Fault detection with Conditional Gaussian Network

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A Bayesian network dealing with measurements and residuals for system monitoring

International audience

Temporal Control of Ion Channel Activation

Ion channels are a large class of integral membrane proteins that allow for the diffusion of ions across a cellular membrane and are found in all forms of life. Pentameric ligand-gated ion channels (pLGICs) comprise a large family of proteins that include the nicotinic acetylcholine receptor (nAChR) and the γ-aminobutyric acid (GABA) receptor. These ion channels are responsible for the fast synaptic transmission that occurs in humans and as a result are of fundamental biological importance. pLGICs bind ligands (neurotransmitters), and upon ligand-binding undergo activation. The activation event causes an ion channel to enter a new physical state that is able to conduct ions. Ion channels allow for the flux of ions across the membrane through a pore that is formed upon ion channel activation. For pLGICs to function properly both ligand-binding and ion channel activation must occur. The ligand-binding event has been studied extensively over the past few decades, and a detailed mechanism of binding has emerged. During activation the ion channel must undergo structural rearrangements that allow the protein to enter a conformation in which ions can flow through. Despite this great and ubiquitous importance, a fundamental understanding of the ion channel activation mechanism and kinetics, as well as concomitant structural arrangements, remains elusive.

This dissertation describes efforts that have been made to temporally control the activation of ligand-gated ion channels. Temporal control of ion channel activation provides a means by which to activate ion channels when desired. The majority of this work examines the use of light to activate ion channels. Several photocages were examined in this thesis; photocages are molecules that release a ligand under irradiation, and, for the work described here, the released ligand then activates the ion channel. First, a new water-soluble photoacid was developed for the activation of proton-sensitive ion channels. Activation of acid-sensing ion channels, ASIC2a and GLIC, was observed only upon irradiation. Next, a variety of Ru²⁺ photocages were also developed for the release of amine ligands. The Ru²⁺ systems interacted in a deleterious manner with a representative subset of biologically essential ion channels. The rapid mixing of ion channels with agonist was also examined. A detection system was built to monitor ion channels activation in the rapid mixing experiments. I have shown that liposomes, and functionally-reconstituted ELIC, are not destroyed during the mixing process. The work presented here provides the means to deliver agonist to ligand-gated ion channels in a controlled fashion.

Development of docetaxel and alendronate-loaded chitosan-conjugated polylactide-co-glycolide nanoparticles: In vitro characterization in osteosarcoma cells

Purpose: To develop docetaxel (DTX)- and alendronate (ALN)-loaded, chitosan (CS)-conjugated polylactide- co-glycolide (PLGA) nanoparticles (NPs) to increase therapeutic efficacy in osteosarcoma cells. Methods: Drug-loaded PLGA NPs were prepared by nanoprecipitation and chemically conjugated by the carboxylic group of PLGA to the amine-bearing CS polymer. The nanocarrier was characterized by dynamic light scattering, transmission electron microscopy, scanning electron microscopy, and differential scanning calorimetry as well as by in vitro drug release and cell culture studies. Results: NP size was within the tumour targeting range (~200 nm) with an effective positive charge (20 mV), thus increasing cellular uptake efficiency. Morphological analysis revealed clear spherical particles with uniform dispersion. The NPs exhibited identical sustained release kinetics for both DTX and ALN. CS-conjugated PLGA with dual-drug-loaded (DTX and AL) NPs showed typical time-dependent cellular uptake and also displayed superior cytotoxicity in MG-63 cells compared with blank NPs, which were safe and biocompatible. Conclusion: Combined loading of DTX and ALN in NPs increased the therapeutic efficacy of the formulation for osteosarcoma treatment, thus indicating the potential benefit of a combinatorial drug regimen using nanocarriers for effective treatment of osteosarcoma.

