WorldCat Identities

Lecomte, Sophie (Directrice de recherche)

Overview
Works: 30 works in 33 publications in 2 languages and 35 library holdings
Roles: Other, Opponent, Thesis advisor, Editor
Publication Timeline
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Most widely held works by Sophie Lecomte
Optimisation de nanostructures plasmoniques pour la détection et la caractérisation structurelle des protéines par Diffusion Raman Exaltée de Surface by Maximilien Cottat( Book )

3 editions published in 2014 in French and held by 4 WorldCat member libraries worldwide

Proteins play an important role in cells via their enzymatic activity and the irinteractions. Their functions are mainly based on the protein structure. In order to detect their presence and to characterize their structure, we used optical properties of nanostructures. The localized surface plasmon resonance (LSPR), as well as the surface enhanced Raman scattering (SERS), allowed us to detect various proteins. We also optimized nanostructures to build a sensitive, reproducible and specific biosensor based on SERS. Indeed, specific detection of one pathological biomarker, the Manganese Super Oxide Dismutase (MnSOD) protein, was investigated by using optically optimized and aptamer-functionalized nanostructures. Using this system, we were able to detect the MnSOD at physiological concentration in body fluids, such as serum and saliva. Finally, the structural study of the Spleen Tyrosine kinase (Syk) protein by SERS, allowed us to demonstrate that its structure varied with its phosphorylation levels. A complementary Western Blot analysis showed that the Syk kinase activity depended also on its phosphorylation state, meaning that the structure and the activity of Syk were linked. Altogether, these data contributed to a better understanding of the interface between physics and biology
Biomolécules et systèmes nanostructurés : caractérisation par spectrométrie Raman exaltée de surface (SERS) by Sébastien Reymond-Laruinaz( Book )

2 editions published in 2014 in French and held by 2 WorldCat member libraries worldwide

Le développement des nano et biotechnologies pousse à la recherche de techniques de caractérisation adaptées à l'étude des systèmes nanostructurés. La spectrométrie Raman exaltée de surface (SERS) est une technique d'analyse en plein essor dans ce domaine.Dans ce travail de thèse nous nous sommes attachés à étudier, par cette technique, différents types de systèmes nanostructurés : des biomolécules et des films minces inorganiques. Le but était d'accéder à des informations sur la structure et les liaisons chimiques présentes dans ces systèmes. L'étude a été complétée par des observations par microscopie électronique en transmission notamment.Dans un premier temps, a été réalisée l'étude de molécules d'intérêt biologique. L'objectif était la compréhension des modes d'interaction nanoparticules métalliques/protéines menée sur des nanoparticules d'argent bio-conjuguées avec des protéines depuis leur synthèse jusqu'à leur caractérisation. Les résultats ont montré la chimisorption des protéines à la surface de nanoparticules d'argent possiblement par leurs terminaisons azotées. La technique SERS a également été expérimentée dans le domaine des basses fréquences pour caractériser la structure de dépôts minces de caféine, molécule d'intérêt pharmaceutique.Dans un second temps, l'étude de couches minces nanostructurées par spectrométrie Raman et SERS a été réalisée. Des couches minces nanocomposites TiO2:Au, ont été étudiées pour décrire les premières étapes de croissance des nanoparticules sous l'effet de la température dans ces matériaux. Des films ultraminces de TiO2 d'épaisseur contrôlée ont été déposés sur substrats fonctionnalisés avec des nanoparticules d'or pour étudier leur exaltation par effet SERS
Apports de la Microscopie à Force Atomique à l'étude de phénomènes dynamiques en biologie et développement instrumental associé by Eléonore Lambert( )

1 edition published in 2018 in French and held by 1 WorldCat member library worldwide

