Divalent Manganese Ions Research Articles

Reactivity toward oxygen and cation distribution in copper-manganese ferrite spinels fine powders

The thermal behaviour of CUyMnxFe3−y−xO4 spinels (0≤x≤1, x+y ≈ 1) obtained at low temperature has been investigated over the temperature range of 50–700 °C mainly by thermogravimetry and infrared spectroscopy. Below 600 °C, Cu-Mn ferrites partly oxidized in cation deficient spinels, CuyMnxFe3−y−xO4+δ, showing an incomplete oxidation of the tetrahedral divalent manganese ions. A quantitative analysis by DTG based on an oxido-reduction mechanism and on a difference of reactivity of copper, iron and manganese ions in relation to the occupied site (octahedral or tetrahedral site) permits a cation distribution to be proposed. For x> 0.70, the vacancies were found to occupy octahedral sites with a vacancy cation ratio closely of 1/5 similar to γ-Fe2O3. Subsequent oxidation of Mn2+ ions required higher temperature and was accompanied by a phase change.

Manganese and the heart: acute cardiodepression and myocardial accumulation of manganese.

The aim of study was to assess acute effects of the divalent manganese ion (Mn2+) in an intact but isolated heart preparation. Rat hearts were perfused in the Langendorff mode at constant flow rate. Left ventricular (LV) developed pressure (LVDP). LV pressure first derivatives (LVdp/dt max and min), heart rate (HR) and aortic pressure (AoP) were recorded. Ventricular contents of high energy phosphate compounds (HEP) and Mn metal were measured at the end of experiment. Infusion of MnCl2 for 5 min with perfusate concentrations 1-3000 microM induced an immediate depression of contractile function at and above 30 microM and negative chronotropy at and above 300 microM. These IC50 values were found (microM): LVDP 250; LVdp/dt max 160; LVdp/dp min 120; HR 1000; and increase in AoP 80. Recovery of function during a 14 min washout period was rapid and extensive except for Mn2+ 3000 microM. Somewhat unexpected, Mr2+ 30-1000 microM raised coronary vascular resistance up to about twice the control level, whereas the vasoconstrictory response was overcome at 3000 microM. Mn2+ 3000 microM reduced tissue HEP Ventricular Mn content rose stepwise for perfusate Mn2+ above 1 microM up to about 55 times the control level for perfusate Mn2+ 3000 microM. It is concluded that: acute effects of Mn2+ like depression of contractility and rate is rapidly reversible; and rat hearts accumulate and buffer large amounts of Mn2+ without affecting cardiac function or energy metabolism in the acute stage.

Derivative spectrophotometry in the determination of metal ions with 4-(pyridyl-2-azo)resorcinol (PAR).

Derivative spectrophotometry has been applied for the elimination of the mutual spectral interferences and the analysis of binary, ternary and quaternary mixtures of complexes of microgram amounts of divalent ions of cobalt, copper, lead, manganese, nickel, zinc and iron with 4-(pyridyl-2-azo)resorcinol (PAR) in the range of 0.05-1 microg/ml (0.2-4 microg/ml for lead). The first derivative spectra can be used for the determination of both components in the majority of binary mixtures except of Cu(II) and Co(II) and systems containing Fe(II). The second and the third derivative spectra allow to determine one constituent in some ternary and quaternary mixtures.

Magnetic properties of lanthanum manganite and valence equilibria of manganese

Abstract The paramagnetic susceptibility of lanthanum manganite has been measured over a wide temperature range (100–1073 K). On the basis of the thermodynamic equilibria between the various manganese ions with different valence and spin states and the magnetic interactions between the various manganese ions, a semiempirical formula has been proposed to calculate the paramagnetic susceptibilities of lanthanum manganite at different temperatures. The results indicate that most of the discrepancies between the calculated and experimental reciprocal susceptibilities of lanthanum manganite are less than 10% and that the relative contents of the various manganese ions in lanthanum manganite vary with temperature. The relative content of the trivalent manganese ion with a high spin state is dominant over the whole temperature range, while the relative content of the tetravalent manganese ion with a high spin state decreases monotonously with increasing temperature. At 300 K the calculated relative content of the tetravalent manganese ion in lanthanum manganite is about 34%, which is in good agreement with the experimental result (30%). There are some divalent manganese ions present in lanthanum manganite from low temperature to high temperature. The ratio of the relative contents of the tetravalent and divalent manganese ions in the compound varies with temperature. Above 750 K the relative content of the tetravalent manganese ion is less than that of the divalent manganese ion. The variation in the electrical resistivity of lanthanum manganite with temperature has also been interpreted reasonably.

