Current-perpendicular-to-plane giant magnetoresistance of a spin valve using Co2MnSi Heusler alloy electrodes

We report the current-perpendicular-to-plane giant magnetoresistance of a spin valve with Co2MnSi (CMS) Heusler alloy ferromagnetic electrodes. A multilayer stack of Cr/Ag/Cr/CMS/Cu/CMS/Fe25Co75/Ir28Mn72/Ru was deposited on a MgO (001) single crystal substrate. The bottom CMS layer was epitaxially grown on the Cr/Ag/Cr buffer layers and was ordered to the L21 structure after annealing at 673 K. The upper CMS layer was found to grow epitaxially on the Cu spacer layer despite the large lattice mismatch between Cu and CMS. The highest MR ratios of 8.6% and 30.7% for CPP-GMR were recorded at room temperature and 6 K, respectively. The high spin polarization of the epitaxial CMS layers is the most likely origin of the high MR ratio.Comment: 14 pages, 3 figures, presented at the 53rd Annual Conference on Magnetism and Magnetic Materials, to be published in J. Appl. Phy

Functional characterization of BcrR:a one-component transmembrane signal transduction system for bacitracin resistance

Bacitracin is a cell wall targeting antimicrobial with clinical and agricultural applications. With the growing mismatch between antimicrobial resistance and development, it is essential we understand the molecular mechanisms of resistance in order to prioritize and generate new effective antimicrobials. BcrR is a unique membrane-bound one-component system that regulates high-level bacitracin resistance in Enterococcus faecalis. In the presence of bacitracin, BcrR activates transcription of the bcrABD operon conferring resistance through a putative ATP-binding cassette (ABC) transporter (BcrAB). BcrR has three putative functional domains, an N-terminal helix-turn-helix DNA-binding domain, an intermediate oligomerization domain and a C-terminal transmembrane domain. However, the molecular mechanisms of signal transduction remain unknown. Random mutagenesis of bcrR was performed to generate loss- and gain-of-function mutants using transcriptional reporters fused to the target promoter PbcrA. Fifteen unique mutants were isolated across all three proposed functional domains, comprising 14 loss-of-function and one gain-of-function mutant. The gain-of-function variant (G64D) mapped to the putative dimerization domain of BcrR, and functional analyses indicated that the G64D mutant constitutively expresses the PbcrA-luxABCDE reporter. DNA-binding and membrane insertion were not affected in the five mutants chosen for further characterization. Homology modelling revealed putative roles for two key residues (R11 and S33) in BcrR activation. Here we present a new model of BcrR activation and signal transduction, providing valuable insight into the functional characterization of membrane-bound one-component systems and how they can coordinate critical bacterial responses, such as antimicrobial resistance.</p

Functional characterization of BcrR:a one-component transmembrane signal transduction system for bacitracin resistance

Bacitracin is a cell wall targeting antimicrobial with clinical and agricultural applications. With the growing mismatch between antimicrobial resistance and development, it is essential we understand the molecular mechanisms of resistance in order to prioritize and generate new effective antimicrobials. BcrR is a unique membrane-bound one-component system that regulates high-level bacitracin resistance in Enterococcus faecalis. In the presence of bacitracin, BcrR activates transcription of the bcrABD operon conferring resistance through a putative ATP-binding cassette (ABC) transporter (BcrAB). BcrR has three putative functional domains, an N-terminal helix-turn-helix DNA-binding domain, an intermediate oligomerization domain and a C-terminal transmembrane domain. However, the molecular mechanisms of signal transduction remain unknown. Random mutagenesis of bcrR was performed to generate loss- and gain-of-function mutants using transcriptional reporters fused to the target promoter PbcrA. Fifteen unique mutants were isolated across all three proposed functional domains, comprising 14 loss-of-function and one gain-of-function mutant. The gain-of-function variant (G64D) mapped to the putative dimerization domain of BcrR, and functional analyses indicated that the G64D mutant constitutively expresses the PbcrA-luxABCDE reporter. DNA-binding and membrane insertion were not affected in the five mutants chosen for further characterization. Homology modelling revealed putative roles for two key residues (R11 and S33) in BcrR activation. Here we present a new model of BcrR activation and signal transduction, providing valuable insight into the functional characterization of membrane-bound one-component systems and how they can coordinate critical bacterial responses, such as antimicrobial resistance.</p

