A novel planar optical sensor for simultaneous monitoring of oxygen, carbon dioxide, pH and temperature

The first quadruple luminescent sensor is presented which enables simultaneous detection of three chemical parameters and temperature. A multi-layer material is realized and combines two spectrally independent dually sensing systems. The first layer employs ethylcellulose containing the carbon dioxide sensing chemistry (fluorescent pH indicator 8-hydroxy-pyrene-1,3,6-trisulfonate (HPTS) and a lipophilic tetraalkylammonium base). The cross-linked polymeric beads stained with a phosphorescent iridium(III) complex are also dispersed in ethylcellulose and serve both for oxygen sensing and as a reference for HPTS. The second (pH/temperature) dually sensing system relies on the use of a pH-sensitive lipophilic seminaphthorhodafluor derivative and luminescent chromium(III)-activated yttrium aluminum borate particles (simultaneously acting as a temperature probe and as a reference for the pH indicator) which are embedded in polyurethane hydrogel layer. A silicone layer is used to spatially separate both dually sensing systems and to insure permeation selectivity for the CO2/O2 layer. The CO2/O2 and the pH/temperature layers are excitable with a blue and a red LED, respectively, and the emissions are isolated with help of optical filters. The measurements are performed at two modulation frequencies for each sensing system and the modified Dual Lifetime Referencing method is used to access the analytical information. The feasibility of the simultaneous four-parameter sensing is demonstrated. However, the practical applicability of the material may be compromised by its high complexity and by the performance of individual indicators

Caractérisation de deux constituants de la surface mycobactérienne (la protéine Erp et le glycopeptidolipide)

Dans la première partie de ma thèse, nous avons caractérisé la protéine Erp, un facteur de la virulence mycobactérienne. Nous avons montré que la protéine est faiblement attachée à la surface de la paroi par sa domaine C-terminale. Cette région n'est pas nécessaire pour la complémentation de la morphologie des colonies du mutant du gène erp et la virulence, mais elle est importante pour la résistance à un détergent. Dans la seconde partie de ma thèse, nous avons caractérisé des gènes impliqués dans la biosynthèse et le transport des glycopeptidolipides (GPL). Nous avons montré que le produit du gène gap est nécessaire pour le transport des GPL à la surface des bacilles. Chez les mycobactéries, la conversion de l'aspect rugueux à muqueux de phénotype a été décrite. Nous avons montré que cette variation est due à la transposition d'une séquence d'insertion dans la région promotrice de l'opéron mps du locus des GPL ou dans le gène lsr2 codant un régulateur négatif de la synthèse de GPL.PARIS5-BU-Necker : Fermée (751152101) / SudocSudocFranceF

Comparative Visualization of Protein Secondary Structures

Background: Protein function is determined by many factors, namely by its constitution, spatial arrangement, and dynamic behavior. Studying these factors helps the biochemists and biologists to better understand the protein behavior and to design proteins with modified properties. One of the most common approaches to these studies is to compare the protein structure with other molecules and to reveal similarities and differences in their polypeptide chains. Results: We support the comparison process by proposing a new visualization technique that bridges the gap between traditionally used 1D and 3D representations. By introducing the information about mutual positions of protein chains into the 1D sequential representation the users are able to observe the spatial differences between the proteins without any occlusion commonly present in 3D view. Our representation is designed to serve namely for comparison of multiple proteins or a set of time steps of molecular dynamics simulation. Conclusions: The novel representation is demonstrated on two usage scenarios. The first scenario aims to compare a set of proteins from the family of cytochromes P450 where the position of the secondary structures has a significant impact on the substrate channeling. The second scenario focuses on the protein flexibility when by comparing a set of time steps our representation helps to reveal the most dynamically changing parts of the protein chain