472 research outputs found
Chemical analysis and aqueous solution properties of Charged Amphiphilic Block Copolymers PBA-b-PAA synthesized by MADIX
We have linked the structural and dynamic properties in aqueous solution of
amphiphilic charged diblock copolymers poly(butyl acrylate)-b-poly(acrylic
acid), PBA-b-PAA, synthesized by controlled radical polymerization, with the
physico-chemical characteristics of the samples. Despite product imperfections,
the samples self-assemble in melt and aqueous solutions as predicted by
monodisperse microphase separation theory. However, the PBA core are abnormally
large; the swelling of PBA cores is not due to AA (the Flory parameter
chiPBA/PAA, determined at 0.25, means strong segregation), but to h-PBA
homopolymers (content determined by Liquid Chromatography at the Point of
Exclusion and Adsorption Transition LC-PEAT). Beside the dominant population of
micelles detected by scattering experiments, capillary electrophoresis CE
analysis permitted detection of two other populations, one of h-PAA, and the
other of free PBA-b-PAA chains, that have very short PBA blocks and never
self-assemble. Despite the presence of these free unimers, the self-assembly in
solution was found out of equilibrium: the aggregation state is history
dependant and no unimer exchange between micelles occurs over months
(time-evolution SANS). The high PBA/water interfacial tension, measured at 20
mN/m, prohibits unimer exchange between micelles. PBA-b-PAA solution systems
are neither at thermal equilibrium nor completely frozen systems: internal
fractionation of individual aggregates can occur.Comment: 32 pages, 16 figures and 4 tables submitted to Journal of Interface
and Colloidal Scienc
Can the jamming transition be described using equilibrium statistical mechanics?
When materials such as foams or emulsions are compressed, they display solid
behaviour above the so-called `jamming' transition. Because compression is done
out-of-equilibrium in the absence of thermal fluctuations, jamming appears as a
new kind of a nonequilibrium phase transition. In this proceeding paper, we
suggest that tools from equilibrium statistical mechanics can in fact be used
to describe many specific features of the jamming transition. Our strategy is
to introduce thermal fluctuations and use statistical mechanics to describe the
complex phase behaviour of systems of soft repulsive particles, before sending
temperature to zero at the end of the calculation. We show that currently
available implementations of standard tools such as integral equations,
mode-coupling theory, or replica calculations all break down at low temperature
and large density, but we suggest that new analytical schemes can be developed
to provide a fully microscopic, quantitative description of the jamming
transition.Comment: 8 pages, 6 figs. Talk presented at Statphys24 (July 2010, Cairns,
Australia
Under-expression Of Chemosensory Genes In Domiciliary Bugs Of The Chagas Disease Vector Triatoma Brasiliensis
In Latin America, the bloodsucking bugs Triatominae are vectors of Trypanosoma cruzi, the parasite that causes Chagas disease. Chemical elimination programs have been launched to control Chagas disease vectors. However, the disease persists because native vectors from sylvatic habitats are able to (re)colonize housesâa process called domiciliation. Triatoma brasiliensis is one example. Because the chemosensory system allows insects to interact with their environment and plays a key role in insect adaption, we conducted a descriptive and comparative study of the chemosensory transcriptome of T. brasiliensis samples from different ecotopes. Methodology/Principal Finding: In a reference transcriptome built using de novo assembly, we found transcripts encoding 27 odorant-binding proteins (OBPs), 17 chemosensory proteins (CSPs), 3 odorant receptors (ORs), 5 transient receptor potential channel (TRPs), 1 sensory neuron membrane protein (SNMPs), 25 takeout proteins, 72 cytochrome P450s, 5 gluthatione S-transferases, and 49 cuticular proteins. Using protein phylogenies, we showed that most of the OBPs and CSPs for T. brasiliensis had well supported orthologs in the kissing bug Rhodnius prolixus. We also showed a higher number of these genes within the bloodsucking bugs and more generally within all Hemipterans compared to the other species in the super-order Paraneoptera. Using both DESeq2 and EdgeR software, we performed differential expression analyses between samples of T. brasiliensis, taking into account their environment (sylvatic, peridomiciliary and domiciliary) and sex. We also searched clusters of co-expressed contigs using HTSCluster. Among differentially expressed (DE) contigs, most were under-expressed in the chemosensory organs of the domiciliary bugs compared to the other samples and in females compared to males. We clearly identified DE genes that play a role in the chemosensory system. Conclusion/Significance: Chemosensory genes could be good candidates for genes that contribute to adaptation or plastic rearrangement to an anthropogenic system. The domiciliary environment probably includes less diversity of xenobiotics and probably has more stable abiotic parameters than do sylvatic and peridomiciliary environments. This could explain why both detoxification and cuticle protein genes are less expressed in domiciliary bugs. Understanding the molecular basis for how vectors adapt to human dwellings may reveal new tools to control disease vectors; for example, by disrupting chemical communication. © 2016 Marchant et al.101
Analyse 3d de la marche en pratique clinique aprĂšs ligamentoplastie du genou par DIDTÂ : utilisation du systĂšme KNEE KG
Phase Behavior of Polyelectrolyte Block Copolymers in Mixed Solvents
We have studied the phase behavior of the poly(n-butyl
acrylate)-b-poly(acrylic acid) block copolymer in a mixture of two miscible
solvents, water and tetrahydrofuran (THF). The techniques used to examine the
different polymers, structures and phases formed in mixed solvents were static
and dynamic light scattering, small-angle neutron scattering, nuclear magnetic
resonance and fluorescence microscopy. By lowering the water/THF mixing ratio
X, the sequence unimers, micron-sized droplets, polymeric micelles was
observed. The transition between unimers and the micron-sized droplets occurred
at X = 0.75, whereas the microstructuration into core-shell polymeric micelles
was effective below X = 0.4. At intermediate mixing ratios, a coexistence
between the micron-sized droplets and the polymeric micelles was observed.