Complexes cationiques POCOP de nickel : synthèse, caractérisation, réactivité et étude catalytique

Ce mémoire traite de la chimie des complexes pinceurs de nickel (II) cationiques ayant un ligand de type POCOP. Elle se divise en deux parties. La première traite de la synthèse, de la caractérisation et de la réactivité des complexes cationiques pinceurs de Ni(II) de type POCOP (POCOP = 1,3-bis(phosphinitobenzene), où C fait partie d’un cycle benzénique et est lié au métal, et P est un ligand phosphoré aussi lié au métal). Ces complexes ont un ligand acétonitrile coordonné au centre métallique et sont du type [(R-POCOPR’)Ni(NCMe)][OSO2CF3], où R est un substituant du cycle benzénique et R’ est un substituant sur le ligand phosphoré (R’ = iPr: R = H (1), p-Me(2), p-OMe(3), p-CO2Me(4), p-Br(5), m,m-tBu2(6), m-OMe(7), m-CO2Me(8); R’ = t-Bu : R = H (9), p-CO2Me(10)). Les complexes cationiques sont préparés en faisant réagir le dérivé Ni(II) neutre correspondant R-(POCOPR’)Ni-Br avec Ag(OSO2CF3¬) dans l’acétonitrile à température ambiante. L’impact des groupements R et R’ du ligand POCOP sur la structure et sur les propriétées électroniques du complexe a été étudié par spectroscopies RMN, UV-VIS et IR, analyse électrochimique, et diffraction des rayons X. Les valeurs de fréquence du lien C≡N (ν(C≡N)) augmentent avec le caractère électroattracteur du complexe, dans l’ordre 7 < 3 ~ 2 ~ 6 < 1 < 5 ~ 8 < 4 et 9 < 10. Ces résultats sont en accord avec le fait qu’une augmentation du caractère électrophile du centre métallique devrait résulter en une augmentation de la donation σ MeCN→Ni. De plus, les complexes cationiques montrent tous un potentiel d’oxydation Ni(II)/Ni(III) plus élevé que leurs analogues neutres Ni-Br. Ensuite, une étude d’équilibre entre un complexe neutre (R-POCOPR’)NiBr et un complexe cationique [(R-POCOPR’)Ni(NCMe)][OSO2CF3] démontre l’échange facile des ligands MeCN et Br. La deuxième partie de ce mémoire consiste en deux chapitres. Le premier (Chapitre 3) est une étude structurelle permettant une meilleure compréhension du mécanisme d’hydroamination des oléfines activées promue par les complexes présentés au chapitre 1, suivi de tentatives de synthèse de nouveaux composés POCOP cationiques comportant un ligand amine et nitrile, et de déplacement du groupement amine par un groupement nitrile. Le deuxième chapitre (4) décrit la réactivité et la cinétique de la réaction d’hydroamination et d’hydroalkoxylation d’oléfines activées, qui permet ainsi de mieux comprendre l’impact des différentes variables du système (groupements R et R’, température, substrats, solvent, etc.) sur la réactivité catalytique.

Complexes cationiques POCOP de nickel : synthèse, caractérisation, réactivité et étude catalytique

