Effect Of High Ionic Strength Research Articles

Lipid digestion profiles of pickering emulsion gels stabilized by β-glucans microgel particles

Pickering emulsion gels (PEGs) stabilized by microgel particles (MPs) have a wide range of applications. However, the extent and mechanisms of lipid digestion in these PEGs are still unclear. In this study, we explored how the concentration of β-glucans MPs and different stabilizers influence the lipid digestion profiles. Our findings revealed a significant role of β-glucans MPs in modulating lipid digestion, with a reduction in lipid digestion rate and extent correlated with an increase in MPs concentration. Notably, compared to droplets stabilized by other agents, emulsions stabilized by β-glucans MPs exhibited the lowest initial release rate (0.81 ± 0.08 FFA%/min) and final degree of digestion (18.96% ± 0.42%) of free fatty acids. Lipid droplets stabilized by β-glucan MPs were able to effectively resist the effects of high ionic strength and complex components in the oral and gastric environments, maintaining their structural integrity and preventing droplet aggregation. Our results indicated that β-glucans MPs are not only effective stabilizers but also provide a novel approach to controlling lipid digestibility.

Identifying safety-relevant knowledge gaps concerning radionuclide mobility – bringing together fundamental research and application in repository safety analysis

Abstract. The mobility of radionuclides in a nuclear waste repository is strongly influenced by their chemical form (e.g. oxidation state and speciation), which determines their solubility and chemical interactions with mineral surfaces. To date, significant efforts have been made to investigate the mechanisms (e.g. sorption and diffusion) underlying radionuclide retention. However, knowledge gaps persist, especially under complex environmental conditions, as may be expected in a deep geological repository (e.g. the complexation of radionuclides with organic compounds, the influence of elevated temperature and the effects of high ionic strength). In order to make reliable predictions about radionuclide mobility and, consequently, about post-closure repository safety, it is necessary to identify, evaluate and, where necessary, close these knowledge gaps. This workshop aims to bring together experts in both fundamental research and its applications to repository safety. It intends to facilitate knowledge exchange between the two fields, promoting more coordinated and goal-oriented safety research. Participants are invited to share their knowledge about the need for further experimental and computational investigations as well as their insight into the data requirements for reliable transport models and implications for safety assessment.

A green initiative for oiled sand cleanup using chitosan/rhamnolipid complex dispersion with pH-stimulus response

The released oil can affect the vulnerable shoreline environment if the oil spills happen in coastal waters. The stranded oil on shorelines is persistent, posing a long-term influence on the intertidal ecosystem after weathering. Therefore, shoreline cleanup techniques are required to remove the oil from the shoreline environment. In this study, a new shoreline cleanup initiative using chitosan/rhamnolipid (CS/RL) complex dispersion with pH-stimulus response was developed for oiled sand cleanup. The results of factorial and single-factor design revealed that the CS/RL complex dispersion maintained high removal efficiency for oiled sand with different levels of oil content in comparison to using rhamnolipid alone. However, the increase of salinity negatively affected the removal efficiency. The electrostatic screening effect of high ionic strength can hinder the formation of the CS/RL complex, and thus reduce removal efficiency. The pH-responsive characteristic of chitosan allows the easy separation of water and oil in washing effluent. The chitosan polyelectrolytes aggregated and precipitated due to the deprotonation of amino groups by adjusting the pH of the washing effluent to above 8. The microscope image demonstrated that the chitosan aggregates wrapped around the oil droplets and settled to the bottom together, thus achieving oil–water separation. Such pH-stimulus response may help achieve an easy oil-water separation after washing. These findings have important implications for developing the new strategies of oil spill response.

Vesicle Self-Assembly of Monoalkyl Amphiphiles under the Effects of High Ionic Strength, Extreme pH, and High Temperature Environments.

