L’attribution des signatures spectrales liées aux défauts dans l’oxyde de zinc fait encore l’objet de controverses. Ceci est probablement dû à la grande variété de défauts possibles, à l’incertitude de leur niveau d’énergie ainsi que leur énergie de formation dans la bande interdite. De plus, l’imprécision concernant les conditions de mesures et la possible présence d’impuretés inhérentes à certaines méthodes de synthèse peuvent souvent mener à des interprétations erronées. Le but de ce travail de thèse est donc d’identifier les défauts intrinsèques naturellement présents dans du ZnO fraîchement préparé ou bien formés via différents types de traitements post-synthèse. Pour atteindre ce but, notre stratégie fut (i) de préparer des nanoparticules modèles de ZnO en utilisant deux types de synthèses en phase vapeur (Combustion et CVS) (ii) de combiner des mesures in situ de photoluminescence (PL) et de RPE, également associées à des spectroscopies complémentaires (Raman, UV visible, FTIR) de façon à révéler, attribuer les défauts et discuter leur comportement selon les conditions de synthèses et de traitements post-synthèse et (iii) de révéler la réactivité des surfaces défectueuses de nos échantillons de ZnO en étudiant leur interaction avec des molécules d’eau ou de 2-méthyl-3-butyn-2-ol (MBOH). Nous avons ainsi observé que VO2+ et Zni+ sont les défauts natifs prédominants dans tous les échantillons fraîchement préparés de ZnO, dans des quantités relatives dépendant de la pression partielle d’oxygène utilisée lors de la synthèse. Les lacunes neutres d’oxygène (VO0) ont également été détectées dans le cas des préparations effectuées dans des conditions particulièrement riches en zinc. VO+ peut se former dans le ZnO smoke après post-traitement (recuit sous vide ou sous vapeur de zinc), la formation d’électrons associée participant à la réduction de Zni+ en Zn0. Au contraire, calciner sous O2 mène à des processus opposés, voire, sous excès d’O2, à la formation de défaut de type Oi. La dissociation de l’eau sur des surfaces préalablement calcinées sous vide mène au remplissage de VO+ et à la réduction de Zn2+ en Zn+. Des tests catalytiques de conversion du MBOH ont montré que de tels processus redox, contrôlés par les conditions de prétraitement, affectent la réactivité de surface de nos matériaux. / By far, the assignment of defects-related spectroscopic features of zinc oxide is still a matter of great controversy. This is probably due to the variety of possible defects in ZnO as well as to their still uncertain formation energies and positions within the band gap. Uncontrolled measurement conditions and impurities related to some synthesis methods can additionally mislead interpretations. The aim of this work is to identify the intrinsic native defects in pure ZnO or formed upon different kind of post-synthesis treatments. To fulfill this goal our strategy was to: i) prepare model zinc oxide nanoparticles using two different vapor-phase synthesis techniques (Combustion and CVS) ii) identify, assign and discuss the occurrence of the defects in line with the synthesis and post treatments conditions by combining in situ PL and EPR measurements together with other complementary spectroscopies (Raman, UV vis, FTIR) and iii) reveal the surface reactivity of defective ZnO samples by studying the interaction with water or 2-methyl-3-butyn-2-ol (MBOH). We observed that in all as-synthesized ZnO samples VO2+ and Zni+ are the predominant native defects with relative amounts depending on the partial pressure of oxygen used during the synthesis. Neutral oxygen vacancies (VO0) are additionally detected in samples prepared in conditions particularly rich in zinc. The formation of Vo+ is demonstrated in ZnO smoke upon post treatment (annealing in high vacuum or zinc vapor) while the associated electron release is shown to participate to the reduction of Zni+ into Zn0. On the contrary, annealing in oxygen leads to reverse processes while if used in an excess, to creation of Oi-related defects. Dissociation of water on vacuum annealed surface leads to the filling up of VO+, and reduction of Zn2+ into Zn+. Such redox processes controlled by the pretreatment conditions affect the surface reactivity through the change of the acid base balance, as revealed by MBOH conversion catalytic tests.

