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Solid oxide cells (SOCs) have attracted a growing attention thanks to their high efficiency and ability to operate in both electrolysis (SOEC) and fuel cell (SOFC) modes. Despite its great potential, the current SOC technology faces significant cell degradation during long-term operation. The degradation phenomena are still not well understood as they involve complex and intricate processes arising at different length scales. Additionally, it has been shown that the degradation rate under SOEC operation is generally higher than in SOFC mode. To address this issue, durability tests were performed in SOEC mode at 750, 800 and 850 °C for 2000 h at -1 A cm-2 in 10/90 vol.% H2/H2O and dry air. The electrochemical performance of the cells was assessed using electrochemical impedance spectroscopy. In addition, advanced characterization techniques with nanometer and atomic resolution have been used to study material degradation after long-term testing.

During HIV-1 infection, the envelope glycoprotein subunit gp41 folds into a six-helix bundle structure (6HB) formed by the interaction between its N-terminal (NHR) and C-terminal (CHR) heptad-repeats, promoting viral and cell membranes fusion. A highly preserved, hydrophobic pocket (HP) on the NHR surface is crucial in 6HB formation and, therefore, HP-binding compounds constitute promising therapeutics against HIV-1. Here, we investigated the conformational and dynamic properties of the HP using a rationally designed single-chain protein (named covNHR) that mimics the gp41 NHR structure. We found that the fluorescent dye 8-anilino-naphtalene- 1-sulfonic acid (ANS) binds specifically to the HP, suggesting that ANS derivatives may constitute lead compounds to inhibit 6HB formation. ANS shows different binding modes to the HP, depending on the occupancy of other NHR pockets. Moreover, in presence of a CHR peptide bound to the N-terminal pockets in gp41, two ANS molecules can occupy the HP showing cooperative behavior. This binding mode was assessed using molecular docking and molecular dynamics simulations. The results show that the HP is conformationally flexible and connected allosterically to other NHR regions, which strongly influence the binding of potential ligands. These findings could guide the development of small-molecule HIV-1 inhibitors targeting the HP., Spanish State Research Agency, SRA/ 10.13039/501100011033 (grants BIO2016-76640-R and PID2019.107515RB.C21), ERDF/ESF

Resume Le nombre de cas de cristallurie sous amoxicilline declares aux centres de pharmacovigilance francais est en augmentation depuis 2010, ceux-ci etant principalement lies aux fortes doses d’amoxicilline utilisees pour le traitement de certaines pathologies infectieuses, endocardite notamment, chez des patients âges et avec comorbidites. Une presentation clinique evocatrice et l’exclusion des autres causes sont proposees pour poser le diagnostic. La recherche de cristaux typiques dans les urines et un examen anatomopathologique renal sont rarement necessaires ou realises pour des raisons techniques le plus souvent. Par ailleurs, l’insuffisance renale aigue est rapidement reversible a l’arret de l’antibiotique. L’interet diagnostique et pronostique des concentrations plasmatiques residuelles de l’antibiotique n’a ete que rarement etudie. Nous presentons 9 cas d’insuffisance renale aigue evocateurs de cristallurie sous amoxicilline, pour lesquels nous avons systematiquement dose les concentrations plasmatiques residuelles et compare a une serie de dosages realises chez d’autres patients issus de notre base de donnees hospitaliere. Tous les patients avaient un taux residuel eleve au diagnostic, mais nous n’avons pas pu determiner de seuil d’amoxicillinemie predictif de tubulopathie afin d’adapter la posologie, d’hydrater le patient et d’alcaliniser les urines pour augmenter la solubilite de l’antibiotique et limiter sa toxicite renale.

Amyloid aggregation is a hallmark in many neuropathologies and other diseases of tremendous impact. It is increasingly evident that neuronal death associated with Alzheimer's disease (AD) is mainly produced by oligomers of the amyloid-β (Aβ) peptide. Yet little is known about the detailed structural and biophysical mechanisms of their formation. This lack of complete understanding comes from the labile nature and handling complexity of the oligomers. Consequently, providing reproducible and robust protocols for oligomer preparation is of particular importance.In this study, we describe detailed methods for the preparation and isolation of micellar oligomers of Aβ that evolve towards larger and more stable oligomers enriched in beta-sheet structure and able to acquire a higher capacity to fibrillate. We also describe briefly some biophysical experiments allowing oligomer characterization.