Vesicles and other bilayered membranous structures can self-assemble from single hydrocarbon chain amphiphiles. Their formation and stability are highly dependent on experimental conditions such as ionic strength, pH, and temperature. The addition of divalent cations, for example, often results in the disruption of vesicles made of a single fatty acid species through amphiphile precipitation. However, membranes composed of amphiphile mixtures have been shown to be more resistant to low millimolar concentrations of divalent cations at room temperature. In this report, several mixtures of amphiphiles are examined for their propensity to self-assemble into membranous vesicular structures under extreme environmental conditions of low pH, high ionic strengths, and temperatures. In particular, mixtures of decylamine with polar cosurfactants were found to efficiently form membranes under these conditions far away from those normally supporting vesicle formation. We further examined decanoic acid/decylamine mixtures in detail. At pH 2 in low ionic strength solutions, the amphiphiles formed oily or crystalline structures; however, the introduction of salts or/and strong acids in conjunction with high temperature induced a stable vesiculation. Thus, extreme environments, such as volcanic or vent environments whose environmental conditions are known to support high chemical reactivity, could have harbored and most significantly promoted the formation of simple organic compartments that preceded cells.

Co-gasification of sewage sludge and woody biomass in a fixed-bed downdraft gasifier: Toxicity assessment of solid residues

As the demand for fossil fuels and biofuels increases, the volume of ash generated will correspondingly increase. Even though ash disposal is now strictly regulated in many countries, the increasing volume of ash puts pressure on landfill sites with regard to cost, capacity and maintenance. In addition, the probability of environmental pollution from leakage of bottom ash leachate also increases. The main aim of this research is to investigate the toxicity of bottom ash, which is an unavoidable solid residue arising from biomass gasification, on human cells in vitro. Two human cell lines i.e. HepG2 (liver cell) and MRC-5 (lung fibroblast) were used to study the toxicity of the bottom ash as the toxins in the bottom ash may enter blood circulation by drinking the contaminated water or eating the food grown in bottom ash-contaminated water/soil and the toxic compounds may be carried all over the human body including to important organs such as lung, liver, kidney, and heart. It was found that the bottom ash extract has a high basicity (pH=9.8–12.2) and a high ionic strength, due to the presence of alkali and alkaline earth metals e.g. K, Na, Ca and Mg. Moreover, it also contains concentrations of heavy metals (e.g. Zn, Co, Cu, Fe, Mn, Ni and Mo) and non-toxic organic compounds. Although human beings require these trace elements, excessive levels can be damaging to the body. From the analyses of cell viability (using MTS assay) and morphology (using fluorescence microscope), the high toxicity of the gasification bottom ash extract could be related to effects of high ionic strength, heavy metals or a combination of these two effects. Therefore, our results suggest that the improper disposal of the bottom ash wastes arising from gasification can create potential risks to human health and, thus, it has become a matter of urgency to find alternative options for the disposal of bottom ash wastes.

Removal of dichloromethane from waste gas streams using a hybrid bubble column/biofilter bioreactor.

The performance of a hybrid bubble column/biofilter (HBCB) bioreactor for the removal of dichloromethane (DCM) from waste gas streams was studied in continuous mode for several months. The HBCB bioreactor consisted of two compartments: bubble column bioreactor removing DCM from liquid phase and biofilter removing DCM from gas phase. Effect of inlet DCM concentration on the elimination capacity was examined in the DCM concentration range of 34–359 ppm with loading rates ranged from 2.2 to 22.8 g/m3.h and constant total empty bed retention time (EBRT) of 200 s. In the equal loading rates, the elimination capacity and removal efficiency of the biofilter were higher than the corresponding values of the bubble column bioreactor. The maximum elimination capacity of the HBCB bioreactor was determined to be 15.7 g/m3.h occurred in the highest loading rate of 22.8 g/m3.h with removal efficiency of 69%. The overall mineralization portion of the HBCB bioreactor was in the range of 72-79%. The mixed liquor acidic pH especially below 5.5 inhibited microbial activity and decreased the elimination capacity. Inhibitory effect of high ionic strength was initiated in the mixed liquor electrical conductivity of 12.2 mS/cm. This study indicated that the HBCB bioreactor could benefit from advantages of both bubble column and biofilter reactors and could remove DCM from waste gas streams in a better manner.

