Transient cerebral hypoperfusion assisted intraarterial cationic liposome delivery to brain tissue

PubMed Central

Joshi, Shailendra; Singh-Moon, Rajinder P.; Wang, Mei; Chaudhuri, Durba B.; Holcomb, Mark; Straubinger, Ninfa L.; Bruce, Jeffrey N.; Bigio, Irving J.; Straubinger, Robert M.

2014-01-01

Object Transient cerebral hypoperfusion (TCH) has empirically been used to assist intraarterial (IA) drug delivery to brain tumors. Transient (< 3 min) reduction of cerebral blood flow (CBF) occurs during many neuro- and cardiovascular interventions and has recently been used to better target IA drugs to brain tumors. In the present experiments, we assessed whether the effectiveness of IA delivery of cationic liposomes could be improved by TCH. Methods Cationic liposomes composed of 1:1 DOTAP:PC (dioleoyl-trimethylammonium-propane:phosphatidylcholine) were administered to three groups of Sprague Dawley rats. In the first group, we tested the effect of blood flow reduction on IA delivery of cationic liposomes. In the second group, we compared TCH-assisted IA liposomal delivery vs. intravenous (IV) administration of the same dose. In the third group, we assessed retention of cationic liposomes in brain four hours after TCH assisted delivery. The liposomes contained a near infrared dye, DilC18(7), whose concentration could be measured in vivo by diffuse reflectance spectroscopy. Results IA injections of cationic liposomes during TCH increased their delivery approximately four-fold compared to injections during normal blood flow. Optical pharmacokinetic measurements revealed that relative to IV injections, IA injection of cationic liposomes during TCH produced tissue concentrations that were 100-fold greater. The cationic liposomes were retained in the brain tissue four hours after a single IA injection. There was no gross impairment of neurological functions in surviving animals. Conclusions Transient reduction in CBF significantly increased IA delivery of cationic liposomes in the brain. High concentrations of liposomes could be delivered to brain tissue after IA injections with concurrent TCH while none could be detected after IV injection. IA-TCH injections were well tolerated and cationic liposomes were retained for at least 4 hours after IA administration. These results should encourage development of cationic liposomal formulations of chemotherapeutic drugs and their IA delivery during TCH. PMID:24664370

Quantitative Characterization of Non-Classic Polarization of Cations on Clay Aggregate Stability

PubMed Central

Hu, Feinan; Li, Hang; Liu, Xinmin; Li, Song; Ding, Wuquan; Xu, Chenyang; Li, Yue; Zhu, Longhui

2015-01-01

Soil particle interactions are strongly influenced by the concentration, valence and ion species and the pH of the bulk solution, which will also affect aggregate stability and particle transport. In this study, we investigated clay aggregate stability in the presence of different alkali ions (Li+, Na+, K+, and Cs+) at concentrations from10−5 to 10−1 mol L−1. Strong specific ion effects on clay aggregate stability were observed, and showed the order Cs+>K+>Na+>Li+. We found that it was not the effects of ion size, hydration, and dispersion forces in the cation–surface interactions but strong non-classic polarization of adsorbed cations that resulted in these specific effects. In this study, the non-classic dipole moments of each cation species resulting from the non-classic polarization were estimated. By comparing non-classic dipole moments with classic values, the observed dipole moments of adsorbed cations were up to 104 times larger than the classic values for the same cation. The observed non-classic dipole moments sharply increased with decreasing electrolyte concentration. We conclude that strong non-classic polarization could significantly suppress the thickness of the diffuse layer, thereby weakening the electric field near the clay surface and resulting in improved clay aggregate stability. Even though we only demonstrated specific ion effects on aggregate stability with several alkali ions, our results indicate that these effects could be universally important in soil aggregate stability. PMID:25874864

Use of marker ion and cationic surfactant plastic membrane electrode for potentiometric titration of cationic polyelectrolytes.

PubMed

Masadome, Takashi; Imato, Toshihiko

2003-07-04

A plasticized poly (vinyl chloride) (PVC) membrane electrode sensitive to stearyltrimethylammonium (STA) ion is applied to the determination of cationic polyelectrolytes such as poly (diallyldimethylammonium chloride) (Cat-floc) by potentiometric titration, using a potassium poly (vinyl sulfate) (PVSK) solution as a titrant. The end-point of the titration is detected as the potential change of the plasticized PVC membrane electrode caused by decrease in the concentration of STA ion added to the sample solution as a marker ion due to the ion association reaction between the STA ion and PVSK. The effects of the concentration of STA ion, coexisting electrolytes in the sample solution and pH of the sample on the degree of the potential change at the end-point were examined. A linear relationship between the concentration of cationic polyelectrolyte and the end-point volume of the titrant exists in the concentration range from 2x10(-5) to 4x10(-4) N for Cat-floc, glycol chitosan, and methylglycol chitosan.

Sorption of the organic cation metoprolol on silica gel from its aqueous solution considering the competition of inorganic cations.

PubMed

Kutzner, Susann; Schaffer, Mario; Börnick, Hilmar; Licha, Tobias; Worch, Eckhard

2014-05-01

Systematic batch experiments with the organic monovalent cation metoprolol as sorbate and the synthetic material silica gel as sorbent were conducted with the aim of characterizing the sorption of organic cations onto charged surfaces. Sorption isotherms for metoprolol (>99% protonated in the tested pH of around 6) in competition with mono- and divalent inorganic cations (Na(+), NH4(+), Ca(2+), and Mg(2+)) were determined in order to assess their influence on cation exchange processes and to identify the role of further sorptive interactions. The obtained sorption isotherms could be described well by an exponential function (Freundlich isotherm model) with consistent exponents (about 0.8). In general, a decreasing sorption of metoprolol with increasing concentrations in inorganic cations was observed. Competing ions of the same valence showed similar effects. A significant sorption affinity of metoprolol with ion type dependent Freundlich coefficients KF,0.77 between 234.42 and 426.58 (L/kg)(0.77) could still be observed even at very high concentrations of competing inorganic cations. Additional column experiments confirm this behavior, which suggests the existence of further relevant interactions beside cation exchange. In subsequent batch experiments, the influence of mixtures with more than one competing ion and the effect of a reduced negative surface charge at a pH below the point of zero charge (pHPZC ≈ 2.5) were also investigated. Finally, the study demonstrates that cation exchange is the most relevant but not the sole mechanism for the sorption of metoprolol on silica gel. Copyright © 2014 Elsevier Ltd. All rights reserved.

Sorption of organic cations onto silica surfaces over a wide concentration range of competing electrolytes.

PubMed

Kutzner, Susann; Schaffer, Mario; Licha, Tobias; Worch, Eckhard; Börnick, Hilmar

2016-12-15

The fundamental understanding of organic cation-solid phase interactions is essential for improved predictions of the transport and ultimate environmental fates of widely used substances (e.g., pharmaceutical compounds) in the aquatic environment. We report sorption experiments of two cationic model compounds using two silica gels and a natural aquifer sediment. The sorbents were extensively characterized and the results of surface titrations under various background electrolyte concentrations were discussed. The salt dependency of sorption was systematically studied in batch experiments over a wide concentration range (five orders of magnitude) of inorganic ions in order to examine the influence of increasing competition on the sorption of organic cations. The organic cation uptake followed the Freundlich isotherm model and the sorption capacity decreases with an increase in the electrolyte concentration due to the underlying cation exchange processes. However, the sorption recovers considerably at high ionic strength (I>1M). To our knowledge, this effect has not been observed before and appears to be independent from the sorbent characteristics and sorbate structure. Furthermore, the recovery of sorption was attributed to specific, non-ionic interactions and a connection between the sorption coefficient and activity coefficient of the medium is presumed. Eventually, the reasons for the differing sorption affinities of both sorbates are discussed. Copyright © 2016 Elsevier Inc. All rights reserved.

On the flocculation and settling characteristics of low- and high-concentration sediment suspensions: effects of particle concentration and salinity conditions.

PubMed

Zhu, Zhongfan; Xiong, Xiangzhong; Liang, Chaohuang; Zhao, Ming

2018-05-01

It remains unclear how the primary particle concentration and salinity conditions influence the flocculation and settling characteristics of water-sediment suspensions. In this study, two sets of experiments were performed to examine the flocculation and settling properties of low- and high-concentration sediment suspensions. In low-concentration suspensions, the sediment concentration undergoes a rapid initial decrease followed by a slow decrease until it approaches zero with increasing flocculation time. Increases in salinity or the valence of cations from the saline solution added to the suspension lead to a more rapidly decreasing sediment concentration with flocculation time. The valence of cations from the saline solution has a larger influence on the flocculation-settling behaviours of the suspension than the salinity. In high-concentration sediment suspensions, the height of the clear water-turbid water interface in the water-sediment suspension experiences an initial, rapidly decreasing phase followed by a slowly decreasing phase with increasing flocculation time. Increasing the primary particle concentration, salinity or valence of cations from the saline solution added to the suspension causes the height reduction of the clear water-turbid water interface to become gentler. Finally, the valence of cations from the saline solution has a greater influence on the settling characteristics of the high-concentration water-sediment suspension than the salinity.

Concentration and purification of plutonium or thorium

DOEpatents

Hayden, John A.; Plock, Carl E.

1976-01-01

In this invention a first solution obtained from such as a plutonium/thorium purification process or the like, containing plutonium (Pu) and/or thorium (Th) in such as a low nitric acid (HNO.sub.3) concentration may have the Pu and/or Th separated and concentrated by passing an electrical current from a first solution having disposed therein an anode to a second solution having disposed therein a cathode and separated from the first solution by a cation permeable membrane, the Pu or Th cation permeating the cation membrane and forming an anionic complex within the second solution, and electrical current passage affecting the complex formed to permeate an anion membrane separating the second solution from an adjoining third solution containing disposed therein an anode, thereby effecting separation and concentration of the Pu and/or Th in the third solution.

Stability and recovery of DNA origami structure with cation concentration

NASA Astrophysics Data System (ADS)

Chen, Yi; Wang, Ping; Liu, Yang; Liu, Ting; Xu, Yan; Zhu, Shanshan; Zhu, Jun; Ye, Kai; Huang, Guang; Dannong, He

2018-01-01

We synthesized triangular and rectangular DNA origami nanostructures and investigated the stability and recovery of them under low cation concentration. Our results demonstrated that the origami nanostructures would melt when incubated in low cation concentration, and recover whilst kept in the concentration for less than 10 min. However, extending the incubation time would lead to irreversible melting. Our results show the possibility of application of DNA origami nanostructures for things such as a sensor for cation concentration response, etc.

The cation-controlled and hydrogen bond-mediated shear-thickening behaviour of a tree-fern isolated polysaccharide.

PubMed

Wee, May S M; Matia-Merino, Lara; Goh, Kelvin K T

2015-10-05

The shear-thickening rheological behaviour (between 5 and 20s(-1)) of a 5% (w/w) viscoelastic gum extracted from the fronds of the native New Zealand black tree fern or mamaku in Māori was further explored by manipulating the salt content. The freeze-dried mamaku gum contained a high mineral content and sugars which upon removal via dialysis, resulted in the loss of shear thickening. However, this loss was reversible by the addition of salts to the dialysed dispersion. The mechanism of shear-thickening behaviour was therefore hypothesised to be due to shear-induced transition of intra- to intermolecular hydrogen bonding, promoted by the screening effect of cations. Mono-, di- and trivalent salts, i.e. Na(+), K(+), N(CH3)4(+), Ca(2+), Mg(2+), Al(3+) and La(3+) at concentrations between 0.001 and 1.0M were tested to support the hypothesis as well as to demonstrate the sensitivity of the biopolymer to cation valency and concentrations. The cation valency and concentration were crucial factors in determining: (i) zero-shear viscosity, (ii) critical shear rate, γ˙c (or shear rate at the onset of shear-thickening) and (iii) the extent of shear-thickening of the solution. For mono- and divalent cations these parameters were similar at equivalent ionic strengths and fairly independent of the cation type. Trivalent cations (La(3+)) however caused precipitation of the gum in the concentration range of 0.005-0.05 M but clear dispersions were obtained above 0.05 M. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effects of Ca, Cu, Al and La on pectin gel strength: implications for plant cell walls.

PubMed

McKenna, Brigid A; Nicholson, Timothy M; Wehr, J Bernhard; Menzies, Neal W

2010-06-16

Rheology of Ca-pectate gels is widely studied, but the behaviour of pectate gels formed by Cu, Al and La is largely unknown. It is well known that gel strength increases with increasing Ca concentration, and it is hypothesised that this would also be the case for other cations. Pectins are a critical component of plant cell walls, imparting various physicochemical properties. Furthermore, the mechanism of metal toxicity in plants is hypothesised to be, in the short term, related to metal interactions with cell wall pectin. This study investigated the influence of Ca, Cu, Al and La ion concentrations at pH 4 on the storage modulus as a function of frequency for metal-pectin gels prepared from pectin (1%) with a degree of esterification of 30%. Gels were formed in situ over 6d in metal chloride solution adjusted daily to pH 4. Cation concentration was varied to develop a relationship between gel strength and cation concentration. At similar levels of cation saturation, gel strength increased in the order of La

Stability of Major Geogenic Cations in Drinking Water-An Issue of Public Health Importance: A Danish Study, 1980⁻2017.

PubMed

Wodschow, Kirstine; Hansen, Birgitte; Schullehner, Jörg; Ersbøll, Annette Kjær

2018-06-08

Concentrations and spatial variations of the four cations Na, K, Mg and Ca are known to some extent for groundwater and to a lesser extent for drinking water. Using Denmark as case, the purpose of this study was to analyze the spatial and temporal variations in the major cations in drinking water. The results will contribute to a better exposure estimation in future studies of the association between cations and diseases. Spatial and temporal variations and the association with aquifer types, were analyzed with spatial scan statistics, linear regression and a multilevel mixed-effects linear regression model. About 65,000 water samples of each cation (1980⁻2017) were included in the study. Results of mean concentrations were 31.4 mg/L, 3.5 mg/L, 12.1 mg/L and 84.5 mg/L for 1980⁻2017 for Na, K, Mg and Ca, respectively. An expected west-east trend in concentrations were confirmed, mainly explained by variations in aquifer types. The trend in concentration was stable for about 31⁻45% of the public water supply areas. It is therefore recommended that the exposure estimate in future health related studies not only be based on a single mean value, but that temporal and spatial variations should also be included.

The effect of cation source and dietary cation-anion difference on rumen ion concentrations in lactating dairy cows.

PubMed

Catterton, T L; Erdman, R A

2016-08-01

Many studies have focused on the influence of dietary cation-anion difference (DCAD) on animal performance but few have examined the effect of DCAD on the rumen ionic environment. The objective of this study was to examine the effects of DCAD, cation source (Na vs. K), and anion source (Cl vs. bicarbonate or carbonate) on rumen environment and fermentation. The study used 5 rumen-fistulated dairy cows and 5 dietary treatments that were applied using a 5×5 Latin square design with 2-wk experimental periods. Treatments consisted of (1) the basal total mixed ration (TMR); (2) the basal TMR plus 340mEq/kg of Na (dry matter basis) using NaCl; (3) the basal TMR plus 340mEq/kg of K using KCl; (4) the basal TMR plus 340mEq/kg of Na using NaHCO3; and (5) the basal TMR plus 340mEq/kg of K using K2CO3. On the last day of each experimental period, rumen samples were collected and pooled from 5 different locations at 0, 1.5, 3, 4.5, 6, 9, and 12h postfeeding for measurement of rumen pH and concentrations of strong ions and volatile fatty acids (VFA). Dietary supplementation of individual strong ions increased the corresponding rumen ion concentration. Rumen Na was decreased by 24mEq/L when K was substituted for Na in the diet, but added dietary Na had no effect on rumen K. Rumen Cl was increased by 10mEq/L in diets supplemented with Cl. Cation source had no effect on rumen pH or total VFA concentration. Increased DCAD increased rumen pH by 0.10 pH units and increased rumen acetate by 4mEq/L but did not increase total VFA. This study demonstrated that rumen ion concentrations can be manipulated by dietary ion concentrations. If production and feed efficiency responses to DCAD and ionophores in the diet are affected by rumen Na and K concentrations, then manipulating dietary Na and K could be used either to enhance or diminish those responses. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

EFFECT OF INORGANIC CATIONS ON BACTERICIDAL ACTIVITY OF ANIONIC SURFACTANTS

PubMed Central

Voss, J. G.

1963-01-01

Voss, J. G. (Procter & Gamble Co., Cincinnati, Ohio). Effect of inorganic cations on bactericidal activity of anionic surfactants. J. Bacteriol. 86:207–211. 1963.—The bactericidal effectiveness of two alkyl benzene sulfonates and of three other types of anionic surfactants against Staphylococcus aureus is increased in the presence of low concentrations of divalent cations, especially alkaline earths and metals of group IIB of the periodic table. The cations may act by decreasing the negative charge at the cell surface and increasing adsorption of the surfactant anions, leading to damage to the cytoplasmic membrane and death of the cell. Increased adsorption of surfactant is also found with Escherichia coli, but does not lead to death of the cell. PMID:14058942

CATION TRANSPORT AND PARTITIONING DURING A FIELD TEST OF ELECTROOSMOSIS

EPA Science Inventory

Field experiments were conducted to evaluate the effects of soil properties, such as the cation exchange capacity and mineral content, on pH, soluble ion concentrations, and electrical conductivity during electroosmosis in a silty clay soil. The soil is composed mainly of quartz ...

Liquid Structure with Nano-Heterogeneity Promotes Cationic Transport in Concentrated Electrolytes.

PubMed

Borodin, Oleg; Suo, Liumin; Gobet, Mallory; Ren, Xiaoming; Wang, Fei; Faraone, Antonio; Peng, Jing; Olguin, Marco; Schroeder, Marshall; Ding, Michael S; Gobrogge, Eric; von Wald Cresce, Arthur; Munoz, Stephen; Dura, Joseph A; Greenbaum, Steve; Wang, Chunsheng; Xu, Kang

2017-10-24

Using molecular dynamics simulations, small-angle neutron scattering, and a variety of spectroscopic techniques, we evaluated the ion solvation and transport behaviors in aqueous electrolytes containing bis(trifluoromethanesulfonyl)imide. We discovered that, at high salt concentrations (from 10 to 21 mol/kg), a disproportion of cation solvation occurs, leading to a liquid structure of heterogeneous domains with a characteristic length scale of 1 to 2 nm. This unusual nano-heterogeneity effectively decouples cations from the Coulombic traps of anions and provides a 3D percolating lithium-water network, via which 40% of the lithium cations are liberated for fast ion transport even in concentration ranges traditionally considered too viscous. Due to such percolation networks, superconcentrated aqueous electrolytes are characterized by a high lithium-transference number (0.73), which is key to supporting an assortment of battery chemistries at high rate. The in-depth understanding of this transport mechanism establishes guiding principles to the tailored design of future superconcentrated electrolyte systems.

Activation by divalent cations of a Ca2+-activated K+ channel from skeletal muscle membrane.

PubMed

Oberhauser, A; Alvarez, O; Latorre, R

1988-07-01

Several divalent cations were studied as agonists of a Ca2+-activated K+ channel obtained from rat muscle membranes and incorporated into planar lipid bilayers. The effect of these agonists on single-channel currents was tested in the absence and in the presence of Ca2+. Among the divalent cations that activate the channel, Ca2+ is the most effective, followed by Cd2+, Sr2+, Mn2+, Fe2+, and Co2+. Mg2+, Ni2+, Ba2+, Cu2+, Zn2+, Hg2+, and Sn2+ are ineffective. The voltage dependence of channel activation is the same for all the divalent cations. The time-averaged probability of the open state is a sigmoidal function of the divalent cation concentration. The sigmoidal curves are described by a dissociation constant K and a Hill coefficient N. The values of these parameters, measured at 80 mV are: N = 2.1, K = 4 X 10(-7) mMN for Ca2+; N = 3.0, K = 0.02 mMN for Cd2+; N = 1.45, K = 0.63 mMN for Sr2+; N = 1.7, K = 0.94 mMN for Mn2+; N = 1.1, K = 3.0 mMN for Fe2+; and N = 1.1 K = 4.35 mMN for Co2+. In the presence of Ca2+, the divalent cations Cd2+, Co2+, Mn2+, Ni2+, and Mg2+ are able to increase the apparent affinity of the channel for Ca2+ and they increase the Hill coefficient in a concentration-dependent fashion. These divalent cations are only effective when added to the cytoplasmic side of the channel. We suggest that these divalent cations can bind to the channel, unmasking new Ca2+ sites.

Spectroscopy and computational studies on the interaction of octyl, dodecyl, and hexadecyl derivatives of anionic and cationic surfactants with adenosine deaminase.

PubMed

Ajloo, Davood; Mahmoodabadi, Najmeh; Ghadamgahi, Maryam; Saboury, Ali Akbar

2016-07-01

Effects of sodium (octyl, dodecyl, hexadecyl) sulfate and their cationic analogous on the structure of adenosine deaminase (ADA) were investigated by fluorescence and circular dichroism spectroscopy as well as molecular dynamics simulation and docking calculation. Root-mean-square derivations, radius of gyration, solvent accessible surface area, and radial distribution function were obtained. The results showed that anionic and cationic surfactants reduce protein stability. Cationic surfactants have more effect on the ADA structure in comparison with anionic surfactants. More concentration and longer surfactants are parallel to higher denaturation. Furthermore, aggregation in the presence of anionic surfactants is more than cationic surfactants. Docking data showed that longer surfactants have more interaction energy and smaller ones bound to the active site.

Reversible changes of canavalin solubility controlled by divalent cation concentration in crude sword bean extract.

PubMed

Nishizawa, Kaho; Arii, Yasuhiro

2016-12-01

Canavalin is a vicilin-class (7S) storage protein found in sword bean (Canavalia gladiata). Our previous report indicated that canavalin is precipitated by the addition of 20 mM MgCl 2 to crude sword bean extract. Here, we examined the solubility changes induced by the addition of Mg 2+ and Ca 2+ at various concentrations. Canavalin tended to be insolubilized at relatively low concentrations of MgCl 2 (< 20 mM) and solubilized at relatively high concentrations (> 20 mM). In addition, canavalin was slightly insolubilized in the presence of NaCl. Overall, the results revealed that solubility changes are reversible and depend on the concentration of divalent cations. Therefore, we suggested a reaction scheme that describes the effects of divalent cations on the solubility of canavalin, which would facilitate the study of its physiological function and the application of canavalin in the food processing industry.

Electrical properties of AC{sub 3}B{sub 4}O{sub 12}-type perovskite ceramics with different cation vacancies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Guizhong; Chen, Zhi; Sun, Xiaojun

2015-05-15

Highlights: • AC{sub 3}B{sub 4}O{sub 12} perovskite with different concentration cation vacancies were prepared. • Cell parameter decreases with the increase of concentration of cation vacancies. • PTCO and CTO remain high dielectric permittivity but depress loss greatly. • Dielectric loss associates with cation vacancies and motion of oxygen vacancies. - Abstract: AC{sub 3}B{sub 4}O{sub 12}-type perovskite CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO), □{sub 0.34}Pr{sub 0.67}Cu{sub 3}Ti{sub 4}O{sub 12} (PCTO), □{sub 1}Cu{sub 3}Ta{sub 2}Ti{sub 2}O{sub 12} (CTTO), □{sub 2}Cu{sub 2}Ta{sub 4}O{sub 12} (CTO) ceramics with different concentration cation vacancies were prepared through traditional solid state reaction method. X-ray diffraction analysis indicatedmore » that CCTO and PCTO are perovskite cubic with space group Im-3 (no. 204) while CTTO and CTO are Pm-3 (no. 200). Cell parameter of the samples dramatically increases with the increase of cation vacancies. Dielectric permittivity of them maintains very high value of ∼10{sup 4} from room temperature to 550 K but the dielectric loss is depressed with the increase of cation vacancies in the same space group. The dielectric properties and conductivity behavior were described by the Debye relaxation and the universal dielectric response, respectively. The effect mechanism of cation vacancy and crystal structure on carrier transposition were discussed.« less

Role of monovalent cations in fluid secretion from the exocrine rabbit pancreas.

PubMed

Kuijpers, G A; Van Nooy, I G; De Pont, J J

1989-08-21

The role of Na+ in fluid secretion by the isolated rabbit pancreas was investigated. The fluid secretion rate is reduced upon replacement of Na+ in the bathing medium by Li+, K+ or choline. The inhibition depends on the nature of the substituting cation, and is largest with choline. Upon replacement, the substituent cation appears in the secreted fluid, and the Na+ concentration in the secreted fluid is decreased in a mirror-like fashion. When Na+ is replaced by Li+ or choline, the secretory Na+ concentration is decreased, although less than in the bathing medium, and the K+ concentration is increased. When Na+ is replaced by K+, the Na+ and the K+ concentration in the secreted fluid are approximately equal to their bathing medium concentrations. In the Li+ and choline medium, stimulation of the pancreas by carbachol or CCK-8 increases the fluid secretion rate. In addition, it increases the Li+ or choline concentration, and decreases the Na+ and K+ concentrations in the secreted fluid. In normal and K+ medium, stimulation causes only a slight increase in fluid secretion rate, with no change in the secretory Na+ concentration. In normal medium, stimulation leads to a decrease in the secretory K+ concentration. The effects of replacing Na+ appear to be the result of a direct inhibition of the active HCO3- transport underlying secretion, and an indirect inhibition related to the permeability of the pancreas for the various cations. The stimulants are likely to act by increasing the permeability of the tight junctions.

Influence of cations on noncovalent interactions between 6-propionyl-2-dimethylaminonaphthalene (PRODAN) and dissolved fulvic and humic acids.

PubMed

Gadad, Praveen; Nanny, Mark A

2008-12-01

The influence of cations (Na(+), Ca(2+) and Mg(2+)) on noncovalent interactions between 6-propionyl-2-dimethylaminonaphthalene (PRODAN) and dissolved fulvic acids (FAs) (Norman landfill leachate fulvic acid (NLFA) and Suwannee River fulvic acid (SRFA)) and dissolved humic acids (HAs) (Suwannee River humic acid (SRHA) and Leonardite humic acid (LHA)) was examined using steady-state fluorescence spectroscopy at pH 4, 7 and 10 as a function of cation concentration (up to 25-100mM). Regardless of pH and cation concentration, PRODAN quenching by FA was unaffected by cations. However, interactions between PRODAN and HA decreased in the presence of cations at pH 7 and 10. Cation concentrations below the HA charge density resulted in the greatest decrease of PRODAN quenching, while very little additional decrease in PRODAN quenching occurred at cation concentrations above the HA charge density. This suggests that as the HA carboxylic acid functional groups form inner sphere complexes with divalent cations, intramolecular interactions result in a contraction of the HA molecular structure, thereby preventing PRODAN from associating with the condensed aromatic, electron accepting moieties inherent within HA molecules and responsible for PRODAN quenching. However, once the HA carboxylic acid functional groups are fully titrated with divalent cations, PRODAN quenching is no longer significantly influenced by the further addition of cations, even though these additional cations facilitate intermolecular interactions between the HA molecules to form supramolecular HA aggregates that can continue to increase in size. Regardless of FA and HA type, pH, cation type and concentration, the lack of blue-shifted fluorescence emission spectra indicated that micelle-like hydrophobic regions, amenable to PRODAN partitioning, were not formed by intra- and intermolecular interactions of FA and HA.

Effect of cations on the solubilization/deposition of triclosan in sediment-water-rhamnolipid system.

PubMed

Chen, Yuanbo; Hu, Yongyou; Guo, Qian; Yan, Jia; Wu, Wenjin

2016-09-01

Cations had great influence on the self-assembly of rhamnolipid, which in turn affected the fate of triclosan. The migration of triclosan from sediment to water benefited its biodegradation but it could be transformed into more toxic compounds. To regulate the fate of triclosan and reduce environmental risks extremely, the effect of four common cations in surface water (Na(+)/K(+)/Ca(2+)/Mg(2+)) on the solubilization/deposition of triclosan in sediment-water-rhamnolipid system was investigated. The interaction among cations, triclosan and rhamnolipid was explored based on self-assembly of rhamnolipid and water solubility of triclosan in rhamnolipid solutions. Results showed that cations had little influence on the fate of triclosan in the absence of rhamnolipid. Cations, especially Ca(2+)/Mg(2+), reduced the critical micelle concentration, micellar size and zeta potential of rhamnolipid solutions. The changes in self-assembly of rhamnolipid with different cations led to the difference of residual rhamnolipid concentration in water, which was nearly invariant with 0.01 M Na(+)/K(+) while decreased significantly with 0.01 M Ca(2+)/Mg(2+). Consequently, water solubility of triclosan in rhamnolipid solutions increased with the addition of Na(+)/K(+) whereas decreased with Ca(2+)/Mg(2+). In sediment-water- rhamnolipid system, triclosan was slightly solubilized from sediment to water with Na(+)/K(+) while deposited in sediment with Ca(2+)/Mg(2+). These findings provided an alternative application of rhamnolipid for the remediation of triclosan-polluted sediment. Copyright © 2016. Published by Elsevier Ltd.

Self-aggregation of cationically modified poly(ε-caprolactone)2-co-poly(ethylene glycol) copolymers: Effect of cationic grafting ligand and poly(ε-caprolactone) chain length.

PubMed

Charoongchit, Pimchanok; Suksiriworapong, Jiraphong; Sripha, Kittisak; Mao, Shirui; Sapin-Minet, Anne; Maincent, Philippe; Junyaprasert, Varaporn Buraphacheep

2017-03-01

Cationic copolymers have been attractive to investigate due to their potential to complexation with anionic drugs and expected to use in the pharmaceutical application. In this study, the modified poly(ε-caprolactone) 2 -co-poly(ethylene glycol) copolymers (P(CL) 2 -PEG) were successfully synthesized by click reaction. The amount of small molecular cationic ligand, propargyltrimethyl ammonium iodide, was varied and grafted onto various mole ratios of P(CL) to PEG. The effects of P(CL) chain length and amount of the grafting cationic ligand on physicochemical properties of polymers and particles were studied. The number-average molecular weights of the copolymers grafted with cationic ligand were found ranging between 10,000 and 23,000g/mol as investigated by NMR. From DSC study, the results showed that the grafting ligand affected thermal behaviors of the copolymers by increasing the glass transition temperature and decreasing the melting temperature of the copolymers. Furthermore, these cationic copolymers could self-aggregate with their critical aggregation concentration depending on mole ratios of hydrophilic to hydrophobic portions. The particles containing higher amounts of the cationic ligand tended to aggregate in both acidic and basic pH environment and at high salt concentration. Additionally, particle size, size distribution (PdI), and morphology of self-assembling particles varied depending on P(CL) chain length and the amount of the grafting cationic ligand. The synthesized cationic copolymer showed a capability to encapsulate a high negatively charged drug, enoxaparin, with an encapsulation efficiency of 87%. After drug incorporation, the particles substantially changed in size, shape, PdI, and zeta potential to become more suitable for drug delivery. These cationic copolymers with flexible properties will be the candidate for further development as carriers for the delivery of negatively charged drugs. Copyright © 2016. Published by Elsevier B.V.

[Effect of univalent cations on the glutamate dehydrogenase of chlorella].

PubMed

Shatilov, V R; Kasparova, M A; Kretovich, V L

1976-09-01

Effect of univalent cations (Li+, K+, Na+ and Cs+) on the activity and some kinetic properties of the constitutive and the inducible glutamate dehydrogenases (GDH) of Chlorella pyrenoidosa Pringsheim 82T has been studied. All the cations used activate the inducible GDH and produced no such effect on the constitutive GDH. From the analysis of the kinetic behaviour in the presence of K+ the conclusion was made that K+ promotes and stabilyzes a catalitically advantagenous conformation of the inducible GDH. This phenomenon appears to have a physiological meaning, because of a higher K+ concentration in Chlorella cells (about 0.1 M) and its important role in metabolism.

Effect of low levels of lipid oxidation on the curvature, dynamics, and permeability of lipid bilayers and their interactions with cationic nanoparticles

NASA Astrophysics Data System (ADS)

Lee, Hwankyu; Malmstadt, Noah

2018-04-01

Lipid bilayers composed of saturated and unsaturated lipids, oxidized lipids, and cholesterol at concentrations of 0–18 mol% oxidized lipid were simulated, showing that the presence of oxidized lipid increases bilayer disorder, curvature, and lateral dynamics at low oxidized-lipid concentrations of 18 mol% or less. The aldehyde terminal of a shortened oxidized-lipid tail tends to interact with water and thus bends toward the bilayer-water interface, in agreement with previous experiments and simulations. In particular, water molecules pass through the oxidized bilayer without pore formation, implying passive permeability. A single nanoparticle, which consists of 300 polystyrene (PS) chains with cationic terminals, added to this bilayer simulation induces negative bilayer curvature and inserts to the bilayer, regardless of the oxidized-lipid concentration. Hydrophobic monomers and cationic terminals of the PS particle interact respectively with lipid tails and headgroups, leading to the wrapping of either lipid monolayer or bilayer along the particle surface. These results indicate that lipid oxidation increases membrane curvature and permeability even at such a low concentration of oxidized lipid, which supports the experimental observations regarding the passive permeability of oxidized bilayer, and also that oxidized lipids of low concentration do not significantly influence the insertion of a cationic PS particle to the bilayer.

Molecular dynamics simulations of the structure and single-particle dynamics of mixtures of divalent salts and ionic liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gómez-González, Víctor; Docampo-Álvarez, Borja; Gallego, Luis J.

2015-09-28

We report a molecular dynamics study of the structure and single-particle dynamics of mixtures of a protic (ethylammonium nitrate) and an aprotic (1-butyl-3-methylimidazolium hexaflurophosphate [BMIM][PF{sub 6}]) room-temperature ionic liquids doped with magnesium and calcium salts with a common anion at 298.15 K and 1 atm. The solvation of these divalent cations in dense ionic environments is analyzed by means of apparent molar volumes of the mixtures, radial distribution functions, and coordination numbers. For the protic mixtures, the effect of salt concentration on the network of hydrogen bonds is also considered. Moreover, single-particle dynamics of the salt cations is studied by means ofmore » their velocity autocorrelation functions and vibrational densities of states, explicitly analyzing the influence of salt concentration, and cation charge and mass on these magnitudes. The effect of the valency of the salt cation on these properties is considered comparing the results with those for the corresponding mixtures with lithium salts. We found that the main structural and dynamic features of the local solvation of divalent cations in ionic liquids are similar to those of monovalent salts, with cations being localized in the polar nanoregions of the bulk mixture coordinated in monodentate and bidentate coordination modes by the [NO{sub 3}]{sup −} and [PF{sub 6}]{sup −} anions. However, stronger electrostatic correlations of these polar nanoregions than in mixtures with salts with monovalent cations are found. The vibrational modes of the ionic liquid (IL) are seen to be scarcely affected by the addition of the salt, and the effect of mass and charge on the vibrational densities of states of the dissolved cations is reported. Cation mass is seen to exert a deeper influence than charge on the low-frequency vibrational spectra, giving a red shift of the vibrational modes and a virtual suppression of the higher energy vibrational modes for the heavier Ca{sup 2+} cations. No qualitative difference with monovalent cations was found in what solvation is concerned, which suggests that no enhanced reduction of the mobility of these cations and their complexes in ILs respective to those of monovalent cations is to be expected.« less

Cell-penetrating cationic siRNA and lipophilic derivatives efficient at nanomolar concentrations in the presence of serum and albumin.

PubMed

Perche, Phanélie; Nothisen, Marc; Bagilet, Jérémy; Behr, Jean-Paul; Kotera, Mitsuharu; Remy, Jean-Serge

2013-08-28

Despite its considerable interest in human therapy, in vivo siRNA delivery is still suffering from hurdles of vectorization. We have shown recently efficient gene silencing by non-vectorized cationic siRNA. Here, we describe the synthesis and in vitro evaluation of new amphiphilic cationic siRNA. C₁₂-, (C₁₂)₂- and cholesteryl-spermine(x)-siRNA were capable of luciferase knockdown at nanomolar concentrations without vectorization (i.e. one to two orders of magnitude more potent than commercially available cholesteryl siRNA). Moreover, incubation in the presence of serum did not impair their efficiency. Finally, amphiphilic cationic siRNA was pre-loaded on albumin. In A549Luc cells in the presence of serum, these siRNA conjugates were highly effective and had low toxicity. Copyright © 2013. Published by Elsevier B.V.

Influence of pH and Metal Cations on Aggregative Growth of Non-Slime-forming Strains of Zoogloea ramigera

PubMed Central

Angelbeck, Donald I.; Kirsch, Edwin J.

1969-01-01

Aggregative growth of non-slime-forming strains of Zoogloea ramigera was induced by growing the organisms at a depressed pH. Calcium and magnesium ion was found to reverse aggregative growth of the organisms. Conversely, aggregation was stimulated when the available inorganic cation concentration of the growth medium was lowered by the use of a chelating agent. The aggregative effects of pH depression or cation depletion and the dispersal effects of cation supplementation were observed only during cellular growth. The data suggest that aggregate formation of non-slime-forming strains of Z. ramigera may be related to the calcium or magnesium metabolism of the organisms, or both. Images PMID:4976326

Increased localized delivery of piroxicam by cationic nanoparticles after intra-articular injection.

PubMed

Kim, Sung Rae; Ho, Myoung Jin; Kim, Sang Hyun; Cho, Ha Ra; Kim, Han Sol; Choi, Yong Seok; Choi, Young Wook; Kang, Myung Joo

2016-01-01

Piroxicam (PRX), a potent nonsteroidal anti-inflammatory drug, is prescribed to relieve postoperative and/or chronic joint pain. However, its oral administration often results in serious gastrointestinal adverse effects including duodenal ulceration. Thus, a novel cationic nanoparticle (NP) was explored to minimize the systemic exposure and increase the retention time of PRX in the joint after intra-articular (IA) injection, by forming micrometer-sized electrostatic clusters with endogenous hyaluronic acid (HA) in the synovial cavity. PRX-loaded NPs consisting of poly(lactic- co -glycolic acid), Eudragit RL, and polyvinyl alcohol were constructed with the following characteristics: particle size of 220 nm, zeta potential of 11.5 mV in phosphate-buffered saline, and loading amount of 4.0% (w/w) of PRX. In optical and hyperspectral observations, the cationic NPs formed more than 50 μm-sized aggregates with HA, which was larger than the intercellular gaps between synoviocytes. In an in vivo pharmacokinetic study in rats, area under the plasma concentration-time curve (AUC 0-24 h ) and maximum plasma concentration ( C max ) of PRX after IA injection of the cationic NPs were <70% ( P <0.05) and 60% ( P <0.05), respectively, compared to those obtained from drug solution. Moreover, the drug concentration in joint tissue 24 h after dosing with the cationic NPs was 3.2-fold ( P <0.05) and 1.8-fold ( P <0.05) higher than that from drug solution and neutrally charged NPs, respectively. Therefore, we recommend the IA cationic NP therapy as an effective alternative to traditional oral therapy with PRX, as it increases drug retention selectively in the joint.

Effect of Cation Ordering on the Performance and Chemical Stability of Layered Double Perovskite Cathodes

PubMed Central

Bernuy-Lopez, Carlos; Rioja-Monllor, Laura; Nakamura, Takashi; Ricote, Sandrine; O’Hayre, Ryan; Amezawa, Koji; Einarsrud, Mari-Ann

2018-01-01

The effect of A-site cation ordering on the cathode performance and chemical stability of A-site cation ordered LaBaCo2O5+δ and disordered La0.5Ba0.5CoO3−δ materials are reported. Symmetric half-cells with a proton-conducting BaZr0.9Y0.1O3−δ electrolyte were prepared by ceramic processing, and good chemical compatibility of the materials was demonstrated. Both A-site ordered LaBaCo2O5+δ and A-site disordered La0.5Ba0.5CoO3−δ yield excellent cathode performance with Area Specific Resistances as low as 7.4 and 11.5 Ω·cm2 at 400 °C and 0.16 and 0.32 Ω·cm2 at 600 °C in 3% humidified synthetic air respectively. The oxygen vacancy concentration, electrical conductivity, basicity of cations and crystal structure were evaluated to rationalize the electrochemical performance of the two materials. The combination of high-basicity elements and high electrical conductivity as well as sufficient oxygen vacancy concentration explains the excellent performance of both LaBaCo2O5+δ and La0.5Ba0.5CoO3−δ materials at high temperatures. At lower temperatures, oxygen-deficiency in both materials is greatly reduced, leading to decreased performance despite the high basicity and electrical conductivity. A-site cation ordering leads to a higher oxygen vacancy concentration, which explains the better performance of LaBaCo2O5+δ. Finally, the more pronounced oxygen deficiency of the cation ordered polymorph and the lower chemical stability at reducing conditions were confirmed by coulometric titration. PMID:29373541

Effect of added sodium chloride on the molecular environment and photoionization of N,N,N',N'-tetramethylbenzidine in micellar solutions as studied by electron spin echo and electron spin resonance spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maldonado, R.; Kevan, L.; Szajdzinska-Pietek, E.

1984-11-01

The electron spin echo modulation (ESEM) and electron spin resonance (ESR) spectra of the cation radical of N,N,N',N'-tetramethylbenzidine (TMB) in frozen sodium dodecyl sulfate (SDS)= and dodecyltrimethylammonium chloride (DTAC) micelles were studied as a function of sodium chloride concentration. TMB/sup +center-dot/ was produced by photoionization at 350 nm of the parent compound in the micelles at 77 K. From the ESEM analysis it is found that the cation--water interactions increase with salt addition in both anionic and cationic micelles to a maximum near 0.2 M NaCl and then decrease somewhat. The increase is interpreted in terms of an increase inmore » the water density at the micellar surface due to an increased surface concentration of hydrated counterions. The decrease may be due to TMB moving further from the polar micellar surface with added salt. From ESR spectra the photoionization yields of TMB at 77 K were determined. For DTAC micelles the yields are found to decrease with salt addition as expected from electrostatic considerations. For SDS micelles the photoionization yields increase for salt concentrations up to about 0.15 M and decrease for greater salt concentrations up to 0.5 M. The initial increase in cation yield correlates with electrostatic expectations. The decrease may be due to TMB moving further from the polar micellar surface with added salt. The possible effect of differing TMB protonation equilibria between anionic and cationic micelles on the photoionization yields was found to be unimportant by adjusting the bulk solution pH. An important conclusion is that salt addition can be used to optimize charge separation for photoionized solutes in anionic micelles.« less

The special features of the crystal structure and properties of oxides with mixed conductivity based on lanthanum gallate

NASA Astrophysics Data System (ADS)

Politova, E. D.; Ivanov, S. A.; Kaleva, G. M.; Mosunov, A. V.; Rusakov, V. S.

2008-10-01

The paper presents a review of works on the synthesis, structural composition effects, phase transitions, and electrical conductivity properties of multicomponent solid solutions based on heterosubstituted lanthanum gallate (La,A)(Ga,M)O3 - y . High-temperature phase transitions and structural and charge ordering effects were studied. The presence of iron cations in different valence states was proved; the relative contents of these cations depended on the x parameter and nonstoichiometry parameter y of the base composition. For M = Fe, antiferromagnetic ordering was observed; its temperature interval was determined by the concentration of iron cations in the high-spin state. The total conductivity was found to increase as the concentration of transition metal cations grew because of an increase in the electronic conductivity component. The data on structural parameters and dc and ac conductivity substantiated the conclusion that the highest ionic conductivity and permeability to oxygen were characteristic of iron-containing oxides. The results obtained are evidence that crystal chemical factors play a determining role in the formation of the ion-conducting properties of anion-deficient perovskite-like oxides.

Opposing effects of cationic antimicrobial peptides and divalent cations on bacterial lipopolysaccharides

NASA Astrophysics Data System (ADS)

Smart, Matthew; Rajagopal, Aruna; Liu, Wing-Ki; Ha, Bae-Yeun

2017-10-01

The permeability of the bacterial outer membrane, enclosing Gram-negative bacteria, depends on the interactions of the outer, lipopolysaccharide (LPS) layer, with surrounding ions and molecules. We present a coarse-grained model for describing how cationic amphiphilic molecules (e.g., antimicrobial peptides) interact with and perturb the LPS layer in a biologically relevant medium, containing monovalent and divalent salt ions (e.g., Mg2+). In our approach, peptide binding is driven by electrostatic and hydrophobic interactions and is assumed to expand the LPS layer, eventually priming it for disruption. Our results suggest that in parameter ranges of biological relevance (e.g., at micromolar concentrations) the antimicrobial peptide magainin 2 effectively disrupts the LPS layer, even though it has to compete with Mg2+ for the layer. They also show how the integrity of LPS is restored with an increasing concentration of Mg2+. Using the approach, we make a number of predictions relevant for optimizing peptide parameters against Gram-negative bacteria and for understanding bacterial strategies to develop resistance against cationic peptides.

Cation-Induced Stabilization and Denaturation of DNA Origami Nanostructures in Urea and Guanidinium Chloride.

PubMed

Ramakrishnan, Saminathan; Krainer, Georg; Grundmeier, Guido; Schlierf, Michael; Keller, Adrian

2017-11-01

The stability of DNA origami nanostructures under various environmental conditions constitutes an important issue in numerous applications, including drug delivery, molecular sensing, and single-molecule biophysics. Here, the effect of Na + and Mg 2+ concentrations on DNA origami stability is investigated in the presence of urea and guanidinium chloride (GdmCl), two strong denaturants commonly employed in protein folding studies. While increasing concentrations of both cations stabilize the DNA origami nanostructures against urea denaturation, they are found to promote DNA origami denaturation by GdmCl. These inverse behaviors are rationalized by a salting-out of Gdm + to the hydrophobic DNA base stack. The effect of cation-induced DNA origami denaturation by GdmCl deserves consideration in the design of single-molecule studies and may potentially be exploited in future applications such as selective denaturation for purification purposes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cation effect on small phosphonium based ionic liquid electrolytes with high concentrations of lithium salt

NASA Astrophysics Data System (ADS)

Chen, Fangfang; Kerr, Robert; Forsyth, Maria

2018-05-01

Ionic liquid electrolytes with high alkali salt concentrations have displayed some excellent electrochemical properties, thus opening up the field for further improvements to liquid electrolytes for lithium or sodium batteries. Fundamental computational investigations into these high concentration systems are required in order to gain a better understanding of these systems, yet they remain lacking. Small phosphonium-based ionic liquids with high concentrations of alkali metal ions have recently shown many promising results in experimental studies, thereby prompting us to conduct further theoretical exploration of these materials. Here, we conducted a molecular dynamics simulation on four small phosphonium-based ionic liquids with 50 mol. % LiFSI salt, focusing on the effect of cation structure on local structuring and ion diffusional and rotational dynamics—which are closely related to the electrochemical properties of these materials.

Mechanistic insights into allosteric regulation of the A 2A adenosine G protein-coupled receptor by physiological cations

DOE PAGES

Ye, Libin; Neale, Chris Andrew; Sljoka, Adnan; ...

2018-04-10

Cations play key roles in regulating G-protein-coupled receptors (GPCRs), although their mechanisms are poorly understood. Here, 19F NMR is used to delineate the effects of cations on functional states of the adenosine A 2A GPCR. While Na + reinforces an inactive ensemble and a partial-agonist stabilized state, Ca 2+ and Mg 2+ shift the equilibrium toward active states. Positive allosteric effects of divalent cations are more pronounced with agonist and a G-protein-derived peptide. In cell membranes, divalent cations enhance both the affinity and fraction of the high affinity agonist-bound state. Molecular dynamics simulations suggest high concentrations of divalent cations bridgemore » specific extracellular acidic residues, bringing TM5 and TM6 together at the extracellular surface and allosterically driving open the G-protein-binding cleft as shown by rigidity-transmission allostery theory. Lastly, an understanding of cation allostery should enable the design of allosteric agents and enhance our understanding of GPCR regulation in the cellular milieu.« less

Mechanistic insights into allosteric regulation of the A 2A adenosine G protein-coupled receptor by physiological cations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Libin; Neale, Chris Andrew; Sljoka, Adnan

Cations play key roles in regulating G-protein-coupled receptors (GPCRs), although their mechanisms are poorly understood. Here, 19F NMR is used to delineate the effects of cations on functional states of the adenosine A 2A GPCR. While Na + reinforces an inactive ensemble and a partial-agonist stabilized state, Ca 2+ and Mg 2+ shift the equilibrium toward active states. Positive allosteric effects of divalent cations are more pronounced with agonist and a G-protein-derived peptide. In cell membranes, divalent cations enhance both the affinity and fraction of the high affinity agonist-bound state. Molecular dynamics simulations suggest high concentrations of divalent cations bridgemore » specific extracellular acidic residues, bringing TM5 and TM6 together at the extracellular surface and allosterically driving open the G-protein-binding cleft as shown by rigidity-transmission allostery theory. Lastly, an understanding of cation allostery should enable the design of allosteric agents and enhance our understanding of GPCR regulation in the cellular milieu.« less

Predicting stability of DNA duplexes in solutions containing magnesium and monovalent cations.

PubMed

Owczarzy, Richard; Moreira, Bernardo G; You, Yong; Behlke, Mark A; Walder, Joseph A

2008-05-13

Accurate predictions of DNA stability in physiological and enzyme buffers are important for the design of many biological and biochemical assays. We therefore investigated the effects of magnesium, potassium, sodium, Tris ions, and deoxynucleoside triphosphates on melting profiles of duplex DNA oligomers and collected large melting data sets. An empirical correction function was developed that predicts melting temperatures, transition enthalpies, entropies, and free energies in buffers containing magnesium and monovalent cations. The new correction function significantly improves the accuracy of predictions and accounts for ion concentration, G-C base pair content, and length of the oligonucleotides. The competitive effects of potassium and magnesium ions were characterized. If the concentration ratio of [Mg (2+)] (0.5)/[Mon (+)] is less than 0.22 M (-1/2), monovalent ions (K (+), Na (+)) are dominant. Effects of magnesium ions dominate and determine duplex stability at higher ratios. Typical reaction conditions for PCR and DNA sequencing (1.5-5 mM magnesium and 20-100 mM monovalent cations) fall within this range. Conditions were identified where monovalent and divalent cations compete and their stability effects are more complex. When duplexes denature, some of the Mg (2+) ions associated with the DNA are released. The number of released magnesium ions per phosphate charge is sequence dependent and decreases surprisingly with increasing oligonucleotide length.

Quantify the loss of major ions induced by CO2 enrichment and nitrogen addition in subtropical model forest ecosystems

NASA Astrophysics Data System (ADS)

Liu, Juxiu; Zhang, Deqiang; Huang, Wenjuan; Zhou, Guoyi; Li, Yuelin; Liu, Shizhong

2014-04-01

Previous studies have reported that atmospheric CO2 enrichment would increase the ion concentrations in the soil water. However, none of these studies could exactly quantify the amount of ion changes in the soil water induced by elevated CO2 and all of these experiments were carried out only in the temperate areas. Using an open-top chamber design, we studied the effects of CO2 enrichment alone and together with nitrogen (N) addition on soil water chemistry in the subtropics. Three years of exposure to an atmospheric CO2 concentration of 700 ppm resulted in accelerated base cation loss via leaching water below the 70 cm soil profile. The total of base cation (K+ + Na+ + Ca2+ + Mg2+) loss in the elevated CO2 treatment was higher than that of the control by 220%, 115%, and 106% in 2006, 2007, and 2008, respectively. The N treatment decreased the effect of high CO2 treatment on the base cation loss in the leachates. Compared to the control, N addition induced greater metal cation (Al3+ and Mn2+) leaching loss in 2008 and net Al3+ and Mn2+ loss in the high N treatment increased by 100% and 67%, respectively. However, the CO2 treatment decreased the effect of high N treatment on the metal cation loss. Changes of ion export followed by the exposure to the elevated CO2, and N treatments were related to both ion concentrations and leached water amount. We hypothesize that forests in subtropical China might suffer from nutrient limitation and some poisonous metal activation in plant biomass under future global change.

Analytical modeling of localized surface plasmon resonance in heterostructure copper sulfide nanocrystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caldwell, Andrew H.; Ha, Don-Hyung; Ding, Xiaoyue

2014-10-28

Localized surface plasmon resonance (LSPR) in semiconductor nanocrystals is a relatively new field of investigation that promises greater tunability of plasmonic properties compared to metal nanoparticles. A novel process by which the LSPR in semiconductor nanocrystals can be altered is through heterostructure formation arising from solution-based cation exchange. Herein, we describe the development of an analytical model of LSPR in heterostructure copper sulfide-zinc sulfide nanocrystals synthesized via a cation exchange reaction between copper sulfide (Cu 1.81S) nanocrystals and Zn ions. The cation exchange reaction produces dual-interface, heterostructure nanocrystals in which the geometry of the copper sulfide phase can be tunedmore » from a sphere to a thin disk separating symmetrically-grown sulfide (ZnS) grains. Drude model electronic conduction and Mie-Gans theory are applied to describe how the LSPR wavelength changes during cation exchange, taking into account the morphology evolution and changes to the local permittivity. The results of the modeling indicate that the presence of the ZnS grains has a significant effect on the out-of-plane LSPR mode. By comparing the results of the model to previous studies on solid-solid phase transformations of copper sulfide in these nanocrystals during cation exchange, we show that the carrier concentration is independent of the copper vacancy concentration dictated by its atomic phase. The evolution of the effective carrier concentration calculated from the model suggests that the out-of-plane resonance mode is dominant. The classical model was compared to a simplified quantum mechanical model which suggested that quantum mechanical effects become significant when the characteristic size is less than ~8 nm. Overall, we find that the analytical models are not accurate for these heterostructured semiconductor nanocrystals, indicating the need for new model development for this emerging field.« less

Analytical modeling of localized surface plasmon resonance in heterostructure copper sulfide nanocrystals

NASA Astrophysics Data System (ADS)

Caldwell, Andrew H.; Ha, Don-Hyung; Ding, Xiaoyue; Robinson, Richard D.

2014-10-01

Localized surface plasmon resonance (LSPR) in semiconductor nanocrystals is a relatively new field of investigation that promises greater tunability of plasmonic properties compared to metal nanoparticles. A novel process by which the LSPR in semiconductor nanocrystals can be altered is through heterostructure formation arising from solution-based cation exchange. Herein, we describe the development of an analytical model of LSPR in heterostructure copper sulfide-zinc sulfide nanocrystals synthesized via a cation exchange reaction between copper sulfide (Cu1.81S) nanocrystals and Zn ions. The cation exchange reaction produces dual-interface, heterostructure nanocrystals in which the geometry of the copper sulfide phase can be tuned from a sphere to a thin disk separating symmetrically-grown sulfide (ZnS) grains. Drude model electronic conduction and Mie-Gans theory are applied to describe how the LSPR wavelength changes during cation exchange, taking into account the morphology evolution and changes to the local permittivity. The results of the modeling indicate that the presence of the ZnS grains has a significant effect on the out-of-plane LSPR mode. By comparing the results of the model to previous studies on solid-solid phase transformations of copper sulfide in these nanocrystals during cation exchange, we show that the carrier concentration is independent of the copper vacancy concentration dictated by its atomic phase. The evolution of the effective carrier concentration calculated from the model suggests that the out-of-plane resonance mode is dominant. The classical model was compared to a simplified quantum mechanical model which suggested that quantum mechanical effects become significant when the characteristic size is less than ˜8 nm. Overall, we find that the analytical models are not accurate for these heterostructured semiconductor nanocrystals, indicating the need for new model development for this emerging field.

Phase behavior in quaternary ammonium ionic liquid-propanol solutions: Hydrophobicity, molecular conformations, and isomer effects

NASA Astrophysics Data System (ADS)

Abe, Hiroshi; Kohki, Erica; Nakada, Ayumu; Kishimura, Hiroaki

2017-07-01

In ionic liquids (ILs), the effects of a quaternary ammonium cation containing a hydroxyl group were investigated and compared with the effect of a standard quaternary ammonium cation. The cation possessing a hydroxyl group is choline, Chol+, and the anion is bis(trifluoromethylsulfonyl)imide, TFSI-. Crystal polymorphism of pure [Chol][TFSI] was observed upon both cooling and heating by simultaneous X-ray diffraction and differential scanning calorimetry measurements. In contrast, [N3111][TFSI] (N3111+: N-trimethyl-N-propylammonium), a standard IL, demonstrated simple crystallization upon cooling. By adding 1-propanol or 2-propanol, the phase behaviors of the [Chol][TFSI]-based and [N3111][TFSI]-based mixtures were clearly distinguished. By Raman spectroscopy, the TFSI- anion conformers in the liquid state were shown to vary according to the propanol concentration, propanol isomer, and type of cation. The anomalous behaviors of pure [Chol][TFSI] and its mixtures are derived from hydrogen bonding of the hydroxyl group of Chol+ cation coupled with the hydrophobicity and packing efficiency of propanol.

Steep declines in atmospheric base cations in regions of Europe and North America

NASA Astrophysics Data System (ADS)

Hedin, Lars O.; Granat, Lennart; Likens, Gene E.; Adri Buishand, T.; Galloway, James N.; Butler, Thomas J.; Rodhe, Henning

1994-01-01

HUMAN activities have caused marked changes in atmospheric chemistry over large regions of Europe and North America. Although considerable attention has been paid to the effects of changes in the deposition of acid anions (such as sulphate and nitrate) on terrestrial and aquatic ecosystems1-7, little is known about whether the concentrations of basic components of the atmosphere have changed over time8,9 and what the biogeochemical consequences of such potential changes might be. In particular, there has been some controversy8-12 as to whether declines in base-cation deposition have countered effects of recent reductions in SO2emission. Here we report evidence for steep declines in the atmospheric concentrations of base cations (sum of non-sea-salt Ca2+, Mg2+, K+ and Na+) over the past 10 to 26 years from high-quality precipitation chemistry records in Europe and North America. To varying but generally significant degrees, these base-cation trends have offset recent reductions in sulphate deposition in the regions examined. The observed trends seem to be ecologically important on decadal timescales, and support earlier contentions8-10 that declines in the deposition of base cations may have contributed to increased sensitivity of poorly buffered ecosystems.

Photochemical Formation and Transformation of Birnessite: Effects of Cations on Micromorphology and Crystal Structure.

PubMed

Zhang, Tengfei; Liu, Lihu; Tan, WenFeng; Suib, Steven L; Qiu, Guohong; Liu, Fan

2018-05-24

As important components with excellent oxidation and adsorption activity in soils and sediments, manganese oxides affect the transportation and fate of nutrients and pollutants in natural environments. In this work, birnessite was formed by photocatalytic oxidation of Mn2+aq in the presence of nitrate under solar irradiation. The effects of concentrations and species of interlayer cations (Na+, Mg2+, and K+) on birnessite crystal structure and micromorphology were investigated. The roles of adsorbed Mn2+ and pH in the transformation of the photosynthetic birnessite were further studied. The results indicated that Mn2+aq was oxidized to birnessite by superoxide radicals (O2•-) generated from the photolysis of NO3- under UV irradiation. The particle size and thickness of birnessite decreased with increasing cation concentration. The birnessite showed a plate-like morphology in the presence of K+, while exhibited a rumpled sheet-like morphology when Na+ or Mg2+ was used. The different micromorphologies of birnessites could be ascribed to the position of cations in the interlayer. The adsorbed Mn2+ and high pH facilitated the reduction of birnessite to low-valence manganese oxides including hausmannite, feitknechtite, and manganite. This study suggests that interlayer cations and Mn2+ play essential roles in the photochemical formation and transformation of birnessite in aqueous environments.

Effects of divalent cations and La3+ on contractility and ecto-ATPase activity in the guinea-pig urinary bladder.

PubMed Central

Ziganshin, A U; Ziganshina, L E; Hoyle, C H; Burnstock, G

1995-01-01

1. Several cations (Ba2+, Cd2+, Co2+, Cu2+, Mn2+, Ni2+, Zn2+ and La3+, all as chloride salts, 1-1000 microM) were tested in the guinea-pig urinary bladder for their ability to: (i) modify contractile responses to electrical field stimulation (EFS), ATP, alpha,beta-methylene ATP (alpha,beta-meATP), carbachol (CCh), and KCl; (ii) affect ecto-ATPase activity. 2. Ba2+ (10-1000 microM) concentration-dependently potentiated contractile responses evoked by EFS (4-16 Hz), ATP (100 microM), alpha,beta-meATP (1 microM), CCh (0.5 microM), and KCl (30 mM). Ni2+ at concentrations of 1-100 microM also potentiated contractility of the urinary bladder, but at concentrations tested its effect was not concentration-dependent. Cu2+ at a concentration of 10 microM and Cd2+ at a concentration of 1 microM potentiated responses to all stimuli, except KCl. Ni2+ at a concentration of 1000 microM and Cd2+ at a concentration of 100 microM inhibited contractions evoked by all stimuli, and at a concentration of 1000 microM Cd2+ abolished any contractions. Responses to ATP and alpha,beta-meATP were selectively inhibited by Cu2+, Zn2+ or La3+, each at a concentration of 1 mM. 3. Cu2+, Ni2+, Zn2+ and La3+ (100-1000 microM) concentration-dependently inhibited ecto-ATPase activity in the urinary bladder smooth muscle preparations, while Ba2+ and Mn2+ were without effect, and Cd2+ and Co2+ caused significant inhibition only at a concentration of 1000 microM. 4. There was no correlation between the extent of ecto-ATPase inhibition and the effect on contractile activity of any of the cations.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7735690

Cationic influences upon synaptic transmission at the hair cell-afferent fiber synapse of the frog

NASA Technical Reports Server (NTRS)

Cochran, S. L.

1995-01-01

The concentrations of inorganic cations (K+, Na+, and Ca2+) bathing the isolated frog labyrinth were varied in order to assess their role in influencing and mediating synaptic transmission at the hair cell-afferent fiber synapse. Experiments employed intracellular recordings of synaptic activity from VIIIth nerve afferents. Recordings were digitized continuously at 50 kHz, and excitatory postsynaptic potentials were detected and parameters quantified by computer algorithms. Particular attention was focused on cationic effects upon excitatory postsynaptic potential frequency of occurrence and excitatory postsynaptic potential amplitude, in order to discriminate between pre- and postsynaptic actions. Because the small size of afferents preclude long term stable recordings, alterations in cationic concentrations were applied transiently and their peak effects on synaptic activity were assessed. Increases in extracellular K+ concentration of a few millimolar produced a large increase in the frequency of occurrence of excitatory postsynaptic potentials with little change in amplitude, indicating that release of transmitter from the hair cell is tightly coupled to its membrane potential. Increasing extracellular Na+ concentration resulted in an increase in excitatory postsynaptic potential amplitude with no significant change in excitatory postsynaptic potential frequency of occurrence, suggesting that the transmitter-gated subsynaptic channel conducts Na+ ions. Decreases in extracellular Ca2+ concentration had little effect upon excitatory postsynaptic potential frequency, but increased excitatory postsynaptic potential frequency and amplitude. These findings suggest that at higher concentrations Ca2+ act presynaptically to prevent transmitter release and postsynaptically to prevent Na+ influx during the generation of the excitatory postsynaptic potential. The influences of these ions on synaptic activity at this synapse are remarkably similar to those reported at the vertebrate neuromuscular junction. The major differences between these two synapses are the neurotransmitters and the higher resting release rate and higher sensitivity of release to increased K+ concentrations of the hair cells over that of motor nerve terminals. These differences reflect the functional roles of the two synapses: the motor nerve terminal response in an all-or-nothing signal consequent from action potential invasion, while the hair cell releases transmitter in a graded fashion, proportionate to the extent of stereocilial deflection. Despite these differences between the two junctions, the similar actions of these elemental cations upon synaptic function at each implies that these ions may participate similarly in the operations of other synapses, independent of the neurotransmitter type.(ABSTRACT TRUNCATED AT 400 WORDS).

Linking trace element variations with macronutrients and major cations in marine mussels Mytilus edulis and Perna viridis.

PubMed

Liu, Fengjie; Wang, Wen-Xiong

2015-09-01

Marine mussels have long been used as biomonitors of contamination of trace elements, but little is known about whether variation in tissue trace elements is significantly associated with those of macronutrients and major cations. The authors examined the variability of macronutrients and major cations and their potential relationships with bioaccumulation of trace elements. The authors analyzed the concentrations of macronutrients (C, N, P, S), major cations (Na, Mg, K, Ca), and trace elements (Al, V, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Ba, Pb) in the whole soft tissues of marine mussels Mytilus edulis and Perna viridis collected globally from 21 sites. The results showed that 12% to 84% of the variances in the trace elements was associated with major cations, and the tissue concentration of major cations such as Na and Mg in mussels was a good proxy for ambient seawater concentrations of the major cations. Specifically, bioaccumulation of most of the trace elements was significantly associated with major cations, and the relationships of major cations with trace cations and trace oxyanions were totally opposite. Furthermore, 14% to 69% of the variances in the trace elements were significantly associated with macronutrients. Notably, more than half of the variance in the tissue concentrations of As, Cd, V, Ba, and Pb was explained by the variance in macronutrients in one or both species. Because the tissue macronutrient concentrations were strongly associated with animal growth and reproduction, the observed coupling relationships indicated that these biological processes strongly influenced the bioaccumulation of some trace elements. The present study indicated that simultaneous quantification of macronutrients and major cations with trace elements can improve the interpretation of biomonitoring data. © 2015 SETAC.

Parturient hypocalcemia in jersey cows fed alfalfa haylage-based diets with different cation to anion ratios.

PubMed

Gaynor, P J; Mueller, F J; Miller, J K; Ramsey, N; Goff, J P; Horst, R L

1989-10-01

Jersey cows were fed three alfalfa haylage-based diets with different cation-anion balances beginning 6 wk preceding third or later calving and ending 24 to 36 h postpartum. Sodium and Cl as percentages of dietary DM were .08 and 1.66 in diet 1 (anionic, 5 cows), .44 and .91 in diet 2 (intermediate, 6 cows), and 1.60 and .34 in diet 3 (cationic, 6 cows). Cation-anion balances were 22, 60, and 126 meq/100 g DM; Ca:P ratios averaged 4:1. Cows fed diet 1 in comparison with cows fed diets 2 or 3 over 6 wk had similar concentrations of Ca, P, and Na but higher concentrations of Mg and K in plasma and higher urinary excretions of Ca and Mg. Concentrations of 1,25-dihydroxyvitamin D 3 d before parturition were higher in cows fed diet 1 than in cows fed diets 2 or 3. Within 36 h after calving, mean concentrations of Ca in plasma (mg/dl, range) of cows fed diets 1 to 3, respectively, were 7 (8.7 to 6.2), 6.5 (7.8 to 3.9), and 6.3 (7.8 to 3.8). Number of cases of clinical milk fever by diet were 0 of 5, 2 of 6, and 1 of 6 cows. Alteration of dietary cation-anion balance by addition of Cl may effectively reduce incidence and severity of parturient hypocalcemia.

Redistribution kinetics of Ga and Al substitutions in yttrium iron garnet

NASA Astrophysics Data System (ADS)

Röschmann, P.

1980-01-01

Results are presented for the octahedral-tetrahedral site redistribution rate of Ga or Al and Fe in YIG in the temperature range 773 to 1523 K. The activation energy for the cation transfer decreases with increasing the oxygen vacancy concentration by annealing. A screening model describes qualitatively the effects of enhanced cation redistribution.

Desorption of intrinsic cesium from smectite: inhibitive effects of clay particle organization on cesium desorption.

PubMed

Fukushi, Keisuke; Sakai, Haruka; Itono, Taeko; Tamura, Akihiro; Arai, Shoji

2014-09-16

Fine clay particles have functioned as transport media for radiocesium in terrestrial environments after nuclear accidents. Because radiocesium is expected to be retained in clay minerals by a cation-exchange reaction, ascertaining trace cesium desorption behavior in response to changing solution conditions is crucially important. This study systematically investigated the desorption behavior of intrinsic Cs (13 nmol/g) in well-characterized Na-montmorillonite in electrolyte solutions (NaCl, KCl, CaCl2, and MgCl2) under widely differing cation concentrations (0.2 mM to 0.2 M). Batch desorption experiments demonstrated that Cs(+) desorption was inhibited significantly in the presence of the environmental relevant concentrations of Ca(2+) and Mg(2+) (>0.5 mM) and high concentrations of K(+). The order of ability for Cs desorption was Na(+) = K(+) > Ca(2+) = Mg(2+) at the highest cation concentration (0.2 M), which is opposite to the theoretical prediction based on the cation-exchange selectivity. Laser diffraction grain-size analyses revealed that the inhibition of Cs(+) desorption coincided with the increase of the clay tactoid size. Results suggest that radiocesium in the dispersed fine clay particles adheres on the solid phase when the organization of swelling clay particles occurs because of changes in solution conditions caused by both natural processes and artificial treatments.

Zeta potential of microfluidic substrates: 1. Theory, experimental techniques, and effects on separations.

PubMed

Kirby, Brian J; Hasselbrink, Ernest F

2004-01-01

This paper summarizes theory, experimental techniques, and the reported data pertaining to the zeta potential of silica and silicon with attention to use as microfluidic substrate materials, particularly for microchip chemical separations. Dependence on cation concentration, buffer and cation type, pH, cation valency, and temperature are discussed. The Debye-Hückel limit, which is often correctly treated as a good approximation for describing the ion concentration in the double layer, can lead to serious errors if it is extended to predict the dependence of zeta potential on the counterion concentration. For indifferent univalent electrolytes (e.g., sodium and potassium), two simple scalings for the dependence of zeta potential on counterion concentration can be derived in high- and low-zeta limits of the nonlinear Poisson-Boltzman equation solution in the double layer. It is shown that for most situations relevant to microchip separations, the high-zeta limit is most applicable, leading to the conclusion that the zeta potential on silica substrates is approximately proportional to the logarithm of the molar counterion concentration. The zeta vs. pH dependence measurements from several experiments are compared by normalizing the zeta based on concentration.

Photoinitiated Polymerization of Cationic Acrylamide in Aqueous Solution: Synthesis, Characterization, and Sludge Dewatering Performance

PubMed Central

Zheng, Huaili; Liao, Yi; Zheng, Meizhen; Zhu, Chuanjun; Ji, Fangying; Ma, Jiangya; Fan, Wei

2014-01-01

A copolymer of acrylamide (AM) with acryloyloxyethyl trimethyl ammonium chloride (DAC) as the cationic monomer was synthesized under the irradiation of high-pressure mercury lamp with 2,2-azobis(2-amidinopropane) dihydrochloride (V-50) as the photoinitiator. The compositions of the photoinduced copolymer were characterized by Fourier transform infrared spectra (FTIR), ultraviolet spectra (UV), and scanning electron microscope (SEM). The effects of 6 important factors, that is, photo-initiators concentration, monomers concentration, CO(NH2)2 (urea) concentrations, pH value, mass ratio of AM to DAC, and irradiation time on the molecular weight and dissolving time, were investigated. The optimal reaction conditions were that the photo-initiators concentration was 0.3%, monomers concentration was 30 wt.%, irradiation time was 60 min, urea concentration was 0.4%, pH value was 5.0, and mass ratio of AM to DAC was 6 : 4. Its flocculation properties were evaluated with activated sludge using jar test. The zeta potential of supernatant at different cationic monomer contents was simultaneously measured. The results demonstrated the superiority of the copolymer over the commercial polyacrylamide as a flocculant. PMID:24683343

Effects of Ionic Dependence of DNA Persistence Length on the DNA Condensation at Room Temperature

NASA Astrophysics Data System (ADS)

Mao, Wei; Liu, Yan-Hui; Hu, Lin; Xu, Hou-Qiang

2016-05-01

DNA persistence length is a key parameter for quantitative interpretation of the conformational properties of DNA and related to the bending rigidity of DNA. A series of experiments pointed out that, in the DNA condensation process by multivalent cations, the condensed DNA takes elongated coil or compact globule states and the population of the compact globule states increases with an increase in ionic concentration. At the same time, single molecule experiments carried out in solution with multivalent cations (such as spermidine, spermine) indicated that DNA persistence length strongly depends on the ionic concentration. In order to revolve the effects of ionic concentration dependence of persistence length on DNA condensation, a model including the ionic concentration dependence of persistence length and strong correlation of multivalent cation on DNA is provided. The autocorrelation function of the tangent vectors is found as an effective way to detect the ionic concentration dependence of toroidal conformations. With an increase in ion concentration, the first periodic oscillation contained in the autocorrelation function shifts, the number of segment contained in the first periodic oscillation decreases gradually. According to the experiments, the average long-axis length is defined to estimate the ionic concentration dependence of condensation process further. The relation between long-axis length and ionic concentration matches the experimental results qualitatively. Supported by National Natural Science Foundation of China under Grant Nos. 11047022, 11204045, 11464004 and 31360215; The Research Foundation from Ministry of Education of China (212152), Guizhou Provincial Tracking Key Program of Social Development (SY20123089, SZ20113069); The General Financial Grant from the China Postdoctoral Science Foundation (2014M562341); The Research Foundation for Young University Teachers from Guizhou University (201311); The West Light Foundation (2015) and College Innovation Talent Team of Guizhou Province, (2014) 32

Synthetic cation-selective nanotube: permeant cations chaperoned by anions.

PubMed

Hilder, Tamsyn A; Gordon, Dan; Chung, Shin-Ho

2011-01-28

The ability to design ion-selective, synthetic nanotubes which mimic biological ion channels may have significant implications for the future treatment of bacteria, diseases, and as ultrasensitive biosensors. We present the design of a synthetic nanotube made from carbon atoms that selectively allows monovalent cations to move across and rejects all anions. The cation-selective nanotube mimics some of the salient properties of biological ion channels. Before practical nanodevices are successfully fabricated it is vital that proof-of-concept computational studies are performed. With this in mind we use molecular and stochastic dynamics simulations to characterize the dynamics of ion permeation across a single-walled (10, 10), 36 Å long, carbon nanotube terminated with carboxylic acid with an effective radius of 5.08 Å. Although cations encounter a high energy barrier of 7 kT, its height is drastically reduced by a chloride ion in the nanotube. The presence of a chloride ion near the pore entrance thus enables a cation to enter the pore and, once in the pore, it is chaperoned by the resident counterion across the narrow pore. The moment the chaperoned cation transits the pore, the counterion moves back to the entrance to ferry another ion. The synthetic nanotube has a high sodium conductance of 124 pS and shows linear current-voltage and current-concentration profiles. The cation-anion selectivity ratio ranges from 8 to 25, depending on the ionic concentrations in the reservoirs.

Transport of K+ and other cations across phospholipid membranes by nonesterified fatty acids.

PubMed

Sharpe, M A; Cooper, C E; Wrigglesworth, J M

1994-07-01

The rate of change of internal pH and transmembrane potential has been monitored in liposomes following the external addition of various cation salts. Oleic acid increases the transmembrane movement of H+ following the imposition of a K+ gradient. An initial fast change in internal pH is seen followed by a slower rate of alkalinization. High concentrations of the fatty acid enhance the rate comparable to that seen in the presence of nigericin in contrast to the effect of FCCP (carbonyl cyanide p-(tri-fluoromethoxy)phenyl hydrazone) which saturates at an intermediate value. The ability of nonesterified fatty acids to catalyze the movement of cations across the liposome membrane increases with the degree of unsaturation and decreases with increasing chain length. Li and Na salts cause a similar initial fast pH change but have less effect on the subsequent slower rate. Similarly, the main effect of divalent cation salts is on the initial fast change. The membrane potential can enhance or inhibit cation transport depending on its polarity with respect to the cation gradient. It is concluded that nonesterified fatty acids have the capability to complex with, and transport, a variety of cations across phospholipid bilayers. However, they do not act simply as proton/cation exchangers analogous to nigericin nor as protonophores analogous to FCCP. The full cycle of ionophoric action involves a combination of both functions.

Mineralogical and hydrochemical effects on adsorption removal of cesium-137 and strontium-90 by kaolinite.

PubMed

Jeong, C H

2001-01-01

Adsorption characteristics of the nuclides onto kaolinite were investigated by batch experiment under various pH conditions and concentrations of groundwater cations (Ca2+, Mg2+, K+ and Na+) and anions (HCO3-, CO3(2-) and SO4(2-). Adsorption removal of 137Cs and 90Sr by kaolinite greatly increased as the concentration of groundwater cations increased from 10(-5) to 10(-1) M. In contrast, the pH exerted a small effect on the adsorption of 137Cs and 90Sr onto kaolinite. The zeta potential of kaolinite particles showed a negative increase of amphoteric surface charge with increasing pH. The adsorption behavior of 90Sr was also highly dependent on the concentration of bicarbonate. The thermodynamic saturation index indicated that bicarbonate exerts great effect on strontium adsorption by the precipitation of a strontianite (SrCO3) and a change in pH.

Oil-water separation property of polymer-contained wastewater from polymer-flooding oilfields in Bohai Bay, China.

PubMed

Chen, Hua-xing; Tang, Hong-ming; Duan, Ming; Liu, Yi-gang; Liu, Min; Zhao, Feng

2015-01-01

In this study, the effects of gravitational settling time, temperature, speed and time of centrifugation, flocculant type and dosage, bubble size and gas amount were investigated. The results show that the simple increase in settling time and temperature is of no use for oil-water separation of the three wastewater samples. As far as oil-water separation efficiency is concerned, increasing centrifugal speed and centrifugal time is highly effective for L sample, and has a certain effect on J sample, but is not valid for S sample. The flocculants are highly effective for S and L samples, and the oil-water separation efficiency increases with an increase in the concentration of inorganic cationic flocculants. There exist critical reagent concentrations for the organic cationic and the nonionic flocculants, wherein a higher or lower concentration of flocculant would cause a decrease in the treatment efficiency. Flotation is an effective approach for oil-water separation of polymer-contained wastewater from the three oilfields. The oil-water separation efficiency can be enhanced by increasing floatation agent concentration, flotation time and gas amount, and by decreasing bubble size.

Structure-biocompatibility and transfection activity relationships of cationic polyaspartamides with (dialkylamino)alkyl and alkyl or hydroxyalkyl side groups.

PubMed

Salakhieva, Diana; Shevchenko, Vesta; Németh, Csaba; Gyarmati, Benjámin; Szilágyi, András; Abdullin, Timur

2017-01-30

A series of 14 cationic derivatives of poly(aspartic acid) i.e. cationic polyaspartamides with different (dialkylamino)alkyl and alkyl or hydroxyalkyl side groups was synthesized by nucleophilic addition on polysuccinimide. The resulting polyaspartamides have moderate amphiphilic properties. Relationships between the structure and ratio of side groups and in vitro properties of polyaspartamides, including their cytotoxic and membrane-damaging activity towards human cell lines, primary skin fibroblasts and erythrocytes, were established and discussed. Cationic polyaspartamides vary in their DNA-binding, condensing and nuclease-protecting characteristics depending on the concentration ratio of (dialkylamino)alkyl and alkyl or hydroxyalkyl side groups. Effective cell transfection was achieved upon polyaspartamide-mediated plasmid DNA delivery in serum-free medium in the presence of chloroquine. Effect of serum proteins adsorption onto polyaspartamide based polyplexes, and the role of concentration of polyplexes in culture medium in their colloidal stability and transfection process were demonstrated. Synthesized polyaspartamides are biocompatible and long-acting gene carriers, which are applied to cells after dilution and without washing, thus providing transfection level comparable to that of commercial transfection reagent. Copyright © 2016 Elsevier B.V. All rights reserved.

Cation radius effects on the helix-coil transition of DNA. Cryptates and other large cations.

PubMed Central

Trend, B L; Knoll, D A; Ueno, M; Evans, D F; Bloomfield, V A

1990-01-01

Most polyelectrolyte theories of the effect of ions on the thermal melting of DNA assume that the predominant influence of the cations comes through their charge. Ion size and structure are treated, for analytic convenience, as negligible variables. We have examined the validity of this assumption by measuring the melting temperature of calf thymus DNA as a function of salt concentration with four univalent cations of different hydrated radii. These are K+ (3.3 A), (n-Pr)4N+ (4.5 A), (EtOH)4N+ (4.5 A), and C222-K+ (5 A). C222-K+ is a complex of cryptand C222 with K+. With K+ as the sole cation, Tm varies linearly with the log of ionic strength over the range 0.001-0.1 M. With all the K+ sequestered by an equimolar amount of C222, Tm is depressed by 10-20 degrees C and the slope of Tm vs. ionic strength is lower. At low ionic strength, an even greater reduction in Tm is achieved with (n-Pr)4N+; but the similar-sized (EtOH)4N+ gives a curve more similar to K+. Theoretical modeling, taking into account cation size through the Poisson-Boltzmann equation for cylindrical polyelectrolytes, predicts that larger cations should be less effective in stabilizing the double helix; but the calculated effect is less than observed experimentally. These results show that valence, cation size, and specific solvation effects are all important in determining the stability of the double-helical form of DNA. PMID:2344467

Metal-organic complexes in geochemical processes: temperature dependence of the standard thermodynamic properties of aqueous complexes between metal cations and dicarboxylate ligands

NASA Astrophysics Data System (ADS)

Prapaipong, Panjai; Shock, Everett L.; Koretsky, Carla M.

1999-10-01

By combining results from regression and correlation methods, standard state thermodynamic properties for aqueous complexes between metal cations and divalent organic acid ligands (oxalate, malonate, succinate, glutarate, and adipate) are evaluated and applied to geochemical processes. Regression of experimental standard-state equilibrium constants with the revised Helgeson-Kirkham-Flowers (HKF) equation of state yields standard partial molal entropies (S¯°) of aqueous metal-organic complexes, which allow determination of thermodynamic properties of the complexes at elevated temperatures. In cases where S¯° is not available from either regression or calorimetric measurement, the values of S¯° can be estimated from a linear correlation between standard partial molal entropies of association (ΔS¯°r) and standard partial molal entropies of aqueous cations (S¯°M). The correlation is independent of cation charge, which makes it possible to predict S¯° for complexes between divalent organic acids and numerous metal cations. Similarly, correlations between standard Gibbs free energies of association of metal-organic complexes (ΔḠ°r) and Gibbs free energies of formation (ΔḠ°f) for divalent metal cations allow estimates of standard-state equilibrium constants where experimental data are not available. These correlations are found to be a function of ligand structure and cation charge. Predicted equilibrium constants for dicarboxylate complexes of numerous cations were included with those for inorganic and other organic complexes to study the effects of dicarboxylate complexes on the speciation of metals and organic acids in oil-field brines. Relatively low concentrations of oxalic and malonic acids affect the speciation of cations more than similar concentrations of succinic, glutaric, and adipic acids. However, the extent to which metal-dicarboxylate complexes contribute to the speciation of dissolved metals depends on the type of dicarboxylic acid ligand; relative concentration of inorganic, mono-, and dicarboxylate ligands; and the type of metal cation. As an example, in the same solution, dicarboxylic acids have a greater influence on the speciation of Fe+2 and Mg+2 than on the speciation of Zn+2 and Mn+2.

Kinetics of caesium and potassium absorption by roots of three grass pastures and competitive effects of potassium on caesium uptake in Cynodon sp.

NASA Astrophysics Data System (ADS)

Ayub, J. Juri; Valverde, L. Rubio; Garcia-Sanchez, M. J.; Fernandez, J. A.; Velasco, R. H.

2008-08-01

Caesium uptake by plant roots has been normally associated with the uptake of potassium as the potassium transport systems present in plants have also the capacity to transport caesium. Three grass species (Eragrostis curvula, Cynodon sp and Distichlis spicata) growing in seminatural grassland of central Argentina were selected to study their capability to incorporate Cs+ (and K+) using electrophysiological techniques. Although the 137Cs soil inventory ranged between 328-730 Bq m-2 in this region, no 137Cs activity was detected in these plants. However, all the species, submitted previously to K+ starvation, showed the uptake of both Cs+ and K+ when micromolar concentrations of these cations were present in the medium. The uptake showed saturation kinetics for both cations that could be fitted to the Michelis-Menten model. KM values were smaller for K+ than for Cs+, indicating a higher affinity for the first cation. The presence of increasing K+ concentrations in the assay medium inhibited Cs+ uptake in Cynodon sp., as expected if both cations are transported by the same transport systems. This effect is due to the competition of both ions for the union sites of the high affinity potassium transporters. In field situation, where soil concentration of Cs+ is smaller than K+ concentration, is then expectable that caesium activity in plants is not detectable. Nevertheless, the studied plants would have the capacity to incorporate caesium if its availability in soil solution increases. In addition, studies of Cs/K interaction can help us to understand the variability in transfer factors.

Do the cations in clay and the polymer matrix affect quantum dot fluorescent properties?

PubMed

Wei, Wenjun; Liu, Cui; Liu, Jiyan; Liu, Xueqing; Zou, Linling; Cai, Shaojun; Shi, Hong; Cao, Yuan-Cheng

2016-06-01

This paper studied the effects of cations and polymer matrix on the fluorescent properties of quantum dots (QDs). The results indicated that temperature has a greater impact on fluorescence intensity than clay cations (mainly K(+) and Na(+) ). Combined fluorescence lifetime and steady-state spectrometer tests showed that QD lifetimes all decreased when the cation concentration was increased, but the quantum yields were steady at various cation concentrations of 0, 0.05, 0.5 and 1 M. Poly(ethylene oxide) (PEO), poly(vinyl alcohol) (PVA) and diepoxy resin were used to study the effects of polymers on QD lifetime and quantum yield. The results showed that the lifetime for QDs 550 nm in PEO and PVA was 17.33 and 17.12 ns, respectively; for the epoxy resin, the lifetime was 0.74 ns, a sharp decrease from 24.47 ns. The quantum yield for QDs 550 nm changed from 34.22% to 7.45% and 7.81% in PEO and PVA, respectively; for the epoxy resin the quantum yield was 2.25%. QDs 580 nm and 620 nm showed the same results as QDs 550 nm. This study provides useful information on the design, synthesis and application of QDs-polymer luminescent materials. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

High-capacity cation-exchange column for enhanced resolution of adjacent peaks of cations in ion chromatography.