One of the therapeutic strategies in HIV neutralization is blocking membrane fusion. In this process, tight interaction between the N-terminal and C-terminal heptad-repeat (NHR and CHR) regions of gp41 is essential to promote membranes apposition and merging. We have previously developed single-chain proteins (named covNHR) that accurately mimic the complete gp41 NHR region in its trimeric conformation. They tightly bind CHR-derived peptides and show a potent and broad HIV inhibitory activity in vitro. However, the extremely high binding affinity (sub-picomolar) is not in consonance with their inhibitory activity (nanomolar), likely due to partial or temporal accessibility of their target in the virus. Here, we have designed and characterized two single-chain covNHR miniproteins each encompassing one of the two halves of the NHR region and containing two of the four sub-pockets of the NHR crevice. The two miniproteins fold as trimeric helical bundles as expected but while the C-terminal covNHR (covNHR-C) miniprotein is highly stable, the N-terminal counterpart (covNHR-N) shows only marginal stability that could be improved by engineering an internal disulfide bond. Both miniproteins bind their respective complementary CHR peptides with moderate (micromolar) affinity. Moreover, the covNHR-N miniproteins can access their target in the context of trimeric native envelope proteins and show significant inhibitory activity for several HIV pseudoviruses. In contrast, covNHR-C cannot bind its target sequence and neither inhibits HIV, indicating a higher vulnerability of C-terminal part of CHR. These results may guide the development of novel HIV inhibitors targeting the gp41 CHR region., Spanish Ministry of Economy and Competitiveness (grant: BIO2016-76640-R), ANRS and the Vaccine Research Institute for the Investissements d'Avenir program to C.M. and by the European Fund for Research and Development from the European Union., Departamento de Química Física, Facultad de Ciencias, Universidad de Granada. Grupo FQM-171 "Biofísica y Biotecnología Molecular"

Development of effective inhibitors of the fusion between HIV-1 and the host cell membrane mediated by gp41 continues to be a grand challenge due to an incomplete understanding of the molecular and mechanistic details of the fusion process. We previously developed single-chain, chimeric proteins (named covNHR) that accurately mimic the N-heptad repeat (NHR) region of gp41 in a highly stable coiled-coil conformation. These molecules bind strongly to peptides derived from the gp41 C-heptad repeat (CHR) and are potent and broad HIV-1 inhibitors. Here, we investigated two covNHR variants differing in two mutations, V10E and Q123R (equivalent to V38E and Q40R in gp41 sequence) that reproduce the effect of HIV-1 mutations associated with resistance to fusion inhibitors, such as T20 (enfuvirtide). A detailed calorimetric analysis of the binding between the covNHR proteins and CHR peptides (C34 and T20) reveals drastic changes in affinity due to the mutations as a result of local changes in interactions at the site of T20 resistance. The crystallographic structure of the covNHR:C34 complex shows a virtually identical CHR–NHR binding interface to that of the post-fusion structure of gp41 and underlines an important role of buried interfacial water molecules in binding affinity and in development of resistance against CHR peptides. Despite the great difference in affinity, both covNHR variants demonstrate strong inhibitory activity for a wide variety of HIV-1 strains. These properties support the high potential of these covNHR proteins as new potent HIV-1 inhibitors. Our results may guide future inhibition approaches., Departamento de Química Física e Instituto de Biotecnología, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain, Ministerio de Economía y Competitividad (grants BIO2016-76640-R and BIO2016-78020-R) y Fondo Europeo para el Desarrollo Regional (FEDER) de la Unión Europea, ANRS and the Vaccine Research Institute for the Investissements d'Avenir program managed by the ANR under reference ANR-10-LABX-77

While high performance of SOFC systems has already been achieved, there is still a need to increase the stack lifetime, while decreasing the system's total cost of ownership, both being linked. The increase in lifetime includes the minimization of performance degradation, but also avoidance of potentially detrimental events during operation, originating from the stack, outside the stack, or a combination of both. The present paper highlights how the detection of faulty operation as early as possible is important to implement adequate mitigation strategies, wherever applicable, according to the fault and its grade of severity. Three types of faults have been considered, fuel starvation, leakage and carbon deposition. Both hardware components and algorithms to monitor, detect, isolate, and finally correct faulty system operation have been developed and will be embedded in a real SOFC system.

The formation of fibrillar aggregates of the amyloid beta peptide (Aβ) in the brain is one of the hallmarks of Alzheimer’s disease (AD). A clear understanding of the different aggregation steps leading to fibrils formation is a keystone in therapeutics discovery. In a recent study, we showed that Aβ40 and Aβ42 form dynamic micellar aggregates above certain critical concentrations, which mediate a fast formation of more stable oligomers, which in the case of Aβ40 are able to evolve towards amyloid fibrils. Here, using different biophysical techniques we investigated the role of different fractions of the Aβ aggregation mixture in the nucleation and fibrillation steps. We show that both processes occur through bimolecular interplay between low molecular weight species (monomer and/or dimer) and larger oligomers. Moreover, we report here a novel self-catalytic mechanism of fibrillation of Aβ40, in which early oligomers generate and deliver low molecular weight amyloid nuclei, which then catalyze the rapid conversion of the oligomers to mature amyloid fibrils. This fibrillation catalytic activity is not present in freshly disaggregated low-molecular weight Aβ40 and is, therefore, a property acquired during the aggregation process. In contrast to Aβ40, we did not observe the same self-catalytic fibrillation in Aβ42 spheroidal oligomers, which could neither be induced to fibrillate by the Aβ40 nuclei. Our results reveal clearly that amyloid fibrillation is a multi-component process, in which dynamic collisions between different interacting species favor the kinetics of amyloid nucleation and growth., Spanish Ministry of Economy and Competitivity (BIO2013-40697-R) (BIO2016-76640-R) - European Regional Development Fund of the European Union.