The effect of high ionic strength on neptunium (V) adsorption to a halophilic bacterium

The mobility of neptunium (V) in subsurface high ionic strength aqueous systems may be strongly influenced by adsorption to the cell wall of the halophilic bacteria Chromohalobacter sp. This study is the first to evaluate the adsorption of neptunium (V) to the surface of a halophilic bacterium as a function of pH from approximately 2 to 10 and at ionic strengths of 2 and 4M. This is also the first study to evaluate the effects of carbonate complexation with neptunium (V) on adsorption to whole bacterial cells under high pH conditions. A thermodynamically-based surface complexation model was adapted to describe experimental adsorption data under high ionic strength conditions where traditional corrections for aqueous ion activity are invalid. Adsorption of neptunium (V) was rapid and reversible under the conditions of the study. Adsorption was significant over the entire pH range evaluated for both ionic strength conditions and was shown to be dependent on the speciation of the sites on the bacterial surface and neptunium (V) in solution. Adsorption behavior was controlled by the relatively strong electrostatic attraction of the positively charged neptunyl ion to the negatively charged bacterial surface at pH below circum-neutral. At pH above circum-neutral, the adsorption behavior was controlled by the presence of negatively charged neptunium (V) carbonate complexes resulting in decreased adsorption, although adsorption was still significant due to the adsorption of negatively charged neptunyl-carbonate species. Adsorption in 4M NaClO4 was enhanced relative to adsorption in 2M NaClO4 over the majority of the pH range evaluated, likely due to the effect of increasing aqueous ion activity at high ionic strength. The protonation/deprotonation characteristics of the cell wall of Chromohalobacter sp. were evaluated by potentiometric titrations in 2 and 4M NaClO4. Bacterial titration results indicated that Chromohalobacter sp. exhibits similar proton buffering capacity to previously studied non-halophilic bacteria. The titration data were used to determine the number of types, concentrations, and associated deprotonation constants of functional groups on the bacterial surface; the neptunium adsorption measurements were used to constrain binding constant values for the important neptunium (V)-bacterial surface species. Together, these results can be incorporated into geochemical speciation models to aid in the prediction of neptunium (V) mobility in complex bacteria-bearing geochemical systems.

Effect of high ionic strength on the extraction of uranium(VI) ions

Preparation and characterization of didodecylphosphoric acid (HDDPA) as an extractant in toluene was carried. Mass spectroscopy showed that the monomer peak at 457.4 amu [M–Na+] is double that of the dimer at 891.9 amu [M–M–Na+] and the monomer molecules concentration dominate the dimer molecules in toluene. HDDPA was used as an extractant for the extraction of U(VI) ion from perchlorate and nitrate media that have ionic strength (1.00, 3.00, 5.00, 7.00 M). The effect of HDDPA concentration, pcH, ionic strength of supporting electrolytes, and temperature in the range 15–45 °C on the extraction process have been studied. The stoichiometry of the extraction of U(VI) ion, the free energy change (ΔG), the enthalpy change (ΔH), the entropy change (ΔS), and Kex at different ionic strength have been calculated. The formula of the complexes, which were formed has been established to be UO2(X)(R2)(HR2) at pcH equal 2.00 and UO2(X)(R2)(HR2) and UO2(X)(R2) at pcH = 1.00, where (X) is ClO4- or NO3- and (HR2) is didodecylphosphoric acid monomer, (R2) is the deprotonated didodecylphosphoric acid, where R is the dodecyl group.

Effect of soil structure disturbance on erosion and phosphorus losses from Finnish clay soil

