Effects Of Ionic Composition Research Articles

Ionic composition and transport mechanisms in microbial desalination cells

Microbial desalination cell (MDC) offers a new and sustainable approach to desalinate saltwater by directly utilizing the electrical power generated by bacteria during organic matter oxidation. The successful MDC development relies on the fundamental understanding of the interactions and removal mechanisms of different ion species present in saline water or wastewater, but there is limited understanding of ion transport mechanisms in MDCs and potential membrane fouling/scaling during treatment of wastewater and saline water. In this study, we investigated the transport behavior of multiple ions in MDCs and the effects of ionic composition on system performance and membrane scaling and fouling. The results showed that the presence of sparingly soluble cations in saltwater negatively affected MDC power generation and desalination. Membrane characterization revealed that the majority of such ions precipitated on the ion exchange membrane surface and caused membrane scaling. Anions such as Br− and SO42− with Na+ as counter-ion did not show significant effects on system performance. Sharp pH changes were observed during MDC operation, which resulted in the inhibited MDC anode microbial activity and the accelerated formation of alkaline precipitations on both sides of the cation exchange membrane. An anode–cathode recirculation approach was proved to be effective to solve such problems and improved the desalination rate by 152% and the electron harvest rate by 98%.

Accurate determination of the Ca2+ activity in milk-based systems by Ca-ISE: Effects of ionic composition on the single Ca2+ activity coefficient and liquid junction potentials

Calcium ion selective electrode (Ca-ISE) was found to underestimate the actual Ca2+ ion activity in simulated milk ultrafiltrate (SMUF) and milk. It is shown that the ionic compositional difference between conventional calibration solutions and milk type samples had a significant effect on the single Ca2+ activity coefficient, which generates the erroneous estimate of Ca2+ activities in SMUF and milk. This study tests new standards with ionic profiles similar to SMUF, aiming at the reduction of the errors generated by the compositional difference between conventional standards and milk samples. As a result, the new standards showed a significant improvement in the accuracy of Ca2+ activity and Ca2+ activity coefficient over the conventional standards. The systematic error is reduced from 20% to 5% for SMUF and from 44% to 15% for milk. In addition, the new standards generate liquid junction potentials that are practically insignificant.

Aggregation of colloidal silica particles in the presence of fulvic acid, humic acid, or alginate: Effects of ionic composition

We have studied the aggregation of model silica particles in the presence of NOMs (fulvic acid, humic acid, or alginate) by using dynamic light scattering. Experiments were performed systematically by changing CaCl 2 concentration, the types and concentration of NOMs: Suwannee river fulvic acid (SRFA), Suwannee river humic acid (SRHA), and alginate. Experimental results demonstrate that the aggregation rate in the presence of the SRFA and Ca 2+ ions was on par with the rate of the diffusion limited aggregation. On the other hand, the addition of SRHA or alginate extremely enhances the rate of aggregation in the presence of CaCl 2 compared to the rate of diffusion limited aggregation. The enhancement of the rate is probably due to the bridging of silica particles by the microgels formed by the Ca-mediated bridging of SRHA/alginate molecules. Also, the enhanced aggregation with alginates/SRHA and Ca 2+ ions is reduced by the coexistence of K + or Mg 2+ ions. We suppose that the breaking of Ca-mediated bridging of alginates/SRHA by ion-exchange reduces the rate of the enhanced aggregation.

Acid generation upon thermal concentration of natural water: The critical water content and the effects of ionic composition