International audience; Three long-term experiments have been performed in SOEC and SOFC modes at different operating temperatures. The durability tests confirm a higher degradation in electrolysis mode with respect to fuel cell operation. In addition, a larger increase of the ohmic resistance is observed for the cell operated at higher temperature in electrolysis mode. The oxygen electrodes of the pristine and tested cells have been characterized by synchrotron X-ray micro-diffraction and micro-fluorescence to assess the relation between the material destabilization and the formation of insulating phases due to interlayer diffusion. The analyses of the pristine cell confirm the presence after the electrode sintering of strontium zirconate and a Gd-rich inter-diffusional layer in the electrolyte just below the zirconates. Moreover, evolutions in the LSCF unit cell volume reveal strontium segregation after aging. The associated material destabilization is linked to the accumulation of SrZrO 3 at the barrier layer-inter-diffusional layer interface in operation and both phenomena are found to be thermally-activated and promoted in electrolysis mode. Finally, the crystallographic evolution of the inter-diffusional layer in electrolysis mode has been investigated by X-ray diffraction. A slight increase of the phase peaks intensity detected at the highest temperature is correlated to the largest formation of SrZrO 3 observed in this condition. Based on these preliminary results, it is proposed that the loss of Zr 4+ from the electrolyte due to the zirconates formation could facilitate the inter-diffusion of Gd, reducing the local ionic conductivity and thus significantly contributing to the largest increase in the ohmic resistance observed in this case.

The aim of this study was to estimate the incidence of COVID-19 disease in the French national population of dialysis patients, their course of illness and to identify the risk factors associated with mortality. Our study included all patients on dialysis recorded in the French REIN Registry in April 2020. Clinical characteristics at last follow-up and the evolution of COVID-19 illness severity over time were recorded for diagnosed cases (either suspicious clinical symptoms, characteristic signs on the chest scan or a positive reverse transcription polymerase chain reaction) for SARS-CoV-2. A total of 1,621 infected patients were reported on the REIN registry from March 16th, 2020 to May 4th, 2020. Of these, 344 died. The prevalence of COVID-19 patients varied from less than 1% to 10% between regions. The probability of being a case was higher in males, patients with diabetes, those in need of assistance for transfer or treated at a self-care unit. Dialysis at home was associated with a lower probability of being infected as was being a smoker, a former smoker, having an active malignancy, or peripheral vascular disease. Mortality in diagnosed cases (21%) was associated with the same causes as in the general population. Higher age, hypoalbuminemia and the presence of an ischemic heart disease were statistically independently associated with a higher risk of death. Being treated at a selfcare unit was associated with a lower risk. Thus, our study showed a relatively low frequency of COVID-19 among dialysis patients contrary to what might have been assumed., Graphical abstract

Since 2010, a lot of cases of amoxicillin induced crystal nephropathy have been reported to the French pharmacovigilance centers partly due to the high doses recommended by infectious disease guidelines. Typical clinical presentation and exclusion of others toxics or immuno-allergic causes are mandatory to assess the diagnostic. Amoxicillin crystals are rarely found or searched and renal biopsy is not frequently performed due to technical reasons and prompt renal recovery after antibiotics withdrawal. Monitoring of residual plasma concentration is rarely used in clinical practice for diagnostic or prognostic interest. We present 9 consecutive cases of acute kidney injury suspected to be due to amoxicillin crystals with residuals plasma levels to disclose a predictive threshold of tubulopathy. All patients had a high residual rate at diagnosis but we cannot find a threshold that would allow to adapt the antibiotic dose, enhance hydratation and alkalinizide urine to increase the medication solubility and limit renal toxicity.