PubMed

Rey, M A

2001-06-22

One of the advantages of ion chromatography [Anal Chem. 47 (1975) 1801] as compared to other analytical techniques is that several ions may be analyzed simultaneously. One of the most important contributions of cation-exchange chromatography is its sensitivity to ammonium ion, which is difficult to analyze by other techniques [J. Weiss, in: E.L. Johnson (Ed.), Handbook of Ion Chromatography, Dionex, Sunnyvale, CA, USA]. The determination of low concentrations of ammonium ion in the presence of high concentrations of sodium poses a challenge in cation-exchange chromatography [J. Weiss, Ion Chromatography, VCH, 2nd Edition, Weinheim, 1995], as both cations have similar selectivities for the common stationary phases containing either sulfonate or carboxylate functional groups. The task was to develop a new cation-exchange stationary phase (for diverse concentration ratios of adjacent peaks) to overcome limitations experienced in previous trails. Various cation-exchange capacities and column body formats were investigated to optimize this application and others. The advantages and disadvantages of two carboxylic acid columns of different cation-exchange capacities and different column formats will be discussed.

The role of surface charge density in cationic liposome-promoted dendritic cell maturation and vaccine-induced immune responses

NASA Astrophysics Data System (ADS)

Ma, Yifan; Zhuang, Yan; Xie, Xiaofang; Wang, Ce; Wang, Fei; Zhou, Dongmei; Zeng, Jianqiang; Cai, Lintao

2011-05-01

Cationic liposomes have emerged as a novel adjuvant and antigen delivery system to enhance vaccine efficacy. However, the role of surface charge density in cationic liposome-regulated immune responses has not yet been elucidated. In the present study, we prepared a series of DOTAP/DOPC cationic liposomes with different surface densities by incorporating varying amounts of DOPC (a neutral lipid) into DOTAP (a cationic lipid). The results showed that DOTAP/DOPC cationic liposome-regulated immune responses relied on the surface charge density, and might occur through ROS signaling. The liposomes with a relatively high charge density, such as DOTAP/DOPC 5 : 0 and 4 : 1 liposomes, potently enhanced dendritic cell maturation, ROS generaion, antigen uptake, as well as the production of OVA-specific IgG2a and IFN-γ. In contrast, low-charge liposomes, such as DOTAP/DOPC 1 : 4 liposome, failed to promote immune responses even at high concentrations, confirming that the immunoregulatory effect of cationic liposomes is mostly attributable to their surface charge density. Moreover, the DOTAP/DOPC 1 : 4 liposome suppressed anti-OVA antibody responses in vivo. Overall, maintaining an appropriate surface charge is crucial for optimizing the adjuvant effect of cationic liposomes and enhancing the efficacy of liposome-based vaccines.

Photochemistry of PAHs in cosmic water ice. The effect of concentration on UV-VIS spectroscopy and ionization efficiency

NASA Astrophysics Data System (ADS)

Cuylle, Steven H.; Allamandola, Louis J.; Linnartz, Harold

2014-02-01

Context. Observations and models show that polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the interstellar medium. Like other molecules in dense clouds, PAHs accrete onto interstellar dust grains, where they are embedded in an ice matrix dominated by water. In the laboratory, mixed molecular ices (not containing PAHs) have been extensively studied using Fourier transform infrared absorption spectroscopy. Experiments including PAHs in ices have started, however, the concentrations used are typically much higher than the concentrations expected for interstellar ices. Optical spectroscopy offers a sensitive alternative. Aims: We report an experimental study of the effect PAH concentration has on the electronic spectra and the vacuum UV (VUV) driven processes of PAHs in water-rich ices. The goal is to apply the outcome to cosmic ices. Methods: Optical spectroscopic studies allow us to obtain in-situ and quasi real-time electronic solid state spectra of two prototypical PAHs (pyrene and coronene) embedded in water ice under VUV photoprocessing. The study is carried out on PAH:H2O concentrations in the range of 1:30 000 to pure PAH, covering the temperature range from 12 to 125 K. Results: PAH concentration strongly influences the efficiency of PAH cation formation. At low concentrations, ionization efficiencies are over 60% dropping to about 15% at 1:1000. Increasing the PAH concentration reveals spectral broadening in neutral and cation PAH spectra attributed to PAH clustering inside the ice. At the PAH concentrations expected for interstellar ices, some 10 to 20% may be present as cations. The presence of PAHs in neutral and ion form will add distinctive absorption bands to cosmic ice optical spectra and this may serve as a tool to determine PAH concentrations.

Promoter Effects of Alkali Metal Cations on the Electrochemical Reduction of Carbon Dioxide

DOE PAGES

Resasco, Joaquin; Chen, Leanne D.; Clark, Ezra; ...

2017-07-24

The electrochemical reduction of CO 2 is known to be influenced by the identity of the alkali metal cation in the electrolyte; however, a satisfactory explanation for this phenomenon has not been developed. Here we present the results of experimental and theoretical studies aimed at elucidating the effects of electrolyte cation size on the intrinsic activity and selectivity of metal catalysts for the reduction of CO 2. Experiments were conducted under conditions where the influence of electrolyte polarization is minimal in order to show that cation size affects the intrinsic rates of formation of certain reaction products, most notably formore » HCOO –, C 2H 4, and C 2H 5OH over Cu(100)- and Cu(111)-oriented thin films, and for CO and HCOO– over polycrystalline Ag and Sn. Interpretation of the findings for CO 2 reduction was informed by studies of the reduction of glyoxal and CO, key intermediates along the reaction pathway to final products. Density functional theory calculations show that the alkali metal cations influence the distribution of products formed as a consequence of electrostatic interactions between solvated cations present at the outer Helmholtz plane and adsorbed species having large dipole moments. As a result, the observed trends in activity with cation size are attributed to an increase in the concentration of cations at the outer Helmholtz plane with increasing cation size.« less

Promoter Effects of Alkali Metal Cations on the Electrochemical Reduction of Carbon Dioxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Resasco, Joaquin; Chen, Leanne D.; Clark, Ezra

The electrochemical reduction of CO 2 is known to be influenced by the identity of the alkali metal cation in the electrolyte; however, a satisfactory explanation for this phenomenon has not been developed. Here we present the results of experimental and theoretical studies aimed at elucidating the effects of electrolyte cation size on the intrinsic activity and selectivity of metal catalysts for the reduction of CO 2. Experiments were conducted under conditions where the influence of electrolyte polarization is minimal in order to show that cation size affects the intrinsic rates of formation of certain reaction products, most notably formore » HCOO –, C 2H 4, and C 2H 5OH over Cu(100)- and Cu(111)-oriented thin films, and for CO and HCOO– over polycrystalline Ag and Sn. Interpretation of the findings for CO 2 reduction was informed by studies of the reduction of glyoxal and CO, key intermediates along the reaction pathway to final products. Density functional theory calculations show that the alkali metal cations influence the distribution of products formed as a consequence of electrostatic interactions between solvated cations present at the outer Helmholtz plane and adsorbed species having large dipole moments. As a result, the observed trends in activity with cation size are attributed to an increase in the concentration of cations at the outer Helmholtz plane with increasing cation size.« less

Metal Cations in G-Quadruplex Folding and Stability

NASA Astrophysics Data System (ADS)

Bhattacharyya, Debmalya; Mirihana Arachchilage, Gayan; Basu, Soumitra

2016-09-01

This review is focused on the structural and physico-chemical aspects of metal cation coordination to G-Quadruplexes (GQ) and their effects on GQ stability and conformation. G-Quadruplex structures are non-canonical secondary structures formed by both DNA and RNA. G-quadruplexes regulate a wide range of important biochemical processes. Besides the sequence requirements, the coordination of monovalent cations in the GQ is essential for its formation and determines the stability and polymorphism of GQ structures. The nature, location and dynamics of the cation coordination and their impact on the overall GQ stability are dependent on several factors such as the ionic radii, hydration energy and the bonding strength to the O6 of guanines. The intracellular monovalent cation concentration and the localized ion concentrations determine the formation of GQs and can potentially dictate their regulatory roles. A wide range of biochemical and biophysical studies on an array of GQ enabling sequences have generated at a minimum the knowledge base that allows us to often predict the stability of GQs in presence of the physiologically relevant metal ions, however, prediction of conformation of such GQs is still out of the realm.

Inversion of membrane surface charge by trivalent cations probed with a cation-selective channel

PubMed Central

Gurnev, Philip A.; Bezrukov, Sergey M.

2014-01-01

We demonstrate that the cation-selective channel formed by gramicidin A can be used as a reliable sensor for studying the multivalent ion accumulation at the surfaces of charged lipid membranes and the “charge inversion” phenomenon. In asymmetrically charged membranes with the individual leaflets formed from pure negative and positive lipids bathed by 0.1 M CsCl solutions the channel exhibits current rectification which is comparable to that of a typical n/p semiconductor diode. We show that even at these highly asymmetrical conditions the channel conductance can be satisfactorily described by the electrodiffusion equation in the constant field approximation but, due to predictable limitations, only when the applied voltages do not exceed 50 mV. Analysis of the changes in the voltage-dependent channel conductance upon addition of trivalent cations allows us to gauge their interactions with the membrane surface. The inversion of the sign of the effective surface charge takes place at the concentrations which correlate with the cation size. Specifically, these concentrations are close to 0.05 mM for lanthanum, 0.25 mM for hexaamminecobalt, and 4 mM for spermidine. PMID:23088396

Inversion of membrane surface charge by trivalent cations probed with a cation-selective channel.

PubMed

Gurnev, Philip A; Bezrukov, Sergey M

2012-11-13

We demonstrate that the cation-selective channel formed by gramicidin A can be used as a reliable sensor for studying the multivalent ion accumulation at the surfaces of charged lipid membranes and the "charge inversion" phenomenon. In asymmetrically charged membranes with the individual leaflets formed from pure negative and positive lipids bathed by 0.1 M CsCl solutions the channel exhibits current rectification, which is comparable to that of a typical n/p semiconductor diode. We show that even at these highly asymmetrical conditions the channel conductance can be satisfactorily described by the electrodiffusion equation in the constant field approximation but, due to predictable limitations, only when the applied voltages do not exceed 50 mV. Analysis of the changes in the voltage-dependent channel conductance upon addition of trivalent cations allows us to gauge their interactions with the membrane surface. The inversion of the sign of the effective surface charge takes place at the concentrations, which correlate with the cation size. Specifically, these concentrations are close to 0.05 mM for lanthanum, 0.25 mM for hexaamminecobalt, and 4 mM for spermidine.

Kinetic Monte Carlo Investigation of the Effects of Vacancy Pairing on Oxygen Diffusivity in Yttria-Stabilized Zirconia

NASA Technical Reports Server (NTRS)

Good, Brian S.

2011-01-01

Yttria-stabilized zirconia s high oxygen diffusivity and corresponding high ionic conductivity, and its structural stability over a broad range of temperatures, have made the material of interest for use in a number of applications, for example, as solid electrolytes in fuel cells. At low concentrations, the stabilizing yttria also serves to increase the oxygen diffusivity through the presence of corresponding oxygen vacancies, needed to maintain charge neutrality. At higher yttria concentration, however, diffusivity is impeded by the larger number of relatively high energy migration barriers associated with yttrium cations. In addition, there is evidence that oxygen vacancies preferentially occupy nearest-neighbor sites around either dopant or Zr cations, further affecting vacancy diffusion. We present the results of ab initio calculations that indicate that it is energetically favorable for oxygen vacancies to occupy nearest-neighbor sites adjacent to Y ions, and that the presence of vacancies near either species of cation lowers the migration barriers. Kinetic Monte Carlo results from simulations incorporating this effect are presented and compared with results from simulations in which the effect is not present.

Cytotoxicity and the effect of cationic peptide fragments against cariogenic bacteria under planktonic and biofilm conditions.

PubMed

Kreling, Paula Fernanda; Aida, Kelly Limi; Massunari, Loiane; Caiaffa, Karina Sampaio; Percinoto, Célio; Bedran, Telma Blanca Lombardo; Spolidorio, Denise Madalena Palomari; Abuna, Gabriel Flores; Cilli, Eduardo Maffud; Duque, Cristiane

2016-10-01

This study evaluated the cytotoxicity and effect of fragments derived from three oral cationic peptides (CP): LL-37, D6-17 and D1-23 against cariogenic bacteria under planktonic and biofilm conditions. For cytotoxicity analysis, two epithelial cell lines were used. The minimum inhibitory concentration and the minimal bactericidal concentration were determined for the CP fragments and the control (chlorhexidine-CHX) against cariogenic bacteria. The fractional inhibitory concentration was obtained for the combinations of CP fragments on Streptococcus mutans. Biofilm assays were conducted with the best antimicrobial CP fragment against S. mutans. The results indicated that D6-17 was not cytotoxic. D1-23, LL-37 and CHX were not cytotoxic in low concentrations. D1-23 presented the best bactericidal activity against S. mutans, S. mitis and S. salivarius. Combinations of CP fragments did not show a synergic effect. D1-23 presented a higher activity against S. mutans biofilm than CHX. It was concluded that D1-23 showed a substantial effect against cariogenic bacteria and low cytotoxicity.

Super-high-affinity binding site for [3H]diazepam in the presence of Co2+, Ni2+, Cu2+, or Zn2+.

PubMed

Mizuno, S; Ogawa, N; Mori, A

1982-12-01

Chloride salts of Li+, Na+, K+, Mg2+, Ca2+, Cr3+, Mn2+, Fe2+, and Fe3+ had no effect on [3H]diazepam binding. Chloride salts of Co2+, Ni2+, Cu2+, and Zn2+ increased [3H]diazepam binding by 34 to 68% in a concentration-dependent fashion. Since these divalent cations potentiated the GABA-enhanced [3H]diazepam binding and the effect of each divalent cation was nearly additive with GABA, these cations probably act at a site different from the GABA recognition site in the benzodiazepine-receptor complex. Scatchard plots of [3H]diazepam binding without an effective divalent cation showed a single class of binding, with a Kd value of 5.3 nM. In the presence of 1 mM Co2+, Ni2+, Cu2+, or Zn2+, two distinct binding sites were evident with apparent Kd values of 1.0 nM and 5.7 nM. The higher-affinity binding was not detected in the absence of an effective divalent cation and is probably a novel, super-high-affinity binding site.

[Effect of salts, stabilizing and destabilizing the structure of water, on the stacking association of adenosine].

PubMed

Maevskiĭ, A A; Sukhorukov, B I

1976-11-01

A spectrophotometric study, based on the concentration relationship of electron absorption spectra, of the effects of salts which stabilize and destabilize the water structure on the constant (K) of adenosine: stacking association has been carried out. A significant decrease of K was observed in NaClO4 which embodied strong destabilizing effect. Opposite effect was observed on other salts studied. According to K value the stacking-interaction of adenosine in the range of salt concentration 0 divided by 3M for different anions and cations are arranged in rows: SO4--greater than Cl- greater than ClO4-; Na+ greater than Li+greater than K+. The data obtained suggest that the effect of salts on thermostability of various oligo- and polynucleotides and on B leads to C DNA transition may be essentially concerned with the effect of both cations and anions of salts on the stacking-interaction of bases.

Cost-Effective Filter Materials Coated with Silver Nanoparticles for the Removal of Pathogenic Bacteria in Groundwater

PubMed Central

Mpenyana-Monyatsi, Lizzy; Mthombeni, Nomcebo H.; Onyango, Maurice S.; Momba, Maggy N. B.

2012-01-01

The contamination of groundwater sources by pathogenic bacteria poses a public health concern to communities who depend totally on this water supply. In the present study, potentially low-cost filter materials coated with silver nanoparticles were developed for the disinfection of groundwater. Silver nanoparticles were deposited on zeolite, sand, fibreglass, anion and cation resin substrates in various concentrations (0.01 mM, 0.03 mM, 0.05 mM and 0.1 mM) of AgNO3. These substrates were characterised by SEM, EDS, TEM, particle size distribution and XRD analyses. In the first phase, the five substrates coated with various concentrations of AgNO3 were tested against E. coli spiked in synthetic water to determine the best loading concentration that could remove pathogenic bacteria completely from test water. The results revealed that all filters were able to decrease the concentration of E. coli from synthetic water, with a higher removal efficiency achieved at 0.1 mM (21–100%) and a lower efficiency at 0.01 mM (7–50%) concentrations. The cation resin-silver nanoparticle filter was found to remove this pathogenic bacterium at the highest rate, namely 100%. In the second phase, only the best performing concentration of 0.1 mM was considered and tested against presumptive E. coli, S. typhimurium, S. dysenteriae and V. cholerae from groundwater. The results revealed the highest bacteria removal efficiency by the Ag/cation resin filter with complete (100%) removal of all targeted bacteria and the lowest by the Ag/zeolite filter with an 8% to 67% removal rate. This study therefore suggests that the filter system with Ag/cation resin substrate can be used as a potential alternative cost-effective filter for the disinfection of groundwater and production of safe drinking water. PMID:22470290

Analytical modeling of localized surface plasmon resonance in heterostructure copper sulfide nanocrystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caldwell, Andrew H.; Ha, Don-Hyung; Robinson, Richard D., E-mail: rdr82@cornell.edu

2014-10-28

Localized surface plasmon resonance (LSPR) in semiconductor nanocrystals is a relatively new field of investigation that promises greater tunability of plasmonic properties compared to metal nanoparticles. A novel process by which the LSPR in semiconductor nanocrystals can be altered is through heterostructure formation arising from solution-based cation exchange. Herein, we describe the development of an analytical model of LSPR in heterostructure copper sulfide-zinc sulfide nanocrystals synthesized via a cation exchange reaction between copper sulfide (Cu{sub 1.81}S) nanocrystals and Zn ions. The cation exchange reaction produces dual-interface, heterostructure nanocrystals in which the geometry of the copper sulfide phase can be tunedmore » from a sphere to a thin disk separating symmetrically-grown sulfide (ZnS) grains. Drude model electronic conduction and Mie-Gans theory are applied to describe how the LSPR wavelength changes during cation exchange, taking into account the morphology evolution and changes to the local permittivity. The results of the modeling indicate that the presence of the ZnS grains has a significant effect on the out-of-plane LSPR mode. By comparing the results of the model to previous studies on solid-solid phase transformations of copper sulfide in these nanocrystals during cation exchange, we show that the carrier concentration is independent of the copper vacancy concentration dictated by its atomic phase. The evolution of the effective carrier concentration calculated from the model suggests that the out-of-plane resonance mode is dominant. The classical model was compared to a simplified quantum mechanical model which suggested that quantum mechanical effects become significant when the characteristic size is less than ∼8 nm. Overall, we find that the analytical models are not accurate for these heterostructured semiconductor nanocrystals, indicating the need for new model development for this emerging field.« less

Application of the diffusive gradients in thin films technique for available potassium measurement in agricultural soils: effects of competing cations on potassium uptake by the resin gel.

PubMed

Zhang, Yulin; Mason, Sean; McNeill, Ann; McLaughlin, Michael J

2014-09-09

The utilization of Amberlite (IRP-69 ion-exchange resin, 100-500 wet mesh) as the binding phase in the diffusive gradients in thin films (DGT) technique has shown potential to improve the assessment of plant-available K in soils. The binding phase has recently been optimized by using a mixed Amberlite and ferrihydrite (MAF) gel which results in linear K uptake over extended deployment periods and in solutions with higher K concentrations. As restriction of K uptake by Ca on the Amberlite based resin gel has been previously proposed, potential competing effects of Ca(2+), Mg(2+) and NH(4+) on K uptake by the MAF gel were investigated. These cations had no effect on K elution efficiency which was 85%. However, K uptake by the MAF gel was restricted in the presence of competing cations in solution. Consequently, the diffusion coefficient of K decreased in the presence of cations compared to previous studies but was stable at 1.12×10(-5)cm(2)s(-1) at 25°C regardless of cation concentrations. Uptake of K by the DGT device was affected by the presence of excessive Ca in more than 30% of twenty typical Australian agricultural soils. However, this problem could be circumvented by using a shorter deployment time than the normal 24 h. Moderate correlation of concentrations of K extracted by DGT with Colwell K (extracted by NaHCO(3), R(2)=0.69) and NH4OAc K (R(2)=0.61) indicates that DGT measures a different pool of K in soils than that measured by the standard extractants used. In addition, the MAF gel has the ability to measure Ca and Mg simultaneously. Copyright © 2014 Elsevier B.V. All rights reserved.

Divalent cation and ionic strength effects on Vinca alkaloid-induced tubulin self-association.

PubMed

Lobert, S; Boyd, C A; Correia, J J

1997-01-01

We present here a systematic study of ionic strength and divalent cation effects on Vinca alkaloid-induced tubulin spiral formation. We used sedimentation velocity experiments and quantitative fitting of weight-average sedimentation coefficients versus free drug concentrations to obtain thermodynamic parameters under various solution conditions. The addition of 50-150 mM NaCl to our standard buffer (10 mM piperazine-N,N'-bis(2-ethanesulfonic acid), 1 mM Mg, 50 microM GDP or GTP, pH 6.9) enhances overall vinblastine- or vincristine-induced tubulin self-association. As demonstrated in previous studies, GDP enhances overall self-association more than GTP, although in the presence of salt, GDP enhancement is reduced. For example, in 150 mM NaCl, GDP enhancement is 0.24 kcal/mol for vinblastine and 0.36 kcal/mol for vincristine versus an average enhancement of 0.87 (+/- 0.34) kcal/mol for the same drugs in the absence of salt. Wyman linkage analysis of experiments with vinblastine or vincristine over a range of NaCl concentrations showed a twofold increase in the change in NaCl bound to drug-induced spirals in the presence of GTP compared to GDP. These data indicate that GDP enhancement of Vinca alkaloid-induced tubulin self-association is due in part to electrostatic inhibition in the GTP state. In the absence of NaCl, we found that vinblastine and 1 mM Mn2+ or Ca2+ causes immediate condensation of tubulin. The predominant aggregates observed by electron microscopy are large sheets. This effect was not found with 1 mM Mg2+. At 100 microM cation concentrations (Mn2+, Mg2+, or Ca2+), GDP enhances vinblastine-induced spiral formation by 0.55 (+/- 0.26) kcal/mol. This effect is found only in K2, the association of liganded heterodimers at the ends of growing spirals. There is no GDP enhancement of K1, the binding of drug to heterodimer, although K1 is dependent upon the divalent cation concentration. NaCl diminishes tubulin condensation, probably by inhibiting lateral association, and allows an investigation of higher divalent cation concentrations. In the presence of 150 mM NaCl plus 1 mM divalent cations (Mn2+, Mg2+, or Ca2+) GDP enhances vinblastine-induced spiral formation by 0.35 (+/- 0.21) kcal/mol. Relaxation times determined by stopped-flow light scattering experiments in the presence of 150 mM NaCl and vincristine are severalfold longer than those in the presence of vinblastine, consistent with a mechanism involving the redistribution of longer polymers. Unlike previous results in the absence of NaCl, relaxation times in the presence of NaCl are only weekly protein concentration dependent, suggesting the absence of annealing or an additional rate-limiting step in the mechanism.

Protein unfolding in detergents: effect of micelle structure, ionic strength, pH, and temperature.

PubMed Central

Otzen, Daniel E

2002-01-01

The 101-residue monomeric protein S6 unfolds in the anionic detergent sodium dodecyl sulfate (SDS) above the critical micelle concentration, with unfolding rates varying according to two different modes. Our group has proposed that spherical micelles lead to saturation kinetics in unfolding (mode 1), while cylindrical micelles prevalent at higher SDS concentrations induce a power-law dependent increase in the unfolding rate (mode 2). Here I investigate in more detail how micellar properties affect protein unfolding. High NaCl concentrations, which induce cylindrical micelles, favor mode 2. This is consistent with our model, though other effects such as electrostatic screening cannot be discounted. Furthermore, unfolding does not occur in mode 2 in the cationic detergent LTAB, which is unable to form cylindrical micelles. A strong retardation of unfolding occurs at higher LTAB concentrations, possibly due to the formation of dead-end protein-detergent complexes. A similar, albeit much weaker, effect is seen in SDS in the absence of salt. Chymotrypsin inhibitor 2 exhibits the same modes of unfolding in SDS as S6, indicating that this type of protein unfolding is not specific for S6. The unfolding process in mode 1 has an activation barrier similar in magnitude to that in water, while the activation barrier in mode 2 is strongly concentration-dependent. The strong pH-dependence of unfolding in SDS and LTAB suggests that the rate of unfolding in anionic detergent is modulated by repulsion between detergent headgroups and anionic side chains, while cationic side chains modulate unfolding rates in cationic detergents. PMID:12324439

Transport interactions of different organic cations during their excretion by the intact rat kidney.

PubMed

Pietruck, F; Ullrich, K J

1995-06-01

Organic cations, in addition to being filtrated, are secreted or reabsorbed in the proximal renal tubule whereby they have to pass the contraluminal and the luminal cell membrane. Interactions with the transport of other organic cations can occur at either cell side, leading to inhibition or stimulation of net secretion or net reabsorption. A qualitative evaluation of such processes is possible by using the in vivo bolus injection of an organic cation as test substance. Measuring its urinary excretion profile in relation to that of inulin, under control conditions and after application of interfering organic cations, in combination with simultaneous registration of its tissue concentration, allows the demonstration of interaction and also the tentative identification of the cell side at which interference has taken place. As test substance the fluorescent organic cation 4-(4-dimethylaminostyryl)-N-methylpyridinium (4-Di-1-ASP+; denotes permanent positively-charged organic cations was used, having a protein binding of 47% under the given experimental conditions. As interfering organic cations amiloride, benzylamiloride, choline+, cimetidine, and 2-methyl-4-(heptafluorobutoxy)-N-methylpyridinium+ were injected. It was found that: (1) 4-Di-1-ASP+ is filtered and net reabsorbed under control conditions (fractional excretion 0.54 +/- 0.1). All net secreted interfering substances, except bidirectional transported choline+, injected simultaneously with 4-Di-1-ASP+, showed an interference with renal excretion of net reabsorbed 4-Di-1-ASP+, by (2) instantaneously increasing its reabsorption, resulting in a 28 to 33% decrease in urinary excretion, and (3) augmenting its tissue concentration by 19 to 58%. (4) A prolonged effect of the interfering substrates could be observed after a third injection of 4-Di-1-ASP+ (without inhibitor) showing an increased tissue concentration of 4-Di-1-ASP+ of 36 to 46%. The complex interfering pattern of the applied organic cations can be explained by a trans-stimulation of 4-Di-1-ASP+ net reabsorption at the luminal cell side, leading to an increased intracellular content of 4-Di-1-ASP+.

Effects of divalent cations, EDTA and chitosan on the uptake and photoinactivation of Escherichia coli mediated by cationic and anionic porphyrins.

PubMed

Gsponer, Natalia S; Spesia, Mariana B; Durantini, Edgardo N

2015-03-01

The effect of divalent cations, EDTA and chitosan (CS) on the uptake and photoinactivation of Escherichia coli produced by 5,10,15,20-tetrakis(4-N,N,N-trimethylammoniumphenyl)porphyrin (TMAP(4+)), 5,10-di(4-methylphenyl)-15,20-di(4-N,N,N-trimethylammoniumphenyl)porphyrin (MPAP(2+)) and 5,10,15,20-tetra(4-sulphonatophenyl)porphyrin (TPPS(4-)) were examined under different conditions. These porphyrins were rapidly bound to E. coli cells (<2.5min) and the uptake of photosensitizers was not dependent on incubation temperature, reaching values of 0.61, 0.18 and 0.08nmol/10(8) cells for TMAP(4+), MPAP(2+) and TPPS(4-), respectively. The addition of Ca(2+) or Mg(2+) to the cultures enhanced the uptake of MPAP(2+) and TPPS(4-) by cells. In contrast, the amount of TMAP(4+) bound to cells was decreased. The presence of EDTA produced an increase in the uptake of porphyrins by cells, while CS mainly enhanced the amount of TPPS(4-) bound to E. coli. The photoinactivation of E. coli cells mediated by TMAP(4+) was highly effective even at low concentration (1μM) and short irradiation period (5min). However, a reduction in the phototoxicity was found for TMAP(4+) in presence of Ca(2+) and Mg(2+). In contrast, the phototoxic activity mediated by MPAP(2+) and TPPS(4-) was increased. Addition of EDTA did not show effect on the photoinactivation induced by cationic porphyrins, while a small enhance was found for TPPS(4-). Moreover, inactivation of E. coli cells was achieved in the presence CS. This cationic polymer was antimicrobial by itself in the dark. Using a slightly toxic CS concentration, the phototoxic activity induced by TMAP(4+) was diminished. This effect was mainly observed at lower concentration of TMAP(4+) (0.5-1μM). In contrast, an increase in E. coli photoinactivation was obtained for MPAP(2+) and TPPS(4-) in presence of CS. Thus, this natural polymeric destabilizer agent mainly benefited the photoinactivation mediated by TPPS(4-). Copyright © 2014 Elsevier B.V. All rights reserved.

Effective charge measurements reveal selective and preferential accumulation of anions, but not cations, at the protein surface in dilute salt solutions

PubMed Central

Gokarn, Yatin R; Fesinmeyer, R Matthew; Saluja, Atul; Razinkov, Vladimir; Chase, Susan F; Laue, Thomas M; Brems, David N

2011-01-01

Specific-ion effects are ubiquitous in nature; however, their underlying mechanisms remain elusive. Although Hofmeister-ion effects on proteins are observed at higher (>0.3M) salt concentrations, in dilute (<0.1M) salt solutions nonspecific electrostatic screening is considered to be dominant. Here, using effective charge (Q*) measurements of hen-egg white lysozyme (HEWL) as a direct and differential measure of ion-association, we experimentally show that anions selectively and preferentially accumulate at the protein surface even at low (<100 mM) salt concentrations. At a given ion normality (50 mN), the HEWL Q* was dependent on anion, but not cation (Li+, Na+, K+, Rb+, Cs+, GdnH+, and Ca2+), identity. The Q* decreased in the order F− > Cl− > Br− > NO3− ∼ I− > SCN− > ClO4− ≫ SO42−, demonstrating progressively greater binding of the monovalent anions to HEWL and also show that the SO42− anion, despite being strongly hydrated, interacts directly with the HEWL surface. Under our experimental conditions, we observe a remarkable asymmetry between anions and cations in their interactions with the HEWL surface. PMID:21432935

Negative effects of divalent mineral cations on the bioaccessibility of carotenoids from plant food matrices and related physical properties of gastro-intestinal fluids.

PubMed

Corte-Real, Joana; Bertucci, Marie; Soukoulis, Christos; Desmarchelier, Charles; Borel, Patrick; Richling, Elke; Hoffmann, Lucien; Bohn, Torsten

2017-03-22

Carotenoid intake and tissue levels have been frequently associated with reduced risk of chronic diseases. However, their bioavailability is low and influenced by many dietary related parameters. Divalent mineral cations have been suggested to interfere with carotenoid digestion and to hamper micellarization, a prerequisite for their uptake, via complexation of bile salts and precipitation of fatty acids. In the present investigation, we have evaluated the effects of increasing concentrations of magnesium (0-300 mg L -1 ), calcium (0-1500 mg L -1 ), zinc (0-200 mg L -1 ), and sodium (0-1500 mg L -1 ; control monovalent cation), on carotenoid bioaccessibility from frequently consumed food items rich in carotenoids (tomato juice, carrot juice, apricot nectar, spinach and field salad), following simulated gastro-intestinal digestion. In addition, physicochemical parameters of digesta (macroviscosity, surface tension), micelle size, and zeta-potential were evaluated. All divalent minerals (DM) reduced bioaccessibility of total carotenoids (P < 0.01), as well as of individual carotenoids. Calcium and magnesium led to reductions of up to 100% at the 2 highest concentrations. Curiously, sodium increased (P < 0.01) carotenoid bioaccessiblity of most investigated matrices. The absolute value of the zeta-potential decreased with increasing concentrations of DM, suggesting a decreased stability of the colloidal digesta dispersion. Viscosity decreased, except for apricot nectar samples, while surface tension increased with DM concentration (P < 0.05). Thus, at physiological ranges, calcium and magnesium could negatively impact carotenoid bioavailability, while for zinc, negative effects were only seen at supplemental concentrations. The potential negative effects of DM on carotenoid bioavailability should be further studied in vivo.

Adsorption of Cationic Peptides to Solid Surfaces of Glass and Plastic

PubMed Central

Kristensen, Kasper; Henriksen, Jonas R.; Andresen, Thomas L.

2015-01-01

Cationic membrane-active peptides have been studied for years in the hope of developing them into novel types of therapeutics. In this article, we investigate an effect that might have significant experimental implications for investigators who wish to study these peptides, namely, that the peptides adsorb to solid surfaces of glass and plastic. Specifically, we use analytical HPLC to systematically quantify the adsorption of the three cationic membrane-active peptides mastoparan X, melittin, and magainin 2 to the walls of commonly used glass and plastic sample containers. Our results show that, at typical experimental peptide concentrations, 90% or more of the peptides might be lost from solution due to rapid adsorption to the walls of the sample containers. Thus, our results emphasize that investigators should always keep these adsorption effects in mind when designing and interpreting experiments on cationic membrane-active peptides. We conclude the article by discussing different strategies for reducing the experimental impact of these adsorption effects. PMID:25932639

Effect of competing self-structure on triplex formation with purine-rich oligodeoxynucleotides containing GA repeats.

PubMed Central

Noonberg, S B; François, J C; Garestier, T; Hélène, C

1995-01-01

Competition between triplex formation with double-stranded DNA and oligonucleotide self-association was investigated in 23mer GA and GT oligonucleotides containing d(GA)5 or d(GT)5 repeats. Whereas triplex formation with GT oligonucleotides was diminished when temperature increased from 4 to 37 degrees C, triplex formation with GA oligonucleotides was enhanced when temperature increased within the same range due to the presence of competing intermolecular GA oligonucleotide self-structure. This self-structure was determined to be a homoduplex stabilized by the internal GA repeats. UV spectroscopy of these homoduplexes demonstrated a single sharp transition with rapid kinetics (Tm = 38.5-43.5 degrees C over strand concentrations of 0.5-4 microM, respectively, with transition enthalpy, delta H = -89 +/- 7 kcal/mol) in 10 mM MgCl2, 100 mM NaCl, pH 7.0. Homoduplex formation was strongly stabilized by multivalent cations (spermine > Mg2+ = Ca2+) and destabilized by low concentrations of monovalent cations (K+ = Li+ = Na+) in the presence of divalent cations. However, unlike GA or GT oligonucleotide-containing triplexes, the homoduplex formed even in the absence of multivalent cations, stabilized by only moderate concentrations of monovalent cations (Li+ > Na+ > K+). Through the development of multiple equilibrium states and the resulting depletion of free oligonucleotide, it was found that the presence of competing self-structure could decrease triplex formation under a variety of experimental conditions. Images PMID:7596824

Insights into gelation kinetics and gel front migration in cation-induced polysaccharide hydrogels by viscoelastic and turbidity measurements: Effect of the nature of divalent cations.

PubMed

Huynh, Uyen T D; Chambin, Odile; du Poset, Aline Maire; Assifaoui, Ali

2018-06-15

Polysaccharide-based hydrogels were prepared by the diffusion of various divalent cations (X 2+ ) into the polygalacturonate (polyGal) solution through a dialysis membrane. The diffusion of various divalent cations (Mg 2+ , Ca 2+ , Zn 2+ and Ba 2+ ) was investigated. The polyGal gel growth was studied as a function of the initial cation concentration by both viscoelastic and turbidity measurements. We have demonstrated for the first time that the determination of the spatiotemporal variation of turbidity during the gelation process allowed to study the gel front migration. For Ca-polyGal, Zn-polyGal and Ba-polyGal, the gel front migration was characterized by the presence of a peak at the sol/gel interface. This peak was not observed in the case of Mg-polyGal where the gel was not formed. The apparent diffusion coefficient of the gel front (D app ) which was calculated from the evolution of this peak increased when the initial cation concentration was increased. Moreover, we have suggested a gelation mechanism based on the presence of a threshold molar ratio R* (=[X 2+ ]/[Galacturonic unit]) in which some point-like crosslinks are precursors of the formation of dimers and multimers inducing the contraction of the gel and thus the formation of the gel front. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effect of co-existing copper and calcium on the removal of As(V) by reused aluminum oxides.

PubMed

Yang, J K; Park, Y J; Kim, K H; Lee, H Y; Min, K C; Lee, S M

2013-01-01

Among the various heavy metals, arsenic is frequently found in abandoned mine drainage and the environmental fate of arsenic in real aqueous solutions can be highly dependent on the presence of co-existing ions. In this study, removal of arsenate through adsorption on the reused aluminum oxide or through precipitation was investigated in a single and in a binary system as a function of pH and concentration. Different removal behaviors of arsenate were observed in the presence of different cations as well as a variation of the molar ratios of arsenate to cations. Co-operative effects on arsenate removal by precipitation in solution occurred with an increase of copper concentration, while a decrease of arsenate removal resulted in increasing calcium concentration. It was observed that the arsenate removal in the presence of calcium would be highly dependent on the molar ratios of both elements.

Acceleration of chemical weathering related to intensive agriculture: evidence from groundwater dating

NASA Astrophysics Data System (ADS)

Aquilina, Luc; Marçais, Jean; de Dreuzy, Jean-Raynald; Labasque, Thierry; Abbott, Ben; Vergnaud, Virginie; Walter, Christian; Viville, Daniel; Chabaux, François; Pinay, Gilles

2017-04-01

Agricultural pollution is a matter of political and scientific concern throughout the world. Intensive agriculture can cause nutrient contamination of groundwater and surface water. Nutrient pollution causes eutrophication in freshwater and estuarine ecosystems. A secondary effect of agricultural intensification is river acidification. Oxidation of chemical fertilizers such as ammonium (NH4+) to nitrate (NO3-) produces H+ ions that cause leaching of cations from soil and deeper material to maintain charge balance. Monitoring of various rivers in Brittany (western France) revealed that agriculture intensification has led to increased cation export starting in the 1980s. From the cation ratios, we deduced that cation increase comes approximately equally from dissolution of carbonate added to soil (liming practices) and silicate dissolution. Cation export represented about 30% of the soil cation exchange potential. If compensated by liming, it may constitute a non-negligible source to atmospheric CO2 (Aquilina et al., 2012). We further investigated the potential for silicate dissolution through the use of groundwater dating in various sites of Brittany. Coupling chemical analyses to groundwater ages in a large range of aquifers and a large range of depths (down to 110m) allowed us to reconstruct a chronicle for the last 50 yrs of the cation concentrations of groundwater. It clearly shows a contemporaneous increase in sodium and nitrate and a decrease in calcium, with the most dramatic changes occurring during the 70s and 80s. Using groundwater dating, we were also able to determine a silica production geochronometer. A tight and linear relationship between silica concentration and groundwater age (Figure) was observed and allowed a production rate in groundwater to be determined. Except for short residence-times (Kerrien), the silica production rate for different granitic catchments was consistent, ranging from 0.3 to 0.4 mg.L-1.yr-1. To assess the role of anthropogenic activity in silica production rate, we compared production rates from Brittany with catchments in the Vosges Mountains, a relatively pristine area. Dissolution rates were much higher in the Brittany catchments, indicating the effect of human activities on chemical weathering and cation export at the catchment scale. Aquilina L. et al., 2012 - Long-term effects of high nitrogen loads on cation and carbon riverine export in agricultural catchments. Env. Sci & Technology 46-17, 9447-9455..

Mechanisms for monovalent cation-dependent depletion of intracellular Mg2+:Na(+)-independent Mg2+ pathways in guinea-pig smooth muscle.

PubMed

Nakayama, Shinsuke; Nomura, Hideki; Smith, Lorraine M; Clark, Joseph F; Uetani, Tadayuki; Matsubara, Tatsuaki

2003-09-15

It has been suggested that magnesium deficiency is correlated with many diseases. 31P NMR experiments were carried out in order to investigate the effects of Na+ substitution on Mg2+ depletion in smooth muscle under divalent cation-free conditions. In the taenia of guinea-pig caeci, the intracellular free Mg2+ concentration ([Mg2+]i) was estimated from the chemical shifts of (1) the beta-ATP peak alone and (2) beta- and gamma-ATP peaks. Both estimations indicated that [Mg2+]i decreased only very slowly in Mg(2+)-free, Ca(2+)-free solutions in which Na+ was substituted with large cations such as NMDG (N-methyl-D-glucamine) and choline. Furthermore, the measurements of tension development supported the suggestion of preservation of intracellular Mg2+ with NMDG substitution. Substituting extracellular Na+ with the small cation, Li+, also shifted the beta-ATP peak towards a lower frequency, but the frequency shift was significantly less than that seen upon Na+ substitution with K+. The estimated [Mg2+]i depletion was, however, comparable with that seen after Na+ substitution with K+ using the titration curves of metal-free and Mg(2+)-bound ATP obtained in Li(+)-based model solutions. It was concluded that Mg2+ rapidly decreases only when small cations were the major electrolyte of the extracellular medium. Na+ substitutions with NMDG, choline or Li+ had little effect on intracellular ATP concentration after 100 min treatment.

Electrolyte effects in a model of proton discharge on charged electrodes

NASA Astrophysics Data System (ADS)

Wiebe, Johannes; Kravchenko, Kateryna; Spohr, Eckhard

2015-01-01

We report results on the influence of NaCl electrolyte dissolved in water on proton discharge reactions from aqueous solution to charged platinum electrodes. We have extended a recently developed combined proton transfer/proton discharge model on the basis of empirical valence bond theory to include NaCl solutions with several different concentrations of cations and anions, both stoichiometric (1:1) compositions and non-stoichiometric ones with an excess of cations. The latter solutions partially screen the electrostatic potential from the surface charge of the negatively charged electrode. 500-1000 trajectories of a discharging proton were integrated by molecular dynamics simulations until discharge occurred, or for at most 1.5 ns. The results show a strong dependence on ionic strength, but only a weak dependence on the screening behavior, when comparing stoichiometric and non-stoichiometric solutions. Overall, the Na+ cations exert a more dominant effect on the discharge reaction, which we argue is likely due to the very rigid arrangements of the cations on the negatively polarized electrode surface. Thus, our model predicts, for the given and very high negative surface charge densities, the fastest discharge reaction for pure water, but obviously cannot take into account the fact that such high charge densities are even more out of reach experimentally than for higher electrolyte concentrations.

Biotic ligand modeling approach: Synthesis of the effect of major cations on the toxicity of metals to soil and aquatic organisms.

PubMed

Ardestani, Masoud M; van Straalen, Nico M; van Gestel, Cornelis A M

2015-10-01

The biotic ligand model (BLM) approach is used to assess metal toxicity, taking into account the competition of other cations with the free metal ions for binding to the biotic ligand sites of aquatic and soil organisms. The bioavailable fraction of metals, represented by the free metal ion, is a better measure than the total concentration for assessing their potential risk to the environment. Because BLMs are relating toxicity to the fraction of biotic ligands occupied by the metal, they can be useful for investigating factors affecting metal bioaccumulation and toxicity. In the present review, the effects of major cations on the toxicity of metals to soil and aquatic organisms were comprehensively studied by performing a meta-analysis of BLM literature data. Interactions at the binding sites were shown to be species- and metal-specific. The main factors affecting the relationships between toxicity and conditional binding constants for metal binding at the biotic ligand appeared to be Ca(2+) , Mg(2+) , and protons. Other important characteristics of the exposure medium, such as levels of dissolved organic carbon and concentrations of other cations, should also be considered to obtain a proper assessment of metal toxicity to soil and aquatic organisms. © 2015 SETAC.

Low Concentrations of Cationic PAMAM Dendrimers Affect Lymphocyte Respiration in In vitro Studies.

PubMed

Labieniec-Watala, Magdalena; Szwed, Marzena; Hertel, Joanna; Wisnik, Ewelina

2017-01-01

In this study, the effect of low concentrations of poly(amido)amine dendrimers (G2-G4) on human lymphocytes was studied. Some works revealed that PAMAMs can adversely affect the morphology of blood components and mitochondria functions. In this context, the present report aimed to investigate the in vitro cationic dendrimers' effect on mitochondrial respiration and cell morphology in lymphocytes isolated from human blood. To monitor the mitochondrial changes, the high-resolution respirometer was used, whereas the cell morphology was analyzed using a flow cytometer and fluorescence microscopy. The concentration-dependent dendrimers' influence on lymphocytes morphology was shown. Changes in mitochondrial respiration revealed the concentration- and generation-dependent differences between dendrimer activity. There were no alterations in the routine respiration and in the state of the inner mitochondrial membrane (L/E), but decreased ADP- and FCCP-stimulated respirations were detected after treatment with G3 and G4 dendrimers. The markers of mitochondrial membrane integrity (RCR) and OXPHOS efficiency (P/E) significantly decreased regardless of the dendrimer generation used. Based on these in vitro evaluations, we state that cationic PAMAM dendrimers can impair both the morphology and the bioenergetics of human lymphocytes, even when used at low concentrations and in a short time (up to 1 h). However, these results do not imply that similar findings could be possible for in vivo observations. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

In search of novel highly active mitochondria-targeted antioxidants: thymoquinone and its cationic derivatives.

PubMed

Severina, Inna I; Severin, Fedor F; Korshunova, Galina A; Sumbatyan, Natalya V; Ilyasova, Tatyana M; Simonyan, Ruben A; Rogov, Anton G; Trendeleva, Tatyana A; Zvyagilskaya, Renata A; Dugina, Vera B; Domnina, Lidia V; Fetisova, Elena K; Lyamzaev, Konstantin G; Vyssokikh, Mikhail Yu; Chernyak, Boris V; Skulachev, Maxim V; Skulachev, Vladimir P; Sadovnichii, Viktor A

2013-06-27

Since the times of the Bible, an extract of black cumin seeds was used as a medicine to treat many human pathologies. Thymoquinone (2-demethylplastoquinone derivative) was identified as an active antioxidant component of this extract. Recently, it was shown that conjugates of plastoquinone and penetrating cations are potent mitochondria-targeted antioxidants effective in treating a large number of age-related pathologies. This review summarizes new data on the antioxidant and some other properties of membrane-penetrating cationic compounds where 2-demethylplastoquinone substitutes for plastoquinone. It was found that such a substitution significantly increases a window between anti- and prooxidant concentrations of the conjugates. Like the original plastoquinone derivatives, the novel compounds are easily reduced by the respiratory chain, penetrate through model and natural membranes, specifically accumulate in mitochondria in an electrophoretic fashion, and strongly inhibit H2O2-induced apoptosis at pico- and nanomolar concentrations in cell cultures. At present, cationic demethylplastoquinone derivatives appear to be the most promising mitochondria-targeted drugs of the quinone series. Copyright © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Changes in apparent molar water volume and DKP solubility yield insights on the Hofmeister effect.

PubMed

Payumo, Alexander Y; Huijon, R Michael; Mansfield, Deauna D; Belk, Laurel M; Bui, Annie K; Knight, Anne E; Eggers, Daryl K

2011-12-15

This study examines the properties of a 4 × 2 matrix of aqueous cations and anions at concentrations up to 8.0 M. The apparent molar water volume, as calculated by subtracting the mass and volume of the ions from the corresponding solution density, was found to exceed the molar volume of ice in many concentrated electrolyte solutions, underscoring the nonideal behavior of these systems. The solvent properties of water were also analyzed by measuring the solubility of diketopiperazine (DKP) in 2.000 M salt solutions prepared from the same ion combinations. Solution rankings for DKP solubility were found to parallel the Hofmeister series for both cations and anions, whereas molar water volume concurred with the cation series only. The results are discussed within the framework of a desolvation energy model that attributes solute-specific changes in equilibria to solute-dependent changes in the free energy of bulk water.

Changes in Apparent Molar Water Volume and DKP Solubility Yield Insights on the Hofmeister Effect

PubMed Central

Payumo, Alexander Y.; Huijon, R. Michael; Mansfield, Deauna D.; Belk, Laurel M.; Bui, Annie K.; Knight, Anne E.; Eggers, Daryl K.

2011-01-01

This study examines the properties of a 4 × 2 matrix of aqueous cations and anions at concentrations up to 8.0 M. The apparent molar water volume, as calculated by subtracting the mass and volume of the ions from the corresponding solution density, was found to exceed the molar volume of ice in many concentrated electrolyte solutions, underscoring the non-ideal behavior of these systems. The solvent properties of water were also analyzed by measuring the solubility of diketopiperazine (DKP) in 2.000 M salt solutions prepared from the same ion combinations. Solution rankings for DKP solubility were found to parallel the Hofmeister series for both cations and anions, whereas molar water volume concurred with the cation series only. The results are discussed within the framework of a desolvation energy model that attributes solute-specific changes in equilibria to solute-dependent changes in the free energy of bulk water. PMID:22029390

Development of a novel method to determine the concentration of heavy metal cations: application of the specific interaction between heavy metal cation and mismatch DNA base pair.

PubMed

Kozasa, Tetsuo; Miyakawa, Yukako; Fukushi, Miyako; Ono, Akira; Torigoe, Hidetaka

2009-01-01

We have already found that Hg(II) cation specifically binds to T:T mismatch base pair in heteroduplex DNA, which increases the melting temperature of heteroduplex DNA involving T:T mismatch base pair by about 4 degrees C. We have also found that Ag(I) cation specifically binds to C:C mismatch base pair in heteroduplex DNA, which increases the melting temperature of heteroduplex DNA involving C:C mismatch base pair by about 4 degrees C. Using the specific interaction, we developed a novel sensor to determine the concentration of each of Hg(II) and Ag(I) cation. The sensor is composed of a dye-labelled T-rich or C-rich DNA oligonucleotide, F2T6W2D: 5'-Fam-T(2)CT(2)CT(2)C(4)T(2)GT(2)GT(2)-Dabcyl-3' or F2C6W2D: 5'-Fam-C(2)TC(2)TC(2)T(4)C(2)AC(2)AC(2)-Dabcyl-3', where 6-carboxyfluorescein (Fam) is a fluorophore and Dabcyl is a quencher. The addition of Hg(II) cation decreased the intensity of Fam emission of F2T6W2D at 520 nm in a concentration-dependent manner. Also, the addition of Ag(I) cation decreased the intensity of Fam emission of F2C6W2D at 520 nm in a concentration-dependent manner. We conclude that, using the novel sensor developed in this study, the concentration of each of Hg(II) and Ag(I) cation can be determined from the intensity of Fam emission at 520 nm.

New cationic vesicles prepared with double chain surfactants from arginine: Role of the hydrophobic group on the antimicrobial activity and cytotoxicity.

PubMed

Pinazo, A; Petrizelli, V; Bustelo, M; Pons, R; Vinardell, M P; Mitjans, M; Manresa, A; Perez, L

2016-05-01

Cationic double chain surfactants have attracted much interest because they can give rise to cationic vesicles that can be used in biomedical applications. Using a simple and economical synthetic approach, we have synthesized four double-chain surfactants with different alkyl chain lengths (LANHCx). The critical aggregation concentration of the double chain surfactants is at least one order of magnitude lower than the CMC of their corresponding single-chain LAM and the solutions prepared with the LANHCx contain stable cationic vesicles. Encouragingly, these new arginine derivatives show very low haemolytic activity and weaker cytotoxic effects than conventional dialkyl dimethyl ammonium surfactants. In addition, the surfactant with the shortest alkyl chain exhibits good antimicrobial activity against Gram-positive bacteria. The results show that a rational design applied to cationic double chain surfactants might serve as a promising strategy for the development of safe cationic vesicular systems. Copyright © 2016 Elsevier B.V. All rights reserved.

Organic cation rhodamines for screening organic cation transporters in early stages of drug development.

PubMed

Ugwu, Malachy C; Oli, Angus; Esimone, Charles O; Agu, Remigius U

The aim of this study was to investigate the suitability of rhodamine-123, rhodamine-6G and rhodamine B as non-radioactive probes for characterizing organic cation transporters in respiratory cells. Fluorescent characteristics of the compounds were validated under standard in vitro drug transport conditions (buffers, pH, and light). Uptake/transport kinetics and intracellular accumulation of the compounds were investigated. Uptake/transport mechanisms were investigated by comparing the effect of pH, temperature, concentration, polarity, OCTs/OCTNs inhibitors/substrates, and metabolic inhibitors on the cationic dyes uptake in Calu-3 cells. Fluorescence stability and intensity of the compounds were altered by buffer composition, light, and pH. Uptake of the dyes was concentration-, temperature- and pH-dependent. OCTs/OCTNs inhibitors significantly reduced intracellular accumulation of the compounds. Whereas rhodamine-B uptake was sodium-dependent, pH had no effect on rhodamine-123 and rhodamine-6G uptake. Transport of the dyes across the cells was polarized: (AP→BL>BL→AP transport) and saturable: {V max =14.08±2.074, K m =1821±380.4 (rhodamine-B); V max =6.555±0.4106, K m =1353±130.4 (rhodamine-123) and V max =0.3056±0.01402, K m =702.9±60.97 (rhodamine-6G)}. The dyes were co-localized with MitoTracker®, the mitochondrial marker. Cationic rhodamines, especially rhodamine-B and rhodamine- 6G can be used as organic cation transporter substrates in respiratory cells. During such studies, buffer selection, pH and light exposure should be taken into consideration. Copyright © 2016 Elsevier Inc. All rights reserved.

Effect of salts on the Co-fermentation of glucose and xylose by a genetically engineered strain of Saccharomyces cerevisiae

PubMed Central

2013-01-01

Background A challenge currently facing the cellulosic biofuel industry is the efficient fermentation of both C5 and C6 sugars in the presence of inhibitors. To overcome this challenge, microorganisms that are capable of mixed-sugar fermentation need to be further developed for increased inhibitor tolerance. However, this requires an understanding of the physiological impact of inhibitors on the microorganism. This paper investigates the effect of salts on Saccharomyces cerevisiae 424A(LNH-ST), a yeast strain capable of effectively co-fermenting glucose and xylose. Results In this study, we show that salts can be significant inhibitors of S. cerevisiae. All 6 pairs of anions (chloride and sulfate) and cations (sodium, potassium, and ammonium) tested resulted in reduced cell growth rate, glucose consumption rate, and ethanol production rate. In addition, the data showed that the xylose consumption is more strongly affected by salts than glucose consumption at all concentrations. At a NaCl concentration of 0.5M, the xylose consumption rate was reduced by 64.5% compared to the control. A metabolomics study found a shift in metabolism to increased glycerol production during xylose fermentation when salt was present, which was confirmed by an increase in extracellular glycerol titers by 4 fold. There were significant differences between the different cations. The salts with potassium cations were the least inhibitory. Surprisingly, although salts of sulfate produced twice the concentration of cations as compared to salts of chloride, the degree of inhibition was the same with one exception. Potassium salts of sulfate were less inhibitory than potassium paired with chloride, suggesting that chloride is more inhibitory than sulfate. Conclusions When developing microorganisms and processes for cellulosic ethanol production, it is important to consider salt concentrations as it has a significant negative impact on yeast performance, especially with regards to xylose fermentation. PMID:23718686

Self-Assembling of Tetradecylammonium Chain on Swelling High Charge Micas (Na-Mica-3 and Na-Mica-2): Effect of Alkylammonium Concentration and Mica Layer Charge.

PubMed

Pazos, M Carolina; Cota, Agustín; Osuna, Francisco J; Pavón, Esperanza; Alba, María D

2015-04-21

A family of tetradecylammonium micas is synthesized using synthetic swelling micas with high layer charge (Na(n)Si(8-n)Al(n)Mg6F4O20·XH2O, where n = 2 and 3) exchanged with tetradecylammonium cations. The molecular arrangement of the surfactant is elucidated on the basis of XRD patterns and DTA. The ordering conformation of the surfactant molecules into the interlayer space of micas is investigated by IR/FT, (13)C, (27)Al, and (29)Si MAS NMR. The structural arrangement of the tetradecylammonium cation in the interlayer space of high-charge micas is more sensitive to the effect of the mica layer charge at high concentration. The surfactant arrangement is found to follow the bilayer-paraffin model for all values of layer charge and surfactant concentration. However, at initial concentration below the mica CEC, a lateral monolayer is also observed. The amount of ordered conformation all-trans is directly proportional to the layer charge and surfactant concentration.

Uptake of photosensitizers by bacteria is influenced by the presence of cations

NASA Astrophysics Data System (ADS)

Kishen, A.; George, S.

2007-05-01

This investigation studies the influence of cations on photosensitizer uptake by Enterococcus faecalis (gram positive) and Actinobacillus actinomycetemcomitans (gram negative). Methods- The uptake of Methylene blue (MB) and Indocyanine Green (ICG), by bacteria were studied under the influence of divalent cations (CaCl II & MgCl II) and EDTA. Further, E. faecalis cells subjected to trypsinisation and calcium channel blocker (verapamil) were also analysed for MB and ICG uptake inorder to understand the mechanism of photosensitizer uptake. Results- Uptake of ICG was enhanced in the presence of divalent cations in E. faecalis and A. actinomycetemcomitans. Treating cells with EDTA had no significant effect on the photosensitizer uptake, although the highest concentration tested showed an enhancement of uptake. In contrast to ICG, MB showed a decreased uptake by bacterial cells on subjecting them to divalent cations and EDTA. Calcium channel blocker had no significant inhibitory effect on photosensitizers uptake. However, trypsin treatment resulted in significant reduction of ICG uptake. The result suggested that ICG uptake by bacteria is mediated through specific transporter protein while MB is associated with the outer surface structures of bacterial cells.

Effects of Monovalent Cations on the Sodium-Alanine Interaction in Rabbit Ileum

PubMed Central

Frizzell, Raymond A.; Schultz, Stanley G.

1970-01-01

H, K, Rb, and Li inhibit Na-dependent alanine influx across the brush border of rabbit ileum. Kinetic analysis indicates that H and K behave as competitive inhibitors of influx so that increasing the concentration of H or K in the mucosal solution is kinetically indistinguishable from decreasing the Na concentration. In addition the coupling between alanine and Na influxes is markedly reduced at pH 2.5. With the exception of H and Li, none of these monovalent cations significantly affects carrier-mediated alanine influx in the absence of Na indicating that their inhibitory effects are largely restricted to the Na-dependent fraction of influx. Increasing H concentration from 0.03 to 3 mM does not affect influx in the absence of Na but markedly inhibits influx in the presence of Na. Li significantly enhances alanine influx in the absence of Na. Ag, UO2, and La also inhibit the Na-dependent fraction of alanine influx. These findings suggest that anionic groups having a pKa of approximately 4 are involved in the interaction between Na and the alanine-carrier complex; present evidence implicates carboxylate groups however, phosphoryl residues cannot be ruled out. The previously proposed kinetic model for the Na-alanine interaction has been extended to accommodate these effects of H and other monovalent cations. The mechanistic and physiological implications of these findings are discussed. PMID:5507092

The rhizotoxicity of metal cations is related to their strength of binding to hard ligands.

PubMed

Kopittke, Peter M; Menzies, Neal W; Wang, Peng; McKenna, Brigid A; Wehr, J Bernhard; Lombi, Enzo; Kinraide, Thomas B; Blamey, F Pax C

2014-02-01

Mechanisms whereby metal cations are toxic to plant roots remain largely unknown. Aluminum, for example, has been recognized as rhizotoxic for approximately 100 yr, but there is no consensus on its mode of action. The authors contend that the primary mechanism of rhizotoxicity of many metal cations is nonspecific and that the magnitude of toxic effects is positively related to the strength with which they bind to hard ligands, especially carboxylate ligands of the cell-wall pectic matrix. Specifically, the authors propose that metal cations have a common toxic mechanism through inhibiting the controlled relaxation of the cell wall as required for elongation. Metal cations such as Al(3+) and Hg(2+), which bind strongly to hard ligands, are toxic at relatively low concentrations because they bind strongly to the walls of cells in the rhizodermis and outer cortex of the root elongation zone with little movement into the inner tissues. In contrast, metal cations such as Ca(2+), Na(+), Mn(2+), and Zn(2+) , which bind weakly to hard ligands, bind only weakly to the cell wall and move farther into the root cylinder. Only at high concentrations is their weak binding sufficient to inhibit the relaxation of the cell wall. Finally, different mechanisms would explain why certain metal cations (for example, Tl(+), Ag(+), Cs(+), and Cu(2+)) are sometimes more toxic than expected through binding to hard ligands. The data presented in the present study demonstrate the importance of strength of binding to hard ligands in influencing a range of important physiological processes within roots through nonspecific mechanisms. © 2013 SETAC.

Column study of Cr(VI) removal by cationic hydrogel for in-situ remediation of contaminated groundwater and soil

NASA Astrophysics Data System (ADS)

Tang, Samuel C. N.; Yin, Ke; Lo, Irene M. C.

2011-07-01

Column experiments were conducted for examining the effectiveness of the cationic hydrogel on Cr(VI) removal from groundwater and soil. For in-situ groundwater remediation, the effects of background anions, humic acid (HA) and pH were studied. Cr(VI) has a higher preference for being adsorbed onto the cationic hydrogel than sulphate, bicarbonate ions and HA. However, the adsorbed HA reduced the Cr(VI) removal capacity of the cationic hydrogel, especially after regeneration of the adsorbents, probably due to the blockage of adsorption sites. The Cr(VI) removal was slightly influenced by the groundwater pH that could be attributed to Cr(VI) speciation. The 6-cycle regeneration and reusability study shows that the effectiveness of the cationic hydrogel remained almost unchanged. On average, 93% of the adsorbed Cr(VI) was recovered in each cycle and concentrated Cr(VI) solution was obtained after regeneration. For in-situ soil remediation, the flushing water pH had an insignificant effect on the release of Cr(VI) from the soils. Multiple-pulse flushing increased the removal of Cr(VI) from the soils. In contrast, more flushing water and longer operation may be required to achieve the same removal level by continuous flushing.

Effect of Hydrotropic Compounds on the Self-Organization and Solubilization Properties of Cationic Surfactants

NASA Astrophysics Data System (ADS)

Gaynanova, G. A.; Valeeva, F. G.; Kushnazarova, R. A.; Bekmukhametova, A. M.; Zakharov, S. V.; Mirgorodskaya, A. B.; Zakharova, L. Ya.

2018-07-01

The effect hydrotropic additives (salts of aromatic acids and choline chloride) have on the micelle-forming properties (the critical concentrations of micelle formation and the Krafft temperature) of cationic surfactants, and on the solubilization capability of mono- and dicationic surfactants toward such hydrophobic compounds as a Sudan I spectral probe and curcumin natural dye, is considered. The factors that govern solubilization capacity, e.g., the structure of the head group of surfactants, the nature of the solubilizate and hydrotropic additives, and the pH of the medium are determined.

Analysis and optimization of flocculation activity and turbidity reduction in kaolin suspension using pectin as a biopolymer flocculant.

PubMed

Ho, Y C; Norli, I; Alkarkhi, Abbas F M; Morad, N

2009-01-01

The performance of pectin in turbidity reduction and the optimum condition were determined using Response Surface Methodology (RSM). The effect of pH, cation's concentration, and pectin's dosage on flocculating activity and turbidity reduction was investigated at three levels and optimized by using Box-Behnken Design (BBD). Coagulation and flocculation process were assessed with a standard jar test procedure with rapid and slow mixing of a kaolin suspension (aluminium silicate), at 150 rpm and 30 rpm, respectively, in which a cation e.g. Al(3+), acts as coagulant, and pectin acts as the flocculant. In this research, all factors exhibited significant effect on flocculating activity and turbidity reduction. The experimental data and model predictions well agreed. From the 3D response surface graph, maximum flocculating activity and turbidity reduction are in the region of pH greater than 3, cation concentration greater than 0.5 mM, and pectin dosage greater than 20 mg/L, using synthetic turbid wastewater within the range. The flocculating activity for pectin and turbidity reduction in wastewater is at 99%.

Effective concentration as a tool for quantitatively addressing preorganization in multicomponent assemblies: application to the selective complexation of lanthanide cations.

PubMed

Canard, Gabriel; Koeller, Sylvain; Bernardinelli, Gérald; Piguet, Claude

2008-01-23

The beneficial entropic effect, which may be expected from the connection of three tridentate binding units to a strain-free covalent tripod for complexing nine-coordinate cations (Mz+ = Ca2+, La3+, Eu3+, Lu3+), is quantitatively analyzed by using a simple thermodynamic additive model. The switch from pure intermolecular binding processes, characterizing the formation of the triple-helical complexes [M(L2)3]z+, to a combination of inter- and intramolecular complexation events in [M(L8)]z+ shows that the ideal structural fit observed in [M(L8)]z+ indeed masks large energetic constraints. This limitation is evidenced by the faint effective concentrations, ceff, which control the intramolecular ring-closing reactions operating in [M(L8)]z+. This predominence of the thermodynamic approach over the usual structural analysis agrees with the hierarchical relationships linking energetics and structures. Its simple estimation by using a single microscopic parameter, ceff, opens novel perspectives for the molecular tuning of specific receptors for the recognition of large cations, a crucial point for the programming of heterometallic f-f complexes under thermodynamic control.

A Novel Ion - selective Polymeric Membrane Sensor for Determining Thallium(I) With High Selectivity

NASA Astrophysics Data System (ADS)

Kassim, Anuar; Rezayi, Majid; Ahmadzadeh, Saeid; Rounaghi, Gholamhossein; Mohajeri, Masoomeh; Azah Yusof, Noor; Tee, Tan Wee; Yook Heng, Lee; Halim Abdullah, Abd

2011-02-01

Thallium is a toxic metal that introduced into the environment mainly as a waste from the production of zinc, cadmium, and lead and by combustion of coal. Thallium causes gastrointestinal irritation and nerve damage when people are exposed to it for relatively short period of time. For long term, thallium has the potential to cause the following effects: change in blood chemistry, damage to liver, kidney, intestinal and testicular tissue, and hair loss. In this work a membrane was prepared by use of 4'-nitrobenzo -18-crown-6 (4'NB18C6) as an ion carrier, polyvinylchloride (PVC) as a matrix, and diocthylphetalate (DOP) as a plasticizer for making an ion selective electrode for measurement of Tl+ cation in solutions. The amount of 4'-nitrobenzo-18C6 and polyvinylchloride were optimized in the preparation of the membrane. The response of the electrode was Nernstian within the concentration range 1.0 × 10-8 to 1.0 × 10-1M. This sensor displays a drift in Nernstian response for this cation with increasing the amount of ionophore and decreasing the amount of polyvinylchloride.The results of potentiometric measurements showed that, this electrode also responses to Cu2+ Ni2+ and Pb2+ cations, but the electrode has a wider dynamic range and a lower detection limit to Tl+ cation. The effects of various parameters such as pH, different cations interferences, effect of the amount of ionophore and polyvinylchloride and time on response of the coated ion selective electrode were investigated. Finally the constructed electrode was used in complexometric and precipitation titrations of Tl+ cation with EDTA and KBr, respectively. The response of the fabricated electrode at concentration range from 1.0 × 10-8 to 1.0 × 10-1M is linear with a Nernstian slope of 57.27 mV.

Transport of cerium oxide nanoparticles in saturated silica media: influences of operational parameters and aqueous chemical conditions

NASA Astrophysics Data System (ADS)

Zhang, Zhaohan; Gao, Peng; Qiu, Ye; Liu, Guohong; Feng, Yujie; Wiesner, Mark

2016-10-01

This paper aimed to investigate the influences of operational parameters and aqueous chemical conditions on transport behaviors of cerium oxides nanoparticles (CeO2-NPs) in saturated silica media. Results indicated that increasing rates of attachment efficiency (α) were related with cationic types, and critical deposition concentration (CDC) for divalent cation (Ca2+ and Mg2+) were more than 31-fold of that for monovalent cation (Na+ and K+). Increase or reduction of electrolyte pH could both promote the mobility of CeO2-NPs in glass beads, while influence was more evident at alkaline conditions. α increased linearly with NPs concentrations, while decreased linearly with flow velocity in the column, and effects were related with electrolyte contents. Presence of surfactants could sharply decreased α, and SDS was more effective to facilitate CeO2-NPs transport than Triton X-100. With DOMs concentrations increasing, α firstly kept constant, then sharply declined, and finally reduced very slowly. The influence of DOMs on NPs deposition was in order of SA > HA > TA >  BSA. Overall, this study revealed that aqueous chemical conditions was crucial to NPs transport in porous media, and would provide significant information for our understanding on the fate and transport of nanoparticles in natural environment.

Large volume sample stacking of positively chargeable analytes in capillary zone electrophoresis without polarity switching: use of low reversed electroosmotic flow induced by a cationic surfactant at acidic pH.

PubMed

Quirino, J P; Terabe, S

2000-01-01

A simple and effective way to improve detection sensitivity of positively chargeable analytes in capillary zone electrophoresis more than 100-fold is described. Cationic species were made to migrate toward the cathode even under reversed electroosmotic flow caused by a cationic surfactant by using a low pH run buffer. For the first time, with such a configuration, large volume sample stacking of cationic analytes is achieved without a polarity-switching step and loss of efficiency. Samples are prepared in water or aqueous acetonitrile. Aromatic amines and a variety of drugs were concentrated using background solutions containing phosphoric acid and cetyltrimethylammonium bromide. Qualitative and quantitative aspects are also investigated.

The bundling of actin with polyethylene glycol 8000 in the presence and absence of gelsolin.

PubMed Central

Goverman, J; Schick, L A; Newman, J

1996-01-01

Actin filament and bundle formation occur in the cytosol under conditions of very high total macromolecular concentration. In this study we have utilized the inert molecule polyethylene glycol 8000 (PEG) as a means of simulating crowded conditions in vitro. Column-purified Ca-actin was polymerized in the absence and presence of gelsolin (to regulate mean filament lengths between 50 and 5000 mers) and PEG (2-8%) using various concentrations of KCl and/or 2 mM divalent cations. Bundling was characterized by the scattered light intensity and mean diffusion coefficients obtained from dynamic light scattering, as well as by fluorescence and phase-contrast microscopy. The minimum concentration of KCl required for bundling decreases both with increasing concentration of PEG at a fixed mean filament length, and with decreasing filament length at a fixed concentration of PEG. In the absence of divalent cation, bundling is reversible on dilution, as determined by intensity levels, diffusion coefficients, and microscopy. However, with either 2 mM Mg2+ or Ca2+ added, bundling is irreversible under conditions of higher PEG concentrations or longer filaments, indicating that osmotic pressure effects cannot fully explain actin bundling with PEG. Weaker divalent cation-binding sites on actin as well as disulfide bonds appear to be involved in the irreversible bundling. Images FIGURE 7 PMID:8874022

Effects of Fructose and Temperature on the Micellization of a Cationic Gemini Surfactant, Pentanediyl-1,5-bis(dimethylcetylammonium) Bromide in Aqueous Solutions

NASA Astrophysics Data System (ADS)

Alam, Md. Sayem; Mohammed Siddiq, A.; Mandal, Asit Baran

2017-12-01

By the conductivity measurements the effects of fructose and temperature (293-308 K) on the micellization of a cationic gemini surfactant (GS), pentanediyl-1,5-bis(dimethylcetylammonium) bromide in aqueous solutions have been investigated. The critical micelle concentration (CMC) of GS was measured at the different temperatures and fructose concentrations. An increasing trend of the CMC values is with addition of fructose. With increasing temperature, the CMC values are in a similar increasing trend. The CMC of GS by dye solubilization method at room temperature have been determined. The standard Gibbs energy, enthalpy and entropy of GS micellization have been evaluated. From these thermodynamic parameters, it was found that in presence of fructose, the stability of the GS aqueous solutions decreases.

Calcium Uptake by Excised Maize Roots and Interactions With Alkali Cations 1

PubMed Central

Maas, E. V.

1969-01-01

Ca2+ uptake was studied in short-term experiments using 5-day-old excised maize roots. This tissue readily absorbs Ca2+, and inhibition by dinitrophenol and low temperature shows that the process is metabolically mediated. The uptake of Ca2+, like that of other cations, is influenced by the counter ion, the pH and concentration of the ambient solution, and the presence of other cations. The rate of uptake from various salts decreases in the following order: NO3− > Cl− = Br− > SO42−. K+ and H+ greatly interfere with Ca2+ absorption, while Li+ and Na+ have only slight effects. PMID:16657169

How the spontaneous insertion of amphiphilic imidazolium-based cations changes biological membranes: a molecular simulation study.

PubMed

Lim, Geraldine S; Jaenicke, Stephan; Klähn, Marco

2015-11-21

The insertion of 1-octyl-3-methylimidazolium cations (OMIM(+)) from a diluted aqueous ionic liquid (IL) solution into a model of a bacterial cell membrane is investigated. Subsequently, the mutual interactions of cations inside the membrane and their combined effect on membrane properties are derived. The ionic liquid solution and the membrane model are simulated using molecular dynamics in combination with empirical force fields. A high propensity of OMIM(+) for membrane insertion is observed, with a cation concentration at equilibrium inside the membrane 47 times larger than in the solvent. Once inserted, cations exhibit a weak effective attraction inside the membrane at a distance of 1.3 nm. At this free energy minimum, negatively charged phosphates of the phospholipids are sandwiched between two OMIM(+) to form energetically favorable OMIM(+)-phosphate-OMIM(+) types of coordination. The cation-cation association free energy is 5.9 kJ mol(-1), whereas the activation barrier for dissociation is 10.1 kJ mol(-1). Subsequently, OMIM(+) are inserted into the leaflet of the membrane bilayer that represents the extracellular side. The cations are evenly distributed with mutual cation distances according to the found optimum distance of 1.3 nm. Because of the short length of the cation alkyl chains compared to lipid fatty acids, voids are generated in the hydrophobic core of the membrane. These voids disorder the fatty acids, because they enable fatty acids to curl into these empty spaces and also cause a thinning of the membrane by 0.6 nm. Additionally, the membrane density increases at its center. The presence of OMIM(+) in the membrane facilitates the permeation of small molecules such as ammonia through the membrane, which is chosen as a model case for small polar solutes. The permeability coefficient of the membrane with respect to ammonia increases substantially by a factor of seven. This increase is caused by a reduction of the involved free energy barriers, which is effected by the cations through the thinning of the membrane and favorable interactions of the delocalized OMIM(+) charge with ammonia inside the membrane. Overall, the results indicate the antimicrobial effect of amphiphilic imidazolium-based cations that are found in various common ILs. This effect is caused by an alteration of the permeability of the bacterial membrane and other property changes.

Kinetic Monte Carlo Simulation of Oxygen and Cation Diffusion in Yttria-Stabilized Zirconia

NASA Technical Reports Server (NTRS)

Good, Brian

2011-01-01

Yttria-stabilized zirconia (YSZ) is of interest to the aerospace community, notably for its application as a thermal barrier coating for turbine engine components. In such an application, diffusion of both oxygen ions and cations is of concern. Oxygen diffusion can lead to deterioration of a coated part, and often necessitates an environmental barrier coating. Cation diffusion in YSZ is much slower than oxygen diffusion. However, such diffusion is a mechanism by which creep takes place, potentially affecting the mechanical integrity and phase stability of the coating. In other applications, the high oxygen diffusivity of YSZ is useful, and makes the material of interest for use as a solid-state electrolyte in fuel cells. The kinetic Monte Carlo (kMC) method offers a number of advantages compared with the more widely known molecular dynamics simulation method. In particular, kMC is much more efficient for the study of processes, such as diffusion, that involve infrequent events. We describe the results of kinetic Monte Carlo computer simulations of oxygen and cation diffusion in YSZ. Using diffusive energy barriers from ab initio calculations and from the literature, we present results on the temperature dependence of oxygen and cation diffusivity, and on the dependence of the diffusivities on yttria concentration and oxygen sublattice vacancy concentration. We also present results of the effect on diffusivity of oxygen vacancies in the vicinity of the barrier cations that determine the oxygen diffusion energy barriers.

Common Ion Effects In Zeoponic Substrates: Dissolution And Cation Exchange Variations Due to Additions of Calcite, Dolomite and Wollastonite

NASA Technical Reports Server (NTRS)

Beiersdorfer, R. E.; Ming, D. W.; Galindo, C., Jr.

2003-01-01

c1inoptilolite-rich tuff-hydroxyapatite mixture (zeoponic substrate) has the potential to serve as a synthetic soil-additive for plant growth. Essential plant macro-nutrients such as calcium, phosphorous, magnesium, ammonium and potassium are released into solution via dissolution of the hydroxyapatite and cation exchange on zeolite charged sites. Plant growth experiments resulting in low yield for wheat have been attributed to a Ca deficiency caused by a high degree of cation exchange by the zeolite. Batch-equilibration experiments were performed in order to determine if the Ca deficiency can be remedied by the addition of a second Ca-bearing, soluble, mineral such as calcite, dolomite or wollastonite. Variations in the amount of calcite, dolomite or wollastonite resulted in systematic changes in the concentrations of Ca and P. The addition of calcite, dolomite or wollastonite to the zeoponic substrate resulted in an exponential decrease in the phosphorous concentration in solution. The exponential rate of decay was greatest for calcite (5.60 wt. % -I), intermediate for wollastonite (2.85 wt.% -I) and least for dolomite (1.58 wt.% -I). Additions of the three minerals resulted in linear increases in the calcium concentration in solution. The rate of increase was greatest for calcite (3.64), intermediate for wollastonite (2.41) and least for dolomite (0.61). The observed changes in P and Ca concentration are consistent with the solubilities of calcite, dolomite and wollastonite and with changes expected from a common ion effect with Ca. Keywords: zeolite, zeoponics, common-ion effect, clinoptilolite, hydroxyapatite

Pyruvate kinase activity as an indicator of the level of K(+), Mg(2+), and Ca(2+) in leaves and fruits of the cucumber: the role of potassium fertilization.

PubMed

Ruiz, J M; Moreno, D A; Romero, L

1999-03-01

Little is known about the effects of K(+) fertilization on pyruvate kinase (PK) activities in cucumber (Cucumis sativus L. cv. Brunex) grown in the greenhouse on calcareous soils. Here, the effect of K rates on the concentrations of K(+), Mg(2+), and Ca(2+) and on the PK activity as a possible indicator of the levels of these cations in the leaves and fruits of cucumber plants has been studied. The treatments consisted of applications of three rates of K in the form of K(2)SO(4) (K1 = 0.075 mg mL(-)(1), K2 = 0.15 mg mL(-)(1), and K3 = 0.30 mg mL(-)(1)). In general, K(+) application in calcareous soils proved beneficial. The highest application of K(+) (K3) to the culture medium reduced, in both the leaves and fruits, the foliar concentrations of Mg(2+) and Ca(2+). These results are reflected by the lowest basal PK activities and the highest differences between the basal PK activity and activities stimulated by these two cations. The opposite effect resulted with K2, with maximal basal PK activity and minimal differences between this activity and activities stimulated by the cations, indicating a better balance in this treatment between the different cations under the experimental conditions. Finally, this trend might partly account for the highest commercial yield in plants treated with K2.

The effects of ion identity and ionic strength on the dissolution rate of a gibbsitic bauxite

NASA Astrophysics Data System (ADS)

Mogollón, José Luis; Pérez-Diaz, Alberto; Lo Monaco, Salvador

2000-03-01

The influence of cation and anion identity and concentration, on the far from equilibrium dissolution rate of gibbsite, was studied at 298°K. Input solutions, with initial pH = 3.5 and variable salt type and concentration, were flowed at different rates, through columns packed with a unconsolidated gibbsitic bauxite from Los Pijigüaos-Venezuela ore deposit. It was observed cations Na +, K +, Mg 2+ and Ca2+ have no influence on the far from equilibrium dissolution rate. Anions have two different effects: concentration increases of monovalent anions (Cl -, NO 3- and ClO 4-) causes a decrease in the rate, as a function of [anion] (-0.11 ± 0.01); and increases of sulfate concentration causes an increase in the rate as a function of [SO 4=] (0.4 ± 0.1). According to our calculations, these two effects have a remarkable influence upon the lifetime of gibbsite under weathering conditions. Based on Transition State Theory, it is proposed the experimental observations are due to an electrostatic effect on the activated complex (AC ♯) of the gibbsite dissolution reaction. For this AC ♯ the product of the charge of the involved chemical entities is negative. When SO 4= participates in the AC ♯ the product of the charges switches to positive and therefore, the electrostatic interaction increase the dissolution rate. The dissolution rates are independent of the solution saturation degree below ΔGr = - 0.74 kcal/mol. It is inferred that the critical ΔGr is a constant of the solid, not affected by the solution characteristics, e.g., pH, ionic strength, cation and anion identities.

Limitations of experiments performed in artificially made OECD standard soils for predicting cadmium, lead and zinc toxicity towards organisms living in natural soils.

PubMed

Sydow, Mateusz; Chrzanowski, Łukasz; Cedergreen, Nina; Owsianiak, Mikołaj

2017-08-01

Development of comparative toxicity potentials of cationic metals in soils for applications in hazard ranking and toxic impact assessment is currently jeopardized by the availability of experimental effect data. To compensate for this deficiency, data retrieved from experiments carried out in standardized artificial soils, like OECD soils, could potentially be tapped as a source of effect data. It is, however, unknown whether such data are applicable to natural soils where the variability in pore water concentrations of dissolved base cations is large, and where mass transfer limitations of metal uptake can occur. Here, free ion activity models (FIAM) and empirical regression models (ERM, with pH as a predictor) were derived from total metal EC50 values (concentration with effects in 50% of individuals) using speciation for experiments performed in artificial OECD soils measuring ecotoxicological endpoints for terrestrial earthworms, potworms, and springtails. The models were validated by predicting total metal based EC50 values using backward speciation employing an independent set of natural soils with missing information about ionic composition of pore water, as retrieved from a literature review. ERMs performed better than FIAMs. Pearson's r for log 10 -transformed total metal based EC50s values (ERM) ranged from 0.25 to 0.74, suggesting a general correlation between predicted and measured values. Yet, root-mean-square-error (RMSE) ranged from 0.16 to 0.87 and was either smaller or comparable with the variability of measured EC50 values, suggesting modest performance. This modest performance was mainly due to the omission of pore water concentrations of base cations during model development and their validation, as verified by comparisons with predictions of published terrestrial biotic ligand models. Thus, the usefulness of data from artificial OECD soils for global-scale assessment of terrestrial ecotoxic impacts of Cd, Pb and Zn in soils is limited due to relatively small variability of pore water concentrations of dissolved base cations in OECD soils, preventing their inclusion in development of predictive models. Our findings stress the importance of considering differences in ionic composition of soil pore water when characterizing terrestrial ecotoxicity of cationic metals in natural soils. Copyright © 2017 Elsevier Ltd. All rights reserved.

Surface modification of ZSM-5 zeolite: effect of cation on selective conversion of biomass-derived oil

NASA Astrophysics Data System (ADS)

Widayatno, W. B.

2017-04-01

This paper reports the surface modification of high silica ZSM-5 zeolite, particularly emphasizing the effect of cation type on selective conversion of biomass-derived oil. XRD spectra of the NaOH-treated HZSM-5 showed notable crystallinity decrease at specific crystal plane orientation. The N2-physisorption tests confirmed mesoporosity evolution as NaOH concentration was increased. NH3-desorption tests revealed a significant change on surface acidity which involved realumination and cation replacement processes. The utilization of untreated HZSM-5 as well as hierarchical NaZSM-5 for catalytic conversion of bio-oil showed the effect of cation type and mesoporosity on chemicals distribution. The untreated HZSM-5 showed high selectivity to aromatics, which degraded gradually due to deactivation and poisoning of the acid sites. Meanwhile, hierarchical NaZSM-5 showed high selectivity to phenolic compound, which became more stable for 0.4M NaOH-treated zeolite (Na04). The current findings provide an additional insight on the potentials of NaZSM-5 for bio-oil valorization.

Effect of a cationic surfactant on the volatilization of PAHs from soil.

PubMed

Lu, Li; Zhu, Lizhong

2012-06-01

Cationic surfactants are common in soils because of their use in daily cosmetic and cleaning products, and their use as a soil amendment for the mitigation and remediation of organic contaminated soils has been proposed. Such surfactant may affect the transfer and fate of organic contaminants in the environment. This study investigated the effect of a cationic surfactant, dodecylpyridinium bromide (DDPB), on the volatilization of polycyclic aromatic hydrocarbons (PAHs) from a paddy soil. The volatilization of PAHs from moist soil amended with different concentrations of DDPB was tested in an open system. The specific effects of DDPB on the liquid-vapor and solid-vapor equilibriums of PAHs were separately investigated in closed systems by headspace analysis. DDPB affects both liquid-vapor and solid-vapor processes of PAHs in soil. At DDPB concentrations below the critical micelle concentration (CMC), movement of PAHs from the bulk solution to the gas-liquid interface appeared to be facilitated by interaction between PAHs and the surfactant monomers adsorbed at the gas-liquid interface, promoting the volatilization of PAHs from solution. However, when DDPB was greater than the CMC, volatilization was inhibited due to the solubilization of PAHs by micelles. On the other hand, the formation of sorbed surfactant significantly inhibited the solid-vapor volatilization of PAHs. The overall effect of the two simultaneous effects of DDPB on liquid-vapor and solid-vapor processes was a decreased volatilization loss of PAHs from soil. Inhibition of PAH volatilization was more significant for the soil with a lower moisture content.