Cette thèse porte sur le développement de nouvelles approches par marquage de spin suivi par spectroscopie RPE. Cette technique est bien adaptée pour suivre la dynamique structurale des protéines. Son principe repose sur l'insertion d'un radical nitroxyde, en un (ou plusieurs) site(s) choisi(s) d'une protéine et permet de sonder localement la structure de la protéine étudiée grâce aux différentes techniques de RPE (en onde continue et impulsionnelle).Dans une première partie, cette technique a été appliquée à la caractérisation de la dynamique structurale de l'IF1 de levure, un peptide inhibiteur de l'ATP-synthase. L'utilisation des spectroscopies de RPE et de dichroïsme circulaire a permis de montrer qu'IF1 de levure dimérise par sa partie médiane et que la partie C-terminale est désordonnée.La seconde partie est plus méthodologique et a pour but d'étudier et de caractériser un marqueur nouvellement synthétisé afin d'élargir les potentialités du marquage de spin. En effet, cette technique est notamment limitée par la faible diversité spectrale offerte par les sondes disponibles (trois raies). Le nouveau marqueur donne un spectre RPE à six raies grâce à la présence d'un noyau magnétique dans l'environnement du radical. Greffé sur une protéine modèle, nous avons montré que ce nouveau marqueur est tout autant capable de rendre compte de variations structurales qu'un marqueur classique. La superposition des signatures spectrales (trois raies + six raies) montre qu'il est possible de différencier les deux signatures spectrales et de sonder simultanément deux sites d'une protéine et de son partenaire. / This thesis focuses on the development of new approaches for site-directed spin labeling followed by EPR spectroscopy. This technique is well suited to monitor the structural dynamics of proteins. The insertion of a nitroxide radical, in one (or several) selected site(s) of a protein, allows probing the structure of the protein using different EPR spectroscopy approaches (continuous wave and pulsed).In a first part, this technique has been applied to characterize the structural dynamics of the yeast IF1, an inhibitory peptide of the ATP-synthase. Using EPR and circular dichroïsm spectroscopies we showed that yeast IF1 dimerizes by its central part and that the C-terminal part remains disordered.The second part is more methodological and the aim is to study and characterize a newly synthesized spin label in order to expand the potential of site-directed spin labeling. In particular, the technique is limited by the poor spectral diversity offered by the available labels (three lines). The new label gives a six lines EPR spectrum thanks to the presence of a magnetic nucleus in the environment of the radical. Grafted on a model protein, we demonstrated that this new label is as able as classical ones to report on structural variations. The superposition of the spectral signatures (three lines + six lines) showed that it is possible to differentiate the two spectral signatures and to probe two sites of a protein and its partner simultaneously.

Les hydrogénases sont des métalloenzymes qui catalysent la conversion réversible du dihydrogène en protons et en électrons. Durant ma thèse, je me suis focalisé sur certains aspects du fonctionnement de l’hydrogénase à [NiFe] hétérodimérique de Desulfovibrio fructosovorans. Nous avons montré que contrairement au mécanisme communément admis d’inactivation aérobie de l’enzyme, l’O2 n’est pas incorporé en tant que ligand au niveau du site actif mais agit plutôt comme un simple oxydant. Ce résultat remet en question le mécanisme proposé pour expliquer la tolérance naturelle à l’O2 de certaines hydrogénases. L’analyse à l’aide d’un modèle cinétique des voltamogrammes cycliques complexes obtenus avec 16 variants a montré que les vitesses d’(in)activation en conditions anaérobies peuvent être accélérées de plusieurs ordres de grandeurs. Nous avons aussi montré et expliqué la corrélation entre ces vitesses et la tolérance à l’O2. Nous avons étudié une série de mutants qui produisent H2 beaucoup plus lentement que l’enzyme sauvage. Nous avons montré que la vitesse de cette réaction est déterminée par celle de l’étape de diffusion du H2, qui est lente dans les mutants. Finalement, nous nous sommes intéressés à une thréonine appartenant à la voie putative de transfert des protons. Nous avons démontré que cet acide aminé est effectivement impliqué dans le transport des protons. Il joue aussi un rôle crucial dans la stabilisation des intermédiaires formés au cours du cycle catalytique et probablement dans la détermination des vitesses de transfert électronique et de diffusion à travers le canal. / Hydrogenases are metalloenzymes which catalyse the reversible conversion of dihydrogen into protons and electrons. In my work, I focused on some aspects of the catalytic mechanism of the heterodimeric NiFe hydrogenase from Desulfovibrio fructosovorans. We demonstrated that, contrary to the commonly accepted mechanism of aerobic inactivation, the attacking O2 is not incorporated as an active site ligand but rather acts as an electron acceptor. This finding calls for a re-examination of the mechanism for O2 tolerance of the natural O2 tolerant NiFe hydrogenases. We also described a simple analytical model that we used to analyse the complex voltammetric signals of 16 mutants obtained by substituting an amino acid near the active site. We demonstrated that this substitution can accelerate anaerobic inactivation and reactivation by up to three orders of magnitude. We also demonstrated and explained the correlation between these rates and O2-tolerance. We studied mutants whose H2-production activity is impaired. We found that the rate limiting step of this reaction is the diffusion of hydrogen out of the enzyme, through the hydrophobic channel. Finally, we focused on a threonine belonging to the putative proton transfer pathway. We demonstrated that this amino acid is indeed implicated in proton transport. It may also play a crucial role in the stabilization of intermediates formed during the catalytic cycle, and probably also in determining the rate of electron transfer and diffusion along the gas channel.