The majority of clinically used antibiotics originate from bacteria. As the need for new antibiotics grows, large-scale genome sequencing and mining approaches are being used to identify novel antibiotics. However, this task is hampered by the fact that many antibiotic biosynthetic clusters are not expressed under laboratory conditions. One strategy to overcome this limitation is the identification of signals that activate the expression of silent biosynthetic pathways. Here, we report the use of high-throughput screening to identify signals that control the biosynthesis of the acetyl-CoA carboxylase inhibitor antibiotic andrimid in the broad-range antibiotic-producing rhizobacterium Serratia plymuthica A153. We reveal that the pathway-specific transcriptional activator AdmX recognizes the auxin indole-3-acetic acid (IAA). IAA binding causes conformational changes in AdmX that result in the inhibition of the expression of the andrimid cluster and the suppression of antibiotic production. We also show that IAA synthesis by pathogenic and beneficial plant-associated bacteria inhibits andrimid production in A153. Because IAA is a signalling molecule that is present across all domains of life, this study highlights the importance of intra- and inter-kingdom signalling in the regulation of antibiotic synthesis. Our discovery unravels, for the first time, an IAA-dependent molecular mechanism for the regulation of antibiotic synthesis.

The aggregation propensity of each particular protein seems to be shaped by evolution according to its natural abundance in the cell. The production and downstream processing of recombinant polypeptides implies attaining concentrations that are orders of magnitude above their natural levels, often resulting in their aggregation; a phenomenon that precludes the marketing of many globular proteins for biomedical or biotechnological applications. Therefore, there is a huge interest in methods aimed to increase the proteins solubility above their natural limits. Here, we demonstrate that an updated version of our AGGRESCAN 3D structural aggregation predictor, that now takes into account protein stability, allows for designing mutations at specific positions in the structure that improve the solubility of proteins without compromising their conformation. Using this approach, we have designed a highly soluble variant of the green fluorescent protein and a human single-domain VH antibody displaying significantly reduced aggregation propensity. Overall, our data indicate that the solubility of unrelated proteins can be easily tuned by in silico-designed nondestabilizing amino acid changes at their surfaces.

A deep understanding of the early molecular mechanism of amyloid beta peptides (Aβ) is crucial to develop therapeutic and preventive approaches for Alzheimer's disease (AD). Using a variety of biophysical techniques, we have found that micelle-like dynamic oligomers are rapidly formed by Aβ40 and Aβ42 above specific critical concentrations. Analysis of the initial aggregation rates at 37 °C measured by thioflavin T and Bis-ANS fluorescence using a mass-action micellization model revealed a concentration-dependent switch in the nucleation mechanism. Bimolecular nucleation appears to occur at low peptide concentration while above the critical micellar concentration, the nucleation takes place more efficiently in the micelles. Upon incubation, these micelles mediate a rapid formation of larger, more stable oligomers enriched in beta-sheet structure. These oligomers formed from Aβ40, enriched in amyloid nuclei, acquire a higher capacity to fibrillate than their micellar precursors. Aβ42 can also form similar oligomers but they have lower beta-sheet structure content and lower capacity to fibrillate. On the other hand, a considerable fraction of the Aβ42 peptide forms morphologically distinct oligomers that are unable to fibrillate and show significant effect on SH-SY5Y cell viability. Overall, our results highlight the importance of micellar structures as mediators of amyloid nucleation and contribute to the understanding of the differences between the aggregation pathways of Aβ40 and Aβ42.

Electrochemical impedance spectroscopy (EIS) is a widely used tool for characterization of fuel cells and other electrochemical conversion systems. When applied to the on-line monitoring in the context of in-field applications, the disturbances, drifts and sensor noise may cause severe distortions in the evaluated spectra, especially in the low-frequency part. Failure to ignore the random effects can result in misinterpreted spectra and, consequently, in misleading diagnostic reasoning. This fact has not been often addressed in the research so far. In this paper, we propose an approach to the quantification of the spectral uncertainty, which relies on evaluating the uncertainty of the equivalent circuit model (ECM). We apply the computationally efficient variational Bayes (VB) method and compare the quality of the results with those obtained with the Markov chain Monte Carlo (MCMC) algorithm. Namely, MCMC algorithm returns accurate distributions of the estimated model parameters, while VB approach provides the approximate distributions. By using simulated and real data we show that approximate results provided by VB approach, although slightly over-optimistic, are still close to the more realistic MCMC estimates. A great advantage of the VB method for online monitoring is low computational load, which is several orders of magnitude lower compared to MCMC. The performance of VB algorithm is demonstrated on a case of ECM parameters estimation in a 6 cell solid oxide fuel cell (SOFC) stack. The complete numerical implementation for recreating the results can be found at https://repo.ijs.si/lznidaric/variational-bayes-supplementary-material., 28 pages, 18 figures. Submitted to: Applied Energy

A set of long-term tests (t ≥ 1000 h) have been carried out in fuel cell and electrolysis modes on typical Ni-YSZ//YSZ//LSCF-CGO cells. The degradation rates were found to be higher in electrolysis than in fuel cell operation. Post-test analyses have revealed that Sr diffusion and formation of SrZrO3 at YSZ/CGO interface occur mainly during electrolysis operation, whereas the process is very limited in fuel cell mode. As a consequence, LSCF destabilization is found to be not involved in the degradation of cell performances during fuel cell operation while it could explain the highest degradation rates recorded in electrolysis mode. An in-house multi-scale model has been used to interpret the role of the cell operating mode on the LSCF demixing mechanism. The simulations have shown that the electrolysis operation leads to a strong depletion of oxygen vacancies in LSCF material (while the fuel cell condition results in an increase in the concentration of oxygen vacancies). It has been proposed that the depletion in oxygen vacancies under electrolysis polarization could drive the Sr release from the structure, and in turn, could explain the experimental results. Based on this proposition, a possible mechanism for the LSCF destabilization and SrZrO3 formation is detailed.

