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The paper discusses development under an ESA TRP activity (Contract No. 4000109879/13/NL/LvH) with a target of high specific energy Lithium-ion cells, capable of operating under low temperature conditions, i.e. −40 °C. Such cells may be encountered in future exploration missions, which do not consider the use of Radioisotope Heater Units. During the activity, ≥1 Ah silicon-based high energy density prototype cells, following components characterization and optimization, were designed, developed, manufactured and tested under room and subzero temperature conditions down to −40 °C. The developed and tested prototype cells exhibited energy density of around 208 Wh/Kg at room temperature under C/10 charge-discharge rate within voltage range of 2.8 V and 4.1 V. Moreover, the prototype cells could retain and deliver more than 75% of their capacity at room temperature upon cycling at −40 °C, demonstrating an energy density of 140 Wh/kg.

Abstract: The effect of electrochemical promotion of catalysis on the SO2 oxidation reaction was investigated over thin (∼40nm) Pt catalyst electrodes interfaced with YSZ, in a monolithic electrochemically promoted (MEP) reactor equipped with five or twenty-two electrocatalytic plates. A mildly oxidizing gas mixture was used at temperatures from 330 to 370°C and flowrates between 1 and 30Lmin−1. It was found that positive potential application, i.e. O2− supply to catalyst surface, can cause an increase of up to 200% in the catalytic oxidation rate of SO2 with Faradaic efficiency values up to 30 at flowrates as high as 30Lmin−1 which corresponds to 3×104 h−1 space velocity or 0.1s residence time. The results show the strong potential of MEP reactors for practical applications of the electrochemical promotion of catalysis (EPOC) effect, in gas treatment units and chemical synthesis and destruction processes. [Copyright &y& Elsevier]

Abstract: This study reports the possibility of working in NO x storage/reduction process under fixed lean burn reaction conditions by using a tubular Pt/K-βAl2O3/Pt electrochemical catalyst. This system allows to electrochemically trap NO x as potassium nitrates in the film polarized negatively, and simultaneously to regenerate from storage compounds the opposite catalyst film (polarized positively), both working under the same lean burn atmosphere. In addition, it has been shown that the system is able to store CO2 as potassium carbonates. The obtained results have been supported by linear sweep voltammetry carried out under different reaction conditions which has provided useful information about the different competitive trapping processes. [Copyright &y& Elsevier]

Polymer electrolyte membrane (PEM) water electrolyzers suffer mainly from slow kinetics regarding the oxygen evolution reaction (OER). Noble metal oxides, like IrO 2 and RuO 2 , are generally more active for OER than metal electrodes, exhibiting low anodic overpotentials and high catalytic activity. However, issues like electrocatalyst stability under continuous operation and cost minimization through a reduction in the catalyst loading are of great importance to the research community. In this study, unsupported IrO 2 of various particle sizes (different calcination temperatures) were evaluated for the OER and as anode electrodes for PEM water electrolyzers. The electrocatalysts were synthesized by the modified Adams method, and the effect of calcination temperature on the properties of IrO 2 electrocatalysts is investigated. Physicochemical characterization was conducted using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area measurement, high-resolution transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analyses. For the electrochemical performance of synthesized electrocatalysts in the OER, cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were conducted in a typical three-cell electrode configuration, using glassy carbon as the working electrode, which the synthesized electrocatalysts were cast on in a 0.5 M H 2 SO 4 solution. The materials, as anode PEM water electrolysis electrodes, were further evaluated in a typical electrolytic cell using a Nafion ® 115 membrane as the electrolyte and Pt/C as the cathode electrocatalyst. The IrO 2 electrocatalyst calcined at 400 °C shows high crystallinity with a 1.24 nm particle size, a high specific surface area (185 m 2 g -1 ), and a high activity of 177 mA cm -2 at 1.8 V for PEM water electrolysis.