Thermal evaporation of a variety of simulated pore waters from the region of Yucca Mountain, Nevada, produced acidic liquids and gases during the final stages of evaporation. Several simulated pore waters were prepared and then thermally distilled in order to collect and analyze fractions of the evolved vapor. In some cases, distillates collected towards the end of the distillation were highly acidic; in other cases the pH of the distillate remained comparatively unchanged during the course of the distillation. The results suggest that the pH values of the later fractions are determined by the initial composition of the water. Acid production stems from the hydrolysis of magnesium ions, especially at near dryness. Near the end of the distillation, magnesium nitrate and magnesium chloride begin to lose water of hydration, greatly accelerating their thermal decomposition to form acid. Acid formation is promoted further when precipitated calcium carbonate is removed. Specifically, calcium chloride-rich pore waters containing moderate (10–20 ppm) levels of magnesium and nitrate and low levels of bicarbonate produced mixtures of nitric and hydrochloric acid, resulting in a precipitous drop in pH to values of 1 or lower after about 95% of the original volume was distilled. Waters with either low or moderate magnesium content coupled with high levels of bicarbonate produced slightly basic fractions (pH 7–9). If calcium was present in excess of bicarbonate, waters containing moderate levels of magnesium produced acid even in the presence of bicarbonate, due to the precipitation of calcium carbonate. Other salts such as halite and anhydrite promote the segregation of acidic vapors from residual basic solids. The concomitant release of wet acid gas has implications for the integrity of the alloys under consideration for containers at the Yucca Mountain nuclear waste repository. Condensed acid gases at very low pH, especially mixtures of nitric and hydrochloric acid, are capable of corroding even alloys, such as nickel-based Alloy 22, which are considered to be corrosion-resistant under milder conditions.

Characterization of phagolysosomal simulant fluid for study of beryllium aerosol particle dissolution

A simulant of phagolysosomal fluid is needed for beryllium particle dissolution research because intraphagolysosomal dissolution is believed to be a necessary step in the cellular immune response associated with development of chronic beryllium disease. Thus, we refined and characterized a potassium hydrogen phthalate (KHP) buffered solution with pH 4.55, termed phagolysosomal simulant fluid (PSF), for use in a static dissolution technique.To characterize the simulant, beryllium dissolution in PSF was compared to dissolution in the J774A.1 murine cell line. The effects of ionic composition, buffer strength, and the presence of the antifungal agent alkylbenzyldimethylammonium chloride (ABDC) on beryllium dissolution in PSF were evaluated.Beryllium dissolution in PSF was not different from dissolution in the J774A.1 murine cell line (p=0.78) or from dissolution in another simulant having the same pH but different ionic composition (p=0.73). A buffer concentration of 0.01-M KHP did not appear adequate to maintain pH under all conditions. There was no difference between dissolution in PSF with 0.01-M KHP and 0.02-M KHP (p=0.12). At 0.04-M KHP, beryllium dissolution was increased relative to 0.02-M KHP (p=0.02). Use of a 0.02-M KHP buffer concentration in the standard formulation for PSF provided stability in pH without alteration of the dissolution rate. The presence of ABDC did not influence beryllium dissolution in PSF (p=0.35).PSF appears to be a useful and appropriate model of in vitro beryllium dissolution when using a static dissolution technique. In addition, the critical approach used to evaluate and adjust the composition of PSF may serve as a framework for characterizing PSF to study dissolution of other metal and oxide particles.

Moulting, survival and calcification: the effects of temperature and water chemistry on an ostracod crustacean (Herpetocypris intermedia) under experimental conditions

Temperature and water chemistry are usually considered as being the two main factors to influence the development and survival of non-marine ostracods. These factors may act upon a wide range of biological parameters, among which, those directly linked to the moulting process are of great importance. In this work, we study the effects of water temperature and ionic composition on survival, moulting success and calcification in the freshwater ostracod Herpetocypris intermedia; we propose a hypothesis on the basis of our general understanding of crustacean physiology to derive a tentative explanation of the ecology and distribution of non-marine ostracods. Several temperatures and water chemistries were used for experimental cultures of the adult and juvenile stages of H. intermedia, in which survival, moulting and shell Ca-uptake were monitored. Water temperatures between 15 degrees C and 20 degrees C resulted in the longest survival times, but high water temperatures (20-24 degrees C) provided the highest rates of moulting and calcification and shortest intermoult times. Despite this, the highest water temperature (24 degrees C) was associated with the shortest survival times, whilst survival time and calcification were low at the lowest temperature examined (13 degrees C). The different effects of ionic composition upon the biological parameters studied show that H. intermedia develops better in bicarbonate-rich than in chloride-rich waters. These experimental findings are in general agreement with field data and allow us to establish different tolerance limits and niche preferences for various congeneric taxa. Taking into account previously published data on calcium incorpora tion and ionic regulation in freshwater Crustacea, our results suggest that there is a trade-off between calcification and ionic regulation in non-marine ostracods; these animals need to precipitate calcite and also to pump bicarbonate ions outwards to maintain internal chloride concentrations. In recent times, water ionic ratios, and particularly bicarbonate/chloride ratios, have been considered to be major factors influencing non-marine ostracod distributions. In this sense, the physiological mechanisms cited in this study to explain our experimental results would also illustrate the major biogeographic and ecological patterns observed in non-marine Ostracoda, i.e. that some species are restricted to brackish waters whilst others dwell only in freshwaters.