Zn2+, not Ca2+, is the most effective cation for activation of dolichol kinase of mammalian brain.

PubMed

Sakakihara, Y; Volpe, J J

1985-12-15

The cation specificity of dolichol kinase of mammalian brain and the potential involvement of a Ca2+-calmodulin system in regulation of this enzyme have been studied. Among 10 divalent cations examined, Zn2+ was found to be most effective for the activation of dolichol kinase of rat and calf brain and cultured C-6 glial cells. The activations with Ca2+, Co2+, and Mg2+ were 53%, 32%, and 18% of the full activation with Zn2+, respectively. No combinations of the cations could activate the enzyme as much as Zn2+ alone. A role for a Ca2+-calmodulin system in the regulation of brain dolichol kinase was not supported by our data. First, the concentration of free Ca2+ required for the maximum activation of dolichol kinase was two to three orders of magnitude greater than the concentration required by typical calmodulin-dependent enzymes. Second, neither the depletion of calmodulin from the microsomal fraction nor the addition of exogenous calmodulin caused an alteration in the activation of dolichol kinase by Ca2+ (or Zn2+). Third, antagonists of calmodulin failed to suppress the activation of the enzyme by Ca2+ (or Zn2+). The data raise the possibility that Zn2+ is involved in the regulation of dolichol kinase in brain.

Silver Dissolution and Release from Ceramic Water Filters.

PubMed

Mittelman, Anjuliee M; Lantagne, Daniele S; Rayner, Justine; Pennell, Kurt D

2015-07-21

Application of silver nanoparticles (nAg) or silver nitrate (AgNO3) has been shown to improve the microbiological efficacy of ceramic water filters used for household water treatment. Silver release, however, can lead to undesirable health effects and reduced filter effectiveness over time. The objectives of this study were to evaluate the contribution of nanoparticle detachment, dissolution, and cation exchange to silver elution, and to estimate silver retention under different influent water chemistries. Dissolved silver (Ag(+)) and nAg release from filter disks painted with 0.03 mg/g casein-coated nAg or AgNO3 were measured as a function of pH (5-9), ionic strength (1-50 mM), and cation species (Na(+), Ca(2+), Mg(2+)). Silver elution was controlled by dissolution as Ag(+) and subsequent cation exchange reactions regardless of the applied silver form. Effluent silver levels fell below the drinking water standard (0.1 mg/L) after flushing with 30-42 pore volumes of pH 7, 10 mM NaNO3 at pH 7. When the influent water was at pH 5, contained divalent cations or 50 mM NaNO3, silver concentrations were 5-10 times above the standard. Our findings support regular filter replacement and indicate that saline, hard, or acidic waters should be avoided to minimize effluent silver concentrations and preserve silver treatment integrity.

Mechanosensitive cation channels in human leukaemia cells: calcium permeation and blocking effect

PubMed Central

Staruschenko, Alexandr V; Vedernikova, Elena A

2002-01-01

Cell-attached and inside-out patch-clamp methods were employed to identify and characterize mechanosensitive (MS) ionic channels in the plasma membrane of human myeloid leukaemia K562 cells. A reversible activation of gadolinium-blockable mechanogated currents in response to negative pressure application was found in 58 % of stable patches (n = 317). I-V relationships measured with a sodium-containing pipette solution showed slight inward rectification. Data analysis revealed the presence of two different populations of channels that were distinguishable by their conductance properties (17.2 ± 0.3 pS and 24.5 ± 0.5 pS), but were indistinguishable with regard to their selective and pharmacological properties. Ion-substitution experiments indicated that MS channels in leukaemia cells were permeable to cations but not to anions and do not discriminate between Na+ and K+. The channels were fully impermeable to large organic cations such as Tris+ and N-methyl-d-glucamine ions (NMDG+). Ca2+ permeation and blockade of MS channels were examined using pipettes containing different concentrations of Ca2+. In the presence of 2 mm CaCl2, when other cations were impermeant, both outward and inward single-channel currents were observed; the I-V relationship showed a unitary conductance of 7.7 ± 1.0 pS. The relative permeability value, PCa/PK, was equal to 0.75, as estimated at physiological Ca2+ concentrations. Partial or full inhibition of inward Ca2+ currents through MS channels was observed at higher concentrations of external Ca2+ (10 or 20 mm). No MS channels were activated when using a pipette containing 90 mm CaCl2. Monovalent mechanogated currents were not significantly affected by extracellular Ca2+ at concentrations within the physiological range (0-2 mm), and at some higher Ca2+ concentrations. PMID:12015421

Concentration-discharge relationships during an extreme event: Contrasting behavior of solutes and changes to chemical quality of dissolved organic material in the Boulder Creek Watershed during the September 2013 flood: SOLUTE FLUX IN A FLOOD EVENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rue, Garrett P.; Rock, Nathan D.; Gabor, Rachel S.

During the week of September 10-17, 2013, close to 20 inches of rain fell across Boulder County, Colorado, USA. This rainfall represented a 1000-year event that caused massive hillslope erosion, landslides, and mobilization of sediments. The resultant stream flows corresponded to a 100-year flood. For the Boulder Creek Critical Zone Observatory (BC-CZO), this event provided an opportunity to study the effect of extreme rainfall on solute concentration-discharge relationships and biogeochemical catchment processes. We observed base cation and dissolved organic carbon (DOC) concentrations at two sites on Boulder Creek following the recession of peak flow. We also isolated three distinct fractionsmore » of dissolved organic matter (DOM) for chemical characterization. At the upper site, which represented the forested mountain catchment, the concentrations of the base cations Ca, Mg and Na were greatest at the peak flood and decreased only slightly, in contrast with DOC and K concentrations, which decreased substantially. At the lower site within urban corridor, all solutes decreased abruptly after the first week of flow recession, with base cation concentrations stabilizing while DOC and K continued to decrease. Additionally, we found significant spatiotemporal trends in the chemical quality of organic matter exported during the flood recession, as measured by fluorescence, 13C-NMR spectroscopy, and FTICR-MS. Similar to the effect of extreme rainfall events in driving landslides and mobilizing sediments, our findings suggest that such events mobilize solutes by the flushing of the deeper layers of the critical zone, and that this flushing regulates terrestrial-aquatic biogeochemical linkages during the flow recession.« less

Cation vacancies and electrical compensation in Sb-doped thin-film SnO2 and ZnO

NASA Astrophysics Data System (ADS)

Korhonen, E.; Prozheeva, V.; Tuomisto, F.; Bierwagen, O.; Speck, J. S.; White, M. E.; Galazka, Z.; Liu, H.; Izyumskaya, N.; Avrutin, V.; Özgür, Ü.; Morkoç, H.

2015-02-01

We present positron annihilation results on Sb-doped SnO2 and ZnO thin films. The vacancy types and the effect of vacancies on the electrical properties of these intrinsically n-type transparent semiconducting oxides are studied. We find that in both materials low and moderate Sb-doping leads to formation of vacancy clusters of variable sizes. However, at high doping levels cation vacancy defects dominate the positron annihilation signal. These defects, when at sufficient concentrations, can efficiently compensate the n-type doping produced by Sb. This is the case in ZnO, but in SnO2 the concentrations appear too low to cause significant compensation.

The effect of various electrolyte cations on electrochemical performance of polypyrrole/RGO based supercapacitors.

PubMed

Zhu, Jianbo; Xu, Youlong; Wang, Jie; Lin, Jun; Sun, Xiaofei; Mao, Shengchun

2015-11-21

In this work, polypyrrole/graphene doped by p-toluenesulfonic is prepared as an active material for supercapacitors, and its capacitance performance is investigated in various aqueous electrolytes including HCl, LiCl, NaCl, and KCl with a concentration of 3 M, respectively. A rising trend of capacitance is observed according to the cationic mobility (Li(+) < Na(+) < K(+) < H(+)), which is due to its effect on the ionic conductivity, efficient ion/charge diffusion/exchange and relaxation time. On the other hand, long-term cycling stability is in the following order: KCl < NaCl < LiCl < HCl, corresponding to the decreasing tendency of cation size (K(+) > Na(+) > Li(+) > H(+)). The reason can be attributed to the fact that the insertion/de-insertion of large size cation brings a significant doping level decrease and an over-oxidation increase during the charging-discharging cycles. Hence, we not only obtain good capacitance performance (280.3 F g(-1) at 5 mV s(-1)), superior rate capability (225.8 F g(-1) at 500 mV s(-1)) and high cycling stability (92.0% capacitance retention after 10,000 cycles at 1 A g(-1)) by employing 3 M HCl as an electrolyte, but also reveal that the electrolyte cations have a significant effect on the supercapacitors' electrochemical performance.

Comparison contemporary methods of regeneration sodium-cationic filters

NASA Astrophysics Data System (ADS)

Burakov, I. A.; Burakov, A. Y.; Nikitina, I. S.; Verkhovsky, A. E.; Ilyushin, A. S.; Aladushkin, S. V.

2017-11-01

Regeneration plays a crucial role in the field of efficient application sodium-cationic filters for softening the water. Traditionally used as regenerant saline NaCl. However, due to the modern development of the energy industry and its close relationship with other industrial and academic sectors the opportunity to use in the regeneration of other solutions. The report estimated data and application possibilities as regenerant solution sodium-cationic filters brine wells a high mineral content, as both primary application and after balneotherapeutic use reverse osmosis and concentrates especially recycled regenerant water repeated. Comparison of the effectiveness of these solutions with the traditional use of NaCl. Developed and tested system for the processing of highly mineralized brines wells after balneological use. Recommendations for use as regeneration solutions for the sodium-cationic unit considered solutions and defined rules of brine for regeneration costs.

The influence of various cations on the catalytic properties of clays. [polymerization of alanine adenylate

NASA Technical Reports Server (NTRS)

Paecht-Horowitz, M.

1978-01-01

The polymerization of alanine adenylate in the presence of the sodium form of various clays was studied, and hectorite was found to cause more polymerization than nontronite and montmorillonite (in that order) although the differences were not great. The effect on polymerization of presaturating montmorillonite with different cations was determined. Hectorite, with increased basicity of the interspatial planes, allows polymerization of lysine, which montmorillonite does not. The general trend is that, for the same amino acid, higher degrees of polymerization are obtained when the cation in the octahedral lattice of the clay is divalent rather than trivalent. With the exchangeable cations the order is reversed, for a reason that is explained. The main role of clays in the polymerization mechanism of amino acids is concentration and neutralization of charges.

Antimicrobial particles from cationic lipid and polyelectrolytes.

PubMed

Melo, Letícia D; Mamizuka, Elsa M; Carmona-Ribeiro, Ana M

2010-07-20

Hybrid nanoparticles from cationic lipid and polymers were prepared and characterized regarding physical properties and antimicrobial activity. Carboxymethylcellulose (CMC) and polydiallyldimethylammonium chloride (PDDA) were sequentially added to cationic bilayer fragments (BF) prepared from ultrasonic dispersion in water of the synthetic and cationic lipid dioctadecyldimethylammonium bromide (DODAB). Particles thus obtained were characterized by dynamic light-scattering for determination of z-average diameter (Dz) and zeta-potential (zeta). Antimicrobial activity of the DODAB BF/CMC/PDDA particles against Pseudomonas aeruginosa or Staphylococcus aureus was determined by plating and CFU counting over a range of particle compositions. DODAB BF/CMC/PDDA particles exhibited sizes and zeta-potentials strictly dependent on DODAB, CMC, and PDDA concentrations. At 0.1 mM DODAB, 0.1 mg/mL CMC, and 0.1 mg/mL PDDA, small cationic particles with Dz = 100 nm and zeta = 30 mV were obtained. At 0.5 mM DODAB, 0.5 mg/mL CMC and 0.5 mg/mL PDDA, large cationic particles with Dz = 470 nm and zeta = 50 mV were obtained. Both particulates were highly reproducible regarding physical properties and yielded 0% of P. aeruginosa viability (10(7) CFU/mL) at 1 or 2 microg/mL PDDA dissolved in solution or in form of particles, respectively. 99% of S. aureus cells died at 10 microg/mL PDDA alone or in small or large DODAB BF/CMC/PDDA particles. The antimicrobial effect was dependent on the amount of positive charge on particles and independent of particle size. A high microbicide potency for PDDA over a range of nanomolar concentrations was disclosed. P. aeruginosa was more sensitive to all cationic assemblies than S. aureus.

First-principles investigations into the thermodynamics of cation disorder and its impact on electronic structure and magnetic properties of spinel Co(Cr1-x Mn x )2O4.

PubMed

Das, Debashish; Ghosh, Subhradip

2017-02-08

Cation disorder over different crystallographic sites in spinel oxides is known to affect their properties. Recent experiments on Mn doped multiferroic [Formula: see text] indicate that a possible distribution of Mn atoms among tetrahedrally and octahedrally coordinated sites in the spinel lattice give rise to different variations in the structural parameters and saturation magnetisations in different concentration regimes of Mn atoms substituting the Cr. A composition dependent magnetic compensation behaviour points to the role conversions of the magnetic constituents. In this work, we have investigated the thermodynamics of cation disorder in [Formula: see text] system and its consequences on the structural, electronic and magnetic properties, using results from first-principles electronic structure calculations. We have computed the variations in the cation-disorder as a function of Mn concentration and the temperature and found that at the annealing temperature of the experiment many of the systems exhibit cation disorder. Our results support the interpretations of the experimental results regarding the qualitative variations in the sub-lattice occupancies and the associated magnetisation behaviour, with composition. We have analysed the variations in structural, magnetic and electronic properties of this system with variations in the compositions and the degree of cation disorder from the variations in their electronic structures and by using the ideas from crystal field theory. Our study provides a complete microscopic picture of the effects that are responsible for composition dependent behavioural differences of the properties of this system. This work lays down a general framework, based upon results from first-principles calculations, to understand and analyse the substitutional magnetic spinel oxides [Formula: see text] in presence of cation disorder.

Proton-coupled organic cation antiporter-mediated uptake of apomorphine enantiomers in human brain capillary endothelial cell line hCMEC/D3.

PubMed

Okura, Takashi; Higuchi, Kei; Kitamura, Atsushi; Deguchi, Yoshiharu

2014-01-01

R(-)-Apomorphine is a dopamine agonist used for rescue management of motor function impairment associated with levodopa therapy in Parkinson's disease patients. The aim of this study was to examine the role of proton-coupled organic cation antiporter in uptake of R(-)-apomorphine and its S-enantiomer in human brain, using human endothelial cell line hCMEC/D3 as a model. Uptake of R(-)- or S(+)-apomorphine into hCMEC/D3 cells was measured under various conditions to evaluate its time-, concentration-, energy- and ion-dependency. Inhibition by selected organic cations was also examined. Uptakes of both R(-)- and S(+)-apomorphine increased with time. The initial uptake velocities of R(-)- and S(+)-apomorphine were concentration-dependent, with similar Km and Vmax values. The cell-to-medium (C/M) ratio of R(-)-apomorphine was significantly reduced by pretreatment with sodium azide, but was not affected by replacement of extracellular sodium ion with N-methylglucamine or potassium. Intracellular alkalization markedly reduced the uptake, while intracellular acidification increased it, suggesting that the uptake is driven by an oppositely directed proton gradient. The C/M ratio was significantly decreased by amantadine, verapamil, pyrilamine and diphenhydramine (substrates or inhibitors of proton-coupled organic cation antiporter), while tetraethylammonium (substrate of organic cation transporters (OCTs)) and carnitine (substrate of carnitine/organic cation transporter 2; (OCTN2)) had no effect. R(-)-Apomorphine uptake was competitively inhibited by diphenhydramine. Our results indicate that R(-)-apomorphine transport in human blood-brain barrier (BBB) model cells is similar to S(+)-apomorphine uptake. The transport was dependent on an oppositely directed proton gradient, but was sodium- or membrane potential-independent. The transport characteristics were consistent with involvement of the previously reported proton-coupled organic cation antiporter.

Cations SkQ1 and MitoQ accumulated in mitochondria delay opening of ascorbate/FeSO4-induced nonspecific pore in the inner mitochondrial membrane.

PubMed

Khailova, L S; Dedukhova, V I; Mokhova, E N

2008-10-01

It is known that an addition of FeSO4 in the presence of ascorbic acid to cells or mitochondria can injure energy coupling and some other functions in mitochondria. The present study demonstrates that decrease in ascorbate concentration from 4 to 0.2 mM in the presence of the same low concentrations of FeSO4 accelerates the nonspecific pore opening, while cyclosporin A prevents and under some conditions reverses the pore opening. Hydrophobic cations SkQ1 and MitoQ (structural analogs of plastoquinone and coenzyme Q(10), respectively) delay pore opening, SkQ1 being more efficient. It is known that an increase in matrix ADP concentration delays pore opening, while an addition of carboxyatractylate to mitochondria accelerates the beginning of pore opening. Preliminary addition of SkQ1 into a mitochondrial suspension increased the effect of ADP and decreased the effect of carboxyatractylate. These results suggest that under the conditions used SkQ1 protects mitochondria from oxidative damage as an antioxidant when added at extremely low concentrations.

Ecotoxicological assessment of flocculant modified soil for lake restoration using an integrated biotic toxicity index.

PubMed

Wang, Zhibin; Zhang, Honggang; Pan, Gang

2016-06-15

Flocculant modified soils/clays are being increasingly studied as geo-engineering materials for lake restoration and harmful algal bloom control. However, the potential impacts of adding these materials in aquatic ecological systems remain unclear. This study investigated the potential effects of chitosan, cationic starch, chitosan modified soils (MS-C) and cationic starch modified soils (MS-S) on the aquatic organisms by using a bioassay battery. The toxicity potential of these four flocculants was quantitatively assessed using an integrated biotic toxicity index (BTI). The test system includes four aquatic species, namely Chlorella vulgaris, Daphnia magna, Cyprinus carpio and Limnodrilus hoffmeisteri, which represent four trophic levels in the freshwater ecosystem. Results showed that median effect concentrations (EC50) of the MS-C and MS-S were 31-124 times higher than chitosan and cationic starch, respectively. D. magna was the most sensitive species to the four flocculants. Histological examination of C. carpio showed that significant pathological changes were found in gills. Different from chitosan and cationic starch, MS-C and MS-S significantly alleviated the acute toxicities of chitosan and cationic starch. The toxicity order of the four flocculants based on BTI were cationic starch > chitosan > MS-S > MS-C. The results suggested that BTI can be used as a quantitative and comparable indicator to assess biotic toxicity for aquatic geo-engineering materials. Chitosan or cationic starch modified soil/clay materials can be used at their optimal dosage without causing substantial adverse effects to the bioassay battery in aquatic ecosystem. Copyright © 2015 Elsevier Ltd. All rights reserved.

Shifting the equilibrium mixture of gramicidin double helices toward a single conformation with multivalent cationic salts.

PubMed Central

Doyle, D A; Wallace, B A

1998-01-01

The conformation of the polypeptide antibiotic gramicidin is greatly influenced by its environment. In methanol, it exists as an equilibrium mixture of four interwound double-helical conformers that differ in their handedness, chain orientation, and alignment. Upon the addition of multivalent cationic salts, there is a shift in the equilibrium to a single conformer, which was monitored in this study by circular dichroism spectroscopy. With increasing concentrations of multivalent cations, both the magnitude of the entire spectrum and the ratio of the 229-nm to the 210-nm peak were increased. The spectral change is not related to the charge on the cation, but appears to be related to the cationic radius, with the maximum change in ellipticity occurring for cations with a radius of approximately 1 A. The effect requires the presence of an anion whose radius is greater than that of a fluoride ion, but is otherwise not a function of anion type. It is postulated that multivalent cations interact with a binding site in one of the conformers, known as species 1 (a left-handed, parallel, no stagger double helix), stabilizing a modified form of this type of structure. PMID:9675165

Cation trapping by cellular acidic compartments: Beyond the concept of lysosomotropic drugs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marceau, François, E-mail: francois.marceau@crchul.ulaval.ca; Bawolak, Marie-Thérèse; Lodge, Robert

“Lysosomotropic” cationic drugs are known to concentrate in acidic cell compartments due to low retro-diffusion of the protonated molecule (ion trapping); they draw water by an osmotic mechanism, leading to a vacuolar response. Several aspects of this phenomenon were recently reexamined. (1) The proton pump vacuolar (V)-ATPase is the driving force of cationic drug uptake and ensuing vacuolization. In quantitative transport experiments, V-ATPase inhibitors, such as bafilomycin A1, greatly reduced the uptake of cationic drugs and released them in preloaded cells. (2) Pigmented or fluorescent amines are effectively present in a concentrated form in the large vacuoles. (3) Consistent withmore » V-ATPase expression in trans-Golgi, lysosomes and endosomes, a fraction of the vacuoles is consistently labeled with trans-Golgi markers and protein secretion and endocytosis are often inhibited in vacuolar cells. (4) Macroautophagic signaling (accumulation of lipidated and membrane-bound LC3 II) and labeling of the large vacuoles by the autophagy effector LC3 were consistently observed in cells, precisely at incubation periods and amine concentrations that cause vacuolization. Vacuoles also exhibit late endosome/lysosome markers, because they may originate from such organelles or because macroautophagosomes fuse with lysosomes. Autophagosome persistence is likely due to the lack of resolution of autophagy, rather than to nutritional deprivation. (5) Increased lipophilicity decreases the threshold concentration for the vacuolar and autophagic cytopathology, because simple diffusion into cells is limiting. (6) A still unexplained mitotic arrest is consistently observed in cells loaded with amines. An extended recognition of relevant clinical situations is proposed for local or systemic drug administration.« less

[Substances transport in an underground river of typical karst watershed during storm events].

PubMed

Yang, Ping-Heng; Kuang, Ying-Lun; Yuan, Wen-Hao; Jia, Peng; He, Qiu-Fang; Lin, Yu-Shi

2009-11-01

Hydrologic process, turbidity, suspended particles matters (SPM), major cations and TOC concentrations during two storm events in late April 2008 were monitored at Jiangjia Spring which is the outlet of Qingmu Guan underground river system. Scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS) analyses of SPM were also performed in order to investigate the transport characteristics of substances, such as SPM, turbidity and major cations in the underground river of typical karst watershed. The results show that at a single and well-developed karst conduit of Jiangjia Spring, discharge, turbidity, and concentrations of SPM, major cations and TOC respond promptly to the rainfall. The carbonate-derived cations including Ca2+, Mg2+ and Sr2+ are subject to dilution effect during the rising limb of discharge. The elevation in turbidity and SPM concentration is a result of the gradual increase of allochthonous substances (soil) flux input from the surface. Al3+, Fe, Mn, Ba2+ and TOC are concomitant substances of SPM. And their concentrations are ascending with turbid rise. The flux of SPM in diameter > 0.45 microm in the underground river is about 9.7 tons during the events. The bad water quality suggests us that the spring water is unfit to drink without purification during the period of rising and recession time of discharge at Jiangjia Spring. Thus, soil erosion and nutrient losing not only strongly destroy the fragile karst ecological environment, but also lead to non-point source pollution, and seriously threaten the drinking water safety of locals.

Solubility and cation exchange in phosphate rock and saturated clinoptilolite mixtures

NASA Technical Reports Server (NTRS)

Allen, E. R.; Hossner, L. R.; Ming, D. W.; Henninger, D. L.

1993-01-01

Mixtures of zeolite and phosphate rock (PR) have the potential to provide slow-release fertilization of plants in synthetic soils by dissolution and ion-exchange reactions. This study was conducted to examine solubility and cation-exchange relationships in mixtures of PR and NH4- and K-saturated clinoptilolite (Cp). Batch-equilibration experiments were designed to investigate the effect of PR source, the proportion of exchangeable K and NH4, and the Cp to PR ratio on solution N, P, K, and Ca concentrations. The dissolution and cation-exchange reactions that occurred after mixing NH4- and K-saturated Cp with PR increased the solubility of the PR and simultaneously released NH4 and K into solution. The more reactive North Carolina (NC) PR rendered higher solution concentrations of NH4 and K when mixed with Cp than did Tennessee (TN) PR. Solution P concentrations for the Cp-NC PR mixture and the Cp-TN PR mixture were similar. Solution concentrations of N, P, K, and Ca and the ratios of these nutrients in solution varied predictably with the type of PR, the Cp/PR ratio, and the proportions of exchangeable K and NH4 on the Cp. Our research indicated that slow-release fertilization using Cp/PR media may provide adequate levels of N, P, and K to support plant growth. Solution Ca concentrations were lower than optimum for plant growth.

Biochemical indicators of nephrotoxicity in blood serum of rats treated with novel 4-thiazolidinone derivatives or their complexes with polyethylene glycol-containing nanoscale polymeric carrier

PubMed

Kоbyli nska, L I; Havrylyuk, D Ya; Mitina, N E; Zaichenko, A S; Lesyk, R B; Zіme nkovsky, B S; Stoika, R S

2016-01-01

The aim of this study was to compare the effect of new synthetic 4-thiazolidinone derivatives (potential anticancer compounds denoted as 3882, 3288 and 3833) and doxorubicin (positive control) in free form and in their complexes with synthetic polyethylene glycol-containing nanoscale polymeric carrier on the biochemical indicators of nephrotoxicity in blood serum of rats. The concentration of total protein, urea, creatinine, glucose, ions of sodium, potassium, calcium, iron and chloride was measured. It was found that after injection of the investigated compounds, the concentration of sodium cations and chloride anions in blood serum was increased compared with control (untreated animals). Doxorubicin’s injection was accompanied by a decrease in the concentration of iron cations. The concentration of total protein, urea and creatinine decreased under the influence of the studied compounds. Complexation of these аntineoplastic substances with a synthetic polymeric nanocarrier lowered the concentration of the investigated metabolites substantially compared to the effect of these compounds in free form. The normalization of concentration of total protein, urea and creatinine in blood serum of rats treated with complexes of the studied compounds with the polymeric carrier comparing with increased concentration of these indicators at the introduction of such compounds in free form was found.

Toxicological effects of cationic nanobubbles on the liver and kidneys: biomarkers for predicting the risk.

PubMed

Pan, Tai-Long; Wang, Pei-Wen; Al-Suwayeh, Saleh A; Huang, Yi-Ju; Fang, Jia-You

2012-11-01

Nanobubbles with acoustical activity are used as both diagnostic and therapeutic carriers for detecting and treating diseases. We aimed to prepare nanobubbles and assess toxic responses to them in the liver and kidneys. The cytotoxicity of nanobubbles was determined by examining the viability of liver (HepG2) and kidney (293T) cell lines after a 24-h treatment at various concentrations (0.01-2%). Toxic effects of different formulations were compared by determining functional markers such as γ-glutamyl transferase (γ-GT) and blood urea nitrogen (BUN) after intravenous administration of nanobubbles. Cationic nanobubbles caused concentration-dependent cytotoxicity against cultured cells with a more significant effect in the liver than in the kidneys. A significant reduction of viability was revealed at a concentration as low as 0.1%. Cational systems with soyaethyl morpholinium ethosulfate (SME) exhibited the greatest γ-GT level at 6-fold higher than the control. Immunohistochemistry detected liver fibrosis and inflammation with nanobubbles treatment, especially SME-containing ones at higher doses. According to plasma proteomic profiles, gelsolin and fetuin-B were significantly downregulated 3-fold in the high-dose SME-treated group. Transthyretin decreased by 6-fold in this group. The fibrinogen gamma chain expression was highly elevated. The results suggest that these protein biomarkers are sensitive for assessing the risk of nanobubble exposure. This study is the first to systematically evaluate the possible toxicity of nanobubbles in the liver and kidneys. Copyright © 2012 Elsevier Ltd. All rights reserved.

Detection of anions by normal Raman spectroscopy and surface-enhanced Raman spectroscopy of cationic-coated substrates.

PubMed

Mosier-Boss, P A; Lieberman, S H

2003-09-01

The use of normal Raman spectroscopy and surface-enhanced Raman spectroscopy (SERS) of cationic-coated silver and gold substrates to detect polyatomic anions in aqueous environments is examined. For normal Raman spectroscopy, using near-infrared excitation, linear concentration responses were observed. Detection limits varied from 84 ppm for perchlorate to 2600 ppm for phosphate. In general, detection limits in the ppb to ppm concentration range for the polyatomic anions were achieved using cationic-coated SERS substrates. Adsorption of the polyatomic anions on the cationic-coated SERS substrates was described by a Frumkin isotherm. The SERS technique could not be used to detect dichromate, as this anion reacted with the coatings to form thiol esters. A competitive complexation method was used to evaluate the interaction of chloride ion with the cationic coatings. Hydrogen bonding and pi-pi interactions play significant roles in the selectivity of the cationic coatings.

Ion exchanger from chemically modified banana leaves.

PubMed

El-Gendy, Ahmed A; Mohamed, Samar H; Abd-Elkader, Amal H

2013-07-25

Cation exchangers from chemically modified banana leaves have been prepared. Banana leaves were treated with different molarities of KMnO4 and cross linked with epichlorohydrin and their effect on metal ion adsorption was investigated. Phosphorylation of chemically modified banana leaves was also studied. The metal ion uptake by these modified banana leaves was clarified. Effect of different varieties, e.g. activation of produced cation exchanger, concentration of metal ions was also investigated. Characterization of the prepared ion exchangers by using infrared and thermal analysis was also taken in consideration. Copyright © 2013 Elsevier Ltd. All rights reserved.

Structure-Antibacterial Activity Relationships of Imidazolium-Type Ionic Liquid Monomers, Poly(ionic liquids) and Poly(ionic liquid) Membranes: Effect of Alkyl Chain Length and Cations.

PubMed

Zheng, Zhiqiang; Xu, Qiming; Guo, Jiangna; Qin, Jing; Mao, Hailei; Wang, Bin; Yan, Feng

2016-05-25

The structure-antibacterial activity relationship between the small molecular compounds and polymers are still elusive. Here, imidazolium-type ionic liquid (IL) monomers and their corresponding poly(ionic liquids) (PILs) and poly(ionic liquid) membranes were synthesized. The effect of chemical structure, including carbon chain length of substitution at the N3 position and charge density of cations (mono- or bis-imidazolium) on the antimicrobial activities against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was investigated by determination of minimum inhibitory concentration (MIC). The antibacterial activities of both ILs and PILs were improved with the increase of the alkyl chain length and higher charge density (bis-cations) of imidazolium cations. Moreover, PILs exhibited lower MIC values relative to the IL monomers. However, the antibacterial activities of PIL membranes showed no correlation to those of their analogous small molecule IL monomers and PILs, which increased with the charge density (bis-cations) while decreasing with the increase of alkyl chain length. The results indicated that antibacterial property studies on small molecules and homopolymers may not provide a solid basis for evaluating that in corresponding polymer membranes.

Cation exchange in a glacial till drumlin at a road salt storage facility

NASA Astrophysics Data System (ADS)

Ostendorf, David W.; Xing, Baoshan; Kallergis, Niki

2009-05-01

We use laboratory and field data to calibrate existing geochemical and transport models of cation exchange induced by contamination of an unconfined aquifer at a road salt storage facility built upon a glacial till drumlin in eastern Massachusetts. A Gaines and Thomas selectivity coefficient K models the equilibrium sodium and divalent cation distribution in the groundwater and solid matrix, while an existing method of characteristics model describes the advective transport of total dissolved cations and sorbed sodium. Laboratory isotherms of split spoon soil samples from the drumlin calibrate K with an average value of 0.0048 (L/g) 1/2 for a measured cation exchange capacity of 0.057 meq/g dry soil. Ten years of monitoring well data document groundwater flow and the advection of conservative chloride due to outdoor storage and handling of road salt at the site. The monitoring well cation data and retarded transport model offer an independent K calibration of 0.0040 to 0.0047 (L/g) 1/2: the consistency of the field and laboratory selectivity coefficient calibrations endorse this application of the Gaines and Thomas and method of characteristics models. The advancing deicing agent plume releases divalent cations from the till into the groundwater, so that monitoring well samples do not reflect the chemical composition of the road salt. In this regard, dissolved divalent cation milliequivalent concentrations are as high as 80% of the total dissolved cationic concentrations in the salt contaminated monitoring well samples, far greater than their 2.5% level in the road salt stored at the site. Cation exchange can thus obscure attempts to hindcast stored road salt sodium water table concentration from monitoring well sample stoichiometry, or to predict sodium impacts on groundwater or receiving stream quality downgradient of the well.

Cation exchange in a glacial till drumlin at a road salt storage facility.

PubMed

Ostendorf, David W; Xing, Baoshan; Kallergis, Niki

2009-05-12

We use laboratory and field data to calibrate existing geochemical and transport models of cation exchange induced by contamination of an unconfined aquifer at a road salt storage facility built upon a glacial till drumlin in eastern Massachusetts. A Gaines and Thomas selectivity coefficient K models the equilibrium sodium and divalent cation distribution in the groundwater and solid matrix, while an existing method of characteristics model describes the advective transport of total dissolved cations and sorbed sodium. Laboratory isotherms of split spoon soil samples from the drumlin calibrate K with an average value of 0.0048 (L/g)(1/2) for a measured cation exchange capacity of 0.057 meq/g dry soil. Ten years of monitoring well data document groundwater flow and the advection of conservative chloride due to outdoor storage and handling of road salt at the site. The monitoring well cation data and retarded transport model offer an independent K calibration of 0.0040 to 0.0047 (L/g)(1/2): the consistency of the field and laboratory selectivity coefficient calibrations endorse this application of the Gaines and Thomas and method of characteristics models. The advancing deicing agent plume releases divalent cations from the till into the groundwater, so that monitoring well samples do not reflect the chemical composition of the road salt. In this regard, dissolved divalent cation milliequivalent concentrations are as high as 80% of the total dissolved cationic concentrations in the salt contaminated monitoring well samples, far greater than their 2.5% level in the road salt stored at the site. Cation exchange can thus obscure attempts to hindcast stored road salt sodium water table concentration from monitoring well sample stoichiometry, or to predict sodium impacts on groundwater or receiving stream quality downgradient of the well.

Ordered DNA-Surfactant Hybrid Nanospheres Triggered by Magnetic Cationic Surfactants for Photon- and Magneto-Manipulated Drug Delivery and Release.

PubMed

Xu, Lu; Wang, Yitong; Wei, Guangcheng; Feng, Lei; Dong, Shuli; Hao, Jingcheng

2015-12-14

Here we construct for the first time ordered surfactant-DNA hybrid nanospheres of double-strand (ds) DNA and cationic surfactants with magnetic counterion, [FeCl3Br](-). The specificity of the magnetic cationic surfactants that can compact DNA at high concentrations makes it possible for building ordered nanospheres through aggregation, fusion, and coagulation. Cationic surfactants with conventional Br(-) cannot produce spheres under the same condition because they lose the DNA compaction ability. When a light-responsive magnetic cationic surfactant is used to produce nanospheres, a dual-controllable drug-delivery platform can be built simply by the applications of external magnetic force and alternative UV and visible light. These nanospheres obtain high drug absorption efficiency, slow release property, and good biocompatibility. There is potential for effective magnetic-field-based targeted drug delivery, followed by photocontrollable drug release. We deduce that our results might be of great interest for making new functional nucleic-acid-based nanomachines and be envisioned to find applications in nanotechnology and biochemistry.

Sorption of uranium in uranyl nitrate solutions on strong cationic resins and its elution with ammonium sulfate. II. Effects of EDTA on thorium decontamination; Estudos de sorpcao de uranio contido em solucoes de nitrato de uranilo por resina cationica forte e sua eluicao com sulfato de amonio. Parte II: efeito de EDTA na descontaminacao do torio (in Portuguese)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ribas, Antonio G.S.; Abrao, Alcidio

1970-05-15

This paper describes the studies of decontamination of thorium present as impurity in uranyl nitrate solutions, which was carried out through strong cationic resin where the thorium was partially retained. Then, the final decontamination was performed percolating the uranyl solution on a second cationic resin, after complexation of thorium (and other impurities) with EDTA. The thorium decontamination and the uranium retention were studied as a function of EDTA/U ratio, uranium concentration and acidity of the influent uranyl nitrate. The elution conditions were also studied as a function of eluent flow rate, concentration and acidity. Several tables and graphs showing themore » final results are included. (tr-auth)« less

pH profile of the adsorption of nucleotides onto montmorillonite. I - Selected homoionic clays

NASA Technical Reports Server (NTRS)

Lawless, J. G.; Church, F. M.; Mazzurco, J.; Banin, A.; Huff, R.; Kao, J.; Cook, A.; Lowe, T.; Orenberg, J. B.; Edelson, E.

1985-01-01

The effect of pH and adsorbed ions on the adsorption of purine and pyrimidine nucleotides on montmorillonite clay was studied experimentally. The specific nucleotides examined were: 5 prime-AMP; 3-prime AMP; and 5 prime-CMP. The pH of the clay samples was adjusted to various levels in the 2-12 pH range using microliter volumes of concentrated acid (1N HCl) and base (1NHNaOH). It was found that preferential adsorption among nulceotides was dependent on the pH level and on the characteristics of the substituted metal cation and anion exchange mechanisms. Below pH 4, adsorption was attributed to cation and anion exchange mechanisms. Above pH 4, however, adsorption was attributed to the complexation mechanisms occurring between the metal cations in the clay exchange site and in the biomolecule. The possible role of homoionic clays in the concentration mechanisms of biomonomers in the prebiotic environment is discussed.

Structural and Dynamical Properties of Alkaline Earth Metal Halides in Supercritical Water: Effect of Ion Size and Concentration.

PubMed

Keshri, Sonanki; Tembe, B L

2017-11-22

Constant temperature-constant pressure molecular dynamics simulations have been performed for aqueous alkaline earth metal chloride [M 2+ -Cl - (M = Mg, Ca, Sr, and Ba)] solutions over a wide range of concentrations (0.27-5.55 m) in supercritical (SC) and ambient conditions to investigate their structural and dynamical properties. A strong influence of the salt concentration is observed on the ion-ion pair correlation functions in both ambient and SC conditions. In SC conditions, significant clustering is observed in the 0.27 m solution, whereas the reverse situation is observed at room temperature and this is also supported by the residence times of the clusters. The concentration and ion size (cation size) seem to have opposite effects on the average number of hydrogen bonds. The simulation results show that the self-diffusion coefficients of water, cations, and the chloride ion increase with increasing temperature, whereas they decrease with increasing salt concentration. The cluster size distribution shows a strong density dependence in both ambient and SC conditions. In SC conditions, cluster sizes display a near-Gaussian distribution, whereas the distribution decays monotonically in ambient conditions.

Cation exchange concentraion of the Americium product from TRUEX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barney, G.S.; Cooper, T.D.; Fisher, F.D.

1991-06-01

A transuranic extraction (TRUEX) process has been developed to separate and recover plutonium, americium, and other transuranic (TRU) elements from acid wastes. The main objective of the process is to reduce the effluent to below the TRU limit for actinide concentrations (<100 nCi/g of material) so it can be disposed of inexpensively. The process yields a dilute nitric acid stream containing low concentrations of the extracted americium product. This solution also contains residual plutonium and trace amounts of iron. The americium will be absorbed into a cation exchange resin bed to concentrate it for disposal or for future use. Themore » overall objective of these laboratory tests was to determine the performance of the cation exchange process under expected conditions of the TRUEX process. Effects of acid, iron, and americium concentrations on americium absorption on the resin were determined. Distribution coefficients for americium absorption from acide solutions on the resin were measured using batch equilibrations. Batch equilibrations were also used to measure americium absorption in the presence of complexants. This data will be used to identify complexants and solution conditions that can be used to elute the americium from the columns. The rate of absorption was measured by passing solutions containing americium through small columns of resin, varying the flowrates, and measuring the concentrations of americium in the effluent. The rate data will be used to estimate the minimum bed size of the columns required to concentrate the americium product. 11 refs. , 10 figs., 2 tabs.« less

Selective Antimicrobial Activities and Action Mechanism of Micelles Self-Assembled by Cationic Oligomeric Surfactants.

PubMed

Zhou, Chengcheng; Wang, Fengyan; Chen, Hui; Li, Meng; Qiao, Fulin; Liu, Zhang; Hou, Yanbo; Wu, Chunxian; Fan, Yaxun; Liu, Libing; Wang, Shu; Wang, Yilin

2016-02-17

This work reports that cationic micelles formed by cationic trimeric, tetrameric, and hexameric surfactants bearing amide moieties in spacers can efficiently kill Gram-negative E. coli with a very low minimum inhibitory concentration (1.70-0.93 μM), and do not cause obvious toxicity to mammalian cells at the concentrations used. With the increase of the oligomerization degree, the antibacterial activity of the oligomeric surfactants increases, i.e., hexameric surfactant > tetrameric surfactant > trimeric surfactant. Isothermal titration microcalorimetry, scanning electron microscopy, and zeta potential results reveal that the cationic micelles interact with the cell membrane of E. coli through two processes. First, the integrity of outer membrane of E. coli is disrupted by the electrostatic interaction of the cationic ammonium groups of the surfactants with anionic groups of E. coli, resulting in loss of the barrier function of the outer membrane. The inner membrane then is disintegrated by the hydrophobic interaction of the surfactant hydrocarbon chains with the hydrophobic domains of the inner membrane, leading to the cytoplast leakage. The formation of micelles of these cationic oligomeric surfactants at very low concentration enables more efficient interaction with bacterial cell membrane, which endows the oligomeric surfactants with high antibacterial activity.

Salinity-Dependent Contact Angle Alteration in Oil/Brine/Silicate Systems: the Critical Role of Divalent Cations

PubMed Central

2017-01-01

The effectiveness of water flooding oil recovery depends to an important extent on the competitive wetting of oil and water on the solid rock matrix. Here, we use macroscopic contact angle goniometry in highly idealized model systems to evaluate how brine salinity affects the balance of wetting forces and to infer the microscopic origin of the resultant contact angle alteration. We focus, in particular, on two competing mechanisms debated in the literature, namely, double-layer expansion and divalent cation bridging. Our experiments involve aqueous droplets with a variable content of chloride salts of Na+, K+, Ca2+, and Mg2+, wetting surfaces of muscovite and amorphous silica, and an environment of ambient decane containing small amounts of fatty acids to represent polar oil components. By diluting the salt content in various manners, we demonstrate that the water contact angle on muscovite, not on silica, decreases by up to 25° as the divalent cation concentration is reduced from typical concentrations in seawater to zero. Decreasing the ionic strength at a constant divalent ion concentration, however, has a negligible effect on the contact angle. We discuss the consequences for the interpretation of core flooding experiments and the identification of a microscopic mechanism of low salinity water flooding, an increasingly popular, inexpensive, and environment-friendly technique for enhanced oil recovery. PMID:28332396

Salinity-Dependent Contact Angle Alteration in Oil/Brine/Silicate Systems: the Critical Role of Divalent Cations.

PubMed

Haagh, M E J; Siretanu, I; Duits, M H G; Mugele, F

2017-04-11

The effectiveness of water flooding oil recovery depends to an important extent on the competitive wetting of oil and water on the solid rock matrix. Here, we use macroscopic contact angle goniometry in highly idealized model systems to evaluate how brine salinity affects the balance of wetting forces and to infer the microscopic origin of the resultant contact angle alteration. We focus, in particular, on two competing mechanisms debated in the literature, namely, double-layer expansion and divalent cation bridging. Our experiments involve aqueous droplets with a variable content of chloride salts of Na + , K + , Ca 2+ , and Mg 2+ , wetting surfaces of muscovite and amorphous silica, and an environment of ambient decane containing small amounts of fatty acids to represent polar oil components. By diluting the salt content in various manners, we demonstrate that the water contact angle on muscovite, not on silica, decreases by up to 25° as the divalent cation concentration is reduced from typical concentrations in seawater to zero. Decreasing the ionic strength at a constant divalent ion concentration, however, has a negligible effect on the contact angle. We discuss the consequences for the interpretation of core flooding experiments and the identification of a microscopic mechanism of low salinity water flooding, an increasingly popular, inexpensive, and environment-friendly technique for enhanced oil recovery.

Cellular cation transport studied by 6/7Li and 23Na NMR in a porous Mo132 Keplerate type nano-capsule as model system.

PubMed

Rehder, Dieter; Haupt, Erhard T K; Müller, Achim

2008-01-01

Li+ ions can interplay with other cations intrinsically present in the intra- and extra-cellular space (i.e. Na+, K+, Mg2+ and Ca2+) have therapeutic effects (e.g. in the treatment of bipolar disorder) or toxic effects (at higher doses), likely because Li+ interferes with the intra-/extra-cellular concentration gradients of the mentioned physiologically relevant cations. The cellular transmembrane transport can be modelled by molybdenum-oxide-based Keplerates, i.e. nano-sized porous capsules containing 132 Mo centres, monitored through 6/7Li as well as 23Na NMR spectroscopy. The effects on the transport of Li+ cations through the 'ion channels' of these model cells, caused by variations in water amount, temperature, and by the addition of organic cationic 'plugs' and the shift reagent [Dy(PPP)2](7-) are reported. In the investigated solvent systems, water acts as a transport mediator for Li+. Likewise, the counter-transport (Li+/Na+, Li+/K+, Li+/Cs+ and Li+/Ca2+) has been investigated by 7Li NMR and, in the case of Li+/Na+ exchange, by 23Na NMR, and it has been shown that most (in the case of Na+ and K+, all (Ca2+) or almost none (Cs+) of the Li cations is extruded from the internal sites of the artificial cell to the extra-cellular medium, while Na+, K+ and Ca2+ are partially incorporated.

The impact of agricultural land use on stream chemistry in the Middle Hills of the Himalayas, Nepal

NASA Astrophysics Data System (ADS)

Collins, Robert; Jenkins, Alan

1996-11-01

The chemistry of streams draining agricultural and forested catchments in the Middle Hills of Nepal is described. Differences between mean streamwater chemistry are attributable to the effects of the terraced agriculture and land management practices. The agricultural catchments were found to exhibit higher mean concentrations of base cations (Na, Mg, K), bicarbonate, acid anions (SO 4, Cl), metals (Al, Fe) and nutrients (NO 3, PO 4). Increased base cations apparently result from tillage practices exposing fresh soil material to weathering. Increased acid anions result from inputs of inorganic fertiliser, notably ammonium sulphate, and from an apparent increase in evapotranspiration from the flooded terraces in the agricultural catchments. Increased metal concentrations may be promoted by increased weathering and erosion rates, and this is further supported by observations of dramatically higher turbidity in the streamwater draining the agricultural catchments. Higher levels of nutrients are the direct result of fertiliser input but concentrations are generally low from all catchments as a result of denitrification, indicating that eutrophication downstream is not a likely consequence of land use change. The major dynamics of water chemistry occur during the monsoon, which is also the main season for agricultural production. Mean wet season concentrations of base cations tend to be lower than in the dry season at all catchments as higher flow dilutes the relatively constant weathering input. Ammonium concentrations are higher from the agricultural catchments in the wet season as a result of direct washout of fertiliser. Detailed monitoring through storm periods at one agricultural catchment indicates that the chemistry responds very rapidly to changing flow, with cations decreasing and acid anions increasing followed by equally rapid recovery as flow recedes. Bicarbonate concentrations also decline markedly but are still sufficiently high to maintain pH near neutral throughout the storm event. The impacts of agricultural land use on streamwater chemistry are unlikely to lead to potentially damaging consequences for the aquatic biota at present or in the short-term future. The potential for acidity generation as a result of the high loads of nitrogenous fertilisers applied is apparently buffered by the land tillage practices, which promote higher weathering and so higher concentrations of base cations.

Molecular crowding has no effect on the dilution thermodynamics of the biologically relevant cation mixtures.

PubMed

Głogocka, Daria; Przybyło, Magdalena; Langner, Marek

2017-04-01

The ionic composition of intracellular space is rigorously maintained in the expense of high-energy expenditure. It has been recently postulated that the cytoplasmic ionic composition is optimized so the energy cost of the fluctuations of calcium ion concentration is minimized. Specifically, thermodynamic arguments have been produced to show that the presence of potassium ions at concentrations higher than 100 mM reduce extend of the energy dissipation required for the dilution of calcium cations. No such effect has been measured when sodium ions were present in the solution or when the other divalent cation magnesium was diluted. The experimental observation has been interpreted as the indication of the formation of ionic clusters composed of calcium, chloride and potassium. In order to test the possibility that such clusters may be preserved in biological space, the thermodynamics of ionic mixtures dilution in solutions containing albumins and model lipid bilayers have been measured. Obtained thermograms clearly demonstrate that the energetics of calcium/potassium mixture is qualitatively different from calcium/sodium mixture indicating that the presence of the biologically relevant quantities of proteins and membrane hydrophilic surfaces do not interfere with the properties of the intracellular aqueous phase.

The adsorption of amino acids and cations onto goethite: a prebiotic chemistry experiment.

PubMed

Farias, Ana Paula S F; Carneiro, Cristine E A; de Batista Fonseca, Inês C; Zaia, Cássia T B V; Zaia, Dimas A M

2016-06-01

Few prebiotic chemistry experiments have assessed the adsorption of biomolecules by iron oxide-hydroxides. The present work investigated the effects of cations in artificial seawaters on the adsorption of Gly, α-Ala and β-Ala onto goethite, and vice versa. Goethite served to concentrate K and Mg cations from solution; these effects could have played important roles in peptide nucleoside formation. Goethite showed low adsorption of Gly and α-Ala. On the other hand, β-Ala (a non-protein amino acid) was highly adsorbed by goethite. Because Gly and α-Ala are the most common amino acids in living beings, and iron oxide-hydroxides are widespread on Earth, additional iron oxides should be studied. Increased ionic strength in artificial seawaters decreased the adsorption of amino acids by goethite. Because Na was highly abundant in the artificial seawater, it showed the highest effect on amino acid adsorption. β-Ala increased the adsorption of K and Ca by goethite, this effect could have been important for peptide synthesis.

Diel plant water use and competitive soil cation exchange interact to enhance NH 4 + and K + availability in the rhizosphere

DOE PAGES

Espeleta, Javier F.; Cardon, Zoe G.; Mayer, K. Ulrich; ...

2016-11-12

Hydro-biogeochemical processes in the rhizosphere regulate nutrient and water availability, and thus ecosystem productivity. We hypothesized that two such processes often neglected in rhizosphere models — diel plant water use and competitive cation exchange — could interact to enhance availability of K + and NH 4 +, both high-demand nutrients. A rhizosphere model with competitive cation exchange was used to investigate how diel plant water use (i.e., daytime transpiration coupled with no nighttime water use, with nighttime root water release, and with nighttime transpiration) affects competitive ion interactions and availability of K + and NH 4 +. Competitive cation exchangemore » enabled lowdemand cations that accumulate against roots (Ca 2+, Mg 2+, Na +) to desorb NH 4 + and K + from soil, generating non-monotonic dissolved concentration profiles (i.e. ‘hotspots’ 0.1–1 cm from the root). Cation accumulation and competitive desorption increased with net root water uptake. Daytime transpiration rate controlled diel variation in NH 4 + and K + aqueous mass, nighttime water use controlled spatial locations of ‘hotspots’, and day-to-night differences in water use controlled diel differences in ‘hotspot’ concentrations. Finally, diel plant water use and competitive cation exchange enhanced NH 4 + and K + availability and influenced rhizosphere concentration dynamics. Demonstrated responses have implications for understanding rhizosphere nutrient cycling and plant nutrient uptake.« less

Investigating the effect of hardness cations on coagulation: The aspect of neutralisation through Al(III)-dissolved organic matter (DOM) binding.

PubMed

Zhou, Yuxuan; Yan, Mingquan; Liu, Ruiping; Wang, Dongsheng; Qu, Jiuhui

2017-05-15

Hardness cations are ubiquitous and abundant in source water, while the effect of hardness on the performance of coagulation for dissolved organic matter (DOM) removal in water treatment remains unclear due to the limitation of methods that can characterise the subtle interactions between DOM, coagulant and hardness cations. This work quantified the competition between coagulant Al 3+ and hardness cations to bind onto DOM using absorbance spectroscopy acquired at different Al 3+ concentrations in the absence and presence of Ca 2+ or Mg 2+ . The results indicate that, in the presence of either Mg 2+ or Ca 2+ , an increasing depression of the binding of Al 3+ -DOM could be observed in the differential spectra of DOM with the increasing of Mg 2+ or Ca 2+ at a level of 10, 100 and 1000 μM, with the observation being more significant at higher pH from 6.5 to 8.5. The results of zeta potentials of DOM indicate that the competition of hardness cations results in the negative DOM being less efficiently neutralised by Al 3+ . This study demonstrates that the removal of DOM by coagulation would significantly deteriorate with the presence of hardness cations, which would compete with coagulant Al 3+ to neutralise the unsaturated sites in DOM. Copyright © 2017 Elsevier Ltd. All rights reserved.

[Antioxidant activity of cationic whey protein isolate].

PubMed

titova, M E; Komolov, S A; Tikhomirova, N A

2012-01-01

The process of lipid peroxidation (LPO) in biological membranes of cells is carried out by free radical mechanism, a feature of which is the interaction of radicals with other molecules. In this work we investigated the antioxidant activity of cationic whey protein isolate, obtained by the cation-exchange chromatography on KM-cellulose from raw cow's milk, in vitro and in vivo. In biological liquids, which are milk, blood serum, fetal fluids, contains a complex of biologically active substances with a unique multifunctional properties, and which are carrying out a protective, antimicrobial, regenerating, antioxidant, immunomodulatory, regulatory and others functions. Contents of the isolate were determined electrophoretically and by its biological activity. Cationic whey protein isolate included lactoperoxidase, lactoferrin, pancreatic RNase, lysozyme and angeogenin. The given isolate significantly has an antioxidant effect in model experimental systems in vitro and therefore may be considered as a factor that can adjust the intensity of lipid oxidation. In model solutions products of lipid oxidation were obtained by oxidation of phosphatidylcholine by hydrogen peroxide in the presence of a source of iron. The composition of the reaction mixture: 0,4 mM H2O2; 50 mcM of hemin; 2 mg/ml L-alpha-phosphatidylcholine from soybean (Sigma, German). Lipid peroxidation products were formed during the incubation of the reaction mixture for two hours at 37 degrees C. In our studies rats in the adaptation period immediately after isolation from the nest obtained from food given orally native cationic whey protein isolate at the concentration three times higher than in fresh cow's milk. On the manifestation of the antioxidant activity of cationic whey protein isolate in vivo evidence decrease of lipid peroxidation products concentration in the blood of rats from the experimental group receipt whey protein isolate in dos 0,6 mg/g for more than 20% (p<0,05) with oral feeding. Thus, significantly cationic whey protein isolate has an antioxidant effect in model experimental systems, and so can be considered as a factor that can regulate the intensity of lipid oxidation.

Seebeck Coefficient of Cation-Substituted Disulfides CuCr1-x Fe x S2 and Cu1-x Fe x CrS2

NASA Astrophysics Data System (ADS)

Korotaev, Evgeniy V.; Syrokvashin, Mikhail M.; Filatova, Irina Yu.; Pelmenev, Konstantin G.; Zvereva, Valentina V.; Peregudova, Natalya N.

2018-03-01

The effect of cation substitution on the Seebeck coefficient of CuCr1-x Fe x S2 (x = 0 to 0.30) and Cu1-x Fe x CrS2 (x = 0 to 0.03) in the temperature range of 100 K to 450 K has been investigated. Increasing iron concentration led to a metal-insulator transition which suppressed the thermoelectric power. However, for low iron concentration (x < 0.03), the Seebeck coefficient of CuCr1-x Fe x S2 and Cu1-x Fe x CrS2 exceeded the values for the undoped copper-chromium disulfide matrix CuCrS2 at temperature below 300 K.

The effect of topography and rock type on soil cation contents and stream solute and phosphorus concentrations of streams in the southwestern Brazilian Amazon basin.

NASA Astrophysics Data System (ADS)

Biggs, T. W.; Dunne, T.; Holmes, K.; Martinelli, L. A.

2001-12-01

Topography plays an important role in determining soil properties, stream solute concentrations and landscape denudation rates. Stallard (1985) suggested that catchment denudation rates should depend on soil thickness. Areas with low slopes are limited by the rate of transport of sediment, and typically contain thick soils that prevent interaction of stream waters with underlying bedrock [Stallard 1985]. Steep areas typically have thin soils, but a lower hydrologic residence time that may prevent soil water from coming into thermodynamic equilibrium with the soil-rock complex. In a survey of streams in the Brazilian Amazon basin, Biggs et al. (2001) found that stream solute concentrations correlate with soil cation contents in the humid tropics, but the mechanism underlying the correlation has not been determined. We combine chemical analyses of water samples from ~40 different streams with soil surveys, geology maps, and a 100m resolution DEM to examine the relationship between topography, rock type, soil cation contents, and stream solute concentrations in the Brazilian Amazon state of Rondônia. The basins are all more than 60% forested at the time of stream sampling and lie on granite-gneiss rocks, tertiary sediments, or sandstone. The catchment-averaged slope correlates positively with both soil cation contents and stream concentrations of P, Na, Ca, Mg, K, Si, ANC, and pH. Though we have no data about the relationship between soil depth and average slope, we assume an inverse correlation, so the data demonstrates that thick soils yield lower solute concentrations. Stream concentrations of Ca, Mg, ANC and pH reach a maximum at intermediate average slopes (3 degrees), suggesting that denudation rates may increase with slope up to a maximum, when the catchment becomes limited by the weathering rate of the basement rock. Catchments on mica-schists or mafic rocks have low average slopes and higher concentrations of Ca, Mg, Si, ANC, and pH than catchments on granite-gneiss, tertiary sediments or sandstone.

Soil properties determine the elevational patterns of base cations and micronutrients in the plant-soil system up to the upper limits of trees and shrubs

NASA Astrophysics Data System (ADS)

Wang, Ruzhen; Wang, Xue; Jiang, Yong; Cerdà, Artemi; Yin, Jinfei; Liu, Heyong; Feng, Xue; Shi, Zhan; Dijkstra, Feike A.; Li, Mai-He

2018-03-01

To understand whether base cations and micronutrients in the plant-soil system change with elevation, we investigated the patterns of base cations and micronutrients in both soils and plant tissues along three elevational gradients in three climate zones in China. Base cations (Ca, Mg, and K) and micronutrients (Fe, Mn, and Zn) were determined in soils, trees, and shrubs growing at lower and middle elevations as well as at their upper limits on Balang (subtropical, SW China), Qilian (dry temperate, NW China), and Changbai (wet temperate, NE China) mountains. No consistent elevational patterns were found for base cation and micronutrient concentrations in both soils and plant tissues (leaves, roots, shoots, and stem sapwood). Soil pH, soil organic carbon (SOC), total soil nitrogen (TN), the SOC to TN ratio (C : N), and soil extractable nitrogen (NO3- and NH4+) determined the elevational patterns of soil exchangeable Ca and Mg and available Fe, Mn, and Zn. However, the controlling role of soil pH and SOC was not universal as revealed by their weak correlations with soil base cations under tree canopies at the wet temperate mountain and with micronutrients under both tree and shrub canopies at the dry temperate mountain. In most cases, soil base cation and micronutrient availabilities played fundamental roles in determining the base cation and micronutrient concentrations in plant tissues. An exception existed for the decoupling of leaf K and Fe with their availabilities in the soil. Our results highlight the importance of soil physicochemical properties (mainly SOC, C : N, and pH) rather than elevation (i.e., canopy cover and environmental factors, especially temperature), in determining base cation and micronutrient availabilities in soils and subsequently their concentrations in plant tissues.

Extrinsic Cation Selectivity of 2D Membranes

PubMed Central

2017-01-01

From a systematic study of the concentration driven diffusion of positive and negative ions across porous 2D membranes of graphene and hexagonal boron nitride (h-BN), we prove their cation selectivity. Using the current–voltage characteristics of graphene and h-BN monolayers separating reservoirs of different salt concentrations, we calculate the reversal potential as a measure of selectivity. We tune the Debye screening length by exchanging the salt concentrations and demonstrate that negative surface charge gives rise to cation selectivity. Surprisingly, h-BN and graphene membranes show similar characteristics, strongly suggesting a common origin of selectivity in aqueous solvents. For the first time, we demonstrate that the cation flux can be increased by using ozone to create additional pores in graphene while maintaining excellent selectivity. We discuss opportunities to exploit our scalable method to use 2D membranes for applications including osmotic power conversion. PMID:28157333

Room-temperature ferroelectricity of SrTiO{sub 3} films modulated by cation concentration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Fang; Zhang, Qinghua; Yang, Zhenzhong

2015-08-24

The room-temperature ferroelectricity of SrTiO{sub 3} is promising for oxide electronic devices controlled by multiple fields. An effective way to control the ferroelectricity is highly demanded. Here, we show that the off-centered antisite-like defects in SrTiO{sub 3} films epitaxially grown on Si (001) play the determinative role in the emergence of room-temperature ferroelectricity. The density of these defects changes with the film cation concentration sensitively, resulting in a varied coercive field of the ferroelectric behavior. Consequently, the room-temperature ferroelectricity of SrTiO{sub 3} films can be effectively modulated by tuning the temperature of metal sources during the molecular beam epitaxy growth.more » Such an easy and reliable modulation of the ferroelectricity enables the flexible engineering of multifunctional oxide electronic devices.« less

Cationic nanoemulsions as potential carriers for intracellular delivery

PubMed Central

Khachane, P.V.; Jain, A.S.; Dhawan, V.V.; Joshi, G.V.; Date, A.A.; Mulherkar, R.; Nagarsenker, M.S.

2014-01-01

Successful cytosolic delivery enables opportunities for improved treatment of various genetic disorders, infectious diseases and cancer. Cationic nanoemulsions were designed using alternative excipients and evaluated for particle size, charge, effect of sterilization on its stability, DNA condensation potential and cellular uptake efficiency. Various concentrations of non-ionic and ionic stabilizers were evaluated to design formula for colloidally stable cationic nanoemulsion. The nanoemulsion comprised of 5% Capmul MCM, 0.5% didodecyldimethylammonium bromide (DDAB), 1% phospholipid, 1% Poloxamer 188 and 2.25% glycerol and possessed particle size of 81.6 ± 3.56 nm and 137.1 ± 1.57 nm before and after steam sterilization, respectively. DNA condensation studies were carried out at various nanoemulsion: DNA ratios ranging from 1:1 to 10:1. Cell uptake studies were conducted on human embryonic kidney (HEK) cell lines which are widely reported for transfection studies. The nanoemulsions showed excellent cellular uptake as evaluated by fluorescence microscopy and flow cytometry. Overall, a colloidally stable cationic nanoemulsion with good DNA condensation ability was successfully fabricated for efficient cytosolic delivery and potential for in vivo effectiveness. PMID:25972740

Enhanced splicing correction effect by an oligo-aspartic acid-PNA conjugate and cationic carrier complexes.

PubMed

Bae, Yun Mi; Kim, Myung Hee; Yu, Gwang Sig; Um, Bong Ho; Park, Hee Kyung; Lee, Hyun-il; Lee, Kang Taek; Suh, Yung Doug; Choi, Joon Sig

2014-02-10

Peptide nucleic acids (PNAs) are synthetic structural analogues of DNA and RNA. They recognize specific cellular nucleic acid sequences and form stable complexes with complementary DNA or RNA. Here, we designed an oligo-aspartic acid-PNA conjugate and showed its enhanced delivery into cells with high gene correction efficiency using conventional cationic carriers, such as polyethylenimine (PEI) and Lipofectamine 2000. The negatively charged oligo-aspartic acid-PNA (Asp(n)-PNA) formed complexes with PEI and Lipofectamine, and the resulting Asp(n)-PNA/PEI and Asp(n)-PNA/Lipofectamine complexes were introduced into cells. We observed significantly enhanced cellular uptake of Asp(n)-PNA by cationic carriers and detected an active splicing correction effect even at nanomolar concentrations. We found that the splicing correction efficiency of the complex depended on the kind of the cationic carriers and on the number of repeating aspartic acid units. By enhancing the cellular uptake efficiency of PNAs, these results may provide a novel platform technology of PNAs as bioactive substances for their biological and therapeutic applications. Copyright © 2013 Elsevier B.V. All rights reserved.

Propranolol transport across the inner blood-retinal barrier: potential involvement of a novel organic cation transporter.

PubMed

Kubo, Yoshiyuki; Shimizu, Yoshimi; Kusagawa, Yusuke; Akanuma, Shin-Ichi; Hosoya, Ken-Ichi

2013-09-01

The influx transport of propranolol across the inner blood-retinal barrier (BRB) was investigated. In the in vivo analysis of carotid artery single-injection method, [(3) H]propranolol uptake by the retina was greater than that of an internal reference compound, and was reduced by several organic cations. In the in vitro uptake study, TR-iBRB2 cells, an in vitro model of the inner BRB, showed a time-, concentration-, pH- and temperature-dependent [(3) H]propranolol uptake, suggesting the involvement of a carrier-mediated transport process in the influx of propranolol across the inner BRB. In the inhibition study, various organic cations, including drugs and candidates for the treatment of the retinal diseases, inhibited the [(3) H]propranolol uptake by TR-iBRB2 cells with no significant effects by the substrates and inhibitors of well-characterized organic cation transporters, suggesting that the influx transport of propranolol is performed by a novel transporter at the inner BRB. An analysis of the relationship between the inhibitory effect and the lipophilicity of inhibitors suggests a lipophilicity-dependent inhibitory effect of amines on the [(3) H]propranolol uptake by TR-iBRB2 cells. These results showed that influx transport of propranolol across the inner BRB is performed by a carrier-mediated transport process, suggesting the involvement of a novel organic cation transporter. Copyright © 2013 Wiley Periodicals, Inc.

Modeling uranium(VI) adsorption onto montmorillonite under varying carbonate concentrations: A surface complexation model accounting for the spillover effect on surface potential

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tournassat, C.; Tinnacher, R. M.; Grangeon, S.

The prediction of U(VI) adsorption onto montmorillonite clay is confounded by the complexities of: (1) the montmorillonite structure in terms of adsorption sites on basal and edge surfaces, and the complex interactions between the electrical double layers at these surfaces, and (2) U(VI) solution speciation, which can include cationic, anionic and neutral species. Previous U(VI)-montmorillonite adsorption and modeling studies have typically expanded classical surface complexation modeling approaches, initially developed for simple oxides, to include both cation exchange and surface complexation reactions. However, previous models have not taken into account the unique characteristics of electrostatic surface potentials that occur at montmorillonitemore » edge sites, where the electrostatic surface potential of basal plane cation exchange sites influences the surface potential of neighboring edge sites (‘spillover’ effect).« less

Modeling uranium(VI) adsorption onto montmorillonite under varying carbonate concentrations: A surface complexation model accounting for the spillover effect on surface potential

DOE PAGES

Tournassat, C.; Tinnacher, R. M.; Grangeon, S.; ...

2017-10-06

The prediction of U(VI) adsorption onto montmorillonite clay is confounded by the complexities of: (1) the montmorillonite structure in terms of adsorption sites on basal and edge surfaces, and the complex interactions between the electrical double layers at these surfaces, and (2) U(VI) solution speciation, which can include cationic, anionic and neutral species. Previous U(VI)-montmorillonite adsorption and modeling studies have typically expanded classical surface complexation modeling approaches, initially developed for simple oxides, to include both cation exchange and surface complexation reactions. However, previous models have not taken into account the unique characteristics of electrostatic surface potentials that occur at montmorillonitemore » edge sites, where the electrostatic surface potential of basal plane cation exchange sites influences the surface potential of neighboring edge sites (‘spillover’ effect).« less

Study of interactions between hyaluronan and cationic surfactants by means of calorimetry, turbidimetry, potentiometry and conductometry.

PubMed

Krouská, J; Pekař, M; Klučáková, M; Šarac, B; Bešter-Rogač, M

2017-02-10

The thermodynamics of the micelle formation of the cationic surfactants tetradecyltrimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB) with and without the addition of hyaluronan of two molecular weights was studied in aqueous solution by titration calorimetry. Macroscopic phase separation, which was detected by calorimetry and also by conductometry, occurs when charges on the surfactant and hyaluronan are balanced. In contrast, turbidimetry and potentiometry showed hyaluronan-surfactant interactions at very low surfactant concentrations. The observed differences between systems prepared with CTAB and TTAB indicate that besides the electrostatic interactions, which probably predominate, hydrophobic effects also play a significant role in hyaluronan interactions with cationic surfactants. Copyright © 2016 Elsevier Ltd. All rights reserved.

Macroscopic and bulk-controlled elastic modes in an interaction of interstitial alcali metal cations within a face-centered cubic crystalline fullerine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tatarenko, V.A.; Tsysman, C.L.; Oltarzhevskaya, Y.T.

1994-12-31

The calculations in a majority of previous works for the fulleride (AqC{sub 60}) crystals were performed within the framework of the rigid-lattice model, neglecting the distoration relaxation of the host fullerene (C{sub 60}) crystal caused by the interstitial alkali-metal (A) cations. However, an each cation is a source of a static distoration field, and the resulting field is a superposition of such fields generated by all cations. This is a reason why the host-crystal distortions depend on the A-cations configurations, i.e. on a type of a spatial bulk distribution of interstitial cations. This paper seeks to find a functional relationmore » between the amplitudes of the doping-induced structure-distortion waves and of statistic concentration ones. A semiphenomenological model is constructed here within the scope of statistical-thermodynamic treatment and using the lattice-statistics simulation method. In this model the effects due to the presence of q solute A cations over available interstices (per unit cell) on the statistic inherent reorientation and/or displacements of the solvent molecules from the average-lattice sites as well as on the lattice parameter a of the elastically-anysotropic cubic C{sub 60} crystal are taken into account.« less

Cationic surfactants in the form of nanoparticles and micelles elicit different human neutrophil responses: a toxicological study.

PubMed

Hwang, Tsong-Long; Sung, Calvin T; Aljuffali, Ibrahim A; Chang, Yuan-Ting; Fang, Jia-You

2014-02-01

Cationic surfactants are an ingredient commonly incorporated into nanoparticles for clinical practicability; however, the toxicity of cationic surfactants in nanoparticles is not fully elucidated. We aimed to evaluate the inflammatory responses of cationic nanobubbles and micelles in human neutrophils. Soyaethyl morpholinium ethosulfate (SME) and hexadecyltrimethyl-ammonium bromide (CTAB) are the two cationic surfactants employed in this study. The zeta potential of CTAB nanobubbles was 80 mV, which was the highest among all formulations. Nanobubbles, without cationic surfactants, showed no cytotoxic effects on neutrophils in terms of inflammatory responses. Cationic nanobubbles caused a concentration-dependent cytotoxicity of degranulation (elastase release) and membrane damage (release of lactate dehydrogenase, LDH). Among all nanoparticles and micelles, CTAB-containing nanosystems showed the greatest inflammatory responses. A CTAB nanobubble diluent (1/150) increased the LDH release 80-fold. Propidium iodide staining and scanning electron microscopy (SEM) verified cell death and morphological change of neutrophils treated by CTAB nanobubbles. SME, in a micelle form, strengthened the inflammatory response more than SME-loaded nanobubbles. Membrane interaction and subsequent Ca(2+) influx were the mechanisms that triggered inflammation. The information obtained from this work is beneficial in designing nanoparticulate formulations for balancing clinical activity and toxicity. Copyright © 2013 Elsevier B.V. All rights reserved.

Macroscopic and bulk-controlled elastic modes in an interaction of interstitial alcali metal cations within a face-centered cubic crystalline fullerine

NASA Technical Reports Server (NTRS)

Tatarenko, Valentine A.; Tsysman, Constantin L.; Oltarzhevskaya, Yelena T.

1995-01-01

The calculations in a majority of previous works for the fulleride (AqC-60) crystals were performed within the framework of the rigid-lattice model, neglecting the distortion relaxation of the host fullerene (C-60) crystal caused by the interstitial alkali-metal (A) cations. However, an each cation is a source of a static distortion field, and the resulting field is a superposition of such fields generated by all cations. This is a reason why the host-crystal distortions depend on the A-cations configurations, i.e. on a type of a spatial bulk distribution of interstitial cations. The given paper seeks to find a functional relation between the amplitudes of the doping-induced structure-distortion waves and of static concentration ones. A semiphenomenological model is constructed here within the scope of statistical-thermodynamic treatment and using the lattice-statistics simulation method(*). In this model the effects due to the presence of q solute A cations over available interstices (per unit cell) on the static inherent reorientation and/or displacements of the solvent molecules from the 'average-lattice' sites' as well as on the lattice parameter a of a elastically-anysotropic 'cubic' C-60 crystal are taken into account.

Asp-Gly based peptides confined at the surface of cationic gemini surfactant aggregates.

PubMed

Brizard, Aurélie; Dolain, Christel; Huc, Ivan; Oda, Reiko

2006-04-11

Cationic gemini surfactants complexed with anionic oligoglycine-aspartate (called gemini peptides hereafter) were synthesized, and their aggregation behaviors were studied. The effects of the hydrophobic chain length (C10-C22) and the length of the oligoglycine (0-4) were investigated, and it was clearly shown by critical micellar concentration, Krafft temperature, and isothermal surface pressure measurements that the hydrophobic effect and interpeptidic interaction influence the aggregation behavior in a cooperative manner. Below their Krafft temperatures, some of them formed both hydro- and organogels with three-dimensional networks and the Fourier transform infrared measurements show the presence of interpeptidic hydrogen bonds.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Espeleta, Javier F.; Cardon, Zoe G.; Mayer, K. Ulrich

Hydro-biogeochemical processes in the rhizosphere regulate nutrient and water availability, and thus ecosystem productivity. We hypothesized that two such processes often neglected in rhizosphere models — diel plant water use and competitive cation exchange — could interact to enhance availability of K + and NH 4 +, both high-demand nutrients. A rhizosphere model with competitive cation exchange was used to investigate how diel plant water use (i.e., daytime transpiration coupled with no nighttime water use, with nighttime root water release, and with nighttime transpiration) affects competitive ion interactions and availability of K + and NH 4 +. Competitive cation exchangemore » enabled lowdemand cations that accumulate against roots (Ca 2+, Mg 2+, Na +) to desorb NH 4 + and K + from soil, generating non-monotonic dissolved concentration profiles (i.e. ‘hotspots’ 0.1–1 cm from the root). Cation accumulation and competitive desorption increased with net root water uptake. Daytime transpiration rate controlled diel variation in NH 4 + and K + aqueous mass, nighttime water use controlled spatial locations of ‘hotspots’, and day-to-night differences in water use controlled diel differences in ‘hotspot’ concentrations. Finally, diel plant water use and competitive cation exchange enhanced NH 4 + and K + availability and influenced rhizosphere concentration dynamics. Demonstrated responses have implications for understanding rhizosphere nutrient cycling and plant nutrient uptake.« less

Thermal Stability of RNA Structures with Bulky Cations in Mixed Aqueous Solutions.

PubMed

Nakano, Shu-Ichi; Tanino, Yuichi; Hirayama, Hidenobu; Sugimoto, Naoki

2016-10-04

Bulky cations are used to develop nucleic-acid-based technologies for medical and technological applications in which nucleic acids function under nonaqueous conditions. In this study, the thermal stability of RNA structures was measured in the presence of various bulky cations in aqueous mixtures with organic solvents or polymer additives. The stability of oligonucleotide, transfer RNA, and polynucleotide structures was decreased in the presence of salts of tetrabutylammonium and tetrapentylammonium ions, and the stability and salt concentration dependences were dependent on cation sizes. The degree to which stability was dependent on salt concentration was correlated with reciprocals of the dielectric constants of mixed solutions, regardless of interactions between the cosolutes and RNA. Our results show that organic solvents affect the strength of electrostatic interactions between RNA and cations. Analysis of ion binding to RNA indicated greater enhancement of cation binding to RNA single strands than to duplexes in media with low dielectric constants. Furthermore, background bulky ions changed the dependence of RNA duplex stability on the concentration of metal ion salts. These unique properties of large tetraalkylammonium ions are useful for controlling the stability of RNA structures and its sensitivity to metal ion salts. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Transport and retention of 14C-perfluorooctanoic acid (PFOA) in saturated limestone and sand porous media: Effects of input concentration, ionic strength and cation type

NASA Astrophysics Data System (ADS)

Xueyan, L.; Gao, B.; Sun, Y.; Wu, J.

2017-12-01

Perfluorooctanoic acid (PFOA) has been used in a wide variety of industrial and consumer product applications. PFOA has been detected around the world at ng/L to μg/L levels in groundwater, and at ng/g levels in soil.The physicochemical properties of porous media were proven to play pivotal roles in determining the transport behavior of various pollutants. It is anticipated that physicochemical properties of porous media will strongly influence the transport behavior of PFOA. In addition, previous investigations have revealed that input concentration significantly influence the transport behavior of nanoparticles and antibiotics. Thus, this study was designed experimentally and fundamentally to gain insight into transport and retention of PFOA in various porous medias at different input concentrations, solution IS and cation type. Unlike in quartz sand porous media, the BTCs in limestone porous media exhibited increasing retention rate and high degree of tailing in limestone porous media. Results showed that higher relative retention occurred in limestone porous media than in quartz sand porous media under the same solution chemistry. This result was attributed to the less negative zeta-potentials, rougher surface and larger specific surface area, and the presence of hydroxyl groups and organic matters of limestone grains. Higher ionic strength and Ca2+ had little impact on the mobility of PFOA in quartz sand porous media, but significantly enhanced the retention of PFOA in limestone porous media. The difference is likely due to the compression of the electrical double layer, and the surface-charge neutralization and cation-bridging effect of Ca2+. Higher input concentration resulted in lower relative PFOA retention in limestone porous media, but the influence were insignificant in quartz sand porous media. This effect is likely because attachment sites in limestone responced to the variety of input concentration differently than quartz.

EFFECT OF CADMIUM AND OTHER METAL CATIONS ON IN VITRO LEYDIG CELL TESTOSTERONE PRODUCTION

EPA Science Inventory

In vivo assessment of toxicant action on Leydig cell function is subject to homeostatic mechanisms which make it difficult to determine whether any changes seen in serum testosterone (T) concentration are due to extragonadal endocrine alternations or to a direct effect on the Ley...

Effect of the pore water composition on the diffusive anion transport in argillaceous, low permeability sedimentary rocks

NASA Astrophysics Data System (ADS)

Wigger, Cornelia; Van Loon, Luc R.

2018-06-01

The effect of the pore water composition on the diffusive anion transport was studied for two different argillaceous, low permeability sedimentary rocks, Opalinus Clay (OPA) and Helvetic Marl (HM). The samples were saturated with different solutions with varying molar concentration and different main cations in the solution: NaCl based pore solutions and CaCl2 based pore solutions. The total porosity was measured by through-diffusion experiments with the neutral tracer HTO. Experiments performed in NaCl solutions resulted in a porosity of 0.12 for OPA and 0.03 for HM, and are consistent with results of the experiments in CaCl2 solutions. The total porosity was independent of the molar concentration, in contrast to the measured anion porosity, which increased with increasing molar concentration. It could further be observed that the pore solution based on the bivalent cation calcium shielded the negative surface charge stronger than the monovalent cation sodium, resulting in a larger measureable anion-accessible porosity in the case of CaCl2 solutions. The data was modelled based on an adapted Donnan approach of Birgersson and Karnland (2009). The model had to be adjusted with a permanent free, uncharged porosity, as well as with structural information on the permanent anion exclusion because of so-called bottleneck pores. Both parameters can only be evaluated from experiments. Nevertheless, taking these two adaptions into account, the effect of varying pore water compositions on the anion-accessible porosity of the investigated argillaceous rocks could be satisfactorily described.

Effect of the pore water composition on the diffusive anion transport in argillaceous, low permeability sedimentary rocks.

PubMed

Wigger, Cornelia; Van Loon, Luc R

2018-06-01

The effect of the pore water composition on the diffusive anion transport was studied for two different argillaceous, low permeability sedimentary rocks, Opalinus Clay (OPA) and Helvetic Marl (HM). The samples were saturated with different solutions with varying molar concentration and different main cations in the solution: NaCl based pore solutions and CaCl 2 based pore solutions. The total porosity was measured by through-diffusion experiments with the neutral tracer HTO. Experiments performed in NaCl solutions resulted in a porosity of 0.12 for OPA and 0.03 for HM, and are consistent with results of the experiments in CaCl 2 solutions. The total porosity was independent of the molar concentration, in contrast to the measured anion porosity, which increased with increasing molar concentration. It could further be observed that the pore solution based on the bivalent cation calcium shielded the negative surface charge stronger than the monovalent cation sodium, resulting in a larger measureable anion-accessible porosity in the case of CaCl 2 solutions. The data was modelled based on an adapted Donnan approach of Birgersson and Karnland (2009). The model had to be adjusted with a permanent free, uncharged porosity, as well as with structural information on the permanent anion exclusion because of so-called bottleneck pores. Both parameters can only be evaluated from experiments. Nevertheless, taking these two adaptions into account, the effect of varying pore water compositions on the anion-accessible porosity of the investigated argillaceous rocks could be satisfactorily described. Copyright © 2018 Elsevier B.V. All rights reserved.

Using digital soil maps to infer edaphic affinities of plant species in Amazonia: Problems and prospects.

PubMed

Moulatlet, Gabriel Massaine; Zuquim, Gabriela; Figueiredo, Fernando Oliveira Gouvêa; Lehtonen, Samuli; Emilio, Thaise; Ruokolainen, Kalle; Tuomisto, Hanna

2017-10-01

Amazonia combines semi-continental size with difficult access, so both current ranges of species and their ability to cope with environmental change have to be inferred from sparse field data. Although efficient techniques for modeling species distributions on the basis of a small number of species occurrences exist, their success depends on the availability of relevant environmental data layers. Soil data are important in this context, because soil properties have been found to determine plant occurrence patterns in Amazonian lowlands at all spatial scales. Here we evaluate the potential for this purpose of three digital soil maps that are freely available online: SOTERLAC, HWSD, and SoilGrids. We first tested how well they reflect local soil cation concentration as documented with 1,500 widely distributed soil samples. We found that measured soil cation concentration differed by up to two orders of magnitude between sites mapped into the same soil class. The best map-based predictor of local soil cation concentration was obtained with a regression model combining soil classes from HWSD with cation exchange capacity (CEC) from SoilGrids. Next, we evaluated to what degree the known edaphic affinities of thirteen plant species (as documented with field data from 1,200 of the soil sample sites) can be inferred from the soil maps. The species segregated clearly along the soil cation concentration gradient in the field, but only partially along the model-estimated cation concentration gradient, and hardly at all along the mapped CEC gradient. The main problems reducing the predictive ability of the soil maps were insufficient spatial resolution and/or georeferencing errors combined with thematic inaccuracy and absence of the most relevant edaphic variables. Addressing these problems would provide better models of the edaphic environment for ecological studies in Amazonia.

Muzzle secretion electrolytes as a possible indicator of sodium status in buffalo (Bubalus bubalis) calves: effects of sodium depletion and aldosterone administration.

PubMed

Kumar, S; Singh, S P

1981-01-01

In two separate experiments, the effects of sodium depletion and aldosterone administration on sodium and potassium concentrations in muzzle secretion, saliva and urine were studied in buffalo calves. Sodium deficiency in the animals was experimentally produced by unilateral parotid saliva deprivation for 18 days. During sodium depletion, the sodium levels in saliva and muzzle secretion gradually fell while the potassium level gradually rose. The concentrations of both of these cations in urine gradually fell during the course of sodium depletion. Aldosterone administration in normal (sodium-replete) animals simulated the effects of sodium depletion as far as cationic changes in saliva were concerned. However, aldosterone did not affect sodium and potassium concentration in the urine and in muzzle secretion in a manner similar to that caused by sodium depletion. Though the hormone decreased urinary sodium without affecting urinary potassium, it did not affect the muzzle sodium or potassium. Results suggest that aldosterone affects the composition of saliva and urine in buffaloes as it does in sheep and other ruminants. Similar changes in composition of muzzle secretion and saliva during sodium depletion indicate that the concentration of sodium in muzzle secretion could possibly be used to evaluate the sodium status of animals.

Effect of cations in the background electrolyte on the adsorption kinetics of copper and cadmium and the isoelectric point of imogolite.

PubMed

Arancibia-Miranda, Nicolás; Silva-Yumi, Jorge; Escudey, Mauricio

2015-12-15

Modification of surface charge and changes in the isoelectric point (IEP) of synthetic imogolite were studied for various cations in the background electrolyte (K(+), NH4(+), Mg(2+), and Ca(2+)). From the electrophoretic mobility data, it was established that the K(+) (KCl) concentration does not affect the IEP of imogolite; therefore, KCl is a suitable background electrolyte. In terms of the magnitude of changes in the IEP and surface charge, the cations may be ranked in the following order: Mg(2+)≈Ca(2+)>NH4(+)>K(+). Four different kinetic models were used to evaluate the influence of Mg(2+), Ca(2+), NH4(+), and K(+) on the adsorption of Cd and Cu on synthetic imogolite. When adsorption occurs in the presence of cations with the exception of K(+), the kinetics of the process is well described by the pseudo-first order model. On the other hand, when adsorption is conducted in the presence of K(+), the adsorption kinetics is well described by the pseudo-second order, Elovich, and Weber-Morris models. From the surface charge measurements, the affinity between imogolite and the cations and their effect on the adsorption of trace elements, namely Cu and Cd, were established. Copyright © 2015 Elsevier B.V. All rights reserved.

