Synthesis and Studies of Polymers Crosslinked with Electrochemically Degradable Crosslinking Reagents

Crosslinked polymers have a covalent bridge that connects two polymer strands at multiple points, creating a network or matrix that is very robust. These types of polymers may either be stable indefinitely, or degrade over time; those that degrade over time typically do so at a constant rate. What is not available currently is a polymer that is stable indefinitely, but then can be degraded on command. Being able to create an adhesive that could undergo de-bonding on command would be very useful. We have designed an electrochemically degradable crosslinking reagent (EDCR) composed of a bi-functional polymer crosslinking moiety and an electroactive core that undergoes degradation under reductive conditions. The EDCR is composed of a quinone center with two terminal amines attached. This crosslinker will be used to make a reversible epoxy adhesive. Epoxys are two-component adhesives that consist of a crosslinking amine hardener and an epoxide-containing polymer resin. Mixing of these components leads to a reaction between the epoxy groups and the terminal amines on the hardener. This work shows the construction of a protected form of an EDCR. Once deprotected, it should work as a hardener that will be stable indefinitely, but will degrade with the application of a low voltage current

Comparison of clinical characteristics of influenza and respiratory syncytial virus infection in hospitalised children and adolescents

While significant morbidity due to respiratory syncytial virus (RSV) infection in the paediatric population has been well acknowledged, little is known about the burden of influenza in primarily healthy children in Europe. In our institution, a University Children's Hospital in Switzerland, medical staff were encouraged to take nasopharyngeal specimens for multiplex polymerase chain reaction assays for influenza A and B, RSV and several other pathogens from patients hospitalised with respiratory symptoms. We took advantage of this strategy and performed a retrospective study to compare specific characteristics of influenza virus infections with those of RSV during two consecutive winter seasons. Overall, 126 patients were positive for RSV and 60 patients were positive for influenza (type A: 45; type B: 15). The median age of children with RSV, influenza A, and influenza B infection was 4 months; 2 years and 4 months; and 6 years and 2 months, respectively (P<0.001). Fever and cough predominated in children with influenza infection whereas cough, rhinorrhoea, feeding difficulties and dyspnoea were the major symptoms in children with RSV infection. Of patients with influenza, 41% suffered from lower respiratory tract infection compared to 91% of those with RSV infection (P<0.001). Of 60 patients hospitalised with influenza, 12 (20%) experienced febrile convulsions. None of the patients with influenza had been immunised in the respective winter season, although 27% of them had at least one underlying medical condition that would have counted as an indication for immunisation in Switzerland. Conclusion: influenza virus infections, like respiratory syncytial virus infections, are a major cause of hospitalisation in children with respiratory illness during the winter season. Since it is impossible to make an aetiological diagnosis on clinical grounds, it is important to apply specific diagnostic tools in children hospitalised with respiratory illness in order to better characterise the relative burden of disease caused by the respective agent

Les QR codes en bibliothèque: un exemple de médiation numérique au service des usagers

Le présent travail propose un ensemble de conseils pour la mise en place d'un nouveau service dont l'objectif est la diffusion et la promotion des services et des ressources de la Bibliothèque de l'Université de Genève par le biais d'un nouvel outil de médiation : les QR Codes. Grâce à leurs capacités d'interactivité et de liaison entre le monde physique et le monde numérique, les QR Codes offrent l'opportunité de suivre les méthodes d'utilisations et les comportements nouveaux des usagers, nés des smartphones, tablettes tactiles et pc portables. A l'heure où certaines de nos ressources ne sont plus que numériques, cette technologie permet une nouvelle voie de médiation auprès des usagers de nos institutions

Análisis de la aplicación del Sistema Contable y su incidencia en los Estados Financieros de la Empresa Agro-Industrial “San Benito Agrícola S.A” del Municipio de San Isidro, Matagalpa, en el I semestre del año 2016