Regulation of Skeletal Muscle Ca2+ Release Channel (Ryanodine Receptor) by Ca2+ and Monovalent Cations and Anions

The effects of ionic composition and strength on rabbit skeletal muscle Ca2+ release channel (ryanodine receptor) activity were investigated in vesicle-45Ca2+ flux, single channel and [3H]ryanodine binding measurements. In <0.01 microM Ca2+ media, the highest 45Ca2+ efflux rate was measured in 0.25 M choline-Cl medium followed by 0.25 M KCl, choline 4-morpholineethanesulfonic acid (Mes), potassium 1,4-piperazinediethanesulfonic acid (Pipes), and K-Mes medium. In all five media, the 45Ca2+ efflux rates were increased when the free [Ca2+] was raised from <0.01 microM to 20 microM and decreased as the free [Ca2+] was further increased to 1 mM. An increase in [KCl] augmented Ca2+-gated single channel activity and [3H]ryanodine binding. In [3H]ryanodine binding measurements, bell-shaped Ca2+ activation/inactivation curves were obtained in media containing different monovalent cations (Li+, Na+, K+, Cs+, and choline+) and anions (Cl-, Mes-, and Pipes-). In choline-Cl medium, substantial levels of [3H]ryanodine binding were observed at [Ca2+] <0.01 microM. Replacement of Cl- by Mes- or Pipes- reduced [3H]ryanodine binding levels at all [Ca2+]. In all media, the Ca2+-dependence of [3H]ryanodine binding could be well described assuming that the skeletal muscle ryanodine receptor possesses cooperatively interacting high-affinity Ca2+ activation and low-affinity Ca2+ inactivation sites. AMP primarily affected [3H]ryanodine binding by decreasing the apparent affinity of the Ca2+ inactivation site(s) for Ca2+, while caffeine increased the apparent affinity of the Ca2+ activation site for Ca2+. Competition studies indicated that ionic composition affected Ca2+-dependent receptor activity by at least three different mechanisms: (i) competitive binding of Mg2+ and monovalent cations to the Ca2+ activation sites, (ii) binding of divalent cations to the Ca2+ inactivation sites, and (iii) binding of anions to specific anion regulatory sites.

Effect of medium conductivity and composition on the uptake of propidium iodide into electropermeabilized myeloma cells

The effects of ionic composition and conductivity of the medium on electropermeabilization of the plasma membrane of mammalian cells were studied. Temporal and spatial uptake of propidium iodide (PI) into field-treated cells was measured by means of flow cytometry, spectrofluorimetry and confocal laser scanning microscopy. Murine myeloma cells were electropulsed in iso-osmolar solutions. These contained 10–100 μg ml −1 PI at different conductivities (0.8–14 mS cm −1) and ionic strengths, adjusted by varying concentrations of K +, Na +, Cl − and SO 4 2−. Field-induced incorporation of PI into reversibly permeabilized cells was (almost) independent of ionic composition and strength (at a fixed medium conductivity), but increased dramatically with decreasing medium conductivity at a fixed field strength. The time-course of PI uptake (which apparently reflected the resealing process of the membrane) could be fitted by a single-exponential curve (relaxation time about 2 min in the absence of Ca 2+) and was independent of medium conductivity and composition. These and other data suggested that the expansion of the ‘electroleaks’ during the breakdown process is field-controlled and depends, therefore, on the (conductivity-dependent) discharging process of the permeabilized membrane. The threshold field strength for dye uptake increased with increasing K + concentration (about 0.6 kV cm −1 in K +-free, NaCl-containing medium and about 0.9 kV cm −1 in 30 mM KCl-containing medium). Also, the spatial uptake pattern of PI shifted from an asymmetric permeation through the cell hemisphere facing the anode to a more symmetric uptake through both hemispheres. These results suggested that the generated potential is superimposed on the (K +-dependent) resting membrane potential. Taking this into account, the breakdown voltage of the membrane was estimated to be about 1 V.