Our laboratory recently acquired a high-speed atomic force microscope (HS-AFM) which enables us to visualize in real time a wide range of biological samples and their dynamics of interaction at nanoscale. Several research fields require the development of new techniques in order to get high resolution imaging and dynamic imaging at the same time. This is why HS-AFM was developed. Its current limitation is that the only data it provides are about the surface which means we can't get access to what occurs beneath. This is limiting the knowledge we could get about the underlying dynamics of some biomolecular system. In order to overcome this issue, we propose to upgrade this nanocharacterization tool by combining optical microscopy and force spectroscopy. This project of instrumental development will be in two major steps: - the adding of conventional optical microscopy : fluorescence, TIRFM, FRAP, FRET, FLIM. The aim is to nanocharacterize sample with highly spatiotemporal data combined in combination with integral data (fundamental to respond to biological issues) - the development of tip functionalization protocols in order to achieve force spectroscopy and get mechanical properties of biological samples This project will take place at the Laboratory of Research in Nanosciences, EA 4682, University of Reims Champagne Ardennes, under the supervision of Pr. Michael Molinari and Dr. Maxime Ewald who started HS-AFM among our team. We will collaborate with Pr. T. Ando from the Biophysics Lab of Kanazawa University (Japan) for the instrumental part and with Dr. Gabriel Paës for the biological samples. The samples used during this thesis will be linked to an ANR project called Lignoprog directed by Dr. Gabriel Paës (INRA, UMR FARE, Reims) and started on the first of November, 2014. In the project, the dynamical aspect of the biological samples is essential. Indeed, lignocellulosic biomass is a complex network of polymers composing plant cell wall. Its architectural and chemical complexity prevents its industrial conversion. In order to be cost-effective, bio refineries need to valorize all the fractions: cellulose, hemicelluloses and lignins. The major challenge is the high cost and low efficiency of the enzymatic hydrolysis of the lignocellulosic biomass. Our aim is to bring some answer to understand better and improve enzymatic hydrolysis thanks to the HS-AFM and the combination of new functionalities. By the way, the disposal might be validated on other biological samples in parallel, such as live cells in order to characterize them, enlighten their reactivity in response to physiological parameters of the medium (pH, concentration, composition) and correlate the results with mechanical properties
Étude de l'influence de modifications structurales sur la neuroglobine humaine by Éric André( )

1 edition published in 2017 in French and held by 1 WorldCat member library worldwide

The physiological function of Human Neuroglobin (Ngb), discovered in 2000, is still unknown. Compared to other classical globins Haemoglobin and Myoglobin, Ngb has some structural specificities. Its haem, which is its reactive centre, is hexacoordinated by distal histidine 64 and exists under two isomer forms A and B. Moreover, Ngb possesses an intramolecular disulfide bridge between two cysteines 46 and 55.The relationship between its structural characteristics and its functions in vivo does not remain well-understood. The goal of this thesis was to underline the impact of some structural features on the Ngb properties and reactivity in vitro. Thus Ngb variants H64V, F106L, A90P and C46G were produced. Experimental studies were performed by UV-Visible spectrophotometry, circular dichroism and NMR. Variants were characterized : their stability as a function of pH were tested and their reactivity trough the CN binding reaction were evaluated.We have shown that the Ngb structure was strongly dependant on the presence of the distal histidine, the disulfide bridge and the haem environment. The first and unique determination of variants' molar absorption coefficients underlined the influence of the haem vicinity and disulfide bridge on the electronic haem environment. We have brought some evidence that the disulfide bridge and the mutated amino acids have an impact on the isomer A Ngb ability to bind the cyanide whereas isomer B is poorly affected by those two parameters. This phenomenon raises the issue of the existence and function of the two isomer forms in vivo
Spectroscopie Raman et microfluidique : application à la diffusion Raman exaltée de surface by Caroline Delhaye( )

1 edition published in 2009 in French and held by 1 WorldCat member library worldwide

