Phosphonic acids are known to bind strongly to a variety of metal oxide surfaces. Phosphonic acids were designed in order to impart specific properties to the surface of a range of metal oxides upon formation of a monolayer. A large number of novel phosphonic acids were synthesized and fully characterized. The binding of phosphonic acids to the surface of several metal oxides, such as indium tin oxide (ITO) and barium titanate, was studied in detail and determined to be a mixture of bidentate and tridentate binding modes. The modification of several key surface properties of ITO by phosphonic acid modification was also studied. The work function of ITO could be increased or decreased with respect to unmodified ITO by controlling the dipole of phosphonic acids bound to the surface. Additionally, the surface energy could be substantially lowered by attaching phosphonic acids with non-polar terminal functional groups to the ITO surface. The ability to control these surface properties resulted in organic light-emitting diodes (OLEDs) which showed superior lifetimes and stability with respect to OLEDs incorporating ITO without a phosphonic acid monolayer. In addition, the binding of phosphonic acids to a number of other oxides, such as zinc oxide and zeolites, was also studied.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 197-202). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 197-202). Also available on the Internet.

Different approaches to surface modification were investigated in this work on gold, glassy carbon, multi-walled carbon nanotube paper and on single-walled carbon nanotubes adsorbed on glassy carbon. These approaches include electrochemical grafting, electropolymerisation, click chemistry, axial ligation, adsorption and self-assembled monolayers. The modified surfaces were characterised using a variety of techniques; predominantly electrochemistry, scanning electrochemical microscopy and X-ray photoelectron spectroscopy. For the formation of self-assembled monolayers on gold, four new manganese(III) phthalocyanines (1a-d), octa-substituted at the peripheral position with pentylthio, decylthio, benzylthio, and phenylthio groups were synthesized and characterised. X-ray photoelectron spectroscopy was used to show the formation of a sulphur-gold bond. A number of approaches using 4-azidoaniline (2a) combined with azide-alkyne click chemistry and electrochemistry were also used to anchor ferrocene and pyridine moieties on to the carbon surfaces, including direct in situ diazotation and grafting, electropolymerisation, and the synthesis of the diazonium salt followed by grafting. Iron phthalocyanine was linked to the pyridine-clicked surfaces through axial ligation, where the strong axial bond formed by the interaction between the central metal and the lone pair of the nitrogen in the pyridine group resulted in stable modified electrodes. The potential of these surfaces for the detection of analytes such as thiocyanate, hydrazine and sulphite are briefly shown as well. This work also describes for the first time the possibility of performing local micro-electrochemical grafting of a gold substrate by 4-azidobenzenediazonium (2b) using scanning electrochemical microscopy in a single and simple one step approach, without complications from adsorption.

No description available.

Fabrication of surfaces with versatile functional groups is an important research area. Hence, it is essential to control and tune the surface properties in a reliable manner. Vinyl-terminated self-assembled monolayers (SAMs) offer significant flexibility for further chemical modification and can serve as a versatile starting point for tailoring of surface properties. Here a synthetic route for the preparation of vinyl-terminated trichlorosilane self-assembling molecules: 9-decenyltrichlorosilane (CH₂=CH-(CH₂)₈-SiCl₃), 10-undecenyltrichlorosilane (CH₂=CH-(CH₂)₉-SiCl₃), and 14-pentadecenyltrichlorosilane (CH₂=CH-(CH₂)₁₃-SiCl₃) is presented. These molecules were used for the preparation of SAMs in either liquid or vapour phase processes. Commercially available methyl-terminated self-assembling molecules: decyltrichlorosilane (CH₃-(CH₂)₉-SiCl₃) and octadecanetrichlorosilane (CH₃-(CH₂)₁₇-SiCl₃) were used as controls. The resultant films were characterised by X-ray photoelectron spectroscopy (XPS), contact angle analysis, ellipsometry, and atomic force microscopy (AFM). Well defined, vinyl-terminated SAMs were further chemically modified with carbenes (:CCl₂, :CBr₂, :CF₂) and hexafluoroacetone azine (HFAA). The reactions were performed in the liquid or the vapour phase. The resulting SAMs were characterised using the same methods as for the vinyl-terminated monolayers. Successful modification was confirmed by the appearance of new signals in the XPS spectrum, with simultaneous changes in water contact angle values and unchanged thickness values. Methyl-terminated SAMs were also exposed to carbenes and HFAA as a control system. These are the first examples of C-C bond formation on SAMs in the vapour phase.

