Plasma membrane H⁺ -ATPase regulation is required for auxin gradient formation preceding phototropic growth.

Phototropism is a growth response allowing plants to align their photosynthetic organs toward incoming light and thereby to optimize photosynthetic activity. Formation of a lateral gradient of the phytohormone auxin is a key step to trigger asymmetric growth of the shoot leading to phototropic reorientation. To identify important regulators of auxin gradient formation, we developed an auxin flux model that enabled us to test in silico the impact of different morphological and biophysical parameters on gradient formation, including the contribution of the extracellular space (cell wall) or apoplast. Our model indicates that cell size, cell distributions, and apoplast thickness are all important factors affecting gradient formation. Among all tested variables, regulation of apoplastic pH was the most important to enable the formation of a lateral auxin gradient. To test this prediction, we interfered with the activity of plasma membrane H⁺ -ATPases that are required to control apoplastic pH. Our results show that H⁺ -ATPases are indeed important for the establishment of a lateral auxin gradient and phototropism. Moreover, we show that during phototropism, H⁺ -ATPase activity is regulated by the phototropin photoreceptors, providing a mechanism by which light influences apoplastic pH

Fabrication et caractérisation de guide plasmonique à longue distance pour les communications à la fréquence du TB/s

Since the 1980s, researchers have been trying to design so-called "optical" computers, in which electrical signals would be replaced by photonic signals. For this, it is necessary to look at interconnection problems between components. This thesis deals with the problem of optical interconnection between electronic components. In order to propose a solution to this problem, we will study two types of plasmonic structures, a first structure of a single solid block where the information wave is reflected on an air prism, this structure is composed of a guide of metal wave covered with a layer of photoresist and it is named "ultra-long-distance plasmonic guide" (ULR-SPP). The second structure is based on a flexible interconnection where the information flows along a flexible guide, this type of wave is called "PlasArc". Through a numerical simulation chapter, we will determine the dimensional characteristics in order to minimize the energy losses by propagation of our waveguides in each of the structures. All our simulations are performed in the waveband of telecom signals. Then, we present the fabrication of two types of plasmonic waveguides as well as their specificities of realization namely a deep etching of 60 μm for ULRSPP structures and the removal of a solid substrate for waveguide named "PlasArc". The characterization of structures will be realized by distinct methods (cut-back, measurements of the loss by propagation along the guide, size of the mode obtained at the end of the guide, ...) on sizes of samples that can go from 5 mm to several centimeters in length. A study of the loss according to the radius of curvature is established on plasmonic waveguides of "PlasArc" typeDepuis les années 1980, les chercheurs essayent de concevoir des ordinateurs dits « optiques », au sein desquels les signaux électriques seraient remplacés par des signaux photoniques. Pour cela, il est nécessaire de s’intéresser aux problèmes d’interconnexions entre les composants. Cette thèse porte sur la problématique de l’interconnexion optique entre composants électroniques. Afin de proposer une solution à cette problématique, nous étudierons deux types de structures plasmoniques, une première structure d’un seul bloc solide où l’onde d’information est réfléchie sur un prisme d’air, cette structure est composée d’un guide d’onde métallique recouverte d’une couche de photoresist et elle est nommée « guide plasmonique à ultra longue distance » (ULR-SPP). La seconde structure est basée sur une interconnexion flexible où l’information circule le longue d’un guide souple, ce type d’onde est qualifié de « PlasArc ». Au travers d’un chapitre de simulation numérique, nous déterminerons les caractéristiques dimensionnelles afin de minimiser les pertes d’énergies par propagations de nos guides d’ondes dans chacune des structures. Toutes nos simulations sont effectuées dans la gamme d’ondes des signaux télécoms. Puis, nous présentons la fabrication de nos deux types de guides d'ondes ainsi que leurs spécificités de réalisation à savoir une gravure profonde sèche de 60 µm pour les structures ULRSPP et le retrait d’un substrat solide pour les guides « PlasArc ». La caractérisation de nos structures seront réalisées par des méthodes distinctes (réduction successive de la longueur des échantillons, mesures de la perte par propagation le long du guide, taille du mode obtenu en bout de guide, …) sur des tailles d’échantillons pouvant aller de 5 mm à plusieurs centimètres de longueurs. Une étude de la perte selon le rayon de courbure est établie sur les guides d’ondes plasmoniques de type « PlasArc

