Effects of linear plasma response currents on non-axisymmetric magnetic field perturbations from the I-coil used for Edge Localized Mode mitigation in DIII-D tokamak are analyzed with the help of a kinetic plasma response model developed for cylindrical geometry. It is shown that these currents eliminate the ergodization of the magnetic field in the core plasma and reduce the size of the ergodic layer at the edge. A simple balance model is proposed which qualitatively reproduces the evolution of the plasma parameters in the pedestal region with the onset of the perturbation.It is suggested that the experimentally observed density pump-out effect in the long mean free path regime is the result of a combined action of ion orbit losses and magnetic field ergodization at the edge.

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Enzymatic fuel cells convert the chemical energy of biofuels into electrical energy. Unlike traditional fuel cell types, which are mainly based on metal catalysts, the enzymatic fuel cells employ enzymes as catalysts. This fuel cell type can be used as an implantable power source for a variety of medical devices used in modern medicine to administer drugs, treat ailments and monitor bodily functions. Some advantages in comparison to conventional fuel cells include a simple fuel cell design and lower cost of the main fuel cell components, however they suffer from severe kinetic limitations mainly due to inefficiency in electron transfer between the enzyme and the electrode surface. In this review article, the major research activities concerned with the enzymatic fuel cells (anode and cathode development, system design, modeling) by highlighting the current problems (low cell voltage, low current density, stability) will be presented. © 1996-2010 MDPI Publishing (Basel, Switzerland) [accessed May 7, 2010

Cytochromebo3ubiquinol oxidase is a transmembrane protein, which oxidizes ubiquinone and reduces oxygen, while pumping protons. Apart from its combination with F1Fo-ATPase to assemble a minimal ATP regeneration module, the utility of the proton pump can be extended to other applications in the context of synthetic cells such as transport, signaling, and control of enzymatic reactions. In parallel, polymers have been speculated to be phospholipid mimics with respect to their ability to self-assemble in compartments with increased stability. However, their usability as interfaces for complex membrane proteins has remained questionable. In the present work, we optimized a fusion/electroformation approach to reconstitutebo3oxidase in giant unilamellar vesicles made of PDMS-g-PEO and/or phosphatidylcholine (PC). This enabled optical access, while microfluidic trapping allowed for online analysis of individual vesicles. The tight polymer membranes and the inward oriented enzyme caused 1 pH unit difference in 30 min, with an initial rate of 0.35 pH·min−1. To understand the interplay in these composite systems, we studied the relevant mechanical and rheological membrane properties. Remarkably, the proton permeability of polymer/lipid hybrids decreased after protein insertion, while the latter also led to a 20% increase of the polymer diffusion coefficient in polymersomes. In addition, PDMS-g-PEO increased the activity lifetime and the resistance to free radicals. These advantageous properties may open diverse applications, ranging from cell-free biotechnology to biomedicine. Furthermore, the presented study serves as a comprehensive road map for studying the interactions between membrane proteins and synthetic membranes, which will be fundamental for the successful engineering of such hybrid systems.

Activated carbon (AC) is a useful and environmentally sustainable catalyst for oxygen reduction in air-cathode microbial fuel cells (MFCs), but there is great interest in improving its performance and longevity. To enhance the performance of AC cathodes, carbon black (CB) was added into AC at CB:AC ratios of 0, 2, 5, 10, and 15 wt % to increase electrical conductivity and facilitate electron transfer. AC cathodes were then evaluated in both MFCs and electrochemical cells and compared to reactors with cathodes made with Pt. Maximum power densities of MFCs were increased by 9-16% with CB compared to the plain AC in the first week. The optimal CB:AC ratio was 10% based on both MFC polarization tests and three electrode electrochemical tests. The maximum power density of the 10% CB cathode was initially 1560 ± 40 mW/m(2) and decreased by only 7% after 5 months of operation compared to a 61% decrease for the control (Pt catalyst, 570 ± 30 mW/m(2) after 5 months). The catalytic activities of Pt and AC (plain or with 10% CB) were further examined in rotating disk electrode (RDE) tests that minimized mass transfer limitations. The RDE tests showed that the limiting current of the AC with 10% CB was improved by up to 21% primarily due to a decrease in charge transfer resistance (25%). These results show that blending CB in AC is a simple and effective strategy to enhance AC cathode performance in MFCs and that further improvement in performance could be obtained by reducing mass transfer limitations.