The mixture of H 2 and CO, the so-called syngas, is the value-added product of H 2 O and CO 2 co-electrolysis and the feedstock for the production of value-added chemicals (mainly through Fischer-Tropsch). The H 2 /CO ratio determines the process in which syngas will be utilized and the type of chemicals it will produce. In the present work, we investigate the effect of H 2 O/CO 2 (steam/carbon dioxide, S/C) ratio of 0.5, 1 and 2 in the feed, on the electrochemical performance of an 8YSZ electrolyte-supported solid oxide cell and the H 2 /CO ratio in the outlet, under co-electrolysis at 900 °C. The B-site iron doped lanthanum strontium chromite La 0 . 75 Sr 0 . 25 Cr 0 . 9 Fe 0 . 1 O 3-δ (LSCF) is used as fuel electrode material while as oxygen electrode the state-of-the art LSM perovskite is employed. LSCF is a mixed ionic-electronic conductor (MIEC) operating both under a reducing and oxidizing atmosphere. The cell is electrochemically characterized under co-electrolysis conditions both in the presence and absence of hydrogen in the feed of the steam and carbon dioxide mixtures. The results indicate that under the same concentration of hydrogen and different S/C ratios, the same electrochemical performance with a maximum current density of approximately 400 mA cm -2 is observed. However, increasing p(H 2 ) in the feed results in higher OCV, smaller iV slope and R p values. Furthermore, the maximum current density obtained from the cell does not seem to be affected by whether H 2 is present or absent from the fuel electrode feed but has a significant effect on the H 2 /CO ratio in the analyzed outlet stream. Moreover, the H 2 /CO ratio seems to be identical under polarization at different current density values. Remarkably, the performance of the LSCF perovskite fuel electrode is not compromised by the exposure to oxidizing conditions, showcasing that this class of electrocatalysts retains their reactivity in oxidizing, reducing, and humid environments.

Peptidoglycan N-acetylglucosamine (GlcNAc) deacetylases (PGNGdacs) from bacterial pathogens are validated targets for the development of novel antimicrobial agents. In this study we examined the in vitro inhibition of hydroxamate ligand N-hydroxy-4-(naphthalene-1-yl)benzamide (NHNB), a selective inhibitor of histone deacetylases-8 (HDAC8), against two PGNGdacs namely BC1974 and BC1960 from B. cereus, highly homologous to BA1977 and BA1961 of B. anthracis, respectively. Kinetic analysis showed that this compound functions as a competitive inhibitor of both enzymes with apparent K i 's of 8.7 μM (for BC1974) and 66 μM (for BC1960), providing thus the most potent CE4 inhibitor reported to date. NHNB was tested in antibacterial assays and showed bactericidal activity against both examined pathogens acting as a multi-target drug. This compound can serve as lead for the development of inhibitors targeting the conserved active sites of the multiple polysaccharide deacetylases (PDAs) of both pathogens., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The cell wall peptidoglycan is recognized as a primary target of the innate immune system, and usually its disintegration results in bacterial lysis. Bacillus cereus, a close relative of the highly virulent Bacillus anthracis, contains 10 polysaccharide deacetylases. Among these, the peptidoglycan N-acetylglucosamine deacetylase Bc1974 is the highest homologue to the Bacillus anthracis Ba1977 that is required for full virulence and is involved in resistance to the host's lysozyme. These metalloenzymes belong to the carbohydrate esterase family 4 (CE4) and are attractive targets for the development of new anti-infective agents. Herein we report the first X-ray crystal structures of the NodB domain of Bc1974, the conserved catalytic core of CE4s, in the unliganded form and in complex with four known metalloenzyme inhibitors and two amino acid hydroxamates that target the active site metal. These structures revealed the presence of two conformational states of a catalytic loop known as motif-4 (MT4), which were not observed previously for peptidoglycan deacetylases, but were recently shown in the structure of a Vibrio clolerae chitin deacetylase. By employing molecular docking of a substrate model, we describe a catalytic mechanism that probably involves initial binding of the substrate in a receptive, more open state of MT4 and optimal catalytic activity in the closed state of MT4, consistent with the previous observations. The ligand-bound structures presented here, in addition to the five Bc1974 inhibitors identified, provide a valuable basis for the design of antibacterial agents that target the peptidoglycan deacetylase Ba1977.

The full extent of proline (Pro) hydroxylation has yet to be established, as it is largely unexplored in bacteria. We describe here a so far unknown Pro hydroxylation activity which occurs in active sites of polysaccharide deacetylases (PDAs) from bacterial pathogens, modifying the protein backbone at the C α atom of a Pro residue to produce 2-hydroxyproline (2-Hyp). This process modifies with high specificity a conserved Pro, shares with the deacetylation reaction the same active site and one catalytic residue, and utilizes molecular oxygen as source for the hydroxyl group oxygen of 2-Hyp. By providing additional hydrogen-bonding capacity, the Pro→2-Hyp conversion alters the active site and enhances significantly deacetylase activity, probably by creating a more favorable environment for transition-state stabilization. Our results classify this process as an active-site "maturation", which is highly atypical in being a protein backbone-modifying activity, rather than a side-chain-modifying one.