Ceramic high-temperature fuel cells and electrolysers are efficient energy conversion systems for electrical power generation and hydrogen production. Their core components are constituted by a stack of electroactive Solid Oxide Cells (SOCs) in which the electrochemical reactions take place. Thanks to their flexibility, the same stack can be alternatively operated in both fuel cell and electrolysis modes. However, the insufficient durability of SOCs still constitutes a major limitation for the technology. The present study addresses this issue and aims to bring some new insights on the effect of the Solid Oxide Fuel Cell (SOFC) versus Solid Oxide Electrolysis Cell (SOEC) operating modes on degradation of a typical Ni-YSZ//YSZ//CGO//LSCF-CGO cell. The electrochemical degradations are generally attributed to several underlying phenomena such as electrode microstructural evolution, material chemical decomposition or electroactive sites poisoning by contaminants. Among them, it is generally considered that Ni agglomeration in the Ni-YSZ cermet and Lanthanum Strontium Cobalt Ferrite (LSCF) material destabilization are two prevalent mechanisms involved in the cell performance deterioration. Therefore, these two mechanisms have been specifically investigated by a coupled approach of long-term testing in both SOFC and SOEC modes (1000 ≤ t (h) ≤9000) and post-test characterizations. The experimental results have then been analyzed in the frame of an in-house multi-scale model with the purpose to interpret them and to quantify the effect of material ageing on cell performances. The extent of Ni agglomeration has been characterized by three-dimensional electrode reconstructions obtained by X-ray nano-holotomography at European Synchrotron Radiation Facility (ESRF) (on the new Nano-Imaging beamline ID16A-NI). The new set-up and protocol enable the reconstructions of valuable 3D volumes (Fig. 1) with a large field of view (~50 µm) along with a high spatial resolution (~50 nm). The electrode morphological properties, which have been measured on the 3D volumes, have revealed a substantial Ni coarsening over time at 850°C and 750°C, whereas no Ni depletion was detected at the electrolyte interface. The increase of the Ni particle size is found to induce a decrease in both (i) the density of Triple Phase Boundary (TPBs) lines and (ii) the interfacial surface area between Ni and gas. Moreover, it was found that the Ni/YSZ interfacial surface area does not evolve during the experiments. This statement indicates that the ceramic backbone in the cermet prevents a massive Ni agglomeration at the SOFC/SOEC operating temperature. The compilation of all experimental data have allowed fitting the parameters of a physically-based law for Ni coarsening that was introduced in the modelling framework. The simulations have revealed that Ni agglomeration explains around 20-25% of the electrochemical degradation at 850°C after 1000 hrs of operation. However, the electrode microstructural evolution is found not to be affected by the cell polarizations. Therefore, the mechanism cannot explain the higher degradation rates recorded in electrolysis mode compared to the fuel cell ones. To explain the impact of the operating modes (SOFC or SOEC) on the degradation rates, several post-test analyses (i.e. Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray µfluorescence and µdiffraction techniques) have been employed to investigate the phase reactivity in the region of the CGO barrier layer. The characterizations have revealed that Sr diffusion across the barrier layer and formation of SrZrO3 secondary phase occur mainly during electrolysis operation, whereas the process is very limited in fuel cell mode (Fig. 2). As a consequence, LSCF destabilization is found not to be involved in the degradation of cell performances during fuel cell operation while it could explain the highest degradation rates recorded in electrolysis mode. The post-test analyses have also revealed a diffusion and an accumulation of Co in the region of the barrier layer which is concomitant with the formation of SrZrO3. The formation of these Co-rich segregates in contact with SrZrO3 grains have been identified as cobalt-ferrite type compound. The in-house multi-scale model has been used to interpret the role of the cell operating mode on the LSCF destabilization mechanism. The cell polarization curves and the local quantities within the O2 electrode have been computed in both fuel cell and electrolysis modes. The simulations have shown that the electrolysis operation leads to a strong depletion of oxygen vacancies in the LSCF material. It has been proposed that the depletion in oxygen vacancies under electrolysis polarization could drive the Sr release from the structure, and in turn, could explain the experimental results. Based on this proposition, a possible mechanism for the LSCF destabilization and SrZrO3 formation has been detailed. Figure 1