Os hormônios peptídicos Angiotensina II (Ang II) e bradicinina (BK) ativam transdução de sinal através da ligação a Receptores Acoplados a Proteínas G (GPCR). Este trabalho propõe o estudo de propriedades conformacionais, através de espectroscopia de fluorescência da Ang II e BK e de seus análogos contendo o marcador de spin ácido 2,2,6,6-tetrametilpiperidina-1-oxil-4-amino-4-carboxílico, TOAC (TOAC1-Ang II, TOAC3-Ang II, TOAC0-BK, TOAC3-BK). Os peptídeos foram estudados em solução (efeito do pH) e também na presença de membranas modelo, micelas e bicamadas, formadas por anfifílicos zwitteriônicos ou aniônicos. Foi monitorada a fluorescência intrínseca dos resíduos aromáticos (Tyr4 na Ang II e Phe5 e Phe8 na BK). O efeito de supressão da fluorescência pelo TOAC foi utilizado para obter informação sobre a proximidade desse resíduo aos grupos fluoróforos. Foi observada dependência da fluorescência com o pH e regiões de pKs dos grupamentos ionizáveis. Os espectros evidenciaram também a interação peptídeo-membrana modelo. Interações mais fortes ocorreram entre os peptídeos e membranas com carga superficial negativa, evidenciando a importância de interações eletrostáticas para a ligação. Porém, interações hidrofóbicas também estão envolvidas, como verificado pela ligação dos peptídeos a membranas zwitteriônicas. Estudos com variação de pH também mostraram o papel dessa variável na interação peptídeo-membrana e a alteração de pKs de resíduos ionizáveis decorrentes da interação. A titulação com concentrações crescentes de membranas permitiu o cálculo das constantes de associação. A ligação a membranas é função da conformação dos peptídeos. Em particular, a presença de TOAC na posição 3 parece diminuir a afinidade desses análogos por membranas. Supressão de fluorescência foi efetuada empregando três diferentes abordagens: 1) supressão pela molécula aquossolúvel acrilamida, 2) supressão da fluorescência de fosfolipídeos contendo o fluoróforo NBD em diferentes posições da molécula pelos análogos marcados com TOAC, 3) supressão da fluorescência dos peptídeos por ésteres metílicos do ácido esteárico contendo o grupamento nitróxido em diferentes posições da cadeia. Esses estudos permitiram determinar a localização dos peptídeos na interface água-membrana. Medidas de anisotropia de fluorescência também evidenciaram a ligação dos peptídeos a membranas, revelando maior imobilidade dos mesmos nessas condições. Foi ainda estudado um peptídeo que contém os resíduos 92-100 (fEL1) do receptor AT1 de Ang II humano. Predições baseadas na estrutura cristalina da rodopsina estimam que essa seqüência localiza-se na primeira alça extra-celular do receptor. A seqüência contém a Tyr92, considerada um resíduo importante para a ligação hormônio-receptor. Resultados preliminares sugeriram que fEL1 interage com Ang II e TOAC1-Ang II, mas não com TOAC3-Ang II. Este último resultado provavelmente deve-se à dobra causada por TOAC que restringe a liberdade de movimento do esqueleto peptídico. Essa característica provavelmente determina a falta de atividade biológica de TOAC3-Ang II e TOAC3-BK, enquanto os análogos marcados no N-terminal retém atividade parcial (Nakaie et al., 2002). Tem sido proposto que peptídeos ligantes de GPCR se ligariam à bicamada lipídica e atingiriam seu receptor através da difusão pela bicamada. Em solução aquosa essas moléculas são flexíveis, existindo um equilíbrio dinâmico entre várias conformações. A ligação à bicamada lipídica estabilizaria uma ou algumas conformações, entre elas aquela que o ligante adota ao ligar-se ao receptor. O presente estudo contribui para a