Acid mist and soil Ca and Al alter the mineral nutrition and physiology of red spruce

Treesearch

P.G. Schaberg; D.H. DeHayes; G.J. Hawley; G.R. Strimbeck; J.R. Cumming; P.F. Murakami; C.H. Borer

2000-01-01

We examined the effects and potential interactions of acid mist and soil solution Ca and Al treatments on foliar cation concentrations, membrane-associated Ca (mCa), ion leaching, growth, carbon exchange, and cold tolerance of red spruce (Picea rubens Sarg.) saplings. Soil solution Ca additions increased foliar Ca and Zn concentrations, and increased...

Distribution of cyclosporine A in ocular tissues after topical administration of cyclosporine A cationic emulsions to pigmented rabbits.

PubMed

Daull, Philippe; Lallemand, Frédéric; Philips, Betty; Lambert, Grégory; Buggage, Ronald; Garrigue, Jean-Sébastien

2013-03-01

The aim of this study was to compare the ocular and systemic distribution of cyclosporine A (CsA) in rabbits after the instillation of preservative-free CsA cationic and anionic emulsions. For the single-dose pharmacokinetic (PK) study, rabbits were instilled with 50 μL of the test material. For the multiple-dose PK study, rabbits were instilled twice daily with Restasis or once daily with NOVA22007 for 10 days. At each time point, the cornea, conjunctiva, and whole blood were harvested for CsA quantification. Ocular and systemic distribution were determined after 4 times daily instillations with 50 μL of 3H-CsA cationic and anionic emulsions for 7 days. Restasis was used as a reference in all studies. Single-dose PK data demonstrated that NOVA22007 0.1% and 0.05% delivered higher CsA concentrations to the cornea than Restasis [concentration maximum (C max): 2692, 1372, and 748 ng/g, respectively] and have a better exposition (area under the curve). Conjunctival Cmax values were 1914, 696, and 849 ng/g and area under the curve values were 3984, 2796, and 2515 ng/g · h, for either dose of the cationic emulsions and Restasis, respectively. The multiple-dose PK and the 3H-CsA distribution data demonstrated that the systemic distribution after repeated instillations was low and comparable for all emulsions. These data demonstrate that the CsA cationic emulsions were more effective than Restasis at delivering CsA to target tissues, thus confirming the potential advantage of cationic emulsions over anionic emulsions as vehicle for ocular drug delivery for the treatment of ocular surface diseases.

Polyamine replacement by magnesium ions in BHK-21/C13 cells

PubMed Central

Melvin, Maureen A. L.; Keir, Hamish M.

1979-01-01

Cultures of BHK-21/C13 cells, whose growth was inhibited by deprivation of serum, were stimulated to grow by addition of serum to the culture medium. Addition of MgCl2 to the medium, to increase the concentration of Mg2+ ions by 15mm, 30min before addition of serum, had no effect on the stimulation of cell growth, but inhibited the accumulation of cellular spermidine, so that the spermidine/spermine molar ratio was lower in these cultures than in cultures that had received no additional cations. The increase in the activity of ornithine decarboxylase that occurs 4–5h after serum `step-up' was substantially diminished by increasing the concentration of Mg2+ ions, but not of Na+ or K+ ions, in the medium by 30mm, 30min before addition of serum, and this inhibition was maintained for at least 24h. Methylglyoxal bis(guanylhydrazone), added to serum-deprived cultures to a concentration of 20μm, 30min before addition of serum, severely inhibited the increase in cell growth. The inhibitory effects of the drug were prevented by simultaneous addition of spermidine to the medium (to 100μm), and were partly prevented by the simultaneous addition of Mg2+ ions (to 30mm). Mg2+ ions were particularly effective in overcoming the inhibitory effect of methylglyoxal bis(guanylhydrazone) on the synthesis of DNA. Thus although a certain lack of specificity for cations exists in BHK-21/C13 cells, in that Mg2+ ions can be substituted for polyamines, particularly spermidine, to some extent, there are cellular processes for which the requirement for polyamines as cations is specific. PMID:444220

Glyphosate sensitivity of 5-enol-pyruvylshikimate-3-phosphate synthase from Bacillus subtilis depends upon state of activation induced by monovalent cations.

PubMed

Fischer, R S; Rubin, J L; Gaines, C G; Jensen, R A

1987-07-01

The 5-enol-pyruvylshikimate-3-phosphate (EPSP) synthase from Bacillus subtilis was activated by monovalent cations, catalytic activity being negligible in the absence of monovalent cations. The order of cation effectiveness (NH4+ greater than K+ greater than Rb+ greater than Na+ = Cs+ = Li+) indicated that the extent of activation was directly related to the unhydrated cation radius. Ammonium salts, at physiological concentrations, were dramatically more effective than other cations. Activation by ammonium was instantaneous, was not influenced by the counter ion, and gave a hyperbolic saturation curve. Hill plots did not show detectable cooperativity in the binding of ammonium. Double-reciprocal plots indicated that ammonium increases the maximal velocity and decreases the apparent Michaelis constants of EPSP synthase with respect to both phosphoenol pyruvate (PEP) and shikimate 3-phosphate (S3P). A direct relationship between sensitivity to inhibition by glyphosate and the activation state of EPSP synthase was demonstrated. Hill plots indicated a single value for glyphosate binding throughout the range of ammonium activation. Double-reciprocal plots of substrate saturation data obtained with ammonium-activated enzyme in the presence of glyphosate showed glyphosate to behave as a competitive inhibitor with respect to PEP and as a mixed-type inhibitor relative to S3P. The increased glyphosate sensitivity of ammonium-activated EPSP synthase is attributed to a lowering of the inhibitor constant of glyphosate with respect to PEP. Erroneous underestimates of sensitivities of some bacterial EPSP synthases to inhibition by glyphosate may result from failure to recognize cation requirements of EPSP synthases.

Ca2+ and Mn2+ Influx Through Receptor-Mediated Activation of Nonspecific Cation Channels in Mast Cells

NASA Astrophysics Data System (ADS)

Fasolato, Cristina; Hoth, Markus; Matthews, Gary; Penner, Reinhold

1993-04-01

Whole-cell patch-clamp recordings of membrane currents and Fura-2 measurements of free intracellular calcium concentration ([Ca2+]_i) were used to study calcium influx through receptor-activated cation channels in rat peritoneal mast cells. Cation channels were activated by the secretagogue compound 48/80, whereas a possible concomitant Ca2+ entry through pathways activated by depletion of calcium stores was blocked by dialyzing cells with heparin. Heparin effectively suppressed the transient Ca2+ release induced by 48/80 and abrogated inositol 1,4,5-trisphosphate-induced calcium influx without affecting activation of 50-pS cation channels. There was a clear correlation between changes in [Ca2+]_i and the activity of 50-pS channels. The changes in [Ca2+]_i increased with elevation of extracellular Ca2+. At the same time, inward currents through 50-pS channels were diminished as more Ca2+ permeated. This effect was due to a decrease in slope conductance and a reduction in the open probability of the cation channels. In physiological solutions, 3.6% of the total current was carried by Ca2+. The cation channels were not only permeable to Ca2+ but also to Mn2+, as evidenced by the quench of Fura-2 fluorescence. Mn2+ current through 50-pS channels could not be resolved at the single-channel level. Our results suggest that 50-pS cation channels partially contribute to sustained increases of [Ca2+]_i in mast cells following receptor activation.

The effect of temperature on experimental and natural chemical weathering rates of granitoid rocks

USGS Publications Warehouse

White, A.F.; Blum, A.E.; Bullen, T.D.; Vivit, D.V.; Schulz, M.; Fitzpatrick, J.

1999-01-01

The effects of climatic temperature variations (5-35??C) on chemical weathering are investigated both experimentally using flow-through columns containing fresh and weathered granitoid rocks and for natural granitoid weathering in watersheds based on annual solute discharge. Although experimental Na and Si effluent concentrations are significantly higher in the fresh relative to the weathered granitoids, the proportional increases in concentration with increasing temperature are similar. Si and Na exhibit comparable average apparent activation energies (E(a)) of 56 and 61 kJ/mol, respectively, which are similar to those reported for experimental feldspar dissolution measured over larger temperature ranges. A coupled temperature-precipitation model, using an expanded database for solute discharge fluxes from a global distribution of 86 granitoid watersheds, produces an apparent activation energy for Si (51 kJ/mol), which is also comparable to those derived from the experimental study. This correlation reinforces evidence that temperature does significantly impact natural silicate weathering rates. Effluent K concentrations in the column study are elevated with respect to other cations compared to watershed discharge due to the rapid oxidation/dissolution of biotite. K concentrations are less sensitive to temperature, resulting in a lower average E(a) value (27 kJ/mol) indicative of K loss from lower energy interlayer sites in biotite. At lower temperatures, initial cation release from biotite is significantly faster than cation release from plagioclase. This agrees with reported higher K/Na ratios in cold glacial watersheds relative to warmer temperate environments. Increased release of less radiogenic Sr from plagioclase relative to biotite at increasing temperature produces corresponding decreases in 87Sr/86Sr ratios in the column effluents. A simple mixing calculation using effluent K/Na ratios, Sr concentrations and 87Sr/86Sr ratios for biotite and plagioclase approximates stoichiometric cation ratios from biotite/plagioclase dissolution at warmer temperatures (35??C), but progressively overestimates the relative proportion of biotite with decreasing temperature. Ca, Mg, and Sr concentrations closely correlate, exhibit no consistent trends with temperature, and are controlled by trace amounts of calcite or exchange within weathered biotite. The inability of the watershed model to differentiate a climate signal for such species correlates with the lower temperature dependence observed in the experimental studies.

Thermal and colloidal behavior of amine-treated clays: the role of amphiphilic organic cation concentration.

PubMed

Marras, S I; Tsimpliaraki, A; Zuburtikudis, I; Panayiotou, C

2007-11-15

The modification of sodium montmorillonite (NaMMT) through the insertion of amphiphilic hexadecylammonium cations into the clay's interlayer spaces has been studied. Alkylammonium concentrations equivalent to 0.15-3.00 times the cation exchange capacity of the clay were used. The conformation of the surfactant cations in the confined space of the silicate galleries was investigated by X-ray diffraction analysis and scanning electron microscopy, while the organoclay's thermal stability was examined by thermogravimetric analysis. The clay's surface properties induced by the ion-exchange process were followed by measurements of the mineral's zeta potential as a function of pH and surfactant concentration, while the coagulation rates of organoclay suspensions in water and in chloroform were examined using dynamic light scattering. All the results are consistent with showing that the overall characteristics and thus the behavior of the modified MMT particles strongly depend on the alkylammonium surfactant concentration used in the modification process. This, however, has very important implications for any attempt to incorporate the organomodified MMT particles into different media for various applications such as polymer nanocomposite preparation.

Local electrostatic interactions determine the diameter of fusion pores

PubMed Central

Guček, Alenka; Jorgačevski, Jernej; Górska, Urszula; Rituper, Boštjan; Kreft, Marko; Zorec, Robert

2015-01-01

In regulated exocytosis vesicular and plasma membranes merge to form a fusion pore in response to stimulation. The nonselective cation HCN channels are involved in the regulation of unitary exocytotic events by at least 2 mechanisms. They can affect SNARE-dependent exocytotic activity indirectly, via the modulation of free intracellular calcium; and/or directly, by altering local cation concentration, which affects fusion pore geometry likely via electrostatic interactions. By monitoring membrane capacitance, we investigated how extracellular cation concentration affects fusion pore diameter in pituitary cells and astrocytes. At low extracellular divalent cation levels predominantly transient fusion events with widely open fusion pores were detected. However, fusion events with predominately narrow fusion pores were present at elevated levels of extracellular trivalent cations. These results show that electrostatic interactions likely help determine the stability of discrete fusion pore states by affecting fusion pore membrane composition. PMID:25835258

Effect of surfactant types and their concentration on the structural characteristics of nanoclay

NASA Astrophysics Data System (ADS)

Zawrah, M. F.; Khattab, R. M.; Saad, E. M.; Gado, R. A.

2014-03-01

A series of organo-modified nanoclays was synthesized using three different surfactants having different alkyl chain lengths and concentrations [0.5-5.0 cation exchange capacity (CEC)]. These surfactants were Ethanolamine (EA), Cetyltrimethylammoniumbromide (CTAB) and Tetraoctadecylammoniumbromide (TO). The obtained modified nanoclays were characterized by X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM) and compared with unmodified nanoclay. The results of XRD analysis indicated that the basal d-spacing has increased with increasing alkyl chain length and surfactant concentration. From the obtained microstructures of these organo-modified nanoclays, the mechanism of surfactant adsorption was proposed. At relatively low loading of surfactant, most of surfactant entered the spacing by an ion-exchange mechanism and is adsorbed onto the interlayer cation sites. When the concentration of the surfactant exceeds the CEC of clay, the surfactant molecules then adhere to the surface adsorbed surfactant. Some surfactants entered the interlayers, whereas the others were attached to the clay surface. When the concentration of surfactant increased further beyond 2.0 CEC, the surfactants might occupy the inter-particle space within the house-of-cards aggregate structure.

Effects of fire temperature on the physical and chemical characteristics of the ash from two plots of Cork oak (Quercus Suber)

USGS Publications Warehouse

Ubeda, X.; Pereira, P.; Outeiro, L.; Martin, D.A.

2009-01-01

Cork oak, (Quercus suber) is widely distributed in the Mediterranean region, an area subject to frequent fires. The ash produced by burning can have impacts on the soil status and water resources that can differ according to the temperature reached during fire and the characteristics of the litter, defined as the dead organic matter accumulated on the soil surface prior to the fire. The aim of this work is to determine the physical and chemical characteristics of ash produced in laboratory experiments to approximate conditions typical of fires in this region. The litter of Quercus suber collected from two different plots on the Iberian Peninsula, Mas Bassets (Catalonia) and Albufeira (Portugal), was combusted at different temperatures for 2h. We measured Mass Loss (ML per cent), ash colour and CaCO3 content, pH, Electrical Conductivity (EC) and the major cations (Ca2+, Mg2+, K+ and Na+) released from ash slurries created by mixing ash with deionized water. The results showed that ML per cent is higher at all temperatures in Albufeira samples compared to Mas Bassets samples, except at 550??C, and the rate of loss increases faster with temperature than the Mas Bassets samples. At 150??C the ash colour is yellowish, becoming reddish at 200- 250??C and black at 300??C. Above 400??C the ash is grey/white. This thermal degradation is mostly observed in Albufeira litter. The formation of CaCO3 was identified at a lower temperature in Albufeira litter. At temperatures <300??C, pH and EC values are lower, rising at higher temperatures, especially in Albufeira slurries. The concentration of cations at lower temperatures does not differ substantially from the unburned sample except for Mg2+. The cation concentration increases at medium temperatures and decrease at higher temperatures, especially the concentration of divalent cations. The monovalent cations showed a larger concentration at moderate temperatures, mainly in Albufeira ash slurries. The analysis of the Ca:Mg ratio also showed that for the same temperature, a higher severity results for Albufeira litter. Potential negative effects on soil properties are observed at medium and higher temperatures. These negative effects include a higher percentage of mass loss, meaning more soil may be exposed to erosion, higher pH values and greater cation release from ash, especially monovalalent cations (K+,Na+) in higher proportions than the divalent ions (Ca2+, Mg2+), that can lead to impacts on soil physical properties like aggregate stability. Furthermore, the ions in ash may alter soil chemistry which may be detrimental to some plants thus altering the recovery of these ecosystems after fire. Low intensity prescribed fire can be a useful tool to land management in these sites, due to the reduced effects of fire temperatures on the physical and chemical properties of surface litter, and can reduce the risk of high temperature wildland fires by reducing fuel loadings. From the perspective of water resources, lower fire temperatures produce fewer impacts on the chemistry of overland flow and there is less probability that the soil surface will be eroded. Copyright ?? 2009 John Wiley & Sons, Ltd.

On the time behaviour of the concentration of pyrazinium radical cations in the early stage of the Maillard reaction

NASA Astrophysics Data System (ADS)

Stoesser, Reinhard; Klein, Jeannette; Peschke, Simone; Zehl, Andrea; Cämmerer, Bettina; Kroh, Lothar W.

2007-08-01

During the early stage of the Maillard reaction pyrazinium radical cations were detected by ESR within the reaction system D-glucose/glycine. The spectra were characterized by completely resolved hyperfine structure. The partial pressure of oxygen and the radical concentrations were measured directly in the reaction mixture by ESR using solutions of the spin probe TEMPOL and of DPPH, respectively. There are quantitative and qualitative relations of the actual concentration of the radical ions to the partial pressure of oxygen, the temperature-time regime and the mechanical mixing of the reaction system. These macroscopic parameters significantly affect both the induction period and the velocity of the time-dependent formation of free radicals. From in situ variations of p(O 2) and p(Ar) including the connected mixing effects caused by the passing the gases through the reaction mixture, steric and chemical effects of the stabilization of the radical ions were established. The determination of suitable and relevant conditions for stabilization and subsequent radical reactions contributes to the elucidation of the macroscopically known antioxidant activity of Maillard products.

Ion pair and solvation dynamics of [Bmim][BF4 ] + water system.

PubMed

Cascão, João; Silva, Wagner; Ferreira, Ana S D; Cabrita, Eurico J

2018-02-01

In this work, 1-butyl-3-methylimidazolium tetrafluoroborate/water mixtures were analysed over the whole water composition (x w ) in order to study the rotational and translational behaviour of the ions. We employed a multinuclear NMR approach to determine anion/cation/water diffusion coefficients and longitudinal relaxation rates at different water content. In neat ionic liquids (IL), the cation diffuses faster than the anion, and at low x w , anions and cations share almost the same diffusion coefficient, but above a critical water concentration, the anion begins to diffuse faster than the cation. We identified this composition as approximately 10% x w where the ions share the same diffusion coefficient. We found that the water at this composition seems to have a much more dramatic effect in the rotational diffusion of the anion that decreases substantially and approaches that of the anion in the diluted IL. Translational and rotational dynamics of the ions suggest that water is first incorporated in pockets in the nanostructure of the IL allowing the ions to maintain most of the cation/anion interactions present in neat IL but already disrupting some anion/cation interactions due to preferential interaction with the anion. HOESY and NOESY data show that water displays contacts both with the cation and the anion in a positive NOE regime in contrary to the negative regime found for the cation/anion and cation/cation cross-relaxation. This is in accordance with the high relative diffusion coefficient of water and suggests that water molecules can exchange between preferential location sites that allow water to maintain contacts both with the anion and cation. Copyright © 2017 John Wiley & Sons, Ltd.

Effects of multivalent cations on cell wall-associated acid phosphatase activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tu, S.I.; Brouillette, J.N.; Nagahashi, G.

1988-09-01

Primary cell walls, free from cytoplasmic contamination were prepared from corn (Zea mays L.) roots and potato (Solanum tuberosum) tubers. After EDTA treatment, the bound acid phosphatase activities were measured in the presence of various multivalent cations. Under the conditions of minimized Donnan effect and at pH 4.2, the bound enzyme activity of potato tuber cell walls (PCW) was stimulated by Cu/sup 2 +/, Mg/sup 2 +/, Za/sup 2 +/, and Mn/sup 2 +/; unaffected by Ba/sup 2 +/, Cd/sup 2 +/, and Pb/sup 2 +/; and inhibited by Al/sup 3 +/. The bound acid phosphatase of PCW was stimulatedmore » by a low concentration but inhibited by a higher concentration of Hg/sup 2 +/. On the other hand, in the case of corn root cells walls (CCW), only inhibition of the bound acid phosphatase by Al/sup 3 +/ and Hg/sup 2 +/ was observed. Kinetic analyses revealed that PCW acid phosphatase exhibited a negative cooperativity under all employed experimental conditions except in the presence of Mg/sup 2 +/. In contrast, CCW acid phosphatase showed no cooperative behavior. The presence of Ca/sup 2 +/ significantly reduced the effects of Hg/sup 2 +/ or Al/sup 3 +/, but not Mg/sup 2 +/, to the bound cell wall acid phosphatases. The salt solubilized (free) acid phosphatases from both PCW and CCW were not affected by the presence of tested cations except for Hg/sup 2 +/ or Al/sup 3 +/ which caused a Ca/sup 2 +/-insensitive inhibition of the enzymes. The induced stimulation or inhibition of bound acid phosphatases was quantitatively related to cation binding in the cell wall structure.« less

Does Cation Size Affect Occupancy and Electrostatic Screening of the Nucleic Acid Ion Atmosphere?

PubMed Central

2016-01-01

Electrostatics are central to all aspects of nucleic acid behavior, including their folding, condensation, and binding to other molecules, and the energetics of these processes are profoundly influenced by the ion atmosphere that surrounds nucleic acids. Given the highly complex and dynamic nature of the ion atmosphere, understanding its properties and effects will require synergy between computational modeling and experiment. Prior computational models and experiments suggest that cation occupancy in the ion atmosphere depends on the size of the cation. However, the computational models have not been independently tested, and the experimentally observed effects were small. Here, we evaluate a computational model of ion size effects by experimentally testing a blind prediction made from that model, and we present additional experimental results that extend our understanding of the ion atmosphere. Giambasu et al. developed and implemented a three-dimensional reference interaction site (3D-RISM) model for monovalent cations surrounding DNA and RNA helices, and this model predicts that Na+ would outcompete Cs+ by 1.8–2.1-fold; i.e., with Cs+ in 2-fold excess of Na+ the ion atmosphere would contain an equal number of each cation (Nucleic Acids Res.2015, 43, 8405). However, our ion counting experiments indicate that there is no significant preference for Na+ over Cs+. There is an ∼25% preferential occupancy of Li+ over larger cations in the ion atmosphere but, counter to general expectations from existing models, no size dependence for the other alkali metal ions. Further, we followed the folding of the P4–P6 RNA and showed that differences in folding with different alkali metal ions observed at high concentration arise from cation–anion interactions and not cation size effects. Overall, our results provide a critical test of a computational prediction, fundamental information about ion atmosphere properties, and parameters that will aid in the development of next-generation nucleic acid computational models. PMID:27479701

Ion-exclusion chromatography with conductimetric detection of aliphatic carboxylic acids on a weakly acidic cation-exchange resin by elution with benzoic acid-beta-cyclodextrin.

PubMed

Tanaka, Kazuhiko; Mori, Masanobu; Xu, Qun; Helaleh, Murad I H; Ikedo, Mikaru; Taoda, Hiroshi; Hu, Wenzhi; Hasebe, Kiyoshi; Fritz, James S; Haddad, Paul R

2003-05-16

In this study, an aqueous solution consisting of benzoic acid with low background conductivity and beta-cyclodextrin (beta-CD) of hydrophilic nature and the inclusion effect to benzoic acid were used as eluent for the ion-exclusion chromatographic separation of aliphatic carboxylic acids with different pKa values and hydrophobicity on a polymethacrylate-based weakly acidic cation-exchange resin in the H+ form. With increasing concentration of beta-cyclodextrin in the eluent, the retention times of the carboxylic acids decreased due to the increased hydrophilicity of the polymethacrylate-based cation-exchange resin surface from the adsorption of OH groups of beta-cyclodextrin. Moreover, the eluent background conductivity decreased with increasing concentration of beta-cyclodextrin in 1 mM benzoic acid, which could result in higher sensitivity for conductimetric detection. The ion-exclusion chromatographic separation of carboxylic acids with high resolution and sensitivity was accomplished successfully by elution with a 1 mM benzoic acid-10 mM cyclodextrin solution without chemical suppression.

Ion sensors based on novel fiber organic electrochemical transistors for lead ion detection.

PubMed

Wang, Yuedan; Zhou, Zhou; Qing, Xing; Zhong, Weibing; Liu, Qiongzhen; Wang, Wenwen; Li, Mufang; Liu, Ke; Wang, Dong

2016-08-01

Fiber organic electrochemical transistors (FECTs) based on polypyrrole and nanofibers have been prepared for the first time. FECTs exhibited excellent electrical performances, on/off ratios up to 10(4) and low applied voltages below 2 V. The ion sensitivity behavior of the fiber organic electrochemical transistors was investigated. It exhibited that the transfer curve of FECTs shifted to lower gate voltage with increasing cations concentration, the sensitivity reached to 446 μA/dec in the 10(-5)-10(-2) M Pb(2+) concentration range. The ion selective properties of the FECTs have also been systematically studied for the detection of potassium, calcium, aluminum, and lead ions. The devices with different cations showed great difference in response curves. It was suitable for selectively monitoring Pb(2+) with respect to other cations. The results indicated FECTs were very effective for electrochemical sensing of lead ion, which opened a promising perspective for wearable electronics in healthcare and biological application. Graphical Abstract The schematic diagram of fiber organic electrochemical transistors based on polypyrrole and nanofibers for ion sensing.

First-principles investigations into the thermodynamics of cation disorder and its impact on electronic structure and magnetic properties of spinel Co(Cr1-x Mn x )2O4

NASA Astrophysics Data System (ADS)

Das, Debashish; Ghosh, Subhradip

2017-02-01

Cation disorder over different crystallographic sites in spinel oxides is known to affect their properties. Recent experiments on Mn doped multiferroic \\text{CoC}{{\\text{r}}2}{{\\text{O}}4} indicate that a possible distribution of Mn atoms among tetrahedrally and octahedrally coordinated sites in the spinel lattice give rise to different variations in the structural parameters and saturation magnetisations in different concentration regimes of Mn atoms substituting the Cr. A composition dependent magnetic compensation behaviour points to the role conversions of the magnetic constituents. In this work, we have investigated the thermodynamics of cation disorder in \\text{Co}{{≤ft(\\text{C}{{\\text{r}}1-x}\\text{M}{{\\text{n}}x}\\right)}2}{{\\text{O}}4} system and its consequences on the structural, electronic and magnetic properties, using results from first-principles electronic structure calculations. We have computed the variations in the cation-disorder as a function of Mn concentration and the temperature and found that at the annealing temperature of the experiment many of the systems exhibit cation disorder. Our results support the interpretations of the experimental results regarding the qualitative variations in the sub-lattice occupancies and the associated magnetisation behaviour, with composition. We have analysed the variations in structural, magnetic and electronic properties of this system with variations in the compositions and the degree of cation disorder from the variations in their electronic structures and by using the ideas from crystal field theory. Our study provides a complete microscopic picture of the effects that are responsible for composition dependent behavioural differences of the properties of this system. This work lays down a general framework, based upon results from first-principles calculations, to understand and analyse the substitutional magnetic spinel oxides A{{≤ft({{B}1-x}{{C}x}\\right)}2}{{\\text{O}}4} in presence of cation disorder.

Characterization of the cation-binding capacity of a potassium-adsorption filter used in red blood cell transfusion.

PubMed

Suzuki, Takao; Muto, Shigeaki; Miyata, Yukio; Maeda, Takao; Odate, Takayuki; Shimanaka, Kimio; Kusano, Eiji

2015-06-01

A K(+) -adsorption filter was developed to exchange K(+) in the supernatant of stored irradiated red blood cells with Na(+) . To date, however, the filter's adsorption capacity for K(+) has not been fully evaluated. Therefore, we characterized the cation-binding capacity of this filter. Artificial solutions containing various cations were continuously passed through the filter in 30 mL of sodium polystyrene sulfonate at 10 mL/min using an infusion pump at room temperature. The cation concentrations were measured before and during filtration. When a single solution containing K(+) , Li(+) , H(+) , Mg(2+) , Ca(2+) , or Al(3+) was continuously passed through the filter, the filter adsorbed K(+) and the other cations in exchange for Na(+) in direct proportion to the valence number. The order of affinity for cation adsorption to the filter was Ca(2+) >Mg(2+) >K(+) >H(+) >Li(+) . In K(+) -saturated conditions, the filter also adsorbed Na(+) . After complete adsorption of these cations on the filter, their concentration in the effluent increased in a sigmoidal manner over time. Cations that were bound to the filter were released if a second cation was passed through the filter, despite the different affinities of the two cations. The ability of the filter to bind cations, especially K(+) , should be helpful when it is used for red blood cell transfusion at the bedside. The filter may also be useful to gain a better understanding of the pharmacological properties of sodium polystyrene sulfonate. © 2015 The Authors. Therapeutic Apheresis and Dialysis © 2015 International Society for Apheresis.

The influence of natural organic matter and cations on the rejection of endocrine disrupting and pharmaceutically active compounds by nanofiltration.

PubMed

Comerton, Anna M; Andrews, Robert C; Bagley, David M

2009-02-01

The impact of natural organic matter (NOM) and cations on the rejection of five endocrine disrupting compounds (EDCs) and pharmaceutically active compounds (PhACs) (acetaminophen, carbamazepine, estrone, gemfibrozil, oxybenzone) by nanofiltration (NF) was examined. The water matrices included membrane bioreactor (MBR) effluent, Lake Ontario water and laboratory-prepared waters modelled to represent the characteristics of the Lake Ontario water. The impact of cations in natural waters on compound rejection was also examined by doubling the natural cation concentration (calcium, magnesium, sodium) in both the Lake Ontario water and the MBR effluent. The presence of Suwannee River NOM spiked into laboratory-grade water was found to cause an increase in compound NF rejection. In addition, the presence of cations alone in laboratory-grade water did not have a significant impact on rejection with the exception of the polar compound gemfibrozil. However, when cation concentration in natural waters was increased, a significant decrease in the rejection of EDCs and PhACs was observed. This suggests that the presence of cations may result in a reduction in the association of EDCs and PhACs with NOM.

Conformational effects on cationization of poly(ethylene glycol) by alkali metal ions in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

NASA Astrophysics Data System (ADS)

Shimada, Kayori; Matsuyama, Shigetomo; Saito, Takeshi; Kinugasa, Shinichi; Nagahata, Ritsuko; Kawabata, Shin-Ichirou

2005-12-01

Conformational effects of polymer chains on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) were studied by using an equimolar mixture of uniform poly(ethylene glycol)s (PEGs) and by molecular dynamics simulations. Uniform PEGs with degrees of polymerization n = 8-39 were separated from commercial PEG samples by preparative supercritical fluid chromatography. MALDI-TOFMS spectra of an equimolar mixture of the uniform PEGs in aqueous ethanol were measured by adding a mixture of 2,5-dihydroxybenzoic acid (as a matrix reagent) and five alkali metal chlorides (LiCl, NaCl, KCl, RbCl, and CsCl). After optimization of the matrix concentration and laser power, five types of adduct cationized by Li+, Na+, K+, Rb+, and Cs+ could be identified simultaneously in the same spectrum. In the lower molecular-mass region around 103, the spectral intensity increase rapidly with increasing molecular mass of PEG; this rapid increase in the spectral intensity started at a lower molecular mass for smaller adduct cations. Molecular dynamics simulations were used to calculated the affinity of PEG for the adduct cations. These experimental and simulated results showed that the observed spectral intensities in MALDI-TOFMS were markedly affected by the species of adduct cations and the degree of polymerization of the PEG, and that they were dependent on the stability of the PEG-cation complex.

Influence of cations on the partition behavior of perfluoroheptanoate (PFHpA) and perfluorohexanesulfonate (PFHxS) on wastewater sludge.

PubMed

Wang, Fei; Shih, Kaimin; Ma, Ruowei; Li, Xiao-yan

2015-07-01

The effects of different cations on the sorption behavior of PFHpA and PFHxS on two types of sludge were investigated in this study. The sodium and potassium ions did not significantly affect PFHpA and PFHxS sorption on different sludge. For calcium and magnesium, the sorption amount of PFAS increased with calcium and magnesium concentration increasing from 1 to 30 mM and then decreased with those increasing from 30 to 100 mM. The sorption level of PFHxS or PFHpA greatly increased with increasing Al3+ and Fe3+ cation concentrations due to the strong sorption and coagulation effects by the formation of aluminum hydroxide (or ferric hydroxide) colloids or precipitates. After the organics in sludge has been removed by thermal treatment, the PFAS sorption on sludge was greatly reduced. Such finding indicated that sorption to organic matter is more important for anionic PFASs than adsorption to mineral surfaces. However, due to the higher content of biological organics, a secondary activated sludge has higher affinity toward PFAS species than chemically enhanced primary treatment sludge. It indicated that the organic types in sludge were also crucial to the sorption levels of PFASs by sludge. Copyright © 2015 Elsevier Ltd. All rights reserved.

Quantitative analysis of changes in cell shape of Amoeba proteus during locomotion and upon responses to salt stimuli.

PubMed

Ueda, T; Kobatake, Y

1983-09-01

A new parameter expressing the complexity of cell shape defined as (periphery)2/(area) in 2D projection was found useful for a quantitative analysis of changes in the cell shape of Amoeba proteus and potentially of any amoeboid cells. During locomotion the complexity and the motive force of the protoplasmic streaming in amoeba varied periodically, and the Fourier analysis of the two showed a similar pattern in the power spectrum, giving a rather broad peak at about 2.5 X 10(-3) Hz. The complexity increased mainly due to elongation of the cell as external Ca2+ increased. This effect was blocked by La3+, half the inhibition being attained at 1/200 amount of the coexisting Ca2+. On the other hand, the complexity decreased due to rounding up of the cell as the concentration of other cations, such as Sr2+, Mg2+, Co2+, Ni2+, Na+, K+ etc., increased. Irrespective of the opposite effects of Ca2+ and other cations on the cell shape, the ATP concentration in amoeba decreased in both cases with increase of all these cations. The irregularity in amoeboid motility is discussed in terms of a dynamic system theory.

Precipitation chemistry at the Marcell Experimental Forest in north central Minnesota

Treesearch

Elon S. Verry

1983-01-01

Concentration (milligrams and microequivalents per liter) values are presented for major ions occurring in rain and snow from July 1978 to July 1980. Ammonium, sodium, and calcium are the largest equivalent weight cations which are largely balanced by sulfate and nitrate anions. Hydrogen is the fourth most abundant cation; but high combined concentrations of other...

The role of modifier cation field strength, oxygen speciation and network cation interaction in pressure-induced structural changes of silicate melts and glasses: 27Al, and 11B MAS NMR studies

NASA Astrophysics Data System (ADS)

Bista, S.; Stebbins, J. F.

2017-12-01

In aluminosilicate melts and glasses, both non-bridging oxygen content (NBO) and modifier cation field strength (Mg>Ca>Na>K) are known to facilitate network cation (e.g. Al, B) coordination increase with pressure. However, the role of these two compositional parameters in pressure-induced structural changes is derived from data for a limited set of compositions, where effects of the interaction between these parameters is less understood. For example, the effects of NBO are largely based on studies of Na and K aluminosilicate glasses, but effects of geologically important, higher field strength modifier cations such as Mg2+ and Fe2+ could well be significantly different. In this study, we look at a wide compositional range of Na, Ca and Mg aluminosilicate glasses (quenched from high pressure melts near to the glass transition temperature) to understand the roles of NBO and modifier cation field strength that can extend our view of processes important for silicate melts common in nature. Our results show that the role of NBO in pressure-induced structural changes varies systematically with increasing field strength of the modifier cation. In Na aluminosilicate glasses recovered from 1.5 to 3 GPa, large increases in average aluminum coordination are observed in glasses with high NBO content, while no detectable increases are seen for low nominal NBO (jadeite). In contrast, Mg aluminosilicate glasses with both high and low NBO show similar, large increases in average aluminum coordination with increasing pressure. The behaviors of Ca aluminosilicates fall between those of Na and Mg-rich glasses. We have also looked at interactions between different network forming cations in pressure-induced structural changes in low NBO Ca-aluminoborosilicate glasses with varying B/Si. Both aluminum and boron increase dramatically in coordination in these compositions 1.5 to 3 GPa. Increases in both average aluminum coordination and densification are larger in compositions containing higher boron concentrations, suggesting an interaction between boron and aluminum network cations in pressure-induced structural changes.

Cation Coordination Alters the Conformation of a Thrombin-Binding G-Quadruplex DNA Aptamer That Affects Inhibition of Thrombin.

PubMed

Zavyalova, Elena; Tagiltsev, Grigory; Reshetnikov, Roman; Arutyunyan, Alexander; Kopylov, Alexey

2016-10-01

Thrombin-binding aptamers are promising anticoagulants. HD1 is a monomolecular antiparallel G-quadruplex with two G-quartets linked by three loops. Aptamer-thrombin interactions are mediated with two TT-loops that bind thrombin exosite I. Several cations were shown to be coordinated inside the G-quadruplex, including K + , Na + , NH 4 + , Ba 2+ , and Sr 2+ ; on the contrary, Mn 2+ was coordinated in the grooves, outside the G-quadruplex. K + or Na + coordination provides aptamer functional activity. The effect of other cations on aptamer functional activity has not yet been described, because of a lack of relevant tests. Interactions between aptamer HD1 and a series of cations were studied. A previously developed enzymatic method was applied to evaluate aptamer inhibitory activity. The structure-function correlation was studied using the characterization of G-quadruplex conformation by circular dichroism spectroscopy. K + coordination provided the well-known high inhibitory activity of the aptamer, whereas Na + coordination supported low activity. Although NH 4 + coordination yielded a typical antiparallel G-quadruplex, no inhibitory activity was shown; a similar effect was observed for Ba 2+ and Sr 2+ coordination. Mn 2+ coordination destabilized the G-quadruplex that drastically diminished aptamer inhibitory activity. Therefore, G-quadruplex existence per se is insufficient for aptamer inhibitory activity. To elicit the nature of these effects, we thoroughly analyzed nuclear magnetic resonance (NMR) and X-ray data on the structure of the HD1 G-quadruplex with various cations. The most reasonable explanation is that cation coordination changes the conformation of TT-loops, affecting thrombin binding and inhibition. HD1 counterparts, aptamers 31-TBA and NU172, behaved similarly with some distinctions. In 31-TBA, an additional duplex module stabilized antiparallel G-quadruplex conformation at high concentrations of divalent cations; whereas in NU172, a different sequence of loops in the G-quadruplex module provided an equilibrium of antiparallel and parallel G-quadruplexes that shifted with cation binding. In conclusion, structures of G-quadruplex aptamers are flexible enough and are fine-tuned with different cation coordination.

Hydrophobically-associating cationic polymers as micro-bubble surface modifiers in dissolved air flotation for cyanobacteria cell separation.

PubMed

Yap, R K L; Whittaker, M; Diao, M; Stuetz, R M; Jefferson, B; Bulmus, V; Peirson, W L; Nguyen, A V; Henderson, R K

2014-09-15

Dissolved air flotation (DAF), an effective treatment method for clarifying algae/cyanobacteria-laden water, is highly dependent on coagulation-flocculation. Treatment of algae can be problematic due to unpredictable coagulant demand during blooms. To eliminate the need for coagulation-flocculation, the use of commercial polymers or surfactants to alter bubble charge in DAF has shown potential, termed the PosiDAF process. When using surfactants, poor removal was obtained but good bubble adherence was observed. Conversely, when using polymers, effective cell removal was obtained, attributed to polymer bridging, but polymers did not adhere well to the bubble surface, resulting in a cationic clarified effluent that was indicative of high polymer concentrations. In order to combine the attributes of both polymers (bridging ability) and surfactants (hydrophobicity), in this study, a commercially-available cationic polymer, poly(dimethylaminoethyl methacrylate) (polyDMAEMA), was functionalised with hydrophobic pendant groups of various carbon chain lengths to improve adherence of polymer to a bubble surface. Its performance in PosiDAF was contrasted against commercially-available poly(diallyl dimethyl ammonium chloride) (polyDADMAC). All synthesised polymers used for bubble surface modification were found to produce positively charged bubbles. When applying these cationic micro-bubbles in PosiDAF, in the absence of coagulation-flocculation, cell removals in excess of 90% were obtained, reaching a maximum of 99% cell removal and thus demonstrating process viability. Of the synthesised polymers, the polymer containing the largest hydrophobic functionality resulted in highly anionic treated effluent, suggesting stronger adherence of polymers to bubble surfaces and reduced residual polymer concentrations. Copyright © 2014 Elsevier Ltd. All rights reserved.

Sulfates Dramatically Stabilize a Salt-Dependent Type of Glucagon Fibrils

PubMed Central

Pedersen, Jesper Søndergaard; Flink, James M.; Dikov, Dantcho; Otzen, Daniel Erik

2006-01-01

Recent work suggests that protein fibrillation mechanisms and the structure of the resulting protein fibrils are very sensitive to environmental conditions such as temperature and ionic strength. Here we report the effect of several inorganic salts on the fibrillation of glucagon. At acidic pH, fibrillation is much less influenced by cations than anions, for which the effects follow the electroselectivity series; e.g., the effect of sulfate is ∼65-fold higher than that of chloride per mole. Increased salt concentrations generally accelerate fibrillation, but result in formation of an alternate type of fibrils. Stability of these fibrils is highly affected by changes in anion concentration; the apparent melting temperature is increased by ∼22°C for any 10-fold concentration increase, indicating that the fibrils cannot exist without anions. In contrast, fibrillation under alkaline conditions is more affected by cations than anions. We conclude that ions interact directly as structural ligands with glucagon fibrils where they coordinate charges and assist in formation of new fibrils. As ex vivo amyloid plaques often contain large amounts of highly sulfated organic molecules, the specific effects of sulfate ions on glucagon may have general relevance in the study of amyloidosis and other protein deposition diseases. PMID:16533857

Role of charge screening and delocalization for lipophilic cation permeability of model and mitochondrial membranes.

PubMed

Trendeleva, Tatiana A; Sukhanova, Evgenia I; Rogov, Anton G; Zvyagilskaya, Renata A; Seveina, Inna I; Ilyasova, Tatiana M; Cherepanov, Dmitry A; Skulachev, Vladimir P

2013-09-01

The effects of the mitochondria-targeted lipophilic cation dodecyltriphenylphosphonium (C12TPP, the charge is delocalized and screened by bulky hydrophobic residues) and those of lipophilic cations decyltriethylammonium bromide and cetyltrimethylammonium bromide (C10TEA and C16TMA, the charges are localized and screened by less bulky residues) on bilayer planar phospholipid membranes and tightly-coupled mitochondria from the yeast Yarrowia lipolytica have been compared. In planar membranes, C12TPP was found to generate a diffusion potential as if it easily penetrates these membranes. In the presence of palmitate, C12TPP induced H(+) permeability like plastoquinonyl decyltriphenilphosphonium that facilitates transfer of fatty acid anions (Severin et al., PNAS, 2010, 107, 663-668). C12TPP was shown to stimulate State 4 respiration of mitochondria and caused a mitochondrial membrane depolarization with a half-maximal effect at 6μM. Besides, C12TPP profoundly potentiated the uncoupling effect of endogenous or added fatty acids. C10TEA and C16TMA inhibited State 4 respiration and decreased the membrane potential, though at much higher concentrations than C12TPP, and they did not promote the uncoupling action of fatty acids. These relationships were modeled by molecular dynamics. They can be explained by different membrane permeabilities for studied cations, which in turn are due to different availabilities of the positive charge in these cations to water dipoles. Copyright © 2012 Elsevier B.V. All rights reserved.

Persister cells, the biofilm matrix and tolerance to metal cations in biofilm and planktonic Pseudomonas aeruginosa.

PubMed

Harrison, Joe J; Turner, Raymond J; Ceri, Howard

2005-07-01

In this study, we examined Pseudomonas aeruginosa ATCC 27853 biofilm and planktonic cell susceptibility to metal cations. The minimum inhibitory concentration (MIC), the minimum bactericidal concentration (MBC) required to eradicate 100% of the planktonic population (MBC 100), and the minimum biofilm eradication concentration (MBEC) were determined using the MBEC trade mark-high throughput assay. Six metals - Co(2+), Ni(2+), Cu(2+), Zn(2+), Al(3+) and Pb(2+)- were each tested at 2, 4, 6, 8, 10 and 27 h of exposure to biofilm and planktonic cultures grown in rich or minimal media. With 2 or 4 h of exposure, biofilms were approximately 2-25 times more tolerant to killing by metal cations than the corresponding planktonic cultures. However, by 27 h of exposure, biofilm and planktonic bacteria were eradicated at approximately the same concentration in every instance. Viable cell counts evaluated at 2 and 27 h of exposure revealed that at high concentrations, most of the metals assayed had killed greater than 99.9% of biofilm and planktonic cell populations. The surviving cells were propogated in vitro and gave rise to biofilm and planktonic cultures with normal sensitivity to metals. Further, retention of copper by the biofilm matrix was investigated using the chelator sodium diethlydithiocarbamate. Formation of visible brown metal-chelates in biofilms treated with Cu(2+) suggests that the biofilm matrix may coordinate and sequester metal cations from the aqueous surroundings. Overall, our data suggest that both metal sequestration in the biofilm matrix and the presence of a small population of 'persister' cells may be contributing factors in the time-dependent tolerance of both planktonic cells and biofilms to high concentrations of metal cations.

Reduction of non-enzymatic browning of orange juice and semi-concentrates by removal of reaction substrate.

PubMed

Sharma, Satish K; Juyal, Shashibala; Rao, V K; Yadav, V K; Dixit, A K

2014-07-01

A study was conducted to standardize the technology for the removal of amino acids (one of the browning reaction substrates) from sweet orange cv. Malta Common juice to reduce colour and quality deterioration in single strength juice and during subsequent concentration. Juice of sweet orange (Citrus sinensis) cv. Malta Common fruits was extracted by screw type juice extractor, preserved in 500 ppm SO2 and clarified by using "Pectinase CCM" enzyme (0.2% for 2 h at 50 ± 2 °C). For removal of amino acids juice was passed under gravity through a glass column packed with an acidic cation exchange resin (CER), Dowex-50 W and quantity to be treated in one lot was standardized. The CER treated and untreated juices were concentrated to 15 and 30°Brix in a rotary vacuum evaporator. Results indicate that 121 ml of orange juice when passed through a glass column (5 cm internal diameter) packed with cation exchange resin (Dowex-50 W) upto a height of 8 cm, could remove about 98.4% of the amino acids with minimum losses in other juice constituents. With cation exchange resin treatment, the non-enzymatic browning and colour deterioration of orange juice semi-concentrates was reduced to about 3 folds in comparison to untreated counterparts. The retention of vitamin C and sugars was also better in semi-concentrates prepared from cation exchange resin treated juice. Thus, cation exchange resin treatment of orange juice prior to concentration and storage is highly beneficial in reduction of non-enzymatic browning, colour deterioration and retention of nutritional, sensory quality of product during preparation and storage.

Studies on the interactions between purified bovine caseins and alkaline-earth-metalions

PubMed Central

Dickson, I. R.; Perkins, D. J.

1971-01-01

1. Alkaline-earth-metal cations at low concentrations form soluble complexes with bovine caseins. The relative order of binding capacities is: Mg2+>Ca2+>Ba2+>Sr2+. 2. The cations interact with both free ionized carboxyl groups of aspartic acid and glutamic acid and with monoester phosphate groups covalently bound to serine and threonine; at low concentrations of the cations interactions are predominantly with the phosphate groups. 3. The order of binding capacities for purified components of the casein complex is: αs1-casein>β-casein>κ-casein. PMID:5166590

Urban Effects on Microbial Processes and Food Webs in Coastal Watershed Streams

EPA Science Inventory

We conducted a stream survey in the Narragansett Bay Watershed that targeted a gradient of development intensity and examined how associated changes in nutrients, carbon, and stressors affected periphyton and macroinvertebrates. Concentrations of nutrients, cations, and anions we...

Determination of Halide Concentrations at the Interface of Zwitterionic Micelles by Chemical Trapping: Influence of the Orientation of the Dipole and the Nature of the Cation.

PubMed

Cuccovia; Romsted; Chaimovich

1999-12-01

The interfacial concentrations of Cl(-) and Br(-) in aqueous zwitterionic micelles were determined by chemical trapping by analyzing product yields from spontaneous dediazoniation of micelle-bound 2,6-dimethyl-4-hexadecylbenzenediazonium ion. Interfacial concentrations of Cl(-) and Br(-) in 3-(N-hexadecyl-N, N-dimethylammonio) propane sulfonate, HPS, micelles were higher than in bulk solutions prepared with Li(+), Na(+), Rb(+), Cs(+), tetramethylammonium (TMA(+)), Mg(+2), and Ca(+2) salts. In contrast, the interfacial concentrations of Cl(-) and Br(-) were generally lower than in bulk solution in hexadecylphosphoryl choline, HDPC, micelles for all salts except Mg(+2) and Ca(+2). In both HPS and HDPC micelles the interfacial concentration of Br(-) was higher than that of Cl(-), showing that binding is anion selective. The cation had a large effect on the interfacial concentration of halide ions with HDPC micelles decreasing in the order Ca(2+) > Mg(2+) > Li(+) > Na(+) > K(+) > Cs(+) > Rb(+) > TMA(+). These results are the first direct and extensive determination of local halide ion concentration at the surface of zwitterionic micelles, and they demonstrate that chemical trapping methodology will work in membranes at physiologically relevant salt concentrations. Copyright 1999 Academic Press.

Exploration on Bioflocculation of Nannochloropsis oculata Using Response Surface Methodology for Biodiesel Production

PubMed Central

Surendhiran, Duraiarasan; Vijay, Mani

2014-01-01

Harvesting of algal biomass in biodiesel production involves high energy input and cost incurred process. In order to overcome these problems, bioflocculation process was employed and the efficiency of this process was further improved by the addition of a cationic inducer. In this work marine Bacillus subtilis was used for bioflocculation of Nannochloropsis oculata and ZnCl2 as cationic inducer. This study worked under the principle of divalent cationic bridging (DCB) theory. Under temperature stress and high pH, the bacterium produced exopolysaccharide that bound with microalga Nannochloropsis oculata and flocculated them. A maximum efficiency of 95.43% was observed with the optimised RSM parameters—temperature 30.78°C, pH 10.8, flocculation time 6.7 h, bioflocculant size 0.38 mL, and cationic inducer concentration 0.035 mM. The present investigation focused on the cost effective harvesting of microalga on a larger scale for biodiesel production than using toxic, ecofriendly chemical flocculants. PMID:24683320

Zeolite A synthesized from alkaline assisted pre-activated halloysite for efficient heavy metal removal in polluted river water and industrial wastewater.

PubMed

Meng, Qingpeng; Chen, Hong; Lin, Junzhong; Lin, Zhang; Sun, Junliang

2017-06-01

High quality zeolite A was synthesized through a hydrothermal process using alkaline-assisted pre-activated halloysite mineral as the alumina and silica source. The synthesis conditions employed in this study were finely tuned by varying the activating temperature, sodium hydroxide content, water content and Si/Al ratio. The obtained zeolite A showed excellent adsorption properties for both single metal cation solutions and mixed cation solutions when the concentrations of the mixed cations were comparable with those in polluted natural river water and industrial wastewater. High adsorptive capacities for Ag + (123.05mg/g) and Pb 2+ (227.70mg/g) were achieved using the synthesized zeolite A. This observation indicates that the zeolite A synthesized from alkaline-assisted pre-activated halloysite can be used as a low-cost and relatively effective adsorbent to purify heavy metal cation polluted natural river water and industrial wastewater. Copyright © 2016. Published by Elsevier B.V.

[Determination of Chloride Salt Solution by NIR Spectroscopy].

PubMed

Zhang, Bin; Chen, Jian-hong; Jiao, Ming-xing

2015-07-01

Determination of chloride salt solution by near infrared spectrum plays a very important role in Biomedicine. The near infrared spectrum analysis of Sodium chloride, potassium chloride, calcium chloride aqueous solution shows that the concentration change of chloride salt can affect hydrogen bond, resulting in the variation of near infrared spectrum of water. The temperature influence on NIR spectrum has been decreased by choosing reasonable wavelength range and the wavelength where the temperature effects are zero (isosbestic point). Chlorine salt prediction model was established based on partial least squares method and used for predicting the concentration of the chlorine ion. The impact on near infrared spectrum of the cation ionic radius, the number of ionic charge, the complex effect of ionic in water has also discussed in this article and the reason of every factor are analysed. Experimental results show that the temperature and concentration will affect the near-infrared spectrum of the solution, It is found that the effect of temperature plays the dominant role at low concentrations of chlorine salt; rather, the ionic dominates at high concentration. Chloride complexes are formed in aqueous solution, It has an effect on hydrogen bond of water combining with the cations in chlorine salt solution, Comparing different chloride solutions at the same concentration, the destruction effects of chloride complexes and catnions on the hydrogen bond of water increases in the sequences: CaCl2 >NaCl>KC. The modeling result shows that the determination coefficients (R2) = 99.97%, the root mean square error of cross validation (RM- SECV) = 4.51, and the residual prediction deviation (RPD) = 62.7, it meets the daily requirements of biochemical detection accuracy.

Cationic Biomimetic Particles of Polystyrene/Cationic Bilayer/Gramicidin for Optimal Bactericidal Activity.

PubMed

Xavier, Gabriel R S; Carmona-Ribeiro, Ana M

2017-12-02

Nanostructured particles of polystyrene sulfate (PSS) covered by a cationic lipid bilayer of dioctadecyldimethylammonium bromide (DODAB) incorporated gramicidin D (Gr) yielding optimal and broadened bactericidal activity against both Escherichia coli and Staphylococcus aureus . The adsorption of DODAB/Gr bilayer onto PSS nanoparticles (NPs) increased the zeta-average diameter by 8-10 nm, changed the zeta-potential of the NPs from negative to positive, and yielded a narrow size distributions for the PSS/DODAB/Gr NPs, which displayed broad and maximal microbicidal activity at very small concentrations of the antimicrobials, namely, 0.057 and 0.0057 mM DODAB and Gr, respectively. The results emphasized the advantages of highly-organized, nanostructured, and cationic particles to achieve hybrid combinations of antimicrobials with broad spectrum activity at considerably reduced DODAB and Gr concentrations.

Interactions of trace metals with hydrogels and filter membranes used in DET and DGT techniques.

PubMed

Garmo, Oyvind A; Davison, William; Zhang, Hao

2008-08-01

Equilibrium partitioning of trace metals between bulk solution and hydrogels/filter was studied. Under some conditions, trace metal concentrations were higher in the hydrogels or filter membranes compared to bulk solution (enrichment). In synthetic soft water, enrichment of cationic trace metals in polyacrylamide hydrogels decreased with increasing trace metal concentration. Enrichment was little affected by Ca and Mg in the concentration range typically encountered in natural freshwaters, indicating high affinity but low capacity binding of trace metals to solid structure in polyacrylamide gels. The apparent binding strength decreased in the sequence: Cu > Pb > Ni approximately to Cd approximately to Co and a low concentration of cationic Cu eliminated enrichment of weakly binding trace metal cations. The polyacrylamide gels also had an affinity for fulvic acid and/or its trace metal complexes. Enrichment of cationic Cd in agarose gel and hydrophilic polyethersulfone filter was independent of concentration (10 nM to 5 microM) but decreased with increasing Ca/ Mg concentration and ionic strength, suggesting that it is mainly due to electrostatic interactions. However, Cu and Pb were enriched even after equilibration in seawater, indicating that these metals additionally bind to sites within the agarose gel and filter. Compared to the polyacrylamide gels, agarose gel had a lower affinity for metal-fulvic complexes. Potential biases in measurements made with the diffusive equilibration in thin-films (DET) technique, identified by this work, are discussed.

Thermo-responsive triblock copolymer phase transition behaviour in imidazolium-based ionic liquids: Role of the effect of alkyl chain length of cations.

PubMed

Umapathi, Reddicherla; Venkatesu, Pannuru

2017-01-01

Different biophysical techniques such as fluorescence spectroscopy, dynamic light scattering (DLS), viscosity (η) and Fourier transform infrared (FTIR) spectroscopy have been carried out to characterize the effect of imidazolium-based ionic liquids (ILs) on the thermo-responsive triblock copolymer, poly(ethylene glycol)-block-poly(propylene glycol)-block-poly-(ethylene glycol) (PEG-PPG-PEG). In addition, to demonstrate the distinct morphological changes of various self-assembled morphologies, we further employed field emission scanning electron microscope (FESEM). To investigate the effect of alkyl chain length of the cation, concentration of the ILs and the related Hofmeister series on the phase behaviour of PEG-PPG-PEG, we used a series of ILs possessing same Cl - anion and a set of cation [C n mim] + with increasing alkyl chain length of cation such as 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]), 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), 1-hexyl-3-methylimidazolium chloride ([Hmim][Cl]) and 1-decyl-3-methylimidazolium chloride ([Dmim][Cl]). The critical micellization temperature (CMT) of the copolymer in the presence of well hydrated cations is directly correlated to their hydration. The overall specific ranking of ILs in decreasing the CMT of PEG-PPG-PEG in aqueous solution was [Emim][Cl]>[Bmim][Cl]>[Hmim][Cl]>[Dmim][Cl]. The trend of these ILs followed the well-known Hofmeister series of cations of ILs. The present study provides important information about the solution properties that can be helpful to tune the IL or temperature-sensitive copolymer CMT and micelle shapes which are crucial for understanding the drug delivery mechanisms. Copyright © 2016 Elsevier Inc. All rights reserved.

Effect of cationic polyelectrolytes on the performance of paper diagnostics for blood typing.

PubMed

McLiesh, Heather; Sharman, Scot; Garnier, Gil

2015-09-01

We investigated the effect that two common types of cationic polyelectrolytes used in papermaking might have on the performance of paper diagnostics using blood typing as an example. The results were analyzed in terms of red blood cells (RBC) retention and antibody-antigen specificity. Two questions were addressed: (1) can poly(amido-amine) epichlorohydrin (PAE) typically used for paper wet strength affect the diagnostic performance? (2) can high molecular weight cationic polyacrylamide (CPAM) employed as retention aid enhance or affect the selectivity and sensitivity of paper diagnostics? A series of paper varying in type of fibers and drying process were constructed with PAE and tested for blood typing performance. Residual PAE has no significant effect on blood typing paper diagnostics under normal conditions. Positives are unaffected with PAE, while negatives lose slight sharpness as some RBCs are unselectively retained. CPAM, the most common retention aid, can also be used to retain cells and biomolecules on paper. Paper towel was treated with CPAM solutions varying in polymer concentration and charge density and tested for blood typing. We found that CPAM dried on paper can retain RBC. CPAM affects the negative tests by retaining non-specifically individual RBC on fibers. RBC retention increases non-linearly with the CPAM charge density and concentration. As expected, wet CPAM retain RBCs at concentrations higher than 0.1wt%. As paper diagnostics are becoming a reality, more realistic papers than the Whatman filter paper will be engineered. This study provides guidance on how best use the required polymeric wet-strength and retention agents. Crown Copyright © 2015. Published by Elsevier B.V. All rights reserved.

Effects of Physicochemical Factors on the Adhesion to Cellulose Avicel of the Ruminal Bacteria Ruminococcus flavefaciens and Fibrobacter succinogenes subsp. succinogenes.

PubMed

Roger, V; Fonty, G; Komisarczuk-Bony, S; Gouet, P

1990-10-01

Ruminococcus flavefaciens adhered instantly to cellulose, while Fibrobacter succinogenes had the highest percentage of adherent cells after about 25 min of contact between bacteria and cellulose. Adhesion of R. flavefaciens was unaffected by high concentrations of sugars (5%), temperature, pH, oxygen, metabolic inhibitors, and lack of Na. In contrast, the attachment was affected by the removal of divalent cations (Mg and Ca), the presence of cellulose derivatives (methylcellulose and hydroxyethylcellulose), and cystine. Adhesion of F. succinogenes was sensitive to low and high temperatures, high concentrations of glucose and cellobiose (5%), hydroxyethylcellulose (0.1%), redox potential, pH, lack of monovalent cations, and the presence of an inhibitor of membrane ATPases or lasalocid and monensin. Cells of F. succinogenes heated at 100 degrees C no longer were adherent. On the other hand, adhesion was insensitive to the lack of divalent cations (Mg and Ca), the presence of 2,4-dinitrophenol, tetrachlorosalicylanilide, or inhibitors of the electron transfer chains. Adhesion of F. succinogenes seems to be related to the metabolic functions of the cell. External proteins and/or cellulases themselves might play a part in the attachment process. Several mechanisms are probably involved in the adhesion of R. flavefaciens, the main one being the interaction between the large glycocalyx and the divalent cations Ca and Mg. Hydrophobic bonds and enzymes may also be involved.

Spleen-specific suppression of TNF-alpha by cationic hydrogel-delivered antisense nucleotides for the prevention of arthritis in animal models.

PubMed

Dong, Lei; Xia, Suhua; Chen, Huan; Chen, Jiangning; Zhang, Junfeng

2009-09-01

This study developed a transplantable platform based on cationic hydrogels to deliver antisense oligodeoxynucleotides (ASOs) targeting the mRNA of TNF-alpha. Cationic agarose (c-agarose) was obtained by conjugating ethylenediamine to agarose via an N,N'-carbonyldiimidazole (CDI)-activation method. ASO-c-agarose system was constructed by mixing ASO in cationic agarose gel of proper concentration and gelation temperature. In vivo assessment of ASO distribution suggested that the system specifically target to spleen, wherein the c-agarose-delivered ASO had a concentration remarkably 50-fold higher than that of the naked ASO. The distribution of c-agarose-delivered ASO was scarcely detectable in liver and kidney. Next, three types of animal models were setup to evaluate the therapeutic efficacies of ASO-Gel, including the adjuvant-induced arthritis (AA), carrageen/lipopolysaccharide (LPS)-induced arthritis (CLA) and collagen-induced arthritis (CIA) models. The effects of ASO-c-agarose in alleviating inflammation and tissue destruction were evidenced in more than 90% of the testing animals, with decrease of main inflammatory cytokines, lightening of joint swelling and tissue damage, as well as increase in their body weights. All these findings suggest that this highly operable devise for the conveyance of antisense nucleotides together with its spleen-targeting property, could become a useful means of antisense-based therapeutics against rheumatoid arthritis and other diseases.

Ultrasmall cationic superparamagnetic iron oxide nanoparticles as nontoxic and efficient MRI contrast agent and magnetic-targeting tool

PubMed Central

Uchiyama, Mayara Klimuk; Toma, Sergio Hiroshi; Rodrigues, Stephen Fernandes; Shimada, Ana Lucia Borges; Loiola, Rodrigo Azevedo; Cervantes Rodríguez, Hernán Joel; Oliveira, Pedro Vitoriano; Luz, Maciel Santos; Rabbani, Said Rahnamaye; Toma, Henrique Eisi; Poliselli Farsky, Sandra Helena; Araki, Koiti

2015-01-01

Fully dispersible, cationic ultrasmall (7 nm diameter) superparamagnetic iron oxide nanoparticles, exhibiting high relaxivity (178 mM−1s−1 in 0.47 T) and no acute or subchronic toxicity in Wistar rats, were studied and their suitability as contrast agents for magnetic resonance imaging and material for development of new diagnostic and treatment tools demonstrated. After intravenous injection (10 mg/kg body weight), they circulated throughout the vascular system causing no microhemorrhage or thrombus, neither inflammatory processes at the mesentery vascular bed and hepatic sinusoids (leukocyte rolling, adhesion, or migration as evaluated by intravital microscopy), but having been spontaneously concentrated in the liver, spleen, and kidneys, they caused strong negative contrast. The nanoparticles are cleared from kidneys and bladder in few days, whereas the complete elimination from liver and spleen occurred only after 4 weeks. Ex vivo studies demonstrated that cationic ultrasmall superparamagnetic iron oxide nanoparticles caused no effects on hepatic and renal enzymes dosage as well as on leukocyte count. In addition, they were readily concentrated in rat thigh by a magnet showing its potential as magnetically targeted carriers of therapeutic and diagnostic agents. Summarizing, cationic ultrasmall superparamagnetic iron oxide nanoparticles are nontoxic and efficient magnetic resonance imaging contrast agents useful as platform for the development of new materials for application in theranostics. PMID:26251595

Theoretical and experimental studies of water interaction in acetate based ionic liquids.

PubMed

Shi, Wei; Damodaran, Krishnan; Nulwala, Hunaid B; Luebke, David R

2012-12-05

Water interactions in 1-ethyl-3-methylimidazolium acetate ([emim][CH(3)COO]) were studied utilizing classical and ab initio simulation methods. The self-diffusivities for water and the ionic liquid (IL) were studied experimentally using pulse field gradient NMR spectroscopy and correlated with computational results. Water forms hydrogen bonding networks with the ionic liquid, and depending on the concentration of water, there are profound effects on the self-diffusivities of the various species. Both simulation and experiments show that the self-diffusivities for species in the water-[emim][CH(3)COO] system exhibit minima at 40-50 mol% water. Water interaction with the [CH(3)COO](-) anion predominates over the water-water and water-cation interactions at most water concentrations. Simulations further indicate that decreasing water-[CH(3)COO](-) interaction will increase the IL and water self-diffusivities. Self-diffusivities in the water-IL systems are dependent upon the cation in a complex way. Water interactions with [P(4444)][CH(3)COO] are reduced compared to [emim][CH(3)COO]. The [P(4444)](+) cation is bulkier than the [emim](+) cation and has a smaller self-diffusivity, but when water was introduced to [P(4444)] [CH(3)COO], the water-[CH(3)COO](-) hydrogen bonding network in the [P(4444)][CH(3)COO] was much smaller than the one observed in [emim][CH(3)COO].

Soil nutrient bioavailability and nutrient content of pine trees (Pinus thunbergii) in areas impacted by acid deposition in Korea.

PubMed

Yang, Jae E; Lee, Wi-Young; Ok, Yong Sik; Skousen, Jeffrey

2009-10-01

Acid deposition has caused detrimental effects on tree growth near industrial areas of the world. Preliminary work has indicated that concentrations of NO(3-), SO(4)(2-), F( - ) and Al in soil solutions were 2 to 33 times higher in industrial areas compared to non-industrial areas in Korea. This study evaluated soil nutrient bioavailability and nutrient contents of red pine (Pinus thunbergii) needles in forest soils of industrial and non-industrial areas of Korea. Results confirm that forest soils of industrial areas have been acidified mainly by deposition of sulfate, resulting in increases of Al, Fe and Mn and decreases of Ca, Mg and K concentrations in soils and soil solutions. In soils of industrial areas, the molar ratios of Ca/Al and Mg/Al in forest soils were <2, which can lead to lower levels and availability of nutrients for tree growth. The Ca/Al molar ratio of Pinus thunbergii needles on non-industrial sites was 15, while that of industrial areas was 10. Magnesium concentrations in needles of Pinus thunbergii were lower in soils of industrial areas and the high levels of acid cations such as Al and Mn in these soils may have antagonized the uptake of base cations like Mg. Continued acidification can further reduce uptake of base cations by trees. Results show that Mg deficiency and high concentrations of Al and Mn in soil solution can be limiting factors for Pinus thunbergii growth in industrial areas of Korea.

Biochar immobilizes soil-borne arsenic but not cationic metals in the presence of low-molecular-weight organic acids.

PubMed

Alozie, Nneka; Heaney, Natalie; Lin, Chuxia

2018-07-15

A batch experiment was conducted to examine the effects of biochar on the behaviour of soil-borne arsenic and metals that were mobilized by three low-molecular-weight organic acids. In the presence of citric acid, oxalic acid and malic acid at a molar concentration of 0.01M, the surface of biochar was protonated, which disfavours adsorption of the cationic metals released from the soil by organic acid-driven mobilization. In contrast, the oxyanionic As species were re-immobilized by the protonated biochar effectively. Biochar could also immobilize oxyanionic Cr species but not cationic Cr species. The addition of biochar increased the level of metals in the solution due to the release of the biochar-borne metals under attack by LMWOAs via cation exchange. Biochar could also have the potential to enhance reductive dissolution of iron and manganese oxides in the soil, leading to enhanced release of trace elements bound to these oxides. The findings obtained from this study have implications for evaluating the role of biochar in immobilizing trace elements in rhizosphere. Adsorption of cationic heavy metals on biochar in the presence of LMWOAs is unlikely to be a mechanism responsible for the impeded uptake of heavy metals by plants growing in heavy metal-contaminated soils. Copyright © 2018 Elsevier B.V. All rights reserved.

Surfactant-free, cationic latices of poly(BMA-co-MMA) using AIBA initiator.

PubMed

Lee, Ki-Chang

2013-09-01

When polymer particles come into use, especially, for photonic crystal applications, their diameter, dispersivity, and refractive indices become very important. Poly(benzyl methacrylate) is known to be a kind of high refracive materials (n = 1.57) compared to poly(methyl methacrylate) (n = 1.49). Not many work was concerned for surfactant-free emulsion polymerization of benzyl methacrylate or its copolymerization using cationic initiators. Narrowly dispersed cationic poly(BMA-co-MMA) and PBMA latices were synthesized successfully by surfactant-free emulsion polymerization with AIBA. The influences of BMA/MMA ratio, BMA/MMA monomer and initiator concentrations, addition of DVB/EGDMA crosslink agent, and polymerization temperature on the kinetics and on the particle size and molecular weight were studied. Monodisperse cationic charged PBMA and poly(BMA-coMMA) latices with particle diameters varying between 160-494 nm and polymer molecular weights of the order 1.25 x 10(4) to 7.55 x 10(4) g/mol were prepared. The rate of polymerization increased with increasing MMA concentration in BMA/MMA ratio, AIBA concentration, DVB crosslink agent, and polymerization temperature. The particle diameter increased with BMA concentration in BMA/MMA ratio, AIBA concentration, and BMA/MMA monomer concentration. The molecular weight increased with BMA concentration in BMA/MMA ratio and BMA/MMA monomer concentration. The glass transition temperature of the latex copolymers decreased with increasing amount of BMA from 375 K for PMMA to 321 K for PBMA. It was, thus, found that the particle diameter and rate of polymerization as well as the polymer molecular weight for surfactant-free emulsion polymerization of BMA and MMA can be controlled easily by controlling the BMA/MMA ratio, BMA/MMA monomer concentration, AIBA concentration, and polymerization temperature.

Preparation of immunoglobulin Y from egg yolk using ammonium sulfate precipitation and ion exchange chromatography.

PubMed

Ko, K Y; Ahn, D U

2007-02-01

The objective of this study was to develop an economical, simple, and large-scale separation method for IgY from egg yolk. Egg yolk diluted with 9 volumes of cold water was centrifuged after adjusting the pH to 5.0. The supernatant was added with 0.01% charcoal or 0.01% carrageenan and centrifuged at 2,800 x g for 30 min. The supernatant was filtered through a Whatman no. 1 filter paper and then the filtrate was concentrated to 20% original volume using ultrafiltration. The concentrated solution was further purified using either cation exchange chromatography or ammonium sulfate precipitation. For the cation exchange chromatography method, the concentrated sample was loaded onto a column equilibrated with 20 mM citrate-phosphate buffer at pH 4.8 and eluted with 200 mM citrate-phosphate buffer at pH 6.4. For the ammonium sulfate precipitation method, the concentrated sample was twice precipitated with 40% ammonium sulfate solution at pH 9.0. The yield and purity of IgY were determined by ELISA and electrophoresis. The yield of IgY from the cation exchange chromatography method was 30 to 40%, whereas that of the ammonium sulfate precipitation was 70 to 80%. The purity of IgY from the ammonium sulfate method was higher than that of the cation exchange chromatography. The cation exchange chromatography could handle only a small amount of samples, whereas the ammonium sulfate precipitation could handle a large volume of samples. This suggests that ammonium sulfate precipitation was a more efficient and useful purification method than cation exchange chromatography for the large-scale preparation of IgY from egg yolk.

Synthesis and Ion-Exchange Properties of Graphene Th(IV) Phosphate Composite Cation Exchanger: Its Applications in the Selective Separation of Lead Metal Ions

PubMed Central

Rangreez, Tauseef Ahmad; Alhogbi, Basma G.; Naushad, Mu.

2017-01-01

In this study, graphene Th(IV) phosphate was prepared by sol–gel precipitation method. The ion-exchange behavior of this cation-exchanger was studied by investigating properties like ion-exchange capacity for various metal ions, the effect of eluent concentration, elution behavior, and thermal effect on ion-exchange capacity (IEC). Several physicochemical properties as Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) study, thermal studies, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies were also carried out. The material possessed an IEC of 1.56 meq·dry·g−1 of the exchanger and was found to be nano-composite. The selectivity studies showed that the material is selective towards Pb(II) ions. The selectivity of this cation-exchanger was demonstrated in the binary separation of Pb(II) ions from mixture with other metal ions. The recovery was found to be both quantitative and reproducible. PMID:28737717

Electrodialytic matrix isolation for metal cations.

PubMed

Ohira, Shin-Ichi; Hiroyama, Yuri; Nakamura, Koretaka; Koda, Takumi; Dasgupta, Purnendu K; Toda, Kei

2015-01-01

Electrodialytic ion transfer was studied as a matrix isolation tool for heavy metal determinations. An ion transfer device (ITD) was used for the transfer of heavy metal cations. Under optimized flow rates applied voltage and receptor composition, heavy metal ions were quantitatively transferred at concentrations spanning µg L(-1) to mg L(-1). As long as the sample pH was acidic, there was no significant sample pH effect on the transfer efficiencies. Significant salt concentrations (>1 mM NaCl), however, decreased the transfer efficiency. This could be ameliorated (up to 5 mM NaCl) by transient instead of continuous sample introduction. The device was applied to the determination of Fe, Cu and Zn in equine and bovine serum; the reproducibility was better than conventional digestion method. Copyright © 2014 Elsevier B.V. All rights reserved.

Identification of cation-binding sites on actin that drive polymerization and modulate bending stiffness

PubMed Central

Kang, Hyeran; Bradley, Michael J.; McCullough, Brannon R.; Pierre, Anaëlle; Grintsevich, Elena E.; Reisler, Emil; De La Cruz, Enrique M.

2012-01-01

The assembly of actin monomers into filaments and networks plays vital roles throughout eukaryotic biology, including intracellular transport, cell motility, cell division, determining cellular shape, and providing cells with mechanical strength. The regulation of actin assembly and modulation of filament mechanical properties are critical for proper actin function. It is well established that physiological salt concentrations promote actin assembly and alter the overall bending mechanics of assembled filaments and networks. However, the molecular origins of these salt-dependent effects, particularly if they involve nonspecific ionic strength effects or specific ion-binding interactions, are unknown. Here, we demonstrate that specific cation binding at two discrete sites situated between adjacent subunits along the long-pitch helix drive actin polymerization and determine the filament bending rigidity. We classify the two sites as “polymerization” and “stiffness” sites based on the effects that mutations at the sites have on salt-dependent filament assembly and bending mechanics, respectively. These results establish the existence and location of the cation-binding sites that confer salt dependence to the assembly and mechanics of actin filaments. PMID:23027950

Recovery process for electroless plating baths

DOEpatents

Anderson, Roger W.; Neff, Wayne A.

1992-01-01

A process for removing, from spent electroless metal plating bath solutions, accumulated byproducts and counter-ions that have deleterious effects on plating. The solution, or a portion thereof, is passed through a selected cation exchange resin bed in hydrogen form, the resin selected from strong acid cation exchangers and combinations of intermediate acid cation exchangers with strong acid cation exchangers. Sodium and nickel ions are sorbed in the selected cation exchanger, with little removal of other constituents. The remaining solution is subjected to sulfate removal through precipitation of calcium sulfate hemihydrate using, sequentially, CaO and then CaCO.sub.3. Phosphite removal from the solution is accomplished by the addition of MgO to form magnesium phosphite trihydrate. The washed precipitates of these steps can be safely discarded in nontoxic land fills, or used in various chemical industries. Finally, any remaining solution can be concentrated, adjusted for pH, and be ready for reuse. The plating metal can be removed from the exchanger with sulfuric acid or with the filtrate from the magnesium phosphite precipitation forming a sulfate of the plating metal for reuse. The process is illustrated as applied to processing electroless nickel plating baths.

Recovery process for electroless plating baths

DOEpatents

Anderson, R.W.; Neff, W.A.

1992-05-12

A process is described for removing, from spent electroless metal plating bath solutions, accumulated byproducts and counter-ions that have deleterious effects on plating. The solution, or a portion thereof, is passed through a selected cation exchange resin bed in hydrogen form, the resin selected from strong acid cation exchangers and combinations of intermediate acid cation exchangers with strong acid cation exchangers. Sodium and nickel ions are sorbed in the selected cation exchanger, with little removal of other constituents. The remaining solution is subjected to sulfate removal through precipitation of calcium sulfate hemihydrate using, sequentially, CaO and then CaCO[sub 3]. Phosphite removal from the solution is accomplished by the addition of MgO to form magnesium phosphite trihydrate. The washed precipitates of these steps can be safely discarded in nontoxic land fills, or used in various chemical industries. Finally, any remaining solution can be concentrated, adjusted for pH, and be ready for reuse. The plating metal can be removed from the exchanger with sulfuric acid or with the filtrate from the magnesium phosphite precipitation forming a sulfate of the plating metal for reuse. The process is illustrated as applied to processing electroless nickel plating baths. 18 figs.

Enrofloxacin sorption on smectite clays: effects of pH, cations, and humic acid.

PubMed

Yan, Wei; Hu, Shan; Jing, Chuanyong

2012-04-15

Enrofloxacin (ENR) occurs widely in natural waters because of its extensive use as a veterinary chemotherapeutic agent. To improve our understanding of the interaction of this emerging contaminant with soils and sediments, sorption of ENR on homoionic smectites and kaolinite was studied as a function of pH, ionic strength, exchangeable cations, and humic acid concentration. Batch experiments and in situ ATR-FTIR analysis suggested multiple sorption mechanisms. Cation exchange was a major contributor to the sorption of cationic ENR species on smectite. The decreased ENR sorption with increasing ionic strength indicated the formation of outer-sphere complexes. Exchangeable cations significantly influenced the sorption capacity, and the observed order was Cs

Ionic Control of the Reversal Response of Cilia in Paramecium caudatum

PubMed Central

Naitoh, Yutaka

1968-01-01

The duration of ciliary reversal of Paramecium caudatum in response to changes in external ionic factors was determined with various ionic compositions of both equilibration and stimulation media. The reversal response was found to occur when calcium ions bound by an inferred cellular cation exchange system were liberated in exchange for externally applied cations other than calcium. Factors which affect the duration of the response were (a) initial amount of calcium bound by the cation exchange system, (b) final amount of calcium bound by the system after equilibration with the stimulation medium, and (c) concentration of calcium ions in the stimulation medium. An empirical equation is presented which relates the duration of the response to these three factors. On the basis of these and previously published data, the following hypothesis is proposed for the mechanism underlying ciliary reversal in response to cationic stimulation: Ca++ liberated from the cellular cation exchange system activates a contractile system which is energized by ATP. Contraction of this component results in the reversal of effective beat direction of cilia by a mechanism not yet understood. The duration of reversal in live paramecia is related to the time course of bound calcium release. PMID:4966766

Competitive separation of di- vs. mono-valent cations in electrodialysis: effects of the boundary layer properties.

PubMed

Kim, Younggy; Walker, W Shane; Lawler, Desmond F

2012-05-01

In electrodialysis desalination, the boundary layer near ion-exchange membranes is the limiting region for the overall rate of ionic separation due to concentration polarization over tens of micrometers in that layer. Under high current conditions, this sharp concentration gradient, creating substantial ionic diffusion, can drive a preferential separation for certain ions depending on their concentration and diffusivity in the solution. Thus, this study tested a hypothesis that the boundary layer affects the competitive transport between di- and mono-valent cations, which is known to be governed primarily by the partitioning with cation-exchange membranes. A laboratory-scale electrodialyzer was operated at steady state with a mixture of 10mM KCl and 10mM CaCl(2) at various flow rates. Increased flows increased the relative calcium transport. A two-dimensional model was built with analytical solutions of the Nernst-Planck equation. In the model, the boundary layer thickness was considered as a random variable defined with three statistical parameters: mean, standard deviation, and correlation coefficient between the thicknesses of the two boundary layers facing across a spacer. Model simulations with the Monte Carlo method found that a greater calcium separation was achieved with a smaller mean, greater standard deviation, or more negative correlation coefficient. The model and experimental results were compared for the cationic transport number as well as the current and potential relationship. The mean boundary layer thickness was found to decrease from 40 to less than 10 μm as the superficial water velocity increased from 1.06 to 4.24 cm/s. The standard deviation was greater than the mean thickness at slower water velocities and smaller at faster water velocities. Copyright © 2012 Elsevier Ltd. All rights reserved.

The Effects of Various Ions on Resting and Spike Potentials of Barnacle Muscle Fibers

PubMed Central

Hagiwara, Susumu; Chichibu, Shiko; Naka, Ken-ichi

1964-01-01

Effects of monovalent cations and some anions on the electrical properties of the barnacle muscle fiber membrane were studied when the intra- or extracellular concentrations of those ions were altered by longitudinal intra-cellular injection. The resting potential of the normal fiber decreases linearly with increase of logarithm of [K+]out and the decrement for a tenfold increase in [K+]out is 58 mv when the product, [K+]out ·[Cl-]out, is kept constant. It also decreases with decreasing [K+]in but is always less than expected theoretically. The deviation becomes larger as [K+]in increases and the resting potential finally starts to decrease with increasing [K+]in for [K+]in > 250 mM. When the internal K+ concentration is decreased the overshoot of the spike potential increases and the time course of the spike potential becomes more prolonged. In substituting for the internal K+, Na+ and sucrose affect the resting and spike potentials similarly. Some organic cations (guanidine, choline, tris, and TMA) behave like sucrose while some other organic cations (TEA, TPA, and TBA) have a specific effect and prolong the spike potential if they are applied intracellularly or extracellularly. In all cases the active membrane potential increases linearly with the logarithm of [Ca++]out/[K+]in and the increment is about 29 mv for tenfold increase in this ratio. The fiber membrane is permeable to Cl- and other smaller anions (Br- and I-) but not to acetate- and larger anions (citrate-, sulfate-, and methanesulfonate-). PMID:14212147

Peroxyoxalate chemiluminescence enhanced by oligophenylenevinylene fluorophores in the presence of various surfactants.

PubMed

Motoyoshiya, Jiro; Takigawa, Setsuko

2014-11-01

The effect of several surfactants on peroxyoxalate chemiluminescence (PO-CL) using oligophenylenevinylene fluorophores was investigated. Among several oligophenylenevinylenes consisting of stilbene units, linearly conjugated ones, such as distyrylbenzene and distyrylstilbene, effectively enhanced PO-CL efficiency. Various effects of anionic, cationic, amphoteric and non-ionic surfactants on the CL efficiency of PO-CL were determined using three oxalates and the distyrylbenzene fluorophore. Anionic and non-ionic surfactants effectively enhanced CL efficiency, in contrast to the negative effect of cationic and amphoteric surfactants. Non-ionic surfactants were also effective in CL reactions of oxalates bearing dodecyl ester groups by the hydrophobic interaction between their alkyl chains. Considering these results, the surfactants not only increase the concentrations of water-insoluble interacting species in the hydrophobic micelle cores, but also control rapid degradation of the oxalates by alkaline hydrolysis. Copyright © 2014 John Wiley & Sons, Ltd.

High affinity capture and concentration of quinacrine in polymorphonuclear neutrophils via vacuolar ATPase-mediated ion trapping: Comparison with other peripheral blood leukocytes and implications for the distribution of cationic drugs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roy, Caroline; Gagné, Valérie; Fernandes, Maria J.G.

Many cationic drugs are concentrated in acidic cell compartments due to low retro-diffusion of the protonated molecule (ion trapping), with an ensuing vacuolar and autophagic cytopathology. In solid tissues, there is evidence that phagocytic cells, e.g., histiocytes, preferentially concentrate cationic drugs. We hypothesized that peripheral blood leukocytes could differentially take up a fluorescent model cation, quinacrine, depending on their phagocytic competence. Quinacrine transport parameters were determined in purified or total leukocyte suspensions at 37 °C. Purified polymorphonuclear leukocytes (PMNLs, essentially neutrophils) exhibited a quinacrine uptake velocity inferior to that of lymphocytes, but a consistently higher affinity (apparent K{sub M} 1.1more » vs. 6.3 μM, respectively). However, the vacuolar (V)-ATPase inhibitor bafilomycin A1 prevented quinacrine transport or initiated its release in either cell type. PMNLs capture most of the quinacrine added at low concentrations to fresh peripheral blood leukocytes compared with lymphocytes and monocytes (cytofluorometry). Accumulation of the autophagy marker LC3-II occurred rapidly and at low drug concentrations in quinacrine-treated PMNLs (significant at ≥ 2.5 μM, ≥ 2 h). Lymphocytes contained more LAMP1 than PMNLs, suggesting that the mass of lysosomes and late endosomes is a determinant of quinacrine uptake V{sub max}. PMNLs, however, exhibited the highest capacity for pinocytosis (uptake of fluorescent dextran into endosomes). The selectivity of quinacrine distribution in peripheral blood leukocytes may be determined by the collaboration of a non-concentrating plasma membrane transport mechanism, tentatively identified as pinocytosis in PMNLs, with V-ATPase-mediated concentration. Intracellular reservoirs of cationic drugs are a potential source of toxicity (e.g., loss of lysosomal function in phagocytes). - Highlights: • Quinacrine is concentrated in acidic organelles via V-ATPase-mediated ion trapping. • Human peripheral blood leukocytes capture and concentrate quinacrine. • Polymorphonuclear leukocytes do so with higher apparent affinity. • Polymorphonuclear are also more competent than lymphocytes for pinocytosis.« less

Observed high aerosol loading during dust events in Delhi

NASA Astrophysics Data System (ADS)

Singh, Khem; Aggarwal, Shankar G.; Jha, Arvind K.; Singh, Nahar; Soni, Daya; Gupta, Prabhat K.