HIV-1 glycoprotein 41 (gp41) mediates fusion between virus and target cells by folding into a fusion active state, in which the C-terminal heptad repeat (CHR) regions associate externally to the N-terminal heptad repeat (NHR) trimer and form a very stable six-helix bundle coiled-coil structure. Therefore, interfering with the NHR-CHR interaction of gp41 is a promising therapeutic approach against HIV-1. However, a full understanding of the molecular and mechanistic details of this interaction is still incomplete. Here, we use single-chain, chimeric proteins (named covNHR) that reproduce accurately the CHR-NHR interactions to analyze the binding thermodynamics of several peptides with different length from the CHR region. The results indicate that cooperative binding involving two or more pockets of the NHR groove is necessary to obtain relevant affinities and that the binding energy is broadly distributed along the interface, underlining a crucial role of a middle pocket to achieve tight binding. In contrast, targeting only the deep hydrophobic pocket is insufficient to achieve significant affinity. Moreover, calorimetry experiments in combination with limited proteolysis performed using a mutant with occluded binding in the N-terminal pocket reveal the existence of an allosteric communication between the different regions. This study is the first detailed thermodynamic dissection of the NHR-CHR interaction in gp41 and contributes therefore to a better understanding of HIV fusion. These results are relevant for the development of potential fusion inhibitors., Grant BIO2016-76640-R from the Spanish Ministry of Economy and Competitiveness and by the European Fund for Research and Development from the European Union., Departamento de Química Física, Facultad de Ciencias, Universidad de Granada. Grupo FQM-171 "Biofísica y Biotecnología Molecular"

Higher exploitation of fuel cell technologies can be achieved employing effective maintenance and condition monitoring tools. Electrochemical impedance spectroscopy (EIS) is a common way for state-of-health characterisation of fuel cells. However, parameters of an equivalent circuit model (ECM) used to describe the EIS seem to be more convenient and informative. Usually, an ECM structure is selected a priori, and an optimisation problem is formulated to fit the parameters of the model and gain their corresponding point estimates. However, for more precise reasoning, better information about the parameters is desirable. This can be achieved through Bayesian inference. In this paper, Bayesian inference is employed to estimate model parameters and so to obtain the posterior marginal density functions of the model’s parameters. It is shown how point estimates may be misleading. The approach is demonstrated on solid oxide fuel cell (SOFC) short stack.

An increasing number of human disorders has been identified as associated to or directly caused by aberrant protein aggregation and especially amyloid fibril formation. In this chapter, we recapitulate the main advances in understanding amyloid aggregation kinetics in vitro. We start by reviewing the main structural and morphological characteristics of protein amyloid aggregates. Then, we continue summarizing the main techniques used to study protein aggregation in vitro and set a special focus in describing the basic and more advanced kinetic mechanisms used to interpret the experimental aggregation data. Finally, we describe specific features of the aggregation kinetics of three highly relevant proteins related to important diseases.

The industrial fluorination of UO2 to UF4 is based on a complex process involving the manipulation of a large amount of HF, a very toxic and corrosive gas. We present here a safer way to accomplish this reaction utilizing ionic liquid [Bmim][PF6] as a unique reaction medium and fluoride source.

Protein amyloid aggregation is a hallmark in neuropathologies and other diseases of tremendous impact such as Alzheimer's or Parkinson's diseases. During the last decade, it has become increasingly evident that neuronal death is mainly induced by proteinaceous oligomers rather than the mature amyloid fibrils. Therefore, the earliest molecular events occurring during the amyloid aggregation cascade represent a growing interest of study. Important breakthroughs have been achieved using experimental data from different proteins, used as models, as well as systems related to diseases. Here, we summarize the structural properties of amyloid oligomeric and fibrillar aggregates and review the recent advances on how biophysical techniques can be combined with quantitative kinetic analysis and theoretical models to study the detailed mechanism of oligomer formation and nucleation of fibrils. These insights into the mechanism of early oligomerization and amyloid nucleation are of relevant interest in drug discovery and in the design of preventive strategies against neurodegenerative diseases.

This paper deals with the monitoring of the internal condition of a 6-cell solid oxide fuel cell stack during a 3600-hour test with short fuel starvation intervals. The relationship between change in condition and change of impedance spectra as well as the parameters of the equivalent circuit models are analysed. Tentative features indicating reduced fuel supply are identified. The analysis uses discrete random binary sequence, a stochastic broadband excitation signal that allows much shorter perturbation times. More than 600 electrochemical impedance spectroscopy curves and the associated equivalent circuit model parameters were analysed. High fuel utilisation interval is detected in two ways: (i) by violating the Z-HIT test in the low-frequency part (below ≈ 1 Hz) and (ii) significant change of the area-specific resistance parameter. The degradation after fuel cut-offs is clearly reflected in the change in area-specific resistance and the serial resistance. The numerical implementation of the proposed algorithms is available at: https://repo.ijs.si/pboskoski/py_eis.git .