compreensão, a nível molecular, do processo de interação entre os hormônios peptídicos e membranas lipídicas. / The peptide hormones Angiotensin II (Ang II) and bradykinin (BK) trigger signal transduction by binding to G Protein Coupled Receptors (GPCR). This work proposes the study of conformational properties of Ang II and BK, as well as their analogues containing the spin label 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid, TOAC (TOAC1-Ang II, TOAC3-Ang II, TOAC0-BK, TOAC3-BK) making use of fluorescence spectroscopy. Studies were performed in solution (effect of pH) and also of the interaction between the peptides and model membranes - micelles and bilayers - formed by amphiphiles, either zwitterionic or negatively charged. The intrinsic fluorescence of aromatic residues (Tyr4 in Ang II and Phe5 and Phe8 in BK) was monitored. Fluorescence quenching by the TOAC-carrying analogues provided information about the proximity between TOAC and the fluorophores. The fluorescence was pH-dependent and evinced regions corresponding to pKs of ionizable groups. Peptide-model membrane interactions were also examined. Stronger interactions were detected between the peptides and membranes formed by negatively charged amphiphiles, pointing to the importance of electrostatic interactions for binding. However, hydrophobic interactions were also involved, as suggested by the fact that the peptides also bound to zwitterionic membranes. Variable pH studies showed the effect of this parameter on peptide-membrane interaction. The peptide-membrane interactions promoted changes in the pKs of ionizable residues. Titrations with increasing membrane concentrations allowed calculation of binding constants. Binding to membranes is a function of peptide conformation. In particular, TOAC at position 3 seems to decrease the affinity of both Ang II and BK for membranes. Fluorescence quenching studies made use of three different approaches: 1) quenching by water soluble acrylamide, 2) quenching of the fluorescence of phospholipids carrying the fluorescent group NBD in different positions by the spin-labeled TOAC-bearing analogues, 3) quenching of the peptides fluorescence by methyl esters of stearic acid containing the nitroxide moiety at different positions in the acyl chain. These studies indicated that the peptides are located at the water-membrane interface. Measurements of fluorescence anisotropy also evinced binding of the peptides to the membranes and showed that the peptides undergo more restricted motion under these conditions. A peptide containing residues 92-100 (fEL1) of the Ang II AT1 human receptor was also studied. Predictions based on rhodopsin crystalline structure estimate that this sequence is located in the receptor´s first extra-cellular loop. Preliminary results suggest that fEL1 interacts with Ang II and TOAC1-Ang II, but not TOAC3-Ang II. This latter result is probably due to the TOAC-induced bend that restricts the freedom of motion of the peptide backbone. This feature is probably the cause of lack of biological activity of TOAC3-Ang II and TOAC3-BK, while the N-terminally labeled analogues retain partial activity (Nakaie et al., 2002). GPCR-binding peptides have been proposed to bind to the lipid bilayer and reach their receptors by diffusion in the bilayer. In aqueous solution these molecules exist as a dynamic equilibrium between various flexible conformations, among them, the receptor-bound conformation. The present study provides contributions for the understanding, at the molecular level, of the interaction between the peptide hormones and lipid membranes.