Ce mémoire traite de la chimie des complexes pinceurs de nickel (II) cationiques ayant un ligand de type POCOP. Elle se divise en deux parties. La première traite de la synthèse, de la caractérisation et de la réactivité des complexes cationiques pinceurs de Ni(II) de type POCOP (POCOP = 1,3-bis(phosphinitobenzene), où C fait partie d’un cycle benzénique et est lié au métal, et P est un ligand phosphoré aussi lié au métal). Ces complexes ont un ligand acétonitrile coordonné au centre métallique et sont du type [(R-POCOPR’)Ni(NCMe)][OSO2CF3], où R est un substituant du cycle benzénique et R’ est un substituant sur le ligand phosphoré (R’ = iPr: R = H (1), p-Me(2), p-OMe(3), p-CO2Me(4), p-Br(5), m,m-tBu2(6), m-OMe(7), m-CO2Me(8); R’ = t-Bu : R = H (9), p-CO2Me(10)). Les complexes cationiques sont préparés en faisant réagir le dérivé Ni(II) neutre correspondant R-(POCOPR’)Ni-Br avec Ag(OSO2CF3¬) dans l’acétonitrile à température ambiante. L’impact des groupements R et R’ du ligand POCOP sur la structure et sur les propriétées électroniques du complexe a été étudié par spectroscopies RMN, UV-VIS et IR, analyse électrochimique, et diffraction des rayons X. Les valeurs de fréquence du lien C≡N (ν(C≡N)) augmentent avec le caractère électroattracteur du complexe, dans l’ordre 7 < 3 ~ 2 ~ 6 < 1 < 5 ~ 8 < 4 et 9 < 10. Ces résultats sont en accord avec le fait qu’une augmentation du caractère électrophile du centre métallique devrait résulter en une augmentation de la donation σ MeCN→Ni. De plus, les complexes cationiques montrent tous un potentiel d’oxydation Ni(II)/Ni(III) plus élevé que leurs analogues neutres Ni-Br. Ensuite, une étude d’équilibre entre un complexe neutre (R-POCOPR’)NiBr et un complexe cationique [(R-POCOPR’)Ni(NCMe)][OSO2CF3] démontre l’échange facile des ligands MeCN et Br. La deuxième partie de ce mémoire consiste en deux chapitres. Le premier (Chapitre 3) est une étude structurelle permettant une meilleure compréhension du mécanisme d’hydroamination des oléfines activées promue par les complexes présentés au chapitre 1, suivi de tentatives de synthèse de nouveaux composés POCOP cationiques comportant un ligand amine et nitrile, et de déplacement du groupement amine par un groupement nitrile. Le deuxième chapitre (4) décrit la réactivité et la cinétique de la réaction d’hydroamination et d’hydroalkoxylation d’oléfines activées, qui permet ainsi de mieux comprendre l’impact des différentes variables du système (groupements R et R’, température, substrats, solvent, etc.) sur la réactivité catalytique.

PROLINE-BASED CHIRAL STATIONARY PHASES: INSIGHTS INTO THE MECHANISM OF CHIRAL SELECTIVITY

Proline (Pro) is a unique amino acid that has been examined previously as a potential chiral selector for high-performance liquid chromatography. In recent years, a new class of promising Pro based enantioselective stationary phases has been studied and the longer peptides were found to be competitive with commercial chiral stationary phases (CSPs). Here, we aim to perform a comprehensive examination of a t-butoxycarbonyl- (t-Boc-) terminated monoproline selector. This selector was grafted through an amide linkage to an aminopropyl siloxane-terminated Si (111) wafer and to a silicon atomic force microscopy tip. To ensure a flat, homogeneous overlayer of selectors suitable for force spectrometric measurements, the prepared surfaces were characterized using XPS, AFM and contact angle measurements. Chemical force spectrometry (CFS) has been used to examine the chiral discrimination in our monoproline CSP by measuring the interaction forces between two D- or L-monoproline monolayers in water and in the presence of a series of amino acids in solution to explore the degree to which binding of amino acids impacts self-selectivity. Chemical force titration (CFT) has been used to observe the influence of variations in pH on the binding interaction of proline modified chiral surfaces. Here we aim to explore the connection between side-chain hydrophobicity and differences in the nature of the binding between different ionic forms of amino acids and the t-Boc-Pro interface, and thereby to gain insight into the mechanism of chiral selectivity. The CFS results show several trends for different proline selector/amino acid combinations and indicate that the binding characteristics of amino acid to the proline surface is strongly dependent on the amino acid side chain where hydrophilic side chain amino acids exhibit a selectivity opposite to that seen for those with hydrophobic side chains. The CFT studies also provide valuable insights into interactions between the proline selector and the amino acids under a wide range of pH conditions, indicating that protonated amine groups of alanine and serine are closely involved in the binding mechanism to proline surfaces. On the other hand, the presence of the second carboxylic group in aspartic acid plays an important role while interacting with proline.

Estudio molecular en dos hermanas afectadas por ictiosis congénita autosómica recesiva : descripción de una nueva mutación causal en TGM1

Se describe la variante homocigota c.320-2A>G de TGM1 en dos hermanas con ictiosis congénita autosómica recesiva. El clonaje de los transcritos generados por esta variante permitió identificar tres mecanismos moleculares de splicing alternativos.

