Molar Ratio Of Metal Ions Research Articles

Morphologies of oriented alginate gels crosslinked with various divalent metal ions

Abstract Optically anisotropic cylinder-shaped alginate gels crosslinked with various divalent metal ions such as Ca, Cu, Zn, and Pb were prepared by the flow-gelation method in which semidilute sodium alginate solution was extruded through a tube into metal nitrate salt solutions. Effects of metal ions on the morphological and structural features of the gels were examined mainly by polarized optical microscopy. The chain orientation was characterized by a planar orientation where the mean chain orientation is primarily parallel to the gel surface and normal to the total flow direction, due to diametric expansion and longitudinal shrinkage on gelation. The degree of chain extension and orientation was shown to increase in the order Pb > Cu > Ca > Zn. Scanning electron microscopy of the gels dried rapidly under vacuum showed that all the metal alginate gels had cylindrically developed sheet strucures. Molar ratios of metal ions bound to alginate chains were estimated, using plasma spectroscopy, to be in th...

Preparation and properties of uniform mixed colloidal particles; VI, copper(II)–yttrium(III), and copper(II)–lanthanum(III) compounds

Uniform spherical colloidal particles of mixed internal composition were obtained by aging at 90 °C solutions containing Cu(NO3)2 + Y(NO3)3 and Cu(NO3)2 + La(NO3)3, respectively, in the presence of urea. The molar ratio of metal ions in the solids precipitated from a given solution varied with the reaction time. After sufficiently long aging, this ratio corresponded closely to that in solutions in which the particles were generated. The original precipitates consisted of basic carbonates, which on calcination converted to mixed oxides of defined composition.

High T c superconductors from metallorganic precursors

High T c cuprate superconductors have been made by pyrolysis of metallorganic precursors incorporating the appropriate molar ratios of metal ions to form the desired copper oxide compounds. Twp processes have been described as representative examples of novel strategies to produce high T c superconductors in bulk and thin film form: pyrolysis of metallorganic powders for bulk processing and spray pyrolysis for thin film fabrication.

The complexation of "crowned" 4-(2,4-dinitrophenylazo)phenol with alkali and alkaline earth metal ions, and its application to the determination of Li(I) in a pharmaceutical preparation.

To characterize crowned 4-(2, 4-dinitrophenylazo)phenol (CDPA), the acid dissociation constant (pKa) was measured together with those of related compounds. The complexation behavior of CDPA was examined in various nonaqueous solvent systems, and it was found that in the CHCl3-MeOH-triethylamine (TEA) system, the ionic radii of the alkali and alkaline earth metal ions are linearly correlated both with the wave numbers of the absorption maxima and with the molar absorptivities of the resulting complexes except for Be(II). The molar ratios of metal ions to CDPA in the complexes were determined by means of the continuous variation method. Next, the complexation of CDPA with Li(I) was fully examined in another solvent system (CHCl3-dimethyl sulfoxide-TEA) and a sensitive colorimetric assay method for Li(I) was established in the range of 25-250 ppb of Li(I). This method was applied to the analysis of a commercial pharmaceutical preparation, lithium carbonate (tablet).

METAL CHELATE FORMATION BYN-PHOSPHONOMETHYLGLYCINE AND RELATED LIGANDS

Abstract Thirteen selected divalent and trivalent metal ions were equilibrated with N-phosphonomethylglycine(PMG) at 1:1 and 1:2 molar ratios of metal ion to ligand at 25.0° and ionic strength μ=0.100 M. Similarly, the same metal ions were also studied with iminobismethylenephosphonic acid (IDP), which has not been previously investigated, as well as the well known ligand, iminodiacetic acid (IDA) (to obtain equilibrium data for the latter not available in the literature). The complexes formed were studied as a function of −log[H+]. All of the appropriate equilibrium stability constants were calculated with the aid of the interactive computer program BEST. The constants obtained generally reproduce the entire experimental potentiometric equilibrium curves to within 0.01 log[H+] units. The protonation constants 10.142, 5.460, 2.229 reproduce the potentiometric equilibrium curve of free PMG to within a σ value of 0.004 log[H+] units while 10.79.6.08, 5.04 and 0.86 are the protonation constants for IDP.

Interaction of protein-bound polysaccharide (PS-K) with microtubule proteins. V. Influence on tubulin-dependent adenosine triphosphatase (ATPase) activity.

