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PubMed2004

A structural and electrochemical investigation of 1-alkyl-3-methylimidazolium salts of the nitratodioxouranate(VI) anions [[UO2(NO3)2]2(mu 4-C2O4)]2-, [UO2(NO3)3]-, and [UO2(NO3)4]2-.

The properties of the 1-butyl-3-methylimidazolium salt of the dinuclear mu(4)-(O,O,O',O'-ethane-1,2-dioato)bis[bis(nitrato-O,O)dioxouranate(VI)] anion have been investigated using electrochemistry, single-crystal X-ray crystallography, and extended X-ray absorbance fine structure spectroscopy: the anion structures from these last two techniques are in excellent agreement with each other. Electrochemical reduction of the complex leads to the a two-electron metal-centered reduction of U(VI) to U(IV), and the production of UO(2), or a complex containing UO(2). Under normal conditions, this leads to the coating of the electrode with a passivating film. The presence of volatile organic compounds in the ionic liquids 1-alkyl-3-methylimidazolium nitrate (where the 1-alkyl chain was methyl, ethyl, propyl, butyl, pentyl, hexyl, dodecyl, hexadecyl, or octadecyl) during the oxidative dissolution of uranium(IV) oxide led to the formation of a yellow precipitate. To understand the effect of the cation upon the composition and structure of the precipitates, 1-alkyl-3-methylimidazolium salts of a number of nitratodioxouranate(VI) complexes were synthesized and then analyzed using X-ray crystallography. It was demonstrated that the length of the 1-alkyl chain played an important role, not only in the composition of the complex salt, but also in the synthesis of dinuclear anions containing the bridging mu(4)-(O,O,O',O'-ethane-1,2-dioato), or oxalato, ligand, by protecting it from further oxidation.

Journal Article↗
PubMed2005

Reduction of uranium(VI) phosphate during growth of the thermophilic bacterium Thermoterrabacterium ferrireducens.

The thermophilic, gram-positive bacterium Thermoterrabacterium ferrireducens coupled organotrophic growth to the reduction of sparingly soluble U(VI) phosphate. X-ray powder diffraction and X-ray absorption spectroscopy analysis identified the electron acceptor in a defined medium as U(VI) phosphate [uramphite; (NH4)(UO2)(PO4) . 3H2O], while the U(IV)-containing precipitate formed during bacterial growth was identified as ningyoite [CaU(PO4)2 . H2O]. This is the first report of microbial reduction of a largely insoluble U(VI) compound.

Microscopy, Electron, Scanning↗
PubMed1972

Chemical methods for removing radon and radon daughters from air.

Liquid bromine trifluoride and the solid complexes ClF(2)SbF(6), BrF(2)SbF(6), BrF(4)Sb(2)F(11), IF(4)(SbF(6))(3) and BrF(2)BiF(6) react spontaneously with radon and radon daughters at 25 degrees C, converting the radioelements to nonvolatile ions and compounds. The reagents can be used in gas-scrubbing units to remove radon and radon daughters from air. The halogen fluoride-antimony pentafluoride complexes may be suitable for purifying air in uranium mines and analyzing radon in air, since they have low dissociation pressures at 25 degrees C and are less hazardous to handle than liquid halogen fluorides.

Air Pollution, Radioactive↗
PubMed1978

Tannic acid-metal salt sequences for light and electron microscopic localization of complex carbohydrates.

Use of tannic acid (TA), in sequence with ferric chloride, uranyl acetate or gold chloride resulted in staining of selective but sometimes different sites in paraffin sections. TA-uranyl acetate of TA-ferric chloride stained sites rich in complex carbohydrates, wherease TA-gold chloride stained the collagen of various connective tissues different shades of red-purple to gray-black. Applied to epoxy-embedded thin sections of tissues fixed with glutaraldehyde and not post-osmicated, TA-uranyl acetate and TA-ferric chloride imparted density to subcellular sites known to contain a high concentration of mucosubstances, such as secretory granules and cisternae of the Golgi complex of certain cells. TA-gold chloride proved unsatisfactory for ultracytochemistry because of its tendency to form globular precipitates on thin sections. The effect of blockage procedures at the light microscopic level indicated that vicinal glycols are not required for binding of TA to tissue sites. Electrostatic forces were shown to be of minimal significance, whereas hydrogen bonding appeared to play a part in both TA-tissue and TA-metal binding mechanisms.