Adenine as an organocatalyst for the ring-opening polymerization of lactide: scope, mechanism and access to adenine-functionalized polylactide

Nucleobase-functionalized polymers are widely used in the fields of supramolecular chemistry and self-assembly, and their development for biomedical applications is also an area of interest. They are usually synthesized by tedious multistep procedures. In this study, we assess adenine as an organoinitiator/ organocatalyst for the ring-opening polymerization of lactide. L-Lactide can be quantitatively polymerized in the presence of adenine. Reaction conditions involving short reaction times and relatively low temperatures enable the access to adenine end-capped polylactide in a simple one-step procedure, in bulk, without additional catalyst. DFT calculations show that the polymerization occurs via hydrogen bond catalysis. The mechanism involves (i) a hydrogen bond between the NH9 of adenine and the carbonyl moiety of lactide, leading to an electron deficient carbon atom, and (ii) a second hydrogen bond between the N3 of adenine and the NH2 of a second adenine molecule, followed by a nucleophilic attack of the latter activated amine on the former electron deficient carbon on the monomer. For longer reaction times and higher temperatures, macrocyclic species are formed, and a mechanism involving the imidazole ring of adenine is proposed based on literature studies. Depending on the reaction conditions, adenine can thus be considered as an organoinitiator or an organocatalyst for the ring-opening polymerization of lactide.

Adenine as an organocatalyst for the ring-opening polymerization of lactide: scope, mechanism and access to adenine-functionalized polylactide

Nucleobase-functionalized polymers are widely used in the fields of supramolecular chemistry and self-assembly, and their development for biomedical applications is also an area of interest. They are usually synthesized by tedious multistep procedures. In this study, we assess adenine as an organoinitiator/organocatalyst for the ring-opening polymerization of lactide. L-Lactide can be quantitatively polymerized in the presence of adenine. Reaction conditions involving short reaction times and relatively low temperatures enable the access to adenine end-capped polylactide in a simple one-step procedure, in bulk, without additional catalyst. DFT calculations show that the polymerization occurs via hydrogen bond catalysis. The mechanism involves (i) a hydrogen bond between the NH9 of adenine and the carbonyl moiety of lactide, leading to an electron deficient carbon atom, and (ii) a second hydrogen bond between the N3 of adenine and the NH2 of a second adenine molecule, followed by a nucleophilic attack of the latter activated amine on the former electron deficient carbon on the monomer. For longer reaction times and higher temperatures, macrocyclic species are formed, and a mechanism involving the imidazole ring of adenine is proposed based on literature studies. Depending on the reaction conditions, adenine can thus be considered as an organoinitiator or an organocatalyst for the ring-opening polymerization of lactide.

DFT STUDIES ON THE MECHANISM OF RING-OPENING POLYMERIZATION OF LACTIDE WITH ADENINE

The use of organic molecules as catalysts for the ring-opening polymerization (ROP) of cyclic esters has gained much interest last years.[1] The use of a molecule of biological interest, able to initiate ROP of cyclic esters without any cocatalyst is even more interesting, as the resulting material will not contain any catalytic residue. Nucleobase-polymer conjugates development is thus an emerging area envisaging biomedical applications.[2] However, they are usually synthesized by tedious multistep procedures. Recently, adenine was used as organoinitiator for the ROP of L-lactide.[3] Reaction conditions involving short reaction times and relatively low temperatures enable the access to adenine-polylactide(Adn-PLA)conjugates in a simple one-step procedure, without additional catalyst and in the absence of solvent. In this study, computational investigations with density functional theory (DFT) were performed in order to clarify the reaction mechanism leading to the desired Adn-PLA. The results show that a hydrogen bond catalytic mechanism, involving a nucleophilic attack of the activated amine group of adenine onto the carbonyl group of lactide, seem to be plausible.