Combining the different aforementioned techniques, it was concluded that the
droplet dispersion resulted from a solvent partitioning that was induced by the
hydrophobic blocks. Comparison of poly(n-butyl acrylate) homopolymers and
poly(n-butyl acrylate)-b-poly(acrylic acid) block copolymers suggested that the
droplets were rich in THF and concentrated in copolymers and that they were
stabilized by the hydrophilic poly(acrylic acid) moieties.Comment: 11 pages, 12 figures, to appear in Macromolecule
Interactions between Magnetic Nanowires and Living Cells : Uptake, Toxicity and Degradation
We report on the uptake, toxicity and degradation of magnetic nanowires by
NIH/3T3 mouse fibroblasts. Magnetic nanowires of diameters 200 nm and lengths
comprised between 1 {\mu}m and 40 {\mu}m are fabricated by controlled assembly
of iron oxide ({\gamma}-Fe2O3) nanoparticles. Using optical and electron
microscopy, we show that after 24 h incubation the wires are internalized by
the cells and located either in membrane-bound compartments or dispersed in the
cytosol. Using fluorescence microscopy, the membrane-bound compartments were
identified as late endosomal/lysosomal endosomes labeled with lysosomal
associated membrane protein (Lamp1). Toxicity assays evaluating the
mitochondrial activity, cell proliferation and production of reactive oxygen
species show that the wires do not display acute short-term (< 100 h) toxicity
towards the cells. Interestingly, the cells are able to degrade the wires and
to transform them into smaller aggregates, even in short time periods (days).
This degradation is likely to occur as a consequence of the internal structure
of the wires, which is that of a non-covalently bound aggregate. We anticipate
that this degradation should prevent long-term asbestos-like toxicity effects
related to high aspect ratio morphologies and that these wires represent a
promising class of nanomaterials for cell manipulation and microrheology.Comment: 21 pages 12 figure
NOVIWAM : Five European countries together for improving water quality and water use efficiency
The European NOVIWAM (NOvel Integrated Water Management Systems for Southern European Regions, www.noviwam.eu) program aims to promote interregional co-operation in the field of water management tools and methods. One of its originality is to analyze in depth the relations between decision makers, stakeholders and researchers in order to disseminate know-how and technologies, and to tackle the compelling water management problems faced in the Euro-Mediterranean climate regions. In a first period, aiming at a good ecological and chemical state of waters and at a sustainable and efficient resource management, five European countries/regions (Albania, Cyprus, Poitou-Charentes in France, Northern Region in Portugal and Andalusia in Spain) are working together. The program will thus contribute to the objectives of the European Water Framework Directive. But additionally, the NOVIWAM program will establish a schedule for the implementation of a « Join action plan », trying to involve other countries into it, and generalize the conclusions of this three year work at a regional and international level.NOVIWAM (Grant Agreement nÂș 245460
Direct and specific chemical control of eukaryotic translation with a synthetic RNAâprotein interaction
Sequence-specific RNAâprotein interactions, though commonly used in biological systems to regulate translation, are challenging to selectively modulate. Here, we demonstrate the use of a chemically-inducible RNAâprotein interaction to regulate eukaryotic translation. By genetically encoding Tet Repressor protein (TetR)-binding RNA elements into the 5âČ-untranslated region (5âČ-UTR) of an mRNA, translation of a downstream coding sequence is directly controlled by TetR and tetracycline analogs. In endogenous and synthetic 5âČ-UTR contexts, this system efficiently regulates the expression of multiple target genes, and is sufficiently stringent to distinguish functional from non-functional RNAâTetR interactions. Using a reverse TetR variant, we illustrate the potential for expanding the regulatory properties of the system through protein engineering strategies
Functional insights from the GC-poor genomes of two aphid parasitoids, Aphidius ervi and Lysiphlebus fabarum.
Parasitoid wasps have fascinating life cycles and play an important role in trophic networks, yet little is known about their genome content and function. Parasitoids that infect aphids are an important group with the potential for biological control. Their success depends on adapting to develop inside aphids and overcoming both host aphid defenses and their protective endosymbionts.
We present the de novo genome assemblies, detailed annotation, and comparative analysis of two closely related parasitoid wasps that target pest aphids: Aphidius ervi and Lysiphlebus fabarum (Hymenoptera: Braconidae: Aphidiinae). The genomes are small (139 and 141 Mbp) and the most AT-rich reported thus far for any arthropod (GC content: 25.8 and 23.8%). This nucleotide bias is accompanied by skewed codon usage and is stronger in genes with adult-biased expression. AT-richness may be the consequence of reduced genome size, a near absence of DNA methylation, and energy efficiency. We identify missing desaturase genes, whose absence may underlie mimicry in the cuticular hydrocarbon profile of L. fabarum. We highlight key gene groups including those underlying venom composition, chemosensory perception, and sex determination, as well as potential losses in immune pathway genes.
These findings are of fundamental interest for insect evolution and biological control applications. They provide a strong foundation for further functional studies into coevolution between parasitoids and their hosts. Both genomes are available at https://bipaa.genouest.org
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