2012-07-01

The present study reports aerosol mass loadings and their chemical property during integrated campaign for aerosol and radiation budget (ICARB) in the month of March to May 2006, at NPL, New Delhi. The Thar Desert in Rajasthan is located on the western end of India and south-west of Delhi is hot and arid region with intense aeolian activity and transport of aerosol by the prevailing southwest-west summer wind. Several dust episodes were observed in Delhi during summer 2006. The dust storm peaked on 29th April, 1 ^{st} and 8 ^{th} May 2006, with very high suspended particulate matter (SPM) concentrations 1986μg/m ^{3}, 1735μg/m ^{3} and 1511μg/m ^{3}, respectively. The average concentration of SPM in the month of March, April and May 2006 was 338 μg/m ^{3}, 698 μg/m ^{3} and 732 μg/m ^{3}, respectively. The SPM filter samples were analysed for water-soluble major cations (Na ^{+}, Ca ^{2+}, K ^{+}, and Mg ^{2+}) by atomic absorption spectrophotometry (AAS). Na ^{+} and Ca ^{2+} contribute about 54% and 20%, respectively of the total identified cation mass, indicating that they were most abundant cations. Strong correlations between Na ^{+}, Ca ^{2+}, K ^{+}, and Mg ^{2+} suggest their soil and dust origin. Such a high particle concentration observed during dust events may also be useful for study the effect of these aerosols on communication medium.

Evaluation of antibacterial properties of novel phthalocyanines against Escherichia coli--comparison of analytical methods.

PubMed

Mikula, Premysl; Kalhotka, Libor; Jancula, Daniel; Zezulka, Stepan; Korinkova, Radka; Cerny, Jiri; Marsalek, Blahoslav; Toman, Petr

2014-09-05

We analyzed antibacterial effects of several novel phthalocyanines against Escherichia coli and evaluated the suitability of flow cytometry for the detection of antibacterial effects of phthalocyanines in comparison with routinely used cultivation. After 3h of exposure under cool white light eight cationic phthalocyanines showed very high antibacterial activity in the concentration of 2.00 mg L(-1) and four of them were even efficient in the concentration of 0.20 mg L(-1). Antibacterial activity of neutral and anionic compounds was considerably lower or even negligible. No antibacterial effect was detected when bacteria were exposed without illumination. Binding affinity to bacterial cells was found to represent an important parameter influencing phthalocyanine antibacterial activity that can be modified by total charge of peripheral substituents and by the presence of suitable functional groups inside them. Agglomeration of cells observed in suspensions treated with a higher concentration of certain cationic phthalocyanines (the strongest binders to bacterial membrane) affected cytometric measurements of total cell counts, thus without appropriate pretreatment of the sample before analysis this parameter seems not to be fully valid in the evaluation of phthalocyanine antibacterial activity. Cytometric measurement of cell membrane integrity appears to be a suitable and even more sensitive parameter than cultivation. Copyright © 2014 Elsevier B.V. All rights reserved.

The effect of harvest intensity on long-term calcium dynamics in soil and soil solution at three coniferous sites in Sweden

NASA Astrophysics Data System (ADS)

Zetterberg, Therese; Olsson, Bengt; Löfgren, Stefan; von Brömssen, Claudia; Brandtberg, Per-Olov

2013-04-01

Bioenergy from forests is a mean to reduce fossil fuel related carbon dioxide (CO2) emissions. The potential to replace fossil fuel with logging residues is large in countries with extensive forest resources such as Sweden where the supply of bioenergy to district heating plants has quintupled since the 1990's, now accounting for 46% of the total energy supply. However, the loss of nutrients and other elements in biomass is higher following harvest for bioenergy purposes (whole-tree harvest, WTH) compared with traditional clear-cutting (conventional harvest, CH). Calcium (Ca2+) is an important base cation, which buffer soils and surface water against acidification. The loss of Ca2+ and other base cations via harvest for bioenergy could therefore result in soil acidification and there is a growing concern in Sweden that the depletion in base cation pools would also lead to surface water acidification associated with lower base cation concentrations in runoff (Swedish Environmental Protection Agency, 2007). Furthermore, WTH may also prevent or delay a recovery from acidification in areas such as the southwestern parts of Sweden, where the pools of exchangeable cations have been substantially depleted as a result of historically high sulfate (SO42-) deposition. In this paper, long-term treatment differences in soil exchangeable Ca2+ pools (down to 20 cm) and soil solution Ca2+ concentrations at 50 cm soil depth were examined at three coniferous sites in Sweden following CH and WTH in 1974-76. The results showed that soil water concentrations of Ca2+were -17 μeq l-1 (or 40%) lower in WTH plots compared with CH plots, 27-30 years after harvest. The main treatment differences had largely disappeared 32 to 35 years after harvest although site specific treatment differences (ΔWTH-CH: -24 μeq l-1) were still measurable at the well-buffered site in northern Sweden. These results are in agreement with soil data showing that previously found treatment differences in Ca2+ pools had diminished in the forest floor but remained in deeper soil layers (-0.29, -0.37 and -0.24 kmolc ha-1 in the 5-10, 10-15 and 15-20 cm soil layer, respectively). The effects on soil Ca2+ pools appeared to be most pronounced at the well-buffered northern site. These results indicate that the effect of WTH on soil and soil solution concentrations is temporary but site specific. Contrary to common beliefs, the greatest effects were observed at the well-buffered site where the loss of Ca2+ during WTH is less likely to lead to acidification effects. The treatment effects on soil solution at the more acidic sites in southern Sweden were much smaller and probably not large enough to fully counterbalance the general recovery from acidification during the study period. References Swedish Environmental Protection Agency, 2007. Bara naturlig försurning. Bilagor till underlagsrapport till fördjupad utvärdering av miljömålen. Rapport 5780. 208 pp. In Swedish.

Geochemical controls on lead concentrations in stream water and sediments

USGS Publications Warehouse

Hem, J.D.

1976-01-01

The equilibrium distribution of lead in solution and adsorbed on cation exchange sites in sediment theoretically may be calculated from equations representing selectivities of substrate for lead over H+, Ca2+ and Na+, and the stabilities of lead solute species. Such calculations include consideration of total concentrations of major ions, cation exchange capacity (CEC) of substrate, and pH, at values expected in various natural systems. Measurements of CEC and selectivity coefficients were made for synthetic halloysite, a finely divided amorphous 1:1 clay prepared by precipitation from a mixture of solutions of aluminum and silica. Where suspended sediment having the same properties is present in concentrations of 10-1,000 mg/1 at pH 6-8, more than 90% of the lead present can be adsorbed on sediment surfaces. The cation exchange behavior of lead and other minor cationic species in natural systems could be predicted by this type of model if enough other supporting information were available. Information of the type needed describing natural stream sediments, however, is presently inadequate for accurate predictions. ?? 1976.

Manipulating the dietary cation-anion difference via drenching to early-lactation dairy cows grazing pasture.

PubMed

Roche, J R; Petch, S; Kay, J K

2005-01-01

Diets offered to grazing dairy cows can vary considerably in their dietary cation-anion difference (DCAD) and are often well in excess of what has been considered optimal. The effects of a range of DCAD on the health and production of pasture-based dairy cows in early lactation was examined in a randomized block design. Four groups of 8 cows were offered a generous allowance of pasture (45 +/- 6 kg/d of dry matter (DM) per cow) for 35 d and achieved mean pasture intakes of approximately 17 kg/d of DM per cow. Cows were drenched twice daily with varying combinations of mineral compounds to alter the DCAD. Dietary cation-anion difference ranged from +23 to +88 mEq/100 g of DM. A linear increase in blood pH and HCO(3)(-) concentration and blood base excess, and a curvilinear increase in the pH of urine with increasing DCAD indicated a nonrespiratory effect of DCAD on metabolic acid-base balance. Plasma concentrations of Mg, K, and Cl declined as DCAD increased, whereas Na concentration increased. Urinary excretion of Ca decreased linearly as DCAD increased, although the data suggest that the decline may be curvilinear. These results in conjunction with the increased concentrations of ionized Ca suggest that intestinal absorption of Ca or bone resorption, or both, increased as DCAD declined. Dry matter intake, as measured using indigestible markers, was not significantly affected by DCAD. However, the linear increase in the yield of linolenic acid, vaccenic acid, and cis-9, trans-11 conjugated linoleic acid in milk, as DCAD increased is consistent with a positive effect of DCAD on DM intake. Increasing DCAD did not significantly affect milk yield or milk protein, but the concentration and yield of milk fat linearly increased with increasing DCAD. The increased milk fat yield was predominantly a result of increased de novo synthesis in the mammary epithelial cells, although an increase in the yield of preformed fatty acids also occurred. Milk production results suggest that DCAD for optimal production on pasture diets may be higher than the +20 mEq/100 g of DM previously identified for total mixed rations.

Effect of experimental variables onto Co(2+) and Sr(2+) sorption behavior in red mud-water suspensions.

PubMed

Milenković, Aleksandra S; Smičiklas, Ivana D; Šljivić-Ivanović, Marija Z; Živković, Ljiljana S; Vukelić, Nikola S

2016-07-02

The prospects of rinsed red mud (alumina production residue) utilization for liquid radioactive waste treatment have been investigated, with Co(2+) and Sr(2+) as model cations of radioactive elements. To evaluate the sorption effectiveness and corresponding binding mechanisms, the process was analyzed in batch conditions, by varying experimental conditions (pH, Co(2+) and Sr(2+) concentrations in single solutions and binary mixtures, contact time, and the concentration of competing cations and ligands common in liquid radioactive waste). Comparison of the Co(2+) and Sr(2+) sorption pH edges with the red mud isoelectric point has revealed that Co(2+) removal took place at both positive and negative red mud surface, while Sr(2+) sorption abruptly increased when the surface became negatively charged. The increase of initial cation content and pH resulted in increased equilibrium times and sorption capacity and decreased rate constants. From single metal solutions and various binary mixtures, Co(2+) was sorbed more efficiently and selectively than Sr(2+). While Sr(2+) sorption was reduced by coexisting cations in the order Al(3+) ≥ Ca(2+) >Na(+) ≥Cs(+), removal of Co(2+) was affected by Al(3+) species and complexing agents (EDTA and citrate). Desorption of Co(2+) was negligible in Ca(2+) and Sr(2+) containing media and in solutions with initial pH 4-7. Sr(2+) desorption was generally more pronounced, especially at low pH and in the presence of Co(2+). Collected macroscopic data signify that Co(2+) sorption by red mud minerals occurred via strong chemical bonds, while Sr(2+) was retained mainly by weaker ion-exchange or electrostatic interactions. Results indicate that the rinsed red mud represent an efficient, low-cost sorbent for Co(2+) and Sr(2+) immobilization.

Cationic uremic toxins affect human renal proximal tubule cell functioning through interaction with the organic cation transporter.

PubMed

Schophuizen, Carolien M S; Wilmer, Martijn J; Jansen, Jitske; Gustavsson, Lena; Hilgendorf, Constanze; Hoenderop, Joost G J; van den Heuvel, Lambert P; Masereeuw, Rosalinde

2013-12-01

Several organic cations, such as guanidino compounds and polyamines, have been found to accumulate in plasma of patients with kidney failure due to inadequate renal clearance. Here, we studied the interaction of cationic uremic toxins with renal organic cation transport in a conditionally immortalized human proximal tubule epithelial cell line (ciPTEC). Transporter activity was measured and validated in cell suspensions by studying uptake of the fluorescent substrate 4-(4-(dimethylamino)styryl)-N-methylpyridinium-iodide (ASP(+)). Subsequently, the inhibitory potencies of the cationic uremic toxins, cadaverine, putrescine, spermine and spermidine (polyamines), acrolein (polyamine breakdown product), guanidine, and methylguanidine (guanidino compounds) were determined. Concentration-dependent inhibition of ASP(+) uptake by TPA, cimetidine, quinidine, and metformin confirmed functional endogenous organic cation transporter 2 (OCT2) expression in ciPTEC. All uremic toxins tested inhibited ASP(+) uptake, of which acrolein required the lowest concentration to provoke a half-maximal inhibition (IC50 = 44 ± 2 μM). A Dixon plot was constructed for acrolein using three independent inhibition curves with 10, 20, or 30 μM ASP(+), which demonstrated competitive or mixed type of interaction (K i = 93 ± 16 μM). Exposing the cells to a mixture of cationic uremic toxins resulted in a more potent and biphasic inhibitory response curve, indicating complex interactions between the toxins and ASP(+) uptake. In conclusion, ciPTEC proves a suitable model to study cationic xenobiotic interactions. Inhibition of cellular uptake transport was demonstrated for several uremic toxins, which might indicate a possible role in kidney disease progression during uremia.

Structure of Polyelectrolyte Brushes in the Presence of Multivalent Counterions

DOE PAGES

Yu, Jing; Mao, Jun; Yuan, Guangcui; ...

2016-07-20

Polyelectrolyte brushes are of great importance to a wide range of fields, ranging from colloidal stabilization to responsive and tunable materials to lubrication. Here, we synthesized high-density polystyrenesulfonate (PSS) brushes using surface initiated atom transfer radical polymerization and performed neutron reflectivity (NR) and surface force measurements using a surface forces apparatus (SFA) to investigate the effect of monovalent Na +, divalent Ca 2+, Mg 2+, and Ba 2+, and trivalent Y 3+ counterions on the structure of the PSS brushes. NR and SFA results demonstrate that in monovalent salt solution the behavior of the PSS brushes agrees with scaling theorymore » well, exhibiting two distinct regimes: the osmotic and salted brush regimes. Introducing trivalent Y 3+ cations causes an abrupt shrinkage of the PSS brush due to the uptake of Y 3+ counterions. The uptake of Y 3+ counterions and shrinkage of the brush are reversible upon increasing the concentration of monovalent salt. Divalent cations, Mg 2+, Ca 2+, and Ba 2+, while all significantly affecting the structure of PSS brushes, show strong ion specific effects that are related to the specific interactions between the divalent cations and the sulfonate groups. Our results demonstrate that the presence of multivalent counterions, even at relatively low concentrations, can strongly affect the structure of polyelectrolyte brushes. Finally, the results also highlight the importance of ion specificity to the structure of polyelectrolyte brushes in solution.« less

Cationic Supramolecular Hydrogels for Overcoming the Skin Barrier in Drug Delivery

PubMed Central

Limón, David; Jiménez‐Newman, Claire; Rodrigues, Mafalda; González‐Campo, Arántzazu; Amabilino, David B.; Calpena, Ana C.

2017-01-01

Abstract A cationic bis‐imidazolium‐based amphiphile was used to form thermoreversible nanostructured supramolecular hydrogels incorporating neutral and cationic drugs for the topical treatment of rosacea. The concentration of the gelator and the type and concentration of the drug incorporated were found to be factors that strongly influenced the gelling temperature, gel‐formation period, and overall stability and morphology. The incorporation of brimonidine tartrate resulted in the formation of the most homogeneous material of the three drugs explored, whereas the incorporation of betamethasone resulted in a gel with a completely different morphology comprising linked particles. NMR spectroscopy studies proved that these gels kept the drug not only at the interstitial space but also within the fibers. Due to the design of the gelator, drug release was up to 10 times faster and retention of the drug within the skin was up to 20 times more effective than that observed for commercial products. Experiments in vivo demonstrated the rapid efficacy of these gels in reducing erythema, especially in the case of the gel with brimonidine. The lack of coulombic attraction between the gelator–host and the guest–drug seemed particularly important in highly effective release, and the intermolecular interactions operating between them were found to lie at the root of the excellent properties of the materials for topical delivery and treatment of rosacea. PMID:28794954

The influence of monovalent cations on trimeric G protein G(i)1α activity in HEK293 cells stably expressing DOR-G(i)1α (Cys(351)-Ile(351)) fusion protein.

PubMed

Vošahlíková, M; Svoboda, P

2011-01-01

The effect of monovalent cations on trimeric G protein G(i)1α was measured at equimolar concentration of chloride anion in pertussis-toxin (PTX)-treated HEK293 cells stably expressing PTX-insensitive DOR- G(i)1α (Cys(351)-Ile(351)) fusion protein by high-affinity [(35)S]GTPgammaS binding assay. The high basal level of binding was detected in absence of DOR agonist and monovalent ions and this high level was inhibited with the order of: Na(+) > K(+) > Li(+). The first significant inhibition was detected at 1 mM NaCl. The inhibition by monovalent ions was reversed by increasing concentrations of DOR agonist DADLE. The maximum DADLE response was also highest for sodium and decreased in the order of: Na(+) > K(+) ~ Li(+). Our data indicate i) an inherently high activity of trimeric G protein G(i)1α when expressed within DOR- G(i)1α fusion protein and determined in the absence of monovalent cations, ii) preferential sensitivity of DOR- G(i)1alpha to sodium as far as maximum of agonist response is involved.

Effects of solvent and alkaline earth metals on the heat-induced precipitation process of sodium caseinate.

PubMed

Lopez, Francesco; Cuomo, Francesca; Nostro, Pierandrea Lo; Ceglie, Andrea

2013-01-01

The precipitation temperatures of sodium caseinate in H(2)O and D(2)O in the presence of Mg(2+), Ca(2+), Sr(2+) and Ba(2+) were investigated through fluorescence, turbidity and conductivity experiments. As for the ability of the divalent cations (1-17.5mM) to induce the precipitation process in H(2)O, the sequence Ba(2+) ≥ Ca(2+)>Mg(2+)>Sr(2+) was found. Remarkably, while at low salt concentrations (<10mM) precipitation temperatures (T(Ps)) were found to change significantly depending on the specific cation, at higher concentrations (>10mM) the differences among the different cations were greatly reduced. By fitting these results with a modified Jones-Dole equation, we confirmed that the less hydrated ions possess a greater capacity to induce precipitation. In D(2)O, the order of ion ability to induce caseinate precipitation was Ba(2+)>Ca(2+)>Sr(2+)>Mg(2+). The different hydrophobicity between D(2)O and H(2)O was shown to affect significantly the T(Ps) of caseinate in the presence of calcium, strontium and barium. Copyright © 2012 Elsevier Ltd. All rights reserved.

Impact of managed moorland burning on peat nutrient and base cation status

NASA Astrophysics Data System (ADS)

Palmer, Sheila; Gilpin, Martin; Wearing, Catherine; Johnston, Kerrylyn; Holden, Joseph; Brown, Lee

2013-04-01

Controlled 'patch' burning of moorland vegetation has been used for decades in the UK to stimulate growth of heather (Calluna vulgaris) for game bird habitat and livestock grazing. Typically small patches (300-900 m2) are burned in rotations of 8-25 years. However, our understanding of the short-to-medium term environmental impacts of the practice on these sensitive upland areas has so far been limited by a lack of scientific data. In particular the effect of burning on concentrations of base cations and acid-base status of these highly organic soils has implications both for ecosystem nutrient status and for buffering of acidic waters. As part of the EMBER project peat chemistry data were collected in ten upland blanket peat catchments in the UK. Five catchments were subject to a history of prescribed rotational patch burning. The other five catchments acted as controls which were not subject to burning, nor confounded by other detrimental activities such as drainage or forestry. Soil solution chemistry was also monitored at two intensively studied sites (one regularly burned and one control). Fifty-centimetre soil cores, sectioned into 5-cm intervals, were collected from triplicate patches of four burn ages at each burned site, and from twelve locations at similar hillslope positions at each control site. At the two intensively monitored sites, soil solution chemistry was monitored at four depths in each patch. Across all sites, burned plots had significantly smaller cation exchange capacities, lower concentrations of exchangeable base cations and increased concentrations of exchangeable H+ and Al3+ in near-surface soil. C/N ratios were also lower in burned compared to unburned surface soils. There was no consistent trend between burn age and peat chemistry across all burned sites, possibly reflecting local controls on post-burn recovery rates or external influences on burn management decisions. At the intensively monitored site, plots burned less than two years prior to sampling had significantly smaller exchange capacities and lower concentrations of soil base cations in surface soils relative to plots burned 15-25 years previously. In contrast, surface soil solutions in recently burned plots were enriched in base cations relative to older plots and relative to the control site, possibly due to enhanced leaching at bare soil surfaces. The results offer evidence for an impact of burning on peat nutrient and acid-base status, but suggest that soils recover given time with no further burning.

Effect of clay in controlling the non-fluorescence H-dimeric states of a cationic dye Nile Blue Chloride (NBC) in hybrid Langmuir-Blodgett (LB) film

NASA Astrophysics Data System (ADS)

Debnath, Chandan; Shil, Ashis; Hussain, S. A.; Bhattacharjee, D.

2018-01-01

Present communication reports the effect of amphiphilic matrices and nano-clay platelets on the aggregation properties of a water soluble cationic fluorescent dye Nile Blue Chloride (NBC) in Langmuir-Blodgett (LB) films. In-situ Brewster Angle Microscopic (BAM) studies showed distinct domain structures of complex and hybrid Langmuir monolayer at the air-water interface. UV-vis absorption spectra showed non-fluorescent H-dimeric band in concentrated aqueous solution of NBC and in complex LB film of NBC with stearic acid. By changing various parameters, a great control over H-dimeric states has been achieved in clay incorporated hybrid LB films. These films can act as efficient fluorescence probe.

Effects of silicate weathering on water chemistry in forested, upland, felsic terrane of the USA

NASA Astrophysics Data System (ADS)

Stauffer, Robert E.; Wittchen, Bruce D.

1991-11-01

We use data from the US EPA National Surface Water Survey (NSWS), the USGS Bench-Mark Station monitoring program, and the National Acid Deposition Program (NADP) to evaluate the role of weathering in supplying base cations to surface waters in forested, upland, felsic terrane of the northeastern, northcentral, and northwestern (Idaho batholith) United States. Multivariate regression reveals differential effects of discharge on individual base cations and silica, but no secular trend in the Ca/Na denudation rate over 24 yr (1965-1988) for the Wild River catchment in the White Mountains. Because the turn-over time for Na in the soil-exchange complex is only ca. 1.5 yr, the long-term behavior of the ratios Ca/Na and Si/Na in waters leaving this catchment indicates that weathering is compensating for base cation export. In every subregion, Ca and Mg concentrations in lakes are statistically linked to nonmarine Na, but the median Ca/Na ratio is greater than the ratio in local plagioclase. We attribute this inequality to nonstoichiometric weathering of calcium in juvenile (formerly glaciated) terrane, not to leaching of exchangeable cations by SO 4, because intraregional and cross-regional statistical analysis reveals no effect of atmospherically derived sulfate ion. The median base cation denudation rates (meq m -2 yr -1) for these American lake regions are: Maine granites (108); western Adirondack felsic gneiss (85); Vermilion batholith (42); Idaho batholith (52). The regional rates are high enough to compensate for present wet deposition of acidifying anions except in some vulnerable lake watersheds in the western Adirondacks.

Positive Allosteric Modulation of the Calcium-sensing Receptor by Physiological Concentrations of Glucose*

PubMed Central

Medina, Johan; Nakagawa, Yuko; Nagasawa, Masahiro; Fernandez, Anny; Sakaguchi, Kazushige; Kitaguchi, Tetsuya; Kojima, Itaru

2016-01-01

The calcium-sensing receptor (CaSR) is activated by various cations, cationic compounds, and amino acids. In the present study we investigated the effect of glucose on CaSR in HEK293 cells stably expressing human CaSR (HEK-CaSR cells). When glucose concentration in the buffer was raised from 3 to 25 mm, a rapid elevation of cytoplasmic Ca2+ concentration ([Ca2+]c) was observed. This elevation was immediate and transient and was followed by a sustained decrease in [Ca2+]c. The effect of glucose was detected at a concentration of 4 mm and reached its maximum at 5 mm. 3-O-Methylglucose, a non-metabolizable analogue of glucose, reproduced the effect of glucose. Sucrose also induced an elevation of [Ca2+]c in HEK-CaSR cells. Similarly, sucralose was nearly as effective as glucose in inducing elevation of [Ca2+]c. Glucose was not able to increase [Ca2+]c in the absence of extracellular Ca2+. The effect of glucose on [Ca2+]c was inhibited by NPS-2143, an allosteric inhibitor of CaSR. In addition, NPS-2143 also inhibited the [Ca2+]c responses to sucralose and sucrose. Glucose as well as sucralose decreased cytoplasmic cAMP concentration in HEK-CaSR cells. The reduction of cAMP induced by glucose was blocked by pertussis toxin. Likewise, sucralose reduced [cAMP]c. Finally, glucose increased [Ca2+]c in PT-r parathyroid cells and in Madin-Darby canine kidney cells, both of which express endogenous CaSR. These results indicate that glucose acts as a positive allosteric modulator of CaSR. PMID:27613866

Cationic Antimicrobial Peptide LL-37 Is Effective against both Extra- and Intracellular Staphylococcus aureus

PubMed Central

Noore, Jabeen; Noore, Adly

2013-01-01

The increasing resistance of bacteria to conventional antibiotics and the challenges posed by intracellular bacteria, which may be responsible for chronic and recurrent infections, have driven the need for advanced antimicrobial drugs for effective elimination of both extra- and intracellular pathogens. The purpose of this study was to determine the killing efficacy of cationic antimicrobial peptide LL-37 compared to conventional antibiotics against extra- and intracellular Staphylococcus aureus. Bacterial killing assays and an infection model of osteoblasts and S. aureus were studied to determine the bacterial killing efficacy of LL-37 and conventional antibiotics against extra- and intracellular S. aureus. We found that LL-37 was effective in killing extracellular S. aureus at nanomolar concentrations, while lactoferricin B was effective at micromolar concentrations and doxycycline and cefazolin at millimolar concentrations. LL-37 was surprisingly more effective in killing the clinical strain than in killing an ATCC strain of S. aureus. Moreover, LL-37 was superior to conventional antibiotics in eliminating intracellular S. aureus. The kinetic studies further revealed that LL-37 was fast in eliminating both extra- and intracellular S. aureus. Therefore, LL-37 was shown to be very potent and prompt in eliminating both extra- and intracellular S. aureus and was more effective in killing extra- and intracellular S. aureus than commonly used conventional antibiotics. LL-37 could potentially be used to treat chronic and recurrent infections due to its effectiveness in eliminating not only extracellular but also intracellular pathogens. PMID:23274662

A comparative study on the effect of Curcumin and Chlorin-p6 on the diffusion of two organic cations across a negatively charged lipid bilayer probed by second harmonic spectroscopy

NASA Astrophysics Data System (ADS)

Saini, R. K.; Varshney, G. K.; Dube, A.; Gupta, P. K.; Das, K.

2014-09-01

The influence of Curcumin and Chlorin-p6 (Cp6) on the real time diffusion kinetics of two organic cations, LDS (LDS-698) and Malachite Green (MG) across a negatively charged phospholipid bilayer is investigated by Second Harmonic (SH) spectroscopy. The diffusion time constant of LDS at neutral pH in liposomes containing either Curcumin or Cp6 is significantly reduced, the effect being more pronounced with Curcumin. At acidic pH, the quantum of reduction in the diffusion time constant of MG by both the drugs was observed to be similar. The relative changes in the average diffusion time constants of the cations with increasing drug concentration at pH 5.0 and 7.4 shows a substantial pH effect for Curcumin induced membrane permeability, while a modest pH effect was observed for Cp6 induced membrane permeability. Based on available evidence this can be attributed to the increased interaction between the drug and the polar head groups of the lipid at pH 7.4 where the drug resides closer to the lipid-water interface.

Synergistic effect of divalent cations in improving technological properties of cross-linked alginate beads.

PubMed

Cerciello, Andrea; Del Gaudio, Pasquale; Granata, Veronica; Sala, Marina; Aquino, Rita P; Russo, Paola

2017-08-01

Gelling solution parameters are some of the most important variables in ionotropic gelation and consequently influence the technological characteristics of the product. To date, only a few studies have focused on the simultaneous use of multiple cations as gelling agents. With the aim to deeply explore this possibility, in this research we investigated the effect of two divalent cations (Ca 2+ and Zn 2+ ) on alginate beads formation and properties. Alginate beads containing prednisolone (P) as model drug were prepared by prilling technique. The main critical variables of the ionotropic gelation process i.e. composition of the aqueous feed solutions (sodium alginate and prednisolone concentration) and cross-linking conditions (Ca 2+ , Zn 2+ or Ca 2+ +Zn 2+ ), were studied. The obtained beads were characterized and their in vitro release performances were assessed in conditions simulating the gastrointestinal environment. Results evidenced a synergistic effect of the two cations, affecting positively both the encapsulation efficiency and the ability of the alginate polymeric matrix to control the drug release. A Ca 2+ /Zn 2+ ratio of 4:1, in fact, exploited the Ca 2+ ability of establish quicker electrostatic interactions with guluronic groups of alginate and the Zn 2+ ability to establish covalent-like bonds with carboxylate groups of both guluronic and mannuronic moieties of alginate. Copyright © 2017 Elsevier B.V. All rights reserved.

Correlation between pH dependence of O2 evolution and sensitivity of Mn cations in the oxygen-evolving complex to exogenous reductants.

PubMed

Semin, Boris K; Davletshina, Lira N; Rubin, Andrei B

2015-08-01

Effects of pH, Ca(2+), and Cl(-) ions on the extraction of Mn cations from oxygen-evolving complex (OEC) in Ca-depleted photosystem II (PSII(-Ca)) by exogenous reductants hydroquinone (H2Q) and H2O2 were studied. Two of 4 Mn cations are released by H2Q and H2O2 at pHs 5.7, 6.5, and 7.5, and their extraction does not depend on the presence of Ca(2+) and Cl(-) ions. One of Mn cations ("resistant" Mn cation) cannot be extracted by H2Q and H2O2 at any pH. Extraction of 4th Mn ion ("flexible" Mn cation) is sensitive to pH, Ca(2+), and Cl(-). This Mn cation is released by reductants at pH 6.5 but not at pHs 5.7 and 7.5. A pH dependence curve of the oxygen-evolving activity in PSII(-Ca) membranes (in the presence of exogenous Ca(2+)) has a bell-shaped form with the maximum at pH 6.5. Thus, the increase in the resistance of flexible Mn cation in OEC to the action of reductants at acidic and alkaline pHs coincides with the decrease in oxygen evolution activity at these pHs. Exogenous Ca(2+) protects the extraction of flexible Mn cation at pH 6.5. High concentration of Cl(-) anions (100 mM) shifts the pH optimum of oxygen evolution to alkaline region (around pH 7.5), while the pH of flexible Mn extraction is also shifted to alkaline pH. This result suggests that flexible Mn cation plays a key role in the water-splitting reaction. The obtained results also demonstrate that only one Mn cation in Mn4 cluster is under strong control of calcium. The change in the flexible Mn cation resistance to exogenous reductants in the presence of Ca(2+) suggests that Ca(2+) can control the redox potential of this cation.

Photodynamic inactivation of Candida albicans sensitized by tri- and tetra-cationic porphyrin derivatives.

PubMed

Cormick, M Paula; Alvarez, M Gabriela; Rovera, Marisa; Durantini, Edgardo N

2009-04-01

The photodynamic action of 5-(4-trifluorophenyl)-10,15,20-tris(4-trimethylammoniumphenyl)porphyrin iodide (TFAP(3+)) and 5,10,15,20-tetra(4-N,N,N-trimethylammonium phenyl)porphyrin p-tosylate (TMAP(4+)) has been studied in vitro on Candida albicans. The results of these cationic porphyrins were compared with those of 5,10,15,20-tetra(4-sulphonatophenyl)porphyrin (TPPS(4-)), which characterizes an anionic sensitizer. In vitro investigations show that these cationic porphyrins are rapidly bound to C. albicans cells, reaching a value of approximately 1.4 nmol/10(6) cells, when the cellular suspensions were incubated with 5 microM sensitizer for 30 min. In contrast, TPPS(4-) is poorly uptaken by yeast cells. The fluorescence spectra of these sensitizers into the cells confirm this behaviour. The amount of porphyrin binds to cells is dependent on both sensitizer concentrations (1-5 microM) and cells densities (10(6)-10(8) cells/mL). Photosensitized inactivation of C. albicans cellular suspensions increases with sensitizer concentration, causing a approximately 5 log decrease of cell survival, when the cultures are treated with 5 microM of cationic porphyrin and irradiated for 30 min. However, the photocytotoxicity decreases with an increase in the cell density, according to its low binding to cells. Under these conditions, the photodynamic activity of TFAP(3+) is quite similar to that produced by TMAP(4+), whereas no important inactivation effect was found for TPPS(4)(-). The high photodynamic activity of cationic porphyrins was confirmed by growth delay experiments. Thus, C. albicans cell growth was not detected in the presence of 5 microM TFAP(3+). Photodynamic inactivation capacities of these sensitizers were also evaluated on C. albicans cells growing in colonies on agar surfaces. Cationic porphyrins produce a growth delay of C. albicans colonies and viability of cells was not observed after 3 h irradiation, indicating a complete inactivation of yeast cells. Therefore, these results indicate that these cationic porphyrins are interesting sensitizers for photodynamic inactivation of yeasts in liquid suspensions or in localized foci of infection.

Acid rain effects on aluminum mobilization clarified by inclusion of strong organic acids

USGS Publications Warehouse

Lawrence, G.B.; Sutherland, J.W.; Boylen, C.W.; Nierzwicki-Bauer, S. W.; Momen, B.; Baldigo, Barry P.; Simonin, H.A.

2007-01-01

Assessments of acidic deposition effects on aquatic ecosystems have often been hindered by complications from naturally occurring organic acidity. Measurements of pH and ANCG, the most commonly used indicators of chemical effects, can be substantially influenced by the presence of organic acids. Relationships between pH and inorganic Al, which is toxic to many forms of aquatic biota, are also altered by organic acids. However, when inorganic Al concentrations are plotted against ANC (the sum of Ca2+, Mg 2+, Na+, and K+, minus SO42-, NO3-, and Cl-), a distinct threshold for Al mobilization becomes apparent. If the concentration of strong organic anions is included as a negative component of ANC, the threshold occurs at an ANC value of approximately zero, the value expected from theoretical charge balance constraints. This adjusted ANC is termed the base-cation surplus. The threshold relationship between the base-cation surplus and Al was shown with data from approximately 200 streams in the Adirondack region of New York, during periods with low and high dissolved organic carbon concentrations, and for an additional stream from the Catskill region of New York. These results indicate that (1) strong organic anions can contribute to the mobilization of inorganic Al in combination with SO42- and NO 3-, and (2) the presence of inorganic Al in surface waters is an unambiguous indication of acidic deposition effects. ?? 2007 American Chemical Society.

Acid rain effects on aluminum mobilization clarified by inclusion of strong organic acids.

PubMed

Lawrence, G B; Sutherland, J W; Boylen, C W; Nierzwicki-Bauer, S W; Momen, B; Baldigo, B P; Simonin, H A

2007-01-01

Assessments of acidic deposition effects on aquatic ecosystems have often been hindered by complications from naturally occurring organic acidity. Measurements of pH and ANCG, the most commonly used indicators of chemical effects, can be substantially influenced by the presence of organic acids. Relationships between pH and inorganic Al, which is toxic to many forms of aquatic biota, are also altered by organic acids. However, when inorganic Al concentrations are plotted against ANC (the sum of Ca2+, Mg2+, Na+, and K+, minus S042-, N03-, and Cl-), a distinct threshold for Al mobilization becomes apparent. If the concentration of strong organic anions is included as a negative component of ANC, the threshold occurs at an ANC value of approximately zero, the value expected from theoretical charge balance constraints. This adjusted ANC is termed the base-cation surplus. The threshold relationship between the base-cation surplus and Al was shown with data from approximately 200 streams in the Adirondack region of New York, during periods with low and high dissolved organic carbon concentrations, and for an additional stream from the Catskill region of New York. These results indicate that (1) strong organic anions can contribute to the mobilization of inorganic Al in combination with SO42- and N03-, and (2) the presence of inorganic Al in surface waters is an unambiguous indication of acidic deposition effects.

Biological and surface-active properties of double-chain cationic amino acid-based surfactants.

PubMed

Greber, Katarzyna E; Dawgul, Małgorzata; Kamysz, Wojciech; Sawicki, Wiesław; Łukasiak, Jerzy

2014-08-01

Cationic amino acid-based surfactants were synthesized via solid phase peptide synthesis and terminal acylation of their α and ε positions with saturated fatty acids. Five new lipopeptides, N-α-acyl-N-ε-acyl lysine analogues, were obtained. Minimum inhibitory concentration and minimum bactericidal (fungicidal) concentration were determined on reference strains of bacteria and fungi to evaluate the antimicrobial activity of the lipopeptides. Toxicity to eukaryotic cells was examined via determination of the haemolytic activities. The surface-active properties of these compounds were evaluated by measuring the surface tension and formation of micelles as a function of concentration in aqueous solution. The cationic surfactants demonstrated diverse antibacterial activities dependent on the length of the fatty acid chain. Gram-negative bacteria and fungi showed a higher resistance than Gram-positive bacterial strains. It was found that the haemolytic activities were also chain length-dependent values. The surface-active properties showed a linear correlation between the alkyl chain length and the critical micelle concentration.

Critical Synergistic Concentration of Lecithin Phospholipids Improves the Antimicrobial Activity of Eugenol against Escherichia coli

PubMed Central

Zhang, Haoshu; Dudley, Edward G.

2017-01-01

ABSTRACT In this study, the effect of individual lecithin phospholipids on the antimicrobial properties of eugenol against Escherichia coli C600 was investigated. We tested five major phospholipids common in soy or egg lecithin (1,2-dihexadecanoyl-sn-glycero-3-phosphocholine [DPPC], 1,2-dioctadecanoyl-sn-glycero-3-phosphocholine [DSPC], 1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine [DPPE], 1,2-dihexadecanoyl-sn-glycero-3-phosphate [sodium salt] [DPPA], and 1,2-dihexadecanoyl-sn-glycero-3-phospho-l-serine [DPPS]) and one synthetic cationic phospholipid (1,2-dioctadecanoyl-sn-glycero-3-ethylphosphocholine [18:0 EPC]). Among the six phospholipids, DPPC, DSPC, DPPE, DPPA, and the cationic 18:0 EPC showed critical synergistic concentrations that significantly improved the inactivation effect of eugenol against E. coli after 30 min of exposure. At the critical synergistic concentration, an additional ca. 0.4 to 1.9 log reduction (ca. 0.66 to 2.17 log CFU/ml reduction) in the microbial population was observed compared to eugenol-only (control) treatments (ca. 0.25 log reduction). In all cases, increasing the phospholipid amount above the critical synergistic concentration (which was different for each phospholipid) resulted in antimicrobial properties similar to those seen with the eugenol-only (control) treatments. DPPS did not affect the antimicrobial properties of eugenol at the tested concentrations. The critical synergistic concentration of phospholipids was correlated with their critical micelle concentrations (CMC). IMPORTANCE Essential oils (EOs) are naturally occurring antimicrobials, with limited use in food due to their hydrophobicity and strong aroma. Lecithin is used as a natural emulsifier to stabilize EOs in aqueous systems. We previously demonstrated that, within a narrow critical-concentration window, lecithin can synergistically enhance the antimicrobial properties of eugenol. Since lecithin is a mixture of different phospholipids, we aimed to identify which phospholipids are crucial for the observed synergistic effect. This research studied the bioactivity of lecithin phospholipids, contributing to a rational design in using lecithin to effectively control foodborne pathogens in foods. PMID:28842540

Molecular mechanisms of ionic liquid cytotoxicity probed by an integrated experimental and computational approach

NASA Astrophysics Data System (ADS)

Yoo, Brian; Jing, Benxin; Jones, Stuart E.; Lamberti, Gary A.; Zhu, Yingxi; Shah, Jindal K.; Maginn, Edward J.

2016-02-01

Ionic liquids (ILs) are salts that remain liquid down to low temperatures, and sometimes well below room temperature. ILs have been called “green solvents” because of their extraordinarily low vapor pressure and excellent solvation power, but ecotoxicology studies have shown that some ILs exhibit greater toxicity than traditional solvents. A fundamental understanding of the molecular mechanisms responsible for IL toxicity remains elusive. Here we show that one mode of IL toxicity on unicellular organisms is driven by swelling of the cell membrane. Cytotoxicity assays, confocal laser scanning microscopy, and molecular simulations reveal that IL cations nucleate morphological defects in the microbial cell membrane at concentrations near the half maximal effective concentration (EC50) of several microorganisms. Cytotoxicity increases with increasing alkyl chain length of the cation due to the ability of the longer alkyl chain to more easily embed in, and ultimately disrupt, the cell membrane.

Molecular mechanisms of ionic liquid cytotoxicity probed by an integrated experimental and computational approach

DOE PAGES

Yoo, Brian; Jing, Benxin; Jones, Stuart E.; ...

2016-02-02

Ionic liquids (ILs) are salts that remain liquid down to low temperatures, and sometimes well below room temperature. ILs have been called “green solvents” because of their extraordinarily low vapor pressure and excellent solvation power, but ecotoxicology studies have shown that some ILs exhibit greater toxicity than traditional solvents. A fundamental understanding of the molecular mechanisms responsible for IL toxicity remains elusive. Here we show that one mode of IL toxicity on unicellular organisms is driven by swelling of the cell membrane. Cytotoxicity assays, confocal laser scanning microscopy, and molecular simulations reveal that IL cations nucleate morphological defects in themore » microbial cell membrane at concentrations near the half maximal effective concentration (EC50) of several microorganisms. Lastly, cytotoxicity increases with increasing alkyl chain length of the cation due to the ability of the longer alkyl chain to more easily embed in, and ultimately disrupt, the cell membrane.« less

Molecular mechanisms of ionic liquid cytotoxicity probed by an integrated experimental and computational approach

PubMed Central

Yoo, Brian; Jing, Benxin; Jones, Stuart E.; Lamberti, Gary A.; Zhu, Yingxi; Shah, Jindal K.; Maginn, Edward J.

2016-01-01

Ionic liquids (ILs) are salts that remain liquid down to low temperatures, and sometimes well below room temperature. ILs have been called “green solvents” because of their extraordinarily low vapor pressure and excellent solvation power, but ecotoxicology studies have shown that some ILs exhibit greater toxicity than traditional solvents. A fundamental understanding of the molecular mechanisms responsible for IL toxicity remains elusive. Here we show that one mode of IL toxicity on unicellular organisms is driven by swelling of the cell membrane. Cytotoxicity assays, confocal laser scanning microscopy, and molecular simulations reveal that IL cations nucleate morphological defects in the microbial cell membrane at concentrations near the half maximal effective concentration (EC50) of several microorganisms. Cytotoxicity increases with increasing alkyl chain length of the cation due to the ability of the longer alkyl chain to more easily embed in, and ultimately disrupt, the cell membrane. PMID:26831599

Synthesis of block copolymers consists on vinylidene chloride and α- Methylstyrene by cationic polymerization using an acid exchanged motmorillonite clay as heterogeneous catalyst (Algerian MMT)

NASA Astrophysics Data System (ADS)

Ayat, Moulkheir; Belbachir, Mohamed; Rahmouni, Abdelkader

2017-07-01

The aim of this study was to develop the efficient and versatile method for the synthesis of block copolymers consists by cationic polymerization vinylidene chloride (VDC) and alpha-methylstyrene (alpha-MS) in the presence of a natural Algerian montmorillonite clay modified by 0.05-0.35 M H2SO4 (Algerian MMT-H+). It was found that H2SO4 concentration allows controlling the chemical composition, the porous structure of the acid-activated clays and their catalytic performance. The maximal yield of polymer is observed in the presence of Algerian MMT modified by 0.25 M H2SO4. Effects of VDC/MS molar ration, catalyst concentration, reaction time, reaction temperature and polarity medium on yield and molecular weight of polymer were revealed in the presence of the most active sample.

Semi-empirical spectrophotometric (SESp) method for the indirect determination of the ratio of cationic micellar binding constants of counterions X⁻ and Br⁻(K(X)/K(Br)).

PubMed

Khan, Mohammad Niyaz; Yusof, Nor Saadah Mohd; Razak, Norazizah Abdul

2013-01-01

The semi-empirical spectrophotometric (SESp) method, for the indirect determination of ion exchange constants (K(X)(Br)) of ion exchange processes occurring between counterions (X⁻ and Br⁻) at the cationic micellar surface, is described in this article. The method uses an anionic spectrophotometric probe molecule, N-(2-methoxyphenyl)phthalamate ion (1⁻), which measures the effects of varying concentrations of inert inorganic or organic salt (Na(v)X, v = 1, 2) on absorbance, (A(ob)) at 310 nm, of samples containing constant concentrations of 1⁻, NaOH and cationic micelles. The observed data fit satisfactorily to an empirical equation which gives the values of two empirical constants. These empirical constants lead to the determination of K(X)(Br) (= K(X)/K(Br) with K(X) and K(Br) representing cationic micellar binding constants of counterions X and Br⁻). This method gives values of K(X)(Br) for both moderately hydrophobic and hydrophilic X⁻. The values of K(X)(Br), obtained by using this method, are comparable with the corresponding values of K(X)(Br), obtained by the use of semi-empirical kinetic (SEK) method, for different moderately hydrophobic X. The values of K(X)(Br) for X = Cl⁻ and 2,6-Cl₂C6H₃CO₂⁻, obtained by the use of SESp and SEK methods, are similar to those obtained by the use of other different conventional methods.

Clarithromycin and Tetracycline Binding to Soil Humic Acid in the Absence and Presence of Calcium.

PubMed

Christl, Iso; Ruiz, Mercedes; Schmidt, J R; Pedersen, Joel A

2016-09-20

Numerous ionizable organic micropollutants contain positively charged moieties at pH values typical of environmental systems. Describing organic cation and zwitterion interaction with dissolved natural organic matter requires explicit consideration of the pH-dependent speciation of both sorbate and sorbent. We studied the pH-, ionic strength-, and concentration-dependent binding of relatively large, organic cations and zwitterions (viz., the antibiotics clarithromycin and tetracycline) to dissolved humic acid in the absence and presence of Ca(2+) and evaluated the ability of the NICA-Donnan model to describe the data. Clarithromycin interaction with dissolved humic acid was well described by the model including the competitive effect of Ca(2+) on clarithromycin binding over a wide range of solution conditions by considering only the binding of the cationic species to low proton-affinity sites in humic acid. Tetracycline possesses multiple ionizable moieties and forms complexes with Ca(2+). An excellent fit to experimental data was achieved by considering tetracycline cation interaction with both low and high proton-affinity sites of humic acid and zwitterion interaction with high proton-affinity sites. In contrast to clarithromycin, tetracycline binding to humic acid increased in the presence of Ca(2+), especially under alkaline conditions. Model calculations indicate that this increase is due to electrostatic interaction of positively charged tetracycline-Ca complexes with humic acid rather than due to the formation of ternary complexes, except at very low TC concentrations.

Water Quality of a Tropical Montane Cloud Forest Watershed, Monteverde, Costa Rica

NASA Astrophysics Data System (ADS)

Rhodes, A. L.; Guswa, A. J.; Dallas, S.; Kim, E. M.; Katchpole, S.; Newell, S. E.; Pufall, A.

2004-05-01

The Rio Guacimal originates in the Monteverde Cloud Forest Preserve, located on the leeward side of the continental divide through Costa Rica. Agriculture and ecotourism has spurred growth adjacent to the preserve. Continued development coupled with changes in precipitation patterns could stress the quality and quantity of water. This study characterizes water chemistry and surface water hydrology of a 21 km2 headwater catchment to evaluate effects of current and projected land use on water quality. Stream samples have been collected from up to 11 sites since March 2000. Two sites located on tributaries in remote, forested areas serve as references for sites located downstream of agricultural and residential areas. Waters were analyzed for specific conductance, pH, DO, acid neutralizing capacity (ANC), Ca, Mg, Na, NH4, SO4, NO3, Cl, PO4 and dissolved silica. In the upland, forested streams, chemical loading is dominated by mineral weathering and cation exchange reactions. Silica, ANC and base cation concentrations all exceed sum of acid anions. During the dry season, concentrations of all dissolved constituents increase synchronously, but at different magnitudes (SO4 and Cl by 15 μ eq/L; silica by 250 μ mol/L; sum of base cations and ANC by 120 μ eq/L), suggesting that increased baseflow has a greater effect on temporal changes of chemical loads in high-elevation, forested streams than does evapotranspiration. Chemical loads of streams receiving runoff from populated areas are 2-5x more concentrated than the upland sites. Highest concentrations occur in Queb. Sucia (QS), which receives grey-water runoff from residential areas. Acidic runoff decreases the ANC of QS by 90-200 μ eq/L; however high alkalinity (ANC=400-1000 μ eq/L) prevents acidification. Acid anions in streams receiving grey-water runoff throughout the year are most concentrated during the dry season when dilution from precipitation is least. Conversely, a site that receives nonpoint source pollution from agricultural areas has its highest concentrations of acid anions during the wet season when surface runoff is the dominant flowpath.

Novel approach for modifying microporous filters for virus concentration from water.

PubMed Central

Preston, D R; Vasudevan, T V; Bitton, G; Farrah, S R; Morel, J L

1988-01-01

Electronegative microporous filters composed of epoxyfiberglass (Filterite) were treated with cationic polymers to enhance their virus-adsorbing properties. This novel and inexpensive approach to microporous filter modification entails soaking filters in an aqueous solution of a cationic polymer such as polyethyleneimine (PEI) for 2 h at room temperature and then allowing the filters to air dry overnight on absorbent paper towels. PEI-treated filters were evaluated for coliphage (MS2, T2, and phi X174) and enterovirus (poliovirus type 1 and coxsackievirus type B5) adsorption from buffer at pH 3.5 to 9.0 and for indigenous coliphages from unchlorinated secondary effluent at ambient pH. Adsorbed viruses were recovered with 3% beef extract (pH 9). Several other cationic polymers were used to modify epoxyfiberglass filters and were evaluated for their ability to concentrate viruses from water. Zeta potentials of disrupted filter material indicated that electronegative epoxyfiberglass filters were made more electropositive when treated with cationic polymers. In general, epoxyfiberglass filters treated with cationic polymers were found to adsorb a greater percentage of coliphages and enteroviruses than were untreated filters. PMID:2843091

Effects of cations and anions as aggregating agents on SERS detection of cotinine (COT) and trans-3'-hydroxycotinine (3HC).

PubMed

Han, Sungyub; Hong, Seongmin; Li, Xiao

2013-11-15

The sensitivity of surface-enhanced Raman spectroscopy (SERS) highly depends on experimental factors including aggregating agents and pH. Using silver nanoparticles as the substrate, the effect of five cationic (K(+), Na(+), Mg(2+), Li(+), Ca(2+)) and three anionic (Cl(-), Br(-), I(-)) aggregating agents was examined on the SERS detection of tobacco-related biomarkers, namely cotinine (COT) and trans-3'-hydroxycotinine (3HC). The optimal concentrations of the aggregating agents with respect to highest SERS intensity varied widely (from 1.5 mM for MgCl2 to 150 mM for LiCl). Both cations and anions strongly influenced the SERS enhancement. When Cl(-) was used as the anion, Mg(2+) and Na(+) exhibited the highest SERS intensities for COT and 3HC, respectively. When Mg(2+) was used as the cation, Cl(-) and Br(-) generated the highest SERS enhancement for COT and 3HC, respectively. Clearly, SERS enhancement also depended on the target molecule. Among the 11 aggregating agent combinations tested, the highest SERS enhancement is obtained using 1.5 mM MgCl2 for COT at pH 7.0 and 50 mM NaBr for 3HC at pH 3.0. Copyright © 2013 Elsevier Inc. All rights reserved.

How do silanes affect the lubricating properties of cationic double chain surfactant on silica surfaces?

PubMed

Beauvais, Muriel; Serreau, Laurence; Heitz, Caroline; Barthel, Etienne

2009-03-01

The effect of an aminosilane on the lubricant properties of a C(18) double-chained cationic surfactant has been investigated in the context of glass fiber forming process. The surfactant adsorption was studied on silica by Fourier transform infrared (FT-IR) spectroscopy in the attenuated total reflexion (ATR) mode as a function of the aminosilane concentration in an organic water based formulation (sizing) used to coat the glass fibers during the process. A reciprocating ball-on-plate tribometer was used to compare friction properties of silica in contact with the aminosilane-surfactant mixture and in presence of each component of the sizing. Surface forces were measured between silica and an atomic force microscope (AFM) silicon nitride tip in the sizing and in the pure cationic surfactant solution. The aminosilane on its own has no lubricant property and reduces or even suppresses the cationic surfactant adsorption on silica. However, the silica-silica contact is lubricated even if the infrared spectroscopy does not detect any surfactant adsorption. The repeated contacts and shear due to the friction experiment itself induce accumulation, organization and compactness of surfactant bilayers.

Characteristics of inositol trisphosphate mediated Ca/sup 2 +/ release from permeabilized hepatocytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joseph, S.K.; Williamson, J.R.

1986-05-01

Ca/sup 2 +/ release triggered by inositol trisphosphate (IP/sub 3/) has been measured in saponin-permeabilized hepatocytes with /sup 45/Ca/sup 2 +/ or Quin 2. The initial rate of Ca/sup 2 +/ release was not markedly affected by the incubation temperature (175 +/- 40 pmol/s/mg at 30/sup 0/C versus 133 +/- 24 pmol/s/mg at 4/sup 0/C). This result is consistent with the membrane translocation of Ca/sup 2 +/ occurring through an ion-channel rather than an ion-carrier. The amount of Ca/sup 2 +/ released by IP/sub 3/ was not affected by pH (6.5-8.0) or by compounds that inhibit voltage-gated Ca/sup 2 +/more » channels. La/sup 3 +/ (100 ..mu..M) markedly inhibits the effect of 1 ..mu..M IP/sub 3/. The possibility that La/sup 3 +/ chelates IP/sub 3/ cannot be excluded since the effect of La/sup 3 +/ can be overcome by increasing the IP/sub 3/ concentration. IP/sub 3/-mediated Ca/sup 2 +/ release displays a requirement for a permeant cation in the incubation medium. Optimal release is observed with K/sup +/ gluconate. Other monovalent cations, with the exception of Li/sup +/, can substitute for K/sup +/. Permeant anions, at concentrations above 40 mM, inhibit Ca/sup 2 +/ release produced by IP/sub 3/. Cl/sup -/, Br/sup -/, I/sup -/, and SO/sub 4//sup 2 -/ were equally effective. Ca/sup 2 +/ release was not inhibited by DIDS or Furosemide. /sup 85/Sr/sup 2 +/ and /sup 54/Mn/sup 2 +/ fluxes were also stimulated by IP/sub 3/. These results suggest that IP/sub 3/ acts to gate a divalent cation channel. The translocation of positive charge through this channel is balanced by ancillary movements of monovalent cations and anions across the reticular membrane.« less

Characteristics of inositol trisphosphate-mediated Ca/sup 2 +/ release from permeabilized hepatocytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joseph, S.K.; Williamson, J.R.

1986-11-05

Ca/sup 2 +/ release triggered by inositol trisphosphate (Ins(1,4,5)P/sub 3/) has been measured in saponin-permeabilized hepatocytes with /sup 45/Ca/sup 2 +/ or Quin 2. The initial rate of Ca/sup 2 +/ release was not greatly affected by the incubation temperature. The amount of Ca/sup 2 +/ released by Ins(1,4,5)P/sub 3/ was not affected by pH (6.5-8.0). La/sup 3 +/ (100 ..mu..M) markedly inhibited the effect of 1 ..mu..M Ins(1,4,5)P/sub 3/. The possibility that La/sup 3 +/ chelates Ins(1,4,5)P/sub 3/ cannot be excluded since the effect of La/sup 3 +/ could be overcome by increasing the Ins(1,4,5)P/sub 3/ concentration. Ins(1,4,5)P/sub 3/-mediatedmore » Ca/sup 2 +/ release showed a requirement for permeant cations in the incubation medium. Optimal release was observed with potassium gluconate. Other monovalent cations, with the exception of Li/sup +/, can substitute for K/sup +/. Permeant anions, at concentrations above 40 mM, inhibited Ca/sup 2 +/ release produced by Ins(1,4,5)P/sub 3/. Cl/sup -/, Br/sup -/, I/sup -/, and SO/sup 2 -//sub 4/ were equally effective as inhibitors. Ins(1,4,5)P/sub 3/ also caused the release of /sup 54/Mn/sup 2 +/ and /sup 85/Sr/sup 2 +/ accumulated by the permeabilized hepatocytes. The results are consistent with Ins(1,4,5)P/sub 3/ promoting the membrane translocation of divalent cations through an ion channel rather than an ion carrier. The translocation of positive charge through this channel is balanced by ancillary movements of monovalent cations and anions across the reticular membranes. The transport systems responsible for these compensatory ion movements may represent a potential site for the regulation of the hormone-mediated Ca/sup 2 +/ signal.« less

Structural vs. intrinsic carriers: contrasting effects of cation chemistry and disorder on ionic conductivity in pyrochlores

DOE PAGES

Perriot, Romain; Uberuaga, Blas P.

2015-04-21

We use molecular dynamics simulations to investigate the role of cation disorder on oxygen diffusion in Gd 2Zr 2O 7 (GZO) and Gd 2Ti 2O 7 (GTO) pyrochlores, a class of complex oxides which contain a structural vacancy relative to the basic fluorite structure. The introduction of disorder has distinct effects depending on the chemistry of the material, increasing the mobility of structural carriers by up to four orders of magnitude in GZO. In contrast, in GTO, there is no mobility at zero or low disorder on the ns timescale, but higher disorder liberates the otherwise immobile carriers, allowing diffusionmore » with rates comparable to GZO for the fully disordered material. Here, we show that the cation disorder enhances the diffusivity by both increasing the concentration of mobile structural carriers and their individual mobility. The disorder also influences the diffusion in materials containing intrinsic carriers, such as additional vacancies VO or oxygen interstitials OI. And while in ordered GZO and GTO the contribution of the intrinsic carriers dominates the overall diffusion of oxygen, OI in GZO contributes along with structural carriers, and the total diffusion rate can be calculated by assuming simple additive contributions from the two sources. Although the disorder in the materials with intrinsic defects usually enhances the diffusivity as in the defect-free case, in low concentrations, cation antisites AB or BA, where A = Gd and B = Zr or Ti, can act as traps for fast intrinsic defects. The trapping results in a lowering of the diffusivity, and causes a non-monotonic behavior of the diffusivity with disorder. Conversely, in the case of slow intrinsic defects, the main effect of the disorder is to liberate the structural carriers, resulting in an increase of the diffusivity regardless of the defect trapping.« less

Solid Solutions of Rare Earth Cations in Mesoporous Anatase Beads and Their Performances in Dye-Sensitized Solar Cells

PubMed Central

Cavallo, Carmen; Salleo, Alberto; Gozzi, Daniele; Di Pascasio, Francesco; Quaranta, Simone; Panetta, Riccardo; Latini, Alessandro

2015-01-01

Solid solutions of the rare earth (RE) cations Pr3+, Nd3+, Sm3+, Gd3+, Er3+ and Yb3+ in anatase TiO2 have been synthesized as mesoporous beads in the concentration range 0.1–0.3% of metal atoms. The solid solutions were have been characterized by XRD, SEM, diffuse reflectance UV-Vis spectroscopy, BET and BJH surface analysis. All the solid solutions possess high specific surface areas, up to more than 100 m2/g. The amount of adsorbed dye in each photoanode has been determined spectrophotometrically. All the samples were tested as photoanodes in dye-sensitized solar cells (DSSCs) using N719 as dye and a nonvolatile, benzonitrile based electrolyte. All the cells were have been tested by conversion efficiency (J–V), quantum efficiency (IPCE), electrochemical impedance spectroscopy (EIS) and dark current measurements. While lighter RE cations (Pr3+, Nd3+) limit the performance of DSSCs compared to pure anatase mesoporous beads, cations from Sm3+ onwards enhance the performance of the devices. A maximum conversion efficiency of 8.7% for Er3+ at a concentration of 0.2% has been achieved. This is a remarkable efficiency value for a DSSC employing N719 dye without co-adsorbents and a nonvolatile electrolyte. For each RE cation the maximum performances are obtained for a concentration of 0.2% metal atoms. PMID:26577287

Impact of cationic surfactant on the self-assembly of sodium caseinate.

PubMed

Vinceković, Marko; Curlin, Marija; Jurašin, Darija

2014-08-27

The impact of a cationic surfactant, dodecylammonium chloride (DDACl), on the self-assembly of sodium caseinate (SC) has been investigated by light scattering, zeta potential, and rheological measurements as well as by microscopy (transmission electron and confocal laser scanning microscopy). In SC dilute solutions concentration-dependent self-assembly proceeds through the formation of spherical associates and their aggregation into elongated structures composed of connected spheres. DDACl interacts with SC via its hydrophilic and hydrophobic groups, inducing changes in SC self-assembled structures. These changes strongly depend on the surfactant aggregation states (monomeric or micellar) as well as concentration ratio of both components, leading to the formation of soluble and insoluble complexes of nano- to microdimensions. DDACl monomers interact with SC self-assembled entities in a different way compared to their micelles. Surfactant monomers form soluble complexes (similar to surfactant mixed micelles) at lower SC concentration but insoluble gelatinous complexes at higher SC concentration. At surfactant micellar concentration soluble complexes with casein chains wrapped around surfactant micelles are formed. This study suggests that the use of proper cationic surfactant concentration will allow modification and control of structural changes of SC self-assembled entities.

Standard Materials for Microbeam Analysis of Lanthanides and Actinides

NASA Astrophysics Data System (ADS)

Ellis, I.; Gorton, M.; Rucklidge, J. C.

2010-12-01

Traces of Th and U in naturally-occuring minerals monazite, xenotime and zircon are used for dating host rocks. Natural variations of actinide concentrations in some rock formations are well documented. Microbeam techniques perform dating in-situ where grains of indicator minerals are left intact in thin sections. Separated individual grains of these minerals are also routinely dated by Pb-isotope mass spectrometry. Ideal calibration materials will be compatible with multiple techniques. Quantitative analysis of low levels of lanthanides (REE), U, Th and Pb found in natural minerals requires standards containing similar concentrations of these elements. The ideal low-level standard suite will have materials with each REE cation present below 5%, similar to natural rare-earth phosphate minerals. In contrast, REE orthophosphates LnPO4 have cation concentrations from 59 to 64%, and ultraphosphates LnP5O14 from 27% to 32%. The concentrations of U and Pb must also be in the 1% range in the host REE phosphate. There are two competing limits to the synthesis of crystals with multiple cations in the REE sites. The crystal structure limits potential cation mixtures to selections within groups (La,Ce, Pr, Nd, Sm, Eu), (Gd, Tb, Dy, Ho), and (Er, Tm,Yb, Lu, Y). Complex L X-ray spectra limit the use of contiguous REE in a single material. There are two general synthetic routes for the preparation of lanthanide/actinide standard materials for beam analysis and dating. Lanthanide orthophosphates (LnPO4) are crystallized from lead-free heterogeneous fluxes; oligomers (metaphosphates LnP3O9 and ultraphosphates LnP5O14) are formed by condensation of phosphoric acid in the presence of cations. All of these trivalent lanthanide phosphate crystal structures are hosts for Th+4 and U+4, and in synthetic materals, Ca+2 is used for charge compensation. Our work focuses on the preparation of mixed-cation lanthanide metaphosphates and ultraphosphates. The solvent (essentially P2O5) provides redox conditions that favour Ce+3, Th+4, and U+4 instead of higher oxidation states. The absence of any cations other than those deliberately added permits positive control of cation mixtures in starting materials. The synthetic pathway—condensation of POx units--provides ideal conditions for the homogeneous distribution of cations including those with different charges. We present the results of synthesis, elemental analysis and imaging by XRF and SEM-EDX for mixed lanthanide-actinide phosphate materials.

Effect of salt solutions on radiosensitivity of mammalian cells. I. Specific ion effects.

PubMed

Raaphorst, G P; Kruuv, J

1977-07-01

The radiation isodose survival curve of cells subjected to a wide concentration range of sucrose solutions has two maxima separated by a minimum. Both cations and anions can alter the cellular radiosensitivity above and beyond the osmotic effect observed for cells treated with sucrose solutions. The basic shape of the isodose curve can also be modulated by changes in temperature and solution exposure times. Some of these alterations in radiosensitivity may be related to changes in the amount and structure of cellular water or macromolecular conformation or to the direct effect of the ions, expecially at high solute concentrations.

Independent modulation of the activity of alpha-ketoglutarate dehydrogenase complex by Ca2+ and Mg2+.

PubMed

Panov, A; Scarpa, A

1996-01-16

The activity of alpha-ketoglutarate dehydrogenase complex (KGDHC), an important enzyme regulating several metabolic pathways, could be regulated by changes in the environment within the mitochondrial matrix. It has been postulated that the activity of this and other dehydrogenases in vivo could be modulated by changes in the intramitochondrial concentrations of Ca2+ or Mg2+. Using a purified alpha-ketoglutarate dehydrogenase from pig hearts, the effect of Ca2+ and/or Mg2+ on the enzyme activity was investigated. Either Ca2+ or Mg2+ increased enzyme activity, and the effects were additive if the concentrations of free divalent cations were below 0.1 and 1 mM for Ca2+ and Mg2+, respectively. In the presence of 1 mM alpha-ketoglutarate and other cofactors, the KM for Mg2+ was 25 microM and less than 1 microM for Ca2+. The KM for alpha-ketoglutarate was a function of the divalent cation(s) present: 4 +/- 1.1 mM in the absence of Ca2+, with or without Mg2+; 2.2 mM in the presence of 1.8 microM Ca2+ alone; and 0.3 mM in the presence of both Ca2+ and Mg2+. Mg2+ increased KGDHC activity only in the presence of thiamine pyrophosphate (TPP) indicating that KGDHC requires both TPP and Mg2+ for enzyme's maximal activity. The affinity of KGDHC for NAD+ is significantly changed by either Mg2+ or Ca2+. The conclusions are that changes in both Ca2+ and Mg2+, in concentrations possibly occurring within mitochondria, could control KGDHC activity and that thiamine pyrophosphate is required for maximal enzyme activity.

Trace element biogeochemistry in the soil-water-plant system of a temperate agricultural soil amended with different biochars.

PubMed

Kloss, Stefanie; Zehetner, Franz; Buecker, Jannis; Oburger, Eva; Wenzel, Walter W; Enders, Akio; Lehmann, Johannes; Soja, Gerhard

2015-03-01

Various biochar (BC) types have been investigated as soil amendment; however, information on their effects on trace element (TE) biogeochemistry in the soil-water-plant system is still scarce. In the present study, we determined aqua-regia (AR) and water-extractable TEs of four BC types (woodchips (WC), wheat straw (WS), vineyard pruning (VP), pyrolyzed at 525 °C, of which VP was also pyrolyzed at 400 °C) and studied their effects on TE concentrations in leachates and mustard (Sinapis alba L.) tissue in a greenhouse pot experiment. We used an acidic, sandy agricultural soil and a BC application rate of 3% (w/w). Our results show that contents and extractability of TEs in the BCs and effectuated changes of TE biogeochemistry in the soil-water-plant system strongly varied among the different BC types. High AR-digestable Cu was found in VP and high B contents in WC. WS had the highest impact on TEs in leachates showing increased concentrations of As, Cd, Mo, and Se, whereas WC application resulted in enhanced leaching of B. All BC types increased Mo and decreased Cu concentrations in the plant tissue; however, they showed diverging effects on Cu in the leachates with decreased concentrations for WC and WS, but increased concentrations for both VPs. Our results demonstrate that BCs may release TEs into the soil-water-plant system. A BC-induced liming effect in acidic soils may lead to decreased plant uptake of cationic TEs, including Pb and Cd, but may enhance the mobility of anionic TEs like Mo and As. We also found that BCs with high salt contents (e.g., straw-based BCs) may lead to increased mobility of both anionic and cationic TEs in the short term.

Bactericidal Efficacy of Hydrogen Peroxide-Based Disinfectants Against Gram-Positive and Gram-Negative Bacteria on Stainless Steel Surfaces.

PubMed

Ríos-Castillo, Abel G; González-Rivas, Fabián; Rodríguez-Jerez, José J

2017-10-01

In order to develop disinfectant formulations that leverage the effectiveness of hydrogen peroxide (H 2 O 2 ), this study evaluated the bactericidal efficacy of hydrogen peroxide-based disinfectants against Gram-positive and Gram-negative bacteria on stainless steel surfaces. Low concentration of hydrogen peroxide as 0.5% with a cationic polymer, ethoxylated fatty alcohol, and ethyl alcohol had bactericidal efficacy (reductions ≥ 4 log 10 CFU/mL) against Escherichia coli, Staphylococcus aureus, Enterococcus hirae, and Pseudomonas aeruginosa. Hydrogen peroxide-based disinfectants were more effective against E. hirae and P. aeruginosa than to S. aureus. However, the efficacy of hydrogen peroxide against catalase positive bacteria such as S. aureus was increased when this compound was formulated with low concentrations of benzalkonium chloride or ethyl alcohol, lactic acid, sodium benzoate, cationic polymer, and salicylic acid. This study demonstrates that the use of hydrogen peroxide with other antimicrobial products, in adequate concentrations, had bactericidal efficacy in Gram-positive and Gram-negative bacteria on stainless steel surfaces, enabling to reduce the effective concentration of hydrogen peroxide. In the same way, the use of hydrogen peroxide-based disinfectants could reduce the concentrations of traditional disinfectants as quaternary ammonium compounds and therefore a reduction of their chemical residues in the environment after being used. The study of the bactericidal properties of environmentally nontoxic disinfectants such as hydrogen peroxide, sole or in formulations with other disinfectants against Gram-positive and Gram-negative bacteria can enhance the efficacy of various commonly used disinfectant formulations with the hygiene benefits that it entails. Also, the use of hydrogen peroxide formulations can reduce the concentration levels of products that generate environmental residues. © 2017 Institute of Food Technologists®.

Kinetics and Mechanisms of Chemical and Biological Agents Release from Biopolymeric Microcapsules.

PubMed

Vinceković, Marko; Jurić, Slaven; Đermić, Edyta; Topolovec-Pintarić, Snježana

2017-11-08

Kinetics and mechanisms of copper cations and Trichoderma viride spores release from uncoated and chitosan coated alginate microcapsules were investigated. The gelation of a fixed amount of sodium alginate at different concentrations of copper ion solutions resulted in distinct kinetics and release mechanisms. The increase in copper cation concentration promoted, but the presence of the chitosan layer on the microcapsule surface and the increase in microcapsule size reduced the rate of active agent release. Fitting to simple Korsmeyer-Peppas empirical model revealed that the underlying release mechanism (Fickian diffusion or a combination of the diffusion and erosion mechanisms) depends on the copper cation concentration and presence of T. viride spores. The investigation pointed out that the proper selection of formulation variables helps in designing microcapsules with the desirable release of copper ions and T. viride for plant protection and nutrition.

The biogeochemical fingerprint of urbanization: increasing carbon quality in Maine headwater streams

NASA Astrophysics Data System (ADS)

Parr, T.; Cronan, C.; Ohno, T.; Simon, K. S.

2012-12-01

Conversion of land cover to urban use is an accelerating global phenomenon. Physical landscape change manifests as the replacement of forests, grasslands, and wetlands with buildings, novel vegetation, and infrastructure. This physical change also brings with it a change in the human management of the landscape for aesthetic and practical purposes (i.e. road salt applications). Although urbanization's effects on inorganic nutrients have been well studied, far less is known about the interactive influences of urbanization and urban landscape management practices on dissolved organic matter (DOM), a key energy source essential to ecosystem function. We examined the seasonal abundance and composition of DOM, nutrients, and common cations in 116 small streams along a gradient of urbanization (0-60% total watershed imperviousness, TWI), in Maine, USA. Dissolved organic carbon concentration ranged from 0.5 to 20 ppm with no clear relationship to watershed urbanization. In contrast, DOM composition, quantified with specific ultra violet absorbance at 254 nm (SUVA_{254}), fluorescence indices, and parallel factor analysis (PARAFAC), changed considerably with increasing urbanization. SUVA_{254} indicated a shift from higher molecular weight humic compounds (SUVA_{254}>4) toward lower molecular weight compounds (SUVA_{254}<2.5) with increasing urbanization. Fluorescence indices (Fluorescence Index, Humification Index, and α:β) indicated DOM source shifted from allochthonous sources (e.g. plant and soil carbon) toward autochthonously derived compounds (e.g. derivatives of in-stream algal and microbial production). Humic acid-like compounds decreased from 40% to 10% of the fluorescent DOM pool, while fluorescence of more labile compounds increased from 10 to 25% with increasing urbanization. Laboratory bioassays of DOM degradation rates showed that increasing urbanization doubled the bioavailability of DOM. Ratios of DOC:DON declined from 20-50 at TWI<8% to <20 above 8% TWI. Changes in the DOM pool were unrelated to inorganic nutrient concentrations, but were related to base cation concentrations. Concentrations of base cations (Ca^{2+}, Mg^{2+}, K^+, Na^+) increased 3-100 fold with increasing impervious cover. The stoichiometric relationships among Na^+, Cl^- and other base cations suggest road salt application may mobilize base cations into streams draining urbanized watersheds. There was a strong negative relationship between humic-like DOM components and Ca^{2+} (R^2=0.3-0.5, p<0.01) across streams. Bottle incubations of ^1+ and ^{2+} base cation salts over a natural range (0 - 6 mM) showed that ^{2+} cations (esp. Ca^{2+}) preferentially flocculated the humic fraction of DOM (R^2=0.6-0.9, p<0.01). These results indicate that the carbon composition change observed with urbanization in Maine may be controlled by multiple concurrent processes linked to the creation and maintenance of urban landscapes. Our data suggest that a key biogeochemical consequence of urbanization may be an increase in abundance of labile carbon which may have important consequences for ecosystem function in urban systems. This process may be driven by a combination of altered landscape C sources reducing terrestrial C inputs, enhancement of in-stream C production, and base cation enrichment that removing terrestrial C from the aquatic DOM pool in urban landscapes.

Sorption of amitriptyline and amphetamine to mixed-mode solid-phase microextraction in different test conditions.

PubMed

Peltenburg, Hester; Droge, Steven T J; Hermens, Joop L M; Bosman, Ingrid J

2015-04-17

A solid-phase microextraction (SPME) method based on a sampler coating that includes strong cation groups (C18/SCX) is explored as a rapid direct sampling tool to detect and quantify freely dissolved basic drugs. Sampling kinetics, sorption isotherms and competitive effects on extraction yields in mixtures were tested for amphetamine and the relatively large/hydrophobic tricyclic antidepressant amitriptyline. Both compounds are >99% ionized at pH 7.4 but their affinity for the C18/SCX fiber is markedly different with distribution coefficients (Dfw values) of 2.49±0.02 for amphetamine and 4.72±0.10 for amitriptyline. Typical changes in electrolyte homeostasis that may occur in biomedical samples were simulated by altering pH and ionic composition (Na(+) and K(+) concentrations). These changes were shown to affect C18/SCX sorption affinities of the tested drugs with less than 0.2log units. At relatively low fiber loadings (<10mmol/L coating) and at all tested exposure times, linear sorption isotherms were obtained for both compounds but at aqueous concentrations of the individual drugs corresponding to concentrations in blood that are lethal, sorption isotherms became strongly nonlinear. Competition effects within binary mixtures occurred only if combinations of aqueous concentrations resulted in total fiber loadings that were in the nonlinear range of the SPME sorption isotherm for the individual compounds. We also compared sorption to the (prototype) C18/SCX SPME coating with analogue (biocompatible) C18 coated SPME fibers. C18/SCX fibers show increased sorption affinity for cationic compounds compared to C18 fibers, as tested using amitriptyline, amphetamine and trimethoprim. Surprisingly, sorption affinity of these ionized compounds for the C18 SPME fibers were within 1log unit of the C18/SCX SPME fibers. This shows that the strong cation exchange groups within the C18/SCX coating only has a relatively small contribution to the total sorption affinity of cationic compounds. Also the role of negatively charged silanol groups in both the C18 and C18/SCX coating seems small, as anionic diclofenac species sorbed strongly to the C18 fiber. Ionized organic species seem to be substantially adsorbed to the high surface area of C18 in SPME types using porous silica based coatings. Copyright © 2015 Elsevier B.V. All rights reserved.

Potentiation of TRPM7 Inward Currents by Protons

PubMed Central

Jiang, Jianmin; Li, Mingjiang; Yue, Lixia

2005-01-01

TRPM7 is unique in being both an ion channel and a protein kinase. It conducts a large outward current at +100 mV but a small inward current at voltages ranging from −100 to −40 mV under physiological ionic conditions. Here we show that the small inward current of TRPM7 was dramatically enhanced by a decrease in extracellular pH, with an ∼10-fold increase at pH 4.0 and 1–2-fold increase at pH 6.0. Several lines of evidence suggest that protons enhance TRPM7 inward currents by competing with Ca2+ and Mg2+ for binding sites, thereby releasing blockade of divalent cations on inward monovalent currents. First, extracellular protons significantly increased monovalent cation permeability. Second, higher proton concentrations were required to induce 50% of maximal increase in TRPM7 currents when the external Ca2+ and Mg2+ concentrations were increased. Third, the apparent affinity for Ca2+ and Mg2+ was significantly diminished at elevated external H+ concentrations. Fourth, the anomalous-mole fraction behavior of H+ permeation further suggests that protons compete with divalent cations for binding sites in the TRPM7 pore. Taken together, it appears that at physiological pH (7.4), Ca2+ and Mg2+ bind to TRPM7 and inhibit the monovalent cationic currents; whereas at high H+ concentrations, the affinity of TRPM7 for Ca2+ and Mg2+ is decreased, thereby allowing monovalent cations to pass through TRPM7. Furthermore, we showed that the endogenous TRPM7-like current, which is known as Mg2+-inhibitable cation current (MIC) or Mg nucleotide–regulated metal ion current (MagNuM) in rat basophilic leukemia (RBL) cells was also significantly potentiated by acidic pH, suggesting that MIC/MagNuM is encoded by TRPM7. The pH sensitivity represents a novel feature of TRPM7 and implies that TRPM7 may play a role under acidic pathological conditions. PMID:16009728

ADSORPTION OF ORGANIC CATIONS TO NATURAL MATERIALS

EPA Science Inventory

The factors that control the extent of adsorption of amphiphilic organic cations on environmental and pristine surfaces have been studied. The sorbents were kaolinite, montmorillonite, two aquifer materials, and a soil; solutions contained various concentrations of NaCl and CaCl,...

Colloidal behavior of goethite nanoparticles modified with humic acid and implications for aquifer reclamation

NASA Astrophysics Data System (ADS)

Tiraferri, Alberto; Saldarriaga Hernandez, Laura Andrea; Bianco, Carlo; Tosco, Tiziana; Sethi, Rajandrea

2017-03-01

Nanosized colloids of iron oxide adsorb heavy metals, enhance the biodegradation of contaminants, and represent a promising technology to clean up contaminated aquifers. Goethite particles for aquifer reclamation were recently synthesized with a coating of humic acids to reduce aggregation. This study investigates the stability and the mobility in porous media of this material as a function of aqueous chemistry, and it identifies the best practices to maximize the efficacy of the related remediation. Humic acid-coated nanogoethite (hydrodynamic diameter ˜90 nm) displays high stability in solutions of NaCl, consistent with effective electrosteric stabilization. However, particle aggregation is fast when calcium is present and, to a lesser extent, also in the presence of magnesium. This result is rationalized with complexation phenomena related to the interaction of divalent cations with humic acid, inducing rapid flocculation and sedimentation of the suspensions. The calcium dose, i.e., the amount of calcium ions with respect to solids in the dispersion, is the parameter governing stability. Therefore, more concentrated slurries may be more stable and mobile in the subsurface than dispersions of low particle concentration. Particle concentration during field injection should be thus chosen based on concentration and proportion of divalent cations in groundwater.

Stimulating effects of a diet negative in dietary cation-anion difference on calcium absorption from the rumen in sheep.

PubMed

Wilkens, M R; Praechter, C; Breves, G; Schröder, B

2016-02-01

The concept of feeding anionic salts in late gestation is widely used to prevent milk fever in dairy cows. While the effects of these diets on renal Ca excretion and tissue responsiveness towards parathyroid hormone have clearly been demonstrated, data on a potential impact on gastrointestinal Ca absorption are conflicting. Therefore, the aim of this study was to investigate the influence of feeding a diet negative in dietary cation-anion difference (DCAD) on ruminal mineral concentrations, fermentation products, electrophysiological properties of rumen epithelia and Ca flux rates. For this purpose, sheep were kept for 3 weeks on diets that were either positive or negative in DCAD. The induction of a compensated hyperchloremic metabolic acidosis could be demonstrated by increased plasma Cl and enhanced concentrations of ionised Ca, while plasma concentrations of HCO3- and base excess were decreased with the low DCAD diet. Neither transmural potential differences nor fermentation products were affected, but ruminal concentrations of Cl and Mg as well as the relation of ionised to total Ca were increased. Ussing chamber experiments revealed alterations of electrophysiological parameters and an increase in the electroneutral component of Ca flux rates from the mucosal to the serosal side of rumen epithelium. As plasma calcitriol concentrations were not affected, it can be concluded that the administration of anionic salts results in a vitamin D-independent stimulation of ruminal Ca transport. Journal of Animal Physiology and Animal Nutrition © 2015 Blackwell Verlag GmbH.

Size Dependent Cation Channel in Nanoporous Prussian Blue Lattice

NASA Astrophysics Data System (ADS)

Moritomo, Yutaka; Igarashi, Kazuhiro; Kim, Jungeun; Tanaka, Hiroshi

2009-08-01

Cation and/or molecule transfer within nanoporous materials can be utilized in, for example, electrochromic devices, hydrogen storage, molecular sensors, and molecular filters. Here, we investigated the mobilities of cations, Na+, K+, and Rb+, in vacancy-controlled Prussian blue film, NaxCo[Fe(CN)6]1-vzH2O (v is vacancy concentration) with a jungle gym structure. We found that only the smallest Na+ ions pass through the cubic planes of the lattice, while the larger cations, i.e., K+ and Rb+, take a detour channel along the [Fe(CN)6] vacancy. The size-dependent cation channel is well understood in terms of the potential curve derived by an ab initio total energy calculation.

Fire Frequency and Vegetation Composition Influence Soil Nitrogen Cycling and Base Cations in an Oak Savanna Ecosystem

NASA Astrophysics Data System (ADS)

McLauchlan, K. K.; Nelson, D. M.; Perakis, S.; Marcotte, A. L.

2017-12-01

Fire frequency is crucial for maintaining savannas in the transition between forests and grasslands. In general, increasing fire frequency has two effects: it increases herbaceous plant cover more than woody plant cover, and it lowers soil organic matter stocks. These effects have been demonstrated at a long-term prescribed fire experiment in an oak savanna ecosystem at Cedar Creek Ecosystem Science Reserve, Minnesota, U.S.A. The fire experiment began in 1964 and oak savannas are burned at various frequencies ranging from every year to not at all. This has led to changes in vegetation ranging from almost 100% grassland to 100% oak forest. Additionally, nitrogen stocks almost doubled in the sites that were not burned, as it accumulated in the trees, leaf litter, and soil. We addressed additional soil changes taking place at this experiment by asking the question: How have fire and oak-grass balance affected soil nutrients, specifically nitrogen and base cations? Surface soils were collected from 12 plots on the oak savanna burn experiment. Soils were collected in increments to 100 cm depth, from under grass-dominated vegetation and from under tree-dominated vegetation. We non-destructively estimated soil base cations by measuring elemental concentrations of dried soil subsamples with a handheld x-ray fluorescence analyzer. We also measured carbon and nitrogen concentrations and isotopic composition of the soil samples. Soils in plots with high fire frequency had higher concentrations of calcium than soils in unburned plots (low fire frequency). Similar trends were seen for soil potassium, magnesium, and phosphorus concentrations. In contrast, soils in plots with high fire frequency had dramatically lowered nitrogen cycling rates and stocks across the oak savanna. The contrast between the responses of different nutrients to changing fire frequency has important implications for the consequences of fire and tree-grass composition on nutrient cycling dynamics.