No-till (NT) has proved to be an effective method to reduce erosion and losses of particulate phosphorus (PP) from fields to watercourses. However, the accumulation of P in the uppermost soil layer and the increased leaching risk of dissolved reactive phosphorus (DRP) in surface runoff reduce the environmental benefits of NT. The objective of this study was to determine whether the concentration of DRP in percolates could be decreased by mixing surface soil (0–5 cm) and deeper soil layers (5–20 cm) and how this affects erosion. We also tested the impact of high ionic strength on erosion from undisturbed and disturbed soil columns. Soil samples were collected from conventionally tilled (CT) and non-tilled (for 5 years) plots from a clay field (Vertic Cambisol) at 0–2.5, 2.5–10 and 10–20 cm depths. Moreover, undisturbed and disturbed soil columns representing the same plots were saturated with water in the laboratory and allowed to drain. The physico-chemical properties of the percolates were analysed to unravel the impact of cultivation methods and disruption of the aggregate structure. To see the effect of high ionic strength on detachment of soil particles, the soil columns were leached with ammonium acetate solution. The low pH of NT surface soil had enhanced the sorption of P and easily-soluble P had accumulated in the uppermost soil layer. Surprisingly, this enrichment did not increase the DRP concentration in the percolates when water percolated through the 0–5 or 0–20 cm soil layers. Disruption of the aggregate structure increased the turbidity and concentrations of suspended solids and PP in the percolates. In the NT samples, this action increased the concentration of DRP relatively more than in the CT samples. When the disturbed soil columns were leached with a solution of high ionic strength, the turbidity of the eluates was almost as low as before the breakage. To prevent erosion and the leaching of PP and DRP, we have to ensure an even water infiltration by improving the soil structure and by avoiding the disruption of stabilized aggregates. Ploughing the surface layer of NT soil can be recommended only if erosion from the field can be kept under control.

Effects of Charge-to-Alanine Substitutions on the Stability of Ribosomal Protein L30e from Thermococcus celer

The ability to rationally engineer a protein with altered stability depends upon the detailed understanding of the role of noncovalent interactions in defining thermodynamic properties of proteins. In this paper, we used T. celer L30e as a model to address the question of the role of charge-charge interactions in defining the stability of this protein. A total of 26 single-site charge-to-alanine variants of this protein were generated, and the stability of these proteins was determined using thermal- and denaturant-induced unfolding. It was found that, although L30e is isolated from a thermophilic organism and is highly thermostable, some of the substitutions lead to a further increase in the transition temperature. Analysis of the effects of high ionic strength on the stabilities of L30e variants shows that the long-range charge-charge interactions are as important as the short-range (salt bridge) interactions. The changes in stabilities of the T. celer L30e protein variants were compared with the changes in the energy of charge-charge interactions calculated using different computational models. It was found that there is a good qualitative agreement between experimental and calculated data: for 70-80% (19-21 of 26, confidence p < 0.003) of the variants, computational models predict correctly the sign of the stability changes. In particular, computational models identify correctly those charged amino acid residue substitutions of which led to enhancement in thermostability. Thus, optimization of the charge-charge interactions might be a useful approach for the rational increase in protein stability.

Calcium phosphate precipitation in catanionic templates

A simple and effective mean for controlling electrostatic interactions during mineral precipitation in water is the use of a “catanionic” template. Such strategy is used to precipitate calcium phosphate (hydroxyapatite or HAP) and obtain mesoporous materials. Mixtures of catanionic surfactants with phosphate head-groups (polyoxyethylene oleyl ether phosphate) and a quaternary ammonium (myristyl trimethyl ammonium bromide) are used in order to obtain a template with adjustable surface charge and test the “charge-matching” effect. This effect manifests by a strong dependence of the template shape on molar fraction, which governs the charge per unit area of the surfactant as well as the growth of inorganic network. We first explore the effect of high ionic strength and pH variation on phase diagram of template. A hexagonal structure is observed for anionic surfactant, and such organization is still preserved in the presence of large quantity of cationic component. Synthesis of HAP is then performed using independently various volume fractions of template and various mole fraction of anionic component in the template. For samples with low amount of surfactant and an excess of anionic component, TOC analysis shows more than 80% of the added surfactant is trapped in the precipitate. These samples display in SAXS three peaks that are characteristic of a hexagonal structure. Such structure, where the repetition distance is much lower than twice surfactant chain length, has not yet been described in surfactant self-assembly. This must be a monolayer microstructure, but symmetry group is not known since higher orders cannot be detected. The HAP-template hybrid structure disappears after calcination, and the BET surface of calcined powders is smaller than for HAP particles synthesized in homogeneous conditions.

