Crystal structure and ionic conductivity of the series A2Bi24Mo8X2O68 (A = Ca, Sr and Ba and X = Cr and W) in the Bi2O3?MoO3 system

A series of A₂Bi₂₄Mo₈X₂O₆₈ compounds, Ca₂Bi₂₄Mo₈Cr₂O₆₈ (CBMC), Sr₂Bi₂₄Mo₈Cr₂O₆₈ (SBMC), Pb₂Bi₂₄Mo₈Cr₂O₆₈ (PBMC) and Ba₂Bi₂₄Mo₈W₂O₆₈ (BBMW) have been synthesized by the solid-state method and characterized by single crystal X-ray diffraction. The compounds index into the monoclinic P2/c system with a=11.687(4) ?, 5.784(2) ?, 24.728(9) ?, 101.911(6)°, Z=1; 11.673(6) ?, 5.775(3) ?, 24.670(2) ?, 101.757(8)°, Z=1; 11.638(3) ?, 5.790(1) ?, 24.655(6) ?, 101.716(4)°, Z=1 and 11.718(6) ?, 5.818(3) ?, 24.716(12) ?, 101.835(9)°, Z=1 for CBMC, SBMC, PBMC and BBMW, respectively. The structures were solved by direct methods and refined to R indices of 0.081, 0.065, 0.080 and 0.079 respectively. These compounds are isostructural with Bi₂₆Mo₁₀O₆₉ and the structure consists of columns of [Bi₁₂O₁₄] along the b-axis, surrounded by Mo/Cr/WO₄ tetrahedra. a.c. impedance studies indicate higher values of ionic conductivity for the tungsten-substituted compounds. Supplementary material The crystal data of CBMC, SBMC, PBMC and BBMW have been deposited at the Fachinformationszentrum Karlsruhe (FIZ) with the numbers CSD 415143, CSD 415145, CSD 415144 and CSD 415142, respectively.     

Radiochemical separation of bismuth activities using Dalzin,and its application to geological problems

A radiochemical method has been devised for the separation of bismuth activities of the natural series,viz.²¹⁴Bi,²¹⁰Bi and²¹²Bi, and applied to the indirect estimation of their corresponding precursors,²²²Rn,²¹⁰Pb and²¹²Pb, in a wide variety of geological materials. The method consists of the solvent extraction of bismuth in radiochemically pure form from the sample solution atpH 2 with diallyldithiocarbamido-hydrazine (Dalzin) in chloroform, and back extraction with 2M acid. The advantages of this method over the dithizone extraction system are discussed.     

An average fock operator technique of approximate open-shell LCAO-MO-SCF calculation

The exchange part of the usual Hartree-Fock potential in the unrestricted Hartree-Fock (UHF) theory is suitablyaveraged to construct an, average one-electron model Hamiltonian which generates a set of spin-restricted one-electron orbitals in a self-consistent manner. These orbitals are then used to calculate the electronic energy of the open-shell system by using the proper functional form for the energy which handles the exchange terms correctly. The eigenvalues ofF ^av can be used for calculating either the spin-polarised or spin-averaged ionisation potentials of different orbitals at theKoopmans’ theorem level of approximation. Comparison ofE ^ac with the UHF-energy shows thatE _UHF<E ^ac in each case revealing some kind of an upper bound nature ofE ^ac. An approximate variational argument is given. Relationship of our model with the hyper-Hartree-Fock theory of slater is explored and the general problem of eliminating ‘self-interaction’ terms in average Fock-operator based theories is discussed.     

Synthesis of 3‐(substituted)‐2,4,8,15‐tetroxa‐3‐phosphadispiro[5.2.5]hexadecane‐3‐oxides

Novel 3‐(substituted)‐2,4,8,15‐tetroxa‐3‐phosphadispiro[5.2.5]hexadecane‐3‐oxides (3‐12) have been synthesized by cyclization of 1,5‐dioxaspiro[5.5]undecande‐3,3‐dimethanol (1) with various substituted aryl phosphorus dichloridates (2) in dry toluene‐THF in the presence of triethylamine at 40‐60 ^oC. Their molecular structures were determined by ir, nmr and mass spectral studies and were screened for antifungal activity against Curvularia lunata and Aspergillus niger, and antibacterial activity on Staphylococcus aureus and Escherichia coli. Most of them possess significant activity.     

Oxidative verdoheme formation and stabilization by axial isocyanide ligation

The effect of isocyanides as axial ligands on the formation and stability of verdoheme by oxidation has been examined. The reaction of [Fe(III)(OEPO)]2 with t-butyl isocyanide under dioxygen-free conditions results in the formation of (t-BuNC)2Fe(II)(OEPO*) with an electron paramagnetic resonance at g=2.009 with a peak-to-peak separation of 23.5 G at 4 K. (OEPO is the trianion of octaethyloxophlorin and OEPO* is the radical dianion obtained from OEPO by one-electron oxidation.) Exposure of chloroform solutions of either (2,6-xylylNC)2Fe(II)(OEPO*) or (t-BuNC)2Fe(II)(OEPO*) to dioxygen followed by the addition of ammonium hexafluorophosphate results in their transformation into the diamagnetic verdohemes, [(2,6-xylylNC)2Fe(II)(OEOP)](PF6) and [(t-BuNC)2Fe(II)(OEOP)](PF6), yields 68 and 70%, respectively. (OEOP is the anion of octaethyl-5-oxaporphyrin.) The oxidation reactions of (2,6-xylylNC)2Fe(II)(OEPO*) and (t-BuNC)2Fe(II)(OEPO*) have also been monitored by 1H NMR spectroscopy. No resonances due to paramagnetic products could be detected, the reactions appear to result only in the formation of the diamagnetic verdohemes, and the products are not susceptible to further oxidation.     