Se realizó estudio sobre análisis de la aplicación del Sistema Contable y su incidencia en los Estados Financieros de la Empresa Agro- Industrial “San Benito Agrícola S.A” del Municipio de San Isidro, departamento Matagalpa, en el I semestre del año 2016. En la actualidad todo proceso Contable requiere de los Sistemas. En una empresa, el funcionamiento de los procesos contables depende de los sistemas, de esto se deduce la importancia que tienen, siendo el propósito de nosotros determinar y conocer si estos sistemas aplicados en la empresa tienen lo necesario para el desarrollo como entidad. Es imposible llevar un adecuado control de operaciones y transacciones financieras sin contar con el auxilio de los sistemas mecanizados en las computadoras, por ende definimos sistemas como un conjunto de elementos, entidades o componentes que se caracterizan por ciertos atributos identificables que tienen relación entre sí; Estos procesos se dejan establecidos mediante diseños de sistemas contables manuales y computarizados donde todo el personal del área administrativa y financiera debe tener conocimientos del uso adecuado correspondiente a su función dentro de la entidad, donde estamos claros que esta es parte imprescindible y que no debe de fallar en el manejo de funciones. La gerencia tiene la responsabilidad de acatar las dificultades existentes en las áreas y garantizar una buena implementación del sistema contable que utiliza en la entidad ya que de esta forma logrará presentar información financiera y administrativa razonable, para que los usuarios puedan tomar decisiones correctas y así puedan dar solución a diferentes hallazgos que arraiguen dificultades para las operaciones de sus funciones. Palabras Claves: Sistemas Contables, Procesos, transacciones, Estados Financiero

Évolution historique et géomorphologique d'une plage anthropique urbaine : le développement et la chute d'un système hydrosédimentaire résilient

Les estuaires font partie des endroits les plus peuplés du monde et sont vastement transformés pour répondre aux activités humaines. Les pressions anthropiques générées par l'aménagement du territoire, les stratégies de gestion déficientes, le manque de communication et les approches décisionnelles non intégrées contribuent à exacerber la vulnérabilité du cadre bâti, des éco- et géosystèmes ainsi que des communautés littorales. L'érosion des côtes sableuses présente un défi significatif pour les municipalités de l'estuaire fluvial du Saint-Laurent (EFSL), lesquelles possèdent un littoral densément aménagé et peuplé. Les plages avec une morphogénèse anthropique sont par ailleurs davantage problématiques, car elles sont généralement plus sensibles à la dynamique hydrosédimentaire locale qui est aussi perturbée par les activités humaines. C'est le cas de l'Anse-Tibbits, située sur le littoral de la Ville de Lévis, qui a été remblayée au 19ᵉ siècle pour recevoir des installations ferroviaires. En fait, depuis la seconde moitié du 20ᵉ siècle, des mécanismes d'érosion ont dégradé ces structures désormais abandonnées et ont exposé un talus peu cohésif à cet aléa. Cette conjoncture a ultimement mené vers le développement d'une plage sableuse atypique au reste du littoral de Lévis, mais grandement apprécié des locaux pour ses aspects récréotouristiques. Par manque d'information sur les processus à l'œuvre sur les plages de l'EFSL, un enrochement a rapidement été mis en place en novembre 2020 afin d'éviter la perte potentielle d'infrastructures à proximité. En effet, peu de connaissances scientifiques portent sur la dynamique morpho-sédimentaire et sur la gestion appropriée de telles plages dans la littérature. Les enjeux d'érosion dans l'EFSL sont bien connus des acteurs locaux, mais peu ont les outils pour comprendre la nature du problème, l'origine de ces enjeux et les interventions adéquates. En documentant de façon scientifique la transition historique d'un site ainsi que son régime de perturbations, il devient plus facile de prendre des décisions éclairées sur des aménagements riverains à court, moyen et long terme. Il est donc impératif de mettre en place un cadre théorique et juridique, afin d'encourager cette pratique et de limiter les décisions hâtives ou motivées par la peur. Cette étude tente de mieux comprendre la dynamique morpho-sédimentaire d'une plage anthropique en milieu estuarien froid, par l'entremise d'une approche multisource de suivi des berges, afin de simplifier les prises de décisions en termes d'aménagements.Estuaries are among the most populated places in the world and are extensively transformed to accommodate human activities. Anthropogenic pressures from land use, poor management strategies and lack of communication contribute to the vulnerability of the built environment, eco- and geosystems, and coastal communities. Sandy shoreline erosion presents a significant challenge to the municipalities of the St. Lawrence Fluvial Estuary (EFSL), which have a densely developed and populated coastline. Beaches with anthropogenic morphogenesis are more problematic because they are generally more responsive to local hydrosedimentary dynamics that are also disturbed by human activities. This is the case of Anse-Tibbits, located on the shoreline of the City of Lévis, which was filled in during the 19th century to accommodate railway installations. In fact, since the second half of the 20th century, erosion mechanisms have degraded these now abandoned structures and have exposed a slope with little cohesion to this hazard. This situation ultimately led to the development of a sandy beach atypical of the rest of the Lévis coastline, but greatly appreciated by the locals. Due to a lack of information on the processes at work on the EFSL beaches, riprap was quickly installed in November 2020 to avoid the potential loss of nearby infrastructure. Indeed, there is little scientific knowledge on the morpho-sedimentary dynamics and appropriate management of such beaches in the literature. Erosion issues in the EFSL are well known to local stakeholders, but few have the tools to understand the nature of the problem, the origin of these issues, and the appropriate interventions. By scientifically documenting the historical transition of a site and its disturbance regime, it becomes easier to make informed decisions on short-, medium- and long-term coastline development. It is therefore imperative that a theoretical and legal framework to be put in place to encourage this practice and to limit hasty or fear-driven decisions. This study attempts to better understand the morpho-sedimentary dynamics of an anthropogenic beach in a cold estuarine environment, through a multisource approach to shoreline monitoring, in order to simplify decision-making in terms of development

