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Search Results: 1 - 10 of 208495 matches for " Rapha?l Mercier "
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Influence of the C/Sn Ratio on the Synthesis and Lithium Electrochemical Insertion of Tin-Supported Graphite Materials Used as Anodes for Li-Ion Batteries
Cédric Mercier,Raphal Schneider,Patrick Willmann,Denis Billaud
International Journal of Electrochemistry , 2011, DOI: 10.4061/2011/381960
Abstract: Novel composites consisting of tin particles associated to graphite were prepared by chemical reduction of tin(+2) chloride by -BuONa-activated sodium hydride in the presence of graphite. The samples obtained using various C/Sn ratios were investigated by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and elemental analyses. The largest tin particles associated to graphite layers were observed for the material with a C/Sn ratio of 16. For the materials with C/Sn ratios of 42 and 24, SEM and TEM experiments demonstrated that Sn aggregates of ca. 250?nm length and composed of Sn particles with an average diameter of ca. 50?nm were homogeneously distributed at the surface of graphite. Electrodes prepared from the material exhibit a high reversible capacity of over 470?mAh up to twenty cycles with stable cyclic performances. 1. Introduction With the development of portable electronic devices and the enormous interest in the hybrid electric vehicle market, the demand for power sources with higher storage capacity, longer operating times, as well as safety, environmental compatibility, and low production costs has markedly increased [1]. Graphite is mainly used as negative electrode materials for lithium ion secondary batteries and yields a theoretical capacity of 372?mAhg?1. Lithium alloys, which can be reversibly formed and decomposed electrochemically in nonaqueous electrolyte solutions, are natural alternative candidates to both lithium and lithiated graphite in rechargeable Li-based batteries. Of special importance in this respect are the lithium-tin compounds. Indeed, both metallic tin and tin oxide (SnO2) were shown as interesting anode materials for Li-ion batteries because of their conducting properties combined with high specific capacities (Sn, 994?mAhg?1 and SnO2, 781?mAhg?1) [2, 3] compared to that of graphite [4, 5]. Lithium can be inserted into tin to form alloys of high Li content up to Li22Sn5, corresponding to a theoretical capacity of 994?mAhg?1 [2]. Although these attractive features have initiated a number of studies on Sn-based hosts [4, 6–19], Li+ ion insertion/extraction into/from Sn causes volume changes [9, 20, 21]. These changes result in cracking and crumbling of the electrode with the concomitant loss of electrical contact both between interparticles, and between particles and the current collector, resulting in poor cycling performance. A promising way of improving the cyclability of Sn-based electrodes is to synthesize small-sized Sn particles. We have recently
Copper-Dependent Trafficking of the Ctr4-Ctr5 Copper Transporting Complex
Raphal Ioannoni,Jude Beaudoin,Alexandre Mercier,Simon Labbé
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0011964
Abstract: In Schizosaccharomyces pombe, copper uptake is carried out by a heteromeric complex formed by the Ctr4 and Ctr5 proteins. Copper-induced differential subcellular localization may play a critical role with respect to fine tuning the number of Ctr4 and Ctr5 molecules at the cell surface.
Turning Meiosis into Mitosis
Isabelle d'Erfurth,Sylvie Jolivet,Nicole Froger,Olivier Catrice,Maria Novatchkova,Raphal Mercier
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1000124
Abstract: Apomixis, or asexual clonal reproduction through seeds, is of immense interest due to its potential application in agriculture. One key element of apomixis is apomeiosis, a deregulation of meiosis that results in a mitotic-like division. We isolated and characterised a novel gene that is directly involved in controlling entry into the second meiotic division. By combining a mutation in this gene with two others that affect key meiotic processes, we created a genotype called MiMe in which meiosis is totally replaced by mitosis. The obtained plants produce functional diploid gametes that are genetically identical to their mother. The creation of the MiMe genotype and apomeiosis phenotype is an important step towards understanding and engineering apomixis.