Life-cycle assessment of domestic and transboundary recycling of post-consumer PET bottles

Abstract Background, aim, and scope In recent years, besides being recycled domestically, a part of Japanese post-consumer polyethylene terephthalate (PET) bottles have been exported to and recycled in mainland China. In this study, life-cycle assessment (LCA) was applied to compare domestic and transboundary recycling scenarios between Japan and China and disposal scenarios from the viewpoints of greenhouse gases (GHG) emission and fossil resource consumption. Methods The following 10 scenarios based on our field surveys were evaluated: Japanese post-consumer PET bottles are (i) recycled into polyester staple in Japan, (ii) recycled into polyester filaments in Japan, (iii) recycled into polyester clothes in Japan, (iv) chemically decomposed and recycled into bottle-grade PET resin in Japan, (v) chemically decomposed and recycled into polyester filaments in Japan, (vi)-(vii) recycled into polyester staple via two different flows in China, (viii) recycled into polyester clothes in China, (ix) incinerated and partly recovered as electricity in Japan, and (x) directly landfilled in Japan. In all the evaluated scenarios, the functional unit is the recycling or disposal of 1 kg of Japanese post-consumer PET bottles. The system boundaries range from waste collection by municipalities to the manufacture of recycled products that can be regarded as substitutes for virgin products, and a credit for the avoided production of equivalent virgin products is given to each scenario. The inventories of both foreground and background processes in Japan were quoted from published reports and databases. The actual conditions of PET bottle recycling that were obtained through field surveys in China were reflected to some inventories of foreground processes in China. The inventories of public electricity supplies in China were based on the national statistics, and the inventories of petroleum products, industrial water supply, and waste treatment are based on our field surveys in China. Other unknown inventories in China were substituted by corresponding inventories in Japan. Results and discussion The results showed that all the domestic and transboundary recycling scenarios had smaller GHG emissions and fossil resource consumptions than the incineration scenario and that the chemical recycling scenarios had larger GHG emissions and fossil resource consumptions than the other recycling scenarios. The landfilling scenario had the largest fossil resource consumption, while it was better than the incineration scenario and slightly better than the chemical recycling scenarios from the viewpoint of GHG emission. The robustness of the results was examined, and it was found that the differences in GHG emission and fossil resource consumption between the domestic and transboundary recycling scenarios, other than the scenarios including cloth-manufacturing processes in system boundaries, were sufficiently large to be robust against the variability of background parameters for electricity supplies. As for the Responsible editor: Shabbir Gheewala Electronic supplementary material The online version of this articl

Coactivators p300 and PCAF physically and functionally interact with the foamy viral trans-activator

BACKGROUND: Foamy virus Bel1/Tas trans-activators act as key regulators of gene expression and directly bind to Bel1 response elements (BRE) in both the internal and the 5'LTR promoters leading to strong transcriptional trans-activation. Cellular coactivators interacting with Bel1/Tas are unknown to date. RESULTS: Transient expression assays, co-immunoprecipitation experiments, pull-down assays, and Western blot analysis were used to demonstrate that the coactivator p300 and histone acetyltransferase PCAF specifically interact with the retroviral trans-activator Bel1/Tas in vivo. Here we show that the Bel1/Tas-mediated trans-activation was enhanced by the coactivator p300, histone acetyltransferases PCAF and SRC-1 based on the crucial internal promoter BRE. The Bel1/Tas-interacting region was mapped to the C/H1 domain of p300 by co-immunoprecipitation and pull-down assays. In contrast, coactivator SRC-1 previously reported to bind to the C-terminal domain of p300 did not directly interact with the Bel1 protein but nevertheless enhanced Bel1/Tas-mediated trans-activation. Cotransfection of Bel1/Tas and p300C with an expression plasmid containing the C/H1domain partially inhibited the p300C-driven trans-activation. CONCLUSIONS: Our data identify p300 and PCAF as functional partner molecules that directly interact with Bel1/Tas. Since the acetylation activities of the three coactivators reside in or bind to the C-terminal regions of p300, a C/H1 expression plasmid was used as inhibitor. This is the first report of a C/H1 domain-interacting retroviral trans-activator capable of partially blocking the strong Bel1/Tas-mediated activation of the C-terminal region of coactivator p300. The potential mechanisms and functional roles of the three histone and factor acetyltransferases p300, PCAF, and SRC-1 in Bel1/Tas-mediated trans-activation are discussed