The crystal structure of the dimerization domain of rabies virus phosphoprotein was determined. The monomer consists of two ␣-helices that make a helical hairpin held together mainly by hydrophobic interactions. The monomer has a hydrophilic and a hydrophobic face, and in the dimer two monomers pack together through their hydrophobic surfaces. This structure is very different from the dimerization domain of the vesicular stomatitis virus phosphoprotein and also from the tetramerization domain of the Sendai virus phosphoprotein, suggesting that oligomerization is conserved but not structure.Rabies virus is a negative-strand RNA virus of the Rhabdovirus family. Its genomic RNA is encapsidated by numerous copies of the viral nucleoprotein (N) that binds to the sugar phosphate backbone of the RNA with a stoichiometry of nine nucleotides per N protomer (1). RNA replication and transcription take place on this N-RNA template (2) and are catalyzed by the viral RNA-dependent RNA polymerase (L). L binds to the N-RNA template with the help of the polymerase cofactor, the phosphoprotein (P) (7). The phosphoproteins of the Rhabdoviridae and of the Paramyxoviridae are oligomers (5, 8); P of the Rhabdoviridae (rabies virus and vesicular stomatitis virus [VSV]) form dimers (6, 9), whereas P of the Paramyxoviridae (Sendai virus) form tetramers (21). These phosphoproteins are modular proteins that have an N-terminal domain that keeps newly produced N (called N 0 ) in a soluble, RNAfree form, a central oligomerization domain and a C-terminal domain that binds to N-RNA. The three domains are connected by two intrinsically disordered regions (10, 13). The atomic structures of the oligomerization domains of the phosphoproteins of VSV and Sendai virus have been determined, and it was found that these structures were quite different (6, 21). Because the secondary structure prediction of the oligomerization domain of rabies virus P was different again from that of Sendai virus and VSV (10), we decided to determine its structure.The sequence analysis of rabies virus P suggests that the oligomerization domain stretches from amino acid residues 92 to 131 (10). The DNA corresponding to residues 91 to 133 was cloned into a pET22b vector and expressed in the Escherichia coli BL21 (DE3-RIL) strain as a His tag fusion protein. The protein was purified by nickel resin and size-exclusion chromatography (S75). In solution the protein behaves as a dimer with a molecular mass of 13.9 kDa (monomer, 6,501 Da) (10). Monomers or higher-order oligomers have never been observed.The protein was crystallized at 20°C in 50 mM sodium cacodylate (pH 6.5)-10 mM MgSO 4 plus 2 M (NH 4 ) 2 SO 4 . Diffraction data on frozen crystals were obtained on beam lines ID14-4 and BM14 (ESRF, Grenoble, France). The crystals diffracted to a 1.5-Å resolution and belong to space group I4 1 22 with one dimer in the asymmetric unit. The phases were solved by the Sulfur-MAD method (Table 1). Integration and scaling of the data were performed with XDS (12). Three methionine sites ...

c Smallpox caused by the poxvirus variola virus is a highly lethal disease that marked human history and was eradicated in 1979 thanks to a worldwide mass vaccination campaign. This virus remains a significant threat for public health due to its potential use as a bioterrorism agent and requires further development of antiviral drugs. The viral genome replication machinery appears to be an ideal target, although very little is known about its structure. Vaccinia virus is the prototypic virus of the Orthopoxvirus genus and shares more than 97% amino acid sequence identity with variola virus. Here we studied four essential viral proteins of the replication machinery: the DNA polymerase E9, the processivity factor A20, the uracil-DNA glycosylase D4, and the helicase-primase D5. We present the recombinant expression and biochemical and biophysical characterizations of these proteins and the complexes they form. We show that the A20D4 polymerase cofactor binds to E9 with high affinity, leading to the formation of the A20D4E9 holoenzyme. Small-angle X-ray scattering yielded envelopes for E9, A20D4, and A20D4E9. They showed the elongated shape of the A20D4 cofactor, leading to a 150-Å separation between the polymerase active site of E9 and the DNA-binding site of D4. Electron microscopy showed a 6-fold rotational symmetry of the helicase-primase D5, as observed for other SF3 helicases. These results favor a rolling-circle mechanism of vaccinia virus genome replication similar to the one suggested for tailed bacteriophages.

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