A physiological saline for lepidopterous insects: Effects of ionic composition on heart beat and neuromuscular transmission

Three species of Lepidoptera, Bombyx mori, Agrius convolvuli and Antheraea yamamai were used to prepare a suitable physiological saline for maintaining heart beat and junctional potentials of somatic muscle cells. A variety of salines designed for Lepidoptera were reexamined. Heart beat in the three species could not be maintained in salines used previously as physiological or culture solutions for Lepidoptera. Ionic compositions were determined for physiological salines that were suitable for maintaining the normal heart beat and normal neuromuscular transmission in body muscle cells. It was found that salines should contain 12–28 mM NaCl, 32-16 mM KCl ([Na +] + [K + ] = 44) and at least 9 mM CaCl 2. In the salines, stimuli to motor nerves evoke action potentials of more than 40 mV in amplitude in ventral muscle cells. The ionic composition of a new physiological saline for Lepidoptera is as follows: NaCl, 12–28; KCl, 32-16([Na +] + [K +] = 44); CaCl 2, 9; NaH 2PO 4, 1.5; Na 2HPO 4, 1.5; MgCl 2, 18; sucrose, 175 (mM), pH 6.5.

High-affinity triple helix formation by synthetic oligonucleotides at a site within a selectable mammalian gene.

Specific recognition of duplex DNA by a single-stranded oligonucleotide via the formation of triplex DNA is a rational approach for targeting specific regions of a genome. By screening a number of potential target sites for triple helix formation within mammalian genes that allow genetic selection in cell culture, we have identified a site within intron 1 of the hamster adenine phosphoribosyltransferase (APRT) gene that specifically binds a triplex-forming oligodeoxyribonucleotide (TFO) with high affinity. Under optimal conditions for triplex formation, the equilibrium dissociation constant is in the nanomolar range (Kd = 7 x 10(-10) M). This high-affinity binding is very specific, as a 10(5)-fold excess of genomic DNA reduced triplex formation less than 10-fold, and within a 6928-bp plasmid bearing the APRT gene, only restriction fragments containing the intron 1 site were found to bind the TFO. Results of DNase I protection assays were consistent with the TFO binding in an antiparallel orientation via reverse Hoogsteen hydrogen bonds in the major groove of the duplex. We have examined the kinetics of triplex formation as well as the effects of ionic composition and chemical modifications of the TFO on triplex formation. While divalent cations were not required for triplex formation, Mg2+ stabilized the triplex apparently through inhibition of TFO dissociation, with a mean bound lifetime of > 17 h for the triplex at Mg2+ concentrations above 5 mM.(ABSTRACT TRUNCATED AT 250 WORDS)

BINDING CHARACTERISTICS OF THE CALCIUM CHANNEL ANTAGONIST [&lt;sup&gt;3&lt;/sup&gt;H]-NITRENDIPINE IN TISSUES FROM ETHANOL-DEPENDENT RATS

Male Sprague-Dawley rats were made physically dependent on ethanol by exposure to ethanol vapour in inhalation chambers for 6-10 days. Animals were sacrificed immediately after removal from the chambers. After sacrifice, membrane preparations from cerebral cortex, heart, vas deferens and thigh skeletal muscle were prepared and studied to determine the characteristics of [3H]-nitrendipine binding. In membranes from cerebral cortex, the number of binding sites (Bmax) was increased 40% in preparations from ethanol-dependent rats compared to controls. Similar results were obtained in heart (Bmax increased 125%), vas deferens (Bmax increased 50%) and skeletal muscle (Bmax increased 33%). Binding affinity (Kd) in all these tissues was unchanged. Membranes from cortex and heart were studied more extensively. Displacement studies using other dihydropyridines and the effects of ionic composition on [3H]-nitrendipine binding provided no evidence to suppose that the binding sites induced by the development of ethanol dependence were from a population different from those in control tissues. The results suggest a generalised 'up-regulation' of the dihydropyridine-sensitive subclass of voltage operated calcium channels in excitable tissues from ethanol-dependent rats.