Les peintures murales de l'Abbaye de Châtres

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Interaction de la créatine kinase mitochondriale avec des membranes biomimétiques (liposomes, monocouches de Langmuir)

La créatine kinase mitochondriale (CKmt) est une protéine octamérique qui, in vivo, est associée à la face externe de la membrane mitochondriale interne. La liaison de l'enzyme, via des lysines C-terminales, à des liposomes contenant des phospholipides acides affecte la fluidité membranaire et entraîne une modification conformationnelle de la CKmt. Nous avons étudié par la technique de Langmuir couplée à la microscopie à l'angle de Brewster le comportement interfacial de la protéine en l'absence et en présence de phospholipides. En l'absence de monocouche, elle s'adsorbe spontanément à l'interface air/eau et doit donc posséder des zones hydrophobes accessibles. En présence de monocouches constituées de phospholipides acides ou zwitterioniques, à chaînes saturées ou insaturées, les isothermes ont un profil différent selon la présence ou non de charges négatives et la pression de surface au moment de l'injection. La présence de phospholipides acides facilite l'adsorption de la protéineLYON1-BU.Sciences (692662101) / SudocSudocFranceF

In-situ electrochemical control of the catalytic activity of platinum for the propene oxidation

International audienceThe development of electrochemical promotion necessitates new solid electrolytes with improved ionic conduction at lower temperatures. Among them, Na Super Ionic Conductor (NaSICon), i.e. Na3Zr2Si2PO12, is a promising Na+ conducting electrolyte. The Pt/NaSICon system was evaluated for the electrochemical promotion of propene combustion both with large excess of oxygen (for volatile organic contaminants, VOCs, abatement) and near the stoichiometry (for energy production)

Coupling catalysis to electrochemistry: a solution to selective reduction of nitrogen oxides in lean-burn engine exhausts?

International audienceThe non-faradaic electrochemical modification of catalytic activity (NEMCA) was investigated in selective catalytic reduction (SCR) of NO by propene on Pt films deposited on NASICON, a Na+ conducting solid electrolyte. This study was carried out under lean-burn conditions. In such a system, electrochemical promotion is shown to strongly enhance both the catalytic activity and the selectivity to N2. Such an improvement can be obtained using low overpotentials, applying −100 mV to the Pt catalyst-electrode enhances the selectivity to N2 from 41 to 61%. The use of NASICON allows work to be done at quite low temperatures (about 300 °C) compatible with the treatment of automotive exhausts

Mitochondrial creatine kinase interaction with heterogeneous monolayers : effect on lipid lateral organization

International audienceOur study highlights the tight relationship between protein binding to monolayers and the phase-state of the phospholipids. Interaction of mitochondrial creatine kinase with phospholipidic membranes was analysed using a two-phase monolayer system containing anionic phospholipids under chain mismatch conditions. Monolayers were made up of mixtures of DMPC/DPPG or DPPC/DMPG containing 40% negatively charged phospholipids which is approximately the negative charge content of the mitochondrial inner membrane. Langmuir isotherms of these monolayers showed that they underwent a phase transition from a liquid expanded state to a liquid-condensed phase at about 2 mN/m and 5 mN/m respectively. Interface morphology modifications caused by injection of mtCK under these monolayers at low or high surface pressure were monitored by Brewster angle microscopy. This work provides evidence that the presence at the air/water interface of discrete domains with increased charge density, may lead to difference in partition of soluble proteins such as mtCK, interacting with the lipid monolayer. Conversely these proteins may help to organize charged phospholipid domains in a membrane

Mitochondrial creatin kinase interaction with heterogeneous monolayers : Effect on lipid lateral organization

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Electrochemical promotion of environmental catalysis

International audienceElectrochemical catalysts were used for environmental applications, such as the clean production of energy from propane and propene combustion, the elimination of VOC's like propene and the NOx abatement All the selected electrochemical catalysts were composed of a Pt film deposited oil YSZ, NASICON or CGO. It was found that all these chemical reactions can be electropromoted. Moreover, the reaction rates can be in-situ tuned by applying a polarisation. Furthermore, the selectivity of Pt-based electrochemical catalysts can be modified in order to avoid the formation of pollutant. Finally, EPOC can improve the lifetime of a catalyst by inhibiting its poisoning by carbonaceous species

Mitochondrial creatine kinase adsorption to biomimetic membranes : a Langmuir monolayer study.

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