Carbohydrates↗
PubMed2004

Profiling of sulfoconjugates in urine by using precursor ion and neutral loss scans in tandem mass spectrometry. Application to the investigation of heavy metal toxicity in rats.

This paper reports a liquid chromatographic/electrospray ionization mass spectrometric (LC/ESI-MS) method for profiling a wide range of structurally different sulfoconjugated compounds in urine and its application to the characterization of biomarkers for heavy metal toxicity in rat urine. Sulfoconjugates were first isolated by solid-phase extraction and the LC separation was performed on a reversed-phase column. Sulfoconjugates were detected in a triple-quadrupole mass spectrometer by simultaneously monitoring constant losses of 80 u (or 80 Th for doubly charged ions), precursors of m/z 80 (SO(3) (-*)) and precursors of m/z 97 (HSO4-). The ESI-MS detection conditions were optimized on dehydroepiandrosterone sulfate and estradiol sulfate and tested on other sulfoconjugates. The analysis of urine samples from humans and rats by using the developed method allowed the detection of about 15 peaks in each mode of detection. It was then applied to the investigation of heavy metal toxicity in rats. Comparative analysis of the chromatographic fingerprints of urine from control and uranium- and cadmium-treated rats showed several variations in the chromatographic pattern of the sulfoconjugates. Diagnostic m/z ratios were confirmed by analyzing individual urine samples and one of the observed variations seemed to be specific to uranium toxicity. The ion responsible for this variation has been identified as 4-ethylphenol sulfate by comparison of its chromatographic retention time and collision-induced dissociation mass spectra (MS(2) and MS(3) performed on a quadrupole ion trap instrument) with those of the synthesized compound.

Animals↗
PubMed2006

Lanthanide and uranium complexes with an SPS-based pincer ligand.

Reactions of Ln(BH4)3(THF)n and [Li(Et2O)]SPS(Me)], the lithium salt of an anionic SPS pincer ligand composed of a central hypervalent lambda4-phosphinine ring bearing two ortho-positioned diphenylphosphine sulfide sidearms, led to the monosubstituted compounds [Ln(BH4)2(SPS(Me))(THF)2] [Ln = Ce (1), Nd (2)], while the homoleptic complexes [Ln(SPS(Me))3] [Ln = Ce (3), Nd (4)] were obtained by treatment of LnX3 (X = I, BH4) with [K(Et2O)][SPS(Me)]. The [UX2(SPS(Me))2] complexes [X = Cl (5), BH4 (6)] were isolated from reactions of UX4 and the lithium or potassium salt of the [SPS(Me)]- anion. The X-ray crystal structures of 1.1.5THF, 2.1.5THF, 3.2THF.2Et2O, and 5.4py reveal that the flexible tridentate [SPS(Me)]- anion is bound to the metal as a tertiary phosphine with electronic delocalization within the unsaturated parts of the ligand.

Journal Article↗
PubMed1975

Size changes in single muscle fibers during fixation and embedding.

During fixation of single muscles fibers with glutaraldehyde, the volume of the fiber shrinks 20%, recovers in rinse and osmium tetroxide to near normal volume and shrinks 20% again when staining with uranyl acetate. This suggest that osmotic properties of membranes may not have been completely lost during fixation, post-fixation and en bloc staining. Dehydration in ethanol and propylene oxide produces a further 10% shrinkage in volume. Infiltration and embedding with Epon causes an additional 15% change in volume. This gives a total shrinkage in volume of 45% which is nearly twice that of the apparent shrinkage in the volume of the myosin lattice as determined by electron microscopy.

Acetates↗
PubMedDate not supplied

Temporal changes in water quality at a childhood leukemia cluster.