Bacillus anthracis has a complex cell wall structure composed of a peptidoglycan (PG) layer to which major structures are anchored such as a neutral polysaccharide, an S-layer, and a poly-γ-D-glutamate (PDGA) capsule. Many of these structures have central roles in the biology of B. anthracis, particularly, in virulence. However, little attention has been devoted to structurally study the PG and how it is modified in the presence of these secondary cell wall components. We present here the fine structure of the PG of the encapsulated RPG1 strain harboring both pXO1 and pXO2 virulence plasmids. We show that B. anthracis has a high degree of cross-linking and its GlcNAc residues are highly modified by N-deacetylation. The PG composition is not dependent on the presence of either LPXTG proteins or the capsule. Using NMR analysis of the PG-PDGA complex, we provide evidence for the anchoring of the PDGA to the glucosamine residues. We show that anchoring of the PDGA capsule is impaired in two PG N-deacetylase mutants, Ba1961 and Ba3679. Thus, these multiple N-deactylase activities would constitute excellent drug targets in B. anthracis by simultaneously affecting its resistance to lysozyme and to phagocytosis impairing B. anthracis survival in the host.

Peptidoglycan deacetylases (PGNG-dacs) belong to the Carbohydrate Esterase Family 4 (CE4) and have been described as required for bacterial evasion to lysozyme and innate immune responses. Interestingly, there is an unusual occurrence of 10 putative polysaccharide deacetylases, including five PGNG-dacs, in the Bacillus sp. genomes, especially B. cereus and B. anthracis. To elucidate the physiological role of these multiple deacetylases, we employed genetic analysis and protein localization studies of five putative PGNG-dacs from B. anthracis as well as biochemical analysis of their corresponding homologues from B. cereus. Our data confirm that three enzymes are PGNG-dacs. While BA1977, associated with lateral peptidoglycan synthesis, is a bona fide peptidoglycan deacetylase involved in resistance to host lysozyme and required for full virulence, BA1961 and BA3679 participate in the biogenesis of the peptidoglycan during both elongation and cell division. Furthermore, two enzymes are important for neutral polysaccharide attachment to PG and consequently anchoring of S-layer proteins (BA5436) and for polysaccharide modification (BA2944). Our results provide novel and fundamental insights into the function of polysaccharide deacetylases in a major bioterrorism agent., (© 2013 Blackwell Publishing Ltd.)

The genomes of Bacillus cereus and its closest relative Bacillus anthracis each contain two LmbE protein family homologs: BC1534 (BA1557) and BC3461 (BA3524). Only a few members of this family have been biochemically characterized including N-acetylglucosaminylphosphatidyl inositol (GlcNAc-PI), 1-D-myo-inosityl-2-acetamido-2-deoxy-alpha-D-glucopyranoside (GlcNAc-Ins), N,N'-diacetylchitobiose (GlcNAc(2)) and lipoglycopeptide antibiotic de-N-acetylases. All these enzymes share a common feature in that they de-N-acetylate the N-acetyl-D-glucosamine (GlcNAc) moiety of their substrates. The bc1534 gene has previously been cloned and expressed in Escherichia coli. The recombinant enzyme was purified and its 3D structure determined. In this study, the bc3461 gene from B. cereus ATCC14579 was cloned and expressed in E. coli. The recombinant enzymes BC1534 (EC 3.5.1.-) and BC3461 were biochemically characterized. The enzymes have different molecular masses, pH and temperature optima and broad substrate specificity, de-N-acetylating GlcNAc and N-acetylchito-oligomers (GlcNAc(2), GlcNAc(3) and GlcNAc(4)), as well as GlcNAc-1P, N-acetyl-D-glucosamine-1 phosphate; GlcNAc-6P, N-acetyl-D-glucosamine-6 phosphate; GalNAc, N-acetyl-D-galactosamine; ManNAc, N-acetyl-D-mannosamine; UDP-GlcNAc, uridine 5'-diphosphate N-acetyl-D-glucosamine. However, the enzymes were not active on radiolabeled glycol chitin, peptidoglycan from B. cereus, N-acetyl-D-glucosaminyl-(beta-1,4)-N-acetylmuramyl-L-alanyl-D-isoglutamine (GMDP) or N-acetyl-D-GlcN-Nalpha1-6-D-myo-inositol-1-HPO(4)-octadecyl (GlcNAc-I-P-C(18)). Kinetic analysis of the activity of BC1534 and BC3461 on GlcNAc and GlcNAc(2) revealed that GlcNAc(2) is the favored substrate for both native enzymes. Based on the recently determined crystal structure of BC1534, a mutational analysis identified functional key residues, highlighting their importance for the catalytic mechanism and the substrate specificity of the enzyme. The catalytic efficiencies of BC1534 variants were significantly decreased compared to the native enzyme. An alignment-based tree places both de-N-acetylases in functional categories that are different from those of other LmbE proteins.