Zip4/Spo22 Is Required for Class I CO Formation but Not for Synapsis Completion in Arabidopsis thaliana
Liudmila Chelysheva,Ghislaine Gendrot,Daniel Vezon,Marie-Pascale Doutriaux,Raphal Mercier,Mathilde Grelon
PLOS Genetics , 2007, DOI: 10.1371/journal.pgen.0030083
Abstract: In budding yeast meiosis, the formation of class I interference-sensitive crossovers requires the ZMM proteins. These ZMM proteins are essential in forming a mature synaptonemal complex, and a subset of these (Zip2, Zip3, and Zip4) has been proposed to compose the core of synapsis initiation complexes (SICs). Zip4/Spo22 functions with Zip2 to promote polymerization of Zip1 along chromosomes, making it a crucial SIC component. In higher eukaryotes, synapsis and recombination have often been correlated, but it is totally unknown how these two processes are linked. In this study, we present the characterization of a higher eukaryote SIC component homologue: Arabidopsis AtZIP4. We show that mutations in AtZIP4 belong to the same epistasis group as Atmsh4 and eliminate approximately 85% of crossovers (COs). Furthermore, genetic analyses on two adjacent intervals of Chromosome I established that the remaining COs in Atzip4 do not show interference. Lastly, immunolocalization studies showed that polymerization of the central element of the synaptonemal complex is not affected in Atzip4 background, even if it may proceed from fewer sites compared to wild type. These results reveal that Zip4 function in class I CO formation is conserved from budding yeast to Arabidopsis. On the other hand, and contrary to the situation in yeast, mutation in AtZIP4 does not prevent synapsis, showing that both aspects of the Zip4 function (i.e., class I CO maturation and synapsis) can be uncoupled.
Turning Meiosis into Mitosis
Isabelle d'Erfurth,Sylvie Jolivet,Nicole Froger,Olivier Catrice,Maria Novatchkova,Raphal Mercier
PLOS Biology , 2009, DOI: 10.1371/journal.pbio.1000124
Abstract: Apomixis, or asexual clonal reproduction through seeds, is of immense interest due to its potential application in agriculture. One key element of apomixis is apomeiosis, a deregulation of meiosis that results in a mitotic-like division. We isolated and characterised a novel gene that is directly involved in controlling entry into the second meiotic division. By combining a mutation in this gene with two others that affect key meiotic processes, we created a genotype called MiMe in which meiosis is totally replaced by mitosis. The obtained plants produce functional diploid gametes that are genetically identical to their mother. The creation of the MiMe genotype and apomeiosis phenotype is an important step towards understanding and engineering apomixis.
Mutations in AtPS1 (Arabidopsis thaliana Parallel Spindle 1) Lead to the Production of Diploid Pollen Grains
Isabelle d'Erfurth,Sylvie Jolivet,Nicole Froger,Olivier Catrice,Maria Novatchkova,Mathieu Simon,Eric Jenczewski,Raphal Mercier
PLOS Genetics , 2008, DOI: 10.1371/journal.pgen.1000274
Abstract: Polyploidy has had a considerable impact on the evolution of many eukaryotes, especially angiosperms. Indeed, most—if not all—angiosperms have experienced at least one round of polyploidy during the course of their evolution, and many important crop plants are current polyploids. The occurrence of 2n gametes (diplogametes) in diploid populations is widely recognised as the major source of polyploid formation. However, limited information is available on the genetic control of diplogamete production. Here, we describe the isolation and characterisation of the first gene, AtPS1 (Arabidopsis thaliana Parallel Spindle 1), implicated in the formation of a high frequency of diplogametes in plants. Atps1 mutants produce diploid male spores, diploid pollen grains, and spontaneous triploid plants in the next generation. Female meiosis is not affected in the mutant. We demonstrated that abnormal spindle orientation at male meiosis II leads to diplogamete formation. Most of the parent's heterozygosity is therefore conserved in the Atps1 diploid gametes, which is a key issue for plant breeding. The AtPS1 protein is conserved throughout the plant kingdom and carries domains suggestive of a regulatory function. The isolation of a gene involved in diplogamete production opens the way for new strategies in plant breeding programmes and progress in evolutionary studies.