Novel Polymyxin Derivatives Carrying Only Three Positive Charges Are Effective Antibacterial Agents ▿

PubMed Central

Vaara, Martti; Fox, John; Loidl, Günther; Siikanen, Osmo; Apajalahti, Juha; Hansen, Frank; Frimodt-Møller, Niels; Nagai, Junya; Takano, Mikihisa; Vaara, Timo

2008-01-01

The lack of novel antibiotics against gram-negative bacteria has reinstated polymyxins as the drugs of last resort to treat serious infections caused by extremely multiresistant gram-negative organisms. However, polymyxins are nephrotoxic, and this feature may complicate therapy or even require its discontinuation. Like that of aminoglycosides, the nephrotoxicity of polymyxins might be related to the highly cationic nature of the molecule. Colistin and polymyxin B carry five positive charges. Here we show that novel polymyxin derivatives carrying only three positive charges are effective antibacterial agents. NAB739 has a cyclic peptide portion identical to that of polymyxin B, but in the linear portion of the peptide, it carries the threonyl-d-serinyl residue (no cationic charges) instead of the diaminobutyryl-threonyl-diaminobutyryl residue (two cationic charges). The MICs of NAB739 for 17 strains of Escherichia coli were identical, or very close, to those of polymyxin B. Furthermore, NAB739 was effective against other polymyxin-susceptible strains of Enterobacteriaceae and against Acinetobacter baumannii. At subinhibitory concentrations, it dramatically sensitized A. baumannii to low concentrations of antibiotics such as rifampin, clarithromycin, vancomycin, fusidic acid, and meropenem. NAB739 methanesulfonate was a prodrug analogous to colistin methanesulfonate. NAB740 was the most active derivative against Pseudomonas aeruginosa. NAB7061 (linear portion of the peptide, threonyl-aminobutyryl) lacked direct antibacterial activity but sensitized the targets to hydrophobic antibiotics by factors up to 2,000. The affinities of the NAB compounds for isolated rat kidney brush border membrane were significantly lower than that of polymyxin B. PMID:18591267

Structure and optical homogeneity of LiNbO{sub 3}:Zn (0.03–4.5 mol.%) crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sidorov, Nikolay, E-mail: sidorov@chemy.kolasc.net.ru, E-mail: tepl-na@chemy.kolasc.net.ru, E-mail: fleischermed@gmail.com, E-mail: Jovial1985@yandex.ru, E-mail: palat-mn@chemy.kolasc.net.ru; Tepljakova, Natalja, E-mail: sidorov@chemy.kolasc.net.ru, E-mail: tepl-na@chemy.kolasc.net.ru, E-mail: fleischermed@gmail.com, E-mail: Jovial1985@yandex.ru, E-mail: palat-mn@chemy.kolasc.net.ru; Gabain, Aleksei, E-mail: sidorov@chemy.kolasc.net.ru, E-mail: tepl-na@chemy.kolasc.net.ru, E-mail: fleischermed@gmail.com, E-mail: Jovial1985@yandex.ru, E-mail: palat-mn@chemy.kolasc.net.ru

2014-11-14

Structure and optical homogeneity of LiNbO{sub 3}:Zn (0.03–4.5 mol.%) crystals were searched by photoinduced light scattering and by Raman spectroscopy. The photorefractive effect depends on Zn{sup 2+} concentration nonmonotonically. Decrease of photorefractive effect is explained by decrease of structure defects with localized electrons. The Zn{sup 2+} cations replace structure defects Nb{sub Li} and Li{sub Nb}, trapping levels appear near the bottom of the conduction band and photo electrons recombine with emission under laser radiation. By the Raman spectra the area of the high structure order is found. In this area the own alternation, the alternation of impurity cations and themore » vacancies along the polar axis is almost perfect.« less

Dendrite-Free Lithium Deposition via Self-Healing Electrostatic Shield Mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding, Fei; Xu, Wu; Graff, Gordon L.

Lithium metal batteries are called the “holy grail” of energy storage systems. However, lithium dendrite growth in these batteries has prevented their practical applications in the last 40 years. Here we show a novel mechanism which can fundamentally change the dendritic morphology of lithium deposition. A low concentration of the second cations (including ions of cesium, rubidium, potassium, and strontium) exhibits an effective reduction potential lower than the standard reduction potential of lithium ions when the chemical activities of these second cations are much lower than that of lithium ions. During lithium deposition, these second cations will form a self-healingmore » electrostatic shield around the initial tip of lithium whenever it is formed. This shield will repel the incoming lithium ions and force them to deposit in the smoother region of the anode so a dendrite-free film is obtained. This mechanism is effective on dendrite prevention in both lithium metal and lithium ion batteries. They may also prevent dendrite growth in other metal batteries and have transformational impact on the smooth deposition in general electrodeposition processes.« less

Structure-directing effects of ionic liquids in the ionothermal synthesis of metal-organic frameworks.

PubMed

Vaid, Thomas P; Kelley, Steven P; Rogers, Robin D

2017-07-01

Traditional synthesis of metal-organic frameworks (MOFs) involves the reaction of a metal-containing precursor with an organic linker in an organic solvent at an elevated temperature, in what is termed a 'solvothermal' reaction. More recently, many examples have been reported of MOF synthesis in ionic liquids (ILs), rather than an organic solvent, in 'ionothermal' reactions. The high concentration of both cations and anions in an ionic liquid allows for the formation of new MOF structures in which the IL cation or anion or both are incorporated into the MOF. Most commonly, the IL cation is included in the open cavities of the MOF, countering the anionic charge of the MOF framework itself and acting as a template around which the MOF structure forms. Ionic liquids can also serve other structure-directing roles, for example, when an IL containing a single enantiomer of a chiral anion leads to a homochiral MOF, even though the IL anion is not itself incorporated into the MOF. A comprehensive review of ionothermal syntheses of MOFs, and the structure-directing effects of the ILs, is given.

Solubilization of octane in cationic surfactant-anionic polymer complexes: Effect of ionic strength.

PubMed

Zhang, Hui; Deng, Lingli; Sun, Ping; Que, Fei; Weiss, Jochen

2016-01-01

Polymers may alter the ability of oppositely charged surfactant micelles to solubilize hydrophobic molecules depending on surfactant-polymer interactions. This study was conducted to investigate the effect of ionic strength on the solubilization thermodynamics of an octane oil-in-water emulsion in mixtures of an anionic polymer (carboxymethyl cellulose) and cationic cetyltrimethylammonium bromide (CTAB) surfactant micelles using isothermal titration calorimetry (ITC). Results indicated that the CTAB binding capacity of carboxymethyl cellulose increased with increasing NaCl concentrations up to 100 mM, and the thermodynamic behavior of octane solubilization in CTAB micelles, either in the absence or presence of polymer, was found to have a strong dependence on ionic strength. The increasing ionic strength caused the solubilization in CTAB micelles to be less endothermic or even exothermic, but increased the solubilization capacity. Based on the phase separation model, the solubilization was suggested to be driven by enthalpy. It is indicated that increasing ionic strength gave rise to a larger Gibbs energy decrease but a smaller unfavorable entropy increase for octane solubilization in cationic surfactant micelles. Copyright © 2015 Elsevier Inc. All rights reserved.

Modulation of slow inactivation in human cardiac Kv1.5 channels by extra- and intracellular permeant cations

PubMed Central

Fedida, David; Maruoka, Neil D; Lin, Shunping

1999-01-01

The properties and regulation of slow inactivation by intracellular and extracellular cations in the human heart K+ channel hKv1.5 have been investigated. Extensive NH2- and COOH-terminal deletions outside the central core of transmembrane domains did not affect the degree of inactivation. The voltage dependence of steady-state inactivation curves of hKv1.5 channels was unchanged in Rb+ and Cs+, compared with K+, but biexponential inactivation over 10 s was reduced from ∼100% of peak current in Na+ to ∼65% in K+, ∼50% in Rb+ and ∼30% in Cs+. This occurred as a result of a decrease in both fast and slow components of inactivation, with little change in inactivation time constants. Changes in extracellular cation species and concentration (5-300 mM) had only small effects on the rates of inactivation and recovery from inactivation (τrecovery∼1 s). Mutation of residues at a putative regulatory site at R487 in the outer pore mouth did not affect slow inactivation or recovery from inactivation of hKv1.5, although sensitivity to extracellular TEA was conferred. Symmetrical reduction of both intra- and extracellular cation concentrations accelerated and augmented both components of inactivation of K+ (Kd = 34.7 mM) and Cs+ (Kd = 20.5 mM) currents. These effects could be quantitatively accounted for by unilateral reduction of intracellular K+ (Ki+) (Kd = 43.4 mM) or Csi+ with constant 135 mM external ion concentrations. We conclude that inactivation and recovery from inactivation in hKv1.5 were not typically C-type in nature. However, the ion species dependence of inactivation was still closely coupled to ion permeation through the pore. Intracellular ion modulatory actions were more potent than extracellular actions, although still of relatively low affinity. These results suggest the presence of ion binding sites capable of regulating inactivation located on both intracellular and extracellular sides of the pore selectivity filter. PMID:10050000

Photocatalytic studies of electrochemically synthesized polysaccharide-functionalized ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Kaur, Simranjeet; Kaur, Harpreet

2018-05-01

The present work reports the electrochemical synthesis of polysaccharide-functionalized ZnO nanoparticles using sodium hydroxide, starch, and zinc electrodes for the degradation of cationic dye (Rhodamine-B) under sunlight. Physiochemical properties of synthesized sample have been characterized by different techniques such as XRD, TEM, FESEM, EDS, IR, and UV-visible spectroscopic techniques. The influence of various factors such as effect of dye concentration, contact time, amount of photocatalyst, and pH has been studied. The results obtained from the photodegradation study showed that degradation rate of Rhodamine-B dye has been increased with increase of amount of photocatalyst and decreased with increase in initial dye concentration. Furthermore, the kinetics of the degradation has been investigated. It has been found that the photodegradation of Rhodamine-B dye follows pseudo-first-order kinetics and prepared photocatalyst can effectively degrade the cationic dye. Thus, this ecofriendly and efficient photocatalyst can be used for the treatment of dye-contaminated water. This catalyst also showed the antibacterial activity against Bacillus pumilus and Escherichia coli bacterial strains, so the synthesized nanoparticles also have the pharmaceutical properties.

Simulation of the influence of EDTA on the sorption of heavy metals by humic acids

NASA Astrophysics Data System (ADS)

Kropacheva, T. N.; Didik, M. V.; Kornev, V. I.

2015-04-01

The results of mathematical simulation of sorption equilibria with the participation of divalent cations of heavy metals (HMs), chelant (EDTA), and insoluble forms of humic acids (HAs) are discussed. It is shown that the formation of chelates of metals with EDTA in solutions results in the decreasing sorption of the metals by humic acids. We also analyzed the effect of the acidity of the medium and the HM: EDTA: HA ratio (in a wide range) on the desorption of metals. The desorbing effect of EDTA on the metals is the highest at pH 3-5 and increases with an increase in the concentration of EDTA and a decrease in the concentration of HAs. With respect to the remobilization of metals under the impact of EDTA, the metal cations can be arranged into the following sequence: Cu(II) > Ni(II) > Pb(II) ≫ Cd(II) > Co(II) > Zn(II). The obtained data have been used to analyze the remobilization / extraction of HMs from soils with a high content of humic substances.

The toxicity of cationic surfactant HDTMA-Br, desorbed from surfactant modified zeolite, towards faecal indicator and environmental microorganisms.

PubMed

Reeve, Peter J; Fallowfield, Howard J

2017-10-05

Surfactant Modified Zeolite (SMZ) represents a versatile, cost-effective permeable reactive material, capable of treating multiple classes of contaminants. The potential for HDTMA-Br, a cationic surfactant commonly used to modify zeolite, to desorb from the zeolite surface has been identified as a potential issue for the ongoing use of SMZ in water remediation contexts. This paper investigates the toxicity of HDTMA-Br towards enteric virus surrogates, F-RNA bacteriophage MS2 and E. coli, Bacillus subtilis, and soil microflora. The concentration of surfactant desorbing from SMZ was quantified through a bioassay using E. coli. Results showed HDTMA-Br concentrations of ≥10 -5 M were toxic to MS2, ≥10 -4 M were toxic to E. coli and ≥10 -6 M were toxic to B. subtilis. No toxic relationship was established between HDTMA-Br and soil microflora. Desorption of ≥10 -4 M of HDTMA-Br was shown for the two SMZ samples under the mixing conditions used. Effects of this surfactant on total soil microflora were ambiguous since no toxic relationship could be established, however, HDTMA-Br, at concentrations desorbing from SMZ, were shown to impact the soil bacterium B. subtilis. Further research is required to determine the effect of this surfactant on microbial populations and species diversity in soils. Copyright © 2017 Elsevier B.V. All rights reserved.

Callitriche cophocarpa biomass as a potential low-cost biosorbent for trivalent chromium.

PubMed

Kyzioł-Komosińska, Joanna; Augustynowicz, Joanna; Lasek, Wojciech; Czupioł, Justyna; Ociński, Daniel

2018-05-15

The present study focused on the use of the dry mass of the macrophyte Callitriche cophocarpa as an effective biosorbent for chromium removal from concentrated solutions, typical for industrial effluents. In order to evaluate the usability of C. cophocarpa as the Cr(III) sorbent, its detailed physicochemical characterization has been performed as well as the preliminary adsorption studies. The biosorbent was characterized by specific surface area (SSA), porosity, total organic carbon (TOC), inorganic content as well as the cation exchange capacity (CEC), dominant exchangeable cations and anion exchange capacity (AEC), point of zero charge (pH pzc ) and buffering capacity. The effect of the initial chromium concentration, solution pH and co-existing anions on the sorption effectiveness have been investigated. Based on theoretical isotherm models, the maximum adsorption capacity of the dry C. cophocarpa has been determined as 77.1 mg Cr(III)/g. Finally, the strength of Cr-binding onto the plant biomass has been evaluated using the BCR extraction method, stating that chromium was strongly and - under environmental conditions - irreversibly bound to the plant biomass. Copyright © 2018 Elsevier Ltd. All rights reserved.

Surfactant properties of human meibomian lipids.

PubMed

Mudgil, Poonam; Millar, Thomas J

2011-03-25

Human meibomian lipids are the major part of the lipid layer of the tear film. Their surfactant properties enable their spread across the aqueous layer and help maintain a stable tear film. The purpose of this study was to investigate surfactant properties of human meibomian lipids in vitro and to determine effects of different physical conditions such as temperature and increased osmolarity, such as occur in dry eye, on these properties. Human meibomian lipids were spread on an artificial tear solution in a Langmuir trough. The lipid films were compressed and expanded to record the surface pressure-area (Π-A) isocycles. The isocycles were recorded under different physical conditions such as high pressure, increasing concentration and size of divalent cations, increasing osmolarity, and varying temperature. Π-A isocycles of meibomian lipids showed that they form liquid films that are compressible and multilayered. The isocycles were unaffected by increasing concentration or size of divalent cations and increasing osmolarity in the subphase. Temperature had a marked effect on the lipids. Increase in temperature caused lipid films to become fluid, an expected feature, but decrease in temperature unexpectedly caused expansion of lipids and an increase in pressure suggesting enhanced surfactant properties. Human meibomian lipids form highly compressible, non-collapsible, multilayered liquid films. These lipids have surfactants that allow them to spread across an aqueous subphase. Their surfactant properties are unaffected by increasing divalent cations or hyperosmolarity but are sensitive to temperature. Cooling of meibomian lipids enhances their surfactant properties.

Simple new method for effective concentration of 188Re solutions from alumina-based 188W-188Re generator.

PubMed

Guhlke, S; Beets, A L; Oetjen, K; Mirzadeh, S; Biersack, H J; Knapp, F F

2000-07-01

(188)Re is a useful generator-produced radioisotope currently under evaluation for a variety of therapeutic applications, including bone pain palliation and intravascular radiation therapy. Because the (188)W parent is available only in a relatively low specific activity (<0.15-0.19 GBq/mg) from reactor irradiation of enriched (186)W, relatively large volumes of 0.9% saline (>15 mL) are required for elution of the (188)Re daughter from traditional alumina-based (188)W-(188)Re generators. Because these large bolus volumes result in solutions with a relatively low specific volume activity of (188)Re (<1 GBq/mL for the 18.5-GBq generator), the availability of effective methods for eluent concentration is important. Our new approach is based on the use of 0.3 mol/L ammonium acetate as a representative salt of a weak acid instead of saline for generator elution. After generator elution, the ammonium acetate generator eluent (15-20 mL) is passed through a tandem IC-H Plus cation (Dowex-H)-anion (QMA Light) column system. Exchange of ammonium cations with hydrogen ions on the cation column forms an acetic acid solution containing perrhenate anions from which the macroscopic levels of the acetate anion of the eluent have been effectively removed. Because perrhenic acid is fully dissociated at this pH, the QMA Light column specifically traps the (188)Re-perrhenate, which is subsequently eluted with a low volume (<1 mL) of saline. Concentration ratios greater than 20:1 are readily achieved with this method. A typical clinical-scale generator loaded with 19.2 GBq (188)W was used to validate the approach. Saline elution provided (188)Re in a 75%-80% yield. Although elution with 0.15 mol/L NH4OAc gave lower yields (55%-60%), use of 0.3 mol/L NH4OAc provided yields comparable with those of saline (70%-75%). (188)W parent breakthrough was not detected after passage of the bolus through the tandem concentration system. Bolus volumes of 15-20 mL, which initially contained as much as 11.1-14.8 GBq (188)Re, were readily concentrated to less than 1 mL saline using QMA Light cartridges. The generator was evaluated for more than 3 mo with no decrease in performance. This approach represents a simple, rapid, and effective method using inexpensive disposable components of concentrating solutions of (188)Re for preparation of therapeutic agents.

Purification and characterization of chromatin-bound DNA-dependent RNA polymerase I from parsley (Petroselinum crispum). Influence of nucleoside triphosphates.

PubMed Central

Grossmann, K; Friedrich, H; Seitz, U

1980-01-01

The isolation and purification of DNA-dependent RNA polymerase I (EC 2.7.7.6) from parsley (Petroselinum crispum) callus cells grown in suspension culture is described. The enzyme was solubilized from isolated chromatin. Purification was achieved by using DEAE- and phospho-cellulose in batches, followed by column chromatography on DEAE- and phospho-cellulose (two columns) and density-gradient centrifugation. The highly purified enzyme was stable over several months. The properties of purified parsley RNA polymerase I were investigated. Optimum concentration for Mn2+ was 1 mM, and for Mg2+ 4-6 mM, Mn2+ was slightly more stimulatory than Mg2+. The enzyme was most active at low ionic strengths [10-20 mM-(NH4)SO4]. The influence of various phosphates was tested: pyrophosphate inhibited RNA polymerase at low concentrations, whereas orthophosphate had no effect on the enzyme activity. ADP was slightly inhibitory, and AMP had no effect on the enzyme reaction. Nucleoside triphosphates and bivalent cations in equimolar concentrations in the range 4-11 mM did not influence the RNA synthesis in vitro. Free nucleoside triphosphates in excess of this 1:1 ratio inhibited the enzyme activity, unlike free bivalent cations, which stimulated RNA polymerase I. PMID:7470092

Purification of gamma-amino butyric acid (GABA) from fermentation of defatted rice bran extract by using ion exchange resin

NASA Astrophysics Data System (ADS)

Tuan Nha, Vi; Phung, Le Thi Kim; Dat, Lai Quoc

2017-09-01

Rice bran is one of the significant byproducts of rice processing with 10 %w/w of constitution of whole rice grain. It is rich in nutrient compounds, including glutamic acid. Thus, it could be utilized for the fermentation with Lactobateria for synthesis of GABA, a valuable bioactive for antihypertensive effects. However, the concentration and purity of GABA in fermentation broth of defatted rice bran extract is low for production of GABA drug. This research focused on the purification of GABA from the fermentation broth of defatted rice bran extract by using cation exchange resin. The results indicate that, the adsorption isotherm of GABA by Purelite C100 showed the good agreement with Freundlich model, with high adsorption capacity. The effects of pH and concentration of NaCl in eluent on the elution were also investigated. The obtained results show that, at the operating conditions of elution as follows: pH 6.5, 0.8 M of NaCl in eluent, 0.43 of bed volume; concentration of GABA in accumulative eluent, the purity and recovery yield of GABA were 743.8 ppm, 44.0% and 84.2%, respectively. Results imply that, it is feasible to apply cation exchange resin for purification of GABA from fermentation broth of defatted rice bran extract.

Interactions between a poorly soluble cationic drug and sodium dodecyl sulfate in dissolution medium and their impact on in vitro dissolution behavior.

PubMed

Huang, Zongyun; Parikh, Shuchi; Fish, William P

2018-01-15

In the pharmaceutical industry, in vitro dissolution testing ofsolid oral dosage forms is a very important tool for drug development and quality control. However, ion-pairing interaction between the ionic drugand surfactants in dissolution medium often occurs, resulting in inconsistent and incomplete drug release. The aim of this study is toevaluate the effects ofsodium dodecyl sulfate (SDS) mediated medium onthe dissolution behaviors of a poorly soluble cationic drug (Drug B). The study was carried out by measuring solubility of Drug B substance and dissolution rate of Drug B product in media containing SDS.Desolubilization of Drug B substance was observed at pH 4.5 in the presence of SDS at concentrations below critical micelle concentration (CMC) which is attributed to the formation of an insoluble di-dodecyl sulfate salt between SDS and Drug B. This ion-pairing effect is less significant with increasing medium pH where Drug B is less ionized and CMC of SDS is lower. In medium at pH 4.5, dissolution of Drug B product was found incomplete with SDS concentration below CMC due to the desolubilization of Drug B substance. In media with SDS level above CMC, the dissolution rate is rather slower with higher inter-vessel variations compared to that obtained in pH 4.5 medium without SDS. The dissolution results demonstrate that the presence of SDS in medium generates unexpected irregular dissolution profiles for Drug B which are attributed to incompatible dissolution medium for this particular drug. Therefore, non-ionic surfactant was selected for Drug B product dissolution method and ion-pairing effect in SDS mediated medium should be evaluated when developing a dissolution method for any poorly soluble cationic drugs. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of phosphonium-based ionic liquids on phospholipid membranes studied by small-angle X-ray scattering.

PubMed

Kontro, Inkeri; Svedström, Kirsi; Duša, Filip; Ahvenainen, Patrik; Ruokonen, Suvi-Katriina; Witos, Joanna; Wiedmer, Susanne K

2016-12-01

The effects of ionic liquids on model phospholipid membranes were studied by small-angle X-ray scattering, dynamic light scattering (DLS) and zeta potential measurements. Multilamellar 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine liposomes and large unilamellar vesicles composed of l-α-phosphatidylcholine (eggPC) and l-α-phosphatidylglycerol (eggPG) (80:20mol%) or eggPC, eggPG, and cholesterol (60:20:20mol%) were used as biomimicking membrane models. The effects of the phosphonium-based ionic liquids: tributylmethylphosphonium acetate, trioctylmethylphosphonium acetate, tributyl(tetradecyl)-phosphonium acetate, and tributyl(tetradecyl)-phosphonium chloride, were compared to those of 1-ethyl-3-methyl-imidazolium acetate. With multilamellar vesicles, the ionic liquids that did not disrupt liposomes decreased the lamellar spacing as a function of concentration. The magnitude of the effect depended on concentration for all studied ionic liquids. Using large unilamellar vesicles, first a slight decrease in the vesicle size, then aggregation of vesicles was observed by DLS for increasing ionic liquid concentrations. At concentrations just below those that caused aggregation of liposomes, large unilamellar vesicles were coated by ionic liquid cations, evidenced by a change in their zeta potential. The ability of phosphonium-based ionic liquids to affect liposomes is related to the length of the hydrocarbon chains in the cation. Generally, the ability of ionic liquids to disrupt liposomes goes hand in hand with inducing disorder in the phospholipid membrane. However, trioctylmethylphosphonium acetate selectively extracted and induced a well-ordered lamellar structure in phospholipids from disrupted cholesterol-containing large unilamellar vesicles. This kind of effect was not seen with any other combination of ionic liquids and liposomes. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Yeast Kch1 and Kch2 membrane proteins play a pleiotropic role in membrane potential establishment and monovalent cation homeostasis regulation.

PubMed

Felcmanova, Kristina; Neveceralova, Petra; Sychrova, Hana; Zimmermannova, Olga

2017-08-01

The Kch1 and Kch2 plasma-membrane proteins were identified in Saccharomyces cerevisiae as being essential for the activation of a high-affinity Ca2+ influx system. We searched for Kch proteins roles in the maintenance of cation homeostasis and tested the effect of kch1 and/or kch2 deletions on various physiological parameters. Compared to wild-type, kch1 kch2 mutant cells were smaller, relatively hyperpolarised, grew better under limited K+ conditions and exhibited altered growth in the presence of monovalent cations. The absence of Kch1 and Kch2 did not change the intracellular pH in cells growing at low potassium or the tolerance of cells to divalent cations, high concentration of sorbitol or extreme external pH. The overexpression of KCH1 only increased the intracellular pH in the presence of elevated K+ in media. None of the phenotypes associated with the deletion of KCH1 and KCH2 in wild type were observed in a strain lacking KCH genes and main K+ uptake systems Trk1 and Trk2. The role of the Kch homologue in cation homeostasis was also tested in Candida albicans cells. Our data demonstrate that Kch proteins significantly contribute to the maintenance of optimal cation homeostasis and membrane potential in S. cerevisiae but not in C. albicans. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Modeling uranium(VI) adsorption onto montmorillonite under varying carbonate concentrations: A surface complexation model accounting for the spillover effect on surface potential

NASA Astrophysics Data System (ADS)

Tournassat, C.; Tinnacher, R. M.; Grangeon, S.; Davis, J. A.

2018-01-01

The prediction of U(VI) adsorption onto montmorillonite clay is confounded by the complexities of: (1) the montmorillonite structure in terms of adsorption sites on basal and edge surfaces, and the complex interactions between the electrical double layers at these surfaces, and (2) U(VI) solution speciation, which can include cationic, anionic and neutral species. Previous U(VI)-montmorillonite adsorption and modeling studies have typically expanded classical surface complexation modeling approaches, initially developed for simple oxides, to include both cation exchange and surface complexation reactions. However, previous models have not taken into account the unique characteristics of electrostatic surface potentials that occur at montmorillonite edge sites, where the electrostatic surface potential of basal plane cation exchange sites influences the surface potential of neighboring edge sites ('spillover' effect). A series of U(VI) - Na-montmorillonite batch adsorption experiments was conducted as a function of pH, with variable U(VI), Ca, and dissolved carbonate concentrations. Based on the experimental data, a new type of surface complexation model (SCM) was developed for montmorillonite, that specifically accounts for the spillover effect using the edge surface speciation model by Tournassat et al. (2016a). The SCM allows for a prediction of U(VI) adsorption under varying chemical conditions with a minimum number of fitting parameters, not only for our own experimental results, but also for a number of published data sets. The model agreed well with many of these datasets without introducing a second site type or including the formation of ternary U(VI)-carbonato surface complexes. The model predictions were greatly impacted by utilizing analytical measurements of dissolved inorganic carbon (DIC) concentrations in individual sample solutions rather than assuming solution equilibration with a specific partial pressure of CO2, even when the gas phase was laboratory air. Because of strong aqueous U(VI)-carbonate solution complexes, the measurement of DIC concentrations was even important for systems set up in the 'absence' of CO2, due to low levels of CO2 contamination during the experiment.

[Study on the aggregation behavior of cationic porphyrins and their interaction with ctDNA].

PubMed

Ma, Hong-Min; Chen, Xin; Sun, Shu-Ting; Zhang, Li-Na; Wu, Dan; Zhu, Pei-Hua; Li, Yan; Du, Bin; Wei, Qin

2009-02-01

Interest in the interaction between cationic porphyrins, particularly derivatives of meso-tetra(N-methylpyridinium-4-yl) porphyrin(TMPyP), and DNA abounds because they are versatile DNA-binding agents that could find application in photodynamic therapy, cancer detection, artificial nucleases, virus inhibition and so on. The interaction of two water-soluble cationic porphyrins, meso-tetrakis(4-N, N, N-trimethylanilinium) porphyrin (TMAP) and 5-phenyl-10,15,20-tris[4-(N-methyl) pyridinium]porphyrin (TriMPyP), with calf thymus DNA (ctDNA) was studied by UV-Vis absorption spectroscopy, fluorescence spectroscopy and resonance light scattering technique. TriMPyP forms aggregate in water due to the molecular asymmetry while TMAP exists as monomers. At lower concentrations of ctDNA (R > 1, R = c(TMAP)/c(DNA) base pair), the interaction of TMAP with DNA leads to significant hypochromicity and bathochromic shift of absorption spectra. And the fluorescence of TMAP was quenched while it showed enhanced resonance light scattering signals. But the extent of enhancement of resonance light scattering signals is very small, so the aggregate of TMAP is not very high. These observations indicate the self-stacking of TMAP along the DNA surface. At higher concentrations of ctDNA (R < 1), TMAP association with DNA is via outside binding which is accompanied with hyperchromic effect and fluorescence enhancement while the resonance light scattering signals is reduced. DNA addition decreases the fluorescence intensity of TriMPyP and it shifts the peak to the higher wavelengths (red shift). The interaction with DNA promotes the aggregation of TriMPyP and no simple outside binding is observed even at higher concentrations of ctDNA. The steric effect of molecular distortion constrains the intercalation or further binding to DNA. The effect of ionic strength on the interaction was investigated at two DNA concentrations, 1.2 and 24.0 micromol x L(-1), for TMAP. The Interactions of both porphyrins with DNA show high sensitivity to ionic strength. By addition of NaCl, electrostatic attraction is decreased, resulting in the change of binding mode.

Toxic effect of metal cation binary mixtures to the seaweed Gracilaria domingensis (Gracilariales, Rhodophyta).

PubMed

Mendes, Luiz Fernando; Stevani, Cassius Vinicius; Zambotti-Villela, Leonardo; Yokoya, Nair Sumie; Colepicolo, Pio

2014-01-01

The macroalga Gracilaria domingensis is an important resource for the food, pharmaceutical, cosmetic, and biotechnology industries. G. domingensis is at a part of the food web foundation, providing nutrients and microelements to upper levels. As seaweed storage metals in the vacuoles, they are considered the main vectors to magnify these toxic elements. This work describes the evaluation of the toxicity of binary mixtures of available metal cations based on the growth rates of G. domingensis over a 48-h exposure. The interactive effects of each binary mixture were determined using a toxic unit (TU) concept that was the sum of the relative contribution of each toxicant and calculated using the ratio between the toxicant concentration and its endpoint. Mixtures of Cd(II)/Cu(II) and Zn(II)/Ca(II) demonstrated to be additive; Cu(II)/Zn(II), Cu(II)/Mg(II), Cu(II)/Ca(II), Zn(II)/Mg(II), and Ca(II)/Mg(II) mixtures were synergistic, and all interactions studied with Cd(II) were antagonistic. Hypotheses that explain the toxicity of binary mixtures at the molecular level are also suggested. These results represent the first effort to characterize the combined effect of available metal cations, based on the TU concept on seaweed in a total controlled medium. The results presented here are invaluable to the understanding of seaweed metal cation toxicity in the marine environment, the mechanism of toxicity action and how the tolerance of the organism.

Potential of single cationic amino acid molecule "Arginine" for stimulating oral absorption of insulin.

PubMed

Kamei, Noriyasu; Khafagy, El-Sayed; Hirose, Jun; Takeda-Morishita, Mariko

2017-04-15

We have reported that cell-penetrating peptides, such as oligoarginine, act as powerful absorption enhancers for the development of oral insulin delivery systems. However, the minimal essential sequence of oligoarginine that stimulates intestinal insulin absorption remains unclear. Therefore, the present study was conducted to clarify this minimum sequence of oligoarginine and to examine the effect of single cationic amino acid arginine on the intestinal and oral absorption of insulin. The results demonstrated that a remarkable enhancement of intestinal insulin absorption was observed after coadministration of insulin with l-arginine. The efficacy of d-forms of oligoarginine/arginine tended to decrease with a decreasing number of amino acid residues, whereas the effect of l-arginine was the strongest of any of the l-forms of oligoarginine/arginine. Interestingly, the effect of l-arginine was stronger than that of d-arginine at various concentrations, and the effect of other cationic amino acids such as lysine and histidine was relatively lower than that of arginine. In addition, no leakage of lactate dehydrogenase from the intestinal epithelium and no change in the transepithelial electrical resistance of a Caco-2 cell monolayer were detected after administration of l-arginine as the single amino acid, which suggests that there were no undesirable effects of arginine on the integrity of cell membranes and paracellular tight junctions. Oral administration study in mice demonstrated that the stronger hypoglycemic effects were observed after coadministration of insulin with l-arginine. In this study, we found that arginine is a key cationic amino acid for delivering insulin across intestinal epithelial barriers and hopefully accelerating the clinical development of oral insulin delivery systems. Copyright © 2017 Elsevier B.V. All rights reserved.

The use of laboratory-determined ion exchange parameters in the predictive modelling of field-scale major cation migration in groundwater over a 40-year period.

PubMed

Carlyle, Harriet F; Tellam, John H; Parker, Karen E

2004-01-01

An attempt has been made to estimate quantitatively cation concentration changes as estuary water invades a Triassic Sandstone aquifer in northwest England. Cation exchange capacities and selectivity coefficients for Na(+), K(+), Ca(2+), and Mg(2+) were measured in the laboratory using standard techniques. Selectivity coefficients were also determined using a method involving optimized back-calculation from flushing experiments, thus permitting better representation of field conditions; in all cases, the Gaines-Thomas/constant cation exchange capacity (CEC) model was found to be a reasonable, though not perfect, first description. The exchange parameters interpreted from the laboratory experiments were used in a one-dimensional reactive transport mixing cell model, and predictions compared with field pumping well data (Cl and hardness spanning a period of around 40 years, and full major ion analyses in approximately 1980). The concentration patterns predicted using Gaines-Thomas exchange with calcite equilibrium were similar to the observed patterns, but the concentrations of the divalent ions were significantly overestimated, as were 1980 sulphate concentrations, and 1980 alkalinity concentrations were underestimated. Including representation of sulphate reduction in the estuarine alluvium failed to replicate 1980 HCO(3) and pH values. However, by including partial CO(2) degassing following sulphate reduction, a process for which there is 34S and 18O evidence from a previous study, a good match for SO(4), HCO(3), and pH was attained. Using this modified estuary water and averaged values from the laboratory ion exchange parameter determinations, good predictions for the field cation data were obtained. It is concluded that the Gaines-Thomas/constant exchange capacity model with averaged parameter values can be used successfully in ion exchange predictions in this aquifer at a regional scale and over extended time scales, despite the numerous assumptions inherent in the approach; this has also been found to be the case in the few other published studies of regional ion exchanging flow.

The use of laboratory-determined ion exchange parameters in the predictive modelling of field-scale major cation migration in groundwater over a 40-year period

NASA Astrophysics Data System (ADS)

Carlyle, Harriet F.; Tellam, John H.; Parker, Karen E.

2004-01-01

An attempt has been made to estimate quantitatively cation concentration changes as estuary water invades a Triassic Sandstone aquifer in northwest England. Cation exchange capacities and selectivity coefficients for Na +, K +, Ca 2+, and Mg 2+ were measured in the laboratory using standard techniques. Selectivity coefficients were also determined using a method involving optimized back-calculation from flushing experiments, thus permitting better representation of field conditions; in all cases, the Gaines-Thomas/constant cation exchange capacity (CEC) model was found to be a reasonable, though not perfect, first description. The exchange parameters interpreted from the laboratory experiments were used in a one-dimensional reactive transport mixing cell model, and predictions compared with field pumping well data (Cl and hardness spanning a period of around 40 years, and full major ion analyses in ˜1980). The concentration patterns predicted using Gaines-Thomas exchange with calcite equilibrium were similar to the observed patterns, but the concentrations of the divalent ions were significantly overestimated, as were 1980 sulphate concentrations, and 1980 alkalinity concentrations were underestimated. Including representation of sulphate reduction in the estuarine alluvium failed to replicate 1980 HCO 3 and pH values. However, by including partial CO 2 degassing following sulphate reduction, a process for which there is 34S and 18O evidence from a previous study, a good match for SO 4, HCO 3, and pH was attained. Using this modified estuary water and averaged values from the laboratory ion exchange parameter determinations, good predictions for the field cation data were obtained. It is concluded that the Gaines-Thomas/constant exchange capacity model with averaged parameter values can be used successfully in ion exchange predictions in this aquifer at a regional scale and over extended time scales, despite the numerous assumptions inherent in the approach; this has also been found to be the case in the few other published studies of regional ion exchanging flow.

The hemolymph of caterpillars Spodoptera littoralis: physico-chemical properties and ionic composition compared to culture media.

PubMed

Smagghe, G; Van Leeuwen, T

2004-01-01

In this paper, we determined some physico-chemical properties like osmotic pressure, pH and electrical conductivity of the hemolymph from caterpillars of Spodoptera littoralis (Lepidoptera: Noctuidae) during the last larval instar. It was of interest that we observed an increase in osmotic pressure with the increase in age in the last instar that may concur with the start of histolysis at metamorphosis. These physicochemical properties were then compared to those of Grace's and modified Grace's tissue culture medium. In addition, concentrations of the cations Na, K, Ca and Mg, and the anions Cl, NO3, PO4 and SO4 were determined in the insect hemolymph of S. littoralis. The cations K and Mg reached high values with a percent of about 52% of the total amount of cations. The concentration of sodium was low. The total sum of the anions consisted about 56 meq/1, and this allows to neutralise about 45 % of the total cations.

Measurements of the streaming potential of clay soils from tropical and subtropical regions using self-made apparatus.

PubMed

Li, Zhong-Yi; Li, Jiu-Yu; Liu, Yuan; Xu, Ren-Kou

2014-09-01

The streaming potential has been wildly used in charged parallel plates, capillaries, and porous media. However, there have been few studies involving the ζ potential of clay soils based on streaming potential measurements. A laboratory apparatus was developed in this study to measure the streaming potential (ΔE) of bulk clay soils' coupling coefficient (C) and cell resistance (R) of saturated granular soil samples. Excellent linearity of ΔE versus liquid pressure (ΔP) ensured the validity of measurements. The obtained parameters of C and R can be used to calculate the ζ potential of bulk soils. The results indicated that the ζ potentials measured by streaming potential method were significantly correlated with the ζ potentials of soil colloids determined by electrophoresis (r (2) = 0.960**). Therefore, the streaming potential method can be used to study the ζ potentials of bulk clay soils. The absolute values of the ζ potentials of four soils followed the order: Ultisol from Jiangxi > Ultisol from Anhui > Oxisol from Guangdong > Oxisol from Hainan, and this was consistent with the cation exchange capacities of these soils. The type and concentration of electrolytes affected soil ζ potentials. The ζ potential became less negative with increased electrolyte concentration. The ζ potentials were more negative in monovalent than in divalent cationic electrolyte solutions because more divalent cations were distributed in the shear plane of the diffuse layer as counter-cations on the soil surfaces than monovalent cations at the same electrolyte concentration.

Single-Walled Carbon Nanotubes: Mimics of Biological Ion Channels.

PubMed

Amiri, Hasti; Shepard, Kenneth L; Nuckolls, Colin; Hernández Sánchez, Raúl

2017-02-08

Here we report on the ion conductance through individual, small diameter single-walled carbon nanotubes. We find that they are mimics of ion channels found in natural systems. We explore the factors governing the ion selectivity and permeation through single-walled carbon nanotubes by considering an electrostatic mechanism built around a simplified version of the Gouy-Chapman theory. We find that the single-walled carbon nanotubes preferentially transported cations and that the cation permeability is size-dependent. The ionic conductance increases as the absolute hydration enthalpy decreases for monovalent cations with similar solid-state radii, hydrated radii, and bulk mobility. Charge screening experiments using either the addition of cationic or anionic polymers, divalent metal cations, or changes in pH reveal the enormous impact of the negatively charged carboxylates at the entrance of the single-walled carbon nanotubes. These observations were modeled in the low-to-medium concentration range (0.1-2.0 M) by an electrostatic mechanism that mimics the behavior observed in many biological ion channel-forming proteins. Moreover, multi-ion conduction in the high concentration range (>2.0 M) further reinforces the similarity between single-walled carbon nanotubes and protein ion channels.

Doxorubicin Delivery Using pH and Redox Dual-Responsive Hollow Nanocapsules with a Cationic Electrostatic Barrier

PubMed Central

Teranishi, Ryoma; Matsuki, Ryota; Yuba, Eiji; Harada, Atsushi; Kono, Kenji

2016-01-01

For the delivery of doxorubicin (DOX), pH and redox dual responsive hollow nanocapsules were prepared through the stabilization of polymer vesicles, which spontaneously formed from polyamidoamine dendron-poly(l-lysine) (PAMAM dendron-PLL), by the introduction of disulfide (SS) bonds between PLLs. The SS-bonded nanocapsules exhibited a very slow release of DOX under an extracellular environment because the cationic PLL membrane acted as an electrostatic barrier against the protonated DOX molecules. However, increasing the glutathione concentration to the intracellular level facilitated the immediate release of DOX through the collapse of nanocapsules by the spontaneous cleavage of SS bonds. SS-bonded nanocapsules also escaped from the endosome by the buffering effect of PAMAM dendrons, and DOX delivery into the cytoplasm was achieved. Furthermore, DOX molecules delivered by SS-bonded nanocapsules exhibited an effective in vitro anticancer effect to HeLa cells. PMID:28042818

Some Surface-Active Agents and Their Virucidal Effect on Foot-and-Mouth Disease Virus

PubMed Central

Fellowes, O. N.

1965-01-01

Selected cationic and anionic surface-active compounds were tested to determine their virucidal effect on the foot-and-mouth disease virus, type O, strain M11, propagated in primary calf kidney cells. The chemical inactivation of the virus was tested with 0.5, 1.0, 2.0, and 5.0% concentrations of the selected compounds. Virus controls with pH adjusted to cover the expected range of the mixtures of the chemicals and virus were also tested. The absence of virus from the mixtures of chemical and virus after reaction at 28 C for 2 hr was assayed by inoculating suckling mice with the mixtures. One cationic compound, alkyl methyl isoquinilinium chloride, showed considerable antiviral activity due largely to pH effect. The use of the surface-active agents investigated in this study, in the presence of organic material, would not be recommended as virucides. PMID:4286396

Regeneration of Cation-Transport Capacity in HeLa Cell Membranes After Specific Blockade by Ouabain

PubMed Central

Vaughan, Gerald L.; Cook, John S.

1972-01-01

The cardiac glycoside, ouabain, inhibits alkali-cation transport in HeLa cells. It binds to 0.75 × 106 sites per cell, and the half-time for its dissociation is 16 hr. After partial blockade by ouabain, the cell generates new ouabain-binding sites, with total restoration of transport in 10% of a cell cycle(∼3 hr). This recovery requires protein synthesis and appears to be a response to altered cell-electrolyte content, since growth of cells in media with low K+ concentration enhances the titer of the transport enzyme in a fashion similar to the effect of ouabain. Totally blocked cells do not recover. PMID:4506784

Polyamines control of cation transport across plant membranes: implications for ion homeostasis and abiotic stress signaling.

PubMed

Pottosin, Igor; Shabala, Sergey

2014-01-01

Polyamines are unique polycationic metabolites, controlling a variety of vital functions in plants, including growth and stress responses. Over the last two decades a bulk of data was accumulated providing explicit evidence that polyamines play an essential role in regulating plant membrane transport. The most straightforward example is a blockage of the two major vacuolar cation channels, namely slow (SV) and fast (FV) activating ones, by the micromolar concentrations of polyamines. This effect is direct and fully reversible, with a potency descending in a sequence Spm(4+) > Spd(3+) > Put(2+). On the contrary, effects of polyamines on the plasma membrane (PM) cation and K(+)-selective channels are hardly dependent on polyamine species, display a relatively low affinity, and are likely to be indirect. Polyamines also affect vacuolar and PM H(+) pumps and Ca(2+) pump of the PM. On the other hand, catabolization of polyamines generates H2O2 and other reactive oxygen species (ROS), including hydroxyl radicals. Export of polyamines to the apoplast and their oxidation there by available amine oxidases results in the induction of a novel ion conductance and confers Ca(2+) influx across the PM. This mechanism, initially established for plant responses to pathogen attack (including a hypersensitive response), has been recently shown to mediate plant responses to a variety of abiotic stresses. In this review we summarize the effects of polyamines and their catabolites on cation transport in plants and discuss the implications of these effects for ion homeostasis, signaling, and plant adaptive responses to environment.

Polyamines control of cation transport across plant membranes: implications for ion homeostasis and abiotic stress signaling

PubMed Central

Pottosin, Igor; Shabala, Sergey

2014-01-01

Polyamines are unique polycationic metabolites, controlling a variety of vital functions in plants, including growth and stress responses. Over the last two decades a bulk of data was accumulated providing explicit evidence that polyamines play an essential role in regulating plant membrane transport. The most straightforward example is a blockage of the two major vacuolar cation channels, namely slow (SV) and fast (FV) activating ones, by the micromolar concentrations of polyamines. This effect is direct and fully reversible, with a potency descending in a sequence Spm4+ > Spd3+ > Put2+. On the contrary, effects of polyamines on the plasma membrane (PM) cation and K+-selective channels are hardly dependent on polyamine species, display a relatively low affinity, and are likely to be indirect. Polyamines also affect vacuolar and PM H+ pumps and Ca2+ pump of the PM. On the other hand, catabolization of polyamines generates H2O2 and other reactive oxygen species (ROS), including hydroxyl radicals. Export of polyamines to the apoplast and their oxidation there by available amine oxidases results in the induction of a novel ion conductance and confers Ca2+ influx across the PM. This mechanism, initially established for plant responses to pathogen attack (including a hypersensitive response), has been recently shown to mediate plant responses to a variety of abiotic stresses. In this review we summarize the effects of polyamines and their catabolites on cation transport in plants and discuss the implications of these effects for ion homeostasis, signaling, and plant adaptive responses to environment. PMID:24795739

Stibonium ions for the fluorescence turn-on sensing of F- in drinking water at parts per million concentrations.

PubMed

Ke, Iou-Sheng; Myahkostupov, Mykhaylo; Castellano, Felix N; Gabbaï, François P

2012-09-19

The 9-anthryltriphenylstibonium cation, [1](+), has been synthesized and used as a sensor for the toxic fluoride anion in water. This stibonium cation complexes fluoride ions to afford the corresponding fluorostiborane 1-F. This reaction, which occurs at fluoride concentrations in the parts per million range, is accompanied by a drastic fluorescence turn-on response. It is also highly selective and can be used in plain tap water or bottled water to test fluoridation levels.

Simultaneous flow of water and solutes through geological membranes-I. Experimental investigation

USGS Publications Warehouse

Kharaka, Y.K.; Berry, F.A.P.

1973-01-01

The relative retardation by geological membranes of cations and anions generally present in subsurface waters was investigated using a high pressure and high temperature 'filtration cell'. The solutions were forced through different clays and a disaggregated shale subjected to compaction pressures up to 9500 psi and to temperatures from 20 to 70??C. The overall efficiences measured increased with increase of exchange capacity of the material used and with decrease in concentration of the input solution. The efficiency of a given membrane increased with increasing compaction pressure but decreased slightly at higher temperatures for solutions of the same ionic concentration. The results further show that geological membranes are specific for different dissolved species. The retardation sequences varied depending on the material used and on experimental conditions. The sequences for monovalent and divalent cations at laboratory temperatures were generally as follows: Li < Na < NH3 < K < Rb < Cs Mg < Ca < Sr < Ba. The sequences for anions at room temperature were variable, but at 70??C, the sequence was: HCO3 < I < B < SO4 < Cl < Br. Monovalent cations contrary to some field data were generally retarded with respect to divalent cations. The differences in the filtration ratios among the divalent cations were smaller than those between the monovalent cations. The passage rate of B, HCO3, I and NH3 was greatly increased at 70??C. ?? 1973.

The controlled preparation of polypyrrole nanostructures via tuning the concentration of acrylic acid.

PubMed

Wang, Yujie; Zhong, Wenbin; Ning, Xutao; Li, Yuntao; Chen, Xiaohua; Wang, Yongxin; Yang, Wantai

2013-03-01

Two types of nanostructures, nanowires and nanoribbons were prepared with polypyrrole (PPy) by controlling the concentration of acrylic acid (AA) in systems containing cationic surfactant, cetyltrimethylammonium bromide (CTAB) at about 12 degrees C. The effect of reaction conditions involving the concentration of AA, CTAB, pyrrole as well as the reaction temperature was systematically studied on the final structures of prepared PPy. The results revealed that the polymerization of AA, resulting in PAA, played a key role in the evolution of PPy nanostructures. A possible mechanism was briefly discussed on the formation of these two nanostructures, nanowires and nanoribbons.

Study of the antimicrobial activity of cyclic cation-based ionic liquids via experimental and group contribution QSAR model.

PubMed

Ghanem, Ouahid Ben; Shah, Syed Nasir; Lévêque, Jean-Marc; Mutalib, M I Abdul; El-Harbawi, Mohanad; Khan, Amir Sada; Alnarabiji, Mohamad Sahban; Al-Absi, Hamada R H; Ullah, Zahoor

2018-03-01

Over the past decades, Ionic liquids (ILs) have gained considerable attention from the scientific community in reason of their versatility and performance in many fields. However, they nowadays remain mainly for laboratory scale use. The main barrier hampering their use in a larger scale is their questionable ecological toxicity. This study investigated the effect of hydrophobic and hydrophilic cyclic cation-based ILs against four pathogenic bacteria that infect humans. For that, cations, either of aromatic character (imidazolium or pyridinium) or of non-aromatic nature, (pyrrolidinium or piperidinium), were selected with different alkyl chain lengths and combined with both hydrophilic and hydrophobic anionic moieties. The results clearly demonstrated that introducing of hydrophobic anion namely bis((trifluoromethyl)sulfonyl)amide, [NTF 2 ] and the elongation of the cations substitutions dramatically affect ILs toxicity behaviour. The established toxicity data [50% effective concentration (EC 50 )] along with similar endpoint collected from previous work against Aeromonas hydrophila were combined to developed quantitative structure-activity relationship (QSAR) model for toxicity prediction. The model was developed and validated in the light of Organization for Economic Co-operation and Development (OECD) guidelines strategy, producing good correlation coefficient R 2 of 0.904 and small mean square error (MSE) of 0.095. The reliability of the QSAR model was further determined using k-fold cross validation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Selective removal of uranium ions from contaminated waters using modified-X nanozeolite.

PubMed

Shakur, H R; Rezaee Ebrahim Saraee, Kh; Abdi, M R; Azimi, G

2016-12-01

In order to efficiently remove of uranium anionic species (which are the most dominant species of uranium in natural water at neutral pH) from contaminated waters, nano-NaX zeolite was synthesized and then modified using various divalent cations (Mg 2+ , Ca 2+ , Mn 2+ ) and ZnO nanoparticles (from 1.7 to 10.3wt%). Different characterization techniques of XRF, XRD, FE-SEM, TEM, FT-IR, and AAS were used to characterize the final synthesized absorbents. Sorption experiments by batch technique were done to study the effect of solid-liquid ratio, initial uranium concentration, contact time and temperature under neutral condition of pH and presence of all anions and cations which are available in the waters. Results showed that although nano-NaX zeolite due to its negative framework charge had a low sorption capacity for adsorption of uranium anionic species, but modification of parent nano-NaX zeolite with ZnO nanoparticles and various cations effectively improved its uranium adsorption capacity. Also, results showed that under optimum condition of pH=7.56, contact time of 60min at 27°C with solid-liquid ratio of 20g/L a maximum uranium removal efficiency of 99.7% can be obtained in the presence of all anions and cations which are available in the drinking waters by NaX/ZnO nanocomposite. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ammonium removal from aqueous solutions by using natural Chinese (Chende) zeolite as adsorbent.

PubMed

Huang, Haiming; Xiao, Xianming; Yan, Bo; Yang, Liping

2010-03-15

This paper presents a study of the removal of ammonium ion from aqueous solutions using natural Chinese (Chende) zeolite. A series of experiments was conducted to examine the effects of solution pH, particle size, contact time, adsorbent dosage, and the presence of other cation- and anion species on ammonium removal. The findings indicated that these parameters named had a significant effect on the removal of ammonium by the zeolite. The effect of other cations on the removal of ammonium followed the order of preference Na(+)>K(+)>Ca(2+)>Mg(2+) at identical mass concentrations, and the effect of the presence of individual anions followed the order of preference carbonate>chloride>sulfate>phosphate at identical mass concentrations of ammonium ions. Kinetic analysis showed that the adsorption of ammonium on zeolite at different ranges of particle size well followed the pseudo-second-order model and followed the intra-particle diffusion model only during the initial 60 min of the adsorption process. Equilibrium isotherm data was fitted to the linear Langmuir- and Freundlich models with the latter model providing the better description of the process (R(2)=0.991-0.997) compared to the former (R(2)=0.902-0.989). (c) 2009 Elsevier B.V. All rights reserved.

Relationships between stream acid anion-base cation chemistry and watershed soil types on the Allegheny high plateau

Treesearch

Gregory P. Lewis

1999-01-01

The leaching of calcium and magnesium from forests by atmospherically-deposited strong acid anions (sulfate and nitrate) is evidenced in some watersheds by the positive correlation in stream water between concentrations of these base cations and acid anions.

Rare-earth element fractionation in uranium ore and its U(VI) alteration minerals

DOE PAGES

Balboni, Enrica; Spano, T; Cook, N; ...

2017-10-20

We developed a cation exchange chromatography method employing sulfonated polysterene cation resin (DOWEX AG50-X8) in order to separate rare-earth elements (REEs) from uranium-rich materials. The chemical separation scheme is designed to reduce matrix effects and consequently yield enhanced ionization efficiencies for concentration determinations of REEs without significant fractionation using solution mode-inductively coupled plasma mass spectrometry (ICP-MS) analysis. This method was then applied to determine REE abundances in four uraninite (ideally UO 2) samples and their associated U(VI) alteration minerals. In three of the samples analyzed, the concentration of REEs for primary uraninite are higher than those for their corresponding secondarymore » uranium alteration phases. The results for U(VI) alteration minerals of two samples indicate enrichment of the light REEs (LREEs) over the heavy REEs (HREEs). This differential mobilization is attributed to differences in the mineralogical composition of the U(VI) alteration. There is a lack of fractionation of the LREEs in the uraninite alteration rind that is composed of U(VI) minerals containing Ca 2+ as the interlayer cation (uranophane and bequerelite); contrarily, U(VI) alteration minerals containing K + and Pb 2+ as interlayer cations (fourmarierite, dumontite) indicate fractionation (enrichment) of the LREEs. Our results have implications for nuclear forensic analyses since a comparison is reported between the REE abundances for the CUP-2 (processed uranium ore) certified reference material and previously determined values for uranium ore concentrate (UOC) produced from the same U deposit (Blind River/Elliott Lake, Canada). UOCs represent the most common form of interdicted nuclear material and consequently is material frequently targeted for forensic analysis. The comparison reveals similar chondrite normalized REE signatures but variable absolute abundances. Based on the results reported here, the latter may be attributed to the differing REE abundances between primary ore and associated alteration phases, and/or is related to varying fabrication processes adopted during production of UOC.« less

Rare-earth element fractionation in uranium ore and its U(VI) alteration minerals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balboni, Enrica; Spano, T; Cook, N

We developed a cation exchange chromatography method employing sulfonated polysterene cation resin (DOWEX AG50-X8) in order to separate rare-earth elements (REEs) from uranium-rich materials. The chemical separation scheme is designed to reduce matrix effects and consequently yield enhanced ionization efficiencies for concentration determinations of REEs without significant fractionation using solution mode-inductively coupled plasma mass spectrometry (ICP-MS) analysis. This method was then applied to determine REE abundances in four uraninite (ideally UO 2) samples and their associated U(VI) alteration minerals. In three of the samples analyzed, the concentration of REEs for primary uraninite are higher than those for their corresponding secondarymore » uranium alteration phases. The results for U(VI) alteration minerals of two samples indicate enrichment of the light REEs (LREEs) over the heavy REEs (HREEs). This differential mobilization is attributed to differences in the mineralogical composition of the U(VI) alteration. There is a lack of fractionation of the LREEs in the uraninite alteration rind that is composed of U(VI) minerals containing Ca 2+ as the interlayer cation (uranophane and bequerelite); contrarily, U(VI) alteration minerals containing K + and Pb 2+ as interlayer cations (fourmarierite, dumontite) indicate fractionation (enrichment) of the LREEs. Our results have implications for nuclear forensic analyses since a comparison is reported between the REE abundances for the CUP-2 (processed uranium ore) certified reference material and previously determined values for uranium ore concentrate (UOC) produced from the same U deposit (Blind River/Elliott Lake, Canada). UOCs represent the most common form of interdicted nuclear material and consequently is material frequently targeted for forensic analysis. The comparison reveals similar chondrite normalized REE signatures but variable absolute abundances. Based on the results reported here, the latter may be attributed to the differing REE abundances between primary ore and associated alteration phases, and/or is related to varying fabrication processes adopted during production of UOC.« less

Salinity effect on the maximal growth temperature of some bacteria isolated from marine enviroments.

PubMed

Stanley, S O; Morita, R Y

1968-01-01

Salinity of the growth medium was found to have a marked effect on the maximal growth temperature of four bacteria isolated from marine sources. Vibrio marinus MP-1 had a maximal growth temperature of 21.2 C at a salinity of 35% and a maximal growth temperature of 10.5 C at a salinity of 7%, the lowest salinity at which it would grow. This effect was shown to be due to the presence of various cations in the medium. The order of effectiveness of cations in restoring the normal maximal growth temperature, when added to dilute seawater, was Na(+) > Li(+) > Mg(++) > K(+) > Rb(+) > NH(4) (+). The anions tested, with the exception of SO(4)=, had no marked effect on the maximal growth temperature response. In a completely defined medium, the highest maximal growth temperature was 20.0 C at 0.40 m NaCl. A decrease in the maximal growth temperature was observed at both low and high concentrations of NaCl.

Sulfate mobility in an outwash soil in western Washington

Treesearch

D. W. Johnson; D. W. Cole

1976-01-01

The effect of acidic precipitation on cation leaching in a second-growth Douglas-fir ecosystem at the Thompson Research Center is reviewed. Sulfate mobility and soil pH buffering power were tested by applications of heavy doses of sulfuric acid to the study plot. Sulfate at high concentrations proved to be immobilized, presumably by adsorption to soil sesquioxide...

The effect of sodium chloride on the dissolution of calcium silicate hydrate gels.

PubMed

Hill, J; Harris, A W; Manning, M; Chambers, A; Swanton, S W

2006-01-01

The use of cement based materials will be widespread in the long-term management of radioactive materials in the United Kingdom. One of the applications could be the Nirex reference vault backfill (NRVB) as an engineered barrier within a deep geological repository. NRVB confers alkaline conditions, which would provide a robust chemical barrier through the control of the solubility of some key radionuclides, enhanced sorption and minimised corrosion of steel containers. An understanding of the dissolution of C-S-H gels in cement under the appropriate conditions (e.g., saline groundwaters) is necessary to demonstrate the expected evolution of the chemistry over time and to provide sufficient cement to buffer the porewater conditions for the required time. A programme of experimental work has been undertaken to investigate C-S-H gel dissolution behaviour in sodium chloride solutions and the effect of calcium/silicon ratio (C/S), temperature and cation type on this behaviour. Reductions in calcium concentration and pH values were observed with samples equilibrated at 45 degrees C compared to those prepared at 25 degrees C. The effect of salt cation type on salt-concentration dependence of the dissolution of C-S-H gels was investigated by the addition of lithium or potassium chloride in place of sodium chloride for gels with a C/S of 1.0 and 1.8. With a C/S of 1.0, similar increases in dissolved calcium concentration with increasing ionic strength were recorded for the different salts. However, at a C/S of 1.8, anomalously high calcium concentrations were observed in the presence of lithium.

Cation disorder in Ga1212.

PubMed

Greenwood, K B; Ko, D; Vander Griend, D A; Sarjeant, G M; Milgram, J W; Garrity, E S; DeLoach, D I; Poeppelmeier, K R; Salvador, P A; Mason, T O

2000-07-24

Substitution of calcium for strontium in LnSr2-xCaxCu2GaO7 (Ln = La, Pr, Nd, Gd, Ho, Er, Tm, and Yb) materials at ambient pressure and 975 degrees C results in complete substitution of calcium for strontium in the lanthanum and praseodymium systems and partial substitution in the other lanthanide systems. The calcium saturation level depends on the size of the Ln cation, and in all cases, a decrease in the lattice parameters with calcium concentration was observed until a common, lower bound, average A-cation size is reached. Site occupancies from X-ray and neutron diffraction experiments for LnSr2-xCaxCu2GaO7 (x = 0 and x = 2) confirm that the A-cations distribute between the two blocking-layer sites and the active-layer site based on size. A quantitative link between cation distribution and relative site-specific cation enthalpy for calcium, strontium, and lanthanum within the gallate structure is derived. The cation distribution in other similar materials can potentially be modeled.

Effect of Zn addition on structural, magnetic properties, antistructural modeling of Co1-xZnxFe2O4 nano ferrite

NASA Astrophysics Data System (ADS)

Raghuvanshi, S.; Kane, S. N.; Tatarchuk, T. R.; Mazaleyrat, F.

2018-05-01

Effect of Zn addition on cationic distribution, structural properties, magnetic properties, antistructural modeling of nanocrystalline Co1-xZnxFe2O4 (0.08 ≤ x ≤ 0.56) ferrite is reported. XRD confirms the formation of single phase cubic spinel nano ferrites with average grain diameter ranging between 41.2 - 54.9 nm. Coercivity (Hc), anisotropy constant (K1) decreases with Zn addition, but experimental, theoretical saturation magnetization (Ms, Ms(t)) increases upto x = 0.32, then decreases, attributed to the breaking of collinear ferrimagnetic phase. Variation of magnetic properties is correlated with cationic distribution. A new antistructural modeling for describing active surface centers is discussed to explain change in concentration of donor's active centers Zn'B, Co'B, acceptor's active centers Fe*A are explained.

Amphiphilic interactions of ionic liquids with lipid biomembranes: a molecular simulation study.

PubMed

Yoo, Brian; Shah, Jindal K; Zhu, Yingxi; Maginn, Edward J

2014-11-21

Current bottlenecks in the large-scale commercial use of many ionic liquids (ILs) include their high costs, low biodegradability, and often unknown toxicities. As a proactive effort to better understand the molecular mechanisms of ionic liquid toxicities, the work herein presents a comprehensive molecular simulation study on the interactions of 1-n-alkyl-3-methylimidazolium-based ILs with a phosphatidylcholine (PC) lipid bilayer. We explore the effects of increasing alkyl chain length (n = 4, 8, and 12) in the cation and anion hydrophobicity on the interactions with the lipid bilayer. Bulk atomistic molecular dynamics (MD) simulations performed at millimolar (mM) IL concentrations show spontaneous insertion of cations into the lipid bilayer regardless of the alkyl chain length and a favorable orientational preference once a cation is inserted. Cations also exhibit the ability to "flip" inside the lipid bilayer (as is common for amphiphiles) if partially inserted with an unfavorable orientation. Moreover, structural analysis of the lipid bilayer show that cationic insertion induces roughening of the bilayer surface, which may be a precursor to bilayer disruption. To overcome the limitation in the timescale of our simulations, free energies for a single IL cation and anion insertion have been determined based on potential of mean force calculations. These results show a decrease in free energy in response to both short and long alkyl chain IL cation insertion, and likewise for a single hydrophobic anion insertion, but an increase in free energy for the insertion of a hydrophilic chloride anion. Both bulk MD simulations and free energy calculations suggest that toxicity mechanisms toward biological systems are likely caused by ILs behaving as ionic surfactants. [Yoo et al., Soft Matter, 2014].

Transient phenomena in the pulse radiolysis of retinyl polyenes. 5. Association of radical cations with parent molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bobrowski, K.; Das, P.K.

1986-02-27

At relatively high concentrations (1-10 mM) in O/sub 2/-saturated acetone, pulse radiolysis of all-trans-retinal, -retinoic acid, and -methyl retinoate gives rise to fast transient absorption processes that are best explained in terms of association of radical cations with parent polyenes to form dimers. From the concentration dependence of initial decay/formation kinetics, equilibrium constants (K) for monomer/dimer interconversion are measured to be 220-440 M/sup -1/ (in acetone). On going from acetone to 1,2-dichloroethane, K values for retinal and retinoic acid increase almost by an order of magnitude. For all trans-retinol and retinyl acetate, radical cation dimer formation appears to be negligiblemore » in the concentration range 1-10 mM of the polyene substrates (based on the lack of transient absorption changes seen with retinal and retinoic acid/ester). 24 references, 6 figures, 1 table.« less

Intensification of the Reverse Cationic Flotation of Hematite Ores with Optimization of Process and Hydrodynamic Parameters of Flotation Cell

NASA Astrophysics Data System (ADS)

Poperechnikova, O. Yu; Filippov, L. O.; Shumskaya, E. N.; Filippova, I. V.

2017-07-01

The demand of high grade iron ore concentrates is a major issue due to the depletion of rich iron-bearing ores and high competitiveness in the iron ore market. Iron ore production is forced out to upgrade flowsheets to decrease the silica content in the pelettes. Different types of ore have different mineral composition and texture-structural features which require different mineral processing methods and technologies. The paper presents a comparative study of the cationic and anionic flotation routes to process a fine-grain oxidized iron ore. The modified carboxymethyl cellulose was found as the most efficient depressant in reverse cationic flotation. The results of flotation optimization of hematite ores using matrix of second-order center rotatable uniform design allowed to define the collector concentration, impeller rotation speed and air flowrate as the main flotation parameters impacting on the iron ore concentrate quality and iron recovery in a laboratory flotation machine. These parameters have been selected as independent during the experiments.

Efficient harvesting of marine Chlorella vulgaris microalgae utilizing cationic starch nanoparticles by response surface methodology.

PubMed

Bayat Tork, Mahya; Khalilzadeh, Rasoul; Kouchakzadeh, Hasan

2017-11-01

Harvesting involves nearly thirty percent of total production cost of microalgae that needs to be done efficiently. Utilizing inexpensive and highly available biopolymer-based flocculants can be a solution for reducing the harvest costs. Herein, flocculation process of Chlorella vulgaris microalgae using cationic starch nanoparticles (CSNPs) was evaluated and optimized through the response surface methodology (RSM). pH, microalgae and CSNPs concentrations were considered as the main independent variables. Under the optimum conditions of microalgae concentration 0.75gdry weight/L, CSNPs concentration 7.1mgdry weight/L and pH 11.8, the maximum flocculation efficiency (90%) achieved. Twenty percent increase in flocculation efficiency observed with the use of CSNPs instead of the non-particulate starch which can be due to the more electrostatic interactions between the cationic nanoparticles and the microalgae. Therefore, the synthesized CSNPs can be employed as a convenient and economical flocculants for efficient harvest of Chlorella vulgaris microalgae at large scale. Copyright © 2017 Elsevier Ltd. All rights reserved.

Cation exchange properties of zeolites in hyper alkaline aqueous media.

PubMed

Van Tendeloo, Leen; de Blochouse, Benny; Dom, Dirk; Vancluysen, Jacqueline; Snellings, Ruben; Martens, Johan A; Kirschhock, Christine E A; Maes, André; Breynaert, Eric

2015-02-03

Construction of multibarrier concrete based waste disposal sites and management of alkaline mine drainage water requires cation exchangers combining excellent sorption properties with a high stability and predictable performance in hyper alkaline media. Though highly selective organic cation exchange resins have been developed for most pollutants, they can serve as a growth medium for bacterial proliferation, impairing their long-term stability and introducing unpredictable parameters into the evolution of the system. Zeolites represent a family of inorganic cation exchangers, which naturally occur in hyper alkaline conditions and cannot serve as an electron donor or carbon source for microbial proliferation. Despite their successful application as industrial cation exchangers under near neutral conditions, their performance in hyper alkaline, saline water remains highly undocumented. Using Cs(+) as a benchmark element, this study aims to assess the long-term cation exchange performance of zeolites in concrete derived aqueous solutions. Comparison of their exchange properties in alkaline media with data obtained in near neutral solutions demonstrated that the cation exchange selectivity remains unaffected by the increased hydroxyl concentration; the cation exchange capacity did however show an unexpected increase in hyper alkaline media.

Cesium migration in Hanford sediment: a multisite cation exchange model based on laboratory transport experiments.

PubMed

Steefel, Carl I; Carroll, Susan; Zhao, Pihong; Roberts, Sarah

2003-12-01

Cs+ transport experiments carried out in columns packed with uncontaminated Hanford formation sediment from the SX tank farm provide strong support for the use of a multisite, multicomponent cation exchange model to describe Cs+ migration in the Hanford vadose zone. The experimental results indicate a strong dependence of the effective Cs+ Kd on the concentrations of other cations, including Na+ that is present at high to extremely high concentrations in fluids leaking from the Hanford SX tanks. A strong dependence of the Cs+ Kd on the aqueous Cs+ concentration is also apparent, with retardation of Cs+ increasing from a value of 41 at a Cs+ concentration of 10(-4) M in the feed solution to as much as 282 at a Cs+ concentration of 5x10(-7) M, all in a background of 1 M NaNO3. The total cation exchange capacity (CEC) of the Hanford sediment was determined using 22Na isotopic equilibrium exchange in a flow-through column experiment. The value for the CEC of 120 microeq/g determined with this method is compatible with a value of 121.9 microeq/g determined by multi-cation elution. While two distinct exchange sites were proposed by Zachara et al. [Geochim. Cosmochim. Acta 66 (2002) 193] based on binary batch exchange experiments, a third site is proposed in this study to improve the fit of the Cs+-Na+ and Cs+-Ca+ exchange data and to capture self-sharpened Cs+ breakthrough curves at low concentrations of Cs+. Two of the proposed exchange sites represent frayed edge sites (FES) on weathered micas and constitute 0.02% and 0.22% of the total CEC. Both of the FES show a very strong selectivity for Cs+ over Na+ (K(Na-Cs)=10(7.22) and 10(4.93), respectively). The third site, accounting for over 99% of the total CEC, is associated with planar sites on expansible clays and shows a smaller Na+-Cs+ selectivity coefficient of 10(1.99). Parameters derived from a fit of binary batch experiments alone tend to under predict Cs+ retardation in the column experiments. The transport experiments indicate 72-90% of the Cs+ sorbed in experiments targeting exchange on FES was desorbed over a 10- and 24-day period, respectively. At high Cs+ concentrations, where sorption is controlled primarily by exchange on planar sites, 95% of the Cs+ desorption was desorbed. Most of the difficulty in desorbing Cs+ from FES is a result of the extremely high selectivity of these sites for Cs+, although truly irreversible sorption as high as 23% was suggested in one experiment. The conclusion that Cs+ exchange is largely reversible in a thermodynamic sense is supported by the ability to match Cs+ desorption curves almost quantitatively with an equilibrium reactive transport simulation. The model for Cs+ retardation developed here qualitatively explains the behavior of Cs+ in the Hanford vadose zone underneath a variety of leaking tanks with differing salt concentrations. The high selectivity of FES for Cs+ implies that future desorption and migration is very unlikely to occur under natural recharge conditions.

Divalent cations in tears, and their influence on tear film stability in humans and rabbits.

PubMed

Wei, Xiaojia Eric; Markoulli, Maria; Millar, Thomas J; Willcox, Mark D P; Zhao, Zhenjun

2012-06-05

Reduced tear film stability is reported to contribute to dry eye. Rabbits are known to have a more stable tear film than humans. Thus, we sought to examine the tears of rabbits and humans for metal cations, and to test how they influence tear film stability. Tears were collected from 10 healthy humans and 6 rabbits. Tear osmolality was measured by vapor pressure osmometer, and metals analyzed using inductively coupled plasma (ICP) mass spectrometry or ICP atomic emission spectroscopy. The influence of divalent cations on tears was analyzed by measuring surface tension using the Langmuir trough in vitro, using different concentrations of cations in the subphase, and grading the tear break-up in rabbits in vivo after instillation of chelating agents. Rabbit tears had a higher osmolality compared to humans. Major metals did not differ between species; however, rabbits had higher levels of Mg(2+) (1.13 vs. 0.39 mM) and Ca(2+) (0.75 vs. 0.36 mM). In rabbit tears in vitro, diminishing divalent cations resulted in a decrease in the maximum surface pressure from 37 to 30 mN/m. In vivo, an increase in the amount of tear film that was broken-up was found. In contrast, when changing divalent cation concentrations in human tears, the maximum surface pressure remained at 26 mN/m. The normal osmolality of rabbit tears is significantly higher than that in humans. While divalent cations had little influence on human tears, they appear to have an important role in maintaining tear film stability in rabbits.

Effect of oxalate on the dissolution rates of oligoclase and tremolite (journal version)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mast, M.A.; Drever, J.I.

1987-01-01

The effect of oxalate, a strong chelator for Al and other cations, on the dissolution rates of oligoclase feldspar and tremolite amphibole was investigated in a flow-through reactor at 22 deg C. Oxalate at concentrations of 0.5 and 1 mM has essentially no effect on the dissolution rate of tremolite, nor on the steady-state rate of release of Si from oligoclase. The fact that oxalate has no effect on dissolution rate suggests that detachment of Si rather than Al or Mg is the rate-limiting step. At pH 4 and 9, oxalate has no effect on the steady-state rate of releasemore » of Al, and dissolution is congruent. At pH 5 and 7, oligoclase dissolution is congruent in the presence of oxalate, but in the absence of oxalate Al is preferentially retained in the solid relative to Si. The rate of dissolution of tremolite is independent of pH over the pH range 2-5, and decreases at higher pH. The rate of dissolution of oligoclase was independent of pH over the pH range 4-9. Since the dissolution rate of these minerals is independent of pH and organic ligand concentration, the effect of acid deposition from the atmosphere on the rate of supply of cations from weathering of granitic rocks should be minor.« less

Interactions of divalent cations with calcium binding sites of BK channels reveal independent motions within the gating ring.

PubMed

Miranda, Pablo; Giraldez, Teresa; Holmgren, Miguel

2016-12-06

Large-conductance voltage- and calcium-activated K + (BK) channels are key physiological players in muscle, nerve, and endocrine function by integrating intracellular Ca 2+ and membrane voltage signals. The open probability of BK channels is regulated by the intracellular concentration of divalent cations sensed by a large structure in the BK channel called the "gating ring," which is formed by four tandems of regulator of conductance for K + (RCK1 and RCK2) domains. In contrast to Ca 2+ that binds to both RCK domains, Mg 2+ , Cd 2+ , or Ba 2+ interact preferentially with either one or the other. Interaction of cations with their binding sites causes molecular rearrangements of the gating ring, but how these motions occur remains elusive. We have assessed the separate contributions of each RCK domain to the cation-induced gating-ring structural rearrangements, using patch-clamp fluorometry. Here we show that Mg 2+ and Ba 2+ selectively induce structural movement of the RCK2 domain, whereas Cd 2+ causes motions of RCK1, in all cases substantially smaller than those elicited by Ca 2+ By combining divalent species interacting with unique sites, we demonstrate that RCK1 and RCK2 domains move independently when their specific binding sites are occupied. Moreover, binding of chemically distinct cations to both RCK domains is additive, emulating the effect of fully occupied Ca 2+ binding sites.

Carrier-Mediated Transport of Nicotine Across the Inner Blood-Retinal Barrier: Involvement of a Novel Organic Cation Transporter Driven by an Outward H(+) Gradient.

PubMed

Tega, Yuma; Kubo, Yoshiyuki; Yuzurihara, Chihiro; Akanuma, Shin-Ichi; Hosoya, Ken-Ichi

2015-09-01

The present study was carried out to investigate the blood-to-retina transport of nicotine across the inner blood-retinal barrier (BRB). Using the in vivo vascular injection method, the blood-to-retina influx clearance of nicotine across the BRB was determined as 131 μL/(min?g retina), which is much higher than that of a nonpermeable paracellular marker, and blood-to-retina transport of nicotine was inhibited by organic cations such as pyrilamine and verapamil. The nicotine uptake by a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2 cells), an in vitro model of the inner BRB, exhibited time, temperature, and concentration dependence with a Km of 492 μM. These results suggest the involvement of a carrier-mediated transport process in nicotine transport in the inner BRB. The nicotine uptake by TR-iBRB2 cells was stimulated by an outwardly directed H(+) gradient, and the uptake was significantly inhibited by bulky and hydrophobic cationic drugs, whereas inhibitors of organic cation transporters did not show inhibitory effect. These results suggest that the novel organic cation transport system driven by an outwardly directed H(+) gradient is involved in the blood-to-retina transport of nicotine across the inner BRB. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

ERYTHROPOIETIC FACTOR PURIFICATION

DOEpatents

White, W.F.; Schlueter, R.J.

1962-05-01

A method is given for purifying and concentrating the blood plasma erythropoietic factor. Anemic sheep plasma is contacted three times successively with ion exchange resins: an anion exchange resin, a cation exchange resin at a pH of about 5, and a cation exchange resin at a pH of about 6. (AEC)

Cation–Anion Interactions within the Nucleic Acid Ion Atmosphere Revealed by Ion Counting

PubMed Central

Gebala, Magdalena; Giambasu, George M.; Lipfert, Jan; Bisaria, Namita; Bonilla, Steve; Li, Guangchao; York, Darrin M.; Herschlag, Daniel

2016-01-01

The ion atmosphere is a critical structural, dynamic, and energetic component of nucleic acids that profoundly affects their interactions with proteins and ligands. Experimental methods that “count” the number of ions thermodynamically associated with the ion atmosphere allow dissection of energetic properties of the ion atmosphere, and thus provide direct comparison to theoretical results. Previous experiments have focused primarily on the cations that are attracted to nucleic acid polyanions, but have also showed that anions are excluded from the ion atmosphere. Herein, we have systematically explored the properties of anion exclusion, testing the zeroth-order model that anions of different identity are equally excluded due to electrostatic repulsion. Using a series of monovalent salts, we find, surprisingly, that the extent of anion exclusion and cation inclusion significantly depends on salt identity. The differences are prominent at higher concentrations and mirror trends in mean activity coefficients of the electrolyte solutions. Salts with lower activity coefficients exhibit greater accumulation of both cations and anions within the ion atmosphere, strongly suggesting that cation–anion correlation effects are present in the ion atmosphere and need to be accounted for to understand electrostatic interactions of nucleic acids. To test whether the effects of cation–anion correlations extend to nucleic acid kinetics and thermodynamics, we followed the folding of P4–P6, a domain of the Tetrahymena group I ribozyme, via single-molecule fluorescence resonance energy transfer in solutions with different salts. Solutions of identical concentration but lower activity gave slower and less favorable folding. Our results reveal hitherto unknown properties of the ion atmosphere and suggest possible roles of oriented ion pairs or anion-bridged cations in the ion atmosphere for electrolyte solutions of salts with reduced activity. Consideration of these new results leads to a reevaluation of the strengths and limitations of Poisson–Boltzmann theory and highlights the need for next-generation atomic-level models of the ion atmosphere. PMID:26517731

Influence of competing inorganic cations on the ion exchange equilibrium of the monovalent organic cation metoprolol on natural sediment.

PubMed

Niedbala, Anne; Schaffer, Mario; Licha, Tobias; Nödler, Karsten; Börnick, Hilmar; Ruppert, Hans; Worch, Eckhard

2013-02-01

The aim of this study was to systematically investigate the influence of the mono- and divalent inorganic ions Na(+) and Ca(2+) on the sorption behavior of the monovalent organic cation metoprolol on a natural sandy sediment at pH=7. Isotherms for the beta-blocker metoprolol were obtained by sediment-water batch tests over a wide concentration range (1-100000 μg L(-1)). Concentrations of the competing inorganic ions were varied within freshwater relevant ranges. Data fitted well with the Freundlich sorption model and resulted in very similar Freundlich exponents (n=0.9), indicating slightly non-linear behavior. Results show that the influence of Ca(2+) compared to Na(+) is more pronounced. A logarithmic correlation between the Freundlich coefficient K(Fr) and the concentration or activity of the competing inorganic ions was found allowing the prediction of metoprolol sorption on the investigated sediment at different electrolyte concentrations. Additionally, the organic carbon of the sediment was completely removed for investigating the influence of organic matter on the sorption of metoprolol. The comparison between the experiments with and without organic carbon removal revealed no significant contribution of the organic carbon fraction (0.1%) to the sorption of metoprolol on the in this study investigated sediment. Results of this study will contribute to the development of predictive models for the transport of organic cations in the subsurface. Copyright © 2012 Elsevier Ltd. All rights reserved.

Ternary mixtures of ionic liquids for better salt solubility, conductivity and cation transference number improvement

PubMed Central

Karpierz, E.; Niedzicki, L.; Trzeciak, T.; Zawadzki, M.; Dranka, M.; Zachara, J.; Żukowska, G. Z.; Bitner-Michalska, A.; Wieczorek, W.

2016-01-01

We hereby present the new class of ionic liquid systems in which lithium salt is introduced into the solution as a lithium cation−glyme solvate. This modification leads to the reorganisation of solution structure, which entails release of free mobile lithium cation solvate and hence leads to the significant enhancement of ionic conductivity and lithium cation transference numbers. This new approach in composing electrolytes also enables even three-fold increase of salt concentration in ionic liquids. PMID:27767069

Cationic PAMAM dendrimers as pore-blocking binary toxin inhibitors.

PubMed

Förstner, Philip; Bayer, Fabienne; Kalu, Nnanya; Felsen, Susanne; Förtsch, Christina; Aloufi, Abrar; Ng, David Y W; Weil, Tanja; Nestorovich, Ekaterina M; Barth, Holger

2014-07-14

Dendrimers are unique highly branched macromolecules with numerous groundbreaking biomedical applications under development. Here we identified poly(amido amine) (PAMAM) dendrimers as novel blockers for the pore-forming B components of the binary anthrax toxin (PA63) and Clostridium botulinum C2 toxin (C2IIa). These pores are essential for delivery of the enzymatic A components of the internalized toxins from endosomes into the cytosol of target cells. We demonstrate that at low μM concentrations cationic PAMAM dendrimers block PA63 and C2IIa to inhibit channel-mediated transport of the A components, thereby protecting HeLa and Vero cells from intoxication. By channel reconstitution and high-resolution current recording, we show that the PAMAM dendrimers obstruct transmembrane PA63 and C2IIa pores in planar lipid bilayers at nM concentrations. These findings suggest a new potential role for the PAMAM dendrimers as effective polyvalent channel-blocking inhibitors, which can protect human target cells from intoxication with binary toxins from pathogenic bacteria.

Characterization of nucleoside triphosphatase activity in isolated pea nuclei and its photoreversible regulation by light

NASA Technical Reports Server (NTRS)

Chen, Y. R.; Roux, S. J.

1986-01-01

A nucleoside triphosphatase (NTPase) present in highly purified preparations of pea nuclei was partially characterized. The activity of this enzyme was stimulated by divalent cations (Mg2+ = Mn2+ > Ca2+), but was not affected by the monovalent cations, Na+ and K+. The Mg(2+)-dependent activity was further stimulated by concentrations of Ca2+ in the low micromolar range. It could catalyze the hydrolysis of ATP, GTP, UTP, and CTP, all with a pH optimum of 7.5. The nuclear NTPase activity was not inhibited by vanadate, oligomycin, or nitrate, but was inhibited by relatively low concentrations of quercetin and the calmodulin inhibitor, compound 48/80. The NTPase was stimulated more than 50% by red light, and this effect was reversed by subsequent irradiation with far-red light. The photoreversibility of the stimulation indicated that the photoreceptor for this response was phytochrome, an important regulator of photomorphogenesis and gene expression in plants.

Cationic PAMAM Dendrimers as Pore-Blocking Binary Toxin Inhibitors

PubMed Central

2015-01-01

Dendrimers are unique highly branched macromolecules with numerous groundbreaking biomedical applications under development. Here we identified poly(amido amine) (PAMAM) dendrimers as novel blockers for the pore-forming B components of the binary anthrax toxin (PA63) and Clostridium botulinum C2 toxin (C2IIa). These pores are essential for delivery of the enzymatic A components of the internalized toxins from endosomes into the cytosol of target cells. We demonstrate that at low μM concentrations cationic PAMAM dendrimers block PA63 and C2IIa to inhibit channel-mediated transport of the A components, thereby protecting HeLa and Vero cells from intoxication. By channel reconstitution and high-resolution current recording, we show that the PAMAM dendrimers obstruct transmembrane PA63 and C2IIa pores in planar lipid bilayers at nM concentrations. These findings suggest a new potential role for the PAMAM dendrimers as effective polyvalent channel-blocking inhibitors, which can protect human target cells from intoxication with binary toxins from pathogenic bacteria. PMID:24954629

[Effects of sub-micro emulsion composition on cellular disposition of incorporated lipophilic drug].