Characterisation of Mn(n) complexes with 2‐(2‐pyridylmethyleneamino)phenol and their dyeing properties

The complexing of the azomethine dye 2‐(2‐pyridylmethyleneamino)phenol (PMAP) with the divalent manganese ion in solution has been investigated. The synthesis of an Mn(II)—PMAP complex is described, together with its characterisation by infra‐red and mass spectrometry. The properties of the Mn(II)—PMAP complex for dyeing wool and nylon 6.6 fabrics have been investigated.

Microwave production of a superconductor powder: T.V. Mani et al (Regional Research Laboratory, Trivandrum, India)

Protein phosphorylation, regulated by protein kinases and protein phosphatases, is crucial for protein structure and function in eukaryotic organisms. Type 2C protein phosphatase (PP2C) belongs to the serine/threonine phosphatase family and its activities require the presence of a divalent magnesium or manganese ion. In the present study, a potential PP2C phosphatase (SjPtc1) was identified in Schistosoma japonicum. The SjPTC1 gene was found to be highly expressed in adult worms. A recombinant SjPtc1 protein showed typical PP2C phosphatase activity. Heterologous SjPTC1 expression reversed the sensitivity of yeast ptc1 null mutants toward H2O2, ZnCl2, cisplatin, and rapamycin. Collectively, the results suggest that SjPtc1 may take part in the regulation of cellular responses to oxidative stress, DNA damage stress, and the TOR (target of rapamycin) signaling pathway.

Direct measurement of temperature-dependent solvation forces between DNA double helices

The assembly of double stranded DNA helices with divalent manganese ion is favored by increasing temperature. Direct force measurements, obtained from the osmotic stress technique coupled with x-ray diffraction, show that the force characteristics of spontaneously precipitated Mn(2+)-DNA closely resemble those observed previously by us for other counterion condensed DNA assemblies. At temperatures below the critical one for spontaneous assembly, we have quantitated the changes in entropy and manganese ion binding associated with the transition from repulsive to attractive interactions between helices mediated by osmotic stress. The release of structured water surrounding the DNA helix to the bulk solution is the most probable source of increased entropy after assembly. Increasing the water entropy of the bulk solution by changing the manganese salt anion from CI- to ClO4- predictably and quantitatively increases the transition entropy. This is further evidence for the dominating role of water in the close interaction of polar surfaces.

Simultaneous spectrophotometric determination of metal ions with 4-(pyridyl-2-azo)resorcinol (PAR)

A new method for the simultaneous determination of the divalent ions of cadmium, cobalt, copper, lead, manganese, nickel and zinc in binary, ternary and quaternary mixtures based on the application of a multiple linear regression programme to the spectra of the complexes of these ions with 4-(pyridyl-2-azo)resorcinol (PAR) was developed. The detection limits afforded by the proposed method range from 0.02 μg/ml for Co(II), Mn(II), Ni(II) and Zn(II) to 0.10 μg/ml for Pb(II). The method is rapid and quite simple as it entails no prior separation, and was successfully applied to the analysis for the above-mentioned ions in synthetic samples and real alloys.

Epr studies of divalent manganese ions in magnesium maleate dihydrate single crystals

Abstract An EPR study of Mn2+ ions doped in single crystals of Dihydrate Magnesium Maleate has been carried out at room temperature at X-band. From the observed spectra, spin-Hamiltonian parameters have been evaluated. Mn2+ ions have been found to enter the lattice interstitially.

A spectroscopic study of NaI containing europium and manganese

NaI crystals containing different concentrations of divalent europium and manganese ions were investigated using the photoluminescence technique. Excitation spectra and decay times of observed Eu2+ and Mn2+ emissions were analysed in the temperature range 80-300 K. The experimental data from the slightly doped quenched crystals suggest the preferential pairing of Eu2+ and Mn2+ ions. At these centres an efficient energy transfer from Eu to Mn takes place. A model is proposed to explain the kinetics of Eu2+ to Mn2+ energy transfer in NaI based on experimental observations. It is established that a short-range interaction mechanism such as an electric dipole-quadrupole interaction or exchange is active between the impurity pairs in which the energy transfer occurs. The results obtained substantiate the ionic radius criterion proposed by Rubio and co-workers to predict impurity pairing in a solid material.

Genetic and Crystallographic Studies of the 3′,5′-Exonucleolytic Site of DNA Polymerase I

Site-directed mutagenesis of the large fragment of DNA polymerase I (Klenow fragment) yielded two mutant proteins lacking 3',5'-exonuclease activity but having normal polymerase activity. Crystallographic analysis of the mutant proteins showed that neither had any alteration in protein structure other than the expected changes at the mutation sites. These results confirmed the presumed location of the exonuclease active site on the small domain of Klenow fragment and its physical separation from the polymerase active site. An anomalous scattering difference Fourier of a complex of the wild-type enzyme with divalent manganese ion and deoxythymidine monophosphate showed that the exonuclease active site has binding sites for two divalent metal ions. The properties of the mutant proteins suggest that one metal ion plays a role in substrate binding while the other is involved in catalysis of the exonuclease reaction.

