988. J. Gen. Physiol. 92:549-567). Taken together, these structural and functional data imply that at physiological ion concentrations a third ion may interact with two ions in the selectivity filter, perhaps by entering from one side and displacing an ion on the opposite side. KEY WORDS: potassium channel * barium * ion channel * ion selectivity * ion conduction

Abstract The movement of anions and cations under different unsaturated flow regimes was studied in 2 large undisturbed cores from a soil under pasture. Sequential leaching of calcium sulfate (Ca[SO.sub.4]) [...]

Abstract In the first part of this study, the movement of anions and cations during sequential leaching of Ca[SO.sub.4] and KBr solutions under different flow regimes in 2 large undisturbed [...]

A simple but highly effective modification of the continuous flow hyperpolarized two-dimensional NMR exchange spectroscopy (CFHP-2D-EXSY) experiment is shown in L-alanyl-L-valine (AV), a polycrystalline nanotube material. The ability to probe longer mixing time will help in the extension of hyperpolarized 2D-EXSY to slower exchange processes or longer diffusion time/length scales for characterization of pore-space architecture, and transport processes in nanotubes and other nanoporous materials.

The hydrogen/deuterium (H/D) exchange of deprotonated amino acids and small peptides is described. The results have shown that the small deprotonated peptide ions can be differentially labeled and the H/D exchange has depended on the primary sequence, both in terms of which amino acids are present and their order in the peptide chain.

The chemical modification methods for polyamide and site-selective printing technology are used to fabricate copper thin-film patterns. This approach can be used to incorporate various kinds of metallic ions on surfaces used for resist-free, site-selective metallization.

Manganese oxide thin films are described, with fast ion-exchange characteristics.

A novel theoretical formulation is proposed for ion conductance in electrolyte solutions. The proposed algorithm provides a microscopic derivation of the Debye-Huckel-Onsager limiting law while allowing a simple interpretation of each term of the law with respect to time correlation function of appropriate dynamical parameters. Experimental results show that the mode coupling theory approach can be extended to higher ion concentrations.

A modified proton-detected 15N Carr-Purcell-Meiboom-Gill spin-echo pulse sequence that overcomes the constraints associated with pulsing rates comparable to the one-bond J(sub NH) scalar coupling constant is described. Experiments were conducted to measure chemical or conformational exchange time constants from 0.5 to 5 ms. The CPMG experiment compensates for evolution between in-phase and antiphase transverse coherences during the spin-echo pulse train.

A study was conducted to characterize the ultraviolet resonance Raman cycle (UVRR) bands of histidine residue 42 in horseradish peroxidase complexed with an inhibitor, cyanide. A quartz capillary tube was utilized to circulate the samples. Results indicated that that UVRR spectroscopy coupled with hydrogen-deuterium exchange can be utilized to effectively study the hydrogen bonding state of catalytically important distal histidine.

There is an unexpectedly large rise in metal-insulator transition temperature and a contrasting strong fall in the Fe...Fe antiferromagnetic interaction in lambda-(BETS)2FeCl4 as a result of the partial exchange of Cl to Br. This indicates a unique 'spin structure model' characteristic of extremely correlated organic conducting systems with magnetic anions. The increased electron correlation indicated by the resistivity measurement of lambda-(BETS)2FeBrxCl4-x and the origin of the anomalous drop of M in lambda-(BETS)2FeCl4 at Tmi indicate that pi-d coupling plays an important role.

It is possible to prevent primary ions from leaching into an ion sample by building up a concentration gradient in the membrane. This produces a constant flux of primary ions towards the inner compartment, preventing their passing into the sample. The concentration gradient is determined by selecting an internal electrolyte with low activity in the primary ion and sufficiently high activity of an interfering ion. This approach could prove useful with miniaturized ion-selective polymeric membrane electrodes.

Surface and buffed planar waveguides have been fabricated in glass microscope slides with purely thermal potassium and sodium ion-exchange techniques. We measured propagation loss as low as 0.08 dB/cm in the partially buried waveguides using an improved two-prism coupling method. The method includes a plastic prism and involves applying heat to soften the base of the outcoupling plastic prism so that the prism is temporarily in extremely close contact with the waveguide surface. Key words: Propagation loss, loss measurement, optical waveguide, ion-exchanged waveguide, glass waveguide.

Ion exchange is a perfect technique for analyzing large biomolecules such as proteins, peptides and oligonucleotides. These complex compounds contain numerous components (amino acids, nucleotides, glycans etc.) many of which [...]

N. Leblanc and J. R. Hume [1] conclude that the intracellular calcium ion concentration ([[Ca.sup.2+]][.sub.i]) of cardiac myocytes can increase transiently, in the absence of an inward [Ca.sup.2+] current, by [...]

