Small Inorganic Anions Research Articles

Some magnetic properties of cation-radical salts derived from giant analogues of TTF

Abstract The temperature dependence of the ESR spectra for cation-radical salts of three π-donors derived from TTF with small inorganic anions were studied. Phase transitions of the semiconductor-semiconductor type are observed for two salts. Discussion of the g-factor, linewidth and magnetic susceptibility is given.

Electrochemical sensor for heparin: further characterization and bioanalytical applications

Further studies regarding the potentiometric response to heparin of polymeric membranes doped with lipophilic quaternary ammonium salts are reported. Among a wide range of membrane formulations examined, optimum response toward macromolecular heparin is achieved using tridodecylmethylammonium chloride as the active membrane component within poly(vinyl chloride) or poly(vinyl chloride)/(vinyl acetate) films plasticized with dioctyl sebacate. Although such membranes are shown to exhibit a typical Hofmeister potentiometric selectivity pattern toward small inorganic and organic anions, a very large and reproducible response to heparin at submicromolar levels is observed in the presence of physiological saline (0.12-0.15 M NaCl), as well as in citrated whole blood. Equal response on a mass basis occurs with fragments of heparin's as small as 2500 Da. Complexation of heparin's anionic sites by macromolecules that bind heparin with high affinity (e.g., protamine and poly(L-lysine)) reduces the membrane electrode's heparin response, indicating that the electrode detects biologically available (unbound) heparin levels in solution. Quantitative potentiometric titrations of protamine with porcine mucosa heparin followed by the sensor yield stoichiometric values in good agreement with the literature. The biomedical utility of the sensor is demonstrated by measuring its response in whole blood from patients undergoing open heart surgery before and after heparin therapy and correlating such response to conventional blood clotting time measurements.

Spectral Study of New Organic Conductors Derived from a Giant Analogue of TTF

Abstract Infrared absorption spectra of salts derived from a new giant analogue of TTF (D) with small inorganic anions have been measured vs temperature. Spectra of the neutral donor (D) and compounds used in its building were studied also. A comparative analysis was used for assignment of the fundamental vibrations of D and its cation-radical salts. Shape of the spectra, i.e. linewidthes and intensities of selected bands, appearance of CT bands above 4000 cm−1 etc., suggest a 1:1 stoichiometry of the salts. T-dependencies of intensities of some bands of DClO4 and DCu(SCN)2 show anomalies which reveal the presence of phase transitions. Observed anomalies are preliminary explained.

Alkyl benzene sulfonate doping of poly(alkylthiophenes)

Abstract We report studies on the doping of poly(3-alkylthiophenes) with dodecylbenzene sulfonate. The electrochemical doping leads to a material of low conductivity and doping level. This material is susceptible to rapid thermal undoping similar to that observed with poly(3-alkylthiophenes) doped with small inorganic anions. Interaction between the side-chains on the electroactive polymer and substituents on the dopants are suggested as a means for increasing the order of polymer-dopant interactions.

The case of the elusive tm values in HPLC

Numerous ideas and procedures have been suggested in the literature for the determination of tm, the retention time of a non-retained species, in high-performance liquid chromatography. In some cases chromatograms have been obtained showing sample components eluting prior to the assumed non-retained species. This phenomenon results in apparent negative capacity factors for the species in question. We have proposed a method employing small inorganic anions which results in a limiting value for tm and eliminates apparent negative capacity factors.

Temperature dependence of quenching of fluorescence of anthracene sulphonates by small inorganic anions

Abstract The fluorescence quenching of water-soluble and amphiphilic anthracene sulphonates (monosulphonates and disulphonates) by I − , N 3 − , Br − and Cl − was studied. The rate constants for quenching depend on the ionic strength of the solution, and at μ = 0 they are observed to be a function of the redox potentials of the quenchers, except for the azide iron. The free energy Δ G ° of the quenching reaction was calculated for anthracene-1-sulphonate and anthracene-1,5-disulphonate from the redox potentials of the fluorescers and quenchers. A linear correlation is observed in the endoergic region of Δ G ° (for Br − and Cl − , including I − in the exoergic region, suggesting an electron transfer mechanism. The slope is only about 2 eV −1 , compared with the ideal value of 17 eV −1 . From the temperature dependence of the quenching the thermodynamic parameters Δ H ≠ , Δ S ≠ and Δ G ≠ were evaluated for I − , N 3 − and Br − , and the results indicate that the entropy of activation Δ S ≠ plays a definite role. N 3 − does not follow an isokinetic plot.