In the presence of 5 mM Ca2+ or 2mM Mg2+, a protein-bound polysaccharide (PS-K) isolated from Basidiomycetes inhibited the tubulin-dependent adenosine triphosphatase (ATPase) activity of microtubule-associated proteins (MAPs) in a concentration-dependent manner, though it had little effect on the activity in the absence of tubulin. The extent of inhibition decreased at lower concentrations of Ca2+ or Mg2+ and an excess amount of tubulin largely restored the inhibitory effect. When Mn2+ was added to the reaction mixture instead of these divalent cations, the presence of PS-K conversely stimulated the tubulin-dependent ATPase activity of MAPs at lower Mn2+ concentrations (<1-2 mM) under the conditions tested, though PS-K inhibited the ATPase activity at high Mn2+ concentrations. Maximal stimulation and inhibition were about 160% and 70% of the original level (i.e., in the absence of PS-K), respectively. PS-K could also enhance MAPs ATPase activity under conditions where it enhanced the activity in the presence of tubulin, indicating that PS-K itself interacts with MAPs ATPase as tubulin does. The addition of a large amount of ATP under experimental conditions where PS-K inhibited tubulin-dependent Mn2+-ATPase activity of MAPs, on the other hand, led to stimulation by PS-K. Thus, the influence of PS-K on the ATPase activity was dependent on the molar ratio of metal ions to adenosine triphosphate (ATP).

電析Ｎｉ‐Ｐ，Ｃｏ‐ＰおよびＮｉ‐Ｃｏ‐Ｐ合金の作製とその特性

Ni-P, Co-P, and Ni-Co-P alloys (0≤P≤16wt%) were electrodeposited from Watts-type plating bath containing phosphorous acid. Effects of bath temperature, current density, content of phosphorous acid in the bath, and molar ratio of metal ions in the bath on the deposition rate and the composition of the deposited alloys were studied. The relation between Vicker's hardness and phosphorous content in the deposited Ni-P and Co-P alloys were also discussed. Moreover, for better understandings of the conformation or the nature of the chemical state of phosphorous, its properties and stability in the deposited Co-P alloys, the differential scanning calorimetry, the small angle X-ray scattering, and the P-Kβ X-ray spectroscopy were measured on the alloys. The results are summerized as follows; (1) The deposition rate and composition of the deposited alloys are greatly influenced by the plating conditions, that is, temperature of the bath, current density, and composition of electrolytes in the bath. (2) The Ni-P, Co-P, and Ni-P, Co-P deposited alloys containing more than 5 wt% phosphorous exhibited the hardness of 600-800Hv. (3) Phosphorous in the Co-P alloys as deposited is bonded to cobalt by metallic bond, and it is suggested that phosphorous in the alloy is neither at the elementary state (red or white) nor constitutes stoichiometric cobalt-phosphides such as CoP, Co1.6 P, and that the deposits are at the state of a super-saturated solid-solution of phosphorous in hcp Co (P<-5wt%) and an amorphous solid (P>-5wt%).

Unusual complexing properties of 2-(2′-pyridyl)- and 2-hydrazino-8-hydroxyquinoline

The ligands 2-(2′-pyridyl)- and 2-hydrazino-8-hydroxyquinoline form terdentate complexes with a 5,5-bicyclic ring system, the stabilities being greater than those of the corresponding 8-hydroxyquinolinates. This study affords a more complete picture of the behaviour of terdentate 2-substituted 8-hydroxyquinolines. Solutions of these ligands and metal ions are complicated by formation of the protonated species MHL 2+, M(HL) 2+ 2 and MLHL +. The existence of the protonated species is dependent not only on pH and ligand:metal-ion molar ratio but also on the nature of the metal ion itself.

The interaction of ions with phosphatidylcholine bilayers

The interaction of lanthanides and other cations with phosphatidylcholine bilayers present as single bilayer vesicles in 2H 2O has been investigated in terms of stoichiometry, apparent binding constants and environmental conditions. Lanthanides are shown to form 2 : 1 (molar ratio) phosphatidylcholine to metal ion complexes. The apparent binding constant K b varies as a function of the quantity of metal ion bound and as a function of the Cl − concentration. The apparent binding constant at “zero loading” is K 0 = 1.25 · 10 4 L 2 · M − at 0.15 M KCl . It decreases exponentially with increased “loading” expressed as the molar ratio of metal ion bound to effective phosphatidylcholine concentration and increases exponential with Cl − concentration. The interaction of lanthanides and divalent cations such as Ca 2+ and Mg 2+ is independent of pH in the pH range 3–7 + and 3–10 respectively, but is sensitive to the nature of the anion. The presence of anions enhances the interaction with polyvalent cations, the chaotropic anions showing the largest effect. The order of enhancement is Cl − < Br − < NO 3 − < SCN − < I − < ClO 4 − . The nature of the monovalent counterion (cation) has little effect on the enhanced binding of lanthanides in the presence of the above anions. The affinity of other polyvalent cations for phosphatidylcholine bilayers has been determined by competition with lanthanides. The physiologically important divalent cations Ca 2+ and Mg 2+ both bind less strongly (by about an order of magnitude) to the lipid surface. The order of binding of cations reflects direct binding to the phosphodiester group, with UO 2 2+ showing the highest affinity.