PubMed

Sun, Xiao-Yi; Xiang, Zhi-Qiang; Wu, Shuo; Lv, Yuan-Yuan; Liang, Wen-Quan

2013-09-01

To investigate the effects of sub-micro emulsion composition on cellular uptake and disposition of incorporated lipophilic drug. Sub-micro emulsions containing 10 % oil, 1.2 % lecithin and 2.25 % glycerol were prepared, and the fluorescent agent coumarin 6 was used as a model drug. The effects of oil types, co-surfactants and cationic lipid on uptake and elimination kinetics of 6-coumarin in HeLa cells were studied. The uptake mechanism of sub-micro emulsions was further investigated. Oil type and Tweens had no influence on the cellular uptake. Modifications of surfactants with Span series increased the cellular influx, among which Span 20 with hydrophilic-lipophilic balance (HLB) value of 8.6 was the best enhancer. The intracellular drug level reached up to (46.09 ± 1.98)ng/μg protein which had significant difference with control group [(38.54 ± 0.34)ng/μg protein]. The positively charged emulsions significantly increased the uptake rate constant and elimination rate constant which were 4 times and 1.5 times of those in anionic groups, respectively. The uptake enhancement was also observed in cationic emulsions, cellular concentrations at plateau were (42.73 ± 0.84)ng/μg protein, which was about 3 times of that in anionic emulsions [(15.71 ± 0.74)ng/μg protein], when extracellular drug concentration kept at 100 ng/ml. Cationic emulsions delivered the payload mainly by direct drug transfer to contacted cells, while the negative ones depended on both drug passive diffusion and clathrin-mediated endocytosis of drug containing oil droplets which accounted for 20% of the intracellular drug. Interfacial characteristic of sub-micro emulsions such as co-surfactants HLB as well as zeta potentials can influence lipophilic drug both in cellular uptake and elimination.

Enhancement of indocyanine green stability and cellular uptake by incorporating cationic lipid into indocyanine green-loaded nanoemulsions.

PubMed

Lee, Eun-Hye; Kim, Jin-Ki; Lim, Joon-Seok; Lim, Soo-Jeong

2015-12-01

Indocyanine green (ICG) is a near-infrared optical dye approved by the Food and Drug Administration. ICG has been investigated as a simultaneous color and fluorescence-imaging tracer for the intraoperative identification of sentinel lymph nodes, but its use has recently expanded to include application as a photosensitizer for the local photodynamic/thermal treatment of identified lymph node metastases. The current study was designed to develop an ICG-loaded nanoemulsion as an effective agent for both the diagnosis and treatment of lymph node metastases. Incorporating the cationic lipid stearylamine (SA) together with ICG in the shell of nanoemulsions did not affect the loaded ICG concentration, but changed the surface charge of nanoemulsions from a negative to a positive value and improved the physical stability of nanoemulsions. Loading ICG into SA-incorporated nanoemulsions more effectively blocked the aggregation and degradation of ICG compared to loading in SA-free nanoemulsions. SA incorporation also enhanced tumor cell uptake of ICG-loaded nanoemulsions, resulting in greater cell killing upon light irradiation. After subcutaneous injection into the footpad of mice, SA-incorporated nanoemulsions increased the concentration of ICG accumulated in popliteal lymph nodes to a greater extent than SA-free nanoemulsions without affecting the kinetics of lymph node uptake of nanoemulsions. These multiple beneficial effects of incorporating SA in nanoemulsions are likely attributable to the electrostatic interaction between anionic ICG and cationic SA, as well as the change in the nanoemulsion surface charge from negative to positive. Our findings indicate that SA-incorporated nanoemulsions are promising ICG carriers for combined diagnosis and treatment of lymph node metastases. Copyright © 2015 Elsevier B.V. All rights reserved.

Effects of membrane composition on release of model hydrophilic compound from osmotic delivery systems.

PubMed

Ozdemir, N; Ozalp, Y; Ozkan, Y

2000-01-01

In this study, the effects of surface-active agents in different types and concentrations, added into the coating solution, on release of model hydrophilic compound have been examined. For this purpose, the tablets, prepared with the use of methylene blue as a model substance, were coated by spray coating technique with cellulose acetate solution containing polyethylene glycol 400 as a plasticizer. In addition, cetylpyridinium chloride as cationic surface-active agent and sodium lauryl sulphate as anionic surface-active agent were added into coating solution in different concentrations. After creating a delivery orifice by a microdrill on the tablets, release of model hydrophilic compound was tested by the USP paddle method. The data obtained were evaluated according to the different kinetics and the mechanism of release from the preparations was examined. The surface properties of the coating material were investigated by scanning electron microscope taken before and after the contact with medium fluid, as well as the mechanical properties by tensile tests. In conclusion, it has been found that the cationic surface active agent, cetylpyridinium chloride reduced the lag time, observed during the release of model hydrophilic compound, as a result of its enhancing effect on wettability of tablets by reducing the contact angle between the medium fluid and the coating material. On the other hand, the anionic surface active agent, sodium lauryl sulphate has been inactivated possibly due to the interaction with model hydrophilic compound that has cationic properties and/or substances contained in membrane composition; thus, the lag time has not decreased and furthermore, a significant decrease in the delivery rate of model hydrophilic compound has been observed.

Cation-induced folding of alginate-bearing bilayer gels: an unusual example of spontaneous folding along the long axis.

PubMed

Athas, Jasmin C; Nguyen, Catherine P; Kummar, Shailaa; Raghavan, Srinivasa R

2018-04-04

The spontaneous folding of flat gel films into tubes is an interesting example of self-assembly. Typically, a rectangular film folds along its short axis when forming a tube; folding along the long axis has been seen only in rare instances when the film is constrained. Here, we report a case where the same free-swelling gel film folds along either its long or short axis depending on the concentration of a solute. Our gels are sandwiches (bilayers) of two layers: a passive layer of cross-linked N,N'-dimethylyacrylamide (DMAA) and an active layer of cross-linked DMAA that also contains chains of the biopolymer alginate. Multivalent cations like Ca2+ and Cu2+ induce these bilayer gels to fold into tubes. The folding occurs instantly when a flat film of the gel is introduced into a solution of these cations. The likely cause for folding is that the active layer stiffens and shrinks (because the alginate chains in it get cross-linked by the cations) whereas the passive layer is unaffected. The resulting mismatch in swelling degree between the two layers creates internal stresses that drive folding. Cations that are incapable of cross-linking alginate, such as Na+ and Mg2+, do not induce gel folding. Moreover, the striking aspect is the direction of folding. When the Ca2+ concentration is high (100 mM or higher), the gels fold along their long axis, whereas when the Ca2+ concentration is low (40 to 80 mM), the gels fold along their short axis. We hypothesize that the folding axis is dictated by the inhomogeneous nature of alginate-cation cross-linking, i.e., that the edges get cross-linked before the faces of the gel. At high Ca2+ concentration, the stiffer edges constrain the folding; in turn, the gel folds such that the longer edges are deformed less, which explains the folding along the long axis. At low Ca2+ concentration, the edges and the faces of the gel are more similar in their degree of cross-linking; therefore, the gel folds along its short axis. An analogy can be made to natural structures (such as leaves and seed pods) where stiff elements provide the directionality for folding.

Cations Modulate Actin Bundle Mechanics, Assembly Dynamics, and Structure.

PubMed

Castaneda, Nicholas; Zheng, Tianyu; Rivera-Jacquez, Hector J; Lee, Hyun-Ju; Hyun, Jaekyung; Balaeff, Alexander; Huo, Qun; Kang, Hyeran

2018-04-12

Actin bundles are key factors in the mechanical support and dynamic reorganization of the cytoskeleton. High concentrations of multivalent counterions promote bundle formation through electrostatic attraction between actin filaments that are negatively charged polyelectrolytes. In this study, we evaluate how physiologically relevant divalent cations affect the mechanical, dynamic, and structural properties of actin bundles. Using a combination of total internal reflection fluorescence microscopy, transmission electron microscopy, and dynamic light scattering, we demonstrate that divalent cations modulate bundle stiffness, length distribution, and lateral growth. Molecular dynamics simulations of an all-atom model of the actin bundle reveal specific actin residues coordinate cation-binding sites that promote the bundle formation. Our work suggests that specific cation interactions may play a fundamental role in the assembly, structure, and mechanical properties of actin bundles.

Critical Synergistic Concentration of Lecithin Phospholipids Improves the Antimicrobial Activity of Eugenol against Escherichia coli.

PubMed

Zhang, Haoshu; Dudley, Edward G; Harte, Federico

2017-11-01

In this study, the effect of individual lecithin phospholipids on the antimicrobial properties of eugenol against Escherichia coli C600 was investigated. We tested five major phospholipids common in soy or egg lecithin (1,2-dihexadecanoyl-sn-glycero-3-phosphocholine [DPPC], 1,2-dioctadecanoyl-sn-glycero-3-phosphocholine [DSPC], 1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine [DPPE], 1,2-dihexadecanoyl-sn-glycero-3-phosphate [sodium salt] [DPPA], and 1,2-dihexadecanoyl-sn-glycero-3-phospho-l-serine [DPPS]) and one synthetic cationic phospholipid (1,2-dioctadecanoyl-sn-glycero-3-ethylphosphocholine [18:0 EPC]). Among the six phospholipids, DPPC, DSPC, DPPE, DPPA, and the cationic 18:0 EPC showed critical synergistic concentrations that significantly improved the inactivation effect of eugenol against E. coli after 30 min of exposure. At the critical synergistic concentration, an additional ca. 0.4 to 1.9 log reduction (ca. 0.66 to 2.17 log CFU/ml reduction) in the microbial population was observed compared to eugenol-only (control) treatments (ca. 0.25 log reduction). In all cases, increasing the phospholipid amount above the critical synergistic concentration (which was different for each phospholipid) resulted in antimicrobial properties similar to those seen with the eugenol-only (control) treatments. DPPS did not affect the antimicrobial properties of eugenol at the tested concentrations. The critical synergistic concentration of phospholipids was correlated with their critical micelle concentrations (CMC). IMPORTANCE Essential oils (EOs) are naturally occurring antimicrobials, with limited use in food due to their hydrophobicity and strong aroma. Lecithin is used as a natural emulsifier to stabilize EOs in aqueous systems. We previously demonstrated that, within a narrow critical-concentration window, lecithin can synergistically enhance the antimicrobial properties of eugenol. Since lecithin is a mixture of different phospholipids, we aimed to identify which phospholipids are crucial for the observed synergistic effect. This research studied the bioactivity of lecithin phospholipids, contributing to a rational design in using lecithin to effectively control foodborne pathogens in foods. Copyright © 2017 American Society for Microbiology.

Water diffusion in silicate glasses: the effect of glass structure

NASA Astrophysics Data System (ADS)

Kuroda, M.; Tachibana, S.

2016-12-01

Water diffusion in silicate melts (glasses) is one of the main controlling factors of magmatism in a volcanic system. Water diffusivity in silicate glasses depends on its own concentration. However, the mechanism causing those dependences has not been fully understood yet. In order to construct a general model for water diffusion in various silicate glasses, we performed water diffusion experiments in silica glass and proposed a new water diffusion model [Kuroda et al., 2015]. In the model, water diffusivity is controlled by the concentration of both main diffusion species (i.e. molecular water) and diffusion pathways, which are determined by the concentrations of hydroxyl groups and network modifier cations. The model well explains the water diffusivity in various silicate glasses from silica glass to basalt glass. However, pre-exponential factors of water diffusivity in various glasses show five orders of magnitude variations although the pre-exponential factor should ideally represent the jump frequency and the jump distance of molecular water and show a much smaller variation. Here, we attribute the large variation of pre-exponential factors to a glass structure dependence of activation energy for molecular water diffusion. It has been known that the activation energy depends on the water concentration [Nowak and Behrens, 1997]. The concentration of hydroxyls, which cut Si-O-Si network in the glass structure, increases with water concentration, resulting in lowering the activation energy for water diffusion probably due to more fragmented structure. Network modifier cations are likely to play the same role as water. With taking the effect of glass structure into account, we found that the variation of pre-exponential factors of water diffusivity in silicate glasses can be much smaller than the five orders of magnitude, implying that the diffusion of molecular water in silicate glasses is controlled by the same atomic process.

Nanostructured protic ionic liquids retain nanoscale features in aqueous solution while precursor Brønsted acids and bases exhibit different behavior.

PubMed

Greaves, Tamar L; Kennedy, Danielle F; Weerawardena, Asoka; Tse, Nicholas M K; Kirby, Nigel; Drummond, Calum J

2011-03-10

Small- and wide-angle X-ray scattering (SWAXS) has been used to investigate the effect that water has on the nanoscale structure of protic ionic liquids (PILs) along with their precursor Brønsted acids and bases. The series of PILs consisted of primary, secondary, and tertiary alkylammonium cations in conjunction with formate, nitrate, or glycolate anions. Significant differences were observed for these systems. The nanoscale aggregates present in neat protic ionic liquids were shown to be stable in size on dilution to high concentrations of water, indicating that the water is localized in the ionic region and has little effect on the nonpolar domains. The Brønsted acid-water solutions did not display nanostructure at any water concentration. Primary amine Brønsted bases formed aggregates in water, which generally displayed characteristics of poorly structured microemulsions or a form of bicontinuous phase. Exceptions were butyl- and pentylamine with high water concentrations, for which the SWAXS patterns fitted well to the Teubner-Strey model for microemulsions. Brønsted base amines containing multiple alkyl chains or hydroxyl groups did not display nanostructure at any water concentration. IR spectroscopy was used to investigate the nature of water in the various solutions. For low PIL concentrations, the water was predominately present as bulk water for PIL molar fractions less than 0.4-0.5. At high PIL concentrations, in addition to the bulk water, there was a significant proportion of perturbed water, which is water influenced in some way by the cations and anions. The molecular state of the water in the studied amines was predominately present as bulk water, with smaller contributions from perturbed water than was seen in the PILs. © 2011 American Chemical Society

The atypical cation-conduction and gating properties of ELIC underscore the marked functional versatility of the pentameric ligand-gated ion-channel fold

PubMed Central

Gonzalez-Gutierrez, Giovanni

2015-01-01

The superfamily of pentameric ligand-gated ion channels (pLGICs) is unique among ionotropic receptors in that the same overall structure has evolved to generate multiple members with different combinations of agonist specificities and permeant-ion charge selectivities. However, aside from these differences, pLGICs have been typically regarded as having several invariant functional properties. These include pore blockade by extracellular quaternary-ammonium cations in the micromolar-to-millimolar concentration range (in the case of the cation-selective members), and a gain-of-function phenotype, which manifests as a slower deactivation time course, as a result of mutations that reduce the hydrophobicity of the transmembrane pore lining. Here, we tested this notion on three distantly related cation-selective members of the pLGIC superfamily: the mouse muscle nicotinic acetylcholine receptor (nAChR), and the bacterial GLIC and ELIC channels. Remarkably, we found that, whereas low millimolar concentrations of TMA+ and TEA+ block the nAChR and GLIC, neither of these two quaternary-ammonium cations blocks ELIC at such concentrations; instead, both carry measurable inward currents when present as the only cations on the extracellular side. Also, we found that, whereas lidocaine binding speeds up the current-decay time courses of the nAChR and GLIC in the presence of saturating concentrations of agonists, the binding of lidocaine to ELIC slows this time course down. Furthermore, whereas mutations that reduce the hydrophobicity of the side chains at position 9′ of the M2 α-helices greatly slowed the deactivation time course of the nAChR and GLIC, these mutations had little effect—or even sped up deactivation—when engineered in ELIC. Our data indicate that caution should be exercised when generalizing results obtained with ELIC to the rest of the pLGICs, but more intriguingly, they hint at the possibility that ELIC is a representative of a novel branch of the superfamily with markedly divergent pore properties despite a well-conserved three-dimensional architecture. PMID:26078054

Cation-induced transcriptional regulation of the dlt operon of Staphylococcus aureus.

PubMed

Koprivnjak, Tomaz; Mlakar, Vid; Swanson, Lindsey; Fournier, Benedicte; Peschel, Andreas; Weiss, Jerrold P

2006-05-01

Lipoteichoic and wall teichoic acids (TA) are highly anionic cell envelope-associated polymers containing repeating polyglycerol/ribitol phosphate moieties. Substitution of TA with D-alanine is important for modulation of many cell envelope-dependent processes, such as activity of autolytic enzymes, binding of divalent cations, and susceptibility to innate host defenses. D-Alanylation of TA is diminished when bacteria are grown in medium containing increased NaCl concentrations, but the effects of increased salt concentration on expression of the dlt operon encoding proteins mediating D-alanylation of TA are unknown. We demonstrate that Staphylococcus aureus transcriptionally represses dlt expression in response to high concentrations of Na(+) and moderate concentrations of Mg(2+) and Ca(2+) but not sucrose. Changes in dlt mRNA are induced within 15 min and sustained for several generations of growth. Mg(2+)-induced dlt repression depends on the ArlSR two-component system. Northern blotting, reverse transcription-PCR, and SMART-RACE analyses suggest that the dlt transcript begins 250 bp upstream of the dltA start codon and includes an open reading frame immediately upstream of dltA. Chloramphenicol transacetylase transcriptional fusions indicate that a region encompassing the 171 to 325 bp upstream of dltA is required for expression and Mg(2+)-induced repression of the dlt operon in S. aureus.

Cation-Induced Transcriptional Regulation of the dlt Operon of Staphylococcus aureus

PubMed Central

Koprivnjak, Tomaz; Mlakar, Vid; Swanson, Lindsey; Fournier, Benedicte; Peschel, Andreas; Weiss, Jerrold P.

2006-01-01

Lipoteichoic and wall teichoic acids (TA) are highly anionic cell envelope-associated polymers containing repeating polyglycerol/ribitol phosphate moieties. Substitution of TA with d-alanine is important for modulation of many cell envelope-dependent processes, such as activity of autolytic enzymes, binding of divalent cations, and susceptibility to innate host defenses. d-Alanylation of TA is diminished when bacteria are grown in medium containing increased NaCl concentrations, but the effects of increased salt concentration on expression of the dlt operon encoding proteins mediating d-alanylation of TA are unknown. We demonstrate that Staphylococcus aureus transcriptionally represses dlt expression in response to high concentrations of Na+ and moderate concentrations of Mg2+ and Ca2+ but not sucrose. Changes in dlt mRNA are induced within 15 min and sustained for several generations of growth. Mg2+-induced dlt repression depends on the ArlSR two-component system. Northern blotting, reverse transcription-PCR, and SMART-RACE analyses suggest that the dlt transcript begins 250 bp upstream of the dltA start codon and includes an open reading frame immediately upstream of dltA. Chloramphenicol transacetylase transcriptional fusions indicate that a region encompassing the 171 to 325 bp upstream of dltA is required for expression and Mg2+-induced repression of the dlt operon in S. aureus. PMID:16672616

Extended Fluorescent Resonant Energy Transfer in DNA Constructs

NASA Astrophysics Data System (ADS)

Oh, Taeseok

This study investigates the use of surfactants and metal cations for the enhancement of long range fluorescent resonant energy transfer (FRET) and the antenna effect in DNA structures with multiple fluorescent dyes. Double-stranded (ds) DNA structures were formed by hybridization of 21mer DNA oligonucleotides with different arrangements of three fluorescent TAMRA donor dyes with two different complementary 21mer oligonucleotides with one fluorescent TexasRed acceptor dye. In such DNA structures, hydrophobic interactions between the fluorescent dyes in close proximity produces dimerization which along with other quenching mechanisms leads to significant reduction of fluorescent emission properties. Addition of the surfactants Triton X-100, cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) along with sodium cations (Na+) and divalent magnesium cations (Mg 2+) were tested for their ability to reduce quenching of the fluorescent dyes and improve overall fluorescent emission, the long range FRET and the antenna effect properties. When the neutral (uncharged) surfactant Triton X-100 was added to the FRET ds-DNA hybrid structures with three TAMRA donors and one TexasRed acceptor, dye dimerization and emission quenching remained unaffected. However, for the positively charged CTAB surfactant at concentrations of 100 uM or higher, the neutralization of the negatively charged ds-DNA backbone by the cationic surfactant micelles was found to reduce TAMRA dye dimerization and emission quenching and improve TexasRed quantum yield, resulting in much higher FRET efficiencies and an enhanced antenna effect. This improvement is likely due to the CTAB molecules covering or sheathing the fluorescent donor and acceptor dyes which breaks up the dimerized dye complexes and prevents further quenching from interactions with water molecules and guanine bases in the DNA structure. While the negatively charged SDS surfactant alone was not able to reduce dimerization and emission quenching due to repulsive forces between DNA and SDS micelles, the addition of cations such as sodium ions (Na+) and divalent magnesium ions (Mg2+) did lead to a significant reduction in the dimerization and emission quenching resulting in much higher FRET efficiency and an enhanced antenna effect. It appears that when the repulsive electrostatic forces are screened by the cations (Mg2+ in particular), the SDS micelles can approach the FRET ds-DNA structures thereby sheathing or insulating the TAMRA and TexasRed dyes. Overall, the study provides a viable strategy for using combinations of surfactants and cations to reduce adverse fluorescent dye and other quenching mechanisms and improve the overall long distance FRET efficiency and the antenna effect in DNA structures with multi-donor and single acceptor fluorescent dye groups.

The Effect of Nizatidine, a MATE2K Selective Inhibitor, on the Pharmacokinetics and Pharmacodynamics of Metformin in Healthy Volunteers

PubMed Central

Morrissey, Kari M.; Stocker, Sophie L.; Chen, Eugene C.; Castro, Richard A.; Brett, Claire M.; Giacomini, Kathleen M.

2015-01-01

Background and Objectives In the proximal tubule, basic drugs are transported from the renal cells to the tubule lumen through the concerted action of the H+/organic cation antiporters, multidrug and toxin extrusion 1 (MATE1) and 2K (MATE2K). Dual inhibitors of the MATE transporters have been shown to have a clinically relevant effect on the pharmacokinetics of concomitantly administered basic drugs. However, the clinical impact of selective renal organic cation transport inhibition on the pharmacokinetics and pharmacodynamics of basic drugs, such as metformin, is unknown. This study sought to identify a selective MATE2K inhibitor in vitro and to determine its clinical impact on the pharmacokinetics and pharmacodynamics of metformin in healthy subjects. Methods A strategic cell-based screen of 71 U.S. Food and Drug Administration (FDA)-approved medications was conducted to identify selective inhibitors of renal organic cation transporters that are capable of inhibiting at clinically relevant concentrations. From this screen, nizatidine was identified and predicted to be a clinically potent and selective inhibitor of MATE2K-mediated transport. The effect of nizatidine on the pharmacokinetics and pharmacodynamics of metformin was evaluated in 12 healthy volunteers in an open-label, randomized, two-phase crossover drug-drug interaction (DDI) study. Results In healthy volunteers, the MATE2K-selective inhibitor, nizatidine, significantly increased the apparent volume of distribution, half-life and hypoglycemic activity of metformin. However, despite achieving unbound maximum concentrations greater than the in vitro inhibition potency (IC50) of MATE2K-mediated transport, nizatidine did not affect the renal clearance or net secretory clearance of metformin. Conclusion This study demonstrates that a selective inhibition of MATE2K by nizatidine, affected the apparent volume of distribution, tissue levels and peripheral effects of metformin. However, nizatidine did not alter systemic concentrations or the renal clearance of metformin, suggesting that specific MATE2K inhibition may not be sufficient to cause renal DDIs with basic drugs. PMID:26507723

EDTA Inhibits Biofilm Formation, Extracellular Vesicular Secretion, and Shedding of the Capsular Polysaccharide Glucuronoxylomannan by Cryptococcus neoformans

PubMed Central

Robertson, Emma J.; Wolf, Julie M.

2012-01-01

The fungal pathogen Cryptococcus neoformans can grow as a biofilm on a range of synthetic and prosthetic materials. Cryptococcal biofilm formation can complicate the placement of shunts used to relieve increased intracranial pressure in cryptococcal meningitis and can serve as a nidus for chronic infection. Biofilms are generally advantageous to pathogens in vivo, as they can confer resistance to antimicrobial compounds, including fluconazole and voriconazole in the case of C. neoformans. EDTA can inhibit biofilm formation by several microbes and enhances the susceptibility of biofilms to antifungal drugs. In this study, we evaluated the effect of sublethal concentrations of EDTA on the growth of cryptococcal biofilms. EDTA inhibited biofilm growth by C. neoformans, and the inhibition could be reversed by the addition of magnesium or calcium, implying that the inhibitory effect was by divalent cation starvation. EDTA also reduced the amount of the capsular polysaccharide glucuronoxylomannan shed into the biofilm matrix and decreased vesicular secretion from the cell, thus providing a potential mechanism for the inhibitory effect of this cation-chelating compound. Our data imply that the growth of C. neoformans biofilms requires the presence of divalent metals in the growth medium and suggest that cations are required for the export of materials needed for biofilm formation, possibly including extracellular vesicles. PMID:22941091

A spatial and seasonal assessment of river water chemistry across North West England.

PubMed

Rothwell, J J; Dise, N B; Taylor, K G; Allott, T E H; Scholefield, P; Davies, H; Neal, C

2010-01-15

This paper presents information on the spatial and seasonal patterns of river water chemistry at approximately 800 sites in North West England based on data from the Environment Agency regional monitoring programme. Within a GIS framework, the linkages between average water chemistry (pH, sulphate, base cations, nutrients and metals) catchment characteristics (topography, land cover, soil hydrology, base flow index and geology), rainfall, deposition chemistry and geo-spatial information on discharge consents (point sources) are examined. Water quality maps reveal that there is a clear distinction between the uplands and lowlands. Upland waters are acidic and have low concentrations of base cations, explained by background geological sources and land cover. Localised high concentrations of metals occur in areas of the Cumbrian Fells which are subjected to mining effluent inputs. Nutrient concentrations are low in the uplands with the exception sites receiving effluent inputs from rural point sources. In the lowlands, both past and present human activities have a major impact on river water chemistry, especially in the urban and industrial heartlands of Greater Manchester, south Lancashire and Merseyside. Over 40% of the sites have average orthophosphate concentrations >0.1mg-Pl(-1). Results suggest that the dominant control on orthophosphate concentrations is point source contributions from sewage effluent inputs. Diffuse agricultural sources are also important, although this influence is masked by the impact of point sources. Average nitrate concentrations are linked to the coverage of arable land, although sewage effluent inputs have a significant effect on nitrate concentrations. Metal concentrations in the lowlands are linked to diffuse and point sources. The study demonstrates that point sources, as well as diffuse sources, need to be considered when targeting measures for the effective reduction in river nutrient concentrations. This issue is clearly important with regards to the European Union Water Framework Directive, eutrophication and river water quality. Copyright 2009 Elsevier B.V. All rights reserved.

In vivo sodium, potassium, and sperm concentrations in the rat epididymis.

PubMed

Turner, T T; Hartmann, P K; Howards, S S

1977-02-01

In vivo samples of epididymal fluids were obtained through the use of micropuncture techniques. Microsamples from four areas of the rat epididymis were analyzed for Na+ and K+ concentrations and for sperm density. Na+ values declined significantly from caput to corpus epididymidis (P less than 0.01), while K+ and sperm concentrations increased significantly (P less than 0.01). A large water loss from the epididymal lumen was calculated, as well as net losses of both cations. Water losses may be explained on the basis of an active Na+ pump; however, the effect of the absolute values of epididymal Na+ and K+ concentrations on sperm motility and fertility remains unresolved.

A Nanocomposite Hydrogel with Potent and Broad-Spectrum Antibacterial Activity.

PubMed

Dai, Tianjiao; Wang, Changping; Wang, Yuqing; Xu, Wei; Hu, Jingjing; Cheng, Yiyun

2018-05-02

Local bacterial infection is a challenging task and still remains a serious threat to human health in clinics. Systemic administration of antibiotics has only short-term antibacterial activity and usually causes adverse effects and bacterial resistance. A bioadhesive hydrogel with broad-spectrum and on-demand antibiotic activity is highly desirable. Here, we designed a pH-responsive nanocomposite hydrogel via a Schiff base linkage between oxidized polysaccharides and cationic dendrimers encapsulated with silver nanoparticles. The antibacterial components, both the cationic dendrimers and silver species, could be released in response to the acidity generated by growing bacteria. The released cationic polymer and silver exhibited a synergistic effect in antibacterial activity, and thus, the nanocomposite hydrogel showed potent antibacterial activity against both Gram-negative ( Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria ( Staphylococcus epidermidis and Staphylococcus aureus). The gel showed superior in vivo antibacterial efficacy against S. aureus infection compared with a commercial silver hydrogel at the same silver concentration. In addition, no obvious hemolytic toxicity, cytotoxicity, and tissue and biochemical toxicity were observed for the antibacterial hydrogel after incubation with cells or implantation. This study provides a facile and promising strategy to develop smart hydrogels to treat local bacterial infections.

Characterization of new polymer-grafted protein cation exchangers developed by partial neutralization of carboxyl groups derivatized by modification of poly(ethylenimine)-Sepharose with succinic anhydride.

PubMed

Zhao, Yangyang; Dong, Xiaoyan; Yu, Linling; Liu, Yang; Sun, Yan

2018-05-18

Previously, we have studied protein adsorption and chromatographic behaviors on poly(ethylenimine) (PEI)-grafted Sepharose FF anion-exchange resins, and found that protein uptake rates increased greatly when PEI grafting density reached over a critical ionic capacity (cIC) due to the occurrence of the "chain delivery" effect. Moreover, by partial charge neutralization of starting resin FF-PEI-L740 (IC = 740 mmol/L, larger than the cIC) with sodium acetate to FF-PEI-R440, it exhibited a three-fold increase in uptake rate over FF-PEI-L740. In this work, to take the advantages of PEI and extend the applications of the PEI-grafted resins in cation-exchange chromatography, a series of cation exchangers of five different ICs were developed. First, the charged of FF-PEI-L740 was reversed from positive to negative by reaction with excess succinic anhydride, which created a cation-exchanger with an IC of 970 mmol/L (FF-FEI-C970). FF-PEI-C970 was further modified with ethanolamine for partial charge neutralizations, leading to the preparation of four charge-reduced cation exchangers with IC values (in mmol/L) of 780, 630, 560 and 430, which were denoted as FF-PEI-CR780, -CR630 -CR560 and -CR430, respectively. Protein adsorption and chromatographic behaviors were investigated using lysozyme (Lys) as the model protein. It was found that, the resins of high and moderate IC values (IC ≥ 560 mmol/L) afforded adsorption capacities up to over 230 mg/mL. Besides, the uptake rate, represented by the effective pore diffusivity (D e/ D 0 ), exhibited significant increase from 0.067 (FF-PEI-C970 and FF-PEI-CR780) to 0.343 (FF-PEI-CR630 and FF-PEI-CR560) and then to 1.035 (FF-PEI-CR430) with decreasing IC. It was considered that decreasing IC led to the decreased protein binding sites (binding strength), which encouraged the occurrence of the "chain delivery" effect. Moreover, the resins of high and moderate IC values, particularly, the resins of moderate IC values (FF-PEI-CR630 and FF-PEI-CR560), presented both high adsorption capacities and uptake kinetics at 0-100 mmol/L NaCl. Besides, dynamic binding capacity achieved 150 mg/mL for the resins of moderate IC values at 0 mmol/L NaCl concentration, and afforded >110 mg/mL for the resin of high IC values at 0-100 mmol/L NaCl concentration. The results proved the excellent IEC performance of the PEI-derived cation exchangers. Copyright © 2018 Elsevier B.V. All rights reserved.

On the real performance of cation exchange resins in wastewater treatment under conditions of cation competition: the case of heavy metal pollution.

PubMed

Prelot, Benedicte; Ayed, Imen; Marchandeau, Franck; Zajac, Jerzy

2014-01-01

Sorption performance of cation-exchange resins Amberlite® IRN77 and Amberlite™ IRN9652 toward Cs(I) and Sr(II) has been tested in single-component aqueous solutions and simulated waste effluents containing other monovalent (Effluent 1) or divalent (Effluent 2) metal cations, as well as nitrate, borate, or carbonate anions. The individual sorption isotherms of each main component were measured by the solution depletion method. The differential molar enthalpy changes accompanying the ion-exchange between Cs+ or Sr2+ ions and protons at the resin surface from single-component nitrate solutions were measured by isothermal titration calorimetry and they showed a higher specificity of the two resins toward cesium. Compared to the retention limits of both resins under such idealized conditions, an important depression in the maximum adsorption capacity toward each main component was observed in multication systems. The overall effect of ion exchange process appeared to be an unpredictable outcome of the individual sorption capacities of the two resins toward various cations as a function of the cation charge, size, and concentration. The cesium retention capacity of the resins was diminished to about 25% of the "ideal" value in Effluent 1 and 50% in Effluent 2; a further decrease to about 15% was observed upon concomitant strontium addition. The uptake of strontium by the resins was found to be less sensitive to the addition of other metal components: the greatest decrease in the amount adsorbed was 60% of the ideal value in the two effluents for Amberlite® IRN77 and 75% for Amberlite™ IRN9652. It was therefore demonstrated that any performance tests carried out under idealized conditions should be exploited with much caution to predict the real performance of cation exchange resins under conditions of cation competition.

Transport of water and ions in partially water-saturated porous media. Part 2. Filtration effects

NASA Astrophysics Data System (ADS)

Revil, A.

2017-05-01

A new set of constitutive equations describing the transport of the ions and water through charged porous media and considering the effect of ion filtration is applied to the problem of reverse osmosis and diffusion of a salt. Starting with the constitutive equations derived in Paper 1, I first determine specific formula for the osmotic coefficient and effective diffusion coefficient of a binary symmetric 1:1 salt (such as KCl or NaCl) as a function of a dimensionless number Θ corresponding to the ratio between the cation exchange capacity (CEC) and the salinity. The modeling is first carried with the Donnan model used to describe the concentrations of the charge carriers in the pore water phase. Then a new model is developed in the thin double layer approximation to determine these concentrations. These models provide explicit relationships between the concentration of the ionic species in the pore space and those in a neutral reservoir in local equilibrium with the pore space and the CEC. The case of reverse osmosis and diffusion coefficient are analyzed in details for the case of saturated and partially saturated porous materials. Comparisons are done with experimental data from the literature obtained on bentonite. The model predicts correctly the influence of salinity (including membrane behavior at high salinities), porosity, cation type (K+ versus Na+), and water saturation on the osmotic coefficient. It also correctly predicts the dependence of the diffusion coefficient of the salt with the salinity.

Electrolyte chemistry control in electrodialysis processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hayes, Thomas D.; Severin, Blaine F.

Methods for controlling electrolyte chemistry in electrodialysis units having an anode and a cathode each in an electrolyte of a selected concentration and a membrane stack disposed therebetween. The membrane stack includes pairs of cationic selective and anionic membranes to segregate increasingly dilute salts streams from concentrated salts stream. Electrolyte chemistry control is via use of at least one of following techniques: a single calcium exclusionary cationic selective membrane at a cathode cell boundary, an exclusionary membrane configured as a hydraulically isolated scavenger cell, a multivalent scavenger co-electrolyte and combinations thereof.

The oxygen content of the high-temperature superconducting compound Bi(2+x)Sr(3-y)CayCu2O(8+d) with respect to varying Ca and Bi contents

NASA Technical Reports Server (NTRS)

Majewski, P.; Su, H.-L.; Aldinger, F.

1995-01-01

The oxygen content of Bi(2+x)Sr(3-y)Cu2O(8+d) (2212 phase) has been determined as a function of its cation concentration. With increasing Ca and Bi content the oxygen content increases and T(sub c) decreases. The oxygen content of Ca rich 2212 phase increases with decreasing annealing temperatures. The study shows that the T(sub c) of the 2212 phase primarily is controlled by its cation concentration.

Determination of Inorganic Cations and Anions in Chitooligosaccharides by Ion Chromatography with Conductivity Detection.

PubMed

Cao, Lidong; Li, Xiuhuan; Fan, Li; Zheng, Li; Wu, Miaomiao; Zhang, Shanxue; Huang, Qiliang

2017-02-22

Chitooligosaccharides (COSs) are a promising drug candidate and food ingredient because they are innately biocompatible, non-toxic, and non-allergenic to living tissues. Therefore, the impurities in COSs must be clearly elucidated and precisely determined. As for COSs, most analytical methods focus on the determination of the average degrees of polymerization (DPs) and deacetylation (DD), as well as separation and analysis of the single COSs with different DPs. However, little is known about the concentrations of inorganic cations and anions in COSs. In the present study, an efficient and sensitive ion chromatography coupled with conductivity detection (IC-CD) for the determination of inorganic cations Na⁺, NH₄⁺, K⁺, Mg 2+ , Ca 2+ , and chloride, acetate and lactate anions was developed. Detection limits were 0.01-0.05 μM for cations and 0.5-0.6 μM for anions. The linear range was 0.001-0.8 mM. The optimized analysis was carried out on IonPac CS12A and IonPac AS12A analytical column for cations and anions, respectively, using isocratic elution with 20 mM methanesulfonic acid and 4 mM sodium hydroxide aqueous solution as the mobile phase at a 1.0 mL/min flow rate. Quality parameters, including precision and accuracy, were fully validated and found to be satisfactory. The fully validated IC-CD method was readily applied for the quantification of various cations and anions in commercial COS technical concentrate.

Determination of Inorganic Cations and Anions in Chitooligosaccharides by Ion Chromatography with Conductivity Detection

PubMed Central

Cao, Lidong; Li, Xiuhuan; Fan, Li; Zheng, Li; Wu, Miaomiao; Zhang, Shanxue; Huang, Qiliang

2017-01-01

Chitooligosaccharides (COSs) are a promising drug candidate and food ingredient because they are innately biocompatible, non-toxic, and non-allergenic to living tissues. Therefore, the impurities in COSs must be clearly elucidated and precisely determined. As for COSs, most analytical methods focus on the determination of the average degrees of polymerization (DPs) and deacetylation (DD), as well as separation and analysis of the single COSs with different DPs. However, little is known about the concentrations of inorganic cations and anions in COSs. In the present study, an efficient and sensitive ion chromatography coupled with conductivity detection (IC-CD) for the determination of inorganic cations Na+, NH4+, K+, Mg2+, Ca2+, and chloride, acetate and lactate anions was developed. Detection limits were 0.01–0.05 μM for cations and 0.5–0.6 μM for anions. The linear range was 0.001–0.8 mM. The optimized analysis was carried out on IonPac CS12A and IonPac AS12A analytical column for cations and anions, respectively, using isocratic elution with 20 mM methanesulfonic acid and 4 mM sodium hydroxide aqueous solution as the mobile phase at a 1.0 mL/min flow rate. Quality parameters, including precision and accuracy, were fully validated and found to be satisfactory. The fully validated IC-CD method was readily applied for the quantification of various cations and anions in commercial COS technical concentrate. PMID:28241416

Co-self-assembly of cationic microparticles to deliver pEGFP-ZNF580 for promoting the transfection and migration of endothelial cells

PubMed Central

Feng, Yakai; Guo, Mengyang; Liu, Wen; Hao, Xuefang; Lu, Wei; Ren, Xiangkui; Shi, Changcan; Zhang, Wencheng

2017-01-01

The gene transfection efficiency of polyethylenimine (PEI) varies with its molecular weight. Usually, high molecular weight of PEI means high gene transfection, as well as high cytotoxicity in gene delivery in vivo. In order to enhance the transfection efficiency and reduce the cytotoxicity of PEI-based gene carriers, a novel cationic gene carrier was developed by co-self-assembly of cationic copolymers. First, a star-shaped copolymer poly(3(S)-methyl-morpholine-2,5-dione-co-lactide) (P(MMD-co-LA)) was synthesized using D-sorbitol as an initiator, and the cationic copolymer (P(MMD-co-LA)-g-PEI) was obtained after grafting low-molecular weight PEI. Then, by co-self-assembly of this cationic copolymer and a diblock copolymer methoxy-poly(ethylene glycol) (mPEG)-b-P(MMD-co-LA), microparticles (MPs) were formed. The core of MPs consisted of a biodegradable block of P(MMD-co-LA), and the shell was formed by mPEG and PEI blocks. Finally, after condensation of pEGFP-ZNF580 by these MPs, the plasmids were protected from enzymatic hydrolysis effectively. The result indicated that pEGFP-ZNF580-loaded MP complexes were suitable for cellular uptake and gene transfection. When the mass ratio of mPEG-b-P(MMD-co-LA) to P(MMD-co-LA)-g-PEI reached 3/1, the cytotoxicity of the complexes was very low at low concentration (20 μg mL−1). Additionally, pEGFP-ZNF580 could be transported into endothelial cells (ECs) effectively via the complexes of MPs/pEGFP-ZNF580. Wound-healing assay showed that the transfected ECs recovered in 24 h. Cationic MPs designed in the present study could be used as an applicable gene carrier for the endothelialization of artificial blood vessels. PMID:28053529

Comparative sensitivity of rat cerebellar neurons to dysregulation of divalent cation homeostasis and cytotoxicity caused by methylmercury

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edwards, Joshua R.; Marty, M. Sue; Atchison, William D.

2005-11-01

The objective of the present study was to determine the relative effectiveness of methylmercury (MeHg) to alter divalent cation homeostasis and cause cell death in MeHg-resistant cerebellar Purkinje and MeHg-sensitive granule neurons. Application of 0.5-5 {mu}M MeHg to Purkinje and granule cells grown in culture caused a concentration- and time-dependent biphasic increase in fura-2 fluorescence. At 0.5 and 1 {mu}M MeHg, the elevations of fura-2 fluorescence induced by MeHg were biphasic in both cell types, but significantly delayed in Purkinje as compared to granule cells. Application of the heavy-metal chelator, TPEN, to Purkinje cells caused a precipitous decline in amore » proportion of the fura-2 fluorescence signal, indicating that MeHg causes release of Ca{sup 2+} and non-Ca{sup 2+} divalent cations. Purkinje cells were also more resistant than granule cells to the neurotoxic effects of MeHg. At 24.5 h after-application of 5 {mu}M MeHg, 97.7% of Purkinje cells were viable. At 3 {mu}M MeHg there was no detectable loss of Purkinje cell viability. In contrast, only 40.6% of cerebellar granule cells were alive 24.5 h after application of 3 {mu}M MeHg. In conclusion, Purkinje neurons in primary cultures appear to be more resistant to MeHg-induced dysregulation of divalent cation homeostasis and subsequent cell death when compared to cerebellar granule cells. There is a significant component of non-Ca{sup 2+} divalent cation released by MeHg in Purkinje neurons.« less

Tailoring charge density and hydrogen bonding of imidazolium copolymers for efficient gene delivery.

PubMed

Allen, Michael H; Green, Matthew D; Getaneh, Hiwote K; Miller, Kevin M; Long, Timothy E

2011-06-13

Conventional free radical polymerization with subsequent postpolymerization modification afforded imidazolium copolymers with controlled charge density and side chain hydroxyl number. Novel imidazolium-containing copolymers where each permanent cation contained one or two adjacent hydroxyls allowed precise structure-transfection efficiency studies. The degree of polymerization was identical for all copolymers to eliminate the influence of molecular weight on transfection efficiency. DNA binding, cytotoxicity, and in vitro gene transfection in African green monkey COS-7 cells revealed structure-property-transfection relationships for the copolymers. DNA gel shift assays indicated that higher charge densities and hydroxyl concentrations increased DNA binding. As the charge density of the copolymers increased, toxicity of the copolymers also increased; however, as hydroxyl concentration increased, cytotoxicity remained constant. Changing both charge density and hydroxyl levels in a systematic fashion revealed a dramatic influence on transfection efficiency. Dynamic light scattering of the polyplexes, which were composed of copolymer concentrations required for the highest luciferase expression, showed an intermediate DNA-copolymer binding affinity. Our studies supported the conclusion that cationic copolymer binding affinity significantly impacts overall transfection efficiency of DNA delivery vehicles, and the incorporation of hydroxyl sites offers a less toxic and effective alternative to more conventional highly charged copolymers.

Cellulose ionics: switching ionic diode responses by surface charge in reconstituted cellulose films.

PubMed

Aaronson, Barak D B; Wigmore, David; Johns, Marcus A; Scott, Janet L; Polikarpov, Igor; Marken, Frank

2017-09-25

Cellulose films as well as chitosan-modified cellulose films of approximately 5 μm thickness, reconstituted from ionic liquid media onto a poly(ethylene-terephthalate) (PET, 6 μm thickness) film with a 5, 10, 20, or 40 μm diameter laser-drilled microhole, show significant current rectification in aqueous NaCl. Reconstituted α-cellulose films provide "cationic diodes" (due to predominant cation conductivity) whereas chitosan-doped cellulose shows "anionic diode" effects (due to predominant anion conductivity). The current rectification, or "ionic diode" behaviour, is investigated as a function of NaCl concentration, pH, microhole diameter, and molecular weight of the chitosan dopant. Future applications are envisaged exploiting the surface charge induced switching of diode currents for signal amplification in sensing.

Sub-nanometer surface chemistry and orbital hybridization in lanthanum-doped ceria nano-catalysts revealed by 3D electron microscopy.

PubMed

Collins, Sean M; Fernandez-Garcia, Susana; Calvino, José J; Midgley, Paul A

2017-07-14

Surface chemical composition, electronic structure, and bonding characteristics determine catalytic activity but are not resolved for individual catalyst particles by conventional spectroscopy. In particular, the nano-scale three-dimensional distribution of aliovalent lanthanide dopants in ceria catalysts and their effect on the surface electronic structure remains unclear. Here, we reveal the surface segregation of dopant cations and oxygen vacancies and observe bonding changes in lanthanum-doped ceria catalyst particle aggregates with sub-nanometer precision using a new model-based spectroscopic tomography approach. These findings refine our understanding of the spatially varying electronic structure and bonding in ceria-based nanoparticle aggregates with aliovalent cation concentrations and identify new strategies for advancing high efficiency doped ceria nano-catalysts.

[Effect of monovalent cations on glutamate metabolism in rat brain].

PubMed

Nilova, N S

1976-10-01

Glutamate oxidation in vitro via deamination and transamination during gramicidin C-induced transport of K+ and Na+ in rat nervous tissue mitochondria was studied. An increase in ammonium production, i.e. in glutamate oxidation due to deamination, was shown to occur with maximal increase of oxygen consumption in the presence of cations. It was found that 1.5 mM Na+ activate oxygen consumption by 15% and accelerate ammonium production from glutamate (by 17%). No changes in aspartate production were observed. 15 mM K+ increase oxygen consumption by 29% and ammonium production by 11% during a decrease in aspartate production as compared to glutamate oxidation in the presence of a lower (10 mM) concentration of K+ in the samples.

Salt taste adaptation: the psychophysical effects of adapting solutions and residual stimuli from prior tastings on the taste of sodium chloride.

PubMed

O'Mahony, M

1979-01-01

The paper reviews how adaptation to sodium chloride, changing in concentration as a result of various experimental procedures, affects measurements of the sensitivity, intensity, and quality of the salt taste. The development of and evidence for the current model that the salt taste depends on an adaptation level (taste zero) determined by the sodium cation concentration is examined and found to be generally supported, despite great methodological complications. It would seem that lower adaptation levels elicit lower thresholds, higher intensity estimates, and altered quality descriptions with predictable effects on psychophysical measures.

Application of edible paraffin oil for cationic dye removal from water using emulsion liquid membrane.

PubMed

Zereshki, Sina; Daraei, Parisa; Shokri, Amin

2018-05-18

Using an emulsion liquid membrane based on edible oils is investigated for removing cationic dyes from aqueous solutions. There is a great potential for using edible oils in food industry extraction processes. The parameters affecting the stability of the emulsion and the extraction rate were studied. These parameters were the emulsification time, the stirring speed, the surfactant concentration, the internal phase concentration, the feed phase concentration, the volume ratio of internal phase to organic phase and the treat ratio. In order to stabilize the emulsion without using a carrier, edible paraffin oil and heptane are used at an 80:20 ratio. The optimum conditions for the extraction of methylene blue (MB), crystal violet and methyl violet (CV and MV) cationic dyes using edible paraffin oil as an environment friendly solvent are represented. A removal percentage of 95% was achieved for a mixture of dyes. The optimum concentration of sodium hydroxide in the internal phase, which results a stabile emulsion with a high stripping efficiency of 96%, was 0.04 M. An excellent membrane recovery was observed and the extraction of dyes did not decrease up to seven run cycles. Copyright © 2018 Elsevier B.V. All rights reserved.

Stream chemistry following a forest fire and urea fertilization in north-central Washington.

Treesearch

Arthur R. Tiedemann

1973-01-01

During 2 years of study, nitrate-N in streamflow increased from background levels of 0.005 part per million (p.p.m.) in a control stream to 0.042 and 0.310 p.p.m. in streams from burned and burned, urea-fertilized watersheds, respectively. Cation concentration increased on the burned, unfertilized watershed, but because of dilution effects,...

Alkalinity generation in snowmelt and rain runoff during short distance flow over rock

Treesearch

James L. Clayton

1998-01-01

High-elevation ecosystems in the western United States typically have patchy, discontinuous areas of surficial soils surrounded by large areas of rock outcrop, talus, and scree. Snowmelt and precipitation that percolate through soil increase in alkalinity, principally by increasing base cation concentration through cation exchange, and by decreasing acid anion...

The effect of synthesis parameters on the geometry and dimensions of mesoporous hydroxyapatite nanoparticles in the presence of 1-dodecanethiol as a pore expander.

PubMed

Bakhtiari, L; Rezaie, H R; Javadpour, J; Erfan, M; Shokrgozar, M A

2015-08-01

Mesoporous hydroxyapatite with different pore diameters and pore volumes were synthesized by the self-assembly method using Cetyltrimethylammonium bromide (CTAB) as the cationic surfactant and 1-dodecanethiol as the pore expander at different micellization pHs, solvent types and surfactant concentrations. Results of field emission scanning electron microscopy (FESEM) showed a decrease in length/diameter ratio of rod-like particles by an increase in micellization pH and also a sphere to rod transition in morphology by an increase in CTAB concentration. Brunauer-Emmett-Teller (BET) surface area and Low angle X-ray diffraction analysis revealed that the optimized mesoporous hydroxyapatite with controlled pore structure can be obtained under basic micellization pH (about 12, pH of complete ionization of 1-dodecanethiol) by using water as the solvent and a high content of cationic surfactant. The results also show that micellization pH has a strong effect on pore structure and changing the pH can shift the mesostructure to a macroporous structure with morphological changes. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of halo-substituted aromatic salts on counterion binding constants obtained from cationic nanoparticle catalyzed reactions of piperidine and phenyl salicylate

NASA Astrophysics Data System (ADS)

Fagge, Ibrahim I.; Yusof, Nor Saadah M.; Zain, Sharifuddin Md; Khan, M. Niyaz

2017-12-01

Halo-substitutions at 3-position of benzene ring of the salts of aromatic carboxylate, MX, revealed the effect of two different halide ions (Br- and Cl-) on the counterion binding constants obtained from cationic nanoparticle catalyzed piperidinolysis of ionized phenyl salicylate (PhS-). The values of observed rate constant, kobs, determined at a constant total concentration of cetyltrimethylammonium bromide, [CTABr]T, piperidine, ([P]T), [PhS-]T, NaOH, and various concentration of MX (MX = 3-BrC6H4CO2Na and 3-ClC6H4CO2Na), were determined using UV-visible X spectrophotometric technique at 35 °C and 370 nm. The average value of nanoparticle binding constant, KXBr, for X- = 3-BrC6H4CO2- (RXBr = 57) was found to be about 2-fold larger than that for X- = 3-ClC6H4CO2- (RXBr = 30). These XX values were dependent of substituents 3-Br and 3-Cl, and independent of [CTABr]T. Both are related to the presence of different extent of viscoelastic worm-like nanoparticles formation in the [CTABr]T of 6 and 10 mM.

Cation distribution and optical properties of Cr-doped MgGa2O4 nanocrystals

NASA Astrophysics Data System (ADS)

Duan, Xiulan; Liu, Jian; Wang, Xinqiang; Jiang, Huaidong

2014-11-01

The distribution of cations in the spinel-type MgCr2yGa2-2yO4 (y = 0-0.6) nanocrystals and their optical properties as a function of annealing temperature and chromium content were investigated by using X-ray photoelectron spectroscopy (XPS) in combination with absorption spectroscopy. The cations in MgCr2yGa2-2yO4 nanocrystals are disorderly distributed with mixing of divalent and trivalent cations occupying the tetrahedral and octahedral sites. With the increase of annealing temperature, the inversion parameter (the fraction of Mg2+ ions in octahedral sites) decreases, which has the same varying tendency with the proportion of tetrahedral Ga3+ or Cr3+ ions. The inversion parameter increases with increasing Cr3+ concentration. The absorption spectra indicate that Cr3+ ions are located in the octahedral sites as well as in the tetrahedral sites. The fraction of tetrahedral Cr3+ decreases with Cr-enrichment. The optical absorption properties of Cr-doped MgGa2O4 nanocrystals may be tuned by varying the preparation temperature or Cr concentration.

Enhanced energy harvesting by concentration gradient-driven ion transport in SBA-15 mesoporous silica thin films.

PubMed

Hwang, Junho; Kataoka, Sho; Endo, Akira; Daiguji, Hirofumi

2016-09-21

Nanofluidic energy harvesting systems have attracted interest in the field of battery application, particularly for miniaturized electrical devices, because they possess excellent energy conversion capability for their size. In this study, a mesoporous silica (MPS)-based nanofluidic energy harvesting system was fabricated and selective ion transport in mesopores as a function of the salt gradient was investigated. Aqueous solutions with three different kinds of monovalent electrolytes-KCl, NaCl, and LiCl-with different diffusion coefficients (D + ) were considered. The highest power density was 3.90 W m -2 for KCl, followed by 2.39 W m -2 for NaCl and 1.29 W m -2 for LiCl. Furthermore, the dependency of power density on the type of cation employed indicates that the harvested energy increases as the cation mobility increases, particularly at high concentrations. This cation-specific dependency suggests that the maximum power density increases by increasing the diffusion coefficient ratio of cations to anions, making this ratio a critical parameter in enhancing the performance of nanofluidic energy harvesting systems with extremely small pores ranging from 2 to 3 nm.

Ion Dynamics in a Mixed-Cation Alkoxy-Ammonium Ionic Liquid Electrolyte for Sodium Device Applications.

PubMed

Pope, Cameron R; Kar, Mega; MacFarlane, Douglas R; Armand, Michel; Forsyth, Maria; O'Dell, Luke A

2016-10-18

The ion dynamics in a novel sodium-containing room-temperature ionic liquid (IL) consisting of an ether-functionalised quaternary ammonium cation and bis(trifluoromethylsulfonyl)amide [NTf 2 ] anion with various concentrations of Na[NTf 2 ] have been characterised using differential scanning calorimetry, impedance spectroscopy, diffusometry and NMR relaxation measurements. The IL studied has been specifically designed to dissolve a relatively large concentration of Na[NTf 2 ] salt (over 2 mol kg -1 ) as this has been shown to improve ion transport and conductivity. Consistent with other studies, the measured ionic conductivity and diffusion coefficients show that the overall ionic mobility decreases with decreasing temperature and increasing salt content. NMR relaxation measurements provide evidence for correlated dynamics between the ether-functionalised ammonium and Na cations, possibly with the latter species acting as cross-links between multiple ammonium cations. Finally, preliminary cyclic voltammetry experiments show that this IL can undergo stable electrochemical cycling and could therefore be potentially useful as an electrolyte in a Na-based device. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of sorption competition on caesium diffusion through compacted argillaceous rock

NASA Astrophysics Data System (ADS)

Jakob, Andreas; Pfingsten, Wilfried; Van Loon, Luc

2009-05-01

We carried out a small-scale laboratory diffusion experiment on a disk-like sample of Opalinus clay from the Mont Terri underground laboratory (Switzerland) using 134Cs as tracer. A through-diffusion phase was followed by an out-diffusion phase where the tracer taken up by the sample was released again. Since the tracer concentration at both boundaries was monitored, careful mass-balance considerations were feasible. A first analysis of the experimental data was done in the frame of a single-species model accounting only for transport and non-linear sorption of caesium. The model could match the data of the through-diffusion phase, however only, when strongly reducing the sorption data based on batch sorption experiments. Yet, such a procedure was in strong contradiction with sorption measurements performed on dispersed and compacted systems. In addition, predictions concerning tracer out-diffusion and mass-balance considerations clearly revealed the shortcomings of this type of model. In a second attempt we applied a multi-species transport model where now the whole water chemistry and a sorption model for caesium were considered. First, the value for the diffusion coefficient was fixed to the best-fit value of the single-species model. But again, the sorption site densities had to be reduced strongly albeit the reduction factor was smaller. Only when fixing the sorption site densities to those values of the sorption model and letting the effective diffusion coefficient D e free for the adjustment, could through-diffusion data be reasonably well fitted and out-diffusion as well as mass-balances be predicted in a satisfying manner. The main results are: (1) The best-fit could be achieved with a value for D e of 1.8 × 10 -10 m 2 s -1 which is rather high but corroborated by results of a molecular modelling study. (2) If caesium arrives in the Opalinus clay sample potassium and sodium (calcium etc.) ions are released and caesium ions are sorbed. The released cations diffuse to lower concentration regions according to their individual concentration gradients. Since locally the cation concentration for potassium, (sodium and calcium) is increased, sorption of these cations is also locally enhanced, affecting in return the sorption behaviour of migrating caesium. Consequently, the sorption process of caesium in such diffusion experiments cannot be addressed by a non-linear isotherm formalism any longer. (3) A reasonable analysis of such single tracer diffusion experiments therefore requires the combined description of transport (diffusion) and sorption of many cations and the whole complex water chemistry of the system. Thus, single-species models can only be applied with care in the considered concentration ranges.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsumura, Yasuo; Kawazoe, Shinka; Ichihara, Toshio

Extracellular high potassium inhibits renin release in vitro by increasing calcium concentrations in the juxtaglomerular cells. The authors found that the decreased response of renin release from rat kidney cortical slices in high potassium solution changed to a strikingly increased one in the presence of nifedipine at doses over 10{sup {minus}6} M. They then examined the stimulatory effect of extracellular high potassium in the presence of nifedipine on renin release. The enhancement of release was significantly suppressed either by propranolol or by metoprolol but not by prazosin. High potassium plus nifedipine-induced increase in renin release was markedly attenuated by renalmore » denervation. The enhancing effect was not observed when the slices were incubated in calcium-free medium. Divalent cations such as Cd{sup 2+}, Co{sup 2+}, and Mn{sup 2+} blocked this enhancement in a concentration-dependent manner. High potassium elicited an increase in {sup 3}H efflux from the slices preloaded with ({sup 3}H)-norepinephrine. The increasing effect was not influenced by nifedipine but was abolished by the removal of extracellular calcium or by the addition of divalent cations. These observations suggest to us that the high potassium plus nifedipine-induced increase in renin release from the slices is mediated by norepinephrine derived from renal sympathetic nerves and that this neuronally released norepinephrine stimulates renin release via activation of {beta}-adrenoceptors.« less

Possible regulation of cation-induced pinocytosis in Amoeba proteus by phospholipase A.

PubMed

Josefsson, J O; Arvidson, G; Cobbold, P

1988-04-01

We have studied the effects of exogenous phospholipids and compounds which are known to alter the activity of phospholipase A (PLA) on Ca2+-dependent, Na+-induced pinocytosis in Amoeba proteus. The PLA-inhibitors mepacrine, p-bromophenacyl bromide (pBPB) and Rosenthal's inhibitor depressed pinocytosis. Normal pinocytotic intensity was restored by the addition of Ca2+ or picomolar concentrations of lysolecithin. Very low concentrations of lysophospholipids and different molecular species of lecithins increased the capacity for pinocytosis in starved amoebae. The effect of the lecithins but not of the corresponding lysolecithins was abolished by PLA-inhibitors. Also, the restoration of the pinocytotic capacity of starved amoebae by melittin and mastoparan, which are known to stimulate PLA, was inhibited by mepacrine and pBPB. Isolated amoeba plasma membranes contain phospholipase A1 and A2 activity and the amoebae secrete a lipid (PRF, pinocytosis regulating factor) which has lysolecithin-like effects on pinocytosis. The enzyme activities and the release of PRF were markedly decreased by the PLA-inhibitors. Our observations support the hypothesis that PRF is a lysophospholipid that may constitute a signal for the formation of pinocytotic channels in the initial stages of pinocytosis. The phospholipase A activity of the amoeba must therefore be assigned an important role in the regulation of the Ca2+-dependent, cation-induced pinocytosis.

Soaping the NMDA receptor: Various types of detergents influence differently [(3)H]MK-801 binding to rat brain membranes.

PubMed

Berger, Michael L

2016-01-01

Membranes prepared from rat brain were treated with increasing concentrations of cationic, neutral, anionic and zwitterionic surfactants. Potent inactivation of [(3)H]MK-801 binding to NMDA receptors (NRs) was provided by the cation cetyl pyridinium (IC50 25 μM) and the neutral digitonin (IC50 37 μM). A 2 h incubation of rat brain membranes at 24°C with 100 μM of the neutral Triton X-100 resulted in about 50% reversible inhibition (without inactivation). Reversible inhibition was also effected by the anion deoxycholate (IC50 700 μM), and by the zwitterions N-lauryl sulfobetaine (12-SB(±), 400 μM) and CHAPS (1.5 mM), with inactivation at higher concentrations. Keeping the NR cation channel in the closed state significantly protected against inactivation by cations and by 12-SB(±), but not by the other detergents. Inactivation depended differentially on the amount of the membranes, on the duration of the treatment, and on the temperature. Varying the amount of membranes by a factor 8 yielded for cetyl trimethylammonium (16-NMe3(+)) IC50s of inactivation from 10 to 80 μM, while for deoxycholate the IC50 of inactivation was 1.2 mM for all tissue quantities. Some compounds inactivated within a few min (16-NMe3(+), digitonin, CHAPS), while inactivation by others took at least half an hour (Triton X-100, deoxycholate, 12-SB(±)). These last 3 ones also exhibited the steepest temperature dependence. Knowledge about the influence of various parameters is helpful in selecting appropriate conditions allowing the treatment of brain membranes with amphiphiles without risking irreversible inactivation. Copyright © 2015 Elsevier B.V. All rights reserved.

Formation and stability of water-soluble, molecular polyelectrolyte complexes: effects of charge density, mixing ratio, and polyelectrolyte concentration.

PubMed

Shovsky, Alexander; Varga, Imre; Makuska, Ricardas; Claesson, Per M

2009-06-02

The formation of complexes with stoichiometric (1:1) as well as nonstoichiometric (2:1) and (1:2) compositions between oppositely charged synthetic polyelectrolytes carrying strong ionic groups and significantly different molecular weights is reported in this contribution. Poly(sodium styrenesulfonate) (NaPSS) was used as polyanion, and a range of copolymers with various molar ratios of the poly(methacryloxyethyltrimethylammonium) chloride, poly(METAC), and the nonionic poly(ethylene oxide) ether methacrylate, poly(PEO45MEMA), were used as polycations. Formation and stability of PECs have been investigated by dynamic and static light scattering (LS), turbidity, and electrophoretic mobility measurements as a function of polyelectrolyte solution concentration, charge density of the cationic polyelectrolyte, and mixing ratio. The data obtained demonstrate that in the absence of PEO45 side chains the 100% charged polymer (polyMETAC) formed insoluble PECs with PSS that precipitate from solution when exact stoichiometry is achieved. In nonstoichiometric complexes (1:2) and (2:1) large colloidally stable aggregates were formed. The presence of even a relatively small amount of PEO45 side chains (25%) in the cationic copolymer was sufficient for preventing precipitation of the formed stoichiometric and nonstoichiometric complexes. These PEC's are sterically stabilized by the PEO45 chains. By further increasing the PEO45 side-chain content (50 and 75%) of the cationic copolymer, small, water-soluble molecular complexes could be formed. The data suggest that PSS molecules and the charged backbone of the cationic brush form a compact core, and with sufficiently high PEO45 chain density (above 25%) molecular complexes are formed that are stable over prolonged times.

Mechanism of host-guest complexation by cucurbituril.

PubMed

Márquez, César; Hudgins, Robert R; Nau, Werner M

2004-05-12

The factors affecting host-guest complexation between the molecular container compound cucurbit[6]uril (CB6) and various guests in aqueous solution are studied, and a detailed complexation mechanism in the presence of cations is derived. The formation of the supramolecular complex is studied in detail for cyclohexylmethylammonium ion as guest. The kinetics and thermodynamics of complexation is monitored by NMR as a function of temperature, salt concentration, and cation size. The binding constants and the ingression rate constants decrease with increasing salt concentration and cation-binding constant, in agreement with a competitive binding of the ammonium site of the guest and the metal cation with the ureido carbonyl portals of CB6. Studies as a function of guest size indicate that the effective container volume of the CB6 cavity is approximately 105 A(3). It is suggested that larger guests are excluded for two reasons: a high activation barrier for ingression imposed by the tight CB6 portals and a destabilization of the complex due to steric repulsion inside. For example, in the case of the nearly spherical azoalkane homologues 2,3-diazabicyclo[2.2.1]hept-2-ene (DBH, volume ca. 96 A(3)) and 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO, volume ca. 110 A(3)), the former forms the CB6 complex promptly with a sizable binding constant (1300 M(-1)), while the latter does not form a complex even after several months at optimized complexation conditions. Molecular mechanics calculations are performed for several CB6/guest complexes. A qualitative agreement is found between experimental and calculated activation energies for ingression as a function of both guest size and state of protonation. The potential role of constrictive binding by CB6 is discussed.

Trends in precipitation and stream-water chemistry in the northeastern United States, water years 1984-96

USGS Publications Warehouse

Clow, D.W.; Mast, M. Alisa

1999-01-01

Trends in precipitation and stream-water chemistry during water years 1984-96 were examined at eight precipitation monitoring sites and five nearby streams operated by the U.S. Geological Survey in the northeastern United States. The statistical analyses indicate the following: 1)Stream-water sulfate (SO4) concentrations decreased at seven of eight precipitation monitoring sites and in each of five streams. 2)Calcium plus magnesium (Ca + Mg) concentrations decreased at seven of eight precipitation monitoring sites and in three of five streams. 3)Precipitation acidity decreased at five of eight precipitation monitoring sites, but alkalinity increased in only one stream. These results indicate that decreases in atmospheric deposition of SO4 have resulted in decreased precipitation acidity. The chemical response of stream water to changes in precipitation chemistry was complex. Decreases in stream-water SO4 concentrations generally matched decreases of precipitation SO4. In stream water, increases in alkalinity were uncommon because decreases in SO4 concentrations often were accompanied by decreases in Ca + Mg concentrations. The decreases in Ca + Mg concentrations might be related to depletion of base cations from soil caused by long-term exposure to acidic deposition. Increases in streamwater alkalinity might not occur until rates of acidic deposition are reduced to substantially less than the rate of cation resupply by weathering and atmospheric deposition. In areas where forests are aggrading, recovery of stream-water alkalinity will be delayed further because of the acidifying effect of biomass accumulation.

Cationic composition and acid-base state of the extracellular fluid, and specific buffer value of hemoglobin from the branchiopod crustacean Triops cancriformis.

PubMed

Pirow, Ralph; Buchen, Ina; Richter, Marc; Allmer, Carsten; Nunes, Frank; Günsel, Andreas; Heikens, Wiebke; Lamkemeyer, Tobias; von Reumont, Björn M; Hetz, Stefan K

2009-04-01

Recent insights into the allosteric control of oxygen binding in the extracellular hemoglobin (Hb) of the tadpole shrimp Triops cancriformis raised the question about the physico-chemical properties of the protein's native environment. This study determined the cationic composition and acid-base state of the animal's extracellular fluid. The physiological concentrations of potential cationic effectors (calcium, magnesium) were more than one order of magnitude below the level effective to increase Hb oxygen affinity. The extracellular fluid in the pericardial space had a typical bicarbonate concentration of 7.6 mM but a remarkably high CO(2) partial pressure of 1.36 kPa at pH 7.52 and 20 degrees C. The discrepancy between this high CO(2) partial pressure and the comparably low values for water-breathing decapods could not solely be explained by the hemolymph-sampling procedure but may additionally arise from differences in cardiovascular complexity and efficiency. T. cancriformis hemolymph had a non-bicarbonate buffer value of 2.1 meq L(-1) pH(-1). Hb covered 40-60% of the non-bicarbonate buffering power. The specific buffer value of Hb of 1.1 meq (mmol heme)(-1) pH(-1) suggested a minimum requirement of two titratable histidines per heme-binding domain, which is supported by available information from N-terminal sequencing and expressed sequence tags.

Characterization of Screen-Printed Organic Electrochemical Transistors to Detect Cations of Different Sizes.

PubMed

Contat-Rodrigo, Laura; Pérez-Fuster, Clara; Lidón-Roger, José Vicente; Bonfiglio, Annalisa; García-Breijo, Eduardo

2016-09-28

A novel screen-printing fabrication method was used to prepare organic electrochemical transistors (OECTs) based on poly(3,4-ethylenedioxythiophene) doped with polysterene sulfonate (PEDOT:PSS). Initially, three types of these screen-printed OECTs with a different channel and gate areas ratio were compared in terms of output characteristics, transfer characteristics, and current modulation in a phosphate buffered saline (PBS) solution. Results confirm that transistors with a gate electrode larger than the channel exhibit higher modulation. OECTs with this geometry were therefore chosen to investigate their ion-sensitive properties in aqueous solutions of cations of different sizes (sodium and rhodamine B). The effect of the gate electrode was additionally studied by comparing these all-PEDOT:PSS transistors with OECTs with the same geometry but with a non-polarizable metal gate (Ag). The operation of the all-PEDOT:PSS OECTs yields a response that is not dependent on a Na⁺ or rhodamine concentration. The weak modulation of these transistors can be explained assuming that PEDOT:PSS behaves like a supercapacitor. In contrast, the operation of Ag-Gate OECTs yields a response that is dependent on ion concentration due to the redox reaction taking place at the gate electrode with Cl - counter-ions. This indicates that, for cation detection, the response is maximized in OECTs with non-polarizable gate electrodes.

Ammonia vapor sensing properties of polyaniline-titanium(IV)phosphate cation exchange nanocomposite.

PubMed

Khan, Asif Ali; Baig, Umair; Khalid, Mohd

2011-02-28

In this study, the electrically conducting polyaniline-titanium(IV)phosphate (PANI-TiP) cation exchange nanocomposite was synthesized by sol-gel method. The cation exchange nanocomposite based sensor for detection of ammonia vapors was developed at room temperature. It was revealed that the sensor showed good reversible response towards ammonia vapors ranging from 3 to 6%. It was found that the sensor with p-toluene sulphonic acid (p-TSA) doped exhibited higher sensing response than hydrochloric acid doped. This sensor has detection limit ≤1% ammonia. The response of resistivity changes of the cation exchange nanocomposite on exposure to different concentrations of ammonia vapors shows its utility as a sensing material. These studies suggest that the cation exchange nanocomposite could be a good material for ammonia sensor at room temperature. Copyright © 2010 Elsevier B.V. All rights reserved.

Compositional engineering of perovskite oxides for highly efficient oxygen reduction reactions.

PubMed

Chen, Dengjie; Chen, Chi; Zhang, Zhenbao; Baiyee, Zarah Medina; Ciucci, Francesco; Shao, Zongping

2015-04-29

Mixed conducting perovskite oxides are promising catalysts for high-temperature oxygen reduction reaction. Pristine SrCoO(3-δ) is a widely used parent oxide for the development of highly active mixed conductors. Doping a small amount of redox-inactive cation into the B site (Co site) of SrCoO(3-δ) has been applied as an effective way to improve physicochemical properties and electrochemical performance. Most findings however are obtained only from experimental observations, and no universal guidelines have been proposed. In this article, combined experimental and theoretical studies are conducted to obtain fundamental understanding of the effect of B-site doping concentration with redox-inactive cation (Sc) on the properties and performance of the perovskite oxides. The phase structure, electronic conductivity, defect chemistry, oxygen reduction kinetics, oxygen ion transport, and electrochemical reactivity are experimentally characterized. In-depth analysis of doping level effect is also undertaken by first-principles calculations. Among the compositions, SrCo0.95Sc0.05O(3-δ) shows the best oxygen kinetics and corresponds to the minimum fraction of Sc for stabilization of the oxygen-vacancy-disordered structure. The results strongly support that B-site doping of SrCoO(3-δ) with a small amount of redox-inactive cation is an effective strategy toward the development of highly active mixed conducting perovskites for efficient solid oxide fuel cells and oxygen transport membranes.

Adsorption of anionic and cationic dyes on activated carbon from aqueous solutions: equilibrium and kinetics.

PubMed

Rodríguez, Araceli; García, Juan; Ovejero, Gabriel; Mestanza, María

2009-12-30

Activated carbon was utilized as adsorbent to remove anionic dye, Orange II (OII), and cationic dye, Methylene blue (MB), from aqueous solutions by adsorption. Batch experiments were conducted to study the effects of temperature (30-65 degrees C), initial concentration of adsorbate (300-500 mg L(-1)) and pH (3.0-9.0) on dyes adsorption. Equilibrium adsorption isotherms and kinetics were investigated. The equilibrium experimental data were analyzed by the Langmuir, Freundlich, Toth and Redlich-Peterson models. The kinetic data obtained with different carbon mass were analyzed using a pseudo-first order, pseudo-second order, intraparticle diffusion, Bangham and Chien-Clayton equations. The best results were achieved with the Langmuir isotherm equilibrium model and with the pseudo-second order kinetic model. The activated carbon was found to be very effective as adsorbent for MB and OII from aqueous solutions.

Concurrent aggregation and transport of graphene oxide in saturated porous media: Roles of temperature, cation type, and electrolyte concentration.

PubMed

Wang, Mei; Gao, Bin; Tang, Deshan; Yu, Congrong

2018-04-01

Simultaneous aggregation and retention of nanoparticles can occur during their transport in porous media. In this work, the concurrent aggregation and transport of GO in saturated porous media were investigated under the conditions of different combinations of temperature, cation type (valence), and electrolyte concentration. Increasing temperature (6-24 °C) at a relatively high electrolyte concentration (i.e., 50 mM for Na + , 1 mM for Ca 2+ , 1.75 mM for Mg 2+ , and 0.03 and 0.05 mM for Al 3+ ) resulted in enhanced GO retention in the porous media. For instance, when the temperature increased from 6 to 24 °C, GO recovery rate decreased from 31.08% to 6.53% for 0.03 mM Al 3+ and from 27.11% to 0 for 0.05 mM Al 3+ . At the same temperature, increasing cation valence and electrolyte concentration also promoted GO retention. Although GO aggregation occurred in the electrolytes during the transport, the deposition mechanisms of GO retention in the media depended on cation type (valence). For 50 mM Na + , surface deposition via secondary minima was the dominant GO retention mechanism. For multivalent cation electrolytes, GO aggregation was rapid and thus other mechanisms such as physical straining and sedimentation also played important roles in controlling GO retention in the media. After passing through the columns, the GO particles in the effluents showed better stability with lower initial aggregation rates. This was probably because less stable GO particles with lower surface charge densities in the porewater were filtered by the porous media, resulting in more stable GO particle with higher surface charge densities in the effluents. An advection-dispersion-reaction model was applied to simulate GO breakthrough curves and the simulations matched all the experimental data well. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mg shallow doping effects on the ac magnetic self-heating characteristics of γ-Fe2O3 superparamagnetic nanoparticles for highly efficient hyperthermia

NASA Astrophysics Data System (ADS)

Jang, Jung-tak; Bae, Seongtae

2017-10-01

The effects of Mg doping on the magnetic and AC self-heating temperature rising characteristics of γ-Fe2O3 superparamagnetic nanoparticles (SPNPs) were investigated for hyperthermia applications in biomedicine. The doping concentration of nonmagnetic Mg2+ cation was systematically controlled from 0 to 0.15 at. % in Mgx-γFe2O3 SPNPs during chemically and thermally modified one-pot thermal decomposition synthesis under bubbling O2/Ar gas mixture. It was empirically observed that the saturation magnetization (Ms) and the out-of-phase magnetic susceptibility ( χm″)of Mgx-γFe2O3 SPNPs were increased by increasing the Mg2+ cation doping concentration from 0.05 to 0.13 at. %. Correspondingly, the AC magnetically induced self-heating temperature (Tac,max) in solid state and the intrinsic loss power in water were increased up to 184 °C and 14.2 nH m2 kg-1 (Mgx-γFe2O3, x = 0.13), respectively, at the biologically and physiologically safe range of AC magnetic field (Happl × fappl = 1.2 × 109 A m-1 s-1). All the chemically and physically analyzed results confirmed that the dramatically improved AC magnetic induction heating characteristics and the magnetic properties of Mgx-γFe2O3 SPNPs (x = 0.13) are primarily due to the significantly enhanced magnetic susceptibility (particularly, χm″) and the improved AC/DC magnetic softness (lower AC/DC magnetic anisotropy) resulting from the systematically controlled nonmagnetic Mg2+ cation concentrations and distributions (occupation ratio) in the Fe vacancy sites of γ-Fe2O3 (approximately 12% vacancy), instead of typically well-known Fe3O4 (no vacancy) SPNPs. The cell viability and biocompatibility with U87 MG cell lines demonstrated that Mgx-γFe2O3 SPNPs (x = 0.13) has promising bio-feasibility for hyperthermia agent applications.

Effects of Organic Anion, Organic Cation, and Dipeptide Transport Inhibitors on Cefdinir in the Isolated Perfused Rat Kidney

PubMed Central

Lepsy, Christopher S.; Guttendorf, Robert J.; Kugler, Alan R.; Smith, David E.

2003-01-01

Cefdinir (Omnicef; Abbott Laboratories) is a cephalosporin antibiotic primarily eliminated by the kidney. Nonlinear renal elimination of cefdinir has been previously reported. Cefdinir renal transport mechanisms were studied in the erythrocyte-free isolated perfused rat kidney. Studies were performed with drug-free perfusate and perfusate containing cefdinir alone to establish the baseline physiology and investigate cefdinir renal elimination characteristics. To investigate cefdinir renal transport mechanisms, inhibition studies were conducted by coperfusing cefdinir with inhibitors of the renal organic anion (probenecid), organic cation (tetraethylammonium), or dipeptide (glycylsarcosine) transport system. Cefdinir concentrations in biological samples were determined using reversed-phase high-performance liquid chromatography. Differences between treatments and controls were evaluated using analysis of variance and Dunnett's test. The excretion ratio (ER; the renal clearance corrected for the fraction unbound and glomerular filtration rate) for cefdinir was 5.94, a value indicating net renal tubular secretion. Anionic, cationic, and dipeptide transport inhibitors all significantly affected the cefdinir ER. With probenecid, the ER was reduced to 0.59, clearly demonstrating a significant reabsorptive component to cefdinir renal disposition. This finding was confirmed by glycylsarcosine studies, in which the ER was elevated to 7.95, indicating that reabsorption was mediated, at least in part, by the dipeptide transporter system. The effects of the organic cation tetraethylammonium, in which the ER was elevated to 7.53, were likely secondary in nature. The anionic secretory pathway was found to be the predominant mechanism for cefdinir renal excretion. PMID:12543679

Prevention of selenite-induced cataractogenesis by rutin in Wistar rats

PubMed Central

Isai, M.; Sakthivel, M.; Ramesh, E.; Thomas, P.A.

2009-01-01

Purpose To investigate whether rutin retards selenite-induced cataractogenesis in Wistar rat pups. Methods On postpartum day ten, Group I rat pups received an intraperitoneal injection of saline. Group II and III rat pups received a subcutaneous injection of sodium selenite. Group III also received an intraperitoneal injection of rutin once daily on postpartum days 9–14. Both eyes of each pup were examined from day 16 up to postpartum day 30. After sacrifice, extricated pup lenses were analyzed for mean activities of catalase, superoxide dismutase, glutathione peroxidase, glutathione S-transferase, and glutathione reductase. In addition, the mean concentrations of reduced glutathione (GSH) and of malondialdehyde were analyzed in samples of lenses and hemolysate. Results There was dense lenticular opacification in all of Group II, minimal opacification in 33.3% of Group III, no opacification in 66.7% of Group III, and no opacification in Group I. Significantly lower mean activities of lenticular antioxidant enzymes were noted in Group II, compared to Group I and III. Significantly lower mean concentrations of GSH and higher mean concentrations of malondialdehyde were noted in samples of hemolysate and lens from Group II, compared to the values in Group I and III. Conclusion Rutin prevents experimental selenite-induced cataractogenesis in rat pups, possibly by preventing depletion of antioxidant enzymes and of GSH, and by inhibiting lipid peroxidation. PMID:20011628

Influence of ionic strength, anions, cations, and natural organic matter on the adsorption of pharmaceuticals to silica.

PubMed

Bui, Tung Xuan; Choi, Heechul

2010-08-01

The adsorption of four wide-use pharmaceuticals (carbamazepine, diclofenac, ibuprofen, and ketoprofen) onto a porous silica was investigated under varied ionic strengths, different anions, divalent cations (Ca(2+) and Mg(2+)), trivalent cations (Al(3+) and Fe(3+)), and natural organic matter (NOM). The experiments demonstrated that at a given pH the adsorption was most affected by ionic strength, trivalent cations, and properties of pharmaceuticals. The increase of ionic strength resulted in an increase in the adsorption of ketoprofen, but a decrease in the adsorption of carbamazepine. Trivalent metal cations made intense increases in the adsorption of three acidic pharmaceuticals, which could be due to the formation of inner-sphere complex of the cations on the surface and/or complexation of the pharmaceuticals with both surface and aqueous metal species. It was found that the adsorption of carbamazepine was not affected by divalent and trivalent cations, whereas the adsorption of diclofenac was solely impacted by the presence of Al(3+). Moreover, divalent cations at low concentration could slightly enhance the adsorption of ibuprofen and ketoprofen, whereas NOM caused a reduction in the adsorption of the tested pharmaceuticals except for diclofenac. These results suggest that ionic strength, divalent cations, trivalent cations, and NOM are notable factors affecting the adsorption of pharmaceuticals and thus the ultimate fate of pharmaceuticals in the aqueous environment. Copyright 2010 Elsevier Ltd. All rights reserved.

A model for the salt effect on adsorption equilibrium of basic protein to dye-ligand affinity adsorbent.

PubMed

Zhang, Songping; Sun, Yan

2004-01-01

A model describing the salt effect on adsorption equilibrium of a basic protein, lysozyme, to Cibacron Blue 3GA-modified Sepharose CL-6B (CB-Sepharose) has been developed. In this model, it is assumed that the presence of salt causes a fraction of dye-ligand molecules to lodge to the surface of the agarose gel, resulting from the induced strong hydrophobic interaction between dye ligand and agarose matrix. The salt effect on the lodging of dye-ligand is expressed by the equilibrium between salt and dye-ligand. For the interactions between protein and vacant binding sites, stoichiometric equations based either on cation exchanges or on hydrophobic interactions are proposed since the CB dye can be regarded as a cation exchanger contributed by the sulfonate groups on it. Combining with the basic concept of steric mass-action theory for ion exchange, which considers both the multipoint nature and the macromolecular steric shielding of protein adsorption, an explicit isotherm for protein adsorption equilibrium on the dye-ligand adsorbent is formulated, involving salt concentration as a variable. Analysis of the model parameters has yielded better understanding of the mechanism of salt effects on adsorption of the basic protein. Moreover, the model predictions are in good agreement with the experimental data over a wide range of salt and ligand concentrations, indicating the predictive nature of the model.

Carbachol regulates pacemaker activities in cultured interstitial cells of Cajal from the mouse small intestine.

PubMed

So, Keum Young; Kim, Sang Hun; Sohn, Hong Moon; Choi, Soo Jin; Parajuli, Shankar Prasad; Choi, Seok; Yeum, Cheol Ho; Yoon, Pyung Jin; Jun, Jae Yeoul

2009-05-31

We studied the effect of carbachol on pacemaker currents in cultured interstitial cells of Cajal (ICC) from the mouse small intestine by muscarinic stimulation using a whole cell patch clamp technique and Ca2+-imaging. ICC generated periodic pacemaker potentials in the current-clamp mode and generated spontaneous inward pacemaker currents at a holding potential of-70 mV. Exposure to carbachol depolarized the membrane and produced tonic inward pacemaker currents with a decrease in the frequency and amplitude of the pacemaker currents. The effects of carbachol were blocked by 1-dimethyl-4-diphenylacetoxypiperidinium, a muscarinic M(3) receptor antagonist, but not by methotramine, a muscarinic M(2) receptor antagonist. Intracellular GDP-beta-S suppressed the carbachol-induced effects. Carbachol-induced effects were blocked by external Na+-free solution and by flufenamic acid, a non-selective cation channel blocker, and in the presence of thapsigargin, a Ca2+-ATPase inhibitor in the endoplasmic reticulum. However, carbachol still produced tonic inward pacemaker currents with the removal of external Ca2+. In recording of intracellular Ca2+ concentrations using fluo 3-AM dye, carbachol increased intracellular Ca2+ concentrations with increasing of Ca2+ oscillations. These results suggest that carbachol modulates the pacemaker activity of ICC through the activation of non-selective cation channels via muscarinic M(3) receptors by a G-protein dependent intracellular Ca2+ release mechanism.

Serum magnesium and calcium levels in infertile women during a cycle of reproductive assistance.