The remarkable metal resistance of many microorganisms is related to the presence of multiple metal resistance operons. Pseudomonas putida KT2440 can be considered a model for these microorganisms since its arsenic resistance is due to the action of proteins encoded by the two paralogous arsenic resistance operons ARS1 and ARS2. Both operons contain the genes encoding the transcriptional regulators ArsR1 and ArsR2 that control operon expression. We show here that purified ArsR1 and ArsR2 bind the trivalent salt of arsenic (arsenite) with similar affinities (~30 μM), whereas no binding is observed for the pentavalent salt (arsenate). Furthermore, trivalent salts of bismuth and antimony showed binding to both paralogues. The positions of cysteines, found to bind arsenic in other homologues, indicate that ArsR1 and ArsR2 employ different modes of arsenite recognition. Both paralogues are dimeric and possess significant thermal stability. Both proteins were used to construct whole-cell, lacZ -based biosensors. Whereas responses to bismuth were negligible, significant responses were observed for arsenite, arsenate, and antimony. Biosensors based on the P. putida arsB1 arsB2 arsenic efflux pump double mutant were significantly more sensitive than biosensors based on the wild-type strain. This sensitivity enhancement by pump mutation may be a convenient strategy for the construction of other biosensors. A frequent limitation found for other arsenic biosensors was their elevated background signal and interference by inorganic phosphate. The constructed biosensors show no interference by inorganic phosphate, are characterized by a very low background signal, and were found to be suitable to analyze environmental samples. IMPORTANCE Arsenic is at the top of the priority list of hazardous compounds issued by the U.S. Agency for Toxic Substances and Disease. The reason for the stunning arsenic resistance of many microorganisms is the existence of paralogous arsenic resistance operons. Pseudomonas putida KT2440 is a model organism for such bacteria, and their duplicated ars operons and in particular their ArsR transcription regulators have been studied in depth by in vivo approaches. Here we present an analysis of both purified ArsR paralogues by different biophysical techniques, and data obtained provide valuable insight into their structure and function. Particularly insightful was the comparison of ArsR effector profiles determined by in vitro and in vivo experimentation. We also report the use of both paralogues to construct robust and highly sensitive arsenic biosensors. Our finding that the deletion of both arsenic efflux pumps significantly increases biosensor sensitivity is of general relevance in the biosensor field.

Infections due to multidrug-resistant bacteria represent a major global health challenge. To combat this problem, new antibiotics are urgently needed and some plant-associated bacteria are a promising source. The rhizobacterium Serratia plymuthica A153 produces several bioactive secondary metabolites, including the anti-oomycete and antifungal haterumalide, oocydin A and the broad spectrum polyamine antibiotic, zeamine. In this study, we show that A153 produces a second broad spectrum antibiotic, andrimid. Using genome sequencing, comparative genomics and mutagenesis, we defined new genes involved in andrimid (adm) biosynthesis. Both the expression of the adm gene cluster and regulation of andrimid synthesis were investigated. The biosynthetic cluster is operonic and its expression is modulated by various environmental cues, including temperature and carbon source. Analysis of the genome context of the adm operon revealed a gene encoding a predicted LysR-type regulator, AdmX, apparently unique to Serratia strains. Mutagenesis and gene expression assays demonstrated that AdmX is a transcriptional activator of the adm gene cluster. At the post-transcriptional level, the expression of the adm cluster is positively regulated by the RNA chaperone, Hfq, in an RpoS-independent manner. Our results highlight the complexity of andrimid biosynthesis - an antibiotic with potential clinical and agricultural utility.

In this work, an online natural aging estimation algorithm is developed, coupled with an Electrochemical Impedance Spectroscopy (EIS)-based diagnostic algorithm, to refine detection features extraction during Solid Oxide Fuel Cell (SOFC) stack operation and to predict its Remaining Useful Life (RUL). A combination of a lumped dynamic model along with features extracted from real-time EIS measurements is herein proposed for on-line applications. An Equivalent Circuit Model (ECM) is considered to identify parameters, such as ohmic and total resistance, that are coupled with an Area Specific Resistance (ASR) approach within the lumped model. The information derived from the EIS spectrum allows to estimate the voltage degradation over time along with its nominal behaviour. Indeed, the time trend of the identified parameters is proportional to the aging of the cell if no other abnormal condition occurs. This guarantees an on-line RUL estimation and a more robust diagnostic algorithm for fault detection and isolation. The approach has been applied to a 6-cells anode supported short stack tested for about 5000 h, and the related RUL estimation identified a critical issue on the middle cell, affecting its neighbours.