This thesis focuses on the development of a microfluidic platform coupled with confocal Raman microscopy, used in excitation conditions of Raman scattering (Surface enhanced Raman scattering, SERS) in order to gain in the detection sensitivity of molecular species flowing in channels of micrometer dimensions. This work aims to demonstrate the feasibility of coupling Raman microscopy / microfluidics for the in situ and local characterization of species and reactions taking place in the fluid flowing in microchannels. We used a T-shaped microchannel, made by soft lithography, in which gold or silver nanoparticles injected at constant speed, in one of the two branches of the channel and a solution of pyridine or pefloxacin in the other one. The laminar flow and the stationarity of the process allowed us to map the mixing zone and highlight the enhancement of the Raman signal of pyridine and pefloxacin, due to the metallic nanoparticles, in the interdiffusion zone. The recording of the both absorption band of the silver nanoparticles (plasmon band) and the Raman signal of pefloxacin, flowing in microchannel, allowed us to establish a link between the shape of the metallic nanostructure, and more precisely the silver nanoparticle aggregation state, and the enhancement of the Raman signal of pefloxacin observed. We then changed the channel geometry to introduce an electrolyte solution (NaCl and NaNO3) and locally modify the surface charge of the colloids. We have put in evidence that the change of the silver nanoparticle aggregation state, induced by the controlled addition of electrolyte solutions, could amplify the SERS signal of pefloxacin and thus optimizing the detection in microfluidics. At last, we established second a approach that consists in the metallic structuring of microchannel walls. This has shown that the surface chemical functionalization through organosilanes (APTES) allowed the pasting of the channel with silver nanoparticles, thus amplifying the Raman signal of the species flowing within the same microchannel
Nanospectroscopie infrarouge avancée : développements instrumentaux et applications by Jérémie Mathurin( )

1 edition published in 2019 in French and held by 1 WorldCat member library worldwide

For 10 years, near-field technologies applied to infrared spectroscopy have reached milestones and now are able to make analysis at nanoscale. In my PhD thesis, I will focus on one of these techniques: the so-called AFM-IR technique which combined an atomic force microscope (AFM) with a pulse laser tunable in the infrared spectral range.The main goal of my PhD thesis will be to present the last developments which appears for this technique such as resonance enhanced AFM-IR, tapping mode AFM-IR or the first measurements of AFM-IR with broadband sources. These developments are major in the field of the technique and have led to high increase of the numbers of users. However, AFM-IR remains a recent and complicated technique where user has to master in the same time atomic force microscopy and infrared spectroscopy.The last technological developments allow measurements at the nanoscale. This has multiple consequences, especially it opens new applications fields. It also generates new problematic and new experimental challenges. As a consequence, it is necessary to understand new technological limitations created by these new developments in order to stay critical of the results obtained with an AFM-IR measurement and avoid analysis and interpretation errors which can have bad consequences on the different fields of study
Détection de l'ADN par spectrométrie de diffusion Raman exaltée de surface couplée à la microfluidique by Enora Prado( )

1 edition published in 2011 in French and held by 1 WorldCat member library worldwide

This work deals with the development of an original label-free method for free bases proportions detection and quantification of nucleic acids. The surface enhanced Raman spectroscopy (SERS) allowed obtaining the specific spectral signature of characteristic nucleotides of RNA (adenosine, cytosine, guanosine and uridine), using silver colloids as SERS substrate and MgCl2 addition as aggregating agent. Then, the condition detection have optimizing to establish a label-free quantification protocol of free nucleobases proportion by SERS spectroscopy. The detection limits obtained are order of few picomoles. The reproducibility improvement of SERS detection requires the precise control of time reaction (adsorption and aggregation), which could be control thanks to microfluidic chips use. We have implemented two different microfluidic chips, one based on single-phase flows and one other based on droplets generation. The analyzed species are containing in droplets, allowing in situ detection by spectroscopy SERS of various nucleotides
Conception de surfaces chimio-structurées pour l'étude de l'adhésion bactérienne et la formation contrôlée des biofilms bactériens by Elena Yunda( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