PubMed

Grossi, Elena; Castiglioni, Sara; Moscheni, Claudia; Antonazzo, Patrizio; Cetin, Irene; Savasi, Valeria Maria

2017-05-01

Magnesium (Mg) and calcium (Ca) are essential cations for women's preconception health. It is well known that, in blood, the concentration of ionized form of these two cations is temporally altered during menstrual cycle, suggesting a correlation between sex steroid hormones and serum calcium and magnesium levels. Evidence from literature suggests that in assisted reproductive technology increasing estrogens during ovarian hyperstimulation may also modulate serum magnesium and calcium levels. Therefore, we first examined total serum magnesium and calcium levels during follicular phase in a large population of infertile patients who underwent intrauterine insemination (IUI). The results were compared to a group of fertile women. Successively, we studied the total serum magnesium and calcium concentrations in infertile patients before and after ovarian hyperstimulation for in vitro fertilization (IVF). Results highlight that total serum concentration of magnesium and calcium does not seem altered in infertile women. During stimulation with gonadotropins, the values of the two cations do not change significantly in ovarian-stimulated women. However, we found a downward trend in the total magnesium and calcium levels in relation to the rising estrogens.

Effects of Hofmeister salt series on gluten network formation: Part I. Cation series.

PubMed

Tuhumury, H C D; Small, D M; Day, L

2016-12-01

Different cationic salts were used to investigate the effects of the Hofmeister salt series on gluten network formation. The effects of cationic salts on wheat flour dough mixing properties, the rheological and the chemical properties of the gluten extracted from the dough with different respective salts, were investigated. The specific influence of different cationic salts on the gluten structure formation during dough mixing, compared to the sodium ion, were determined. The effects of different cations on dough and gluten of different flours mostly followed the Hofmeister series (NH4(+), K(+), Na(+), Mg(2+) and Ca(2+)). The impacts of cations on gluten structure and dough rheology at levels tested were relatively small. Therefore, the replacement of sodium from a technological standpoint is possible, particularly by monovalent cations such as NH4(+), or K(+). However the levels of replacement need to take into account sensory attributes of the cationic salts. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sorption of Fluorotelomer Sulfonates, Fluorotelomer Sulfonamido Betaines, and a Fluorotelomer Sulfonamido Amine in National Foam Aqueous Film-Forming Foam to Soil.

PubMed

Barzen-Hanson, Krista A; Davis, Shannon E; Kleber, Markus; Field, Jennifer A

2017-11-07

During fire-fighter training, equipment testing, and emergency responses with aqueous film-forming foams (AFFFs), milligrams per liter concentrations of anionic, zwitterionic, and cationic per- and polyfluoroalkyl substances (PFASs) enter the environment. Because the behavior of zwitterionic and cationic PFASs in the subsurface is unknown, batch sorption experiments were conducted using National Foam AFFF, which contains anionic fluorotelomer sulfonates (FtSs), zwitterionic fluorotelomer sulfonamido betaines (FtSaBs), and cationic 6:2 fluorotelomer sulfonamido amine (FtSaAm). Sorption of the FtSs, FtSaBs, and 6:2 FtSaAm to six soils with varying organic carbon, effective cation-exchange capacity, and anion-exchange capacity was evaluated to determine sorption mechanisms. Due to the poor recovery of the FtSaBs and 6:2 FtSaAm with published PFAS soil extraction methods, a new soil extraction method was developed to achieve good (90-100%) recoveries. The 6:2 FtSaAm was depleted from the aqueous phase in all but one soil, which is attributed to electrostatic and hydrophobic interactions. Sorption of the FtSs was driven by hydrophobic interactions, while the FtSaBs behave more like cations that strongly associate with the solid phase relative to groundwater. Thus, the sorption mechanisms of the FtSs, FtSaBs, and 6:2 FtSaAm are more complex than expected and cannot be predicted by bulk soil properties.

Electrostatic Origin of Salt-Induced Nucleosome Array Compaction

PubMed Central

Korolev, Nikolay; Allahverdi, Abdollah; Yang, Ye; Fan, Yanping; Lyubartsev, Alexander P.; Nordenskiöld, Lars

2010-01-01

The physical mechanism of the folding and unfolding of chromatin is fundamentally related to transcription but is incompletely characterized and not fully understood. We experimentally and theoretically studied chromatin compaction by investigating the salt-mediated folding of an array made of 12 positioning nucleosomes with 177 bp repeat length. Sedimentation velocity measurements were performed to monitor the folding provoked by addition of cations Na+, K+, Mg2+, Ca2+, spermidine3+, Co(NH3)63+, and spermine4+. We found typical polyelectrolyte behavior, with the critical concentration of cation needed to bring about maximal folding covering a range of almost five orders of magnitude (from 2 μM for spermine4+ to 100 mM for Na+). A coarse-grained model of the nucleosome array based on a continuum dielectric description and including the explicit presence of mobile ions and charged flexible histone tails was used in computer simulations to investigate the cation-mediated compaction. The results of the simulations with explicit ions are in general agreement with the experimental data, whereas simple Debye-Hückel models are intrinsically incapable of describing chromatin array folding by multivalent cations. We conclude that the theoretical description of the salt-induced chromatin folding must incorporate explicit mobile ions that include ion correlation and ion competition effects. PMID:20858435

Efficient Removal of Cationic and Anionic Radioactive Pollutants from Water Using Hydrotalcite-Based Getters.

PubMed

Bo, Arixin; Sarina, Sarina; Liu, Hongwei; Zheng, Zhanfeng; Xiao, Qi; Gu, Yuantong; Ayoko, Godwin A; Zhu, Huaiyong

2016-06-29

Hydrotalcite (HT)-based materials are usually applied to capture anionic pollutants in aqueous solutions. Generally considered anion exchangers, their ability to capture radioactive cations is rarely exploited. In the present work, we explored the ability of pristine and calcined HT getters to effectively capture radioactive cations (Sr(2+) and Ba(2+)) which can be securely stabilized at the getter surface. It is found that calcined HT outperforms its pristine counterpart in cation removal ability. Meanwhile, a novel anion removal mechanism targeting radioactive I(-) is demonstrated. This approach involves HT surface modification with silver species, namely, Ag2CO3 nanoparticles, which can attach firmly on HT surface by forming coherent interface. This HT-based anion getter can be further used to capture I(-) in aqueous solution. The observed I(-) uptake mechanism is distinctly different from the widely reported ion exchange mechanism of HT and much more efficient. As a result of the high local concentrations of precipitants on the getters, radioactive ions in water can be readily immobilized onto the getter surface by forming precipitates. The secured ionic pollutants can be subsequently removed from water by filtration or sedimentation for safe disposal. Overall, these stable, inexpensive getters are the materials of choice for removal of trace ionic pollutants from bulk radioactive liquids, especially during episodic environmental crisis.

Charged anaesthetics alter LM-fibroblast plasma-membrane enzymes by selective fluidization of inner or outer membrane leaflets.

PubMed Central

Sweet, W D; Schroeder, F

1986-01-01

The functional consequences of the differences in lipid composition and structure between the two leaflets of the plasma membrane were investigated. Fluorescence of 1,6-diphenylhexa-1,3,5-triene(DPH), quenching, and differential polarized phase fluorimetry demonstrated selective fluidization by local anaesthetics of individual leaflets in isolated LM-cell plasma membranes. As measured by decreased limiting anisotropy of DPH fluorescence, cationic (prilocaine) and anionic (phenobarbital and pentobarbital) amphipaths preferentially fluidized the cytofacial and exofacial leaflets respectively. Unlike prilocaine, procaine, also a cation, fluidized both leaflets of these membranes equally. Pentobarbital stimulated 5'-nucleotidase between 0.1 and 5 mM and inhibited at higher concentrations, whereas phenobarbital only inhibited, at higher concentrations. Cationic drugs were ineffective. Two maxima of (Na+ + K+)-ATPase activation were obtained with both anionic drugs. Only one activation maximum was obtained with both cationic drugs. The maximum in activity below 1 mM for all four drugs clustered about a single limiting anisotropy value in the cytofacial leaflet, whereas there was no correlation between activity and limiting anisotropy in the exofacial leaflets. Therefore, although phenobarbital and pentobarbital below 1 mM fluidized the exofacial leaflet more than the cytofacial leaflet, the smaller fluidization in the cytofacial leaflet was functionally significant for (Na+ + K+)-ATPase. Mg2+-ATPase was stimulated at 1 mM-phenobarbital, unaffected by pentobarbital and slightly stimulated by both cationic drugs at concentrations fluidizing both leaflets. Thus the activity of (Na+ + K+)-ATPase was highly sensitive to selective fluidization of the leaflet containing its active site, whereas the other enzymes examined were little affected by fluidization of either leaflet. PMID:3028369

Ce, Ti modified MCM-48 mesoporous photocatalysts: Effect of the synthesis route on support and metal ion properties

NASA Astrophysics Data System (ADS)

Mureseanu, Mihaela; Filip, Mihaela; Somacescu, Simona; Baran, Adriana; Carja, Gabriela; Parvulescu, Viorica

2018-06-01

New Ti-MCM-48 and CeTi-MCM-48 photocatalysts were obtained by impregnation of the MCM-48 silica support synthesized by a hydrothermal process with aqueous solution of Ti and Ce precursors. The immobilization of metal cations presented a low effect on the porosity, morphology and structure of MCM-48 mesoporous silica support as was evidenced by N2 adsorption-desorption, X-ray diffraction, SEM and TEM electron microscopy. EDAX analysis and X-ray photoelectron microscopy (XPS) indicated that titanium cations were present on the mesoporous silica surface only as Ti4+ species and the effect of ceria on titanium speciation was different, compared to the CeTi-MCM-48 sample, previously obtained by direct synthesis. The photocatalytic properties of mono- and bimetallic catalysts were evaluated in degradation of phenol from water and correlated with the active metallic species concentration, distribution, speciation and their interaction with the support or each other. An advanced oxidation mechanism for phenol degradation by radical species was proposed.

Removal of 226Ra and 228Ra from TENORM sludge waste using surfactants solutions.

PubMed

Attallah, M F; Hamed, Mostafa M; El Afifi, E M; Aly, H F

2015-01-01

The feasibility of using surfactants as extracting agent for the removal of radium species from TENORM sludge produced from petroleum industry is evaluated. In this investigation cationic and nonionic surfactants were used as extracting agents for the removal of radium radionuclides from the sludge waste. Two surfactants namely cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX100) were investigated as the extracting agents. Different parameters affecting the removal of both (226)Ra and (228)Ra by the two surfactants as well as their admixture were studied by the batch technique. These parameters include effect of shaking time, surfactants concentration and temperature as well as the effect of surfactants admixture. It was found that, higher solution temperature improves the removal efficiency of radium species. Combined extraction of nonionic and cationic surfactants produces synergistic effect in removal both (226)Ra and (228)Ra, where the removals reached 84% and 80% for (226)Ra and (228)Ra, respectively, were obtained using surfactants admixture. Copyright © 2014 Elsevier Ltd. All rights reserved.

A New Microfluidic Polymer Chip with an Embedded Cationic Surfactant Ion-selective Optode as a Detector for the Determination of Cationic Surfactants.

PubMed

Ashagre, Mekonnen Abiyot; Masadome, Takashi

2018-01-01

A new microfluidic polymer chip with an embedded cationic surfactant (CS) ion-selective optode (CS-optode) as a detector of flow-injection analysis (FIA) for the determination of CSs was developed. The optode sensing membrane is based on a poly(vinyl chloride) membrane plasticized with 2-nitrophenyl octyl ether containing tetrabromophenolphthalein ethyl ester. Under the optimal flow conditions of the FIA system, the CS-optode showed a good linear relationship between the peak heights in the absorbance, and the concentrations of CS in a concentration range from 50 to 400 μmol dm -3 . The sample throughput of the present system for the determination of a CS ion (300 μmol dm -3 zephiramine) was ca. 11 samples h -1 . The proposed FIA system was applied to determine the level of CS in dental rinses.

A shell-resolved analysis of preferential solvation of coffee ingredients in aqueous mixtures of the ionic liquid 1-ethyl-3-methylimidazolium acetate

NASA Astrophysics Data System (ADS)

Zeindlhofer, Veronika; Berger, Magdalena; Steinhauser, Othmar; Schröder, Christian

2018-05-01

Ionic liquids increase the solubility of various coffee ingredients in aqueous solution but little is known about the underlying mechanism. Kirkwood-Buff integrals as well as the potential of mean force indicate that the imidazolium cations are accumulated at the surface of the solutes, removing water molecules from the solute surface. Although hydrogen bonding of the anions to hydroxy groups of the solutes can be detected, their concentration at the surface is less enhanced compared to the cations. The decomposition into solvation shells by Voronoi tessellation reveals that structural features are only observed in the first solvation shell. Nevertheless, the depletion of water and the excess concentration of the ions and, in particular, of the cations are visible in the next solvation shells as well. Therefore, classical arguments of hydrotropic theory fail to explain this behavior.

The ionic selectivity and calcium dependence of the light-sensitive pathway in toad rods.

PubMed Central

Hodgkin, A L; McNaughton, P A; Nunn, B J

1985-01-01

A new method is described for determining the effects of rapid changes in ionic concentration on the light-sensitive currents of rod outer segments. Replacing Na with another monovalent cation caused a rapid change in current followed by an exponential decline of time constant 0.5-2 s. From the magnitude of the initial rapid change in current we conclude that Li, Na, and K and Rb ions pass readily through the light-sensitive channel in the presence of 1 mM-Ca, whereas Cs crosses with difficulty and choline, tetramethylammonium and tetraethylammonium not at all. The effect of reducing Ca in the external medium indicates that the residual inward current recorded for a few seconds when Na is replaced by an impermeant ion is carried largely by Ca ions. With 1 microM-Ca in the external medium the relative ability of monovalent cations to carry light-sensitive current is Li:Na:K:Rb:Cs = 1.4:1:0.8:0.6:0.15. The same order applied in the physiological region but the values are less certain. Large transient inward currents are seen if external Ca is raised form 1 microM to 5 mM or more; these currents which are maximal in an isotonic Ca solution are presumably carried by Ca. The effect of monovalent cations on the number of open light-sensitive channels was tested by adding the cation to a solution containing 55 mM-Na. Na ions open light-sensitive channels with a delay, probably by promoting Na-Ca exchange; K and Rb close channels by inhibiting exchange; Li and Cs seem inert in the exchange mechanism. The rate at which inward current declines in low [Na]o or high [Ca]o is accelerated by weak background lights and slowed by 3-isobutyl-1-methylxanthine (IBMX), which inhibits the hydrolysis of cGMP. On returning to Ringer solution after a period in low [Na]o the current recovers with a delay of about 1 s which decreases as the Ca concentration of the low [Na]o medium is reduced. We conclude that intracellular Ca has a strong effect on the number of open light-sensitive channels. None the less, several observations are inconsistent with channel closure being dependent simply on combination with internal Ca. PMID:2580087

Cesium-specific phenolic ion exchange resin

DOEpatents

Bibler, J.P.; Wallace, R.M.

1995-08-15

A phenolic, cesium-specific, cation exchange resin is prepared by neutralizing resorcinol with potassium hydroxide, condensing/polymerizing the resulting intermediate with formaldehyde, heat-curing the resulting polymer to effect cross-linking and grinding it to desired particle size for use. This resin will selectively and efficiently adsorb cesium ions in the presence of a high concentration of sodium ions with a low carbon to cesium ratio. 2 figs.

Cesium-specific phenolic ion exchange resin

DOEpatents

Bibler, Jane P.; Wallace, Richard M.

1995-01-01

A phenolic, cesium-specific, cation exchange resin is prepared by neutralizing resorcinol with potassium hydroxide, condensing/polymerizing the resulting intermediate with formaldehyde, heat-curing the resulting polymer to effect cross-linking and grinding it to desired particle size for use. This resin will selectively and efficiently adsorb cesium ions in the presence of a high concentration of sodium ions with a low carbon to cesium ratio.

Response of a benzoxainone derivative linked to monoaza-15-crown-5 with divalent heavy metals.

PubMed

Addleman, R S; Bennett, J; Tweedy, S H; Elshani, S; Wai, C M

1998-08-01

The response of a monoaza-15-crown-5 with an optically active aminobenzoxazinone moiety to divalent cations was investigated. The crown ether was found to undergo a strong emission shift to the blue when complexed with specific divalent metals that have ionic diameters between 1.9-2.4 A. Consequently the photoactive macrocycle is responsive to Mg(2+), Ca(2+), Ba(2+), Sr(2+), Cd(2+), and particularly responsive to Hg(2+)and Pb(2+). Macrocycle emission spectra are shown to be a function of cation concentration. Alkaline metal cations and smaller transition metals ions such as Ni(2+), Co(2+)and Zn(2+)do not cause significant changes in the macrocycle emission spectra. Emission, absorption, and complex stability constants are determined. Mechanisms of cation selectivity and spectral emission shifts are discussed. Challenges involving immobilization of the macrocycle while preserving its spectral response to cations are explored.

Ion Counting from Explicit-Solvent Simulations and 3D-RISM

PubMed Central

Giambaşu, George M.; Luchko, Tyler; Herschlag, Daniel; York, Darrin M.; Case, David A.

2014-01-01

The ionic atmosphere around nucleic acids remains only partially understood at atomic-level detail. Ion counting (IC) experiments provide a quantitative measure of the ionic atmosphere around nucleic acids and, as such, are a natural route for testing quantitative theoretical approaches. In this article, we replicate IC experiments involving duplex DNA in NaCl(aq) using molecular dynamics (MD) simulation, the three-dimensional reference interaction site model (3D-RISM), and nonlinear Poisson-Boltzmann (NLPB) calculations and test against recent buffer-equilibration atomic emission spectroscopy measurements. Further, we outline the statistical mechanical basis for interpreting IC experiments and clarify the use of specific concentration scales. Near physiological concentrations, MD simulation and 3D-RISM estimates are close to experimental results, but at higher concentrations (>0.7 M), both methods underestimate the number of condensed cations and overestimate the number of excluded anions. The effect of DNA charge on ion and water atmosphere extends 20–25 Å from its surface, yielding layered density profiles. Overall, ion distributions from 3D-RISMs are relatively close to those from corresponding MD simulations, but with less Na+ binding in grooves and tighter binding to phosphates. NLPB calculations, on the other hand, systematically underestimate the number of condensed cations at almost all concentrations and yield nearly structureless ion distributions that are qualitatively distinct from those generated by both MD simulation and 3D-RISM. These results suggest that MD simulation and 3D-RISM may be further developed to provide quantitative insight into the characterization of the ion atmosphere around nucleic acids and their effect on structure and stability. PMID:24559991

Mixed hemimicelles solid-phase extraction based on sodium dodecyl sulfate-coated nano-magnets for selective adsorption and enrichment of illegal cationic dyes in food matrices prior to high-performance liquid chromatography-diode array detection detection.

PubMed

Qi, Ping; Liang, Zhi-An; Wang, Yu; Xiao, Jian; Liu, Jia; Zhou, Qing-Qiong; Zheng, Chun-Hao; Luo, Li-Ni; Lin, Zi-Hao; Zhu, Fang; Zhang, Xue-Wu

2016-03-11

In this study, mixed hemimicelles solid-phase extraction (MHSPE) based on sodium dodecyl sulfate (SDS) coated nano-magnets Fe3O4 was investigated as a novel method for the extraction and separation of four banned cationic dyes, Auramine O, Rhodamine B, Basic orange 21 and Basic orange 22, in condiments prior to HPLC detection. The main factors affecting the extraction of analysts, such as pH, surfactant and adsorbent concentrations and zeta potential were studied and optimized. Under optimized conditions, the proposed method was successful applied for the analysis of banned cationic dyes in food samples such as chili sauce, soybean paste and tomato sauce. Validation data showed the good recoveries in the range of 70.1-104.5%, with relative standard deviations less than 15%. The method limits of determination/quantification were in the range of 0.2-0.9 and 0.7-3μgkg(-1), respectively. The selective adsorption and enrichment of cationic dyes were achieved by the synergistic effects of hydrophobic interactions and electrostatic attraction between mixed hemimicelles and the cationic dyes, which also resulted in the removal of natural pigments interferences from sample extracts. When applied to real samples, RB was detected in several positive samples (chili powders) within the range from 0.042 to 0.177mgkg(-1). These results indicate that magnetic MHSPE is an efficient and selective sample preparation technique for the extraction of banned cationic dyes in a complex matrix. Copyright © 2016 Elsevier B.V. All rights reserved.

Quantitative Measurement of Cationic Polymer Vector and Polymer-pDNA Polyplex Intercalation into the Cell Plasma Membrane.

PubMed

Vaidyanathan, Sriram; Anderson, Kevin B; Merzel, Rachel L; Jacobovitz, Binyamin; Kaushik, Milan P; Kelly, Christina N; van Dongen, Mallory A; Dougherty, Casey A; Orr, Bradford G; Banaszak Holl, Mark M

2015-06-23

Cationic gene delivery agents (vectors) are important for delivering nucleotides, but are also responsible for cytotoxicity. Cationic polymers (L-PEI, jetPEI, and G5 PAMAM) at 1× to 100× the concentrations required for translational activity (protein expression) induced the same increase in plasma membrane current of HEK 293A cells (30-50 nA) as measured by whole cell patch-clamp. This indicates saturation of the cell membrane by the cationic polymers. The increased currents induced by the polymers are not reversible for over 15 min. Irreversibility on this time scale is consistent with a polymer-supported pore or carpet model and indicates that the cell is unable to clear the polymer from the membrane. For polyplexes, although the charge concentration was the same (at N/P ratio of 10:1), G5 PAMAM and jetPEI polyplexes induced a much larger current increase (40-50 nA) than L-PEI polyplexes (<20 nA). Both free cationic lipid and lipid polyplexes induced a lower increase in current than cationic polymers (<20 nA). To quantify the membrane bound material, partition constants were measured for both free vectors and polyplexes into the HEK 293A cell membrane using a dye influx assay. The partition constants of free vectors increased with charge density of the vectors. Polyplex partition constants did not show such a trend. The long lasting cell plasma permeability induced by exposure to the polymer vectors or the polyplexes provides a plausible mechanism for the toxicity and inflammatory response induced by exposure to these materials.

Electrolyte induced rheological modulation of graphene oxide suspensions and its applications in adsorption

NASA Astrophysics Data System (ADS)

Ojha, Abhijeet; Thareja, Prachi

2018-03-01

In this study, we report the microstructure, rheology and adsorption characteristics of aqueous suspensions of Graphene Oxide (GO) at a volume fraction (ϕGO) = 0.018, which can be transformed into gels by cation induced charge shielding and cross-linking between GO nanosheets. GO nanosheets of average thickness ∼1.5 nm and a lateral dimension of ∼750 nm are synthesized by Hummer's process. At ϕGO= 0.018, cations of varying size and valence are systematically introduced with electrolytes NH4Cl, LiCl, NaCl, KCl, MgCl2 and FeCl3 at concentrations ranging from 10-5-10-1 M to investigate their effect on the rheology of GO suspensions. Our results suggest that depending on the electrolyte concentration, size and the valence of the cation: low viscosity suspensions, fragile gels and solid-like GO-electrolyte gels are formed. The storage modulus (G') of all GO-electrolyte gels increases with the increase in electrolyte concentration and G' follows the order GO-FeCl3 > GO-MgCl2> GO-KCl > GO-NaCl > GO-LiCl > GO-NH4Cl. FESEM analysis shows that lyophilized GO-electrolyte gels with 10-1 M electrolytes have a porous morphology resulting from the aggregation of GO nanosheets. The GO-electrolyte gels are shown to adsorb high quantities of oils, with GO-FeCl3 gels showing a higher adsorption capacity. The GO-NaCl and GO-FeCl3 lyophilized gels are also shown to adsorb methylene blue dye and follow the pseudo-second-order kinetics of adsorption. Along with higher oil and dye adsorption efficiency, GO-electrolyte gels are easy to recollect after the adsorption, thus avoiding the potential toxicity for bio-organisms in water caused by GO nanosheets.

Influence of Surfactants on Sodium Chloride Crystallization in Confinement

PubMed Central

2017-01-01

We study the influence of different surfactants on NaCl crystallization during evaporation of aqueous salt solutions. We found that at concentrations of sodium chloride close to saturation, only the cationic surfactant CTAB and the nonionic surfactant Tween 80 remain stable. For the nonionic surfactant, the high concentration of salt does not significantly change either the critical micellar concentration (CMC) or the surface tension at the CMC; for the cationic surfactant, the CMC is reduced by roughly 2 orders of magnitude upon adding the salt. The presence of both types of surfactants in the salt solution delays the crystallization of sodium chloride with evaporation. This, in turn, leads to high supersaturation which induces the rapid precipitation of a hopper crystal in the bulk. The crystallization inhibitor role of these surfactants is shown to be mainly due to the passivation of nucleation sites at both liquid/air and solid/liquid interfaces rather than a change in the evaporation rate which is found not to be affected by the presence of the surfactants. The adsorption of surfactants at the liquid/air interface prevents the crystallization at this location which is generally the place where the precipitation of sodium chloride is observed. Moreover, sum frequency generation spectroscopy measurements show that the surfactants are also present at the solid/liquid interface. The incorporation of the surfactants into the salt crystals is investigated using a novel, but simple, method based on surface tension measurements. Our results show that the nonionic surfactant Tween 80 is incorporated in the NaCl crystals but the cationic surfactant CTAB is not. Taken together, these results therefore allow us to establish the effect of the presence of surfactants on sodium chloride crystallization. PMID:28425711

Synthesis of [Zn-Al-CO 3] layered double hydroxides by a coprecipitation method under steady-state conditions

NASA Astrophysics Data System (ADS)

Chang, Z.; Evans, D. G.; Duan, X.; Vial, C.; Ghanbaja, J.; Prevot, V.; de Roy, M.; Forano, C.

2005-09-01

A continuous co-precipitation method under steady-state conditions has been investigated for the preparation of nanometer-size layered double hydroxide (LDH) particles using Zn 2Al(OH) 6(CO 3) 0.5·2H 2O as a prototype. The objective was to shorten the preparation time by working without an aging step, using a short and controlled residence time in order to maintain a constant supersaturation level in the reactor and constant particle properties in the exit stream over time. The effects of varying the operating conditions on the structural and textural properties of the LDHs have been studied, including total cation concentration, solvent, residence time, pH and intercalation anion. The products have been characterized using ICP, XRD, FTIR, BET, SEM and TEM. The LDHs prepared by the continuous coprecipitation method have a poorer crystallinity and lower crystallite sizes than those synthesized by the conventional batch method. The results have shown that increasing either cation concentration or the fraction of monoethylene glycol (MEG) in MEG/H 2O mixtures up to 80% (v/v) affect salt solubility and supersaturation, which gives rise to smaller crystallites, larger surface areas and more amorphous compounds. This increase is however limited by the precipitation of zinc and aluminum hydroxides occurring around a total cation concentration of 3.0×10 -1 M in pure water and 3.0×10 -2 M in H 2O/EtOH mixtures. Crystallite size increases with residence time, suggesting a precipitation process controlled by growth. Finally, the continuous coprecipitation method under steady-state conditions has been shown to be a promising alternative to the traditional coprecipitation technique in either pure water or mixed H 2O/MEG solvents.

Structure-activity relationship for hydrophobic salts as viscosity-lowering excipients for concentrated solutions of monoclonal antibodies.

PubMed

Guo, Zheng; Chen, Alvin; Nassar, Roger A; Helk, Bernhard; Mueller, Claudia; Tang, Yu; Gupta, Kapil; Klibanov, Alexander M

2012-11-01

To discover, elucidate the structure-activity relationship (SAR), and explore the mechanism of action of excipients able to drastically lower the viscosities of concentrated aqueous solutions of humanized monoclonal antibodies (MAbs). Salts prepared from hydrophobic cations and anions were dissolved into humanized MAbs solutions. Viscosities of the resulting solutions were measured as a function of the nature and concentration of the salts and MAbs. Even at moderate concentrations, some of the salts prepared herein were found to reduce over 10-fold the viscosities of concentrated aqueous solutions of several MAbs at room temperature. To be potent viscosity-lowering excipients, the ionic constituents of the salts must be hydrophobic, bulky, and aliphatic. A mechanistic hypothesis explaining the observed salt effects on MAb solutions' viscosities was proposed and verified.

Heavy metal cations permeate the TRPV6 epithelial cation channel.

PubMed

Kovacs, Gergely; Danko, Tamas; Bergeron, Marc J; Balazs, Bernadett; Suzuki, Yoshiro; Zsembery, Akos; Hediger, Matthias A

2011-01-01

TRPV6 belongs to the vanilloid family of the transient receptor potential channel (TRP) superfamily. This calcium-selective channel is highly expressed in the duodenum and the placenta, being responsible for calcium absorption in the body and fetus. Previous observations have suggested that TRPV6 is not only permeable to calcium but also to other divalent cations in epithelial tissues. In this study, we tested whether TRPV6 is indeed also permeable to cations such as zinc and cadmium. We found that the basal intracellular calcium concentration was higher in HEK293 cells transfected with hTRPV6 than in non-transfected cells, and that this difference almost disappeared in nominally calcium-free solution. Live cell imaging experiments with Fura-2 and NewPort Green DCF showed that overexpression of human TRPV6 increased the permeability for Ca(2+), Ba(2+), Sr(2+), Mn(2+), Zn(2+), Cd(2+), and interestingly also for La(3+) and Gd(3+). These results were confirmed using the patch clamp technique. (45)Ca uptake experiments showed that cadmium, lanthanum and gadolinium were also highly efficient inhibitors of TRPV6-mediated calcium influx at higher micromolar concentrations. Our results suggest that TRPV6 is not only involved in calcium transport but also in the transport of other divalent cations, including heavy metal ions, which may have toxicological implications. Copyright © 2010 Elsevier Ltd. All rights reserved.

The Urinary Antibiotic 5-Nitro-8-Hydroxyquinoline (Nitroxoline) Reduces the Formation and Induces the Dispersal of Pseudomonas aeruginosa Biofilms by Chelation of Iron and Zinc

PubMed Central

Klinger, M.; Hermann, B.; Sachse, S.; Nietzsche, S.; Makarewicz, O.; Keller, P. M.; Pfister, W.; Straube, E.

2012-01-01

Since cations have been reported as essential regulators of biofilm, we investigated the potential of the broad-spectrum antimicrobial and cation-chelator nitroxoline as an antibiofilm agent. Biofilm mass synthesis was reduced by up to 80% at sub-MIC nitroxoline concentrations in Pseudomonas aeruginosa, and structures formed were reticulate rather than compact. In preformed biofilms, viable cell counts were reduced by 4 logs at therapeutic concentrations. Complexation of iron and zinc was demonstrated to underlie nitroxoline's potent antibiofilm activity. PMID:22926564

Nanoprobing of the effect of Cu2+ cations on misfolding, interaction and aggregation of amyloid β peptide

PubMed Central

Lv, Zhengjian; Condron, Margaret M.; Teplow, David B.; Lyubchenko, Yuri L.

2012-01-01

Misfolding and aggregation of the amyloid β-protein (Aβ) are hallmarks of Alzheimer’s disease. Both processes are dependent on the environmental conditions, including the presence of divalent cations, such as Cu2+. Cu2+ cations regulate early stages of Aβ aggregation, but the molecular mechanism of Cu2+ regulation is unknown. In this study we applied single molecule AFM force spectroscopy to elucidate the role of Cu2+ cations on interpeptide interactions. By immobilizing one of two interacting Aβ42 molecules on a mica surface and tethering the counterpart molecule onto the tip, we were able to probe the interpeptide interactions in the presence and absence of Cu2+ cations at pH 7.4, 6.8, 6.0, 5.0, and 4.0. The results show that the presence of Cu2+ cations change the pattern of Aβ interactions for pH values between pH 7.4 and pH 5.0. Under these conditions, Cu2+ cations induce Aβ42 peptide structural changes resulting in N–termini interactions within the dimers. Cu2+ cations also stabilize the dimers. No effects of Cu2+ cations on Aβ–Aβ interactions were observed at pH 4.0, suggesting that peptide protonation changes the peptide-cation interaction. The effect of Cu2+ cations on later stages of Aβ aggregation was studied by AFM topographic images. The results demonstrate that substoichiometric Cu2+ cations accelerate the formation of fibrils at pH 7.4 and 5.0, whereas no effect of Cu2+ cations was observed at pH 4.0. Taken together, the combined AFM force spectroscopy and imaging analyses demonstrate that Cu2+ cations promote both the initial and the elongation stages of Aβ aggregation, but protein protonation diminishes the effect of Cu2+. PMID:23143330

Cytosolic calcium homeostasis in bovine parathyroid cells and its modulation by protein kinase C.

PubMed Central

Racke, F K; Nemeth, E F

1993-01-01

1. The effects of protein kinase C (PKC) activators and inhibitors on the mechanisms regulating cytosolic Ca2+ homeostasis in dissociated bovine parathyroid cells loaded with fura-2 were examined. 2. Stepwise increases in the concentration of extracellular Ca2+ (from 0.5 to 2 or 3 mM) elicited transient followed by sustained increases in the concentration of intracellular free Ca2+ ([Ca2+]i). Cytosolic Ca2+ transients reflected the mobilization of intracellular Ca2+ and influx of extracellular Ca2+ whereas sustained increases in [Ca2+]i resulted from the influx of extracellular Ca2+. Brief (1-2 min) pretreatment with phorbol myristate acetate (PMA) shifted the concentration-response curve for extracellular Ca(2+)-induced cytosolic Ca2+ transients to the right without affecting the maximal response. Cytosolic Ca2+ transients elicited by extracellular Mg2+ were similarly affected by PMA. 3. These effects of PMA were mimicked by various other activators of PKC with the rank order of potency PMA > phorbol dibutyrate > bryostatin , > (-)indolactam V > mezerein. Isomers or analogues of these compounds that do not alter PKC activity (4 alpha-phorbols and (+)indolactam V) did not alter [Ca2+]i. 4. PKC activators depressed evoked increases in [Ca2+]i when influx of extracellular Ca2+ was blocked with Gd3+. Cytosolic Ca2+ transients elicited by extracellular Mg2+ in the absence of extracellular Ca2+ were similarly inhibited by PKC activators. Activation of PKC thus inhibits the mobilization of intracellular Ca2+ elicited by extracellular divalent cations. 5. Increases in the concentration of extracellular Ca2+ caused corresponding increases in the formation of [3H]inositol 1,4,5-trisphosphate ([3H]InsP3). Pretreatment with PMA shifted the concentration-response curve for extracellular Ca(2+)-induced [3H]InsP3 formation to the right without affecting the maximal response. 6. PKC activators also caused some depression of steady-state increases in [Ca2+]i elicited by extracellular Ca2+. In contrast, PMA did not affect increases in [Ca2+]i elicited by ionomycin or thapsigargin. 7. Ba2+ was used to monitor divalent cation influx. PMA decreased the rate of rise of the fluorescent signal elicited by extracellular Ba2+. 8. All these effects of PKC activators on [Ca2+]i were blocked or reversed by staurosporine at concentrations (30-100 nM) that inhibited PKC activity in parathyroid cells. Staurosporine alone potentiated cytosolic Ca2+ responses evoked by submaximal concentrations of extracellular divalent cations. 9. PKC thus depresses both the mobilization of intracellular Ca2+ and the influx of extracellular Ca2+ in parathyroid cells. The effects on [Ca2+]i provide evidence for a Ca2+ receptor on the surface of parathyroid cells that uses transmembrane signalling mechanisms common to some other Ca(2+)-mobilizing receptors.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:8254504

Concentration of perrhenate and pertechnetate solutions

DOEpatents

Knapp, F.F.; Beets, A.L.; Mirzadeh, S.; Guhlke, S.

1998-03-17

A method is described for preparing a concentrated solution of a carrier-free radioisotope which includes the steps of: (a) providing a generator column loaded with a composition containing a parent radioisotope; (b) eluting the generator column with an eluent solution which includes a salt of a weak acid to elute a target daughter radioisotope from the generator column in a first eluate; (c) eluting a cation-exchange column with the first eluate to exchange cations of the salt for hydrogen ions and to elute the target daughter radioisotope and a weak acid in a second eluate; (d) eluting an anion-exchange column with the second eluate to trap and concentrate the target daughter radioisotope and to elute the weak acid solution therefrom; and (e) eluting the concentrated target daughter radioisotope from the anion-exchange column with a saline solution. 1 fig.

Concentration of perrhenate and pertechnetate solutions

DOEpatents

Knapp, Furn F.; Beets, Arnold L.; Mirzadeh, Saed; Guhlke, Stefan

1998-01-01

A method of preparing a concentrated solution of a carrier-free radioisotope which includes the steps of: a. providing a generator column loaded with a composition containing a parent radioisotope; b. eluting the generator column with an eluent solution which includes a salt of a weak acid to elute a target daughter radioisotope from the generator column in a first eluate. c. eluting a cation-exchange column with the first eluate to exchange cations of the salt for hydrogen ions and to elute the target daughter radioisotope and a weak acid in a second eluate; d. eluting an anion-exchange column with the second eluate to trap and concentrate the target daughter radioisotope and to elute the weak acid solution therefrom; and e. eluting the concentrated target daughter radioisotope from the anion-exchange column with a saline solution.

Optical, electrical, and photovoltaic properties of PbS thin films by anionic and cationic dopants

NASA Astrophysics Data System (ADS)

Cheraghizade, Mohsen; Jamali-Sheini, Farid; Yousefi, Ramin

2017-06-01

Lead sulfide (PbS) thin films were deposited by CVD method to examine the effects of anionic and cationic dopants on optical and electrical properties for photovoltaic applications. XRD diffractograms verified the formation of cubic phase of multicrystalline PbS thin films. FESEM images showed surface morphologies in nano-dimensions (rods and flowers). UV-Vis-NIR spectrum revealed absorbance in the visible and NIR regions for all samples, in which dopants decreased the intensity of absorbance. Se as an anionic dopant for PbS thin films increased electrical resistance, acceptor concentrations, and crystallite defects, and decreased flat-band voltage and depletion width. Finally, photovoltaic measurements indicated that Zn-doped PbS thin film, as a photovoltaic cell, exhibited higher conversion efficiency and external quantum efficiency (EQE).

Simulation of polyethylene glycol and calcium-mediated membrane fusion

NASA Astrophysics Data System (ADS)

Pannuzzo, Martina; De Jong, Djurre H.; Raudino, Antonio; Marrink, Siewert J.

2014-03-01

We report on the mechanism of membrane fusion mediated by polyethylene glycol (PEG) and Ca2+ by means of a coarse-grained molecular dynamics simulation approach. Our data provide a detailed view on the role of cations and polymer in modulating the interaction between negatively charged apposed membranes. The PEG chains cause a reduction of the inter-lamellar distance and cause an increase in concentration of divalent cations. When thermally driven fluctuations bring the membranes at close contact, a switch from cis to trans Ca2+-lipid complexes stabilizes a focal contact acting as a nucleation site for further expansion of the adhesion region. Flipping of lipid tails induces subsequent stalk formation. Together, our results provide a molecular explanation for the synergistic effect of Ca2+ and PEG on membrane fusion.

Divalent cation shrinks DNA but inhibits its compaction with trivalent cation.

PubMed

Tongu, Chika; Kenmotsu, Takahiro; Yoshikawa, Yuko; Zinchenko, Anatoly; Chen, Ning; Yoshikawa, Kenichi

2016-05-28

Our observation reveals the effects of divalent and trivalent cations on the higher-order structure of giant DNA (T4 DNA 166 kbp) by fluorescence microscopy. It was found that divalent cations, Mg(2+) and Ca(2+), inhibit DNA compaction induced by a trivalent cation, spermidine (SPD(3+)). On the other hand, in the absence of SPD(3+), divalent cations cause the shrinkage of DNA. As the control experiment, we have confirmed the minimum effect of monovalent cation, Na(+) on the DNA higher-order structure. We interpret the competition between 2+ and 3+ cations in terms of the change in the translational entropy of the counterions. For the compaction with SPD(3+), we consider the increase in translational entropy due to the ion-exchange of the intrinsic monovalent cations condensing on a highly charged polyelectrolyte, double-stranded DNA, by the 3+ cations. In contrast, the presence of 2+ cation decreases the gain of entropy contribution by the ion-exchange between monovalent and 3+ ions.

Cubic phase stabilization in nanoparticles of hafnia-zirconia oxides: Particle-size and annealing environment effects

NASA Astrophysics Data System (ADS)

Lu, Chih-Hsin; Raitano, Joan M.; Khalid, Syed; Zhang, Lihua; Chan, Siu-Wai

2008-06-01

Amorphous hafnia (HfO2-y), zirconia (ZrO2-y), and hafnia-zirconia (xHfO2-y-(1-x)(ZrO2-y)) nanoparticles were prepared by combining aqueous solutions of hexamethylenetetramine (HMT) with hafnium dichloride oxide (HfOCl2ṡ8H2O), zirconium dichloride oxide (ZrOCl2ṡ8H2O), or a mixture of these two salts at room temperature. For pure hafnia, transmission electron microscopy showed that the lower cation concentration (0.01M) resulted in the precipitation of smaller amorphous nanoparticles relative to higher concentrations (0.015M-0.04M). Consequently, the lower concentration preparation route coupled with a reducing environment (H2:N2=9:91) during annealing at temperatures between 650 and 850°C allowed for nanoparticles with a cubic structure to be prepared as determined by x-ray diffraction. The structurally cubic hafnia nanoparticles were 6nm or less in diameter and equiaxed. Using the same method (0.01M total metal cation concentration and reducing environment during annealing), nanoparticles of cubic structure were prepared across the entire hafnia-zirconia compositional spectrum, with a critical particle size for the cubic structure of about 6nm. Nanoparticles of tetragonal and monoclinic structure were prepared by increasing the annealing temperature and/or using a less reducing environment. The unique role of HMT in sample preparation is discussed as well.

Analysis of amphetamine and methamphetamine in municipal wastewater influent and effluent using weak cation-exchange SPE and LC-MS/MS.

PubMed

Boles, Tammy H; Wells, Martha J M

2016-12-01

Amphetamine and methamphetamine are emerging contaminants-those for which no regulations currently require monitoring or public reporting of their presence in our water supply. In this research, a protocol for weak cation-exchange (WCX) SPE coupled with LC-MS/MS was developed for determination of emerging contaminants amphetamine and methamphetamine in a complex wastewater matrix. Gradient LC parameters were adjusted to yield baseline separation of methamphetamine from other contaminants. Methamphetamine-D5 was used as the internal standard (IS) to compensate for sample loss during SPE and for signal loss during MS (matrix effects). Recoveries were 102.1 ± 7.9% and 99.4 ± 4.0% for amphetamine and methamphetamine, respectively, using WCX sorbent. Notably, methamphetamine was determined to be present in wastewater influent at each sampling date tested. Amphetamine was present in wastewater influent on two of four sampling dates. Amphetamine concentrations ranged from undetectable to 86.4 ng/L in influent, but it was undetectable in wastewater effluent. Methamphetamine was detected in influent at concentrations ranging from 27.0-60.3 ng/L. Methamphetamine concentration was reduced but incompletely removed at this facility. Although absent in one post-UV effluent sample, concentrations of methamphetamine ranged from 10.8-14.8 ng/L. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly efficient removal of heavy metals by polymer-supported nanosized hydrated Fe(III) oxides: behavior and XPS study.

PubMed

Pan, Bingjun; Qiu, Hui; Pan, Bingcai; Nie, Guangze; Xiao, Lili; Lv, Lu; Zhang, Weiming; Zhang, Quanxing; Zheng, Shourong

2010-02-01

The present study developed a polymer-based hybrid sorbent (HFO-001) for highly efficient removal of heavy metals [e.g., Pb(II), Cd(II), and Cu(II)] by irreversibly impregnating hydrated Fe(III) oxide (HFO) nanoparticles within a cation-exchange resin D-001 (R-SO(3)Na), and revealed the underlying mechanism based on X-ray photoelectron spectroscopy (XPS) study. HFO-001 combines the excellent handling, flow characteristics, and attrition resistance of conventional cation-exchange resins with the specific affinity of HFOs toward heavy metal cations. As compared to D-001, sorption selectivity of HFO-001 toward Pb(II), Cu(II), and Cd(II) was greatly improved from the Ca(II) competition at greater concentration. Column sorption results indicated that the working capacity of HFO-001 was about 4-6 times more than D-001 with respect to removal of three heavy metals from simulated electroplating water (pH approximately 4.0). Also, HFO-001 is particularly effective in removing trace Pb(II) and Cd(II) from simulated natural waters to meet the drinking water standard, with treatment volume orders of magnitude higher than D-001. The superior performance of HFO-001 was attributed to the Donnan membrane effect exerted by the host D-001 as well as to the impregnated HFO nanoparticles of specific interaction toward heavy metal cations, as further confirmed by XPS study on lead sorption. More attractively, the exhausted HFO-001 beads can be effectively regenerated by HCl-NaCl solution (pH 3) for repeated use without any significant capacity loss. (c) 2009 Elsevier Ltd. All rights reserved.

A comparative study of a preservative-free latanoprost cationic emulsion (Catioprost) and a BAK-preserved latanoprost solution in animal models.

PubMed

Daull, Philippe; Buggage, Ronald; Lambert, Grégory; Faure, Marie-Odile; Serle, Janet; Wang, Rong-Fang; Garrigue, Jean-Sébastien

2012-10-01

Benzalkonium chloride (BAK), a common preservative in eye drops, can induce ocular surface toxicity that may decrease glaucoma therapy compliance. The ocular hypotensive effect, pharmacokinetic (PK) profiles, and local tolerance of a preservative-free latanoprost 0.005% cationic emulsion (Catioprost(®)), and a BAK-preserved latanoprost 0.005% solution (Xalatan(®)), were compared. The ocular hypotensive effect was evaluated in monkeys with elevated intraocular pressure (IOP) induced by laser photocoagulation of the trabecular meshwork. Each monkey (n=8) received both latanoprost formulations once daily for 5 consecutive treatment days in a crossover design with at least a 2-week washout period between treatments. IOP was measured at baseline (on day 1, no instillation), on vehicle treatment day (day 0), and on treatment days 1, 3, and 5 before drug instillation and then hourly for 6 h. In rabbits, the ocular and systemic concentrations of latanoprost free acid were determined following a single instillation and the local tolerance of twice daily instillations over 28 days was assessed. Both the preservative-free and BAK-preserved latanoprost formulations shared the same efficacy profile with the maximum IOP reduction occurring 2 h after each morning dose (-15%, -20%, and -26%; -15%, -23%, and -23% on days 1, 3, and 5, respectively) and lasting through 24 h. The equivalence in efficacy was confirmed by the PK data demonstrating similar area under the curves (AUCs). While both formulations were well tolerated, the incidence of conjunctival hyperemia was reduced by 42% with the BAK-free latanoprost cationic emulsion. In animal models, a preservative-free latanoprost cationic emulsion was as effective as Xalatan(®) for lowering IOP with an improved ocular tolerance profile.

The exchangeable fraction of selectively sorbed 137Cs in soils and natural sorbents as a function of the K+ and NH{4/+} concentrations

NASA Astrophysics Data System (ADS)

Stepina, I. A.; Popov, V. E.

2011-06-01

The exchangeable portion of the selectively sorbed 137Cs extractable by a 1 M ammonium acetate solution (α Ex ) for soils, illite, bentonite, and tripolite was found to increase with the increasing concentration of the competitive cation M+ (K+ or NH{4/+}) and can be approximated by a logarithmic relationship. For clinoptilolite, the values of α Ex did not depend on the concentration of M+. The expression 1 - α Ex ( C M= n )/α Ex ( C M = 16) as a function of the M+ concentration (where α Ex ( C M= n ) is the α Ex value at the competitive cation concentration equal to 16 mmol/dm3) was proposed to compare the dependence of α Ex on the concentration of K+ or NH{4/+}in different sorbents. For soils and illite, these dependences almost coincided, which indicated that the selective sorption of 137Cs in soils is determined by the presence of illite-group minerals.

Hereditary stomatocytosis: association of low 2,3-diphosphoglycerate with increased cation pumping by the red cell.

PubMed

Wiley, J S; Cooper, R A; Adachi, K; Asakura, T

1979-01-01

The levels of glycolytic intermediates have been measured in red cells from patients with both overhydrated and dehydrated varieties of the hereditary stomatocytosis syndrome. Red cell 2,3-diphosphoglycerate was reduced by 33% below normal in all patients with either stomatocyte or target cell morphologies (i.e. over or under hydrated varieties respectively). The relative decrement in 2,3-diphosphoglycerate was even greater when abnormal cells were compared with control cells with similar reticulocytosis. Red cell ADP concentrations in stomatocytosis were significantly increased above normal but ATP concentrations were not significantly changed. Whole blood oxygen affinity in stomatocytosis was increased in proportion to the lowered content of diphosphoglycerate. Some new parameters of membrane transport in hereditary stomatocytosis have been measured. Platelet K+ and Na+ concentrations and platelet K+ permeability were normal in stomatocytosis. The number of 3H-uridine transport sites in stomatocytes were increased by 9-39% above normal and this increment was the same as the increment in red cell lipids (0-38%). Hereditary stomatocytes contain 2-10-fold more cation pumps than normal and the increased active cation pumping may explain the high ADP, the low 2,3-diphosphoglycerate concentration and the increased oxygen affinity in this syndrome.

Effects of dietary cation-anion difference on intake, milk yield, and blood components of the early lactation cow.

PubMed

Chan, P S; West, J W; Bernard, J K; Fernandez, J M

2005-12-01

Early lactation Holsteins cows (15 primiparous and 18 multiparous) were offered rations with dietary cation-anion difference, calculated as mEq (Na + K - Cl - S)/100 g of feed dry matter (DCAD:S), of 20, 35, or 50 mEq from d 0 (calving) to 42 d postpartum (August 20, 2000 to January 9, 2001) to determine the effects of increasing DCAD:S on dry matter intake (DMI), milk yield, and blood metabolites. For DCAD:S of 20, 35, and 50, DMI was 3.30, 3.38, 2.96 kg/100 kg of body weight (BW); milk yield was 25.5, 24.2, and 22.4 kg/d, respectively. No differences were observed for concentration or yield of milk fat or milk protein. Serum Ca, P, Mg, Na, K, Cl, cation-anion difference, insulin, and glucose did not differ with DCAD. Serum HCO3- was 26.07, 25.88, and 27.64 mEq/L for 20, 35, and 50 DCAD:S. Serum Ca, Mg, Na, and K concentrations were greater for primiparous cows (9.52 mg/dL, 2.35 mg/dL, 140.03 mEq/L, 4.66 mEq/L, respectively) than for multiparous cows (9.27 mg/dL, 2.12 mg/dL, 137.63 mEq/L, 4.46 mEq/ L, respectively). A DCAD:S between 23 and 33 mEq/100 g of dry matter (DM) appears to be adequate during cool weather for the milk yield that occurred in the present study based on DMI (kg/100 kg of BW), whereas DCAD:S of 50 mEq/100 g of DM may be excessive and could be too alkaline or unpalatable, resulting in decreased DMI (kg/100 kg of BW).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perriot, Romain; Uberuaga, Blas P.

We use molecular dynamics simulations to investigate the role of cation disorder on oxygen diffusion in Gd 2Zr 2O 7 (GZO) and Gd 2Ti 2O 7 (GTO) pyrochlores, a class of complex oxides which contain a structural vacancy relative to the basic fluorite structure. The introduction of disorder has distinct effects depending on the chemistry of the material, increasing the mobility of structural carriers by up to four orders of magnitude in GZO. In contrast, in GTO, there is no mobility at zero or low disorder on the ns timescale, but higher disorder liberates the otherwise immobile carriers, allowing diffusionmore » with rates comparable to GZO for the fully disordered material. Here, we show that the cation disorder enhances the diffusivity by both increasing the concentration of mobile structural carriers and their individual mobility. The disorder also influences the diffusion in materials containing intrinsic carriers, such as additional vacancies VO or oxygen interstitials OI. And while in ordered GZO and GTO the contribution of the intrinsic carriers dominates the overall diffusion of oxygen, OI in GZO contributes along with structural carriers, and the total diffusion rate can be calculated by assuming simple additive contributions from the two sources. Although the disorder in the materials with intrinsic defects usually enhances the diffusivity as in the defect-free case, in low concentrations, cation antisites AB or BA, where A = Gd and B = Zr or Ti, can act as traps for fast intrinsic defects. The trapping results in a lowering of the diffusivity, and causes a non-monotonic behavior of the diffusivity with disorder. Conversely, in the case of slow intrinsic defects, the main effect of the disorder is to liberate the structural carriers, resulting in an increase of the diffusivity regardless of the defect trapping.« less

Formulation studies on ibuprofen sodium-cationic dextran conjugate: effect on tableting and dissolution characteristics of ibuprofen.

PubMed

Abioye, Amos Olusegun; Kola-Mustapha, Adeola

2016-01-01

The effect of electrostatic interaction between ibuprofen sodium (IbS) and cationic diethylaminoethyl dextran (Ddex), on the tableting properties and ibuprofen release from the conjugate tablet was investigated. Ibuprofen exhibits poor flow, compaction (tableting) and dissolution behavior due to its hydrophobic structure, high cohesive, adhesive and viscoelastic properties therefore it was granulated with cationic Ddex to improve its compression and dissolution characteristics. Electrostatic interaction and hydrogen bonding between IbS and Ddex was confirmed with FT-IR and DSC results showed a stepwise endothermic solid-solid structural transformation from racemic to anhydrous forms between 120 and 175 °C which melted into liquid form at 208.15 °C. The broad and diffused DSC peaks of the conjugate granules as well as the disappearance of ibuprofen melting peak provided evidence for their highly amorphous state. It was evident that Ddex improved the flowability and densification of the granules and increased the mechanical and tensile strengths of the resulting tablets as the tensile strength increased from 0.67 ± 0.0172 to 1.90 ± 0.0038 MPa with increasing Ddex concentration. Both tapping and compression processes showed that the most prominent mechanism of densification were particle slippage, rearrangement and plastic deformation while fragmentation was minimized. Ddex retarded the extent of dissolution in general, indicating potentials for controlled release formulations. Multiple release mechanisms including diffusion; anomalous transport and super case II transport were noted. It was concluded that interaction between ibuprofen sodium and Ddex produced a novel formulation with improved flowability, tableting and dissolution characteristics with potential controlled drug release characteristics dictated by Ddex concentration.

Effects on the accumulation of calcium, magnesium, iron, manganese, copper and zinc of adding the two inorganic forms of selenium to solution cultures of Zea mays.

PubMed

Longchamp, M; Angeli, N; Castrec-Rouelle, M

2016-01-01

The addition of selenate or selenite to common fertilizers for crop production could be an effective way of producing selenium-rich food and feed. However, this would be feasible only if the increase in plant selenium (Se) content did not negatively influence the uptake of other essential elements. We therefore need to understand the interactions between Se and other major and trace elements during uptake by the plant. This study aimed to evaluate the influence of inorganic forms of Se on the accumulation of selected macronutrients (Ca and Mg) and micronutrients (Fe, Zn, Mn and Cu). Those essential elements are involved in the oxidative balance of cells. Zea mays seedlings were grown hydroponically in growth chambers in nutrient solutions to which we added 10, 50 or 1000 μg.L(-1) of selenate and/or selenite. Cation accumulation was significantly affected by the addition of 50 μg.L(-1) or 1000 μg.L(-1) Se, but not by the presence of 10 μg.L(-1) of Se in the nutrient solution. The highest concentration (1000 μg.L(-1)) of Se in the nutrient solution affected the accumulation of essential cations in Zea mays: selenate tended to increase the accumulation of Mg, Zn and Mn, whereas a selenate/selenite mixture tended to decrease the accumulation of Ca, Mg, Zn and Mn. Only Fe accumulation was unaffected by Se whatever its form or concentration. Selenium may also affect the distribution of cations on Zea mays. For example, levels of Mg and Zn translocation to the shoots were lower in the presence of selenite. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Remediating munitions-contaminated soil with zerovalent iron and cationic surfactants.

PubMed

Park, J; Comfort, S D; Shea, P J; Machacek, T A

2004-01-01

Soils contaminated from military operations often contain mixtures of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), and TNT (2,4,6-trinitrotoluene) rather than a single explosive. Differences among explosives in solubility and reactivity make developing a single remediation treatment difficult. When Fe(0) was used to treat a munitions-contaminated soil, we observed high rates of destruction for RDX and TNT (98%) but not HMX. Our objective was to determine if HMX destruction by Fe(0) could be enhanced by increasing HMX solubility by physical (temperature) or chemical (surfactants) means. To determine electron acceptor preference, we treated RDX and HMX with Fe(0) in homogeneous solutions and binary mixtures. Increasing aqueous temperature (20 to 55 degrees C) increased HMX solubility (2 to 22 mg L(-1)) but did not increase destruction by Fe(0) in a contaminated soil slurry that also contained RDX and TNT. Batch experiments using equal molar concentrations of RDX and HMX demonstrated that RDX was preferentially reduced over HMX by Fe(0). By testing various surfactants, we found that the cationic surfactants (HDTMA [hexadecyltrimethylammonium bromide], didecyl, and didodecyl) were most effective in increasing HMX concentration in solution. Didecyl and HDTMA were also found to be highly effective in facilitating the transformation of HMX by Fe(0). Using HDTMA or didecyl solutions (3%, w/v) containing solid-phase HMX, we observed that 100% of the added HMX was transformed by Fe(0) in the didecyl matrix and 60% in the HDTMA matrix. These results indicate that cationic surfactants can increase HMX solubility and facilitate Fe(0)-mediated transformation kinetics but HMX destruction rates will be slowed when RDX is present.

Monitoring of photoluminescence decay by alkali and alkaline earth metal cations using a photoluminescent bolaamphiphile self-assembly as an optical probe.

PubMed

Kim, Sunhyung; Kwak, Jinyoung; Lee, Sang-Yup

2014-05-01

Photoluminescence (PL) decay induced by the displacement of an ionic fluorescence component, Tb(3+), with alkali and alkaline earth metal cations was investigated using photoluminescent spherical self-assemblies as optical probes. The photoluminescent spherical self-assembly was prepared by the self-organization of a tyrosine-containing bolaamphiphile molecule with a photosensitizer and Tb(3+) ion. The lanthanide ion, Tb(3+), electrically bound to the carboxyl group of the bolaamphiphile molecule, was displaced by alkali and alkaline earth metal cations that had stronger electrophilicity. The PL of the self-assembly decayed remarkably due to the substitution of lanthanide ions with alkali and alkaline earth metal cations. The PL decay showed a positive correlation with cation concentration and was sensitive to the cation valency. Generally, the PL decay was enhanced by the electrophilicity of the cations. However, Ca(2+) showed greater PL decay than Mg(2+) because Ca(2+) could create various complexes with the carboxyl groups of the bolaamphiphile molecule. Microscopic and spectroscopic investigations were conducted to study the photon energy transfer and displacement of Tb(3+) by the cation exchange. This study demonstrated that the PL decay by the displacement of the ionic fluorescent compound was applied to the detection of various cations in aqueous media and is applicable to the development of future optical sensors. Copyright © 2014 Elsevier B.V. All rights reserved.

Impact of cationic substances on biofilm formation from sieved fine particles of anaerobic granular sludge at high salinity.

PubMed

Kobayashi, Takuro; Hu, Yong; Xu, Kai-Qin

2018-06-01

This study investigated early stages of biofilm formation from sieved fine particles of anaerobic granules in the presence of various cationic substances using a quartz crystal sensor to improve biofilm formation in the anaerobic treatment of saline wastewater. The biomass attached on the sensor was greatly increased with Ca within the low range (8-16 mM), which was not affected by 50 mM of Na. However, the positive effect of 16 mM of Ca was strongly reduced in the co-presence of Ca and Na when Na concentrations were in the range from 25 to 150 mM because Ca may compete with Na for the limited binding sites in biofilm. The addition of cationic polymer at 150 mM of Na increased biomass adhesion by several folds at only 10-80 mg/L compared to the addition of 16 mM of Ca. Moreover, no methanogenic inhibition was presented below the polymer content of 20 mg/L. Copyright © 2018 Elsevier Ltd. All rights reserved.

Calcium and zinc differentially affect the structure of lipid membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kučerka, Norbert; Dushanov, Ermuhammad; Kholmurodov, Kholmirzo T.

Interactions of calcium (Ca 2+) and zinc (Zn 2+) cations with biomimetic membranes made of dipalmitoylphosphatidylcholine (DPPC) were studied by small angle neutron diffraction (SAND). Experiments show that the structure of these lipid bilayers is differentially affected by the two divalent cations. Initially, both Ca 2+ and Zn 2+ cause DPPC bilayers to thicken, while further increases in Ca 2+ concentration result in the bilayer thinning, eventually reverting to having the same thickness as pure DPPC. The binding of Zn 2+, on the other hand, causes the bilayers to swell to a maximum thickness, and the addition of more Znmore » 2+ does not result in a further thickening of the membrane. Agreement between our results obtained using oriented planar membranes and those from vesicular samples implies that the effect of cations on bilayer thickness is the result of electrostatic interactions, rather than geometrical constraints due to bilayer curvature. This notion is further reinforced by MD simulations. Lastly, the radial distribution functions reveal a strong interaction between Ca 2+ and the phosphate oxygens, while Zn 2+ shows a much weaker binding specificity.« less

Effect of cation structure on the oxygen solubility and diffusivity in a range of bis{(trifluoromethyl)sulfonyl}imide anion based ionic liquids for lithium-air battery electrolytes.

PubMed

Neale, Alex R; Li, Peilin; Jacquemin, Johan; Goodrich, Peter; Ball, Sarah C; Compton, Richard G; Hardacre, Christopher

2016-04-28

This paper reports on the solubility and diffusivity of dissolved oxygen in a series of ionic liquids (ILs) based on the bis{(trifluoromethyl)sulfonyl}imide anion with a range of related alkyl and ether functionalised cyclic alkylammonium cations. Cyclic voltammetry has been used to observe the reduction of oxygen in ILs at a microdisk electrode and chronoamperometric measurements have then been applied to simultaneously determine both the concentration and the diffusion coefficient of oxygen in different ILs. The viscosity of the ILs and the calculated molar volume and free volume are also reported. It is found that, within this class of ILs, the oxygen diffusivity generally increases with decreasing viscosity of the neat IL. An inverse relationship between oxygen solubility and IL free volume is reported for the two IL families implying that oxygen is not simply occupying the available empty space. In addition, it is reported that the introduction of an ether-group into the IL cation structure promotes the diffusivity of dissolved oxygen but reduces the solubility of the gas.

Calcium and zinc differentially affect the structure of lipid membranes

DOE PAGES

Kučerka, Norbert; Dushanov, Ermuhammad; Kholmurodov, Kholmirzo T.; ...

2017-03-09

Interactions of calcium (Ca 2+) and zinc (Zn 2+) cations with biomimetic membranes made of dipalmitoylphosphatidylcholine (DPPC) were studied by small angle neutron diffraction (SAND). Experiments show that the structure of these lipid bilayers is differentially affected by the two divalent cations. Initially, both Ca 2+ and Zn 2+ cause DPPC bilayers to thicken, while further increases in Ca 2+ concentration result in the bilayer thinning, eventually reverting to having the same thickness as pure DPPC. The binding of Zn 2+, on the other hand, causes the bilayers to swell to a maximum thickness, and the addition of more Znmore » 2+ does not result in a further thickening of the membrane. Agreement between our results obtained using oriented planar membranes and those from vesicular samples implies that the effect of cations on bilayer thickness is the result of electrostatic interactions, rather than geometrical constraints due to bilayer curvature. This notion is further reinforced by MD simulations. Lastly, the radial distribution functions reveal a strong interaction between Ca 2+ and the phosphate oxygens, while Zn 2+ shows a much weaker binding specificity.« less

Halloysite nanotubule clay for efficient water purification.

PubMed

Zhao, Yafei; Abdullayev, Elshad; Vasiliev, Alexandre; Lvov, Yuri

2013-09-15

Halloysite clay has chemical structure similar to kaolinite but it is rolled in tubes with diameter of 50 nm and length of ca. 1000 nm. Halloysite exhibits higher adsorption capacity for both cationic and anionic dyes because it has negative SiO2 outermost and positive Al2O3 inner lumen surface; therefore, these clay nanotubes have efficient bivalent adsorbancy. An adsorption study using cationic Rhodamine 6G and anionic Chrome azurol S has shown approximately two times better dye removal for halloysite as compared to kaolin. Halloysite filters have been effectively regenerated up to 50 times by burning the adsorbed dyes. Overall removal efficiency of anionic Chrome azurol S exceeded 99.9% for 5th regeneration cycle of halloysite. Chrome azurol S adsorption capacity decreases with the increase of ionic strength, temperature and pH. For cationic Rhodamine 6G, higher ionic strength, temperature and initial solution concentration were favorable to enhanced adsorption with optimal pH 8. The equilibrium adsorption data were described by Langmuir and Freundlich isotherms. Copyright © 2013 Elsevier Inc. All rights reserved.

Selective monovalent cation association and exchange around Keplerate polyoxometalate macroanions in dilute aqueous solutions.

PubMed

Pigga, Joseph M; Teprovich, Joseph A; Flowers, Robert A; Antonio, Mark R; Liu, Tianbo

2010-06-15

The interaction between water-soluble Keplerate polyoxometalate {Mo(72)Fe(30)} macroions and small countercations is explored by laser light scattering, anomalous small-angle X-ray scattering (ASAXS), and isothermal titration calorimetry (ITC) techniques. The macroions are found to be able to select the type of associated counterions based upon the counterions' valence state and hydrated size, when multiple types of additional cations are present in solution (even among different monovalent cations). The preference goes to the cations with higher valences or smaller hydrated sizes if the valences are identical. This counterion exchange process changes the magnitude of the macroion-counterion interaction and, thus, is reflected in the dimension of the self-assembled {Mo(72)Fe(30)} blackberry supramolecular structures. The hydrophilic macroions exhibit a competitive recognition of various monovalent counterions in dilute solutions. A critical salt concentration (CSC) for each type of cation exists for the blackberry formation of {Mo(72)Fe(30)} macroions, above which the blackberry size increases significantly with the increasing total ionic strength in solution. The CSC values are much smaller for cations with higher valences and also decrease with the cations' hydrated size for various monovalent cations. The change of blackberry size corresponding to the change of ionic strength in solution is reversible.

Cation Uptake and Allocation by Red Pine Seedlings under Cation-Nutrient Stress in a Column Growth Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Zhenqing; Balogh-Brunstad, Zsuzsanna; Grant, Michael R.

Background and Aims Plant nutrient uptake is affected by environmental stress, but how plants respond to cation-nutrient stress is poorly understood. We assessed the impact of varying degrees of cation-nutrient limitation on cation uptake in an experimental plant-mineral system. Methods Column experiments, with red pine (Pinus resinosa Ait.) seedlings growing in sand/mineral mixtures, were conducted for up to nine months under a range of Ca- and K-limited conditions. The Ca and K were supplied from both minerals and nutrient solutions with varying Ca and K concentrations. Results Cation nutrient stress had little impact on carbon allocation after nine months ofmore » plant growth and K was the limiting nutrient for biomass production. The Ca/Sr and K/Rb ratio results allowed independent estimation of dissolution incongruency and discrimination against Sr and Rb during cation uptake processes. The fraction of K in biomass from biotite increased with decreasing K supply from nutrient solutions. The mineral anorthite was consistently the major source of Ca, regardless of nutrient treatment. Conclusions Red pine seedlings exploited more mineral K in response to more severe K deficiency. This did not occur for Ca. Plant discrimination factors must be carefully considered to accurately identify nutrient sources using cation tracers.« less

Ion aggregation in high salt solutions. VII. The effect of cations on the structures of ion aggregates and water hydrogen-bonding network

NASA Astrophysics Data System (ADS)

Choi, Jun-Ho; Choi, Hyung Ran; Jeon, Jonggu; Cho, Minhaeng

2017-10-01

Ions in high salt solutions have a strong propensity to form polydisperse ion aggregates with broad size and shape distributions. In a series of previous comparative investigations using femtosecond IR pump-probe spectroscopy, molecular dynamics simulation, and graph theoretical analysis, we have shown that there exists a morphological difference in the structures of ion aggregates formed in various salt solutions. As salt concentration increases, the ions in high salt solutions form either cluster-like structures excluding water molecules or network-like structures entwined with water hydrogen-bonding networks. Interestingly, such morphological characteristics of the ion aggregates have been found to be in correlation with the solubility limits of salts. An important question that still remains unexplored is why certain salts with different cations have notably different solubility limits in water. Here, carrying out a series of molecular dynamics simulations of aqueous salt solutions and analyzing the distributions and connectivity patterns of ion aggregates with a spectral graph analysis method, we establish the relationship between the salt solubility and the ion aggregate morphology with a special emphasis on the cationic effects on water structures and ion aggregation. We anticipate that the understanding of large scale ion aggregate structures revealed in this study will be critical for elucidating the specific ion effects on the solubility and conformational stability of co-solute molecules such as proteins in water.

Enhancing tonoplast Cd/H antiport activity increases Cd, Zn, and Mn tolerance, and impacts root/shoot Cd partitioning in Nicotiana tabacum L.

USDA-ARS?s Scientific Manuscript database

Sequestration mechanisms that prevent high concentrations of free metal ions from persisting in metabolically active compartments of cells are thought to be central in tolerance of plants to high levels of divalent cation metals. Expression of "AtCAX2" or "AtCAX4", which encode divalent cation/proto...

Soil chemistry in lithologically diverse datasets: the quartz dilution effect

USGS Publications Warehouse

Bern, Carleton R.

2009-01-01

National- and continental-scale soil geochemical datasets are likely to move our understanding of broad soil geochemistry patterns forward significantly. Patterns of chemistry and mineralogy delineated from these datasets are strongly influenced by the composition of the soil parent material, which itself is largely a function of lithology and particle size sorting. Such controls present a challenge by obscuring subtler patterns arising from subsequent pedogenic processes. Here the effect of quartz concentration is examined in moist-climate soils from a pilot dataset of the North American Soil Geochemical Landscapes Project. Due to variable and high quartz contents (6.2–81.7 wt.%), and its residual and inert nature in soil, quartz is demonstrated to influence broad patterns in soil chemistry. A dilution effect is observed whereby concentrations of various elements are significantly and strongly negatively correlated with quartz. Quartz content drives artificial positive correlations between concentrations of some elements and obscures negative correlations between others. Unadjusted soil data show the highly mobile base cations Ca, Mg, and Na to be often strongly positively correlated with intermediately mobile Al or Fe, and generally uncorrelated with the relatively immobile high-field-strength elements (HFS) Ti and Nb. Both patterns are contrary to broad expectations for soils being weathered and leached. After transforming bulk soil chemistry to a quartz-free basis, the base cations are generally uncorrelated with Al and Fe, and negative correlations generally emerge with the HFS elements. Quartz-free element data may be a useful tool for elucidating patterns of weathering or parent-material chemistry in large soil datasets.

Influence of PCR reagents on DNA polymerase extension rates measured on real-time PCR instruments.

PubMed

Montgomery, Jesse L; Wittwer, Carl T

2014-02-01

Radioactive DNA polymerase activity methods are cumbersome and do not provide initial extension rates. A simple extension rate assay would enable study of basic assumptions about PCR and define the limits of rapid PCR. A continuous assay that monitors DNA polymerase extension using noncovalent DNA dyes on common real-time PCR instruments was developed. Extension rates were measured in nucleotides per second per molecule of polymerase. To initiate the reaction, a nucleotide analog was heat activated at 95 °C for 5 min, the temperature decreased to 75 °C, and fluorescence monitored until substrate exhaustion in 30-90 min. The assay was linear with time for over 40% of the reaction and for polymerase concentrations over a 100-fold range (1-100 pmol/L). Extension rates decreased continuously with increasing monovalent cation concentrations (lithium, sodium, potassium, cesium, and ammonium). Melting-temperature depressors had variable effects. DMSO increased rates up to 33%, whereas glycerol had little effect. Betaine, formamide, and 1,2-propanediol decreased rates with increasing concentrations. Four common noncovalent DNA dyes inhibited polymerase extension. Heat-activated nucleotide analogs were 92% activated after 5 min, and hot start DNA polymerases were 73%-90% activated after 20 min. Simple DNA extension rate assays can be performed on real-time PCR instruments. Activity is decreased by monovalent cations, DNA dyes, and most melting temperature depressors. Rational inclusion of PCR components on the basis of their effects on polymerase extension is likely to be useful in PCR, particularly rapid-cycle or fast PCR.

Experimental characterization and modelization of ion exchange kinetics for a carboxylic resin in infinite solution volume conditions. Application to monovalent-trivalent cations exchange.

PubMed

Picart, Sébastien; Ramière, Isabelle; Mokhtari, Hamid; Jobelin, Isabelle

2010-09-02

This study is devoted to the characterization of ion exchange inside a microsphere of carboxylic resin. It aims at describing the kinetics of this exchange reaction which is known to be controlled by interdiffusion in the particle. The fractional attainment of equilibrium function of time depends on the concentration of the cations in the resin which can be modelized by the Nernst-Planck equation. A powerful approach for the numerical resolution of this equation is introduced in this paper. This modeling is based on the work of Helfferich but involves an implicit numerical scheme which reduces the computational cost. Knowing the diffusion coefficients of the cations in the resin and the radius of the spherical exchanger, the kinetics can be hence completely determined. When those diffusion parameters are missing, they can be deduced by fitting experimental data of fractional attainment of equilibrium. An efficient optimization tool coupled with the implicit resolution has been developed for this purpose. A monovalent/trivalent cation exchange had been experimentally characterized for a carboxylic resin. Diffusion coefficients and concentration profiles in the resin were then deduced through this new model.

Organic molecules as sorbing tracers for the assessment of surface areas in consolidated aquifer systems

NASA Astrophysics Data System (ADS)

Schaffer, Mario; Warner, Wiebke; Kutzner, Susann; Börnick, Hilmar; Worch, Eckhard; Licha, Tobias

2017-03-01

Based on the assumption that the specific surface area to volume ratio Asurf/V of consolidated rock materials is proportional to the surface area available for sorption, several inorganic cations were recently proposed as sorbing (cation exchanging) tracers for estimating these ratios in aquifers (e.g., for deriving the efficient heat exchange area of geothermal reservoirs). The main disadvantages of inorganic ions, however, are the limited number of suitable ions, their potential geogenic background, and their challenging online detection at trace concentrations. In this work, the spectrum of chemical substances used as sorbing tracers expands by considering fluorescent organic compounds that are cationic. They have the advantage of being highly water soluble and easy to measure online at very low concentrations. Results from systematic lab column experiments with seven selected organic cations under various conditions (different salinities and temperatures) are presented, emphasizing the potential of organic molecules as alternative sorbing tracers especially in consolidated aquifer systems. This work is a first stepping stone in identifying suitable molecular structures that can be selected or even individually adapted to the requirements of the tracer tests and prevailing aquifer conditions.

Effect of polymers in solution culture on growth and mineral composition of tomatoes. [Lycopersicon esculentum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wallace, A.

Tomato (Lycopersicon esculentum Mill. cv. Tropic) plants were grown for 26 days from transplanting in full nutrient solution with and without polymers in nutrient solution at two different pH values. An aninoic polyacrylamide and a polysaccharide (from guar bean) each at 100 mg L/sup -1/ in solution slightly improved yields at both pH values. A cationic polymer at the same concentration decreased yields. There were no apparent nutritional reasons for the effects. 1 table.

Biphasic interactions between a cationic dendrimer and actin.

PubMed

Ruenraroengsak, Pakatip; Florence, Alexander T

2010-12-01

Gene delivery systems face the problem not only of the route toward the cell and tissues in question, but also of the molecularly crowded environment of both the cytoplasm and the nucleus itself. One of the physical barriers in the cytoplasm for diffusing nanoparticles is an actin network. Here, we describe the finding that a self-fluorescent sixth generation cationic dendrimer (6 nm in diameter) interacts reversibly and possibly electrostatically with actin filaments in vitro. Not only does this interaction slow the diffusion of the dendrimer but it also affects actin polymerization in a biphasic manner. At low concentrations the dendrimer behaves like a G-binding actin protein, retarding actin polymerization, whereas at high concentrations the dendrimer acts as a nucleating protein accelerating the polymerization. Thus in vivo the diffusion of a dendrimer carrier such as this has both physical and chemical elements: by decreasing polymerization it might accelerate its own transport, and by enhancing actin polymerization retard it. This finding suggests that such a dendrimer may have a role as an anticancer agent through its inhibitory effect on actin polymerization.

Fast and efficient mesoporous adsorbents for the separation of toxic compounds from aqueous media.

PubMed

Anbia, Mansoor; Mohammadi, Nourali; Mohammadi, Kaveh

2010-04-15

The effect of cationic template on the adsorption of chromium (VI), furfural and copperphthalocyanine-3,4',4'',4'''-tetrasulfonic acid tetrasodium salt (CuPc) in MCM-41 and MCM-48 mesoporous materials was investigated in this work. We used cetyltrimethylammonium bromide (CTAB) as the cationic template and sodiummetasilicate (for MCM-41) and tetraethyl-orthosilicon (for MCM-48) as the silica source for the synthesis of mesoporous materials. The properties of synthesized samples were characterized with XRD-low angle, SEM, N(2) adsorption-desorption and TG-DT analysis. The extent of adsorption was investigated as a function of solution pH, shaking speed, contact time, analyte concentration, reaction temperature and supporting electrolyte (sodium chloride) concentration. Langmuir and Freundlich isotherms were used to model the adsorption equilibrium data. The as-synthesized mesoporous samples showed very high adsorption capacity for the analytes and adsorption uptakes were rapid on the adsorbents reaching equilibrium in less than 2 h. The materials without surfactant did not show significant affinity for the analytes. 2009 Elsevier B.V. All rights reserved.

Overview on mitigation of acrylamide in starchy fried and baked foods.

PubMed

Baskar, G; Aiswarya, R

2018-03-23

Acrylamide in fried and baked foods causes potential toxic effect in aniamls and humans. The major challenging task lies in developing an effective strategies for acrylamide mitigation in foods without altering its basic properties. Food scientists around the world have developed various methods to mitigate the presence of acrylamide in fired food products. The mitigation techniques such as addition of additives like salts, amino acids, cations and organic acids along with blanching of foods have reduced the concentration of acrylamide. The use of secondary metabolites like polyphenols also reduces acrylamide concentration in fried food products. The other mitigation techniques such as Asparaginase pre-treatment and low-temperature air frying with chitosan were effective in mitigating the concentration of acrylamide. Combined pre-treatment process preceding with use of additives, are the latest trend in acrylamide mitigation. This article is protected by copyright. All rights reserved.

Preconditioning with cations increases the attachment of Anoxybacillus flavithermus and Geobacillus species to stainless steel.

PubMed

Somerton, Ben; Flint, Steve; Palmer, Jon; Brooks, John; Lindsay, Denise

2013-07-01

Preconditioning of Anoxybacillus flavithermus E16 and Geobacillus sp. strain F75 with cations prior to attachment often significantly increased (P ≤ 0.05) the number of viable cells that attached to stainless steel (by up to 1.5 log CFU/cm(2)) compared with unconditioned bacteria. It is proposed that the transition of A. flavithermus and Geobacillus spp. from milk formulations to stainless steel product contact surfaces in milk powder manufacturing plants is mediated predominantly by bacterial physiological factors (e.g., surface-exposed adhesins) rather than the concentrations of cations in milk formulations surrounding bacteria.

Cations in component reactions of `malic' enzyme catalysis

PubMed Central

Tsai, C. S.; Tsai, Y. H.; Samad, R. A.

1971-01-01

The `malic' enzyme (EC 1.1.1.40) has been purified (300-fold) from wheat germ and its abilities to catalyse the decarboxylation and the hydrogenation of oxaloacetic acid and oxaloacetate esters was studied. The free 1-carboxyl group is essential for the interaction of oxaloacetates and substituted oxaloacetates with the enzyme via cations. The free 4-carboxyl group is required for the decarboxylation but is not indispensable for the hydrogenation. At high concentrations, cations inhibit the enzymic hydrogenation of oxaloacetic acid but not that of 4-ethyl oxaloacetate. A plausible inhibitory mechanism is proposed. PMID:4399519

Different effects of copper (II), cadmium (II) and phosphate on the sorption of phenanthrene on the biomass of cyanobacteria.

PubMed

Tao, Yuqiang; Li, Wei; Xue, Bin; Zhong, Jicheng; Yao, Shuchun; Wu, Qinglong

2013-10-15

Due to the large surface area and high organic carbon content of cyanobacteria, organic contaminants can be readily sorbed on cyanobacteria during algal blooms, and then be transferred to the food web. This process is likely to be affected by the coexisting metals and nutrients, however, the possible impacts remain unclear. Effects of Cu(2+), Cd(2+), and phosphate on the sorption of phenanthrene on cyanobacterial biomass collected from an algal bloom were therefore studied. Continuous decrease in phenanthrene sorption was observed in the presence of low concentrations of Cu(2+), and Cd(2+) (<0.04 mmol L(-1)), because Cu(2+) and Cd(2+) were coadsorbed with phenanthrene on the surface of cyanobacteria as suggested by scanning electron microscopy-energy dispersive X-ray (SEM-EDX) and Fourier transform infrared (FTIR) analyses. Phenanthrene sorption began to increase with the further increase in Cu(2+) concentration, but remained lower than that in the absence of Cu(2+). This increase in sorption was ascribed to the cation-π interaction between Cu(2+) and phenanthrene, as suggested by the enhanced ultraviolet absorbance at 251 nm. In contrast, sorption rebounding of phenanthrene did not occur in the presence of higher concentrations of Cd(2+). The different effects of Cu(2+) and Cd(2+) on phenanthrene sorption were attributed to that Cd(2+) required much more energy than Cu(2+) to form cation-π complexes with phenanthrene in the solutions. Phenanthrene sorption decreased continuously with the increase in phosphate concentration. Phosphate blocked the binding sites, modified the cell morphology, and increased the negative charge as well as the hydrophilicity of the cyanobacterial surface, thereby suppressing phenanthrene sorption. This study indicates that sorption of aromatic organic compounds by cyanobacteria could be significantly alerted by concentrations and properties of the coexisting transition metals and phosphates, which may subsequently affect their transfer to the food web in eutrophic waters. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

Cationic niosomes an effective gene carrier composed of novel spermine-derivative cationic lipids: effect of central core structures.

PubMed

Opanasopit, Praneet; Leksantikul, Lalita; Niyomtham, Nattisa; Rojanarata, Theerasak; Ngawhirunpat, Tanasait; Yingyongnarongkul, Boon-Ek

2017-05-01

Cationic niosomes formulated from Span 20, cholesterol (Chol) and novel spermine-based cationic lipids of multiple central core structures (di(oxyethyl)amino, di(oxyethyl)amino carboxy, 3-amino-1,2-dioxypropyl and 2-amino-1,3-dioxypropyl) were successfully prepared for improving transfection efficiency in vitro. The niosomes composed of spermine cationic lipid with central core structure of di(oxyethyl)amino revealed the highest gene transfection efficiency. To investigate the factors affecting gene transfection and cell viability including differences in the central core structures of cationic lipids, the composition of vesicles, molar ratio of cationic lipids in formulations and the weight ratio of niosomes to DNA. Cationic niosomes composed of nonionic surfactants (Span20), cholesterol and spermine-based cationic lipids of multiple central core structures were formulated. Gene transfection and cell viability were evaluated on a human cervical carcinoma cell line (HeLa cells) using pDNA encoding green fluorescent protein (pEGFP-C2). The morphology, size and charge were also characterized. High transfection efficiency was obtained from cationic niosomes composed of Span20:Chol:cationic lipid at the molar ratio of 2.5:2.5:0.5 mM. Cationic lipids with di(oxyethyl)amino as a central core structure exhibited highest transfection efficiency. In addition, there was also no serum effect on transfection efficiency. These novel cationic niosomes may constitute a good alternative carrier for gene transfection.

Synthesis and antibacterial evaluation of novel cationic chalcone derivatives possessing broad spectrum antibacterial activity.

PubMed

Chu, Wen-Chao; Bai, Peng-Yan; Yang, Zhao-Qing; Cui, De-Yun; Hua, Yong-Gang; Yang, Yi; Yang, Qian-Qian; Zhang, En; Qin, Shangshang

2018-01-01

There is an urgent need to identify new antibiotics with novel mechanisms that combat antibiotic resistant bacteria. Herein, a series of chalcone derivatives that mimic the essential properties of cationic antimicrobial peptides were designed and synthesized. Antibacterial activities against drug-sensitive bacteria, including Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Salmonella enterica, as well as clinical multiple drug resistant isolates of methicillin-resistant S. aureus (MRSA), KPC-2-producing and NDM-1-producing Carbapenem-resistant Enterobacteriaceae were evaluated. Representative compounds 5a (MIC: 1 μg/mL against S. aureus, 0.5 μg/mL against MRSA) and 5g (MIC: 0.5 μg/mL against S. aureus, 0.25 μg/mL against MRSA) showed good bactericidal activity against both Gram-positive and Gram-negative bacteria, including the drug-resistant species MRSA, KPC and NDM. These membrane-active antibacterial compounds were demonstrated to reduce the viable cell counts in bacterial biofilms effectively and do not induce the development of resistance in bacteria. Additionally, these representative molecules exhibited negligible toxicity toward mammalian cells at a suitable concentration. The combined results indicate that this series of cationic chalcone derivatives have potential therapeutic effects against bacterial infections. Copyright © 2017 Elsevier Masson SAS. All rights reserved.