Corrosion of Depleted Uranium in an Arid Environment: Soil-Geomorphology,SEM/EDS,XRD, and Electron Microprobe Analyses

Corrosion of anthropogenic uranium in natural environments is not well understood, but is important for determining potential health risks and mobility in the environment. A site in the southwestern United States contains depleted uranium that has been weathering for approximately 22 years. Soil-geomorphic, SEM/EDS, XRD, and electron microprobe analyses were conducted to determine the processes controlling the uranium corrosion. Schoepite and metaschoepite are the primary products of corrosion, and occur as silica-cemented, mixed schoepite-metaschoepite/clay/silt aggregates, as schoepite/metaschoepite-only aggregates, or rarely as coatings upon soil grains. Current extraction procedures do not adequately explain the behavior of uranium in alkaline soils when amorphous silica and clay coatings are present. Soil geomorphology and chemistry at this site limit uranium mobility and decreases potential health risks. However, if land-use and/or regional climate changes occur, uranium mobility could increase.     

Selective immobilization of Bacillus subtilis lipase A from cell culture supernatant: Improving catalytic performance and thermal resistance

Bacillus subtilis lipase A (BSLA) has been extensively studied through protein engineering; however, its immobilization and behavior as an insoluble biocatalyst have not been extensively explored. In this work, for the first time, a direct immobilization of recombinant BSLA from microbial culture supernatant was reported, using chemically modified porous with different electrostatic, hydrophobic, hydrophilic, and hydrophilic−hydrophobic enzyme-support interactions. The resulting biocatalysts were evaluated based on their immobilization kinetics, activity expression (pH 7.4), thermal stability (50 °C), solvent resistance and substrate preference. Biocatalysts obtained using glyoxyl silica support resulted in the selective immobilization of BSLA, resulting in an activity recovery of 50 % and an outstanding aqueous stabilization factor of 436, and 9.5 in isopropyl alcohol, compared to the free enzyme. This selective immobilization methodology of BSLA allows to efficiently generate immobilized biocatalysts, thus avoiding laborious purification steps from cell culture supernatant, which is usually a limiting step when large amounts of enzyme variants or candidates are assessed as immobilized biocatalysts. Direct enzyme immobilization from cell supernatant provides an interesting tool which can be used to facilitate the development and assessment of immobilized biocatalysts from engineered enzyme variants and mutant libraries, especially in harsh conditions, such as high temperatures or non-aqueous solvents, or against non-water-soluble substrates. Furthermore, selective immobilization approaches from cell culture supernatant or clarified lysates could help bridging the gap between protein engineering and enzyme immobilization, allowing for the implementation of immobilization steps in high throughput enzyme screening platforms for their potential use in directed evolution campaigns.     

The role of oxidative stress in diseases caused by mineral dusts and fibres: Current status and future of prophylaxis and treatment

Inhalation of silica and asbestos fibres by humans can lead to fibrosis of the lung and cancer. Different mechanistic approaches, including oxidative stress, are used for prophylactic and therapeutic interventions to attenuate the fibrogenic and carcinogenic effects of these particles. Thus far, most of these therapeutic interventions have been only partly successful. A review of the mechanisms which are thought to be involved in mineral particle-induced toxicity and the relevant therapeutic interventions used to date to counteract these mechanisms, will help formulate better prophylactic and treatment intervention strategies in the future.     

A Method for Isolating and Preparing Silica Bodies in Grasses for Scanning Electron Microscopy

Silica bodies are discrete deposits of dehydrated silica within epidermal cells. To describe these bodies completely, surrounding organic and unsilicified material must be removed. Methods generally used for isolating and preparing silica bodies were unsuitable for most grass species. An effective method for studying grasses is described here. After ashing the plant tissue, the ash was repeatedly rinsed with HCl in a specialized multiple funnel manifold and collected on Nuclepore filters. In addition, the silica bodies were sonicated for a few minutes to remove any remaining mineral impurities. Compared to conventional procedures, this method has a number of advantages: unsilicified material and mineral impurities were removed effectively, smaller quantities of plant tissue could be used, and the loss of silica bodies was minimized.     

Probing TGF-β1-induced cytoskeletal rearrangement by fluorescent-labeled silica nanoparticle uptake assay

Cytoskeletal proteins are essential in maintaining cell morphology, proliferation, and viability as well as internalizing molecules in phagocytic and non-phagocytic cells. Orderly aligned cytoskeletons are disturbed by a range of biological processes, such as the epithelial–mesenchymal transition, which is observed in cancer metastasis. Although many biological methods have been developed to detect cytoskeletal rearrangement, simple and quantitative in vitro approaches are still in great demand. Herein, we applied a flow cytometry-based nanoparticle uptake assay to measure the degree of cytoskeletal rearrangement induced by transforming growth factor β1 (TGF-β1). For the assay, silica nanoparticles, selected for their high biocompatibility, were fluorescent-labeled to facilitate quantification with flow cytometry. Human keratinocyte HaCaT cells were treated with different concentrations of TGF-β1 and then exposed to FITC-labeled silica nanoparticles. Increasing concentrations of TGF-β1 induced gradual changes in cytoskeletal rearrangement, as confirmed by conventional assays. The level of nanoparticle uptake increased by TGF-β1 treatment in a dose-dependent manner, indicating that our nanoparticle uptake assay can be used as a quick and non-destructive approach to measure cytoskeletal rearrangement.