The characterization of cellular proteomes is important for understanding biochemical processes ranging from cell differentiation to cancer development. In one highly promising approach, whole protein extracts or fractions are digested (e.g., with trypsin) and injected into a packed capillary column for subsequent separation. The separated peptides are then introduced on-line to an electrospray ionization source of a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer for the detection of peptide accurate mass tags that serve as biomarkers for their parent proteins. In this work, we report the use of data-dependent selective external ion ejection in conjunction with FTICR and on-line capillary LC separations for the enhanced characterization of peptide mixtures and a yeast extract proteome. The number of peptides identified in an LC-FTICR analysis of a yeast proteome digest employing data-dependent rf-only dipolar ejection of the most abundant ion species prior to ion accumulation was 40% higher than that detected in a separate LC-FTICR analysis using conventional nonselective ion accumulation.

Unpolluted rivers and streams that drain marine shalen show an excess of sodium compared to chloride and a deficiency of calcium and magnesium compared to sulfate and alkalinity. This is due in part to cation exchange of sodium for divulent cations on clay minerals. Consideration of the global weathering budget suggests that up to 34% of the sodium in the total dissolved stream load may be due to cation exchange rather than sodium production via silicate dissolution weathering reactions. These results suggest that the weathering budgets for sodium and calcium are in need of revision because of the inclusion of cation-exchange processes in the weathering cycle. This implies that silicate dissolution is less important in determining the composition of global river water than was previously thought.

Ion Channels in Yeast ION CHANNELS ARE FOUND IN A WIDE variety of tissues and organisms in both plants and animals. Ion channels are a class of proteins that function [...]

The expression of anion exchanger 2 (AE2) mRNA and protein in the mouse intestine was characterized. AE2 mRNA abundance was higher in colon than in more proximal segments. AE2a mRNA was more abundant than AE2b mRNA throughout the intestine, and AE2c mRNA was expressed at very low levels. AE2 polypeptide was more abundant in colonic surface cells than in crypts, while ileal crypts and villi showed similar AE2 abundance. AE2 was also found in mural vascular smooth muscle.

A study on microsolvated reactions was conducted to extend previous research on certain intramolecularly solvated reactions, where all of the substrates used feature the structure X(CH2)nCl (n being the number of methylene groups separating the chloride leaving group from the solvating substituent X). reactivity strongly correlates with the dipole moment of the solvating group and it is concluded that ion-solvent interactions are secondary in determining reactivity though they are important in determining the stability of the intermediate complex.

Spatio-temporal flux equations were formulated, taking into account the influence of physical diffusion of the electroactive species on the mechanism of charge transport in chemically modified electrodes. The important role played by the physical displacement on parameters such as effective diffusion coefficient, steady-state current, conductivity, transport number and motility, among others, was demonstrated. The schematic variations of these parameters on fractional loading and applied potential were shown for bounded and free diffusion conditions. The qualitative influence of solvent medium on the apparent diffusion coefficient was pointed out.

An investigation of acid-base interaction influence on protonated peptide gas-phase dissociation revealed that the amount of ionizing protons in relation to the amount of basic residues in peptides with acidic residues is a factor that contributes to fragmentation behavior. These intraionic interactions in gas-phase peptide ions and their influence on dissociations are seen as strong proof of the existence of peptide secondary structure in the gas phase.

A study was conducted to analyze the cloning and functional expression of the Na+/H+ exchanger (NHE) from Amphiuma red blood cells. The first-strand cDNA templates were amplified in th presence of primers while the rapid amplification of cDNA ends was carried out by ligating adapters. Experimental results indicated a high similarity between the sequences of human hNHE1 and Amphiuma tridactylum NHE1.

COOH-terminal truncation mutants were used to delineate specific domains in the COOH terminus of the cloned epithelial cell-specific fibroblast growth factor isoform NHE2 that are related to growth factor and/or protein kinase regulation. Results indicated that the COOH terminus of NHE2 is organized into separate inhibitory and stimulatory growth factor/protein kinase regulatory subdomains. This finding suggests that the tertiary structures of the putative COOH termini of NHE2 and NHE3 are very much alike.

Saccharomyces cerevisiae strains that express the human MDR 1 protein were isolated and analyzed. The growth rates in various media and in the presence or absence of valinomycin were determined. The strains were used to prepare purified plasma membrane fractions and inside-out vesicles. The results of the analysis of growth curve data, Delta(psi) and delta(pH) of intact cells, intracellular K= levels, ATPase activity of plasma membrane fractions, ion dependencies of valinomycin resistance and H+ transport by the membrane vesicles are presented.