La formation de biofilms bactériens pathogènes est un problème important, particulièrement dans les secteurs médicaux et agro-alimentaires. La formation contrôlée de biofilms de la bactérie probiotique Lactobacillus rhamnosus GG (LGG) est sélectionnée ici comme méthode potentielle pour prévenir la contamination de surfaces par des bactéries pathogènes. Nous avons étudié le développement de biofilms de LGG ainsi que leur possible contrôle en combinant des approches physico-chimiques et de fonctionnalisation de surface. L'impact des conditions environnementales sur la cinétique de croissance des biofilms et sur leur composition biochimique a été analysé par des mesures in situ et en temps réel par spectroscopie infrarouge à transformée de Fourier en réflexion totale atténuée (ATR-FTIR) sous conditions de flux. Ces données ont été complétées par des images de microscopie en épifluorescence permettant d'obtenir des informations sur la distribution et la forme des cellules bactériennes sur la surface à des étapes clé du développement du biofilm. Compatible avec les mesures ATR-FTIR, un cristal de séléniure de zinc a été choisi comme substrat, nu ou fonctionnalisé avec des monocouches auto-assemblées d'alcane-thiols (SAMs). Différents groupes fonctionnels ont été étudiés : méthyl (-CH3), hydroxyle (-OH) ou amine (-NH2) pour obtenir respectivement des substrats hydrophobe, hydrophile ou chargé positivement. La cinétique d'auto-assemblage des SAMs, leur organisation et l'énergie de surface ont été étudiées en combinant ATR-FTIR, spectroscopie de rétrodiffusion de Rutherford à hautes énergies et mesures d'angles de contact. L'analyse des spectres ATR-FTIR des biofilms de LGG enregistrés in situ et en temps réel pendant 24 heures a montré un rôle important du milieu nutritif sur la composition biochimique et le métabolisme bactériens. Les propriétés du substrat ont un impact faible sur la composition biochimique des biofilms, mais ont un rôle crucial sur leur force d'attachement à la surface. Ce travail pluridisciplinaire a fourni des informations sur l'influence de l'environnement, et particulièrement des caractéristiques du support, sur les propriétés des biofilms aux échelles moléculaire et cellulaire. La méthodologie développée dans ce travail peut notamment être utilisée dans la recherche des conditions les plus favorables à la croissance des biofilms de bactéries probiotiques
Synthès de nano-films bio-fonctionnels pour l'immobilisation spécifique d'espèces biologiques by Yannick Mousli( )

1 edition published in 2017 in French and held by 1 WorldCat member library worldwide

Le contrôle des propriétés physicochimiques et de l'état de surface des solides constituent un enjeu majeur pour le développement des biotechnologies, et notamment des bio-capteurs. Pour des applications en analyse et diagnostic biologique, la fonctionnalisation des surfaces à base de silicium peut être réalisée grâce à la formation d'un nano-film organique appelé SAM (Self-Assembled Monolayer). L'objectif de ce travail de thèse est ainsi de synthétiser des monocouches sur des substrats de silice afin de les rendre biofonctionnels en vue de développer une plateforme de biodétection polyvalente.Pour ce faire, deux types d'agents de couplages ont été envisagés : l'un possédant un motif azoture et l'autre une biotine. L'obtention de ces deux types de molécules a fait l'objet d'un travail de synthèse permettant d'aboutir à de nouveaux organosilanes fonctionnels directement greffables sur des surfaces de SiO2. La biofonctionnalité est introduite sur le substrat par la biotine, soit directement lors de la formation de la SAM, soit par chimie click sur les monocouches fonctionnalisées par des azotures.Les différentes surfaces obtenues ont ensuite été caractérisées par Spectroscopie Infrarouge de Réflexion-Absorption par Modulation de Polarisation (PM-IRRAS) et par Microscopie de Force Atomique (AFM). La bioactivité des SAMs biotinylées a enfin été évaluée par un protocole mettant en jeu une streptavidine modifiée par une enzyme (la HRP) capable de catalyser des réactions d'oxydoréduction de molécules chromogènes
Techniques de structuration et d'émulsification de la matière grasse laitière by Lucie Goibier( )

1 edition published in 2018 in French and held by 1 WorldCat member library worldwide

