Cloning, purification and characterization of the 6-phospho-3-hexulose isomerase YckF from Bacillus subtilis

The enzyme 6-phospho-3-hexulose isomerase (YckF) from Bacillus subtilis has been prepared and crystallized in a form suitable for X-ray crystallographic analysis. Crystals were grown by the hanging-drop method at 291 K using polyethylene glycol 2000 monomethylether as precipitant. They diffract beyond 1.7 A using an in-house Cu Kalpha source and belong to either space group P6(5)22 or P6(1)22, with unit-cell parameters a = b = 72.4, c = 241.2 A, and have two molecules of YckF in the asymmetric unit

Impacts of epigeic, anecic and endogeic earthworms on metal and metalloid mobility and availability

The introduction of earthworms into soils contaminated with metals and metalloids has been suggested to aid restoration practices. Eisenia veneta (epigeic), Lumbricus terrestris (anecic) and Allolobophora chlorotica (endogeic) earthworms were cultivated in columns containing 900 g soil with 1130, 345, 113 and 131 mg kg1 of As, Cu, Pb and Zn, respectively, for up to 112 days, in parallel with earthworm-free columns. Leachate was produced by pouring water on the soil surface to saturate the soil and generate downflow. Ryegrass was grown on the top of columns to assess metal uptake into biota. Different ecological groups affected metals in the same way by increasing concentrations and free ion activities in leachate, but anecic L. terrestris had the greatest effect by increasing leachate concentrations of As by 267%, Cu by 393%, Pb by 190%, and Zn by 429% compared to earthworm-free columns. Ryegrass grown in earthworm-bearing soil accumulated more metal and the soil microbial community exhibited greater stress. Results are consistent with earthworm enhanced degradation of organic matter leading to release of organically bound elements. The degradation of organic matter also releases organic acids which decrease the soil pH. The earthworms do not appear to carry out a unique process, but increase the rate of a process that is already occurring. The impact of earthworms on metal mobility and availability should therefore be considered when inoculating earthworms into contaminated soils as new pathways to receptors may be created or the flow of metals and metalloids to receptors may be elevated

Microbial Reduction of U(VI) under Alkaline Conditions: Implications for Radioactive Waste Geodisposal

Although there is consensus that microorganisms significantly influence uranium speciation and mobility in the subsurface under circumneutral conditions, microbiologically mediated U(VI) redox cycling under alkaline conditions relevant to the geological disposal of cementitious intermediate level radioactive waste, remains unexplored. Here, we describe microcosm experiments that investigate the biogeochemical fate of U(VI) at pH 10–10.5, using sediments from a legacy lime working site, stimulated with an added electron donor, and incubated in the presence and absence of added Fe(III) as ferrihydrite. In systems without added Fe(III), partial U(VI) reduction occurred, forming a U(IV)-bearing non-uraninite phase which underwent reoxidation in the presence of air (O2) and to some extent nitrate. By contrast, in the presence of added Fe(III), U(VI) was first removed from solution by sorption to the Fe(III) mineral, followed by bioreduction and (bio)magnetite formation coupled to formation of a complex U(IV)-bearing phase with uraninite present, which also underwent air (O2) and partial nitrate reoxidation. 16S rRNA gene pyrosequencing showed that Gram-positive bacteria affiliated with the Firmicutes and Bacteroidetes dominated in the post-reduction sediments. These data provide the first insights into uranium biogeochemistry at high pH and have significant implications for the long-term fate of uranium in geological disposal in both engineered barrier systems and the alkaline, chemically disturbed geosphere

The acceptability of iterative reconstruction algorithms in head CT: An assessment of sinogram affirmed iterative reconstruction (SAFIRE) vs. filtered back projection (FBP) using phantoms

Computed tomography (CT) is the primary imaging investigation for many neurologic conditions with a proportion of patients incurring cumulative doses. Iterative reconstruction (IR) allows dose optimization, but head CT presents unique image quality complexities and may lead to strong reader preferences. OBJECTIVES: This study evaluates the relationships between image quality metrics, image texture, and applied radiation dose within the context of IR head CT protocol optimization in the simulated patient setting. A secondary objective was to determine the influence of optimized protocols on diagnostic confidence using a custom phantom. METHODS AND SETTING: A three-phase phantom study was performed to characterize reconstruction methods at the local reference standard and a range of exposures. CT numbers and pixel noise were quantified supplemented by noise uniformity, noise power spectrum, contrast-to-noise ratio (CNR), high- and low-contrast resolution. Reviewers scored optimized protocol images based on established reporting criteria. RESULTS: Increasing strengths of IR resulted in lower pixel noise, lower noise variance, and increased CNR. At the reference standard, the image noise was reduced by 1.5 standard deviation and CNR increased by 2.0. Image quality was maintained at </=24% relative dose reduction. With the exception of image sharpness, there were no significant differences between grading for IR and filtered back projection reconstructions. CONCLUSIONS: IR has the potential to influence pixel noise, CNR, and noise variance (image texture); however, systematically optimized IR protocols can maintain the image quality of filtered back projection. This work has guided local application and acceptance of lower dose head CT protocols.N/

