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Mécanisme membranotrope de l'ovotransferrine sur membranes modèles de bactéries : impact du chauffage à sec de la protéine

Abstract : The use of antibacterial agents is very important, firstly, on the fight against bacterial infections, and secondly, to keep food products until its consumption. The loss of antibiotics effectiveness through the development of bacterial resistance and the toxicity of synthetic preservatives necessitates the development of new natural antibacterial products. Antibacterial proteins and peptides acting on the bacterial membranes appear as an alternative to limit the introduction of bacterial resistances. Ovotransferrin is an egg-white protein with membranotropic properties responsible among other things for its antibacterial activity. The aim of this thesis is to study the membranotropic mechanisms of ovotransferrin towards the outer and cytoplasmic membranes of E. coli using respectively monolayers of LPS (lipopolysaccharides) and phospholipids as experimental membrane models. Ovotransferrin has an insertion capacity in LPS monolayer that is dependent on protein concentration, monolayer compactness, and LPS molecule conformation. Ovotransferrin weakly adsorbs to the monolayer of phospholipids. Thus, the monolayers are disturbed by the disorganization of the lipids. Comparative analysis of dry-heated ovotransferrin with the native form showed conservation of secondary and tertiary structures with an increase of surface hydrophobicity and probably of flexibility and higher affinity to hydrophilic/hydrophobic interfaces (water/air). The insertion capacity in the LPS monolayer is amplified with greater affinity. Insertion capacity in the phospholipid monolayer is generated for the dry heated form associated with higher adsorption. Dry-heated ovotransferrin induces greater disruption of monolayers at lower protein concentrations.
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Youcef Menacer. Mécanisme membranotrope de l'ovotransferrine sur membranes modèles de bactéries : impact du chauffage à sec de la protéine. Bactériologie. Université Rennes 1, 2017. Français. ⟨NNT : 2017REN1S144⟩. ⟨tel-01822384⟩

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