ED Sciences Chimiques
Metallacarborane-based silica nanohelices: Innovative chiral nanocatalysts for asymmetric transformation in water
by Hao WANG (Institut de Chimie & de Biologie des Membranes & des Nano-objets)
The defense will take place at 14h00 - IECB Amphitheatre 2 Rue Robert Escarpit, 33600 Pessac
in front of the jury composed of
- Sylvain NLATE - Maître de conférences - Université de Bordeaux - Directeur de these
- Reiko ODA - Directrice de recherche - CNRS - CoDirecteur de these
- Stéphane BELLEMIN-LAPONNAZ - Directeur de recherche - CNRS - Rapporteur
- Riina AAV - Full professor - Tallinn University - Rapporteur
- Brigitte BIBAL - Professeure - Université de Bordeaux - Examinateur
- Emmanuel CADOT - Professeur des universités - Université de Versailles Saint-Quentin-en-Yvelines - Examinateur
Chiral materials have attracted particular interest in recent years due to their remarkable properties and potential applications, particularly in the field of asymmetric catalysis. The objective of this thesis is to prepare, characterize and study the chiroptical properties of a series of enantiopure helical nanostructures based on cobaltabis(dicarbollide) (COSAN) and polyoxometalate (POM). The effectiveness of these nanomaterials as heterogeneous photocatalysts in the enantioselective oxidation of alcohols will then be evaluated. Firstly, left-handed and right-handed enantiopure silica hybrid nanohelices based on COSAN were prepared and characterized. In these helical structures, achiral COSAN anions are encapsulated into organic-inorganic hybrid nanohelices, which serve as a chiral platform to induce chirality in COSAN for enantioselective transformations. The morphology and structural composition of these hybrids, as well as the presence of COSAN anions were confirmed by UV/Vis, Raman, TEM, NMR and EELS. Their optical activity was demonstrated by CD and ROA, highlighting the chirality induction of chiral hybrid nanohelices to achiral COSAN anions. Furthermore, these hybrids exhibit excellent catalytic activity and enantioselectivity in the photooxidation of aromatic secondary alcohols in water, reaching up to 85% enantiomeric excess. Remarkably, these catalysts were recovered and reused at least three times without loss of catalytic activity or enantioselectivity. We then focused on the chirality induction of silica nanohelices on POMs. Thus, a series of right-handed and left-handed hybrid silica nanohelices based on the trianionic Keggin POM [α-PW12O40]3− was prepared by anion exchange. They were characterized by TEM, EDX, UV/Vis, CD and ROA, confirming their helical structure and their optical activity. These POM-based hybrid silica nanohelices are efficient catalysts in the photooxidation of aromatic secondary alcohols, with an enantioselectivity of up to 56%. They are stable, recoverable and reusable for at least three cycles without loss of catalytic activity or enantioselectivity.
ED Sciences de la Vie et de la Santé
CONTRIBUTIONS OF AMYGDALAR BASKET AND AXO-AXONIC CELLS TO AVERSIVE STATES
by Cloé L'HERAUX (Neurocentre Magendie)
The defense will take place at 14h30 - Amphitéatre Broca Centre Broca, 146 rue Léo Saignat, 33076 BORDEAUX CEDEX
in front of the jury composed of
- Thomas BIENVENU - Professeur des universités - praticien hospitalier - Université de Bordeaux - Directeur de these
- Camilla BELLONE - Professor - Université de Genève - Examinateur
- François GEORGE - Directeur de recherche - Centre Broca - Institut des Maladies Neurodégénératives - Examinateur
- Antoine ADAMANTIDIS - Professor - University of Bern, Department of Neurology, Inselspital University Hospital Bern - Rapporteur
- Stéphanie TROUCHE - Directrice de recherche - Institut de Génomique Fonctionnelle - Rapporteur
- Guillaume FERREIRA - Directrice de recherche - INRAE - Université de Bordeaux - Examinateur
The survival of animals depends on their ability to detect, assess, and respond effectively to threats. Aversive emotions such as fear and anxiety are essential to these adaptive responses. The basolateral amygdala (BLA) plays a central role in regulating these emotions by integrating danger signals and coordinating appropriate behavioral responses. Within the BLA, excitatory principal neurons transmit emotional information, while GABAergic interneurons provide fine inhibitory control of their activity. Among these, parvalbumin-expressing (PV) interneurons are crucial for regulating anxiety- and fear-related behaviors. Traditionally considered as a homogeneous population, PV interneurons actually comprise functionally distinct subtypes, notably basket cells (BCs), which target the soma of principal neurons, and axo-axonic cells (AACs), which exclusively innervate the axon initial segment, a key site for action potential initiation. This anatomical specificity suggests that BCs and AACs may play complementary roles in modulating emotional states. In this thesis, we developed a novel transgenic mouse line allowing the specific targeting of BCs and AACs in the BLA. Using this strategy, we recorded their activity in vivo using fiber photometry, and selectively inhibited them through optogenetics during anxiety-related and conditioned fear behaviors. Our recordings revealed distinct dynamic activity patterns of AACs and BCs during anxiety-related behaviors. While both BCs and AACs were more active in anxiogenic spaces, only AACs were active during behaviors of high alert. Optogenetic inhibition of AACs disrupted avoidance and vigilance behaviors in the elevated plus maze, whereas BC inhibition did not lead to significant behavioral changes. During conditioned fear behaviors, both AACs and BCs were activated during specific phases: in response to aversive stimuli, their predictive cues, and during behavioral expression of fear. However, AACs were particularly active in response to cues that strongly predicted the aversive stimulus, while BCs showed no specificity. Their selective inhibition revealed that AACs promote adaptive regulation of fear learning, whereas BCs appeared dispensable during the learning phase. Finally, in vivo electrophysiological recordings allowed us to characterize the direct influence of AACs on pyramidal neurons in the medial prefrontal cortex. Optogenetic activation of AACs led to a rapid and transient inhibition of activity in a subset of neurons, although overall, effects were limited to a minority of cells, underscoring a sparse influence. In conclusion, this work provides the first evidence for distinct contributions of two PV interneuron subtypes in the regulation of aversive emotional states. It sheds new light on the complexity of inhibitory microcircuits in the BLA and opens the way for targeted approaches in understanding anxiety disorders.