Internal Solute Concentrations Research Articles

Development of a New Copper(II) Ion-selective Poly(vinyl chloride) Membrane Electrode Based on 2-Mercaptobenzoxazole

Copper(II) ion-selective PVC membrane electrode based on 2-mercaptobenzoxazole as a new ionophore and o-nitrophenyl octyl ether (o-NPOE) as plasticizer is proposed. This electrode revealed good selectivity for Cu 2 + overa wide variety of other metal ions. Effects of experimental parameters such as membrane composition, nature and amount of plasticizer, and concentration of internal solution on the potential response of Cu 2 + sensor were investigated. The electrode exhibits good response for Cu 2 + in a wide linear range of 5.0 x 10 - 6 -1.6 x 10 - 2 mol/L with a slope of 29.2 ′ 2.0 mV/decade. The response time of the sensor is less than 10 s, and the detection limit is 2.0 x 10 - 6 mol/L. The electrode response was stable in pH range of 4-6. The lifetime of the electrode was about 2 months. The electrode revealed comparatively good selectivities with respect to many alkali, alkaline earth, and transition metal ions.

Lanthanum-selective membrane electrode based on 2,2′-dithiodipyridine

In this study, a new poly(vinyl chloride) (PVC) membrane sensor for La 3+ ion based on 2,2′-dithiodipyridine as an ion carrier was prepared. This electrode revealed good selectivity for La 3+ over a wide variety of other metal ions. Effects of experimental parameters such as membrane composition, nature and amount of plasticizer, the amount of additive and concentration of internal solution on the potential response of La 3+ sensor were investigated. The electrode exhibited a Nernstian slope of 20.0 ± 1.0 mV per decade of La 3+ over a concentration range of 7.1 × 10 −6 to 2.2 × 10 −2 M of La 3+ in the pH range 3.3–8.0. The response time was about 7 s and the detection limit was 3.1 × 10 −6 M. The electrode can be used for at least 2 months without a considerable divergence in potential. The proposed electrode was used as an indicator electrode in potentiometric titration of oxalate and fluoride ions and was applied for determination of F − ion in mouthwash solution.

The first use of a Rh(III) complex as a novel ionophore for thiocyanate-selective polymeric membrane electrodes

The feasibility of a newly synthesized Rh(III) complex, Rh[(trpy)(bpy)Cl](PF 6) 2, as a novel ionophore for the preparation of anion-selective polymeric membrane electrodes was tested. The ionophore exhibited anti-Hofmeister behavior with enhanced potentiometric selectivity toward thiocyanate ion compared to other anions. The influence of some experimental parameters such as membrane composition, nature and amount of plasticizer and additive and concentration of internal solution on the potential response of the SCN − sensor were investigated. The electrode exhibits a Nernstian response for SCN − over a wide concentration range (1.0 × 10 −5 to 1.0 × 10 −1 M) with a slope −58.7 ± 0.5 mV per decade and a detection limit of 4.0 × 10 −6 M (0.23 ppm). It could be used in a pH range of 3.0–8.0 and has a fast response time of about 15 s. The proposed sensor was used for the determination of thiocyanate ions in real samples such as urine and saliva of smokers and nonsmokers and, as an indicator electrode, in potentiometric titrations of SCN − ion.

The Nature of the Internal Acid Solution in Sulfonated Poly(styrene-co-divinylbenzene) Resins

The acidities of a series of fully hydrated sulfonated poly(styrene-co-divinylbenzene) resins with varying levels of sulfonation from 0.80 to 5.25 mequiv g-1 have been characterized. Enthalpies of neutralization with aqueous NaOH have been measured by titration calorimetry. The degrees of acid dissociation (α) have been measured using FT-Raman spectroscopy, based on the intensity of the –SO3- stretching band at 1033 cm-1. The same measurements have been made on aqueous solutions of p-toluenesulfonic acid (p-TsOH), on the basis that these solutions are analogs of the internal solutions in the hydrated resin gels. For resins with low levels of sulfonation, and therefore relatively dilute internal acid solutions, the internal and the equivalent p-TsOH solutions are similar. However, significant differences are seen in highly sulfonated resins where the internal solution concentration is above 4.0 mol kg-1. At these concentrations, p-TsOH solutions show essentially complete dissociation and enthalpies of neutralization typical of a strong, fully dissociated acid in aqueous solution. In contrast, the acid groups in hydrated resins are largely undissociated and exhibit numerically higher enthalpies of neutralization, and catalytic activity measurements indicate that these acid groups are stronger than normal. It is proposed that this acidity enhancement is associated with networks of sulfonic acid groups which form in highly sulfonated resins. Although such networks have been previously proposed in dehydrated resins, this paper reports the first evidence for their existence in resins under conditions of full hydration.

