Structure Of Na Research Articles

ChemInform Abstract: Na2Hg3S4; a Thiomercurate with Layered Anions

Abstract Dark red crystals of Na 2 Hg 3 S 4 were obtained by reacting a stoichiometric mixture of Na 2 S and HgS at 870 K. Na 2 Hg 3 S 4 is orthorhombic, oP36 , space group Pbca with a=7.308(5) A , b=14.011(8) A , c=8.231(3) A and Z =4. The crystal structure was determined from four-circle diffractometer data and refined to a conventional R of 0.056 for 718 reflections with F 0 2 >3 σ ( F o 2 ) and 43 variables ( R w =0.065). Na 2 Hg 3 S 4 crystallizes with a new structure type whose outstanding feature is the formation of strongly corrugated anionic layers, α 2 - [Hg 3 S 4 ] 2− , running parallel to (010). These layers are based on a network of 16-membered rings formed by alternating mercury and sulphur atoms. Two thirds of the mercury atoms are in a trigonal planar co-ordination by sulphur (d Hg-S ≈ 2.49 A ) while the remaining atoms are linearly coordinated (d Hg-S =2.344 A ). The Na + ions are coordinated by five sulphur atoms in a distorted square pyramidal configuration. The structure of Na 2 Hg 3 S 4 can formally be derived from a distorted close-packed array of chalcogen atoms (stacking sequence, ( hc ) 2 ; stacking direction, [010]).

Parallel G-Quadruplex-Specific Fluorescent Probe for Monitoring DNA Structural Changes and Label-Free Detection of Potassium Ion

Here we demonstrate an anionic porphyrin, protoporphyrin IX (PPIX), as a parallel G-quadruplex-specific fluorescent probe for monitoring DNA structural changes and utilize it to develop a DNA-based K(+) sensor. The interactions of PPIX with different DNA structures in K(+) or Na(+) solution are investigated by using circular dichroism, fluorescence, and UV-vis spectroscopy. The observations reveal that PPIX has an ∼100-fold selectivity for parallel G-quadruplexes against duplexes and antiparallel G-quadruplexes. Meanwhile, the fluorescence intensity of PPIX increases by over 10-fold upon binding to parallel G-quadruplexes. On the basis of the selectivity and fluorescence property of PPIX, we introduce a facile, label-free approach to monitoring DNA structural changes via fluorescence signal readout that is tuned by PPIX binding and release. To illustrate it, we utilize PPIX and a G-rich DNA PS2.M to construct a fluorescent K(+) sensor based on an antiparallel-to-parallel conformation transition of the G-quadruplex. PS2.M adopts an antiparallel quadruplex structure in Na(+) solution, whereas it gradually converts into a parallel G-quadruplex upon addition of increasing K(+). This conformational change is indicated by a sharp increase in the fluorescence intensity of PPIX, owing to the good ability of PPIX to discriminate parallel G-quadruplexes from antiparallel ones. Even in the presence of 100 mM Na(+), such a "turn-on" fluorescent sensor can respond to low concentrations of K(+), with a limit of detection (0.5 mM) for K(+) analysis. In addition, this sensor exhibits a high selectivity for K(+) over other common metal ions, which ensures its practical applications to real samples. These results reveal that PPIX is promising for use as a specific DNA structural probe in sensing applications.

Mesoscopic structure of Ni2 + x Mn1 − x Ga alloys in the concentration range corresponding to a coupled magnetic-structural phase stransition

The Ni2 + xMn1 − xGa magnetic shape memory alloys at concentrations x = 0.18–0.36 have been studied using small-angle polarized neutron scattering in magnetic fields 0 0.27, the relationship between the characteristic temperatures is changed, i.e., Tm > TC. The small-angle polarized neutron scattering data indicate that, in the concentration range under investigation, there occurs a complex transformation of the magnetic and atomic structures. All phase transitions exhibit a temperature hysteresis of scattering and polarization, which is characteristic of first-order phase transitions. A comparative analysis of the mesoscopic structures of the Ni2 + xMn1 − xGa and Ni2 + x + yMn1 − xGa1 − y alloys studied using the small-angle polarized neutron scattering technique has been carried out.

ChemInform Abstract: Synthesis and Structure of the Zintl Compounds Na2BaTt4 (Tt: Si, Ge).