Synthesis, Characterization and Conformational Studies of Modified Carbazole-bis-aryl-boranes

During this project we have synthetized different compounds belonging to the class of amino-boranes for the study of bis-aryl-B=N system. We have decided to keep unchanged the aryl components and change only the amine to observe the effect of that on the B=N bond. The used amines are modified carbazoles with functional groups chosen to amplify or disempower the steric and the conjugation effect. We have found that the evaluation of steric barrier was possible studying the gearing aryls rotation around the C-B bonds, while the conjugation barrier is instead given by the energy needed to break the formal double bond B=N and allow the amine rotation. The work started with a proposed synthesis, improved for every reaction, then the products are characterized by NMR, fluorometric spectroscopy, mass spectrometry and X-Ray diffraction on single crystal. The following study on rotational energy barrier was possible theoretically through DFT calculation and experimentally with techniques like Dynamic NMR and EXSY. The fluorometric analysis was done for the study of the solvatochromic propriety of the products.

Cadmium Telluride Magic-Sized Clusters and Superstructures

The aim of the present work is to gain new insights into the formation mechanism of CdTe magic-sized clusters (MSCs) at low temperatures, as well as on their evolution towards 1D and 2D nanostructures and assemblies thereof, under mild reaction conditions. The reaction system included toluene as solvent, octylamine as primary alkylamine, trioctylphosphine-Te as chalcogenide precursor and Cd(oleate)2 as metal precursor. UV-Vis absorption spectroscopy and transmission electron microscopy (TEM) were used to analyze samples containing concentrations of octylamine of 0.2, 0.8 and 2 M: well-defined, sharp absorption peaks were observed, with peaks maxima at 449, 417 and 373 nm respectively, and 1D structures with a string-like appearance were displayed in the TEM images. Investigating peaks growth, step-wise peaks shift to lower energies and reverse, step-wise peak shift to higher energies allowed to propose a model to describe the system, based on interconnected [CdTe]x cluster units originating an amine-capped, 1-dimensional, polymer-like structure, in which different degrees of electronic coupling between the clusters are held responsible for the different absorption transitions. The many parameters involved in the synthesis procedure were then investigated, starting from the Cd:Te ratio, the role of the amine, the use of different phosphine-Te and Cd precursors. The results allowed to gain important information of the reaction mechanism, as well as on the different behavior of the species featuring the sharp absorption peaks in each case. Using Cd(acetate)2 as metal precursor, 2D structures were found to evolve from the MSCs solutions over time, and their tendency to self-assemble was then analyzed employing two amines of different alkyl chain length, octylamine (C-8) and oleylamine (C-18). Their co-presence led to the formation of free-floating triangular nanosheets, which tend to readily aggregate if only octylamine is present in solution.

Computational study on the asymmetric aminocatalysed Michael addition reaction of cyclohexanone to trans–β–nitrostyrene

Asymmetric organocatalysed reactions are one of the most fascinating synthetic strategies which one can adopt in order to induct a desired chirality into a reaction product. From all the possible practical applications of small organic molecules in catalytic reaction, amine–based catalysis has attracted a lot of attention during the past two decades. The high interest in asymmetric aminocatalytic pathways is to account to the huge variety of carbonyl compounds that can be functionalized by many different reactions of their corresponding chiral–enamine or –iminium ion as activated nucleophile and electrophile, respectively. Starting from the employment of L–Proline, many useful substrates have been proposed in order to further enhance the catalytic performances of these reaction in terms of enantiomeric excess values, yield, conversion of the substrate and turnover number. In particular, in the last decade the use of chiral and quasi–enantiomeric primary amine species has got a lot of attention in the field. Contemporaneously, many studies have been carried out in order to highlight the mechanism through which these kinds of substrates induct chirality into the desired products. In this scenario, computational chemistry has played a crucial role due to the possibility of simulating and studying any kind of reaction and the transition state structures involved. In the present work the transition state geometries of primary amine–catalysed Michael addition reaction of cyclohexanone to trans–β–nitrostyrene with different organic acid cocatalysts has been studied through different computational techniques such as density functional theory based quantum mechanics calculation and force–field directed molecular simulations.