Fluid motion and solute distribution around sinking aggregates. I. Small-scale fluxes and heterogeneity of nutrients in the pelagic environment

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 211:1-13 (2001) - doi:10.3354/meps211001 Fluid motion and solute distribution around sinking aggregates. I. Small-scale fluxes and heterogeneity of nutrients in the pelagic environment Thomas Kiørboe1,*, Helle Ploug2, Uffe H. Thygesen1 1Danish Institute for Fisheries Research, Kavalergården 6, 2920 Charlottenlund, Denmark 2Marine Biological Laboratory, Strandpromenaden 5, 3000 Helsingør, Denmark *E-mail: tk@dfu.min.dk ABSTRACT: Marine snow aggregates are sites of elevated biological activity. This activity depends on the exchange of solutes (O2, CO2, mineral nutrients, dissolved organic material, etc.) between the aggregate and the environment and causes heterogeneity in the distribution of dissolved substances in the ambient water. We described the fluid flow and solute distribution around a sinking aggregate by solving the Navier-Stokes¹ equations and the advection-diffusion equations numerically. The model is valid for Reynolds numbers characteristic of marine snow, up to Re = 20. The model demonstrates the importance of a correct flow environment when making biological rate-measurements on aggregates (e.g., oxygen consumption/production, growth rates of bacteria and phytoplankton) because both solute fluxes and internal solute concentrations depend strongly on the flow environment. Observations of flow and oxygen-concentration fields in the vicinity of both artificial and natural oxygen-consuming aggregates that are suspended in a flow compare well with model predictions, thus suggesting that our set-up is suitable for making biological rate measurements. The sinking aggregate leaves a long slender plume in its wake, where solute concentration is either elevated (leaking substances) or depressed (consumed substances) relative to ambient concentration. Such plumes may impact the nutrition of osmotrophs. For example, based on published solubilization rates of aggregates we describe the amino acid plume behind a sinking aggregate (0.1 to 1.0 cm radius). The volume of the plume with amino acid concentrations high enough to significantly affect bacterial uptake rates is ca 100x the volume of the aggregate itself. Thus, sinking aggregates may create significant microniches also for free-living bacteria. KEY WORDS: Marine snow · Mass transport · Bulk Sherwood number · Local Sherwood number · Aggregate respiration rate Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 211. Online publication date: February 14, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.

Lead selective membrane electrode using cryptand(222) neutral carrier

The construction, performance characteristics and applications of a polymeric membrance electrode for lead(II) ion are reported. The electrode was prepared by incorporating cryptand(222) as the neutral carrier into a plasticized poly(vinyl chloride) membrane. The influence of membrane composition, pH and concentration of internal reference solution were investigated. The electrode exhibits a potentiometric response for Pb2+ ion over the concentration range 10–1–10–5 M with a detection limit of 5 × 10–6 M Pb2+. It shows a relatively fast response time of about 30 s and can be used for about two months without any considerable divergence in potential. The proposed sensor revealed good selectivities for Pb2+ in the presence of several metal ions and could be used in the pH range of 2.5 to 7.5. It was used as an indicator electrode in the potentiometric titration of Pb2+ with EDTA.

