ED Sciences Chimiques
Organic photosensitizers for photoelectrochemical cells based on metal oxide semiconductor of delafossite structure: toward sustainable hydrogen production
by Quentin STEMBAUER (Institut des Sciences Moléculaires)
The defense will take place at 10h00 - Amphithéâtre 87 Avenue du Docteur Schweitzer, ICMCB, 33608, Pessac
in front of the jury composed of
- Thierry TOUPANCE - Professeur des universités - Université de Bordeaux - Directeur de these
- Aline ROUGIER - Directrice de recherche - CNRS - ICMCB Bordeaux - CoDirecteur de these
- Sylvie CHARDON - Directrice de recherche - CNRS - Département de Chimie Moléculaire (DCM) Grenoble - Examinateur
- Laurence CROGUENNEC - Directrice de recherche - CNRS - ICMCB Bordeaux - Examinateur
- Antoine BARNABé - Professeur des universités - Université de Tolouse - Rapporteur
- Bruno JOUSSELME - Directeur de recherche - Centre CEA Paris-Saclay - Rapporteur
Dye-sensitized solar cells (DSSCs) and their photoelectrochemical variants (DSPECs) are promising devices for converting solar energy into electrical or chemical energy. Inspired by natural photosynthesis, these systems rely on light absorption by a chromophore, followed by charge injection into a mesoporous semiconductor. This thesis aims to enhance the performance of DSSCs and DSPECs, with a particular focus on p-type architectures. The work focuses on the rational design of push-pull organic dyes, the optimization of anchoring groups, and the broadening of the spectral absorption window. Special attention is given to the synthesis and integration of the delafossite oxide CuGaO₂ as a p-type semiconductor, to improve charge transport and minimize interfacial recombination. In this context, new chromophores featuring phosphonic acid anchoring functions were synthesized and characterized. Simultaneously, an original microwave-assisted synthesis yielded CuGaO₂ nanoparticles that were twice as small as those reported in the literature, in a very short reaction time. These nanoparticles enabled the fabrication of mesoscopic p-type photocathodes, which were successfully sensitized with the aforementioned chromophores. The sensitized photocathodes were then integrated into DSSC and DSPEC devices, yielding promising results in solar energy conversion. Altogether, these studies contribute to a better understanding of structure–property–performance relationships and open new perspectives for the direct conversion of solar energy into hydrogen.
Efficient room-temperature photocatalytic reduction of nitrogen to ammonia using water as a sacrificial donor
by Doha ZIDOUHIA (Institut des Sciences Moléculaires)
The defense will take place at 13h30 - Salle de conférence, 3ᵉ étage Institut des Sciences Moléculaires (ISM), groupe THEO, CNRS UMR 5255, Bâtiment A12, 351 cours de la Libération, 33405 Talence Cedex
in front of the jury composed of
- Dario BASSANI - Directeur de recherche - Université de Bordeaux - Directeur de these
- Etienne GRAU - Assistant professor - Université de Bordeaux - CoDirecteur de these
- Murielle CHAVAROT-KERLIDOU - Directrice de recherche - Université Grenoble Alpes - Examinateur
- Nicolas MEZAILLES - Directeur de recherche - Université Paul Sabatier - Rapporteur
- Elsje Alessandra QUADRELLI - Directrice de recherche - Université Claude Bernard Lyon 1 - Rapporteur
The industrial production of ammonia from atmospheric nitrogen, although essential for fertilizers and the chemical industry, remains highly energy-intensive and a significant source of CO₂ emissions, contributing approximately 1.44% of global CO₂ emissions and thus playing a non-negligible role in climate change. In recent years, considerable progress has been made in designing new catalysts capable of converting dinitrogen into ammonia; however, many of these systems still rely on strong, sacrificial and often hazardous rare or expensive reductants such as sodium/mercury or SmI₂. In this work, we explored a simpler and more sustainable alternative: the use of iron(II) salts, activated by UV light, to generate solvated electrons capable of driving a molybdenum-based catalyst for N₂ reduction During the reaction, the resulting iron(III) is in turn reduced, generating hydroxyl radicals, a pathway well-known from photo-Fenton-type reactions. This system presents several advantages: it operates effectively even in the presence of high salt concentrations, including seawater, and its efficiency can be significantly enhanced under pressure (up to 200 bar), achieving quantum yields exceeding 10%. A particularly interesting aspect of this mechanism is that water, in addition to serving as the solvent, acts as an electron source, with the overall process resulting in the formation of ammonia and dioxygen from N₂ and H₂O. This strategy opens promising prospects for aqueous catalytic reduction processes using simple, inexpensive reagents compatible with greener chemical production. Keywords: nitrogen, ammonia, hydrated electrons, photoreduction