Since 1997, 15 cases of acute lymphocytic leukemia and one case of acute myelocytic leukemia have been diagnosed in children and teenagers who live, or have lived, in an area centered on the town of Fallon, Nevada. The expected rate for the population is about one case every five years. In 2001, 99 domestic and municipal wells and one industrial well were sampled in the Fallon area. Twenty-nine of these wells had been sampled previously in 1989. Statistical comparison of concentrations of major ions and trace elements in those 29 wells between 1989 and 2001 using the nonparametric Wilcoxon signed-rank test indicate water quality did not substantially change over that period; however, short-term changes may have occurred that were not detected. Volatile organic compounds were seldom detected in ground water samples and those that are regulated were consistently found at concentrations less than the maximum contaminant level (MCL). The MCL for gross-alpha radioactivity and arsenic, radon, and uranium concentrations were commonly exceeded, and sometimes were greatly exceeded. Statistical comparisons using the nonparametric Wilcoxon rank-sum test indicate gross-alpha and -beta radioactivity, arsenic, uranium, and radon concentrations in wells used by families having a child with leukemia did not statistically differ from the remainder of the domestic wells sampled during this investigation. Isotopic measurements indicate the uranium was natural and not the result of a 1963 underground nuclear bomb test near Fallon. In arid and semiarid areas where trace-element concentrations can greatly exceed the MCL, household reverse-osmosis units may not reduce their concentrations to safe levels. In parts of the world where radon concentrations are high, water consumed first thing in the morning may be appreciably more radioactive than water consumed a few minutes later after the pressure tank has been emptied because secular equilibrium between radon and its immediate daughter progeny is attained in pressure tanks overnight.

Arsenic↗
PubMed2006

Suspension array analysis of 16S rRNA from Fe- and SO(4)2- reducing bacteria in uranium-contaminated sediments undergoing bioremediation.

A 16S rRNA-targeted tunable bead array was developed and used in a retrospective analysis of metal- and sulfate-reducing bacteria in contaminated subsurface sediments undergoing in situ U(VI) bioremediation. Total RNA was extracted from subsurface sediments and interrogated directly, without a PCR step. Bead array validation studies with total RNA derived from 24 isolates indicated that the behavior and response of the 16S rRNA-targeted oligonucleotide probes could not be predicted based on the primary nucleic acid sequence. Likewise, signal intensity (absolute or normalized) could not be used to assess the abundance of one organism (or rRNA) relative to the abundance of another organism (or rRNA). Nevertheless, the microbial community structure and dynamics through time and space and as measured by the rRNA-targeted bead array were consistent with previous data acquired at the site, where indigenous sulfate- and iron-reducing bacteria and near neighbors of Desulfotomaculum were the organisms that were most responsive to a change in injected acetate concentrations. Bead array data were best interpreted by analyzing the relative changes in the probe responses for spatially and temporally related samples and by considering only the response of one probe to itself in relation to a background (reference) environmental sample. By limiting the interpretation of the data in this manner and placing it in the context of supporting geochemical and microbiological analyses, we concluded that ecologically relevant and meaningful information can be derived from direct microarray analysis of rRNA in uncharacterized environmental samples, even with the current analytical uncertainty surrounding the behavior of individual probes on tunable bead arrays.

Bacteria↗
PubMed2006

Probing actinide electronic structure using fluorescence and multi-photon ionization spectroscopy.

The role of the 5f orbitals in actinide bond formation is one of the central issues of actinide chemistry. This question can be explored using relativistic quantum chemistry calculations, but the theoretical methods must be validated using definitive experimental data. For simple ionic compounds such as actinide oxides and halides, the electronic structure can be examined using electronic and photoelectron spectroscopy of gas phase molecules. The present article surveys recent spectroscopic and theoretical studies of the oxides of thorium and uranium. The results show that the 5f-like states are spectators and that the complex patterns of low-lying electronic states for these molecules can be understood in terms of a semi-empirical ligand field model. Comparisons with recent high-level theoretical calculations are presented and discussed.

Journal Article↗
PubMed1981

Influence of uranyl nitrate upon tubular reabsorption and glomerular filtration in blood perfused isolated dog kidneys.

The early changes in tubular reabsorption, glomerular filtration, blood flow and sodium excretion brought about by uranyl nitrate were investigated in isolated, blood-perfused dog kidneys during water diuresis. No significant changes in urine volume were observed; the decrease in fluid reabsorption was counterbalanced quantitatively by a reduction in glomerular filtration rate; only a small diminution of renal blood flow was found. The balance between reabsorption and filtration was observed as well when angiotensin action or prostaglandin synthesis were inhibited. The intrarenal venous pressure rose, suggesting that an increase in proximal intratubular hydrostatic pressure caused the decrease in filtration. Tubular back-leak of fluid, or back-diffusion, induced by the toxin, were excluded. The presence of natriuretic compounds in the urine was confirmed.

Absorption↗
PubMed1981

Occupational cancer: experience in Ontario.

