The geomeffy, bond valences, and polymerization ofhexavalent uranium polyhedra from 105 well-refined structures are analyzed. The Utu cation is almost always present in crystal stnrctures as part of a nearly linear (UOr)z* uranyl ion that is coordinated by four, five or six equatorial anions in an approximately planar arangement perpendicular to the uranyl ion, giving square, pentagonal and hex...

The d. c. and a. c. polarography and cyclic voltammetry were applied to the study of uranyl-salicylate and uranyl-phthalate complexes. The study was limited to the pH range <5, because insoluble uranyl-hydroxydes are formed above this pH value. Uranyl-salicylate and -phthalate are irreversibly reduced. The electrode process is preceded by the chemical reaction of the complex with protons. By th...

A polypyrrolic macrocycle with naphthalenyl linkers between the N(4)-donor compartments (L(2)) was designed theoretically according to its experimentally-known analogues with phenylenyl (L(1)) and anthracenyl (L(3)) linkers. The uranyl and bis(uranyl) complexes formed by this L(2) ligand have been examined using scalar-relativistic density functional theory. The calculated structural properties...

In order to evaluate uranyl photocleavage as a tool to identify and characterize structural and dynamic properties in RNA, we compared uranyl cleavage sites in five RNA molecules with known X-ray structures, namely the hammerhead and hepatitis delta virus ribozymes, the P4-P6 domain of the Tetrahymena group I intron, as well as tRNA(Phe) and tRNA(Asp) from yeast. Uranyl photocleavage was observ...

Uranyl-carboxyl-ate hybrid materials dominate the catalog of uranyl compounds owing in part to the affinity between COO(-) functional groups and UO2 (2+). Polycarboxyl-ate organic ligands may present a degree of steric hindrance and could thus influence the resulting uranyl topology. Single crystals of the title compound, {(NH4)2[(UO2)2(C12O12)(H2O)2]} n , were synthesized hydro-thermally as a ...

The title compound, [(UO(2))(2)Cl(2)(OH)(2)(H(2)O)(4)], was obtained unintentionally as the product of an attempted reaction between uranium(VI) oxide dihydrate, UO(3)·2H(2)O, and hydrogen bis-(trifluoro-methyl-sulfon-yl)imide (HTf(2)N), in an experiment to obtain crystals of uranyl bis-(trifluoro-methyl-sulfon-yl)imide, UO(2)(Tf(2)N)(2)·xH(2)O. The structure consists of neutral dimers of urany...

Better understanding of uranyl toxicity in bacteria is necessary to optimize strains for bioremediation purposes or for using bacteria as biodetectors for bioavailable uranyl. In this study, after different steps of optimization, Escherichia coli cells were exposed to uranyl at low pH to minimize uranyl precipitation and to increase its bioavailability. Bacteria were adapted to mid acidic pH be...

Uranium is one of the most important metal resources, and the technology for the recovery of uranyl ions (UO22+) from aqueous solutions is required to ensure a semi-permanent supply of uranium. The NikR protein is a Ni2+-dependent transcriptional repressor of the nickel-ion uptake system in Escherichia coli, but its mutant protein (NikRm) is able to selectively bind uranyl ions in the interface...

In this study, we use solubility and drop-solution calorimetry measurements to determine the thermodynamic properties of the uranyl phosphate phases autunite, uranyl hydrogen phosphate, and uranyl orthophosphate. Conducting the solubility measurements from both supersaturated and undersaturated conditions and under different pH conditions rigorously demonstrates attainment of equilibrium and yi...

For more than 2 years, a double-staining of sections of OsO 4-fixed and Epon-embedded tissues with uranyl acetate followed by lead hydroxide has been routine technique in this laboratory. It was found to give substantially higher contrast, thus permitting the use of thinner sections. It facilitated focusing and routinely provided clearer pictures of cell fine structure than could be obtained wi...