Intracellular changes in ions and organic solutes in halotolerant brevibacterium sp. Strain JCM 6894 after exposure to hyperosmotic shock

In the present study we aimed to observe the intracellular responses when there was a hyperosmotic shock with a large shift in ionic strength in nutrient-rich and nutrient-poor external environments in order to clarify the availability of substrates. To do this, we used the halotolerant organism Brevibacterium sp. strain JCM 6894, which is able to grow in the presence of a wide range of salt concentrations. Hyperosmotic shock was induced by transferring cells in the late exponential phase of growth in a complex medium containing 0.5 M NaCl into either old or fresh culture medium containing 2 M NaCl. Changes in the growth rate, in the pH of the medium, and in the internal cation or organic solute concentrations in the cytosol after an upshock were analyzed as a function of incubation time. The cells exhibited very different responses to upshocks in fresh culture medium and in old culture medium; in fresh culture medium, growth was stimulated and the medium became more acidic, whereas the old culture medium repressed growth and the medium became more alkaline. The intracellular free Na+ concentrations remained low (80 nmol mg of protein-1) after an upshock in fresh culture medium, although they quickly increased twofold in the old culture medium. In contrast, K+ ions immediately accumulated in the cells in fresh culture medium, whereas K+ ions were taken up quite slowly in old culture medium. Furthermore, the cells placed in fresh culture medium transiently accumulated alanine and glutamine in response to the upshock, but the cells placed in old culture medium did not. Growth of the Brevibacterium strain at higher levels of salinity was supported by ectoine synthesis but was not observed after the shift to high-osmolarity conditions in the old culture. In the fresh culture, however, ectoine was vigorously synthesized in cells for more than 5 h after the upshock; the concentration of ectoine in cells was more than 3,500 nmol mg of protein-1 at 10 h, which corresponded to a ninefold increase compared to the concentration before the shock. These findings are consistent with the results of an analysis of the extracellular medium composition before and after the upshock.

Membrane stress causes inhibition of water channels in brush border membrane vesicles from kidney proximal tubule

Brush border membrane vesicles (BBMV) from rabbit kidney proximal tubule cells, prepared with different internal solute concentrations (cellobiose buffer 13, 18 or 85 mosM) developed an hydrostatic pressure difference across the membrane of 18.7 mosM, that causes a membrane tension close to 5 x 10(-5) N cm-1. When subjected to several hypertonic osmotic shocks an initial delay of osmotic shrinkage (a lag time), corresponding to a very small change in initial volume was apparent. This initial osmotic response, which is significantly retarded, was correlated with the initial period of elevated membrane tension, suggesting that the water permeability coefficient is inhibited by membrane stress. We speculate that this inhibition may serve to regulate cell volume in the proximal tubule.

Rubidium ion-selective electrodes based on indanopyrazolo[1,5-a]pyrimidines

Rubidium ion-selective PVC membrane electrodes based on indanopyrazolo[1,5-a]pyrimidines as a novel class of neutral carriers were prepared. The electrode based on indano-3-amino-4-p-chlorophenylazopyrazolo[1,5-a]pyrimidine containing potassium tetrakis(4-chlorophenyl)borate as lipophilic salt and 2-nitrophenyl octyl ether as plasticizer gave the best performance. The electrode function was linear within the activity range 10–1–10–4 mol l–1 and the Nernstian slope was 59 mV decade–1. The selectivity and response time of the electrode were investigated and it was found that the electrode exhibits good selectivity towards rubidium with respect to alkali, alkaline earth and some other metal ions. The electrode response and selectivity remained almost unchanged for at least 1 month. The effects of the internal solution concentration and pH on the potential response of the electrode were also studied.

Effects of solute concentration on the entrapment of solutes in phospholipid vesicles prepared by freeze-thaw extrusion

Phospholipid vesicles prepared by the freeze-thaw extrusion method contain internal solute concentrations which are much higher than the external values (entrapment ratios ⪢ 1). This concentrating effect is a complex function of the total impermeant solute concentration in the medium used to prepare vesicles, the presence or absence of permeant solutes in the medium and the apparent competitive binding interactions between solutes and phospholipid. Increases in water phase solute concentration during freezing are thought to underlie the concentrating phenomenon, while osmotic pressure driven lysis of vesicles during thawing appears to limit its magnitude. By judicious selection of solute concentration and physical properties, further increases in the entrapment ratio should be obtainable, improving the usefulness of these vesicles as drug delivery vesicles and experimental systems.