Cette thèse présente une étude de films monomoléculaires d'acides gras à l'interface eau-air, principalement par microscopie à l'angle de Brewster. Cette technique permet l'observation directe des coexistences de phases lors de transitions de phases du premier ordre; de plus elle est sensible à l'anisotropie optique des films. La première partie contient une étude du diagramme de phase des acides gras, qui comporte des mésophases analogues aux phases de cristaux liquides smectiques. Nous avons montré que lors des transitions de phases entre phases denses, la texture (l'arrangement moléculaire)des phases est réversible et nous avons obtenu des informations sur l'ordre des transitions. Nous avons aussi mis en évidence, dans deux phases constituées de molécules verticales, une très faible anisotropie optique due à la forme rectangulaire du réseau moléculaire. Nous avons ensuite étudié une film d'acide myristique adsorbé à la surface d'une solution aqueuse d'acide myristique. Nous avons observé des domaines d'une mésophase "inclinée" contenant des lignes de défauts d'orientationmoléculaire présentant des fluctuations thermiques. La mesure de leur amplitude a permis de déterminer la tension de ces lignes. Nous nous sommes aussi intéressés aux constantes élastiques qui gouvernent la forme et la texture à l'équilibre des domaines de mésophase. Nous avons d'une part déterminé la tension de ligne de l'interface entre une phase liquide et une mésophase "inclinée" en étudiant la forme des domaines. Celle-ci résulte de l'équilibre entre la tension de ligne, qui favorise des domaines circulaires, et les interactions répulsives à longue portée entre dipoles moléculaires, qui forment les domaines. Des mesures de potentiel de surface ont permis de calculer l'intensité des forces dipolaires. d'autre part, la texture d'autre domaines de cette mésophaseinclinée nous a renseigné sur la valeur du rapport entre l'élasticité de courbure de la direction moléculaire et l'anisotropie de la tension de ligne.

La microscopie à l'angle de Brewster est une nouvelle et tres puissante technique d'étude des films monomoléculaires à la surface de l'eau. Son principe est basé sur les propriétés de réflectivité des interfaces. Elle est sensible à l'épaisseur, la densité et l'anisotropie optique des films. Cette technique a été appliquée à l'étude de couches adsorbées à la surface de solutions aqueuses d'acides gras (acides palmitiques et myristiques). Ces couches traversent pendant leur formation des transitions de phases. Le nombre, la nature et la morphologie de ces phases dépendent de nombreux paramètres dont le pH. Nous avons entre autres observé des phases optiquement anisotropes, contituées de molécules inclinées par rapport à la normale à la solution.Ces phases sont sans doute des mésophases "verrouillées", c'est à dire que la direction des molécules est fixée par rapport aux directions intermoléculaires. Elles présentent différents types de défauts d'orientation, dont des structures en étoile. L'existence de telles structures est expliquée par application d'un modèle d'élasticité continue développé pour l'étude des films minces de cristaux liquides smectiques. Des structures en zig-zag, en spirales et en bandes de largeur déterminée ont également été observées. Nous avons également étudié les couches d'un polymère (le PDMS) à la surface de l'eau. Nous y avons observé la séparation latérale en domaines de densités de surface différentes, à la fois dans le régime monocouche et le régime multicouches.