Mechanism of anion-cation selectivity of amphotericin B channels

Zero current potential and conductance of ionic channels formed by polyene antibiotic amphotericin B in a lipid bilayer were studied in various electrolyte solutions. Nonpermeant magnesium and sulphate ions were used to independently vary the concentration of monovalent anions and cations as well as to maintain the high ionic strength of the two solutions separated by the membrane. Under certain conditions the channels select very strongly for anions over cations. They are permeable to small inorganic anions. However, in the absence of these anions the channels are practically impermeable to any cation. In the presence of a permeant anion the contribution of monovalent cations to channel conductance grows with an increase in the anion concentration. The ratio of cation-to-anion permeability coefficients is independent of the membrane potential and cation concentration, but it does depend linearly on the sum of concentrations of a permeant anion in the two solutions. These results are accounted for on the assumption that a cation can enter only an anion-occupied channel to form an ionic pair at the center of the channel. The cation is also assumed to slip past the anion and then to leave the channel for the opposite solution. This model with only few parameters can quantitatively describe the concentration dependences of conductance and zero current potential under various conditions.

Calcium acetate induces calcium uptake and formation of calcium-oxalate crystals in isolated leaflets of Gleditsia triacanthos L.

During treatment of isolated, peeled leaflets of Gleditsia triacanthos with 0.5-2 mM [(45)Ca]acetate, saturation of the cell-wall free space with Ca(2+) occurred within 10 min and was followed by a period of 6-10 h during which there was no significant Ca-uptake into the protoplast, but apoplastic Ca(2+) was periodically released into the medium. Later, Ca(2+) was absorbed for 3-4 d at rates of up to 2.2 μmol Ca(2+)·h(-1)·(g FW)(-1) to final concentrations of 350 μmol Ca(2+)· (g FW)(-1). The distribution of absorbed Ca(2+) between cell wall, vacuole and Ca-oxalate crystals was determined during Ca-uptake. Wheras intact, cut leaflets deposited absorbed Ca(2+) as Ca-oxalate in the crystal cells, peeled leaflets lacking crystal cells accumulated at least 40-50 μmol·(g FW)(-1) soluble Ca(2+) before the absorbed Ca(2+) was precipitated as Ca-oxalate. These observations indicate that the mechanisms for the continuous uptake of Ca(2+), the synthesis of oxalate and the precipitation of Ca(2+) as Ca-oxalate are operational in the crystal cells of intact leaflets, but not in the mesophyll cells of peeled leaflets where they must be induced by exposure to Ca(2+). The precipitation of absorbed Ca(2+) as Ca-oxalate by the crystal cells of isolated Gleditsia leaflets illustrates the role of these cells in the excretion of surplus Ca(2+) which enters normal, attached leaves with the transpiration stream.In addition to acetate, only Ca-lactate and Ca-carbonate lead to Ca-uptake, but at rates well below those observed with Ca-acetate. Other small organic anions (citrate, glycolate, glyoxalate, malate) and inorganic anions (chloride, nitrate, sulfate) did not permit Ca-uptake. Acetate-(14)C was rapidly absorbed during Ca-uptake, but less than 20% was incorporated into Ca-oxalate; the rest remained mostly in the soluble fraction or was metabolized to CO2. Acetate, as a permeable weak acid, may enable rapid Ca-uptake by stimulating proton extrusion at the plasmalemma and by serving as a counterion during Ca-accumulation in the vacuole, but is unlikely to function as the principal substrate for oxalate synthesis.

Determination of sulfate and nitrate anions in rainwater by mass spectrometry

In recent years mass spectrometry has emerged as one of the most powerful trace analysis techniques. Mass spectrometry is characterized by exceptional sensitivity (10/sup -12/ g) combined with the ability to distinguish elemental and isotopic compositions. The advantages of this technique have been, however, largely limited to organic analysis and to elemental analysis. Attempts to analyze complex anions such as the sulfate and nitrate involved in acid precipitation processes have invariably produced results which were unsatisfactory for routine analytical use. Small inorganic anions can be analyzed from glycerol solution with very high sensitivity if a cationic surfactant is added to the solution prior to analysis. The surfactant covers the surface of the analyte droplet and behaves much like an anion exchange resin in that it can bind certain anions selectively to the surface. Quantities of nitrate as small as 10/sup -5/ M in the analyte solution are readily detected. In this paper the application of this methodology to the analysis of natural precipitation is reported. 15 references, 1 figure, 1 table.