ED Sciences de la Vie et de la Santé
Role of TMEM70 in the biogenesis of subunit c of the human ATP synthase and characterization of its variants
by Narda ARDDA (Institut de Biochimie et Génétique Cellulaires)
The defense will take place at 14h00 - Salle de conférences Institut de Biochimie et Génétique Cellulaires UMR5095 CNRS, Université de Bordeaux 1, rue Camille Saint-Saëns 33077 Bordeaux cedex, France
in front of the jury composed of
- Stéphane DUVEZIN-CAUBET - Chargé de recherche - Université de Bordeaux - Directeur de these
- Nathalie LELEU - Professeure des universités - Université de Versailles Saint Quentin en Yvelines - Rapporteur
- Vincent PROCACCIO - Professeur des universités - praticien hospitalier - Université d'Angers - Rapporteur
- Marion BOUCHECAREILH - Directrice de recherche - Université de Bordeaux - Examinateur
- Metodi METODIEV - Chargé de recherche - Université Paris Cité - Examinateur
Mitochondria are essential organelles in eukaryotic cells, best known for their central role in energy production in the form of adenosine triphosphate (ATP) through oxidative phosphorylation. This system relies on the respiratory chain, which generates an electrochemical proton gradient across the inner membrane, and on the F1Fo-ATP synthase. This enzyme is a multi-subunit protein complex of approximately 600 kDa that functions as a rotary nanomotor, coupling proton translocation across the inner mitochondrial membrane to ATP production from ADP and Pi in the matrix. The assembly of this enzyme is a highly complex and still poorly understood process that requires assembly factors, i.e. proteins that are not part of the final complex but play an essential role during the assembly steps. TMEM70 is one such assembly factor, localized in the inner mitochondrial membrane. Mutations in TMEM70 are the most frequent cause of nuclear-encoded ATP synthase deficiencies associated with autosomal recessive neonatal mitochondrial encephalocardiomyopathies. Several research groups, including ours, have shown that TMEM70 is required for the biogenesis of the ATP synthase subunit c, a hydrophobic protein present in eight identical copies forming a transmembrane oligomeric ring within the proton-translocating Fo domain of ATP synthase. However, the molecular mechanism of TMEM70 remains poorly understood. In a first chapter, several selected pathogenic missense mutations of TMEM70 were studied. The different TMEM70 variants were expressed in a TMEM70 knock-out cell line. The results show that three of the five mutations strongly affect TMEM70 stability by markedly increasing its turnover, providing insight into the pathogenic mechanism of these variants, whereas the other two do not show any detectable alteration. These same variants are associated with a decrease in total subunit c levels as well as reduced physical interactions between TMEM70 and this subunit. However, at the functional level, overexpression of these mutated forms of TMEM70 in knock-out cells is nevertheless able to restore normal amounts of ATP synthase, indicating only a partial impairment of TMEM70 variant activity. In another chapter of this thesis, we address the question of additional potential interaction partners of the subunit c and TMEM70. Indeed, on the one hand, both proteins were observed migrating within high-molecular-weight complexes far beyond the size of subunit c oligomeric rings, and on the other hand, several other proteins have been described as being involved in subunit c biogenesis in humans and/or other organisms. Among the candidates, we provide evidence for the direct involvement of the insertase protein OXA1L, which was found to physically interact with both TMEM70 and the subunit c. Finally, in the last chapter, I present the development of a method for importing radioactive protein precursors into isolated mitochondria from mammalian cells in order to follow their fate. In particular, I describe the optimization and validation of the use of previously frozen mitochondria for this type of experiment, which had not yet been reported for mammalian mitochondria and represented a limitation to the application of this approach. Our results provide new insights into the molecular mechanisms by which TMEM70 mutations can impair ATP synthase assembly, as well as new knowledge on the biogenesis of the ATP synthase subunit c and the role of TMEM70 in this process.