Characterization of non-transferrin-bound iron clearance by rat liver.

Recent evidence suggests that the hepatic iron-loading characteristic of hemochromatosis may result in part from efficient hepatic clearance of non-transferrin-bound iron, which is increased in this disorder. However, this hypothesis assumes that hepatic clearance remains highly efficient despite excess iron stores. We therefore studied hepatic uptake of non-transferrin-bound iron in the single-pass perfused rat liver under varying conditions. Animals were iron loaded or depleted by dietary manipulation, but no changes in the efficiency of ferrous iron uptake or the kinetic parameters were seen (single-pass extraction, 59-74%; Km, 16-19 microM; Vmax, 30-32 nmol X min-1 X g liver-1). Added divalent zinc, cobalt, and manganese ions reversibly inhibited ferrous iron uptake and the inhibition by zinc was shown to be competitive. Uptake required calcium, was markedly temperature-sensitive (delta E = 14.3 Kcal/mol), and was relatively insensitive to inhibition of cellular energy metabolism. Particles consistent with ferritin cores were seen in lysosomes of hepatic parenchymal cells within 30 min of perfusion with ferrous iron. These results suggest that ferrous iron is cleared from plasma by a passive, saturable transport process that is not regulated by the iron content of the liver and that may be shared with other transition metal ions. Because clearance is highly efficient, increased levels of non-transferrin-bound iron in plasma may present the liver with an obligatory iron load resulting in progressive accumulation and toxicity.

Electrochemical behaviour of a platinum electrode in SiO 2CaOMnO molten slags

Abstract The electrochemical behaviour of a platinum electrode in SiO 2 CaOMnO molten slags has been studied by cyclic voltammetry. The anodic oxidation of divalent manganese ions is a diffusion controlled process which have been confirmed by electrode impedance measurements.

18] Prenyltransferase from human liver

This chapter describes the isolation of prenyltransferase from human liver. Prenyltransferase has been purified to homogeneity from yeast, pig liver, and in crystalline form from chicken liver. The homogeneous human liver enzyme, the first sterol synthesizing enzyme to be purified from a human tissue, has properties distinct from the enzyme from these sources. Human liver prenyltransferase has an absolute requirement for divalent magnesium or manganese ions for activity. Not more than background activity is observed in the absence of divalent metals. This chapter highlights purification process of this enzyme. It consists of six steps namely—crude extract, ammonium sulfate fractionation, batch treatment with carboxymethyl cellulose, DEAE-cellulose column chromatography, butyl-agarose column chromatography, and calcium phosphate column chromatography.

On the nature of the phase transitions in α-MnS

X-ray diffraction measurements on various (ranging in thickness from approximately 30 to approximately 330 mu m) platelet-shaped crystals of alpha -MnS (bounded by (111) planes) and temperature-dependent neutron diffraction measurements on a polycrystalline sample are reported. It is found that a previously reported sign reversal of the rhombohedral lattice distortion Delta ( Delta = alpha - pi /2 with alpha the corner angle of a pseudo-cubic rhombohedron) at T approximately=130K observed for thick crystals is not substantiated. The observed anomalies for these crystals are related to a spontaneous domain rearrangement from a multiple T domain structure in the region 130K<T<or=152K into nearly exclusively single T1 domains for T<or=130K. Thin crystals show a continuous temperature dependence of Delta ; Delta is positive for all temperatures below TN. The formation of T1 domains in these iodine-grown crystals of alpha -MnS is presumably related to the presence of a monolayer of iodine on top of a (111) plane of divalent positive manganese ions. Temperature-dependent neutron diffraction experiments show that for all temperatures below TN the magnetic ordering is best described by a collinear in-plane FCC type-II antiferromagnetic spin structure.

The role of metals in carcinogenesis: biochemistry and metabolism.

The oxyanions of vanadium, chromium, molybdenum, arsenic, and selenium are stable forms of these elements in high oxidation states which cross cell membranes using the normal phosphate and/or sulfate transport systems of the cell. Once inside the cell, these oxyanions may sulfuryl transfer reactions. Often the oxyanions serve as alternate enzyme substrates but form ester products which are hydrolytically unstable compared with the sulfate and phosphate esters and, therefore, decompose readily in aqueous solution. Arsenite and selenite are capable of reacting with sulfhydryl groups in proteins. Some cells are able to metabolize redox active oxyanions to forms of the elements in other stable oxidation states. Specific enzymes may be involved in the metabolic processes. The metabolites of these elements may form complexes with small molecules, proteins and nucleic acids which inhibit their ability to function properly. The divalent ions of beryllium, manganese, cobalt, nickel, cadmium, mercury, and lead are stable forms of these elements which may mimic essential divalent ions such as magnesium, calcium, iron, copper, or zinc. These ions may complex small molecules, enzymes, and nucleic acids in such a way that the normal activity of these species is altered. Free radicals may be produced in the presence of these metal ions which damage critical cellular molecules.