Use of treated mine water for rainbow trout (Oncorhynchus mykiss) culture: a production scale assessment

In previous proof-of-concept work, it was shown that the use of treated coal mine water for rainbow trout (Oncorhynchus mykiss) culture in a cage was technically feasible, though only a 50-fish bioassay was grown and no work on production-related issues was conducted. To further advance the use of treated mine water, an under-utilized water resource throughout Mid Appalachia, work was conducted to assess the effects of using treated coal mine water for the intensive production of rainbow trout in a flow-through system. During this study, comprehensive water quality data were collected to supplement fish weight and length data taken during routine monthly sampling events. The 8000 fish grew well in the raceway system over the 9 months of production, where a feed conversion ratio of 1.4 and a condition factor of 5.1 × 10−4 were measured with stocking and harvest densities of 26.4 and 50.2kg/m3, respectively. Further, total net production was 3275kg (7220lb) with 98.6% survival. Throughout the study, dissolved ion concentrations (Fe, Al, Mg, Ca, and SO4) often exceeded recommended tolerance limits. Further, elevated ammonia nitrogen concentrations generated from a component of the mine water-treatment process were identified as a potential limiting factor for aquaculture development. However, when the non-ideal effects of high ionic strength and the speciation of dissolved metal–ligand complexes were taken into account, the concentrations of free metal ions were within recommended tolerance limits.

NADP-glutamate dehydrogenase activity is increased under hyperosmotic conditions in the halotolerant yeast Debaryomyces hansenii.

Glutamate plays an important role in osmoprotection in various bacteria. In these cases, increased intracellular glutamate pools are not attributable to the NADP-dependent glutamate dehydrogenase (NADP-GDH) or the glutamate synthase, which do not increase their activities under hyperosmotic conditions, but rather to changes in other enzymes involved in glutamate metabolism. We performed a study which indicates that, as opposed to what happens in bacteria, the activity of NADP-GDH is fivefold higher when the halotolerant yeast Debaryomyces hansenii is grown in the presence of 1 M NaCl, compared with growth in media with no added salt. Since purified NADP-GDH activity in vitro was not enhanced by the presence of salt and was more sensitive to ionic strength than the two isoenzymes from S. cerevisiae, increased enzyme synthesis is the most plausible mechanism to explain our results. We discuss the possibility that increased NADP-GDH activity in D. hansenii plays a role in counteracting the inhibitory effect of high ionic strength on the activity of this enzyme.

Use of treated mine water for rainbow trout (Oncorhynchus mykiss) culture—a preliminary assessment

Treated waters from active and abandoned coal mines are a potentially valuable, though underutilized resource, which may be used to expand the aquaculture industry in West Virginia and other mid-Appalachian states. A preliminary investigation of the technical feasibility of using treated acid mine waters to rear rainbow trout (Oncorhynchus mykiss) was conducted. In the study, a regimen of water quality monitoring was initiated to fully characterize a treated mine water and allow for comparison with requirements for salmonid culture. To complement water quality studies, a bioassay consisting of fifty rainbow trout were grown in a net pen in the treated mine water; production-scale studies were not the focus of this initial work. Although aqueous phase concentrations of metals associated with acid mine drainage (AMD) (Fe, Al, Mn, Ca, Mn) often exceeded limits recommended for salmonid culture, the fish grew and exhibited no physiological signs of stress. The lack of anticipated water quality impacts on the fish was attributed to a combination of the effects of high ionic strength on the chemical activity of dissolved metal species and the formation of dissolved metal–ligand pairs in the treated mine waters. Thus, non ideal effects of high ionic strength and the coordination chemistry of treated mine waters must be considered when assessing the suitability of such waters for aquaculture, as many water resources otherwise considered too impaired for aquaculture use may be rendered viable.

Kinetics of Heterogeneous Electron Transfer at Liquid/Liquid Interfaces As Studied by SECM

Scanning electrochemical microscopy (SECM) was used to investigate the kinetics of heterogeneous electron transfer (ET) as a function of driving force at the interface between two immiscible electrolyte solutions. At high driving force, experimental rate constants decreased with increasing overpotential, deviating from predictions based on Butler−Volmer kinetics. This decrease in ET rate with increasing driving force is consistent with Marcus theory inverted region behavior. At low driving force, the potential dependence of the forward and reverse ET rate constants followed Butler−Volmer theory. SECM is also demonstrated to be a useful means of studying the effect of high ionic strength on the kinetics of heterogeneous ET.