Yoghurts and ice creams are food materials obtained from dairy emulsions. This study is concerned with the development of strategies for fat reduction in ice creams and yoghurts without altering physico-chemical and organoleptic properties. For that purpose, we first worked on a model dairy emulsion based on anhydrous milk fat dispersed in an aqueous solution containing sodium caseinate. The first approach is based on the increase of the fat droplets' size induced by an instability occurring in oil-in-water emulsions composed of crystallizable triglycerides: partial coalescence. To induce partial coalescence, low molecular weight surfactants must be added to displace proteins from the interface. We performed a screening of various surfactants according to their ability to induce partial coalescence in a dairy emulsion. We showed that liquid surfactants induced partial coalescence, whereas this phenomenon was prevented when crystallizable surfactants, composed of long saturated fatty acid chains, were added. In this latter case, we provided evidence for the formation of a rigid barrier protecting fat droplets against partial coalescence. The second strategy was based on the incorporation of a fat free fraction in fat droplets. Two systems were developed: Water-in-Oil-in-Water (W/O/W) and Air-in-Oil-in-Water (A/O/W) double emulsions. Both systems were formulated without lipophilic surfactant, the fat free fraction being stabilized solely by endogenous fat crystals. The characteristics of these systems, as the fat droplets' size and the encapsulation yield were finely tuned by varying the shear rate. We generalized the concept to other crystallizable oils such as palm, coconut oil or cocoa butter. We also evidenced original properties of these double emulsions, especially their resistance to an osmotic stress (W/OW emulsions) and their thermo-responsiveness. Both strategies were finally transposed to the pilot scale
Spectroscopies vibrationnelles (MCR et ATR-FTIR) et Chromatographie Liquide couplée à la Spectrométrie de Masse Haute Résolution (LC-HR-MS) : Outils d'investigation in vivo de l'impact du vieillissement cutané sur le Stratum Corneum aux niveaux tissulaire, supra-moléculaire et moléculaire by Elise Boireau-Adamezyk( )

1 edition published in 2015 in French and held by 1 WorldCat member library worldwide

Skin is the external surface defining the human body in space. Its outer-most layer is a thin biological membrane, called Stratum Corneum(SC), that protects the internal organs from desiccation as well as chemical or mechanical external aggressions. The present thesis aimsin a first step, to summarize the current knowledge regarding the effects of intrinsic and extrinsic aging on SCphysiology,based on available literature. The experimental part addresses the gaps in our understanding of the effects of chronological aging and photoaging on the SC barrier function and hydration, using traditional methods (such as trans epidermal water loss and skin conductance) as well as more advanced ones (vibrational spectroscopies, liquid chromatography in normal phase tandem mass spectrometry high resolution with an APCI source and an Orbitrap detector. As these methods are non-invasive, all studies have been carried out in vivo. The evolution of the barrier function has been studied at the tissular, molecular and supramolecular levels using confocal Raman micro-spectroscopy and infrared spectroscopy. Then the link between the intrinsic aging and the ceramides of the intercorneocytary lipid matrix has been studied by liquid chromatography tandem mass spectrometry. The discriminant molecules between young and old population have been identified by a chemometric analysis. The evolution of cutaneous hydration at the tissular, molecular and supramolecular level has also been investigated. The variations in the NMF composition and the SC water content have been studied by Raman spectral descriptors. Moreover, the structural variations of water molecules impacting the supramolecular organization of the lipid structures have been evaluated. Chronological aging and chronic exposure to environmental factors mildly affect SC barrier function and hydration levels. However, the processes controlling these properties are affected by aging in a site-dependent fashion
Identification et caractérisation de composés produits par des bactéries environnementales pour la lutte biologique contre Legionella pneumophila by Marie-Hélène Corre( )

1 edition published in 2018 in French and held by 1 WorldCat member library worldwide

