4,789 research outputs found

    Ergodic BSDEs and related PDEs with Neumann boundary conditions under weak dissipative assumptions

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    We study a class of ergodic BSDEs related to PDEs with Neumann boundary conditions. The randomness of the drift is given by a forward process under weakly dissipative assumptions with an invertible and bounded diffusion matrix. Furthermore, this forward process is reflected in a convex subset of Rd\R^d not necessary bounded. We study the link of such EBSDEs with PDEs and we apply our results to an ergodic optimal control problem

    gem-Dibromocyclopropanes and enzymatically derived cis-1,2-dihydrocatechols as building blocks in alkaloid synthesis

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    The application of the title building blocks, the 6,6-dibromobicyclo[3.1.0]hexanes and the cis-1,2-dihydrocatechols, to the total synthesis of crinine and lycorinine alkaloids is described.We thank the Australian Research Council and the Institute of Advanced Studies for generous financial support

    Préface

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    La REMI a fêté son 30ème anniversaire en 2016 avec les numéros 3 et 4 du volume 32 et voici aujourd’hui son 100ème numéro ou plus exactement sa 100ème parution, car certains numéros sont doubles. Ceci atteste d’une continuité certaine et d’une préoccupation constante d’accompagner, de favoriser, de renouveler les problématiques à propos de phénomènes en métamorphose rapide. La question migratoire était encore périphérique lors de la première parution de la revue ; elle est devenue tout à fait..

    Oxidoreductase disulfide bond proteins DsbA and DsbB form an active redox pair in Chlamydia trachomatis, a bacterium with disulfide dependent infection and development

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    © 2019 Christensen et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Chlamydia trachomatis is an obligate intracellular bacterium with a distinctive biphasic developmental cycle that alternates between two distinct cell types; the extracellular infectious elementary body (EB) and the intracellular replicating reticulate body (RB). Members of the genus Chlamydia are dependent on the formation and degradation of protein disulfide bonds. Moreover, disulfide cross-linking of EB envelope proteins is critical for the infection phase of the developmental cycle. We have identified in C. trachomatis a homologue of the Disulfide Bond forming membrane protein Escherichia coli (E. coli) DsbB (hereafter named CtDsbB) and—using recombinant purified proteins—demonstrated that it is the redox partner of the previously characterised periplasmic oxidase C. trachomatis Disulfide Bond protein A (CtDsbA). CtDsbA protein was detected in C. trachomatis inclusion vacuoles at 20 h post infection, with more detected at 32 and similar levels at 44 h post infection as the developmental cycle proceeds. As a redox pair, CtDsbA and CtDsbB largely resemble their homologous counterparts in E. coli; CtDsbA is directly oxidised by CtDsbB, in a reaction in which both periplasmic cysteine pairs of CtDsbB are required for complete activity. In our hands, this reaction is slow relative to that observed for E. coli equivalents, although this may reflect a non-native expression system and use of a surrogate quinone cofactor. CtDsbA has a second non-catalytic disulfide bond, which has a small stabilising effect on the protein’s thermal stability, but which does not appear to influence the interaction of CtDsbA with its partner protein CtDsbB. Expression of CtDsbA during the RB replicative phase and during RB to EB differentiation coincided with the oxidation of the chlamydial outer membrane complex (COMC). Together with our demonstration of an active redox pairing, our findings suggest a potential role for CtDsbA and CtDsbB in the critical disulfide bond formation step in the highly regulated development cycle

    Toxic gas removal – metal–organic frameworks for the capture and degradation of toxic gases and vapours

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    The release of anthropogenic toxic pollutants into the atmosphere is a worldwide threat of growing concern. In this regard, it is possible to take advantage of the high versatility of MOFs materials in order to develop new technologies for environmental remediation purposes. Consequently, one of the main scientific challenges to be achieved in the field of MOF research should be to maximize the performance of these solids towards the sensing, capture and catalytic degradation of harmful gases and vapors by means of a rational control of size and reactivity of the pore walls that are directly accessible to guest molecules.The authors are grateful for the generous support by the Spanish Ministries of Economy (project: CTQ2011-22787) and Defense (COINCIDENTE Program) as well as Junta de Andalucia (P09-FQM-4981)

    C4-C5 fused pyrazol-3-amines: when the degree of unsaturation and electronic characteristics of the fused ring controls regioselectivity in Ullmann and acylation reactions

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    Pyrazol-3-amine is a scaffold present in a large number of compounds with a wide range of biological activities and, in many cases, the heterocycle is C4-C5 fused to a second ring. Among the different reactions used for the decoration of the pyrazole ring, Ullmann and acylation have been widely applied. However, there is some confusion in the literature regarding the regioselectivity of such reactions (substitution at N1 or N2 of the pyrazole ring) and no predictive rule has been so far established. As a part of our work on 3-amino-pyrazolo[3,4-b]pyridones 13, we have studied the regioselectivity of such reactions in different C4-C5 fused pyrazol-3-amines. As a rule of thumb, the Ullmann and acylation reactions take place, predominantly, at the NH and non-protonated nitrogen atom of the pyrazole ring respectively, of the most stable initial tautomer (1H- or 2H-pyrazole), which can be easily predicted by using DFT calculations

    The conserved C-terminus of the PcrA/UvrD helicase interacts directly with RNA polymerase

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    Copyright: © 2013 Gwynn et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by a Wellcome Trust project grant to MD (Reference: 077368), an ERC starting grant to MD (Acronym: SM-DNA-REPAIR) and a BBSRC project grant to PM, NS and MD (Reference: BB/I003142/1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

    An Unequivocal Synthesis of 2-Aryl Substituted 3-Amino-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-ones

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    The reaction between pyridones (1) and substituted hydrazines 4 can afford two different regioisomeric pyrazolo[3,4-b]pyridin - 6-ones 2 and 3 depending on the initial substitution of the methoxy group and the direction of the cyclization. In the case of phenylhydrazine 4 (R3 = Ph), we have clearly shown that the treatment of pyridones 1a-d with 4 (R3 = Ph) in MeOH at temperatures below 1408C yields, independently of the nature and position of the substituents present in the pyridone ring, the open intermediates 7a-d. When the reaction is carried at 1408C under microwave irradiation, the corresponding 2-aryl substituted pyrazolo[3,4-b]pyridines 3a-d are always formed. We have experimentally determined, using DSC techniques, the activation energies of the two steps involved in the formation of 3: a) substitution of the methoxy group present in pyridones 1 with phenylhydrazine 4 (R3 = Ph) to afford intermediates 7 and b) cyclization of intermediates 7 to yield pyrazolopyridines 3. The results obtained, 15 and 42 kcal·mol 1 respectively, are in agreement with the experimental findings
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