L'une des particularités de Mycobacterium tuberculosis, agent pathogène de la tuberculose, est sa capacité à accumuler des lipides dans son cytoplasme, ce qui favorise son entrée en dormance. Le séquençage du génome de M. tuberculosis a permis d'identifier certains gènes codant pour des enzymes lipolytiques, parmi ceux-ci : le gène codant pour la protéine Rv3097c aussi appelée LipY (composée d'un domaine PE et d'un domaine lipase relié par un Linker). Dans la première partie de ce travail de thèse, nous avons procédé à la caractérisation biochimique de LipY, mais aussi de ses formes mutantes LipY(∆PE), LipY(∆149) et LipY(∆170), et à l'étude d'inhibition des membres de la famille Lip apparentés à la lipase hormono-sensible humaine (Lip-HSL). Nous avons pu déterminer les propriétés cinétiques de l'activité lipase de LipY et de ses différentes formes mutantes.Dans la seconde partie, nous nous sommes intéressés à la compréhension du rôle des différents domaines de LipY, et du linker dans l'hydrolyse des lipides au cours de l'infection en utilisant des macrophages spumeux (macrophage riche en lipides) infectés au préalable par des souches de M. bovis BCG recombinantes. Ces résultats et les hypothèses posées durant ce travail de thèse, pourraient être appuyés par l'obtention de la structure tridimensionnelle de LipY. Pour cela, nous avons initié et procédé à la cristallogenèse de LipY. La poursuite des études d'optimisation des cristaux obtenus pourrait permettre d'aller plus en profondeur dans l'élucidation du rôle et du mécanisme d'action de LipY. / Mycobacterium tuberculosis is a pathogenic agent, responsible of the tuberculosis, which can store lipids into the cytoplasm. This accumulation allows the bacteria to enter in the dormancy phase. The sequencing of M. tuberculosis genome, allows to identify some genes coding for lipolytic enzymes, among which a gene coding for Rv3097c protein, also called LipY. (possessing PE domain linkto a lipase domain). During my PhD thesis, we first biochemically characterized LipY and its mutant forms LipY(ΔPE); LipY(Δ149) and Lip(YΔ170) and studied the inhibition of Lip family members related to the human hormone-sensible lipase (Lip-HSL). We determined the kinetic properties for the lipase activity of LipY and its mutants. In the second part, based on these previous results, we studied the role of these different domains and the linker on the hydrolysis of lipids during the infection phase, in infected foamy macrophages (lipids rich). For these studies, we used foamy macrophages infected by recombinants strains of M. bovis BCG (LipY(wt) and its mutants.These results and hypothesis can be confirmed and supported by resolving the tridimensional structure of LipY. Crystallogenesis tests allowed us to have some crystals of LipY(wt), which after optimization would allow us to have a better understanding of the role and action mechanism of LipY.

Indiana University-Purdue University Indianapolis (IUPUI) / Cell membranes have remarkable properties both at the microscopic level and the molecular level. The current research describes the use of physisorbed polymer-grafted lipids in model membranes to investigate some of these properties on both of these length scales. On the microscopic scale, plasma membranes can be thought of as heterogenous thin films. Cell membranes adhered to elastic substrates are capable of sensing substrate/film mismatches and modulating their membrane stiffness to more closely match the substrate. Membrane/substrate mismatch can be modeled by constructing lipopolymer-enriched lipid monolayers with different bending stiffnesses and physisorbing them to rigid substrates which causes buckling. This report describes the use of atomic force microscopy and epimicroscopy to characterize these buckled structures and to illustrate the use of the buckled structures as diffusion barriers in lipid bilayers. In addition, a series of monolayers with varying bending stiffnesses and thicknesses are constructed on rigid substrates to analyze changes in buckling patterns and relate the experimental results to thin film buckling theory. On the molecular scale, plasma membranes can also be thought of as heterogeneous mixtures of lipids where the specific lipid environment is a crucial factor affecting membrane protein function. Unfortunately, heterogeneities involving cholesterol, labeled lipid rafts, are small and transient in live cells. To address this difficulty, the present work describes a model platform based on polymer-supported lipid bilayers containing stable raft-mimicking domains into which transmembrane proteins are incorporated (αvβ3, and α5β1integrins). This flexible platform enables the use of confocal fluorescence fluctuation spectroscopy to quantitatively probe the effect of cholesterol concentrations and the binding of native ligands (vitronectin and fibronectin for αvβ3, and α5β1) on protein oligomerization state and on domain-specific protein sequestration. In particular, the report shows significant ligand-induced integrin sequestration with a low level of dimerization. Cholesterol concentration increases rate of dimerization, but only moderately. Ligand addition does not affect rate of dimerization in either system. The combined results strongly suggest that ligands induce changes to integrin conformation and/or dynamics without inducing changes in integrin oligomerization state, and in fact these ligand-induce conformational changes impact protein-lipid interactions.