Water is essential to sustain life and water sources used for human consumption must be biologically safe, to avoid any risk for health. Indeed, the most common and widespread health risk associated with drinking water are infectious diseases caused by pathogenic microorganisms such as Legionella pneumophila. However, more efforts are needed to control disinfection by-products and minimize people exposure to potentially hazardous chemicals while maintaining adequate disinfection to ensure good water quality. Thus, this work aimed to find natural antibacterial compounds to control L. pneumophila growth using bacteria from freshwater environments. Environmental aquatic bacteria were sampled from five freshwater sources to get a large culturable bacterial collection. A total of 273 bacterial isolates were recovered and screened for their ability to produce anti-Legionella compounds. Among those, 178 (65%) were shown to be active against L. pneumophila. Four strains (Aeromonas bestiarum SW257, Rahnella aquatilis SW265, Flavobacterium spp. PW52, and Pseudomonas spp PW329) were next selected for the characterization of their active compounds. A. bestiarum SW257 produces an anti-Legionella peptide, and Flavobacterium spp PW52 produces a mixture of anti-Legionella compounds with surface active properties, named flavolipids. Finally Pseudomonas sp. PW329 delivers many volatile organic compounds, and R. aquatilis SW26 produces a anti-Legionella siderophore
Développement de techniques physiques et chimiques pour l'étude et l'inhibition de l'oligomérisation et de l'agrégation de IAPP : intérêt dans le diabète de type II by Corentin Berardet( )

1 edition published in 2018 in French and held by 1 WorldCat member library worldwide

The rising prevalence of type II diabetes, and associated adverse cardiovascular risks, is now considered as a major public health challenge. The aggregation of human islet amyloid polypeptide (hIAPP) is linked to beta-cell degeneration and to the pathogenesis of type II diabetes. The mechanism of hIAPP toxicity and the species involved (oligomers and/or fibrils) are far to be elucidated, although recent studies have shown that early formed species could be the most toxic species. Very few techniques are currently available to monitor in real time this oligomerization and to evaluate inhibitors of this pathological process. During this PhD project, we investigated CE and IMS-MS as potential techniques to monitor in vitro and in real time the oligomerization of hIAPP. A CE-UV method has been developed, which allows the activity evaluation of new inhibitors. An IMS-MS method has also been developed to investigate the interactions formed between hIAPP and the inhibitors. Peptidomimetics inhibitors have been rationally designed and synthesized in order to destabilize beta-sheets structures formed during the oligomerization process of hIAPP. The evaluation of those compounds revealed a relation between their structures and their inhibitory activities. Cellular viability tests are on-going to get more insights on those molecules activity
Infrared spectroscopic study of the conformational movements in membrane proteins from the respiratory chain by introducing a CN label in critical positions by Ana Filipa Santos Seiça( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

Étude de la stabilité, de l'occupation des cages et de la sélectivité moléculaire des hydrates de gaz par spectroscopie Raman by Claire Pétuya-Poublan( )

1 edition published in 2017 in French and held by 1 WorldCat member library worldwide

Les hydrates de gaz sont des cristaux composés de molécules d'eau formant des cages, piégeant des molécules de gaz. A l'état naturel, ces hydrates se forment en présence de mélanges gazeux dans les fonds océaniques et seraient impliqués dans la formation des comètes et des planètes. Comprendre la sélectivité moléculaire et la stabilité des hydrates mixtes (co-incluant plusieurs espèces gazeuses) est primordiale et constitue le coeur de ce travail de doctorat. En s'appuyant sur la spectroscopie Raman et la diffraction des neutrons, complétés de calculs de chimie quantique, les hydrates formés à partir de mélanges de CO, N2 et de CO2 ont été étudiés.Outre leur intérêt astrophysique, ces systèmes permettent d'appréhender l'impact de propriétés physico-chimiques (moment dipolaire,solubilité, adsorption sur la glace) sur la sélectivité.La cinétique de formation et les signatures vibrationnelles des molécules encapsulées dans différents types de cages ontété analysées pour la première fois dans les hydrates purs de CO et de N2. En variant pression et température, une capacité exceptionnelle de diffusion des molécules gazeuses à travers les cages est révélée. La sélectivité moléculaire, la stabilité structurale et l'occupation des cages ont été étudiées dans les hydrates mixtes CO-N2, CO-CO2 et CO2-N2.L'affinité aqueuse et le moment dipolaire des molécules gazeuses pilotent la sélectivité des gaz piégés (encapsulation préférentielle du CO et du CO2). De plus, l'azote joue un rôle de promoteur cinétique des structures formées. Ces résultats fondamentaux ouvrent de nouvelles perspectives tant appliquées (séparation des gaz) que fondamentales (hydrates en milieu naturel)
SERS NanoBiosensor with high sensitivity and selectivity : application to early disease diagnosis by Wafa Safar( )