In order to rationalize the production of porous Metal-Organic Frameworks (MOFs) in ionic liquids (ILs) as main solvent, we selected the archetype UiO-66(Zr) to analyze its precipitation in four commercial candidates of ILs commonly used in the literature. We did the choice to investigate the reactivity of two hydrophobic salts, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][NTf2]) and 1-butyl-3-methylimidazolium hexafluorophosphate [Bumim][PF6]), as well as two other salts considered as hydrophilic, ([Omim][Cl]) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([Emim][TFO]). Whereas the synthesis in hydrophilic ILs gave rise to the crystallization of pure UiO-66(Zr), the solvo-thermal reaction (120 °C) performed in hydrophobic salts did not lead to the same results. In the case of [Bumim][PF6], we noted the precipitation of zirconium phosphate Zr(HPO4)2 H2O, while the synthesis in [Emim][NTf2] favored the formation of distinct zirconium terephthalate called hcp UiO-66. These different phases have been characterized by powder X-ray diffraction, BET, IR and SEM.

International audience; The present article reviews a selection of results obtained in the AREVA/CNRS/UCA joint research laboratory. It focuses on interfaces formed by uranium hexafluoride (UF6) with chemical filter (purification), carbon (UF6 storage), and metallic substrate (corrosion). As a matter of fact, along the nuclear fuel cycle, metallic surfaces of the fluorination reactors, cooling systems (for the liquefaction of UF6), and storage containers are in contact with UF6, either in the gas or in the liquid phase. For the removal of volatile impurities before the enrichment, surface of chemical filters with a high specific surface area must be enhanced for both selectivity and efficiency. To store depleted UF6 (238U), graphite intercalation compounds are proposed and preliminary results are presented.

The applicability of online total harmonic distortion analysis (THDA) for the operation and monitoring of solid oxide fuel cell (SOFC) power systems is investigated by experiments as well as analysis of the algorithm, with a focus on the relationship between stack fuel utilization rate and the corresponding THD index. An online THDA algorithm is implemented in a programmable logic controller (PLC) and operated with a 6 kW SOFC power system demonstration unit. Laboratory experiments on the solid oxide fuel cell technology are carried out to determine key parameters for the algorithm. The embedded implementation of the THDA algorithm, including several modifications to reduce its computational load, and its parameterization is analyzed and the program code is given in the Appendix. The experimental results verify that THDA can be a reliable means for quantitatively monitoring the fuel utilization rate experienced by the stack and that the algorithm is simple to implement on an embedded controller.

Mutations or cellular conditions that destabilize the native protein conformation promote the population of partially unfolded conformations, which in many cases assemble into insoluble amyloid fibrils, a process associated with multiple human pathologies. Therefore, stabilization of protein structures is seen as an efficient way to prevent misfolding and subsequent aggregation. This has been suggested to be the underlying reason why proteins living in harsh environments, such as the extracellular space, have evolved disulfide bonds. The effect of protein disulfides on the thermodynamics and kinetics of folding has been extensively studied, but much less is known on its effect on aggregation reactions. Here, we designed a single point mutation that introduces a disulfide bond in the all-α FF domain, a protein that, despite being devoid of preformed β-sheets, forms β-sheet-rich amyloid fibrils. The novel and unique covalent bond in the FF domain dramatically increases its thermodynamic stability and folding speed. Nevertheless, these optimized properties cannot counteract the inherent aggregation propensity of the protein, thus indicating that a high global protein stabilization does not suffice to prevent amyloid formation unless it contributes to hide from exposure the specific regions that nucleate the aggregation reaction.

Although it is well established that one- and two-component regulatory systems participate in regulating biofilm formation, there also exists evidence suggesting that chemosensory pathways are also involved. However, little information exists about which chemoreceptors and signals modulate this process. Here we report the generation of the complete set of chemoreceptor mutants of Pseudomonas putida KT2440 and the identification of four mutants with significantly altered biofilm phenotypes. These receptors are a WspA homologue of Pseudomonas aeruginosa, previously identified to control biofilm formation by regulating c-di-GMP levels, and three uncharacterized chemoreceptors. One of these receptors, named McpU, was found to mediate chemotaxis towards different polyamines. The functional annotation of McpU was initiated by high-throughput thermal shift assays of the receptor ligand binding domain (LBD). Isothermal titration calorimetry showed that McpU-LBD specifically binds putrescine, cadaverine and spermidine, indicating that McpU represents a novel chemoreceptor type. Another uncharacterized receptor, named McpA, specifically binds 12 different proteinogenic amino acids and mediates chemotaxis towards these compounds. We also show that mutants in McpU and WspA-Pp have a significantly reduced ability to colonize plant roots. Data agree with other reports showing that polyamines are signal molecules involved in the regulation of bacteria-plant communication and biofilm formation.