MCM8 Is Required for a Pathway of Meiotic Double-Strand Break Repair Independent of DMC1 in Arabidopsis thaliana
Wayne Crismani equal contributor,Virginie Portemer equal contributor,Nicole Froger,Liudmila Chelysheva,Christine Horlow,Nathalie Vrielynck,Raphal Mercier
PLOS Genetics , 2013, DOI: 10.1371/journal.pgen.1003165
Abstract: Mini-chromosome maintenance (MCM) 2–9 proteins are related helicases. The first six, MCM2–7, are essential for DNA replication in all eukaryotes. In contrast, MCM8 is not always conserved in eukaryotes but is present in Arabidopsis thaliana. MCM8 is required for 95% of meiotic crossovers (COs) in Drosophila and is essential for meiosis completion in mouse, prompting us to study this gene in Arabidopsis meiosis. Three allelic Atmcm8 mutants showed a limited level of chromosome fragmentation at meiosis. This defect was dependent on programmed meiotic double-strand break (DSB) formation, revealing a role for AtMCM8 in meiotic DSB repair. In contrast, CO formation was not affected, as shown both genetically and cytologically. The Atmcm8 DSB repair defect was greatly amplified in the absence of the DMC1 recombinase or in mutants affected in DMC1 dynamics (sds, asy1). The Atmcm8 fragmentation defect was also amplified in plants heterozygous for a mutation in either recombinase, DMC1 or RAD51. Finally, in the context of absence of homologous chromosomes (i.e. haploid), mutation of AtMCM8 also provoked a low level of chromosome fragmentation. This fragmentation was amplified by the absence of DMC1 showing that both MCM8 and DMC1 can promote repair on the sister chromatid in Arabidopsis haploids. Altogether, this establishes a role for AtMCM8 in meiotic DSB repair, in parallel to DMC1. We propose that MCM8 is involved with RAD51 in a backup pathway that repairs meiotic DSB without giving CO when the major pathway, which relies on DMC1, fails.
Sex-Specific Crossover Distributions and Variations in Interference Level along Arabidopsis thaliana Chromosome 4
Jan Drouaud equal contributor,Raphal Mercier equal contributor,Liudmila Chelysheva,Aurélie Bérard,Matthieu Falque,Olivier Martin,Vanessa Zanni,Dominique Brunel,Christine Mézard
PLOS Genetics , 2007, DOI: 10.1371/journal.pgen.0030106
Abstract: In many species, sex-related differences in crossover (CO) rates have been described at chromosomal and regional levels. In this study, we determined the CO distribution along the entire Arabidopsis thaliana Chromosome 4 (18 Mb) in male and female meiosis, using high density genetic maps built on large backcross populations (44 markers, >1,300 plants). We observed dramatic differences between male and female map lengths that were calculated as 88 cM and 52 cM, respectively. This difference is remarkably parallel to that between the total synaptonemal complex lengths measured in male and female meiocytes by immunolabeling of ZYP1 (a component of the synaptonemal complex). Moreover, CO landscapes were clearly different: in particular, at both ends of the map, male CO rates were higher (up to 4-fold the mean value), whereas female CO rates were equal or even below the chromosomal average. This unique material gave us the opportunity to perform a detailed analysis of CO interference on Chromosome 4 in male and female meiosis. The number of COs per chromosome and the distances between them clearly departs from randomness. Strikingly, the interference level (measured by coincidence) varied significantly along the chromosome in male meiosis and was correlated to the physical distance between COs. The significance of this finding on the relevance of current CO interference models is discussed.