The Role of Metals in Carcinogenesis: Biochemistry and Metabolism

The oxyanions of vanadium, chromium, molybdenum, arsenic, and selenium are stable forms of these elements in high oxidation states which cross cell membranes using the normal phosphate and/or sulfate transport systems of the cell. Once inside the cell, these oxyanions may sulfuryl transfer reactions. Often the oxyanions serve as alternate enzyme substrates but form ester products which are hydrolytically unstable compared with the sulfate and phosphate esters and, therefore, decompose readily in aqueous solution. Arsenite and selenite are capable of reacting with sulfhydryl groups in proteins. Some cells are able to metabolize redox active oxyanions to forms of the elements in other stable oxidation states. Specific enzymes may be involved in the metabolic processes. The metabolites of these elements may form complexes with small molecules, proteins and nucleic acids which inhibit their ability to function properly. The divalent ions of beryllium, manganese, cobalt, nickel, cadmium, mercury, and lead are stable forms of these elements which may mimic essential divalent ions such as magnesium, calcium, iron, copper, or zinc. These ions may complex small molecules, enzymes, and nucleic acids in such a way that the normal activity of these species is altered. Free radicals may be produced in the presence of these metal ions which damage critical cellular molecules.

Analysis of the spin–Hamiltonian parameters for Mn2+ in orthorhombic and axial symmetry sites of the alkali chlorides. Binding energies of the Mn2+ cation vacancy complexes

The superposition model is used to analyze for the first time the second-order spin–Hamiltonian parameters b02 and b22 for the Mn2+ ion in orthorhombic C2v symmetry sites of the alkali chlorides LiCl, NaCl, KCl, and RbCl. Values for the intrinsic parameter ?2 and for the power-law exponent t2 are reported for the divalent manganese ion surrounded by chlorine ligands. In order to test the applicability of the superposition model a calculation was made of the quadrupole b02 term describing the 6S5/2 ground state splitting of the Mn2+ ion in axial symmetry sites of the alkali chlorides, using the intrinsic parameters ?2 and the power-law exponent t2 previously obtained from the analysis of the spin–Hamiltonian parameters corresponding to the orthorhombic symmetry site. In order to carry out the analysis mentioned above, a theoretical calculation was made of the lattice distortion around the impurity ion caused by its substitution for the host alkali ion in all the alkali halides. Values for the binding energy of the ground and first excited states of the impurity Mn2+ -cation vacancy pair are also reported.

Adhesion of rat hepatocytes to collagen.

Abstract Rat hepatocytes, freshly isolated with a collagenase perfusion technique, were found to attach within 1 h on collagen substrates and on culture dishes coated with cold insoluble globulin (CIG) or asialoceruloplasmin (AC). Spreading was observed on collagen and CIG but not on AC. Both attachment and spreading occurred in a simple balanced salt solution in the absence of serum. In the absence of serum no attachment was observed on plain plastic dishes or on dishes coated with serum albumin or other plasma proteins, unless divalent manganese ions were present. In the presence of manganese the hepatocytes attached to all surfaces tested, but no spreading occurred. Attachment to collagen occurred equally well to collagens type I or type III both in the native, fibrillar state and in the denatured state. Collagen attachment required magnesium ions but did not appear to involve the collagen-linked carbohydrates. Different mechanisms were found to operate in hepatocyte attachment to collagen and to AC; the latter is most likely mediated by the hepatocyte surface receptor involved in recognition and uptake of asialoglycoproteins. The role of CIG in hepatocyte attachment to collagen was investigated. Data are presented suggesting that this glycoprotein, which mediates the adhesion of fibroblasts to collagen, is not required for hepatocyte attachment to collagen.

X-ray photoelectron spectroscopy of Co3O4, Fe3O4, Mn3O4, and related compounds

Abstract The metal 2p region spectra of the mixed valence spinels, Co3O4, Fe3O4, Mn3O4, and related compounds were studied. The satellite splittings of Co 2p 3 2 for the octahedrally coordinated cobaltous ions are 6.2 eV and those for the tetrahedrally coordinated ones are about 5.3 eV. The Co 2p spectrum for Co3O4 is considered to be the sum of spectra of magnetic cobaltous ions and low-spin cobaltic ions. In the cases of Fe3O4 and Mn3O4, the oxidation states were not clearly distinguished because both the divalent and trivalent ions of iron and manganese are high-spin.