Les métaux sont impliqués dans de nombreux processus biologiques essentiels pour le vivant. Ils interviennent au sein de métallo-enzymes sélectives et efficaces, qui catalysent des réactions chimiques dans des conditions douces. Les plus illustres sont les RiboNucléotide Réductases (RNR), essentiels à la synthèse de l'ADN, ou bien encore la Méthane MonoOxygènase (MMO) capable à partir du méthane de former le méthanol, molécule à fort potentiel énergétique. Ces métallo-enzymes fonctionnent au travers d'un site actif contenant deux fers. Récemment, un nouveau membre de cette famille a été isolé et présente un nouveau site actif hétérodinucléaire à fer et manganèse. Le potentiel chimique de ces enzymes commence juste a être caractérisé, mais les premières études suggèrent une réactivité semblable aux enzymes homodinucléaires à fer. Puisque le comportement de l'ion métallique dans les protéines n'est pas très différent de la chimie fondamentale du métal, l'étude de petits analogues synthétiques de site actif est particulièrement utile. Nous proposons la synthèse de complexes dinucléaires à Fe-Mn pour étudier la réactivité et les propriétés électroniques de ce nouveau site actif. Par une étude physicochimique approfondie et des études de réactivités, nous avons apporté une meilleure compréhension sur la réactivité de ce nouveau système enzymatique. / Nonheme enzymes possessing a dinuclear active site are performing many essential functions such as Ribonucleotide reductase (RNR) in DNA production and Methane oxygenation (MMO) to convert gas toxic methane in combustible methanol. While most of these enzymes have been shown to possess a diiron active site, new members of this protein family were recently isolated from bacteria and found to possess instead a heterodinuclear Fe-Mn active site. The chemical potential of the heterodinuclear metal site is just starting to be evaluated, but available data suggest that it may have capabilities for similarly versatile chemistry as the extensively studied diiron-carboxylate cofactor. In recent years, the study of models based on simple dinuclear metal complexes has became an important tool for gaining insight into the biological functions of such bimetallic cores. The design of binucleating ligands capable of providing asymmetric dinuclear complexes is a subject of great interest. We propose to synthesize dinuclear Fe-Mn complexes to investigate the reactivity and the electronic properties of this new active site. By combining spectroscopic and electronical studies we have gain a better understanding on the reactivity of this new enzymatic system.

No description available.

Bei der Altersabhängigen Makuladegeneration (AMD) handelt es sich um eine Erkrankung des Auges, die die Macula lutea, die Stelle des schärfsten Sehens betrifft. Sie ist verbunden mit der Degeneration von RPE-Zellen, die zur Dystrophie von Photorezeptoren und damit zum Verlust des zentralen Sehvermögens führt. Eine ähnliche Pathophysiologie ist bei der sogenannten Retinalen Pigmentepitheldystrophie (RPED) des Hundes zu beobachten. Die Transplantation von gesunden RPE-Zellen in das betroffene Gebiet stellt eine vielversprechende Therapiemöglichkeit dar. Die Transplantatabstoßung als Kom-plikation schränkt die klinische Anwendung ein. Eine beim Patienten nach Transplantation lebenslang durchgeführte systemische Immunsuppression ist mit erheblichen Nebenwirkungen verbunden. Deshalb bietet die Gentherapie unter Einbezug immunsuppressiver Zytokine wie beispielsweise des Interleukin-10 (IL-10) eine Lösung. In der vorliegenden Arbeit wurde ein selbst konstruierter IL-10-Expressionsvektor (Plasmid pCIneoIL-10) mittels Gentransfer in humane RPE-Zellen in vitro eingebracht. Untersucht wurde die Wirkung des sezernierten IL-10 auf die Proliferation von allogenen T-Lymphozyten mit und ohne allogene Makrophagen als professionelle antigenpräsentierende Zellen (APC). Neben humanen Spender RPE-Zellen (Spender-hRPE-Zellen) wurde eine immortalisierte Permanent-Zelllinie (hTERT-RPE1-Zellen) eingesetzt, deren Hauptvorteil in einer gleichbleibend hohen Wachstumsrate lag. Als transientes Transfektions-system für den Transfer von IL-10-DNA in hRPE-Zellen wurden kationische Lipide gewählt. Drei verschiedene Lipidformulierungen wurden miteinander verglichen und das optimale Transfektionsreagenz:DNA-Verhältnis, mit dem die höchste Transfektionseffizienz erreicht werden konnte, evaluiert. Eine Transfektionseffizienz von 23,3 ± 9,0 % (hTERT-RPE1-Zellen) beziehungsweise 10,3 ± 4,5 % (Spender-hRPE-Zellen) konnte erreicht werden. Die Transfektion hatte weder einen negativen Einfluss auf die Vitalität der hRPE-Zellen, noch wurde der natürliche Zelltod, die Apoptose, erhöht. Die IL-10-mRNA-Expression wurde mittels RT-PCR nachgewiesen. Lediglich bei den transfizierten hRPE-Zellen konnte IL-10-mRNA gefunden werden. Mittels ELISA