Abstract The isotypic title compounds ate obtained from reactions of stoichiometric mixtures of the elements in welded Ta containers at 700–800 °C. The structure of Na 2 BaSi 4 was determined by single-crystal X-ray diffraction (orthorhombic, Ima2 (No. 46), Z = 8, a = 9.524, b = 17.980(3), c = 8.570(3) A). The compound crystallizes in a novel structure type with Na + and Ba 2+ cations and two crystallographically-independent isolated Si 4 4− anions. The anions are nearly regular tetrahedra with bond distances of 2.385(3) to 2.448(4) A and bond angles between 59.2 and 61.7°. The overall structure may be described as a distorted face-centered-cubic array of Si 4 4− anions in which Na + and Ba 2+ atoms occupy all tetrahedral and octahedral holes in an ordered way. The result is closely related to the topology of f.c.c. Li 3 Bi type but with ordering of the two cations. Magnetic measurements showed that Na 2 BaSi 4 is diamagnetic, and its family can be formulated in terms of oxidation states as Zintl phases (Na + ) 2 Ba 2+ (Tt 4 4− ).

Synthesis, Characterization, and Crystal Structure of a New Trisodium Triborate, Na3[B3O4(OH)4

The preparation of a new trisodium triborate, Na(3)[B(3)O(4)(OH)(4)], and its complete characterization in terms of molecular structure and thermal behavior are reported. Synthesis of this compound was achieved either by NaBH(4) hydrolysis or by thermal treatment of Na[B(OH)(4)].2H(2)O. The crystal structure was determined by single-crystal X-ray diffraction. The trisodium triborate crystallized in the monoclinic system (a = 12.8274(6) A, b = 7.7276(4) A, c = 6.9690(3) A, and beta = 98.161(3) degrees ), space group Cc, Z = 2. The structure of Na(3)[B(3)O(4)(OH)(4)] comprised [B(3)O(4)(OH)(4)](3-) polyanions, based on B-O-containing rings with two tetracoordinated boron atoms and one tricoordinated boron atom in the fragments BO(2)(OH)(2) and BO(3), respectively. These polyanions are interconnected by four intermolecular hydrogen bonds and presented a tilt of 10.470(4) degrees compared to the a axis. Thus, they are stacked by rotation of about 180 degrees around an axis defined by the three-coordinated boron atoms and parallel to the c axis. Such polyanions were only observed previously in two synthetic compounds, M(3)[B(3)O(4)(OH)(4)].2H(2)O with M = K and Rb, which were isostructural. The originality of the present work was the synthesis and the description of a different crystallographic structure containing this polyanion. Characteristic peaks ranging from 500 to 1500 cm(-1) and around 3300 cm(-1) highlighted the presence of the B-O rings and hydroxyl groups, respectively. The decomposition temperature T = 155 degrees C was obtained by thermogravimetric analysis, and the following equivalent formula in terms of hydration degree was proposed: NaBO(2).(2)/(3)H(2)O. Na(3)[B(3)O(4)(OH)(4)] decomposed into Na(3)[B(3)O(5)(OH)(2)] in equilibrium with its vapor.

Stabilization of over-stoichiometric Mn 4+ in layered Na 2/3MnO 2

Sodium manganates with nominal composition Na 2/3MnO 2 were prepared by solid state reaction between Na 2CO 3 and MnCO 3 at 1000 °C. The composition and structure of Na x MnO 2 were controlled by the rate of cooling from the temperature of preparation. This is a consequence of the capability of Na 2/3MnO 2 to accommodate over ‐stoichiometric Mn 4+ ions up to 12.5%. Structural characterization was carried out by XRD powder diffractions, TEM analysis and Raman spectroscopy. The composition and oxidation state of manganese were determined by chemical analysis and magnetic susceptibility measurements. The manganese distribution in the layers was analysed using electron paramagnetic resonance (EPR) spectroscopy. By quenching from 1000 °C, the orthorhombic distorted modification is stabilized. A phase separation into orthorhombic and hexagonal modifications takes place when Na 2/3MnO 2 is slow cooled. The structure changes are concomitant with an increase in the oxidation state of Mn. The over ‐stoichiometric Mn 4+ ions are accommodated in the hexagonal modification by creation of vacancies in the MnO 2 ‐layers.

Synthesis and structure of Na+-intercalated WO3(4,4′-bipyridyl)0.5

WO3(4,4-bipyridyl)0.5 was doped with Na+ by ion implantation so as to alter the electronic structure. Single-crystal X-ray diffraction reveals layers of corner-shared WO5N octahedra linked by bipyridine. In the observed space group of Pbca, the fully-ordered bipyridyls form cages with Na+ disordered bimodally about the cage centre.

Effect of ball milling on the structure of Na +-montmorillonite and organo-montmorillonite (Cloisite 30B)

The effect of high energy ball milling under different conditions on the structure of Na +-montmorillonite (Na-MMT), and the organo-montmorillonite (Cloisite 30B) was investigated. Ball milling increased the structural disorder: peeling off of layers from the particles was observed, followed by the exfoliation of the particles, indicated by the disappearance of the (001) reflection. X-ray diffraction and infrared spectra revealed that the exfoliated layers did not show deteriorated structures. The presence of the alkylammonium ions seemed to stabilize the structure by reducing exfoliation.