This paper reviews the experience of the Workmen's Compensation Board of Ontario in identifying cases of cancer that could be attributed to occupational hazards. Worker's claims for compensation are allowed if there is reasonable medical evidence that their cancer was caused by exposure to risk factors associated with their occupation. Details of the types of cancer associated with specific carcinogens or fields of employment are discussed. About 50% of the cases were related to exposure in particular industrial operations that functioned for relatively brief periods. The number of deaths from cancer identified as being caused by occupational factors is compared with the total for cancer from all causes in Ontario during the period 1971 through 1975. Although all workers eligible for compensation may not have been identified, the data suggest that less than 1% of cancer is presently caused by occupational factors.

Aniline Compounds↗
PubMed2004

Cation-cation interactions between uranyl cations in a polar open-framework uranyl periodate.

Novel open-framework alkali metal uranyl periodates, having the formula A[(UO2)3(HIO6)(OH)(O)(H2O)].1.5H2O (A = Li, Na, K, Rb, Cs), have been prepared through mild hydrothermal synthesis. These isostructural compounds contain distorted UO7 pentagonal bipyramids that are linked through a uranyl (UO22+) to uranyl cation-cation interaction. This interaction arises from a single axial uranyl oxygen coordinating at an equatorial site of an adjacent uranyl unit. These uranium oxide polyhedra are further bound by IO6 distorted octahedra creating an open-framework structure whose channels contain the alkali metal cations.

Journal Article↗
PubMed2001

A new oxoanion: [IO]3- containing I(V) with a stereochemically active lone-pair in the silver uranyl iodate tetraoxoiodate(V), Ag4(UO2)4(IO3)2(IO4)2O2 .

The hydrothermal reaction of elemental Ag, or water-soluble silver sources, with UO3 and I2O5 at 200 degrees C for 5 days yields Ag4(UO2)4(IO3)2(IO4)2O2 in the form of orange fibrous needles. Single-crystal X-ray diffraction studies on this compound reveal a highly complex network structure consisting of three interconnected low-dimensional substructures. The first of these substructures are ribbons of UO8 hexagonal bipyramids that edge-share to form one-dimensional chains. These units further edge-share with pentagonal bipyramidal UO7 units to create ribbons. The edges of the ribbons are partially terminated by tetraoxoiodate(V), [IO4]3-, anions. The uranium oxide ribbons are joined by bridging iodate ligands to yield two-dimensional undulating sheets. These sheets help to form, and are linked together by, one-dimensional chains of edge-sharing AgO7 capped octahedral units and ribbons formed by corner-sharing capped trigonal planar AgO4 polyhedra, AgO6 capped square pyramids, and AgO6 octahedra. The [IO4]3- anions in Ag4(UO2)4(IO3)2)(IO4)2O2 are tetraoxoiodate(V), not metaperiodate, and contain I(V) with a stereochemically active lone-pair. Bond valence sum calculations are consistent with this formulation. Differential scanning calorimetry measurements show distinctly different thermal behavior of Ag4(UO2)4(IO3)2(IO4)2O2 versus other uranyl iodate compounds with endotherms at 479 and 494 degrees C. Density functional theory (DFT) calculations demonstrate that the approximate C2v geometry of the [IO4]3- anion can be attributed to a second-order Jahn-Teller distortion. DFT optimized geometry for the [IO4]3- anion is in good agreement with those measured from single-crystal X-ray diffraction studies on Ag4(UO2)4(IO3)2(IO4)2O2.

Journal Article↗
PubMed1995

Microbial diversity in uranium mine waste heaps.

Two different uranium mine waste heaps near Ronneburg, Thuringia, Germany, which contain the remains of the activity of the former uranium-mining Soviet-East German company Wismut AG, were analyzed for the occurrence of lithotrophic and chemoorganotropic leach bacteria. A total of 162 ore samples were taken up to a depth of 5 m. Cell counts of ferrous iron-, sulfur-, sulfur compound-, ammonia-, and nitrite-oxidizing bacteria were determined quantitatively by the most-probable-number technique. Sulfate-, nitrate-, ferric iron-, and manganese-reducing bacteria were also detected. In addition, the metabolic activity of sulfur- and iron-oxidizing bacteria was measured by microcalorimetry. Generally, all microorganisms mentioned above were detectable in the heaps. Aerobic and anaerobic microorganisms thrived up to a depth of 1.5 to 2 m. Up to 99% of Thiobacillus ferrooxidans cells, the dominant leaching bacteria, occurred to this depth. Their numbers correlated with the microbial activity measurements. Samples below 1.5 to 2 m exhibited reduced oxygen concentrations and reduced cell counts for all microorganisms.

Journal Article↗