konnte das IL-10-Protein gemessen werden. Die Sekretion des IL-10 in den Kulturüberstand von transfizierten hRPE-Zellen wurde dafür über einen Zeitraum von 7 Tagen untersucht. Es konnte festgestellt werden, dass die maximale IL-10-Proteinkonzentration bei beiden Zelllinien am Tag 3 mit Werten von 10,3 ± 0,8 ng/ml (hTERT-RPE1-Zellen) und 3,1 ng/ml (Spender-hRPE-Zellen) lag. Es bestand überdies eine positive Korrelation zwischen Transfektionseffizienz und synthetisiertem IL-10. Es wurde außerdem gezeigt, dass durch Stimulation mit dem immunmodulatorischen Zytokin Interferon-gamma (IFN-g) hRPE-Zellen MHC Klasse II-Moleküle vermehrt exprimierten. Damit sind sie ebenso wie die Makrophagen zur Antigenpräsentation fähig. Die Wirkung des von den transfizierten hRPE-Zellen sezernierten IL-10 auf die Proliferation von T-Lymphozyten wurde zwischen Tag 2 und Tag 6 (hTERT-RPE1-Zellen) beziehungsweise zwischen Tag 2 und Tag 4 (Spender-hRPE-Zellen) photometrisch untersucht. Die Proliferation allogener T-Lymphozyten mit beziehungsweise ohne Makrophagen konnte durch das sezernierte IL-10 supprimiert werden. Bei den hTERT-RPE1-Zellen lag ohne die Anwesenheit von professionellen APC am Tag 6 eine signifikante Reduktion der T-Lymphozytenproliferation vor, während bei Kokultivierung mit Makrophagen Signifikanzen am Tag 5 und Tag 6 erkennbar waren. Die immunsuppressive Wirkung von IL-10 konnte mittels Anti-IL-10-Antikörper neutralisiert werden. Damit wurde bewiesen, dass die proliferations-supprimierende Wirkung auf IL-10 zurückzuführen war. Diese Ergebnisse könnten demnach neue Möglichkeiten zur Verhinderung einer Abstoßungsreaktion nach RPE-Zelltransplantation bei Patienten mit AMD eröffnen / Age-related macular degeneration (AMD) is a disease of eyes affecting the macula lutea, the area of the retina with the highest density of retinal pigment epithelial cells (RPE cells). The disease is characterized by degeneration of RPE cells resulting in dystrophy of photoreceptors and finally loss of central vision. Transplantation of healthy RPE cells is a promising possibility for therapy but rejection of the allotransplant limits clinical application. One way to avoid this complications is a systemic immunosuppression of the recipient but this is combined with many side effects. In this thesis a self-constructed IL-10 expression vector (plasmid pCIneoIL-10) has been transferred into human RPE cells in vitro by gene transfer. In addition to human donor RPE cells a permanent RPE cell line (hTERT-RPE1 cells) was employed. Kationic lipids were used as transient transfection system for transfer of pCIneoIL-10 into hRPE cells. Three different lipid formulations and various ratios of transfection reagent:DNA were evaluated for highest transfection efficacy. With the optimized protocols a transfection efficacy of 23,3 ± 9,0 % (hTERT-RPE1 cells) and 10,3 ± 4,5 % (donor hRPE cells) was achieved. A negative influence on the viability of the hRPE cells after transfection was not observed. The IL-10 mRNA expression was analysed by reverse transcription-polymerase chain reaction (RT-PCR). Only in transfected hRPE cells the IL-10 mRNA-amplicon with 383 bp in size was found. Secretion of IL-10 protein in the cell culture supernatants of transfected hRPE cells was investigated using an enzyme-linked immunosorbent assay (ELISA) daily for 7 days. The IL-10 protein concentrations peaked at day 3 with 10,3 ± 0,8 ng/ml (hTERT-RPE1 cells) and 3,1 ng/ml (donor hRPE cells). The amount of secreted IL-10 positively correlated with transfection efficacy. After stimulation with the immunmodulatory cytokine interferon-gamma (IFN-g) the expression of MHC class II molecules on hRPE cells is increasing. Therefore they are able to present antigens similar to macrophages. Hence, the effects of recombinantly expressed IL-10 on the proliferation of allogeneic T lymphocytes were investigated both with and without allogeneic macrophages as professional antigen presenting cells (APC). Proliferation of T lymphocytes has been investigated colorimetrically between day 2 and day 6 (hTERT-RPE1 cells) and day 2 and day 4 (donor hRPE cells) respectively. The proliferation of allogeneic T lymphocytes with and without macrophages could be suppressed by the secreted IL-10. Signifikant reduction of proliferation was observed at day 6 in absence of professional APC (14,1 ± 1,1 % to 100% of untransfected control) and between day 5 (44,1 ± 4,9 %) and day 6 (37,4 ± 6,3%) in the presence of macrophages. It was possible to neutralize the immunosuppressive effect of IL-10 with anti-IL-10 antibodies. Proving that the suppressive effect of T lymphocyte proliferation was caused by IL-10. Thus, the specific IL-10 gene transfer into hRPE cells prior to transplantation may prevent rejection process and could prove a reliable method to help prevent loss of central vision due to AMD.