Effect of High Ionic Strength and Inhibitors of H,K-ATPase on the Ouabain-Sensitive K-p-Nitrophenylphosphatase Activity in the Sea Anemone Stichodactyla helianthus

The ouabain-sensitive, K-stimulated p-nitrophenyl phosphatase (K-pNPPase) activity, an associated activity of the Na,K-ATPase, was assayed in tentacles of the sea anemone Stichodactyla helianthus to investigate the possibility that the sea anemone Na,K-ATPase activity is an associated activity of an H,K-ATPase. Activity was maximal at pH 6.5–7.0, decreasing only slightly in acidic medium but falling abruptly in alkaline medium to 60% of maximum at pH 7.4. The pH of maximum activity was not remarkably altered in high ionic strength medium (560 mM choline chloride), but ouabain-sensitive K-pNPPase activity of both rat and sea anemone was strongly inhibited. Inhibitors of the gastric H,K-ATPase, 100 μM omeprazole and 10 μM SCH 28080, did not inhibit the ouabain-sensitive K-pNPPase activity. Activity of the sea anemone enzyme was inhibited by 10 μM ammonium vanadate, an inhibitor of P-type ATPases, and not by 2.5 mM sodium azide, an inhibitor of both F-type and V-type ATPases. Because the sea anemone K-pNPPase activity was previously found to be more sensitive to ouabain than the Na,K-ATPase activity, K+-ouabain antagonism was investigated and found to be relatively muted, whereas K+-Na+ competition was stronger than in the rat kidney.

Effect of the interdomain basic region of cytochrome f on its redox reactions in vivo.

The prominent interdomain basic surface region seen in the high-resolution structure of the active lumen-side C-terminal fragment of turnip cytochrome f, containing the conserved Lys58,65,66 (large domain) and Lys187 (small domain), has been inferred from in vitro studies to be responsible for docking of its physiological oxidant, plastocyanin. The effect of the putative docking region of cyt f on its reactivity in vivo was tested by site-directed mutagenesis in Chlamydomonas reinhardtii. Three charge-neutralizing mutants were constructed involving: (i)the two lysines (Lys188Asn-Lys189Gln) in the small domain, (ii) the three lysines (Lys58Gln-Lys65Ser-Lys66Glu) in the large domain, and (iii) all five of these lysines spanning both domains. All mutants grew phototrophically. The mutants displayed a 20-30% increase in average generation time, and comparable decreases in rates of steady-state oxygen evolution and the slow (millisecond) electrochromic 515 nm band shift. The magnitude of the changes was greatest in the 5-fold Lys-minus mutant (Lys58Gln-Lys65Ser-Lys66Glu-Lys188Asn-Lys189G ln). The mutants showed a small increase (approximately 25%) in the t1/2, from 0.2 to 0.25 ms, of cyt f photooxidation, far less than anticipated (ca. 100-fold) from in vitro studies of the effect of high ionic strength on the cyt f-PC interaction. The t1/2 of cyt f dark reduction via the Rieske protein increased from 5-6 ms in the wild type to 11-12 ms in the 5-fold Lys-minus mutant. Cells grown phototrophically in the absence of Cu, where cyt c6 is the electron acceptor of cyt f, displayed net rates of cytochrome photooxidation that were slightly faster than those in the presence of Cu, which also decreased by a factor of < or = 25% in the Lys-minus mutants. It was concluded that (a) the net effect of electrostatic interaction between cytochrome f and its electron acceptor in vivo is much smaller than measured in vitro and is not rate-limiting. This may be a consequence of a relatively high ionic strength environment and the small diffusional space available for collision and docking in the internal thylakoid lumen of log phase C. reinhardtii. (b) The efficiency of electron transfer to cytochrome f from the Rieske protein is slightly impaired by the neutralization of the lysine-rich domain.