Structural and Mechanistic Basis for Anaerobic Ergothioneine Biosynthesis

Ergothioneine is an emergent factor in cellular redox biochemistry in humans and pathogenic bacteria. Broad consensus has formed around the idea that ergothioneine protects cells against reactive oxygen species. The recent discovery that anaerobic microorganisms make the same metabolite using oxygen-independent chemistry indicates that ergothioneine also plays physiological roles under anoxic conditions. In this report, we describe the crystal structure of the anaerobic ergothioneine biosynthetic enzyme EanB from green sulfur bacterium Chlorobium limicola. This enzyme catalyzes the oxidative sulfurization of N-alpha-trimethyl histidine. On the basis of structural and kinetic evidence, we describe the catalytic mechanism of this unusual C-S bond-forming reaction. Significant active-site conservation among distant EanB homologues suggests that the oxidative sulfurization of heterocyclic substrates may occur in a broad range of bacteria

Structure determination of channel and transport proteins by high-resolution microscopy techniques

High-resolution microscopy techniques provide a plethora of information on biological structures from the cellular level down to the molecular level. In this review, we present the unique capabilities of transmission electron and atomic force microscopy to assess the structure, oligomeric state, function and dynamics of channel and transport proteins in their native environment, the lipid bilayer. Most importantly, membrane proteins can be visualized in the frozen-hydrated state and in buffer solution by cryo-transmission electron and atomic force microscopy, respectively. We also illustrate the potential of the scintillation proximity assay to study substrate binding of detergent-solubilized transporters prior to crystallization and structural characterizatio

An Alternative Active Site Architecture for O2 Activation in the Ergothioneine Biosynthetic EgtB from Chloracidobacterium thermophilum

Sulfoxide synthases are nonheme iron enzymes that catalyze oxidative carbon-sulfur bond formation between cysteine derivatives and N-α-trimethylhistidine as a key step in the biosynthesis of thiohistidines. The complex catalytic mechanism of this enzyme reaction has emerged as the controversial subject of several biochemical and computational studies. These studies all used the structure of the γ-glutamyl cysteine utilizing sulfoxide synthase, MthEgtB from Mycobacterium thermophilum (EC 1.14.99.50), as a structural basis. To provide an alternative model system, we have solved the crystal structure of CthEgtB from Chloracidobacterium thermophilum (EC 1.14.99.51) that utilizes cysteine as a sulfur donor. This structure reveals a completely different configuration of active site residues that are involved in oxygen binding and activation. Furthermore, comparison of the two EgtB structures enables a classification of all ergothioneine biosynthetic EgtBs into five subtypes, each characterized by unique active-site features. This active site diversity provides an excellent platform to examine the catalytic mechanism of sulfoxide synthases by comparative enzymology, but also raises the question as to why so many different solutions to the same biosynthetic problem have emerged

Frog oocytes to unveil the structure and supramolecular organization of human transport proteins

Structural analyses of heterologously expressed mammalian membrane proteins remain a great challenge given that microgram to milligram amounts of correctly folded and highly purified proteins are required. Here, we present a novel method for the expression and affinity purification of recombinant mammalian and in particular human transport proteins in Xenopus laevis frog oocytes. The method was validated for four human and one murine transporter. Negative stain transmission electron microscopy (TEM) and single particle analysis (SPA) of two of these transporters, i.e., the potassium-chloride cotransporter 4 (KCC4) and the aquaporin-1 (AQP1) water channel, revealed the expected quaternary structures within homogeneous preparations, and thus correct protein folding and assembly. This is the first time a cation-chloride cotransporter (SLC12) family member is isolated, and its shape, dimensions, low-resolution structure and oligomeric state determined by TEM, i.e., by a direct method. Finally, we were able to grow 2D crystals of human AQP1. The ability of AQP1 to crystallize was a strong indicator for the structural integrity of the purified recombinant protein. This approach will open the way for the structure determination of many human membrane transporters taking full advantage of the Xenopus laevis oocyte expression system that generally yields robust functional expression