Determination of intracellular volume and internal solute concentrations of the green alga Chlorococcum submarinum

A method is described for measuring the cell volume of the unicellular green alga Chlorococcum submarinum, which depends on measurements of bromide concentration before and after disruption of the cells by ammonium hydroxide. Simultaneous equations are derived, which along with direct determination of cell water weight, allow the calculation of the intracellular volume in three different ways. The volumes calculated are in agreement indicating the validity of the method. The cell volumes and internal concentrations of glycerol, proline, potassium and sodium were determined for algae adapted to three salinities, 0.1, 0.5 and 1.0 M NaCl. The results showed that glycerol was the major internal solute and that the total measured solutes balanced the external osmotic pressure at all three salinities.

Plant Growth, Metabolism and Adaptation in Relation to Stress Conditions. XIV. Effect of Salinity on the Internal Solute Concentrations in Phaseolus vulgaris

Summary In response to salinity, remarkable changes in ion distribution and concentration, proline content, relative growth rate (RGR) and in transpiration rate were maintained in 4-week-old Phaseolus vulgaris plants. Thus increasing salinity levels in the growth medium induced a reduction in the RGR and in the rate of transpiration. In all of the plant organs, Na, Cl and proline concentrations increased continuously whereas K and Ca concentrations decreased with increasing salinity except in the second and third trifoliate leaves. The magnitude of increase in Na concentration in roots was more profound than in leaves. Moreover, Mg was almost unaffected by increasing salinity. On the other hand, desalinization of the growth medium increased the internal contents of K and Ca and largely decreased that content of Na in all of the plant organs. The present changes in the internal ion concentrations are discussed in relation to K-Na selectivity and ion transport in the plant.

Factors affecting solute entrapment in phospholipid vesicles prepared by the freeze-thaw extrusion method: a possible general method for improving the efficiency of entrapment

It is often assumed that the internal solute concentrations of phospholipid vesicles are equal to those in the medium in which they were prepared, particularly when freeze-thaw cycles are employed during the procedure. Conditions are reported here which when used to prepare vesicles by the polycarbonate filter extrusion method, produce ∼ 12- and ∼ 7-fold higher internal concentrations of Ca 2+ and sucrose, respectively, than exist in the external medium. Formation of these large gradients is dependent upon the use of freeze-thaw cycles during preparation on the presence of tetraethylammonium perchlorate in the medium, and is independent of media pH across the region of pH 5–9. Gradient formation is antagonized by high concentrations of an impermeant solute (NaCl). It is proposed that gradients form because solutes are concentrated by exclusion from ice during freezing but that they are normally dissipated by osmotic lysis during thawing. The presence of a permeant solute such as tetraethylammonium perchlorate provides an alternative mechanism to balance osmotic pressure, thereby preserving the gradients of impermeable species.

Role of melanin in appressorium function

Appressoria of certain pathogenic fungi appear darkly pigmented due to a discrete cell wall layer of melanin. We have studied the function of appressorial melanin using wild-type and melanin-deficient strains of the rice blast pathogen Magnaporthe grisea and the melanin biosynthesis inhibitor tricyclazole. All appressoria exhibited a single, circular, wall-less pore against the substratum. Pores in both melanized and unmelanized appressoria were circumscribed by a ring of material, the pore ring, which might function to seal the pore-substratum interface. Experimental evidence demonstrated that appressoria adhered tightly to surfaces and that melanin did not play a major role in that adhesion. Melanin-less appressoria were consistently and uniformly plasmolyzed by low solute concentrations, whereas melanized appressoria, if formed on a solid surface, were plasmolyzed only by much higher solute concentrations. In addition, the cell wall of living or heat-killed melanized, but never unmelanized, appressoria collapsed during plasmolysis due to cytorrhysis. Melanin, having a differential permeability to water and solute, allowed sealed appressoria to establish and maintain a high internal solute concentration that created a high internal hydrostatic pressure. It is that pressure, we suggest, that empowers the pathogen to penetrate the surface of a plastic coverslip as well as the host.