Physicochemical, Biochemical and Instrumental Attributes and Consumer Acceptability of Dry-Fermented Sausages Elaborated with Combined Partial Substitutions of Sodium Chloride and Pork Backfat  [PDF]
Hassan Safa, Philippe Gatellier, Jean-Louis Berdagué, Nathalie Kondjoyan, Frédéric Mercier, Stéphane Portanguen, Raphal Favier, Pierre-Sylvain Mirade
Food and Nutrition Sciences (FNS) , 2016, DOI: 10.4236/fns.2016.714119
Abstract: We performed 6 fabrications of dry-fermented sausages to investigate, at laboratory scale, the effects of combined partial substitutions of sodium chloride by potassium chloride and pork backfat by sunflower oil on key physical-chemical and biochemical parameters, instrumental colour and texture measurements, and the consumer acceptability of the end-products. Regarding the physical-chemical parameters, statistical analysis of results showed that final product weight loss was impacted by fat content and use of sunflower oil; final mean water activity value was only affected by salt level; and animal fat content impacted pH values, only at the end of drying. Regarding the biochemical parameters investigated, we statistically found a marked impact of partial substitution of NaCl by KCl on the proteolysis evolution, of fat level and sodium content on the end-product lipolysis, and finally, a significant effect of animal fat level and incorporation of sunflower oil on both protein and lipid oxidations. However, the new product formulations combining salt and fat substitutions lead to globally acceptable water loss and water activity values and similar rates of proteolysis, lipolysis and lipid oxidation, but less protein oxidation. From a practical point of view, the results clearly showed that sodium and animal fat contents in dryfermented sausages can be drastically reduced with no too marked adverse effect on colour, final textural properties or consumer acceptability. On the basis of these laboratory results, new healthier dry-fermented products can be manufactured by an industrial company in the near future.
A High Throughput Genetic Screen Identifies New Early Meiotic Recombination Functions in Arabidopsis thaliana
Arnaud De Muyt equal contributor,Lucie Pereira equal contributor,Daniel Vezon,Liudmila Chelysheva,Ghislaine Gendrot,Aurélie Chambon,Sandrine Lainé-Choinard,Georges Pelletier,Raphal Mercier,Fabien Nogué,Mathilde Grelon
PLOS Genetics , 2009, DOI: 10.1371/journal.pgen.1000654
Abstract: Meiotic recombination is initiated by the formation of numerous DNA double-strand breaks (DSBs) catalysed by the widely conserved Spo11 protein. In Saccharomyces cerevisiae, Spo11 requires nine other proteins for meiotic DSB formation; however, unlike Spo11, few of these are conserved across kingdoms. In order to investigate this recombination step in higher eukaryotes, we took advantage of a high-throughput meiotic mutant screen carried out in the model plant Arabidopsis thaliana. A collection of 55,000 mutant lines was screened, and spo11-like mutations, characterised by a drastic decrease in chiasma formation at metaphase I associated with an absence of synapsis at prophase, were selected. This screen led to the identification of two populations of mutants classified according to their recombination defects: mutants that repair meiotic DSBs using the sister chromatid such as Atdmc1 or mutants that are unable to make DSBs like Atspo11-1. We found that in Arabidopsis thaliana at least four proteins are necessary for driving meiotic DSB repair via the homologous chromosomes. These include the previously characterised DMC1 and the Hop1-related ASY1 proteins, but also the meiotic specific cyclin SDS as well as the Hop2 Arabidopsis homologue AHP2. Analysing the mutants defective in DSB formation, we identified the previously characterised AtSPO11-1, AtSPO11-2, and AtPRD1 as well as two new genes, AtPRD2 and AtPRD3. Our data thus increase the number of proteins necessary for DSB formation in Arabidopsis thaliana to five. Unlike SPO11 and (to a minor extent) PRD1, these two new proteins are poorly conserved among species, suggesting that the DSB formation mechanism, but not its regulation, is conserved among eukaryotes.
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