New Methods of Syntheses of Ammonium, Sodium & Potassium Triacetatodioxouranates (VI) & Diacetatodioxouranium (VI) Dihydrate

1048-104

Synthesis, characterisation, and some properties of molecular mixed-ligand peroxo complexes of uranium(VI) containing amines or aminocarboxylic acids as coligands

Molecular peroxo complexes of [UO2]2+, viz. [UO2(O2)(phen)](phen = 1,10-phenanthroline), [UO2(O2)(bipy)](bipy = 2,2'-bipyridyl), [UO2(O2)(en)](en = ethylenediamine), [UO2(O2)(H4edta)](H4edta = ethylenediamine-NNN'N'-tetra-acetic acid), and [UO2(O2)(gly)](gly = glycine), have been synthesised at different pH values of the reaction medium. They are diamagnetic. On the basis of spectroscopic evidence, both peroxide and each of the coligands, except gly, are co-ordinated to the metal in a bidentate manner, while gly occurs in its zwitterionic form and acts as a monodentate ligand. The complex [UO2(O2)(gly)] oxidises triphenylphosphine, cyclohexene, styrene, and SO2(g) to triphenylphosphine oxide, 1,2-cyclohexanediol, 1-phenylethylene glycol, and sulphate respectively

Synthesis and structural assessment of ammonium and caesium difluorodioxoperoxouranates(VI), A<SUB>2</SUB>[UO<SUB>2</SUB>(O<SUB>2</SUB>)F<SUB>2</SUB>](A = NH<SUB>4</SUB> or Cs), and alkali-metal difluorodioxoperoxouranate(VI) monohydrates,A<SUB>2</SUB>[UO<SUB>2</SUB>(O<SUB>2</SUB>)F<SUB>2</SUB>].H<SUB>2</SUB>O (A = K or Rb)

The product obtained by treating an aqueous solution of UO2(NO3)2.6H2O with NH4OH or KOH reacts with AF (A = NH4, Rb, or Cs) or KF, 30% H2O2, and a very small amount of 40% HF, in the mol ratio UO2(NO3)2.6H2O:AF:H2O2 of 1:4:110.8, at pH 6.5-7 to afford ammonium and caesium difluorodioxoperoxouranates(VI), A2[UO2(O2) F2](A = NH4 or Cs), and potassium and rubidium difluorodioxoperoxouranate(VI) monohydrates, A2[UO2(O2)F2].H2O (A = K or Rb). The i.r. spectra suggest that the peroxo-ligand is bonded to the UO22+ centre in a triangular bidentate (C2v,) manner

Complex peroxyuranates. Synthesis and structural assessment of alkali dioxoxperoxy(sulfato)aquouranates(VI), A<SUB>2</SUB>[UO<SUB>2</SUB>(O<SUB>2</SUB>)SO<SUB>4</SUB>(H<SUB>2</SUB>O)] (A = NH<SUB>4</SUB>, Na), and alkali dioxoperoxy(oxalato)uranate(VI) hydrates, A<SUB>2</SUB>[UO<SUB>2</SUB>(O<SUB>2</SUB>)C<SUB>2</SUB>O<SUB>4</SUB>].H<SUB>2</SUB>O

Yellow microcrystalline alkali-metal and ammonium dioxoperoxy(sulfato)aquouranates(VI), A2(UO2(O2)SO 4(H2O)) (A = NH4, Na), and alkali-metal and ammonium dioxoperoxy(oxalato)uranate(VI) hydrates, A2UO 2(O2)C2O).H2O (A = NH4, Na, K), have been synthesized from the reaction of the product obtained by treating an aqueous solution of UO2(NO3)2.6H2O with alkali-metal or ammonium hydroxide, AOH, with 30% H2O2 and aqueous sulfuric acid and oxalic acid solution, respectively, in the mole ratio UO2(NO3)2.6H2O:H2O2:SO42 - or C2O42- of 1:111:5 or 1, at pH 6 maintained by the addition of the corresponding alkali-metal or ammonium hydroxide. Precipitation was completed by the addition of ethanol. IR and laser Raman spectra suggest that the O22 - and SO42 - ions in (UO2(O2)SO4(H2O))2- are bonded to the UO22 + center in a bridging and in a monodentate manner, respectively, while both the O22 - and C2O42 - ions in (UO2(O2)C2O) 2 - bind the uranyl center in bidentate chelated fashion. The complex peroxyuranates are diamagnetic and insoluble. The A2(UO2(O2)SO4(H2O)) compounds, unlike A2(UO2(O2)C2O4).H2O, are stable up to 110&#176;C. Whereas H2O in A2(UO(O2SO4(H2O)) is coordinated to the UO22+ center, it occurs as a water of crystallization in the corresponding peroxy oxalato compounds