Intracellular Solutes, Photosynthesis and Respiration of the Green Alga Blidingia minima in Response to Salinity Stress

AbstractThe effects of different salinities ranging from 7–68‰ on the internal inorganic and organic solute concentrations, and on the photosynthesis and respiration have been investigated in the green alga Bladingia minima (Näg. ex Kütz.) Kylin. The levels of the main osmotic solutes K+, sucrose and proline increased with increasing salinities and vice versa, while Na+, Mg2+, Cl− and PO3–4 played a minor role in the osmotic acclimation. In contrast to related Enteromorpha species, B. minima exhibited high NO−3 concentrations, which decreased under hypo‐ and hypersaline conditions. B. minima differs also from Enteromorpha by accumulating the tertiary sulphonium compound DMSP in osmotically significant amounts under gentle hypersaline conditions.B. minima revealed typical characteristics of a “sun‐plant” having a high light compensation point together with a saturation of photosynthesis at high photon flux densities. The alga showed a broad photosynthetic stability under osmotic stress; only with extreme hypersaline conditions was photosynthesis partly inhibited. The rate of respiration remained constant in hypersaline media, and was stimulated under hyposaline conditions.

Determination of Volume ofDunaliellaCells by Lithium Dilution Measurements and Derivation of Internal Solute Concentrations

A method has been developed to measure the cell volume of the unicellular green alga Dunaliella parva 19/9 using Li + measurements only. Concentrations of internal solutes can also be calculated if they are assayed in the same samples as Li + . We found that D. parva cells grown in 0-4 kmol m~3 NaCl have an average aqueous cell volume of 65-1 +2-9 /nm3, a K + concentration of 126 + 6 mol m-3, a Na+ concentration of 9+ 11 mol m~3 and a glycerol concentration of 615 + 27 mol m-3 (n= 12). Algae grown in 1-5 kmol m~3 NaCl have an average aqueous cell volume of 131+7-5 ??m3, a K+ concentration of 109 + 4 mol m-3, a Na+ concentration of 10 + 39 mol m3 and a glycerol concentration of 1 425 + 59 mol m-3 (n= 12). These results indicate that D. parva cells adapted to high salinities have larger cell volumes than those adapted to lower salinities. However, there is no evidence for a significant difference in internal Na+ concentration, despite the almost 4-fold difference in the concentration of external NaCl. The intracellular glycerol concentration alone accounts for 65% and 54%, respectively, of the osmotic balance in low and high salt grown cells.

Iron (III) Ion Selective Electrode Based on Dithia 12‐Crown‐4

AbstractAn iron (III) ion selective PVC membrane electrode based on 1,7‐dithia 12‐crown‐4 as a neutral carrier was prepared. Monovalent responses with a Nerstian slope of 56+1 mV/decade was observed for the Fe (III) ion‐selective electrode within the concentration range 10−3–10−5 M Fe (NO3)3. The monovalent responses may be attributed to the formation of Fe (OH)2+ or Fe (OH)2(H2O)+4 species in aqueous solutions and the absorption of these ions into the PVC electrode membrane. The electrode exhibited good selectivity for Fe (III) in comparison with various alkali, alkali‐earth and some heavy metal ions. The effects of the composition of the membrame, addition of STPB (sodium tetraphenyl borate), the concentration of internal solution of the electrode and anions in the test solutions were discussed.

Development of salt-resistant active transport in a moderately halophilic bacterium.