Regulation of oxidoreductive yeast metabolism by extracellular factors

Since antiquity man has consumed ethanol produced by yeast as sugars are metabolized. Industrial alcohol and alcoholic beverages play major roles in our economy. Although the processes have been anaerobic except for the beneficial introduction of a trace of air or oxygen, the focus may shift to a novel approach to yeast bioprocessing using recent understanding of the aerobic ethanol production. In this minireview, we address glycolysis, oxidoreductive metabolism, and ion transport in yeast, and we introduce high-rate bioprocess control strategies that hinge on the effects of ionic composition. Consideration of maintenance requirements for glycolysis leads to an assessment of the role of monitoring and control of ionic concentrations for optimization of ethanol production.

Influence of methylcellulose-coated paper separators on the corrosion, polarization and impedance characteristics of zinc in concentrated ammonium chloride solution. II. Comparison of data obtained in flooded electrolyte and battery environments

An attempt has been made to determinein situ the corrosion rate of the zinc anode in Leclanche batteries devoid of ZnCl2 in the electrolyte using steady-state polarization and a.c. impedance techniques. Previously obtained corrosion data for zinc immersed in flooded NH4Cl electrolyte has been used as a point of reference with which to compare thein situ data and hence gauge its legitimacy. It is shown that in the case of cells containinguncoated paper separators, good agreement between the two sets of data is obtained, thus demonstrating thatin situ corrosion rate measurements can be made. This allows the effects of ionic composition, zinc alloying constituents, amalgamation level, electrolyte impurities, and the role of oxygen, etc, to be determined in the battery environment. However, the anode polarization and impedance characteristics of ZnCl2-free cells containing methylcellulose-coated paper separators do not reflect corrosion processes. In fact the electrochemical data is almost indistinguishable from that obtained in ZnCl2-containing cells. It is postulated that the presence of the methylcellulose layer permits the zinc ion concentration to build up adjacent to the anode causing the cathodic hydrogen evolution process to be electrochemically masked by zinc deposition. The electrochemical characteristics therefore reflect zincexchange processes only. Neither the presence of the separator coating itself nor the restricted volume of electrolyte appear to be unilaterally responsible for the anomalous behaviour of ZnCl2-free cells, but rather a combination of these two conditions is necessary. Thus considerably restricted diffusion and the near absence of convection would appear to be the important factors which dictate the observations.

Lipid biosynthesis in rat-liver slices: Effects of ions, ATP and substrate concentration on glycerol incorporation

The effects of ionic composition and substrate concentration on the metabolism of glycerol by rat-liver slices have been investigated. Of the ions tested, HCO 3− decreased incorporation into lipid but had little effect on incorporation into glycogen. Ca 2+ stimulated incorporation into lipid. ATP and related nucleotides decreased this incorporation in Krebs-Ringer solution buffered with Tris or phosphate but increased it in the presence of HCO 3−. Inclusion of either HCO 3− or ATP in the incubation medium resulted in an increased percentage of label in the acidic lipid fraction. At saturating substrate concentrations, more label appeared in lecithin and less in neutral lipids than at tracer concentrations. The results indicate that changes in ionic composition or substrate concentration within physiological limits can alter metabolic patterns observed in isolated tissues, and suggest that such parameters may be important in the regulation of lipid metabolism in vivo.

Measurement of axonal membrane conductances and capacity by means of a varying potential control voltage clamp

A new mode of voltage clamping in the squid giant axon is introduced and its advantages are analyzed, tested, and utilized to investigate membrane conductances and capacity. This method replaces the constant command potentials of the standard voltage clamp with potentials which vary with time. Some of the advantages in using the varying potential clamp are: (1) slowly varying potentials generate practically pureI K ; (2) rapidly varying potentials generate practically pureI Na; (3) triangular waves generate, under proper conditions, pure capacity currents and easy-to-analyze leakage currents; (4) the method gives direct, on-line display of sodium or potassium I-V characteristics within milliseconds; (5) it enables rapid and accurateE Na andE K determinations; and (6) it enables simple and accurate determination ofC m. The method was utilized to study the effects of various ions on membrane conductances and the effects of ionic composition, ionic strength, and temperature on membrane capacity. Membrane capacity was found to be practically independent of frequency in the 200 to 2,000 Hz range. Replacement of external sodium by Ca(++), by impermeable Tris(+), or even by dextrose or sucrose (low ionic-strength solutions) had negligible effects onC m.C m showed a small, positive temperature coefficient of 1.39% per °C in the 3 to 21°C range, and little change with temperature in the 20 to 40°C range. Above 40°C, bothC m andg L increased considerably with temperature.