1 edition published in 2021 in English and held by 1 WorldCat member library worldwide

The objective of this thesis was the development of a biosensor based on the exploitation of the optical properties of metallic nanostructures and more especially on the surface enhanced Raman scattering (SERS) to detect very small quantities of molecules. The optimization of the Raman enhancement requires a better understanding of the plasmonic properties of the nanostructures, of the influence of the geometry (size, shape and arrangement) of the nanoparticles and of the nature of the metal. Moreover, the SERS substrate is then grafted with a bioreceptor specific to the targeted analyte. The bioreceptor used in our biosensor is anaptamer, a single strand of DNA, which has a strong affinity with the molecule to be detected by the formation of a specific secondary structure. The optimization of the biosensor signal also requires a better understanding of the bioreceptor/biomolecule interactions. We therefore studied these interactions by SERS and determined the influence of experimental conditions (buffer solution, addition of a spacer, liquid or dry environment...) on the orientation of the aptamer and on its interaction. The determination of the spectral characteristics of the aptamer allowed us to identify the interaction and to provide a deep insight on the interaction mechanisms. These results pave the way to a new kind of SERS-based biosensor using aptamers
Tip-enhanced Raman spectroscopy on electrochemical systems by Thomas Touzalin( )

1 edition published in 2018 in English and held by 1 WorldCat member library worldwide

L'analyse in situ d'interfaces électrochimiques à l'échelle nanométriques est un enjeu majeur pour la compréhension des mécanismes de transferts de charges et d'électrons dans les domaines du stockage d'énergie ou de l'électrocatalyse. Ce travail a permis le développement de la spectroscopie Raman exaltée de pointe (TERS) en milieu liquide et en conditions électrochimiques. Le TERS permet l'analyse de la structure de molécules ou de matériaux à l'échelle nanométrique du fait de l'exaltation localisée du champ électrique à l'extrémité d'une sonde de microscope à effet tunnel (STM) en or ou en argent. Un dispositif reposant sur l'illumination d'une pointe au travers d'un solvant organique a démontré la possibilité d'imager les inhomogénéités d'une monocouche auto-assemblée sur or. Une seconde approche reposant sur l'exaltation du signal Raman à l'apex d'une pointe de taille nanométrique utilisée comme microélectrode (spectroscopie Raman exaltée de surface de pointe, tip SERS) a permis de suivre la réduction d'une monocouche auto-assemblée et d'améliorer la compréhension de son mécanisme. Afin d'imager la surface d'une électrode polarisée, le couplage d'un STM utilisant une pointe TERS en conditions électrochimiques a montré une résolution latérale de moins de 8 nm pour sonder de variations locales de l'exaltation du champ électromagnétique induites par des singularités géométriques de surface. Par ailleurs, l'analyse TERS de couches organiques formées à partir de sels d'aryldiazoniums a permis de montrer des différences de structures selon type de greffage. Ce travail constitue donc une avancée majeure pour l'analyse locale de surfaces modifiées
Détection d'ADN par spectroscopie SERRS et interactions entre nucléotides et surfaces des minéraux phyllosilicatés ferromagnésiens dans le contexte de l'origine de la Vie by Cécile Feuillie( )

1 edition published in 2012 in French and held by 1 WorldCat member library worldwide