The moderately halophilic bacterium Vibrio costicola accumulates alpha-aminoisobutyric acid (AIB) by active transport. Substantial amounts of Na(+) ions are needed for this transport. This is not due to an ionic requirement for respiration; cells respire as well as KCl as in NaCl but do not transport AIB in KCl. In cells grown in the presence of 1.0 or 2.0 M NaCl, AIB transport took place in higher NaCl concentrations than in cells grown in the presence of 0.5 M NaCl. The latter cells developed salt-resistant transport when they were exposed to 1.0 M NaCl in the presence of chloramphenicol and other antibiotics that inhibit protein synthesis. Two levels of salt-resistant transport were observed. One level (resistance to 3.0 M NaCl) developed in 1.0 M NaCl without the addition of nutrients, did not seem to require an increase in internal solute concentration, and was not lost when cells grown in 1.0 M NaCl were suspended in 0.5 M NaCl. The second level (resistance to 4.0 M NaCl) developed in 1.0 M NaCl only when nutrients were added, may have required an increased internal solute concentration, and was lost when 1.0 M NaCl-grown cells were suspended in 0.5 M NaCl or KCl. Among the substances that stimulated the development of salt-resistant AIB transport, betaine was especially active. Furthermore, direct addition of betaine permitted cells to transport AIB at higher NaCl concentrations. High salt concentrations inhibited endogenous respiration to a lesser extent than AIB transport, especially in 0.5 M NaCl-grown cells. Thus, these concentrations of salt did not inhibit AIB transport by inhibiting respiration. However, oxidation of glucose and oxidation of succinate were at least as sensitive to high salt concentrations as AIB transport, suggesting that a salt-sensitive transport step(s) is involved in the oxidation of these substrates.

Regulation of internal solute concentrations of marine Vibrio alginolyticus in response to external NaCl concentration.

Slightly halophilic marine Vibrio alginolyticus grown in the range of NaCl from 0.2 to 1.5 M maintained the total internal solute concentration always higher than the external medium by about 0.25 osM. The concentrations of macromolecules such as DNA, RNA, and protein were little affected by the increase in medium NaCl. The internal K+ concentration was kept to about 400 mM in the range of medium NaCl from 0.4 to 0.8 M; it rose to 510 mM when the bacterium was grown in 1.5 M NaCl, indicating that K+ increased only slightly in response to the large increase in medium NaCl. Thus, in contrast to the case of nonhalophilic and extremely halophilic bacteria, K+ was unlikely to act as a major component to regulate the internal solute concentration of marine V. alginolyticus. The internal Na+ and Cl- concentrations were maintained always lower than those in the growth medium, but they increased in response to the increase in medium NaCl. The concentration of internal Na+ was close to that of K+ at the concentration of medium NaCl that supports the optimal growth of this organism. The total amino acid content of V. alginolyticus increased from 76 to 413 mM by the increase in medium NaCl from 0.2 to 1.5 M. The concentrations of glutamic acid and prolined were 254 and 72 mM, respectively, when grown in 1.5 M NaCl. These results indicated that Na+, Cl- and amino acids, especially glutamic acid and proline, contributed to the regulation of internal solute concentration of V. alginolyticus in response to the increased external NaCl.

Effects of internal and external cations and of ATP on sodium-calcium and calcium-calcium exchange in squid axons

Calcium-45 efflux was measured in squid axons whose internal solute concentration was controlled by internal dialysis. Most of the Ca efflux requires either external Na (Na-Ca exchange) or external Ca plus in alkali metal ion (Ca-Ca exchange; cf. Blaustein & Russell, 1975). Both Na-Ca and Ca-Ca exchange are apparently mediated by a single mechanism because both are inhibited by Sr and Mn, and because addition of Na to an external medium optimal for Ca-Ca exchange inhibits Ca efflux. The transport involves simultaneous (as opposed to sequential) ion counterflow because the fractional saturation by internal Ca (Cai) does not affect the external Na (Nao) activation kinetics; also, Nao promotes Ca efflux whether or not an alkali metal ion is present inside, whereas Ca-Ca exchange requires alkali metal ions both internally and externally (i.e., internal and external sites must be appropriately loaded simultaneously). ATP increases the affinity of the transport mechanism for both Cai and Nao, but it does not affect the maximal transport rate at saturating [Ca2+]i and [Na+]o; this suggest that ATP may be acting as a catalyst of modulator, and not as an energy source. Hill plots of the Nao activation data yield slopes congruent to 3 for both ATP-depleted and ATP-fueled axons, compatible with a 3 Na+-for-1 Ca2+ exchange. With this stoichiometry, the Na electrochemical gradient alone could provide sufficient energy to maintain ionized [Ca2+]i in the physiological range (about 10(-7) M).