The retinal pigment epithelium (RPE) is a monolayer of cells located directly behind the photoreceptor cells in the retina. These cells are involved in a variety of functions that support the visual process in the eye, namely 1) they form a blood-retina barrier which separates the neural retina from the choroid's blood supply, 2) the apical processes of RPE cells diurnally phagocytose the outer segments of photoreceptor cells, and 3) they participate in the renewal of the photopigment 11-cis retinal. Age-related macular degneration (AMD) is the leading cause of blindness in people over the age of 50 years in North America and other developed countries. AMD involves the death of retinal pigment epithelial (RPE) cells in the macula early in the progress of the disease. Like some other postmitotic cells, the RPE accumulates autofluorescent lysosomal storage bodies (lipofuscin) during senescence. Lipofuscin is reported to begin accumulating in the human RPE around age 20 and continues to accumulate throughout an individual's life. This progressive accumulation of lipofuscin can eventually occupy a substantial fraction of the RPE cytoplasmic volume and may lead to impairment of normal RPE functions, resulting in retinal degeneration and loss of visual function as in AMD. Another autofluorescent granule that accumulates in RPE cells and may contribute to the etiology of AMD is a complex granule exhibiting properties of both melanosomes and lipofuscin granules called melanolipofuscin (MLF). In contrast with the accumulation of LF in the RPE, MLF accumulation has been reported by Feeney-Burns to more closely reflect the onset of AMD. Although there have been significant advances in our understanding of AMD, knowledge of the mechanisms responsible for its progression remain unclear. This dissertation details experiments that were designed to better understand the factors that may play a causal role in AMD as well as the development of methods to assist in AMD research. Specifically, the protein composition of retinal LF was assessed to elucidate its origin. These findings are reported in chapter 2. The accumulation, composition and phototoxicity of MLF were analyzed to assess MLF's origin and possible contribution to AMD. These results are reported in chapter 3. Because protein oxidation is possibly a common posttranslational modification to proteins which accumulate in lipofuscin and melanolipofuscin granules, a method for the detection and analysis of oxidized proteins was developed and is reported in chapter 4. Chapter 5 details the proteomic differences between ARPE-19 cells - the only human RPE cell line available for research - in their differentiated and undifferentiated states and compares these to the proteome of human RPE cells. These results are also compared to the phenotypic difference of these cells as observed by transmission electron microscopy.

This thesis is divided into two parts.Part I describes the organic extraction, separation, and liquid chromatographic-mass spectrometric analysis of chromophores from human and bovine retinal pigment epithelium. Flurorophores in the retinal pigment epithelium have been implicated in age related macular degeneration. In addition, the synthesis and characterization of a number of bis-retinoid type compounds that may potentially be found in such extracts, or that may be used for insight into pyridinium bis-retinoid reactivity, was accomplished.Part II describes a study of pyridinium bis-retinoid-folic acid coupling with respect to linker type, linker length, and nature of the linkage. Folic acid has been used as a targeting compound for a variety of cancer types. Development of HPLC and UV-Vis conditions suitable for the analysis of this new type of macromolecule was performed.

No description available.