Vita. / Digitized by Kansas Correctional Industries

The aim of this project is to develop strategies for fabrication of carbon electrode surfaces with a view to creating stable and versatile monolayer systems for sensing and other applications. Glassy carbon (GC) electrodes have been successfully modified with versatile monolayers via the electrochemical reduction of aryl diazonium salts. The surfaces modified with diazonium salt monolayers were properly characterised by electrochemistry, AFM and XPS. The rates of heterogeneous electron transfer through organic monolayers on GC, Pyrolysed Photoresist Films (PPF) and gold surfaces have been studied using ferrocene as the redox probe. The diazonium salt monolayers created on GC surfaces demonstrated very stable ability and can serve as a good alternative to alkanethiol selfassembled monolayers on gold electrodes for sensing purposes. Tripeptide Gly-Gly-His modified GC electrodes have been successfully used as the electrochemical copper sensors and were found to be extremely stable. PPF has proved to be a good alternative to the GC electrode for the commercialisation of the fabricated electrochemical sensors. The most important and difficult task of this project is to fabricate glucose biosensors and immunosensors on carbon electrodes. The rigid and conjugated molecular wires (MW) as the efficient conduit for electron transfer, and a molecule with poly(ethylene glycol) chains (PEG) as an insulator for reducing the non-specific protein adsorption were successfully synthesised and introduced in the sensing systems. MW modified on GC electrodes can be used to explore the deeply buried active site of glucose oxidase to achieve direct electron transfer of GOx from the active centre FAD through the MW to the underlying GC electrode, and to fabricate third generation biosensors. The interface comprising mixed monolayers of MW and PEG has the ability to facilitate efficient electron transfer. A label-free immunosensor system has been successfully developed for electrochemical detection of biomolecular pairs such as biotin/antibiotin with low detection limitation based on mixed monolayers of MW and PEG modified GC electrode surfaces. In addition, a displacement assay has shown that the free biotin can compete with the attached biotin for binding antibiotin. SWNTs can be used as an alternative to MW to fabricate another label-free immunosensor system due to the high efficiency of electron transfer that SWNTs have demonstrated.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1956. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 163-170).

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Call number: LD2668 .T4 1978 L546 / Master of Science

Thesis (doctoral)--Westfälische Wilhelms-Universität zu Münster. / Vita. Includes bibliographical references (p. 116-121).

Le motif cyclopropanique est présent dans de nombreux composés bioactifs d'origine naturelle ou non-naturelle auxquels il confère une certaine rigidité structurale, qui permet d'augmenter leur biodisponibilité et leur stabilité métabolique. Par ailleurs, l'atome de fluor possède des propriétés particulières dues entre autres à sa forte électronégativité et sa petite taille. Cela permet de modifier les propriétés physico-chimiques des molécules qui le contiennent, telles que l'acidité, la lipophilie ou encore la solubilité. Par conséquent, les cyclopropanes fluorés représentent des motifs intéressants dans la mesure où ils combinent les propriétés des cyclopropanes et celles de l'atome de fluor. Dans ce contexte, nous nous sommes tout d'abord intéressés à la synthèse énantiosélective de cyclopropanes fluorés polyfonctionnalisés à partir d'oléfines fluorées et de composés diazos, par catalyse au rhodium. Pour cela, deux types de composés diazos ont été utilisés : les diaccepteurs et les donneur-accepteurs. Cette méthodologie a été étendue à la synthèse de cyclopropanes chlorés et bromés. Afin de mettre en valeur les composés ainsi obtenus, nous avons ensuite étudié la synthèse de molécules d'intérêt biologique, et plus précisément de mimes d'aminoacides contenant un cyclopropane fluoré. En effet, leur introduction dans des peptides pourrait permettre d'en modifier la conformation et l'interaction avec les récepteurs biologiques. Dans ce cadre, la synthèse d'un mime de proline contenant un cyclopropane fluoré a été développée. Par ailleurs, un mime de leucine contenant un cyclopropane fluoré a été introduit dans la séquence minimum active de la neurotensine et permet d'obtenir une bonne sélectivité pour le récepteur NTS2, ce qui ouvre des perspectives pour le développement de nouveaux analgésiques possédant moins d'effets secondaires. Pour terminer, nous avons examiné la synthèse de composés diazos en flux continu. A l'heure actuelle, ceux-ci sont peu utilisés dans l'industrie car ils présentent une certaine toxicité, une potentielle explosivité et une instabilité qui limite leur stockage. La chimie en flux continu constitue donc une alternative pour les utiliser, puisque leur synthèse, leur purification et leur mise en réaction se fait en continu sur de petites quantités à la fois et ne nécessite pas d'intervention de la part d'un opérateur. Ainsi, les risques présentés par la montée en échelle de la réaction de cyclopropanation précédemment développée sont fortement diminués. / The cyclopropane ring is present in many natural or non-natural bioactive compounds, whose biodisponibility and metabolic stability is increased by its structural rigidity. Besides, the fluorine atom displays singular properties due to its high electronegativity and its small size. This enables to modify the physico-chemical properties of molecules such as acidity, lipophilicity or solubility. As a consequence, fluorinated cyclopropanes represent interesting scaffolds since they combine the properties of cyclopropanes and fluorine atom. In this context, we were interested in the enantioselective synthesis of polyfunctionalized fluorinated cyclopropanes from fluorinated olefins and diazo compounds under rhodium catalysis. For this purpose, two types of diazo compounds were investigated: diacceptor and donor-acceptor. This methodology was further extended to the synthesis of chlorinated and brominated cyclopropanes. To highlight the versatility of these compounds, we then turned our attention to the synthesis of biorelevant targets, and more precisely aminoacids containing a fluorocyclopropane moiety. Indeed, their introduction into peptides could allow to modify their conformation and interactions with biological receptors. In that aim, the synthesis of an analogue of proline containg a fluorocyclopropane was developed. An analogue of leucine containing a fluorocyclopropane was also introduced in the minimum active sequence of neurotensin and shows a good selectivity for the NTS2 receptor. This opens up prospects for the development of new analgesics with less side effects. Finally, we examined the flow synthesis of diazo compounds. Nowadays, diazo compounds are scarcely used in the industry because they exhibit some toxicity, potential explosibility and instability, which restrict their storage. Flow chemistry may constitute an alternative to use them since their synthesis, purification and reaction is continuously made on small quantities at a time and do not require any manipulation from an operator. Hence, the hazards arising from the scale up of the cyclopropanation reaction are highly reduced.

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