Passage of ions and dextran molecules across the rete mirabile of the eel. The effects of charge.

The countercurrent-perfused rete mirabile of the eel is a preparation in which capillary permeability values can be determined accurately in broadscale fashion. To provide insight into charge effects on transendothelial passage, the permeability values of small inorganic cations (labeled sodium and rubidium, and stable potassium) and anions (labeled chloride, iodide, sulfate, and ferrocyanide) were compared to those expected for neutral solutes with approximately matched diffusion coefficients, and that of a neutral dextran fraction was compared to that of a negatively charged dextran sulfate with a similar diffusion coefficient. In the small ion experiments, the labeled iodide values were unexpectedly high, apparently due to the contamination of the labeled iodide solution with I-3. The permeabilities of the rest of the ions clustered at a level about 0.5 of the values which would have been expected for neutral solutes with similar diffusion coefficients. The decrement was interpreted to reflect the presence of both positive and negative charges along the transendothelial pathway, which effectively decrease the dimensions of the limiting part of the pathway for the charged microions relative to that accessible to comparable nonelectrolytes. The larger negatively charged dextran sulfate was also reduced in its passage, in comparison with its matching neutral dextran; this was taken to indicate the presence of a larger scale average net negative charge along its pathway. The data indicate the presence of a staggering of positive and negative charges along the transendothelial pathway accessible to the microions, and a net negative charge in the more restricted part of the pathway available to the dextrans.

The analysis of inorganic anions from liquid solutions using cationic surfactants and negative secondary ion mass spectrometry

Small inorganic anions such as nitrate, nitrite, iodate, bromate, cyanate, thiocyanate, chlorate, perchlorate, iodide, bromide, chloride, and tetrafluoroborate can be analyzed at low levels from glycerol solution using negative secondary ion mass spectrometry provided a long chain cationic surfactant such as tetradecyltrimethylammonium hydroxide is present in the solution. Sensitivities are directly related to the extent of association of the anion with the surface monolayer generated by the surfactant. Strongly interacting anions such as nitrate are detectable as intact ions at the 1 ng level (10−5 M in glycerol, two μl of solution). The degree of interaction between the anion and the monolayer parallels the behavior of the same ions on quaternary ammonium ion exchange resins. Fluoride and hydroxide do not interact strongly and do not give signals of useful intensity. Quantification can be readily obtained using stable isotope dilution techniques. The technique has been applied to the analysis of nitrate anion in natural precipitation.