A Linear Relationship between Fitness and the Logarithm of the Critical Bottleneck Size in Vesicular Stomatitis Virus Populations▿ §

We explored the relationship between fitness change and population size during transmission in vesicular stomatitis populations of very high fitness. The results show a linear correlation between the logarithm of the critical bottleneck size (population size at which there are no significant fitness changes after 20 passages) and the initial fitness of the population. In addition, limits to fitness increases during large-population passages of very-high-fitness strains were abolished by increasing the population size during transmission, indicating that beneficial variation is still available in these populations

First synthesis and structural assessment of alkali-metal carbonatodioxoperoxouranate(VI) monohydrates, A<SUB>2</SUB>[UO<SUB>2</SUB>(O<SUB>2</SUB>)(CO<SUB>3</SUB>)].H<SUB>2</SUB>O, and carbonato-oxodiperoxovanadate(V) trihydrates, A<SUB>3</SUB>[VO(O<SUB>2</SUB>)<SUB>2</SUB>(CO3)].3H<SUB>2</SUB>O

The complexes A2[UO2(O2)(CO3)].H2O (A = Na or K) have been synthesised from the reaction of the product obtained by treating UO2(NO3)2.6H2O with AOH and AHCO3(ratio U : CO32-= 1:4) with an excess of 30% H2O2 at pH 7-8, and A3[VO(O2)2(CO3)].3H2O (A = Na or K) have been synthesised by treating V2O5 with A2CO3(ratio V: CO32-= 1 :1.5) and an excess of 30% H2O2 at pH ca. 7. They were precipitated with ethanol. The occurrence of trans OUO and terminal VO in the [UO2(O2)(CO3)]2- and [VO(O2)2(CO3)]3- ions, respectively, and the presence of triangular bidentate O22- and chelated bidentate CO32- groups, have been ascertained from i.r. and laser Raman spectra. The complexes A2[UO2(O2)(CO3)].H2O can be dehydrated at Ca. 100 &#176;C, a temperature at which A3[VO(O2)2(CO3)].3H2O starts to decompose

Rapid Adaptive Amplification of Preexisting Variation in an RNA Virus▿

The amount and nature of preexisting variation in a population of RNA viruses is an important determinant of the virus's ability to adapt rapidly to a changed environment. However, direct quantification of this preexisting variation may be cumbersome, because potentially beneficial alleles are typically rare, and isolation of a large number of subclones is required. Here, we propose a simpler method. We infer the initial population structure of vesicular stomatitis virus (VSV) by fitting a mathematical model of asexual evolution to an extensive set of measurements of VSV fitness dynamics under various conditions, including new and previously published data. The inferred variation of fitness in the initial population agrees very well with the results of direct experiments with subclone fitness quantification. From the same procedure, we also estimate the mean fitness effect of beneficial mutations (selection coefficient s), the percentage of sites in the genome that are under moderate positive or negative selection, and the percentage of sites where beneficial mutations may potentially occur. For VSV strain MARM U evolving in BHK-21 cells, the three parameters have values of 0.39, 9%, and 0.06%, respectively. The method can be generalized and applied easily to other rapidly evolving microbes, including both asexual microorganisms and those with recombination

Genomic Evolution of Vesicular Stomatitis Virus Strains with Differences in Adaptability ▿ †

Virus strains with a history of repeated genetic bottlenecks frequently show a diminished ability to adapt compared to strains that do not have such a history. These differences in adaptability suggest differences in either the rate at which beneficial mutations are produced, the effects of beneficial mutations, or both. We tested these possibilities by subjecting four populations (two controls and two mutants with lower adaptabilities) to multiple replicas of a regimen of positive selection and then determining the fitnesses of the progeny through time and the changes in the consensus, full-length sequences of 56 genomes. We observed that at a given number of passages, the overall fitness gains observed for control populations were larger than fitness gains in mutant populations. However, these changes did not correlate with differences in the numbers of mutations accumulated in the two types of genomes. This result is consistent with beneficial mutations having a lower beneficial effect on mutant strains. Despite the overall fitness differences, some replicas of one mutant strain at passage 50 showed fitness increases similar to those observed for the wild type. We hypothesized that these evolved, high-fitness mutants may have a lower robustness than evolved, high-fitness controls. Robustness is the ability of a virus to avoid phenotypic changes in the face of mutation. We confirmed our hypothesis in mutation-accumulation experiments that showed a normalized fitness loss that was significantly larger in mutant bottlenecked populations than in control populations