Effects of Concentration, Temperature and Hydrostatic Pressure on the Local Lattice Structure of Ni2+ Doped Zn(BF4)2 · 6H2O Crystal

Abstract A theoretical method for studying the inter-relationship between electronic and molecular structure is presented by means of complete energy matrices. As an application, the effects of temperature, concentration and hydrostatic pressure on the local structures of Ni2+ doped Zn(BF4)2 ・6H2O crystal have been studied. Our results show that the local lattice structures of [Ni(H2O)6]2+ coordination complex have expansion distortions as the temperature rises. Meanwhile, we find that the local structure parameter θ becomes smaller with the increasing concentration of Ni2+ ions doped in Zn(BF4)2 ・6H2O crystal. Furthermore, the pressure dependence of θ and anisotropic g-factors are discussed and the relationship between zero-field splitting parameter D and Δg is determined.

Variational cellular method in molecular and crystal electronic structure calculations

The variational cellular method (VCM) is applied to calculate the electronic structure of ground-state CO and Na metallic crystal. The results are in fairly good agreement with other calculations and experiment. The free-electron energy eigenvalues in a body-centered-cubic lattice were also obtained. It is found that VCM yields the correct solution to the “empty-lattice test.”

Functional Interactions between Distinct Sodium Channel Cytoplasmic Domains through the Action of Calmodulin

Sodium channels are fundamental signaling molecules in excitable cells, and are molecular targets for local anesthetic agents and intracellular free Ca(2+) ([Ca(2+)](i)). Two regions of Na(V)1.5 have been identified previously as [Ca(2+)](i)-sensitive modulators of channel inactivation. These include a C-terminal IQ motif that binds calmodulin (CaM) in different modes depending on Ca(2+) levels, and an immediately adjacent C-terminal EF-hand domain that directly binds Ca(2+). Here we show that a mutation of the IQ domain (A1924T; Brugada Syndrome) that reduces CaM binding stabilizes Na(V)1.5 inactivation, similarly and more extensively than even reducing [Ca(2+)](i). Because the DIII-DIV linker is an essential structure in Na(V)1.5 inactivation, we evaluated this domain for a potential CaM binding interaction. We identified a novel CaM binding site within the linker, validated its interaction with CaM by NMR spectroscopy, and revealed its micromolar affinity by isothermal titration calorimetry. Mutation of three consecutive hydrophobic residues (Phe(1520)-Ile(1521)-Phe(1522)) to alanines in this CaM-binding domain recapitulated the electrophysiology phenotype observed with mutation of the C-terminal IQ domain: Na(V)1.5 inactivation was stabilized; moreover, mutations of either CaM-binding domain abolish the well described stabilization of inactivation by lidocaine. The direct physical interaction of CaM with the C-terminal IQ domain and the DIII-DIV linker, combined with the similarity in phenotypes when CaM-binding sites in either domain are mutated, suggests these cytoplasmic structures could be functionally coupled through the action of CaM. These findings have bearing upon Na(+) channel function in genetically altered channels and under pathophysiologic conditions where [Ca(2+)](i) impacts cardiac conduction.

Nonpair interactions in Na+(H2O) n clusters under thermal fluctuation conditions

The influence of many-particle interactions on the structure of Na+(H2O) n clusters at 298 K was studied by the Monte Carlo method. The interaction parameters were reproduced from the experimental data on the Gibbs energy of hydration in water vapor. The interaction of induced dipoles results in the displacement of part of molecules through large distances from the ion. Covalent interactions strengthen the bond with the first attached molecule and weaken bonds with the other molecules.

Studies of the Spin Hamiltonian Parameters for NiX<sub>2</sub> and CdX<sub>2</sub>:Ni<sup>2+</sup> (X=Cl, Br)

The spin Hamiltonian parameters (zero-field splitting D and the g factors) for NiX2 and CdX2:Ni2+ (X=Cl, Br) are quantitatively investigated from the perturbation formulas of these parameters for a 3d8 ion in trigonally distorted octahedra based on the cluster approach. In the calculations, the trigonal field parameters  and ′ are determined from the superposition model and the local structures of Ni2+ in the halides. The theoretical g factors show reasonable agreement with the observed values, and the experimental D for CdX2:Ni2+ are also interpreted by considering suitable lattice distortions (angular decreases) in the impurity-ligand bond angles related to the C3 axis due to the size mismatching substitution. The contributions from the ligand orbital and spin-orbit coupling interactions are important and should be taken into account.