Comparisons of NMR spectral quality and success in crystallization demonstrate that NMR and X-ray crystallography are complementary methods for small protein structure determination

X-ray crystallography and NMR spectroscopy provide the only sources of experimental data from which protein structures can be analyzed at high or even atomic resolution. The degree to which these methods complement each other as sources of structural knowledge is a matter of debate; it is often proposed that small proteins yielding high quality, readily analyzed NMR spectra are a subset of those that readily yield strongly diffracting crystals. We have examined the correlation between NMR spectral quality and success in structure determination by X-ray crystallography for 159 prokaryotic and eukaryotic proteins, prescreened to avoid proteins providing polydisperse and/or aggregated samples. This study demonstrates that, across this protein sample set, the quality of a protein's [15N-1H]-heteronuclear correlation (HSQC) spectrum recorded under conditions generally suitable for 3D structure determination by NMR, a key predictor of the ability to determine a structure by NMR, is not correlated with successful crystallization and structure determination by X-ray crystallography. These results, together with similar results of an independent study presented in the accompanying paper (Yee, et al., J. Am. Chem. Soc., accompanying paper), demonstrate that X-ray crystallography and NMR often provide complementary sources of structural data and that both methods are required in order to optimize success for as many targets as possible in large-scale structural proteomics efforts.     

The gene-protein database of Escherichia coli: edition 5.

The gene-protein database of Escherichia coli is both an index relating a gene to its protein product on two-dimensional gels, and a catalog of information about the function, regulation, and genetics of individual proteins obtained from two-dimensional gel analysis or collated from the literature. Edition 5 has 102 new entries--a 15% increase in the number of annotated two-dimensional gel spots. The large increase in this edition was accomplished in part by the use of a new method for expression analysis of ordered segments of the E. coli genome, which has resulted in linking 50 gel spots to their genes (or open reading frames) and another 45 to specific regions of the chromosome awaiting the availability of DNA sequence information. Communication of information from the scientific community resulted in additional identifications and regulatory information. To increase accessibility of the database it has been placed in the repository at the National Center for Biotechnology Information (NCBI) at the National Library of Medicine under the name ECO2DBASE. It will be updated twice yearly. This edition of the gene-protein database is estimated to contain entries for one-sixth of the protein-encoding genes of E. coli.     

Growth of hair and the trace element profile a study by sectional analysis

Correlations between the growth of hair and the trace element profile have been investigated by non-destructive neuron activation analysis through gamma-ray speetrometry using NaI(Tl) as well as Ge(Li) detectors. After preliminary investigations to establish the experimental errors, the effect of washing procedures and in-person variations, hair samples belonging to ladies with known case histories, particularly with regard to dietary habits, health and profession, were examined. Scalp-hair samplex 50–100 cm in length, representing an average time span of ∼5–10 years were collected by combing. Samples in their non-anagen phase, differentiated by their roots, were analysed in 10 cm sections. The concentrations of the following elements were determined: Na, Cl, Mn, Co, Cu, Zn, As, Se, Ag, I, Au and Hg. Absolute values for the concentrations are reported for most of the elements, while for the rest relative values for the various sections are given. The values for the different sections vary by large factors for many elements although for some elements, like Cu and Mn, the variations are not appreciable. The unusually large concentrations of elements like Se ang Hg are in broad agreement with the case histories. However, detailed examination of the results with regard to time-dependent variations seem to pose serious problems in the applications to forensic science.     

Role of dimethyl sulfoxide as a solvent for vinyl polymerization

Dimethyl sulfoxide has been used as a solvent in the polymerization of methyl methacrylate and styrene. The chain-transfer coefficients of the solvent and the values of δ [i.e., (2k_t)^1/2/k_p] in solvent-monomer mixtures of various compositions were determined. δ was observed to be dependent on the solvent concentration in the case of methyl methacrylate but remained constant in case of styrene. The lowering of the values of δ with increasing solvent concentration in case of methyl methacrylate has been attributed to an interaction between the solvent and poly(methyl methacrylate) radical resulting in lower termination rate.     

Synthesis and chelation properties of new polymeric ligand derived from 8-hydroxy-5-azoquinoline hydroxy benzene

8-Hydroxy-5-azoquinoline phenyl methacrylate-formaldehyde (8H5AQPMA-F) macromonomer was prepared from methacryloyl chloride with condensation products of 8-hydroxy-5-azoquinoline phenol-formaldehyde, and polymerized in DMF at 70 °C using benzoyl peroxide as free radical initiator. Poly(8H5AQPMA-F) was characterized by infrared and nuclear magnetic resonance spectroscopic techniques. Polychelates were obtained when the DMF solution of the resin containing few drops of ammonia was treated with the aqueous solution of Cu(II)/Ni(II). Elemental analysis of the polychelates indicates that the metal to ligand ratio was about 1:2. The IR spectra of polychelates suggest that the metals were coordinated through the oxygen of the phenolic-OH group and nitrogen of the quinoline ligand. The DRS and magnetic moment data indicate a square planar for Cu(II) complex whereas octahedral for Ni(II) complex. The TGA data revealed the thermal stability of the resin and the polychelates. X-ray diffraction study revealed the incorporation of the metal ions significantly enhanced the degree of crystallinity. The sorption properties of the chelate-forming resin towards various divalent metal ions [Cu(II) and Ni(II)] were studied as a function of pH and electrolyte.