Speciation studies in natural waters

Abstract The central theme of man's quest for an understanding of the importance of metal ions in the environment is ‘bioavailability’. We may be concerned with problems such as the increased leaching of heavy metals from soils due to acid rain or the return to man of high level radioactive waste eluted by ground waters from its deeply buried container. Unfortunately, the total concentration of a species is seldom a measure of its bioavailability [1]. Rather, a knowledge of whether an element is like to form species that are in appropriate forms, either to be transported from one system to another or to take part in processes within systems is required. The study of ‘specification’ (meaning the existence of the individual physicochemical forms of an element which make up its total concentration) is therefore becoming increasingly important. An experimental speciation study can prove a difficult task. Coarse separations of molecular from colloidal species make use of techniques such as ionexchange, ultrafiltration, dialysis and gel chromatography [2]. More detailed analyses can be achieved by anodic stripping voltammetry for aqueous species [3] and gas chromatography for volatile species. Ion-selective electrodes can measure activities of metal cations and small inorganic anions directly [4]. However, problems such as the high degree of skill often required, the disturbance to equilibria, nonspecificity and insensitivity at the concentrations occurring in the environment, often severely limit the usefulness of these experimental approaches. Computer simulation of equilibrium systems is becoming increasingly capable of providing useful information concerning speciation. The general requirements of such a study are the total concentrations (or free concentrations, if available) of all components and the formation constants and solubility products of complexes and solids formed from the components. A priori predictions of extent of complexation cannot merely be based on the size of formation constants so computer programs (such as GEOCHEM [5], ECCLES [6] and WATEQ [7]) that can solve large systems of non-linear equations, have been developed. Total concentrations can be determined at very low levels using such techniques as flame emmission and atomic absorption spectrophotometry and radiometry [8]. Also, critically evaluated formation constants and solubility products are becoming available for an increasingly large number of complexes and of solids [9]. The assumption that an environmental system is at equilibrium is only valid if equilibrium between all species is reached very quickly. However, if some reactions are very slow, the equilibrium between the species involved can sometimes be ignored. The extent to which reactions with intermediate rates are a problem depends on the application. The inclusion of equilibria involving complex macromolecular species such as fulvic and humic acids has been either avoided or approximated by making use of conditional stability constants [10,11]. However, a new method, whereby concentrations of many individual metal binding sites on the macromolecules can be estimated from ‘random’ computer generated fulvic acid molecules, does provide more detailed insight into the mode of metal binding by these substances [12]. Equilibrium calculations on large systems have received widespread application. The sea has been studied for many years [13, 14]. Fresh water, lakes and river systems have been investigated [7, 10] as well as the so-called ‘soil solution’ [15]. Other important areas include human blood plasma [6] and plant xylem fluid [16] Computer models, nevertheless, must be judged on their ability to predict real behavior [17]. They should be supported, wherever possible, by experimental investigations, the direction of which can often be indicated by the results of the model itself. The current trend of investigations into the identity of important naturally occurring ligands and the determination of their formation constants with metal ions needs also to continue unabated.

Oxygen-linked binding sites for inorganic anions to hemoglobin.

A hemoglobin hybrid (alpha 2c beta 2 Prov) in which the alpha chains have NH2-terminal residues that have been blocked specifically by carbamylation and beta chains that have been derived from hemoglobin Providence I (beta 82 Lys leads to Asn) was prepared. This derivative shows a small but significant dependence of its oxygen equilibrium curve on the concentration of chloride, phosphate, or nitrate. These data were compared with oxygen-linked anion binding to hemoglobins A and Providence, and to the carbamylated hybrid, alpha 2c beta 2, by fitting equations to the data with the use of MULTIFIT II, a nonlinear curve-fitting program. Dependence of the anion dissociation constants from deoxygenated (KD) and fully oxygenated (Ko) hemoglobins upon the mathematical model is described. The data provide further support that Val-1 (alpha) and Lys-82 (beta) of hemoglobin are major, oxygen-linked binding sites for small inorganic anions and suggested that a third oxygen-linked site may also be present.

Anion transport across the red blood cell membrane mediated by dielectric pores.

The anion transport across the red blood cell membrane is assumed to occur by ionic diffusion through dielectric pores which are formed by protein molecules spanning the red blood cell membrane. The access of anions to the dielectric pores is regulated by anion adsorption sites positioned at the entrances of the pores. The adsorption of small inorganic anions to the adsorption sites is facilitated by ionizing cationic groups setting up a surface potential at the respective membrane surfaces. Applying the transition state theory of rate processes, flux equations for the unidirectional flux were derived expressing the unidirectional flux as a function of the fractional occupancies of anion adsorption sites at both membrane surfaces. The basic properties of the transport model were investigated. The concentration-dependence and the pH-dependence of the unidirectional fluxes were shown to depend upon the surface charge density and upon the affinity of the transported anion species to the anion binding sites. The concentration-response and the pH-response of the unidirectional fluxes of different anion species may differ substantially even if the anion species are transported by the same anion transport system. The model predicts a characteristic behavior of the Lineweaver-Burk plot and of the Dixon plot. A comparison between computer simulated and experimentally determined flux curves was made. By choosing a suitable set of parameters, the anion transport model is capable of simulating the concentration-dependencies and the pH-dependencies of the unidirectional sulfate and chloride flux. It is sufficient to change one single constant in order to convert the “sulfate transport system” into a “chloride transport system”. Furthermore, the model is capable of predicting the inhibitory action of chloride on the sulfate transport system. No attempts were made to fit the experimental data to the model. The behavior of the model was qualitatively in accordance with the experimental results.