ED Sociétés, Politique, Santé Publique
Role of cardiometabolic factors in the incidence of age-related macular degeneration: methodological considerations
by Blondy KAYEMBE MULUMBA (Bordeaux Population Health Research Center)
The defense will take place at 14h00 - Amphithéâtre A. LOUIS ISPED - Université de Bordeaux (Campus Carreire) 146 rue Léo Saignat 33076 Bordeaux Cedex
in front of the jury composed of
- Marie-Noëlle DELYFER - Professeure des universités - praticienne hospitalière - Université de Bordeaux - Directeur de these
- Cécile DELCOURT - Directrice de recherche - Université de Bordeaux - CoDirecteur de these
- Karen LEFFONDRÉ - Professeure des universités - Université de Bordeaux - Examinateur
- Vincent DAÏEN - Professeur des universités - praticien hospitalier - Université de Montpellier - Examinateur
- Jean-Philippe EMPANA - Directeur de recherche - Université Paris Cité - Rapporteur
- Vanina BONGARD - Professeure des universités - praticienne hospitalière - Université de Toulouse - Rapporteur
Age-related macular degeneration (AMD) is the second cause of vision loss among older adults in developed countries. Seeking to identify its modifiable risk factors, previous studies have reported conflicting results regarding the associations between cardiometabolic factors and AMD. This controversy may be partly explained by methodological limitations. Thus, this thesis aimed to investigate the links between cardiometabolic factors and AMD onset using more robust. The specific objectives focused on analyzing the associations between (1) long-term blood pressure variability (BPV) and the incidence of AMD, (2) high-density lipoprotein cholesterol (HDL-C) levels and incident AMD, and (3) statin use and the incidence of AMD. We used data from the ALIENOR study, a prospective population-based cohort of French elderly in Bordeaux (2006-2020). AMD was assessed at each visit by multimodal imaging and classified into intermediate and advanced AMD. In objective 1, shared random-effects joint models analyzed the association between current BPV (mmHg) and incident AMD. In objective 2, illness-death models for interval-censored data quantified the association between plasma HDL-C levels (mmol/L) at baseline and incident AMD. Finally, in objective 3, time-dependent Cox models estimated the link between current statin use and incident AMD using propensity scores methods to account for the confounding by indication. Overall, we analyzed about 475 participants at risk for intermediate AMD and 692 for advanced AMD in the ALIENOR cohort. Independent of BP levels, a high current BPV value was associated with an increased hazard of advanced AMD, although statistical significance was only reached for diastolic BPV. These inaugural results suggest that high BPV between medical visits could represent a novel modifiable cardiovascular risk factor for AMD. After accounting for survival bias, no significant association was found between high HDL-C levels and the occurrence of AMD, although all estimated effects were greater than 1. These findings indicate that HDL-C may not be involved in the pathological processes of AMD. Finally, after accounting for confounding by indication using propensity scores, current statin use was not associated with incident AMD. These robust methodological approaches, original regarding the data currently available in the international literature, allowed for reliable modeling of complex cardiometabolic exposures to better understand their individual role in AMD incidence. These results suggest that AMD prevention strategies should also aim to control BP fluctuations between medical visits, beyond the management of hypertension, on the one hand, and on the other hand, reinforce the scientific data supporting that currently HDL-C should not be targeted as a risk factor for AMD, and that statins should not be primarily prescribed for AMD prevention. However, given the relatively low statistical power in the ALIENOR study, this thesis provides a solid basis for the replication of these methods in larger cohorts. Such an approach is necessary to confirm these results, as planned within the E3N (Étude Épidémiologique auprès de femmes de l'Éducation Nationale) cohort in the Macu-Life (Lifestyle-related exposome and age-related Macular degeneration risk) project.