Interaction of cis- and trans-dichlorodiammineplatinum(II) with synthetic polydeoxyribonucleotides: Effect on equilibrium buoyant densities

Equilibrium buoyant densities in Cs 2SO 4 of four synthetic double-stranded polydeoxyribonucleotides were compared following reaction with either cis-Pt(NH 3) 2Cl 2, trans-Pt(NH 3) 2Cl 2 or PtCl 4. While both Pt(NH 3) 2Cl 2 isomers caused significant increases in the buoyant densities (ϱ) of the two G + C polymers, the cis- isomer increased the ϱ of poly[d(G−C)] and the trans- isomer increased the ϱ of poly(dG) · poly(dC) more sharply than the corresponding isomer at low molar ratios of metal ion to polymer. Chloroplatinic acid was without effect. Only cis-Pt(NH 3) 2Cl 2 produced substantial increases in the ϱ of poly[d(A−T)] and poly(dA) · poly(dT) with increasing metal ion concentrations. These increases were accompanied by a proportional decrease in the thermal transition temperature (T m) of poly(dA)-poly(dT) and a sharp increase in the T m of poly[d(A−T)]. Our results indicate that the cis- isomer reacts with all four polymers to produce ϱ changes clearly distinct from those values observed after reaction with either the trans- isomer or PtCl 4. These results help explain the observation by others that the cis- isomer produces greater ϱ changes in native DNA than the trans- isomer. On the basis of our data and the published results of others, one may rationalize the quantitative differences between the cis- and trans- compounds on the buoyant densities of naturally occurring DNA; however, additional studies are clearly needed.

Potentiometric Studies of Some Bivalent Metal Ion Complexes of a New Ligand,o-(2-Thiazolylazo)-4-Ethylphenol

Abstract The complexations of a new ligand, o-(2-thiazolylazo)-4-ethylphenol(TAEP) with Ca(II), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hq(II) and Pb(II) have been studied by potentiometric titrations, at 25.0 ± 0.2°C and an ionic strength of 0.1 in 30% v/v dioxane-water mixture. The dissociation constant and spectral data of TAEP and formation constants of the complexes containing various molar ratios of metal ion to ligand, are reported. It is observed that Ca(II) forms only an ML complex in any molar ratios, whereas other metal ions react in two steps forming ML and ML2 complexes in a 1:3 molar ratio. In the case of 1:1 and 1:2 molar ratios, Mn(II), Co(II), Cd(II) and Hg(II) seemed to form bi- or poly-nuclear complexes because of slightly different formation curves from those of 1:3 molar ratio. The sequence of the first successive formation constant is Cu > Hg > Ni > Pb > Co > Zn > Cd > Mn > Ca, showing Mellor-Maley's order. Further correlation is shown between the formation constants and the second ionization potentials of the metals.

Dissociation constants and metal chelate stabilities of picolinic acid and pipecolinic acid in 1-propanol-water mixtures: The dependence of the zwitterion form on the dielectric constant of the solvent

The interaction of Ni(II) and Zn(II) with picolinic acid and pipecolinic acid has been studied by potentiometric titrations at 0, 25, and 40°C and ionic strength of 0·02 M in 1-propanol-water mixtures. Dissociation constants of the ligands and formation constants of the chelates containing 1:1 and 1:2 molar ratios of metal ion to ligand in a dielectric constant range of 30–80 are reported. A computer program used in obtaining the dissociation constants is discussed. The predominance of the neutral molecule over the zwitterion form for picolinic acid is discussed.

Potentiometric studies on stepwise mixed ligand complex formation Cu(II), Ni(II) or Zn(II)-nitrilotriacetic acid-hydroxy acid

Potentiometric studies of the interaction between copper(II), nickel(II) and zinc(II) nitrilotriacetates with certain bidentate ligands, such as salicylic acid(SA),5-sulphosalicylic acid (SSA) and 1,2-dihydroxy benzene-3,5-disulphonic acid (Tiron) are reported. Ternary complexes having a 1 : 1 : 1 molar ratio of metal ion to nitrolotriacetic acid (NTA) to be secondary ligand are formed. Their formation constants (Log K MAB) are reported and the probable reaction mechanism is discussed. The order of stability in terms of metal ion has been found to be Cu(II) > Zn(II) > Ni(II) and in terms of secondary ligand as Tiron > SA > SSA.

Potentiometric Studies on Stepwise Mixed Ligand Complex Formation

Stepwise mixed ligand complex formation is observed in the systems containing metal ion, iminodiacetic acid (IMDA) as primary ligand and one of the diamines, such as ethylenediamine (en), 1,2-propanediamine (1,2-pn) and 1,3-propanediamine (1,3-pn) as secondary ligands. Potentionmetric titrations indicate the formation of ternary complexes having a 1:1:1 molar ratio of metal ion to iminodiacetic acid to the secondary ligand. Initially, metal-IMDA (1:1) complex is formed in the lower buffer region prior to the formation of the ternary complex and the addition of the secondary ligand takes place only after the combination with the primary ligand is complete. Formation constants (log KMAB) of the ternary complexes have been calculated and the probable reaction mechanism is suggested. The order of stability in terms of metal ion has been found to be Cu (II) &gt; Ni (II) &gt;Zn (II) &gt;Cd (II) and in terms of secondary ligand as 1,2-pn&gt;en&gt;1,3-pn.