Incest in the 1990s: reading Anais Nin's 'Father Story'

In the summer of 1933, diarist, author and critic Anaïs Nin joined her father for a short vacation in France. Nin wrote about the trip in her diary afterwards, referring to it as the ‘Father Story.’ In the story, she details how, aged 30, she embarked upon an affair with her father which would last for several months. Rather than displaying the signs of trauma that we have come to expect from the incest narrative such as dissociation, blame and recrimination, the ‘Father Story’ is more ambiguous in its tone. Part-tribute to the father, part-seduction narrative, part-confession, this is a story that resists categorisation – a resistance that has ethical, critical and formal ramifications for our reading of incest narratives. Upon its publication in the early 1990s, critics responded to the ‘Father Story’ as fantastical, excessive and vulgar. These responses form part of a wider American father story during this period; a story about memory, therapy culture, family values and the concealed rules of testimony. This article reads Anaïs Nin’s narrative as a text which raises fundamental questions about why certain father (and daughter) stories are culturally acceptable and others are not

An X-ray magnetic circular dichroism (XMCD) study of Fe ordering in a synthetic MgAl₂O₄ – Fe₃O₄ (spinel – magnetite) solid solution series; implications for magnetic properties.

Fe L₂,₃-edge XAS and XMCD studies have been used to unravel structural trends in the MgAl₂O₄-Fe₃O₄ solid solution where thermodynamic modelling has presented a challenge due to the complex ordering arrangements of the end-members. Partitioning of Fe³⁺ and Fe²⁺ between tetrahedral (Td) and octahedral (Oh) sites has been established. In the most Fe-rich samples, despite rapid quenching from a disordered state, Fe²⁺_Td is not present, which matches the ordered, inverse spinel nature of end-member magnetite (Mgt) at room-T. However, in intermediate compositions Al and Mg substantially replace Fe and small amounts of Fe²⁺_Td are found, stabilized or trapped by decreasing occurrence of the continuous nearest neighbour Fe – Fe interactions which facilitate charge redistribution by electron transfer. Furthermore, in the composition range ~Mgt₀.₄₋₀.₉, XAS and XMCD bonding and site occupancy data suggest that nano- scale, magnetite-like Fe clusters are present. By contrast, at the spinel-rich end of the series, Mgt₀.₁₇and Mgt₀.₂₃ have a homogeneous long-range distribution of Fe, Mg and Al. These relationships are consistent with the intermediate and Fe-rich samples falling within a wide solvus in this system such that the Fe- clusters occur as proto-nuclei for phases which would exsolve following development of long-range crystalline order during slow cooling. Unit cell edges calculated from the spectroscopy-derived site occupancies show excellent agreement with those measured by X-ray powder diffraction on the bulk samples. Calculated saturation magnetic moments (M_s) for the Fe-rich samples also show excellent agreement with measured values but for the most Mg-rich samples are displaced to slightly higher values; this displacement is due to the presence of abundant Mg and Al disrupting the anti-parallel alignment of electron spins for Fe atoms

Venus trapped, Mars transits: Cu and Fe redox chemistry, cellular topography, and in situ ligand binding in terrestrial isopod hepatopancreas

Woodlice efficiently sequester copper (Cu) in ‘cuprosomes' within hepatopancreatic ‘S' cells. Binuclear ‘B’ cells in the hepatopancreas form iron (Fe) deposits; these cells apparently undergo an apocrine secretory diurnal cycle linked to nocturnal feeding. Synchrotron-based µ-focus X-ray spectroscopy undertaken on thin sections was used to characterize the ligands binding Cu and Fe in S and B cells of Oniscus asellus (Isopoda). Main findings were: (i) morphometry confirmed a diurnal B-cell apocrine cycle; (ii) X-ray fluorescence (XRF) mapping indicated that Cu was co-distributed with sulfur (mainly in S cells), and Fe was co-distributed with phosphate (mainly in B cells); (iii) XRF mapping revealed an intimate morphological relationship between the basal regions of adjacent S and B cells; (iv) molecular modelling and Fourier transform analyses indicated that Cu in the reduced Cu+ state is mainly coordinated to thiol-rich ligands (Cu–S bond length 2.3 Å) in both cell types, while Fe in the oxidized Fe3+ state is predominantly oxygen coordinated (estimated Fe–O bond length of approx. 2 Å), with an outer shell of Fe scatterers at approximately 3.05 Å; and (v) no significant differences occur in Cu or Fe speciation at key nodes in the apocrine cycle. Findings imply that S and B cells form integrated unit-pairs; a functional role for secretions from these cellular units in the digestion of recalcitrant dietary components is hypothesized