The structure of the Na+,K+-ATPase and mapping of isoform differences and disease-related mutations

The Na+,K+-ATPase transforms the energy of ATP to the maintenance of steep electrochemical gradients for sodium and potassium across the plasma membrane. This activity is tissue specific, in particular due to variations in the expressions of the alpha subunit isoforms one through four. Several mutations in alpha2 and 3 have been identified that link the specific function of the Na+,K+-ATPase to the pathophysiology of neurological diseases such as rapid-onset dystonia parkinsonism and familial hemiplegic migraine type 2. We show a mapping of the isoform differences and the disease-related mutations on the recently determined crystal structure of the pig renal Na+,K+-ATPase and a structural comparison to Ca2+-ATPase. Furthermore, we present new experimental data that address the role of a stretch of three conserved arginines near the C-terminus of the alpha subunit (Arg1003-Arg1005).

Studies of the defect structure from the calculations of optical and electron paramagnetic resonance spectra for Ni2+ centre in α-LiIO3 crystal

By calculating the optical spectrum band positions and EPR parameters (g factors, g‖, g⊥ and zero-field splitting D) by diagonalizing the complete energy matrix of 3d8 ions in trigonal symmetry, the defect structure of Ni2+ centre in α-LiIO3 crystal is studied. It is found that to reach the good fits of optical and EPR data between calculation and experiment, the Ni2+ ion should shift by Δz ≈ 0.298 A along C3-axis and the O2− ions between the Ni2+ ion and Li+ vacancy (V Li) should be displaced away from the V Li by Δx ≈ 0.097 A because of the electrostatic interaction. The results are discussed.

Hydrothermal synthesis and crystal structure of Na(NH4)[C13N2H16]2[Mo7O24] · 8H2O: A novel 3-D extended supramolecular network with 1-D channels

A novel three-dimensional (3-D) supramolecular assembly of organic bicapped heptamolybdate Na(NH4)[C13N2H16]2[Mo7O24]·8H2O has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectra, elemental analysis, and thermogravimetric analysis (TGA). X-ray analyses show that compound 1 represent a novel 3-D extended supramolecular “host” networks with 1-D channels encapsulating flexible cation “guests”.

Synthesis and structure of Na[UO2(SeO3)(HSeO3)] · 4H2O

Compound Na[UO2(SeO3)(HSeO3)] · 4H2O (I) has been synthesized and studied by single-crystal X-ray diffraction. The crystals of I are monoclinic with the unit cell parameters a = 8.8032(5) A, b = 10.4610(7) A, c = 13.1312(7) A, β = 105.054(2)°, space group P21/n, Z = 4, V = 1167.76(12) A3, R = 0.0394. The main structural units of crystals I are the [UO2(SeO3)(HSeO3)]− layers belonging to the AT3B2 crystal-chemical group (A = UO22+, T3 = SeO32−, B2 =HSeO3−) of the uranyl complexes. The sodium ions are linked with oxygen atoms of two uranyl ions of the same layer and with four water molecules. Electroneutral packets that formed are linked into a three-dimensional framework through a system of hydrogen bonds.

Na<SUP>+</SUP>-Implanted Membrane for a Capacitive Sodium Electrolyte-Insulator-Semiconductor Microsensors

Ion implanted Insulator-Semiconductor (IS) sensor that specifically detects Na+ ions have been developed using ion implantation technique. Na+ ions were directly implanted with ion energies 30, 45, and 60 keV into the IS (oxidized Si3N4/Si3N4/SiO2/P-Si) structures previously covered with a thin aluminum layer. X-ray photoelectron spectroscopy (XPS) characterization shows that sodium and aluminum ions were implanted into the oxidized Si3N4 insulating layer surface. Their atomic percentage depending on energy, fluence of the implanted ion and of the annealing temperature. The sen sitivity of the ion-implanted IS structure for Na+ and of some interfering (K+, Li+, H+, and NH4+) ions was investigated using high frequency capacitance-voltage measurements. Under optimal i mplantation conditions such as energy, fluence and annealing temperature, the developed sodium microsensor demonstrates quasi-nernstian sensitivity (50 +/- 2 mV/pNa) in the concentration range from 10(-3.7) to 10(-1) M and high lifetime greater than 16 months without any loss of sensitivity.

Substitutional site and defect structure of Ni2+ in LiNbO3 crystal studied from the optical and electron paramagnetic resonance spectra

The energy levels (which are related to optical spectra) and effective spin-Hamiltonian parameters (g factors g //, g ⊥ and zero-field splitting D which are measured by electron paramagnetic resonance (EPR) spectra) of Ni2+ ion in LiNbO3 are calculated from the complete diagonalization (of energy matrix) method. In the calculations, the Ni2+ ion is suggested to replace Li+ ion with the local relaxation in LiNbO3. This point is in disagreement with the opinions in many previous papers in which the substitutional site and structural data of Ni2+ at Nb5+ site are used to explain the experimental data obtained by the optical and EPR spectra. The present calculated results are also consistent with the experimental values. The reasonableness of the substitutional site and defect structure of Ni2+ at Li+ site is discussed.

Crystal Structures of Na1/2Ln1/2TiO3 (Ln: La, Eu, Tb).

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