High Ca is not the primary factor in poor growth of Lupinus angustifolius L. in high pH soil

Poor growth of Lupinus angustifolius L. on alkaline soils has been suggested to be due to effects of both high calcium concentrations and high ionic strength in soil solutions on growth. This glasshouse study investigated the effect of calcium supplied as either CaCO3 or CaSO4 to an acid soil on the growth of N-fertilized and N2-fixing plants of L. angustifolius cv. Gungurru, and compared responses of L. angustifolius and Lupinus pilosus Murr., an alkaline-tolerant species, to high ionic strength in high pH solutions. Increasing CaCO3 application increased soil solution pH, and decreased shoot and root growth and chlorophyll concentration in the youngest fully expanded leaflets of both Na-fixing and N-fertilized plants of L. angustifolius. The effect of CaCO3 in decreasing root length was prior to and more pronounced than that on shoot weight and chlorophyll concentration. Adding CaSO4 increased calcium concentration in soil solution by 1.7-6.6 fold and calcium concentration in leaves by 10-30%, but did not markedly decrease the growth of plants grown at any rate of added CaCO3. Increasing pH in nutrient solution from 5 2 to 7.0 decreased shoot weight of L. angustifolius, but slightly increased that of L. pilosus. Plant growth of both L. angustifolius and L. pilosus was slightly decreased as solution ionic strength increased. The effect of high ionic strength was similar whether CaCl2 or KCl was the source of ions. The results suggest that poor growth of L. angustzfolius relative to L. pilosus on some alkaline soils is not caused by excessive calcium or high ionic strength, rather high pH effects on root extension appear to be the major cause of the poor growth.

Effects of high ionic strength on 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine multilamellar and vesicle mesophases: A comparative electron spin resonance study

The effects of high NaCl concentrations on DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine) multilamellar and vesicle mesophases have been investigated by electron spin resonance spectroscopy with the spin labels 5-nitroxide stearic acid and di- tert-butyl-nitroxide to get information on the molecular order and fluidity of the bilayers. In the presence of up to 3 M NaCl the multilamellar phase shows an increase in molecular order, mainly in the gel phase, and a decrease of the bilayer permeability. An upward shift from about 34.3 to 38.5°C and from 40.6 to 42.5°C of both the pre- and main-phase transition temperatures is also observed. Negligible effects are observed on the liquid crystal phase. An increase in the permeability and a decrease in molecular order with a downward shift of the main transition temperature from 37.5 to 36.0°C are observed for small sonicated unilamellar vesicles. Furthermore, the effect on the liquid-crystal phase is very strong. The data are interpreted in terms of ion-induced perturbations either of the hydrogen bond network or of the electrostatic interaction in the polar zone of the DPPC bilayers. The different radii of curvature of the multilamellar and vesicle mesophases triggers the phenomena observed.

Mechanism of DNA (southern) and protein (western) blotting on cellulose nitrate and other membranes

The transfer of DNA fractions from hydrophilic gels to nitrocellulose membranes (Southern blotting) which was soon followed by the description of an analogous procedure for RNA (Northern blotting), and somewhat later for proteins (Western blotting), has rapidly become an important separation and characterization method in molecular biology, genetic engineering, and immunological detection. Surface tension measurements have shown that the interfacial attraction between DNA and cellulose esters (− ΔG 132) in aqueous media can be considerable. The weaker binding energy of proteins to cellulose nitrate and to cellulose acetate may be compared to hydrophobic interaction chromatography, as on account of the somewhat lower ∣ − ΔG 132∣ values, it often is necessary to “fix” them more tightly onto nitro-cellulose by using high salt concentrations. The binding energy of RNA to both cellulose esters also is rather low. In addition to the effect of high ionic strength, the effect of adding methanol, and the effects of denaturation, heating and drying on the energy of attachment of the biopolymers to cellulose esters, have been studied. Cationized nylon membranes have been advocated recently, especially for electrophoretic transfer of nucleic acids (in which process high salt concentrations cannot easily be used). With positively charged nylon membranes, the attachment mainly occurs through the electrostatic attraction between the strongly negatively charged nucleic acids (or proteins) and the positively charged membrane. Also, more apolar membranes (of polyvinyl difluoride) have been proposed, which manifest a strong interfacial (hydrophobic) attraction to all the above biopolymers (regardless of their electrostatic charge). However, with these two novel membrane types it is no longer possible to exploit the large difference in binding energy between DNA and RNA, which makes cellulose nitrate membranes so uniquely suited for RNA-DNA hybridization assays.