The first goal of this thesis was the development of a non-enzymatic DNA detection method. Current enzymatic techniques such as Polymerase Chain Reaction (PCR) often fail in analyzing ancient or processed samples. Indeed DNA undergoes numerous post-mortem degradations, among which some are known to block the bypass of DNA-polymerases. Our method combines hybridization and SERRS (Surface Enhanced Resonant Raman Scattering) spectroscopy, and allows the detection and quantification of degraded DNA sequences that are refractory to PCR analysis. This novel detection method therefore opens new perspectives, especially in paleogenetics. This thesis also aims at studying the role of mineral surfaces in the origin of nucleic acids. Mineral surfaces might have trapped and concentrated the elementary bricks of those biopolymers, thus contributing in their formation. Previous work has focused on minerals such as montmorillonite, although it might not have been abundant during the Hadean/Archean. The primitive Earth's mineralogy would have been preferentially dominated by Fe-Mg rich phyllosilicates. We have therefore studied the adsorption of nucleotides on minerals we think are relevant to the geological context, and have varied the environmental conditions. This work allows characterizing the adsorption mechanism of nucleotides on mineral surfaces, as well as environmental conditions of the origin of genetic material
Alzheimer's disease neurotoxic peptides : towards a comprehension of their modes of action on model membranes. by Mehdi Azouz( )

1 edition published in 2019 in English and held by 1 WorldCat member library worldwide

Alzheimer's disease is a complex neuropathological disorder that constitutes the prime form of dementia. Intimately related to ageing, it is associated to the gradual loss of memory and cognitive functions in individual suffering from the pathology. With nearly 30 million people concerned today, and the alarming trends predicting this figure to increase fourfold by 2050, Alzheimer's disease will constitute a major burden for our societies in the upcoming decades. The cerebral atrophy occurring within the brain results from slow and progressive neurodegenerative mechanisms triggered many years before the appearance of the first symptoms. Two histopathological markers have been identified as strongly associated to the neurodegeneration: the senile plaques, majorly composed of the amyloid peptide Abeta, and the neurofibrillary tangles, constituted of the abnormally phosphorylated form of Tau protein. These two molecules, hence considered as the main culprits of the disease, are therefore under the spotlight of researchers who try to better understand the respective roles in the neurodegeneration process and uncover therapeutic solutions to a still uncurable disease.One of the promising research axis is focusing on the interplay between these molecules and the plasma membrane as potential interactions could convincingly rationalize the neural cell deaths if they happened to be deleterious. Therefore, investigate these interactions in detail is of primary importance to identify the factors that might drive Abeta and Tau to cause damages on membranes. A strong body of evidences has demonstrated that certain lipids could promote these interactions and are then suspected to be involved into detrimental phenomena. However, numerous results appear to be contradicting and consensual conclusions are still lacking.This PhD was dedicated to the investigation of the effects of Abeta and K18, a key peptide fragment of Tau protein, on membranes with a particular focus on the influence of lipids. The aim of this work was to elucidate the action mechanisms of these peptides.To first comprehend how membrane damages can be induced, we first focused on the solubilising ability of extensively used amphiphile agents: detergents. As a first study, we revealed that the membrane composition and the physicochemical properties of lipids play an important role in driving the solubilisation of the bilayer, a process that can even lead to a selectivity during the lipid extraction.The core part of the project was to visualize the effects of the amyloid peptides Abeta and K18 on supported lipid bilayers as membrane models, using atomic force microscopy as an investigation technique. With its high spatial resolution and its ability to operate in physiological milieu, this approach has shown that the membrane composition could promote membrane disruption induced by Abeta oligomers in a lipid-dependent manner. More importantly, we propose that packing defects at the interface of membrane domains act as adsorption and nucleation sites leading to membrane damages.Using the same strategy, we observed that K18 could also induce solubilisation phenomenon and demonstrated to be sensitive to the aspect of lipid order in membranes.In both cases, we highlighted that these peptides could be detrimental to supported lipid bilayers and that their disruptive abilities, associated to detergent-like mechanisms, were intimately dependent of lipids. We also show that the aggregation, a phenomenon that can lead to the peptides fibrillation can only be triggered in presence of certain lipids.This work provides important insights about the decisive role of membrane composition in modulating interactions with the Abeta and K18. This interplay could constitute one of the numerous factors that promote neurotoxic phenomena, taking part in the complex neurodegenerative processes associated to Alzheimer's disease
 
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Alternative Names
Sophie Lecomte wetenschapper

Languages
French (18)

English (5)